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Sample records for sio4 tetrahedra linked

  1. Ab initio calculations for the substitutions of Al(OH)4- and SO42- with Si tetrahedra

    International Nuclear Information System (INIS)

    Rahman, Md.Mazibur; Tanaka, Satoru; Nagasaki, Shinya

    2001-01-01

    We have studied the interaction phenomena for the substitutions of Al(OH) 4 - and SO 4 2- with both paired and bridging Si tetrahedra likely to be occurred in C-S-H gel coexisting with ettringite system. Gaussian 94 program has been used to obtain the total energy of the molecule in the optimized structure employing HF/3-21G level of theory. It has been investigated that the net charge on the substitution site causes the modification of the original structure during the substitution. The substitutions of Al(OH) 4 - with Si tetrahedra were found to be thermodynamically possible in both paired and bridging Si tetrahedra at chemical equilibrium. The substitutions of SO 4 2- with Si tetrahedra were found to be thermodynamically possible at the limited positions as well. It this work, these possibilities are also discussed with the estimated activated energies for the substitutions of Al(OH) 4 - and SO 4 2- with paired Si tetrahedra. (author)

  2. Are Sb4n (n>1) clusters weakly interacting tetrahedra?

    International Nuclear Information System (INIS)

    Kumar, V.

    1993-03-01

    The electronic and atomic structure of Sb 4 and Sb 8 clusters is studied using the ab-initio molecular dynamics method in the local density approximation. While for Sb 4 we obtain a regular tetrahedron to be about 2.0 eV lower in energy than a bent rhombus, for Sb 8 two structures, (1) two weakly interaction tetrahedra and (2) a bent rhombus interacting with a stretched tetrahedron, obtained from the simulated annealing lie only within about 0.1 eV indicating the importance of the bent rhombus structure for larger clusters. As compared to two isolated tetrahedra, the binding energy of Sb 8 is about 0.5 eV. Our results are thus in excellent agreement with the experimental data which show predominantly the abundance of tetramers above room temperature. (author). 18 refs, 5 figs, 1 tab

  3. Effect of SiO2 addition and gamma irradiation on the lithium borate glasses

    Science.gov (United States)

    Raut, A. P.; Deshpande, V. K.

    2018-01-01

    The physical properties like density, glass transition temperature (Tg), and ionic conductivity of lithium borate (LB) glasses with SiO2 addition were measured before and after gamma irradiation. Remarkable changes in properties have been obtained in the physical properties of LB glasses with SiO2 addition and after gamma irradiation. The increase in density and glass transition temperature of LB glasses with SiO2 addition has been explained with the help of increase in density of cross linking due to SiO4 tetrahedra formation. The increase in ionic conductivity with SiO2 addition was explained with the help of ‘mixed glass former effect’. The increase in density and Tg of LB glasses with SiO2 addition after gamma irradiation has been attributed to fragmentation of bigger ring structure into smaller rings, which increases the density of cross linking and hence compaction. The exposure of gamma irradiation has lead to decrease in ionic conductivity of LB glasses with SiO2 addition. The atomic displacement caused by gamma irradiation resulted in filling of interstices and decrease in trapping sites. This explains the obtained decrease in ionic conductivity after gamma irradiation of glasses. The obtained results of effect of SiO2 addition and gamma irradiation on the density, Tg and ionic conductivity has been supported by FTIR results.

  4. The atomic arrangement of iimoriite-(Y), Y2(SiO4)(CO3)

    Science.gov (United States)

    Hughes, J.M.; Foord, E.E.; Jai-Nhuknan, J.; Bell, J.M.

    1996-01-01

    Iimoriite-(Y) from Bokan Mountain, Prince of Wales Island, Alaska has been studied using single-crystal X-ray-diffraction techniques. The mineral, ideally Y2(SiO4)(CO3), crystallizes in space group P1, with a 6.5495(13), b 6.6291(14), c 6.4395(11)A??, ?? 116.364(15), ?? 92.556(15) and ?? 95.506(17)??. The atomic arrangement has been solved and refined to an R value of 0.019. The arrangement of atoms consists of alternating (011) slabs of orthosilicate groups and carbonate groups, with no sharing of oxygen atoms between anionic complexes in adjacent slabs. Y1 atoms separate adjacent tetrahedra along [100] within the orthosilicate slab, and Y2 atoms separate adjacent carbonate groups along [100] within the carbonate slab. Adjacent orthosilicate and carbonate slabs are linked in (100) by bonding Y atoms from each slab to oxygen atoms of adjacent slabs, in the form of YO8 polyhedra. The Y1 atoms exist in Y12O14 dimers in the orthosilicate slab, and the Y2 atoms exist in continuous [011] ribbons of edge-sharing Y2O8 polyhedra in the carbonate slab.

  5. Raman and infrared investigations of glass and glass-ceramics with composition 2Na2O·1CaO·3SiO2

    OpenAIRE

    Ziemath, Ervino C.; Aegerter, Michel A.

    1994-01-01

    Precursor glass and glass-ceramics with molar composition 2Na2O·1CaO·3SiO2 are studied by infrared, conventional, and microprobe Raman techniques. The Gaussian deconvoluted Raman spectrum of the glass presents bands at 625 and 660 cm-1, attributed to bending vibrations of Si-O-Si bonds, and at 860, 920, 975 and 1030 cm-1, attributed to symmetric stretching vibrations of SiO4 tetrahedra with 4, 3, 2, and 1 nonbridging oxygens, respectively. The Raman microprobe spectrum of a highly crystalliz...

  6. Cotton fabric finishing with TiO2/SiO2 composite hydrosol based on ionic cross-linking method

    International Nuclear Information System (INIS)

    Xu, Z.J.; Tian, Y.L.; Liu, H.L.; Du, Z.Q.

    2015-01-01

    Highlights: • We studied the cotton finishing with TiO 2 /SiO 2 based on ionic cross-linking method. • The samples treated with CHTAC had lower value of whiteness. • The samples treated with BTCA achieved higher crease recovery angle and lower tensile strength. • The ionic cross-linking treatment (CHTAC + BTCA + TiO 2 /SiO 2 ) was better than with TiO 2 /SiO 2 sol alone. - Abstract: Cotton fabric was successfully modified by 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHTAC), 1,2,3,4-butanetetracarboxylic acid (BTCA) and TiO 2 /SiO 2 sol. Self-cleaning characteristic was investigated using a Color Measuring and Matching System with 6 h sunlight irradiation. And the stability of TiO 2 /SiO 2 coatings was explored by measuring the washing fastness and wrinkle resistance of treated cotton samples. In addition, whiteness index, crease recovery angle and tensile strength retention (%) of treated samples were evaluated. Moreover, the morphology, structure change and crystallinity of samples were observed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. The results revealed that the samples treated with CHTAC had lower value of whiteness index as compared with original cotton fabric. It was also found that samples treated with BTCA achieved higher crease recovery angle and lower tensile strength. Moreover, the treatment of CHTAC and BTCA had adverse effect on the crystallinity of cotton samples, as treated samples had lower crystallinity in comparison with raw cotton fabrics. Nevertheless, the stability of self-cleaning coatings was better for samples treated with ionic cross-linking treatment (CHTAC + BTCA + TiO 2 /SiO 2 ) than samples treated with TiO 2 /SiO 2 sol alone. Furthermore, compared with original samples the UV-blocking property of ionic cross-linking treated samples was obviously enhanced

  7. Photoluminescence analysis of Ce3+:Zn2SiO4 & Li++ Ce3+:Zn2SiO4: phosphors by a sol-gel method

    Science.gov (United States)

    Babu, B. Chandra; Vandana, C. Sai; Guravamma, J.; Rudramadevi, B. Hemalatha; Buddhudu, S.

    2015-06-01

    Here, we report on the development and photoluminescence analysis of Zn2SiO4, Ce3+:Zn2SiO4 & Li+ + Ce3+: Zn2SiO4 novel powder phosphors prepared by a sol-gel technique. The total amount of Ce3+ ions was kept constant in this experiment at 0.05 mol% total doping. The excitation and emission spectra of undoped (Zn2SiO4) and Ce3+ doped Zn2SiO4 and 0.05 mol% Li+ co-doped samples have been investigated. Cerium doped Zn2SiO4 powder phosphors had broad blue emission corresponding to the 2D3/2→2FJ transition at 443nm. Stable green-yellow-red emission has been observed from Zn2SiO4 host matrix and also we have been observed the enhanced luminescence of Li+ co-doped Zn2SiO4:Ce3+. Excitation and emission spectra of these blue luminescent phosphors have been analyzed in evaluating their potential as luminescent screen coating phosphors.

  8. Synthesis and Luminescence Properties of Yellow-emitting SiO2/Zn2SiO4: Mn Nanocomposite

    Directory of Open Access Journals (Sweden)

    Karim OMRI

    2014-05-01

    Full Text Available Yellow light emitting Mn2+-doped b-Zn2SiO4 phosphor nanoparticles embedded in SiO2 host matrix, were prepared by a simple solid-phase reaction under natural atmosphere at 1500 °C for 2 hours after the incorporation of manganese doped zinc oxide nanoparticles in silica using sol-gel method. The SiO2/Zn2SiO4:Mn nanocomposite was characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM and photoluminescence (PL. The nanopowder was crystallized in triclinic b-Zn2SiO4 phase with a particles size varies between 70 nm and 84 nm. The SiO2/b-Zn2SiO4:Mn nanocomposite exhibited a broad yellow emission band at 575 nm under UV excitation light. The dependence of the intensity and energy position of the obtained PL band on measurement temperature and power excitation will be discussed.

  9. Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

    Science.gov (United States)

    Li, Yue; Wang, Xiang-Yu; Jiang, Xiao-Ping; Ye, Jing-Jing; Zhang, Ye-Wang; Zhang, Xiao-Yun

    2015-01-01

    Fe3O4@SiO2-graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe3O4@SiO2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe3O4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe3O4@SiO2 NPs was 24 ± 0.3 nm, similar to that of Fe3O4@SiO2-NH2. Fe3O4@SiO2-GO composites were synthesized by linking of Fe3O4@SiO2-NH2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe3O4@SiO2-GO composite has potential applications in the production of bioethanol.

  10. Magnetic SiO2/Fe3O4 colloidal crystals

    International Nuclear Information System (INIS)

    Huang, C-K; Hou, C-H; Chen, C-C; Tsai, Y-L; Chang, L-M; Wei, H-S; Hsieh, K-H; Chan, C-H

    2008-01-01

    We proposed a novel technique to fabricate colloidal crystals by using monodisperse SiO 2 coated magnetic Fe 3 O 4 (SiO 2 /Fe 3 O 4 ) microspheres. The magnetic SiO 2 /Fe 3 O 4 microspheres with a diameter of 700 nm were synthesized in the basic condition with ferric sulfate, ferrous sulfate, tartaric acid and tetraethyl orthosilicate (TEOS) in the reaction system. Monodisperse SiO 2 /Fe 3 O 4 superparamagnetic microspheres have been successfully used to fabricate colloidal crystals under the existing magnetic field

  11. Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

    International Nuclear Information System (INIS)

    Li, Yue; Wang, Xiang-Yu; Jiang, Xiao-Ping; Ye, Jing-Jing; Zhang, Ye-Wang; Zhang, Xiao-Yun

    2015-01-01

    Fe 3 O 4 @SiO 2 –graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe 3 O 4 @SiO 2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe 3 O 4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO 2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe 3 O 4 @SiO 2 NPs was 24 ± 0.3 nm, similar to that of Fe 3 O 4 @SiO 2 –NH 2 . Fe 3 O 4 @SiO 2 –GO composites were synthesized by linking of Fe 3 O 4 @SiO 2 –NH 2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe 3 O 4 @SiO 2 –GO composite has potential applications in the production of bioethanol

  12. Thermal cycling tests on Li4SiO4 and beryllium pebbles

    International Nuclear Information System (INIS)

    Dalle Donne, M.; Norajitra, P.; Weisenburger, A.

    1995-01-01

    The European B.O.T. Demo-relevant solid breeder blanket is based on the use of beds of beryllium and Li 4 SiO 4 pebbles. Particularly dangerous for the pebble integrity are the rapid temperature changes which could occur, for instance, by a sudden blanket power shut-down. A series of thermal cycle tests have been performed for various beds of beryllium and Li 4 SiO 4 pebbles. No breaking was observed in the beryllium pebbles, however the Li 4 SiO 4 pebbles broke by temperature rates of change of about -50 C/sec independently on pebbles size and lithium enrichment. This value is considerably higher than the peak temperature rates of change expected in the blanket. (orig.)

  13. Navigating Weighted Regions with Scattered Skinny Tetrahedra

    KAUST Repository

    Cheng, Siu-Wing; Chiu, Man-Kwun; Jin, Jiongxin; Vigneron, Antoine E.

    2015-01-01

    We propose an algorithm for finding a (1 + ε)-approximate shortest path through a weighted 3D simplicial complex T. The weights are integers from the range [1,W] and the vertices have integral coordinates. Let N be the largest vertex coordinate magnitude, and let n be the number of tetrahedra in T. Let ρ be some arbitrary constant. Let κ be the size of the largest connected component of tetrahedra whose aspect ratios exceed ρ. There exists a constant C dependent on ρ but independent of T such that if κ ≤ 1 C log log n + O(1), the running time of our algorithm is polynomial in n, 1/ε and log(NW). If κ = O(1), the running time reduces to O(nε(log(NW))).

  14. Navigating Weighted Regions with Scattered Skinny Tetrahedra

    KAUST Repository

    Cheng, Siu-Wing

    2015-11-26

    We propose an algorithm for finding a (1 + ε)-approximate shortest path through a weighted 3D simplicial complex T. The weights are integers from the range [1,W] and the vertices have integral coordinates. Let N be the largest vertex coordinate magnitude, and let n be the number of tetrahedra in T. Let ρ be some arbitrary constant. Let κ be the size of the largest connected component of tetrahedra whose aspect ratios exceed ρ. There exists a constant C dependent on ρ but independent of T such that if κ ≤ 1 C log log n + O(1), the running time of our algorithm is polynomial in n, 1/ε and log(NW). If κ = O(1), the running time reduces to O(nε(log(NW))).

  15. Er2S[SiO4]: An erbium sulfide ortho-oxosilicate with unusual sulfide anion coordination

    International Nuclear Information System (INIS)

    Hartenbach, Ingo; Lauxmann, Petra; Schleid, Thomas

    2004-01-01

    During the reaction of cadmium sulfide with erbium and sulfur in evacuated silica ampoules pink lath-shaped crystals of Er 2 S[SiO 4 ] occur as by-product which were characterized by X-ray single crystal structure analysis. The title compound crystallizes orthorhombically in the space group Cmce (a = 1070.02(8), b = 1235.48(9), c = 683.64(6) pm) with eight formula units per unit cell. Besides isolated ortho-oxosilicate units [SiO 4 ] 4- , the crystal structure contains two crystallographically independent Er 3+ cations which are both eightfold coordinated by six oxygen and two sulfur atoms. The sulfide anions are surrounded by four erbium cations each in the shape of very distorted tetrahedra. These excentric [SEr 4 ] 10+ tetrahedra build up layers according to 2 ∞ [SEr 4/2 ] 4+ by vertex- and edge-connection. They are piled parallel to (010) and separated by the isolated ortho-oxosilicate tetrahedra. (Abstract Copyright [2004], Wiley Periodicals, Inc.) [de

  16. Towards understanding the thermoanalysis of water sorption on lithium orthosilicate (Li4SiO4)

    International Nuclear Information System (INIS)

    Ortiz-Landeros, J.; Martinez-dlCruz, L.; Gomez-Yanez, C.; Pfeiffer, H.

    2011-01-01

    A systematic thermogravimetric study of hygroscopic and reactivity behaviors, at low temperatures of lithium orthosilicate (Li 4 SiO 4 ), are presented. Li 4 SiO 4 sample was prepared by solid-state reaction and then treated at different temperature-humidity conditions. Li 4 SiO 4 samples previously treated under different temperature-humidity conditions were characterized by Fourier transform infrared spectroscopy and thermogravimetric analyses. Different processes, adsorption and absorption, take place between the Li 4 SiO 4 and water vapor. Absorbed water produces superficial hydroxylated species such as Si-OH and Li-OH. In addition, a kinetic analysis was performed, and the different water absorption activation enthalpies were calculated. It was found that activation enthalpy (ΔH) values decrease when the relative humidity is incremented, from 5528.6 J/mol to 2074.2 J/mol at relative humidity levels of 60% and 75% respectively. These results show the impact of different humidity and temperature conditions on the stability and/or chemical reactivity of Li 4 SiO 4 , if this ceramic is used in different application fields, such as carbon dioxide captor or as a breeder ceramic into the fusion reactors.

  17. Immobilization of glucose oxidase using CoFe2O4/SiO2 nanoparticles as carrier

    Science.gov (United States)

    Wang, Hai; Huang, Jun; Wang, Chao; Li, Dapeng; Ding, Liyun; Han, Yun

    2011-04-01

    Aminated-CoFe2O4/SiO2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. Glucose oxidase (GOD) was immobilized on CoFe2O4/SiO2 NPs via cross-linking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, cross-linking time of 3 h, solution pH of 7.0 and 0.4 mg GOD (in 3.0 mg carrier). The immobilized GOD showed maximal catalytic activity at pH 6.5 and 40 °C. After immobilization, the GOD exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 80% of its initial activity after the incubation at 50 °C for 25 min, whereas free enzyme had only 20% of initial activity after the same incubation. After kept at 4 °C for 28 days, the immobilized and free enzyme retained 87% and 40% of initial activity, respectively. The immobilized GOD maintained approximately 57% of initial activity after reused 7 times. The KM (Michaelis-Menten constant) values for immobilized GOD and free GOD were 14.6 mM and 27.1 mM, respectively.

  18. Effect of surface water on tritium release behavior from Li4SiO4

    International Nuclear Information System (INIS)

    Hanada, T.; Fukada, S.; Nishikawa, M.; Suematsu, K.; Yamashita, N.; Kanazawa, T.

    2010-01-01

    The tritium release model to represent the release behavior of bred tritium from solid breeder materials has been developed by the blanket group of Kyushu University. It has been found that water is released to the purge gas from solid breeder materials and that this water affects the tritium release behavior. In this study, the amount of surface water released from Li 4 SiO 4 is quantified by the experiment. In addition, the tritium release behavior from Li 4 SiO 4 are estimated based on the tritium release model using parameters obtained in our studies under conditions of commercial reactor operation and ITER test blanket module operation. The effect of the surface water on tritium release behavior is discussed from the obtained results. Moreover, the tritium inventory of Li 4 SiO 4 is discussed based on calculation under the unsteady state condition. Further, the effects of grain size and temperature on distribution of tritium inventory under the steady state condition are evaluated, and the optimal grain size is discussed from the view point of tritium release from Li 4 SiO 4 .

  19. Hindered rotational energy barriers of BH4- tetrahedra in β-Mg(BH4)2 from quasielastic neutron scattering and DFT calculations

    DEFF Research Database (Denmark)

    Blanchard, Didier; Maronsson, Jon Bergmann; Riktor, M.D.

    2012-01-01

    , around the 2-fold (C2) and 3-fold (C3) axes were observed at temperatures from 120 to 440 K. The experimentally obtained activation energies (EaC2 = 39 and 76 meV and EaC3 = 214 meV) and mean residence times between reorientational jumps are comparable with the energy barriers obtained from DFT......In this work, hindered rotations of the BH4- tetrahedra in Mg(BH4)2 were studied by quasielastic neutron scattering, using two instruments with different energy resolution, in combination with density functional theory (DFT) calculations. Two thermally activated reorientations of the BH4- units...... calculations. A linear dependency of the energy barriers for rotations around the C2 axis parallel to the Mg-Mg axis with the distance between these two axes was revealed by the DFT calculations. At the lowest temperature (120 K) only 15% of the BH4- units undergo rotational motion and from comparison with DFT...

  20. Total Ionizing Dose Effects of Si Vertical Diffused MOSFET with SiO2 and Si3N4/SiO2 Gate Dielectrics

    Directory of Open Access Journals (Sweden)

    Jiongjiong Mo

    2017-01-01

    Full Text Available The total ionizing dose irradiation effects are investigated in Si vertical diffused MOSFETs (VDMOSs with different gate dielectrics including single SiO2 layer and double Si3N4/SiO2 layer. Radiation-induced holes trapping is greater for single SiO2 layer than for double Si3N4/SiO2 layer. Dielectric oxidation temperature dependent TID effects are also studied. Holes trapping induced negative threshold voltage shift is smaller for SiO2 at lower oxidation temperature. Gate bias during irradiation leads to different VTH shift for different gate dielectrics. Single SiO2 layer shows the worst negative VTH at VG=0 V, while double Si3N4/SiO2 shows negative VTH shift at VG=-5 V, positive VTH shift at VG=10 V, and negligible VTH shift at VG=0 V.

  1. Cd2SiO4/Graphene nanocomposite: Ultrasonic assisted synthesis, characterization and electrochemical hydrogen storage application.

    Science.gov (United States)

    Masjedi-Arani, Maryam; Salavati-Niasari, Masoud

    2018-05-01

    For the first time, a simple and rapid sonochemical technique for preparing of pure Cd 2 SiO 4 nanostructures has been developed in presence of various surfactants of SDS, CTAB and PVP. Uniform and fine Cd 2 SiO 4 nanoparticle was synthesized using of polymeric PVP surfactant and ultrasonic irradiation. The optimized cadmium silicate nanostructures added to graphene sheets and Cd 2 SiO 4 /Graphene nanocomposite synthesized through pre-graphenization. Hydrogen storage capacity performances of Cd 2 SiO 4 nanoparticle and Cd 2 SiO 4 /Graphene nanocomposite were compared. Obtained results represent that Cd 2 SiO 4 /Graphene nanocomposites have higher hydrogen storage capacity than Cd 2 SiO 4 nanoparticles. Cd 2 SiO 4 /Graphene nanocomposites and Cd 2 SiO 4 nanoparticles show hydrogen storage capacity of 3300 and 1300 mAh/g, respectively. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Cross-linked Composite Gel Polymer Electrolyte using Mesoporous Methacrylate-Functionalized SiO2 Nanoparticles for Lithium-Ion Polymer Batteries

    Science.gov (United States)

    Shin, Won-Kyung; Cho, Jinhyun; Kannan, Aravindaraj G.; Lee, Yoon-Sung; Kim, Dong-Won

    2016-01-01

    Liquid electrolytes composed of lithium salt in a mixture of organic solvents have been widely used for lithium-ion batteries. However, the high flammability of the organic solvents can lead to thermal runaway and explosions if the system is accidentally subjected to a short circuit or experiences local overheating. In this work, a cross-linked composite gel polymer electrolyte was prepared and applied to lithium-ion polymer cells as a safer and more reliable electrolyte. Mesoporous SiO2 nanoparticles containing reactive methacrylate groups as cross-linking sites were synthesized and dispersed into the fibrous polyacrylonitrile membrane. They directly reacted with gel electrolyte precursors containing tri(ethylene glycol) diacrylate, resulting in the formation of a cross-linked composite gel polymer electrolyte with high ionic conductivity and favorable interfacial characteristics. The mesoporous SiO2 particles also served as HF scavengers to reduce the HF content in the electrolyte at high temperature. As a result, the cycling performance of the lithium-ion polymer cells with cross-linked composite gel polymer electrolytes employing methacrylate-functionalized mesoporous SiO2 nanoparticles was remarkably improved at elevated temperatures. PMID:27189842

  3. Thermal analysis and vibrational spectroscopic characterization of the boro silicate mineral datolite - CaBSiO4(OH)

    Science.gov (United States)

    Frost, Ray L.; Xi, Yunfei; Scholz, Ricardo; Lima, Rosa Malena Fernandes; Horta, Laura Frota Campos; Lopez, Andres

    2013-11-01

    The objective of this work is to determine the thermal stability and vibrational spectra of datolite CaBSiO4(OH) and relate these properties to the structure of the mineral. The thermal analysis of datolite shows a mass loss of 5.83% over a 700-775 °C temperature range. This mass loss corresponds to 1 water (H2O) molecules pfu. A quantitative chemical analysis using electron probe was undertaken. The Raman spectrum of datolite is characterized by bands at 917 and 1077 cm-1 assigned to the symmetric stretching modes of BO and SiO tetrahedra. A very intense Raman band is observed at 3498 cm-1 assigned to the stretching vibration of the OH units in the structure of datolite. BOH out-of-plane vibrations are characterized by the infrared band at 782 cm-1. The vibrational spectra are based upon the structure of datolite based on sheets of four- and eight-membered rings of alternating SiO4 and BO3(OH) tetrahedra with the sheets bonded together by calcium atoms.

  4. Fabrication and tritium release property of Li2TiO3-Li4SiO4 biphasic ceramics

    Science.gov (United States)

    Yang, Mao; Ran, Guangming; Wang, Hailiang; Dang, Chen; Huang, Zhangyi; Chen, Xiaojun; Lu, Tiecheng; Xiao, Chengjian

    2018-05-01

    Li2TiO3-Li4SiO4 biphasic ceramic pebbles have been developed as an advanced tritium breeder due to the potential to combine the advantages of both Li2TiO3 and Li4SiO4. Wet method was developed for the pebble fabrication and Li2TiO3-Li4SiO4 biphasic ceramic pebbles were successfully prepared by wet method using the powders synthesized by hydrothermal method. The tritium release properties of the Li2TiO3-Li4SiO4 biphasic ceramic pebbles were evaluated. The biphasic pebbles exhibited good tritium release property at low temperatures and the tritium release temperature was around 470 °C. Because of the isotope exchange reaction between H2 and tritium, the addition of 0.1%H2 to purge gas He could significantly enhance the tritium gas release and the fraction of molecular form of tritium increased from 28% to 55%. The results indicate that the Li2TiO3-Li4SiO4 biphasic ceramic pebbles fabricated by wet method exhibit good tritium release property and hold promising potential as advanced breeder pebbles.

  5. Atomic-scale structure of GeSe2 glass revisited: a continuous or broken network of Ge-(Se1/2)4 tetrahedra?

    International Nuclear Information System (INIS)

    Petkov, V; Le Messurier, D

    2010-01-01

    The atomic-scale structure of germanium diselenide (GeSe 2 ) glass has been revisited using a combination of high-energy x-ray diffraction and constrained reverse Monte Carlo simulations. The study shows that the glass structure may be very well described in terms of a continuous network of corner- and edge-sharing Ge-Se 4 tetrahedra. The result is in contrast to other recent studies asserting that the chemical order and, hence, network integrity in GeSe 2 glass are intrinsically broken. It is suggested that more elaborate studies are necessary to resolve the controversy.

  6. The ceramic SiO2 and SiO2-TiO2 coatings on biomedical Ti6Al4VELI titanium alloy

    International Nuclear Information System (INIS)

    Surowska, B.; Walczak, M.; Bienias, J.

    2004-01-01

    The paper presents the study of intermediate SiO 2 and SiO 2 -TiO 2 sol-gel coatings and dental porcelain coatings on Ti6Al4VELI titanium alloy. Surface microstructures and wear behaviour by pin-on-disc method of the ceramic coatings were investigated. The analysis revealed: (1) a compact, homogeneous SiO 2 and SiO 2 -TiO 2 coating and (2) that intermediate coatings may provide a durable joint between metal and porcelain, and (3) that dental porcelain on SiO 2 and TiO 2 coatings shows high wear resistance. (author)

  7. Effective surface modification of MnFe2O4@SiO2@PMIDA magnetic nanoparticles for rapid and high-density antibody immobilization

    Science.gov (United States)

    Rashid, Zahra; Soleimani, Masoud; Ghahremanzadeh, Ramin; Vossoughi, Manouchehr; Esmaeili, Elaheh

    2017-12-01

    The present study is aimed at the synthesis of MnFe2O4@SiO2@PMIDA in terms of highly efficient sensing platform for anti-prostate specific membrane antigen (PSMA) immobilization. Superparamagnetic manganese ferrite nanoparticles were synthesized following co-precipitation method and then SiO2 shell was coated on the magnetic core with tetraethyl orthosilicate (TEOS) through a silanization reaction to prevent oxidation, agglomeration and, increase the density of OH groups on the surface of MnFe2O4. Subsequently, MnFe2O4@SiO2@PMIDA obtained as a result of the reaction between N-(phosphonomethyl)iminodiacetic acid (PMIDA) and MnFe2O4@SiO2. The reactive carboxyl groups on the surface of magnetic nanoparticles can efficiently conjugate to a monoclonal antibody, specific to PSMA, which was confirmed by enzyme-linked immune sorbent assay (ELISA). Thus, this kind of functionalized magnetic nanoparticles is promising to be utilized in the improvement of ELISA-based biosensors and also will be effective in a variety of biomedical applications such as cell separation, diagnosis, and monitoring of human diseases.

  8. Luminescence characteristics of Mg2SiO4:Nd

    International Nuclear Information System (INIS)

    Indira, P.; Subrahmanyam, R.V.; Murthy, K.V.R.

    2011-01-01

    Thermoluminescence (TL) properties of Magnesium Ortho silicate (2:1) Mg 2 SiO 4 doped with various concentrations of rare earth (Nd) have been studied. The phosphor material were prepared using standard solid state reaction technique and heated specimens at 1100 ± 20 deg C for two hours. 4% Ammonium chloride was used as flux. The received material was grinded in an agate mortar and pestle. The TL exhibited by the Mg 2 SiO 4 with varying concentration of Nd is interesting in nature. It is interesting to note but as the concentration of Nd increases the peak around 125 deg C TL peak intensity increases. But the hump around 200 deg C resolved as TL peak at 253 deg C with high intensity. (author)

  9. Synthesis, structure, and electronic structure calculation of a new centrosymmetric borate Pb{sub 2}O[BO{sub 2}(OH)] based on anion-centered OPb{sub 4} tetrahedra

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Feng [College of Chemistry and Chemical Engineering, Xinjiang Normal University, Urumqi 830054 (China); Wang, Li, E-mail: wangliresearch@163.com [College of Chemistry and Chemical Engineering, Xinjiang Normal University, Urumqi 830054 (China); Stoumpos, Constantinos C. [Department of Chemistry, Northwestern University, Evanston, IL 60208 (United States)

    2016-08-15

    The synthesis, structure, and characterization of a new centrosymmetric borate Pb{sub 2}O[BO{sub 2}(OH)] based on anion-centered OPb{sub 4} tetrahedra are reported. Pb{sub 2}O[BO{sub 2}(OH)] crystallizes in monoclinic space group C2/m with a=12.725(7) Å, b=5.698(3) Å, c=7.344(4) Å, β=116.277(6)°. The electronic band structure and density of states of Pb{sub 2}O[BO{sub 2}(OH)] have been calculated via the density functional theory (DFT). Electron density difference calculation indicates that lone-pair electrons of Pb{sup 2+} cation should be stereoactive. - Graphical abstract: An indirect gap compound of Pb{sub 2}O[BO{sub 2}(OH)] with 2D inorganic layers motif based on OPb{sub 4} tetrahedra has been synthesized and full characterized by crystallographic, IR, TG, UV–vis-NIR Diffuse Reflectance, and theoretical calculations. Display Omitted - Highlights: • A centrosymmetric borate Pb{sub 2}O[BO{sub 2}(OH)] was synthesized and characterized. • The crystalstructure, electronic band and density states was analyzed. • The lone-pair electrons of Pb{sup 2+} were proved to be stereoactive.

  10. Unusual structure in forsterite glass synthesized by an aero-acoustic levitation technique

    International Nuclear Information System (INIS)

    Kohara, Shinji; Suzuya, Kentaro; Takeuchi, Ken

    2005-01-01

    Forsterite Mg 2 SiO 4 exhibits an orthorhombic structure consisted of two kinds of MgO 6 octahedra. One of them forms edge-sharing ribbons along the [001] direction which are linked by the other kind of edge-sharing MgO 6 octahedra, resulting in a three-dimensional framework. Given only 33.3 mol% of SiO 2 in the material, the SiO 4 tetrahedra are isolated within the framework, sharing the O-O bonds with the common edges of the MgO 6 octahedra. If forsterite can be vitrified, an interesting question concerning the glass structure arises because there is insufficient glass forming SiO 2 to establish the corner-sharing SiO 4 tetrahedral net-work needed in conventional silicate glasses. A bulk Mg 2 SiO 4 glass was synthesized using an aero-acoustic levitation technique and to visualize the short-to intermediate-range structure by a combined high-energy synchrotron x-ray and neutron diffraction and reverse Monte Carlo computer simulation. We found that the role of network former is largely taken on by corner-and edge-sharing ionic magnesium species that adopt 4-, 5- and 6-coordination with oxygen. (author)

  11. Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

    Indian Academy of Sciences (India)

    Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres. K C BARICK and D BAHADUR*. Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay,. Mumbai 400 076, India. Abstract. The assembly of superparamagnetic Fe3O4 nanoparticles on submicroscopic SiO2 ...

  12. Enhancement of reactivity in Li4SiO4-based sorbents from the nano-sized rice husk ash for high-temperature CO2 capture

    International Nuclear Information System (INIS)

    Wang, Ke; Zhao, Pengfei; Guo, Xin; Li, Yimin; Han, Dongtai; Chao, Yang

    2014-01-01

    Highlights: • The Li 4 SiO 4 sorbent from nano-sized rice husk ash was prepared and characterized. • The Aerosil and Quartz were comparably used for synthesized Li 4 SiO 4 . • The structure of sorbent was depended on the morphology of heated silicon materials. • The pretreatment sorbent showed increase in the CO 2 uptake and kinetic behavior. • This promising sorbent also maintained higher capacities during the multiple cycles. - Abstract: Using the cost-effective, renewable and nano-sized of citric acid pretreatment rice husk ash (CRHA) as silicon source, high efficient Li 4 SiO 4 (lithium orthosilicate)-based sorbents (CRHA-Li 4 SiO 4 ) for high-temperature CO 2 capture were prepared through the solid-state reaction at lower temperature (700 °C). Two typical raw materials (nano-structured Aerosil and crystalline Quartz powders) were used to synthesize Li 4 SiO 4 sorbents (Aerosil-Li 4 SiO 4 and Quartz-Li 4 SiO 4 ) for comparison purposes. The phase composition behavior, surface area, and morphology of the silicon sources, heat treated raw materials and as-received Li 4 SiO 4 sorbents were studied by analytical techniques. The CO 2 adsorption capacity and adsorption–desorption performance were tested by the thermo-gravimetric analyses (CO 2 atmosphere) and a fixed bed reactor, respectively. Compared with the case of its original samples, the morphology of heat treated raw materials had a greater effect on the phase composition, microstructure, special surface area and CO 2 adsorption properties of their resulting sorbents. Although the calcined Quartz sample maintained the structure of micron particles, its reactivity was not enough to react completely with Li 2 CO 3 . Due to the greater reactivity of nanoparticles, Aerosil-Li 4 SiO 4 presented pure of Li 4 SiO 4 whereas it obtained large particles with dense morphology, which was coming from the pronounced fusing of silica nanoparticles during the calcined process. Conversely, CRHA-Li 4 SiO 4

  13. CoFe2O4-SiO2 Composites: Preparation and Magnetodielectric Properties

    Directory of Open Access Journals (Sweden)

    T. Ramesh

    2016-01-01

    Full Text Available Cobalt ferrite (CoFe2O4 and silica (SiO2 nanopowders have been prepared by the microwave hydrothermal (M-H method using metal nitrates as precursors of CoFe2O4 and tetraethyl orthosilicate as a precursor of SiO2. The synthesized powders were characterized by XRD and FESEM. The (100-x (CoFe2O4 + xSiO2 (where x = 0%, 10%, 20%, and 30% composites with different weight percentages have been prepared using ball mill method. The composite samples were sintered at 800°C/60 min using the microwave sintering method and then their structural and morphological studies were investigated using X-ray diffraction (XRD, Fourier transformation infrared (FTIR spectra, and scanning electron microscopy (SEM, respectively. The effect of SiO2 content on the magnetic and electrical properties of CoFe2O4/SiO2 nanocomposites has been studied via the magnetic hysteresis loops, complex permeability, permittivity spectra, and DC resistivity measurements. The synthesized nanocomposites with adjustable grain sizes and controllable magnetic properties make the applicability of cobalt ferrite even more versatile.

  14. Investigation of TL, OSL and PTTL properties of Mg2SiO4:Tb dosimeters

    International Nuclear Information System (INIS)

    Oguz, K. F.; Goekce, M.; Karali, T.; Harmansah, C.

    2010-01-01

    In this study thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of Mg 2 SiO 4 :Tb in the form of sintered pellets were investigated. Mg 2 SiO 4 :Tb is a recently developed dosimetric material which offers high sensitivity for TL and OSL in dosimetric applications. Thermoluminescence glow curve of Tb doped Mg 2 SiO 4 samples show a glow peak at about 200 degree Celsius with two small peaks at about 275 and 330 degree Celsius, respectively. OSL experiments showed that blue light (470 nm) is six times more efficient than green light (532 nm) to stimulate the OSL emission. The aim of this study was to determine the TL and OSL fading properties of Mg 2 SiO 4 : Tb using OSL and TL methods. In addition, PTTL properties of the Mg 2 SiO 4 : Tb was investigated by using blue LEDs, UV lamp and blue laser. Investigations on the fading properties also showed that the TL signal fades % 10 in a period of 1 month and OSL signal fades % 10 in a period of 3 month, which then the signal remains relatively stable for longer periods.

  15. Nano-Ticl 4 .SiO 2 : a Versatile and Efficient Catalyst for Synthesis of ...

    African Journals Online (AJOL)

    Nano-TiCl4.SiO2 has been found to be an extremely efficient catalyst for the preparation of 3,4-dihydropyrimidinones/thiones via three-component reactions of an aldehyde, β-ketoester or β-diketone and urea or thiourea under mild conditions. Nano-TiCl4.SiO2 as a solid Lewis acid has been synthesized by reaction of ...

  16. Photoluminescence properties of X5SiO4Cl6:Tb (X = Sr, Ba) green ...

    Indian Academy of Sciences (India)

    attracted more attention due to their potential applications ... materials were thoroughly mixed and ground in an agate mortar. ... Figure 2. Excitation spectra of Ba5SiO4Cl6:Tb3+ phosphor. spectrum of Tb3+ singly doped phosphor Ba5SiO4Cl6,.

  17. PENGUJIAN AKTIVITAS KOMPOSIT Fe2O3-SiO2 SEBAGAI FOTOKATALIS PADA FOTODEGRADASI 4-KLOROFENOL (The Activity Test of Fe2O3-SiO2 Composite As Photocatalyst on 4-Chlorophenol Photodegradation

    Directory of Open Access Journals (Sweden)

    Eko Sri Kunarti

    2009-03-01

    Full Text Available ABSTRAK  Pada penelitian ini telah dilakukan pengujian aktivitas komposit Fe2O3-SiO2 sebagai fotokatalis pada fotodegradasi 4-klorofenol. Penelitian diawali dengan preparasi dan karakterisasi fotokatalis Fe2O3-SiO2. Preparasi dilakukan dengan metode sol-gel pada temperatur kamar menggunakan tetraetil ortosilikat (TEOS dan besi (III nitrat sebagai prekursor diikuti dengan perlakuan termal pada temperature 500 oC. Karakterisasi dilakukan dengan metode spektrometri inframerah, difraksi sinar-X dan spektrometri fluoresensi sinar-X. Uji aktivitas komposit untuk fotodegradasi 4-klorofenol dilakukan dalam reaktor tertutup yang dilengkapi dengan lampu UV. Pada uji ini telah dipelajari pengaruh waktu penyinaran dan pH larutan terhadap efektivitas fotodegradasi 4-klorofenol. Hasil penelitian menunjukkan bahwa komposit Fe2O3-SiO2 dapat dipreparasi dengan metode sol-gel pada temperatur kamar diikuti perlakuan termal. Komposit Fe2O3-SiO2 dapat meningkatkan efektivitas fotodegradasi 4-klorofenol dari 11,86 % menjadi 55,38 %. Efektivitas fotodegradasi 4- klorofenol dipengaruhi waktu penyinaran dan pH larutan yang semakin lama waktu penyinaran efektifitas fotodegradasi semakin tinggi, namun waktu penyinaran yang lebih lama dari 4 jam dapat menurunkan efektivitasnya. pH larutan memberikan pengaruh yang berbeda-beda pada efektivitas fotodegradasi 4-klorofenol.   ABSTRACT The activity test of Fe2O3-SiO2 composite as photocatalyst on 4-chlorophenol photodegradation has been studied. The research was initiated by preparation of Fe2O3-SiO2 photocatalyst and followed by characterization. The preparation was conducted by sol-gel method at room temperature using tetraethylorthosilicate (TEOS and iron (III nitrate as precursors followed by thermal treatment at a temperature of 500oC. The characterizations were performed by X-ray Diffraction (XRD, Infrared and X-ray Fluorescence Spectrophotometry. The photocatalytic activity test of composites for 4 chlorophenol

  18. Highly efficient transparent Zn2SiO4:Mn2+ phosphor film on quartz glass

    International Nuclear Information System (INIS)

    Seo, K.I.; Park, J.H.; Kim, J.S.; Kim, G.C.; Yoo, J.H.

    2009-01-01

    Highly efficient transparent Zn 2 SiO 4 :Mn 2+ film phosphors on quartz substrates were deposited by the thermal diffusion of sputtered ZnO:Mn film. They show a textured structure with some preferred orientations. Our film phosphor shows, for the best photoluminescence (PL) brightness, a green PL brightness of about 20% of a commercial Zn 2 SiO 4 :Mn 2+ powder phosphor screen. The film shows a high transmittance of more than 10% at the red-color region. The excellence in PL brightness and transmittance can be explained in terms of the textured crystal growth with a continuous gradient of Zn 2 SiO 4 : Mn 2+ crystals.

  19. A new high-pressure phase of Fe2SiO4 and the relationship between spin and structural transitions

    Science.gov (United States)

    Yamanaka, T.; Kyono, A.; Nakamoto, Y.; Kharlamova, S. A.; Struzhkin, V. V.; Gramsch, S.; Mao, H.; Hemley, R. J.

    2013-12-01

    Structure transformation of Fe2SiO4 Angle-dispersive powder x-ray diffraction was carried out at beam line 16-BMD APS. Structure of a new high-pressure phase of I-Fe2SiO4 spinel was determined by Rietveld profile fitting of x-ray diffraction data up to 64GPa at ambient temperature. A structural transition from the cubic spinel to the new structure was observed at 34GPa. Diffraction patterns taken at 44.6GPa and 54.6GPa indicate a two-phase mixture of spinel and new high-pressure phase. Reversible transition from I-Fe2SiO4 to spinel was confirmed. Laser heating experiment at 1500K proved the decomposition of Fe2SiO4 spinel to two oxides of FeO and SiO2. Spin transition X-ray emission measurements of Fe2SiO4 were carried out up to 65GPa at ambient temperature at beam line 16-IDD APS. The spin transition exerts an influence to Fe2SiO4 spinel structure and triggers two distinct curves of the lattice constant in the spinel phase. Although the compression curve of the spinel is discontinuous at approximately 20 GPa, Fe Kβ emission measurements show that the transition from a high spin (HS) to an intermediate spin (IS) state begins at 17GPa in the spinel phase. The IS electronic state is gradually enhanced with pressure, which results in an isostructural phase transition. HS-to-LS transition of iron bearing spinels starts from 15.6GPa in Fe3O4 and 19.6GPa in Fe2TiO4. The transition is more capable due to Fe2+ in the octahedral site. The extremely shortened octahedral bonds result in a distortion of 6-fold cation site. New structure of Fe2SiO4 Monte Carlo method was applied to find candidates for the high-pressure phase using the diffraction intensities with fixed lattice constants determined by DICVOL. Rietveld profile fitting was then performed using the initial model. The new structure is a body centered orthorhombic phase (I-Fe2SiO4) with space group Imma and Z=4, with two crystallographically distinct FeO6 octahedra. Silicon exists in six-fold coordination in I-Fe2SiO

  20. Structure of (NH4)3H(SeO4)2 in high-temperature phases I and II

    International Nuclear Information System (INIS)

    Lukaszewicz, K.; Pietraszko, A.; Augustyniak, M.A.

    1993-01-01

    Triammonium hydrogenbis(tetraoxoselenate), (NH 4 ) 3 H(SeO 4 ) 2 , M r =341.04, Z=3, λ(Mo K anti α)=0.71073 A, F(000)=498. Phase I: trigonal, R anti 3m, a=6.090(1), c=22.759(5) A, V=731.0(2) A 3 , D x =2.32 g cm -3 , μ=68.7 cm -1 , T=355 K, R=0.0336 for 241 unique reflections with I>4σ(I). Phase II: trigonal, R anti 3, a=6.064(1), c=22.904(5) A, V=729.4(2) A 3 , D x =2.33 g cm -3 , μ=68.8 cm -1 , T=310 K, R=0.0374 for 397 unique reflections with I>4σ(I). In both phases, SeO 4 tetrahedra are linked by a dynamic system of symmetrically disordered hydrogen bonds in planes perpendicular to the trigonal axis. In phase II, SeO 4 tetrahedra deviate from the (210) plane owing to a small rotation of about 4 about the trigonal axis. In phase I, owing to symmetry enhancement, both orientations of SeO 4 tetrahedra are equally probable on both sides of (210), which is therefore a mirror plane. (orig.)

  1. [Effect of charge compensation on emission spectrum of Sr2SiO4 : Dy3+ phosphor].

    Science.gov (United States)

    Li, Pan-Lai; Wang, Zhi-Jun; Yang, Zhi-Ping; Guo, Qing-Lin

    2009-01-01

    The Sr2SiO4 : Dy3+ phosphor was synthesized by the high temperature solid-state reaction method in air. Dy2O3 (99.9%), SiO2 (99.9%), SrCO3 (99.9%), Li2CO3 (99.9%), Na2CO3 (99.9%) and K2CO3 (99.9%) were used as starting materials, and the Dy3+ doping concentration was 2 mol%. The emission spectrum was measured by a SPEX1404 spectrophotometer, and all the characterization of the phosphors was conducted at room temperature. The emission spectrum of Sr2 SiO4 : Dy3+ phosphor showed several bands centered at 486, 575 and 665 nm under the 365 nm excitation. The effect of Li+, Na+ and K+ on the emission spectra of Sr2SiO4 : Dy3+ phosphor was studied. The results show that the location of the emission spectrum of Sr2SiO4 : Dy3+ phosphor was not influenced by Li+, Na+ and K+. However, the emission spectrum intensity was greatly influenced by Li+, Na+ and K+, and the evolvement trend was monotone with different charge compensation, i. e. the emission spectrum intensity of Sr2SiO4 : Dy3+ phosphor firstly increased with increasing Li+ concentration, then decreased. However the charge compensation concentration corresponding to the maximum emission intensity was different with different charge compensation, and the concentration is 4, 3 and 3 mol% corresponding to Li+, Na+ and K+, respectively. And the theoretical reason for the above results was analyzed.

  2. Li4SiO4-Based Artificial Passivation Thin Film for Improving Interfacial Stability of Li Metal Anodes.

    Science.gov (United States)

    Kim, Ji Young; Kim, A-Young; Liu, Guicheng; Woo, Jae-Young; Kim, Hansung; Lee, Joong Kee

    2018-03-14

    An amorphous SiO 2 (a-SiO 2 ) thin film was developed as an artificial passivation layer to stabilize Li metal anodes during electrochemical reactions. The thin film was prepared using an electron cyclotron resonance-chemical vapor deposition apparatus. The obtained passivation layer has a hierarchical structure, which is composed of lithium silicide, lithiated silicon oxide, and a-SiO 2 . The thickness of the a-SiO 2 passivation layer could be varied by changing the processing time, whereas that of the lithium silicide and lithiated silicon oxide layers was almost constant. During cycling, the surface of the a-SiO 2 passivation layer is converted into lithium silicate (Li 4 SiO 4 ), and the portion of Li 4 SiO 4 depends on the thickness of a-SiO 2 . A minimum overpotential of 21.7 mV was observed at the Li metal electrode at a current density of 3 mA cm -2 with flat voltage profiles, when an a-SiO 2 passivation layer of 92.5 nm was used. The Li metal with this optimized thin passivation layer also showed the lowest charge-transfer resistance (3.948 Ω cm) and the highest Li ion diffusivity (7.06 × 10 -14 cm 2 s -1 ) after cycling in a Li-S battery. The existence of the Li 4 SiO 4 artificial passivation layer prevents the corrosion of Li metal by suppressing Li dendritic growth and improving the ionic conductivity, which contribute to the low charge-transfer resistance and high Li ion diffusivity of the electrode.

  3. Synthesis of Hollow Nanotubes of Zn2SiO4 or SiO2: Mechanistic Understanding and Uranium Adsorption Behavior.

    Science.gov (United States)

    Tripathi, Shalini; Bose, Roopa; Roy, Ahin; Nair, Sajitha; Ravishankar, N

    2015-12-09

    We report a facile synthesis of Zn2SiO4 nanotubes using a two-step process consisting of a wet-chemical synthesis of core-shell ZnO@SiO2 nanorods followed by thermal annealing. While annealing in air leads to the formation of hollow Zn2SiO4, annealing under reducing atmosphere leads to the formation of SiO2 nanotubes. We rationalize the formation of the silicate phase at temperatures much lower than the temperatures reported in the literature based on the porous nature of the silica shell on the ZnO nanorods. We present results from in situ transmission electron microscopy experiments to clearly show void nucleation at the interface between ZnO and the silica shell and the growth of the silicate phase by the Kirkendall effect. The porous nature of the silica shell is also responsible for the etching of the ZnO leading to the formation of silica nanotubes under reducing conditions. Both the hollow silica and silicate nanotubes exhibit good uranium sorption at different ranges of pH making them possible candidates for nuclear waste management.

  4. Batisite, Na2BaTi2(Si4O12)O2, from Inagli massif, Aldan, Russia: crystal-structure refinement and high-temperature X-ray diffraction study

    Science.gov (United States)

    Zolotarev, Andrey A.; Zhitova, Elena S.; Gabdrakhmanova, Faina A.; Krzhizhanovskaya, Maria G.; Zolotarev, Anatoly A.; Krivovichev, Sergey V.

    2017-12-01

    The crystal structure of batisite, Na2BaTi2 (Si4O12)O2, from the Inagli massif (Aldan, Yakutia, Russia) was refined to R 1 = 0.032 for 1449 unique observed reflections. The mineral is orthorhombic, Imma, a = 8.0921(5), b = 10.4751(7), c = 13.9054(9) Å, V = 1178.70(13) Å3. The mineral is based upon three-dimensional titanosilicate framework consisting of chains of corner-sharing MO6 octahedra ( M = Ti, Nb, Fe and Zr) and vierer chains of corner-sharing SiO4 tetrahedra. Both chains are parallel to the a axis and are linked by sharing peripheral O atoms. The octahedral chains display disorder of M atoms and bridging O sites related to the out-of-center distortion of octahedral geometry around Ti4+ cations. Electron microprobe analysis gives SiO2 39.46, TiO2 24.66, BaO 21.64, Na2O 7.56, K2O 4.38, Fe2O3 0.90, ZrO2 0.66, Nb2O5 0.36, (H2O)calc 0.58, sum 99.76 wt%. The seven strongest X-ray powder-diffraction lines [listed as d in Å (I) hkl] are: 8.39 (94) 011, 3.386 (56) 031, 3.191 (36) 123, 2.910 (46) 222, 2.896 (100) 024, 2.175 (45) 035, 1.673 (57) 055. The thermal behaviour of batisite in the temperature range from 25 to 950 °C was studied using high-temperature powder X-ray diffraction. The thermal expansion coefficients along the principal crystallographic axes are: α a = 14.4 × 10-6, α b = 8.7 × 10-6, α c = 8.4 × 10-6, α V = 31.5 °C-1 for the temperature range 25-500 °C and α a = 19.6 × 10-6, α b = 9.1 × 10-6, α c = 8.8 × 10-6, α V = 37.6 °C-1 for the temperature range 500-900 °C. The direction of maximal thermal expansion is parallel to the chains of both MO6 octahedra and SiO4 tetrahedra, which can be explained by the stretching of silicate chains due to the increasing thermal vibrations of the Ba2+ cations. At 1000 °C, the titanosilicate framework in batisite collapses with the formation of fresnoite, Ba2TiSi2O7O.

  5. A promising tritium breeding material: Nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles

    Science.gov (United States)

    Dang, Chen; Yang, Mao; Gong, Yichao; Feng, Lan; Wang, Hailiang; Shi, Yanli; Shi, Qiwu; Qi, Jianqi; Lu, Tiecheng

    2018-03-01

    As an advanced tritium breeder material for the fusion reactor blanket of the International Thermonuclear Experimental Reactor (ITER), Li2TiO3-Li4SiO4 biphasic ceramic has attracted widely attention due to its merits. In this paper, the uniform precursor powders were prepared by hydrothermal method, and nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles were fabricated by an indirect wet method at the first time. In addition, the composition dependence (x/y) of their microstructure characteristics and mechanical properties were investigated. The results indicated that the crush load of biphasic ceramic pebbles was better than that of single phase ceramic pebbles under identical conditions. The 2Li2TiO3-Li4SiO4 ceramic pebbles have good morphology, small grain size (90 nm), satisfactory crush load (37.8 N) and relative density (81.8 %T.D.), which could be a promising breeding material in the future fusion reactor.

  6. Mechanical Properties and Fabrication of Nanostructured Mg_2SiO_4-MgAl_2O_4 Composites by High-Frequency Induction Heated Combustion

    International Nuclear Information System (INIS)

    Shon, In-Jin; Kang, Hyun-Su; Hong, Kyung-Tae; Doh, Jung-Mann; Yoon, Jin-Kook

    2011-01-01

    Nanopowders of MgO, Al_2O_3 and SiO_2 were made by high energy ball milling. The rapid sintering of nanostructured MgAl_2O_4-Mg_2SiO_4 composites was investigated by a high-frequency induction heating sintering process. The advantage of this process is that it allows very quick densification to near theoretical density and inhibition of grain growth. Nanocrystalline materials have received much attention as advanced engineering materials with improved physical and mechanical properties. As nanomaterials possess high strength, high hardness, excellent ductility and toughness, undoubtedly, more attention has been paid for the application of nanomaterials. Highly dense nanostructured MgAl_2O_4-Mg_2SiO_4 composites were produced with simultaneous application of 80 MPa pressure and induced output current of total power capacity (15 kW) within 2 min. The sintering behavior, gain size and mechanical properties of MgAl_2O_4-Mg_2SiO_4 composites were investigated.

  7. Hydrothermal synthesis and crystal structure of the Ni2(C4H4N2)(V4O12)(H2O)2 and Ni3(C4H4N2)3(V8O23) inorganic-organic hybrid compounds. Thermal, spectroscopic and magnetic studies of the hydrated phase

    International Nuclear Information System (INIS)

    Larrea, Edurne S.; Mesa, Jose L.; Pizarro, Jose L.; Arriortua, Maria I.; Rojo, Teofilo

    2007-01-01

    Ni 2 (C 4 H 4 N 2 )(V 4 O 12 )(H 2 O) 2 , 1, and Ni 3 (C 4 H 4 N 2 ) 3 (V 8 O 23 ), 2, have been synthesized using mild hydrothermal conditions at 170 deg. C under autogenous pressure. Both phases crystallize in the P-1 triclinic space group, with the unit-cell parameters, a=7.437(7), b=7.571(3), c=7.564(4) A, α=65.64(4), β=76.09(4), γ=86.25(3) o for 1 and a=8.566(2), b=9.117(2), c=12.619(3) A, α=71.05(2), β=83.48(4), γ=61.32(3) o for 2, being Z=2 for both compounds. The crystal structure of the three-dimensional 1 is constructed from layers linked between them through the pyrazine molecules. The sheets are formed by edge-shared [Ni 2 O 6 (H 2 O) 2 N 2 ] nickel(II) dimers octahedra and rings composed by four [V 4 O 12 ] vanadium(V) tetrahedra linked through vertices. The crystal structure of 2 is formed from vertex shared [VO 4 ] tetrahedra that give rise to twelve member rings. [NiO 4 (C 4 H 4 N 2 ) 2 ] ∞ chains, resulting from [NiO 4 N 2 ] octahedra and pyrazine molecules, give rise to a 3D skeleton when connecting to [VO 4 ] tetrahedra. Diffuse reflectance measurements of 1 indicate a slightly distorted octahedral geometry with values of Dq=880, B=980 and C=2700 cm -1 . Magnetic measurements of 1, carried out in the 5.0-300 K range, indicate the existence of antiferromagnetic couplings with a Neel temperature near to 38 K. - Graphical abstract: Crystal structure of a sheet of Ni 2 (C 4 H 4 N 2 )(V 4 O 12 )(H 2 O) 2

  8. Excellent Brightness with Shortening Lifetime of Textured Zn2SiO4:Mn2+ Phosphor Films on Quartz Glass

    Science.gov (United States)

    Park, Jehong; Park, Kwangwon; Lee, Jaebum; Kim, Jongsu; Kim, Seongsin Margaret; Kung, Patrick

    2010-04-01

    Green-emissive textured Zn2SiO4:Mn2+ phosphor films were fabricated by the thermal diffusion of ZnO:Mn on quartz glass. The Zn2SiO4:Mn2+ phosphor films became textured along several hexagonal directions and their chemical composition was continuously graded at the interface. The decay time of Mn2+ was as short as 4.4 ms, and the optical transition probability of the films defined as the inverse of decay time showed a strong correlation with film texture degree as a function of annealing temperature. The brightest Zn2SiO4:Mn2+ film showed a photoluminescent brightness as high as 65% compared with a commercial Zn2SiO4:Mn2+ phosphor powder screen and a maximum absolute transparency of 70%. These excellent optical properties are explained by the combination of the unique textured structure and continuous grading of the Zn2SiO4:Mn2+ chemical composition at the interface.

  9. Fluorocarbon based atomic layer etching of Si_3N_4 and etching selectivity of SiO_2 over Si_3N_4

    International Nuclear Information System (INIS)

    Li, Chen; Metzler, Dominik; Oehrlein, Gottlieb S.; Lai, Chiukin Steven; Hudson, Eric A.

    2016-01-01

    Angstrom-level plasma etching precision is required for semiconductor manufacturing of sub-10 nm critical dimension features. Atomic layer etching (ALE), achieved by a series of self-limited cycles, can precisely control etching depths by limiting the amount of chemical reactant available at the surface. Recently, SiO_2 ALE has been achieved by deposition of a thin (several Angstroms) reactive fluorocarbon (FC) layer on the material surface using controlled FC precursor flow and subsequent low energy Ar"+ ion bombardment in a cyclic fashion. Low energy ion bombardment is used to remove the FC layer along with a limited amount of SiO_2 from the surface. In the present article, the authors describe controlled etching of Si_3N_4 and SiO_2 layers of one to several Angstroms using this cyclic ALE approach. Si_3N_4 etching and etching selectivity of SiO_2 over Si_3N_4 were studied and evaluated with regard to the dependence on maximum ion energy, etching step length (ESL), FC surface coverage, and precursor selection. Surface chemistries of Si_3N_4 were investigated by x-ray photoelectron spectroscopy (XPS) after vacuum transfer at each stage of the ALE process. Since Si_3N_4 has a lower physical sputtering energy threshold than SiO_2, Si_3N_4 physical sputtering can take place after removal of chemical etchant at the end of each cycle for relatively high ion energies. Si_3N_4 to SiO_2 ALE etching selectivity was observed for these FC depleted conditions. By optimization of the ALE process parameters, e.g., low ion energies, short ESLs, and/or high FC film deposition per cycle, highly selective SiO_2 to Si_3N_4 etching can be achieved for FC accumulation conditions, where FC can be selectively accumulated on Si_3N_4 surfaces. This highly selective etching is explained by a lower carbon consumption of Si_3N_4 as compared to SiO_2. The comparison of C_4F_8 and CHF_3 only showed a difference in etching selectivity for FC depleted conditions. For FC accumulation conditions

  10. Excimer laser crystallization of InGaZnO4 on SiO2 substrate

    NARCIS (Netherlands)

    Chen, T.; Wu, M.Y.; Ishihara, R.; Nomura, K.; Kamiya, T.; Hosono, H.; Beenakker, C.I.M.

    2011-01-01

    In this paper, we were able to crystallize InGaZnO4 (IGZO) by excimer laser on SiO2 substrate. It was observed that uniform [0001] textured polycrystalline IGZO film has been obtained without any grain boundaries and oxygen vacancies on SiO2 substrate. This process is very promising in fabricating

  11. Improving thermal insulation of TC4 using YSZ-based coating and SiO2 aerogel

    Directory of Open Access Journals (Sweden)

    Lei Jin

    2015-04-01

    Full Text Available In this paper, air plasmas spray (APS was used to prepare YSZ and Sc2O3–YSZ (ScYSZ coating in order to improve the thermal insulation ability of TC4 alloy. SiO2 aerogel was also synthesized and affixed on TC4 titanium alloy to inhabit thermal flow. The microstructures, phase compositions and thermal insulation performance of three coatings were analyzed in detail. The results of thermal diffusivity test by a laser flash method showed that the thermal diffusivities of YSZ, Sc2O3–YSZ and SiO2 aerogel are 0.553, 0.539 and 0.2097×10−6 m2/s, respectively. Then, the thermal insulation performances of three kinds of coating were investigated from 20 °C to 400 °C using high infrared radiation heat flux technology. The experimental results indicated that the corresponding temperature difference between the top TC4 alloy (400 °C and the bottom surface of YSZ is 41.5 °C for 0.6 mm thickness coating. For 1 mm thickness coating, the corresponding temperature difference between the top TC4 alloys (400 °C and the bottom surface of YSZ, ScYSZ, SiO2 aerogel three specimens is 54, 54.6 and 208 °C, respectively. The coating thickness and species were found to influence the heat insulation ability. In these materials, YSZ and ScYSZ exhibited a little difference for heat insulation behavior. However, SiO2 aerogel was the best one among them and it can be taken as protection material on TC4 alloys. In outer space, SiO2 aerogel can meet the need of thermal insulation of TC4 of high-speed aircraft.

  12. Enhancement of photoluminescence properties and modification of crystal structures of Si3N4 doping Li2Sr0.995SiO4:0.005Eu2+ phosphors

    International Nuclear Information System (INIS)

    Song, Kaixin; Zhang, Fangfang; Chen, Daqin; Wu, Song; Zheng, Peng; Huang, Qingming; Jiang, Jun; Xu, Junming; Qin, Huibin

    2015-01-01

    Highlights: • Si 3 N 4 modified Li 2 Sr 0.995 SiO 4 :0.005Eu 2+ phosphors were prepared. • The luminescence intensity of Li 2 Sr 0.995 SiO 4 :Eu 2+ was enhanced by doping Si 3 N 4 . • The fluorescence decay times and thermal stability were enhanced by doping Si 3 N 4 . - Abstract: Si 3 N 4 modified Li 2 Sr 0.995 SiO 4 :0.005Eu 2+ (Li 2 Sr 0.995 SiO 4−3x/2 N x :0.005Eu 2+ ) phosphors were synthesized with the conventional solid-state reaction in the reduced atmosphere. The crystal structure and vibrational modes were analyzed by X-ray diffraction, Raman scattering spectroscopy and Rietveld crystal structure refinement. Photoluminescence (PL) and photoluminescence excitation (PLE) spectra showed that Li 2 Sr 0.995 SiO 4−3x/2 N x :0.005Eu 2+ powder exhibited a broad yellow emission band centered at 560 nm under the excitation of 460 nm visible light, due to the 4f 6 5d 1 → 4f 7 transition of Eu 2+ . The partial nitridation of Li 2 Sr 0.995 SiO 4−3x/2 N x :0.005Eu 2+ (x = 0.01) phosphors led to a large enhancement in the luminescence intensity, as much as 190%. At the same time, the fluorescence decay behavior curves further showed that the photoluminescence efficiencies of Li 2 Sr 0.995 SiO 4−3x/2 N x :0.005Eu 2+ phosphors were enhanced by addition of Si 3 N 4 . The temperature quenching characteristics confirmed that the oxynitride based Li 2 Sr 0.995 SiO 4−3x/2 N x :0.005Eu 2+ showed slightly higher stability. It is implied that Li 2 Sr 0.995 SiO 4−3x/2 N x :0.005Eu 2+ phosphors had a possible potential application on white LEDs to match blue light chips

  13. Functionalization of Fe3O4/SiO2 with N-(2-Aminoethyl-3-aminopropyl for Sorption of [AuCl4]-

    Directory of Open Access Journals (Sweden)

    Nuryono Nuryono

    2016-08-01

    Full Text Available Synthesis of Fe3O4/SiO2 modified with N-(2-aminoethyl-3-aminopropyl group (Fe3O4/SiO2/ED via coating method and its application for adsorption-desorption of anionic gold in aqueous solution have been conducted. The synthesized product was characterized with an X-ray diffractometer (XRD, a Fourier transform infrared (FT-IR spectrophotometer and a transmission electron microscopy (TEM. Adsorption of Au(III was conducted in a batch system and the variables included pH, contact time, and initial concentration were investigated. Results showed that magnetite/silica has been successfully functionalized with N-(2-aminoethyl-3-aminopropyl in a homogeneous system. Kinetics study showed that adsorption of Au(III followed the pseudo-second order model with rate constant of 0.710 g mmol L-1min-1. Furthermore, the experimental data fitted well with the Langmuir isotherm model with the maximum adsorption capacity for Au(III of 142.9 mg g-1 and the energy of 25.0 kJ mol-1. Gold loaded on the Fe3O4/SiO2/ED could be easily desorbed with 0.2 mol L-1 HCl containing 2 wt.% of thiourea with recovery of 99.8%. Fe3O4/SiO2/ED was reusable and stable in 5 cycles of adsorption-desorption with recovery more than 90%. Fe3O4/SiO2/ED showed high selectivity towards Au(III in the multimetal system Au(III/Cu(II/Cr(VI with the coefficient selectivity for αAu-Cu of 227.5and for αAu-Cr of 12.3.

  14. Super-bright and short-lived photoluminescence of textured Zn2SiO4:Mn2+ phosphor film on quartz glass

    Science.gov (United States)

    Park, Jehong; Park, Kwangwon; Lee, Jaebum; Kim, Jongsu; Seo, Kwangil; Kwon, Kevin; Kung, Patrick; Kim, Seongsin M.

    2010-02-01

    Green-emissive textured Zn2SiO4:Mn2+ phosphor film was fabricated by a thermal diffusion of ZnO:Mn on quartz glass. The characterization has been performed in terms of Mn2+ ions concentration (Mn/Zn=1~9 mol %). As an increase of Mn2+ ions concentration in the Zn2SiO4:Mn2+ phosphor film, the emission peak was red shifted from 519 nm to 526 nm, and the decay time to 10% of the maximum intensity was shorter from 20 ms to 0.5 ms. All annealed Zn2SiO4:Mn2+ phosphor films became textured along some hexagonal directions on the amorphous quartz glass. The brightest Zn2SiO4:Mn2+ film at optimal Mn2+ concentration of 5 % showed the photoluminescence brightness of 65 % and the shortened decay time of 4.4 ms in comparison with a commercially Zn2SiO4: Mn2+ powder phosphor screen. The excellencies can be attributed to a unique textured structure.

  15. Conductivity And Thermal Stability of Solid Acid Composites CsH2PO4 /NaH2PO4/ SiO2

    International Nuclear Information System (INIS)

    Norsyahida Mohammad; Abu Bakar Mohamad; Abu Bakar Mohamad; Abdul Amir Hassan Kadhum

    2016-01-01

    Solid acid composites CsH 2 PO 4 / NaH 2 PO 4 / SiO 2 with different mole ratios of CsH 2 PO 4 and NaH 2 PO 4 to SiO 2 were synthesized and characterized. Preliminary infrared measurements of CsH 2 PO 4 and its composites indicated that hydrogen bonds breaking and formation were detected between 1710 to 2710 cm -1 , while the rotation of phosphate tetrahedral anions occurred between 900 and 1200 cm -1 . The superprotonic transition of CsH 2 PO 4 / NaH 2 PO 4 / SiO 2 composite was identified at superprotonic temperatures between 230 and 260 degree Celcius, under atmospheric pressure. This study reveals higher conductivity values for composites with higher CsH 2 PO 4 (CDP) content. Solid acid composite CDP 613 appeared as the composite with the highest conductivity that is 7.2x10 -3 S cm -1 at 230 degree Celcius. Thermal stability of the solid acid composites such as temperature of dehydration, melting and decomposition were investigated. The addition of NaH 2 PO 4 lowers the dehydration temperature of the solid acid composites. (author)

  16. Stacking fault tetrahedra formation in the neighbourhood of grain boundaries

    CERN Document Server

    Samaras, M; Van Swygenhoven, H; Victoria, M

    2003-01-01

    Large scale molecular dynamics computer simulations are performed to study the role of the grain boundary (GB) during the cascade evolution in irradiated nanocrystalline Ni. At all primary knock-on atom (PKA) energies in cascades near GBs, the damage produced after cooling down is vacancy dominated. Truncated stacking fault tetrahedra (TSFTs) are easily formed at 10 keV and higher PKA energies. At the higher energies a complex partial dislocation network forms, consisting of TSFTs. The GB acts as an interstitial sink without undergoing major structural changes.

  17. The PrPS4 type structure and a filled variant: the compounds TbPS4 and LiEuPS4

    International Nuclear Information System (INIS)

    Joergens, S.; Alili, L.; Mewis, A.

    2005-01-01

    Colourless single crystals of TbPS 4 (a = 10.696(2), c = 19.053(4) Aa) were obtained by reaction of the elements (750 C; 30 h). The compound crystallizes with the PrPS 4 type structure (I4 1 /acd; Z = 16). The structure consists of isolated PS 4 tetrahedra each surrounded by four Tb 3+ cations. Both crystallographically different Tb 3+ cations are coordinated by eight sulfur atoms which are part of four PS 4 tetrahedra. Orange single crystals of LiEuPS 4 (a = 11.498(2), c = 19.882(4) Aa) were prepared by reaction of Eu and P with Li 2 S 4 (700 C; 20 h). The crystal structure corresponds to the PrPS 4 type, in which tubes running along [001] are occupied by Li atoms, which are surrounded by four S atoms in strongly distorted tetrahedra. LiS 4 and PS 4 tetrahedra are connected via common edges into alternating chains. (orig.)

  18. Ag-Decorated Fe3O4@SiO2 Nanorods: Synthesis, Characterization, and Applications in Degradation of Organic Dyes

    Directory of Open Access Journals (Sweden)

    Chao Li

    2016-01-01

    Full Text Available Well-dispersed Ag nanoparticles (NPs are successfully decorated on Fe3O4@SiO2 nanorods (NRs via a facile step-by-step strategy. This method involves coating α-Fe2O3 NRs with uniform silica layer, reduction in 10% H2/Ar atmosphere at 450°C to obtain Fe3O4@SiO2 NRs, and then depositing Ag NPs on the surface of Fe3O4@SiO2 NRs through a sonochemical step. It was found that the as-prepared Ag-decorated magnetic Fe3O4@SiO2 NRs (Ag-MNRs exhibited a higher catalytic efficiency than bare Ag NPs in the degradation of organic dye and could be easily recovered by convenient magnetic separation, which show great application potential for environmental protection applications.

  19. UV Light-Driven Photodegradation of Methylene Blue by Using Mn0.5Zn0.5Fe2O4/SiO2 Nanocomposites

    Science.gov (United States)

    Indrayana, I. P. T.; Julian, T.; Suharyadi, E.

    2018-04-01

    The photodegradation activity of nanocomposites for 20 ppm methylene blue solution has been investigated in this work. Nanocomposites Mn0.5Zn0.5Fe2O4/SiO2 have been synthesized using coprecipitation method. The X-ray diffraction (XRD) pattern confirmed the formation of three phases in sample Mn0.5Zn0.5Fe2O4/SiO2 i.e., Mn0.5Zn0.5Fe2O4, Zn(OH)2, and SiO2. The appearance of SiO2 phase showed that the encapsulation process has been carried out. The calculated particles size of Mn0.5Zn0.5Fe2O4/SiO2 is greater than Mn0.5Zn0.5Fe2O4. Bonding analysis via vibrational spectra for Mn0.5Zn0.5Fe2O4/SiO2 confirmed the formation of bonds Me-O-Si stretching (2854.65 cm-1) and Si-O-Si asymmetric stretching (1026.13 cm-1). The optical gap energy of Mn0.5Zn0.5Fe2O4/SiO2 was smaller (2.70 eV) than Mn0.5Zn0.5Fe2O4 (3.04 eV) due to smaller lattice dislocation and microstrain that affect their electronic structure. The Mn0.5Zn0.5Fe2O4/SiO2 showed high photodegradation ability due to smaller optical gap energy and the appearance of SiO2 ligand that can easily attract dye molecules. The Mn0.5Zn0.5Fe2O4/SiO2 also showed high degradation activity even without UV light radiation. The result showed that photodegradation reaction doesn’t follow pseudo-first order kinetics.

  20. A facile approach to fabricate Au nanoparticles loaded SiO2 microspheres for catalytic reduction of 4-nitrophenol

    International Nuclear Information System (INIS)

    Tang, Mingyi; Huang, Guanbo; Li, Xianxian; Pang, Xiaobo; Qiu, Haixia

    2015-01-01

    Hydrophilic and biocompatible macromolecules were used to improve and simplify the process for the fabrication of core/shell SiO 2 @Au composite particles. The influence of polymers on the morphology of SiO 2 @Au particles with different size of SiO 2 cores was analyzed by transmission electron microscopy and scanning electron microscopy. The optical property of the SiO 2 @Au particles was studied with UV–Vis spectroscopy. The results indicate that the structure and composition of macromolecules affect the morphology of Au layers on SiO 2 microspheres. The SiO 2 @Au particles prepared in the presence of polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) have thin and complete Au nanoshells owing to their inducing act in preferential growth of Au nanoparticles along the surface of SiO 2 microspheres. SiO 2 @Au particles can be also prepared from SiO 2 microspheres modified with 3-aminopropyltrimethoxysilane in the presence of PVA or PVP. This offers a simple way to fabricate a Au layer on SiO 2 or other microspheres. The SiO 2 @Au particles demonstrated high catalytic activity in the reduction of 4-nitrophenol. - Highlights: • Facile direct deposition method for Au nanoparticles on silica microspheres. • Influence of different types of macromolecule on the formation of Au shell. • High catalytic performance of Au nanoparticles on silica microspheres

  1. Hydrated aluminophosphate (AlPO/sub 4/. 1. 5H/sub 2/O) with PO/sub 4/, AlO/sub 4/ and AlO/sub 4/(H/sub 2/O)/sub 2/ groups and encapsulated water

    Energy Technology Data Exchange (ETDEWEB)

    Pluth, J.J.; Smith, J.V.

    1986-09-15

    Aluminium phosphate hydrate, AlPO/sub 4/ /sub ./ 1.5H/sub 2/O, M/sub r/=148.98, orthorhombic, Pbca, a=19.3525(13), b=9.7272(7), c=9.7621(8) A, V=1837.7(1) A/sup 3/, Z=16, D/sub x/=2.15 g cm/sup -3/, lambda(CuK..cap alpha..)=1.5418 A, ..mu..=68.2 cm/sup -1/, F(000)=1200, Tproportional to 295 K, R=0.033 for 1530 diffractions. A 4-connected framework contains PO/sub 4/ tetrahedra interposed between AlO/sub 4/ tetrahedra and AlO/sub 4/(H/sub 2/O)/sub 2/ octahedra at the nodes of cross-linked alternate 6/sup 3/ and 4.8/sup 2/ nets. A two-dimensional channel system, limited by 8-rings, lies between adjacent 6/sup 3/ nets. One H/sub 2/O of each octahedron lies in a 6-ring, and the other forms a continuous chain with a third H/sub 2/O which is held in place only by hydrogen bonds.

  2. Improving thermal insulation of TC4 using YSZ-based coating and SiO2 aerogel

    OpenAIRE

    Jin, Lei; Li, Peizhong; Zhou, Haibin; Zhang, Wei; Zhou, Guodong; Wang, Chun

    2015-01-01

    In this paper, air plasmas spray (APS) was used to prepare YSZ and Sc2O3–YSZ (ScYSZ) coating in order to improve the thermal insulation ability of TC4 alloy. SiO2 aerogel was also synthesized and affixed on TC4 titanium alloy to inhabit thermal flow. The microstructures, phase compositions and thermal insulation performance of three coatings were analyzed in detail. The results of thermal diffusivity test by a laser flash method showed that the thermal diffusivities of YSZ, Sc2O3–YSZ and SiO2...

  3. Effect of sweep gas chemistry on vaporization of Li4SiO4

    International Nuclear Information System (INIS)

    Yamawaki, M.; Yamaguchi, K.

    1995-01-01

    Gas/solid equilibria in the system Li 4 SiO 4 -D 2 -D 2 O were studied by means of Knudsen effusion mass spectrometry. A Knudsen effusion mass spectrometer was modified to enable studies of reactions of hydrogen and/or water vapor with ceramic breeder materials. A gas inlet system was constructed to allow the introduction of gases into a platinum Knudsen cell, from which the equilibrated gaseous reaction products effuse. From the experimental results, it has been deduced that the equilibrium constants of vaporization reactions differ correspondingly to the nonstoichiometry of lithium orthosilicate. ((orig.))

  4. Synthesis of LiFePO4/Li2SiO3/reduced Graphene Oxide (rGO) Composite via Hydrothermal Method

    Science.gov (United States)

    Arifin, M.; Iskandar, F.; Aimon, A. H.; Munir, M. M.; Nuryadin, B. W.

    2016-08-01

    LiFePO4 is a type of cathode active material used for lithium ion batteries. It has a high electrochemical performance. However, it suffers from certain disadvantages such as a very low intrinsic electronic conductivity and low ionic diffusion. This study was conducted to increase the conductivity of LiFePO4. We have investigated the addition of Li2SiO3 and reduced graphene oxide (rGO) to LiFePO4. The objective of this research was to synthesize LiFePO4/Li2SiO3/rGO via hydrothermal method. Fourier transform infrared spectroscopy (FTIR) measurement showed that the peaks corresponded to the vibration of LiFePO4/Li2SiO3. Further, X-ray diffraction (XRD) measurement confirmed a single phase of LiFePO4. Finally, scanning electron microscopy (SEM) images showed that rGO was distributed on the LiFePO4/Li2SiO3 structure.

  5. Synthesis of LiFePO4/Li2SiO3/reduced Graphene Oxide (rGO) Composite via Hydrothermal Method

    International Nuclear Information System (INIS)

    Arifin, M; Iskandar, F; Aimon, A H; Munir, M M; Nuryadin, B W

    2016-01-01

    LiFePO 4 is a type of cathode active material used for lithium ion batteries. It has a high electrochemical performance. However, it suffers from certain disadvantages such as a very low intrinsic electronic conductivity and low ionic diffusion. This study was conducted to increase the conductivity of LiFePO4. We have investigated the addition of Li2SiO3 and reduced graphene oxide (rGO) to LiFePO4. The objective of this research was to synthesize LiFePO 4 /Li 2 SiO 3 /rGO via hydrothermal method. Fourier transform infrared spectroscopy (FTIR) measurement showed that the peaks corresponded to the vibration of LiFePO 4 /Li 2 SiO 3 . Further, X-ray diffraction (XRD) measurement confirmed a single phase of LiFePO4. Finally, scanning electron microscopy (SEM) images showed that rGO was distributed on the LiFePO 4 /Li 2 SiO 3 structure. (paper)

  6. Study on Formation Mechanism of Fayalite (Fe2SiO4) by Solid State Reaction in Sintering Process

    Science.gov (United States)

    Wang, Zhongbing; Peng, Bing; Zhang, Lifeng; Zhao, Zongwen; Liu, Degang; Peng, Ning; Wang, Dawei; He, Yinghe; Liang, Yanjie; Liu, Hui

    2018-04-01

    The sintering behaviors among SiO2, FeS and Fe3O4 were detected to reveal the formation mechanism of Fe2SiO4. The results indicated that the formation mechanism is divided into five steps: (1) migration of O2- induced by S2- under a reducing atmosphere; (2) formation of Fe3O4- β ; (3) migration of Fe(II) into a ferrite cluster structure to gain oxygen and form Fe3- x O4; (4) Fe(II) invaded the silicon atomic position and released Si(IV); and (5) formation of the stable structure of Fe2SiO4 through chemical diffusion between cations of Fe(II) and Si(IV). These findings can provide theoretical support for controlling the process of the recovery of valuable metals in copper slag through the combined roasting modification-magnetic separation process.

  7. Shock and Release Data on Forsterite (Mg2SiO4) Single Crystals

    Science.gov (United States)

    Root, S.; Townsend, J. P.; Shulenburger, L.; Davies, E.; Kraus, R. G.; Spaulding, D.; Stewart, S. T.; Jacobsen, S. B.; Mattsson, T. R.

    2016-12-01

    The Kepler mission has discovered numerous extra-solar rocky planets with sizes ranging from Earth-size to the super-Earths with masses 40 times larger than Earth. The solid solution series of (Mg, Fe)2SiO4 (olivine) is a major component in the mantle of Earth and likely these extra-solar rocky planets. However, understanding how the (Mg, Fe)2SiO4 system behaves at Earth like and super-Earth like pressures is still unknown. Using Sandia's Z machine facility, we shock compress single crystal forsterite, the Mg end-member of the olivine series. Solid aluminum flyers are accelerated up to 28 km/s to generate steady shock states up to 950 GPa. Release states from the Hugoniot are determined as well. In addition to experiments, we perform density functional theory (DFT) calculations to examine the potential phases along the Mg2SiO4 Hugoniot. We compare our results to other recent shock experiments on forsterite. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  8. Ti-catalyzed HfSiO4 formation in HfTiO4 films on SiO2 studied by Z-contrast scanning electron microscopy

    Directory of Open Access Journals (Sweden)

    Elizabeth Ellen Hoppe

    2013-08-01

    Full Text Available Hafnon (HfSiO4 as it is initially formed in a partially demixed film of hafnium titanate (HfTiO4 on fused SiO2 is studied by atomic number (Z contrast high resolution scanning electron microscopy, x-ray diffraction, and Raman spectroscopy and microscopy. The results show exsoluted Ti is the catalyst for hafnon formation by a two-step reaction. Ti first reacts with SiO2 to produce a glassy Ti-silicate. Ti is then replaced by Hf in the silicate to produce HfSiO4. The results suggest this behavior is prototypical of other Ti-bearing ternary or higher order oxide films on SiO2 when film thermal instability involves Ti exsolution.

  9. Failure initiation and propagation of Li4SiO4 pebbles in fusion blankets

    International Nuclear Information System (INIS)

    Zhao Shuo; Gan Yixiang; Kamlah, Marc

    2013-01-01

    Lithium orthosilicate (Li 4 SiO 4 ) pebbles are considered to be a candidate as solid tritium breeder in the helium cooled pebble bed (HCPB) blanket. These ceramic pebbles might be crushed during thermomechanical loading in the blanket. In this work, the failure initiation and propagation of pebbles in pebble beds is investigated using the discrete element method (DEM). Pebbles are simplified as mono-sized elastic spheres. Every pebble has a contact strength in terms of critical strain energy, which is derived from a validated strength model and crush test data for pebbles from a specific batch of Li 4 SiO 4 pebbles. Pebble beds are compressed uniaxially and triaxially in DEM simulations. When the strain energy absorbed by a pebble exceeds its critical energy it fails. The failure initiation is defined as a given small fraction of pebbles crushed. It is found that the load level for failure initiation can be very low. For example, if failure initiation is defined as soon as 0.02% of the pebbles have been crushed, the pressure required for uniaxial loading is about 2.5 MPa. Therefore, it is essential to study the influence of failure propagation on the macroscopic response of pebble beds. Thus a reduction ratio defined as the size ratio of a pebble before and after its failure is introduced. The macroscopic stress–strain relation is investigated with different reduction ratios. A typical stress plateau is found for a small reduction ratio.

  10. Atomic-scale details of dislocation-stacking fault tetrahedra interaction

    International Nuclear Information System (INIS)

    Osetsky, Yu. N.; Stoller, R.E.; Rodney, D.; Bacon, D.J.

    2005-01-01

    Stacking fault tetrahedra (SFTs) are formed during irradiation of f.c.c. metals and alloys with low stacking fault energy. The high number density of SFTs observed suggests that they should contribute to radiation-induced hardening and, therefore, be taken into account when estimating mechanical property changes of irradiated materials. Key issue is to describe the interaction between a moving dislocation and an individual SFT, which is characterized by a small physical scale of about 100 nm. In this paper we present results of an atomistic simulation of edge and screw dislocations interacting with small SFTs at different temperatures and strain rates and present mechanisms which can explain the formation of defect-free channels observed experimentally

  11. The principal Hugoniot of Mg2SiO4 to 950 GPa

    Science.gov (United States)

    Townsend, J. P.; Root, S.; Shulenburger, L.; Lemke, R. W.; Kraus, R. G.; Jacobsen, S. B.; Spaulding, D.; Davies, E.; Stewart, S. T.

    2017-12-01

    We present new measurements and ab-initio calculations of the principal Hugoniot states of forsterite Mg2SiO4 in the liquid regime between 200-950 GPa.Forsterite samples were shock compressed along the principal Hugoniot using plate-impact shock compression experiments on the Sandia National Laboratories Z machine facility.In order to gain insight into the physical state of the liquid, we performed quantum molecular dynamics calculations of the Hugoniot and compare the results to experiment.We show that the principal Hugoniot is consistent with that of a single molecular fluid phase of Mg2SiO4, and compare our results to previous dynamic compression experiments and QMD calculations.Finally, we discuss how the results inform planetary accretion and impact models.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

  12. Osteoblast interaction with laser cladded HA and SiO2-HA coatings on Ti-6Al-4V

    International Nuclear Information System (INIS)

    Yang Yuling; Serpersu, Kaan; He Wei; Paital, Sameer R.; Dahotre, Narendra B.

    2011-01-01

    In order to improve the bioactivity and biocompatibility of titanium endosseous implants, the morphology and composition of the surfaces were modified. Polished Ti-6Al-4V substrates were coated by a laser cladding process with different precursors: 100 wt.% HA and 25 wt.% SiO 2 -HA. X-ray diffraction of the laser processed samples showed the presence of CaTiO 3 , Ca 3 (PO 4 ) 2 , and Ca 2 SiO 4 phases within the coatings. From in vitro studies, it was observed that compared to the unmodified substrate all laser cladded samples presented improved cellular interactions and bioactivity. The samples processed with 25 wt.% SiO 2 -HA precursor showed a significantly higher HA precipitation after immersion in simulated body fluid than 100 wt.% HA precursor and titanium substrates. The in vitro biocompatibility of the laser cladded coatings and titanium substrate was investigated by culturing of mouse MC3T3-E1 pre-osteoblast cell line and analyzing the cell viability, cell proliferation, and cell morphology. A significantly higher cell attachment and proliferation rate were observed for both laser cladded 100 wt.% HA and 25 wt.% SiO 2 -HA samples. Compared to 100 wt.% HA sample, 25 wt.% SiO 2 -HA samples presented a slightly improved cellular interaction due to the addition of SiO 2 . The staining of the actin filaments showed that the laser cladded samples induced a normal cytoskeleton and well-developed focal adhesion contacts. Scanning electron microscopic image of the cell cultured samples revealed better cell attachment and spreading for 25 wt.% SiO 2 -HA and 100 wt.% HA coatings than titanium substrate. These results suggest that the laser cladding process improves the bioactivity and biocompatibility of titanium. The observed biological improvements are mainly due to the coating induced changes in surface chemistry and surface morphology. Highlights: → Laser cladding of Ti alloys with bioceramics creates new phases. → Laser cladded samples with SiO 2 -doped

  13. Composited reduced graphene oxide into LiFePO4/Li2SiO3 and its electrochemical impedance spectroscopy properties

    Science.gov (United States)

    Arifin, M.; Rus, Y. B.; Aimon, A. H.; Iskandar, F.; Winata, T.; Abdullah, M.; Khairurrijal, K.

    2017-03-01

    LiFePO4 is commonly used as cathode material for Li-ion batteries due to its stable operational voltage and high specific capacity. However, it suffers from certain disadvantages such as low intrinsic electronic conductivity and low ionic diffusion. This study was conducted to analyse the effect of reduced graphene oxide (rGO) on the electrochemical properties of LiFePO4/Li2SiO3 composite. This composite was synthesized by a hydrothermal method. Fourier transform infrared spectroscopy measurement identified the O-P-O, Fe-O, P-O, and O-Si-O- bands in the LiFePO4/Li2SiO3 composite. X-ray diffraction measurement confirmed the formation of LiFePO4. Meanwhile, Raman spectroscopy confirmed the number of rGO layers. Further, scanning electron microscopy images showed that rGO was distributed around the LiFePO4/Li2SiO3 particles. Finally, the electrochemical impedance spectroscopy results showed that the addition of 1 wt% of rGO to the LiFePO4/Li2SiO3 composite reduced charge transfer resistance. It may be concluded that the addition of 1 wt% rGO to LiFePO4/Li2SiO3 composite can enhance its electrochemical performance as a cathode material.

  14. XAFS study on silica glasses irradiated in a nuclear reactor

    International Nuclear Information System (INIS)

    Yoshida, Tomoko; Yoshida, Hisao; Hara, Takanobu; Ii, Tatsuya; Okada, Tomohisa; Tanabe, Tetsuo

    2000-01-01

    X-ray absorption technique (XANES and EXAFS) was applied to study the local structures of silica glasses before and after the irradiation in a nuclear reactor. Although our separate photoluminescence (PL) measurements clearly showed the different aspects about oxygen vacancies in these samples, i.e., at least the B 2β type oxygen-deficient center exists as an intrinsic defect in the fused silica glass while another type B 2α center is formed in the synthesized silica glass, such differences did not directly reflect on the X-ray absorption spectra (XANES and EXAFS). However, the curve-fitting analysis of EXAFS showed that the number of oxygen atoms coordinated to Si relatively increased after the irradiation. This result may indicate the occurrence of the structural relaxation in the irradiated samples, that is, a slightly distorted SiO 4 tetrahedra in silica glasses relaxed to the regular SiO 4 tetrahedra due to the break of some connections between SiO 4 units in the silica glasses. Thus, the X-ray absorption technique gave the important information of the in-reactor irradiated silica glasses which complements the results obtained from PL measurements

  15. Syntheses and crystal structures of two novel alkaline uranyl chromates A2(UO2)(CrO4)2 (A=Rb, Cs) with bidentate coordination mode of uranyl ions by chromate anions

    International Nuclear Information System (INIS)

    Siidra, Oleg I.; Nazarchuk, Evgeny V.; Krivovichev, Sergey V.

    2012-01-01

    Single crystals of Cs 2 (UO 2 )(CrO 4 ) 2 and Rb 2 (UO 2 )(CrO 4 ) 2 were prepared by solid state reactions. The structures are based upon the [(UO 2 )(CrO 4 ) 2 ] 2− chains. Within the chains, UrO 5 pentagonal bipyramids (Ur=uranyl) form Ur 2 O 8 dimers, which are linked via CrO 4 tetrahedra into one-dimensional chains. The CrO 4 tetrahedra coordinate uranyl ions in both mono- and bidentate fashion, which is unusual for uranyl chromates. The bidentate coordination has a strong influence upon geometrical parameters of both U and Cr coordination polyhedra. The conformation of the chains in 1 and 2 is different due to the different size of the Cs + and Rb + cations. - Graphical abstract: Uranyl chromate chain with monodentate and bidentate coordination mode of uranyl cations by CrO 4 tetrahedra in Cs 2 (UO 2 )(CrO 4 ) 2 . Highlights: ► Single crystals of novel uranyl chromates were prepared by solid state reactions. ► The CrO 4 tetrahedra coordinate uranyl ions in both mono- and bidentate fashion. ►The bidentate coordination has a strong influence upon geometrical parameters.

  16. Luminescence mechanisms of organic/inorganic hybrid organic light-emitting devices fabricated utilizing a Zn2SiO4:Mn color-conversion layer

    International Nuclear Information System (INIS)

    Choo, D.C.; Ahn, S.D.; Jung, H.S.; Kim, T.W.; Lee, J.Y.; Park, J.H.; Kwon, M.S.

    2010-01-01

    Zn 2 SiO 4 :Mn phosphor layers used in this study were synthesized by using the sol-gel method and printed on the glass substrates by using a vehicle solution and a heating process. Organic/inorganic hybrid organic light-emitting devices (OLEDs) utilizing a Zn 2 SiO 4 :Mn color-conversion layer were fabricated. X-ray diffraction data for the synthesized Zn 2 SiO 4 :Mn phosphor films showed that the Zn ions in the phosphor were substituted into Mn ions. The electroluminescence (EL) spectrum of the deep blue OLEDs showed that a dominant peak at 461 nm appeared. The photoluminescence spectrum for the Zn 2 SiO 4 :Mn phosphor layer by using a 470 nm excitation source showed that a dominant peak at 527 nm appeared, which originated from the 4 T 1 - 6 A 1 transitions of Mn ions. The appearance of the peak around 527 nm of the EL spectra for the OLEDs fabricated utilizing a Zn 2 SiO 4 :Mn phosphor layer demonstrated that the emitted blue color from the deep blue OLEDs was converted into a green color due to the existence of the color-conversion layer. The luminescence mechanisms of organic/inorganic hybrid OLEDs fabricated utilizing a Zn 2 SiO 4 :Mn color-conversion layer are described on the basis of the EL and PL spectra.

  17. Structure of Mg2SiO4 glass up to 140 GPa

    Science.gov (United States)

    Prescher, C.; Prakapenka, V.; Wang, Y.; Skinner, L. B.

    2014-12-01

    The physical properties of melts at temperature and pressure conditions of the Earth's mantle have a fundamental influence on the chemical and thermal evolution of the Earth. However, direct investigations of melt structures at these conditions are experimentally very difficult or even impossible with current capabilities. In order to still be able to obtain an estimate of the structural behavior of melts at high pressures and temperatures, amorphous materials have been widely used as analogue materials. In particular the investigation of sound wave velocities of amorphous SiO2 and MgSiO3 as analogues for silicate melts indicate structural changes at about ~30-40 GPa and ~130-140 GPa [1]. The transition pressures are lower for MgSiO3 than for SiO2 indicating that these transitions are affected by the degree of polymerization of the SiO2 network of the glasses. Nevertheless, these measurements only give a hint about the occurrence of structural transitions but lack information on the actual structural changes accompanied by the sound wave velocity discontinuities. The pressure of the second structural transition at ~130-140 GPa is of vital importance for geophysics. If it causes silicate melts to become denser than the surrounding solid material, it would result in negatively buoyant melts close to the core-mantle boundary, which could be a major factor affecting the chemical stratification of the Earth's mantle during an early magma ocean after the moon forming impact. In order to resolve the structural transition and estimate the effect of a different degree of polymerization further, we studied the structural behavior of Mg2SiO4 glass up to 140 GPa using X-ray total scattering and pair distribution function analysis. The measurements were performed at the GSECARS 13-IDD beamline at the APS employing the newly developed multichannel collimator (MCC) setup. The MCC effectively removes unwanted Compton scattering of the diamond anvils and enables easy extraction of

  18. Synthesis of ZnFe2O4/SiO2 composites derived from a diatomite template.

    Science.gov (United States)

    Liu, Zhaoting; Fan, Tongxiang; Zhou, Han; Zhang, Di; Gong, Xiaolu; Guo, Qixin; Ogawa, Hiroshi

    2007-03-01

    A novel porous ZnFe2O4/SiO2 composite product has been generated with a template-directed assembly method from porous diatomite under different synthesis conditions, such as precursor concentrations (metallic nitrates), calcination temperature and diatomite type. The phase composition and morphology of all the materials were examined by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results indicated that an inherited hierarchical porous structure from the diatomite template can be obtained, and the synthesis conditions were found to have clear effects on the formation of the ZnFe2O4/SiO2 composite. The ideal composite of ZnFe2O4/SiO2 can be obtained through optimization of diatomite template type, precursor solution and calcination temperature. Furthermore, the adsorption abilities of two types of diatomites were analyzed in detail using FTIR spectra and nitrogen adsorption measurements etc, which proved that A-diatomite (Shengzhou-diatomite) is better than B-diatomite (Changbai-diatomite) on the aspect of adsorbing Zn and Fe ions, and of forming the ZnFe2O4.

  19. Vancomycin-modified Fe3O4@SiO2@Ag microflowers as effective antimicrobial agents

    Directory of Open Access Journals (Sweden)

    Wang C

    2017-04-01

    Full Text Available Chongwen Wang,1,2,* Kehan Zhang,2,* Zhe Zhou,2,* Qingjun Li,2 Liting Shao,2 Rong Zhang Hao,3 Rui Xiao,2 Shengqi Wang1,2 1College of Life Sciences & Bio-Engineering, Beijing University of Technology, 2Beijing Key Laboratory of New Molecular Diagnosis Technologies for Infectious Diseases, Beijing Institute of Radiation Medicine, Beijing, 3Institute for Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, People’s Republic of China *These authors contributed equally to this work Abstract: Nanomaterials combined with antibiotics exhibit synergistic effects and have gained increasing interest as promising antimicrobial agents. In this study, vancomycin-modified magnetic-based silver microflowers (Van/Fe3O4@SiO2@Ag microflowers were rationally designed and prepared to achieve strong bactericidal ability, a wide antimicrobial spectrum, and good recyclability. High-performance Fe3O4@SiO2@Ag microflowers served as a multifunction-supporting matrix and exhibited sufficient magnetic response property due to their 200 nm Fe3O4 core. The microflowers also possessed a highly branched flower-like Ag shell that provided a large surface area for effective Ag ion release and bacterial contact. The modified-vancomycin layer was effectively bound to the cell wall of bacteria to increase the permeability of the cell membrane and facilitate the entry of the Ag ions into the bacterium, resulting in cell death. As such, the fabricated Van/Fe3O4@SiO2@Ag microflowers were predicted to be an effective and environment-friendly antibacterial agent. This hypothesis was verified through sterilization of Gram-negative Escherichia coli and Gram-positive methicillin-resistant Staphylococcus aureus, with minimum inhibitory concentrations of 10 and 20 µg mL-1, respectively. The microflowers also showed enhanced effect compared with bare Fe3O4@SiO2@Ag microflowers and free-form vancomycin, confirming the synergistic effects of the combination of the

  20. A novel approach for the synthesis of ultrathin silica-coated iron oxide nanocubes decorated with silver nanodots (Fe3O4/SiO2/Ag) and their superior catalytic reduction of 4-nitroaniline

    Science.gov (United States)

    Abbas, Mohamed; Torati, Sri Ramulu; Kim, Cheolgi

    2015-07-01

    A novel sonochemical approach was developed for the synthesis of different core/shell structures of Fe3O4/SiO2/Ag nanocubes and SiO2/Ag nanospheres. The total reaction time of the three sonochemical steps for the synthesis of Fe3O4/SiO2/Ag nanocubes is shorter than that of the previously reported methods. A proposed reaction mechanism for the sonochemical functionalization of the silica and the silver on the surface of magnetic nanocubes was discussed in detail. Transmission electron microscopy revealed that the surface of Fe3O4/SiO2 nanocubes was decorated with small Ag nanoparticles of approximately 10-20 nm in size, and the energy dispersive spectroscopy mapping analysis confirmed the morphology of the structure. Additionally, X-ray diffraction data were used to confirm the formation of both phases of a cubic inverse spinel structure for Fe3O4 and bcc structures for Ag in the core/shell structure of the Fe3O4/SiO2/Ag nanocubes. The as-synthesized Fe3O4/SiO2/Ag nanocubes showed a high efficiency in the catalytic reduction reaction of 4-nitroaniline to 4-phenylenediamine and a better performance than both Ag and SiO2/Ag nanoparticles. The grafted silver catalyst was recycled and reused at least fifteen times without a significant loss of catalytic efficiency.A novel sonochemical approach was developed for the synthesis of different core/shell structures of Fe3O4/SiO2/Ag nanocubes and SiO2/Ag nanospheres. The total reaction time of the three sonochemical steps for the synthesis of Fe3O4/SiO2/Ag nanocubes is shorter than that of the previously reported methods. A proposed reaction mechanism for the sonochemical functionalization of the silica and the silver on the surface of magnetic nanocubes was discussed in detail. Transmission electron microscopy revealed that the surface of Fe3O4/SiO2 nanocubes was decorated with small Ag nanoparticles of approximately 10-20 nm in size, and the energy dispersive spectroscopy mapping analysis confirmed the morphology of the

  1. Chlorellestadite, Ca5(SiO4)1.5(SO4)1.5Cl, a new ellestadite- group mineral from the Shadil-Khokh volcano, South Ossetia

    Science.gov (United States)

    Środek, Dorota; Galuskina, Irina O.; Galuskin, Evgeny; Dulski, Mateusz; Książek, Maria; Kusz, Joachim; Gazeev, Viktor

    2018-05-01

    Chlorellestadite (IMA2017-013), ideally Ca5(SiO4)1.5(SO4)1.5Cl, the Cl-end member of the ellestadite group was discovered in a calcium-silicate xenolith in rhyodacite lava from the Shadil Khokh volcano, Greater Caucasus, South Ossetia. Chlorellestadite forms white, tinged with blue or green, elongate crystals up to 0.2-0.3 mm in length. Associated minerals include spurrite, larnite, chlormayenite, rondorfite, srebrodolskite, jasmundite and oldhamite. The empirical crystal chemical formula of the holotype specimen is Ca4.99Na0.01(SiO4)1.51(SO4)1.46(PO4)0.03(Cl0.61OH0.21F0.11)Σ0.93. Unit-cell parameters of chlorellestadite are: P63/m, a = 9.6002(2), c = 6.8692(2) Å, V = 548.27(3)Å3, Z = 2. Chlorellestadite has a Mohs hardness of 4-4.5 and a calculated density of 3.091 g/cm3. The cleavage is indistinct, and the mineral shows irregular fracture. The Raman spectrum of chlorellestadite is similar to the spectra of other ellestadite group minerals, with main bands located at 267 cm-1 (Ca-O vibrations), and between 471 and 630 cm-1 (SiO4 4- and SO4 2- bending vibrations) and 850-1150 cm-1 (SiO4 4- and SO4 2- stretching modes). Chlorellestadite forms in xenoliths of calcium-silicate composition when they are exposed to Cl-bearing volcanic exhalations at about 1000 °C under low pressure conditions.

  2. Rapid removal of uranium from aqueous solutions using magnetic Fe3O4@SiO2 composite particles.

    Science.gov (United States)

    Fan, Fang-Li; Qin, Zhi; Bai, Jing; Rong, Wei-Dong; Fan, Fu-You; Tian, Wei; Wu, Xiao-Lei; Wang, Yang; Zhao, Liang

    2012-04-01

    Rapid removal of U(VI) from aqueous solutions was investigated using magnetic Fe(3)O(4)@SiO(2) composite particles as the novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, shaking time and initial U(VI) concentrations on uranium sorption efficiency as well as the desorbing of U(VI). The sorption of uranium on Fe(3)O(4)@SiO(2) composite particles was pH-dependent, and the optimal pH was 6.0. In kinetics studies, the sorption equilibrium can be reached within 180 min, and the experimental data were well fitted by the pseudo-second-order model, and the equilibrium sorption capacities calculated by the model were almost the same as those determined by experiments. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 20-200 mg/L. The maximum uranium sorption capacity onto magnetic Fe(3)O(4)@SiO(2) composite particles was estimated to be about 52 mg/g at 25 °C. The highest values of uranium desorption (98%) was achieved using 0.01 M HCl as the desorbing agent. Fe(3)O(4)@SiO(2) composite particles showed a good selectivity for uranium from aqueous solution with other interfering cation ions. Present study suggested that magnetic Fe(3)O(4)@SiO(2) composite particles can be used as a potential adsorbent for sorption uranium and also provided a simple, fast separation method for removal of heavy metal ion from aqueous solution. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Stress-induced formation mechanism of stacking fault tetrahedra in nano-cutting of single crystal copper

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Quanlong [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China); Bai, Qingshun [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Chen, Jiaxuan, E-mail: wangquanlong0@hit.edu.cn [Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China); Guo, Yongbo [Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xie, Wenkun [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-11-15

    Graphical abstract: In this paper, molecular dynamics simulation is performed to study the distribution of dislocation defects and local atomic crystal structure of single crystal copper. The stress distribution is investigated which is calculated by virial stress and analyzed by static pressure. The results are shown in (a)–(d). It is indicated that the compressive stress mainly spreads over the shear-slip zone, and the tensile stress is consisted in flank friction zone, shown in (a). The high tensile stress in subsurface is the source of stress, shown in (b). By the driven action of the stress source, the initial stair-rod dislocation nucleates. Then the dislocation climbs along four {1 1 1} planes under the stress driven action, shown in (d). Finally, the SFT is formed by the interaction of the compressive stress and the tensile stress which come from the shear-slip zone and friction zone, respectively. Besides, stair-rod dislocation, stacking faults and dislocation loop are also nucleated in the subsurface, shown in (c). Dislocation distribution, local atomic crystal structure state and stress-induced formation process of SFT by atomic. - Highlights: • A novel defect structure “stress-induced stacking fault tetrahedra” is revealed. • Atomic structural evolution and stress state distribution of the SFT are studied. • The stress-induced formation mechanism of the SFT is proposed. - Abstract: Stacking fault tetrahedra commonly existed in subsurface of deformed face center cubic metals, has great influence on machining precision and surface roughness in nano-cutting. Here we report, a stacking fault tetrahedra is formed in subsurface of workpiece during nano-cutting. The variation of cutting force and subsurface defects distribution are studied by using molecular dynamics simulation. The stress distribution is investigated which is calculated by virial stress and analyzed by static compression. The result shows that the cutting force has a rapidly

  4. Stress-induced formation mechanism of stacking fault tetrahedra in nano-cutting of single crystal copper

    International Nuclear Information System (INIS)

    Wang, Quanlong; Bai, Qingshun; Chen, Jiaxuan; Guo, Yongbo; Xie, Wenkun

    2015-01-01

    Graphical abstract: In this paper, molecular dynamics simulation is performed to study the distribution of dislocation defects and local atomic crystal structure of single crystal copper. The stress distribution is investigated which is calculated by virial stress and analyzed by static pressure. The results are shown in (a)–(d). It is indicated that the compressive stress mainly spreads over the shear-slip zone, and the tensile stress is consisted in flank friction zone, shown in (a). The high tensile stress in subsurface is the source of stress, shown in (b). By the driven action of the stress source, the initial stair-rod dislocation nucleates. Then the dislocation climbs along four {1 1 1} planes under the stress driven action, shown in (d). Finally, the SFT is formed by the interaction of the compressive stress and the tensile stress which come from the shear-slip zone and friction zone, respectively. Besides, stair-rod dislocation, stacking faults and dislocation loop are also nucleated in the subsurface, shown in (c). Dislocation distribution, local atomic crystal structure state and stress-induced formation process of SFT by atomic. - Highlights: • A novel defect structure “stress-induced stacking fault tetrahedra” is revealed. • Atomic structural evolution and stress state distribution of the SFT are studied. • The stress-induced formation mechanism of the SFT is proposed. - Abstract: Stacking fault tetrahedra commonly existed in subsurface of deformed face center cubic metals, has great influence on machining precision and surface roughness in nano-cutting. Here we report, a stacking fault tetrahedra is formed in subsurface of workpiece during nano-cutting. The variation of cutting force and subsurface defects distribution are studied by using molecular dynamics simulation. The stress distribution is investigated which is calculated by virial stress and analyzed by static compression. The result shows that the cutting force has a rapidly

  5. Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography

    NARCIS (Netherlands)

    Perea, Daniel E.; Arslan, Ilke; Liu, Jia; Ristanovic, Zoran; Kovarik, Libor; Arey, Bruce W.; Lercher, Johannes A.; Bare, Simon R.; Weckhuysen, Bert M.

    Zeolite catalysis is determined by a combination of pore architecture and Bronsted acidity. As Bronsted acid sites are formed by the substitution of AlO4 for SiO4 tetrahedra, it is of utmost importance to have information on the number as well as the location and neighbouring sites of framework

  6. Prediction study on mechanical and thermodynamic properties of orthorhombic Mg2SiO4 under high temperature

    International Nuclear Information System (INIS)

    Zhou, Jianting; Zhang, Hong; Chen, Yue; Shong, Jun; Chen, Zhuo; Yang, Juan; Zheng, Zhou; Wang, Feng

    2014-01-01

    In this work, based on density functional theory and quasi-harmonic Debye model, mechanical and thermodynamic properties of orthorhombic Mg 2 SiO 4 under high temperature are predicted. We found out that α-Mg 2 SiO 4 is mechanically stable under the condition from about 0 to 74 GPa. Results indicate that the main cause of mechanical instability is high pressure, and the effect caused by high temperature is small. C 11 , C 22 , C 33 , B and v p reduce with temperature just a little and increase with pressure obviously. Mg 2 SiO 4 has excellent resistance to strong compression; however the resistance to shear is unsatisfactory. The C v tends to the Petit and Dulong limit at high temperature under any pressure, and it is proportional to T 3 at extremely low temperature. Pressure has an opposite effect on C v than temperature. The suppressed effect on C v caused by pressure is not obvious under low and very high temperature. Mg 2 SiO 4 has three different thermal expansion coefficients (α) along a-, b- and c-axes, and α a <α c <α b . α increases rapidly at low temperature (about <300 K), and slows down at high temperature. High pressure would greatly suppress expansion caused by temperature. Nevertheless, increasing tendency of α b and α c is still obvious under high pressure, especially α b . All the properties are mainly due to Si–O covalent bonds and their directions

  7. Enstatite, Mg2Si2O6: A neutron diffraction refinement of the crystal structure and a rigid-body analysis of the thermal vibration

    International Nuclear Information System (INIS)

    Ghose, S.; Schomaker, V.; McMullan, R.K.

    1986-01-01

    Synthetic enstatite, Mg 2 Si 2 O 6 , is orthorhombic, space group Pbca, with eight formula units per cell and lattice parameters a = 18.235(3), b = 8.818(1), c = 5.179(1) A at 23 0 C. A least-squares structure refinement based on 1790 neutron intensity data converged with an agreement factor R(F 2 ) = 0.032, yielding Mg-O and Si-O bond lengths with standard deviations of 0.0007 and 0.0008 A, respectively. The variations observed in the Si-O bond lengths within the silicate tetrahedra A and B are caused by the differences in primary coordination of the oxygen atoms and the proximity of the magnesium ions to the silicon atoms. The latter effect is most pronounced for the bridging bonds of tetrahedron. A. The smallest O-Si-O angle is the result of edge-sharing by the Mg(2) octahedron and the A tetrahedron. An analysis of rigid-body thermal vibrations of the two crystallographically independent [SiO 4 ] tetrahedra indicates considerable librational motion, leading to a thermal correction of apparent Si-O bond lengths as large as +0.002 A at room temperature. (orig.)

  8. Preparation and characterization of Fe3O4/SiO2/Bi2MoO6 composite as magnetically separable photocatalyst

    International Nuclear Information System (INIS)

    Hou, Xuemei; Tian, Yanlong; Zhang, Xiang; Dou, Shuliang; Pan, Lei; Wang, Wenjia; Li, Yao; Zhao, Jiupeng

    2015-01-01

    Highlights: • Fe 3 O 4 /SiO 2 /Bi 2 MoO 6 composite was prepared by a hydrothermal method. • The composite has an enhanced visible absorption compared with pure Bi 2 MoO 6 . • The magnetic photocatalyst displayed excellent stability and reusability. • O 2 ·− and · OH play a major role during the photocatalytic process. - Abstract: In this paper, Fe 3 O 4 /SiO 2 /Bi 2 MoO 6 microspheres were prepared by a facile hydrothermal method. The scanning electron microscope (SEM) results revealed that flower-like three dimensional (3D) Bi 2 MoO 6 microspheres were decorated with Fe 3 O 4 /SiO 2 magnetic nanoparticles. The UV–vis diffuse reflection spectra showed extended absorption within the visible light range compared with pure Bi 2 MoO 6 . We evaluated the photocatalytic activities of Fe 3 O 4 /SiO 2 /Bi 2 MoO 6 microspheres on the degradation of Rhodamine B (RhB) under visible light irradiation and found that the obtained composite exhibited higher photocatalytic activity than pure Bi 2 MoO 6 and P25. Moreover, the Fe 3 O 4 /SiO 2 /Bi 2 MoO 6 composite also displayed excellent stability and their photocatalytic activity decreased slightly after reusing 5 cycles. Meanwhile, the composite could be easily separated by applying an external magnetic field. The trapping experiment results suggest that superoxide radical species O 2 ·− and hydroxyl radicals · OH play a major role in Fe 3 O 4 /SiO 2 /Bi 2 MoO 6 system under visible light irradiation. The combination of flower-like three dimensional (3D) Bi 2 MoO 6 microspheres and Fe 3 O 4 /SiO 2 magnetic nanospheres provides a useful strategy for designing multifunctional nanostructure materials with enhanced photocatalytic activities in the potential applications of water purification

  9. Copper(II hydrogenphosphate, CuHPO4

    Directory of Open Access Journals (Sweden)

    Dörte Stachel

    2009-12-01

    Full Text Available The title compound, CuHPO4, has been synthesized from a mixture of phosphoric acid and copper oxide. It has the same composition as MHPO4 (M = Ca, Ba, Pb, Sr or Sn, but adopts a rhombohedral structure with all atoms on general positions. The structure features distorted PO4 tetrahedra linked by copper, forming 12-membered rings. The CuII atom is coordinated by five O atoms in a distorted square-pyramidal manner. O—H...O hydrogen bonding leads to an additional stabilization of the structure.

  10. Highly selective SiO2 etching over Si3N4 using a cyclic process with BCl3 and fluorocarbon gas chemistries

    Science.gov (United States)

    Matsui, Miyako; Kuwahara, Kenichi

    2018-06-01

    A cyclic process for highly selective SiO2 etching with atomic-scale precision over Si3N4 was developed by using BCl3 and fluorocarbon gas chemistries. This process consists of two alternately performed steps: a deposition step using BCl3 mixed-gas plasma and an etching step using CF4/Ar mixed-gas plasma. The mechanism of the cyclic process was investigated by analyzing the surface chemistry at each step. BCl x layers formed on both SiO2 and Si3N4 surfaces in the deposition step. Early in the etching step, the deposited BCl x layers reacted with CF x radicals by forming CCl x and BF x . Then, fluorocarbon films were deposited on both surfaces in the etching step. We found that the BCl x layers formed in the deposition step enhanced the formation of the fluorocarbon films in the CF4 plasma etching step. In addition, because F radicals that radiated from the CF4 plasma reacted with B atoms while passing through the BCl x layers, the BCl x layers protected the Si3N4 surface from F-radical etching. The deposited layers, which contained the BCl x , CCl x , and CF x components, became thinner on SiO2 than on Si3N4, which promoted the ion-assisted etching of SiO2. This is because the BCl x component had a high reactivity with SiO2, and the CF x component was consumed by the etching reaction with SiO2.

  11. Preparation of orthophosphate glasses in the MgO-CaO-SiO2-Nb2O5-P2O5 system.

    Science.gov (United States)

    Lee, Sungho; Ueda, Kyosuke; Narushima, Takayuki; Nakano, Takayoshi; Kasuga, Toshihiro

    2017-01-01

    Niobia/magnesia-containing orthophosphate invert glasses were successfully prepared in our earlier work. Orthophosphate groups in the glasses were cross-linked by tetrahedral niobia (NbO4) and magnesia. The aim of this work is to prepare calcium orthophosphate invert glasses containing magnesia and niobia, incorporating silica, and to evaluate their structures and releasing behaviors. The glasses were prepared by melt-quenching, and their structures and ion-releasing behaviors were evaluated. 31P solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies showed the glasses consist of orthophosphate (PO4), orthosilicate (SiO4), and NbO4 tetrahedra. NbO4 and MgO in the glasses act as network formers. By incorporating SiO2 into the glasses, the chemical durability of the glasses was slightly improved. The glasses reheated at 800°C formed the orthophosphate crystalline phases, such as β-Ca3(PO4)2, Mg3(PO4)2 and Mg3Ca3(PO4)4 in the glasses. The chemical durability of the crystallized glasses was slightly improved. Orthosilicate groups and NbO4 in the glasses coordinated with each other to form Si-O-Nb bonds. The chemical durability of the glasses was slightly improved by addition of SiO2, since the field strength of Si is larger than that of Ca or Mg.

  12. Study of the structural characteristics of a group of natural silicates by means of their Kβ emission spectra

    International Nuclear Information System (INIS)

    Torres Deluigi, Maria Torres; Strasser, Edgardo N.; Vasconcellos, Marcos A.Z.; Riveros, Jose A.

    2006-01-01

    In this work, the Si Kβ and Al Kβ emission spectra of a group of natural silicates typical of a region in San Luis (Argentina) are described qualitatively within the frame of the Molecular Orbital (MO) theory. Since these spectra come from electron transitions from valence orbitals, they offer information on the chemical bonds that are present and on the molecular orbitals involved. The spectra were obtained by means of an electron microprobe. The energies, intensities and full-width at half-maximum (FWHM) of the lines that conform the silicon and aluminium Kβ spectra were quantified. It was observed that an increase in the number of oxygen ions shared by the tetrahedra (SiO 4 ) 4- caused a lineal increase in the FWHM of the Si Kβ 1,3 and Al Kβ 1,3 lines. This behavior is caused by the increase of the covalent character of the Si-O and Al-O bonds with the quantity of oxygen ions shared by the adjacent tetrahedra

  13. Controlled synthesis and relationship between luminescent properties and shape/crystal structure of Zn2SiO4:MN2+ phosphor

    International Nuclear Information System (INIS)

    Wan Junxi; Wang Zhenghua; Chen Xiangying; Mu Li; Yu Weichao; Qian Yitai

    2006-01-01

    Mn-doped Zn 2 SiO 4 phosphors with different morphology and crystal structure, which show different luminescence and photoluminescence intensity, were synthesized via a low-temperature hydrothermal route without further calcining treatment. As-synthesized zinc silicate nanostructures show green or yellow luminescence depending on their different crystal structure obtained under different preparation conditions. The yellow peak occurring at 575 nm comes from the β-phase zinc silicate, while the green peak centering at 525 nm results from the usual α-phase zinc silicate. From photoluminescence spectra, it is found that Zn 2 SiO 4 nanorods have higher photoluminescence intensity than Zn 2 SiO 4 nanoparticles. It can be ascribed to reduced surface-damaged region and high crystallinity of nanorods

  14. [H3N(CH2)4NH3]2[Al4(C2O4)(H2PO4)2(PO4)4].4[H2O]: A new layered aluminum phosphate-oxalate

    International Nuclear Information System (INIS)

    Peng Li; Li Jiyang; Yu Jihong; Li Guanghua; Fang Qianrong; Xu Ruren

    2005-01-01

    A new layered inorganic-organic hybrid aluminum phosphate-oxalate [H 3 N(CH 2 ) 4 NH 3 ] 2 [Al 4 (C 2 O 4 )(H 2 PO 4 ) 2 (PO 4 ) 4 ].4[H 2 O](AlPO-CJ25) has been synthesized hydrothermally, by using 1,4-diaminobutane (DAB) as structure-directing agent. The structure has been solved by single-crystal X-ray diffraction analysis and further characterized by IR, 31 P MAS NMR, TG-DTA as well as compositional analyses. Crystal data: the triclinic space group P-1, a=8.0484(7) A, b=8.8608(8) A, c=13.2224(11) A, α=80.830(6) deg. , β=74.965(5) deg. , γ=78.782(6) deg. , Z=2, R 1[ I >2 σ ( I )] =0.0511 and wR 2(alldata) =0.1423. The alternation of AlO 4 tetrahedra and PO 4 tetrahedra gives rise to the four-membered corner-sharing chains, which are interconnected through AlO 6 octahedra to form the layered structure with 4,6-net sheet. Interestingly, oxalate ions are bis-bidentately bonded by participating in the coordination of AlO 6 , and bridging the adjacent AlO 6 octahedra. The layers are held with each other through strong H-bondings between the terminal oxygens. The organic ammonium cations and water molecules are located in the large cavities between the interlayer regions. -- Graphical abstract: The alternation of AlO 4 tetrahedra and PO 4 tetrahedra gives rise to the four-membered corner-sharing chains, which are interconnected through AlO 6 octahedra to form the layered structure with 4,6-net sheet. Oxalate ions are bis-bidentately boned by participating in the coordination of AlO 6 , and bridging the adjacent AlO 6 octahedra

  15. Effects of (NH4)2S x treatment on the surface properties of SiO2 as a gate dielectric for pentacene thin-film transistor applications

    Science.gov (United States)

    Hung, Cheng-Chun; Lin, Yow-Jon

    2018-01-01

    The effect of (NH4)2S x treatment on the surface properties of SiO2 is studied. (NH4)2S x treatment leads to the formation of S-Si bonds on the SiO2 surface that serves to reduce the number of donor-like trap states, inducing the shift of the Fermi level toward the conduction band minimum. A finding in this case is the noticeably reduced value of the SiO2 capacitance as the sulfurated layer is formed at the SiO2 surface. The effect of SiO2 layers with (NH4)2S x treatment on the carrier transport behaviors for the pentacene/SiO2-based organic thin-film transistor (OTFT) is also studied. The pentacene/as-cleaned SiO2-based OTFT shows depletion-mode behavior, whereas the pentacene/(NH4)2S x -treated SiO2-based OTFT exhibits enhancement-mode behavior. Experimental identification confirms that the depletion-/enhancement-mode conversion is due to the dominance competition between donor-like trap states in SiO2 near the pentacene/SiO2 interface and acceptor-like trap states in the pentacene channel. A sulfurated layer between pentacene and SiO2 is expected to give significant contributions to carrier transport for pentacene/SiO2-based OTFTs.

  16. Effects of cobalt doping on structural, morphological, and optical properties of Zn2SiO4 nanophosphors prepared by sol-gel method

    Directory of Open Access Journals (Sweden)

    Norhafizah Mohd Rasdi

    Full Text Available In this paper, undoped and cobalt (II (3, and 5 mol % doped zinc silicate nanophosphors prepared by a sol-gel method which were heated at 1000 °C were studied in detail. From the XRD result, undoped and Co2+ doped zinc silicate sample yields α- and β-Zn2SiO4. This also shows that α-Zn2SiO4 acts as the primary phase in the crystal structure of the sample. For FESEM, the grain size decreases as the dopant increases where undoped sample indicates average grain size of 181 nm while 3 and 5 mol % exhibits containing ones 136.89 nm and 176.22 nm respectively. With FTIR transmission a major peak at range of 1100 cm−1, 880, 550, and 350 assigning as Si-O-Si asymmetric stretching, SiO4 asymmetric stretching, ZnO4 symmetric stretching, and Si-O asymmetric deformation vibration were observed respectively. The absorption band of doped Zn2SiO4 exhibited a higher absorbance intensity in the UV region compared to undoped Zn2SiO4. Besides, all the samples depict that the sample was having a red shift in which the band shifted to the longer wavelength. The energy band gap value of undoped sample shows 3.07 eV and when Co2+ dopant (3 and 5 mol % was introduced, the energy band gap started to decrease (2.46 and 2.42 eV respectively. PL emission presents two peaks at blue emissions (420 and 480 nm and a green emission (525 nm. The result present that Co2+:Zn2SiO4 is potentially good to use as blue and green phosphors for luminescent optical material. Keywords: Cobalt (II doped zinc silicate, Transition metal, Sol-gel method, Nanophosphors, Photoluminescence

  17. Sheet-like Li3V2(PO4)3 nanocomposite coated by SiO2 + C with better electrochemical properties for lithium-ion batteries

    International Nuclear Information System (INIS)

    Lai, Chunyan; Wu, Tingting; Wang, Zhen

    2016-01-01

    Sheet-like Li 3 V 2 (PO 4 ) 3 nanocomposite coated by SiO 2  + C layer was synthesized with one-step solid-state method. Dihydroxydiphenylsilane (DPSD) was used as the source of SiO 2 and C. The sheet-like Li 3 V 2 (PO 4 ) 3 nanocomposite has a thickness in the range of 20–30 nm. Because of the SiO 2  + C-coated layer and the sheet-like morphology, the Li 3 V 2 (PO 4 ) 3 /(SiO 2  + C) composites show better stability and higher capacity than pure Li 3 V 2 (PO 4 ) 3 material and granular Li 3 V 2 (PO 4 ) 3 /(SiO 2  + C) composites. The best sample, Li 3 V 2 (PO 4 ) 3 /(SiO 2  + C)(2:8), shows a discharge capacity of 193.7 mAh g −1 at 1C within the voltage range of 3.0–4.8 V and retains almost 90 % of the capacity after 50 cycles.

  18. Cube-like Fe3O4@SiO2@Au@Ag magnetic nanoparticles: a highly efficient SERS substrate for pesticide detection

    Science.gov (United States)

    Sun, Mei; Zhao, Aiwu; Wang, Dapeng; Wang, Jin; Chen, Ping; Sun, Henghui

    2018-04-01

    As a novel surface-enhanced Raman spectroscopic (SERS) nanocomposite, cube-like Fe3O4@SiO2@Au@Ag magnetic nanoparticles (NPs) were synthesized for the first time. Cube-like α-Fe2O3 NPs with uniform size were achieved by optimizing reaction temperature and time. Firstly, the cube-like Fe3O4@SiO2 with good dispersity was achieved by calcining α-Fe2O3@SiO2 NPs in hydrogen atmosphere at 360 °C for 2.5 h, followed by self-assembling a PEI shell via sonication. Furthermore, the Au@Ag particles were densely assembled on the Fe3O4@SiO2 NPs to form the Fe3O4@SiO2@Au@Ag composite structure via strong Ag-N interaction. The obtained nanocomposites exhibited an excellent SERS behavior, reflected by the low detection of limit (p-ATP) at the 5 × 10-14 M level. Moreover, these nanocubes were used for the detection of thiram, and the detection limit can reach 5 × 10-11 M. Meanwhile, the U.S. Environmental Protection Agency specifies that the residue in fruit must be lower than 7 ppm. Hence, the resulting substrate with high SERS activity has great practical potential applications in the rapid detection of chemical, biological, and environment pollutants with a simple portable Raman instrument at trace level.

  19. A graphene quantum dot@Fe3O4@SiO2 based nanoprobe for drug delivery sensing and dual-modal fluorescence and MRI imaging in cancer cells.

    Science.gov (United States)

    Su, Xiaoqian; Chan, Chunyu; Shi, Jingyu; Tsang, Ming-Kiu; Pan, Yi; Cheng, Changming; Gerile, Oudeng; Yang, Mo

    2017-06-15

    A novel graphene quantum dot (GQD)@Fe 3 O 4 @SiO 2 based nanoprobe was reported for targeted drug delivery, sensing, dual-modal imaging and therapy. Carboxyl-terminated GQD (C-GQD) was firstly conjugated with Fe 3 O 4 @SiO 2 and then functionalized with cancer targeting molecule folic acid (FA). DOX drug molecules were then loaded on GQD surface of Fe 3 O 4 @SiO 2 @GQD-FA nanoprobe via pi-pi stacking, which resulted in Fe 3 O 4 @SiO 2 @GQD-FA/DOX conjugates based on a FRET mechanism with GQD as donor molecules and DOX as acceptor molecules. Meanwhile, we successfully performed in vitro MRI and fluorescence imaging of living Hela cells and monitored intracellular drug release process using this Fe 3 O 4 @SiO 2 @GQD-FA/DOX nanoprobe. Cell viability study demonstrated the low cytotoxicity of Fe 3 O 4 @SiO 2 @GQD-FA nanocarrier and the enhanced therapeutic efficacy of Fe 3 O 4 @SiO 2 @GQD-FA/DOX nanoprobe for cancer cells. This luminomagnetic nanoprobe will be a potential platform for cancer accurate diagnosis and therapy. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. [O{sub 2}Pb{sub 3}]{sub 2}(BO{sub 3})Br. An oxidoborate oxide bromide with the {sub ∞}{sup 1}[O{sub 2}Pb{sub 3}] double chains based on edge-sharing OPb{sub 4} tetrahedra

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Lingyun [College of Chemistry and Environmental Science, Hebei University, Baoding (China); Biology and Chemistry Department, Baoding University (China); Yang, Jiao; Shen, Shigang; Liu, Zhenzhen; Sun, Sufang [College of Chemistry and Environmental Science, Hebei University, Baoding (China); Chen, Xiaojing [Biology and Chemistry Department, Baoding University (China)

    2017-04-04

    Through extensive research on the PbO / PbBr{sub 2} / B{sub 2}O{sub 3} system, a new single crystal of yellow lead-containing oxyborate bromine, [O{sub 2}Pb{sub 3}]{sub 2}(BO{sub 3})Br, was grown from the melt. It crystallizes in the centrosymmetric space group Cmcm (no. 63) of the orthorhombic system with the following unit cell dimensions: a = 9.5748(8) Aa, b = 20.841(2) Aa, c = 5.7696(5) Aa, and Z = 4. The whole structure is characterized by an infinite one-dimensional (1D) {sub ∞}{sup 1}[O{sub 2}Pb{sub 3}] double chain, which is based on the OPb{sub 4} oxocentered tetrahedra and considered as the derivative of the continuous sheet of OPb{sub 4} tetrahedra from the tetragonal modification of α-PbO. The 1D {sub ∞}{sup 1}[O{sub 2}Pb{sub 3}] double chains are further bridged by the BO{sub 3} units through common oxygen atoms to form two-dimensional (2D) {sub ∞}{sup 1}[(O{sub 2}Pb{sub 3})(BO{sub 3})] layers, with Br atoms situated between the layers. IR spectroscopy, UV/Vis/NIR diffuse reflectance spectroscopy, and thermal analysis were also performed on the reported material. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Angular dependence of Si3N4 etch rates and the etch selectivity of SiO2 to Si3N4 at different bias voltages in a high-density C4F8 plasma

    International Nuclear Information System (INIS)

    Lee, Jin-Kwan; Lee, Gyeo-Re; Min, Jae-Ho; Moon, Sang Heup

    2007-01-01

    The dependence of Si 3 N 4 etch rates and the etch selectivity of SiO 2 to Si 3 N 4 on ion-incident angles was studied for different bias voltages in a high-density C 4 F 8 plasma. A Faraday cage and specially designed substrate holders were used to accurately control the angles of incident ions on the substrate surface. The normalized etch yield (NEY), defined as the etch yield obtained at a given ion-incident angle normalized to that obtained on a horizontal surface, was unaffected by the bias voltage in Si 3 N 4 etching, but it increased with the bias voltage in SiO 2 etching in the range of -100 to -300 V. The NEY changed showing a maximum with an increase in the ion-incident angle in the etching of both substrates. In the Si 3 N 4 etching, a maximum NEY of 1.7 was obtained at 70 deg. in the above bias voltage range. However, an increase in the NEY at high ion-incident angles was smaller for SiO 2 than for Si 3 N 4 and, consequently, the etch selectivity of SiO 2 to Si 3 N 4 decreased with an increase in the ion-incident angle. The etch selectivity decreased to a smaller extent at high bias voltage because the NEY of SiO 2 had increased. The characteristic changes in the NEY for different substrates could be correlated with the thickness of a steady-state fluorocarbon (CF x ) film formed on the substrates

  2. Photocatalytic application of TiO2/SiO2-based magnetic nanocomposite (Fe3O4@SiO2/TiO2 for reusing of textile wastewater

    Directory of Open Access Journals (Sweden)

    Laleh Enayati Ahangar

    2016-01-01

    Full Text Available In this research we have developed a treatment method for textile wastewater by TiO2/SiO2-based magnetic nanocomposite. Textile wastewater includes a large variety of dyes and chemicals and needs treatments. This manuscript presents a facile method for removing dyes from the textile wastewater by using TiO2/SiO2-based nanocomposite (Fe3O4@SiO2/TiO2 under UV irradiation. This magnetic nanocomposite, as photocatalytically active composite, is synthesized via solution method in mild conditions. A large range of cationic, anionic and neutral dyes including: methyl orange, methylene blue, neutral red, bromocresol green and methyl red are used for treatment investigations. Neutral red and bromocresol green have good results in reusing treatment. The high surface area of nanocomposites improve the kinetic of wastewater treatment. In this method, by using the magnetic properties of Fe3O4 nanoparticles, TiO2-based photocatalyst could be separated and reused for 3 times. The efficiency of this method is respectively 100% and 65% for low concentration (10 ppm and high concentration (50 ppm of neutral red and bromocrosol green after 3 h treatment. The efficiency of treatment using the second used nanocomposite was 90% for 10 ppm of the same dyes.

  3. Structural characterization and optical properties of Eu"2"+ and Dy"2"+ doped Sr_2SiO_4 phosphor by solid state reaction method

    International Nuclear Information System (INIS)

    Verma, Durga; Verma, Mohan L.; Upma; Patel, R.P.

    2016-01-01

    Thermoluminescence, SEM, FTIR Divalent dysprosium and europium doped strontium silicate (Sr_2SiO_4) phosphors were synthesized with the high-temperature solid-state reaction technique. The obtained phosphor was well characterized by powder X-ray diffraction, scanning electron microscopy, FTIR, UV-visible spectroscopy and thermoluminescence. The crystal structure of the prepared phosphor has an orthorhombic structure with space group Pnma. From scanning electron microscopy (SEM), agglomerations of particles were observed due to the high temperature synthesis process. The chemical composition of the sintered Sr_2SiO_4:Dy"2"+ and Sr_2SiO_4: Eu"2"+ phosphor was confirmed by energy dispersive X-ray spectroscopy (EDX). The UV-VIS analysis can be thought as a good quality check for the optical behavior of materials. The Fourier transmission infrared spectroscopy (FTIR) confirms the present elements in phosphor. Thermoluminescence study was carried out for the phosphor with UV irradiation show one glow peak. The trapping parameters associated with the prominent glow peak of Sr_2SiO_4:Dy"2"+ and Sr_2SiO_4:Eu"2"+ are calculated using Chen's glow curve method. The release of holes/electrons from defect centers at the characteristic trap site initiates the luminescence process in this material. (author)

  4. Structural and electronic properties of the transition layer at the SiO2/4H-SiC interface

    Directory of Open Access Journals (Sweden)

    Wenbo Li

    2015-01-01

    Full Text Available Using first-principles methods, we generate an amorphous SiO2/4H-SiC interface with a transition layer. Based this interface model, we investigate the structural and electronic properties of the interfacial transition layer. The calculated Si 2p core-level shifts for this interface are comparable to the experimental data, indicating that various SiCxOy species should be present in this interface transition layer. The analysis of the electronic structures reveals that the tetrahedral SiCxOy structures cannot introduce any of the defect states at the interface. Interestingly, our transition layer also includes a C-C=C trimer and SiO5 configurations, which lead to the generation of interface states. The accurate positions of Kohn-Sham energy levels associated with these defects are further calculated within the hybrid functional scheme. The Kohn-Sham energy levels of the carbon trimer and SiO5 configurations are located near the conduction and valence band of bulk 4H-SiC, respectively. The result indicates that the carbon trimer occurred in the transition layer may be a possible origin of near interface traps. These findings provide novel insight into the structural and electronic properties of the realistic SiO2/SiC interface.

  5. Compositional and optical properties of SiO x films and (SiO x /SiO y ) junctions deposited by HFCVD

    Science.gov (United States)

    2014-01-01

    In this work, non-stoichiometric silicon oxide (SiO x ) films and (SiO x /SiO y ) junctions, as-grown and after further annealing, are characterized by different techniques. The SiO x films and (SiO x /SiO y ) junctions are obtained by hot filament chemical vapor deposition technique in the range of temperatures from 900°C to 1,150°C. Transmittance spectra of the SiO x films showed a wavelength shift of the absorption edge thus indicating an increase in the optical energy band gap, when the growth temperature decreases; a similar behavior is observed in the (SiO x /SiO y ) structures, which in turn indicates a decrease in the Si excess, as Fourier transform infrared spectroscopy (FTIR) reveals, so that, the film and junction composition changes with the growth temperature. The analysis of the photoluminescence (PL) results using the quantum confinement model suggests the presence of silicon nanocrystal (Si-nc) embedded in a SiO x matrix. For the case of the as-grown SiO x films, the absorption and emission properties are correlated with quantum effects in Si-nc and defects. For the case of the as-grown (SiO x /SiO y ) junctions, only the emission mechanism related to some kinds of defects was considered, but silicon nanocrystal embedded in a SiO x matrix is present. After thermal annealing, a phase separation into Si and SiO2 occurs, as the FTIR spectra illustrates, which has repercussions in the absorption and emission properties of the films and junctions, as shown by the change in the A and B band positions on the PL spectra. These results lead to good possibilities for proposed novel applications in optoelectronic devices. PACS 61.05.-a; 68.37.Og; 61.05.cp; 78.55.-m; 68.37.Ps; 81.15.Gh PMID:25342935

  6. Modifier cation effects on (29)Si nuclear shielding anisotropies in silicate glasses.

    Science.gov (United States)

    Baltisberger, Jay H; Florian, Pierre; Keeler, Eric G; Phyo, Pyae A; Sanders, Kevin J; Grandinetti, Philip J

    2016-07-01

    We have examined variations in the (29)Si nuclear shielding tensor parameters of SiO4 tetrahedra in a series of seven alkali and alkaline earth silicate glass compositions, Cs2O·4.81 SiO2, Rb2O·3.96 SiO2, Rb2O·2.25 SiO2, K2O·4.48 SiO2, Na2O·4.74 SiO2, BaO·2.64 SiO2, and SrO·2.36 SiO2, using natural abundance (29)Si two-dimensional magic-angle flipping (MAF) experiments. Our analyses of these 2D spectra reveal a linear dependence of the (29)Si nuclear shielding anisotropy of Q((3)) sites on the Si-non-bridging oxygen bond length, which in turn depends on the cation potential and coordination of modifier cations to the non-bridging oxygen. We also demonstrate how a combination of Cu(2+) as a paramagnetic dopant combined with echo train acquisition can reduce the total experiment time of (29)Si 2D NMR measurements by two orders of magnitude, enabling higher throughput 2D NMR studies of glass structure. Copyright © 2016 Elsevier Inc. All rights reserved.

  7. Modifier cation effects on 29Si nuclear shielding anisotropies in silicate glasses

    Science.gov (United States)

    Baltisberger, Jay H.; Florian, Pierre; Keeler, Eric G.; Phyo, Pyae A.; Sanders, Kevin J.; Grandinetti, Philip J.

    2016-07-01

    We have examined variations in the 29Si nuclear shielding tensor parameters of SiO4 tetrahedra in a series of seven alkali and alkaline earth silicate glass compositions, Cs2O · 4.81 SiO2, Rb2O · 3.96 SiO2, Rb2O · 2.25 SiO2, K2O · 4.48 SiO2, Na2O · 4.74 SiO2, BaO · 2.64 SiO2, and SrO · 2.36 SiO2, using natural abundance 29Si two-dimensional magic-angle flipping (MAF) experiments. Our analyses of these 2D spectra reveal a linear dependence of the 29Si nuclear shielding anisotropy of Q(3) sites on the Si-non-bridging oxygen bond length, which in turn depends on the cation potential and coordination of modifier cations to the non-bridging oxygen. We also demonstrate how a combination of Cu2+ as a paramagnetic dopant combined with echo train acquisition can reduce the total experiment time of 29Si 2D NMR measurements by two orders of magnitude, enabling higher throughput 2D NMR studies of glass structure.

  8. High Photocatalytic Activity of Fe3O4-SiO2-TiO2 Functional Particles with Core-Shell Structure

    Directory of Open Access Journals (Sweden)

    Chenyang Xue

    2013-01-01

    Full Text Available This paper describes a novel method of synthesizing Fe3O4-SiO2-TiO2 functional nanoparticles with the core-shell structure. The Fe3O4 cores which were mainly superparamagnetic were synthesized through a novel carbon reduction method. The Fe3O4 cores were then modified with SiO2 and finally encapsulated with TiO2 by the sol-gel method. The results of characterizations showed that the encapsulated 700 nm Fe3O4-SiO2-TiO2 particles have a relatively uniform size distribution, an anatase TiO2 shell, and suitable magnetic properties for allowing collection in a magnetic field. These magnetic properties, large area, relative high saturation intensity, and low retentive magnetism make the particles have high dispersibility in suspension and yet enable them to be recovered well using magnetic fields. The functionality of these particles was tested by measuring the photocatalytic activity of the decolouring of methyl orange (MO and methylene blue (MB under ultraviolet light and sunlight. The results showed that the introduction of the Fe3O4-SiO2-TiO2 functional nanoparticles significantly increased the decoloration rate so that an MO solution at a concentration of 10 mg/L could be decoloured completely within 180 minutes. The particles were recovered after utilization, washing, and drying and the primary recovery ratio was 87.5%.

  9. Comparative Study of the Corrosion Resistance of Air-Plasma-Sprayed Ca2SiO4 and Al2O3 Coatings in Salt Water

    Directory of Open Access Journals (Sweden)

    Yuan Xiao

    2018-03-01

    Full Text Available In this study, Ca2SiO4 coating was sprayed on stainless steel substrate and the corrosion resistance of the as-sprayed coating was studied in salt water. At the same time, Al2O3 coatings were produced by air-plasma-sprayed technology as comparison. Immersion test was carried out to evaluate the protection performance of coatings. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS plots were also analyzed. The results indicated that Ca2SiO4 coatings showed a better protection performance than Al2O3 coatings. During the immersion, various calcium carbonate crystals appeared on the surface of Ca2SiO4 coatings. Ca(OH2 was released from Ca2SiO4 coatings into NaCl aqueous solution, increasing the alkalinity, which is in favor of the formation of passivation film, and thus improves the corrosion resistance. Ca2SiO4 coatings became denser after immersion due to the fact that the pores and micro cracks were filled with hydration products i.e., hydrated calcium silicate (C–S–H gel. On the contrary, the microstructure of Al2O3 coatings became loose and obvious rusty spots were observed on the surface after the immersion test.

  10. Lattice-dynamical estimation of atomic thermal parameters for silicates: Forsterite α-Mg2SiO4

    International Nuclear Information System (INIS)

    Pilati, T.; Bianchi, R.; Gramaccioli, C.M.

    1990-01-01

    As an example of extending harmonic lattice-dynamical procedures to silicates, the atomic thermal parameters for forsterite Mg 2 SiO 4 , an important constituent of earth's crust, have been calculated on this basis. For this purpose, Iishi's rigid-ion model was used, with slight modifications. Although such potentials were derived exclusively from fitting IR and Raman-active frequencies, the reproduction of the phonon-dispersion curves is good, and the calculation of thermodynamic functions such as entropy provides values which are near to calorimetric estimates. The calculated atomic thermal parameters are in good agreement with the experimental values reported by most authors. The calculations at various temperatures show the effect of zero-point motion very clearly: its contribution to temperature factors is about half of the total at room temperature. Bond-length corrections for thermal libration can be applied using the general-case formula: these amount to 0.003 A for the Si-O bonds at room temperature. Although the thermal parameters in the SiO 4 group fit a rigid-body model, the correction obtained using the Schomaker-Trueblood procedure gives a significantly different result: this is essentially due to the weak librational character of the motion of silicate groups in the structure. (orig.)

  11. Fabrication of hierarchical graphene@Fe3O4@SiO2@polyaniline quaternary composite and its improved electrochemical performance

    International Nuclear Information System (INIS)

    Wang, Lei; Zhu, Jianfeng; Yang, Haibo; Wang, Fen; Qin, Yi; Zhao, Ting; Zhang, Pei

    2015-01-01

    Highlights: • Graphene@Fe 3 O 4 @SiO 2 @polyaniline hierarchical structures have been fabricated. • The reflection loss of the composites is below −10 dB in 10.5–16.3 GHz. • The maximum absorption of the composites is −40.7 dB at 12.5 GHz. - Abstract: Hierarchical graphene@Fe 3 O 4 @SiO 2 @polyaniline quaternary composite is fabricated subtly. Their microwave absorption properties are also investigated in the 2–18 GHz frequency range. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) reveal that Fe 3 O 4 @SiO 2 @polyaniline core@shell@shell heteronanostructures are densely covered on the surfaces of graphene, and form hierarchical structures. Compared with two-dimensional binary nanocomposites of graphene@Fe 3 O 4 , the hierarchical structure exhibits enhanced EM absorption in terms of both the maximum reflection loss value and the absorption bandwidth. The maximum reflection loss value can reach −40.7 dB at 12.5 GHz with a thickness of 2.5 mm and the bandwidth corresponding to the reflection loss below −10 dB is 5.8 GHz (from 10.5 to 16.3 GHz)

  12. Site Occupancies, Luminescence, and Thermometric Properties of LiY9(SiO4)6O2:Ce3+ Phosphors.

    Science.gov (United States)

    Zhou, Weijie; Pan, Fengjuan; Zhou, Lei; Hou, Dejian; Huang, Yan; Tao, Ye; Liang, Hongbin

    2016-10-04

    In this work, we report the tunable emission properties of Ce 3+ in an apatite-type LiY 9 (SiO 4 ) 6 O 2 compound via adjusting the doping concentration or temperature. The occupancies of Ce 3+ ions at two different sites (Wyckoff 6h and 4f sites) in LiY 9 (SiO 4 ) 6 O 2 have been determined by Rietveld refinements. Two kinds of Ce 3+ f-d transitions have been studied in detail and then assigned to certain sites. The effects of temperature and doping concentration on Ce 3+ luminescence properties have been systematically investigated. It is found that the Ce 3+ ions prefer occupying Wyckoff 6h sites and the energy transfer between Ce 3+ at two sites becomes more efficient with an increase in doping concentration. In addition, the charge-transfer vibronic exciton (CTVE) induced by the existence of free oxygen ion plays an important role in the thermal quenching of Ce 3+ at 6h sites. Because of the tunable emissions from cyan to blue with increasing temperature, the phosphors LiY 9 (SiO 4 ) 6 O 2 :Ce 3+ are endowed with possible thermometric applications.

  13. Design Of A Bi-Functional α-Fe2O3/Zn2SiO4:Mn2+ By Layer-By-Layer Assembly Method

    Directory of Open Access Journals (Sweden)

    Yu Ri

    2015-06-01

    Full Text Available This work describes the design of bi-functional α-Fe2O3/Zn2SiO4:Mn2+ using a two-step coating process. We propose a combination of pigments (α-Fe2O3 and phosphor (Zn2SiO4:Mn2+ glaze which is assembled using a layer-by-layer method. A silica-coated α-Fe2O3 pigment was obtained by a sol-gel method and a Zn2+ precursor was then added to the silica-coated α-Fe2O3 to create a ZnO layer. Finally, the Zn2SiO4:Mn2+ layer was prepared with the addition of Mn2+ ions to serve as a phosphor precursor in the multi-coated α-Fe2O3, followed by annealing at a temperature above 1000°C. Details of the phase structure, color and optical properties of the multi-functional α-Fe2O3/Zn2SiO4:Mn2+ were characterized by transmission electron microscopy and X-ray diffraction analyses.

  14. Raman spectroscopy of garnet-group minerals

    Science.gov (United States)

    Mingsheng, P.; Mao, Ho-kwang; Dien, L.; Chao, E.C.T.

    1994-01-01

    The Raman spectra of the natural end members of the garnet-group minerals, which include pyrope, almandine and spessarite of Fe-Al garnet series and grossularite, andradite and uvarovite of Ca-Fe garnet series, have been studied. Measured Raman spectra of these minerals are reasonably and qualitatively assigned to the internal modes, translational and rotatory modes of SiO4 tetrahedra, as well as the translational motion of bivalent cations in the X site. The stretch and rotatory Alg modes for the Fe-Al garnet series show obvious Raman shifts as compared with those for the Ca-Fe garnet series, owing to the cations residing in the X site connected with SiO4 tetrahedra by sharing the two edges. The Raman shifts of all members within either of the series are attributed mainly to the properties of cations in the X site for the Fe-Al garnet series and in the Y site for the Ca-Fe garnet series. ?? 1994 Institute of Geochemistry, Chinese Academy of Sciences.

  15. Enstatite, Mg/sub 2/Si/sub 2/O/sub 6/: A neutron diffraction refinement of the crystal structure and a rigid-body analysis of the thermal vibration

    Energy Technology Data Exchange (ETDEWEB)

    Ghose, S.; Schomaker, V.; McMullan, R.K.

    1986-01-01

    Synthetic enstatite, Mg/sub 2/Si/sub 2/O/sub 6/, is orthorhombic, space group Pbca, with eight formula units per cell and lattice parameters a = 18.235(3), b = 8.818(1), c = 5.179(1) A at 23/sup 0/C. A least-squares structure refinement based on 1790 neutron intensity data converged with an agreement factor R(F/sup 2/) = 0.032, yielding Mg-O and Si-O bond lengths with standard deviations of 0.0007 and 0.0008 A, respectively. The variations observed in the Si-O bond lengths within the silicate tetrahedra A and B are caused by the differences in primary coordination of the oxygen atoms and the proximity of the magnesium ions to the silicon atoms. The latter effect is most pronounced for the bridging bonds of tetrahedron. A. The smallest O-Si-O angle is the result of edge-sharing by the Mg(2) octahedron and the A tetrahedron. An analysis of rigid-body thermal vibrations of the two crystallographically independent (SiO/sub 4/) tetrahedra indicates considerable librational motion, leading to a thermal correction of apparent Si-O bond lengths as large as +0.002 A at room temperature.

  16. Dehydration of glucose to 5-hydroxymethylfurfural by a core-shell Fe3O4@SiO2-SO3H magnetic nanoparticle catalyst

    Science.gov (United States)

    This paper discusses the potential use of (Fe3O4@SiO2-SO3H) nanoparticle catalyst for the dehydration of glucose into 5-hydroxymethylfurfural (HMF). A magnetically recoverable (Fe3O4@SiO2-SO3H) nanoparticle catalyst was successfully prepared by supporting sulfonic acid groups (SO3H) on the surface o...

  17. Physicochemical characterization of Fe3O4/SiO2/Au multilayer nanostructure

    International Nuclear Information System (INIS)

    Khosroshahi, Mohammad E.; Ghazanfari, Lida

    2012-01-01

    Highlights: ► The purpose of the research was to synthesize and characterize Fe 3 O 4 /SiO 2 /Au NPs. ► Uncoated MNPs showed an Ms range of 80–100 emu g −1 for particles between 35–96 nm. ► The magnetic NPs were modified with a thin layer of silica using Stober method. ► Small gold colloids (1–3 nm) were covered the amino functionalized particle surface. ► An absorption peak of 550 nm was obtained for a gold thickness of about 35 nm. - Abstract: The purpose of this research was to synthesize and characterize gold-coated Fe 3 O 4 /SiO 2 nanoshells for biomedical applications. Magnetite nanoparticles (NPs) were prepared using co-precipitation method. Smaller particles were synthesized by decreasing the NaOH concentration, which in our case this corresponded to 35 nm using 0.9 M of NaOH at 750 rpm with a specific surface area of 41 m 2 g −1 . For uncoated Fe 3 O 4 NPs, the results showed an octahedral geometry with saturation magnetization range of 80–100 emu g −1 and coercivity of 80–120 Oe for particles between 35 and 96 nm, respectively. The magnetic NPs were modified with a thin layer of silica using Stober method. Small gold colloids (1–3 nm) were synthesized using Duff method and covered the amino functionalized particle surface. Magnetic and optical properties of gold nanoshells were assessed using Brunauer–Emmett–Teller (BET), vibrating sample magnetometer (VSM), UV–Vis spectrophotometer, atomic and magnetic force microscope (AFM, MFM), and transmission electron microscope (TEM). Based on the X-ray diffraction (XRD) results, three main peaks of Au (1 1 1), (2 0 0) and (2 2 0) were identified. The formation of each layer of a nanoshell is also demonstrated by Fourier transform infrared (FTIR) results. The Fe 3 O 4 /SiO 2 /Au nanostructures, with 85 nm as particle size, exhibited an absorption peak at ∼550 nm with a magnetization value of 1.3 emu g −1 with a specific surface area of 71 m 2 g −1 .

  18. Wear Characteristics According of Heat Treatment of Si3N4 with Different Amounts of SiO2 Nano-Colloid

    International Nuclear Information System (INIS)

    Ahn, Seok Hwan; Nam, Ki Woo

    2014-01-01

    This study sintered Si 3 N 4 with different amounts of SiO 2 nano-colloid. The surface of a mirror-polished specimen was coated with SiO 2 nano-colloid, and cracks were healed when the specimen was treated at a temperature of 1273 K for 1 h in air. Wear specimen experiments were conducted after heat treatments for 10 min at 1073, 1273, and 1573 K. The heat-treated surface that was coated with the SiO 2 nano-colloid was slightly rougher than the noncoated surface. The oxidation state of the surface according to the heat treatment temperature showed no correlation with the surface roughness. Moreover, the friction coefficient, wear loss, and bending strength were not related to the surface roughness. Si 3 N 4 exhibited an abrasive wear behavior when SKD11 was used as an opponent material. The friction coefficient was proportional to the wear loss, and the bending strength was inversely proportional to the friction coefficient and wear loss. The friction coefficient and wear loss increased with increasing amounts of the SiO 2 nanocolloid. In addition, the friction coefficient was slightly increased by increasing the heat treatment temperature

  19. Crystallization behavior of (1 - x)Li2O.xNa2O.Al2O3.4SiO2 glasses

    International Nuclear Information System (INIS)

    Wang, Moo-Chin; Cheng, Chih-Wei; Chang, Kuo-Ming; Hsi, Chi-Shiung

    2010-01-01

    The crystallization behavior of the (1 - x)Li 2 O.xNa 2 O.Al 2 O 3 .4SiO 2 glasses has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron diffraction (ED) and energy dispersive spectroscopy (EDS). The crystalline phase was composed of β-spodumene. The isothermal crystallization kinetics of β-spodumene from the (1 - x)Li 2 O.xNa 2 O.Al 2 O 3 .4SiO 2 glasses has also been studied by a quantitative X-ray diffraction method. The activation energy of β-spodumene formation decreases from 359.2 to 317.8 kJ/mol when the Na 2 O content increases from 0 to 0.4 mol and it increases from 317.8 to 376.9 kJ/mol when the Na 2 O content increases from 0.4 to 0.6 mol. The surface nucleation and plate-like growth were dominant in the crystallization of the (1 - x)Li 2 O.xNa 2 O.Al 2 O 3 .4SiO 2 glasses.

  20. Two new ternary chalcogenides Ba{sub 2}ZnQ{sub 3} (Q = Se, Te) with chains of ZnQ{sub 4} tetrahedra. Syntheses, crystal structure, and optical and electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Jai; Beard, Jessica; Malliakas, Christos D.; Ibers, James A. [Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry; Mesbah, Adel [Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry; ICSM, UMR 5257 CEA/CNRS/UM2/ENSCM, Bagnols-sur-Ceze (France); Rocca, Dario; Lebegue, Sebastien [Univ. de Lorraine, Vandoeuvre-les-Nancy (France). Lab. de Cristallographie, Resonance Magnetique et Modelisations (CRM2, UMR CNRS 7036)

    2016-08-01

    Single crystals of Ba{sub 2}ZnQ{sub 3} (Q = Se, Te) were obtained by solid-state reactions at 1173 K. These isostructural compounds crystallize in the K{sub 2}AgI{sub 3} structure type. The Zn atoms in this structure are coordinated to four Q atoms (2 Q1, 1 Q2, 1 Q3) and these form a distorted tetrahedron around each Zn atom. Each ZnQ{sub 4} tetrahedron shares two corners with neighboring ZnQ{sub 4} tetrahedra resulting in the formation of infinite chains of [ZnQ{sub 4}{sup 4-}] units. The absorption spectrum of a single crystal of Ba{sub 2}ZnTe{sub 3} shows an absorption edge at 2.10(2) eV, consistent with the dark-red color of the crystals. From DFT calculations Ba{sub 2}ZnSe{sub 3} and Ba{sub 2}ZnTe{sub 3} are found to be semiconductors with electronic band gaps of 2.6 and 1.9 eV, respectively.

  1. Sol-Gel Synthesis and Luminescence of Green Light Emitting Phosphors Zn2SiO4/Mn2+

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Mn2+ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn2+ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precursor with strong green emission intensities is better than zinc acetate based precursor. The intensity of green light emission reaches a peak at 254 nm when the Mn2+ dopant concentration is about 5%( molar percentage). Structural details of the phosphors were examined through X-ray diffractometry, thermogravimetric and differential thermal analysis. The result indicates that they are both rhombohedral structures, which remain amorphous below 700 ℃and crystallize completely around 1 000℃. The luminescent properties of Zn2SiO4/Mn2+ phosphors were characterized by excitation and emission spectra.

  2. The oxidation of ReCl_5 with oleum: synthesis and crystal structure of Re_2O_4Cl_4(SO_4)

    International Nuclear Information System (INIS)

    Betke, Ulf; Wickleder, Mathias S.

    2012-01-01

    The reaction of ReCl_5 and fuming sulfuric acid (25 % SO_3) in a sealed glass tube at 200 C led to red, needle shaped single crystals of Re_2O_4Cl_4(SO_4) (monoclinic, C2/c, a = 1501.8(2) pm, b = 1545.9(2) pm, c = 945.18(8) pm, β = 98.761(9) , Z = 8). In the crystal structure the [ReO_2] moieties are linked by [SO_4]"2"- tetrahedra to chains along the [101] direction. Each sulfate ion connects four rhenium atoms, additional two chloride ions complete the octahedral coordination sphere of each rhenium atom according to "1_∞[ReO_2_/_1Cl_2_/_1(SO_4)_2_/_4]. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Deployment and future prospects of high performance diagnostics featuring serial I/O (SIO) data acquisition (DAQ) at ASDEX Upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Behler, K., E-mail: karl.behler@ipp.mpg.de [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching bei Muenchen (Germany); Blank, H.; Eixenberger, H. [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching bei Muenchen (Germany); Fitzek, M. [Unlimited Computer Systems GmbH, Seeshaupterstr. 15, D-82393 Iffeldorf (Germany); Lohs, A. [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching bei Muenchen (Germany); Lueddecke, K. [Unlimited Computer Systems GmbH, Seeshaupterstr. 15, D-82393 Iffeldorf (Germany); Merkel, R. [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 2, D-85748 Garching bei Muenchen (Germany)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer The high sustained data rates transferring measured data from periphery into memory of computers. Black-Right-Pointing-Pointer The achieved low latency in real-time interrupt handling under Solaris 10. Black-Right-Pointing-Pointer The new prototype of an even more powerful 2nd generation SIO II device. Black-Right-Pointing-Pointer The fusion of all blocks of board logic (serializer, FIFO, TDC, merge engine, PCIe controller) into one single FPGA simplifying the boards physical layout significantly. - Abstract: The SIO DAQ concept used at the ASDEX Upgrade fusion experiment features data acquisition from a modular front-end (a modular crate-and-interface-cards concept for analog and digital input and output) over standardized serial lines and via a serial input/output computer interface card (the SIO card) in real-time directly into the main memory of a host computer. Deployment of a series of diagnostics using SIO led to various solutions and configurations for the different requirements. Experience has been gained and lessons learned applying the SIO concept at its technical limits. Requirements for a further development of the SIO concept have been identified, and a performance improvement by a factor of 4-8 beyond its current limits seems achievable. An effort has been started to develop a SIO version 2 (SIO II) featuring upgraded serial links and a more powerful FPGA for merging and forwarding data streams to host computer memory. (Compatibility with the existing SIO (SIO I) front-end system has to be maintained.) This paper presents results achieved and experiences gained in the deployment of SIO I, the status of SIO II development (currently in the prototype phase), and projected enhancements and updates to existing implementations.

  4. Oxalate molecule as the trap for gamma-irradiation energy in the amorphous aluminosilicate Al2(OH)6H4SiO4

    International Nuclear Information System (INIS)

    Nothig-Laslo, V.; Horvath, L.; Bilinski, H.

    1990-01-01

    Paramagnetic species which were the products of gamma irradiation at 77 K and at room temperature were studied by ESR spectroscopy in the amorphous aluminosilicate, Al2(OH)6H4SiO4, prepared in the presence and in the absence of oxalate ion. The aluminosilicate precipitated from the solution containing the oxalate ion in 10(-4) mol dm-3 concentration contained the oxalate only in trace amounts. When gamma-irradiated at 77 K and at room temperature, this compound gave the stable paramagnetic species represented by the single ESR line centered at g = 2.000. We ascribe this spectrum to the CO2- radical formed from the oxalate ion. The same aluminosilicate prepared in the absence of the oxalate either produced no stable paramagnetic product after gamma irradiation at room temperature or resulted in composite ESR spectra, indicating the presence of several paramagnetic species if irradiated at 77 K. Complex ESR spectra were transformed by heating to the stable paramagnetic centers which differed from the one obtained from oxalate ion. We conclude that in Al2(OH)6H4SiO4 oxalate acts as a trap for the gamma-radiation energy

  5. Phase formation in the Li2MoO4–Rb2MoO4–Fe2(MoO4)3 system and crystal structure of a novel triple molybdate LiRb2Fe(MoO4)3

    International Nuclear Information System (INIS)

    Khal'baeva, Klara M.; Solodovnikov, Sergey F.; Khaikina, Elena G.; Kadyrova, Yuliya M.; Solodovnikova, Zoya A.; Basovich, Olga M.

    2013-01-01

    X-ray investigation of solid state interaction of the components in the Li 2 MoO 4 –Rb 2 MoO 4 –Fe 2 (MoO 4 ) 3 system was carried out, and a subsolidus phase diagram of the said system was constructed. The subsystem Rb 2 MoO 4 –LiRbMoO 4 –RbFe(MoO 4 ) 2 was shown to be non-quasiternary. Formation of a novel triple molybdate LiRb 2 Fe(MoO 4 ) 3 was established, conditions of solid state synthesis and crystallization of the compound were found. Its crystal structure (orthorhombic, space group Pnma, Z=4, a=24.3956(6), b=5.8306(1), c=8.4368(2) Å) represents a new structure type and includes infinite two-row ribbons ([Fe(MoO 4 ) 3 ] 3− ) ∞ parallel to the b axis and composed of FeO 6 octahedra, terminal Mo(3)O 4 tetrahedra, and bridge Mo(1)O 4 and Mo(2)O 4 tetrahedra connecting two or three FeO 6 octahedra. The ribbons are connected to form 3D framework via corner-sharing LiO 4 tetrahedra. Rubidium cations are 11- and 13-coordinated and located in cavities of this heterogeneous polyhedral framework. - Graphical abstract: Exploring the Li 2 MoO 4 –Rb 2 MoO 4 –Fe 2 (MoO 4 ) 3 system showed its partial non-quasiternarity and revealed a new compound LiRb 2 Fe(MoO 4 ) 3 which was structurally studied. - Highlights: • The Li 2 MoO 4 –Rb 2 MoO 4 –Fe 2 (MoO 4 ) 3 system study revealed a new compound LiRb 2 Fe(MoO 4 ) 3 . • Its structure of a new type includes ribbons of FeO 6 octahedra and MoO 4 tetrahedra. • The ribbons are connected into a 3D framework via corner-sharing LiO 4 tetrahedra

  6. Red, Green, and Blue Photoluminescence of Ba2SiO4:M (M = Eu3+, Eu2+, Sr2+ Nanophosphors

    Directory of Open Access Journals (Sweden)

    Claudia Wickleder

    2013-07-01

    Full Text Available Divalent europium doped barium orthosilicate is a very important phosphor for the production of light emitting diodes (LEDs, generally associated to the green emission color of micron-sized crystals synthesized by means of solid-state reactions. This work presents the combustion synthesis as an energy and time-saving preparation method for very small nano-sized Ba2SiO4 particles, flexibly doped to acquire different emission energies. The size of the resulting spherical nanoparticles (NPs of the green emitting Ba2SiO4:Eu2+ was estimated to about 35 nm applying the Scherrer equation and further characterized with aid of atomic force microscopy (AFM as well as scanning electron microscopy (SEM. This phosphor is able to build homogeneous luminescent suspensions and was successfully down-sized without changing the optical properties in comparison to the bulk phosphors. Besides the X-ray diffraction (XRD analysis and the different types of microscopy, the samples were characterized by luminescence spectroscopy. Undoped Ba2SiO4 NPs are not luminescent, but show characteristic red emission of the 5D0 → 7FJ (J = 0–4 electronic transitions when doped with Eu3+ ions. Moreover, these orthosilicate nanoparticles generate blue light at low temperatures due to impurity-trapped excitons, introduced by the partial substitution of the Ba2+ with Sr2+ ions in the Ba2SiO4 lattice causing a substantial distortion. A model for the temperature behavior of the defect luminescence as well as for their nature is provided, based on temperature-dependent luminescence spectra and lifetime measurements.

  7. Sustainable synthesis of magnetically separable SiO2/Co@Fe2O4 nanocomposite and its catalytic applications for the benzimidazole synthesis

    Science.gov (United States)

    Jithendra Kumara, K. S.; Krishnamurthy, G.; Sunil Kumar, N.; Naik, Nagaraja; Praveen, T. M.

    2018-04-01

    The Co(II) and Fe(III) centres magnetically separable two new mesoporous nanocatalyst were synthesised via chemical synthesis method. The transmission electron microscopic studies (TEM) show that, the particles are spherical shape with mean size of 20 nm. The Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) reveals that SiO2 is coating on the surface of the cobalt ferrate nanoparticle (CoFe2O4). The SiO2 coating is efficiently preventing the aggregated collision of nanoparticles. Magnetic measurements show that diamagnetic character of the SiO2 is unaffected to the coercivity of SiO2 coated CoFe2O4 particles. In addition, these nanoparticles are used as nanocatalyst for high yielding, facile and expeditious synthesis of various functionalized 2-arylbenzimidazoles via one-pot condensation. The cascade including imine formation, cyclization, condensation, and aromatization occurs, without addition of any reducing or oxidizing agents. In all situations, the desired product was synthesised with excellent yield. The shorter reaction time, mild reaction condition, simplicity, non-toxicity, safe reaction and easy workup are the impotent merits of this protocol.

  8. Synthesis and crystal structure of Bi6.4Pb0.6P2O15.2

    International Nuclear Information System (INIS)

    Arumugam, N.; Lynch, V.; Steinfink, H.

    2007-01-01

    Bi 6.4 Pb 0.6 P 2 O 15.2 is a polymorph of structures with the general stoichiometry Bi 6+x M 1-x P 2 O 15+y . However, unlike previously published structures that consist of layers formed by edge sharing OBi 4 tetrahedra bridged by PO 4 and TO 6 (T=transition metal) tetrahedra and octahedra the title compound's structure is more complex. It is monoclinic, C2, a=19.4698(4) A, b=11.3692(3) A, c=16.3809(5) A, β=101.167(1) o , Z=10. Single-crystal X-ray diffraction data were refined by least squares on F 2 converging to R 1 =0.0387, wR 2 =0.0836 for 7023 intensities. The crystal twins by mirror reflection across (001) as the twin plane and twin component 1 equals 0.74(1). Oxygen ions are in tetrahedral coordination to four metal ions and the O(BiPb) 4 units share corners to form layers that are part of the three-dimensional framework. Eight oxygen ions form a cube around the two crystallographically independent Pb ions. Pb-O bond lengths vary from 2.265(14) to 2.869(14) A. Pairs of such cubes share an edge to form a Pb 3 O 20 unit. The two oxygen ions from the unshared edges are part of irregular Bi polyhedra. Other oxygen ions of Bi polyhedra are part only of O(BiPb) 4 units, and some oxygen ions of the polyhedra are also part of PO 4 tetrahedra. One, two, three and or four PO 4 moieties are connected to the Bi polyhedra. Bi-O bond lengths ≤3.1 A vary from 2.090(12) to 3.07(3) A. The articulations of Pb cubes, Bi polyhedra and PO 4 tetrahedra link into the three-dimensional structure. - Graphical abstract: View of the structure of Bi 6.4 Pb 0.6 P 2 O 15.2 parallel to the b-axis

  9. Fe3O4@SiO2@CS-TETA functionalized graphene oxide for the adsorption of methylene blue (MB) and Cu(II)

    Science.gov (United States)

    Wang, Fan; Zhang, Lijuan; Wang, Yeying; Liu, Xijian; Rohani, Sohrab; Lu, Jie

    2017-10-01

    The graphene oxide (GO) functionalized by Fe3O4@SiO2@CS-TETA nanoparticles, Fe3O4@SiO2@CS-TETA-GO, was firstly fabricated in a mild way as a novel adsorbent for the removal of Cu(II) ions and methylene blue (MB) from aqueous solutions. The magnetic composites showed a good dispersity in water and can be conveniently collected for reuse through magnetic separation due to its excellent magnetism. When the Fe3O4@SiO2@CS- TETA-GO was used as an absorbent for the absorption of MB and Cu(II), the adsorption kinetics and isotherms data well fitted the pseudo-second-order model and the Langmuir model, respectively. Under the optimized pH and initial concentration, the maximum adsorption capacity was about 529.1 mg g-1 for MB in 20 min and 324.7 mg g-1 for Cu(II) in 16 min, respectively, exhibiting a better adsorption performance than other GO-based adsorbents reported recently. More importantly, the synthesized adsorbent could be effectively regenerated and repeatedly utilized without significant capacity loss after six times cycles. All the results demonstrated that Fe3O4@SiO2@CS-TETA-GO could be used as an excellent adsorbent for the adsorption of Cu(II) and MB in many fields.

  10. The collapse of stacking-fault tetrahedra by interaction with gliding dislocations

    International Nuclear Information System (INIS)

    Matsukawa, Y.; Osetsky, Yu.N.; Stoller, R.E.; Zinkle, S.J.

    2005-01-01

    The collapse of stacking-fault tetrahedra (SFT) by gliding dislocations was observed in in situ straining experiments in a transmission electron microscope (TEM). A stacking-fault tetrahedron was collapsed by intersection with a gliding perfect dislocation: only the base portion divided by the gliding plane of the dislocation annihilated, while the apex portion remained intact. As a result of analysis on evolution of atom configuration induced by intersection with perfect dislocation in SFT, it was found that an unusual atom configuration inevitably appeared in one of the ledges formed on stacking-fault planes, which is traditionally called I-ledge: the atoms on adjacent (1 1 1) planes were overlapping each other. The overlapping configuration provides a strong repulsive force, being a conceivable driving force to induce a chain reaction of atom displacements that collapses the SFT base portion

  11. Incorporation of the Fe3O4 and SiO2 nanoparticles in epoxy-modified silicone resin as the coating for soft magnetic composites with enhanced performance

    Science.gov (United States)

    Luo, Dahao; Wu, Chen; Yan, Mi

    2018-04-01

    Three inorganic-organic hybrids have been designed by incorporating epoxy-modified silicone resin (ESR) with SiO2, Fe3O4 and their mixture in the application as the coating of Fe soft magnetic composites (SMCs). The introduced SiO2 nanoparticles are well dispersed in the ESR, while the Fe3O4 tends to agglomerate or even separate from the ESR. Simultaneous addition of the SiO2 and Fe3O4 gives rise to satisfactory distribution of both nanoparticles and optimized magnetic performance of the SMCs with high permeability (124.6) and low loss (807.8 mW/cm3). On one hand, introduction of the ferromagnetic Fe3O4 reduces the magnetic dilution effect, which is beneficial for improved magnetization and permeability. On the other hand, SiO2 incorporation prevents the agglomeration of the Fe3O4 nanoparticles and gives rise to increased electrical resistivity for reduced core loss as well as enhanced mechanical strength of the SMCs.

  12. Photoluminescence and scintillation properties of Ce-doped Sr2(Gd1-xLux)8(SiO4)6O2 (x = 0.1, 0.2, 0.4, 0.5, 0.6) crystals

    Science.gov (United States)

    Igashira, Takuya; Kawano, Naoki; Okada, Go; Kawaguchi, Noriaki; Yanagida, Takayuki

    2018-05-01

    Apatite crystals with chemical compositions of 0.5% Ce-doped Sr2(Gd1-xLux)8(SiO4)6O2 (x = 0.1, 0.2, 0.4, 0.5, 0.6) were synthesized by the Floating Zone method, and then we evaluated their photoluminescence (PL) and scintillation properties. All the Ce-doped samples exhibited PL and scintillation with an intense broad emission in 400-550 nm in which the origin was attributed to the 5d-4f transition of Ce3+, and the emission peak became broader with increasing the concentration of Lu3+. Both PL and scintillation decay time profiles were best-approximated by a sum of two exponential decay functions, and the origin of slower component was attributed to the 5d-4f transition of Ce3+. In the X-ray induced afterglow measurements, the Ce-doped Sr2(Gd0.4Lu0.6)8(SiO4)6O2 sample exhibited the lowest afterglow level. Furthermore, the Ce-doped Sr2(Gd0.5Lu0.5)8(SiO4)6O2 and Sr2(Gd0.4Lu0.6)8(SiO4)6O2 samples showed a clear full energy deposited peak under 5.5 MeV 241Am α-ray irradiation, and the estimated absolute scintillation light yields were around 290 and 1300 ph/5.5 MeV-α, respectively.

  13. Efficient one-pot sonochemical synthesis of thickness-controlled silica-coated superparamagnetic iron oxide (Fe3O4/SiO2) nanospheres

    Science.gov (United States)

    Abbas, Mohamed; Abdel-Hamed, M. O.; Chen, Jiangang

    2017-12-01

    A facile and eco-friendly efficient sonochemical approach was designed for the synthesis of highly crystalline Fe3O4 and Fe3O4/SiO2 core/shell nanospheres in single reaction. The generated physical properties (shock waves, microjets, and turbulent flows) from ultrasonication as a consequence of the collapse of microbubbles and polyvinylpyrrolidone (PVP) as a chemical linker were found to play a crucial role in the successful formation of the core/shell NPs within short time than the previously reported methods. Transmission electron microscopy revealed that a uniform SiO2 shell is successfully coated over Fe3O4 nanospheres, and the thickness of the silica shell could be easily controlled in the range from 5 to 15 nm by adjusting the reaction parameters. X-ray diffraction data were employed to confirm the formation of highly crystalline and pure phase of a cubic inverse spinel structure for magnetite (Fe3O4) nanospheres. The magnetic properties of the as-synthesized Fe3O4 and Fe3O4/SiO2 core/shell nanospheres were measured at room temperature using vibrating sample magnetometer, and the results demonstrated a high magnetic moment values with superparamagnetic properties.

  14. Toluene and chlorobenzene dinitration over solid H3PO4/MoO3/SiO2 catalyst

    International Nuclear Information System (INIS)

    Adamiak, Joanna; Kalinowska-Alichnewicz, Dorota; Szadkowski, Michal; Skupinski, Wincenty

    2011-01-01

    Highlights: → A novel catalyst H 3 PO 4 /MoO 3 /SiO 2 was characterized and used in nitration. → On the surface domains of phosphomolybdic acid (HPM) are obtained. → Dinitrotoluene is obtained with very high yield i.e. 96 wt.% in mild conditions. → Dinitrochlorobenzene is obtained with only twelve-fold excess of nitric acid. → It is sulfuric acid free and solvent free nitration of aromatic compounds. - Abstract: A new catalyst, H 3 PO 4 /MoO 3 /SiO 2 , was prepared by modification of MoO 3 /SiO 2 using phosphoric acid. The characterization of the catalyst was performed using Infrared and Raman Spectroscopy, potentiometric titration and nitrogen adsorption-desorption methods. Molybdenum oxides were identified along with phosphomolybdic acid and polymolybdates on the modified surface. The suitability of the catalysts for toluene and chlorobenzene nitration in continuous process was examined. Toluene is effectively nitrated to dinitrotoluene (DNT) in one-stage process (96 wt.% of DNT in the product) and in mild conditions i.e. at room temperature and only with ten-fold excess of nitric acid. In chlorobenzene nitration only twelve-fold excess of nitric acid is needed to obtain as high yield as 95 wt.%. Most importantly, the novel catalysts we have developed, provide the opportunity for sulfuric acid- free nitration of aromatic compounds.

  15. Luminescence enhancement of (Sr1-x Mx )2 SiO4 :Eu2+ phosphors with M (Ca2+ /Zn2+ ) partial substitution for white light-emitting diodes.

    Science.gov (United States)

    Wang, Yulong; Zhang, Wentao; Gao, Yang; Long, Jianping; Li, Junfeng

    2017-02-01

    Eu 2 + -doped Sr 2 SiO 4 phosphor with Ca 2 + /Zn 2 + substitution, (Sr 1-x M x ) 2 SiO 4 :Eu 2 + (M = Ca, Zn), was prepared using a high-temperature solid-state reaction method. The structure and luminescence properties of Ca 2 + /Zn 2 + partially substituted Sr 2 SiO 4 :Eu 2 + phosphors were investigated in detail. With Ca 2 + or Zn 2 + added to the silicate host, the crystal phase could be transformed between the α-form and the β-form of the Sr 2 SiO 4 structure. Under UV excitation at 367 nm, all samples exhibit a broad band emission from 420 to 680 nm due to the 4f 6 5d 1  → 4f 7 transition of Eu 2 + ions. The broad emission band consists of two peaks at 482 and 547 nm, which correspond to Eu 2 + ions occupying the ten-fold oxygen-coordinated Sr.(I) site and the nine-fold oxygen-coordinated Sr.(II) site, respectively. The luminescence properties, including the intensity and lifetime of Sr 2 SiO 4 :Eu 2 + phosphors, improved remarkably on Ca 2 + /Zn 2 + addition, and promote its application in white light-emitting diodes. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  16. Effects of Na2WO4 and Na2SiO3 additives in electrolytes on microstructure and properties of PEO coatings on Q235 carbon steel

    International Nuclear Information System (INIS)

    Wang Yunlong; Jiang Zhaohua; Yao Zhongping

    2009-01-01

    Ceramic coatings were achieved on Q235 carbon steel by plasma electrolytic oxidation in aluminate system with and without Na 2 WO 4 and Na 2 SiO 3 additives in electrolyte. Influence of Na 2 WO 4 and Na 2 SiO 3 on surface morphology, phase and elemental composition of PEO coatings were examined by means of scanning electron microscope (SEM), thin-film X-ray diffraction (TF-XRD) and energy dispersive X-ray spectroscopy (EDS). Effects of the two additives on the properties of the coatings including surface roughness, surface micro hardness and friction coefficient were studied. The results showed that W from Na 2 WO 4 and Si from Na 2 SiO 3 in electrolytes entered into the coatings. Na 2 WO 4 additive had no evident effect on phase composition of the coating, while Na 2 SiO 3 additive resulted in the coating changing from crystalline state to amorphous state and increased the content of P in the coating. Both additives reduced the surface roughness of the coatings. With Na 2 WO 4 or Na 2 SiO 3 into the electrolytes, the surface micro hardness of the coating was enhanced to 1433 and 1478, respectively, and the friction coefficients were also decreased to below 0.1.

  17. Synthesis and Characterization of V2O5/SiO2 Nanoparticles as Efficient Catalyst for Aromatization 1,4 Dihydropyridines

    International Nuclear Information System (INIS)

    Farzaneh, F.; Zamanifar, E.; Jafari Foruzin, L.; Ghandi, M.

    2012-01-01

    V 2 O 5 /SiO 2 nanoparticles was prepared via an one-pot sol gel method from vanadyl- acetylacetonate and tetraethyl orthosilicate in refluxing MeOH, followed by calcination at 700 °C for 2 hours. The resultant nanoparticles was characterized by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction, TGA and FTIR techniques. Rapid and efficient aromatization of 1,4-dihydropyridines catalyzed by V 2 O 5 /SiO 2 nanoparticles is described in this presentation.

  18. Preparation and Characterization of SiO2/SiCN Core-shell Ceramic Microspheres

    Directory of Open Access Journals (Sweden)

    ZHANG Hai-yuan

    2017-05-01

    Full Text Available The SiO2/PSN core-shell microspheres were prepared via an emulsion reaction combined with the polymer-derived ceramics (PDCs method using polysilazane (PSN in situ polymerization on the surface of SiO2 modified by silane coupling agents MPS, followed by pyrolysis process to obtain SiO2/SiCN core-shell ceramic microspheres. The effects of raw mass ratio, curing time and pyrolysis temperature on the formation and the morphology of core-shell microspheres were studied. The morphology, chemical composition and phase transformation were characterized by SEM, EDS, TEM, FT-IR and XRD. The results show that after reaction for 4h at 200℃, SiO2 completely coated PSN forms a core-shell microsphere with rough surface when the mass ratio of SiO2 and PSN is 1:4; when pyrolysis temperature is at 800-1200℃, amorphous SiO2/SiCN core-shell ceramic microspheres are prepared; at 1400℃, the amorphous phase partially crystallizes to produce SiO2, SiC and Si3N4 phase.

  19. Band alignment of atomic layer deposited SiO2 and HfSiO4 with (\\bar{2}01) β-Ga2O3

    Science.gov (United States)

    Carey, Patrick H., IV; Ren, Fan; Hays, David C.; Gila, Brent P.; Pearton, Stephen J.; Jang, Soohwan; Kuramata, Akito

    2017-07-01

    The valence band offset at both SiO2/β-Ga2O3 and HfSiO4/β-Ga2O3 heterointerfaces was measured using X-ray photoelectron spectroscopy. Both dielectrics were deposited by atomic layer deposition (ALD) onto single-crystal β-Ga2O3. The bandgaps of the materials were determined by reflection electron energy loss spectroscopy as 4.6 eV for Ga2O3, 8.7 eV for Al2O3 and 7.0 eV for HfSiO4. The valence band offset was determined to be 1.23 ± 0.20 eV (straddling gap, type I alignment) for ALD SiO2 on β-Ga2O3 and 0.02 ± 0.003 eV (also type I alignment) for HfSiO4. The respective conduction band offsets were 2.87 ± 0.70 eV for ALD SiO2 and 2.38 ± 0.50 eV for HfSiO4, respectively.

  20. Structural aspects of B2O3-substituted (PbO)0.5(SiO2)0.5 glasses

    International Nuclear Information System (INIS)

    Sudarsan, V.; Kulshreshtha, S.K.; Shrikhande, V.K.; Kothiyal, G.P.

    2002-01-01

    Lead borosilicate glasses having general formulae (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x with 0.0≤x≤0.4 and (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y with 0.0≤y≤0.5 have been prepared by a conventional melt-quench method and characterized by 29 Si, 11 B magic angle spinning (MAS) NMR techniques and infrared spectroscopy, as regards their structural features. From 29 Si NMR results, it has been inferred that with increasing concentration of boron oxide, (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 )x glasses exhibit a systematic increase in the number of Q 4 structural units of Si at the expense of Q 2 structural units, along with the formation of Si-O-B linkages. On the other hand, for (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y glasses, there is no direct interaction between SiO 2 and B 2 O 3 in the glass network, as revealed by the 29 Si MAS NMR studies. Boron exists in both trigonal and tetrahedral configurations for these two series of glasses and for the (PbO) 0.5 (SiO 2 ) 0.5-y (B 2 O 3 ) y series of glasses; the relative concentration of these two structural units remains almost constant with increasing B 2 O 3 concentration. In contrast, for (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x glasses, there is a slight increase in the number of BO 3 structural units above x = 0.2, as there is a competition between SiO 2 and B 2 O 3 for interaction with Pb 2+ , thereby leading to the formation of BO 3 structural units. For both series of glasses, the thermal expansion coefficient is found to decrease with increasing B 2 O 3 concentration, the effect being more pronounced for the (PbO) 0.5-x (SiO 2 ) 0.5 (B 2 O 3 ) x series of glasses due to the increased concentration of Q 4 structural units of silicon and better cross-linking as a result of the formation of Si-O-B-type linkages. (author)

  1. Magnetic interactions in high-energy ball-milled NiZnFe2O4/SiO2 composites

    International Nuclear Information System (INIS)

    Pozo Lopez, G.; Silvetti, S.P.; Urreta, S.E.; Cabanillas, E.D.

    2007-01-01

    Composites Ni 0.5 Zn 0.5 Fe 2 O 4 /SiO 2 are obtained after high-energy ball milling precursor oxides, in stoichiometric proportions, for 200 h at room temperature and further isothermal annealing for 1 h at 1273 K, under air and argon atmosphere, respectively. After 200 h grinding, a complex microstructure develops with small hematite crystals mixed with SiO 2 and remanent NiO and ZnO particles, and very small NiZn ferrite clusters, reaching a mean size of ∼9 nm. The high temperature treatments remove the hematite grains from the powder and promote the growth of NiZn ferrite grains to reach mean sizes nearly ∼20 nm. For treatments in oxidizing atmospheres, the major phases are SiO 2 and NiZn ferrite, while for annealing in Ar a new phase appears, fayalite, which is paramagnetic at room temperature. The M-H loops are all well described by the sum of a ferromagnetic and a superparamagnetic-like contribution. The observed properties are interpreted considering the different magnetic phases obtained, their crystal sizes and their mutual interactions

  2. Tritium breeding optimization of Li4SiO4/Be/He/SS blankets for the NET

    International Nuclear Information System (INIS)

    Greenspan, E.; Karni, Y.

    1986-01-01

    In previous tritium breeding optimization studies, we considered idealized, machine-independent blankets. The purpose of the present work is to investigate possibilities for maximizing tritium production in more realistic blankets. The Li 4 /SiO 4 /Be/He/SS blanket recently designed for the Next European Torus (NET) is used as the reference. The one-dimensional tritium breeding ratio calculated for this blanket is 1.38, promising tritium self-sufficiency even when the NET blanket is expected to have a coverage efficiency of 80%. A specific goal of the present study is to determine whether a NET-like device could be designed to be tritium self-sufficient when tritium production is limited to the outer blanket. If realizable, it might be possible to simplify the reactor design, significantly, make it more compact, and lower the cost

  3. Revising the Subsystem Nurse’s A-Phase-Silicocarnotite within the System Ca3(PO42–Ca2SiO4

    Directory of Open Access Journals (Sweden)

    Patricia Ros-Tárraga

    2016-04-01

    Full Text Available The subsystem Nurse’s A-phase-silicocarnotite within the system Ca3(PO42–Ca2SiO4 was conducted as a preliminary step toward obtaining new biomaterials with controlled microstructures. Phase composition of the resulting ceramics was studied by X-ray diffraction, differential thermal analysis, and scanning electron microscopy with attached wavelength dispersive spectroscopy. The results showed that the sub-system presents an invariant eutectoid point at 1366 ± 4 °C with a composition of 59.5 wt % Ca3(PO42 and 40.5 wt % Ca2SiO4, and typical eutectoid microstructure of lamellae morphology. These results are in disagreement with the previous reported data, which locate the invariant eutectoid point at 1250 ± 20 °C with a composition of 55 wt % Ca3(PO42 and 45 wt % Ca2SiO4. In addition, cell attachment testing showed that the new eutectoid material supported the mesenchymal stem cell adhesion and spreading, and the cells established close contact with the ceramic after 28 days of culture. These findings indicate that the new ceramic material with eutectoid microstructure of lamellae morphology possesses good bioactivity and biocompatibility and might be a promising bone implant material.

  4. PECVD SiO2 dielectric for niobium Josephson IC process

    International Nuclear Information System (INIS)

    Lee, S.Y.; Nandakumar, V.; Murdock, B.; Hebert, D.

    1991-01-01

    PECVD SiO 2 dielectric has been evaluated as an insulator for a Nb-based, all-refractory Josephson integrated circuit process. First, the properties of PECVD SiO 2 films were measured and compared with those of evaporated SiO films. Second, the PECVD SiO 2 dielectric film was used in our Nb-based Josephson integrated circuit process. The main problem was found to be the deterioration of the critical temperature of the superconducting niobium adjacent to the SiO 2 . The cause and a solution of the problem were investigated. Finally, a Josephson integrated sampler circuit was fabricated and tested. This paper shows acceptable junction I-V characteristics and a measured time resolution of a 4.9 ps pulse in liquid helium

  5. Constructing Fluorine-Free and Cost-Effective Superhydrophobic Surface with Normal-Alcohol-Modified Hydrophobic SiO2 Nanoparticles.

    Science.gov (United States)

    Ye, Hui; Zhu, Liqun; Li, Weiping; Liu, Huicong; Chen, Haining

    2017-01-11

    Superhydrophobic coatings have drawn much attention in recent years for their wide potential applications. However, a simple, cost-effective, and environmentally friendly approach is still lacked. Herein, a promising approach using nonhazardous chemicals was proposed, in which multiple hydrophobic functionalized silica nanoparticles (SiO 2 NPs) were first prepared as core component, through the efficient reaction between amino group containing SiO 2 NPs and the isocyanate containing hydrophobic surface modifiers synthesized by normal alcohols, followed by simply spraying onto various substrates for superhydrophobic functionalization. Furthermore, to further improve the mechanical durability, an organic-inorganic composite superhydrophobic coating was fabricated by incorporating cross-linking agent (polyisocyanate) into the mixture of hydrophobic-functionalized SiO 2 NPs and hydroxyl acrylic resin. The hybrid coating with cross-linked network structures is very stable with excellent mechanical durability, self-cleaning property and corrosion resistance.

  6. Stability analysis of SiO2/SiC multilayer coatings

    International Nuclear Information System (INIS)

    Fu Zhiqiang; Jean-Charles, R.

    2006-01-01

    The stability behaviours of SiC coatings and SiO 2 /SiC coatings in helium with little impurities are studied by HSC Chemistry 4.1, the software for analysis of Chemical reaction and equilibrium in multi-component complex system. It is found that in helium with a low partial pressure of oxidative impurities under different total pressure, the key influence factor controlling T cp of SiC depends is the partial pressure of oxidative impurities; T cp of SiC increases with the partial pressure of oxidative impurities. In helium with a low partial pressure of different impurities, the key influence factor of T cs of SiO 2 are both the partial pressure of impurities and the amount of impurities for l mol SiO 2 ; T cs of SiO 2 increases with the partial pressure of oxidative impurities at the same amount of the impurities for 1 mol SiO 2 while it decreases with the amount of the impurities for 1 mm SiO 2 at the same partial pressure of the impurities. The influence of other impurities on T cp of SiC in He-O 2 is studied and it is found that CO 2 , H 2 O and N-2 increase T cp of SiC in He-O 2 while H 2 , CO and CH 4 decrease T cp of SiC He-O 2 . When there exist both oxidative impurities and reductive impurities, their effect on T cs of SiO 2 can be suppressed by the other. In HTR-10 operation atmosphere, SiO 2 /SiC coatings can keep stable status at higher temperature than SiC coatings, so SiO 2 /SiC coatings is more suitable to improve the oxidation resistance of graphite in HTR-10 operation atmosphere compared with SiC coatings. (authors)

  7. Local structure of Rb2Li4(SeO4)3·2H2O by the modeling of X-ray diffuse scattering — from average-structure to microdomain model

    International Nuclear Information System (INIS)

    Komornicka, Dorota; Wołcyrz, Marek; Pietraszko, Adam

    2012-01-01

    Local structure of dirubidium tetralithium tris(selenate(VI)) dihydrate — Rb 2 Li 4 (SeO 4 ) 3 · 2H 2 O has been determined basing on the modeling of X-ray diffuse scattering. The origin of observed structured diffuse streaks is SeO 4 tetrahedra switching between two alternative positions in two quasi-planar layers existing in each unit cell and formation of domains with specific SeO 4 tetrahedra configuration locally fulfilling condition for C-centering in the 2a×2b×c superstructure cell. The local structure solution is characterized by a uniform distribution of rather large domains (ca. thousand of unit cells) in two layers, but also monodomains can be taken into account. Inside a single domain SeO 4 tetrahedra are ordered along ab-diagonal forming two-string ribbons. Inside the ribbons SeO 4 and LiO 4 tetrahedra share the oxygen corners, whereas ribbons are bound to each other by a net of hydrogen bonds and fastened by corner sharing SeO 4 tetrahedra of the neighboring layers. - Graphical abstract: Experimental sections of the reciprocal space showing diffraction effects observed for RLSO. Bragg spots are visible on sections with integer indices (1 kl section — on the left), streaks — on sections with fractional ones (1.5 kl section — on the right). At the center: resulting local structure of the A package modeled as a microdomain: two-string ribbons of ordered oxygen-corners-sharing SeO 4 and LiO 4 terahedra extended along ab-diagonal are seen; ribbons are bound by hydrogen bonds (shown in pink); the multiplied 2a×2b unit cell is shown. Highlights: ► X-ray diffuse scattering in RLSO was registered and modeled. ► The origin of diffuse streaks is SeO 4 tetrahedra switching in two structure layers. ► The local structure is characterized by a uniform distribution of microdomains. ► Inside a single domain SeO 4 tetrahedra are ordered along ab-diagonal forming ribbons. ► The ribbons are bound to each other by a net of hydrogen bonds.

  8. Role of the interface region on the optoelectronic properties of silicon nanocrystals embedded in SiO2

    International Nuclear Information System (INIS)

    Daldosso, N.; Dalba, G.; Fornasini, P.; Grisenti, R.; Pavesi, L.; Luppi, M.; Magri, R.; Ossicini, S.; Degoli, E.; Rocca, F.; Boninelli, S.; Priolo, F.; Spinella, C.; Iacona, F.

    2003-01-01

    Light-emitting silicon nanocrystals embedded in SiO 2 have been investigated by x-ray absorption measurements in total electron and photoluminescence yields, by energy filtered transmission electron microscopy and by ab initio total energy calculations. Both experimental and theoretical results show that the interface between the silicon nanocrystals and the surrounding SiO 2 is not sharp: an intermediate region of amorphous nature and variable composition links the crystalline Si with the amorphous stoichiometric SiO 2 . This region plays an active role in the light-emission process

  9. Angular dependence of the redeposition rates during SiO2 etching in a CF4 plasma

    International Nuclear Information System (INIS)

    Cho, Byeong-Ok; Hwang, Sung-Wook; Lee, Gyeo-Re; Moon, Sang Heup

    2001-01-01

    The angular dependence of the redeposition rates during SiO 2 etching in a CF 4 plasma was studied using three types of Faraday cages located in a transformer coupled plasma etcher. The SiO 2 substrates were fixed on sample holder slopes that have different angles to the cathode. The substrate was subjected to one of three processes depending on the design of the Faraday cage, i.e., redeposition of sputtered particles from the SiO 2 bottom surface (case I), substrate etching by incident ions (case II), or simultaneous etching and redeposition (case III). Both the redeposition and the etch rates were measured by changing the substrate-surface angle and the self-bias voltage in the range of -100 to -800 V. The redeposition-only rates (case I) at -450 and -800 V closely followed the quadratic curve of the angle whereas the rates at -100 V followed the cubic curve, indicating different mechanisms of the bottom SiO 2 etching depending on the energy regimes. The steep increase of the redeposition rate with the angle was attributed to three factors: the substrate-bottom distance, the angular distribution of emitted particles from the bottom surface, and the particle incident angle on the substrate surface. The etch-only rate curves (case II) closely followed the cosine of the surface angle. The etch-rate curve changed into a reverse-S shape when the substrate was subjected to simultaneous etching and redeposition (case III). The net etch rate for case III decreased drastically above 60 deg. , showing a negative value, i.e., a net redeposition, beyond 75 deg. . The drastic decrease in the net etch rate coincided with the steep increase in the redeposition rate, implying the significant effect of redeposition

  10. SiO2-induced release of sVEGFRs from pulmonary macrophages.

    Science.gov (United States)

    Chao, Jie; Lv, Yan; Chen, Jin; Wang, Jing; Yao, Honghong

    2018-01-01

    The inhalation of silicon dioxide (SiO 2 ) particles causes silicosis, a stubborn pulmonary disease that is characterized by alveolar inflammation during the early stage. Soluble cytokine receptors (SCRs) play important roles in regulating inflammation by either attenuating or promoting cytokine signaling. However, the role of SCRs in silicosis remains unknown. Luminex assays revealed increased soluble vascular endothelial growth factor receptor (sVEGFR) family levels in the plasma of silicosis patients. In an enzyme-linked immunosorbent assay (ELISA), cells from the differentiated human monocytic cell line U937 released sVEGFR family proteins after exposure to SiO 2 (50μg/cm 2 ). Further Western blot experiments revealed that VEGFR expression was also elevated in U937 cells. In contrast, levels of sVEGFR family members did not change in the supernatants of human umbilical vein endothelial cells (HUVECs) after exposure to SiO 2 (50μg/cm 2 ). Interestingly, VEGFR expression in HUVECs decreased after SiO 2 treatment. In a scratch assay, HUVECs exhibited cell migration ability, indicating the acquisition of mesenchymal properties. Our findings highlight the important role of sVEGFRs in both inflammation and fibrosis induced by SiO 2 , suggesting a possible mechanism for the fibrogenic effects observed in pulmonary diseases associated with fibrosis. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Analysis of thermoluminescence kinetics of Mg2SiO4:Tb compounds employing an interactive model

    International Nuclear Information System (INIS)

    Marcazzo, J.; Prokic, M.; Santiago, M.; Molina, P.; Caselli, E.

    2009-01-01

    The kinetics involved in the thermoluminescence (TL) of Mg 2 SiO 4 :Tb compounds has been investigated by unfolding glow curves employing both the General Order model and a model that takes into account interactions among traps. The dependence of the glow curve shape on dose is only correctly described if interaction among traps is included in the analysis.

  12. LOW-TEMPERATURE SINTERED (ZnMg2SiO4 MICROWAVE CERAMICS WITH TiO2 ADDITION AND CALCIUM BOROSILICATE GLASS

    Directory of Open Access Journals (Sweden)

    BO LI

    2011-03-01

    Full Text Available The low-temperature sintered (ZnMg2SiO–TiO2 microwave ceramic using CaO–B2O3–SiO2 (CBS as a sintering aid has been developed. Microwave properties of (Zn1-xMgx2SiO4 base materials via sol-gel method were highly dependent on the Mg-substituted content. Further, effects of CBS and TiO2 additives on the crystal phases, microstructures and microwave characteristics of (ZnMg2SiO4 (ZMS ceramics were investigated. The results indicated that CBS glass could lower the firing temperature of ZMS dielectrics effectively from 1170 to 950°C due to the liquid-phase effect, and significantly improve the sintering behavior and microwave properties of ZMS ceramics. Moreover, ZMS–TiO2 ceramics showed the biphasic structure and the abnormal grain growth was suppressed by the pinning effect of second phase TiO2. Proper amount of TiO2 could tune the large negative temperature coefficient of resonant frequency (tf of ZMS system to a near zero value. (Zn0.8Mg0.22SiO4 codoped with 10 wt.% TiO2 and 3 wt.% CBS sintered at 950°C exhibits the dense microstructure and excellent microwave properties: εr = 9.5, Q·f = 16 600 GHz and tf = −9.6 ppm/°C.

  13. Two new three-dimensional zinc phosphites templated by piperazine: [H2pip][Zn3(HPO3)4(H2O)2] and K[H2pip]0.5[Zn3(HPO3)4

    Science.gov (United States)

    Zhang, Xiao; Wang, Guo-Ming; Wang, Zong-Hua; Wang, Ying-Xia; Lin, Jian-Hua

    2014-01-01

    Two three-dimensional open-framework zinc phosphites with the same organically templated, [H2pip][Zn3(HPO3)4(H2O)2] (1) and K[H2pip]0.5[Zn3(HPO3)4] (2) (pip = piperazine), have been solvothermally synthesized and structurally characterized by IR, elemental analysis, thermogravimetric analysis, powder and single-crystal X-ray diffractions. Compound 1 consists of ZnO4 tetrahedra, [HPO3] pseudopyramids and [ZnO4(H2O)2] octahedra, which are linked through their vertexes to generate three-dimensional architecture with intersecting 8-membered channels along the [1 0 0], [0 0 1] and [1 0 1] directions. Compound 2 is constructed from strictly alternating ZnO4 tetrahedra and [HPO3] pseudopyramids, and exhibits (3,4)-connected inorganic framework with 8-, and 12-membered channels, in which the K+ and diprotonated H2pip2+ extra-framework cations reside, respectively. The coexistence of inorganic K+ and organic piperazine mixed templates in the structure is unique and, to the best of our knowledge, firstly observed in metal-phosphite materials. In addition, the participation of left-handed and right-handed helical chains in construction of the puckered 4.82 sheet structure in 2 is also noteworthy.

  14. Silicon K-edge XANES spectra of silicate minerals

    Science.gov (United States)

    Li, Dien; Bancroft, G. M.; Fleet, M. E.; Feng, X. H.

    1995-03-01

    Silicon K-edge x-ray absorption near-edge structure (XANES) spectra of a selection of silicate and aluminosilicate minerals have been measured using synchrotron radiation (SR). The spectra are qualitatively interpreted based on MO calculation of the tetrahedral SiO{4/4-}cluster. The Si K-edge generally shifts to higher energy with increased polymerization of silicates by about 1.3 eV, but with considerable overlap for silicates of different polymerization types. The substitution of Al for Si shifts the Si K-edge to lower energy. The chemical shift of Si K-edge is also sensitive to cations in more distant atom shells; for example, the Si K-edge shifts to lower energy with the substitution of Al for Mg in octahedral sites. The shifts of the Si K-edge show weak correlation with average Si-O bond distance (dSi-O), Si-O bond valence (sSi-O) and distortion of SiO4 tetrahedra, due to the crystal structure complexity of silicate minerals and multiple factors effecting the x-ray absorption processes.

  15. Precipitation of amorphous SiO2 particles and their properties

    Directory of Open Access Journals (Sweden)

    S. Musić

    2011-03-01

    Full Text Available The experimental conditions were optimized for the synthesis of amorphous SiO2 particles by the reaction of neutralization of sodium silicate solution with H2SO4 solution. Amorphous SiO2 particles were characterized by XRD, FT-IR, FE-SEM, EDS and microelectrophoresis. The amorphous peak was located at 2θ = 21.8º in the XRD pattern. Primary SiO2 particles were ~ 15 to ~ 30 nm in size and they aggregated into bigger particles. Amorphous SiO2 particles showed a specific surface area up to 130 m²g-1, dependent on the parameters of the precipitation process. The EDS spectrum of amorphous SiO2 particles did not show contamination with sulfate or other ions, which cannot be excluded in traces. pHzpc =1.7 was obtained by microelectrophoresis.

  16. The Silicon Environment in Silica Polymorphs, Aluminosilicate Crystals and Melts: An In Situ High Temperature XAS Study

    International Nuclear Information System (INIS)

    Cormier, L.; Neuville, D. R.; Roux, J.; Ligny, D. de; Henderson, G. S.; Flank, A.-M.; Lagarde, P.

    2007-01-01

    High temperature X-ray absorption spectroscopy at the Si K-edge has been used to obtain in situ information on SiO2 phase transitions upon heating. Important modifications are observed for the XANES spectra of the high temperature polymorphs, in relation to disordering of the SiO4 tetrahedra beyond the short-range correlations. This paper also presents the XANES spectra of anorthite (CaAl2Si2O8) from room temperature up to the melt (1900 K). This study shows the possibilities for determining the Si environment in crystals and glasses up to the liquid state using in situ XANES measurements

  17. Thermal expansion of lanthanum silicate oxyapatite (La9.33+2x(SiO4)6O2+3x), lanthanum oxyorthosilicate (La2SiO5) and lanthanum sorosilicate (La2Si2O7)

    International Nuclear Information System (INIS)

    Fukuda, Koichiro; Asaka, Toru; Uchida, Tomohiro

    2012-01-01

    Four types of powder specimens of La 9.33 (SiO 4 ) 6 O 2 (space group P6 3 /m and Z=1), La 9.33+2x (SiO 4 ) 6 O 2+3x with 0.06≤x≤0.13 (P6 3 /m and Z=1), La 2 SiO 5 (P2 1 /c and Z=4) and La 2 Si 2 O 7 (P2 1 /c and Z=4) were examined by high-temperature X-ray powder diffractometry to determine the changes in unit-cell dimensions up to 1473 K. The anisotropy of thermal expansion was demonstrated for the former two crystals to clarify the thermal behaviors of the highly c-axis-oriented polycrystals. With La 9.33 (SiO 4 ) 6 O 2 , the linear expansion coefficient of the a-axis (α a ) was 4.8×10 −6 K −1 and that of the c-axis (α c ) was 1.8×10 −6 K −1 in the temperature range from 298 to 1473 K. The α a - and α c -values of La 9.33+2x (SiO 4 ) 6 O 2+3x (0.06≤x≤0.13) were, respectively, 5.9×10 −6 K −1 and 2.3×10 −6 K −1 . The coefficients of mean linear thermal expansion were 4.9×10 −6 K −1 for La 2 SiO 5 and 6.0×10 −6 K −1 for La 2 Si 2 O 7 , which describe the thermal expansion behaviors of the randomly grain-oriented polycrystalline materials. - Graphical abstarct: Temperature dependence of the coefficients of thermal expansion (CTE). The linear CTE along the a-axes for La 9.33 (SiO 4 ) 6 O 2 and La 9.33+2x (SiO 4 ) 6 O 2+3x with 0.06≤x≤0.13. The mean linear CTE for La 2 SiO 5 and La 2 Si 2 O 7 . Highlights: ► We examined the thermal expansion of La 9.33+2x (SiO 4 ) 6 O 2+3x (x=0 and 0.06≤x≤0.13), La 2 SiO 5 and La 2 Si 2 O 7 ► Unit-cell dimensions were determined up to 1473 K by high-temperature X-ray diffraction ► Anisotropic expansion was clarified for La 9.33+2x (SiO 4 ) 6 O 2+3x (x=0 and 0.06≤x≤0.13) ► Mean linear thermal expansion was determined for La 2 SiO 5 and La 2 Si 2 O 7.

  18. Structural and optical properties of (Sr,Ba)2SiO4:Eu2+ thin films grown by magnetron sputtering

    International Nuclear Information System (INIS)

    Li, Leliang; Zheng, Jun; Zuo, Yuhua; Cheng, Buwen; Wang, Qiming

    2014-01-01

    (Sr,Ba) 2 SiO 4 :Eu 2+ thin films were deposited on Si at different substrate temperatures by magnetron sputtering. The morphology and crystalline phases of the films were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements, respectively. The silicate crystal phase was presented when films were annealed above 900 °C and the annealing temperature had great impact on the film morphology. The samples annealed at 1000 °C in a non-reducing atmosphere for 30 s show intense room temperature Eu 2+ emission. These findings may open a promising way to prepare efficient phosphor thin films for on-chip light emitting diodes application. - Highlights: • The (Sr, Ba) 2 SiO 4 :Eu 2+ films are fabricated by magnetron sputtering. • A very strong RT PL emission at 540 nm is achieved. • The morphology and optical properties dependent on temperature are studied

  19. Pr{sub 3}S{sub 2}Cl{sub 2}[AsS{sub 3}]: a praseodymium(III) sulfide chloride thioarsenate(III) with double chains of condensed [SPr{sub 4}]{sup 10+} tetrahedra

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Dong-Hee [Institute for Inorganic Chemistry, University of Stuttgart (Germany); Department of Chemistry, University of Waterloo, ON (Canada); Korea Research Institute of Standards and Science (KRISS), Daejeon (Korea, Republic of); Ledderboge, Florian; Schleid, Thomas [Institute for Inorganic Chemistry, University of Stuttgart (Germany); Kleinke, Holger [Department of Chemistry, University of Waterloo, ON (Canada)

    2015-02-15

    Single crystals of Pr{sub 3}S{sub 2}Cl{sub 2}[AsS{sub 3}] were obtained by reacting praseodymium sesquisulfide and trichloride with arsenic and sulfur (molar ratio: 7:4:6:9) in torch-sealed evacuated silica ampoules at 850 C for a week and subsequent slow cooling to room temperature. The transparent, pale yellowish green platelets crystallize monoclinically (Pr{sub 3}S{sub 2}Cl{sub 2}[AsS{sub 3}]: a = 2190.96(9) pm, b = 685.49(3) pm, c = 701.87(3) pm, β = 98.752(3) ) in the non-centrosymmetric space group Cc with Z = 4. The crystal structure of Pr{sub 3}S{sub 2}Cl{sub 2}[AsS{sub 3}] comprises three crystallographically different Pr{sup 3+} cations. (Pr1){sup 3+} and (Pr2){sup 3+} exhibit bicapped trigonal prismatic environments of five sulfur and three chlorine atoms (C.N. = 8) each, whereas only seven sulfur atoms arranged as capped trigonal prism (C.N. = 7) are present in the case of (Pr3){sup 3+}. Two of the five crystallographically different sulfur atoms (S1 and S2) are coordinated by four Pr{sup 3+} cations, each in the shape of slightly distorted [SPr{sub 4}]{sup 10+} tetrahedra (d(S-Pr) = 278-294 pm). Hence, the crystal structure of Pr{sub 3}S{sub 2}Cl{sub 2}[AsS{sub 3}] contains double chains with the composition {sup 1}{sub ∞}{[S_2Pr_3]"5"+}, consisting of two parallel edge-fused chains of anti-SiS{sub 2}-analogous single strands {sup 1}{sub ∞}{[SPr_2]"4"+}, formed by trans-edge sharing [SPr{sub 4}]{sup 10+} tetrahedra. The arrangement of the {sup 1}{sub ∞}{[S_2Pr_3]"5"+} double chains running along [001] can be described as a hexagonal rod-packing. Chloride anions (Cl1 and Cl2) as well as the isolated, ψ{sup 1}-tetrahedral thioarsenate(III) groups [AsS{sub 3}]{sup 3-} (d(As-S) = 228-229 pm) consisting of three sulfur atoms (S3, S4, and S5) and an As{sup 3+} cation carrying a stereochemically active non-bonding electron pair take care of the three-dimensional interconnection and the charge balance of the {sup 1}{sub ∞}{[S_2Pr_3]"5"+} double

  20. Structural study of caesium-based britholites Sr7La2Cs(PO4)5(SiO4)F2

    International Nuclear Information System (INIS)

    Boughzala, K.; Gmati, N.; Bouzouita, K.; Ben Cherifa, A.; Gravereau, P.

    2010-01-01

    Several studies demonstrated the ability of britholites to retain radionuclides such as the caesium and actinides. Therefore, three compounds with formulas Sr 8 LaCs(PO 4 ) 6 F 2 , Sr 7 La 2 Cs(PO 4 ) 5 (SiO 4 )F 2 and Sr 2 La 7 Cs(SiO 4 ) 6 F 2 , were prepared by solid state reaction. However, it seems that only the mono-silicated composition was obtained in a pure state. In this present work, the X-ray diffraction and magnetic nuclear resonance have been used to investigate the structure for this composition. The results showed that in fact this phase was not pure, but it was mixed with a secondary phase, SrLaCs(PO 4 ) 2 . The refinement by the Rietveld method allowed also to precise the distribution of La 3+ and Cs + ions between the two cationic sites of the apatite. (authors)

  1. Synthesis and characterization of novel Cu(II) complex coated Fe3O4@SiO2 nanoparticles for catalytic performance

    Science.gov (United States)

    Nasrollahzadeh, Mahmoud; Sajjadi, Mohaddeseh; Khonakdar, Hossein Ali

    2018-06-01

    In this study, a convenient method for the synthesis of arylaminotetrazoles has been developed using a copper (II)-aminotetrazole complex immobilized on silica-coated Fe3O4 (Fe3O4@SiO2) nanoparticles (Fe3O4@SiO2-aminotet-Cu(II)) as a novel and efficient magnetically catalyst. The constructed superparamagnetic core-shell nanoparticles were successfully prepared, as proven using different spectroscopic techniques such as fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscope (TEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetry and differential thermogravimetry (TG-DTG) and vibrating sample magnetometer (VSM) analysis. The applicability of Fe3O4@SiO2-aminotet-Cu(II) magnetic catalyst allows the efficient synthesis of a variety of arylaminotetrazoles from the reaction between various arylcyanamides with sodium azide in high yields. The effect of catalyst loading was investigated. In addition, the reaction mechanism for the synthesis of arylaminotetrazoles was reasonably proposed. Results show that the 1-aryl-5-amino-1H-tetrazole (B isomer) and 5-arylamino-1H-tetrazole (A isomer) can be obtained from the arylcyanamides carrying electron-donating and electron-withdrawing substituents, respectively. This procedure offers a simple methodology, relatively short reaction times, easy work-up, high yields of the products and a cleaner reaction with elimination of hydrazoic acid (HN3). Moreover, catalyst can be conveniently recovered through the use of external magnet and reused for at least 6 times without any significant loss of its activity.

  2. A facile synthesis of Li_2Fe_1_/_3Mn_1_/_3Ni_1_/_3SiO_4/C composites as cathode materials for lithium-ion batteries

    International Nuclear Information System (INIS)

    Yang, Rong; Wang, Liqing; Deng, Kunfa; Lv, Mengni; Xu, Yunhua

    2016-01-01

    The novel Li_2Fe_1_/_3Mn_1_/_3Ni_1_/_3SiO_4/C has been successfully synthesized by a feasible solution process in ternary system. The spherical carbon-coated composites are obtained using a heat treatment in the presence of sucrose. X-ray diffraction (XRD) diffractogram displays that the Li_2Fe_1_/_3Mn_1_/_3Ni_1_/_3SiO_4/C crystallized in an orthorhombic structure with a space group of Pmn21. The energy-dispersive X-ray spectroscopy mappings indicate that Fe, Mn and Ni elements are distributed homogenously in Li_2Fe_1_/_3Mn_1_/_3Ni_1_/_3SiO_4/C nano-spherical particle with size less than 50 nm. The lithium storage capacity and cycling performance of the Li_2Fe_1_/_3Mn_1_/_3Ni_1_/_3SiO_4/C presents good results when tested as cathode materials in lithium cells at room temperature. It delivers an initial discharge capacity of 181.4 mAh g"−"1 and a discharge capacity of 172.9 mAh g"−"1 after 20 cycles at 0.1C in the voltage range of 1.5–4.6V. Furthermore, it also exhibits an excellent rate capability with a capacity under different current densities of about 144.0 mAh g"−"1 (0.2 C), 117.9 mAh g"−"1 (0.5 C), 106.1 mAh g"−"1 (1 C), respectively and a good capacity cycling maintenance of 153.7 mAh g"−"1 after 60 cycles. Above results indicate that the spherical Li_2Fe_1_/_3Mn_1_/_3Ni_1_/_3SiO_4/C becomes a very promising candidate for cathode material in lithium-ion batteries. - Highlights: • Li_2Fe_1_/_3Mn_1_/_3Ni_1_/_3SiO_4/C was obtained by solution process in a ternary system. • The material was pure phase ternary solid solution with tetrahedral morphology. • The spherical particle size was less than 50 nm with graphitized carbon coating. • The nanocomposite revealed high discharge capacity and excellent rate capability.

  3. Light coupling and distribution for Si3N4/SiO2 integrated multichannel single-mode sensing system

    Science.gov (United States)

    Kaźmierczak, Andrzej; Dortu, Fabian; Schrevens, Olivier; Giannone, Domenico; Bouville, David; Cassan, Eric; Gylfason, Kristinn B.; Sohlström, Hans; Sanchez, Benito; Griol, Amadeu; Hill, Daniel

    2009-01-01

    We present an efficient and highly alignment-tolerant light coupling and distribution system for a multichannel Si3N4/SiO2 single-mode photonics sensing chip. The design of the input and output couplers and the distribution splitters is discussed. Examples of multichannel data obtained with the system are given.

  4. Crystal structure of alluaudite-type Na4Co(MoO4)3.

    Science.gov (United States)

    Nasri, Rawia; Fakhar Bourguiba, Noura; Zid, Mohamed Faouzi; Driss, Ahmed

    2014-09-01

    The title compound, tetra-sodium cobalt(II) tris-[molyb-date(IV)], was prepared by solid-state reactions. The structure is isotypic with Na3In2(AsO4)3 and Na3In2(PO4)3. The main structural feature is the presence of infinite chains of edge-sharing X 2O10 (X = Co/Na) dimers, which are linked by MoO4 tetra-hedra, forming a three-dimensional framework enclosing two types of hexa-gonal tunnels in which Na(+) cations reside. In this alluaudite structure, Co and Na atoms are located at the same general site with occupancies of 0.503 (5) and 0.497 (6), respectively. The other three Na and one of the two Mo atoms lie on special positions (site symmetries 2, -1, 2 and 2, respectively). The structure is compared with similar structures and other members of alluaudite family.

  5. The oxidation of ReCl{sub 5} with oleum: synthesis and crystal structure of Re{sub 2}O{sub 4}Cl{sub 4}(SO{sub 4})

    Energy Technology Data Exchange (ETDEWEB)

    Betke, Ulf; Wickleder, Mathias S. [Carl von Ossietzky University of Oldenburg, Institute of Pure and Applied Chemistry (Germany)

    2012-01-15

    The reaction of ReCl{sub 5} and fuming sulfuric acid (25 % SO{sub 3}) in a sealed glass tube at 200 C led to red, needle shaped single crystals of Re{sub 2}O{sub 4}Cl{sub 4}(SO{sub 4}) (monoclinic, C2/c, a = 1501.8(2) pm, b = 1545.9(2) pm, c = 945.18(8) pm, β = 98.761(9) , Z = 8). In the crystal structure the [ReO{sub 2}] moieties are linked by [SO{sub 4}]{sup 2-} tetrahedra to chains along the [101] direction. Each sulfate ion connects four rhenium atoms, additional two chloride ions complete the octahedral coordination sphere of each rhenium atom according to {sup 1}{sub ∞}[ReO{sub 2/1}Cl{sub 2/1}(SO{sub 4}){sub 2/4}]. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Photocatalytic degradation of Acephate, Omethoate, and Methyl parathion by Fe_3O_4@SiO_2@mTiO_2 nanomicrospheres

    International Nuclear Information System (INIS)

    Zheng, Lingling; Pi, Fuwei; Wang, Yifan; Xu, Hui; Zhang, Yinzhi; Sun, Xiulan

    2016-01-01

    Highlights: • An efficient photocatalyst Fe_3O_4@SiO_2@mTiO_2 with high magnetic response and large specific surface area was synthesized. • Photocatalytic efficiency of Fe_3O_4@SiO_2@mTiO_2 on Acephate, Omethoate, and Methyl Parathion was higher than TiO_2 P-25. • Possible photocatalytic degradation mechanisms for the Acephate, Omethoate, and Methyl Parathion were proposed. - Abstract: A novel magnetic mesoporous nanomicrospheres Fe_3O_4@SiO_2@mTiO_2 were synthetized and characterized by a series of techniques including FE-TEM, EDS, FE-SEM, PXRD, XPS, BET, TGA as well as VSM, and subsequently tested as a photocatalyst for the degradation of Acephate, Omethoate, and Methyl parathion under UV irradiation. The well-designed nanomicrospheres exhibit a pure and highly crystalline anatase TiO_2 layer, large specific surface area, and high-magnetic-response. Photocatalytic degradation of the three organophosphorus pesticides (OPPs) and the formation intermediates were identified using HPLC, TOC-V_c_p_n, IC, pH meter and GC–MS. Acephate, Omethoate, and Methyl parathion disappeared after 45 min, 45 min, and 80 min UV illumination, respectively. At the end of the treatment, the total organic carbon (TOC) of the OPPs was reduced 80–85%. The main mineralization products were SO_4"2"−, NO_3"− and PO_4"3"− and Omethoate additionally formed NO_2"−. Based on the results, we proposed the photocatalytic degradation pathways for Acephate, Omethoate, and Methyl parathion.

  7. Silica-induced initiation of circular ZC3H4 RNA/ZC3H4 pathway promotes the pulmonary macrophage activation.

    Science.gov (United States)

    Yang, Xiyue; Wang, Jing; Zhou, Zewei; Jiang, Rong; Huang, Jie; Chen, Lulu; Cao, Zhouli; Chu, Han; Han, Bing; Cheng, Yusi; Chao, Jie

    2018-01-22

    Phagocytosis of silicon dioxide (SiO 2 ) into lung cells causes an inflammatory cascade that results in fibroblast proliferation and migration, followed by fibrosis. Circular RNAs (circRNAs) are a subclass of noncoding RNAs that are present within mammalian cells; however, researchers have not determined whether circRNAs are involved in the pathophysiologic process of silicosis. To elucidate the role of these RNAs in SiO 2 -induced inflammation in pulmonary macrophages, we investigated the upstream molecular mechanisms and functional effects of circRNAs on cell apoptosis, proliferation, and migration. Primary cultures of alveolar macrophages from healthy donors and from patients and the RAW264.7 macrophage cell line were used to explore the functions of circZC3H4 RNA in macrophage activation. The experimental results indicated the following: 1) SiO 2 concomitantly increased circZC3H4 RNA expression and increased ZC3H4 protein levels; 2) circular ZC3H4 (circZC3H4) RNA and ZC3H4 protein participated in SiO 2 -induced macrophage activation; and 3) SiO 2 -activated macrophages promoted fibroblast proliferation and migration via the circZC3H4 RNA/ZC3H4 pathway. The up-regulation of the ZC3H4 protein was confirmed in tissue samples from patients with silicosis. Our study elucidates a link between SiO 2 -induced macrophage activation and the circZC3H4 RNA/ZC3H4 pathway, thereby providing novel insight into the potential use of ZC3H4 to develop novel therapeutic strategies for silicosis.-Yang, X., Wang, J., Zhou, Z., Jiang, R., Huang, J., Chen, L., Cao, Z., Chu, H., Han, B., Cheng, Y., Chao, J. Silica-induced initiation of circular ZC3H4 RNA/ZC3H4 pathway promotes the pulmonary macrophage activation.

  8. On a two-layer Si_3N_4/SiO_2 dielectric mask for low-resistance ohmic contacts to AlGaN/GaN HEMTs

    International Nuclear Information System (INIS)

    Arutyunyan, S. S.; Pavlov, A. Yu.; Pavlov, B. Yu.; Tomosh, K. N.; Fedorov, Yu. V.

    2016-01-01

    The fabrication of a two-layer Si_3N_4/SiO_2 dielectric mask and features of its application in the technology of non-fired epitaxially grown ohmic contacts for high-power HEMTs on AlGaN/GaN heterostructures are described. The proposed Si_3N_4/SiO_2 mask allows the selective epitaxial growth of heavily doped ohmic contacts by nitride molecular-beam epitaxy and the fabrication of non-fired ohmic contacts with a resistance of 0.15–0.2 Ω mm and a smooth surface and edge morphology.

  9. Hydrothermal synthesis and characterization of a new three-dimensional hybrid zinc phosphate [Zn2(HPO4)2(4,4'-bipy)].3H2O with neutral porous framework

    International Nuclear Information System (INIS)

    Wang Lei; Yang Ming; Li Guanghua; Shi Zhan; Feng Shouhua

    2006-01-01

    Employing 4,4'-bipyridine as a bridged ligand, a new three-dimensional (3-D) hybrid zinc phosphate [Zn 2 (HPO 4 ) 2 (4,4'-bipy)].3H 2 O has been prepared under hydrothermal conditions and characterized by single crystal X-ray diffraction. This compound crystallizes in the monoclinic space group C2/c, with cell parameters, a=21.188(4)A, b=10.229(2)A, c=9.0656(18)A, β=90.21(3) o , V=1964.8(7)A 3 and Z=4. The connectivity of the ZnO 3 N and HPO 4 tetrahedra results in a 2-D neutral layer that with interesting 4,8 2 net along the bc plane. Furthermore, the 4,4'-bipyridine molecule links the 4,8 2 net into a 3-D structure. The water molecules sit in the middle of the channels and interact with the framework via hydrogen bonds. The compound exhibits intense photoluminescence at room temperature

  10. European DEMO BOT Solid Breeder Blanket: the concept based on the use of cooling plates and beds of beryllium and Li4SiO4 pebbles

    International Nuclear Information System (INIS)

    Dalle Donne, M.; Fischer, U.; Norajitra, P.; Reimann, G.; Reiser, H.

    1995-01-01

    The paper presents an important modification of the European DEMO BOT Solid Breeder Blanket. The new design uses cooling plates rather than tubes. This allows a considerable simplification of the blanket and the separation of the beryllium from the Li 4 SiO 4 pebbles. The neutronic, thermohydraulic and tritium performance of the new design is quite good and equivalent to that of the previous one. (orig.)

  11. Toluene and chlorobenzene dinitration over solid H3PO4/MoO3/SiO2 catalyst.

    Science.gov (United States)

    Adamiak, Joanna; Kalinowska-Alichnewicz, Dorota; Szadkowski, Michał; Skupiński, Wincenty

    2011-11-15

    A new catalyst, H(3)PO(4)/MoO(3)/SiO(2), was prepared by modification of MoO(3)/SiO(2) using phosphoric acid. The characterization of the catalyst was performed using Infrared and Raman Spectroscopy, potentiometric titration and nitrogen adsorption-desorption methods. Molybdenum oxides were identified along with phosphomolybdic acid and polymolybdates on the modified surface. The suitability of the catalysts for toluene and chlorobenzene nitration in continuous process was examined. Toluene is effectively nitrated to dinitrotoluene (DNT) in one-stage process (96 wt.% of DNT in the product) and in mild conditions i.e. at room temperature and only with ten-fold excess of nitric acid. In chlorobenzene nitration only twelve-fold excess of nitric acid is needed to obtain as high yield as 95 wt.%. Most importantly, the novel catalysts we have developed, provide the opportunity for sulfuric acid- free nitration of aromatic compounds. Copyright © 2011 Elsevier B.V. All rights reserved.

  12. Ge 3P 6Si 2O 25: A cage structure closely related to the intersecting tunnel structure KMo 3P 6Si 2O 25

    Science.gov (United States)

    Leclaire, A.; Raveau, B.

    1988-08-01

    A germanosilicophosphate Ge 3P 6Si 2O 25 has been isolated. Its structure was solved from a single-crystal study in the space group P overline31c . Its cell parameters are a = b = 7.994(1) Å, c = 16.513(2) Å, Z = 2. The refinement by full-matrix least-squares calculations leads to R = 0.043 with 686 independent reflections. The structure of this oxide is built up from corner-sharing PO 4 and SiO 4 tetrahedra and GeO 6 octahedra. One observes a feature common to several silicophosphates: the presence of the structural unit P 6Si 2O 25 built up from a disilicate group sharing its corners with six PO 4 tetrahedra. The structural relationships between this oxide and the silicophosphates AMo 3P 6Si 2O 25 and Si 3P 6Si 2O 25 (or Ge 3P 6 Ge 2O 25) are described.

  13. Radiation damage in lithium orthosilicate

    Energy Technology Data Exchange (ETDEWEB)

    Noda, K.; Nakazawa, T.; Ishii, Y.; Fukai, K.; Watanabe, H. (Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment); Matsui, H.; Vollath, D.

    1993-11-01

    Radiation damage in lithium orthosilicate (Li[sub 4]SiO[sub 4]) and Al-doped Li[sub 4]SiO[sub 4] (Li[sub 3.7]Al[sub 0.1]SiO[sub 4]) irradiated with oxygen ions was studied with ionic conductivity measurements, Raman spectroscopy, Fourier transform infrared photo-acoustic spectroscopy (FT-IR PAS) and transmission electron microscopy. It was seen from the ionic conductivity measurements that lithium-ion vacancies were introduced as irradiation defects for Li-ions sites in both materials due to the irradiation. By the Raman spectroscopy, oxygen atoms in SiO[sub 4] tetrahedra were considered to be preferentially displaced due to the irradiation for Li[sub 4]SiO[sub 4], although only a decrease of the number of SiO[sub 4] tetrahedra occurred for Li[sub 3.7]Al[sub 0.1]SiO[sub 4] by displacement of both silicon and oxygen atoms. Decomposition of SiO[sub 4] tetrahedra and formation of some new phases having Si-O-Si and Si-O bonds were found to take place for both Li[sub 4]SiO[sub 4] and Li[sub 3.7]Al[sub 0.1]SiO[sub 4] by FT-IR PAS. In the electron microscopy, damage microstructure consisting of many voids or cavities and amorphization were observed for Li[sub 4]SiO[sub 4] irradiated with oxygen ions. The recovery behavior of radiation damage mentioned above was also investigated. (author).

  14. SiO2 Glass Density to Lower-Mantle Pressures

    DEFF Research Database (Denmark)

    Petitgirard, Sylvain; Malfait, Wim J.; Journaux, Baptiste

    2017-01-01

    and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range...... for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60...... GPa. The density data present two discontinuities at similar to 17 and similar to 60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at similar to 40 GPa, and its density...

  15. Polyetherimide-grafted Fe3O4@SiO2 nanoparticles as theranostic agents for simultaneous VEGF siRNA delivery and magnetic resonance cell imaging

    Directory of Open Access Journals (Sweden)

    Li T

    2015-07-01

    Full Text Available Tingting Li,1 Xue Shen,1 Yin Chen,1 Chengchen Zhang,1 Jie Yan,1 Hong Yang,1 Chunhui Wu,1,2 Hongjun Zeng,1,2 Yiyao Liu1,21Department of Biophysics, School of Life Science and Technology, 2Center for Information in Biomedicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, People’s Republic of ChinaAbstract: Engineering a safe and high-efficiency delivery system for efficient RNA interference is critical for successful gene therapy. In this study, we designed a novel nanocarrier system of polyethyleneimine (PEI-modified Fe3O4@SiO2, which allows high efficient loading of VEGF small hairpin (shRNA to form Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites for VEGF gene silencing as well as magnetic resonance (MR imaging. The size, morphology, particle stability, magnetic properties, and gene-binding capacity and protection were determined. Low cytotoxicity and hemolyticity against human red blood cells showed the excellent biocompatibility of the multifunctional nanocomposites, and also no significant coagulation was observed. The nanocomposites maintain their superparamagnetic property at room temperature and no appreciable change in magnetism, even after PEI modification. The qualitative and quantitative analysis of cellular internalization into MCF-7 human breast cancer cells by Prussian blue staining and inductively coupled plasma atomic emission spectroscopy analysis, respectively, demonstrated that the Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites could be easily internalized by MCF-7 cells, and they exhibited significant inhibition of VEGF gene expression. Furthermore, the MR cellular images showed that the superparamagnetic iron oxide core of our Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites could also act as a T2-weighted contrast agent for cancer MR imaging. Our data highlight multifunctional Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites as a potential platform for simultaneous gene delivery and MR cell imaging, which are promising

  16. ZnAl2O4@SiO2 nanocomposite catalyst for the acetylation of alcohols, phenols and amines with acetic anhydride under solvent-free conditions

    Institute of Scientific and Technical Information of China (English)

    Saeed Farhadi; Kosar Jahanara

    2014-01-01

    A ZnAl2O4@SiO2 nanocomposite was prepared from metal nitrates and tetraethyl orthosilicate by the sol-gel process, and characterized by X-ray diffraction, Fourier transform infrared, transmission electron microscopy, and N2 adsorption-desorption measurements. The nanocomposite was tested as a heterogeneous catalyst for the acetylation of alcohols, phenols, and amines under solvent-free conditions. Under optimized conditions, efficient acetylation of these substrates with acetic anhy-dride over the ZnAl2O4@SiO2 nanocomposite was obtained. Acetylation of anilines and primary aliphatic amines proceeded rapidly at room temperature, while the reaction time was longer for the acetylation of alcohols and phenols, showing that an amine NH2 group can be selectively acetylated in the presence of alcoholic or phenolic OH groups. The catalyst can be reused without obvious loss of catalytic activity. The catalytic activity of the ZnAl2O4@SiO2 nanocomposite was higher than that of pure ZnAl2O4. The method gives high yields, and is clean, cost effective, compatible with sub-strates having other functional groups and it is suitable for practical organic synthesis.

  17. Compatibility of hydrogarnet, Ca3Al2(SiO4)x(OH)4(3−x), with sulfate and carbonate-bearing cement phases: 5–85 °C

    International Nuclear Information System (INIS)

    Okoronkwo, Monday Uchenna; Glasser, Fredrik Paul

    2016-01-01

    The stable existence of hydrogarnet in Portland cement compositions cured at temperatures below 55 °C has long been predicted from application of equilibrium thermodynamics. However hydrogarnet is not often reported in hydrated commercial Portland cements. The substitutions (SO 4 –CO 3 –OH) in AFm have previously been shown to stabilise AFm to higher temperatures and raise the temperature at which AFm converts to Si-free hydrogarnet, C 3 AH 6 . But unanswered question remains about the compatibility of AFm and AFm solid solutions with Si-substituted hydrogarnet, Ca 3 Al 2 (SiO 4 ) x (OH) 4(3 − x) . Phase relations of C 3 AH 6 and Ca 3 Al 2 (SiO 4 ) x (OH) 4(3 − x) at sulfate and carbonate activities conditioned respectively by (gypsum and SO 4 -AFt) and (calcite and CO 3 -AFt) have been determined experimentally in the range 5–85 °C. The results confirm the instability of Si-free hydrogarnet with carbonate and sulfate-bearing cement phases, but do indicate that a range of silica-substituted hydrogarnet solid solutions are stable under conditions likely to be encountered in blended cement systems.

  18. Structure of Na/sub 2/AlBAs/sub 4/O/sub 14/, a condensed aluminoboroarsenate

    Energy Technology Data Exchange (ETDEWEB)

    Driss, A.; Jouini, T.

    1988-05-15

    M/sub r/=607.45, monoclinic, P2/sub 1//c, a=4.5916(5), b=20.706(3), c=10.933(1) A, ..beta..=90.39(1)/sup 0/, V=1039.4 A/sup 3/, Z=4, D/sub x/=3.88, D/sub m/ (in bromobenzene)=3.93 Mg m/sup -3/, MoK anti ..cap alpha.., lambda=0.7107 A, ..mu..=13.7 mm/sup -1/, F(000)=1136, T=293 K, R=0.035, ..omega..R=0.047 for 1029 independent reflections. The main feature of this structure is the existence of a novel aluminoboroarsenate anion (Al/sub 2/B/sub 2/As/sub 8/O/sub 28/)/sup 4n-//sub n/ built up from centrosymmetrical B/sub 2/As/sub 4/O/sub 18/ rings formed by corner-sharing of AsO/sub 4/ and BO/sub 4/ tetrahedra and having two As/sub 2/O/sub 7/ pyroarsenate branches. The rings form infinite chains parallel to the a direction by As-O-B linkages. The chains are linked by sharing edges of AsO/sub 4/ tetrahedra and AlO/sub 6/ octahedra to form an infinite three-dimensional framework containing tunnels parallel to the chains where the Na/sup +/ cations are located. This structure is the first ternary heteropolyanion including B, Al and As atoms.

  19. Atomic motion of resonantly vibrating quartz crystal visualized by time-resolved X-ray diffraction

    International Nuclear Information System (INIS)

    Aoyagi, Shinobu; Osawa, Hitoshi; Sugimoto, Kunihisa; Fujiwara, Akihiko; Takeda, Shoichi; Moriyoshi, Chikako; Kuroiwa, Yoshihiro

    2015-01-01

    Transient atomic displacements during a resonant thickness-shear vibration of AT-cut α-quartz are revealed by time-resolved X-ray diffraction under an alternating electric field. The lattice strain resonantly amplified by the alternating electric field is ∼10 4 times larger than that induced by a static electric field. The resonantly amplified lattice strain is achieved by fast displacements of oxygen anions and collateral resilient deformation of Si−O−Si angles bridging rigid SiO 4 tetrahedra, which efficiently transduce electric energy into elastic energy

  20. Potential energy landscape of an interstitial O2 molecule in a SiO2 film near the SiO2/Si(001) interface

    Science.gov (United States)

    Ohta, Hiromichi; Watanabe, Takanobu; Ohdomari, Iwao

    2008-10-01

    Potential energy distribution of interstitial O2 molecule in the vicinity of SiO2/Si(001) interface is investigated by means of classical molecular simulation. A 4-nm-thick SiO2 film model is built by oxidizing a Si(001) substrate, and the potential energy of an O2 molecule is calculated at Cartesian grid points with an interval of 0.05 nm in the SiO2 film region. The result shows that the potential energy of the interstitial site gradually rises with approaching the interface. The potential gradient is localized in the region within about 1 nm from the interface, which coincides with the experimental thickness of the interfacial strained layer. The potential energy is increased by about 0.62 eV at the SiO2/Si interface. The result agrees with a recently proposed kinetic model for dry oxidation of silicon [Phys. Rev. Lett. 96, 196102 (2006)], which argues that the oxidation rate is fully limited by the oxidant diffusion.

  1. THE THERMODYNAMIC PROPERTIES OF MELTS OF DOUBLE SYSTEM MgO – Al2O3, MgO – SiO2, MgO – CaF2, Al2O3 – SiO2, Al2O3 – CaF2, SiO2 – CaF2

    Directory of Open Access Journals (Sweden)

    В. Судавцова

    2012-04-01

    Full Text Available Methodology of prognostication of thermodynamics properties of melts is presented from the coordinatesof liquidus of diagram of the state in area of equilibria a hard component is solution, on which energies ofmixing of Gibbs are expected in the double border systems of MgO – Al2O3, MgO – SiO2, MgO – CaF2,Al2O3 – SiO2, Al2O3 - CaF2, SiO2 - CaF2. For the areas of equilibrium there is quasibinary connection(MgAl2O4, Mg2SiO4, Al6Si2O13 – a grout at calculations was used equalization of Hauffe-Wagner. Theobtained data comport with literary

  2. SiO2@FeSO4 nano composite: A recoverable nano-catalyst for eco-friendly synthesis oximes of carbonyl compounds

    Directory of Open Access Journals (Sweden)

    Mostafa Karimkoshteh

    2016-01-01

    Full Text Available Various aldoximes and ketoximes synthesis of corresponding aldehydes and ketones in the presence of SiO2@FeSO4 nano composite as recoverable nano catalyst and NH2OH·HCl. The SiO2@FeSO4 nano composite system was carried out between 10 to 15 min in oil bath (70-80 °C under solvent-free condition in excellent yields in addition this protocol can be used for industrial scales. This method offers some advantages in term of clean reaction conditions, easy work-up procedure, short reaction time, applied to convert α-diketones to α-diketoximes (as longer than other carbonyl compounds, α,β-unsaturated aldehydes and ketones to corresponding oximes and suppression of any side product. So we think that NH2OH•HCl/SiO2@FeSO4 nano composite system could be considered a new and useful addition to the present methodologies in this area. Structure of products and nano composite elucidation was carried out by 1H NMR, 13C NMR, FT-IR, scanning electron microscopy (SEM.

  3. Unusual Features of Crystal Structures of Some Simple Copper Compounds

    Science.gov (United States)

    Douglas, Bodie

    2009-01-01

    Some simple copper compounds have unusual crystal structures. Cu[subscript 3]N is cubic with N atoms at centers of octahedra formed by 6 Cu atoms. Cu[subscript 2]O (cuprite) is also cubic; O atoms are in tetrahedra formed by 4 Cu atoms. These tetrahedra are linked by sharing vertices forming two independent networks without linkages between them.…

  4. Fabrication and evaluation of magnetic phosphodiesterase-5 linked nanoparticles as adsorbent for magnetic dispersive solid-phase extraction of inhibitors from Chinese herbal medicine prior to ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry analysis.

    Science.gov (United States)

    Tao, Yi; Gu, Xianghui; Li, Weidong; Cai, Baochang

    2018-01-12

    In the present study, the preparation of the magnetic phosphodiesterase-5 linked Fe 3 O 4 @ SiO 2 nanoparticles was successfully achieved by amide reaction and the magnetic phosphodiesterase-5 linked Fe 3 O 4 @SiO 2 nanoparticles were evaluated as a new adsorbent for magnetic dispersive solid-phase extraction of ligands from medicinal plant samples before the analysis by UHPLC-Q-TOF/MS. The prepared phosphodiesterase-5 linked Fe 3 O 4 @SiO 2 nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, vibration sample magnetometer and potential laser particle size analyzer. The effects of EDC concentration, incubation time and bead-protein ratio on the amount of immobilized protein were studied. The main experimental parameters affect extraction efficiency of ligands, such as wash times, wash solvents, incubation pH, ion strength and incubation temperature, were investigated and optimized by using echinacoside as a model compound. The absolute recovery of echinacoside was ranged from 98.36%-102.16% in Cistanche tubulosa sample under the optimal extraction conditions. Good linearity was observed in the investigated concentration range of 0.006 mgmL -1 -0.97 mgmL -1 (R 2  = 0.9999). The limit of detection was 0.002 mgmL -1 . The RSDs of within-day and between-day precision were less than 2.3%. Due to the excellent magnetic behavior of Fe 3 O 4 @SiO 2 nanoparticles, the proposed method was shown to be simple and rapid. Remarkably, the magnetic phosphodiesterase-5 linked Fe 3 O 4 @SiO 2 nanoparticles could be recycled for ten times with loss of 10% activity. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Photoemission study on electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces

    International Nuclear Information System (INIS)

    Fujimura, Nobuyuki; Ohta, Akio; Ikeda, Mitsuhisa; Makihara, Katsunori; Miyazaki, Seiichi

    2017-01-01

    Electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces have been investigated by X-ray photoelectron spectroscopy (XPS) under monochromatized Al Kα radiation. From the analysis of the cut-off energy for secondary photoelectrons measured at each thinning step of a dielectric layer by wet-chemical etching, an abrupt potential change caused by electrical dipole at SiO_2/Si and HfO_2/SiO_2 interfaces has been clearly detected. Al-gate MOS capacitors with thermally-grown SiO_2 and a HfO_2/SiO_2 dielectric stack were fabricated to evaluate the Al work function from the flat band voltage shift of capacitance-voltage (C-V) characteristics. Comparing the results of XPS and C-V measurements, we have verified that electrical dipole formed at the interface can be directly measured by photoemission measurements. (author)

  6. Thermodynamics of Bi2O3-SiO2 system

    Directory of Open Access Journals (Sweden)

    Onderka B.

    2017-01-01

    Full Text Available Thermodynamic properties of the liquid Bi2O3-SiO2 solutions were determined from the results of the electrochemical measurements by use of the solid oxide galvanic cells with YSZ (Yttria-Stabilized-Zirconia electrolyte. Activities of Bi2O3 in the solutions were determined for 0.2, 0.3, 0.4, and 0.5 SiO2 mole fractions in the temperature range 1073-1293 K from measured electromotive force (e.m.f of the solid electrolyte galvanic cell: Bi, Bi2O3-SiO2 | YSZ | air (pO2 = 0.213 bar Additionally, heat capacity data obtained for two solid phases 6Bi2O3•SiO2 and 2Bi2O3•3SiO2 were included into optimization of thermodynamic properties of the system. Optimization procedure was supported by differential thermal analysis (DTA data obtained in this work as well as those accepted from the literature. Using the data obtained in this work, and the information about phase equilibria found in the literature, binary system Bi2O3-SiO2 was assessed with the ThermoCalc software.

  7. Ag-decorated Fe_3O_4@SiO_2 core-shell nanospheres: Seed-mediated growth preparation and their antibacterial activity during the consecutive recycling

    International Nuclear Information System (INIS)

    Li, Miaomiao; Wu, Wenjie; Qiao, Ru; Tan, Linxiang; Li, Zhengquan; Zhang, Yong

    2016-01-01

    We demonstrated a seed-mediated growth approach to synthesize Ag nanoparticles-decorated Fe_3O_4@SiO_2 core-shell nanospheres without use of surface functionalization. The particle size and decoration density of the immobilized Ag nanoparticles on SiO_2 surface were tunable by adjusting the added AgNO_3 concentration and the alternating repetition times in seed-mediated growth procedure. The as-prepared Ag-decorated Fe_3O_4@SiO_2 nanospheres exhibited excellent antibacterial activities against Escherichia coli, Bacillus subtilis and Candida albicans, in which the minimum inhibitory concentration were 12.5 μg mL"−"1, 50 μg mL"−"1 and 50 μg mL"−"1, respectively. It is speculated that their antibacterial activity is attributed to both the interaction of released Ag ions with the functional groups of vital enzymes and proteins and the strong oxidation of reactive oxygen species generated under the action of photoinduced electrons in Ag nanoparticles. Besides studying their antibacterial mechanism, we also investigated the variation of antibacterial activity of these heterostructured nanospheres during the consecutive magnetic separation and recycling. It shows that the magnetic antibacterial agent could be reused and its activity remained stable even after nine cycles, which enable it to be promisingly applied in biomedical areas. - Highlights: • Ag-decorated Fe_3O_4@SiO_2 were synthesized via a seed-mediated growth method. • The core-shell heterostructures exhibited excellent antibacterial activity. • The activity was attributed to the effect of released Ag"+ with ROS oxidation. • The antibacterial agent was reused during magnetic separation and recycling.

  8. K/sub 4/Si/sub 4/Te/sub 10/, the first tellurosilicate with adamantane-like Si/sub 4/Te/sub 10//sup 4 -/ anions

    Energy Technology Data Exchange (ETDEWEB)

    Eisenmann, B; Schaefer, H [Technische Hochschule Darmstadt (Germany, F.R.). Fachbereich Anorganische Chemie und Kernchemie

    1982-08-01

    The new compound K/sub 4/Si/sub 4/Te/sub 10/ crystallizes in the orthorhombic system (space group Pnma) with following constants: a = 2125.8(8) pm, b = 1200.5(7) pm, c = 1060.8(7) pm. The structure is characterized by SiTe/sub 4/ tetrahedra, connected by common corners to adamantane-like Si/sub 4/Te/sub 10//sup 4 -/ units.

  9. Raman and optical absorption spectroscopic investigation of Yb-Er codoped phosphate glasses containing SiO2

    Institute of Scientific and Technical Information of China (English)

    Youkuo Chen; Lei Wen; Lili Hu; Wei Chen; Y. Guyot; G. Boulon

    2009-01-01

    Yb-Er codoped Na2O-Al2O3-P2Os-xSiO2 glasses containing 0 鈥? 20 mol% SiO2 were prepared successfully. The addition of SiO2 to the phosphate glass not only lengthens the bond between P5+ and non-bridging oxygen but also reduces the number of P=O bond. In contrast with silicate glass in which there is only four-fold coordinated Si4+, most probably there coexist [SiO4] tetrahedron and [SiO6] octahedron in our glasses. Within the range of 0 鈥? 20 mol% SiO2 addition, the stimulated emission cross-section of Er3+ ion only decreases no more than 10%. The Judd-Ofelt intensity parameters of Er3+, 惟.2 does not change greatly, but 惟74 and 惟6 decrease obviously with increasing SiO2 addition, because the bond between Er + and O2- is more strongly covalently bonded.

  10. Vibrational mode frequencies of silica species in SiO2-H2O liquids and glasses from ab initio molecular dynamics.

    Science.gov (United States)

    Spiekermann, Georg; Steele-MacInnis, Matthew; Schmidt, Christian; Jahn, Sandro

    2012-04-21

    Vibrational spectroscopy techniques are commonly used to probe the atomic-scale structure of silica species in aqueous solution and hydrous silica glasses. However, unequivocal assignment of individual spectroscopic features to specific vibrational modes is challenging. In this contribution, we establish a connection between experimentally observed vibrational bands and ab initio molecular dynamics (MD) of silica species in solution and in hydrous silica glass. Using the mode-projection approach, we decompose the vibrations of silica species into subspectra resulting from several fundamental structural subunits: The SiO(4) tetrahedron of symmetry T(d), the bridging oxygen (BO) Si-O-Si of symmetry C(2v), the geminal oxygen O-Si-O of symmetry C(2v), the individual Si-OH stretching, and the specific ethane-like symmetric stretching contribution of the H(6)Si(2)O(7) dimer. This allows us to study relevant vibrations of these subunits in any degree of polymerization, from the Q(0) monomer up to the fully polymerized Q(4) tetrahedra. Demonstrating the potential of this approach for supplementing the interpretation of experimental spectra, we compare the calculated frequencies to those extracted from experimental Raman spectra of hydrous silica glasses and silica species in aqueous solution. We discuss observed features such as the double-peaked contribution of the Q(2) tetrahedral symmetric stretch, the individual Si-OH stretching vibrations, the origin of the experimentally observed band at 970 cm(-1) and the ethane-like vibrational contribution of the H(6)Si(2)O(7) dimer at 870 cm(-1).

  11. Crystal structure of strontium dinickel iron orthophosphate

    Directory of Open Access Journals (Sweden)

    Said Ouaatta

    2015-10-01

    Full Text Available The title compound, SrNi2Fe(PO43, synthesized by solid-state reaction, crystallizes in an ordered variant of the α-CrPO4 structure. In the asymmetric unit, two O atoms are in general positions, whereas all others atoms are in special positions of the space group Imma: the Sr cation and one P atom occupy the Wyckoff position 4e (mm2, Fe is on 4b (2/m, Ni and the other P atom are on 8g (2, one O atom is on 8h (m and the other on 8i (m. The three-dimensional framework of the crystal structure is built up by [PO4] tetrahedra, [FeO6] octahedra and [Ni2O10] dimers of edge-sharing octahedra, linked through common corners or edges. This structure comprises two types of layers stacked alternately along the [100] direction. The first layer is formed by edge-sharing octahedra ([Ni2O10] dimer linked to [PO4] tetrahedra via common edges while the second layer is built up from a strontium row followed by infinite chains of alternating [PO4] tetrahedra and FeO6 octahedra sharing apices. The layers are held together through vertices of [PO4] tetrahedra and [FeO6] octahedra, leading to the appearance of two types of tunnels parallel to the a- and b-axis directions in which the Sr cations are located. Each Sr cation is surrounded by eight O atoms.

  12. Rietveld refinement of the orthorhombic Pbca structures of Rb2CdSi5O12, Cs2MnSiO5O12, Cs2CoSi5O12 and Cs2NiSi5O12 leucites by synchrotron X-ray powder diffraction

    International Nuclear Information System (INIS)

    Bell, A.M.T.; Henderson, C.M.B.

    1996-01-01

    Analysis of high-resolution synchrotron X-ray powder diffraction patterns for hydrothermally synthesized Rb 2 CdSi 5 O 12 and Cs 2 MnSi 5 O 12 leucite analogues, and dry-synthesized Cs 2 CoSi 5 O 12 and Cs 2 NiSi 5 O 12 leucite analogues showed that they have an orthorhombic Pbca structure. The structures have been refined by the Rietveld method, showing that the tetrahedrally coordinated atoms (Si, Cd, Mn, Co and Ni) are ordered on separate sites. The Cs 2 MnSi 5 O 12 , Cs 2 CoSi 5 O 12 and Cs 2 NiSi 5 O 12 leucite samples are unusual in containing SiO 4 tetrahedra which are more distorted, on average, than the larger MnO 4 , CoO 4 and NiO 4 tetrahedra. The JCPDS file numbers for Rb 2 CdSi 5 O 12 , Cs 2 MnSi 5 O 12 and Cs 2 CoSi 5 O 12 are 46-1491, 46-1492 and 46-1493, respectively. (orig.)

  13. Synthesize and characterization of a novel anticorrosive cobalt ferrite nanoparticles dispersed in silica matrix (CoFe2O4-SiO2) to improve the corrosion protection performance of epoxy coating

    International Nuclear Information System (INIS)

    Gharagozlou, M.; Ramezanzadeh, B.; Baradaran, Z.

    2016-01-01

    Highlights: • An anticorrosive cobalt ferrite nanopigment dispersed in silica matrix was synthesized. • The nanopigment showed proper inhibition performance in solution study. • The nanopigment significantly improved the corrosion resistance of the epoxy coating. - Abstract: This study aimed at studying the effect of an anticorrosive nickel ferrite nanoparticle dispersed in silica matrix (NiFe 2 O 4 -SiO 2 ) on the corrosion protection properties of steel substrate. NiFe 2 O 4 and NiFe 2 O 4 -SiO 2 nanopigments were synthesized and then characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscope (TEM). Then, 1 wt.% of nanopigments was dispersed in an epoxy coating and the resultant nanocomposites were applied on the steel substrates. The corrosion inhibition effects of nanopigments were tested by an electrochemical impedance spectroscopy (EIS) and salt spray test. Results revealed that dispersing nickel ferrite nanoparticles in a silica matrix (NiFe 2 O 4 -SiO 2 ) resulted in the enhancement of the nanopigment dispersion in the epoxy coating matrix. Inclusion of 1 wt.% of NiFe 2 O 4 -SiO 2 nanopigment into the epoxy coating enhanced its corrosion protection properties before and after scratching.

  14. Screen-Printed Photochromic Textiles through New Inks Based on SiO2@naphthopyran Nanoparticles.

    Science.gov (United States)

    Pinto, Tânia V; Costa, Paula; Sousa, Céu M; Sousa, Carlos A D; Pereira, Clara; Silva, Carla J S M; Pereira, Manuel Fernando R; Coelho, Paulo J; Freire, Cristina

    2016-10-26

    Photochromic silica nanoparticles (SiO 2 @NPT), fabricated through the covalent immobilization of silylated naphthopyrans (NPTs) based on 2H-naphtho[1,2-b]pyran (S1, S2) and 3H-naphtho[2,1-b]pyran (S3, S4) or through the direct adsorption of the parent naphthopyrans (1, 3) onto silica nanoparticles (SiO 2 NPs), were successfully incorporated onto cotton fabrics by a screen-printing process. Two aqueous acrylic- (AC-) and polyurethane- (PU-) based inks were used as dispersing media. All textiles exhibited reversible photochromism under UV and solar irradiation, developing fast responses and intense coloration. The fabrics coated with SiO 2 @S1 and SiO 2 @S2 showed rapid color changes and high contrasts (ΔE* ab = 39-52), despite presenting slower bleaching kinetics (2-3 h to fade to the original color), whereas the textiles coated with SiO 2 @S3 and SiO 2 @S4 exhibited excellent engagement between coloration and decoloration rates (coloration and fading times of 1 and 2 min, respectively; ΔE* ab = 27-53). The PU-based fabrics showed excellent results during the washing fastness tests, whereas the AC-based textiles evidenced good results only when a protective transfer film was applied over the printed design.

  15. Electron excitations in BeAl2O4, Be2SiO4 and Be3Al2Si6O18 crystals

    International Nuclear Information System (INIS)

    Ivanov, V.Yu.; Pustovarov, V.A.; Shlygin, E.S.; Korotaev, A.V.; Kruzhalov, A.V.

    2005-01-01

    Low-temperature (T = 7 K) time-resolved selectively photoexcited luminescence spectra (2-6 eV) and luminescence excitation spectra (8-35 eV) of wide-bandgap chrysoberyl BeAl 2 O 4 , phenacite Be 2 SiO 4 , and beryl Be 3 Al 2 Si 6 O 18 crystals have been studied using time-resolved VUV spectroscopy. Both the intrinsic luminescence of the crystals and the luminescence associated with structural defects were assigned. Energy transfer to impurity luminescence centers in alexandrite and emerald was investigated. Luminescence characteristics of stable crystal lattice defects were probed by 3.6-MeV accelerated helium ion beams [ru

  16. Performance of NiFe2O4-SiO2-TiO2 Magnetic Photocatalyst for the Effective Photocatalytic Reduction of Cr(VI in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Mike O. Ojemaye

    2017-01-01

    Full Text Available Investigation into the reduction of Cr(VI in aqueous solution was carried out through some batch photocatalytic studies. The photocatalysts used were silica coated nickel ferrite nanoparticles (NiFe2O4-SiO2, nickel ferrite titanium dioxide (NiFe2O4-TiO2, nickel ferrite silica titanium dioxide (NiFe2O4-SiO2-TiO2, and titanium dioxide (TiO2. The characterization of the materials prepared via stepwise synthesis using coprecipitation and sol-gel methods were carried out with the aid of X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM, Fourier transform infrared (FTIR spectroscopy, thermal gravimetric analysis (TGA, and vibrating sample magnetometry (VSM. The reduction efficiency was studied as a function of pH, photocatalyst dose, and contact time. The effects of silica interlayer between the magnetic photocatalyst materials reveal that reduction efficiency of NiFe2O4-SiO2-TiO2 towards Cr(VI was higher than that of NiFe2O4-TiO2. However, TiO2 was observed to have the highest reduction efficiency at all batch photocatalytic experiments. Kinetics study shows that photocatalytic reduction of Cr(VI obeyed Langmuir-Hinshelwood model and first-order rate kinetics. Regenerability study also suggested that the photocatalyst materials can be reused.

  17. Development of nano SiO2 incorporated nano zinc phosphate coatings on mild steel

    International Nuclear Information System (INIS)

    Tamilselvi, M.; Kamaraj, P.; Arthanareeswari, M.; Devikala, S.; Selvi, J. Arockia

    2015-01-01

    Highlights: • Nano SiO 2 incorporated nano zinc phosphate coating on mild steel was developed. • Coatings showed enhanced corrosion resistance. • The nano SiO 2 is adsorbed on mild steel surface and become nucleation sites. • The nano SiO 2 accelerates the phosphating process. - Abstract: This paper reports the development of nano SiO 2 incorporated nano zinc phosphate coatings on mild steel at low temperature for achieving better corrosion protection. A new formulation of phosphating bath at low temperature with nano SiO 2 was attempted to explore the possibilities of development of nano zinc phosphate coatings on mild steel with improved corrosion resistance. The coatings developed were studied by Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Electrochemical measurements. Significant variation in the coating weight, morphology and corrosion resistance was observed as nano SiO 2 concentrations varied from 0.5–4 g/L. The results showed that, the nano SiO 2 in the phosphating solution changed the initial potential of the interface between mild steel substrate and phosphating solution and reduce the activation energy of the phosphating process, increase the nucleation sites and yielded zinc phosphate coatings of higher coating weight, greater surface coverage and enhanced corrosion resistance. Better corrosion resistance was observed for coatings derived from phosphating bath containing 1.5 g/L nano SiO 2 . The new formulation reported in the present study was free from Ni or Mn salts and had very low concentration of sodium nitrite (0.4 g/L) as accelerator

  18. SiO EMISSION AS A TRACER OF X-RAY DOMINATED CHEMISTRY IN THE GALACTIC CENTER

    International Nuclear Information System (INIS)

    Amo-Baladron, M. A.; Martin-Pintado, J.; Morris, M. R.; Muno, M. P.; RodrIguez-Fernandez, N. J.

    2009-01-01

    We present emission maps of the Sgr A molecular cloud complex at the Galactic center (GC) in the J = 2 → 1 line of SiO observed with the IRAM 30 m telescope at Pico Veleta. Comparing our SiO(2-1) data cube with that of CS(1-0) emission with similar angular and velocity resolution, we find a correlation between the SiO/CS line intensity ratio and the equivalent width of the Fe Kα fluorescence line at 6.4 keV. We discuss the SiO abundance enhancement in terms of the two most plausible scenarios for the origin of the 6.4 keV Fe line: X-ray reflection nebula (XRN) and low-energy cosmic rays (LECRs). Both scenarios could explain the enhancement in the SiO/CS intensity ratio with the intensity of the 6.4 keV Fe line, but both present difficulties. The XRN scenario requires a population of very small grains to produce the SiO abundance enhancement, together with a past episode of bright X-ray emission from some source in the GC, possibly the central supermassive black hole, SgrA*, ∼300 yr ago. The LECR scenario needs higher gas column densities to produce the observed 6.4 keV Fe line intensities than those derived from our observations. It is possible to explain the SiO abundance enhancement if the LECRs originate in supernovae and their associated shocks produce the SiO abundance enhancement. However, the LECR scenario cannot account for the time variability of the 6.4 keV Fe line, which can be naturally explained by the XRN scenario.

  19. Enhanced Photocatalytic Activity of ZrO2-SiO2 Nanoparticles by Platinum Doping

    Directory of Open Access Journals (Sweden)

    Mohammad W. Kadi

    2013-01-01

    Full Text Available ZrO2-SiO2 mixed oxides were prepared via the sol-gel method. Photo-assisted deposition was utilized for doping the prepared mixed oxide with 0.1, 0.2, 0.3, and 0.4 wt% of Pt. XRD spectra showed that doping did not result in the incorporation of Pt within the crystal structure of the material. UV-reflectance spectrometry showed that the band gap of ZrO2-SiO2 decreased from 3.04 eV to 2.48 eV with 0.4 wt% Pt doping. The results show a specific surface area increase of 20%. Enhanced photocatalysis of Pt/ZrO2-SiO2 was successfully tested on photo degradation of cyanide under illumination of visible light. 100% conversion was achieved within 20 min with 0.3 wt% of Pt doped ZrO2-SiO2.

  20. Synthesis of ceramic powders of La9,56 (SiO4)6O2,34 and La9,8Si5,7MgO,3O26,4 by modified sol-gel process

    International Nuclear Information System (INIS)

    Lira, Sabrina Lopes; Paiva, Mayara Rafaela Soares; Misso, Agatha Matos; Elias, Daniel Ricco; Yamagata, Chieko

    2012-01-01

    Lanthanum silicate oxyapatite materials are promising for application as electrolyte in solid oxide fuel cells because of high ionic conductivity at temperatures between 600 deg C and 800 deg C. In this work, oxyapatites with the composition La 9,56 (SiO 4 ) 6 O 2,34 , and La 9,8 Si 5,7 Mg 0,3 O 26,4 were synthesized by using the sol-gel method, followed by precipitation. Initially, the gel of silica was synthesized from sodium silicate solution, by acid catalysis using lanthanum and magnesium chloride solution. Then, the La and Mg hydroxides were precipitated with NaOH in the gel. The powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and measurements of specific surface area. The crystalline oxyapatite phase of La 9,56 (SiO 4 ) 6 O 2,34 , and was La 9,8 Si 5,7 Mg 0,3 O 26,4 obtained by calcination at 900 deg C for 2 and 1h respectively (author)

  1. Synthesis of C14/Fe3O4@SiO2 and Its Performance in Removing Uranium (VI from Aqueous Solutions and Real Wastewater Using Benzamide

    Directory of Open Access Journals (Sweden)

    Zohreh Akbari Jonoosh

    2016-09-01

    Full Text Available Uranium separation and removal are important from environmental, public health, and strategic veiwpoints. Scientits have put great efforts to develop technologies for uranium removal and regeneration because of its important applications and beneficial uses. In this study, efforts have been made to synthesize a modified form of Fe3O4@SiO2 and benzamide uranium complexes that can be exploited to remove and adsorb uranium onto an adsorbent that can be recycled. In the first step, Fe3O4@SiO2 was synthesized and later modified with trimethoxysilane. The adsorbent was subsequently characterized by SEM and FTIR.  In a second step, experiments were performed to determine optimum stirring speed, contact time, ion strength, and adsorbent reusability. Finally, the performance of the adsorbent was tested in samples of real wastewater. SEM and FTIR analyses confirmed the satisfactory synthesis and modification of Fe3O4@SiO2 Nps. Statistical analyses revealed that although contact time, ion strength, and stirring speed were effective in adsorbent performance, they only led to a removal enhancement of 5% and a decrease of only 17% with increasing RPM to 250 and the enhancement of ion strength to 1.5M. The highest U(VI removal efficiency in the synthetic solution was found to be 97%, which reduced to 49% in real wastewater samples. It was concluded that the nano-composite C14/SiO2_Fe3O4 adsorbent with its magnetic core and resistant surface not only offers the possibility for easy separation of urnaium from solutions but is also reusable and is only slightly affected by changes in stirring speed or ion strength. It, therefore, has a good capability for use as a U(VI adsorbent in wastewater treatment.

  2. TiO2/SiO2 prepared via facile sol-gel method as an ideal support for green synthesis of Ag nanoparticles using Oenothera biennis extract and their excellent catalytic performance in the reduction of 4-nitrophenol

    Directory of Open Access Journals (Sweden)

    Bahar Khodadadi

    2017-01-01

    Full Text Available In the present study, the extract of the plant of Oenothera biennis was used to green synthesis of silver nanoparticles (Ag NPs as an environmentally friendly, simple and low cost method. And Additionally, TiO2/SiO2 was prepared via facile sol-gel method using starch as an important, naturally abundant organic polymer as an ideal support. The Ag NPs/TiO2/SiO2 as an effective catalyst was prepared through reduction of Ag+ ions using Oenothera biennis extract as the reducing and stabilizing agent and Ag NPs immobilization on TiO2/SiO2 surface in the absence of any stabilizer or surfactant. Several techniques such as FT-IR spectroscopy, UV-Vis spectroscopy, X-ray Diffraction (XRD, sScanning eElectron mMicroscopy (FE-SEM, Eenergy dDispersive X-ray sSpectroscopy (EDS, and Ttransmission Eelectron Mmicroscopy (TEM were used to characterize TiO2/SiO2, silver nanoparticles (Ag NPs, and Ag NPs/TiO2/SiO2. Moreover, the catalytic activity of the Ag NPs/ TiO2/SiO2 was investigated in the reduction of 4-nitrophenol (4-NP at room temperature. On the basis of the results, the Ag NPs/TiO2/SiO2 was found to be high catalytic activity highly active catalyst according to the experimental results in this study. In addition, Ag NPs/TiO2/SiO2 can be recovered and reused several times in the reduction of 4-NP with no significant loss of catalytic activity.

  3. Mild hydrothermal synthesis, crystal structure, thermal behavior, spectroscopic and magnetic properties of the (NH4)[Fe(AsO4)1-x(PO4)xF] (x=0.3, 0.6, 0.8) series. Thermal transformation of (NH4)[Fe(AsO4)0.7(PO4)0.3F] into the textural porous orthorhombic Fe(AsO4)0.7(PO4)0.3

    International Nuclear Information System (INIS)

    Berrocal, Teresa; Mesa, Jose L.; Pizarro, Jose L.; Bazan, Begona; Lezama, Luis; Arriortua, Maria I.; Rojo, Teofilo

    2009-01-01

    The (NH 4 )[Fe(AsO 4 ) 1-x (PO 4 ) x F] (x=0.3, 0.6, 0.8) series of compounds has been synthesized under mild hydrothermal conditions. The compounds crystallize in the orthorhombic Pna2 1 space group, with the unit-cell parameters a=13.1718(1), b=6.5966(6), c=10.797(1) A for x=0.3; a=13.081(1), b=6.5341(6), c=10.713(1) A for x=0.6 and a=13.0329(9), b=6.4994(4), c=10.6702(6) A for x=0.8, with the volumes 938.6(1), 915.7(1) and 903.8(1) A 3 , respectively, with Z=8. Single crystals of (NH 4 )[Fe(AsO 4 ) 0.7 (PO 4 ) 0.3 F] heated under air atmosphere at 465 deg. C remain as single crystals, changing the composition to Fe(AsO 4 ) 0.7 (PO 4 ) 0.3 . This later phase belongs to the orthorhombic Imam space group, with the unit cell parameters a=13.328(2), b=6.5114(5), c=10.703(1) A, V=928.9(2) A 3 and Z=12. The crystal structure of the ammonium phases consists of a KTP three-dimensional framework constructed by chains formed by alternating Fe(2)O 4 F 2 or Fe(1)O 4 F 2 octahedra and As/P(2)O 4 or As/P(1)O 4 tetrahedra, respectively. These octahedra and tetrahedra are linked by a common oxygen vertex. The chains run along the 'a' and 'b' crystallographic axes. The crystal structure of Fe(AsO 4 ) 0.7 (PO 4 ) 0.3 is a three-dimensional skeleton derived from that of the precursor, formed from (100) sheets stacked along the [001] direction, and interconnected by chains of alternating Fe(2)O 6 octahedra and As/P(2)O 4 tetrahedra sharing a vertex in the 'a' direction. Transmission electronic microscopy of this compound indicates the existence of unconnected external cavities with a BET surface area of 3.91(3) m 2 g -1 . The diffuse reflectance spectra in the visible region show the forbidden electronic transitions characteristic of the Fe(III) d 5 -high spin cation in slightly distorted octahedral geometry, for all the compounds. The ESR spectra for all the compounds, carried out from room temperature to 4.2 K, remain isotropic with variation in temperature; the g-value is 1

  4. FE3O4@SIO2-OSO3H NANOCOMPOSITE AS AN EFFICIENT CATALYST FOR THE PREPARATION OF TRICARBOXAMIDES

    Directory of Open Access Journals (Sweden)

    Mohammad Ali Ghasemzadeh

    Full Text Available In this research a highly efficient one-pot preparation of tricarboxamide derivatives via five-component reactions of isocyanides, aldehydes Meldrum's acid and 2equiv. of amines have been developed in the presence of Fe3O4@SiO2-OSO3H nanocomposite. Nano-Fe3O4 encapsulated-silica particles bearing sulfonic acid was readily recovered using an external magnet and could be reused several times without significant loss of reactivity. The catalyst was fully characterized by VSM, FT-IR, SEM, XRD, EDX and TEM analysis.

  5. Summary of mechanical properties data and correlations for Li2O, Li4SiO4, LiAlO2, and Be

    International Nuclear Information System (INIS)

    Billone, M.C.; Grayhack, W.T.

    1988-04-01

    The data base for thermal expansion, elastic constants, compressive and tensile failure strengths and secondary thermal creep of leading solid-breeder (Li 2 O, Li 4 SiO 4 , and LiAlO 2 ) and multiplier (Be) materials is reviewed, porosity, grain size, and stress (for thermal creep). Because the data base is rather sparse in some areas, general properties of ceramics and metals are used to help guide the formulation of the correlations. The primary purpose of the data base summary and correlation development is to pave the way for stress analysis sensitivity studies. These studies will help determine which properties are important enough to structural lifetime and deformation assessments to require more data. 18 refs., 5 figs., 20 tabs

  6. Do SiO 2 and carbon-doped SiO 2 nanoparticles melt? Insights from QM/MD simulations and ramifications regarding carbon nanotube growth

    Science.gov (United States)

    Page, Alister J.; Chandrakumar, K. R. S.; Irle, Stephan; Morokuma, Keiji

    2011-05-01

    Quantum chemical molecular dynamics (QM/MD) simulations of pristine and carbon-doped SiO 2 nanoparticles have been performed between 1000 and 3000 K. At temperatures above 1600 K, pristine nanoparticle SiO 2 decomposes rapidly, primarily forming SiO. Similarly, carbon-doped nanoparticle SiO 2 decomposes at temperatures above 2000 K, primarily forming SiO and CO. Analysis of the physical states of these pristine and carbon-doped SiO 2 nanoparticles indicate that they remain in the solid phase throughout decomposition. This process is therefore one of sublimation, as the liquid phase is never entered. Ramifications of these observations with respect to presently debated mechanisms of carbon nanotube growth on SiO 2 nanoparticles will be discussed.

  7. Microstructural, thermal, physical and mechanical behavior of the self compacting concrete containing SiO2 nanoparticles

    International Nuclear Information System (INIS)

    Nazari, Ali; Riahi, Shadi

    2010-01-01

    Research highlights: → TiO 2 nanoparticles effects on flexural strength of self compacting concrete. → Physical and microstructural consideration. → Mechanical tests. → Thermal analysis. → Porosimetry. - Abstract: In the present study, flexural strength, thermal properties and microstructure of self compacting concrete with different amount of SiO 2 nanoparticles has been investigated. SiO 2 nanoparticles with the average particle size of 15 nm were partially added to self compacting concrete and various behaviors of the specimens have been measured. The results indicate that SiO 2 nanoparticles are able to improve the flexural strength of self compacting concrete and recover the negative effects of superplasticizer on flexural strength of the specimens. SiO 2 nanoparticle as a partial replacement of cement up to 4 wt% could accelerate C-S-H gel formation as a result of the increased crystalline Ca(OH) 2 amount at the early ages of hydration. The increased the SiO 2 nanoparticles' content more than 4 wt%, causes the reduced the flexural strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all also indicate that SiO 2 nanoparticles up to 4 wt% could improve the mechanical and physical properties of the specimens. Finally, SiO 2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.

  8. Surface Phenomena During Plasma-Assisted Atomic Layer Etching of SiO2.

    Science.gov (United States)

    Gasvoda, Ryan J; van de Steeg, Alex W; Bhowmick, Ranadeep; Hudson, Eric A; Agarwal, Sumit

    2017-09-13

    Surface phenomena during atomic layer etching (ALE) of SiO 2 were studied during sequential half-cycles of plasma-assisted fluorocarbon (CF x ) film deposition and Ar plasma activation of the CF x film using in situ surface infrared spectroscopy and ellipsometry. Infrared spectra of the surface after the CF x deposition half-cycle from a C 4 F 8 /Ar plasma show that an atomically thin mixing layer is formed between the deposited CF x layer and the underlying SiO 2 film. Etching during the Ar plasma cycle is activated by Ar + bombardment of the CF x layer, which results in the simultaneous removal of surface CF x and the underlying SiO 2 film. The interfacial mixing layer in ALE is atomically thin due to the low ion energy during CF x deposition, which combined with an ultrathin CF x layer ensures an etch rate of a few monolayers per cycle. In situ ellipsometry shows that for a ∼4 Å thick CF x film, ∼3-4 Å of SiO 2 was etched per cycle. However, during the Ar plasma half-cycle, etching proceeds beyond complete removal of the surface CF x layer as F-containing radicals are slowly released into the plasma from the reactor walls. Buildup of CF x on reactor walls leads to a gradual increase in the etch per cycle.

  9. Silane effects on the surface morphology and abrasion resistance of transparent SiO2/UV-curable resin nano-composites

    International Nuclear Information System (INIS)

    Hsiang, Hsing-I.; Chang, Yu-Lun; Chen, Chi-Yu; Yen, Fu-Su

    2011-01-01

    Transparent ultraviolet curable nano-composite coatings consisting of nano-sized SiO 2 and acrylate resin have been developed to improve the abrasion resistance of organic polymers. The nano-sized SiO 2 particles were surface-modified using various amounts of 3-methacryloxypropyltrimethoxysilane. The 3-methacryloxypropyltrimethoxysilane concentration effects on the surface morphology and abrasion resistance of the transparent SiO 2 /ultraviolet-curable resin nano-composites were investigated using scanning electron microscopy, atomic force microscopy, and ultraviolet-visible spectrophotometer. The results showed that as the 3-methacryloxypropyltrimethoxysilane/SiO 2 weight ratio increased from 0.2 to 0.6, the dispersion, compatibility and cross-linking density between the 3-methacryloxypropyltrimethoxysilane-modified SiO 2 particles and acrylate resin were improved, leading to an increase in abrasion resistance. However, as the 3-methacryloxypropyltrimethoxysilane/SiO 2 weight ratio was increased to 1.5, the additional 3-methacryloxypropyltrimethoxysilane may exceed that needed to fill the pores with the probability of SiO 2 nano-particles existing on the coating surface was lower than that for samples with a 3-methacryloxypropyltrimethoxysilane/SiO 2 weight ratio of 0.6. This produced a decrease in abrasion resistance.

  10. Exploring the Phase Diagram SiO2-CO2 at High Pressures and Temperatures

    Science.gov (United States)

    Kavner, A.

    2015-12-01

    CO2 is an important volatile system relevant for planetary sciences and fundamental chemistry. Molecular CO2 has doubly bonded O=C=O units but high pressure-high temperature (HP-HT) studies have recently shown its transformation into a three-dimensional network of corner-linked [CO4] units analogous to the silica mineral polymorphs, through intermediate non-molecular phases. Here, we report P-V-T data on CO2-IV ice from time-of-flight neutron diffraction experiments, which allow determining the compressibility and thermal expansivity of this intermediate molecular-to-non-molecular phase.1 Aditionally, we have explored the SiO2-CO2 phase diagram and the potential formation of silicon carbonate compounds. New data obtained by laser-heating diamond-anvil experiments in CO2-filled microporous silica polymorphs will be shown. In particular, these HP-HT experiments explore the existence of potential CO2/SiO2 compounds with tetrahedrally-coordinated C/Si atoms by oxygens, which are predicted to be stable (or metastable) by state-of-the-art ab initio simulations.2,3 These theoretical predictions were supported by a recent study that reports the formation of a cristobalite-type Si0.4C0.6O2 solid solution at high-pressures and temperatures, which can be retained as a metastable solid down to ambient conditions.4 Entirely new families of structures could exist based on [CO4]4- units in various degrees of polymerisation, giving rise to a range of chain, sheet and framework solids like those found in silicate chemistry. References[1] S. Palaich et al., Am. Mineral. Submitted (2015) [2] A. Morales-Garcia et al., Theor. Chem. Acc. 132, 1308 (2013) [3] R. Zhou et al., Phys. Rev. X, 4, 011030 (2014) [4] M. Santoro et al. Nature Commun. 5, 3761 (2014)

  11. The millimeter-wave spectrum of highly vibrationally excited SiO

    International Nuclear Information System (INIS)

    Mollaaghababa, R.; Gottlieb, C.A.; Vrtilek, J.M.; Thaddeus, P.

    1991-01-01

    The millimeter-wave rotational spectra of SiO in high vibrational states (v = 0-40) in its electronic ground state were measured between 228 and 347 GHz in a laboratory discharge through SiH4 and CO. On ascending the vibrational ladder, populations decline precipitously for the first few levels, with a vibrational temperature of about 1000 K; at v of roughly 3, however, they markedly flatten out, and from there to v of roughly 40 the temperature is of the order of 10,000 K. With the Dunham coefficients determined here, the rotational spectrum of highly vibrationally excited SiO can now be calculated into the far-infrared to accuracies required for radioastronomy. Possible astronomical sources of highly vibrationally excited SiO are certain stellar atmospheres, ultracompact H II regions, very young supernova ejecta, and dense interstellar shocks. 16 refs

  12. Structure of Na/sub 2/As/sub 4/O/sub 11/

    Energy Technology Data Exchange (ETDEWEB)

    Driss, A.; Jouini, T.; Omezzine, M.

    1988-05-15

    Disodium tetraarsenate, M/sub r/=521.66, monoclinic, C2/c, a=9.049(3), b=8.287(3), c=11.508(5) A, ..beta..=102.74(4)/sup 0/, V=842(2) A/sup 3/, Z=4, D/sub m/=4.06 (by flotation), D/sub x/=4.11 Mg m/sup -3/, lambda(AgK anti ..cap alpha..)=0.5608 A, ..mu..=8.6 mm/sup -1/, F(000)=968, room temperature, final R=0.046 and ..omega..R=0.048 for 1153 independent reflections. The main feature of this structure is the existence of the first three-dimensional anion (As/sub 4/O/sub 11/)/sub n//sup 2n-/ in the chemistry of the condensed arsenates. It has the lowest O/As ratio (2.75) of the known arsenates showing marked condensation: all the O atoms are shared except one per AsO/sub 4/ tetrahedron. The structural unit is the As/sub 4/O/sub 15/ ring with point symmetry 2, built up from alternate AsO/sub 4/ tetrahedra and AsO/sub 6/ octahedra sharing corners. In addition, the two octahedra share one O atom located on the 2 axis. The As/sub 4/O/sub 15/ ring derives from the known centrosymmetric As/sub 4/O/sub 14/ ring by the cleavage of one As-O-As linkage between the two octahedra of the ring to form two new As-O-As linkages with AsO/sub 4/ tetrahedra connecting two rings, leading to a decrease of the O/As ratio. The As/sub 4/O/sub 15/ rings are further linked by sharing edges of AsO/sub 6/ octahedra to form a three-dimensional framework. This completes the set of the already known arrangements of the As/sub 4/O/sub 14/ ring (isolated units, infinite chains, layers).

  13. Association behaviour of 241Am(III) on SiO2(amorphous) and SiO2(quartz) colloids

    International Nuclear Information System (INIS)

    Degueldre, C.; Wernli, B.

    1993-01-01

    SiO 2 colloids have been identified as a potential vector for enhancing radionuclide transport in granitic groundwater and in concrete pore water. The sorption behaviour of 241 Am(III) on SiO 2 colloids was studied as a function of americium concentration pH (5-12), colloid concentration, ionic strength, temperature and SiO 2 allotropic species. The Am(III) sorption mechanism on amorphous silica is different from that on quartz. For SiO 2(amorphous) solution, the variation of log K p (ml g -1 ) with pH is linear (pH=5-9) with a slope of +1 indicating a one proton exchange mechanism. The colloid concentration (ppm) affects the sorption and log K p 3.7-0.67 log [SiO 2 ] (pH = 6). K p increases insignificantly when the ionic strength decreases. It shows no significant variation, however, with the Am concentration. On amorphous silica, the Am(III) sorption is driven by proton exchange from the silanol groups. For SiO 2 (quartz), log K p is constant over a large range of quartz concentration in suspension and the variation of log K p with pH is about linear (pH = 5-12), with a slope of 0.28, indicating a more complex exchange mechanism. Reactions taking into account the interaction of positive Am(OH) w (3-w)+ species on to the negatively charged quartz surface are suggested. (author)

  14. Crystal structure, equation of state, and elasticity of hydrous aluminosilicate phase, topaz-OH (Al2SiO4(OH)2) at high pressures

    Science.gov (United States)

    Mookherjee, Mainak; Tsuchiya, Jun; Hariharan, Anant

    2016-02-01

    We examined the equation of state and high-pressure elasticity of the hydrous aluminosilicate mineral topaz-OH (Al2SiO4(OH)2) using first principles simulation. Topaz-OH is a hydrous phase in the Al2O3-SiO2-H2O (ASH) ternary system, which is relevant for the mineral phase relations in the hydrated sedimentary layer of subducting slabs. Based on recent neutron diffraction experiments, it is known that the protons in the topaz-OH exhibit positional disorder with half occupancy over two distinct crystallographic sites. In order to adequately depict the proton environment in the topaz-OH, we examined five crystal structure models with distinct configuration for the protons in topaz-OH. Upon full geometry optimization we find two distinct space group, an orthorhombic Pbnm and a monoclinic P21/c for topaz-OH. The topaz-OH with the monoclinic P21/c space group has a lower energy compared to the orthorhombic Pbmn space group symmetry. The pressure-volume results for the monoclinic topaz-OH is well represented by a third order Birch-Murnaghan formulation, with V0mon = 348.63 (±0.04) Å3, K0mon = 164.7 (±0.04) GPa, and K0mon = 4.24 (±0.05). The pressure-volume results for the orthorhombic topaz-OH is well represented by a third order Birch-Murnaghan formulation, with V0orth = 352.47 (±0.04) Å3, K0orth = 166.4 (±0.06) GPa, and K0orth = 4.03 (±0.04). While the bulk moduli are very similar for both the monoclinic and orthorhombic topaz-OH, the shear elastic constants and the shear moduli are very sensitive to the position of the proton, orientation of the O-H dipole, and the space group symmetry. The S-wave anisotropy for the orthorhombic and monoclinic topaz-OH are also quite distinct. In the hydrated sedimentary layer of subducting slabs, transformation of a mineral assemblage consisting of coesite (SiO2) and diaspore (AlOOH) to topaz-OH (Al2SiO4(OH)2) is likely to be accompanied by an increase in density, compressional velocity, and shear wave velocity. However

  15. Mixed hemimicelles solid-phase extraction based on ionic liquid-coated Fe3O4/SiO2 nanoparticles for the determination of flavonoids in bio-matrix samples coupled with high performance liquid chromatography.

    Science.gov (United States)

    He, Huan; Yuan, Danhua; Gao, Zhanqi; Xiao, Deli; He, Hua; Dai, Hao; Peng, Jun; Li, Nan

    2014-01-10

    A novel magnetic solid-phase extraction (MSPE) method based on mixed hemimicelles of room temperature ionic liquids (RTILs) coated Fe3O4/SiO2 nanoparticles (NPs) was developed for simultaneous extraction of trace amounts of flavonoids in bio-matrix samples. A comparative study on the use of RTILs (C16mimBr) and CTAB-coated Fe3O4/SiO2 NPs as sorbents was presented. Owing to bigger adsorption amounts for analytes, RTILs-coated Fe3O4/SiO2 NPs was selected as MSPE materials and three analytes luteolin, quercetin and kaempferol can be quantitatively extracted and simultaneously determined coupled with high performance liquid chromatography (HPLC) in urine samples. No interferences were caused by proteins or endogenous compounds. Good linearity (R(2)>0.9993) for all calibration curves was obtained, and the limits of detection (LOD) for luteolin, quercetin and kaempferol were 0.10 ng/mL, 0.50 ng/mL and 0.20 ng/mL in urine samples, respectively. Satisfactory recoveries (93.5-97.6%, 90.1-95.4% and 93.3-96.6% for luteolin, quercetin and kaempferol) in biological matrices were achieved. It was notable that while using a small amount of Fe3O4/SiO2 NPs (4.0 mg) and C16mimBr (1.0 mg), satisfactory preconcentration factors and extraction recoveries for the three flavonoids were obtained. To the best of our knowledge, this is the first time a mixed hemimicelles MSPE method based on RTILs and Fe3O4/SiO2 NPs magnetic separation has ever been used for pretreatment of complex biological samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  16. Bioactivity and mineralization of hydroxyapatite with bioglass as sintering aid and bioceramics with Na3Ca6(PO4)5 and Ca5(PO4)2SiO4 in a silicate matrix

    International Nuclear Information System (INIS)

    Demirkiran, Hande; Mohandas, Arunesh; Dohi, Motokazi; Fuentes, Alonso; Nguyen, Kytai; Aswath, Pranesh

    2010-01-01

    Hydroxyapatite and Bioglass-45S5 were sintered together creating new ceramic compositions that yielded increased apatite deposition and osteoblast differentiation and proliferation in vitro compared to hydroxyapatite. The sintered products characterized by X-ray diffraction, revealed hydroxyapatite as the main phase when small quantities (1, 2.5 and 5 wt.%) of bioglass was added. Bioglass behaved as a sintering aid with β-TCP (Ca 3 (PO 4 ) 2 ) being the minor phase. The amount of β-TCP increased with the amount of bioglass added. In compositions with larger additions of bioglass (10 and 25 wt.%), new phases with compositions of calcium phosphate silicate (Ca 5 (PO 4 ) 2 SiO 4 ) and sodium calcium phosphate (Na 3 Ca 6 (PO 4 ) 5 ) were formed respectively within amorphous silicate matrices. In vitro cell culture studies of the ceramic compositions were examined using bone marrow stromal cell (BMSC). Cell proliferation and differentiation of bone marrow stromal cells into osteoblasts were determined by Pico Green DNA assays and alkaline phosphatase (ALP) activity, respectively. All hydroxyapatite-bioglass co-sintered ceramics exhibited larger cell proliferation compared to pure hydroxyapatite samples. After 6 days in cell culture, the ceramic with Ca 5 (PO 4 ) 3 SiO 4 in a silicate matrix formed by reacting hydroxyapatite with 10 wt.% bioglass exhibited the maximum proliferation of the BMSC's. The ALP activity was found to be largest in the ceramic with Na 3 Ca 6 (PO 4 ) 5 embedded in a silicate matrix synthesized by reacting hydroxyapatite with 25 wt.% bioglass.

  17. Viscosity Measurements of SiO2-"FeO"-MgO System in Equilibrium with Metallic Fe

    Science.gov (United States)

    Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

    2014-01-01

    The present study delivers the measurements of viscosities in the SiO2-"FeO"-MgO system in equilibrium with metallic Fe. The rotational spindle technique was used for the measurements at the temperature range of 1523 K to 1773 K (1250 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The viscosity measurements were carried out at 31 to 47 mol pct SiO2 and up to 18.8 mol pct MgO. Analysis of the quenched sample by Electron probe X-ray microanalysis after the viscosity measurement enables the composition and microstructure of the slag to be directly linked with the viscosity. The replacement of "FeO" by MgO was found to increase viscosity and activation energy of the SiO2-"FeO"-MgO slags. The modified Quasi-chemical Viscosity Model was further optimized in this system based on the current viscosity measurements.

  18. Imprinted sol-gel electrochemical sensor for the determination of benzylpenicillin based on Fe3O4/SiO2 multi-walled carbon nanotubes-chitosans nanocomposite film modified carbon electrode

    International Nuclear Information System (INIS)

    Hu Yufang; Li Jiaxing; Zhang Zhaohui; Zhang Huabin; Luo Lijuan; Yao Shouzhuo

    2011-01-01

    Graphical abstract: A novel imprinted sol-gel electrochemical sensor based on Fe 3 O 4 /SiO 2 -MWNTs-CTS nanocomposite film and a thin MIP film has been developed on a carbon electrode. Highlights: → A novel imprinted sol-gel electrochemical sensor based on Fe 3 O 4 /SiO 2 -MWNTs-CTS nanocomposites has been developed. → Fe 3 O 4 /SiO 2 -MWNTs-CTS nanocomposites act as 'electronic wires' to enhance the electron transfer. → The inherent specificity of the MIPs brings about highly selectivity. The imprinted sensor detects benzylpenicillin in real samples successfully. - Abstract: Herein, a novel imprinted sol-gel electrochemical sensor based on multi-walled carbon nanotubes (MWNTs) doped with chitosan film on a carbon electrode has been developed. Prior to doped, the MWNTs have been decorated with Fe 3 O 4 nanoparticles which have been coated uniformly with SiO 2 layer. The characterization of imprinted sensor has been carried out by X-ray diffraction and scanning electron microscopy. The performance of the proposed imprinted sensor has been investigated using cyclic voltammetry and differential pulse voltammetry. The imprinted sensor offers a fast response and sensitive benzylpenicillin quantification. The fabricated benzylpenicillin imprinted sensor exhibits a linear response from 5.0 x 10 -8 to 1.0 x 10 -3 mol L -1 with a detection limit of 1.5 x 10 -9 mol L -1 . For samples analysis, perfect recoveries of the imprinted sensor for benzylpenicillin indicated that the imprinted sensor was able to detect benzylpenicillin in real samples successfully.

  19. Gold Nanoparticles on Mesoporous SiO2-Coated Magnetic Fe3O4 Spheres: A Magnetically Separatable Catalyst with Good Thermal Stability

    Directory of Open Access Journals (Sweden)

    Huan Liu

    2013-11-01

    Full Text Available Fe3O4 spheres with an average size of 273 nm were prepared in the presence of CTAB by a solvothermal method. The spheres were modified by a thin layer of SiO2, and then coated by mesoporous SiO2 (m-SiO2 films, by using TEOS as a precursor and CTAB as a soft template. The resulting m-SiO2/Fe3O4 spheres, with an average particle size of 320 nm, a high surface area (656 m2/g, and ordered nanopores (average pore size 2.5 nm, were loaded with gold nanoparticles (average size 3.3 nm. The presence of m-SiO2 coating could stabilize gold nanoparticles against sintering at 500 °C. The material showed better performance than a conventional Au/SiO2 catalyst in catalytic reduction of p-nitrophenol with NaBH4. It can be separated from the reaction mixture by a magnet and be recycled without obvious loss of catalytic activity. Relevant characterization by XRD, TEM, N2 adsorption-desorption, and magnetic measurements were conducted.

  20. Fluorescent Quantification of DNA Based on Core-Shell Fe3O4@SiO2@Au Nanocomposites and Multiplex Ligation-Dependent Probe Amplification.

    Science.gov (United States)

    Fan, Jing; Yang, Haowen; Liu, Ming; Wu, Dan; Jiang, Hongrong; Zeng, Xin; Elingarami, Sauli; Ll, Zhiyang; Li, Song; Liu, Hongna; He, Nongyue

    2015-02-01

    In this research, a novel method for relative fluorescent quantification of DNA based on Fe3O4@SiO2@Au gold-coated magnetic nanocomposites (GMNPs) and multiplex ligation- dependent probe amplification (MLPA) has been developed. With the help of self-assembly, seed-mediated growth and chemical reduction method, core-shell Fe3O4@SiO2@Au GMNPs were synthesized. Through modified streptavidin on the GMNPs surface, we obtained a bead chip which can capture the biotinylated probes. Then we designed MLPA probes which were tagged with biotin or Cy3 and target DNA on the basis of human APP gene sequence. The products from the thermostable DNA ligase induced ligation reactions and PCR amplifications were incubated with SA-GMNPs. After washing, magnetic separation, spotting, the fluorescent scanning results showed our method can be used for the relative quantitative analysis of the target DNA in the concentration range of 03004~0.5 µM.

  1. Redetermination of clinobaryl-ite, BaBe(2)Si(2)O(7).

    Science.gov (United States)

    Domizio, Adrien J Di; Downs, Robert T; Yang, Hexiong

    2012-10-01

    Clinobaryl-ite, ideally BaBe(2)Si(2)O(7) (chemical name barium diberyllium disilicate), is a sorosilicate mineral and dimorphic with baryl-ite. It belongs to a group of compounds characterized by the general formula BaM(2+) (2)Si(2)O(7), with M(2+) = Be, Mg, Fe, Mn, Zn, Co, or Cu, among which the Be-, Fe-, and Cu-members have been found in nature. The crystal structure of clinobaryl-ite has been re-examined in this study based on single-crystal X-ray diffraction data collected from a natural sample from the type locality (Khibiny Massif, Kola Peninsula, Russia). The structure of clinobaryl-ite can be considered as a framework of BeO(4) and SiO(4) tetra-hedra, with one of the O atoms coordinated to two Be and one Si, one coordinated to two Si, and two O atoms coordinated to one Si and one Be atom. The BeO(4) tetra-hedra share corners, forming chains parallel to the c axis, which are inter-linked by the Si(2)O(7) units oriented parallel to the a axis. The Ba(2+) cations (site symmetry m..) are in the framework channels and are coordinated by eleven O atoms in form of an irregular polyhedron. The Si-O(br) (bridging O atom, at site symmetry m..) bond length, the Si-O(nbr) (non-bridging O atoms) bond lengths, and the Si-O-Si angle within the Si(2)O(7) unit are in marked contrast to the corresponding values determined in the previous study [Krivovichev et al. (2004 ▶). N. Jb. Miner. Mh. pp. 373-384].

  2. PAC study in the HfO2-SiO2 system

    International Nuclear Information System (INIS)

    Chain, C.Y.; Damonte, L.C.; Ferrari, S.; Munoz, E.; Torres, C. Rodriguez; Pasquevich, A.F.

    2010-01-01

    A high-k HfO 2 /SiO 2 gate stack is taking the place of SiO 2 as a gate dielectric in field effect transistors. This fact makes the study of the solid-state reaction between these oxides very important. Nanostructure characterization of a high-energy ball milled and post-annealed equimolar HfO 2 and amorphous SiO 2 powder mixture has been carried out by perturbed angular correlations (PAC) technique. The study was complemented with X-ray diffraction and positron annihilation lifetime spectroscopy (PALS). The experimental results revealed that the ball milling of equimolar mixtures increases the defects concentration in hafnium oxide. No solid-state reaction occurred even after 8 h of milling. The formation of HfSiO 4 (hafnon) was observed in the milled blends annealed at high temperatures.The PAC results of the milled samples are compared with those obtained for pure m-ZrO 2 subjected to high-energy ball milling and with reported microstructure data for the system ZrO 2 -SiO 2 .

  3. Irradiation-induced hardening/softening in SiO2 studied with instrumented indentation

    International Nuclear Information System (INIS)

    Nakano, Shinsuke; Muto, Shunsuke; Tanabe, Tetsuo

    2005-01-01

    To understand the plastic deformation mechanism of SiO 2 polytypes, we measured the mechanical parameters of He + -irradiated crystalline SiO 2 (α-quartz, c-SiO 2 ) and vitreous SiO 2 (silica glass, v-SiO 2 ) as functions of the irradiation dose, by using the instrumented indentation method combined with a finite-element analysis. We extracted the effects of local rotation and bending of the SiO 4 framework (the degree of local structural freedom), which play key roles in the plastic deformation, and expressed the hardness change with a simple formula. For v-SiO 2 , the changes in the density and the number of broken bonds correlated well with the change in the degree of freedom. In contrast, for c-SiO 2 the present formulation was insufficient to fully express the hardness change in the structural disordering regime. The structure change by irradiation peculiar to this material is discussed, based on the theoretical formulation

  4. Synthesis and Characterization of Ti-Phenyl at SiO2 Core-Shell Nanoparticles Catalyst

    International Nuclear Information System (INIS)

    Syamsi Aini; Jon Efendi; Syamsi Aini; Jon Efendi

    2012-01-01

    This study highlights the potential use of Ti-Phenyl at SiO 2 core-shell nanoparticles as heterogeneous catalysis in oxidation reaction. The Ti-Phenyl at SiO 2 was synthesized by reduction of TiCl 4 and diazonium salt with sodium borohydride to produce phenyl titanium nanoparticles (Ti-Phenyl), followed by the silica shell coating using tetraethyl orthosilicate (TEOS). The Ti-Phenyl at SiO 2 nanoparticles were characterized by Fourier transform infrared (FTIR) spectrometer, diffuse reflectance (DR) UV-visible spectrometer, thermogravimetric analyzer (TGA), X-ray diffraction (XRD) spectrometer, field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The core-shell size of Ti-Phenyl at SiO 2 was in the range of 40 to 100 nm with its core composed with an agglomeration of Ti-Phenyl. The Ti-Phenyl at SiO 2 was active as a catalyst in the liquid phase epoxidation of 1-octene with aqueous hydrogen peroxide as an oxidant. (author)

  5. Microwave electromagnetic and absorption properties of SiO2/C core/shell composites plated with metal cobalt

    Science.gov (United States)

    Shen, Guozhu; Fang, Xumin; Wu, Hongyan; Wei, Hongyu; Li, Jingfa; Li, Kaipeng; Mei, Buqing; Xu, Yewen

    2017-04-01

    A facile method has been developed to fabricate magnetic core/shell SiO2/C/Co sub-microspheres via the pyrolysis of SiO2/PANI (polyaniline) and electroless plating method. The electromagnetic parameters of these SiO2/C and SiO2/C/Co composites were measured and the microwave reflection loss properties were evaluated in the frequency range of 2-18 GHz. The results show that the dielectric loss of SiO2/C composite increases with the increase of carbonization temperature and the magnetic loss enhances due to the deposition of cobalt on the SiO2/C sub-microspheres. The reflection loss results exhibit that the microwave absorption properties of the SiO2/C/Co composites are more excellent than those of SiO2/C composites for each thickness. The maximum effective absorption bandwidth (reflection loss ≤ -10 dB) arrives at 5.0 GHz (13.0-18 GHz) for SiO2/C/Co composite with 1.5 mm of thickness and the minimum reflection loss value is -24.0 dB at 5.0 GHz with 4.0 mm of thickness. The microwave loss mechanism of the SiO2/C/Co composites was also discussed in this paper.

  6. Ultrasonic attenuation measurements in neutron-irradiated quartz: a microscopic model for the tunneling states

    International Nuclear Information System (INIS)

    Keppens, V.; Laermans, C.; Coeck, M.

    1996-01-01

    Ultrasonic attenuation measurements are carried out in neutron-irradiated z-cut quartz for three different doses, in a frequency range from 70 to 320 MHz. The data are analyzed using the tunneling model, and the typical TS-parameters are derived. A comparison with the results obtained from similar x-cut samples shows that the coupling of the tunneling states with the longitudinal phonons is direction-dependent. This confirms the anisotropic behaviour of the tunneling states and gives support to the microscopic picture of the TS as a rotation of coupled SiO 4 tetrahedra. (orig.)

  7. LOW-VELOCITY SHOCKS TRACED BY EXTENDED SiO EMISSION ALONG THE W43 RIDGES: WITNESSING THE FORMATION OF YOUNG MASSIVE CLUSTERS

    International Nuclear Information System (INIS)

    Nguyen-Luong, Q.; Martin, P. G.; Motte, F.; Louvet, F.; Hill, T.; Hennemann, M.; Didelon, P.; Carlhoff, P.; Schilke, P.; Lesaffre, P.; Gusdorf, A.; Schneider, N.; Bontemps, S.; Duarte-Cabral, A.; Menten, K. M.; Wyrowski, F.; Bendo, G.; Roussel, H.; Bernard, J.-P.; Bronfman, L.

    2013-01-01

    The formation of high-mass stars is tightly linked to that of their parental clouds. Here, we focus on the high-density parts of W43, a molecular cloud undergoing an efficient event of star formation. Using a column density image derived from Herschel continuum maps, we identify two high-density filamentary clouds, called the W43-MM1 and W43-MM2 ridges. Both have gas masses of 2.1 × 10 4 M ☉ and 3.5 × 10 4 M ☉ above >10 23 cm -2 and within areas of ∼6 and ∼14 pc 2 , respectively. The W43-MM1 and W43-MM2 ridges are structures that are coherent in velocity and gravitationally bound, despite their large velocity dispersion measured by the N 2 H + (1-0) lines of the W43-HERO IRAM large program. Another intriguing result is that these ridges harbor widespread (∼10 pc 2 ) bright SiO (2-1) emission, which we interpret to be the result of low-velocity shocks (≤10 km s –1 ). We measure a significant relationship between the SiO (2-1) luminosity and velocity extent and show that it distinguishes our observations from the high-velocity shocks associated with outflows. We use state-of-the-art shock models to demonstrate that a small percentage (10%) of Si atoms in low-velocity shocks, observed initially in gas phase or in grain mantles, can explain the observed SiO column density in the W43 ridges. The spatial and velocity overlaps between the ridges of high-density gas and the shocked SiO gas suggest that ridges could be forming via colliding flows driven by gravity and accompanied by low-velocity shocks. This mechanism may be the initial conditions for the formation of young massive clusters

  8. Preparation and Characterization of Fluorescent SiO2 Microspheres

    Science.gov (United States)

    Xu, Cui; Zhang, Hao; Guan, Ruifang

    2018-01-01

    Fluorescent compound without typical fluorophores was synthesized with citric acid (CA) and aminopropyltriethoxysilane (APTS) firstly, and then it was grafted to the surface of the prepared SiO2 microspheres by chemical reaction. The fluorescent SiO2 microspheres with good fluorescent properties were obtained by optimizing the reaction conditions. And the morphology and structure of the fluorescent SiO2 microspheres have been characterized by scanning electron microscopy (SEM) and fourier transform infrared (FTIR) spectroscopy. The results showed that the preparation of fluorescent SiO2 microspheres have good monodispersity and narrow particle size distribution. Moreover, the fluorescent SiO2 microspheres can be applied to detect Fe3+ in aqueous solution, prepare fluorescent SiO2 rubber, and have potential to be applied in the fluorescent labeling and fingerprint appearing technique fields.

  9. Synthesis and luminescence characterization of Pr3+ doped Sr1.5Ca0.5SiO4 phosphor

    Science.gov (United States)

    Vidyadharan, Viji; Mani, Kamal P.; Sajna, M. S.; Joseph, Cyriac; Unnikrishnan, N. V.; Biju, P. R.

    2014-12-01

    Luminescence properties of Pr3+ activated Sr1.5Ca0.5SiO4 phosphors synthesized by solid state reaction method are reported in this work. Blue, orange red and red emissions were observed in the Pr3+ doped sample under 444 nm excitation and these emissions are assigned as 3P0 → 3H4, 3P0 → 3H6 and 3P0 → 3F4 transitions. The emission intensity shows a maximum corresponding to the 0.5 wt% Pr3+ ion. The decay analysis was done for 0.05 and 0.5 wt% Pr3+ doped samples for the transition 3P0 → 3H6. The life times of 0.05 and 0.5 wt% Pr3+ doped samples were calculated by fitting to exponential and non-exponential curve respectively, and are found to be 156 and 105 μs respectively. The non-exponential behaviour arises due to the statistical distribution of the distances between the ground state Pr3+ ions and excited state Pr3+ ions, which cause the inhomogeneous energy transfer rate. The XRD spectrum confirmed the triclinic phase of the prepared phosphors. The compositions of the samples were determined by the energy dispersive X-ray spectra. From the SEM images it is observed that the particles are agglomerated and are irregularly shaped. IR absorption bands were assigned to different vibrational modes. The well resolved peaks shown in the absorption spectra are identical to the excitation spectra of the phosphor samples. Pr3+ activated Sr1.5Ca0.5SiO4 phosphors can be efficiently excited with 444 nm irradiation and emit multicolour visible emissions. From the CIE diagram it can be seen that the prepared phosphor samples give yellowish-green emission.

  10. Cationic surfactant assisted sonochemical synthesis of Nd3+ doped Zn2SiO4 nanostructures for solid state lighting applications

    Science.gov (United States)

    Basavaraj, R. B.; Malleshappa, J.; Darshan, G. P.; Prasad, B. Daruka; Nagabhushana, H.

    2018-04-01

    For the first time cationic surfactant assisted ultrasound synthesis route has been used for the preparation of pure and Nd3+ (0.5-9 mol %) doped Zn2SiO4 nanophosphors. The shape, size and morphology of the products were tuned by controlling the various experimental parameters. The final product was well characterized by sophisticated techniques viz. powder X-ray diffraction (PXRD), Ultraviolet visible spectroscopy (UV-Vis) and photoluminescence (PL). The powder X-ray diffraction patterns confirmed that the synthesized samples exhibit hexagonal phase without any impurity. The DRS spectra showed major peaks at 275, 360, 529, 586, 680, 742 and 806 nm due to the transitions of the 4f electrons of Nd3+ from the ground-state 4I9/2 to 2F5/2, 4D3/2 + 4D5/2 + 2I11/2, 2K13/2 + 4G7/2 + 4G9/2, 4G5/2 + 2G7/2, 4F7/2 + 4S3/2, 4F5/2 + 2H9/2 and 4F3/2 respectively. The band energy gap (Eg) of the samples were estimated and found to be in the range 5.32 - 5.52 eV. Under 421 nm excitation, PL spectra exhibit strong near ultraviolet emission peaks at˜444 nm, 459 nm and 520 nm were attributed to 2P3/2 → 4I13/2, 2P3/2 → 4I15/2, 1I6 → 3H4, 2P1/2 → 4I9/2 and 4G7/2 → 4I9/2 transitions respectively. The photometric studies indicate that the synthesized Zn2SiO4: Nd3+ nanophosphors can be tuned from blue to pale green by varying the dopant concentration. The current synthesis route is rapid, environmentally benign, cost-effective and useful for industrial applications such as solid state lighting and display devices.

  11. Self-assembly and electrical characteristics of 4-pentynoic acid functionalized Fe3O4-γ-Fe2O3 nanoparticles on SiO2/n-Si

    Science.gov (United States)

    Baharuddin, Aainaa Aqilah; Ang, Bee Chin; Wong, Yew Hoong

    2017-11-01

    A novel investigation on a relationship between temperature-influential self-assembly (70-300 °C) of 4-pentynoic acid functionalized Fe3O4-γ-Fe2O3 nanoparticles (NPs) on SiO2/n-Si with electrical properties was reported with the interests for metal-oxide-semiconductor applications. X-ray diffractometer (XRD) analysis conveyed that 8 ± 1 nm of the NPs were assembled. Increasing heating temperature induced growth of native oxide (SiO2). Raman analysis confirmed the coexistence of Fe3O4-γ-Fe2O3. Attenuated Total Reflectance Infrared (ATR-IR) spectra showed that self-assembly occurred via Sisbnd Osbnd C linkages. While Sisbnd Osbnd C linkages were broken down at elevated temperatures, formations of Si-OH defects were amplified; a consequence of physisorbed surfactants disintegration. Atomic force microscopy (AFM) showed that sample with more physisorbed surfactants exhibited the highest root-mean-square (RMS) roughness (18.12 ± 7.13 nm) whereas sample with lesser physisorbed surfactants displayed otherwise (12.99 ± 4.39 nm RMS roughness). Field Emission Scanning Electron Microscope (FE-SEM) analysis showed non-uniform aggregation of the NPs, deposited as film (12.6 μm thickness). The increased saturation magnetization (71.527 A m2/kg) and coercivity (929.942 A/m) acquired by vibrating sample magnetometer (VSM) of the sample heated at 300 °C verified the surfactants' disintegration. Leakage current density-electric field (J-E) characteristics showed that sample heated at 150 °C with the most aggregated NPs as well as the most developed Sisbnd Osbnd C linkages demonstrated the highest breakdown field and barrier height at 2.58 × 10-3 MV/cm and 0.38 eV respectively. Whereas sample heated at 300 °C with the least Sisbnd Osbnd C linkages as well as lesser aggregated NPs showed the lowest breakdown field and barrier height at 1.08 × 10-3 MV/cm and 0.19 eV respectively. This study opens up better understandings on how formation and breaking down of covalent

  12. Use of MnO2 and MnO2 SiO2 for sorbing of Sr-90 from liquid rad waste

    International Nuclear Information System (INIS)

    Subiarto; Las, Thamzil; Aan BH, Martin; Utomo, Cahyo Hari

    1998-01-01

    The synthesis of MnO 2 adsorbent and MnO 2 -SiO 2 composite has been done. MnO 2 synthesis is done by the reaction of KMnO 4 , Mn(NO 3 ) 2 .4H 2 O and Na 2 S 2 O 4 ( MnO 2 -A, MnO 2 -B, and MnO 2 -T ). MnO 2 . SiO 2 is made from KMnO 4 , Na 2 SiO 3 , and H 2 O 2 . The result obtained show the best Sr-90 sorption by MnO 2 -A with Kd = 2085.63 ml/g, by MnO 2 -L with Kd = 755.09 ml/g, and by MnO 2 - SiO 2 composite with Kd = 1466.51 ml/g. From this result, we can conclude that MnO 2 -SiO 2 can be expanded for Sr-90 sorption from liquid radioactive waste. (author)

  13. Gamma radiation induced sensitization and photo-transfer in Mg2SiO4:Tb TLD phosphor

    International Nuclear Information System (INIS)

    Lakshmanan, A.R.; Vohra, K.G.

    1979-01-01

    Mg 2 SiO 4 :Tb TLD phosphor was found to show enhanced TL sensitivity to both gamma and UV radiations after high pre-gamma exposures (>100 R) and a post-annealing treatment at 300 0 C for 1 h. Maximum sensitization factors of 2.8 and 55 were obtained at the pre-expsoure levels of 5.2x10 1 C/kg and 1.3x10 3 C/kg for gamma and UV test radiations respectively. The near constancy of the intensity of the residual TL (RTL) peak at 500 0 C for the sensitized sample with increasing test-gamma exposures has ruled out the re-trapping model proposed earlier for the gamma radiation induced sensitization in this phosphor. The Tsub(max) for the sensitized phosphor was found to occur at a higher temperature compared to that for the virgin phosphor. The dependence of sensitization on RTL was explained qualitatively on the basis of competition between sensitization traps (having higher energy than the dosimetry traps) and RTL traps while capturing the charge carriers generated during the test-gamma exposure. The sensitization observed in this phosphor to UV test radiation was found to be a consequence of the photo-transfer of charge carriers from deep (RTL) traps to the shallow (dosimetry) traps. The reduction in RTL peak (500 0 C) intensity of the sensitized sample with increasing test-UV exposure has demonstrated the photo-transfer mechanism in this phosphor. The TL response of the virgin Mg 2 SiO 4 :Tb phosphor was found to be supralinear to both gamma and UV radiations. The TL response of the sensitized phosphor was found to be linear to gamma radiation and sublinear to UV radiation. (Auth.)

  14. Effect of Ni/Al2O3-SiO2 and Ni/Al2O3-SiO2 with K2O Promoter Catalysts on H2, CO and CH4 Concentration by CO2 Gasification of Rosa Multiflora Biomass

    Directory of Open Access Journals (Sweden)

    Tursunov Obid

    2017-11-01

    Full Text Available The thermal behaviour of the Rosa mutiflora biomass by thermogravimetric analysis was studied at heating rate 3 K min−1 from ambient temperature to 950 °C. TGA tests were performed in high purity carbon dioxide (99 998% with a flow rate 200 ml/min and 100 mg of sample, milled and sieved to a particle size below 250 µm. Moreover, yields of gasification products such as hydrogen (H2, carbon monoxide (CO and methane (CH4 were determined based on the thermovolumetric measurements of catalytic (Ni/Al2O3-SiO2 and Ni/Al2O3-SiO2 with K2O promoter catalysts and non-catalytic gasification of the Rosa multiflora biomass. Additionally, carbon conversion degrees are presented. Calculations were made of the kinetic parameters of carbon monoxide and hydrogen formation reaction in the catalytic and non-catalytic CO2 gasification processes. A high temperature of 950 °C along with Ni/Al2O3-SiO2and Ni/Al2O3-SiO2 with K2O promoter catalysts resulted in a higher conversion of Rosa multiflora biomass into gaseous yield production with greatly increasing of H2 and CO contents. Consequently, H2 and CO are the key factors to produce renewable energy and bio-gases (synthesis gas. The parameters obtained during the experimental examinations enable a tentative assessment of plant biomasses for the process of large-scale gasification in industrial sectors.

  15. Effect of pressure on the Raman-active modes of zircon (ZrSiO4): a first-principles study

    Science.gov (United States)

    Sheremetyeva, Natalya; Cherniak, Daniele J.; Watson, E. Bruce; Meunier, Vincent

    2018-02-01

    Density-functional theory (DFT) was employed in a first-principles study of the effects of pressure on the Raman-active modes of zircon (ZrSiO4), using both the generalized gradient and local density approximations (GGA and LDA, respectively). Beginning with the equilibrium structure at zero pressure, we conducted a calibration of the effect of pressure in a manner procedurally similar to an experimental calibration. For pressures between 0 and 7 GPa, we find excellent qualitative agreement of frequency-pressure slopes partial ω /partial P calculated from GGA DFT with results of previous experimental studies. In addition, we were able to rationalize the ω vs. P behavior based on details of the vibrational modes and their atomic displacements. Most of the partial ω /partial P slopes are positive as expected, but the symmetry of the zircon lattice also results in two negative slopes for modes that involve slight shearing and rigid rotation of SiO4 tetrahedra. Overall, LDA yields absolute values of the frequencies of the Raman-active modes in good agreement with experimental values, while GGA reproduces the shift in frequency with pressure especially well.

  16. High-temperature crystal chemistry of layered calcium borosilicates: CaBSiO4(OH) (datolite), Ca4B5Si3O15(OH)5 (`bakerite') and Ca2B2SiO7 (synthetic analogue of okayamalite)

    Science.gov (United States)

    Krzhizhanovskaya, Maria G.; Gorelova, L. A.; Bubnova, R. S.; Pekov, I. V.; Krivovichev, S. V.

    2018-05-01

    The high-temperature behaviour of three Ca borosilicates has been studied by in situ powder high-temperature X-ray diffraction (HTXRD), differential scanning calorimetry and thermogravimetry in the temperature range 30-900 °C for natural samples of datolite, CaBSiO4(OH), and `bakerite', Ca4B5Si3O15(OH)5, and a synthetic analogue of okayamalite, Ca2B2SiO7. The latter was obtained by heating datolite at 800 °C for 5 h. Datolite and bakerite start to dehydroxylate above 700 and 500 °C, respectively, and decompose fully to form a high-temperature modification of okayamalite, HT-Ca2B2SiO7, and wollastonite, CaSiO3 at about 730 °C. Above 900 °C, HT-okayamalite decomposes with the formation of wollastonite, CaSiO3, and metaborate CaB2O4. The latter melts at about 990 °C. Above 1000 °C, only the existence of wollastonite, CaSiO3 and cristobalite, SiO2 was observed. According to the HTXRD data, in the temperature range 30-500 °C, datolite and `bakerite' demonstrate very similar and relatively low volumetric thermal expansion: α v = 29 and 27 × 10-6 °C-1, respectively. A high thermal expansion anisotropy ( α max/ α min 3) is caused by both the layered character of the crystal structures and the shear deformations of their monoclinic unit cells. The direction of maximum expansion is intermediate between the normal direction to the layers and the ( a + c) vector. A possible transformation mechanism from the datolite to the okayamalite structure topology is proposed from geometrical considerations. The synthetic analogue of okayamalite, Ca2B2SiO7, undergoes a reversible polymorphic transition at about 550 °C with a decrease in symmetry from tetragonal to orthorhombic. The crystal structure of the high-temperature (HT) modification of okayamalite was solved from the powder-diffraction data [900 °C: P21212, a = 7.3361(4), b = 7.1987(4), c = 4.8619(4) Å, V = 256.76(3) Å3, R wp = 6.61, R Bragg = 2.68%].

  17. Preparation and characterization of layer-by-layer self-assembled polyelectrolyte multilayer films doped with surface-capped SiO2 nanoparticles.

    Science.gov (United States)

    Yang, Guangbin; Ma, Hongxia; Yu, Laigui; Zhang, Pingyu

    2009-05-15

    SiO(2) nanoparticles capped with gamma-aminopropyltrimethoxysilane were doped into polyelectrolyte (poly(allylamine hydrochloride), PAH, and poly(acrylic acid), PAA) multilayer films via spin-assisted layer-by-layer self-assembly. The resulting as-prepared multilayer films were heated at a proper temperature to generate cross-linked composite films with increased adhesion to substrates. The tribological behavior of the multilayer films was evaluated on a microtribometer. It was found that SiO(2)-doped composite films had better wear resistance than pure polyelectrolyte multilayers, possibly because doped SiO(2) nanoparticles were capable of enhancing load-carrying capacity and had "miniature ball bearings" effect. Moreover, heat-treatment had significant effect on the morphology of the composite films. Namely, heat-treated (SiO(2)/PAA)(9) film had a larger roughness than the as-prepared one, due to heat-treatment-induced agglomeration of SiO(2) nanoparticles and initiation of defects. However, heat-treated (PAH/PAA)(3)/(SiO(2)/PAA)(3)(PAH/PAA)(3) film had greatly reduced roughness than the as-prepared one, and it showed considerably improved wear resistance as well. This could be closely related to the "sandwich-like" structure of the composite multilayer film. Namely, the outermost strata of composite multilayer film were able to eliminate defects associated with the middle strata, allowing nanoparticles therein to maintain strength and robustness while keeping soft and fluid-like exposed surface. And the inner strata were well anchored to substrate and acted as an initial "bed" for SiO(2) nanoparticles to be inhabited, resulting in good antiwear ability.

  18. Crystallization behaviour of nanostructured hybrid SiO2-TiO2 gel glasses to nanocomposites.

    Science.gov (United States)

    Tsvetelina, Gerganova; Yordanka, Ivanova; Yuliya, Vueva; Miranda, Salvado Isabel M; Helena, Fernandes Maria

    2010-04-01

    The crystallization behaviour of hybrid SiO2-TiO2 nanocomposites derived from titanosiloxanes by sol-gel method has been investigated depending on the type of siloxane precursor and the pirolysis temperature. The resulting hybrid titanosiloxanes, crosslinked with trimethylsilil isocyanate (nitrogen-modified) or methyltrietoxisilane (carbon-modified), were pirolyzed in an inert atmosphere in the temperature range between 600 to 1100 degrees C in order to form C-(N)-Si-O-TiO2 nanocomposites. By means of XRD, FTIR, 29Si NMR, SEM, TEM and AFM investigations have been established that the transformation of the nanostructured SiO2-TiO2 hybrid materials into nanocomposites as well as the crystalline size depend on the titanium content and the type of cross-linking agents used in the synthesizes.

  19. Magnetic SiO2 gel microspheres for arterial embolization hyperthermia

    International Nuclear Information System (INIS)

    Li Zhixia; Kawashita, Masakazu; Araki, Norio; Mitsumori, Michihide; Hiraoka, Masahiro; Doi, Masaaki

    2010-01-01

    We have prepared magnetic SiO 2 microspheres with a diameter of 20-30 μm as thermoseeds for hyperthermia of cancer. These were prepared by directly introducing preformed magnetic iron oxide nanoparticles (IONPs) into microspheres of a SiO 2 gel matrix derived from the hydrolysis of tetramethoxysilane (TMOS) in a water-in-oil (W/O) emulsion. Dimethylformamide (DMF) was used as a stabilizer, methanol (CH 3 OH) as a dispersant and ammonia (NH 4 OH) as the catalyst for the formation of the spherical particles in the aqueous phase of the W/O emulsion. The magnetic IONPs were synthesized hydrochemically in an aqueous system composed of ferrous chloride, sodium nitrate and sodium hydroxide. Mono-dispersed magnetic SiO 2 gel microspheres with a diameter of approximately 20 μm were successfully obtained by adding a determined amount of solution with a molar ratio of TMOS/DMF/CH 3 OH/H 2 O/NH 4 OH = 1:1.4:9:20:0.03 to kerosene with a surfactant (sorbitan monooleate/sorbitan monostearate = 3:1 by weight ratio) that was 30 wt% of the total amount of the oil phase. These were estimated to contain up to 60 wt% of IONPs that consisted mainly of Fe 3 O 4 and showed a higher specific absorption rate (SAR = 27.9-43.8 W g -1 ) than that of the starting IONPs (SAR = 25.3 W g -1 ) under an alternating current magnetic field of 300 Oe and 100 kHz.

  20. Enhanced Coagulation-Flocculation Performance of Iron-Based Coagulants: Effects of PO4(3-) and SiO3(2-) Modifiers.

    Science.gov (United States)

    Chen, Wei; Zheng, Huaili; Teng, Houkai; Wang, Yili; Zhang, Yuxin; Zhao, Chuanliang; Liao, Yong

    2015-01-01

    PO4(3-) and SiO3(2-) are often used as modifier to improve stability and aggregating ability of the iron-base coagulants, however, there are few reports about their detailed comparison between the coagulation performance and mechanisms. In this study, three coagulants--polyferric phosphoric sulfate (PFPS), polysilicon ferric sulfate (PFSS), and polyferric sulfate (PFS) were synthesized; their structure and morphology were characterized by Fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscope (SEM). Alkali titration and Ferron species analysis were employed to investigate the hydrolysis performance and species distribution. Jar test was conducted to measure their coagulation behaviors at different dosage, pH, and temperatures in which the flocs properties were measured. The results showed that a number of new compounds were formed due to the presence of PO4(3-) and SiO3(2-). Moreover, PFPS and PFSS had similar level in Fea as well as Feb. Among them, PFPS produced more multi-core iron atoms polymer and content of Feb, and the formed flocs were larger and denser. It exhibited superior coagulation performance in terms of turbidity reduction, UV254 removal and residual ferric concentration. Jar test and floc breakage/regrowth experiments indicated other than charge neutrality, the dominated mechanism involved in PFSS was the adsorption between polysilicic acid and solution particle, while PFPS was sweeping, entrapment/adsorption resulting from larger polymer colloid of Fe-P chemistry bond.

  1. Enhanced Coagulation-Flocculation Performance of Iron-Based Coagulants: Effects of PO4(3- and SiO3(2- Modifiers.

    Directory of Open Access Journals (Sweden)

    Wei Chen

    Full Text Available PO4(3- and SiO3(2- are often used as modifier to improve stability and aggregating ability of the iron-base coagulants, however, there are few reports about their detailed comparison between the coagulation performance and mechanisms. In this study, three coagulants--polyferric phosphoric sulfate (PFPS, polysilicon ferric sulfate (PFSS, and polyferric sulfate (PFS were synthesized; their structure and morphology were characterized by Fourier transformed infrared (FT-IR spectroscopy, X-ray diffraction (XRD and Scanning electron microscope (SEM. Alkali titration and Ferron species analysis were employed to investigate the hydrolysis performance and species distribution. Jar test was conducted to measure their coagulation behaviors at different dosage, pH, and temperatures in which the flocs properties were measured. The results showed that a number of new compounds were formed due to the presence of PO4(3- and SiO3(2-. Moreover, PFPS and PFSS had similar level in Fea as well as Feb. Among them, PFPS produced more multi-core iron atoms polymer and content of Feb, and the formed flocs were larger and denser. It exhibited superior coagulation performance in terms of turbidity reduction, UV254 removal and residual ferric concentration. Jar test and floc breakage/regrowth experiments indicated other than charge neutrality, the dominated mechanism involved in PFSS was the adsorption between polysilicic acid and solution particle, while PFPS was sweeping, entrapment/adsorption resulting from larger polymer colloid of Fe-P chemistry bond.

  2. Colloidal GdVO4:Eu3+@SiO2 nanocrystals for highly selective and sensitive detection of Cu2+ ions

    Science.gov (United States)

    Liang, Yanjie; Noh, Hyeon Mi; Park, Sung Heum; Choi, Byung Chun; Jeong, Jung Hyun

    2018-03-01

    Nowadays, in view of health and safety demands, the controlled design of selective and sensitive sensors for Cu2+ detection is of considerable importance. Therefore, we construct herein core-shell colloidal GdVO4:Eu3+@SiO2 nanocrystals (NCs) as optical sensor for the detection of Cu2+, which were synthesized by a facile hydrothermal reaction and encapsulated with a uniform layer of ultrathin silica through a sol-gel strategy. The NCs present strong red emission due to energy transfer from VO43- groups to Eu3+ when exciting with ultraviolet (UV) light. This intense red emission from Eu3+ could be selectively quenched in the presence of Cu2+ in comparison to other metal ions and the limit of detection is as low as 80 nM in aqueous solution. It is revealed that the spectral overlap between the emission band of NCs and the absorption of Cu2+ accounts for this intriguing luminescence behavior. The detection ability is highly reversible by the addition of ethylenediaminetetraacetic acid (EDTA) with the recovery of almost 100% of the original luminescence. The luminescence quenching and recovery processes can be performed repeatedly with good sensing ability. These remarkable performances allow the colloidal GdVO4:Eu3+@SiO2 NCs a promising fluorescence chemosensor for detecting Cu2+ ions in aqueous solution.

  3. Structure and crystallization of SiO2 and B2O3 doped lithium disilicate glasses from theory and experiment.

    Science.gov (United States)

    Erlebach, Andreas; Thieme, Katrin; Sierka, Marek; Rüssel, Christian

    2017-09-27

    Solid solutions of SiO 2 and B 2 O 3 in Li 2 O·2SiO 2 are synthesized and characterized for the first time. Their structure and crystallization mechanisms are investigated employing a combination of simulations at the density functional theory level and experiments on the crystallization of SiO 2 and B 2 O 3 doped lithium disilicate glasses. The remarkable agreement of calculated and experimentally determined cell parameters reveals the preferential, kinetically controlled incorporation of [SiO 4 ] and [BO 4 ] at the Li + lattice sites of the Li 2 O·2SiO 2 crystal structure. While the addition of SiO 2 increases the glass viscosity resulting in lower crystal growth velocities, glasses containing B 2 O 3 show a reduction of both viscosities and crystal growth velocities. These observations could be rationalized by a change of the chemical composition of the glass matrix surrounding the precipitated crystal phase during the course of crystallization, which leads to a deceleration of the attachment of building units required for further crystal growth at the liquid-crystal interface.

  4. Simple and efficient synthesis of copper(II)-modified uniform magnetic Fe3O4@SiO2 core/shell microspheres for immobilization of cellulase

    Science.gov (United States)

    Li, Shi-Kuo; Hou, Xiao-Cheng; Huang, Fang-Zhi; Li, Chuan-Hao; Kang, Wen-Juan; Xie, An-Jian; Shen, Yu-Hua

    2013-11-01

    In this paper, we reported a simple and efficient protocol for preparation of Cu2+-modified magnetic Fe3O4@SiO2 core/shell microspheres for immobilization of cellulase. The uniform magnetic Fe3O4@SiO2 core/shell microspheres with a thin shell of 20 nm were synthesized through a solvothermal method followed by a sol-gel process. An amino-terminated silane coupling agent of (3-aminopropyl)triethoxysilane (APTS) was then grafted on them for capturing Cu2+ ions. The reaction process is very simple, efficient, and economical. Noticeably, the content of Cu2+ ions on the magnetic core/shell microspheres can reach 4.6 Wt%, endowing them possess as high immobilization capacity as 225.5 mg/g for cellulase. And the immobilized cellulase can be retained over 90 % on the magnetic microspheres after six cycles. Meanwhile, the magnetic microspheres decorated with Cu2+ ions show a superparamagnetic character with a high magnetic saturation of 58.5 emu/g at room temperature, suggesting conveniently and rapidly recycle the enzyme from solution. This facile, recyclable, high immobilization capacity and activity strategy may find potential applications in enzyme catalytic reactions with low cost.

  5. Simple and efficient synthesis of copper(II)-modified uniform magnetic Fe3O4@SiO2 core/shell microspheres for immobilization of cellulase

    International Nuclear Information System (INIS)

    Li, Shi-Kuo; Hou, Xiao-Cheng; Huang, Fang-Zhi; Li, Chuan-Hao; Kang, Wen-Juan; Xie, An-Jian; Shen, Yu-Hua

    2013-01-01

    In this paper, we reported a simple and efficient protocol for preparation of Cu 2+ -modified magnetic Fe 3 O 4 @SiO 2 core/shell microspheres for immobilization of cellulase. The uniform magnetic Fe 3 O 4 @SiO 2 core/shell microspheres with a thin shell of 20 nm were synthesized through a solvothermal method followed by a sol–gel process. An amino-terminated silane coupling agent of (3-aminopropyl)triethoxysilane (APTS) was then grafted on them for capturing Cu 2+ ions. The reaction process is very simple, efficient, and economical. Noticeably, the content of Cu 2+ ions on the magnetic core/shell microspheres can reach 4.6 Wt%, endowing them possess as high immobilization capacity as 225.5 mg/g for cellulase. And the immobilized cellulase can be retained over 90 % on the magnetic microspheres after six cycles. Meanwhile, the magnetic microspheres decorated with Cu 2+ ions show a superparamagnetic character with a high magnetic saturation of 58.5 emu/g at room temperature, suggesting conveniently and rapidly recycle the enzyme from solution. This facile, recyclable, high immobilization capacity and activity strategy may find potential applications in enzyme catalytic reactions with low cost

  6. Synthesis and Characterization of New Nickel Phosphates, ANi4(PO4)3 (A=K, Rb)

    International Nuclear Information System (INIS)

    Im, Yoonmi; Kim, Pilsoo; Yun, Hoseop

    2014-01-01

    Quaternary nickel orthophosphates, ANi 4 (PO 4 ) 3 (A=Alkali metals) have been extensively investigated because they show interesting properties such as ionic conductivities, optical, and magnetic behaviors. They are built up from NiO 6 octahedra and PO 4 tetrahedra. These basic building blocks are connected via common oxygen atoms to form the three-dimensional frameworks and the alkali metal ions reside in the empty space. For NaNi 4 (PO 4 ) 3 , two different structures have been reported and this can be caused by the different reaction conditions. While NaNi 4 (PO 4 ) 3 prepared as single crystals with the use of NaCl flux at 1373 K crystallizes in the space group Amam and show a partial disorder of one of the PO 4 tetrahedra, NaNi 4 (PO 4 ) 3 and KNi 4 (PO 4 ) 3 synthesized with alkali metal nitrate at 1073 K as powders adopt an ordered structure with the space group Pnnm. As far as we know, no structural studies of KNi 4 (PO 4 ) 3 from single crystal diffraction data have been reported yet and RbNi 4 (PO 4 ) 3 is a new compound. In this paper we report on the synthesis and structural investigations using single crystals of two nickel orthophosphates, KNi 4 (PO 4 ) 3 and RbNi 4 (PO 4 ) 3

  7. Characterization of anodic SiO2 films on P-type 4H-SiC

    International Nuclear Information System (INIS)

    Woon, W.S.; Hutagalung, S.D.; Cheong, K.Y.

    2009-01-01

    The physical and electronic properties of 100-120-nm thick anodic silicon dioxide film grown on p-type 4H-SiC wafer and annealed at different temperatures (500, 600, 700, and 800 deg. C ) have been investigated and reported. Chemical bonding of the films has been analyzed by Fourier transform infra red spectroscopy. Smooth and defect-free film surface has been revealed under field emission scanning electron microscope. Atomic force microscope has been used to study topography and surface roughness of the films. Electronic properties of the film have been investigated by high frequency capacitance-voltage and current-voltage measurements. As the annealing temperature increased, refractive index, dielectric constant, film density, SiC surface roughness, effective oxide charge, and leakage current density have been reduced until 700 deg. C . An increment of these parameters has been observed after this temperature. However, a reversed trend has been demonstrated in porosity of the film and barrier height between conduction band edge of SiO 2 and SiC

  8. Observation of microstructure of hydrated Ca3SiO5

    International Nuclear Information System (INIS)

    Mori, Kazuhiro; Sato, Takashi; Fukunaga, Toshiharu; Oishi, Koji; Kimura, Katsuhiko; Iwase, Kenji; Sugiyama, Masaaki; Itoh, Keiji; Shikanai, Fumihito; Wuernisha, Tuerxun; Yonemura, Masao; Sulistyanintyas, Dyah; Tsukushi, Itaru; Takata, Shinich; Otomo, Toshiya; Kamiyma, Takashi; Kawai, Masayoshi

    2006-01-01

    Quasi-elastic neutron scattering experiments were carried out to evaluate the hydration rate of tricalcium silicate (Ca 3 SiO 5 ). Furthermore, in the early hydration period, a variation in surface roughness of Ca 3 SiO 5 was observed in nano-scale by the small-angle neutron scattering. From these results, it was found that the hydration rate of Ca 3 SiO 5 is suppressed when the surface of Ca 3 SiO 5 becomes rough through the creation of hydration products C-S-H gel and Ca(OH) 2 , and this roughness is associated with changes in the Ca 3 SiO 5 hydration rate

  9. Lithium conductivity in glasses of the Li2O-Al2O3-SiO2 system.

    Science.gov (United States)

    Ross, Sebastian; Welsch, Anna-Maria; Behrens, Harald

    2015-01-07

    To improve the understanding of Li-dynamics in oxide glasses, i.e. the effect of [AlO4](-) tetrahedra and non-bridging oxygens on the potential landscape, electrical conductivity of seven fully polymerized and partly depolymerized lithium aluminosilicate glasses was investigated using impedance spectroscopy (IS). Lithium is the only mobile particle in these materials. Data derived from IS, i.e. activation energies, pre-exponential factors and diffusivities for lithium, are interpreted in light of Raman spectroscopic analyses of local structures in order to identify building units, which are crucial for lithium dynamics and migration. In polymerized glasses (compositional join LiAlSiO4-LiAlSi4O10) the direct current (DC) electrical conductivity continuously increases with increasing lithium content while lithium diffusivity is not affected by the Al/Si ratio in the glasses. Hence, the increase in electrical conductivity can be solely assigned to lithium concentration in the glasses. An excess of Li with respect to Al, i.e. the introduction of non-bridging oxygen into the network, causes a decrease in lithium mobility in the glasses. Activation energies in polymerized glasses (66 to 70 kJ mol(-1)) are significantly lower than those in depolymerized networks (76 to 78 kJ mol(-1)) while pre-exponential factors are nearly constant across all compositions. Comparison of the data with results for lithium silicates from the literature indicates a minimum in lithium diffusivity for glasses containing both aluminium tetrahedra and non-bridging oxygens. The findings allow a prediction of DC conductivity for a large variety of lithium aluminosilicate glass compositions.

  10. Neutron diffraction study of structural changes in ammonium halides ND4Br and ND4Cl under high pressure

    International Nuclear Information System (INIS)

    Balagurov, A.M.; Kozlenko, D.P.; Savenko, B.N.; Glazkov, V.P.; Somenkov, V.A.

    1997-01-01

    Structural changes in ammonium halides ND 4 Br and ND 4 Cl at pressures up to 45 kbar and up to 35 kbar, respectively, have been studied with the DN-12 diffractometer at the IBR-2 pulsed reactor. For both systems, the equation of state and the position parameter of deuterium atoms as functions of pressure were obtained. The obtained equations of state are nearly the same as the ones for the nondeuterated systems NH 4 Br and NH 4 Cl obtained by the piston displacement technique. It was found that the order - disorder phase transition from the phase in which the ammonium tetrahedra are randomly oriented (CsCl-type cubic structure, space group Pm3m) into the phase in which the ammonium tetrahedra are oriented in parallel (CsCl-type cubic structure, space group P4 bar 3m), occurs at equal critical value of the position parameter u=0.153 ± 0.002 in both systems. It appears to be valid for all of the ammonium halides, and, possibly, for other similar compounds. (author)

  11. Defect layer in SiO2-Sic interface proved by a slow positron beam

    International Nuclear Information System (INIS)

    Maekawa, M.; Kawasuso, A.; Yoshikawa, M.; Miyashita, A.; Suzuki, R.; Ohdaira, T.

    2006-01-01

    The structure of the SiO 2 -4ph-SiC interface layer produced by dry oxidation has been studied by positron annihilation spectroscopy using slow positron beams. From Doppler broadening measurements, the interface layer was clearly distinguished from the SiO 2 and SiC layers and was observed to be defective. At the interface layer, a single long positron lifetime of 451 ps, which is close to the second lifetime in the SiO 2 layer, was obtained, thus suggesting that the structure of the interface layer resembles an amorphous SiO 2 network. A comparison was made between the obtained electron momentum distribution at the interface layer and the theoretical calculation. It was found that positrons annihilate with oxygen valence electrons. By annealing after the oxidation, the annihilation probability of the positrons with oxygen valence electrons and the number of interface traps decreased in the same temperature range, thus suggesting a correlation between interface traps and positron annihilation sites

  12. Luminescence and origin of lead-related centers in single crystalline films of Y2SiO5 and Lu2SiO5

    International Nuclear Information System (INIS)

    Babin, V.; Gorbenko, V.; Krasnikov, A.; Mihokova, E.; Nikl, M.; Zazubovich, S.; Zorenko, Yu.

    2013-01-01

    In the temperature range 4.2–350 K, the steady-state and time-resolved emission and excitation spectra and luminescence decay kinetics are studied for the undoped Y 2 SiO 5 and Lu 2 SiO 5 single crystalline films grown by liquid phase epitaxy method from the PbO-based flux and, owing to that, containing lead ions substituting for Y 3+ or Lu 3+ ions. Luminescence characteristics of Pb-related centers of different types are identified. On the basis of the results obtained, we suggest that the ultraviolet emission of Pb-related centers arises from the Pb 2+ ions substituting for Y 3+ or Lu 3+ ions in the Y1 and Lu1 lattice sites of the X 2 structure. Possible hypotheses on the origin of the intense complex lead-related blue emission are discussed. We propose phenomenological models describing the excited-state dynamics of the studied luminescence centers. We also determine characteristic parameters of the corresponding relaxed excited states, in particular, the energy separations between the excited states and the rates of the radiative and non-radiative transitions from these states. -- Highlights: •Emission of lead centers in Y 2 SiO 5 and Lu 2 SiO 5 single crystalline films is studied. •The ultraviolet emission arises from Pb 2+ ions located in Y1 or Lu1 lattice sites. •Possible hypotheses on the origin of the blue emission are proposed and discussed. •The relaxed excited states parameters of various Pb-related centers are determined

  13. Network rigidity and properties of SiO2 and GeO2 glasses under pressure.

    Science.gov (United States)

    Trachenko, Kostya; Dove, Martin T; Brazhkin, Vadim; El'kin, F S

    2004-09-24

    We report in situ studies of SiO2 glass under pressure and find that temperature-induced densification takes place in a pressure window. To explain this effect, we study how rigidity of glasses changes under pressure, with rigidity percolation affecting the dynamics of local relaxation events. We link rigidity percolation in glasses to other effects, including a large increase of crystallization temperature and logarithmic relaxation under pressure.

  14. Influence of CaCO3 and SiO2 additives on magnetic properties of M-type Sr ferrites

    Science.gov (United States)

    Huang, Ching-Chien; Jiang, Ai-Hua; Hung, Yung-Hsiung; Liou, Ching-Hsuan; Wang, Yi-Chen; Lee, Chi-Ping; Hung, Tong-Yin; Shaw, Chun-Chung; Kuo, Ming-Feng; Cheng, Chun-Hu

    2018-04-01

    An experiment was carried out to investigate the influence of CaCO3 and SiO2 additives on the magnetic and physical properties of M-type Sr ferrites by changing experimental parameters such as the additive composition and Ca/Si ratio. Specimens were prepared by conventional ceramic techniques. It was found that the magnetic properties (Br = 4.42 kG, iHc = 3.32 kOe and (BH)max = 4.863 MGOe) were considerably improved upon adding CaCO3 = 1.1% and SiO2 = 0.4 wt% together with Co3O4, and the mechanical properties thereof were acceptable for motor applications. It was revealed that CaCO3 and SiO2 additives led to an upswing in the magnetic properties via the enhancement of uniform grain growth, particle alignment, and the densification of Sr ferrite.

  15. K(MoO24O3(AsO4

    Directory of Open Access Journals (Sweden)

    Raja Jouini

    2013-06-01

    Full Text Available A new compound with a non-centrosymmetric structure, potassium tetrakis[dioxomolybdenum(IV] arsenate trioxide, K(MoO24O3(AsO4, has been synthesized by a solid-state reaction. The [(MoO24O3(AsO4]+ three-dimensional framework consists of single arsenate AsO4 tetrahedra, MoO6 octahedra, MoO5 bipyramids and bioctahedral units of edge-sharing Mo2O10 octahedra. The [Mo2O8]∞ octahedral chains running along the a-axis direction are connected through their corners to the AsO4 tetrahedra, MoO6 octahedra and MoO5 bipyramids, so as to form large tunnels propagating along the a axis in which the K+ cations are located. This structure is compared with compounds containing M2O10 (M = Mo, V, Fe dimers and with those containing M2O8 (M = V chains.

  16. Anísio Teixeira e a psicologia: o diálogo com a psicanálise - Anísio Teixeira and psychology: dialogue with psychoanalysis

    Directory of Open Access Journals (Sweden)

    Karen Fernanda Bortoloti

    2013-08-01

    Full Text Available Este trabalho analisa as ideias e a atuação de Anísio Teixeira nos primeiros anos da década de 1930, focalizando as suas concepções acerca do valor da Psicanálise para a renovação educacional no Brasil. Considerando que as ideias e as práticas de Teixeira devem ser compreendidas no contexto histórico em que se desenvolveram, o trabalho apresenta um histórico da inserção dos conhecimentos psicanalíticos no movimento educacional renovador brasileiro, destacando a relevância do higienismo na difusão das teses de Freud na educação. As conclusões indicam que Teixeira interagiu com os conceitos da Psicanálise por intermédio do movimento higienista e das ideias de Arthur Ramos, considerando o indivíduo como um ser vinculado ao ambiente social.Palavras-chave: história da educação brasileira, escola nova, Anísio Teixeira, psicologia, psicanálise. ANÍSIO TEIXEIRA AND PSYCHOLOGY: DIALOGUE WITH PSYCHOANALYSISAbstractThis paper analyses the ideas and the work of Anísio Teixeira in the first years of the 1930s, focusing his conceptions concerning the value of Psychoanalysis for Educational Reform in Brazil. Whereas the ideas and practices Teixeira should be understood in the historical context in which they were developed, the work presents the history of the introduction of the psychoanalytic knowledge in the Brazilian Renovator Educational Movement, highlighting the relevance of hygienism in the dissemination of Freud’s theses in education. The findings indicate that Teixeira interacted with the concepts of Psychoanalysis through the hygienist movement and the ideas of Arthur Ramos, considering the individual as being linked to the social environment.Key-words: history of brazilian education, new school, Anísio Teixeira, psychology, psychoanalysis. ANÍSIO TEIXEIRA Y PSICOLOGÍA: DIÁLOGO CON EL PSICOANÁLISISResumemEste trabajo analiza las ideas y el trabajo de Anísio Teixeira en los primeros años de la década de 1930

  17. Growth of Bi 12SiO 20 single crystals by the pulling-down method with continuous feeding

    Science.gov (United States)

    Maida, Shigeru; Higuchi, Mikio; Kodaira, Kohei

    1999-09-01

    Bi 12SiO 20 single crystals were successfully grown by the pulling-down method with continuous feeding. As-grown crystals were amber in color and transparent, and had no cracks or inclusions. A crystal with homogeneous composition was obtained from Bi-rich feed powder having a composition of 14.1 mol% SiO 2, whereas precipitates of Bi 4Si 3O 12 were observed on the surface of a crystal grown with stoichiometric powder. The shape of the solid-liquid interface during the crystal growth was estimated to be almost flat, which was favorable to avoid core formation. Average dislocation density was 4×10 3/cm 2, which was comparable to that of Bi 12SiO 20 crystals grown by the Czochralski method.

  18. Effect of Commercial SiO2 and SiO2 from rice husk ash loading on biodegradation of Poly (lactic acid) and crosslinked Poly (lactic acid)

    Science.gov (United States)

    Prapruddivongs, C.; Apichartsitporn, M.; Wongpreedee, T.

    2017-09-01

    In this work, biodegradation behavior of poly (lactic acid) (PLA) and crosslinked PLA filled with two types of SiO2, precipitated SiO2 (commercial SiO2) and SiO2 from rice husk ash, were studied. Rice husks were first treated with 2 molar hydrochloric acid (HCl) to produce high purity SiO2, before burnt in a furnace at 800°C for 6 hours. All components were melted bending by an internal mixer then hot pressed using compression molder to form tested specimens. FTIR spectra of SiO2 and PLA samples were investigated. The results showed the lack of silanol group (Si-OH) of rice husk ash after steric acid surface modification, while the addition of particles can affect the crosslinking of the PLA. For biodegradation test by evaluating total amount of carbon dioxide (CO2) evolved during 60 days incubation at a controlled temperature of 58±2°C, the results showed that the biodegradation of crosslinked PLA occurred slower than the neat PLA. However, SiO2 incorporation enhanced the degree of biodegradation In particular, introducing commercial SiO2 in PLA and crosslinked PLA tended to clearly increase the degree of biodegradation as a consequence of the more accelerated hydrolysis degradation.

  19. Surface spins disorder in uncoated and SiO2 coated maghemite nanoparticles

    International Nuclear Information System (INIS)

    Zeb, F.; Nadeem, K.; Shah, S. Kamran Ali; Kamran, M.; Gul, I. Hussain; Ali, L.

    2017-01-01

    We studied the surface spins disorder in uncoated and silica (SiO 2 ) coated maghemite (γ-Fe 2 O 3 ) nanoparticles using temperature and time dependent magnetization. The average crystallite size for SiO 2 coated and uncoated nanoparticles was about 12 and 29 nm, respectively. Scanning electron microscopy (SEM) showed that the nanoparticles are spherical in shape and well separated. Temperature scans of zero field cooled (ZFC)/field cooled (FC) magnetization measurements showed lower average blocking temperature (T B ) for SiO 2 coated maghemite nanoparticles as compared to uncoated nanoparticles. The saturation magnetization (M s ) of SiO 2 coated maghemite nanoparticles was also lower than the uncoated nanoparticles and is attributed to smaller average crystallite size of SiO 2 coated nanoparticles. For saturation magnetization vs. temperature data, Bloch's law (M(T)= M(0).(1− BT b )) was fitted well for both uncoated and SiO 2 coated nanoparticles and yields: B =3×10 −7 K -b , b=2.22 and B=0.0127 K -b , b=0.57 for uncoated and SiO 2 coated nanoparticles, respectively. Higher value of B for SiO 2 coated nanoparticles depicts decrease in exchange coupling due to enhanced surface spins disorder (broken surface bonds) as compared to uncoated nanoparticles. The Bloch's exponent b was decreased for SiO 2 coated nanoparticles which is due to their smaller average crystallite size or finite size effects. Furthermore, a sharp increase of coercivity at low temperatures (<25 K) was observed for SiO 2 coated nanoparticles which is also due to contribution of increased surface anisotropy or frozen surface spins in these smaller nanoparticles. The FC magnetic relaxation data was fitted to stretched exponential law which revealed slower magnetic relaxation for SiO 2 coated nanoparticles. All these measurements revealed smaller average crystallite size and enhanced surface spins disorder in SiO 2 coated nanoparticles than in uncoated γ-Fe 2 O 3 nanoparticles

  20. Topotactic reduction as a route to new close-packed anion deficient perovskites: structure and magnetism of 4H-BaMnO(2+x).

    Science.gov (United States)

    Hadermann, Joke; Abakumov, Artem M; Adkin, Josephine J; Hayward, Michael A

    2009-08-05

    The anion-deficient perovskite 4H-BaMnO(2+x) has been obtained by a topotactic reduction, with LiH, of the hexagonal perovskite 4H-BaMnO(3-x). The crystal structure of 4H-BaMnO(2+x) was solved using electron diffraction and X-ray powder diffraction and further refined using neutron powder diffraction (S.G. Pnma, a = 10.375(2) A, b = 9.466(2) A, c = 11.276(3) A, at 373 K). The orthorhombic superstructure arises from the ordering of oxygen vacancies within a 4H (chch) stacking of close packed c-type BaO(2.5) and h-type BaO(1.5) layers. The ordering of the oxygen vacancies transforms the Mn(2)O(9) units of face-sharing MnO(6) octahedra into Mn(2)O(7) (two corner-sharing tetrahedra) and Mn(2)O(6) (two edge-sharing tetrahedra) groups. The Mn(2)O(7) and Mn(2)O(6) groups are linked by corner-sharing into a three-dimensional framework. The structures of the BaO(2.5) and BaO(1.5) layers are different from those observed previously in anion-deficient perovskites providing a new type of order pattern of oxygen atoms and vacancies in close packed structures. Magnetization measurements and neutron diffraction data reveal 4H-BaMnO(2+x) adopts an antiferromagnetically ordered state below T(N) approximately 350 K.

  1. Preliminary study in development of glass-ceramic based on SiO2-LiO2 system, starting of different SiO2 starting powders

    International Nuclear Information System (INIS)

    Daguano, J.K.M.F.; Santos, F.A.; Santos, C.; Marton, L.F.M.; Conte, R.A.; Rodrigues Junior, D.; Melo, F.C.L.

    2009-01-01

    In this work, lithium disilicate glass-ceramics were developed starting of the rice ash- SiO 2 and Li 2 CO 3 powders. The results were compared with glass ceramics based on the lithium disilicate obtained by commercial SiO 2 powders. Glass were melted at 1580 deg C, and annealed at 850 deg C. X-Ray diffraction and scanning electron microscopy were used for characterization of the materials, and hardness and fracture toughness were evaluated using Vickers indentation method. Glasses with amorphous structure were obtained in both materials. After annealing, 'rice-ash' samples presented Li 2 SiO 3 and residual SiO 2 as crystalline phases. On the other side, commercial SiO 2 - Samples presented only Li 2 Si 2 O 5 as crystalline phases and the better results of hardness and fracture toughness. (author)

  2. The phase transformation and crystallization kinetics of (1 - x)Li2O-xNa2O-Al2O3-4SiO2 glasses

    International Nuclear Information System (INIS)

    Wang, Moo-Chin; Li, Wang-Long; Cheng, Chih-Wei; Chang, Kuo-Ming; Chen, Yong-Feng; Hsi, Chi-Shiung

    2010-01-01

    The phase transformation and crystallization kinetics of (1 - x)Li 2 O-xNa 2 O-Al 2 O 3 -4SiO 2 glasses have been studied by using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED) analysis. The crystallization temperature at the exothermic peak increases from 1171 to 1212 K when the Na 2 O content increases from 0 to 0.6 mol. The crystalline phase is composed of spodumene crystallization when the Na 2 O content increases from 0 to 0.6 mol. The activation energy of spodumene crystallization decreases from 444.0 ± 22.2 to 284.0 ± 10.8 kJ mol -1 when the Na 2 O content increases from 0 to 0.4 mol. Moreover, the activation energy increases from 284.0 ± 10.8 to 446.0 ± 23.2 kJ mol -1 when the Na 2 O content increases from 0.4 to 0.6 mol. The crystallization parameters m and n approach 2, indicating that the surface nucleation and two-dimensional growth are dominant in (1 - x)Li 2 O-xNa 2 O-Al 2 O 3 -4SiO 2 glasses.

  3. The improvement of SiO2 nanotubes electrochemical behavior by hydrogen atmosphere thermal treatment

    Science.gov (United States)

    Spataru, Nicolae; Anastasescu, Crina; Radu, Mihai Marian; Balint, Ioan; Negrila, Catalin; Spataru, Tanta; Fujishima, Akira

    2018-06-01

    Highly defected SiO2 nanotubes (SiO2-NT) were obtained by a simple sol-gel procedure followed by calcination. Boron-doped diamond (BDD) polycrystalline films coated with SiO2-NT were used as working electrodes and, unexpectedly, cyclic voltammetric experiments have shown that the concentration of both positive and negative defects at the surface is high enough to enable redox processes involving positively charged Ru(bpy)32+/3+ to occur. Conversely, no electrochemical activity was put into evidence for Fe(CN)63-/4- species, most likely as a result of the strong electrostatic repulsion exerted by the negatively charged SiO2 surface. The concentration of surface defects was further increased by a subsequent thermal treatment in a hydrogen atmosphere which, as EIS measurements have shown, significantly promotes Ru(bpy)32+ anodic oxidation. Digital simulation of the voltammetric responses demonstrated that this treatment does not lead to a similar increase of the number of electron-donor sites. It was also found that methanol anodic oxidation at hydrogenated SiO2-NT-supported platinum results in Tafel slopes of 116-220 mV decade-1, comparable to those reported for both conventional PtRu and Pt-oxide catalysts.

  4. Thickness measurement of SiO2 films thinner than 1 nm by X-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Joong Kim, Kyung; Park, Ki Tae; Lee, Jong Wan

    2006-01-01

    The thickness measurement of ultra-thin SiO 2 films thinner than 1 nm was studied by X-ray photoelectron spectroscopy (XPS). Amorphous SiO 2 thin films were grown on amorphous Si films to avoid the thickness difference due to the crystalline structure of a substrate. SiO 2 thin films were grown by ion beam sputter deposition under oxygen gas flow and the thickness was measured by in situ XPS. The attenuation length was determined experimentally by a SiO 2 film with a known thickness. The straight line fit between the measured thickness using XPS and the nominal thickness showed a good linear relation with a gradient of 0.969 and a small offset of 0.126 nm. The gradient measured at the range of 3.4-0.28 nm was very close to that measured at sub-nanometer range of 1.13-0.28 nm. This result means that the reliable measurement of SiO 2 film thickness below 1 nm is possible by XPS

  5. A novel fabrication of a high performance SiO(2)-graphene oxide (GO) nanohybrids: Characterization of thermal properties of epoxy nanocomposites filled with SiO(2)-GO nanohybrids.

    Science.gov (United States)

    Haeri, S Z; Ramezanzadeh, B; Asghari, M

    2017-05-01

    In this study it has been aimed to enhance the thermal resistance of epoxy coating through incorporation of SiO 2 -GO nanohybrids. SiO 2 -GO nanohybrids were synthesized through one-step sol-gel route using a mixture of Tetraethylorthosilane (TEOS) and 3-Aminopropyl triethoxysilane (APTES) silanes. The SiO 2 -GO nanohybrids were prepared at various hydrolysis times of 24, 48 and 72h. Then 0.2wt.% of GO and SiO 2 -GO nanohybrids were separately incorporated into the epoxy coating. Results revealed that amino functionalized SiO 2 nanoparticles with particle size around 20-30nm successfully synthesized on the basal plane of GO. Results showed significant improvement of dispersion and interfacial interactions between nanohybrids and epoxy composite arising from covalent bonding between the SiO 2 -GO and the epoxy matrix. It was found that the thermal resistance of SiO 2 -GO nanohybrids and SiO 2 -GO/Epoxy nanocomposite was noticeably higher than GO and epoxy matrix, respectively. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Coupling between Ge-nanocrystals and defects in SiO2

    International Nuclear Information System (INIS)

    Skov Jensen, J.; Franzo, G.; Leervad Petersen, T.P.; Pereira, R.; Chevallier, J.; Christian Petersen, M.; Bech Nielsen, B.; Nylandsted Larsen, A.

    2006-01-01

    Room temperature photoluminescence (PL) at around 600 nm from magnetron-sputtered SiO 2 films co-doped with Ge is reported. The PL signal is observed in pure SiO 2 , however, its intensity increases significantly in the presence of Ge-nanocrystals (Ge-nc). The PL intensity has been optimized by varying the temperature of heat treatment, type of gas during heat treatment, concentration of Ge in the SiO 2 films, and gas pressure during deposition. Maximum intensity occurs when Ge-nc of around 3.5 nm are present in large concentration in SiO 2 layers deposited at fairly high gas pressure. Based on time resolved PL, and PL measurements after α-particle irradiation or H passivation, we attribute the origin of the PL to a defect in SiO 2 (probably an O deficiency) that is excited through an energy transfer from Ge-nc. There is no direct PL from the Ge-nc; however, there is a strong coupling between excitons created in the Ge-nc and the SiO 2 defect

  7. Calcium aluminates hydration in presence of amorphous SiO2 at temperatures below 90 deg. C

    International Nuclear Information System (INIS)

    Rivas Mercury, J.M.; Turrillas, X.; Aza, A.H. de; Pena, P.

    2006-01-01

    The hydration behaviour of Ca 3 Al 2 O 6 , Ca 12 Al 14 O 33 and CaAl 2 O 4 with added amorphous silica at 40, 65 and 90 deg. C has been studied for periods ranging from 1 to 31 days. In hydrated samples crystalline phases like katoite (Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x ) and gibbsite, Al(OH) 3 , were identified, likewise amorphous phases like Al(OH) x , calcium silicate hydrates, C-S-H, and calcium aluminosilicate hydrates, C-S-A-H, were identified. The stoichiometry of Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x (0≤3-x≤0.334), which was the main crystalline product, was established by Rietveld refinement of X-ray and neutron diffraction data and by transmission electron microscopy. - Graphical abstract: Katoite, Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x (0≤3-x≤0.334), was identified besides gibbsite, Al(OH) 3 , as a crystalline stable hydration products in Ca 3 Al 2 O 6 , Ca 12 Al 14 O 33 and CaAl 2 O 4 hydrated with added amorphous silica between 40 and 90 deg. C

  8. Phase transformation of Ca4[Al6O12]SO4 and its disordered crystal structure at 1073 K

    International Nuclear Information System (INIS)

    Kurokawa, Daisuke; Takeda, Seiya; Colas, Maggy; Asaka, Toru; Thomas, Philippe; Fukuda, Koichiro

    2014-01-01

    The phase transformation of Ca 4 [Al 6 O 12 ]SO 4 and the crystal structure of its high-temperature phase were investigated by differential thermal analysis, temperature-dependent Raman spectroscopy and high-temperature X-ray powder diffraction (CuKα 1 ). We determined the starting temperature of the orthorhombic-to-cubic transformation during heating (=711 K) and that of the reverse transformation during cooling (=742 K). The thermal hysteresis was negative (=−31 K), suggesting the thermoelasticity of the transformation. The space group of the high temperature phase is I4 ¯ 3m with the unit-cell dimensions of a=0.92426(2) nm and V=0.78955(2) nm 3 (Z=2) at 1073 K. The initial structural model was derived by the direct methods and further refined by the Rietveld method. The final structural model showed the orientational disordering of SO 4 tetrahedra. The maximum-entropy method-based pattern fitting method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. At around the transformation temperature during heating, the vibrational spectra, corresponding to the Raman-active SO 4 internal stretching mode, showed the continuous and gradual change in the slope of full width at half maximum versus temperature curve. This strongly suggests that the orthorhombic-to-cubic phase transformation would be principally accompanied by the statistical disordering in orientation of the SO 4 tetrahedra, without distinct dynamical reorientation. - Graphical abstract: (Left) Three-dimensional electron-density distributions of the SO 4 tetrahedron with the split-atom model, and (right) a bird's eye view of electron densities on the plane parallel to (111). - Highlights: • Crystal structure of Ca 4 [Al 6 O 12 ]SO 4 at 1073 K is determined by powder XRD. • The atom arrangements are represented by the split-atom model. • The MPF method is used to confirm the validity of the model.

  9. Synthesis of raspberry-like monodisperse magnetic hollow hybrid nanospheres by coating polystyrene template with Fe(3)O(4)@SiO(2) particles.

    Science.gov (United States)

    Wang, Chunlei; Yan, Juntao; Cui, Xuejun; Wang, Hongyan

    2011-02-01

    In this paper, we present a novel method for the preparation of raspberry-like monodisperse magnetic hollow hybrid nanospheres with γ-Fe(2)O(3)@SiO(2) particles as the outer shell. PS@Fe(3)O(4)@SiO(2) composite nanoparticles were successfully prepared on the principle of the electrostatic interaction between negatively charged silica and positively charged polystyrene, and then raspberry-like magnetic hollow hybrid nanospheres with large cavities were achieved by means of calcinations, simultaneously, the magnetite (Fe(3)O(4)) was transformed into maghemite (γ-Fe(2)O(3)). Transmission electron microscopy (TEM) demonstrated that the obtained magnetic hollow silica nanospheres with the perfect spherical profile were well monodisperse and uniform with the mean size of 253nm. The Fourier transform infrared (FTIR) spectrometry, energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) provided the sufficient evidences for the presence of Fe(3)O(4) in the silica shell. Moreover, the magnetic hollow silica nanospheres possessed a characteristic of superparamagnetic with saturation magnetization value of about 7.84emu/g by the magnetization curve measurement. In addition, the nitrogen adsorption-desorption measurement exhibited that the pore size, BET surface area, pore volume of magnetic hollow silica nanospheres were 3.5-5.5nm, 307m(2)g(-1) and 1.33cm(3)g(-1), respectively. Therefore, the magnetic hollow nanospheres possess a promising future in controlled drug delivery and targeted drug applications. Copyright © 2010 Elsevier Inc. All rights reserved.

  10. Matrix solid-phase dispersion extraction of organophosphorus pesticide using SiO2-poly(N-vinylimidazole)

    International Nuclear Information System (INIS)

    Gutiérrez-Solís, M C; Muñoz-Rodríguez, D; Carrera-Figueiras, C; Ávila-Ortega, A; Medina-Peralta, S

    2013-01-01

    A sorbent material based on silica particles modified with poly(N-vinylimidazole) (SiO 2 -PVI) has been evaluated for the treatment of samples by matrix solid-phase dispersion (MSPD). The extraction of four organophosphorus pesticides was done from a spiked tomato and the extracts were analyzed by gas chromatography coupled to mass spectrometry. Six elution solvents were evaluated and acetone was selected due to better recovery of the four pesticides and low background signal in the chromatograms. A factorial design 2 4 was used for selection of extraction conditions. The factors were contact time, acetone volume, treatment (with or without freeze-drying) and adsorbent (SiO 2 or SiO 2 -PVI). The best recoveries were obtained using 15 minutes of contact, 2 mL of solvent and sorbent without freeze-drying. The recoveries were between 60 and 83% for SiO 2 -PVI in spiked tomato with 0.2 and 0.8μg/g.

  11. Experimental determination of nanofluid specific heat with SiO2 nanoparticles in different base fluids

    Science.gov (United States)

    Akilu, S.; Baheta, A. T.; Sharma, K. V.; Said, M. A.

    2017-09-01

    Nanostructured ceramic materials have recently attracted attention as promising heat transfer fluid additives owing to their outstanding heat storage capacities. In this paper, experimental measurements of the specific heats of SiO2-Glycerol, SiO2-Ethylene Glycol, and SiO2-Glycerol/Ethylene Glycol mixture 60:40 ratio (by mass) nanofluids with different volume concentrations of 1.0-4.0% have been carried out using differential scanning calorimeter at temperatures of 25 °C and 50 °C. Experimental results indicate lower specific heat capacities are found with SiO2 nanofluids compared to their respective base fluids. The specific heat was decreasing with the increase of concentration, and this decrement depends on upon the type of the base fluid. It is observed that temperature has a positive impact on the specific heat capacity. Furthermore, the experimental values were compared with the theoretical model predictions, and a satisfactory agreement was established.

  12. Characterization of remote O2-plasma-enhanced CVD SiO2/GaN(0001) structure using photoemission measurements

    Science.gov (United States)

    Truyen, Nguyen Xuan; Ohta, Akio; Makihara, Katsunori; Ikeda, Mitsuhisa; Miyazaki, Seiichi

    2018-01-01

    The control of chemical composition and bonding features at a SiO2/GaN interface is a key to realizing high-performance GaN power devices. In this study, an ∼5.2-nm-thick SiO2 film has been deposited on an epitaxial GaN(0001) surface by remote O2-plasma-enhanced chemical vapor deposition (O2-RPCVD) using SiH4 and Ar/O2 mixture gases at a substrate temperature of 500 °C. The depth profile of chemical structures and electronic defects of the O2-RPCVD SiO2/GaN structures has been evaluated from a combination of SiO2 thinning examined by X-ray photoelectron spectroscopy (XPS) and the total photoelectron yield spectroscopy (PYS) measurements. As a highlight, we found that O2-RPCVD is effective for fabricating an abrupt SiO2/GaN interface.

  13. Neutron diffraction study of high temperature phase of K2SeO4

    International Nuclear Information System (INIS)

    Iwata, Yutaka; Koyano, Nobumitsu; Shibuya, Iwao; Hidaka, Masanori; Okazaki, Atsushi.

    1984-01-01

    The crystal structure of high-temperature phase of K 2 SeO 4 has been determined by means of single crystal neutron diffraction. The space group is P6 3 /mmc of hexagonal system with two formula units per unit cell. The structure is characterized by an averaged dispositions of SeO 4 tetrahedra with one of its Se-O bonds pointing parallel and antiparallel to the hexagonal c-axis in addition to the split distribution of potassium atoms. Heavily distorted distribution of oxygen atoms in SeO 4 is observed in Fourier maps corrersponding to split positions and reorientational motion of tetrahedra. This disordered arrangement is found to have close relation with the room temperature orthorhombic structure. The hexagonal-orthorhombic phase transition of K 2 SeO 4 at 472 0 C is grouped to an order-disorder type. (author)

  14. The structure of pumice by neutron diffraction

    International Nuclear Information System (INIS)

    Floriano, M.A.; Venezia, A.M.; Deganello, G.; Svensson, E.C.; Root, J.H.

    1994-01-01

    Small-angle neutron scattering (SANS) and wide-angle neutron scattering (WANS) measurements on pumice, an amorphous natural aluminosilicate used as support for metals in the preparation of catalysts, are reported. The SANS spectrum indicates the presence of a broad size distribution of pores and the absence of volume fractality. Surface fractality, however, cannot be ruled out. The structure of pumice, suggested by the pair-correlation function derived from the WANS spectrum and simulated by a random-network structure model, is very similar to that of vitreous silica, consisting mainly of SiO 4- 4 tetrahedra interconnected by bridging O atoms with additional local disorder generated by the replacement, on average, of one in ten Si atoms by aluminium. (orig.)

  15. A New Open-framework Iron Borophosphate from Ionic Liquids: KFe[BP2O8(OH

    Directory of Open Access Journals (Sweden)

    Guangmei Wang

    2011-04-01

    Full Text Available A new open-framework iron borophosphate, KFe[BP2O8(OH], has been obtained by ionothermal synthesis from KH2PO4, FeCl3∙4H2O, H3BO3 and [C4mpyr]Br (1-butyl-1-methylpyrrolidinium bromide. Single-crystal X-ray diffraction analysis shows that KFe[BP2O8(OH] (monoclinic, P21/c, a = 9.372(2 Å , b = 8.146(2Å , c = 9.587(2 Å, β = 101.18(3°, V = 718.0(2Å3 and Z = 4 has a three-dimensional (3-D framework structure composed by {Fe(IIIO5(OH} octahedra as well as {BO3(OH} and {PO4} tetrahedra. As anionic structural sub-unit, KFe[BP2O8(OH], contains an infinite open-branched {[BP2O8(OH]4-} chain which is formed by alternating {BO3(OH} and {PO4} tetrahedra. {Fe(IIIO5(OH} octahedra share common O corners with five phosphate tetrahedra and the OH corner links to the hydrogen borate group to give a 3D framework. The negative charges of the inorganic framework are balanced by K+ ions.

  16. Crystal structure of NH4[La(SO42(H2O

    Directory of Open Access Journals (Sweden)

    Meriem Benslimane

    2015-06-01

    Full Text Available The principal building units in the crystal structure of ammonium aquabis(sulfatolanthanate(III are slightly distorted SO4 tetrahedra, LaO9 polyhedra in the form of distorted tricapped trigonal prisms, and NH4+ ions. The La3+ cation is coordinated by eight O atoms from six different sulfate tetrahedra, two of which are bidentate coordinating and four monodentate, as well as one O atom from a water molecule; each sulfate anion bridges three La3+ cations. These bridging modes result in the formation of a three-dimensional anionic [La(SO42(H2O]− framework that is stabilized by O—H...O hydrogen-bonding interactions. The disordered ammonium cations are situated in the cavities of this framework and are hydrogen-bonded to six surrounding O atoms.

  17. Synthesis and Photoluminescence Properties of Ca2Ga2SiO7:Eu(3+) Red Phosphors with an Intense (5)D0 → (7)F4 Transition.

    Science.gov (United States)

    Behrh, Gaganpreet Kaur; Gautier, Romain; Latouche, Camille; Jobic, Stéphane; Serier-Brault, Hélène

    2016-09-19

    Novel melilite-type Ca2Ga2SiO7:Eu(3+) red-emitting phosphors with different Eu(3+) contents were synthesized via high-temperature solid-state reaction. The crystal structure, optical absorption, and photoluminescence properties were investigated, while density functional theory calculations were performed on the host lattice. The excitation spectra indicate that phosphors can be effectively excited by near-UV light for a potential application in white-light-emitting diodes. Because of the abnormally high intensity emission at about 700 nm arising from the (5)D0 → (7)F4 transition of Eu(3+), the phosphors Ca2Ga2SiO7:Eu(3+) show a deep-red emission with chromaticity coordinates (0.639, 0.358).

  18. Uptake properties of Ni2+ by nCaO.Al2O3.2SiO2 (n=1-4) prepared from solid-state reaction of kaolinite and calcite.

    Science.gov (United States)

    Jha, Vinay Kumar; Kameshima, Yoshikazu; Nakajima, Akira; Okada, Kiyoshi; MacKenzie, Kenneth J D

    2005-08-31

    A series of nCaO.Al2O3.2SiO2 samples (n=1-4) were prepared by solid-state reaction of mechanochemically treated mixtures of kaolinite and calcite fired at 600-1000 degrees C for 24 h. All the samples were X-ray amorphous after firing at 600-800 degrees C but had crystallized by 900 degrees C. The main crystalline phases were anorthite (n=1), gehlenite (n=2 and 3) and larnite (n=4). The uptake of Ni2+ by nCaO.Al2O3.2SiO2 samples fired at 800 and 900 degrees C was investigated at room temperature using solutions with initial Ni2+ concentrations of 0.1-50 mmol/l. Amorphous samples (fired at 800 degrees C) showed a higher Ni2+ uptake capacity than crystalline samples (fired at 900 degrees C). Ni2+ uptake was found to increase with increasing of CaO content. Amorphous 4CaO.Al2O3.2SiO2 showed the highest Ni2+ uptake capacity (about 9 mmol/g). The Ni2+ uptake abilities of the present samples are higher than those of other materials reported in the literature. Since the sorbed Ni2+/released Ca2+ ratios of these samples are close to unity, ion replacement of Ni2+ for Ca2+ is thought to be the principal mechanism of Ni2+ uptake by the present samples.

  19. Thickness and composition of ultrathin SiO2 layers on Si

    International Nuclear Information System (INIS)

    Marel, C. van der; Verheijen, M.A.; Tamminga, Y.; Pijnenburg, R.H.W.; Tombros, N.; Cubaynes, F.

    2004-01-01

    Ultrathin SiO 2 layers are of importance for the semiconductor industry. One of the techniques that can be used to determine the chemical composition and thickness of this type of layers is x-ray photoelectron spectroscopy (XPS). As shown by Seah and Spencer [Surf. Interface Anal. 33, 640 (2002)], it is not trivial to characterize this type of layer by means of XPS in a reliable way. We have investigated a series of ultrathin layers of SiO 2 on Si (in the range from 0.3 to 3 nm) using XPS. The samples were also analyzed by means of transmission electron microscopy (TEM), Rutherford backscattering (RBS), and ellipsometry. The thickness of the SiO 2 layers (d) was determined from the XPS results using three different approaches: the 'standard' equation (Seah and Spencer) for d, an overlayer-substrate model calculation, and the QUASES-Tougaard [Surf. Interface Anal. 26, 249 (1998), QUASES-Tougaard: Software package for Quantitative Analysis of Surfaces by Electron Spectroscopy, version 4.4 (2000); http://www.quases.com] method. Good agreement was obtained between the results of XPS analyses using the 'standard' equation, the overlayer-substrate model calculation, and RBS results. The QUASES-Tougaard results were approximately 62% above the other XPS results. The optical values for the thickness were always slightly higher than the thickness according to XPS or RBS. Using the model calculation, these (relatively small) deviations from the optical results could be explained as being a consequence of surface contaminations with hydrocarbons. For a thickness above 2.5 nm, the TEM results were in good agreement with the results obtained from the other techniques (apart from QUASES-Tougaard). Below 2.5 nm, significant deviations were found between RBS, XPS, and optical data on the one hand and TEM results on the other hand; the deviations became larger as the thickness of the SiO 2 decreased. This effect may be related to interface states of oxygen, which have been

  20. Preparation and characterization of silane-modified SiO2 particles reinforced resin composites with fluorinated acrylate polymer.

    Science.gov (United States)

    Liu, Xue; Wang, Zengyao; Zhao, Chengji; Bu, Wenhuan; Na, Hui

    2018-04-01

    A series of fluorinated dental resin composites were prepared with two kinds of SiO 2 particles. Bis-GMA (bisphenol A-glycerolate dimethacrylate)/4-TF-PQEA (fluorinated acrylate monomer)/TEGDMA (triethylene glycol dimethacrylate) (40/30/30, wt/wt/wt) was introduced as resin matrix. SiO 2 nanopartices (30nm) and SiO 2 microparticles (0.3µm) were silanized with 3-methacryloxypropyl trimethoxysilane (γ-MPS) and used as fillers. After mixing the resin matrix with 0%, 10%, 20%, 30% SiO 2 nanopartices and 0%, 10%, 20%, 30%, 40%, 50% SiO 2 microparticles, respectively, the fluorinated resin composites were obtained. Properties including double bond conversion (DC), polymerization shrinkage (PS), water sorption (W p ), water solubility (W y ), mechanical properties and cytotoxicity were investigated in comparison with those of neat resin system. The results showed that, filler particles could improve the overall performance of resin composites, particularly in improving mechanical properties and reducing PS of composites along with the addition of filler loading. Compared to resin composites containing SiO 2 microparticles, SiO 2 nanoparticles resin composites had higher DC, higher mechanical properties, lower PS and lower W p under the same filler content. Especially, 50% SiO 2 microparticles reinforced resins exhibited the best flexural strength (104.04 ± 7.40MPa), flexural modulus (5.62 ± 0.16GPa), vickers microhardness (37.34 ± 1.13 HV), compressive strength (301.54 ± 5.66MPa) and the lowest polymerization (3.42 ± 0.22%). Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Study on spectroscopic properties and effects of tungsten ions in 2Bi2O3-3GeO2/SiO2 glasses.

    Science.gov (United States)

    Yu, Pingsheng; Su, Liangbi; Cheng, Junhua; Zhang, Xia; Xu, Jun

    2017-04-01

    The 2Bi 2 O 3 -3GeO 2 /SiO 2 glass samples have been prepared by the conventional melt quenching technique. XRD patterns, absorption spectra, excitation-emission spectra and Raman measurements were utilized to characterize the synthesized glasses. When substitute SiO 2 for GeO 2 , the 0.4Bi 2 O 3 -(0.4-0.1)GeO 2 -(0.2-0.5)SiO 2 glasses exhibit strong emission centered at about 475nm (under 300nm excitation), and the decay constants are within the scope of 20-40ns. W doping into 2Bi 2 O 3 -3SiO 2 glass could increase the emission intensity of 470nm, and the W-doped 2Bi 2 O 3 -3SiO 2 glass has shown another emission at about 433nm with much shorter decay time (near 10ns). The 2Bi 2 O 3 -3GeO 2 /SiO 2 glass system could be the possible candidate for scintillator in high energy physics applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Carboxylated SiO2-coated α-Fe nanoparticles: towards a versatile platform for biomedical applications.

    Science.gov (United States)

    Kohara, Kaori; Yamamoto, Shinpei; Seinberg, Liis; Murakami, Tatsuya; Tsujimoto, Masahiko; Ogawa, Tetsuya; Kurata, Hiroki; Kageyama, Hiroshi; Takano, Mikio

    2013-03-28

    Carboxylated SiO2-coated α-Fe nanoparticles have been successfully prepared via CaH2-mediated reduction of SiO2-coated Fe3O4 nanoparticles followed by surface carboxylation. These α-Fe-based nanoparticles, which are characterized by ease of coating with additional functional groups, a large magnetization of 154 emu per g-Fe, enhanced corrosion resistivity, excellent aqueous dispersibility, and low cytotoxicity, have potential to be a versatile platform in biomedical applications.

  3. The far infrared radiation characteristics for Li2O.Al2O3.4SiO2(LAS) glass-ceramics and transition-metal oxide

    International Nuclear Information System (INIS)

    Huh, Nam Jung; Yang, Joong Sik

    1991-01-01

    The far infrared radiation characteristic for Li 2 O.Al 2 O 3 .4SiO 2 (LAS) glass, the LAS glass-ceramic and sintered transition metal oxides such as CuO, Fe 2 O 3 and Co 3 O 4 , were investigated. LAS glass and LAS glass-ceramic was higher than that of the LAS glass. Heat-treated CuO and Co 3 o 4 had radiation characteristic of high efficiency infrared radiant, and heat-treated Fe 2 O 3 had radiation characteristic that infrared emissivity decreased in higher was length above 15μm. (Author)

  4. Effect of oxide charge trapping on x-ray photoelectron spectroscopy of HfO2/SiO2/Si structures

    International Nuclear Information System (INIS)

    Abe, Yasuhiro; Miyata, Noriyuki; Suzuki, Haruhiko; Kitamura, Koji; Igarashi, Satoru; Nohira, Hiroshi; Ikenaga, Eiji

    2009-01-01

    We examined the effects of interfacial SiO 2 layers and a surface metal layer on the photoelectron spectra of HfO 2 /SiO 2 /Si structures by hard X-ray photoemission spectroscopy with synchrotron radiation as well as conventional X-ray photoelectron spectroscopy (XPS). The Hf 4f and Hf 3d photoelectron peaks broadened and shifted toward a higher binding energy with increasing thickness of the interfacial SiO 2 layer, even though photoelectrons may have been emitted from the HfO 2 layer with the same chemical composition. Thinning the interfacial Si oxide layer to approximately one monolayer and depositing a metal layer on the HfO 2 surface suppressed these phenomena. The O 1s photoelectron spectra revealed marked differences between the metal- and nonmetal-deposited HfO 2 /SiO 2 /Si structures; HfO 2 and SiO 2 components in the O 1s photoelectron spectra for the metal-deposited structures were observed at reasonably separated binding energies, but those for the nonmetal-deposited structures were not separated clearly. From this behavior concerning the effects of interfacial SiO 2 and surface metal layers, we concluded that the Hf 4f, Hf 3d, and O 1s spectra measured from the HfO 2 /SiO 2 /Si structures did not reflect actual chemical bonding states. We consider that potential variations in the HfO 2 film owing to charge trapping strongly affect the measured photoelectron spectra. On the basis of angle-resolved XPS measurements, we propose that positive charges are trapped at the HfO 2 surface and negative charges are trapped inside the HfO 2 layer. (author)

  5. Physical and Electrical Properties of SiO2 Layer Synthesized by Eco-Friendly Method

    Science.gov (United States)

    Kim, Jong-Woong; Kim, Young-Seok; Hong, Sung-Jei; Hong, Tae-Hwan; Han, Jeong-In

    2010-05-01

    SiO2 thin film has a wide range of applications, including insulation layers in microelectronic devices, such as semiconductors and flat panel displays, due to its advantageous characteristics. Herein, we developed a new eco-friendly method for manufacturing SiO2 nanoparticles and, thereby, SiO2 paste to be used in the digital printing process for the fabrication of SiO2 film. By excluding harmful Cl- and NO3- elements from the SiO2 nanoparticle synthetic process, we were able to lower the heat treatment temperature for the SiO2 precursor from 600 to 300 °C and the diameter of the final SiO2 nanoparticles to about 14 nm. The synthesized SiO2 nanoparticles were dispersed in an organic solvent with additives to make a SiO2 paste for feasibility testing. The SiO2 paste was printed onto a glass substrate to test the feasibility of using it for digital printing. The insulation resistance of the printed film was high enough for it to be used as an insulation layer for passivation.

  6. Strong piezoelectricity in single-layer graphene deposited on SiO2 grating substrates.

    Science.gov (United States)

    da Cunha Rodrigues, Gonçalo; Zelenovskiy, Pavel; Romanyuk, Konstantin; Luchkin, Sergey; Kopelevich, Yakov; Kholkin, Andrei

    2015-06-25

    Electromechanical response of materials is a key property for various applications ranging from actuators to sophisticated nanoelectromechanical systems. Here electromechanical properties of the single-layer graphene transferred onto SiO2 calibration grating substrates is studied via piezoresponse force microscopy and confocal Raman spectroscopy. The correlation of mechanical strains in graphene layer with the substrate morphology is established via Raman mapping. Apparent vertical piezoresponse from the single-layer graphene supported by underlying SiO2 structure is observed by piezoresponse force microscopy. The calculated vertical piezocoefficient is about 1.4 nm V(-1), that is, much higher than that of the conventional piezoelectric materials such as lead zirconate titanate and comparable to that of relaxor single crystals. The observed piezoresponse and achieved strain in graphene are associated with the chemical interaction of graphene's carbon atoms with the oxygen from underlying SiO2. The results provide a basis for future applications of graphene layers for sensing, actuating and energy harvesting.

  7. Plasma diagnostic studies of the influence of process variables upon the atomic and molecular species ejected from (1-x)Li4SiO4:xLi3PO4 targets during rf-magnetron sputtering

    International Nuclear Information System (INIS)

    Wachs, A.L.; Bates, J.B.; Dudney, N.J.; Luck, C.F.

    1990-01-01

    The deposition of thin-film electrolytes is a critical step in the development of lithium microbatteries with the potential for circuit integration. We have performed a preliminary study of the rf-magnetron sputtering of (1-x)Li 4 SiO 4 :xLi 3 PO 4 targets used to deposit amorphous thin-film electrolytes formed of the three-component system Li 2 O--SiO 2 --P 2 O 5 . Mass and optical emission spectroscopies have been used to investigate the effects of target composition and the deposition conditions upon the atomic and molecular species ejected from the targets. The data provide important information for understanding the mechanism of film formation and for monitoring the Li atomic flux onto the substrates during film growth. 5 refs., 7 figs., 1 tab

  8. Red/blue-shift dual-directional regulation of α-(Ca, Sr)2SiO4:Eu(2+) phosphors resulting from the incorporation content of Eu(2+)/Sr(2+) ions.

    Science.gov (United States)

    Lu, Zhijuan; Mao, Zhiyong; Chen, Jingjing; Wang, Dajian

    2015-09-21

    In this work, tunable emission from green to red and the inverse tuning from red to green in α-(Ca, Sr)2SiO4:Eu(2+) phosphors were demonstrated magically by varying the incorporation content of Eu(2+) and Sr(2+) ions, respectively. The tunable emission properties and the tuning mechanism of red-shift resulting from the Eu(2+) content as well as that of blue-shift induced by the Sr(2+) content were investigated in detail. As a result of fine-controlling the incorporation content of Eu(2+), the emission peak red-shifts from 541 nm to 640 nm. On the other hand, the emission peak inversely blue-shifts from 640 nm to 546 nm through fine-adjusting the incorporation content of Sr(2+). The excellent tuning characteristics for α-(Ca, Sr)2SiO4:Eu(2+) phosphors presented in this work exhibited their various application prospects in solid-state lighting combining with a blue chip or a near-UV chip.

  9. X-ray and neutron single-crystal diffraction on [Rbx(NH4)1-x]3H(SO4)2. I. Refinement of crystal structure of phase II with x=0.11 at 300 K

    International Nuclear Information System (INIS)

    Loose, A.; Wozniak, K.; Dominiak, P.; Smirnov, L.S.; Natkaniec, I.; Frontas'eva, M.V.; Pomyakushina, E.V.; Baranov, A.I.; Dolbinina, V.V

    2006-01-01

    The study of [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals by X-ray single-crystal diffraction is known up to now only for x=0.57 at the temperatures 293 and 180 K. The crystal structures at these temperatures as was determined [1] belong to monoclinic phase II (C2/c sp. gr., Z=4). In accordance with this work, ammonium ions should be considered as deformed tetrahedra. Monoclinic phase II on the x-T phase diagram of [Rb x (NH 4 ) 1-x ] 3 H(SO 4 ) 2 mixed crystals, which has earlier been determined by the dielectric spectroscopy, is stabilized below room temperature if Rb concentration exceeds 9%. The presented results of X-ray and neutron single-crystal diffraction of the [Rb 0.11 (NH 4 ) 0.89 ] 3 H(SO 4 ) 2 mixed crystal at T= 300 K show that ammonium ions could be considered as regular tetrahedra

  10. Facile preparation of polyethylenimine-tannins coated SiO2 hybrid materials for Cu2+ removal

    Science.gov (United States)

    Huang, Qiang; Liu, Meiying; Zhao, Jiao; Chen, Junyu; Zeng, Guangjian; Huang, Hongye; Tian, Jianwen; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2018-01-01

    Polyethylenimine-tannins coated SiO2 (SiO2@PEI-TA) hybrid materials have been prepared via a single-step multifunctional coating with polyethylenimine (PEI) and tannins (TA), and characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The as-prepared SiO2@PEI-TA composites were examined as adsorbents to remove the Cu2+ from aqueous solution. The effects of contact time, initial Cu2+ concentration, solution pH and temperature, on Cu2+ adsorption have been investigated. The results show that the adsorption of Cu2+ onto SiO2@PEI-TA is dependent on the contact time, Cu2+ concentration, pH and temperature. The SiO2@PEI-TA composites show a 2.4-fold increase in adsorption capacity, implying that the introduction of PEI-TA coating is in favor of the Cu2+ adsorption. Based on the analysis of kinetic data, the kinetics of Cu2+ adsorption is more accurately described by the pseudo-second-order model. The equilibrium data are analyzed by Langmuir and Freundlich isotherms. Results of isotherms show that the better agreement is Freundlich isotherm model with correlation coefficient of 0.9914, which suggests that the adsorption of Cu2+ onto SiO2@PEI-TA is mainly a heterogeneous adsorption process. Thermodynamic analyses show that the adsorption interaction is actually a spontaneous and endothermic chemical process, which might involve the chemical chelation between Cu2+ and functional groups (amine and carboxyl groups) on the surface of SiO2@PEI-TA. In addition, the Cu2+ ions could desorb from SiO2@PEI-TA by using acid solution and the adsorption efficiency remains at high level after five adsorption-desorption recycles. These results provide potential applications of these novel adsorbents for the removal of heavy metal Cu2+ from aqueous solution and also provide strong evidence to support the adsorption mechanism proposed in the study.

  11. On the Relation of Silicates and SiO Maser in Evolved Stars

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jiaming; Jiang, Biwei, E-mail: bjiang@bnu.edu.cn [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)

    2017-04-01

    The SiO molecule is one of the candidates for the seed of silicate dust in the circumstellar envelope of evolved stars, but this opinion is challenged. In this work we investigate the relation of the SiO maser emission power and the silicate dust emission power. With both our own observation by using the PMO/Delingha 13.7 m telescope and archive data, a sample is assembled of 21 SiO v  = 1, J  = 2 − 1 sources and 28 SiO v  = 1, J  = 1 − 0 sources that exhibit silicate emission features in the ISO /SWS spectrum as well. The analysis of their SiO maser and silicate emission power indicates a clear correlation, which is not against the hypothesis that the SiO molecules are the seed nuclei of silicate dust. On the other hand, no correlation is found between SiO maser and silicate crystallinity, which may imply that silicate crystallinity does not correlate with mass-loss rate.

  12. Non-LTE Analysis of Interstellar Line Spectra of SiO

    Science.gov (United States)

    Zhang, Ziwei; Stancil, Phillip C.

    2016-01-01

    SiO emission lines are important probes of chemical processes in diverse astrophysical environments. In circumstellar outflows of AGB stars, the production of silicate grains is preceded by SiO formation, making SiO a useful measure of Si depletion. SiO is also commonly observed in shocks associated with the outflows of young stellar objects, both low- and high-mass. To model SiO emission for non-LTE conditions requires collisional rate coefficients due to H2 impact which are currently unavailable. Unknown collisional rate coefficients are often estimated from known systems. For the case of SiO-H2, rate coefficients have previously been adapted from a different collider, He (Dayau & Balanca 2006), based on a reduced-mass scaling approach. Recently it has been suggested that scaling via the interaction potential well depth and the reduced masses of the collisional systems may be more reliable (Walker et al. 2014). Using the non-LTE spectral modeling package Radex (van der Tak et al. 2007), we construct diagnostic plots of SiO line ratios using SiO-H2 collisional rate coefficients based on (i) reduced-mass scaling from the LAMDA database, (ii) potential well-depth scaling, and (iii) a more comprehensive input with multiple colliders (H2, He and H). Our goal is to give a more rigorous approach to SiO line emission simulations to better understand Si chemistry, dust formation/destruction, and other astrophysical processes.This work was supported by NASA ATP grant NNX15AI61G.

  13. First investigations on the quaternary system Na2O-K2O-CaO-SiO2: synthesis and crystal structure of the mixed alkali calcium silicate K1.08Na0.92Ca6Si4O15

    Science.gov (United States)

    Kahlenberg, Volker; Mayerl, Michael Jean-Philippe; Schmidmair, Daniela; Krüger, Hannes; Tribus, Martina

    2018-04-01

    In the course of an exploratory study on the quaternary system Na2O-K2O-CaO-SiO2 single crystals of the first anhydrous sodium potassium calcium silicate have been obtained from slow cooling of a melt in the range between 1250 and 1050 °C. Electron probe micro analysis suggested the following idealized molar ratios of the oxides for the novel compound: K2O:Na2O:CaO:SiO2 = 1:1:12:8 (or KNaCa6Si4O15). Single-crystal diffraction measurements on a crystal with chemical composition K1.08Na0.92Ca6Si4O15 resulted in the following basic crystallographic data: monoclinic symmetry, space group P 21/ c, a = 8.9618(9) Å, b = 7.3594(6) Å, c = 11.2453(11) Å, β= 107.54(1)°, V = 707.2(1) Å3, Z = 2. Structure solution was performed using direct methods. The final least-squares refinement converged at a residual of R(|F|) = 0.0346 for 1288 independent reflections and 125 parameters. From a structural point of view, K1.08Na0.92Ca6Si4O15 belongs to the group of mixed-anion silicates containing [Si2O7]- and [SiO4]-units in the ratio 1:2. The mono- and divalent cations occupy a total of four crystallographically independent positions located in voids between the tetrahedra. Three of these sites are exclusively occupied by calcium. The fourth site is occupied by 54(1)% K and 46%(1) Na, respectively. Alternatively, the structure can be described as a heteropolyhedral framework based on corner-sharing silicate tetrahedra and [CaO6]-octahedra. The network can build up from kröhnkite-like [Ca(SiO4)2O2]-chains running along [001]. A detailed comparison with other A2B6Si4O15-compounds including topological and group-theoretical aspects is presented.

  14. Adsorption of cationic dye on a biohybrid SiO2-alginate

    International Nuclear Information System (INIS)

    Barrón Zambrano, J A; Ávila Ortega, A; Muñoz Rodríguez, D; Carrera Figueiras, C; López-Pérez, A J

    2013-01-01

    In this work, a biohybrid material based on SiO 2 -alginate was obtained and its properties of adsorption evaluated using methylene blue as a model dye. The experimental results showed that the biohybrid SiO 2 -alginate has a higher adsorption ability compared to their base compounds (SiO 2 and alginate). Methylene blue adsorption is pH dependent, resulting in a maximum adsorption at pH = 8. The sorption kinetics rate is similar to SiO 2 . Kinetic data were fitted to a model of pseudosecond order. The experimental isotherms fit well the Langmuir model.

  15. Thermal equation of state of (Mg 0.9Fe 0.1) 2SiO 4 olivine

    Science.gov (United States)

    Liu, Wei; Li, Baosheng

    2006-08-01

    In situ synchrotron X-ray diffraction measurements have been carried out on San Carlos olivine (Mg 0.9Fe 0.1) 2SiO 4 up to 8 GPa and 1073 K. Data analysis using the high-temperature Birch-Murnaghan (HTBM) equation of state (EoS) yields the temperature derivative of the bulk modulus (∂ KT/∂ T) P = -0.019 ± 0.002 GPa K -1. The thermal pressure (TH) approach gives αKT = 4.08 ± 0.10 × 10 -3 GPa K -1, from which (∂ KT/∂ T) P = -0.019 ± 0.001 GPa K -1 is derived. Fitting the present data to the Mie-Grüneisen-Debye (MGD) formalism, the Grüneisen parameter at ambient conditions γ0 is constrained to be 1.14 ± 0.02 with fixed volume dependence q = 1. Combining the present data with previous results on iron-bearing olivine and fitting to MGD EoS, we obtain γ0 = 1.11 ± 0.01 and q = 0.54 ± 0.36. In this study the thermoelastic parameters obtained from various approaches are in good agreement with one another and previous results.

  16. Redeposition of etch products on sidewalls during SiO2 etching in a fluorocarbon plasma. I. Effect of particle emission from the bottom surface in a CF4 plasma

    International Nuclear Information System (INIS)

    Min, Jae-Ho; Hwang, Sung-Wook; Lee, Gyeo-Re; Moon, Sang Heup

    2002-01-01

    The effect of etch-product redeposition on sidewall properties during the etching of step-shaped SiO 2 patterns in a CF 4 plasma was examined using a Faraday cage located in a transformer coupled plasma etcher. Sidewall properties were observed for two cases: with and without particles emitted from the bottom surface in normal contact with the sidewall. Particles sputtered from the bottom surface were redeposited on the sidewall, which contributes to the formation of a passivation layer on the surface of the latter. The passivation layer consisted of silicon oxide, Si x O y , and fluorocarbon, C x F y , the latter comprising the major species. Ar plasma experiments confirmed that C x F y or a fluorocarbon polymer must be present on the sidewall in order for the Si x O y species to be deposited on the surface. The redeposited particles, which were largely F-deficient fluorocarbon species, as evidenced by x-ray photoelectron spectroscopy analyses, functioned as precursors for fluorocarbon polymerization, resulting in a rough sidewall surface. The chemical etch rates of SiO 2 were retarded by the redeposition of particles, which eventually formed a thick layer, eventually covering the bulk SiO 2 . Auger electron spectroscopy analyses of the sidewall surface affected by the emission from the bottom suggest that the surface consists of three distinct layers: a surface-carbon layer, a redeposition-etch combined layer, and bulk SiO 2

  17. Ultraefficient separation and sensing of mercury and methylmercury ions in drinking water by using aminonaphthalimide-functionalized Fe(3)O(4)@SiO(2) core/shell magnetic nanoparticles.

    Science.gov (United States)

    Park, Minsung; Seo, Sungmin; Lee, In Su; Jung, Jong Hwa

    2010-07-07

    A new fluorogenic based aminonaphthalimide-functionalized Fe(3)O(4)@SiO(2) core/shell magnetic nanoparticles 1 has been prepared, and its abilities to sense and separate metal ions were evaluated by fluorophotometry. The nanoparticles 1 exhibited a high affinity and selectivity for Hg(2+) and CH(3)Hg(+) ions over competing metal ions.

  18. Concentration effect of Tm3+ on cathodoluminescence properties of SiO2: Tm3+ and SiO2:Ho3+, Tm3+ systems

    CSIR Research Space (South Africa)

    Dhlamini, MS

    2012-05-01

    Full Text Available .physb.2011.09.091 Concentration effect of Tm3+ on cathodoluminescence properties of SiO2: Tm 3+ and SiO2:Ho 3+, Tm3+ systems M.S. Dhlamini, G.H. Mhlongo, H.C. Swart, O.M. Ntwaeaborwa, K.T. Hillie ABSTRACT: Cathodoluminescence (CL) properties of Si...O2 powders activated with thulium (Tm3+) and holmium (Ho3+) ions prepared by a sol–gel process were investigated. Different molar concentrations of Tm3+ co-doped with Ho3+ were studied. The 460 nm peak was monitored and the influence of the beam...

  19. Roymillerite, Pb24Mg9(Si9AlO28)(SiO4)(BO3)(CO3)10(OH)14O4, a new mineral: mineralogical characterization and crystal chemistry

    Science.gov (United States)

    Chukanov, Nikita V.; Jonsson, Erik; Aksenov, Sergey M.; Britvin, Sergey N.; Rastsvetaeva, Ramiza K.; Belakovskiy, Dmitriy I.; Van, Konstantin V.

    2017-11-01

    The new mineral roymillerite Pb24Mg9(Si9AlO28)(SiO4)(BO3)(CO3)10(OH)14O4, related to britvinite and molybdophyllite, was discovered in a Pb-rich assemblage from the Kombat Mine, Grootfontein district, Otjozondjupa region, Namibia, which includes also jacobsite, cerussite, hausmannite, sahlinite, rhodochrosite, barite, grootfonteinite, Mn-Fe oxides, and melanotekite. Roymillerite forms platy single-crystal grains up to 1.5 mm across and up to 0.3 mm thick. The new mineral is transparent, colorless to light pink, with a strong vitreous lustre. Cleavage is perfect on (001). Density calculated using the empirical formula is equal to 5.973 g/cm3. Roymillerite is optically biaxial, negative, α = 1.86(1), β ≈ γ = 1.94(1), 2 V (meas.) = 5(5)°. The IR spectrum shows the presence of britvinite-type tetrahedral sheets, {CO}3^{2 - }, {BO}3^{3 - }, and OH- groups. The chemical composition is (wt%; electron microprobe, H2O and CO2 determined by gas chromatography, the content of B2O3 derived from structural data): MgO 4.93, MnO 1.24, FeO 0.95, PbO 75.38, B2O3 0.50, Al2O3 0.74, CO2 5.83, SiO2 7.90, H2O 1.8, total 99.27. The empirical formula based on 83 O atoms pfu (i.e. Z = 1) is Pb24.12Mg8.74Mn1.25Fe0.94B1.03Al1.04C9.46Si9.39H14.27O83. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is triclinic, space group P \\bar{1}, with a = 9.315(1), b = 9.316(1), c = 26.463(4) Å, α = 83.295(3)°, β = 83.308(3)°, γ = 60.023(2)°, V = 1971.2(6) Å3. The crystal structure of roymillerite is based built by alternating pyrophyllite-type TOT-modules Mg9(OH)8[(Si,Al)10O28] and I-blocks Pb24(OH)6O4(CO3)10(BO3,SiO4). The strongest lines of the powder X-ray diffraction pattern [ d, Å (I, %) ( hkl)] are: 25.9 (100) (001), 13.1 (11) (002), 3.480 (12) (017, 107, -115, 1-15), 3.378 (14) (126, 216), 3.282 (16) (-2-15, -1-25), 3.185 (12) (-116, 1-16), 2.684 (16) (031, 301, 030, 300, 332, -109, 0-19, 1-18), 2.382 (11) (0.0.-11). Roymillerite is

  20. Passivation of pigment-grade TiO2 particles by nanothick atomic layer deposited SiO2 films

    International Nuclear Information System (INIS)

    King, David M; Liang Xinhua; Weimer, Alan W; Burton, Beau B; Akhtar, M Kamal

    2008-01-01

    Pigment-grade TiO 2 particles were passivated using nanothick insulating films fabricated by atomic layer deposition (ALD). Conformal SiO 2 and Al 2 O 3 layers were coated onto anatase and rutile powders in a fluidized bed reactor. SiO 2 films were deposited using tris-dimethylaminosilane (TDMAS) and H 2 O 2 at 500 deg. C. Trimethylaluminum and water were used as precursors for Al 2 O 3 ALD at 177 deg. C. The photocatalytic activity of anatase pigment-grade TiO 2 was decreased by 98% after the deposition of 2 nm SiO 2 films. H 2 SO 4 digest tests were performed to exhibit the pinhole-free nature of the coatings and the TiO 2 digest rate was 40 times faster for uncoated TiO 2 than SiO 2 coated over a 24 h period. Mass spectrometry was used to monitor reaction progress and allowed for dosing time optimization. These results demonstrate that the TDMAS-H 2 O 2 chemistry can deposit high quality, fully dense SiO 2 films on high radius of curvature substrates. Particle ALD is a viable passivation method for pigment-grade TiO 2 particles

  1. Photoluminescence and excited state structure in Bi3+-doped Y2SiO5 single crystalline films

    International Nuclear Information System (INIS)

    Babin, V.; Gorbenko, V.; Krasnikov, A.; Mihokova, E.; Nikl, M.; Zazubovich, S.; Zorenko, Yu.

    2013-01-01

    Single crystalline films of Bi-doped Y 2 SiO 5 are studied at 4.2–350 K by the time-resolved luminescence methods under excitation in the 3.8–6.2 eV energy range. Ultraviolet luminescence of Y 2 SiO 5 :Bi (≈3.6 eV) is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi 3+ centers which are related to the 3 P 0 and 3 P 1 levels of a free Bi 3+ ion, respectively. The lowest-energy excitation band of this emission, located at ≈4.5 eV, is assigned to the 1 S 0 → 3 P 1 transitions of a free Bi 3+ ion. The phenomenological model is proposed to describe the excited-state dynamics of Bi 3+ centers in Y 2 SiO 5 :Bi, and parameters of the triplet RES are determined. -- Highlights: •Luminescence of Y 2 SiO 5 :Bi is investigated for the first time. •Ultraviolet emission arises from Bi 3+ ions located in Y lattice sites. •The triplet relaxed excited states parameters of Bi 3+ centers are determined

  2. Synthesis and Crystal Structure of a New Ruthenium Silicophosphate: RuP 3SiO 11

    Science.gov (United States)

    Fukuoka, Hiroshi; Imoto, Hideo; Saito, Taro

    1996-01-01

    A new ruthenium silicophosphate RuP3SiO11was obtained and the structure was determined by single-crystal X-ray diffraction. It crystallizes in the trigonal space groupR3cwitha= 8.253(3)Å,c= 39.317(4)Å,V= 2319(2)Å3,Z= 12,R= 0.029, andRW= 0.026. The structure is composed of RuO6, Si2O7, and P2O7units. The Si2O7unit shares the six oxygen atoms with six P2O7units, while the P2O7unit shares the six oxygen atoms with two Si2O7units and four RuO6octahedra. The anionic part forms an infinite three-dimensional network of silicophosphate. RuP3SiO11is isotypic with MoP3SiO11.

  3. Energetics of cobalt phosphate frameworks: α, β, and red NaCoPO4

    International Nuclear Information System (INIS)

    Le, So-Nhu; Eng, Hank W.; Navrotsky, Alexandra

    2006-01-01

    Thermal behavior, relative stability, and enthalpy of formation of α (pink phase), β (blue phase), and red NaCoPO 4 are studied by differential scanning calorimetry, X-ray diffraction, and high-temperature oxide melt drop solution calorimetry. Red NaCoPO 4 with cobalt in trigonal bipyramidal coordination is metastable, irreversibly changing to α NaCoPO 4 at 827 K with an enthalpy of phase transition of -17.4±6.9 kJ mol -1 . α NaCoPO 4 with cobalt in octahedral coordination is the most stable phase at room temperature. It undergoes a reversible phase transition to the β phase (cobalt in tetrahedra) at 1006 K with an enthalpy of phase transition of 17.6±1.3 kJ mol -1 . Enthalpy of formation from oxides of α, β, and red NaCoPO 4 are -349.7±2.3, -332.1±2.5, and -332.3±7.2 kJ mol -1 ; standard enthalpy of formation of α, β, and red NaCoPO 4 are -1547.5±2.7, -1529.9±2.8, and -1530.0±7.3 kJ mol -1 , respectively. The more exothermic enthalpy of formation from oxides of β NaCoPO 4 compared to a structurally related aluminosilicate, NaAlSiO 4 nepheline, results from the stronger acid-base interaction of oxides in β NaCoPO 4 (Na 2 O, CoO, P 2 O 5 ) than in NaAlSiO 4 nepheline (Na 2 O, Al 2 O 3 , SiO 2 ). - Graphical abstract: Relative stability of NaCoPO 4 polymorphs compared to the most stable phase, α NaCoPO 4

  4. Enhanced field emission properties of carbon nanotube bundles confined in SiO2 pits

    Science.gov (United States)

    Lim, Yu Dian; Grapov, Dmitry; Hu, Liangxing; Kong, Qinyu; Tay, Beng Kang; Labunov, Vladimir; Miao, Jianmin; Coquet, Philippe; Aditya, Sheel

    2018-02-01

    It has been widely reported that carbon nanotubes (CNTs) exhibit superior field emission (FE) properties due to their high aspect ratios and unique structural properties. Among the various types of CNTs, random growth CNTs exhibit promising FE properties due to their reduced inter-tube screening effect. However, growing random growth CNTs on individual catalyst islands often results in spread out CNT bundles, which reduces overall field enhancement. In this study, significant improvement in FE properties in CNT bundles is demonstrated by confining them in microfabricated SiO2 pits. Growing CNT bundles in narrow (0.5 μm diameter and 2 μm height) SiO2 pits achieves FE current density of 1-1.4 A cm-2, which is much higher than for freestanding CNT bundles (76.9 mA cm-2). From the Fowler Nordheim plots, confined CNT bundles show a higher field enhancement factor. This improvement can be attributed to the reduced bundle diameter by SiO2 pit confinement, which yields bundles with higher aspect ratios. Combining the obtained outcomes, it can be conclusively summarized that confining CNTs in SiO2 pits yields higher FE current density due to the higher field enhancement of confined CNTs.

  5. UV-VUV laser induced phenomena in SiO2 glass

    International Nuclear Information System (INIS)

    Kajihara, Koichi; Ikuta, Yoshiaki; Oto, Masanori; Hirano, Masahiro; Skuja, Linards; Hosono, Hideo

    2004-01-01

    Creation and annihilation of point defects were studied for SiO 2 glass exposed to ultraviolet (UV) and vacuum UV (VUV) lights to improve transparency and radiation toughness of SiO 2 glass to UV-VUV laser light. Topologically disordered structure of SiO 2 glass featured by the distribution of Si-O-Si angle is a critical factor degrading transmittance near the fundamental absorption edge. Doping with terminal functional groups enhances the structural relaxation and reduces the number of strained Si-O-Si bonds by breaking up the glass network without creating the color centers. Transmittance and laser toughness of SiO 2 glass for F 2 laser is greatly improved in fluorine-doped SiO 2 glass, often referred as 'modified silica glass'. Interstitial hydrogenous species are mobile and reactive at ambient temperature, and play an important role in photochemical reactions induced by exposure to UV-VUV laser light. They terminate the dangling-bond type color centers, while enhancing the formation of the oxygen vacancies. These findings are utilized to develop a deep-UV optical fiber transmitting ArF laser photons with low radiation damage

  6. Efficient VEGF targeting delivery of DOX using Bevacizumab conjugated SiO2@LDH for anti-neuroblastoma therapy.

    Science.gov (United States)

    Zhu, Rongrong; Wang, Zhaoqi; Liang, Peng; He, Xiaolie; Zhuang, Xizhen; Huang, Ruiqi; Wang, Mei; Wang, Qigang; Qian, Yechang; Wang, Shilong

    2017-11-01

    Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis and is highly expressed in carcinoma, which make it an important target for tumor targeting therapy. Neuroblastoma is the main cause for cancer-related death in children. Like most solid tumors, it is also accompanied with the overexpression of VEGF. Doxorubicin Hydrochloride (DOX), a typical chemotherapeutic agent, exhibits efficient anticancer activities for various cancers. However, DOX, without targeting ability, usually causes severe damage to normal tissues. To overcome the shortages, we designed a novel nano-composite, which is Bevacizumab (Bev) modified SiO 2 @LDH nanoparticles (SiO 2 @LDH-Bev), loading with DOX to achieve targeting ability and curative efficiency. SiO 2 @LDH-DOX and SiO 2 @LDH-Bev-DOX nanoparticles were synthesized and the physicochemical properties were characterized by TEM detection, Zeta potential analysis, FTIR, Raman and XPS analysis. Then in vitro and in vivo anti-neuroblastoma efficiency, targeting ability and mechanisms of anti-carcinoma and anti-angiogenesis of SiO 2 @LDH-Bev-DOX were explored. Our results indicated that we obtained the core-shell structure SiO 2 @LDH-Bev with an average diameter of 253±10nm and the amount of conjugated Bev was 4.59±0.38μg/mg SiO 2 @LDH-Bev. SiO 2 @LDH-Bev-DOX could improve the cellular uptake and the targeting effect of DOX to brain and tumor, enhance the anti-neuroblastoma and anti-angiogenesis efficiency both in vitro and in vivo, and alleviate side effects of DOX sharply, especially hepatic injury. In addition, we also demonstrated that angiogenesis inhibitory effect was mediated by DOX and VEGF triggered signal pathways, including PI3K/Akt, Raf/MEK/ERK, and adhesion related pathways. In summary, SiO 2 @LDH-Bev could be a potential VEGF targeting nanocarrier applied in VEGF positive cancer therapy. This paper explored that a novel core-shell structure nanomaterial SiO 2 @LDH and modified SiO 2 @LDH with

  7. Silicon electrodeposition from chloride-fluoride melts containing K2SiF6 and SiO2

    Directory of Open Access Journals (Sweden)

    Zhuk Sergey I.

    2017-01-01

    Full Text Available Silicon electrodeposition on glassy carbon from the KF-KCl-K2SiF6, KF-KCl-K2SiF6-KOH and KF-KCl-K2SiF6-SiO2 melts was studied by the cyclic voltammetry. Тhe electroreduction of Si(IV to metallic Si was observed as a single 4-electron wave under all considered conditions. The reactions of cathode reduction of silicon from fluoride and oxyfluoride complexes were suggested. It was shown that the process can be controlled by the preliminary transformation of SiO44- to SiF62- and SiOxFyz-. The influence of the current density on structure and morphology of silicon deposits obtained during galvanostatic electrolysis of the KF-KCl-K2SiF6-SiO2 melt was studied.

  8. Circulating angiopoietin-like 4 links proteinuria with hypertriglyceridemia in nephrotic syndrome

    NARCIS (Netherlands)

    Clement, L.C.; Mace, C.; Avila-Casado, C.; Joles, J.A.; Kersten, A.H.; Chugh, S.S.

    2014-01-01

    The molecular link between proteinuria and hyperlipidemia in nephrotic syndrome is not known. We show in the present study that plasma angiopoietin-like 4 (Angptl4) links proteinuria with hypertriglyceridemia through two negative feedback loops. In previous studies in a rat model that mimics human

  9. Long lasting yellow phosphorescence and photostimulated luminescence in Sr3SiO5 : Eu2+ and Sr3SiO5 : Eu2+, Dy3+ phosphors

    International Nuclear Information System (INIS)

    Sun Xiaoyuan; Zhang Jiahua; Zhang Xia; Luo Yongshi; Wang Xiaojun

    2008-01-01

    We report the observation of long lasting yellow phosphorescence and photostimulated luminescence (PSL) in Sr 3 SiO 5 : Eu 2+ and Sr 3 SiO 5 : Eu 2+ , Dy 3+ phosphors. The decay patterns of phosphorescence and thermoluminescence curves demonstrate that introduction of Dy 3+ into Sr 3 SiO 5 : Eu 2+ can generate a large number of shallow traps and deep traps. The generated deep traps prolong the phosphorescence up to 6 h after UV irradiation. The PSL is studied under 808 nm excitation. Slow rising and falling edges of the emission in Sr 3 SiO 5 : Eu 2+ , Dy 3+ are observed, showing a retrapping process by the generated shallow traps due to co-doping Dy 3+ .

  10. Fabrication and properties of highly luminescent materials from Tb(OH)3-SiO2 and Tb(OH)3-SiO2:Eu3+ nanotubes

    International Nuclear Information System (INIS)

    Tran Thu Huong; Tran Kim Anh; Le Quoc Minh

    2009-01-01

    Luminescent nanomaterials with one-dimensional (1D) structures have attracted much attention due to their unique properties and potential applications in nanophotonics and nanobiophotonics. In this paper, we report a synthesis of terbium - hydroxide - at - silica Tb(OH) 3 -SiO 2 and Tb(OH) 3 -SiO 2 :Eu 3+ nanotubes. Terbium - hydroxide tubes were synthesized by soft template method. The size of the tubes can be controlled precisely and have outer diameters ranging from 80 to 120 nm, wall thickness of about 30 nm, and lengths ranging from 300 to 800 nm. To fabricate core/shell materials, the seed growth method is used. FESEM, X-ray diffraction, Raman spectra of Tb(OH) 3 and Tb(OH) 3 -SiO 2 nanotubes were investigated. The photoluminescence (PL) spectrum of Tb(OH) 3 under 325 nm excitation consists of four main peaks at 488, 542, 582, and 618 nm. Furthermore, a preliminary suggestion for the mechanism of growth of the Tb(OH) 3 nanotubes using the soft - template synthesis technique has been proposed. The PL intensity from Tb(OH) 3 -SiO 2 or Tb(OH) 3 -SiO 2 :Eu 3+ nanotubes is much stronger than that of Tb(OH) 3 .

  11. Interferometric Observation of the Highly Polarized SiO Maser Emission from the v = 1, J = 5-4 Transition Associated with VY Canis Majoris

    Science.gov (United States)

    Shinnaga, Hiroko; Moran, James M.; Young, Ken H.; Ho, Paul T. P.

    2004-11-01

    We used the Submillimeter Array to image the SiO maser emission in the v=1, J=5-4 transition associated with the peculiar red supergiant VY Canis Majoris. We identified seven maser components and measured their relative positions and linear polarization properties. Five of the maser components are coincident to within about 150 mas (~200 AU at the distance of 1.5 kpc); most of them may originate in the circumstellar envelope at a radius of about 50 mas from the star along with the SiO masers in the lowest rotational transitions. Our measurements show that two of the maser components may be offset from the inner stellar envelope (at the 3 σ level of significance) and may be part of a larger bipolar outflow associated with VY CMa identified by Shinnaga et al. The strongest maser feature at a velocity of 35.9 km s-1 has a 60% linear polarization, and its polarization direction is aligned with the bipolar axis. Such a high degree of polarization suggests that maser inversion is due to radiative pumping. Five of the other maser features have significant linear polarization.

  12. Tracer diffusion studies of 26Mg, 30Si and 18O in single crystal forsterite (Mg2SiO4) and of 18O in single crystal SiO2

    International Nuclear Information System (INIS)

    Schachtner, R.

    1981-01-01

    Tracer diffusion coefficients of Mg, Si and O in monocrystalline forsterite were determined by Sims as a function of temperature and crystal orientation. Former results on oxygen diffusion in SiO 2 single crystals using nuclear activation methods were confirmed by Sims data. The influence of crystal defects and impurities is discussed. (TW)

  13. Interferometric Observation of the Highly Polarized SiO Maser Emission from the v = 1, J = 5-4 Transition Associated with VY Canis Majoris

    OpenAIRE

    Shinnaga, Hiroko; Moran, James M.; Young, Ken Harbour; Ho, Paul T. P.

    2004-01-01

    We used the Submillimeter Array to image the SiO maser emission in the $v=1$, \\$J=5-4$ transition associated with the peculiar red supergiant VY Canis Majoris. We identified seven maser components and measured their relative positions and linear polarization properties. Five of the maser components are coincident to within about 150 mas ($\\sim$ 200 AU at the distance of 1.5 kpc); most of them may originate in the circumstellar envelope at a radius of about 50 mas from the star along with the ...

  14. ATLASGAL-selected massive clumps in the inner Galaxy. II. Characterisation of different evolutionary stages and their SiO emission

    Science.gov (United States)

    Csengeri, T.; Leurini, S.; Wyrowski, F.; Urquhart, J. S.; Menten, K. M.; Walmsley, M.; Bontemps, S.; Wienen, M.; Beuther, H.; Motte, F.; Nguyen-Luong, Q.; Schilke, P.; Schuller, F.; Zavagno, A.; Sanna, C.

    2016-02-01

    Context. The processes leading to the birth of high-mass stars are poorly understood. The key first step to reveal their formation processes is characterising the clumps and cores from which they form. Aims: We define a representative sample of massive clumps in different evolutionary stages selected from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), from which we aim to establish a census of molecular tracers of their evolution. As a first step, we study the shock tracer, SiO, mainly associated with shocks from jets probing accretion processes. In low-mass young stellar objects (YSOs), outflow and jet activity decreases with time during the star formation processes. Recently, a similar scenario was suggested for massive clumps based on SiO observations. Here we analyse observations of the SiO (2-1) and (5-4) lines in a statistically significant sample to constrain the change of SiO abundance and the excitation conditions as a function of evolutionary stage of massive star-forming clumps. Methods: We performed an unbiased spectral line survey covering the 3-mm atmospheric window between 84-117 GHz with the IRAM 30 m telescope of a sample of 430 sources of the ATLASGAL survey, covering various evolutionary stages of massive clumps. A smaller sample of 128 clumps has been observed in the SiO (5-4) transition with the APEX telescope to complement the (2-1) line and probe the excitation conditions of the emitting gas. We derived detection rates to assess the star formation activity of the sample, and we estimated the column density and abundance using both an LTE approximation and non-LTE calculations for a smaller subsample, where both transitions have been observed. Results: We characterise the physical properties of the selected sources, which greatly supersedes the largest samples studied so far, and show that they are representative of different evolutionary stages. We report a high detection rate of >75% of the SiO (2-1) line and a >90% detection

  15. Electrical and physical characterizations of the effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and (000\\bar{1})

    Science.gov (United States)

    Shiomi, Hiromu; Kitai, Hidenori; Tsujimura, Masatoshi; Kiuchi, Yuji; Nakata, Daisuke; Ono, Shuichi; Kojima, Kazutoshi; Fukuda, Kenji; Sakamoto, Kunihiro; Yamasaki, Kimiyohi; Okumura, Hajime

    2016-04-01

    The effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and (000\\bar{1}) were investigated using both electrical and physical characterization methods. Hall measurements and split capacitance-voltage (C-V) measurements revealed that the difference in field-effect mobility between wet oxide and dry oxynitride interfaces was mainly attributed to the ratio of the mobile electron density to the total induced electron density. The surface states close to the conduction band edge causing a significant trapping of inversion carriers were also evaluated. High-resolution Rutherford backscattering spectroscopy (HR-RBS) analysis and high-resolution elastic recoil detection analysis (HR-ERDA) were employed to show the nanometer-scale compositional profile of the SiC-MOS interfaces for the first time. These analyses, together with cathode luminescence (CL) spectroscopy and transmission electron microscopy (TEM), suggested that the deviations of stoichiometry and roughness at the interface defined the effects of oxynitridation and wet oxidation at the interface of SiO2/4H-SiC(0001) and (000\\bar{1}).

  16. Gibbs energies of formation of zircon (ZrSiO4), thorite (ThSiO4), and phenacite (Be2SiO4)

    International Nuclear Information System (INIS)

    Schuiling, R.D.; Vergouwen, L.; Rijst, H. van der

    1976-01-01

    Zircon, thorite, and phenacite are very refractory compounds which do not yield to solution calorimetry. In In order to obtain approximate Gibbs energies of formation for these minerals, their reactions with a number of silica-undersaturated compounds (silicates or oxides) were studied. Conversely baddeleyite (ZrO 2 ), thorianite (ThO 2 ), and bromellite (BeO) were reacted with the appropriate silicates. As the Gibbs energies of reaction of the undersaturated compounds with SiO 2 are known, the experiments yield the following data: Δ G 298 , 1 /sub bar/ 0 = -459.02 +- 1.04 kcal for zircon, -489.67 +- 1.04 for thorite, and -480.20 +- 1.01 for phenacite

  17. Nano-TiCl4.SiO2: A Versatile and Efficient Catalyst for Synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes

    OpenAIRE

    B. F. Mirjalili; A. Bamoniri; L. Zamani

    2013-01-01

    Nano-silica supported titanium tetrachloride (TiCl4.SiO2) was prepared and used as an acid catalyst for the 14-aryl or alkyl-14H-dibenzo[a,,j]xanthenesreaction under solvent-free conditions. Compared to the classical 14-aryl or alkyl-14H-dibenzo[a,j]xanthenesreaction conditions, this method consistently has the advantage of excellent yields, mild reaction conditions, ease of workup, survival of different functional groups and short reaction times.

  18. Fabrication of hierarchical structured SiO2/polyetherimide-polyurethane nanofibrous separators with high performance for lithium ion batteries

    International Nuclear Information System (INIS)

    Zhai, Yunyun; Xiao, Ke; Yu, Jianyong; Ding, Bin

    2015-01-01

    Highlights: • Electrospinning followed by dip-coating was used to fabricate SiO 2 /PEI-PU membranes. • Introducing PEI, PU and SiO 2 improved safety, tensile strength and ionic conductivity. • Coating SiO 2 also restrained the micro-shorting and migrated the self-discharge. • SiO 2 /PEI-PU membranes based cell exhibited prominent cycling and rate performance. - ABSTRACT: The performance of lithium ion battery based on electrospun nanofibrous membranes has gained a great deal of attention in the past decades, but the intrinsic low mechanical strength and large pore size of electrospun membranes limit their battery performance. To overcome this limitation, a powerful strategy for designing, fabricating and evaluating silica nanoparticles coated polyetherimide-polyurethane (SiO 2 /PEI-PU) nanofibrous composite membranes is easily developed via electrospinning followed by a dip-coating process. Benefiting from the high porosity, interpenetrating network structure and synergetic effect of PU, PEI and SiO 2 nanoparticles, the as-prepared composite membranes exhibit high ionic conductivity (2.33 mS cm −1 ), robust tensile strength (15.65 MPa) and improved safety (excellent thermal resistance and flame retardant property). Additionally, the as-prepared composite membranes possess relatively narrow pore size distribution with average pore size of 0.58 μm after coating SiO 2 nanoparticles, which plays an important role in hindering the micro-shorting and mitigating self-discharge. Significantly, the SiO 2 /PEI-PU membranes based Li/LiFePO 4 cell exhibits more excellent cycling stability with capacity retention of 98.7% after 50 cycles at 0.2 C rate and better rate capability compared with the Celgard membrane based cell. The results clearly demonstrate that this is a promising separator candidate for next-generation lithium ion batteries, which may represent a significant step toward separators with improved performance

  19. Non-isothermal crystallization kinetics and phase transformation of Bi2O3-SiO2 glass-ceramics

    Directory of Open Access Journals (Sweden)

    Guo H.W.

    2011-01-01

    Full Text Available The Bi2O3-SiO2 (BS glass-ceramics were prepared by melt-quench technique, and the crystallization kinetics and phase transformation behavior were investigated in accordance with Kissinger and Johson-Mehl-Avrami equation, DSC, XRD and SEM. The results show that in the heat treatment process (or termed as re-crystallizing process Bi2SiO5 and Bi4Si3O12 crystals were found consequently. Respectively, the crystallization activation energies of the two crystals are Ep1=14.8kJ/mol and Ep2=34.1kJ/mol. And the average crystallization index of n1=1.73 and n2=1.38 suggested volume nucleation, one-dimensional growth and surface nucleation, one-dimensional growth from surface to the inside respectively. The meta-stable needle-like Bi2SiO5 crystals are easily to be transformed into stable prismatic Bi4Si3O12 crystals. By quenching the melt and hold in 850°C for 1h, the homogenous single Bi4Si3O12 crystals were found in the polycrystalline phase of the BS glassceramics system.

  20. Fabrication of cube-like Fe3O4@SiO2@Ag nanocomposites with high SERS activity and their application in pesticide detection

    International Nuclear Information System (INIS)

    Li, Lei; Zhao, Aiwu; Wang, Dapeng; Guo, Hongyan; Sun, Henghui; He, Qinye

    2016-01-01

    The cube-like Fe 3 O 4 @SiO 2 @Ag (FSA) nanocomposites with great SERS activity have been successfully synthesized by a layer-by-layer procedure in this paper. The cube-like Fe 3 O 4 @SiO 2 core–shell structures were prepared via a new route and Ag nanoparticles were introduced onto their surface through a one-pot hydrothermal reaction. By controlling the reaction time, the coverage rate of Ag on the FSA surface could be tuned, and then a series of FSA composites were obtained. The SERS properties of these FSA composites were investigated using p-aminothiophenol (p-ATP) as the probe molecule. It was found that the FSA composites synthesized with a reaction time of 6 h showed the best SERS performance, and the detection limit for p-ATP could reach 1 × 10 −7 M. For practical application, the FSA composites were also used to detect thiram, one of the dithiocarbamate fungicides that has been widely used as a pesticide in agriculture. The detection limit is as low as 1 × 10 −6 M (0.24 ppm), lower than the maximal residue limit of 7 ppm in fruit prescribed by the US Environmental Protection Agency. The resulting substrate with high SERS activity, stability and strong magnetic responsivity makes the FSA composite a perfect choice for practical SERS detection applications.

  1. Enhancement of photocatalytic properties of TiO2 nanoparticles doped with CeO2 and supported on SiO2 for phenol degradation

    International Nuclear Information System (INIS)

    Hao, Chunjing; Li, Jing; Zhang, Zailei; Ji, Yongjun; Zhan, Hanhui; Xiao, Fangxing; Wang, Dan; Liu, Bin; Su, Fabing

    2015-01-01

    Highlights: • CeO 2 -TiO 2 /SiO 2 composites were prepared via a facile co-precipitation method. • Introduction of SiO 2 support increases the dispersion of CeO 2 -TiO 2 . • CeO 2 -TiO 2 /SiO 2 exhibits an enhanced photocatalytic efficiency for phenol degradation. • Ce 3+ /Ce 4+ pair coexisting in CeO 2 improves electron–hole pairs separation efficiency. - Abstract: A series of CeO 2 -TiO 2 and CeO 2 -TiO 2 /SiO 2 composites were prepared with TiCl 4 and Ce (NO 3 ) 3 ·6H 2 O as precursors via a facile co-precipitation method. The obtained samples were characterized by various techniques such as X-ray diffraction (XRD), nitrogen adsorption (N 2 -BET), Fourier transformation infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis spectroscopy measurements. The results indicated that TiO 2 doped with CeO 2 and supported on SiO 2 could reduce the crystallite size, inhibit the phase transformation, enhance the thermal stability, and effectively extend the spectral response from UV to visible range. When applied to the phenol photodegradation on a homemade batch reactor with an external cooling jacket, the CeO 2 -TiO 2 /SiO 2 catalysts exhibited significantly enhanced photodegradation efficiency in comparison with commercial Degussa P25 and CeO 2 -TiO 2 . The unique catalytic properties of CeO 2 -TiO 2 /SiO 2 were ascribed to improved electron–hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce 3+ /Ce 4+ , as well as high dispersion of active component of CeO 2 -TiO 2 as a result of the introduction of SiO 2 support. Furthermore, the catalysts can be easily recovered from the reaction solution by centrifugation and reused for four cycles without significant loss of activity

  2. VARIABILITY OF THE SiO THERMAL LINE EMISSION TOWARD THE YOUNG L1448-mm OUTFLOW

    International Nuclear Information System (INIS)

    Jimenez-Serra, I.; MartIn-Pintado, J.; RodrIguez-Franco, A.; Winters, J.-M.; Caselli, P.

    2011-01-01

    The detection of narrow SiO thermal emission toward young outflows has been proposed to be a signature of the magnetic precursor of C-shocks. Recent modeling of the SiO emission across C-shocks predicts variations in the SiO line intensity and line shape at the precursor and intermediate-velocity regimes in only a few years. We present high angular resolution (3.''8 x 3.''3) images of the thermal SiO J = 2→1 emission toward the L1448-mm outflow in two epochs (2004 November-2005 February, 2009 March-April). Several SiO condensations have appeared at intermediate velocities (20-50 km s -1 ) toward the redshifted lobe of the outflow since 2005. Toward one of the condensations (clump D), systematic differences of the dirty beams between 2005 and 2009 could be responsible for the SiO variability. At higher velocities (50-80 km s -1 ), SiO could also have experienced changes in its intensity. We propose that the SiO variability toward L1448-mm is due to a real SiO enhancement by young C-shocks at the internal working surface between the jet and the ambient gas. For the precursor regime (5.2-9.2 km s -1 ), several narrow and faint SiO components are detected. The narrow SiO components tend to be compact, transient and show elongated (bow-shock) morphologies perpendicular to the jet. We speculate that these features are associated with the precursor of C-shocks appearing at the interface of the new SiO components seen at intermediate velocities.

  3. SIMULTANEOUS OBSERVATIONS OF SiO AND H2O MASERS TOWARD SYMBIOTIC STARS

    International Nuclear Information System (INIS)

    Cho, Se-Hyung; Kim, Jaeheon

    2010-01-01

    We present the results of simultaneous observations of SiO v = 1, 2, J = 1-0, 29 SiO v = 0, J = 1-0, and H 2 O 6 16 -5 23 maser lines performed with the KVN Yonsei 21 m radio telescope from 2009 November to 2010 January. We searched for these masers in 47 symbiotic stars and detected maser emission from 21 stars, giving the first time detection from 19 stars. Both SiO and H 2 O masers were detected from seven stars of which six were D-type symbiotic stars and one was an S-type star, WRAY 15-1470. In the SiO maser emission, the 28 SiO v = 1 maser was detected from 10 stars, while the v = 2 maser was detected from 15 stars. In particular, the 28 SiO v = 2 maser emission without the v = 1 maser detection was detected from nine stars with a detection rate of 60%, which is much higher than that of isolated Miras/red giants. The 29 SiO v = 0 maser emission was also detected from two stars, H 2-38 and BF Cyg, together with the 28 SiO v = 2 maser. We conclude that these different observational results between isolated Miras/red giants and symbiotic stars may be related with the presence of hot companions in a symbiotic binary system.

  4. Ion-beam-driven amorphization of Ca2La8(SiO4)6O2 single crystals

    International Nuclear Information System (INIS)

    Weber, W.J.; Hess, N.J.; Wang, L.M.

    1993-11-01

    Single crystals of Ca 2 La 8 (SiO 4 ) 6 O 2 , with 1% Nd substituted for La, were irradiated with 0.8 MeV Ne + and 1.5 MeV Kr + ions from 15 to 773 K. The irradiations were carried out using the HVEM-Tandem Facility at Argonne National Laboratory. The structural changes and the ion fluence for complete amorphization were determined by in situ transmission electron microscopy. The ion fluence for complete amorphization increased with temperature in two stages associated with defect annealing processes. The critical temperature for amorphization increased from ∼360 K for 0.8 MeV Ne + to ∼710 K for 1.5 MeV Kr + . During in situ annealing studies, irradiation-enhanced recrystallization was observed at 923 K. Spatially-resolved fluorescence spectra of the Nd ion excited with 488.0 mn laser excitation showed marked line-broadening toward the center of the amorphous regions. Initial measurements indicate the subtle shifts of the 9 I 9/2 groundstate energy levels can be measured by pumping directly into the excited state 4 F 3/2 manifold suggesting that the line broadening observed originates from a distribution of geometrically distorted Nd sites

  5. Composition and crystallization kinetics of R2O-Al2O3-SiO2 glass-ceramics

    International Nuclear Information System (INIS)

    Xiong, Dehua; Cheng, Jinshu; Li, Hong

    2010-01-01

    The crystallization behavior and microstructure of R 2 O-Al 2 O 3 -SiO 2 (R means K, Na and Li) glass were investigated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallization kinetic parameters including the crystallization apparent activation energy (E a ), the Avrami parameter (n), glass transition temperature (T g ) and the activity energy of glass transition (E t ) were also measured with different methods. The results have shown that: the DSC traces of composition A parent glass have two different precipitation crystallization peaks corresponding to E a1 (A) = 151.4 kJ/mol (Li 2 SiO 3 ) and E a2 (A) = 623.1 kJ/mol (Li 2 Si 2 O 5 ), the average value of n = 1.70 (Li 2 Si 2 O 5 ) for the surface crystallization and E t (A) = 202.8 kJ/mol. And E a (B) = 50.7 kJ/mol (Li 2 SiO 3 ), the average value of n = 3.89 (Li 2 SiO 3 ) for the bulk crystallization and E t (B) = 220.4 kJ/mol for the composition B parent glass. Because of the content of R 2 O is bigger than composition A, composition B parent glass has a lower E a , T g and a larger n, E t .

  6. Silver nanoparticle deposition on inverse opal SiO2 films embedded in protective polypropylene micropits for SERS applications

    Science.gov (United States)

    Ammosova, Lena; Ankudze, Bright; Philip, Anish; Jiang, Yu; Pakkanen, Tuula T.; Pakkanen, Tapani A.

    2018-01-01

    Common methods to fabricate surface enhanced Raman scattering (SERS) substrates with controlled micro-nanohierarchy are often complex and expensive. In this study, we demonstrate a simple and cost effective method to fabricate SERS substrates with complex geometries. Microworking robot structuration is used to pattern a polypropylene (PP) substrate with micropits, facilitating protective microenvironment for brittle SiO2 inverse opal (IO) structure. Hierarchical SiO2 IO patterns were obtained using polystyrene (PS) spheres as a sacrificial template, and were selectively embedded into the hydrophilized PP micropits. The same microworking robot technique was subsequently used to deposit silver nanoparticle ink into the SiO2 IO cavities. The fabricated multi-level micro-nanohierarchy surface was studied to enhance Raman scattering of the 4-aminothiophenol (4-ATP) analyte molecule. The results show that the SERS performance of the micro-nanohierarchical substrate increases significantly the Raman scattering intensity compared to substrates with structured 2D surface geometries.

  7. Preparation and characterization of Sio2CaCl2 nanocomposite by the sol-gel method

    International Nuclear Information System (INIS)

    Tohidi, S. H.; Ziaie, F.; Abdolmaleki, A.

    2009-01-01

    The SiO 2 CaCl 2 hybrid porous materials were prepared by the sol-gel method. This process was conducted by the hydrolysis and condensation of Tetraethyl orthosilicate by replacement of ethanol from alcogel and drying at the ambient temperature to obtain xerogel structure. The alcogel samples were synthesized from Tetraethyl orthosilicate, EtOH, H 2 O, HCl, NH 4 OH and CaCl 2 , while the total molar ratio of the compounds was 1: 9: 4: 8 x 10 -4 , 8 x 10 -3 , respectively. Xerogel containing 30 wt % of CaCl 2 (dry matter) was prepared and characterized by Scanning Electron Microscopy, Transmission Electron Microscopy, Fourier Transmittance Infra Red spectrum, Energy Dispersive X-ray and Thermal Gravimetric Analysis systems. The results obtained from Scanning Electron Microscopy and Energy Dispersive X-ray showed the micrograph of CaCl 2 on the silica and chemical elemental analysis, respectively. On the other hand, The Transmission Electron Microscopy micrograph confirmed average particle size of SiO 2 -CaCl 2 about 50 nm and Fourier Transmittance Infra Red spectrum described the functional groups of the nano composite. The thermal analysis of SiO 2 -CaCl 2 nano composite was performed using Thermal Gravimetric Analysis system and the results showed that the suitable temperature for initial thermal treatment was about 200 d eg C .

  8. Experimental observations of the chemistry of the SiO2/Si interface

    Science.gov (United States)

    Grunthaner, F. J.; Maserjian, J.

    1977-01-01

    Changes in silicon surface preparation prior to thermal oxidation are shown to leave a signature by altering the final SiO2/Si interface structure. Surface analytical techniques, including XPS, static SIMS, ion milling, and newly developed wet-chemical profiling procedures are used to obtain detailed information on the chemical structure of the interface. The oxides are shown to be essentially SiO2 down to a narrow transitional interface layer (3-7 A). A number of discrete chemical species are observed in this interface layer, including different silicon bonds (e.g., C-, OH-, H-) and a range of oxidation states of silicon (0 to +4). The effect of surface preparation and the observed chemical species are correlated with oxide growth rate, surface-state density, and flatband shifts after irradiation.

  9. Photocatalytic Removal of Phenol under Natural Sunlight over N-TiO2-SiO2 Catalyst: The Effect of Nitrogen Composition in TiO2-SiO2

    Directory of Open Access Journals (Sweden)

    Viet-Cuong Nguyen

    2009-01-01

    Full Text Available In this present work, high specific surface area and strong visible light absorption nitrogen doped TiO2-SiO2 photocatalyst was synthesized by using sol-gel coupled with hydrothermal treatment method. Nitrogen was found to improve the specific surface area while it also distorted the crystal phase of the resulting N-TiO2-SiO2 catalyst. As the N/ (TiO2-SiO2 molar ratio was more than 10%, the derived catalyst presented the superior specific surface area up to 260 m2/g. Nevertheless, its photoactivity towards phenol removal was observed to significantly decrease, which could results from the too low crystallinity. The nitrogen content in N-TiO2-SiO2 catalyst was therefore necessary to be optimized in terms of phenol removal efficiency and found at ca. 5%. Under UVA light and natural sunlight irradiation of 80 min, N(5%-TiO2-SiO2 catalyst presented the phenol decomposition efficiencies of 68 and 100%, respectively. It was also interestingly found in this study that the reaction rate was successfully expressed using a Langmuir-Hinshelwood (L-H model, indicating the L-H nature of photocatalytic phenol decomposition reaction on the N-TiO2-SiO2 catalyst.

  10. Nano-TiCl4.SiO2: A Versatile and Efficient Catalyst for Synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes

    Directory of Open Access Journals (Sweden)

    B. F. Mirjalili

    2013-12-01

    Full Text Available Nano-silica supported titanium tetrachloride (TiCl4.SiO2 was prepared and used as an acid catalyst for the 14-aryl or alkyl-14H-dibenzo[a,,j]xanthenesreaction under solvent-free conditions. Compared to the classical 14-aryl or alkyl-14H-dibenzo[a,j]xanthenesreaction conditions, this method consistently has the advantage of excellent yields, mild reaction conditions, ease of workup, survival of different functional groups and short reaction times.

  11. Novel synthetic alkali-yttrium silicates with a new microporous mixed framework topology: (Rb,Cs)9Y7Si24O63 and isotypic Rb9Y7Si24O63

    International Nuclear Information System (INIS)

    Kolitsch, U.; Tillmanns, E.; Wierzbicka-Wieczorek, M.

    2008-01-01

    Prismatic colourless crystals of the two novel, isotypic title compounds were obtained by the flux growth technique. The crystal structures have been determined from single-crystal intensity data in space group R anti 3 with a=28.819(4)/28.799(4), c=13.916(3)/13.864(3) A, V=10009(3)/9958(3) A 3 , Z=6, R(F) =4.99/6.44%, respectively. They represent a novel structure type with microporous character. The framework is built from six-membered silicate rings (approximate UDUDUD orientation) containing isolated YO 6 octahedra and compressed ''six-membered rings'', which in fact build a spiral of corner-sharing SiO 4 tetrahedra. Approximately parallel to[111] run two different irregular channels hosting the Rb/Cs and Rb atoms. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Ammonium iron(III phosphate(V fluoride, (NH40.5[(NH40.375K0.125]FePO4F, with ammonium partially substituted by potassium

    Directory of Open Access Journals (Sweden)

    Lei Wang

    2009-01-01

    Full Text Available The title compound, ammonium potassium iron(III phosphate fluoride, (NH40.875K0.125FePO4F, is built from zigzag chains ∞1{[FeO4F2]7−}, with Fe3+ in a distorted octahedral coordination, extending along both the [011] and [0overline{1}1] directions. These chains are made up of alternating trans-[FeO4F2] and cis-[FeO4F2] octahedra via shared F-atom corners, and are linked by PO4 tetrahedra, resulting in an open-framework structure with channels along the [010] and [100] directions. There are two crystallographically independent ammonium sites: one in the [010] channels and the other, partially substituted by K+ ions, in the [100] channels. The ammonium in the [010] channels is fixed to the framework via eight hydrogen bonds (six N—H...O and two N—H...F.

  13. Temperature coefficient of elastic constants of SiO2 over-layer on LiNbO3 for a temperature stable SAW device

    International Nuclear Information System (INIS)

    Tomar, Monika; Gupta, Vinay; Sreenivas, K

    2003-01-01

    The influence of sputtered SiO 2 over-layer on the SAW propagation characteristics of a 128 deg. rotated Y-cut X-propagating lithium niobate SAW filter has been studied. Experimentally measured SAW phase velocity and temperature coefficient of delay (TCD), with varying SiO 2 over-layer thickness, show a significant deviation from the theoretically calculated values using the bulk material parameters of SiO 2 . The observed deviation is attributed to the differences in the material parameters (density, elastic and dielectric constants and their temperature coefficient) of the deposited SiO 2 over-layer. The density and the dielectric constant of the deposited SiO 2 layer were determined separately, and the elastic constants and their temperature coefficients were estimated by fitting the experimental velocity and TCD data, respectively. The deviation in the dielectric constant and the density in comparison to the bulk was insignificant, and the estimated values of the elastic constants (C 11 = 0.75x10 11 N m -2 and C 44 0.225x10 11 N m -2 ) were found to be lower, and the respective temperature coefficients (5.0x10 -4 deg C -1 and 2.0x10 -4 deg C -1 ) were high in comparison to the bulk material parameters

  14. Effects of four step sintering on Y2O3: SiO2 nanocomposite

    International Nuclear Information System (INIS)

    Ahlawat, Rachna

    2015-01-01

    Need for high performance materials for advanced applications have led to the development of new concepts in materials design processing and their fabrication. The development of nanocrystalline materials with improved and novel properties is an important turning point in materials research. In present work, we report synthesis and structural characterization of Y 2 O 3 : SiO 2 nanocomposite. Sol-gel technique is being used to prepare-Y 2 O 3 SiO 2 nanocomposite due to its effectiveness in preparing samples with good mixing of starting materials and at relatively low reaction temperature. We have used Y(NO 3 ) 3 .4H 2 O and TEOS as precursors and followed usual approach of sol-gel technique, the final product of Y 2 O 3 : SiO 2 nanocomposite is obtained in the form of powder. The powder samples were sintered at different temperature for different time durations in programmable muffle furnace. The samples were characterized by complementary techniques as X-Ray Diffraction (XRD), Fourier Transforms Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). (author)

  15. Microwave absorption properties and mechanism of cagelike ZnO /SiO2 nanocomposites

    Science.gov (United States)

    Cao, Mao-Sheng; Shi, Xiao-Ling; Fang, Xiao-Yong; Jin, Hai-Bo; Hou, Zhi-Ling; Zhou, Wei; Chen, Yu-Jin

    2007-11-01

    In this paper, cagelike ZnO /SiO2 nanocomposites were prepared and their microwave absorption properties were investigated in detail. Dielectric constants and losses of the pure cagelike ZnO nanostructures were measured in a frequency range of 8.2-12.4GHz. The measured results indicate that the cagelike ZnO nanostructures are low-loss material for microwave absorption in X band. However, the cagelike ZnO /SiO2 nanocomposites exhibit a relatively strong attenuation to microwave in X band. Such strong absorption is related to the unique geometrical morphology of the cagelike ZnO nanostructures in the composites. The microcurrent network can be produced in the cagelike ZnO nanostructures, which contributes to the conductive loss.

  16. Phase transformation of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} and its disordered crystal structure at 1073 K

    Energy Technology Data Exchange (ETDEWEB)

    Kurokawa, Daisuke [Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); R and D Center, Taiheiyo Cement Corporation, Chiba 285-8655 (Japan); Takeda, Seiya [Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Colas, Maggy [Science des Proce' de' s Ce' ramiques et de Traitements de Surface (SPCTS), UMR 7315 CNRS, Universite' de Limoges, Centre Europe' en de la Ce' ramique, 12 Rue Atlantis, 87068 Limoges Cedex (France); Asaka, Toru [Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Thomas, Philippe [Science des Proce' de' s Ce' ramiques et de Traitements de Surface (SPCTS), UMR 7315 CNRS, Universite' de Limoges, Centre Europe' en de la Ce' ramique, 12 Rue Atlantis, 87068 Limoges Cedex (France); Fukuda, Koichiro, E-mail: fukuda.koichiro@nitech.ac.jp [Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

    2014-07-01

    The phase transformation of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} and the crystal structure of its high-temperature phase were investigated by differential thermal analysis, temperature-dependent Raman spectroscopy and high-temperature X-ray powder diffraction (CuKα{sub 1}). We determined the starting temperature of the orthorhombic-to-cubic transformation during heating (=711 K) and that of the reverse transformation during cooling (=742 K). The thermal hysteresis was negative (=−31 K), suggesting the thermoelasticity of the transformation. The space group of the high temperature phase is I4{sup ¯}3m with the unit-cell dimensions of a=0.92426(2) nm and V=0.78955(2) nm{sup 3} (Z=2) at 1073 K. The initial structural model was derived by the direct methods and further refined by the Rietveld method. The final structural model showed the orientational disordering of SO{sub 4} tetrahedra. The maximum-entropy method-based pattern fitting method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. At around the transformation temperature during heating, the vibrational spectra, corresponding to the Raman-active SO{sub 4} internal stretching mode, showed the continuous and gradual change in the slope of full width at half maximum versus temperature curve. This strongly suggests that the orthorhombic-to-cubic phase transformation would be principally accompanied by the statistical disordering in orientation of the SO{sub 4} tetrahedra, without distinct dynamical reorientation. - Graphical abstract: (Left) Three-dimensional electron-density distributions of the SO{sub 4} tetrahedron with the split-atom model, and (right) a bird's eye view of electron densities on the plane parallel to (111). - Highlights: • Crystal structure of Ca{sub 4}[Al{sub 6}O{sub 12}]SO{sub 4} at 1073 K is determined by powder XRD. • The atom arrangements are represented by the split

  17. Crystallization and chemical durability of glasses in the system Bi2O3-SiO2

    International Nuclear Information System (INIS)

    Fredericci, C.

    2011-01-01

    The crystallization of the Bi 2 O 3 -SiO 2 -TiO 2 -Al 2 O 3 -Na 2 O-K 2 O and Bi 2 O 3 -SiO 2 -ZnO-Al 2 O 3 -B 2 O 3 -Na 2 O glasses was studied using glass samples prepared by traditional melt-quench method. Differential thermal analysis (DTA) curves suggested that surface crystallization played a major role in the crystallization of the glass samples. X-ray diffraction (XRD) analysis revealed the crystallization of bismuth silicate for both glasses and bismuth silicate and zinc silicate for the glass containing ZnO. Through scanning electron microscopy (MEV) and energy dispersive spectroscopy (EDS), it was possible to observe that the crystals of zinc silicate (Zn 2 SiO 4 ) were readily attacked by hot 0,1 N sulfuric acid, whereas bismuth silicate crystals were more resistant to acidic attack etching. (author)

  18. Single crystal structures of the new vanadates CuMgVO{sub 4} and AgMgVO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Ben Yahia, Hamdi, E-mail: Hyahia@qf.org.qa [Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, PO Box 5825, Doha (Qatar); Shikano, Masahiro, E-mail: shikano.masahiro@aist.go.jp [Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Essehli, Rachid; Belharouak, Ilias [Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, Qatar Foundation, PO Box 5825, Doha (Qatar)

    2016-08-01

    The new compounds CuMgVO{sub 4} and AgMgVO{sub 4} have been synthesized by a solid state reaction route. Their crystal structures were determined from single-crystal X-ray diffraction data. CuMgVO{sub 4} crystallizes with Na{sub 2}CrO{sub 4}-type structure with space group Cmcm, a = 5.6932 (10), b = 8.7055 (15), c = 6.2789 (10) Å, V = 311.20 (9) Å{sup 3}, and Z = 4, whereas AgMgVO{sub 4} crystallizes in the maricite-type structure with space group Pnma, a = 9.4286 (14), b = 6.7465 (10), c = 5.3360 (8) Å, V = 339.42 (9) Å{sup 3}, and Z = 4. Both structures of CuMgVO{sub 4}, and AgMgVO{sub 4} contain MgO{sub 4} chains made up of edge-sharing MgO{sub 6} octahedra. In CuMgVO{sub 4} the MgO{sub 4} chains are interconnected through CuVO{sub 4} double chains made up of VO{sub 4} and CuO{sub 4} tetrahedra sharing corners and edges, however in AgMgVO{sub 4} the chains are interlinked by the VO{sub 4} and AgO{sub 4} tetrahedra sharing only corners. - Highlights: • We have been able to grow CuMgVO{sub 4} and AgMgVO{sub 4} single crystals. • We solved their crystal structures using single crystal data. • We compared the crystal structures of CuMgVO{sub 4} and AgMgVO{sub 4}.

  19. Application of Molecular Imprinted Magnetic Fe3O4@SiO2 Nanoparticles for Selective Immobilization of Cellulase.

    Science.gov (United States)

    Tao, Qing-Lan; Li, Yue; Shi, Ying; Liu, Rui-Jiang; Zhang, Ye-Wang; Guo, Jianyong

    2016-06-01

    Magnetic Fe3O4@SiO2 nanoparticles were prepared with molecular imprinting method using cellulase as the template. And the surface of the nanoparticles was chemically modified with arginine. The prepared nanoparticles were used as support for specific immobilization of cellulase. SDS-PAGE results indicated that the adsorption of cellulase onto the modified imprinted nanoparticles was selective. The immobilization yield and efficiency were obtained more than 70% after the optimization. Characterization of the immobilized cellulase revealed that the immobilization didn't change the optimal pH and temperature. The half-life of the immobilized cellulase was 2-fold higher than that of the free enzyme at 50 degrees C. After 7 cycles reusing, the immobilized enzyme still retained 77% of the original activity. These results suggest that the prepared imprinted nanoparticles have the potential industrial applications for the purification or immobilization of enzymes.

  20. Comparison of the scintillation and luminescence properties of the (Lu1−xGdx)2SiO5:Ce single crystal scintillators

    International Nuclear Information System (INIS)

    Jarý, V; Mihóková, E; Mareš, J A; Beitlerová, A; Nikl, M; Kurtsev, D; Sidletskiy, O

    2014-01-01

    We provide a systematic comparison of the scintillation and luminescence properties, including emission mechanisms, of the highly efficient cerium-doped scintillators lutetium-(gadolinium) orthosilicates Lu 2 (SiO 4 )O (LSO), (Lu 1−x Gd x ) 2 (SiO) 4 O(LGSO) and Gd 2 (SiO 4 )O (GSO). Determined characteristics manifest an advantage of LGSO:Ce with respect to both LSO:Ce and GSO:Ce for scintillator applications around room temperature. This is thanks to combined fast decay (faster than both limit compositions) high light yield, similar to that of LSO:Ce (twice higher than GSO:Ce) and low afterglow, similar to that of GSO:Ce (almost two orders of magnitude lower than LSO:Ce). High temperature applications do not, however, seem to be a suitable option for LGSO:Ce due to evidenced thermal ionization of both Ce1 and Ce2 centres above room temperature. (paper)

  1. Processing of SiO2 protective layer using HMDS precursor by combustion CVD.

    Science.gov (United States)

    Park, Kyoung-Soo; Kim, Youngman

    2011-08-01

    Hexamethyldisilazane (HMDS, [(CH3)3Si]2NH) was used as a precursor to form SiO2 protective coatings on IN738LC alloys by combustion chemical vapor deposition (CCVD). SEM and XPS showed that the processed coatings were composed mainly of SiO2. The amount of HMDS had the largest effect on the size of the SiO2 agglomerates and the thickness of the deposited coatings. The specimens coated with SiO2 using the 0.05 mol/l HMDS solution showed a significantly higher temperature oxidation resistance than those deposited under other conditions.

  2. High throughput production of nanocomposite SiO x powders by plasma spray physical vapor deposition for negative electrode of lithium ion batteries

    Directory of Open Access Journals (Sweden)

    Keiichiro Homma

    2014-04-01

    Full Text Available Nanocomposite Si/SiO x powders were produced by plasma spray physical vapor deposition (PS-PVD at a material throughput of 480 g h−1. The powders are fundamentally an aggregate of primary ~20 nm particles, which are composed of a crystalline Si core and SiO x shell structure. This is made possible by complete evaporation of raw SiO powders and subsequent rapid condensation of high temperature SiO x vapors, followed by disproportionation reaction of nucleated SiO x nanoparticles. When CH4 was additionally introduced to the PS-PVD, the volume of the core Si increases while reducing potentially the SiO x shell thickness as a result of the enhanced SiO reduction, although an unfavorable SiC phase emerges when the C/Si molar ratio is greater than 1. As a result of the increased amount of Si active material and reduced source for irreversible capacity, half-cell batteries made of PS-PVD powders with C/Si = 0.25 have exhibited improved initial efficiency and maintenance of capacity as high as 1000 mAh g−1 after 100 cycles at the same time.

  3. High throughput production of nanocomposite SiO x powders by plasma spray physical vapor deposition for negative electrode of lithium ion batteries.

    Science.gov (United States)

    Homma, Keiichiro; Kambara, Makoto; Yoshida, Toyonobu

    2014-04-01

    Nanocomposite Si/SiO x powders were produced by plasma spray physical vapor deposition (PS-PVD) at a material throughput of 480 g h -1 . The powders are fundamentally an aggregate of primary ∼20 nm particles, which are composed of a crystalline Si core and SiO x shell structure. This is made possible by complete evaporation of raw SiO powders and subsequent rapid condensation of high temperature SiO x vapors, followed by disproportionation reaction of nucleated SiO x nanoparticles. When CH 4 was additionally introduced to the PS-PVD, the volume of the core Si increases while reducing potentially the SiO x shell thickness as a result of the enhanced SiO reduction, although an unfavorable SiC phase emerges when the C/Si molar ratio is greater than 1. As a result of the increased amount of Si active material and reduced source for irreversible capacity, half-cell batteries made of PS-PVD powders with C/Si = 0.25 have exhibited improved initial efficiency and maintenance of capacity as high as 1000 mAh g -1 after 100 cycles at the same time.

  4. Quantitative analysis of CTEM images of small dislocation loops in Al and stacking fault tetrahedra in Cu generated by molecular dynamics simulation

    International Nuclear Information System (INIS)

    Schaeublin, R.; Almazouzi, A.; Dai, Y.; Osetsky, Yu.N.; Victoria, M.

    2000-01-01

    The visibility of conventional transmission electron microscopy (CTEM) images of small crystalline defects generated by molecular dynamics (MD) simulation is investigated. Faulted interstitial dislocation loops in Al smaller than 2 nm in diameter and stacking fault tetrahedra (SFT) in Cu smaller than 4 nm in side are assessed. A recent approach allowing to simulate the CTEM images of computer generated samples described by their atomic positions is applied to obtain bright field and weak beam images. For the dislocation loop-like cluster it appears that the simulated image is comparable to experimental images. The contrast of the g(3.1g) near weak beam image decreases with decreasing size of the cluster but is still 20% of the background intensity for a 2 interstitial cluster. This indicates a visibility at the limit of the experimental background noise. In addition, the cluster image size, which is here always larger than the real size, saturates at about 1 nm when the cluster real size decreases below 1 nm, which corresponds to a cluster of 8 interstitials. For the SFT in Cu the g(6.1g) weak beam image is comparable to experimental images. It appears that the image size is larger than the real size by 20%. A large loss of the contrast features that allows to identify an SFT is observed on the image of the smallest SFT (21 vacancies)

  5. Diffusive charge transport in graphene on SiO 2

    Science.gov (United States)

    Chen, J.-H.; Jang, C.; Ishigami, M.; Xiao, S.; Cullen, W. G.; Williams, E. D.; Fuhrer, M. S.

    2009-07-01

    We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO 2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density ( σ(n)∝n) in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates; increased dielectric screening reduces the scattering from charged impurities, but increases the scattering from short-range scatterers. We evaluate the effects of the corrugations (ripples) of graphene on SiO 2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity that is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO 2 substrate give rise to an activated, carrier density-dependent resistivity. Together the results paint a complete picture of charge carrier transport in graphene on SiO 2 in the diffusive regime.

  6. Effect of SiO2 concentration in silica sol on interface reaction during titanium alloy investment casting

    Directory of Open Access Journals (Sweden)

    Ya-meng Wei

    2018-01-01

    Full Text Available Using silica sol as a binder for titanium investment casting is very attractive due to its good stability and reasonable cost as compared with yttrium sol and zirconium sol. However, the mechanism of interface reaction in the related system remains unclear. In this investigation, the interface reaction between Y2O3-SiO2 (Y-Si shell mold and titanium alloys was studied. A group of shell molds were prepared by using Y2O3 sand and silica sol with different contents of SiO2. Ti-6Al-4V alloy was cast under vacuum by gravity casting through cold crucible induction melting (CCIM method. Scanning electron microscopy (SEM and energy dispersive x-ray spectroscopy (EDS were employed to characterize the micromorphology and composition of the reaction area, respectively. X-ray photoelectron spectroscopy (XPS was used to confirm the valence state of relevant elements. White light interferometer (WLI was used to obtain the surface topography of Y-Si shells. The results show that the thickness of reaction layers is below 3 μm when the SiO2 content of silica sol is below 20wt.%. Whereas, when the SiO2 content increases to 25wt.%, the thickness of the reaction layer increases sharply to about 15 μm. There is a good balance between chemical inertness and mechanical performance when the SiO2 content is between 15 and 20wt.%. Moreover, it was found that the distribution of SiO2 and the roughness at the surface of the shell are the key factors that determine the level of reaction.

  7. Thermal evolution of the morphology, structure, and optical properties of multilayer nanoperiodic systems produced by the vacuum evaporation of SiO and SiO2

    International Nuclear Information System (INIS)

    Ershov, A. V.; Chugrov, I. A.; Tetelbaum, D. I.; Mashin, A. I.; Pavlov, D. A.; Nezhdanov, A. V.; Bobrov, A. I.; Grachev, D. A.

    2013-01-01

    The alternate vacuum evaporation of SiO and SiO 2 from separate sources is used to produce amorphous a-SiO x /SiO 2 multilayer nanoperiodic structures with periods of 5–10 nm and a number of layers of up to 64. The effect of annealing at temperatures T a = 500–1100°C on the structural and optical properties of the nanostructures is studied. The results of transmission electron microscopy of the samples annealed at 1100°C indicate the annealing-induced formation of vertically ordered quasiperiodic arrays of Si nanocrystals, whose dimensions are comparable to the a-SiO x -layer thickness in the initial nanostructures. The nanostructures annealed at 1100°C exhibit size-dependent photoluminescence in the wavelength range 750–830 nm corresponding to Si nanocrystals. The data on infrared absorption and Raman scattering show that the thermal evolution of structural and phase state of the SiO x layers with increasing annealing temperature proceeds through the formation of amorphous Si nanoinclusions with the subsequent formation and growth of Si nanocrystals.

  8. Dependence of Photocatalytic Activity of TiO2-SiO2 Nanopowders

    Directory of Open Access Journals (Sweden)

    M. Riazian

    2014-10-01

    Full Text Available Structural properties and chemical composition change the photocatalytic activity in TiO2-SiO2 nanopowder composite. The SiO2-TiO2 nanostructure is synthesized based on sol–gel method. The nanoparticles are characterized by x-ray fluorescents (XRF, x- ray diffraction (XRD, tunneling electron microscopy (TEM, field emission scanning electron microscopy (FE-SEM, UV-vis. Spectrophotometer and furrier transmission create infrared absorption (FTIR techniques. The rate constant k for the degradation of methylen blue in its aqueous solution under UV irradiation is determined as a measure of photocatalytic activity. Dependence between photocatalytic activity and SiO2 content in the composite is determined. Rate constant k is found dependent on the content of SiO2 in the composite that calcined at 900 oC. The addition of low composition SiO2 to the TiO2 matrix (lower than 45% enhances the photocatalytic activity due to thermal stability and increasing in the surface area. The effects of chemical compositions on the surface topography and the crystallization of phases are studied.

  9. Beyond sixfold coordinated Si in SiO2 glass at ultrahigh pressures.

    Science.gov (United States)

    Prescher, Clemens; Prakapenka, Vitali B; Stefanski, Johannes; Jahn, Sandro; Skinner, Lawrie B; Wang, Yanbin

    2017-09-19

    We investigated the structure of SiO 2 glass up to 172 GPa using high-energy X-ray diffraction. The combination of a multichannel collimator with diamond anvil cells enabled the measurement of structural changes in silica glass with total X-ray diffraction to previously unachievable pressures. We show that SiO 2 first undergoes a change in Si-O coordination number from fourfold to sixfold between 15 and 50 GPa, in agreement with previous investigations. Above 50 GPa, the estimated coordination number continuously increases from 6 to 6.8 at 172 GPa. Si-O bond length shows first an increase due to the fourfold to sixfold coordination change and then a smaller linear decrease up to 172 GPa. We reconcile the changes in relation to the oxygen-packing fraction, showing that oxygen packing decreases at ultrahigh pressures to accommodate the higher than sixfold Si-O coordination. These results give experimental insight into the structural changes of silicate glasses as analogue materials for silicate melts at ultrahigh pressures.

  10. Visible Light Excited Catalysis and Reusability Performances of TiO2@Pr:Y2SiO5 Upconversion Materials

    Directory of Open Access Journals (Sweden)

    Yan Jiao

    2017-01-01

    Full Text Available To get high efficiency photodegradation on pollutants under visible light, Pr(III doped Y2SiO5 upconversion materials and anatase TiO2 nanofilm coated Pr:Y2SiO5 composite have been prepared by using a sol-gel method. XRD and SEM test results indicated that TiO2 nanofilm was well coated on Pr:Y2SiO5 to form TiO2@Pr:Y2SiO5 composite particles with the sizes of 0.5–1.0 μm. To avoid secondary pollution resulting from incomplete recovery of catalyst particles, TiO2@Pr:Y2SiO5 was loaded on the glass fiber filters by using a dip-coating method. It is found that the catalyst particles were embedded into the carrier firmly, even after having been reused for 6 times. The luminescence intensities of TiO2@Pr:Y2SiO5 were getting down sharply with the coating contents of TiO2 increased, which was attributed to the adsorption of the luminescence by the TiO2 film in situ. As a result, TiO2@Pr:Y2SiO5 with 4% TiO2, which presented lowest luminescence intensity, showed the highest efficiency on the photodegradation of nitrobenzene wastewater. The catalysts loaded on glass fiber filters showed excellent reusability on the photodegradation of nitrobenzene and presented a photodegradation rate of 95% at the first time and up to 75.9% even after 6 times of reusing by the treatment time of 12 h.

  11. Deformation mechanisms during nanoindentation of sodium borosilicate glasses of nuclear interest.

    Science.gov (United States)

    Kilymis, D A; Delaye, J-M

    2014-07-07

    In this paper we analyze results of Molecular Dynamics simulations of Vickers nanoindentation, performed for sodium borosilicate glasses of interest in the nuclear industry. Three glasses have been studied in their pristine form, as well as a disordered one that is analogous to the real irradiated glass. We focused in the behavior of the glass during the nanoindentation in order to reveal the mechanisms of deformation and how they are affected by microstructural characteristics. Results have shown a strong dependence on the SiO2 content of the glass, which promotes densification due to the open structure of SiO4 tetrahedra and also due to the strength of Si-O bonds. Densification for the glasses is primarily expressed by the relative decrease of the Si-O-Si and Si-O-B angles, indicating rotation of the structural units and decrease of free volume. The increase of alkali content on the other hand results to higher plasticity of the matrix and increased shear flow. The most important effect on the deformation mechanism of the disordered glasses is that of the highly depolymerized network that will also induce shear flow and, in combination with the increased free volume, will result in the decreased hardness of these glasses, as has been previously observed.

  12. Nondegradative Dielectric Coating of Graphene using Thermal Evaporation of SiO

    Science.gov (United States)

    Suzuki, Seiya; Lee, Chien-Chung; Nagamori, Takashi; Schibli, Thomas; Yoshimura, Masamichi

    2013-03-01

    Deposition of dielectrics onto graphene is a challenging technique due to the difficulties of fabricating high quality oxide on pristine graphene without introducing atomic defects. Here we report on a novel method to fabricate silicon oxide layer on graphene by vacuum thermal evaporation of silicon monoxide (SiO). Raman spectroscopy and mapping showed the present method did not degrade graphene, in contrast to the e-beam evaporated SiO2 coating method previously reported. We fabricated graphene field effect transistor devices with four metal electrodes to measure gate voltage dependence of sheet resistance of the graphene, and deposited a top coating of SiO on the graphene channel. The electrical measurements before and after the top-coating revealed that the top coating suppressed chemical shift of the graphene from strong p-dope to nearly undoped. Since SiO is transparent for visible and infrared light, the coating can be available as a protection layer for optical devices of graphene such as photodetectors and electro-optic modulators. Since the SiO top coating is a simple vacuum evaporation, it is much easier than atomic-layer-deposition which requires additional functionalization of graphene, and compatible with industrial use. This research was supported in part by Toyoaki Scholarship Foundation

  13. Charge and structural ordering in the brownmillerite phases: La1-xSrxMnO2.5 (0.24)

    International Nuclear Information System (INIS)

    Casey, Peter S.; Barker, Daniel; Hayward, Michael A.

    2006-01-01

    The topotactic reduction of La 1-x Sr x MnO 3 (0.2 1-x Sr x MnO 2.5 brownmillerite phases with NaH is described. Neutron and electron diffraction data show the x=0.25 and 0.2 phases adopt structures with an unusual ordered L-R-L-R alternation of twisted chains of Mn(II) tetrahedra within each anion-deficient layer. This is accompanied by Mn(II)/(III) charge ordering within the remaining MnO 6 octahedral layers. In contrast, the x=0.4 phase adopts a structure in which the twisted chains of tetrahedra are disordered

  14. SiO2@TiO2 Coating: Synthesis, Physical Characterization and Photocatalytic Evaluation

    Directory of Open Access Journals (Sweden)

    A. Rosales

    2018-03-01

    Full Text Available Use of silicon dioxide (SiO2 and titanium dioxide (TiO2 have been widely investigated individually in coatings technology, but their combined properties promote compatibility for different innovative applications. For example, the photocatalytic properties of TiO2 coatings, when exposed to UV light, have interesting environmental applications, such as air purification, self-cleaning and antibacterial properties. However, as reported in different pilot projects, serious durability problems, associated with the adhesion between the substrate and TiO2, have been evidenced. Thus, the aim of this work is to synthesize SiO2 together with TiO2 to increase the durability of the photocatalytic coating without affecting its photocatalytic potential. Therefore, synthesis using sonochemistry, synthesis without sonochemistry, physical characterization, photocatalytic evaluation, and durability of the SiO2, SiO2@TiO2 and TiO2 coatings are presented. Results indicate that using SiO2 improved the durability of the TiO2 coating without affecting its photocatalytic properties. Thus, this novel SiO2@TiO2 coating shows potential for developing long-lasting, self-cleaning and air-purifying construction materials.

  15. Effects of substrate temperature on structural and electrical properties of SiO2-matrix boron-doped silicon nanocrystal thin films

    International Nuclear Information System (INIS)

    Huang, Junjun; Zeng, Yuheng; Tan, Ruiqin; Wang, Weiyan; Yang, Ye; Dai, Ning; Song, Weijie

    2013-01-01

    In this work, silicon-rich SiO 2 (SRSO) thin films were deposited at different substrate temperatures (T s ) and then annealed by rapid thermal annealing to form SiO 2 -matrix boron-doped silicon-nanocrystals (Si-NCs). The effects of T s on the micro-structure and electrical properties of the SiO 2 -matrix boron-doped Si-NC thin films were investigated using Raman spectroscopy and Hall measurements. Results showed that the crystalline fraction and dark conductivity of the SiO 2 -matrix boron-doped Si-NC thin films both increased significantly when the T s was increased from room temperature to 373 K. When the T s was further increased from 373 K to 676 K, the crystalline fraction of 1373 K-annealed thin films decreased from 52.2% to 38.1%, and the dark conductivity reduced from 8 × 10 −3 S/cm to 5.5 × 10 −5 S/cm. The changes in micro-structure and dark conductivity of the SiO 2 -matrix boron-doped Si-NC thin films were most possibly due to the different amount of Si-O 4 bond in the as-deposited SRSO thin films. Our work indicated that there was an optimal T s , which could significantly increase the crystallization and conductivity of Si-NC thin films. Also, it was illumined that the low-resistivity SiO 2 -matrix boron-doped Si-NC thin films can be achieved under the optimal substrate temperatures, T s .

  16. Antiperovskite nitridophosphate oxide Ho{sub 3}[PN{sub 4}]O by high-pressure metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Kloss, Simon D.; Weidmann, Niels; Schnick, Wolfgang [Department of Chemistry, University of Munich (LMU), Butenandtstrasse 5-13, 81377, Munich (Germany)

    2017-04-03

    Rare-earth nitridophosphates are a recently discovered class of materials, which are accessible by high-pressure metathesis. Antiperovskite-type Ho{sub 3}[PN{sub 4}]O was synthesized from HoF{sub 3}, LiPN{sub 2}, Li{sub 3}N, and Li{sub 2}O at 5 GPa and ca. 1025 C by this method and the multianvil technique. Ho{sub 3}[PN{sub 4}]O contains rarely observed isolated PN{sub 4} tetrahedra and can be derived by the hierarchical substitution of the ABX{sub 3} perovskite, in which Ho occupies the X positions, O occupies the B position, and the PN{sub 4} tetrahedra occupy the A position. The structure was refined on the basis of powder diffraction data [I4/mcm, a = 6.36112(3), c = 10.5571(1) Aa, Z = 4, R{sub wp} = 0.04, R{sub Bragg} = 0.01, χ{sup 2} = 2.275] starting from the structural model of isotypic Gd{sub 3}[SiN{sub 3}O]O. To characterize Ho{sub 3}[PN{sub 4}]O, elemental analyses were performed through energy-dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Ho{sub 3}[PN{sub 4}]O is paramagnetic down to low temperatures with μ{sub eff} = 10.43(1) μ{sub B} and a Curie temperature (Θ) of 0.11(4) K. It shows the optical characteristics of Ho{sup 3+} ions and vibrations corresponding to isolated PN{sub 4} tetrahedra. On the basis of DFT calculations [generalized gradient approximation (GGA)], Ho{sub 3}[PN{sub 4}]O has an indirect band gap of 1.87 eV. We demonstrate the versatility of high-pressure metathesis by attaining the low end of the P/N atomic ratio κ = 1/4. This confirms the previous assumption that rare-earth nitridophosphates with κ = 1/2 to 1/4 are feasible by this method. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Cytotoxicity and effect on GJIC of SiO2 nanoparticles in HL-7702 cells

    International Nuclear Information System (INIS)

    Pan Tao; Jin Minghua; Liu Xiaomei; Du Zhongjun; Zhou Xianqing; Huang Peili; Sun Zhiwei

    2013-01-01

    Objective: To study the cytotoxicity and effect on gap junction intracellular communication (GJIC) of SiO 2 nanoparticles in HL-7702 cells, and to provide experimental basis for toxicity assessment and the security applications of SiO 2 nanoparticles. Methods: Transmission electron microscope (TEM) was used to characterize two kinds of SiO 2 nanoparticles, verifying their size, dispersion and shape; dynamic light scattering (DLS) method was used to analyze the water dispersion and culture medium dispersion of the SiO 2 nanoparticles; MTT assay was carried out to examine the cytotoxicities of the two sizes SiO 2 nanoparticles on the cells; lactate dehydrogenase (LDH) release assay was performed to examine the integrity nano of the cell membrane; Scrape-loading and dye transfer assay was performed to examine the effect of SiO 2 nanoparticles on GJIC. Results: Based on the result of TEM, two kinds of SiO 2 nanoparticles were spherically shaped, uniformly sized and sporadically dispersed; the statistical analysis results showed the diameters of the two nanoparticles were (447.60±20.78) nm and (67.42±5.69) nm, respectively, thus they could be categorized as submicron scale and nano scale. The DLS method results manifested that the hydration nanoparticle sizes of the two SiO 2 nanoparticles were (684.37±18.76) nm, (128.31±7.64) nm in high purity water and (697.02±19.57) nm, (133.74±8.97) nm in RPMI-1640 solution, all the two nanoparticles were well dispersed without aggregation. MTT assay indicated that 24 h after treatment of SiO 2 nanoparticles, the cell viabilities were affected by both the size and the dose of the SiO 2 nanoparticles; the higher the dose was, the less viability the cells exhibited. Moreover, the nano scale particles inflicted more damage to the cells. LDH release assay indicated that the SiO 2 particles could also damage the cell membrane in a dose-dependent and size-dependent way. Scrape-loading and dye transfer assay indicated that the nano

  18. Ontology-Based Querying with Bio2RDF's Linked Open Data.

    Science.gov (United States)

    Callahan, Alison; Cruz-Toledo, José; Dumontier, Michel

    2013-04-15

    A key activity for life scientists in this post "-omics" age involves searching for and integrating biological data from a multitude of independent databases. However, our ability to find relevant data is hampered by non-standard web and database interfaces backed by an enormous variety of data formats. This heterogeneity presents an overwhelming barrier to the discovery and reuse of resources which have been developed at great public expense.To address this issue, the open-source Bio2RDF project promotes a simple convention to integrate diverse biological data using Semantic Web technologies. However, querying Bio2RDF remains difficult due to the lack of uniformity in the representation of Bio2RDF datasets. We describe an update to Bio2RDF that includes tighter integration across 19 new and updated RDF datasets. All available open-source scripts were first consolidated to a single GitHub repository and then redeveloped using a common API that generates normalized IRIs using a centralized dataset registry. We then mapped dataset specific types and relations to the Semanticscience Integrated Ontology (SIO) and demonstrate simplified federated queries across multiple Bio2RDF endpoints. This coordinated release marks an important milestone for the Bio2RDF open source linked data framework. Principally, it improves the quality of linked data in the Bio2RDF network and makes it easier to access or recreate the linked data locally. We hope to continue improving the Bio2RDF network of linked data by identifying priority databases and increasing the vocabulary coverage to additional dataset vocabularies beyond SIO.

  19. FeCl3.nano SiO2: An Efficient Heterogeneous Nano Catalyst for the ...

    African Journals Online (AJOL)

    NICO

    2012-05-28

    May 28, 2012 ... low cost, ease of preparation, and catalyst recycling.3,4 Among various solid .... FeCl3-SiO2 (np) to produce 1,8-dioxo-octahydro-xanthenes. RESEARCH ..... 38 G. Song, B. Wang, H. Luo and L. Yang, Catal. Commun., 2007, 8 ...

  20. Structural colors of the SiO2/polyethyleneimine thin films on poly(ethylene terephthalate) substrates

    International Nuclear Information System (INIS)

    Jia, Yanrong; Zhang, Yun; Zhou, Qiubao; Fan, Qinguo; Shao, Jianzhong

    2014-01-01

    The SiO 2 /polyethyleneimine (PEI) films with structural colors on poly(ethylene terephthalate) (PET) substrates were fabricated by an electrostatic self-assembly method. The morphology of the films was characterized by Scanning Electron Microscopy. The results showed that there was no distinguishable multilayered structure found of SiO 2 /PEI films. The optical behaviors of the films were investigated through the color photos captured by a digital camera and the color measurement by a multi-angle spectrophotometer. Different hue and brightness were observed at various viewing angles. The structural colors were dependent on the SiO 2 particle size and the number of assembly cycles. The mechanism of the structural colors generated from the assembled films was elucidated. The morphological structures and the optical properties proved that the SiO 2 /PEI film fabricated on PET substrate formed a homogeneous inorganic/organic SiO 2 /PEI composite layer, and the structural colors were originated from single thin film interference. - Highlights: • SiO 2 /PEI thin films were electrostatic self-assembled on PET substrates. • The surface morphology and optical behavior of the film were investigated. • The structural colors varied with various SiO 2 particle sizes and assembly cycles. • Different hue and lightness of SiO 2 /PEI film were observed at various viewing angles. • Structural color of the SiO 2 /PEI film originated from single thin film interference

  1. Photovoltaic performance of bifacial dye sensitized solar cell using chemically healed binary ionic liquid electrolyte solidified with SiO2 nanoparticles

    International Nuclear Information System (INIS)

    Cosar, Burak; Icli, Kerem Cagatay; Yavuz, Halil Ibrahim; Ozenbas, Macit

    2013-01-01

    Highlights: ► A bifacial DSSC is realized and irradiated from front and rear sides. ► Maximum efficiency was found for 70% PMII/30% (EMIB(CN) 4 ) electrolyte composition. ► A significant increase in photocurrent using 0.1 M GuSCN and 0.4 M NMB was observed. ► Addition of SiO 2 nanoparticles to the electrolyte enhanced photovoltaic efficiency. ► Dispersed SiO 2 particles are found to be more efficient compared to SiO 2 overlayer. - Abstract: In this study, we investigated the effect of electrolyte composition, photoanode thickness, and the additions of GuSCN (guanidinium thiocyanate), NMB (N-methylbenimidazole), and SiO 2 on the photovoltaic performance of DSSCs (dye sensitized solar cells). A bifacial DSSC is realized and irradiated from front and rear sides. The devices give maximum photovoltaic efficiencies for 70% PMII (1-propyl-3-methyl-imidazolium iodide)/30% (EMIB(CN) 4 ) (1-ethyl-3-methyl-imidazolium tetracyanoborate) electrolyte composition and 10 μm thick photoanode coating which is considered to be the ideal coating thickness for the diffusion length of electrolyte and dye absorption. A significant increase in the photocurrent for DSSCs with optimum molarity of 0.1 M GuSCN was observed due to decreased recombination which is believed to be surface passivation effect at photoanode electrolyte interface suppressing recombination rate. Moreover, optimum NMB molarity was found to be 0.4 for maximum efficiency. Addition of SiO 2 to the electrolyte both as an overlayer and dispersed particles enhanced rear side illuminated cells where dispersed particles are found to be more efficient for the front side illuminated cells due to additional electron transport properties. Best rear side illuminated cell efficiency was 3.2% compared to front side illuminated cell efficiency of 4.2% which is a promising result for future rear side dye sensitized solar cell applications where front side illumination is not possible like tandem structures and for cells

  2. Self-Ordered Voids Formation in SiO2 Matrix by Ge Outdiffusion

    OpenAIRE

    B. Pivac; P. Dubček; J. Dasović; H. Zorc; S. Bernstorff; J. Zavašnik; B. Vlahovic

    2018-01-01

    The annealing behavior of very thin SiO2/Ge multilayers deposited on Si substrate by e-gun deposition in high vacuum was explored. It is shown that, after annealing at moderate temperatures (800°C) in inert atmosphere, Ge is completely outdiffused from the SiO2 matrix leaving small (about 3 nm) spherical voids embedded in the SiO2 matrix. These voids are very well correlated and formed at distances governed by the preexisting multilayer structure (in vertical direction) and self-organization ...

  3. DISCOVERY OF SiO BAND EMISSION FROM GALACTIC B[e] SUPERGIANTS

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, M. [Astronomický ústav, Akademie věd České republiky, Fričova 298, 251 65 Ondřejov (Czech Republic); Oksala, M. E. [LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Université Paris Diderot, 5 place Jules Janssen, F-92190, Meudon (France); Cidale, L. S.; Arias, M. L.; Torres, A. F. [Departamento de Espectroscopía Estelar, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata (Argentina); Fernandes, M. Borges, E-mail: michaela.kraus@asu.cas.cz [Observatório Nacional, Rua General José Cristino 77, 20921-400 São Cristovão, Rio de Janeiro (Brazil)

    2015-02-20

    B[e] supergiants (B[e]SGs) are evolved massive stars in a short-lived transition phase. During this phase, these objects eject large amounts of material, which accumulate in a circumstellar disk-like structure. The expelled material is typically dense and cool, providing the cradle for molecule and dust condensation and for a rich, ongoing chemistry. Very little is known about the chemical composition of these disks, beyond the emission from dust and CO revolving around the star on Keplerian orbits. As massive stars preserve an oxygen-rich surface composition throughout their life, other oxygen-based molecules can be expected to form. As SiO is the second most stable oxygen compound, we initiated an observing campaign to search for first-overtone SiO emission bands. We obtained high-resolution near-infrared L-band spectra for a sample of Galactic B[e]SGs with reported CO band emission. We clearly detect emission from the SiO first-overtone bands in CPD-52 9243 and indications for faint emission in HD 62623, HD 327083, and CPD-57 2874. From model fits, we find that in all these stars the SiO bands are rotationally broadened with a velocity lower than observed in the CO band forming regions, suggesting that SiO forms at larger distances from the star. Hence, searching for and analyzing these bands is crucial for studying the structure and kinematics of circumstellar disks, because they trace complementary regions to the CO band formation zone. Moreover, since SiO molecules are the building blocks for silicate dust, their study might provide insight in the early stage of dust formation.

  4. Efficient photocatalytic activity with carbon-doped SiO2 nanoparticles

    KAUST Repository

    Zhang, Dongen

    2013-01-01

    Photocatalysis provides a \\'green\\' approach to completely eliminate various kinds of contaminants that are fatal for current environmental and energy issues. Semiconductors are one of the most frequently used photocatalysts as they can absorb light over a wide spectral range. However, it is also well known that naked SiO2 is not an efficient photocatalyst due to its relatively large band gap, which could only absorb shortwave ultraviolet light. In this report, nanoscale particles of carbon-doped silicon dioxide (C-doped SiO2) for use in photocatalysis were successfully prepared by a facile one-pot thermal process using tetraethylorthosilicate (TEOS) as the source of both silicon and carbon. These particles were subsequently characterized by thermogravimetric analysis, X-ray diffraction, standard and high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The C-doped SiO2 displayed outstanding photocatalytic properties, as evidenced by its catalysis of Rhodamine B degradation under near-UV irradiation. We propose that carbon doping of the SiO2 lattice creates new energy states between the bottom of the conduction band and the top of the valence band, which narrows the band gap of the material. As a result, the C-doped SiO2 nanoparticles exhibit excellent photocatalytic activities in a neutral environment. The novel synthesis reported herein for this material is both energy efficient and environmentally friendly and as such shows promise as a technique for low-cost, readily scalable industrial production. © 2013 The Royal Society of Chemistry.

  5. Isotopic effect in phase transitions of (NH4)2HPO4 and (ND4)2DPO4

    International Nuclear Information System (INIS)

    Diosa, J.E.; Coral, E.E.; Vargas, R.A.

    1996-01-01

    Specific heat and dielectric constant measurements at low frequency, have shown two transitions in the ionic systems (NH4)2HPO4 and (ND4)2DPO4 bellow 300 K. For (NH4)2HPO4, the transition are observed at 174 K and 246 K, while (ND4)2DPO4, they are observed at 147 K and 229 K. We have also found a shift of the transition temperatures to smaller values when the hydrogen is replaced by deuterium. The specific heat anomalies associated with these transitions are reversible in successive thermal cycles (heating and cooling) and we did not detect latent heat through them. Furthermore, we have detected anomalies in the dielectric constant in the same transition points. We have attributed these transition phases to reorientations of the tetrahedra of NH4 and ND4, so that the activation energy Ea for these process that we associated with the thermal energy KBTt required for the transition, is inversely related to the mass of the hydrogen isotope

  6. Efeitos neurotóxicos de sulfato de magnésio intratecal

    Directory of Open Access Journals (Sweden)

    Levent Ozdogan

    2013-02-01

    Full Text Available JUSTIFICATIVA E OBJETIVOS: Avaliar os potenciais efeitos neurotóxicos em nível ultraestrutural desulfato de magnésio administrado por via intratecal em dose única ou múltipla. MÉTODOS: Estudo realizado com 24 ratos Sprague-Dawley, peso médio entre 250 e 300 g. Apósjejum de 4 horas, os ratos receberam 10 mg.kg-1 de cloreto de xilazina por via intraperitoneale, em seguida, foram divididos aleatoriamente em três grupos. Grupo I (n = 8 recebeu 0,9% desoro fisiológico normal, Grupo II (n = 8 recebeu uma injeção de 0,02 mL de sulfato de magnésioa 15% por via intratecal e Grupo III (n = 8 recebeu 0,02 mL de sulfato de magnésio a 15% umavez por dia durante sete dias. As injeções foram aplicadas dentro de 0,40x50 milímetros daárea lombar. Após sete dias, os animais foram sacrificados sob anestesia com uma injeção deformaldeído a 10% na aorta e os tecidos foram fixados. A medula espinal foi, então, examinadae histopatologicamente avaliada sob microscópio eletrônico. O teste de Kruskal-Wallis foi usadopara avaliação estatística. Um valor de p < 0,05 foi considerado estatisticamente significativo. RESULTADOS: Neurodegeneração significativa foi detectada nos ratos que receberam uma únicainjeção ou injeções repetidas de sulfato de magnésio, em comparação com o grupo controle. O escore na avaliação histopatológica desse grupo também foi alto. CONCLUSÃO: Com base no exame de microscopia eletrônica, descobrimos que a administraçãointratecal de sulfato de magnésio induziu neurodegeneração.

  7. Equation of state of molten fayalite (Fe2SiO4)

    Science.gov (United States)

    Waller, C.; Liu, Q.; Agee, C. B.; Asimow, P. D.; Lange, R. A.

    2010-12-01

    We have conducted new equation of state measurements on liquid fayalite (Fe2SiO4) in a collaborative, multi-technique study. Using a shared bulk starting material, we have measured the liquid density, the bulk modulus (K), and its pressure derivative (K’) from 1 atm to 163 GPa using 1-atm double-bob Archimedean and ultrasonic, sink/float, and shock wave techniques to form a coherent, internally consistent equation of state. Previous shock studies of liquid fayalite were conducted up to pressures of 40 GPa1; we extended this data set with two additional pre-heated, molten (1573 K) fayalite shock compression experiments at 121 and 163 GPa. Linear fitting of this data in shock velocity (US)-particle velocity (up) space defines a Hugoniot with an unconstrained zero-pressure intercept that crosses within error at the bulk sound speed (Co) determined by ultrasonic techniques. Fixing the intercept at this ultrasonic value reduces the error on the linear fit and yields the relation: US =1.65(0.02)up+ 2.4377(0.006) km/s. This relationship indicates that the behavior of the liquid is relaxed during shock compression and demonstrates consistency across experimental methods. Likewise, results from new static compression sink/float experiments conducted in piston-cylinder and multi-anvil devices are in agreement with shock wave and ultrasonic data, consistent with an isothermal K=19.4 and K’=5.57 at 1500°C. In solid materials, the Grüneisen parameter (γ) generally decreases upon compression. However, preliminary calculations for γ of this liquid using additional initially solid shock data from Chen et al.(2002) indicate that γ increases upon compression. Using the functional form γ = γo(ρo/ρ)q at a density of 7.65 Mg/m3 yields a q value of -1.77 (γo = 0.41 is known from low-pressure data), which is similar to the reported q values of forsterite2, enstatite3, and anorthite-diopside liquids4. This result shows that iron-bearing mafic to ultramafic silicate liquids

  8. Semiconductor nanocrystals formed in SiO2 by ion implantation

    International Nuclear Information System (INIS)

    Zhu, J.G.; White, C.W.; Budai, J.D.; Withrow, S.P.; Chen, Y.

    1994-11-01

    Nanocrystals of group IV (Si, Ge and SiGe), III-V (GaAs), and II-VI (CdSe) semiconductor materials have been fabricated inside SiO 2 by ion implantation and subsequent thermal annealing. The microstructure of these nanocrystalline semiconductor materials has been studied by transmission electron microscopy (TEM). The nanocrystals form in near-spherical shape with random crystal orientations in amorphous SiO 2 . Extensive studies on the nanocrystal size distributions have been carried out for the Ge nanocrystals by changing the implantation doses and the annealing temperatures. Remarkable roughening of the nanocrystals occurs when the annealing temperature is raised over the melting temperature of the implanted semiconductor material. Strong red photoluminescence peaked around 1.67 eV has been achieved in samples with Si nanocrystals in SiO 2

  9. Ternary CaCu4P2-type pnictides AAg4Pn2 (A=Sr, Eu; Pn=As, Sb)

    International Nuclear Information System (INIS)

    Stoyko, Stanislav S.; Khatun, Mansura; Scott Mullen, C.; Mar, Arthur

    2012-01-01

    Four ternary pnictides AAg 4 Pn 2 (A=Sr, Eu; Pn=As, Sb) were prepared by reactions of the elements at 850 °C and their crystal structures were determined from single-crystal X-ray diffraction studies. These silver-containing pnictides AAg 4 Pn 2 adopt the trigonal CaCu 4 P 2 -type structure (Pearson symbol hR21, space group R3-bar m, Z=3; a=4.5555(6) Å, c=24.041(3) Å for SrAg 4 As 2 ; a=4.5352(2) Å, c=23.7221(11) Å for EuAg 4 As 2 ; a=4.7404(4) Å, c=25.029(2) Å for SrAg 4 Sb 2 ; a=4.7239(3) Å, c=24.689(2) Å for EuAg 4 Sb 2 ), which can be derived from the trigonal CaAl 2 Si 2 -type structure of the isoelectronic zinc-containing pnictides AZn 2 Pn 2 by insertion of additional Ag atoms into trigonal planar sites within [M 2 Pn 2 ] 2− slabs built up of edge-sharing tetrahedra. Band structure calculations on SrAg 4 As 2 and SrAg 4 Sb 2 revealed that these charge-balanced Zintl phases actually exhibit no gap at the Fermi level and are predicted to be semimetals. - Graphical abstract: SrAg 4 As 2 and related pnictides adopt a CaCu 4 P 2 -type structure in which additional Ag atoms enter trigonal planar sites within slabs built from edge-sharing tetrahedra. Highlights: ► AAg 4 Pn 2 are the first Ag-containing members of the CaCu 4 P 2 -type structure. ► Ag atoms are stuffed in trigonal planar sites within CaAl 2 Si 2 -type slabs. ► Ag–Ag bonding develops through attractive d 10 –d 10 interactions.

  10. Enhanced antioxidation and microwave absorbing properties of SiO2-coated flaky carbonyl iron particles

    Science.gov (United States)

    Zhou, Yingying; Xie, Hui; Zhou, Wancheng; Ren, Zhaowen

    2018-01-01

    SiO2 was successfully coated on the surface of flaky carbonyl iron particles using a chemical bath deposition method in the presence of 3-aminopropyl triethoxysilane (APTES). The morphologies, composition, valence states of elements, as well as antioxidation and electromagnetic properties of the samples were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) and microwave network analyzer. TG curve shows the obvious weight gain of carbonyl iron was deferred to 360 °C after SiO2-coated, which can be ascribed to the exits of SiO2 overlayer. Compared with the raw carbonyl iron, SiO2-coated sample shows good wave absorption performance due to its impedance matching. The electromagnetic properties of raw and SiO2-coated carbonyl iron particles were characterized in X band before and after heat treatment at 250 °C for 10 h. It was established that SiO2-coated carbonyl iron demonstrate good thermal stability, indicating SiO2-coating is useful in the usage of microwave absorbers operating at temperature up to 250 °C.

  11. Synthesis, crystal structure and spectroscopy properties of Na 3AZr(PO 4) 3 ( A=Mg, Ni) and Li 2.6Na 0.4NiZr(PO 4) 3 phosphates

    Science.gov (United States)

    Chakir, M.; El Jazouli, A.; de Waal, D.

    2006-06-01

    Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates were prepared at 750 °C by coprecipitation route. Their crystal structures have been refined at room temperature from X-ray powder diffraction data using Rietveld method. Li 2.6Na 0.4NiZr(PO 4) 3 was synthesized through ion exchange from the sodium analog. These materials belong to the Nasicon-type structure. Raman spectra of Na 3AZr(PO 4) 3 ( A=Mg, Ni) phosphates present broad peaks in favor of the statistical distribution in the sites around PO 4 tetrahedra. Diffuse reflectance spectra indicate the presence of octahedrally coordinated Ni 2+ ions.

  12. Electron irradiation response on Ge and Al-doped SiO 2 optical fibres

    Science.gov (United States)

    Yaakob, N. H.; Wagiran, H.; Hossain, I.; Ramli, A. T.; Bradley, D. A.; Hashim, S.; Ali, H.

    2011-05-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  13. Electron irradiation response on Ge and Al-doped SiO2 optical fibres

    International Nuclear Information System (INIS)

    Yaakob, N.H.; Wagiran, H.; Hossain, I.; Ramli, A.T.; Bradley, D.A; Hashim, S.; Ali, H.

    2011-01-01

    This paper describes the thermoluminescence response, sensitivity, stability and reproducibility of SiO 2 optical fibres with various electron energies and doses. The TL materials that comprise Al- and Ge-doped silica fibres were used in this experiment. The TL results are compared with those of the commercially available TLD-100. The doped SiO 2 optical fibres and TLD-100 are placed in a solid phantom and irradiated with 6, 9 and 12 MeV electron beams at doses ranging from 0.2 to 4.0 Gy using the LINAC at Hospital Sultan Ismail, Johor Bahru, Malaysia. It was found that the commercially available Al- and Ge-doped optical fibres have a linear dose-TL signal relationship. The intensity of TL response of Ge-doped fibre is markedly greater than that of the Al-doped fibre.

  14. Analysis of SiO2 nanoparticles binding proteins in rat blood and brain homogenate

    Directory of Open Access Journals (Sweden)

    Shim KH

    2014-12-01

    Full Text Available Kyu Hwan Shim,1 John Hulme,1 Eun Ho Maeng,2 Meyoung-Kon Kim,3 Seong Soo A An1 1Department of Bionano Technology, Gachon Medical Research Institute, Gachon University, Sungnam-si, 2Department of Analysis, KTR, Kimpo, Gyeonggi-do, 3Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seoul, South Korea Abstract: A multitude of nanoparticles, such as titanium oxide (TiO2, zinc oxide, aluminum oxide, gold oxide, silver oxide, iron oxide, and silica oxide, are found in many chemical, cosmetic, pharmaceutical, and electronic products. Recently, SiO2 nanoparticles were shown to have an inert toxicity profile and no association with an irreversible toxicological change in animal models. Hence, exposure to SiO2 nanoparticles is on the increase. SiO2 nanoparticles are routinely used in numerous materials, from strengthening filler for concrete and other construction composites, to nontoxic platforms for biomedical application, such as drug delivery and theragnostics. On the other hand, recent in vitro experiments indicated that SiO2 nanoparticles were cytotoxic. Therefore, we investigated these nanoparticles to identify potentially toxic pathways by analyzing the adsorbed protein corona on the surface of SiO2 nanoparticles in the blood and brain of the rat. Four types of SiO2 nanoparticles were chosen for investigation, and the protein corona of each type was analyzed using liquid chromatography-tandem mass spectrometry technology. In total, 115 and 48 plasma proteins from the rat were identified as being bound to negatively charged 20 nm and 100 nm SiO2 nanoparticles, respectively, and 50 and 36 proteins were found for 20 nm and 100 nm arginine-coated SiO2 nanoparticles, respectively. Higher numbers of proteins were adsorbed onto the 20 nm sized SiO2 nanoparticles than onto the 100 nm sized nanoparticles regardless of charge. When proteins were compared between the two charges, higher numbers of proteins were

  15. Comparative study of neurologic effects of nano-TiO2 versus SiO2 after direct intracerebral exposure in mice

    International Nuclear Information System (INIS)

    Balvay, A; Bencsik, A; Thieriet, N; Lakhdar, L

    2013-01-01

    Titanium and silicon dioxide nanoparticles (TiO 2 and SiO 2 NPs) are now in daily use in many commercial products of which food, sunscreens, toothpastes or cosmetics. However, their effects on human body, especially on the central nervous system, are still unclear. The aim of this study was to determine whether direct exposition of the brain to TiO 2 and SiO 2 NPs results in alternations in nervous system function. C57Bl6 mice were exposed to 5 and 10 μg doses of TiO 2 and SiO 2 NPs through intracerebroventricular administration using a stereotaxic approach. Then the neurologic effects were investigated using motor performance parameters, measured on a rotarod at 20 rpm or at an accelerating rod (from 4 to 40 rpm). Before and after injection, motor activity is registered individually for each mouse exposed, once a week, for 8 weeks. Besides, a group of 3 mice is culled at 1, 2, 3, 4 and 8 weeks after exposure in order to study the time dependant effect on the histopathology of the brain (gliosis, inflammatory process...). Both rotarod tests (accelerating and at 20 rpm) showed that TiO 2 and SiO 2 NPs exposure could significantly impair the motor performances, even several weeks after initial acute exposure. The first examination of the brain histopathology revealed microglial activation. As it appeared to grow throughout the brain in a time dependant manner this suggests the induction of a long lasting neuroinflammation. These primary findings indicated that exposure to TiO 2 and SiO 2 NPs could possibly impair the locomotor ability and this deficit may be possibly attributed at least to an inflammatory process maintained till 8 weeks after exposure in the mouse brain. To fully investigate the neurotoxicological consequences of TiO 2 and SiO 2 NPs exposure, brain contents in these NPs will be also investigated as well as other alterations like neurotransmitter levels. These preliminary data already underline the necessity of more in vivo studies to better

  16. Comparative study of neurologic effects of nano-TiO2 versus SiO2 after direct intracerebral exposure in mice

    Science.gov (United States)

    Balvay, A.; Thieriet, N.; Lakhdar, L.; Bencsik, A.

    2013-04-01

    Titanium and silicon dioxide nanoparticles (TiO2 and SiO2 NPs) are now in daily use in many commercial products of which food, sunscreens, toothpastes or cosmetics. However, their effects on human body, especially on the central nervous system, are still unclear. The aim of this study was to determine whether direct exposition of the brain to TiO2 and SiO2 NPs results in alternations in nervous system function. C57Bl6 mice were exposed to 5 and 10 μg doses of TiO2 and SiO2 NPs through intracerebroventricular administration using a stereotaxic approach. Then the neurologic effects were investigated using motor performance parameters, measured on a rotarod at 20 rpm or at an accelerating rod (from 4 to 40 rpm). Before and after injection, motor activity is registered individually for each mouse exposed, once a week, for 8 weeks. Besides, a group of 3 mice is culled at 1, 2, 3, 4 and 8 weeks after exposure in order to study the time dependant effect on the histopathology of the brain (gliosis, inflammatory process...). Both rotarod tests (accelerating and at 20 rpm) showed that TiO2 and SiO2 NPs exposure could significantly impair the motor performances, even several weeks after initial acute exposure. The first examination of the brain histopathology revealed microglial activation. As it appeared to grow throughout the brain in a time dependant manner this suggests the induction of a long lasting neuroinflammation. These primary findings indicated that exposure to TiO2 and SiO2 NPs could possibly impair the locomotor ability and this deficit may be possibly attributed at least to an inflammatory process maintained till 8 weeks after exposure in the mouse brain. To fully investigate the neurotoxicological consequences of TiO2 and SiO2 NPs exposure, brain contents in these NPs will be also investigated as well as other alterations like neurotransmitter levels. These preliminary data already underline the necessity of more in vivo studies to better characterize TiO2

  17. A semi-empirical molecular orbital model of silica, application to radiation compaction

    International Nuclear Information System (INIS)

    Tasker, P.W.

    1978-11-01

    Semi-empirical molecular-orbital theory is used to calculate the bonding in a cluster of two SiO 4 tetrahedra, with the outer bonds saturated with pseudo-hydrogen atoms. The basic properties of the cluster, bond energies and band gap are calculated using a very simple parameterisation scheme. The resulting cluster is used to study the rebonding that occurs when an oxygen vacancy is created. It is suggested that a vacancy model is capable of producing the observed differences between quartz and vitreous silica, and the calculations show that the compaction effect observed in the glass is of a magnitude compatible with the relaxations around the vacancy. More detailed lattice models will be needed to examine this mechanism further. (author)

  18. Fourier transform infrared spectroscopic study of gamma irradiated SiO2 nanoparticles

    Science.gov (United States)

    Huseynov, Elchin; Garibov, Adil; Mehdiyeva, Ravan; Huseynova, Efsane

    2018-03-01

    In the present work, nano SiO2 particles are investigated before and after gamma irradiation (25, 50, 75, 100 and 200 kGy) using Fourier transform infrared (FTIR) spectroscopy method for the wavenumber between 400-4000 cm-1. It is found that as a result of spectroscopic analysis, five new peaks have appeared after gamma radiation. Two of new obtained peaks (which are located at 687 cm-1 and 2357 cm-1 of wavenumber) were formed as a result of gamma radiation interaction with Si-O bonds. Another three new peaks (peaks appropriate to 941, 2052 and 2357 cm-1 values of wavenumber) appear as a result of interaction of water with nano SiO2 particles after gamma irradiation. It has been defined as asymmetrical bending vibration, symmetrical bending vibration, symmetrical stretching vibration and asymmetrical stretching vibration of Si-O bonds appropriate to peaks.

  19. Geometry of VY Canis Majoris derived from SiO maser lines

    International Nuclear Information System (INIS)

    Van Blerkom, D.; Auer, L.

    1976-01-01

    A radiation reveals transfer calculation reveals that the SiO maser lines observed in the spectrum of VY CMa are formed in a rotating equatorial disk seen nearly edge-on. Other geometries are considered and eliminated. It is suggested that the SiO lines of NML Cyg also show evidence that they are formed in a disk

  20. Enterocin F4-9, a Novel O-Linked Glycosylated Bacteriocin.

    Science.gov (United States)

    Maky, Mohamed Abdelfattah; Ishibashi, Naoki; Zendo, Takeshi; Perez, Rodney Honrada; Doud, Jehan Ragab; Karmi, Mohamed; Sonomoto, Kenji

    2015-07-01

    Enterococcus faecalis F4-9 isolated from Egyptian salted-fermented fish produces a novel bacteriocin, termed enterocin F4-9. Enterocin F4-9 was purified from the culture supernatant by three steps, and its molecular mass was determined to be 5,516.6 Da by mass spectrometry. Amino acid and DNA sequencing showed that the propeptide consists of 67 amino acid residues, with a leader peptide containing a double glycine cleavage site to produce a 47-amino-acid mature peptide. Enterocin F4-9 is modified by two molecules of N-acetylglucosamine β-O-linked to Ser37 and Thr46. The O-linked N-acetylglucosamine moieties are essential for the antimicrobial activity of enterocin F4-9. Further analysis of the enterocin F4-9 gene cluster identified enfC, which has high sequence similarity to a glycosyltransferase. The antimicrobial activity of enterocin F4-9 covered a limited range of bacteria, including, interestingly, a Gram-negative strain, Escherichia coli JM109. Enterocin F4-9 is sensitive to protease, active at a wide pH range, and moderately resistant to heat. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  1. Npas4: Linking Neuronal Activity to Memory.

    Science.gov (United States)

    Sun, Xiaochen; Lin, Yingxi

    2016-04-01

    Immediate-early genes (IEGs) are rapidly activated after sensory and behavioral experience and are believed to be crucial for converting experience into long-term memory. Neuronal PAS domain protein 4 (Npas4), a recently discovered IEG, has several characteristics that make it likely to be a particularly important molecular link between neuronal activity and memory: it is among the most rapidly induced IEGs, is expressed only in neurons, and is selectively induced by neuronal activity. By orchestrating distinct activity-dependent gene programs in different neuronal populations, Npas4 affects synaptic connections in excitatory and inhibitory neurons, neural circuit plasticity, and memory formation. It may also be involved in circuit homeostasis through negative feedback and psychiatric disorders. We summarize these findings and discuss their implications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Optical properties of the Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings

    Science.gov (United States)

    Marszałek, Konstanty; Winkowski, Paweł; Jaglarz, Janusz

    2014-01-01

    Investigations of bilayer and trilayer Al2O3/SiO2 and Al2O3/HfO2/SiO2 antireflective coatings are presented in this paper. The oxide films were deposited on a heated quartz glass by e-gun evaporation in a vacuum of 5 × 10-3 [Pa] in the presence of oxygen. Depositions were performed at three different temperatures of the substrates: 100 °C, 200 °C and 300 °C. The coatings were deposited onto optical quartz glass (Corning HPFS). The thickness and deposition rate were controlled with Inficon XTC/2 thickness measuring system. Deposition rate was equal to 0.6 nm/s for Al2O3, 0.6 nm - 0.8 nm/s for HfO2 and 0.6 nm/s for SiO2. Simulations leading to optimization of the thin film thickness and the experimental results of optical measurements, which were carried out during and after the deposition process, have been presented. The optical thickness values, obtained from the measurements performed during the deposition process were as follows: 78 nm/78 nm for Al2O3/SiO2 and 78 nm/156 nm/78 nm for Al2O3/HfO2/SiO2. The results were then checked by ellipsometric technique. Reflectance of the films depended on the substrate temperature during the deposition process. Starting from 240 nm to the beginning of visible region, the average reflectance of the trilayer system was below 1 % and for the bilayer, minima of the reflectance were equal to 1.6 %, 1.15 % and 0.8 % for deposition temperatures of 100 °C, 200 °C and 300 °C, respectively.

  3. Fluorescence of Pentavalent Chromium in SiO2 Sol-Gel Glasses

    Science.gov (United States)

    Jia, Weiyi; Castro, Lymari; Wang, Yanyun; Liu, Huimin

    1998-01-01

    Chromium ions are very attractive to optical spectroscopy and laser physics. It is well known that the first laser in the history is a ruby laser activated with Cr(3+). It was found in early nineties that Cr(4+) was also an interesting lasing ion in the near infrared, and various Cr(4+) lasers have been developed. Very recently, it was reported that Cr(2+) doped in CdSe crystals showed lasing action in the infrared. The above achievement have stimulated an interest in searching for Cr(5+) and investigating its optical properties. Cr(5+) is isoelectronic with Ti(3+) and V(4+), having electron configuration 3d1. Ti(3+) is the active center of commercial cw and femtosecond sapphire lasers, tunable in the range 680-1100 nm. V(4+) doped in YAlO3 and Al2O3 showed broad band emission near 635 nm. Although EPR results of Cr(5+) were reported, the optical properties were less studied. Herren et al. reported an observation of luminescence from Cr doped in SiO2 sol-gel glass. The luminescence spectrum was assigned to pentavalent ions in their first paper, and later it was identified to be the emission from the charge transfer transition of Cr(6+). The first observation of photoluminescence from octahedrally coordinated Cr(5+) in BaCaMg aluminate glasses was reported very recently. In this work, we report luminescence results of Cr doped SiO2 sol-gel glasses. The fluorescence spectra are very different from Herrens' results, and we believe it originates from pentavalent Cr.

  4. Growth and characterization of Nd:Bi12SiO20 single crystal

    Science.gov (United States)

    Xu, Honghao; Zhang, Yuanyuan; Zhang, Huaijin; Yu, Haohai; Pan, Zhongben; Wang, Yicheng; Sun, Shangqian; Wang, Jiyang; Boughton, R. I.

    2012-09-01

    A Nd:Bi12SiO20 crystal was grown by the Czochralski method. The thermal properties of the crystal were systematically studied. The thermal expansion coefficient was measured to be α=11.42×10-6 K-1 over the temperature range of 295-775 K, and the specific heat and thermal diffusion coefficient were measured to be 0.243 Jg-1 k-1 and 0.584 mm2/s, respectively at 302 K. The density was measured to be 9.361 g/cm3 by the buoyancy method. The thermal conductivity of Nd:Bi12SiO20 was calculated to be 1.328 Wm-1 K-1 at room temperature (302 K). The refractive index of Nd:Bi12SiO20 was measured at room temperature at eight different wavelengths. The absorption and emission spectra were also measured at room temperature. Continuous-wave (CW) laser output of a Nd:Bi12SiO20 crystal pumped by a laser diode (LD) at 1071.5 nm was achieved with an output power of 65 mW. To our knowledge, this is the first time LD pumped laser output in this crystal has been obtained. These results show that Nd:Bi12SiO20 can serve as a laser crystal.

  5. Um novo Fundef? As idéias de Anísio Teixeira

    Directory of Open Access Journals (Sweden)

    Amaral Nelson Cardoso

    2001-01-01

    Full Text Available O professor Anísio Teixeira, na década de 1960, preocupado com o financiamento da educação, apresentou uma proposta de como definir e implantar um fundo que garantisse recursos permanentes para o ensino primário. Em seus aspectos metodológicos, o Fundo de Manutenção e Desenvolvimento do Ensino Fundamental e de Valorização do Magistério (Fundef, criado pelo Governo, assemelha-se à proposta apresentada por Anísio Teixeira. Existem, entretanto, diferenças importantes e fundamentais, pelo fato do professor Anísio definir o volume total de recursos a partir do estabelecimento do salário dos docentes. Nesse estudo apresentam-se as semelhanças e diferenças entre os dois fundos e realiza-se uma simulação do que se poderia chamar "Um novo Fundef", baseado nas idéias de Anísio Teixeira. Como resultado, obtém-se valores perfeitamente viáveis para serem financiados por uma economia com a dimensão da economia brasileira, assim como ocorreu no estudo apresentado por Anísio Teixeira no livro Educação é um direito.

  6. Densification of ∼5 nm-thick SiO_2 layers by nitric acid oxidation

    International Nuclear Information System (INIS)

    Choi, Jaeyoung; Joo, Soyeong; Park, Tae Joo; Kim, Woo-Byoung

    2017-01-01

    Highlights: • Leakage current density of the commercial PECVD grown ∼5 nm SiO_2 layer has been decreased about three orders of magnitude by densification. • The densification of SiO_2 layer is achieved by high oxidation ability of O·. • Densities of suboxide, fixed charge (N_f) and defect state (N_d) in SiO_2/Si interface are decreased by NAOS and PMA. • Tunneling barrier height (Φ_t) is increased because of the increase of atomic density in SiO_2 layer. - Abstract: Low-temperature nitric acid (HNO_3) oxidation of Si (NAOS) has been used to improve the interface and electrical properties of ∼5 nm-thick SiO_2/Si layers produced by plasma-enhanced chemical vapor deposition (PECVD). Investigations of the physical properties and electrical characteristics of these thin films revealed that although their thickness is not changed by NAOS, the leakage current density at a gate bias voltage of −1 V decreases by about two orders of magnitude from 1.868 × 10"−"5 A/cm"2. This leakage current density was further reduced by post-metallization annealing (PMA) at 250 °C for 10 min in a 5 vol.% hydrogen atmosphere, eventually reaching a level (5.2 × 10"−"8 A/cm"2) approximately three orders of magnitude less than the as-grown SiO_2 layer. This improvement is attributed to a decrease in the concentration of suboxide species (Si"1"+, Si"2"+ and Si"3"+) in the SiO_2/Si interface, as well as a decrease in the equilibrium density of defect sites (N_d) and fixed charge density (N_f). The barrier height (Φ_t) generated by a Poole-Frenkel mechanism also increased from 0.205 to 0.371 eV after NAOS and PMA. The decrease in leakage current density is therefore attributed to a densification of the SiO_2 layer in combination with the removal of OH species and increase in interfacial properties at the SiO_2/Si interface.

  7. Phase formation in the Li2MoO4–K2MoO4–In2(MoO4)3 system and crystal structures of new compounds K3InMo4O15 and LiK2In(MoO4)3

    International Nuclear Information System (INIS)

    Khal’baeva, Klara M.; Solodovnikov, Sergey F.; Khaikina, Elena G.; Kadyrova, Yuliya M.; Solodovnikova, Zoya A.; Basovich, Olga M.

    2012-01-01

    XRD study of solid-phase interaction in the Li 2 MoO 4 –K 2 MoO 4 –In 2 (MoO 4 ) 3 system was performed. The boundary K 2 MoO 4 –In 2 (MoO 4 ) 3 system is an non-quasibinary join of the K 2 O–In 2 O 3 –MoO 3 system where a new polymolybdate K 3 InMo 4 O 15 isotypic to K 3 FeMo 4 O 15 was found. In the structure (a=33.2905(8), b=5.8610(1), c=15.8967(4) Å, β=90.725(1)°, sp. gr. C2/c, Z=8, R(F)=0.0407), InO 6 octahedra, Mo 2 O 7 diortho groups and MoO 4 tetrahedra form infinite ribbons {[In(MoO 4 ) 2 (Mo 2 O 7 )] 3− } ∞ along the b-axis. Between the chains, 8- to 10-coordinate potassium cations are located. A subsolidus phase diagram of the Li 2 MoO 4 –K 2 MoO 4 –In 2 (MoO 4 ) 3 system was constructed and a novel triple molybdate LiK 2 In(MoO 4 ) 3 was revealed. Its crystal structure (a=7.0087(2), b=9.2269(3), c=10.1289(3) Å, β=107.401(1)°, sp. gr. P2 1 , Z=2, R(F)=0.0280) contains an open framework of vertex-shared MoO 4 tetrahedra, InO 6 octahedra and LiO 5 tetragonal pyramids with nine- and seven-coordinate potassium ions in the framework channels. - Graphical abstract: Exploring the Li 2 MoO 4 –K 2 MoO 4 –In 2 (MoO 4 ) 3 system showed its partial non-quasibinarity and revealed new compounds K 3 InMo 4 O 15 (isotypic to K 3 FeMo 4 O 15 ) and LiK 2 In(MoO 4 ) 3 which were structurally studied. An open framework of the latter is formed by vertex-shared MoO 4 tetrahedra, InO 6 octahedra and LiO 5 tetragonal pyramids. Highlights: ► Subsolidus phase relations in the Li 2 MoO 4 –K 2 MoO 4 –In 2 (MoO 4 ) 3 system were explored. ► The K 2 MoO 4 –In 2 (MoO 4 ) 3 system is a non-quasibinary join of the K 2 O–In 2 O 3 –MoO 3 system. ► New compounds K 3 InMo 4 O 15 and LiK 2 In(MoO 4 ) 3 were obtained and structurally studied. ► K 3 InMo 4 O 15 is isotypic to K 3 FeMo 4 O 15 and carries bands of InO 6 , MoO 4 and Mo 2 O 7 units. ► An open framework of LiK 2 In(MoO 4 ) 3 is formed by polyhedra MoO 4 , InO 6 and LiO 5 .

  8. Constructing dual-defense mechanisms on membrane surfaces by synergy of PFSA and SiO2 nanoparticles for persistent antifouling performance

    Science.gov (United States)

    Zhou, Linjie; Gao, Kang; Jiao, Zhiwei; Wu, Mengyuan; He, Mingrui; Su, Yanlei; Jiang, Zhongyi

    2018-05-01

    Synthetic antifouling membrane surfaces with dual-defense mechanisms (fouling-resistant and fouling-release mechanism) were constructed through the synergy of perfluorosulfonic acid (PFSA) and SiO2 nanoparticles. During the nonsolvent induced phase separation (NIPS) process, the amphiphilic PFSA polymers spontaneously segregated to membrane surfaces and catalyzed the hydrolysis-polycondensation of tetraethyl orthosilicate (TEOS) to generate hydrophilic SiO2 nanoparticles (NPs). The resulting PVDF/PFSA/SiO2 hybrid membranes were characterized by contact angle measurements, FTIR, XPS, SEM, AFM, TGA, and TEM. The hydrophilic microdomains and low surface energy microdomains of amphiphilic PFSA polymers respectively endowed membrane surfaces with fouling-resistant mechanism and fouling-release mechanism, while the hydrophilic SiO2 NPs intensified the fouling-resistant mechanism. When the addition of TEOS reached 3 wt%, the hybrid membrane with optimal synergy of PFSA and SiO2 NPs displayed low flux decline (17.4% DRt) and high flux recovery (99.8% FRR) during the filtration of oil-in-water emulsion. Meanwhile, the long-time stability test verified that the hybrid membrane possessed persistent antifouling performance.

  9. Conflicting results for the deformation properties of forsterite, Mg2SiO4

    International Nuclear Information System (INIS)

    Wal, R.J. van der; Vos, A.; Kirfel, A.

    1987-01-01

    Deformation properties of forsterite have been deduced simultaneously from X-ray diffraction data affected by extinction in Bonn-Pittsburgh (B), and in Groningen (G). For the G crystals, GI and GII, extinction is anisotropic and considerably larger than for crystal B. Measurements were made with Mo radiation for B, and with Mo and Ag radiation for GI and GII. As the Becker and Coppens extinction model is not exact, the deformation properties had to be filtered from the data with refinement models. The flexible B model [α's and populations for single exponential functions (SEF's) refined for l=0-4] and the more rigid G model (SEF's populations refined for l=0-3 and α for l=0; further α's and n's fixed at standard values) yield different results. Refinement of α makes the majority of the SEF's notably diffuse, presumably due to correlation with incorrect extinction corrections. The order of the deformation potentials at the Mg(1) and Mg(2) sites is reversed for B and G. Maxima on the Si-O bonds, which are polarized towards O, are smaller for G (0.20-0.25 e A -3 ) than for B (0.25-0.45 e A -3 ). Although each of the two sets of deformation properties looks acceptable by itself, the present comparison shows that neither of them may be sufficiently close to the truth. The diffraction data are available on request from the Electron Density Data Bank (Professor H. Burzlaff, Institut fuer Angewandte Physik, Bismarckstrasse 10, D-8520 Erlangen, Federal Republic of Germany). Details of the measurements are described in the paper. (orig.)

  10. Lattice-dynamical estimation of atomic thermal parameters for silicates: Forsterite. alpha. -Mg sub 2 SiO sub 4

    Energy Technology Data Exchange (ETDEWEB)

    Pilati, T.; Bianchi, R. (Consiglio Nazionale delle Ricerche, Milan (Italy). Centro per lo Studio delle Relazioni tra Struttura e Reattivita' Chimica); Gramaccioli, C.M. (Milan Univ. (Italy). Dipt. di Scienze della Terra)

    1990-06-01

    As an example of extending harmonic lattice-dynamical procedures to silicates, the atomic thermal parameters for forsterite Mg{sub 2}SiO{sub 4}, an important constituent of earth's crust, have been calculated on this basis. For this purpose, Iishi's rigid-ion model was used, with slight modifications. Although such potentials were derived exclusively from fitting IR and Raman-active frequencies, the reproduction of the phonon-dispersion curves is good, and the calculation of thermodynamic functions such as entropy provides values which are near to calorimetric estimates. The calculated atomic thermal parameters are in good agreement with the experimental values reported by most authors. The calculations at various temperatures show the effect of zero-point motion very clearly: its contribution to temperature factors is about half of the total at room temperature. Bond-length corrections for thermal libration can be applied using the general-case formula: these amount to 0.003 A for the Si-O bonds at room temperature. Although the thermal parameters in the SiO{sub 4} group fit a rigid-body model, the correction obtained using the Schomaker-Trueblood procedure gives a significantly different result: this is essentially due to the weak librational character of the motion of silicate groups in the structure. (orig.).

  11. Facile synthesis of microporous SiO2/triangular Ag composite nanostructures for photocatalysis

    Science.gov (United States)

    Sirohi, Sidhharth; Singh, Anandpreet; Dagar, Chakit; Saini, Gajender; Pani, Balaram; Nain, Ratyakshi

    2017-11-01

    In this article, we present a novel fabrication of microporous SiO2/triangular Ag nanoparticles for dye (methylene blue) adsorption and plasmon-mediated degradation. Microporous SiO2 nanoparticles with pore size aminopropyl) trimethoxysilane) to introduce amine groups. Amine-functionalized microporous silica was used for adsorption of triangular silver (Ag) nanoparticles. The synthesized microporous SiO2 nanostructures were investigated for adsorption of different dyes including methylene blue, congo red, direct green 26 and curcumin crystalline. Amine-functionalized microporous SiO2/triangular Ag nanostructures were used for plasmon-mediated photocatalysis of methylene blue. The experimental results revealed that the large surface area of microporous silica facilitated adsorption of dye. Triangular Ag nanoparticles, due to their better charge carrier generation and enhanced surface plasmon resonance, further enhanced the photocatalysis performance.

  12. Photocatalytic and Escherichia antibacterial activities of Ag-TiO2-SiO2 nanocomposite powder under simulated solar light irradiation

    Science.gov (United States)

    Van Dang, Han; Le, Vien Minh; Hoang, Hoang Anh

    2017-09-01

    The photocatalytic nanocomposite powder TiO2, TiO2-SiO2 and Ag-TiO2-SiO2 (ATS) were synthesized by sol-gel method assisted with hydrothermal treatment and characterized by X-ray diffraction (XRD), Raman spectroscopy (RAMAN), Fourier transformed infrared spectroscopy (FT-IR), Energy dispersive X-ray (EDX), Transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET) surface area and UV-Vis absorption spectra analysis. The Escherichia coli (E. coli) antibacterial activity of synthesized photo-catalysts under simulated solar light have been also investigated. The heterogeneous A4TS10 with the 4 wt.% Ag and 10 wt.% SiO2 had anatase and rutile phase, spherical in shape with the particle size about 20 - 30 nm, specific surface area (SSA) of 218.4 m2/g, the band gap of 3.06 eV. The E. coli antibacterial activities of the synthesized samples under simulated solar light were also investigated under simulated solar light with 25 W of light intensity. The E. coli antibacterial ability of A4TS10 performed the highest photo-activity. E. coli bacteria was entirely killed after 30-minute irradiation and no bacterial regrowth was observed after 24 hours. The research results demonstrated that the photocatalytic A4TS10 is a promising green material to treatment wastewater infected bacteria application.

  13. Ca2 Al2 SiO7 :Ce3+ phosphors for mechanoluminescence dosimetry.

    Science.gov (United States)

    Tiwari, Geetanjali; Brahme, Nameeta; Sharma, Ravi; Bisen, D P; Sao, Sanjay Kumar; Sahu, Ishwar Prasad

    2016-12-01

    A series of Ce 3+ ion single-doped Ca 2 Al 2 SiO 7 phosphors was synthesized by a combustion-assisted method at an initiating temperature of 600 °C. The samples were annealed at 1100 °C for 3 h and their X-ray diffraction patterns confirmed a tetragonal structure. The phase structure, particle size, surface morphology and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. Thermoluminescence (TL) intensity increased with increase in ultraviolet (UV) light exposure time up to 15 min. With further increase in the UV irradiation time the TL intensity decreases. The increase in TL intensity indicates that trap concentration increased with UV exposure time. A broad peak at 121 °C suggested the existence of a trapping level. The peak of mechanoluminescence (ML) intensity versus time curve increased linearly with increasing impact velocity of the moving piston. Mechanoluminescence intensity increased with increase in UV irradiation time up to 15 min. Under UV-irradiation excitation, the TL and ML emission spectra of Ca 2 Al 2 SiO 7 :Ce 3+ phosphor showed the characteristic emission of Ce 3+ peaking at 400 nm (UV-violet) and originating from the Ce 3+ transitions of 5d-4f ( 2 F 5/2 and 2 F 7/2 ). The photoluminescence (PL) emission spectra for Ca 2 Al 2 SiO 7 :Ce 3+ were similar to the ML/TL emission spectra. The mechanism of ML excitation and the suitability of the Ca 2 Al 2 SiO 7 :Ce 3+ phosphor for radiation dosimetry are discussed. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  14. Comparisons between TiO2- and SiO2-flux assisted TIG welding processes.

    Science.gov (United States)

    Tseng, Kuang-Hung; Chen, Kuan-Lung

    2012-08-01

    This study investigates the effects of flux compounds on the weld shape, ferrite content, and hardness profile in the tungsten inert gas (TIG) welding of 6 mm-thick austenitic 316 L stainless steel plates, using TiO2 and SiO2 powders as the activated fluxes. The metallurgical characterizations of weld metal produced with the oxide powders were evaluated using ferritoscope, optical microscopy, and Vickers microhardness test. Under the same welding parameters, the penetration capability of TIG welding with TiO2 and SiO2 fluxes was approximately 240% and 292%, respectively. A plasma column made with SiO2 flux exhibited greater constriction than that made with TiO2 flux. In addition, an anode root made with SiO2 flux exhibited more condensation than that made with TiO2 flux. Results indicate that energy density of SiO2-flux assisted TIG welding is higher than that of TiO2-flux assisted TIG welding.

  15. Crystal structure of 1,4-bis(3-ammoniopropylpiperazine-1,4-diium bis[dichromate(VI

    Directory of Open Access Journals (Sweden)

    S. Vetrivel

    2016-05-01

    Full Text Available The asymmetric unit of the organic–inorganic title salt, (C10H28N4[Cr2O7]2, comprises one half of an 1,4-bis(3-ammoniopropylpiperazinediium cation (the other half being generated by the application of inversion symmetry and a dichromate anion. The piperazine ring of the cation adopts a chair conformation, and the two CrO4 tetrahedra of the anion are in an almost eclipsed conformation. In the crystal, the cations and anions form a layered arrangement parallel to (001. N—H...O hydrogen bonds between the cations and anions and additional C—H...O interactions lead to the formation of a three-dimensional network structure.

  16. Boson peak of alkali and alkaline earth silicate glasses: influence of the nature and size of the network-modifying cation.

    Science.gov (United States)

    Richet, Nicolas F

    2012-01-21

    The influence of the size of the alkaline earth cation on the boson peak of binary metasilicate glasses, MSiO(3) (M = Mg, Ca, Sr, Ba), has been investigated from vibrational densities of states determined by inversion of low-temperature heat capacities. As given both by C(p)/T(3) and g(ω)/ω(2), the intensity of the boson peak undergoes a 7-fold increase from Mg to Ba, whereas its temperature and frequency correlatively decrease from 18 to 10 K and from 100 to 20 cm(-1), respectively. The boson peak results from a combination of librations of SiO(4) tetrahedra and localized vibrations of network-modifying cations with non-bridging oxygens whose contribution increases markedly with the ionic radius of the alkaline earth. As a function of ionic radii, the intensity for Sr and Ba varies in the same way as previously found for alkali metasilicate glasses. The localized vibrations involving alkali and heavy alkaline earth cations appear to be insensitive to the overall glass structure. Although the new data are coherent with an almost linear relationship between the temperature of the boson peak and transverse sound velocity, pure SiO(2) and SiO(2)-rich glasses make marked exceptions to this trend because of the weak transverse character of SiO(4) librations. Finally, the universality of the calorimetric boson peak is again borne out because all data for silicate glasses collapse on the same master curve when plotted in a reduced form (C(P)∕/T(3))/(C(P)/T(3))(b) vs. T/T(b). © 2012 American Institute of Physics

  17. Study of epitaxial lateral overgrowth of semipolar (1 1 − 2 2) GaN by using different SiO2 pattern sizes

    International Nuclear Information System (INIS)

    Song, Ki-Ryong; Lee, Jae-Hwan; Han, Sang-Hyun; Yi, Hye-Rin; Lee, Sung-Nam

    2013-01-01

    Graphical abstract: - Highlights: • We examine comparative studies of semipolar ELO-GaN film. • Semipolar ELO-GaN film was grown by three step growth method. • The achievement of smooth surface morphology of semipolar ELO-GaN. • The crystal and optical properties was significantly improved by ELO process. - Abstract: We investigated the growth mode and the crystal properties of lateral epitaxial overgrowth (LEO) semipolar (1 1 − 2 2) GaN by using the various SiO 2 pattern sizes of 6, 8, 10 and 12 μm with the window width of 4.0 μm. By using three-step growth technique, we successfully obtained the fully-coalescenced semipolar (1 1 − 2 2) LEO-GaN films regardless of the SiO 2 pattern sizes. However, the coalescence thickness of LEO-GaN film was decreased with decreasing SiO 2 pattern size, indicating that the coalescence of semipolar (1 1 − 2 2) GaN was easily formed by decreasing the pattern size of SiO 2 mask. The full width at half maximums (FWHMs) of X-ray rocking curves (XRCs) of LEO-GaN films decreased with increasing SiO 2 pattern size. In the pattern size of 4 × 10 μm, we achieved the minimum XRCs FWHM of 537 and 368 arc s with two different X-ray incident beam directions of [1 1 − 2 − 3] and [1 − 1 0 0], respectively. Moreover, the photoluminescence bandedge emission of semipolar (1 1 − 2 2) GaN was 45 times increased by LEO process. Based on these results, we concluded that the LEO pattern size of 4 × 10 μm would effectively decrease crystal defects of semipolar (1 1 − 2 2) GaN epilayer, resulting in an improvement of the optical properties

  18. The electrorheological properties of nano-sized SiO2 particle materials doped with rare earths

    International Nuclear Information System (INIS)

    Liu Yang; Liao Fuhui; Li Junran; Zhang Shaohua; Chen Shumei; Wei Chenguan; Gao Song

    2006-01-01

    Electrorheological (ER) materials of pure SiO 2 and SiO 2 doped with rare earths (RE = Ce, Gd, Y) (non-metallic glasses (silicates)) were prepared using Na 2 SiO 3 and RECl 3 as starting materials. The electrorheological properties are not enhanced by all rare earth additions. The material doped with Ce exhibits the best ER performance

  19. SiO MASERS AROUND WX PSC MAPPED WITH THE KVN AND VERA ARRAY (KaVA)

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Youngjoo; Cho, Se-Hyung; Kim, Jaeheon; Choi, Yoon Kyung; Kim, Dong-Jin; Yoon, Dong-Hwan; Byun, Do-Young; Chung, Hyunsoo; Chung, Moon-Hee; Han, Myoung-Hee [Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong, Daejeon 305-348 (Korea, Republic of); Imai, Hiroshi; Oyadomari, Miyako [Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Asaki, Yoshiharu [National Astronomical Observatory of Japan (NAOJ) Chile Observatory/Joint ALMA Observatory (JAO), Alonso de Cordova 3107, Vitacura 763 0355, Santiago (Chile); Chibueze, James O. [Department of Physics and Astronomy, Faculty of Physical Sciences, University of Nigeria, Carver Building, 1 University Road, Nsukka (Nigeria); Dodson, Richard; Rioja, María J. [International Centre for Radio Astronomy Research, M468, The University of Western Australia, 35 Stirling Hwy, Crawley, Western Australia 6009 (Australia); Kusuno, Kozue [Department of Space and Astronautical Science, School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), 3-1-1 Yoshinodai, Chuou-Ku, Sagamihara, Kanagawa 252-5210 (Japan); Matsumoto, Naoko; Hagiwara, Yoshiaki [Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Min, Cheulhong, E-mail: yjyun@kasi.re.kr, E-mail: cho@kasi.re.kr [Department of Astronomical Sciences, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); and others

    2016-05-01

    We present the first images of the v = 1 and v = 2 J = 1 → 0 SiO maser lines taken with KaVA, i.e., the combined array of the Korean Very Long Baseline Interferometry (VLBI) Network and the VLBI Exploration of Radio Astrometry (VERA), toward the OH/IR star WX Psc. The combination of long and short antenna baselines enabled us to detect a large number of maser spots, which exhibit a typical ring-like structure in both the v = 1 and v = 2 J = 1 → 0 SiO masers as those that have been found in previous VLBI observational results of WX Psc. The relative alignment of the v = 1 and v = 2 SiO maser spots are precisely derived from astrometric analysis, due to the absolute coordinates of the reference maser spot that were well determined in an independent astrometric observation with VERA. The superposition of the v = 1 and v = 2 maser spot maps shows a good spatial correlation between the v = 1 and v = 2 SiO maser features. Nevertheless, it is also shown that the v = 2 SiO maser spot is distributed in an inner region compared to the v = 1 SiO maser by about 0.5 mas on average. These results provide good support for the recent theoretical studies of the SiO maser pumping, in which both the collisional and the radiative pumping predict the strong spatial correlation and the small spatial discrepancy between the v = 1 and v = 2 SiO maser.

  20. Ion assisted deposition of SiO2 film from silicon

    Science.gov (United States)

    Pham, Tuan. H.; Dang, Cu. X.

    2005-09-01

    Silicon dioxide, SiO2, is one of the preferred low index materials for optical thin film technology. It is often deposited by electron beam evaporation source with less porosity and scattering, relatively durable and can have a good laser damage threshold. Beside these advantages the deposition of critical optical thin film stacks with silicon dioxide from an E-gun was severely limited by the stability of the evaporation pattern or angular distribution of the material. The even surface of SiO2 granules in crucible will tend to develop into groove and become deeper with the evaporation process. As the results, angular distribution of the evaporation vapor changes in non-predicted manner. This report presents our experiments to apply Ion Assisted Deposition process to evaporate silicon in a molten liquid form. By choosing appropriate process parameters we can get SiO2 film with good and stable property.

  1. SiO2 stabilized Pt/C cathode catalyst for proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Zhu Tong; Du Chunyu; Liu Chuntao; Yin Geping; Shi Pengfei

    2011-01-01

    This paper describes the preparation of SiO 2 stabilized Pt/C catalyst (SiO 2 /Pt/C) by the hydrolysis of alkoxysilane, and examines the possibility that the SiO 2 /Pt/C is used as a durable cathode catalyst for proton exchange membrane fuel cells (PEMFCs). TEM and XRD results revealed that the hydrolysis of alkoxysilane did not significantly change the morphology and crystalline structure of Pt particles. The SiO 2 /Pt/C catalyst exhibited higher durability than the Pt/C one, due to the facts that the silica layers covered were beneficial for reducing the Pt aggregation and dissolution as well as increasing the corrosion resistance of supports, although the benefit of silica covering was lower than the case of Pt/CNT catalyst. Also, it was observed that the activity of the SiO 2 /Pt/C catalyst for the oxygen reduction reaction was somewhat reduced compared to the Pt/C one after the silica covering. This reduction was partially due to the low oxygen kinetics as revealed by the rotating-disk-electrode measurement. Silica covering by hydrolysis of only 3-aminopropyl trimethoxysilane is able to achieve a good balance between the durability and activity, leading to SiO 2 /Pt/C as a promising cathode catalyst for PEMFCs.

  2. Motor activation in SPG4-linked hereditary spastic paraplegia

    DEFF Research Database (Denmark)

    Scheuer, KH; Nielsen, JE; Krabbe, Katja

    2006-01-01

    OBJECTIVE: The aim of this study was to investigate the extent of motor cortical functional reorganisation in patients with SPG4-linked hereditary spastic paraplegia by exploring cortical motor activation related to movements of clinically affected (lower) and unaffected (upper) limbs. METHODS: T...

  3. An SFG study of interfacial amino acids at the hydrophilic SiO2 and hydrophobic deuterated polystyrene surfaces.

    Science.gov (United States)

    Holinga, George J; York, Roger L; Onorato, Robert M; Thompson, Christopher M; Webb, Nic E; Yoon, Alfred P; Somorjai, Gabor A

    2011-04-27

    Sum frequency generation (SFG) vibrational spectroscopy was employed to characterize the interfacial structure of eight individual amino acids--L-phenylalanine, L-leucine, glycine, L-lysine, L-arginine, L-cysteine, L-alanine, and L-proline--in aqueous solution adsorbed at model hydrophilic and hydrophobic surfaces. Specifically, SFG vibrational spectra were obtained for the amino acids at the solid-liquid interface between both hydrophobic d(8)-polystyrene (d(8)-PS) and SiO(2) model surfaces and phosphate buffered saline (PBS) at pH 7.4. At the hydrophobic d(8)-PS surface, seven of the amino acids solutions investigated showed clear and identifiable C-H vibrational modes, with the exception being l-alanine. In the SFG spectra obtained at the hydrophilic SiO(2) surface, no C-H vibrational modes were observed from any of the amino acids studied. However, it was confirmed by quartz crystal microbalance that amino acids do adsorb to the SiO(2) interface, and the amino acid solutions were found to have a detectable and widely varying influence on the magnitude of SFG signal from water at the SiO(2)/PBS interface. This study provides the first known SFG spectra of several individual amino acids in aqueous solution at the solid-liquid interface and under physiological conditions.

  4. Ultra-high sensitive substrates for surface enhanced Raman scattering, made of 3 nm gold nanoparticles embedded on SiO2 nanospheres

    Science.gov (United States)

    Phatangare, A. B.; Dhole, S. D.; Dahiwale, S. S.; Bhoraskar, V. N.

    2018-05-01

    The surface properties of substrates made of 3 nm gold nanoparticles embedded on SiO2 nanospheres enabled fingerprint detection of thiabendazole (TBZ), crystal violet (CV) and 4-Aminothiophenol (4-ATP) at an ultralow concentration of ∼10-18 M by surface enhanced Raman spectroscopy (SERS). Gold nanoparticles of an average size of ∼3 nm were synthesized and simultaneously embedded on SiO2 nanospheres by the electron irradiation method. The substrates made from the 3 nm gold nanoparticles embedded on SiO2 nanospheres were successfully used for recording fingerprint SERS spectra of TBZ, CV and 4-ATP over a wide range of concentrations from 10-6 M to 10-18 M using 785 nm laser. The unique features of these substrates are roughness near the surface due to the inherent structural defects of 3 nm gold nanoparticles, nanogaps of ≤ 1 nm between the embedded nanoparticles and their high number. These produced an abundance of nanocavities which act as active centers of hot-spots and provided a high electric field at the reporter molecules and thus an enhancement factor required to record the SERS spectra at ultra low concentration of 10-18 M. The SERS spectra recorded by the substrates of 4 nm and 6 nm gold nanoparticles are discussed.

  5. In vitro cytotoxicity of SiO2 or ZnO nanoparticles with different sizes and surface charges on U373MG human glioblastoma cells

    Directory of Open Access Journals (Sweden)

    Kim JE

    2014-12-01

    Full Text Available Jung-Eun Kim,1,* Hyejin Kim,1,* Seong Soo A An,2 Eun Ho Maeng,3 Meyoung-Kon Kim,4 Yoon-Jae Song1 1Department of Life Science, 2Department of Bionano Technology, Gachon University, Seongnam-Si, South Korea; 3Korea Testing and Research Institute, Seoul, South Korea; 4Department of Biochemistry and Molecular Biology, Korea University Medical School and College, Seoul, South Korea *These authors contributed equally to this work Abstract: Silicon dioxide (SiO2 and zinc oxide (ZnO nanoparticles are widely used in various applications, raising issues regarding the possible adverse effects of these metal oxide nanoparticles on human cells. In this study, we determined the cytotoxic effects of differently charged SiO2 and ZnO nanoparticles, with mean sizes of either 100 or 20 nm, on the U373MG human glioblastoma cell line. The overall cytotoxicity of ZnO nanoparticles against U373MG cells was significantly higher than that of SiO2 nanoparticles. Neither the size nor the surface charge of the ZnO nanoparticles affected their cytotoxicity against U373MG cells. The 20 nm SiO2 nanoparticles were more toxic than the 100 nm nanoparticles against U373MG cells, but the surface charge had little or no effect on their cytotoxicity. Both SiO2 and ZnO nanoparticles activated caspase-3 and induced DNA fragmentation in U373MG cells, suggesting the induction of apoptosis. Thus, SiO2 and ZnO nanoparticles appear to exert cytotoxic effects against U373MG cells, possibly via apoptosis. Keyword: apoptosis

  6. Synthesis, luminescence, and energy-transfer properties of β-Na2Ca4(PO4)2(SiO4):A (A = Eu(2+), Dy(3+), Ce(3+)/Tb(3+)) phosphors.

    Science.gov (United States)

    Li, Kai; Shang, Mengmeng; Geng, Dongling; Lian, Hongzhou; Zhang, Yang; Fan, Jian; Lin, Jun

    2014-07-07

    A series of β-Na2Ca4(PO4)2(SiO4) (β-NCPS):A (A = Eu(2+), Dy(3+), Ce(3+)/Tb(3+)) phosphors were prepared via a high-temperature solid-state reaction route. The X-ray diffraction, Fourier transform infrared, photoluminescence (PL), cathodoluminescence (CL) properties, fluorescent lifetimes, and absolute quantum yield were exploited to characterize the samples. Under UV radiation, the β-NCPS:Eu(2+) phosphors present bright green emissions, and the β-NCPS:Ce(3+) phosphors show strong blue emissions, which are attributed to their 4f(6)5d(1) → 4f(7) and 5d-4f allowed transitions, respectively. The β-NCPS:Ce(3+), Tb(3+) phosphors display intense tunable color from blue to green and high absolute quantum yields (81% for β-NCPS:0.12Ce(3+) and 83% for β-NCPS:0.12Ce(3+), 0.08Tb(3+)) when excited at 365 nm. Simultaneously, the energy transfer from Ce(3+) to Tb(3+) ions is deduced from the spectral overlap between Ce(3+) emission and Tb(3+) excitation spectra and demonstrated by the change of emission spectra and decay lifetimes. Moreover, the energy-transfer mechanism from Ce(3+) to Tb(3+) ions is confirmed to be exchange interaction according to the discussion of expression from Dexter and Reisfeld. Under a low-voltage electron-beam excitation, the β-NCPS:A (A = Eu(2+), Dy(3+), Ce(3+)/Tb(3+)) phosphors exhibit their characteristic emissions, and the emission profiles of β-NCPS:Ce(3+),Tb(3+) phosphors are obviously different from those of the PL spectra; this difference might be ascribed to their different luminescence mechanisms. These results in PL and CL properties suggest that β-NCPS:A (A = Eu(2+), Dy(3+), Ce(3+)/Tb(3+)) phosphors are potential candidates for solid-state lighting and field-emission displays.

  7. Characterization of the implantation damage in SiO2 with x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Ajioka, T.; Ushio, S.

    1986-01-01

    X-ray photoelectron spectroscopy (XPS) has been applied to characterize the damage introduced into SiO 2 by ion implantation. By measuring the peak width of Si/sub 2p/ from SiO 2 which corresponds to perturbation of the SiO 2 network, good depth profiles of the damage have been obtained for implanted samples and subsequently annealed samples. The results show that the damage distributed more widely than that calculated from energy deposition and that the perturbation of the network is caused not only by radiation damage but also by the existence of impurities in the network. It has been found that the XPS method is effective to understand the atomic structure, and thus, electrical properties of SiO 2

  8. Optical properties of ZrO2, SiO2 and TiO2-SiO2 xerogels and coatings doped with Eu3+ and Eu2+

    Directory of Open Access Journals (Sweden)

    Gonçalves Rogéria R.

    1999-01-01

    Full Text Available Eu3+ doped bulk monoliths and thin films were obtained by sol-gel methods in the ZrO2, SiO2 and SiO2-TiO2 systems. Eu3+ 5D0 ® 7FJ emission and decay time characteristics were measured during the entire experimental preparation route from the initial sol to the final xerogels. The crystalline phases identified were tetragonal ZrO2 and mixtures of rutile and anatase TiO2 at high temperature treatments in bulk samples. Good quality thin films were obtained for all systems by dip-coating optical glasses (Schott BK270. The same spectroscopic features were observed either for the bulk monoliths or the films. By appropriate heat treatments under H2 atmosphere Eu2+ containing samples could be obtained in the SiO2-TiO2 system.

  9. In-situ synthesis of SiO2@MOF composites for high-efficiency removal of aniline from aqueous solution

    Science.gov (United States)

    Han, Tongtong; Li, Caifeng; Guo, Xiangyu; Huang, Hongliang; Liu, Dahuan; Zhong, Chongli

    2016-12-01

    A series of SiO2@aluminum-MOF(MIL-68) composites with different SiO2 loadings have been synthesized by a simple and mild compositing strategy for high-efficiency removal of aniline. As evidenced from SEM and TEM images as well as the particle size distribution, the incorporation of SiO2 can improve the dispersity of MIL-68(Al) in composites, and result in the smaller particle size than that of pristine MIL-68(Al). Besides, the adsorption of aniline over SiO2, MIL-68(Al), the physical mixture of these two materials, and SiO2@MIL-68(Al) composites was investigated comparatively, demonstrating a relatively high adsorption capacity (531.9 mg g-1) of 7% SiO2@MIL-68(Al) towards aniline. Combining the ultrafast adsorption dynamics (reaching equilibrium within 40 s) and great reusability, 7% SiO2@MIL-68(Al) shows excellent adsorption performance. This indicates that the SiO2@MIL-68(Al) composites possess great potential applications as a kind of fascinating adsorbent in water pollution protection.

  10. Preparation of Raspberry-like Superhydrophobic SiO2 Particles by Sol-gel Method and Its Potential Applications

    Directory of Open Access Journals (Sweden)

    Xu Gui-Long

    2011-12-01

    Full Text Available Raspberry‐like SiO2 particles with a nano‐micro‐binary structure were prepared by a simple sol‐gel method using tetraethoxysilane (TEOS and methyltriethoxysilane (MTES as precursors. The chemical components and morphology of the SiO2 particles were characterized by Fourier transform infrared spectroscopy (FT‐IR and a Transmission electron microscope (TEM. The surface topography and wetting behaviour of the raspberry‐like SiO2 surface were observed with a Scanning electron microscope (SEM and studied by the water/oil contact angle (CA, respectively. The thermal stability of the prepared SiO2 particles was characterized by TGA analysis. The results show that the highly dispersed SiO2 particles initially prepared by the sol‐gel method turn into raspberry‐like particles with during the aging process. The raspberry‐like SiO2 particles show superhydrophobicity and superoleophilicity across a wide range of pH values. The SiO2 particles were thermally stable up to 475°C, while above this temperature the hydrophobicity decreases and finally becomes superhydrophobic when the temperature reaches 600°C. The raspberry‐like SiO2 particles which were prepared have potential applications in the fields of superhydrophobic surfaces, water‐oil separation, anti‐corrosion and fluid transportation.

  11. Positron annihilation in SiO 2-Si studied by a pulsed slow positron beam

    Science.gov (United States)

    Suzuki, R.; Ohdaira, T.; Uedono, A.; Kobayashi, Y.

    2002-06-01

    Positron and positronium (Ps) behavior in SiO 2-Si have been studied by means of positron annihilation lifetime spectroscopy (PALS) and age-momentum correlation (AMOC) spectroscopy with a pulsed slow positron beam. The PALS study of SiO 2-Si samples, which were prepared by a dry-oxygen thermal process, revealed that the positrons implanted in the Si substrate and diffused back to the interface do not contribute to the ortho-Ps long-lived component, and the lifetime spectrum of the interface has at least two components. From the AMOC study, the momentum distribution of the ortho-Ps pick-off annihilation in SiO 2, which shows broader momentum distribution than that of crystalline Si, was found to be almost the same as that of free positron annihilation in SiO 2. A varied interface model was proposed to interpret the results of the metal-oxide-semiconductor (MOS) experiments. The narrow momentum distribution found in the n-type MOS with a negative gate bias voltage could be attributed to Ps formation and rapid spin exchange in the SiO 2-Si interface. We have developed a two-dimensional positron lifetime technique, which measures annihilation time and pulse height of the scintillation gamma-ray detector for each event. Using this technique, the positronium behavior in a porous SiO 2 film, grown by a sputtering method, has been studied.

  12. Effect of SiO2 passivation overlayers on hillock formation in Al thin films

    International Nuclear Information System (INIS)

    Kim, Deok-kee

    2012-01-01

    Hillock formation in Al thin films with varying thicknesses of SiO 2 as a passivation layer was investigated during thermal cycling. Based on the stress measurements and the number of hillocks, 250 nm thick SiO 2 was thick enough to suppress the hillock formation and the suppression of hillock at 250 nm passivation and the lack of suppression at thinner passivation is related to the presence/absence of protection against the diffusive flow of atoms from the surrounding area to the surface due to the biaxial compressive stresses present in the film through the weak spots in the passivation layer. The stress state of Al films measured during annealing (the driving force for hillock formation) did not vary much with SiO 2 thickness. A small number of hillocks formed during the plasma enhanced chemical vapor deposition of SiO 2 overlayers at 300 °C. - Highlights: ► We examined the effect of SiO 2 overlayers on hillock formation in Al thin films. ► Thin overlayers were not effective in suppressing diffusive flow to the surface. ► A thick overlayer suppressed the diffusive flow from the interior to the surface. ► The stress state of Al films did not vary much with SiO 2 passivation thickness. ► High mechanical strength provided a large driving force for the large grain growth.

  13. A geometrical model of VY Canis Majoris for SiO maser lines

    International Nuclear Information System (INIS)

    Zhou Zhen-Pu; Kaifu, N.

    1984-01-01

    A new geometrical model of VY CMa is proposed to explain the three-peaked spectra of transition upsilon=1,2 J=1-0 of SiO maser emission. In this model the circumstellar envelope of VY CMa is a rotating disk of gas and dust seen nearly edge-on. The disk consists of two regions: a decelerated steady stream near the photosphere of the star and an accelerated one further away. Other geometries are discussed and eliminated. Calculated profiles of SiO maser lines fit well the observations. It is possible to explain the three-peaked profiles of SiO maser lines emitted by NML Cyg, RR Aql, NML Tau, etc. (orig.)

  14. Fiber-optic thermometer application of thermal radiation from rare-earth end-doped SiO2 fiber

    International Nuclear Information System (INIS)

    Katsumata, Toru; Morita, Kentaro; Komuro, Shuji; Aizawa, Hiroaki

    2014-01-01

    Visible light thermal radiation from SiO 2 glass doped with Y, La, Ce, Pr, Nd, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu were studied for the fiber-optic thermometer application based on the temperature dependence of thermal radiation. Thermal radiations according to Planck's law of radiation are observed from the SiO 2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu at the temperature above 1100 K. Thermal radiations due to f-f transitions of rare-earth ions are observed from the SiO 2 fibers doped with Nd, Dy, Ho, Er, Tm, and Yb at the temperature above 900 K. Peak intensities of thermal radiations from rare-earth doped SiO 2 fibers increase sensitively with temperature. Thermal activation energies of thermal radiations by f-f transitions seen in Nd, Dy, Ho, Er, Tm, and Yb doped SiO 2 fibers are smaller than those from SiO 2 fibers doped with Y, La, Ce, Pr, Eu, Tb, and Lu. Thermal radiation due to highly efficient f-f transitions in Nd, Dy, Ho, Er, Tm, and Yb ions emits more easily than usual thermal radiation process. Thermal radiations from rare-earth doped SiO 2 are potentially applicable for the fiber-optic thermometry above 900 K

  15. Synthesis, structure and magnetic properties of a new iron phosphonate-oxalate with 3D framework: [Fe(O3PCH3)(C2O4)0.5(H2O)

    International Nuclear Information System (INIS)

    Zhang Yangyang; Qi Yue; Zhang Ying; Liu Ziyu; Zhao Yinfeng; Liu Zhongmin

    2007-01-01

    A new iron phosphonate-oxalate [Fe(O 3 PCH 3 )(C 2 O 4 ) 0.5 (H 2 O)] (1), has been synthesized under hydrothermal condition. The single-crystal X-ray diffraction studies reveal that 1 consists of layers of vertex-linked FeO 6 octahedra and O 3 PC tetrahedra, which are further connected by bis-chelate oxalate bridges, giving to a 3D structure with 10-membered channels. Crystal data: monoclinic, P2 1 /n (no. 14), a=4.851(2)A, b=16.803(7)A, c=7.941(4)A, β=107.516(6) o , V=617.2(5)A 3 , Z=4, R 1 =0.0337 and wR 2 =0.0874 for 1251 reflections [I>2σ(I)]. Mossbauer spectroscopy measurement confirms the existence of high-spin Fe(III) in 1. Magnetic studies show that 1 exhibits weak ferromagnetism with T N =30K due to a weak spin canting

  16. Si nanocrystals embedded in SiO2: Optical studies in the vacuum ultraviolet range

    DEFF Research Database (Denmark)

    Pankratov, V.; Osinniy, Viktor; Kotlov, A.

    2011-01-01

    done. It is demonstrated that the experimentally determined blueshift of the photoluminescence excitation and absorption spectra is larger than the theoretical predictions. The influence of point defects in the SiO2 matrix on the optical and luminescence properties of the embedded Si nanocrystals...... is discussed. Moreover, it is demonstrated that no energy transfer takes place between the SiO2 and Si nanocrystals when the excitation energy is higher than the band-to-band transition energy in SiO2....

  17. Formation of radiative centers in SiO2 by tin high-dose implantation

    International Nuclear Information System (INIS)

    Komarov, F.F.; Parkhomenko, I.N.; Vlasukova, L.A.; Mil'chanin, O.V.; Mokhovikov, M.A.; Wendler, E.; Wesch, W.

    2013-01-01

    The structural transformations in SiO 2 layers implanted with high fluence of Sn ions have been investigated. It has been found that post-implantation annealing results in the β-Sn precipitation as well as the formation of SnO 2 -enriched regions in SiO 2 :Sn matrix. The intensive emission in the range of photon energies 1.5 – 3.5 eV is registered for the implanted and annealed samples. We attribute it to the oxygen deficiency centers created in the SiO 2 :Sn matrix and at the 'nanocluster/SiO 2 ' interfaces. (authors)

  18. Tunable graphene doping by modulating the nanopore geometry on a SiO2/Si substrate

    KAUST Repository

    Lim, Namsoo

    2018-02-28

    A tunable graphene doping method utilizing a SiO2/Si substrate with nanopores (NP) was introduced. Laser interference lithography (LIL) using a He–Cd laser (λ = 325 nm) was used to prepare pore size- and pitch-controllable NP SiO2/Si substrates. Then, bottom-contact graphene field effect transistors (G-FETs) were fabricated on the NP SiO2/Si substrate to measure the transfer curves. The graphene transferred onto the NP SiO2/Si substrate showed relatively n-doped behavior compared to the graphene transferred onto a flat SiO2/Si substrate, as evidenced by the blue-shift of the 2D peak position (∼2700 cm−1) in the Raman spectra due to contact doping. As the porosity increased within the substrate, the Dirac voltage shifted to a more positive or negative value, depending on the initial doping type (p- or n-type, respectively) of the contact doping. The Dirac voltage shifts with porosity were ascribed mainly to the compensation for the reduced capacitance owing to the SiO2–air hetero-structured dielectric layer within the periodically aligned nanopores capped by the suspended graphene (electrostatic doping). The hysteresis (Dirac voltage difference during the forward and backward scans) was reduced when utilizing an NP SiO2/Si substrate with smaller pores and/or a low porosity because fewer H2O or O2 molecules could be trapped inside the smaller pores.

  19. Synthesis, crystal structure, and ionic conductivity of a new layered metal phosphate, Li2Sr2Al(PO4)3

    International Nuclear Information System (INIS)

    Kim, Sung-Chul; Kwak, Hyun-Jung; Yoo, Chung-Yul; Yun, Hoseop; Kim, Seung-Joo

    2016-01-01

    A new layered metal phosphate, Li 2 Sr 2 Al(PO 4 ) 3 , was synthesized in the form of either a single-crystal or polycrystalline powder using the molten hydroxide flux method or a solid-state reaction, respectively. Li 2 Sr 2 Al(PO 4 ) 3 crystallizes to the P2 1 /n (Z=4) monoclinic space group with lattice parameters a≈4.95 Å, b≈22.06 Å, c≈8.63 Å, and β≈91.5°. The structure is composed of stacked [LiSrAl(PO 4 ) 2 ] layers alternating regularly with [LiSrPO 4 ] layers. In the [LiSrAl(PO 4 ) 2 ] sublattice, the AlO 6 octahedra and PO 4 tetrahedra are tilted cooperatively to form an anionic, corrugated, two-dimensional [Al(PO 4 ) 2 ] 3− framework that can be regarded as a “distorted-glaserite” structure. The [LiSrPO 4 ] sublattice is that of a layered block containing a six-membered ring formed from alternating linkages of LiO 4 and PO 4 tetrahedra. The six-membered rings show a boat-type arrangement with the up(U) or down(D) pointing sequence, UUDUUD. The interspace between the two sublattices generates a two-dimensional pathway for Li + ion conduction. The impedance measurement indicated that Li 2 Sr 2 Al(PO 4 ) 3 had a moderate ion conductivity (σ≈1.30×10 −4 S cm −1 at 667 K), with an activation energy E a ≈1.02 eV. - Graphical abstract: Polyhedral view of Li 2 Sr 2 Al(PO 4 ) 3 . Li + ions are represented by green spheres, Sr atoms by white spheres, AlO 6 groups by octahedra, and PO 4 groups by tetrahedra. - Highlights: • New compound Li 2 Sr 2 Al(PO 4 ) 3 is reported. • The crystal structure is investigated by single-crystal XRD analysis. • The structure is formed by the alternate stacking of two different sublattices. • Correlation between the crystal structure and ionic conductivity is discussed.

  20. SIOS: A regional cooperation of international research infrastructures as a building block for an Arctic observing system

    Science.gov (United States)

    Holmen, K. J.; Lønne, O. J.

    2016-12-01

    The Svalbard Integrated Earth Observing System (SIOS) is a regional response to the Earth System Science (ESS) challenges posed by the Amsterdam Declaration on Global Change. SIOS is intended to develop and implement methods for how observational networks in the Arctic are to be designed in order to address such issues in a regional scale. SIOS builds on the extensive observation capacity and research installations already in place by many international institutions and will provide upgraded and relevant Observing Systems and Research Facilities of world class in and around Svalbard. It is a distributed research infrastructure set up to provide a regional observational system for long term measurements under a joint framework. As one of the large scale research infrastructure initiatives on the ESFRI roadmap (European Strategy Forum on Research Infrastructures), SIOS is now being implemented. The new research infrastructure organization, the SIOS Knowledge Center (SIOS-KC), is instrumental in developing methods and solutions for setting up its regional contribution to a systematically constructed Arctic observational network useful for global change studies. We will discuss cross-disciplinary research experiences some case studies and lessons learned so far. SIOS aims to provide an effective, easily accessible data management system which makes use of existing data handling systems in the thematic fields covered by SIOS. SIOS will, implement a data policy which matches the ambitions that are set for the new European research infrastructures, but at the same time be flexible enough to consider `historical' legacies. Given the substantial international presence in the Svalbard archipelago and the pan-Arctic nature of the issue, there is an opportunity to build SIOS further into a wider regional network and pan-Arctic context, ideally under the umbrella of the Sustaining Arctic Observing Networks (SAON) initiative. It is necessary to anchor SIOS strongly in a European

  1. Effect of Si implantation on the microstructure of silicon nanocrystals and surrounding SiO2 layer

    International Nuclear Information System (INIS)

    Ross, G.G.; Smirani, R.; Levitcharsky, V.; Wang, Y.Q.; Veilleux, G.; Saint-Jacques, R.G.

    2005-01-01

    Si nanocrystals (Si-nc) embedded in a SiO 2 layer have been characterized by means of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). For local Si concentration in excess 8 x 10 21 Si + /cm 3 , the size of the Si-nc was found to be ∼3 nm and comparatively homogeneous throughout the whole implanted layer. For local Si concentration in excess of ∼2.4 x 10 22 Si + /cm 3 , the Si-nc diameter ranges from ∼2 to ∼12 nm in the sample, the Si-nc in the middle region of the implanted layer being bigger than those near the surface and the bottom of the layer. Also, Si-nc are visible deeper than the implanted depth. Characterization by XPS shows that a large quantity of oxygen was depleted from the first ∼25 nm in this sample (also visible on TEM image) and most of the SiO 2 bonds have been replaced by Si-O bonds. Experimental and simulation results suggest that a local Si concentration in excess of ∼3 x 10 21 Si/cm 3 is required for the production of Si-nc

  2. Crystal structure, quantum mechanical investigation, IR and NMR spectroscopy of two new organic perchlorates: (C6H18N3)·(ClO4)3H2O (I) and (C9H11N2)·ClO4(II)

    Science.gov (United States)

    Bayar, I.; Khedhiri, L.; Soudani, S.; Lefebvre, F.; Ferretti, V.; Ben Nasr, C.

    2018-06-01

    The reaction of perchloric acid with 1-(2-aminoethyl)piperazine or 5,6-dimethyl-benzimidazole results in the formation of 1-(2-amonioethyl)piperazine-1,4-dium triperchlorate hydrate (C6H18N3)·(ClO4)3·H2O (I) or 5,6-dimethyl-benzylimidazolium perchlorate (C9H11N2)·ClO4(II). Both compounds were fully structurally characterized including single crystal X-ray diffraction analysis. Compound (I) crystallizes in the centrosymmetric triclinic space group P 1 bar with the lattice parameters a = 7.455 (2), b = 10.462 (2), c = 10.824 (2) Å, α = 80.832 (2), β = 88.243 (2), γ = 88.160 (2) °, Z = 2 and V = 832.77 (3) Å3. Compound (II) has been found to belong to the P21/c space group of the monoclinic system, with a = 7.590 (3), b = 9.266 (3), c = 16.503 (6) Å, β = 107.38 (2) °, V = 1107.69 (7) Å3 and Z = 4. The structures of (I) and (II) consist of slightly distorted [ClO4]- tetrahedra anions and 1-(2-amonioethyl)piperazine-1,4-dium trication (I) or 5,6-dimethyl-benzylimidazolium cations (II) and additionally a lattice water in (I). The crystal structures of (I) and (II) exhibit complex three-dimensional networks of H-bonds connecting all their components. In the atomic arrangement of (I), the ClO4- anions form corrugated chains, while in (II) the atomic arrangement exhibits wide pseudo-hexagonal channels of ClO4 tetrahedra including the organic entities. The lattice water serves as a link between pairs of cations and pairs of anions via several Osbnd H⋯O and N-H⋯O interactions in compound (I). The vibrational absorption bands were identified by infrared spectroscopy. These compounds were also investigated by solid-state 13C, 35Cl and 15N NMR spectroscopy. DFT calculations allowed the attribution of the IR and NMR bands. Intermolecular interactions were investigated by Hirshfeld surfaces. Electronic properties such as HOMO and LUMO energies were derived.

  3. Liquidus Temperature of SrO-Al2O3-SiO2 Glass-Forming Compositions

    DEFF Research Database (Denmark)

    Abel, Brett M.; Morgan, James M.; Mauro, John C.

    2013-01-01

    . In the composition range of interest for industrial glasses, Tliq tends to decrease with increasing strontium-to-alumina ratio. We find that cristobalite, mullite, and slawsonite are the dominant devitrification phases for the compositions with high SiO2, SiO2+Al2O3, and SrO contents, respectively. By comparison...... with the phase diagrams for CaO-Al2O3-SiO2 and MgO-Al2O3-SiO2 systems, we have found that for the highest [RO]/[Al2O3] ratios, Tliq exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging...... to the SrO-Al2O3-SiO2 family may be designed with a more exact control of the glass-forming ability by avoiding the regions of high liquidus temperature....

  4. Sol-gel synthesis and characterization of single-phase Ni ferrite nanoparticles dispersed in SiO2 matrix

    International Nuclear Information System (INIS)

    Nadeem, K.; Traussnig, T.; Letofsky-Papst, I.; Krenn, H.; Brossmann, U.; Wuerschum, R.

    2010-01-01

    Nanoparticles of NiFe 2 O 4 dispersed in SiO 2 (25 wt%) matrix were synthesized by sol-gel method using tetraethyl orthosilicate (TEOS), as a precursor for SiO 2 . The sol-gel method for nanocomposites normally provides multi-phase nanoparticles. We investigated by a synopsis of different analysis methods, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SQUID-magnetometry, how the various chemical phases are transformed to a single-phase spinel structure during the various stages of annealing from 300 to 900 o C. We have developed a full phase diagram of chemical phases as a function of annealing temperature. The average particle size lies in the range 16-27 nm. The chemical phases formed below 900 o C are NiFe, NiO, γ-Fe 2 O 3 , α-Fe 2 O 3 , and NiFe 2 O 4 , respectively. The role of the TEOS prepared SiO 2 matrix is to restrict the particle size in a small range in order to rule out particle size effects. In the mid-infrared, a shift of the vibrational Fe-O bond is observed from 568 to 586 cm -1 for annealing between 500 and 700 o C which indicates an increasing NiFe 2 O 4 phase formation. A systematic study of coercivity field (ranging from 32 to 200 Oe) and saturation magnetic moment (ranging from 12.2 to 32.1 emu/g) for differently annealed samples supports our findings about the evolution of single-phase NiFe 2 O 4 at 900 o C. The opposite trend of saturation magnetic moment and coercivity with respect to annealing temperature clearly separates the different phases of metallic, antiferromagnetic, and finally single-phase spinel NiFe 2 O 4 .

  5. Satellite line mapping in Eu3+–Ce3+ and Pr3+–Ce3+ codoped Y2SiO5

    International Nuclear Information System (INIS)

    Serrano, D.; Karlsson, J.; Zheng, L.; Dong, Y.; Ferrier, A.; Goldner, P.; Walther, A.; Rippe, L.; Kröll, S.

    2016-01-01

    In this work we perform a high-resolution spectroscopic investigation of Eu 3+ –Ce 3+ and Pr 3+ –Ce 3+ codoped Y 2 SiO 5 crystals. Satellite line spectra were recorded at low temperatures around the Eu 3+ : 7 F 0 → 5 D 0 and the Pr 3+ : 3 H 4 → 1 D 2 transitions. It is observed that the incorporation of Ce 3+ as a codopant notably changes the Eu 3+ and Pr 3+ satellite line patterns. Satellite lines measured in singly doped Eu 3+ :Y 2 SiO 5 were found at the same spectral positions in Eu 3+ –Ce 3+ codoped crystals. These coincident lines were concluded to be due to pairs of Eu 3+ ions. Extra satellite lines appeared in the codoped crystals, which were assigned to Ce 3+ related structures such as Ce 3+ –Eu 3+ pairs. The analysis of the Pr 3+ satellite line spectra presents further challenges. Satellite lines associated to Pr 3+ pairs show weaker intensity, presumably due to the efficient quenching of the Pr 3+1 D 2 emission through cross-relaxation paths ( 1 D 2 → 1 G 4 ; 3 H 4 → 3 F 4 ). The investigation of the Eu 3+ and Pr 3+ satellite line patterns in Y 2 SiO 5 is particularly interesting for their exploitation in rare-earth based quantum computation schemes. - Highlights: • We recorded Eu and Pr satellite lines in Y 2 SiO 5 with and without Ce as a codopant. • The presence of Ce leads to the appearance of extra satellite lines in the spectra. • The satellite lines are associated to minor crystal sites such as ion pairs. • Less than 100 ion pairs were detected per satellite line. • The exploitation of the satellite line structure is proposed for quantum computing.

  6. Molten (Mg0.88Fe0.12)2SiO4 at lower mantle conditions - Melting products and structure of quenched glasses

    Science.gov (United States)

    Williams, Quentin

    1990-01-01

    Infrared spectra of quenched magnesium silicate glasses synthesized by fusing olivine at pressures in excess of 50 GPa and temperatures greater than 2500 K demonstrate that silicon is dominantly present in four-fold coordination with respect to oxygen within these quenched glasses. This low coordination is attributed, by analogy with the structural behavior of glasses compressed at 300 K, to the instability of higher coordinations in glasses of these compositions on decompression. Spectra of glasses formed in a hydrous environment document that water is extensively soluble in melts at these high pressures and temperatures. Also, these results are consistent with the melting of (Mg0.88Fe0.12)2SiO4 compositions to liquids near pyroxene in stoichiometry under these conditions, with iron-rich magnesiowuestite being the liquidus phase.

  7. Study of the atomic dynamics of nanoclusters Y2SiO5:Pr3+ by the confocal fluorescent microscopy

    International Nuclear Information System (INIS)

    Malyukin, Yu.V.; Zhmurin, P.N.; Syrkin, E.S.; Feodosyev, S.B.; Mamalui, M.A.

    2004-01-01

    The system under consideration consists of a Pr 3+ ion placed into a nanodimensional Y 2 SiO 5 crystal (∝20 nm), which rests on a glass substrate. The spectrum and attenuation of the fluorescence of the Pr 3+ ion have been studied by the method of confocal fluorescent microscopy. The rapid electron relaxation in J-multiplets of rare earth impurity ions split by the crystal field (for a usual bulk crystal τ∝10 -9 -10 -12 sec) is shown to be suppressed in the nanodimensional crystal of Y 2 SiO 5 :Pr 3+ . For the excited Stark components of 1 D 2 multiplet, the electron relaxation appears to be more than 10 4 times suppressed, while an average splitting of the 1 D 2 multiplet by the crystal field of ligands is 200 cm -1 . The observed phenomena strongly depends on the interaction of the Y 2 SiO 5 :Pr 3+ cluster with the substrate and the surrounding ('matrix'). Experimental results and theoretical calculations show the noticeable changes in the structure of vibrational spectrum and the density of vibrational states of the nanodimensional Y 2 SiO 5 :Pr 3+ crystal. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Study on adsorption of rhodamine B onto Beta zeolites by tuning SiO2/Al2O3 ratio.

    Science.gov (United States)

    Cheng, Zhi-Lin; Li, Yan-Xiang; Liu, Zan

    2018-02-01

    The exploration of the relationship between zeolite composition and adsorption performance favored to facilitate its better application in removal of the hazardous substances from water. The adsorption capacity of rhodamine B (RB) onto Beta zeolite from aqueous solution was reported. The relationship between SiO 2 /Al 2 O 3 ratio and adsorption capacity of Beta zeolite for RB was explored. The structure and physical properties of Beta zeolites with various SiO 2 /Al 2 O 3 ratios were determined by XRD, FTIR, TEM, BET, UV-vis and so on characterizations. The adsorption behavior of rhodamine B onto Beta zeolite matched to Langmuir adsorption isotherm and more suitable description for the adsorption kinetics was a pseudo-second-order reaction model. The maximum adsorption capacity of the as-prepared Beta zeolite with SiO 2 /Al 2 O 3 = 18.4 was up to 27.97mg/g. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Atmospheric Plasma Deposition of SiO2 Films for Adhesion Promoting Layers on Titanium

    Directory of Open Access Journals (Sweden)

    Liliana Kotte

    2014-12-01

    Full Text Available This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al in comparison to an anodizing process (NaTESi process. The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process.

  10. Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

    Directory of Open Access Journals (Sweden)

    Ling Wang

    2017-02-01

    Full Text Available Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms, the highest gain coefficient (1.10 ms·pm2, the maximum Stark splitting manifold of 2F7/2 level (781 cm−1, and the largest scalar crystal-field NJ and Yb3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO2 promoted the formation of P=O linkages, but broke the P=O linkages when the SiO2 content was greater than 26.7 mol %. Based on the previous 29Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO6] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb3+-doped gain medium for solid-state lasers and optical fiber amplifiers.

  11. Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

    Science.gov (United States)

    Wang, Ling; Zeng, Huidan; Yang, Bin; Ye, Feng; Chen, Jianding; Chen, Guorong; Smith, Andew T.; Sun, Luyi

    2017-01-01

    Yb3+-doped phosphate glasses containing different amounts of SiO2 were successfully synthesized by the conventional melt-quenching method. The influence mechanism of SiO2 on the structural and spectroscopic properties was investigated systematically using the micro-Raman technique. It was worth noting that the glass with 26.7 mol % SiO2 possessed the longest fluorescence lifetime (1.51 ms), the highest gain coefficient (1.10 ms·pm2), the maximum Stark splitting manifold of 2F7/2 level (781 cm−1), and the largest scalar crystal-field NJ and Yb3+ asymmetry degree. Micro-Raman spectra revealed that introducing SiO2 promoted the formation of P=O linkages, but broke the P=O linkages when the SiO2 content was greater than 26.7 mol %. Based on the previous 29Si MAS NMR experimental results, these findings further demonstrated that the formation of [SiO6] may significantly affect the formation of P=O linkages, and thus influences the spectroscopic properties of the glass. These results indicate that phosphosilicate glasses may have potential applications as a Yb3+-doped gain medium for solid-state lasers and optical fiber amplifiers. PMID:28772601

  12. Synthesis and characterization of Al2O3 and SiO2 films with fluoropolymer content using rf-plasma magnetron sputtering technique

    International Nuclear Information System (INIS)

    Islam, Mohammad; Inal, Osman T.

    2008-01-01

    Pure and molecularly mixed inorganic films for protection against atomic oxygen in lower earth orbit were prepared using radio-frequency (rf) plasma magnetron sputtering technique. Alumina (Al 2 O 3 ) and silica (SiO 2 ) films with average grain size in the range of 30-80 nm and fully dense or dense columnar structure were synthesized under different conditions of pressure and power. Simultaneous oxide sputtering and plasma polymerization (PP) of hexafluoropropylene (HFP) led to the formation of molecularly mixed films with fluoropolymer content. The degree of plasma polymerization was strongly influenced by total chamber pressure and the argon to HFP molar ratio (n Ar /n M ). An order of magnitude increase in pressure due to argon during codeposition changed the plasma-polymerization mechanism from radical-chain- to radical-radical-type processes. Subsequently, a shift from linear CH 2 group based chain polymerization to highly disordered fluoropolymer content with branching and cross-linking was observed. Fourier transform infrared spectroscopy studies revealed chemical interaction between depositing SiO 2 and PP-HFP through appearance of absorption bands characteristic of Si-F stretching and expansion of SiO 2 network. The relative amount and composition of plasma-polymerized fluoropolymer in such films can be controlled by changing argon to HFP flow ratio, total chamber pressure, and applied power. These films offer great potential for use as protective coatings in aerospace applications

  13. Electric properties of La2O3/SiO2/4H-SiC MOS capacitors with different annealing temperatures

    Directory of Open Access Journals (Sweden)

    Yucheng Wang

    2015-08-01

    Full Text Available In this work, we describe a rapid thermal annealing (RTA process for the La2O3/SiO2/4H-SiC interface and investigate its effect on the material’s electrical properties. Our results indicate that the trap charge density and interface state density (Dit are reduced as the RTA temperature increases due to the termination of residual carbon and dangling bonds. We demonstrate that the sample obtained after RTA at 500 °C has the highest breakdown electric field (Efb (7 MV/cm due to a decrease in the trap charge density and an improvement in the interfacial properties. However, when the RTA temperature reaches 600 °C or higher, a lower Efb value (1.2 MV/cm is obtained due to leakage routes generated by the crystallization of La2O3. Based on our results, we conclude that the ideal choice for the RTA temperature is 500 °C.

  14. TiO2 nanoparticles supported on the Fe3O4@SiO2 nanocomposites: a novel magnetic nanocatalyst for the synthesis of 2-aminothiazoles

    International Nuclear Information System (INIS)

    Safari, Javad; Abedi-Jazini, Zahra; Zarnegar, Zohre; Sadeghi, Masoud

    2015-01-01

    Nano TiO 2 supported on the Fe 3 O 4 @SiO 2 nanocomposites is introduced as a novel catalyst for the environmental synthesis of 2-aminothiazoles in PEG-200 as a green medium at room temperature. In this reaction, thiourea and N-bromosuccinimide were reacted with various ketones affording the desired 2-aminothiazole compounds. This green protocol has promising features for the reaction response such as simple procedure, high yields, and the ease of separation of pure product, short reaction time, and convenient manipulation. This catalyst was easily separated by an external magnet, and the recovered catalyst was reused several times without any significant loss of activity.Graphical abstract

  15. Origin of the incommensurate phase of quartz. Pt. 2

    International Nuclear Information System (INIS)

    Vallade, M.; Berge, B.; Dolino, G.

    1992-01-01

    The results of an inelastic neutron scattering investigation of the low-frequency modes of β quartz, described in the preceding paper [1], are interpreted using two different approaches: i) a phenomenological model directly derived from a Landau-Ginzburg type expansion of the free energy; this model is only relevant for the long-wavelength part of the phonon spectrum but it allows an easy connection with thermodynamical data; ii) a microscopic lattice dynamical model, which is an extension of the Grimm-Dorner model; it is shown that the main properties of the low-frequency phonon spectrum and, in particular, the softening of a Σ 2 mode at an incommensurate wave vector close to the zone-center, can be understood by analysing the motions of nearly rigid SiO 4 tetrahedra. (orig.)

  16. Optical properties of amorphous SiO2-TiO2 multi-nanolayered coatings for 1064-nm mirror technology

    Science.gov (United States)

    Magnozzi, M.; Terreni, S.; Anghinolfi, L.; Uttiya, S.; Carnasciali, M. M.; Gemme, G.; Neri, M.; Principe, M.; Pinto, I.; Kuo, L.-C.; Chao, S.; Canepa, M.

    2018-01-01

    The use of amorphous, SiO2-TiO2 nanolayered coatings has been proposed recently for the mirrors of 3rd-generation interferometric detectors of gravitational waves, to be operated at low temperature. Coatings with a high number of low-high index sub-units pairs with nanoscale thickness were found to preserve the amorphous structure for high annealing temperatures, a key factor to improve the mechanical quality of the mirrors. The optimization of mirror designs based on such coatings requires a detailed knowledge of the optical properties of sub-units at the nm-thick scale. To this aim we have performed a Spectroscopic Ellipsometry (SE) study of amorphous SiO2-TiO2 nanolayered films deposited on Si wafers by Ion Beam Sputtering (IBS). We have analyzed films that are composed of 5 and 19 nanolayers (NL5 and NL19 samples) and have total optical thickness nominally equivalent to a quarter of wavelength at 1064 nm. A set of reference optical properties for the constituent materials was obtained by the analysis of thicker SiO2 and TiO2 homogeneous films (∼ 120 nm) deposited by the same IBS facility. By flanking SE with ancillary techniques, such as TEM and AFM, we built optical models that allowed us to retrieve the broad-band (250-1700 nm) optical properties of the nanolayers in the NL5 and NL19 composite films. In the models which provided the best agreement between simulation and data, the thickness of each sub-unit was fitted within rather narrow bounds determined by the analysis of TEM measurements on witness samples. Regarding the NL5 sample, with thickness of 19.9 nm and 27.1 nm for SiO2 and TiO2 sub-units, respectively, the optical properties presented limited variations with respect to the thin film counterparts. For the NL19 sample, which is composed of ultrathin sub-units (4.4 nm and 8.4 nm for SiO2 and TiO2, respectively) we observed a significant decrease of the IR refraction index for both types of sub-units; this points to a lesser mass density with

  17. Ultralow-density SiO2 aerogels prepared by a two-step sol-gel process

    International Nuclear Information System (INIS)

    Wang Jue; Li Qing; Shen Jun; Zhou Bin; Chen Lingyan; Jiang; Weiyang

    1996-01-01

    Low density SiO 2 gels are prepared by a two-step sol-gel process from TEOS. The influence of various solution ratios on the gelation process is investigated. The comparative characterization of gels using different solvent, such as ethanol, acetone and methyl cyanide, is also given. The ultralow-density SiO 2 aerogels with density less than 10 kg/m 3 are prepared by CO 2 supercritical drying technique. The structure difference between SiO 2 aerogels prepared by conventional single-step process and the two-step process is also presented

  18. Fracto- mechanoluminescence and thermoluminescence properties of orange-red emitting Eu3+ doped Ca2Al2SiO7 phosphors

    International Nuclear Information System (INIS)

    Tiwari, Geetanjali; Brahme, Nameeta; Sharma, Ravi; Bisen, D.P.; Sao, Sanjay K.; Khare, Ayush

    2017-01-01

    The suitability of nano-structured Ca 2 Al 2 SiO 7 :Eu 3+ phosphors for thermoluminescence and mechanoluminescence dosimeter were investigated. Europium doped di-calcium di-aluminum silicate phosphor was synthesised by the combustion assisted method and annealed at 1100 °C for 4 h in reducing and oxidizing environments. The prepared Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDX), photoluminescence (PL) and decay characteristics. The phase structure of sintered phosphor has akermanite type which belongs to the tetragonal crystallography; this structure is a member of the melilite group and forms a layered compound. The chemical composition of the sintered Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was confirmed by EDX spectra. Mechanoluminescence (ML) and thermoluminescence (TL) studies revealed that the ML and TL intensity increases with activator concentration. Optimum ML was observed for the sample having 2 mol% of Eu ions. The TL intensity of Ca 2 Al 2 SiO 7 :Eu 3+ was recorded for different exposure times of γ -irradiation and it was observed that TL intensity is maximum for γ dose of 1770 Gy. The PL spectra indicated that Ca 2 Al 2 SiO 7 :Eu 3+ could be excited effectively by near ultraviolet (NUV) light and exhibited bright orange-red emission with excellent colour stability. CIE colour coordinates of the prepared Ca 2 Al 2 SiO 7 :Eu 3+ phosphor was found suitable as orange-red light emitting phosphor with a CIE value of (x=0.6142, y=0.3849) and correlated colour temperature (CCT) is 1250 K. Therefore, it is considered to be a new promising orange-red emitting phosphor for white light emitting diode (LED) application.

  19. SiO2 Antireflection Coatings Fabricated by Electron-Beam Evaporation for Black Monocrystalline Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Minghua Li

    2014-01-01

    Full Text Available In this work we prepared double-layer antireflection coatings (DARC by using the SiO2/SiNx:H heterostructure design. SiO2 thin films were deposited by electron-beam evaporation on the conventional solar cell with SiNx:H single-layer antireflection coatings (SARC, while to avoid the coverage of SiO2 on the front side busbars, a steel mask was utilized as the shelter. The thickness of the SiNx:H as bottom layer was fixed at 80 nm, and the varied thicknesses of the SiO2 as top layer were 105 nm and 122 nm. The results show that the SiO2/SiNx:H DARC have a much lower reflectance and higher external quantum efficiency (EQE in short wavelengths compared with the SiNx:H SARC. A higher energy conversion efficiency of 17.80% was obtained for solar cells with SiO2 (105 nm/SiNx:H (80 nm DARC, an absolute conversion efficiency increase of 0.32% compared with the conventional single SiNx:H-coated cells.

  20. B2O3/SiO2 substitution effect on structure and properties of Na2O-CaO-SrO-P2O5-SiO2 bioactive glasses from molecular dynamics simulations.

    Science.gov (United States)

    Ren, Mengguo; Lu, Xiaonan; Deng, Lu; Kuo, Po-Hsuen; Du, Jincheng

    2018-05-23

    The effect of B2O3/SiO2 substitution in SrO-containing 55S4.3 bioactive glasses on glass structure and properties, such as ionic diffusion and glass transition temperature, was investigated by combining experiments and molecular dynamics simulations with newly developed potentials. Both short-range (such as bond length and bond angle) and medium-range (such as polyhedral connection and ring size distribution) structures were determined as a function of glass composition. The simulation results were used to explain the experimental results for glass properties such as glass transition temperature and bioactivity. The fraction of bridging oxygen increased linearly with increasing B2O3 content, resulting in an increase in overall glass network connectivity. Ion diffusion behavior was found to be sensitive to changes in glass composition and the trend of the change with the level of substitution is also temperature dependent. The differential scanning calorimetry (DSC) results show a decrease in glass transition temperature (Tg) with increasing B2O3 content. This is explained by the increase in ion diffusion coefficient and decrease in ion diffusion energy barrier in glass melts, as suggested by high-temperature range (above Tg) ion diffusion calculations as B2O3/SiO2 substitution increases. In the low-temperature range (below Tg), the Ea for modifier ions increased with B2O3/SiO2 substitution, which can be explained by the increase in glass network connectivity. Vibrational density of states (VDOS) were calculated and show spectral feature changes as a result of the substitution. The change in bioactivity with B2O3/SiO2 substitution is discussed with the change in pH value and release of boric acid into the solution.

  1. Characterization of heterogeneous SiO2 materials by scanning electron microscope and micro fluorescence XAS techniques

    International Nuclear Information System (INIS)

    Khouchaf, L.; Boinski, F.; Tuilier, M.H.; Flank, A.M.

    2006-01-01

    Micro X-ray absorption near edge structure XANES and micro fluorescence experiments have been carried out using X-ray microbeam from synchrotron radiation source with high brightness to investigate the local structural evolutions of heterogeneous and natural SiO 2 submitted to alkali-silica reaction ASR process. Compared to elemental maps obtained by Environmental Scanning Electron Microscope ESEM, micro fluorescence X maps showed the diffusion of potassium cations inside the grains with higher accuracy. Si K-edge spectra show the disorder induced by the dissolution of the grain from the outside to the inside. Potassium K-edge spectra do not show significant changes around K cations. The breaking of Si-O-Si bonds and the disorder of the (SiO 4 ) n network may be affected to potassium cations

  2. Synthesis of metallic nanoparticles in SiO2 matrices

    International Nuclear Information System (INIS)

    Gutierrez W, C.; Mondragon G, G.; Perez H, R.; Mendoza A, D.

    2004-01-01

    Metallic nanoparticles was synthesized in SiO 2 matrices by means of a process of two stages. The first one proceeded via sol-gel, incorporating the metallic precursors to the reaction system before the solidification of the matrix. Later on, the samples underwent a thermal treatment in atmosphere of H 2 , carrying out the reduction of the metals that finally formed to the nanoparticles. Then it was detected the presence of smaller nanoparticles than 20 nm, dispersed and with the property of being liberated easily of the matrix, conserving a free surface, chemically reactive and with response to external electromagnetic radiation. The system SiO 2 -Pd showed an important thermoluminescent response. (Author)

  3. Self-Ordered Voids Formation in SiO2 Matrix by Ge Outdiffusion

    Directory of Open Access Journals (Sweden)

    B. Pivac

    2018-01-01

    Full Text Available The annealing behavior of very thin SiO2/Ge multilayers deposited on Si substrate by e-gun deposition in high vacuum was explored. It is shown that, after annealing at moderate temperatures (800°C in inert atmosphere, Ge is completely outdiffused from the SiO2 matrix leaving small (about 3 nm spherical voids embedded in the SiO2 matrix. These voids are very well correlated and formed at distances governed by the preexisting multilayer structure (in vertical direction and self-organization (in horizontal direction. The formed films produce intensive photoluminescence (PL with a peak at 500 nm. The explored dynamics of the PL decay show the existence of a very rapid process similar to the one found at Ge/SiO2 defected interface layers.

  4. Ionic conductivity of the lithium titanium phosphate (Li/sub 1+x/M/sub x/Ti/sub 2-x/(PO/sub 4/)/sub 3/, M=Al, Sc, Y, and La) systems

    International Nuclear Information System (INIS)

    Aono, H.; Sugimoto, E.; Sadaaka, Y.; Imanaka, N.; Adachi, G.Y.

    1989-01-01

    High lithium ionic conductivity was obtained in Li/sub 1+X/M/sub X/Ti/sub 2-X/(PO/sub 4/)/sub 3/ (M=Al, Sc, Y, and La) systems. Lithium titanium phosphate, LiTi/sub 2/(PO/sub 4/)/sub 3/, is composed of both TiO/sub 6/ octahedra and PO/sub 4/ tetrahedra, which are linked by corners to form a three dimensional network, with a space group R3-barC. Some workers have already described that the conductivity increased considerably if Ti/sup 4+/ in LiTi/sub 2/(PO/sub 4/)/sub 3/ was substituted by slightly larger cations such as Ga/sup 3+/(1),Sc/sup 3+/(2), and In/sup 3+/(3,4). These results are similar to each other because of their close ionic radii. In this communication, substitution effects of Ti/sup 4+/ in LiTi/sub 2/(PO/sub 4/)/sub 3/ by various ions (Al/sup 3+/, Sc/sup 3+/, Y/sup 3+/, and La/sup 3+/) on their conductivities are reported

  5. Synthesis, structure, and physicochemical investigations of the new α Cu 0.50TiO(PO 4) oxyphosphate

    Science.gov (United States)

    Benmokhtar, S.; Belmal, H.; El Jazouli, A.; Chaminade, J. P.; Gravereau, P.; Pechev, S.; Grenier, J. C.; Villeneuve, G.; de Waal, D.

    2007-02-01

    The room-temperature crystal structure of a new Cu(II) oxyphosphate— α Cu 0.50IITiO(PO 4)—was determined from X-ray single crystals diffraction data, in the monoclinic system, space group P2 1/c. The refinement from 5561 independent reflections lead to the following parameters: a=7.5612(4)Å, b=7.0919(4)Å, c=7.4874(4)Å, β=122.25(1)°, Z=4, with the final R=0.0198, wR=0.0510. The structure of α Cu 0.50IITiO(PO 4) can be described as a TiOPO 4 framework constituted by chains of tilted corner-sharing [TiO 6] octahedra running parallel to the c-axis and cross linked by phosphate [PO 4] tetrahedra, where one-half of octahedral cavities created are occupied by Cu atoms. Ti atoms are displaced from the center of octahedra units in alternating long (2.308 Å) and short (1.722 Å) Ti-O(1) bonds along chains. Such O(1) atoms not linked to P atoms justify the oxyphosphate formulation α Cu 0.50TiO(PO 4). The divalent cations Cu 2+ occupy a Jahn-Teller distorted octahedron sharing two faces with two [TiO 6] octahedra. EPR and optical measurements are in good agreement with structural data. The X-ray diffraction results are supported by Raman and infrared spectroscopy studies that confirmed the existence of the infinite chains -Ti-O-Ti-O-Ti-. α Cu 0.50TiO(PO 4) shows a Curie-Weiss paramagnetic behavior in the temperature range 4-80 K.

  6. Adsorption of uranyl in SiO2 porous glass

    International Nuclear Information System (INIS)

    Benedetto, F. E.; Prado, M. O.

    2013-01-01

    Vitreous SiO 2 porous matrices can be used in many applications involving the uptake of chemical species on its solid surface. In this work, vitreous silica sponges were prepared from a sodium borosilicate glass manufactured in our laboratory. The product obtained was then separated into phases with subsequent leaching of the soluble phase rich in B and Na. The resulting porous matrices have a specific surface of 35 m2/gr. Adsorption of uranyl ions onto the SiO 2 porous surface was studied to evaluate the use of this material as a filter for treatment of uranium containing water. The effects of contact time, adsorbent mass and equilibrium concentration of solution were studied. The porous adsorbent exhibits a pseudo-second-order kinetic behavior. The sponges with adsorbed uranium were thermally sealed as a way of U immobilization. Retention of uranium was confirmed during the matrix sealing by TGA. Uranium concentration before and after adsorption tests were made by means of ICP-OES. For uranium concentration of 800 ppm, 72 hours contact time and pH of 3.5, the amount of uranium adsorbed was 21.06 ± 0.02 mg U per gram of vitreous porous SiO 2 . (author)

  7. Absorption of acoustic waves in La3Ga5SiO14 monocrystals

    International Nuclear Information System (INIS)

    Mansfel'd, G.D.; Bezdelkin, V.V.; Freik, A.D.; Kucheryavaya, E.S.

    1995-01-01

    Frequency dependences of longitudinal and transverse acoustic wave absorption coefficient in the basic crystallographic La 3 Ga 5 SiO 14 directions are measured by composite resonator method. The obtained values of absorption coefficient for all directions appear to be lower or approximately equal to the values of absorption coefficient in quartz monocrystals. Application of the resonator methods allows one to study factors affecting the resonator high-quality as well. 9 refs., 4 figs

  8. Temperature stability of c-axis oriented LiNbO3/SiO2/Si thin film layered structures

    International Nuclear Information System (INIS)

    Tomar, Monika; Gupta, Vinay; Mansingh, Abhai; Sreenivas, K.

    2001-01-01

    Theoretical calculations have been performed for the temperature stability of the c-axis oriented LiNbO 3 thin film layered structures on passivated silicon (SiO 2 /Si) substrate with and without a non-piezoelectric SiO 2 overlayer. The phase velocity, electromechanical coupling coefficient and temperature coefficient of delay (TCD) have been calculated. The thicknesses of various layers have been determined for optimum SAW performance with zero TCD. The presence of a non-piezoelectric SiO 2 overlayer on LiNbO 3 film is found to significantly enhance the coupling coefficient. The optimized results reveal that a high coupling coefficient of K 2 =3.45% and a zero TCD can be obtained in the SiO 2 /LiNbO 3 /SiO 2 /Si structure with a 0.235λ thick LiNbO 3 layer sandwiched between 0.1λ thick SiO 2 layers. (author)

  9. Water droplet behavior on superhydrophobic SiO2 nanocomposite films during icing/deicing cycles

    NARCIS (Netherlands)

    Lazauskas, A.; Guobiene, A.; Prosycevas, I.; Baltrusaitis, V.; Grigaliunas, V.; Narmontas, P.; Baltrusaitis, Jonas

    2013-01-01

    This work investigates water droplet behavior on superhydrophobic (water contact angle value of 162 ± 1°) SiO2 nanocomposite films subjected to repetitive icing/deicing treatments, changes in SiO2 nanocomposite film surface morphology and their non-wetting characteristics. During the experiment,

  10. Transfer free graphene growth on SiO2 substrate at 250 °C

    Science.gov (United States)

    Vishwakarma, Riteshkumar; Rosmi, Mohamad Saufi; Takahashi, Kazunari; Wakamatsu, Yuji; Yaakob, Yazid; Araby, Mona Ibrahim; Kalita, Golap; Kitazawa, Masashi; Tanemura, Masaki

    2017-03-01

    Low-temperature growth, as well as the transfer free growth on substrates, is the major concern of graphene research for its practical applications. Here we propose a simple method to achieve the transfer free graphene growth on SiO2 covered Si (SiO2/Si) substrate at 250 °C based on a solid-liquid-solid reaction. The key to this approach is the catalyst metal, which is not popular for graphene growth by chemical vapor deposition. A catalyst metal film of 500 nm thick was deposited onto an amorphous C (50 nm thick) coated SiO2/Si substrate. The sample was then annealed at 250 °C under vacuum condition. Raman spectra measured after the removal of the catalyst by chemical etching showed intense G and 2D peaks together with a small D and intense SiO2 related peaks, confirming the transfer free growth of multilayer graphene on SiO2/Si. The domain size of the graphene confirmed by optical microscope and atomic force microscope was about 5 μm in an average. Thus, this approach will open up a new route for transfer free graphene growth at low temperatures.

  11. Integrated nanophotonic hubs based on ZnO-Tb(OH3/SiO2 nanocomposites

    Directory of Open Access Journals (Sweden)

    Lin Yu

    2011-01-01

    Full Text Available Abstract Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH3/SiO2 as well as SnO2-Tb(OH3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.

  12. A combined interfacial and in-situ polymerization strategy to construct well-defined core-shell epoxy-containing SiO2-based microcapsules with high encapsulation loading, super thermal stability and nonpolar solvent tolerance

    Directory of Open Access Journals (Sweden)

    Yin Jia

    2016-10-01

    Full Text Available SiO2-based microcapsules containing hydrophobic molecules exhibited potential applications such as extrinsic self-healing, drug delivery, due to outstanding thermal and chemical stability of SiO2. However, to construct SiO2-based microcapsules with both high encapsulation loading and long-term structural stability is still a troublesome issue, limiting their further utilization. We herein design a single-batch route, a combined interfacial and in-situ polymerization strategy, to fabricate epoxy-containing SiO2-based microcapsules with both high encapsulation loading and long-term structural stability. The final SiO2-based microcapsules preserve high encapsulation loading of 85.7 wt% by controlling exclusively hydrolysis and condensed polymerization at oil/water interface in the initial interfacial polymerization step. In the subsequent in-situ polymerization step, the initial SiO2-based microcapsules as seeds could efficiently harvest SiO2 precursors and primary SiO2 particles to finely tune the SiO2 wall thickness, thereby enhancing long-term structural stability of the final SiO2-based microcapsules including high thermal stability with almost no any weight loss until 250°C, and strong tolerance against nonpolar solvents such as CCl4 with almost unchanged core-shell structure and unchanged core weight after immersing into strong solvents for up to 5 days. These SiO2-based microcapsules are extremely suited for processing them into anticorrosive coating in the presence of nonpolar solvents for self-healing application.

  13. Crystal structure and Mössbauer spectroscopy of a new iron phosphate Mg{sub 2.88}Fe{sub 4.12}(PO{sub 4}){sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Saad, Y. [UR Matériaux Inorganiques, Faculté des Sciences, 5019 Monastir (Tunisia); Hidouri, M., E-mail: mourad_hidouri@yahoo.fr [UR Matériaux Inorganiques, Faculté des Sciences, 5019 Monastir (Tunisia); Álvarez-Serrano, I.; Veiga, M.L. [Departamento de Química Inorgánica I, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid (Spain); Wattiaux, A. [Institut de Chimie de la Matière Condensée de Bordeaux, CNRS, Université de Bordeaux I, 87 Avenue du Dr. A. Schweitzer, 33608 Pessac-Cedex (France); Amara, Mongi B. [UR Matériaux Inorganiques, Faculté des Sciences, 5019 Monastir (Tunisia)

    2014-01-25

    Highlights: • This study reports the synthesis and characterization of a new iron phosphate. • The cationic distribution is supported by a Mössbauer spectroscopy study. • The magnetic susceptibility results are discussed. -- Abstract: A new mixed valence iron phosphate Mg{sub 2.88}Fe{sub 4.12}(PO{sub 4}){sub 6} has been prepared as single crystals by the flux method and as a powder by solid state reaction and its crystal structure has been determined by X-ray diffraction. This compound crystallises in the triclinic system with space group P1{sup ¯} and a = 6.325(5) Å, b = 7.911(3) Å, c = 9.271(3) Å, α = 104.62(1)°, β = 108.41(1)° and γ = 101.24(1)° and Z = 1. Its structure is similar to that of the mineral howardevansite. It consists of Fe{sub 2}O{sub 10} bioctahedral units and MgO{sub 5} trigonal bipyramids sharing edges to form infinite zigzag chains. Such chains are linked to each other by MO{sub 6} (0.88 Mg{sup 2+} + 0.12 Fe{sup 2+}) octahedra and PO{sub 4} tetrahedra resulting in a 3D covalent framework. Magnetic measurements indicated two successive transitions at 46 K and 22 K. Mössbauer spectroscopy confirmed the mixed valence of iron and gave accurate information about its local environment.

  14. The Crystal Structure of Cu4Bi4Se9

    DEFF Research Database (Denmark)

    Makovicky, E.; Søtofte, Inger; Karup-Møller, S.

    2002-01-01

    contains three square pyramidal Bi sites, an octahedrally coordinated Bi site as well as two tetrahedrally and two irregularly coordinated Cu sites. The structure is an intergrowth of PbS-like slabs with irregularly configured slabs of Bi pyramids and Cu tetrahedra. It contains covalently bonded Se-2...

  15. Poly[(μ3-benzene-1,3,5-tricarboxylato-κ3O1:O3:O5(μ2-2-methylimidazolato-κ2N:N′tris(2-methylimidazole-κNdizinc(II

    Directory of Open Access Journals (Sweden)

    Palanikumar Maniam

    2011-06-01

    Full Text Available Hydrothermal reaction involving zinc nitrate hexahydrate, trisodium benzene-1,3,5-tricarboxylate (Na3BTC and 2-methylimidazole (2-MeImH yielded the title compound, [Zn2(C9H3O6(C4H5N2(C4H6N23]. In this mixed-ligand metal-organic compound, Zn2+ ions are coordinated by N atoms from 2-MeImH molecules and (2-MeIm− ions, as well as by O atoms from (BTC3− ions. This results in two different distorted tetrahedra, viz. ZnN3O and ZnN2O2. These tetrahedra are interconnected via (BTC3− ions and N:N′-bridging (2-MeIm− ions, thus forming a layered structure in the bc plane. Hydrogen bonds between the O atoms of carboxylate ions and NH groups of 2-MeImH ligands link the layers into a three-dimensional structure.

  16. Batagayite, CaZn2(Zn,Cu)6(PO4)4(PO3OH)3·12H2O, a new phosphate mineral from Këster tin deposit (Yakutia, Russia): occurrence and crystal structure

    Science.gov (United States)

    Yakovenchuk, Victor N.; Pakhomovsky, Yakov A.; Konopleva, Nataliya G.; Panikorovskii, Taras L.; Bazai, Ayya; Mikhailova, Julia A.; Bocharov, Vladimir N.; Ivanyuk, Gregory Yu.; Krivovichev, Sergey V.

    2017-12-01

    -2.678-2 \\overline {3} \\overline {3} , 16-2.411-044. The crystal structure of batagayite was solved by direct methods and refined to R 1 = 0.069 for 3847 independent reflections with F o > 4σ(F o). It is based upon complex heteropolyhedral [M 8(PO4)4(PO3OH)3(H2O)9]2- layers parallel to the (001) plane. The layer can be considered as consisting of three sublayers, one A and two B. The central A layer has the composition [M 4(PO4)4(H2O)4]4- and consists of the zigzag chains of edge-sharing (MO6) octahedra running parallel to the a axis and linked into layers by sharing peripheral O atoms. The (PO4) tetrahedra are attached above and below the holes created by the linkage of zigzag octahedral chains. The B sublayer consists of chains of (ZnO4) and (PO3OH) tetrahedra. The interlayer space is occupied by the Ca2+ cations and H2O molecules. Batagayite is a secondary low-temperature mineral formed as a result of alteration of primary minerals such as native copper and fluorapatite. On the basis of its structural complexity calculated as 1058.257 bits/cell (taking into account contributions from H atoms), batagayite should be considered as a very complex mineral. The high complexity of batagayite is due to its high hydration state and the modular character of its structure, which contains both octahedral-tetrahedral layers and tetrahedral chains.

  17. Calibration of Mg2SiO4(Tb) thermoluminescent dosimeters for use in determining diagnostic X-ray doses to Adult Health Study participants

    International Nuclear Information System (INIS)

    Kato, Kazuo; Antoku, Shigetoshi; Sawada, Shozo; Russell, W.J.

    1989-11-01

    Characteristics of Mg 2 SiO 4 (Tb) thermoluminescent dosimeters (TLD) were ascertained preparatory to measuring dose from diagnostic X-ray examinations received by Adult Health Study participants. These detectors are small, relatively sensitive to low-dose X rays, and are appropriate for precise dosimetry. Extensive calibration is necessary for precisely determining doses according to their thermoluminescent intensities. Their sensitivities were investigated, by dose according to X-ray tube voltage, and by exposure direction, to obtain directional dependence. Dosimeter sensitivity lessened due to the fading effect and diminution of the planchet. However, these adverse effects can be avoided by storing the dosimeters at least 1.5 hours and by using fresh silver-plated planchets. Thus, the TLDs, for which sensitivities were determined in this study, will be useful in subsequent diagnostic X-ray dosimetry. (author)

  18. Sol-gel synthesis of TiO2-SiO2 photocatalyst for β-naphthol photodegradation

    International Nuclear Information System (INIS)

    Qourzal, S.; Barka, N.; Tamimi, M.; Assabbane, A.; Nounah, A.; Ihlal, A.; Ait-Ichou, Y.

    2009-01-01

    Silica gel supported titanium dioxide particles (TiO 2 -SiO 2 ) prepared by sol-gel method was as photocatalyst in the degradation of β-naphthol in water under UV-illumination. The prepared sample has been characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The supported catalyst had large surface area and good sedimentation ability. The photodegradation rate of β-naphthol under UV-irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The experiments were measured by high performance liquid chromatography (HPLC). The photodegradation rate of β-naphthol using 60% TiO 2 -SiO 2 particles was faster than that using TiO 2 'Degussa P-25', TiO 2 'PC-50' and TiO 2 'Aldrich' as photocatalyst by 2.7, 4 and 7.8 times, respectively. The kinetics of photocatalytic β-naphthol degradation was found to follow a pseudo-first-order rate law. The effect of the TiO 2 loading on the photoactivity of TiO 2 -SiO 2 particles was also discussed. With good photocatalytic activity under UV-irradiation and the ability to be readily separated from the reaction system, this novel kind of catalyst exhibited the potential effective in the treatment of organic pollutants in aqueous systems.

  19. High-throughput multipesticides residue analysis in earthworms by the improvement of purification method: Development and application of magnetic Fe3 O4 -SiO2 nanoparticles based dispersive solid-phase extraction.

    Science.gov (United States)

    Sun, Yuhan; Qi, Peipei; Cang, Tao; Wang, Zhiwei; Wang, Xiangyun; Yang, Xuewei; Wang, Lidong; Xu, Xiahong; Wang, Qiang; Wang, Xinquan; Zhao, Changshan

    2018-06-01

    As a key representative organism, earthworms can directly illustrate the influence of pesticides on environmental organisms in soil ecosystems. The present work aimed to develop a high-throughput multipesticides residue analytical method for earthworms using solid-liquid extraction with acetonitrile as the solvent and magnetic material-based dispersive solid-phase extraction for purification. Magnetic Fe 3 O 4 nanoparticles were modified with a thin silica layer to form Fe 3 O 4 -SiO 2 nanoparticles, which were fully characterized by field-emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffractometry, and vibrating sample magnetometry. The Fe 3 O 4 -SiO 2 nanoparticles were used as the separation media in dispersive solid-phase extraction with primary secondary amine and ZrO 2 as the cleanup adsorbents to eliminate matrix interferences. The amounts of nanoparticles and adsorbents were optimized for the simultaneous determination of 44 pesticides and six metabolites in earthworms by liquid chromatography with tandem mass spectrometry. The method performance was systematically validated with satisfactory results. The limits of quantification were 20 μg/kg for all analytes studied, while the recoveries of the target analytes ranged from 65.1 to 127% with relative standard deviation values lower than 15.0%. The developed method was subsequently utilized to explore the bioaccumulation of bitertanol in earthworms exposed to contaminated soil, verifying its feasibility for real sample analysis. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. ORELA data acquisition system hardware. Vol. 5. SEL 810B/PDP-4/PDP-9 intercomputer link

    International Nuclear Information System (INIS)

    Reynolds, J.W.; Holladay, J.H.

    1977-01-01

    A report is given describing the IOT assignments and programming for the PDP-4 and PDP-9, the ground isolation wiring, the connector pin assignments, a simplified theory of operation for the SEL 810B link interface, a detailed theory of operation for the link interfaces at the PDP-4 and the PDP-9, and the use of the PDP-4 and PDP-9 link interfaces as an input to the SEL 810B Four-Channel Priority Multiplexer

  1. Aluminum-induced dreierketten chain cross-links increase the mechanical properties of nanocrystalline calcium aluminosilicate hydrate

    Science.gov (United States)

    Geng, Guoqing; Myers, Rupert J.; Li, Jiaqi; Maboudian, Roya; Carraro, Carlo; Shapiro, David A.; Monteiro, Paulo J. M.

    2017-03-01

    The incorporation of Al and increased curing temperature promotes the crystallization and cross-linking of calcium (alumino)silicate hydrate (C-(A-)S-H), which is the primary binding phase in most contemporary concrete materials. However, the influence of Al-induced structural changes on the mechanical properties at atomistic scale is not well understood. Herein, synchrotron radiation-based high-pressure X-ray diffraction is used to quantify the influence of dreierketten chain cross-linking on the anisotropic mechanical behavior of C-(A-)S-H. We show that the ab-planar stiffness is independent of dreierketten chain defects, e.g. vacancies in bridging tetrahedra sites and Al for Si substitution. The c-axis of non-cross-linked C-(A-)S-H is more deformable due to the softer interlayer opening but stiffens with decreased spacing and/or increased zeolitic water and Ca2+ of the interlayer. Dreierketten chain cross-links act as ‘columns’ to resist compression, thus increasing the bulk modulus of C-(A-)S-H. We provide the first experimental evidence on the influence of the Al-induced atomistic configurational change on the mechanical properties of C-(A-)S-H. Our work advances the fundamental knowledge of C-(A-)S-H on the lowest level of its hierarchical structure, and thus can impact the way that innovative C-(A-)S-H-based cementitious materials are developed using a ‘bottom-up’ approach.

  2. Synthesis of Fe3O4@SiO2@OSi(CH2)3NHRN(CH2PPh2)2PdCl2 type nanocomposite complexes: Highly efficient and magnetically-recoverable catalysts in vitamin K3 synthesis.

    Science.gov (United States)

    Uruş, Serhan

    2016-12-15

    The synthesis of aminomethylphosphine-metal complexes have opened a new perspective to the catalytic applications of organic compounds. Magnetic Fe3O4 nano-core was synthesized using the closed quartz tube with Teflon cover and microwaved 200°C for 1h with power controlled instrument set to max. 600W. Novel nano-composite supported; Fe3O4@SiO2(CH2)3NHArN(CH2PPh2)2 and Fe3O4@SiO2(CH2)3N(CH2PPh2)2 type bis(diphenylphosphinomethyl)amino ligands and their Pd(II) complexes have been synthesized and characterized with FT-IR, SEM, EDX, TEM, UV-Visible, XRD and TG/DTA techniques. All the complexes were used as heterogeneous catalysts in the oxidation of 2-methyl naphthalene (2MN) to 2-methyl-1, 4-naphthoquinone (vitamin K3, menadione, 2MNQ) in the presence of hydrogen peroxide and acetic acid. Selectivity reached about 55-60% with a conversion of 90-96% using the nano-magnetite supported aminomethylphosphine-Pd(II) complexes. The complexes were very active in three times in the catalytic recycling experiments in five catalytic cycles. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Male homosexuality and maternal immune responsivity to the Y-linked protein NLGN4Y.

    Science.gov (United States)

    Bogaert, Anthony F; Skorska, Malvina N; Wang, Chao; Gabrie, José; MacNeil, Adam J; Hoffarth, Mark R; VanderLaan, Doug P; Zucker, Kenneth J; Blanchard, Ray

    2018-01-09

    We conducted a direct test of an immunological explanation of the finding that gay men have a greater number of older brothers than do heterosexual men. This explanation posits that some mothers develop antibodies against a Y-linked protein important in male brain development, and that this effect becomes increasingly likely with each male gestation, altering brain structures underlying sexual orientation in their later-born sons. Immune assays targeting two Y-linked proteins important in brain development-protocadherin 11 Y-linked (PCDH11Y) and neuroligin 4 Y-linked (NLGN4Y; isoforms 1 and 2)-were developed. Plasma from mothers of sons, about half of whom had a gay son, along with additional controls (women with no sons, men) was analyzed for male protein-specific antibodies. Results indicated women had significantly higher anti-NLGN4Y levels than men. In addition, after statistically controlling for number of pregnancies, mothers of gay sons, particularly those with older brothers, had significantly higher anti-NLGN4Y levels than did the control samples of women, including mothers of heterosexual sons. The results suggest an association between a maternal immune response to NLGN4Y and subsequent sexual orientation in male offspring. Copyright © 2018 the Author(s). Published by PNAS.

  4. Synthesis of TiO2-doped SiO2 composite films and its applications

    Indian Academy of Sciences (India)

    Wintec

    structure of the titanium oxide species in the TiO2-doped SiO2 composite films and the photocatalytic reactiv- ity in order to ... gaku D-max γA diffractometer with graphite mono- chromized ... FT–IR absorption spectra of TiO2-doped SiO2 com-.

  5. Crystal structures of NiSO4·9H2O and NiSO4·8H2O: magnetic properties, stability with respect to morenosite (NiSO4·7H2O), the solid-solution series (Mg x Ni1-x )SO4·9H2O

    Science.gov (United States)

    Fortes, A. D.; Knight, K. S.; Gibbs, A. S.; Wood, I. G.

    2018-02-01

    Since being discovered initially in mixed-cation systems, a method of forming end-member NiSO4·9H2O and NiSO4·8H2O has been found. We have obtained powder diffraction data from protonated analogues (with X-rays) and deuterated analogues (using neutrons) of these compounds over a range of temperatures, allowing us to determine their crystal structures—including all H-atoms—and to characterise the transitions on warming from 220 to 278 K; glass → 9-hydrate → 8-hydrate + ice → 7-hydrate + ice → partial melt (7-hydrate + liquid). NiSO4·8D2O is triclinic, space-group P\\bar {1} , Z = 2, with unit cell parameters at 150 K, a = 6.12463(8) Å, b = 6.8401(1) Å, c = 12.5339(2) Å, α = 92.846(1)°, β = 97.822(1)°, γ = 96.627(1)° and V = 515.58(1) Å3. The structure consists of two symmetry-inequivalent Ni(D2O)6 octahedra on sites of \\bar {1} symmetry. These are directly joined by a water-water H-bond to form chains of octahedra parallel with the c-axis at x = 0. Two interstitial water molecules serve both to bridge the Ni(D2O)6 octahedral chains in the b-c plane and also to connect with the SO4 2- tetrahedral oxyanion. These tetrahedra are linked by the two interstitial water molecules in a reticular motif to form sheets perpendicular to c. NiSO4·9D2O is monoclinic, space-group P21/c, Z = 4, with unit-cell parameters at 150 K, a = 6.69739(6) Å, b = 11.8628(1) Å, c = 14.5667(1) Å, β = 94.9739(8)° and V = 1152.96(1) Å3. The structure is isotypic with the Mg analogue described elsewhere (Fortes et al., Acta Cryst B 73:47‒64, 2017b). It shares the motif of H-bonded octahedral chains with NiSO4·8D2O, although in the enneahydrate these run parallel with the b-axis at x = 0. Three interstitial water molecules bridge the Ni(D2O)6 octahedra to the SO4 2- tetrahedral oxyanion. The tetrahedra sit at x ≈ 0.5 and are linked by two of the three interstitial water molecules in a pentagonal motif to form ribbons parallel with b. A solid-solution series

  6. More accurate definition of liquation dome in Na2O-B2O3-SiO2 system

    International Nuclear Information System (INIS)

    Alekseeva, Z.D.; Mazurin, O.V.; Aver'yanov, V.I.; Galakhov, F.Ya.

    1977-01-01

    The liquation region in the system Na 2 O-B 2 O 3 -SiO 2 was investigated. The liquation temperatures were determined by the boundary of disappearance of opalescence in specimens with pre-induced opalescence. Extrapolation of the concentration dependences of the liquation temperature along sections with a constant SiO 2 content to a point indicates that with a SiO 2 content of 20-40% the liquation boundary in the system B 2 O 3 -SiO 2 hardly lies above 450 deg C

  7. Thermal SiO as a probe of high velocity motions in regions of star formation

    International Nuclear Information System (INIS)

    Downes, D.; Genzel, R.; Hjalmarson, A.; Nyman, L.A.; Roennaeng, B.

    1982-01-01

    New observations of the v = 0, J = = 2→1 line of SiO at 86.8 GHz show a close association of the thermal SiO emission and infrared and maser sources in regions of star formation. In addition to SiO emission with low velocity dispersion (Δν -1 ), we report the first detection of high velocity (''plateau'') emission toward W49 and W51. The low velocity SiO component may come from the core of the molecular cloud which contains the infrared and maser sources. The ''plateau'' may indicate mass clusters. In Orion KL, the positional centroid of the high velocity SiO emission (Vertical BarΔνVertical Bar> or =20 km s -1 ) is near that of the component we identify as the ''18 km s -1 flow''. However, the centriods of the blue- and redshifted wings are displaced from each other by a few arcseconds, to the NW and NE of the position of the 18 km s -1 component. The mass-loss rates of the high velocity flow and the 18 km s -1 flow are similar

  8. SiO maser emission as a density tracer of circumstellar envelopes

    Science.gov (United States)

    Stroh, Michael; Pihlstrom, Ylva; Sjouwerman, Lorant

    2018-06-01

    The circumstellar envelopes (CSEs) of evolved stars offer a method to construct a sample of point-masses along the full Galactic plane, which can be used to test models of the gravitational potential. In the CSEs of red giants, SiO maser emission is frequently observed at 43 and 86 GHz, providing line-of-sight velocities. The Bulge Asymmetries and Dynamical Evolution (BAaDE) project aims to explore the complex structure of the inner Galaxy and Galactic Bulge, by observing 43 GHz SiO at the Very Large Array and 86 GHz SiO at the Atacama Large Millimeter/submillimeter Array, with an expected final sample of about 20,000 line-of-sight velocities and positions. We observed the 43 GHz and 86 GHz transitions near-simultaneously in a subsample of the sources using the Australia Telescope Compact Array and found that on average the 43 GHz v=1 line is 1.3 times stronger than the 86 GHz v=1 line. The presence of a detectable 43 GHz v=3 line alters the statistics, consistent with the SiO masers displaying 43 GHz v=3 emission arising in a denser regime in the circumstellar shell compared to those without. Comparing our results with radiative models implies that the 43 GHz v=3 line is a tracer of density variations caused by stellar pulsations. We will discuss these results in the context of the BAaDE project.

  9. Synthesis of unidirectional structures of SiO2-Ag using Au nanoparticles as nucleation centers

    International Nuclear Information System (INIS)

    Villa S, G.; Mendoza A, D.; Gutierrez W, C.; Perez H, R.

    2008-01-01

    This paper reports a method to synthesize Ag unidirectional structures covered with SiO 2 by sol-gel technique using Au nanoparticles as nucleation centers of the unidirectional structures. In the first phase unidirectional structures of SiO 2 -Ag CI are obtained by sol-gel, using TEOS as a precursor of metallic structures (Ag) and the incorporation of Au nanoparticles as nucleation centers for growth of unidirectional structures. In the second stage, one-way systems are subjected to thermal treatment in H 2 atmosphere for obtain AG 0 particles through mechanisms that diffusion and coalescence of silver to form structures that have a thin cover of SiO 2 . Analysis by scanning electron microscopy, transmission and atomic force microscopy allowed to determine the chemical composition and microstructural properties of unidirectional systems SiO 2 -Ag. (Author)

  10. Positron annihilation spectroscopy of the interface between nanocrystalline Si and SiO2

    International Nuclear Information System (INIS)

    Pi, X.D.; Coleman, P.G.; Harding, R.; Davies, G.; Gwilliam, R.M.; Sealy, B.J.

    2003-01-01

    Positron annihilation spectroscopy has been employed to study changes in the interface region between nanocrystalline Si and SiO 2 , following annealing between 400 deg. C and 900 deg. C in nitrogen or oxygen. With the support of photoluminescence spectroscopy we find that nitrogen and oxygen are trapped in voids at the interface at low temperatures. At temperatures above 700 deg. C both nitrogen and oxygen react with Si nanocrystals, and the resulting volume increase introduces stress in the SiO 2 matrix which is relaxed by the shrinkage of its intrinsic open volume. Oxygen appears to enhance Si diffusion in SiO 2 so that the agglomeration of Si nanocrystals occurs more readily during annealing in oxygen than in nitrogen

  11. Si-O compound formation by oxygen ion implantation into silicon

    International Nuclear Information System (INIS)

    Hensel, E.; Wollschlaeger, K.; Kreissig, U.; Skorupa, W.; Schulze, D.; Finster, J.

    1985-01-01

    High dose oxygen ion implantation into silicon at 30 keV was performed to produce understoichiometric and stoichiometric surface oxide layers of approx. 160 nm thickness. The oxygen depth profile and oxide stoichiometry was determined by RBS and XPS. Si-O compound formation was found by IR spectroscopy and XPS in the unannealed samples as well as after target heating, furnace or flash lamp annealing. As implanted understoichiometric layers consist of random bonding like SiOsub(x) (O 2 after annealing. Unannealed stoichiometric layers are bond strained SiO 2 . The activation energies of demixing and of the annealing of bond strains are determined to 0.19 and 0.13 eV, respectively. The removing of bond strains occurs at temperatures >= 800 C in a time shorter than 1 s. The SiO 2 /Si transition region of unannealed stoichiometric layers consists of SiOsub(x) with an extent of about 10 nm. After annealing this extent diminishes to 0.8 to 1 nm in consequence of oxidation by excess oxygen from the overstoichiometric oxide region. This thickness is comparable with that of thermal oxide. (author)

  12. Synthesis of branched and linear 1,4-linked galactan oligosaccharides

    DEFF Research Database (Denmark)

    Andersen, Mathias C. Franch; Boos, Irene; Kinnaert, Christine

    2018-01-01

    We report the synthesis of linear and branched (1→4)-D-galactans. Four tetra- and one pentasaccharide were accessed by adopting a procedure of regioselective ring opening of a 4,6-O-naphthylidene protecting group followed by glycosylation using phenyl thioglycoside donros. The binding of the linear...... pentasaccharide with galectin-3 is also investigated by determination of a co-crystal structure. The binding of the (1→4)-linked galactan to Gal-3 highlights oligosaccharides of pectic galactan, which is abundant in the human diet, as putative Gal-3 ligands....

  13. Link Investigation of IEEE 802.15.4 Wireless Sensor Networks in Forests.

    Science.gov (United States)

    Ding, Xingjian; Sun, Guodong; Yang, Gaoxiang; Shang, Xinna

    2016-06-27

    Wireless sensor networks are expected to automatically monitor the ecological evolution and wildlife habits in forests. Low-power links (transceivers) are often adopted in wireless sensor network applications, in order to save the precious sensor energy and then achieve long-term, unattended monitoring. Recent research has presented some performance characteristics of such low-power wireless links under laboratory or outdoor scenarios with less obstacles, and they have found that low-power wireless links are unreliable and prone to be affected by the target environment. However, there is still less understanding about how well the low-power wireless link performs in real-world forests and to what extent the complex in-forest surrounding environments affect the link performances. In this paper, we empirically evaluate the low-power links of wireless sensors in three typical different forest environments. Our experiment investigates the performance of the link layer compatible with the IEEE 802.15.4 standard and analyzes the variation patterns of the packet reception ratio (PRR), the received signal strength indicator (RSSI) and the link quality indicator (LQI) under diverse experimental settings. Some observations of this study are inconsistent with or even contradict prior results that are achieved in open fields or relatively clean environments and thus, provide new insights both into effectively evaluating the low-power wireless links and into efficiently deploying wireless sensor network systems in forest environments.

  14. Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

    Science.gov (United States)

    Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

    2015-12-30

    This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Luminescence properties of Ca2 Ga2 SiO7 :RE phosphors for UV white-light-emitting diodes.

    Science.gov (United States)

    Jiao, Mengmeng; Lv, Wenzhen; Lü, Wei; Zhao, Qi; Shao, Baiqi; You, Hongpeng

    2015-03-16

    A series of Eu(2+) -, Ce(3+) -, and Tb(3+) -doped Ca2 Ga2 SiO7 phosphors is synthesized by using a high-temperature solid-state reaction. The powder X-ray diffraction and structure refinement data indicate that our prepared phosphors are single phased and the phosphor crystalizes in a tetrahedral system with the ${P\\bar 42m}$ (113) space group. The Eu(2+) - and Ce(3+) -doped phosphors both have broad excitation bands, which match well with the UV light-emitting diodes chips. Under irradiation of λ=350 nm, Ca2 Ga2 SiO7 :Eu(2+) and Ca2 Ga2 SiO7 :Ce(3+) , Li(+) have green and blue emissions, respectively. Luminescence of Ca2 Ga2 SiO7 :Tb(3+) , Li(+) phosphor varies with the different Tb(3+) contents. The thermal stability and energy-migration mechanism of Ca2 Ga2 SiO7 :Eu(2+) are also studied. The investigation results indicate that the prepared Ca2 Ga2 SiO7 :Eu(2+) and Ca2 Ga2 SiO7 :Ce(3+) , Li(+) samples show potential as green and blue phosphors, respectively, for UV-excited white-light-emitting diodes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Unique edge-sharing sulfate-transition metal coordination in Na2M(SO4)2 (M=Ni and Co)

    International Nuclear Information System (INIS)

    Fry, Allyson M.; Sweeney, Owen T.; Adam Phelan, W.; Drichko, Natalia; Siegler, Maxime A.; McQueen, Tyrel M.

    2015-01-01

    Two compounds, Na 2 Ni(SO 4 ) 2 and Na 2 Co(SO 4 ) 2 , were synthesized and their structure and properties were characterized. They adopt a structure that contains a bidentate coordination of sulfate to the transition metal center, which was determined via single crystal X-ray diffraction combined with model refinements to both laboratory X-ray and time-of-flight neutron powder diffraction data. The compounds were both found to crystallize in the C2/c space group with Z=24 and a unit cell of a=23.3461(3) Å, b=10.3004(1) Å, c=17.4115(2) Å, β=98.8659(9)°, and V=4136.99(8) Å 3 for the cobalt analog and a=23.2253(1) Å, b=10.26155(6) Å, c=17.3353(1) Å, β=99.0376(5)°, and V=4080.20(5) Å 3 for the nickel analog. Magnetization measurements show that the transition metal centers have negligible interactions with neighboring sites. Infrared and Raman spectroscopies were used to further probe the unique sulfate-transition metal coordination, and confirm the bidentate binding motif. The resulting pseudo-trigonal bipyramidal coordination produces vivid violet, Na 2 Co(SO 4 ) 2 , and yellow, Na 2 Ni(SO 4 ) 2 , colors that were probed by diffuse reflectance. - Graphical abstract: Two blue distorted transition metal octahedra (oxygen in red) bridged by two sulfate tetrahedra are shown here. Each bridging sulfate tetrahedra shares an edge with one octahedron and a corner with the other. All of the remaining corners of the octahedra are corner sharing with four tetrahedra forming a polyhedral network. - Highlights: • Structure of Na2Ni(SO4)2 and Na2Co(SO4)2 is determined. • Unique sulfate-transition metal binding observed in the new structure. • Combined diffraction and spectroscopic techniques were used. • Magnetization measurements show negligible interactions between sites

  17. Redetermination of eveite, Mn2AsO4(OH, based on single-crystal X-ray diffraction data

    Directory of Open Access Journals (Sweden)

    Yongbo W. Yang

    2011-12-01

    Full Text Available The crystal structure of eveite, ideally Mn2(AsO4(OH [dimanganese(II arsenate(V hydroxide], was refined from a single crystal selected from a co-type sample from Långban, Filipstad, Varmland, Sweden. Eveite, dimorphic with sarkinite, is structurally analogous with the important rock-forming mineral andalusite, Al2OSiO4, and belongs to the libethenite group. Its structure consists of chains of edge-sharing distorted [MnO4(OH2] octahedra (..2 symmetry extending parallel to [001]. These chains are cross-linked by isolated AsO4 tetrahedra (..m symmetry through corner-sharing, forming channels in which dimers of edge-sharing [MnO4(OH] trigonal bipyramids (..m symmetry are located. In contrast to the previous refinement from Weissenberg photographic data [Moore & Smyth (1968. Am. Mineral. 53, 1841–1845], all non-H atoms were refined with anisotropic displacement parameters and the H atom was located. The distance of the donor and acceptor O atoms involved in hydrogen bonding is in agreement with Raman spectroscopic data. Examination of the Raman spectra for arsenate minerals in the libethenite group reveals that the position of the peak originating from the O—H stretching vibration shifts to lower wavenumbers from eveite, to adamite, zincolivenite, and olivenite.

  18. SiO2 coating of silver nanoparticles by photoinduced chemical vapor deposition

    International Nuclear Information System (INIS)

    Boies, Adam M; Girshick, Steven L; Roberts, Jeffrey T; Zhang Bin; Nakamura, Toshitaka; Mochizuki, Amane

    2009-01-01

    Gas-phase silver nanoparticles were coated with silicon dioxide (SiO 2 ) by photoinduced chemical vapor deposition (photo-CVD). Silver nanoparticles, produced by inert gas condensation, and a SiO 2 precursor, tetraethylorthosilicate (TEOS), were exposed to vacuum ultraviolet (VUV) radiation at atmospheric pressure and varying temperatures. The VUV photons dissociate the TEOS precursor, initiating a chemical reaction that forms SiO 2 coatings on the particle surfaces. Coating thicknesses were measured for a variety of operation parameters using tandem differential mobility analysis and transmission electron microscopy. The chemical composition of the particle coatings was analyzed using energy dispersive x-ray spectrometry and Fourier transform infrared spectroscopy. The highest purity films were produced at 300-400 0 C with low flow rates of additional oxygen. The photo-CVD coating technique was shown to effectively coat nanoparticles and limit core particle agglomeration at concentrations up to 10 7 particles cm -3 .

  19. The Effect of SiO2 Shell on the Suppression of Photocatalytic Activity of TiO2 and ZnO Nanoparticles

    International Nuclear Information System (INIS)

    Lee, Min Hee; Lee, Choon Soo; Patil, Umakant Mahadev; Kochuveedu, Saji Thomas

    2012-01-01

    In this study, we investigate the potential use of TiO 2 SiO 2 and ZnO SiO 2 core/shell nanoparticles (NPs) as effective UV shielding agent. In the typical synthesis, SiO 2 was coated over different types of TiO 2 (anatase and rutile) and ZnO by sol-gel method. The synthesized TiO 2 SiO 2 and ZnO SiO 2 Nps were characterized by UV-Vis, XRD, Sem and TEM. The UV-vis absorbance and transmittance spectra of core shell NPs showed an efficient blocking effect in the UV region and more than 90% transmittance in the visible region. XRD and SAED studies confirmed the formation of amorphous SiO 2 coated over the TiO 2 and ZnO NPs. The FESEM and TEM images shows that coating of SiO 2 over the surface of anatase, rutile TiO 2 and ZnO NPs resulted in the increase in particle size by ∼30 nm. In order to study the UV light shielding capability of the samples, photocatalytic degradation of methylene blue dye on TiO 2 SiO 2 and ZnO SiO 2 NPs was performed. Photocatalytic activity for both types of TiO 2 NPs was partially suppressed. In comparison, the photocatalytic activity of ZnO almost vanished after the SiO 2 coating

  20. A new cataluminescence gas sensor based on SiO2 nanotubes fabricated using carbon nanotube templates.

    Science.gov (United States)

    Wang, Yali; Cao, Xiaoan; Li, Jinwen; Chen, Nan

    2011-05-15

    In the present work, two morphologies of SiO(2) nanomaterials (SiO(2) nanotubes and nanoparticles) have been successfully synthesized in supercritical fluids (SCFs). The cataluminescence (CTL) features of the two SiO(2) nanomaterials to some common harmful gases were compared, and the results showed that SiO(2) nanotubes had better CTL sensing characteristic to some common harmful gases. The SiO(2) nanotubes not only had uniform size and shape with a high specific surface area, but also exhibited superior sensitivity and selectivity to ethyl acetate vapor. Using the SiO(2) nanotubes as sensing material, a CTL sensor for ethyl acetate vapor was developed. The proposed sensor showed high sensitivity and specificity to ethyl acetate at optimal temperature of 293°C, a wavelength of 425 nm and a flow rate of 345 mL/min. With a detection limit of 0.85 ppm, the linear range of CTL intensity versus concentrations of ethyl acetate vapor was 2.0-2000 ppm. None or only very low levels of interference were observed while the foreign substances such as acetone, acetaldehyde, acetic acid, formaldehyde, ammonia, ethanol, benzene and methanol were passing through the sensor. This method allows rapid determination of gaseous ethyl acetate at workshop. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. Synthesis, structural characterization and dielectric properties of Nb doped BaTiO3/SiO2 core–shell heterostructure

    International Nuclear Information System (INIS)

    Cernea, M.; Vasile, B.S.; Boni, A.; Iuga, A.

    2014-01-01

    Highlights: • Optimal parameters for preparation by sol–gel of core–shell (BT-Nb 0.005 )/SiO 2 are presented in this paper. • Single crystalline BT-Nb 0.005 /SiO 2 core–shell composite with ∼34 nm shell thick was prepared. • The core–shell ceramic exhibits good dielectric properties and ferroelectric characteristics. -- Abstract: Perovskite complex ceramic oxides, BaTiO 3 doped with 0.5 mol%Nb 2 O 5 and then nanocoated with SiO 2 (abbreviated as BT-Nb 0.005 /SiO 2 ) was successful prepared using conventional sol–gel processing. Phase composition, particle morphology, structure, and electric properties of BT-Nb 0.005 core and BT-Nb 0.005 /SiO 2 core–shell were examined and compared, using X-ray diffraction, transmission electron microscopy and, dielectric and ferroelectric measurements. Core–shell composite with well-defined perovskite tetragonal phase of BaTiO 3 was achieved. Furthermore, single crystalline BT-Nb 0.005 /SiO 2 core–nanoshell heterostructure with ∼34 nm shell thick was prepared, which is a novelty in ferroelectrics field. The ferroelectric quality of BT-Nb 0.005 has suffered an alteration when the (BT-Nb 0.005 )/SiO 2 core–shell heterostructure was realized. One-dimensional BT-Nb 0.005 /SiO 2 core–shell heterostructure exhibits an improvement of dielectric losses and a decrease of dielectric constant, compared to uncoated BT-Nb 0.005 . The (BT-Nb 0.005 )/SiO 2 core–shell material could be interesting for application in the composite capacitors

  2. Three new chalcohalides, Ba4Ge2PbS8Br2, Ba4Ge2PbSe8Br2 and Ba4Ge2SnS8Br2: Syntheses, crystal structures, band gaps, and electronic structures

    International Nuclear Information System (INIS)

    Lin, Zuohong; Feng, Kai; Tu, Heng; Kang, Lei; Lin, Zheshuai; Yao, Jiyong; Wu, Yicheng

    2014-01-01

    Highlights: • Three new chalcohalides: Ba 4 Ge 2 PbS 8 Br 2 , Ba 4 Ge 2 PbSe 8 Br 2 and Ba 4 Ge 2 SnS 8 Br 2 have been synthesized. • The MQ 5 Br octahedra and GeQ 4 tetrahedra form a three-dimensional framework with Ba 2+ in the channels. • Band Gaps and electronic structures of the three compounds were studied. - Abstract: Single crystals of three new chalcohalides: Ba 4 Ge 2 PbS 8 Br 2 , Ba 4 Ge 2 PbSe 8 Br 2 and Ba 4 Ge 2 SnS 8 Br 2 have been synthesized for the first time. These isostructural compounds crystallize in the orthorhombic space group Pnma. In the structure, the tetra-valent Ge atom is tetrahedrally coordinated with four Q (Q = S, Se) atoms, while the bi-valent M atom (M = Pb, Sn) is coordinated with an obviously distorted octahedron of five Q (Q = S, Se) atoms and one Br atom, showing the stereochemical activity of the ns 2 lone pair electron. The MQ 5 Br (M = Sn, Pb; Q = S, Se) distorted octahedra and the GeQ 4 (Q = S, Se) tetrahedra are connected to each other to form a three-dimensional framework with channels occupied by Ba 2+ cations. Based on UV–vis–NIR spectroscopy measurements and the electronic structure calculations, Ba 4 Ge 2 PbS 8 Br 2 , Ba 4 Ge 2 PbSe 8 Br 2 and Ba 4 Ge 2 SnS 8 Br 2 have indirect band gaps of 2.054, 1.952, and 2.066 eV respectively, which are mainly determined by the orbitals from the Ge, M and Q atoms (M = Pb, Sn; Q = S, Se)

  3. Improved biodegradation of synthetic azo dye by horseradish peroxidase cross-linked on nano-composite support.

    Science.gov (United States)

    Sun, Huaiyan; Jin, Xinyu; Long, Nengbing; Zhang, Ruifeng

    2017-02-01

    A ZnO nanowires/macroporous SiO 2 composite was used as support to immobilize horseradish peroxidase (HRP) by in-situ cross-linking method. Using diethylene glycol diglycidyl ether (DDE) as a long-chained cross-linker, it was adsorbed on the surface of ZnO nanowires before reaction with HRPs, the resulted composite was quite different from the traditional cross-linking enzyme aggregates (CLEAs) on both structure and catalytic performance. The immobilized HRP showed high activity in the decolorization of azo dyes. The effect of various conditions such as the loading amount of HRP, solution pH, temperature, contact time and concentration of dye were optimized on the decolorization. The decolorization percentage of Acid Blue 113 and Acid black 10 BX reached as high as 95.4% and 90.3%, respectively. The immobilized HRP gave the highest decolorization rate under dye concentration as 50mg/L and reaction time of 35min. The immobilized HRP exhibited much better resistance to temperature and pH inactivation than free HRP. The storage stability and reusability were greatly improved through the immobilization, from the decolorization of Acid blue 113 it was found that 80.4% of initial efficiency retained after incubation at 4°C for 60 days, and that 79.4% of decolorization efficiency retained after 12 cycles reuse. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Bulk properties and near-critical behaviour of SiO2 fluid

    Science.gov (United States)

    Green, Eleanor C. R.; Artacho, Emilio; Connolly, James A. D.

    2018-06-01

    Rocky planets and satellites form through impact and accretion processes that often involve silicate fluids at extreme temperatures. First-principles molecular dynamics (FPMD) simulations have been used to investigate the bulk thermodynamic properties of SiO2 fluid at high temperatures (4000-6000 K) and low densities (500-2240 kg m-3), conditions which are relevant to protoplanetary disc condensation. Liquid SiO2 is highly networked at the upper end of this density range, but depolymerises with increasing temperature and volume, in a process characterised by the formation of oxygen-oxygen (Odbnd O) pairs. The onset of vaporisation is closely associated with the depolymerisation process, and is likely to be non-stoichiometric at high temperature, initiated via the exsolution of O2 molecules to leave a Si-enriched fluid. By 6000 K the simulated fluid is supercritical. A large anomaly in the constant-volume heat capacity occurs near the critical temperature. We present tabulated thermodynamic properties for silica fluid that reconcile observations from FPMD simulations with current knowledge of the SiO2 melting curve and experimental Hugoniot curves.

  5. Ge nanocrystals embedded in ultrathin Si3N4 multilayers with SiO2 barriers

    Science.gov (United States)

    Bahariqushchi, R.; Gundogdu, Sinan; Aydinli, A.

    2017-04-01

    Multilayers of germanium nanocrystals (NCs) embedded in thin films of silicon nitride matrix separated with SiO2 barriers have been fabricated using plasma enhanced chemical vapor deposition (PECVD). SiGeN/SiO2 alternating bilayers have been grown on quartz and Si substrates followed by post annealing in Ar ambient from 600 to 900 °C. High resolution transmission electron microscopy (HRTEM) as well as Raman spectroscopy show good crystallinity of Ge confined to SiGeN layers in samples annealed at 900 °C. Strong compressive stress for SiGeN/SiO2 structures were observed through Raman spectroscopy. Size, as well as NC-NC distance were controlled along the growth direction for multilayer samples by varying the thickness of bilayers. Visible photoluminescence (PL) at 2.3 and 3.1 eV with NC size dependent intensity is observed and possible origin of PL is discussed.

  6. Investigation of luminescence properties in SiO2: Tb, Yb upconversion inverse opal

    International Nuclear Information System (INIS)

    Yang Zhengwen; Yan Dong; Song Zhiguo; Zhou Dacheng; Yu Xue; Yang Yong; Yin Zhaoyi; Yan Lei; Wang Rongfei; Wu Hangjun; Qiu Jianbei

    2012-01-01

    The SiO 2 : Tb, Yb inverse opals with photonic band gap at 465 or 543 nm were prepared, and an effect of photonic band gap on upconversion spontaneous emission from Tb 3+ was investigated. The results show that the photonic band gap has a significant influence on the upconversion emission of the SiO 2 : Tb, Yb inverse opals. The upconversion luminescence of the Tb 3+ ions is suppressed in the inverse opal compared with the luminescence of that of the reference sample. - Highlights: ► Upconversion emission from Tb 3+ was observed in the SiO 2 : Tb, Yb inverse opal. ► UC emission of Tb 3+ was modulated by controlling the structure of inverse opal. ► UC emission of Tb 3+ was depressed in the inverse opal.

  7. Fabrication of 3D SiO x structures using patterned PMMA sacrificial layer

    Science.gov (United States)

    Li, Zhiqin; Xiang, Quan; Zheng, Mengjie; Bi, Kaixi; Chen, Yiqin; Chen, Keqiu; Duan, Huigao

    2018-02-01

    Three-dimensional (3D) nanofabrication based on electron-beam lithography (EBL) has drawn wide attention for various applications with its high patterning resolution and design flexibility. In this work, we present a bilayer EBL process to obtain 3D freestanding SiO x structures via the release of the bottom sacrificial layer. This new kind of bilayer process enables us to define various 3D freestanding SiO x structures with high resolution and low edge roughness. As a proof of concept for applications, metal-coated freestanding SiO x microplates with an underlying air gap were fabricated to form asymmetric Fabry-Perot resonators, which can be utilized for colorimetric refractive index sensing and thus also have application potential for biochemical detection, anti-counterfeiting and smart active nano-optical devices.

  8. Low-velocity Shocks Traced by Extended SiO Emission along the W43 Ridges: Witnessing the Formation of Young Massive Clusters

    Science.gov (United States)

    Nguyen-Lu'o'ng, Q.; Motte, F.; Carlhoff, P.; Louvet, F.; Lesaffre, P.; Schilke, P.; Hill, T.; Hennemann, M.; Gusdorf, A.; Didelon, P.; Schneider, N.; Bontemps, S.; Duarte-Cabral, A.; Menten, K. M.; Martin, P. G.; Wyrowski, F.; Bendo, G.; Roussel, H.; Bernard, J.-P.; Bronfman, L.; Henning, T.; Kramer, C.; Heitsch, F.

    2013-10-01

    The formation of high-mass stars is tightly linked to that of their parental clouds. Here, we focus on the high-density parts of W43, a molecular cloud undergoing an efficient event of star formation. Using a column density image derived from Herschel continuum maps, we identify two high-density filamentary clouds, called the W43-MM1 and W43-MM2 ridges. Both have gas masses of 2.1 × 104 M ⊙ and 3.5 × 104 M ⊙ above >10^{23}\\, {{cm}^{-2}} and within areas of ~6 and ~14 pc2, respectively. The W43-MM1 and W43-MM2 ridges are structures that are coherent in velocity and gravitationally bound, despite their large velocity dispersion measured by the N2H+ (1-0) lines of the W43-HERO IRAM large program. Another intriguing result is that these ridges harbor widespread (~10 pc2) bright SiO (2-1) emission, which we interpret to be the result of low-velocity shocks (models to demonstrate that a small percentage (10%) of Si atoms in low-velocity shocks, observed initially in gas phase or in grain mantles, can explain the observed SiO column density in the W43 ridges. The spatial and velocity overlaps between the ridges of high-density gas and the shocked SiO gas suggest that ridges could be forming via colliding flows driven by gravity and accompanied by low-velocity shocks. This mechanism may be the initial conditions for the formation of young massive clusters.

  9. Tunable graphene doping by modulating the nanopore geometry on a SiO2/Si substrate

    KAUST Repository

    Lim, Namsoo; Yoo, Tae Jin; Kim, Jin Tae; Pak, Yusin; Kumaresan, Yogeenth; Kim, Hyeonghun; Kim, Woochul; Lee, Byoung Hun; Jung, Gun Young

    2018-01-01

    A tunable graphene doping method utilizing a SiO2/Si substrate with nanopores (NP) was introduced. Laser interference lithography (LIL) using a He–Cd laser (λ = 325 nm) was used to prepare pore size- and pitch-controllable NP SiO2/Si substrates

  10. Synthesis and effect of copper incorporation on the thermoluminescence and structural properties of SiO2 particles

    International Nuclear Information System (INIS)

    Burruel I, S. E.; Cruz V, C.; Salas J, Ch. J.; Bernal, R.; Garcia H, A. R.; Castano, V. M.

    2015-10-01

    Full text: In this work, we evaluated the effect of Cu-dopant concentration in SiO 2 particles on structural and thermoluminescence (Tl) properties, prepared by the sol-gel technique. Tl studies in silica samples containing Cu show an important enhancement of their Tl response when compared with pure silica samples. In the copper doped silica a prominent Tl peak is observed, the glow curve was observed between 70 and 450 degrees C after exposure to beta irradiation. The maximum temperature of the glow peak centered at around 140 degrees C shifts to higher values and the intensity enhancement with increasing Cu content, this glow curve is surely composed of several overlapped individual Tl peaks. Also, the particle size is affected by the concentration of Cu dopant. In the case SiO 2 , only is observed a glow peak centered to 95 degrees C, which is interesting for non-Tl dosimetry of ionizing radiation, which is based in detecting the afterglow response following exposure to radiation. The dose response of SiO 2 :Cu showed a linear behaviour in the interval studied with no saturation evidence until 6.4 kGy, which makes this material suitable and promising for medical, industrial and also space dosimetry applications. (Author)

  11. New process of preparation, X-ray characterisation, structure and vibrational studies of a solid solution LiTiOAs 1-xP xO 4 (0⩽ x⩽1)

    Science.gov (United States)

    Chakir, M.; El Jazouli, A.; Chaminade, J. P.; Bouree, F.; de Waal, D.

    2006-01-01

    LiTiOAs 1-xP xO 4 (0⩽ x⩽1) compounds have been prepared using solutions of Li, Ti, As and P elements as starting products. Selected compositions have been investigated by powder X-ray or neutrons diffraction analysis, Raman and infrared spectroscopy. The structure of LiTiOAs 1-xP xO 4 ( x=0, 0.5 and 1) samples determined by Rietveld analysis is orthorhombic with Pnma space group. It is formed by a 3D network of TiO 6 octahedra and XO 4 ( X=As 1-xP x) tetrahedra where octahedral cavities are occupied by lithium atoms. TiO 6 octahedra are linked together by corners and form infinite chains along a-axis. Ti atoms are displaced from the centre of octahedral units in alternating short (1.700-1.709 Å) and long (2.301-2.275 Å) Ti-O bonds. Raman and infrared studies confirm the existence of Ti-O-Ti chains. Thermal stability of LiTiOAsO 4 has been reported.

  12. SiO2 Nanopillars on Microscale Roughened Surface of GaN-Based Light-Emitting Diodes by SILAR-Based Method

    Directory of Open Access Journals (Sweden)

    X. F. Zeng

    2013-01-01

    Full Text Available We reported the SiO2 nanopillars on microscale roughened surface on GaN-based LED to enhance light-extraction efficiency. ZnO nanoparticles were deposited on SiO2 as an etching mask before ICP etching SiO2 by successive ionic layer adsorption and reaction method (SILAR, and the different heights of SiO2 nanopillars on microroughened ITO/GaN were obtained after etching. Compared to a regular (flat surface GaN-based LED, the light output power for a LED with microroughening was increased by 33%. Furthermore, the proposed LEDs with SiO2 nanopillars on microroughened surface show the enhancement in light output power by 42.7%–49.1% at 20 mA. The increase in light output power is mostly attributed to reduction in Fresnel reflection by rough surface. The height of SiO2 nanopillars was increasing cause resulting in more rough on the microscale surface of GaN-based LEDs.

  13. Analysis by the reductive-cleavage method of linkage positions in a polysaccharide containing 4-linked D-glucopyranosyluronic residues.

    Science.gov (United States)

    Vodonik, S A; Gray, G R

    1988-04-01

    The fate of 4-linked D-glucopyranosyluronic residues under reductive-cleavage conditions was investigated by using the Klebsiella aerogenes type 54 strain A3 capsular polysaccharide. Treatment of the fully methylated polysaccharide with triethylsilane and trimethylsilyl trifluoromethanesulfonate in dichloromethane, followed by in situ acetylation, yielded 1,5-anhydro-2,3,4,6-tetra-O-methyl-D-glucitol, 3,4-di-O-acetyl-1,5-anhydro-2,6-di-O-methyl-D-glucitol, and 3-O-acetyl-1,5-anhydro-2,4-di-O-methyl-L-fucitol, as expected, but the expected product of reductive cleavage of the 4-linked D-glucopyranosyluronic residue, namely, methyl 3-O-acetyl-2,6-anhydro-4,5-di-O-methyl-L-gulonate, was not observed. Instead, methyl 2-O-acetyl-3,6-anhydro-4,5-di-O-methyl-L-gulonate (6) was identified as the sole product of reductive cleavage of the 4-linked D-glucopyranosyluronic residue. That compound 6 arose as a result of rearrangement during reductive cleavage rather than by reductive cleavage of a 5-linked D-glucofuranosyluronic residue, was established by reductive cleavage of the fully methylated polysaccharide following reduction of its ester groups with either lithium aluminum hydride or lithium aluminum deuteride. The products of the latter reductive cleavage were the same as before, except for the absence of 6 and the presence of 4,6-di-O-acetyl-1,5-anhydro-2,3-di-O-methyl-D-glucitol, or its 6,6-dideuterio isomer. Although the reductive-cleavage technique is suitable for the direct analysis of polysaccharides containing 4-linked D-glucopyranosyluronic residues, it does not establish whether the uronic residue is a 4-linked pyranoside or a 5-linked furanoside. The expected product is, however, derived from the 4-linked D-glucopyranosyluronic residue after sequential methylation, reduction of its ester group and reductive cleavage.

  14. Substitution of indium for chromium in TlIn5−xCrxSe8: crystal structure of TlIn4.811(5Cr0.189(5Se8

    Directory of Open Access Journals (Sweden)

    Robin Lefèvre

    2017-04-01

    Full Text Available The new thallium penta(indium/chromium octaselenide, TlIn4.811(5Cr0.189(5Se8, has been synthesized by solid-state reaction. It crystallizes isotypically with TlIn5Se8 in the space group C2/m. Although the two Tl positions are disordered and only partially occupied, no Tl deficiency was observed. The insertion of chromium in the structure has been confirmed by EDS analysis. Chromium substitutes indium exclusively at one of three In sites, viz. at one of the positions with site symmetry 2/m (Wyckoff position 2a. In the crystal structure, edge-sharing InSe6 octahedra, and (In,CrSe6 octahedra and InSe4 tetrahedra make up two types of columns that are linked into a framework in which two different types of channels parallel to [010] are present. The Tl atoms are located in the larger of the channels, whereas the other, smaller channel remains unoccupied.

  15. Algorithm of dynamic stabilization system for a car 4x4 with a link rear axle

    Directory of Open Access Journals (Sweden)

    M. M. Jileikin

    2014-01-01

    Full Text Available The slow development of active safety systems of the automobile all-wheel drive vehicles is the cause of lack of researches in the field of power distribution under the specific conditions of movement. The purpose of work is to develop methods to control a curvilinear motion of 4x4 cars with a link to the rear axle that provides the increase in directional and trajectory stability of the car. The paper analyses the known methods to increase wheeled vehicles movement stability. It also offers a method for power flow redistribution in the transmission of the car 4x4 with a link to the rear axle, providing the increase in directional and trajectory stability of the car.To study the performance and effectiveness of the proposed method a mathematical model of the moving car 4x4 with a link to the rear axle is developed. Simulation methods allowed us to establish the following:1. for car 4x4 with redistribution of torque between the driving axles in the range of 100:0 - 50:50 and with redistribution of torque between the wheels of the rear axle in the range of 0:100 the most effective are the stabilization algorithms used in combination “Lowing power consumption of the engine +Creation of stabilizing the moment due to the redistribution of torque on different wheels", providing the increase in directional and trajectory stability by 12...93%;2. for car 4x4 with redistribution of torque between the driving axles in the range 100:0 - 0:100 and with redistribution of torque between the wheels of the rear axle in the range of 0:100 the best option is a combination of algorithms "Lowing power consumption of the engine + Creation of stabilizing moment due to redistribution of torques on different wheels", providing the increase in directional and trajectory stability by 27...93%.A comparative analysis of algorithms efficiency of dynamic stabilization system operation for two-axle wheeled vehicles depending on the torque redistribution between the driving

  16. Core-shelled mesoporous CoFe2O4-SiO2 material with good adsorption and high-temperature magnetic recycling capabilities

    Science.gov (United States)

    Li, Zhi'ang; Wang, Jianlin; Liu, Min; Chen, Tong; Chen, Jifang; Ge, Wen; Fu, Zhengping; Peng, Ranran; Zhai, Xiaofang; Lu, Yalin

    2018-04-01

    Residues of organic dye in industrial effluents cause severe water system pollution. Although several methods, such as biodegradation and activated carbon adsorption, are available for treating these effluents before their discharge into waterbodies, secondary pollution by adsorbents and degrading products remains an issue. Therefore, new materials should be identified to solve this problem. In this work, CoFe2O4-SiO2 core-shell structures were synthesized using an improved Stöber method by coating mesoporous silica onto CoFe2O4 nanoparticles. The specific surface areas of the synthesized particles range from 30 m2/g to 150 m2/g and vary according to the dosage amount of tetraethoxysilane. Such core-shelled nanoparticles have the following advantages for treating industrial effluents mixed with dye: good adsorption capability, above-room-temperature magnetic recycling capability, and heat-enduring stability. Through adsorption of methylene blue, a typical dyeing material, the core-shell-structured particles show a good adsorption capability of approximately 33 mg/L. The particles are easily and completely collected by magnets, which is possible due to the magnetic property of core CoFe2O4. Heat treatment can burn out the adsorbed dyes and good adsorption performance is sustained even after several heat-treating loops. This property overcomes the common problem of particles with Fe3O4 as a core, by which Fe3O4 is oxidized to nonmagnetic α-Fe2O3 at the burning temperature. We also designed a miniature of effluent-treating pipeline, which demonstrates the potential of the application.

  17. Photoluminescence of Eu2+-doped CaMgSi2xO6+2x (1.00≤x≤1.20) phosphors in UV-VUV region

    International Nuclear Information System (INIS)

    Zhang Zhiya; Wang Yuhua

    2008-01-01

    Alkaline-earth silicate phosphors CaMgSi 2x O 6+2x :Eu 2+ (1.00≤x≤1.20) were prepared by traditional solid-state reaction. The phosphors showed an intense blue emission centered around 453 nm, with both 254 and 147 nm excitations. The host absorption below 200 nm in the excitation spectra consisted of two bands around 160 and 190 nm. The band around 160 nm was ascertained to be associated with the SiO 4 -tetrahedra and MgO 6 -polyhedra, and that around 190 nm was due to the CaO 8 -polyhedra or some impurities. The incorporation of excess Si of less than 15% would not lead to formation of impurities and the results indicated that an appropriate Si excess could improve the Photoluminescence (PL) intensity in both ultraviolet (UV) and vacuum ultraviolet (VUV) regions

  18. High ink absorption performance of inkjet printing based on SiO2@Al13 core-shell composites

    Science.gov (United States)

    Chen, YiFan; Jiang, Bo; Liu, Li; Du, Yunzhe; Zhang, Tong; Zhao, LiWei; Huang, YuDong

    2018-04-01

    The increasing growth of the inkjet market makes the inkjet printing more necessary. A composite material based on core-shell structure has been developed and applied to prepare inkjet printing layer. In this contribution, the ink printing record layers based on SiO2@Al13 core-shell composite was elaborated. The prepared core-shell composite materials were characterized by X-ray photoelectron spectroscopy (XPS), zeta potential, X-ray diffraction (XRD), scanning electron microscopy (SEM). The results proved the presence of electrostatic adsorption between SiO2 molecules and Al13 molecules with the formation of the well-dispersed system. In addition, based on the adsorption and the liquid permeability analysis, SiO2@Al13 ink printing record layer achieved a relatively high ink uptake (2.5 gmm-1) and permeability (87%), respectively. The smoothness and glossiness of SiO2@Al13 record layers were higher than SiO2 record layers. The core-shell structure facilitated the dispersion of the silica, thereby improved its ink absorption performance and made the clear printed image. Thus, the proposed procedure based on SiO2@Al13 core-shell structure of dye particles could be applied as a promising strategy for inkjet printing.

  19. SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR H{sub 2}O MASER SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jaeheon [Yonsei University Observatory, Seongsan-ro 262, Seodaemun, Seoul 120-749 (Korea, Republic of); Cho, Se-Hyung [Korean VLBI Network Yonsei Radio Astronomy Observatory, Yonsei University, Seongsan-ro 262, Seodaemun, Seoul 120-749 (Korea, Republic of); Kim, Sang Joon, E-mail: jhkim@kasi.re.kr, E-mail: cho@kasi.re.kr, E-mail: sjkim1@khu.ac.kr [Department of Astronomy and Space Science, Kyung Hee University, Seocheon-Dong, Giheung-Gu, Yongin, Gyeonggi-Do 446-701 (Korea, Republic of)

    2013-01-01

    We present the results of simultaneous observations of SiO v = 1, 2, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines toward 152 known stellar H{sub 2}O maser sources using the Yonsei 21 m radio telescope of the Korean VLBI Network from 2009 June to 2011 January. Both SiO and H{sub 2}O masers were detected from 62 sources with a detection rate of 40.8%. The SiO-only maser emission without H{sub 2}O maser detection was detected from 27 sources, while the H{sub 2}O-only maser without SiO maser detection was detected from 22 sources. Therefore, the overall SiO maser emission was detected from 89 sources, resulting in a detection rate of 58.6%. We have identified 70 new detections of the SiO maser emission. For both H{sub 2}O and SiO maser detected sources, the peak and integrated antenna temperatures of SiO masers are stronger than those of H{sub 2}O masers in both Mira variables and OH/IR stars and the relative intensity ratios of H{sub 2}O to SiO masers in OH/IR stars are larger than those in Mira variables. In addition, distributions of 152 observed sources were investigated in the IRAS two-color diagram.

  20. LEACHABILITY OF CHROME FROM MAGNESIA-CHROMITE REFRACTORY BRICKS CORRODED BY Cu/CuO- Na2O.2SiO2 SLAGS

    Directory of Open Access Journals (Sweden)

    David Medved

    2015-06-01

    Full Text Available The interactions of magnesia-chromite refractory brick with Cu-Na2O.2SiO2 and CuO-Na2O.2SiO2 melts are studied and the chemical durability of corrosion products in water is evaluated. The corrosion tests confirm intensive infiltration of the slag melts into the tested refractory bricks and formation of Cr(6+ compounds. The molten copper partially oxidizes during corrosion test by air and penetrates into bricks. Interactions among periclase (MgO and chromite (FeCr2O4 grains with the melt Na2O.2SiO2 and copper oxides makes possible to form several compounds (e.g. Cu2MgO3, CuCrO4, CaCrO4, Na2CrO4, MgCrO4. Just the marked yellow spots, which were observed on the corroded brick surface after 30 days of free storage, suggest hydration of the high-temperature corrosion products. The yellow color of spots points out to chromates as Na2CrO4 and MgCrO4, which are well soluble in water. The leaching of corroded bricks in water (batch leaching test of a ratio of S (solid : W (water = 0.1 taking up to 28 days confirmed the Cr, Na, Mg and Ca ions leach-out. The pH value of solution increased up to 9 during leaching mainly as a consequence of elevated Na+ ion concentration. The Cr ion concentration rises in the solution up to 1 mmol.l-1. The observed moderate decrease of Cr ion concentration in the solution with the length of leaching indicates super-saturation of the solution and precipitation of the products.