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...

Intercalation of Si between MoS2 layers

Directory of Open Access Journals (Sweden)

Rik van Bremen

2017-09-01

Full Text Available We report a combined experimental and theoretical study of the growth of sub-monolayer amounts of silicon (Si on molybdenum disulfide (MoS2. At room temperature and low deposition rates we have found compelling evidence that the deposited Si atoms intercalate between the MoS2 layers. Our evidence relies on several experimental observations: (1 Upon the deposition of Si on pristine MoS2 the morphology of the surface transforms from a smooth surface to a hill-and-valley surface. The lattice constant of the hill-and-valley structure amounts to 3.16 Å, which is exactly the lattice constant of pristine MoS2. (2 The transitions from hills to valleys are not abrupt, as one would expect for epitaxial islands growing on-top of a substrate, but very gradual. (3 I(V scanning tunneling spectroscopy spectra recorded at the hills and valleys reveal no noteworthy differences. (4 Spatial maps of dI/dz reveal that the surface exhibits a uniform work function and a lattice constant of 3.16 Å. (5 X-ray photo-electron spectroscopy measurements reveal that sputtering of the MoS2/Si substrate does not lead to a decrease, but an increase of the relative Si signal. Based on these experimental observations we have to conclude that deposited Si atoms do not reside on the MoS2 surface, but rather intercalate between the MoS2 layers. Our conclusion that Si intercalates upon the deposition on MoS2 is at variance with the interpretation by Chiappe et al. (Adv. Mater. 2014, 26, 2096–2101 that silicon forms a highly strained epitaxial layer on MoS2. Finally, density functional theory calculations indicate that silicene clusters encapsulated by MoS2 are stable.

Surface Chemistry Involved in Epitaxy of Graphene on 3C-SiC(111/Si(111

Directory of Open Access Journals (Sweden)

Abe Shunsuke

2010-01-01

Full Text Available Abstract Surface chemistry involved in the epitaxy of graphene by sublimating Si atoms from the surface of epitaxial 3C-SiC(111 thin films on Si(111 has been studied. The change in the surface composition during graphene epitaxy is monitored by in situ temperature-programmed desorption spectroscopy using deuterium as a probe (D2-TPD and complementarily by ex situ Raman and C1s core-level spectroscopies. The surface of the 3C-SiC(111/Si(111 is Si-terminated before the graphitization, and it becomes C-terminated via the formation of C-rich (6√3 × 6√3R30° reconstruction as the graphitization proceeds, in a similar manner as the epitaxy of graphene on Si-terminated 6H-SiC(0001 proceeds.

Surface acoustic wave devices on AlN/3C–SiC/Si multilayer structures

International Nuclear Information System (INIS)

Lin, Chih-Ming; Lien, Wei-Cheng; Riekkinen, Tommi; Senesky, Debbie G; Pisano, Albert P; Chen, Yung-Yu; Felmetsger, Valery V

2013-01-01

Surface acoustic wave (SAW) propagation characteristics in a multilayer structure including a piezoelectric aluminum nitride (AlN) thin film and an epitaxial cubic silicon carbide (3C–SiC) layer on a silicon (Si) substrate are investigated by theoretical calculation in this work. Alternating current (ac) reactive magnetron sputtering was used to deposit highly c-axis-oriented AlN thin films, showing the full width at half maximum (FWHM) of the rocking curve of 1.36° on epitaxial 3C–SiC layers on Si substrates. In addition, conventional two-port SAW devices were fabricated on the AlN/3C–SiC/Si multilayer structure and SAW propagation properties in the multilayer structure were experimentally investigated. The surface wave in the AlN/3C–SiC/Si multilayer structure exhibits a phase velocity of 5528 m s −1 and an electromechanical coupling coefficient of 0.42%. The results demonstrate the potential of AlN thin films grown on epitaxial 3C–SiC layers to create layered SAW devices with higher phase velocities and larger electromechanical coupling coefficients than SAW devices on an AlN/Si multilayer structure. Moreover, the FWHM values of rocking curves of the AlN thin film and 3C–SiC layer remained constant after annealing for 500 h at 540 °C in air atmosphere. Accordingly, the layered SAW devices based on AlN thin films and 3C–SiC layers are applicable to timing and sensing applications in harsh environments. (paper)

Correlation of the Na2SiO3 to NaOH Ratios and Solid to Liquid Ratios to the Kedah’s Soil Strength

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Nur Hamzah Hazamaah

2016-01-01

Full Text Available Geopolymer was used for the soil stabilization of Kedah’s soil at different ratios of solid to liquid and Na2SiO3 to NaOH in order to achieve the desired compressive strength. The geopolymerization process which produces an aluminosilicate gel was occurred due to the mixing of Kedah’s soil and fly ash with Na2SiO3 and NaOH. Soil stabilization by geopolymer was synthesized by the activation of fly ash and Kedah’s soil with Na2SiO3 and NaOH at different ratios of solid to liquid (1.5, 2.0, 2.5 and 3.0 and Na2SiO3 to NaOH (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 at a specific constant concentration of NaOH solution of 6M. The compressive strength up to 5.12 MPa was obtained at 3.0 of solid to liquid ratio and 2.5 of Na2SiO3 to NaOH ratio in 7 days curing at room temperature.

New compounds bearing [M(S_2O_7)_3]"2"- anions (M = Si, Ge, Sn): Syntheses and characterization of A_2[Si(S_2O_7)_3] (A = Na, K, Rb), A_2[Ge(S_2O_7)_3] (A = Li, Na, K, Rb, Cs), A_2[Sn(S_2O_7)_3] (A = Na, K), and the unique germanate Hg_2[Ge(S_2O_7)_3]Cl_2 with cationic "1_∞[HgCl_2_/_2]"+ chains

International Nuclear Information System (INIS)

Logemann, Christian; Witt, Julia; Wickleder, Mathias S.; Gunzelmann, Daniel; Senker, Juergen

2012-01-01

The reaction of the group 14 tetrachlorides MCl_4 (M = Si, Ge, Sn) with oleum (65 % SO_3) at elevated temperatures led to the unique anionic complexes [M(S_2O_7)_3]"2"- that show the central M atoms in coordination of three chelating S_2O_7"2"- groups. The mean distances M-O within the complexes increase from 175 pm (M = Si) via 186 pm (M = Ge) up to 200 pm (M = Sn). The charge balance for the [M(S_2O_7)_3]"2"- anions is achieved by alkaline metal ions A"+ (A = Li, Na, K, Rb, Cs) which were implemented in the syntheses in form of their sulfates. The size of the A"+ ions, i.e. their coordination requirement causes the crystallographic differences in the crystal structures, while the structure of the complex [M(S_2O_7)_3]"2"- anions remains essentially unaffected. Furthermore, we were able to characterize the unique germanate Hg_2[Ge(S_2O_7)_3]Cl_2 which forms when HgCl_2 is added as a source for the counter cation. The Hg"2"+ and the Cl"- ions form infinite cationic chains according to "1_∞[HgCl_2_/_2]"+ which take care for the charge compensation. For selected examples of the compounds the thermal behavior has been monitored by means of thermal analyses and X-ray powder diffraction. For A being an alkaline metal the decomposition product is a mixture of the sulfates A_2SO_4 and the dioxides MO_2, whereas Hg_2[Ge(S_2O_7)_3]Cl_2 shows a more complicated decomposition. The tris-(disulfato)-silicate Na_2[Si(S_2O_7)_3] has additionally been examined by solid state "2"9Si and "2"3Na NMR spectroscopic measurements. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Pressureless sintering of dense Si3N4 and Si3N4/SiC composites with nitrate additives

International Nuclear Information System (INIS)

Kim, J.Y.; Iseki, Takayoshi; Yano, Toyohiko

1996-01-01

The effect of aluminum and yttrium nitrate additives on the densification of monolithic Si 3 N 4 and a Si 3 N 4 /SiC composite by pressureless sintering was compared with that of oxide additives. The surfaces of Si 3 N 4 particles milled with aluminum and yttrium nitrates, which were added as methanol solutions, were coated with a different layer containing Al and Y from that of Si 3 N 4 particles milled with oxide additives. Monolithic Si 3 N 4 could be sintered to 94% of theoretical density (TD) at 1,500 C with nitrate additives. The sintering temperature was about 100 C lower than the case with oxide additives. After pressureless sintering at 1,750 C for 2 h in N 2 , the bulk density of a Si 3 N 4 /20 wt% SiC composite reached 95% TD with nitrate additives

Quaternary rare-earth sulfides RE{sub 3}M{sub 0.5}GeS{sub 7} (RE=La–Nd, Sm; M=Co, Ni) and Y{sub 3}Pd{sub 0.5}SiS{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Iyer, Abishek K. [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Yin, Wenlong [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Institute of Chemical Materials, China Academy of Engineering Physics, Mianyang 621900 (China); Lee, Emma J. [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada); Lin, Xinsong [Centre for Oil Sands Sustainability, Northern Alberta Institute of Technology, Edmonton, Alberta, Canada T6N 1E5 (Canada); Mar, Arthur, E-mail: arthur.mar@ualberta.ca [Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2 (Canada)

2017-06-15

The two metal-deficient series of quaternary Ge-containing sulfides RE{sub 3}M{sub 0.5}GeS{sub 7} (RE = La–Nd, Sm; M = Co, Ni), as well as the related Si-containing sulfide Y{sub 3}Pd{sub 0.5}SiS{sub 7}, were prepared by reactions of the elements at 1050 °C. Single-crystal X-ray diffraction analysis performed on all compounds confirmed noncentrosymmetric hexagonal structures (space group P6{sub 3}, Z =2) with cell parameters in the ranges of a =10.0–10.3 Å and c =5.7–5.8 Å for RE{sub 3}Co{sub 0.5}GeS{sub 7} and RE{sub 3}Ni{sub 0.5}GeS{sub 7}, or a =9.7891(3) Å and c =5.6840(4) Å for Y{sub 3}Pd{sub 0.5}SiS{sub 7}. They are classified as La{sub 3}Mn{sub 0.5}SiS{sub 7}-type structures, with M atoms centred within octahedra (in contrast to La{sub 3}CuSiS{sub 7}-type structures in which M atoms occupy trigonal planar sites) and Ge atoms centred within tetrahedra, both types of polyhedra being arranged in one-dimensional stacks aligned along the c-direction. Charge balance requirements dictate half-occupancy of the M sites. However, bond valence sum arguments indicated that the M atoms are somewhat underbonded within these octahedral sites, so that there is evidence that in some compounds, they can also enter the trigonal planar site at low occupancy (~5%). Magnetic measurements on RE{sub 3}Co{sub 0.5}GeS{sub 7} (RE = Ce, Pr, Sm) revealed paramagnetic behaviour for the Ce and Pr members and apparent antiferromagnetic ordering (T{sub N} =14 K) for the Sm member; fitting to the Curie-Weiss law gave effective magnetic moments consistent with the presence of RE{sup 3+} and Co{sup 2+} species. Band structure calculations on ordered models of La{sub 3}M{sub 0.5}GeS{sub 7} (M = Co, Ni) showed that the Fermi level cuts through M 3d states in the DOS curve and supported the presence of strong M–S and Ge–S bonding interactions. - Graphical abstract: RE{sub 3}M{sub 0.5}GeS{sub 7} (M = Co, Ni) and Y{sub 3}Pd{sub 0.5}SiS{sub 7} contain M atoms partially occupying

Cathodoluminescence properties of SiO2:Pr3+and ZnO.SiO2:Pr3+ phosphor nanopowders

CSIR Research Space (South Africa)

Mhlongo, GH

2010-10-01

Full Text Available regardless of the incorporation of Pr3+ and nanocrystalline ZnO or annealing at 600 °C. The particles were mostly spherical and agglomerated as confirmed by Field Emission Scanning Electron Microscopy. Thermogravimetric analysis of dried gels performed... Science, vol. 45(19): 5228-5236 Cathodoluminescence properties of SiO2:Pr 3+and ZnO·SiO2:Pr 3+ phosphor nanopowders G. H. Mhlongo, O. M. Ntwaeaborwa, M. S. Dhlamini, H. C. Swart, K. T. Hillie ABSTRACT: The successful incorporation of Zn...

Effect of Adding Elements on Microstructure of Mg-3Si Alloy

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CUI Bin

2017-03-01

Full Text Available The microstructure of alloy Mg-3Si(mass fraction/%, same as below after successive additions with different elements of Zn, Nd, Gd and Y was observed and the microstructure evolution was investigated by scanning electron microscopy and X-ray diffraction. The results show the primary Mg2Si particles co-exist with eutectic Mg2Si particles in binary alloy Mg-Si. With minor addition of Zn element, only primary Mg2Si can be found in ternary Mg-3Si-3Zn system while eutectic Mg2Si particles disappear. In quaternary alloy Mg-2.0Nd-3.0Zn-3.0Si, the addition of Nd element can effectively refine the primary Mg2Si particles and form some Mg41Nd5 particles. After continuous adding of Gd and Y elements into quaternary system, Gd5Si3 and YSi particles increase significantly in the alloy Mg-8.0Gd-4.0Y-2.0Nd-3.0Zn-3.0Si, while volume fraction of primary Mg2Si decrease significantly. Thermo-Calc calculation predicts that the Gibbs free energy for primary particles Gd5Si3, YSi is lower, and therefore Gd, Y atom and Si are more likely to form compounds. In Mg-8Gd-4Y-2Nd-3Zn-3Si alloy, room temperature Gibbs free energy for primary particles Mg2Si, Gd5Si3, YSi is -9.56×104, -8.72×104, -2.83×104J/mol, respectively, and the mass fraction of these particles is 8.07%, 5.27%, 1.40% respectively.

Characterization of rare-earth doped Si 3 N4 /SiC micro/nanocomposites

Directory of Open Access Journals (Sweden)

Peter Tatarko

2010-03-01

Full Text Available Influence of various rare-earth oxide additives (La2O3, Nd2O3, Sm2O3, Y2O3, Yb2O3 and Lu2O3 on the mechanical properties of hot-pressed silicon nitride and silicon nitride/silicon carbide micro/nano-composites has been investigated. The bimodal character of microstructures was observed in all studied materials where elongated β-Si3N4 grains were embedded in the matrix of much finer Si3N4 grains. The fracture toughness values increased with decreasing ionic radius of rare-earth elements. The fracture toughness of composites was always lower than that of monoliths due to their finer Si3N4/SiC microstructures. Similarly, the hardness and bending strength values increased with decreasing ionic radius of rare-earth elements either in monoliths or composites. On the other hand, the positive influence of finer microstructure of the composites on strength was not observed due to the present defects in the form of SiC clusters and non-reacted carbon zones. Wear resistance at room temperature also increased with decreasing ionic radius of rare-earth element. Significantly improved creep resistance was observed in case either of composite materials or materials with smaller radius of RE3+.

Physical and electrical properties of melt-spun Fe-Si (3–8 wt.%) soft magnetic ribbons

Energy Technology Data Exchange (ETDEWEB)

Overman, Nicole R.; Jiang, Xiujuan; Kukkadapu, Ravi K.; Clark, Trevor; Roosendaal, Timothy J.; Coffey, Gregory; Shield, Jeffrey E.; Mathaudhu, Suveen N.

2018-02-01

Fe-Si alloys ranging from 3 to 8 wt% Si were rapidly solidified using melt spinning. Wheel speeds of 30 m/s and 40 m/s were employed to vary cooling rates. Mössbauer spectroscopic studies indicated the Si content significantly influenced the number of Fe sites, relative abundance of various Fe species, and internal magnetic fields/structural environments. Wheel speed altered Fe speciation only in the 3 wt% sample. Scanning electron microscopy confirmed that increasing the wheel speed refined both the ribbon thickness and grain size. Electron backscatter diffraction results suggest tailoring melt spinning process parameters and alloy chemistry may offer the ability to manipulate {001} texture development. Electrical resistivity measurements were observed to increase in response to elevated Si content. Increased hardness was correlated to elevated Si content and wheel speed.

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

Magnetic order of Y{sub 3}NiSi{sub 3}-type R{sub 3}NiSi{sub 3} (R=Gd–DY) compounds

Energy Technology Data Exchange (ETDEWEB)

Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Faculty of Geology, Moscow State University, Leninskie Gory, Moscow 119992 (Russian Federation); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600036 (India); Malik, S.K.; Quezado, S. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970 (Brazil); Yao, Jinlei; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada); Nigam, A.K. [Tata Institute of Fundamental Research, Mumbai 400005 (India); Isnard, O. [Université Grenoble Alpes, Inst NEEL, BP166, F-38042 Grenoble (France); CNRS, Institut NEEL, 25 rue des martyrs, F-38042 Grenoble (France)

2016-01-15

Magnetic measurements and neutron powder diffraction investigations on the Y{sub 3}NiSi{sub 3}-type R{sub 3}NiSi{sub 3} compounds (R=Gd, Tb, Dy) reveal their complex antiferromagnetic ordering. Magnetic measurements on Gd{sub 3}NiSi{sub 3}, Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} indicate antiferromagnetic-like transition at temperatures 260 K, 202 K and 140 K, respectively. Also, the Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} compounds show spin-reorientation transition at 132 K and 99 K, respectively. Below the spin-reorientation transition, the isothermal magnetization curves indicate the metamagnetic-like behavior of Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3}. The magnetocaloric effect of Dy{sub 3}NiSi{sub 3} is calculated in terms of isothermal magnetic entropy change and it reaches a maximum value of −1.2 J/kg K and −1.1 J/kg K for a field change of 50 kOe near 146 K and 92 K, respectively. The neutron diffraction studies of Tb{sub 3}NiSi{sub 3} suggest the magnetic ordering of the Tb2 4j sublattice and no magnetic ordering of the Tb1 2a sublattice. Tb{sub 3}NiSi{sub 3} transforms from the high temperature paramagnetic state to the commensurate high-temperature a- and c-axis antiferromagnet of I′2/m magnetic space group below 250 K. Below 150 K, the high-temperature antiferromagnet transforms into the low-temperature a-, b- and c-axis antiferromagnet of I′i magnetic space group. At 1.5 K, the terbium magnetic moment in Tb2 sublattice and its a-, b- and c-axis components reach the values of M{sub Tb2}=8.2(1) μ{sub B}, M{sub aTb2}=5.9(1) μ{sub B}, M{sub bTb2}=4.3(2) μ{sub B} and M{sub cTb2}=3.7(2) μ{sub B}, respectively. - Highlights: • Gd{sub 3}NiSi{sub 3}, Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} have Neel points of 260. 202 and 140 K. • Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} show spin-reorientation transition at 132 and 99 K. • Tb{sub 3}NiSi{sub 3} exhibits the commensurate magnetic ordering of Tb2 4j sublattice

Electrical and optical properties of Si-doped Ga2O3

Science.gov (United States)

Li, Yin; Yang, Chuanghua; Wu, Liyuan; Zhang, Ru

2017-05-01

The charge densities, band structure, density of states, dielectric functions of Si-doped β-Ga2O3 have been investigated based on the density functional theory (DFT) within the hybrid functional HSE06. The heavy doping makes conduction band split out more bands and further influences the band structure. It decreases the band gap and changes from a direct gap to an indirect gap. After doping, the top of the valence bands is mainly composed by the O-2p states, Si-3p states and Ga-4p states and the bottom of the conduction bands is almost formed by the Si-3s, Si-3p and Ga-4s orbits. The anisotropic optical properties have been investigated by means of the complex dielectric function. After the heavy Si doping, the position of absorption band edges did not change much. The slope of the absorption curve descends and indicates that the absorption became more slow for Si-doped β-Ga2O3 than undoped one due to the indirect gap of Si-doped β-Ga2O3.

Y2O3:Yb,Er@mSiO2-CuxS double-shelled hollow spheres for enhanced chemo-/photothermal anti-cancer therapy and dual-modal imaging

Science.gov (United States)

Yang, Dan; Yang, Guixin; Wang, Xingmei; Lv, Ruichan; Gai, Shili; He, Fei; Gulzar, Arif; Yang, Piaoping

2015-07-01

Multifunctional composites have gained significant interest due to their unique properties which show potential in biological imaging and therapeutics. However, the design of an efficient combination of multiple diagnostic and therapeutic modes is still a challenge. In this contribution, Y2O3:Yb,Er@mSiO2 double-shelled hollow spheres (DSHSs) with up-conversion fluorescence have been successfully prepared through a facile integrated sacrifice template method, followed by a calcination process. It is found that the double-shelled structure with large specific surface area and uniform shape is composed of an inner shell of luminescent Y2O3:Yb,Er and an outer mesoporous silica shell. Ultra small CuxS nanoparticles (about 2.5 nm) served as photothermal agents, and a chemotherapeutic agent (doxorubicin, DOX) was then attached onto the surface of mesoporous silica, forming a DOX-DSHS-CuxS composite. The composite exhibits high anti-cancer efficacy due to the synergistic photothermal therapy (PTT) induced by the attached CuxS nanoparticles and the enhanced chemotherapy promoted by the heat from the CuxS-based PTT when irradiated by 980 nm near-infrared (NIR) light. Moreover, the composite shows excellent in vitro and in vivo X-ray computed tomography (CT) and up-conversion fluorescence (UCL) imaging properties owing to the doped rare earth ions, thus making it possible to achieve the target of imaging-guided synergistic therapy.Multifunctional composites have gained significant interest due to their unique properties which show potential in biological imaging and therapeutics. However, the design of an efficient combination of multiple diagnostic and therapeutic modes is still a challenge. In this contribution, Y2O3:Yb,Er@mSiO2 double-shelled hollow spheres (DSHSs) with up-conversion fluorescence have been successfully prepared through a facile integrated sacrifice template method, followed by a calcination process. It is found that the double-shelled structure with large

On the line intensity ratios of prominent Si II, Si III, and Si IV multiplets

International Nuclear Information System (INIS)

Djenize, S.; Sreckovic, A.; Bukvic, S.

2010-01-01

Line intensities of singly, doubly and triply ionized silicon (Si II, Si III, and Si IV, respectively) belonging to the prominent higher multiplets, are of interest in laboratory and astrophysical plasma diagnostics. We measured these line intensities in the emission spectra of pulsed helium discharge. The Si II line intensity ratios in the 3s3p 22 D-3s 2 4p 2 P o , 3s 2 3d 2 D-3s 2 4f 2 F o , and 3s 2 4p 2 P o -3s 2 4d 2 D transitions, the Si III line intensity ratios in the 3s3d 3 D-3s4p 3 P o , 3s4p 3 P o -3s4d 3 D, 3s4p 3 P o -3s5s 3 S, 3s4s 3 S-3s4p 3 P o , and 3s4f 3 F o -3s5g 3 G transitions, and the Si IV line intensity ratios in the 4p 2 P o -4d 2 D and 4p 2 P o -5s 2 S transitions were obtained in a helium plasma at an electron temperature of about 17,000 ± 2000 K. Line shapes were recorded using a spectrograph and an ICCD camera as a highly-sensitive detection system. The silicon atoms were evaporated from a Pyrex discharge tube designed for the purpose. They represent impurities in the optically thin helium plasma at the silicon ionic wavelengths investigated. The line intensity ratios obtained were compared with those available in the literature, and with values calculated on the basis of available transition probabilities. The experimental data corresponded well with line intensity ratios calculated using the transition probabilities obtained from a Multi Configuration Hartree-Fock approximation for Si III and Si IV spectra. We recommend corrections of some Si II transition probabilities.

Effect of Sulfur on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-S System in Equilibrium with Metallic Iron

Science.gov (United States)

Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

2011-10-01

The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-S system have been determined experimentally in equilibrium with metallic iron. A pseudoternary section of the form ZnO-"FeO"-(Al2O3+CaO+SiO2) for CaO/SiO2 = 0.71 (weight), (CaO+SiO2)/Al2O3 = 5.0 (weight), and fixed 2.0 wt pct S concentration has been constructed. It was found that the addition of 2.0 wt pct S to the liquid extends the spinel primary phase field significantly and decreases the size of the wustite primary phase field. The liquidus temperature in the wustite primary phase field is decreased by approximately 80 K and the liquidus temperature in the spinel primary phase field is decreased by approximately 10 K with addition of 2.0 wt pct S in the composition range investigated. It was also found that iron-zinc sulfides are present in some samples in the spinel primary phase field, which are matte appearing at low zinc concentrations and sphalerite (Zn,Fe)S at higher zinc concentrations. The presence of sulfur in the slag has a minor effect on the partitioning of ZnO between the wustite and liquid phases but no effect on the partitioning of ZnO between the spinel and liquid phases.

Supraconductivity of TR-Ru3Si2 compounds (TR = La, Ce)

International Nuclear Information System (INIS)

Godart, C.; Gupta, L.C.; Parks, R.D.; Rauschwalbe, U.; Alheim, U.; Gottwick, U.; Lieke, W.; Steglich, F.

1984-01-01

A new family of superconducting ternary silicides MRu 3 Si 2 with M = La (Tsub(s) approximately 7 K), Y and Th was discovered by Barz and Vandenberg. Same compounds with M from Nd to Tm are magnetic and not superconductors. We studied superconductivity in the solid solution Cesub(1-x)Lasub(x)Ru 3 Si 2 of hexagonal structure from x = 0 to 1. CeRu 3 Si 2 is type II superconductor (Tsub(s) approximately 1 K), like LaRu 3 Si 2 , and is mixed valent (M.V.). Spin fluctuations temperature (Tsub(sf) approximately 440 K) is between these of non superconducting M.V. like CeSn 3 (Tsub(sf) approximately 270) and these of superconducting M.V. like CeRu 2 (Tsub(sf) approximately 770 K). Cesub(1-x)Lasub(x)Ru 3 Si 2 is the first M.V. system of Ce which is superconductor from x = 0 to 1 [fr

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)

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

Application of bias correction methods to improve U3Si2 sample preparation for quantitative analysis by WDXRF

International Nuclear Information System (INIS)

Scapin, Marcos A.; Guilhen, Sabine N.; Azevedo, Luciana C. de; Cotrim, Marycel E.B.; Pires, Maria Ap. F.

2017-01-01

The determination of silicon (Si), total uranium (U) and impurities in uranium-silicide (U 3 Si 2 ) samples by wavelength dispersion X-ray fluorescence technique (WDXRF) has been already validated and is currently implemented at IPEN's X-Ray Fluorescence Laboratory (IPEN-CNEN/SP) in São Paulo, Brazil. Sample preparation requires the use of approximately 3 g of H 3 BO 3 as sample holder and 1.8 g of U 3 Si 2 . However, because boron is a neutron absorber, this procedure precludes U 3 Si 2 sample's recovery, which, in time, considering routinely analysis, may account for significant unusable uranium waste. An estimated average of 15 samples per month are expected to be analyzed by WDXRF, resulting in approx. 320 g of U 3 Si 2 that would not return to the nuclear fuel cycle. This not only impacts in production losses, but generates another problem: radioactive waste management. The purpose of this paper is to present the mathematical models that may be applied for the correction of systematic errors when H 3 BO 3 sample holder is substituted by cellulose-acetate {[C 6 H 7 O 2 (OH) 3-m (OOCCH 3 )m], m = 0∼3}, thus enabling U 3 Si 2 sample’s recovery. The results demonstrate that the adopted mathematical model is statistically satisfactory, allowing the optimization of the procedure. (author)

Computer Aided Multi-scale Design of SiC-Si3N4 Nanoceramic Composites for High-Temperature Structural Applications

Energy Technology Data Exchange (ETDEWEB)

Vikas Tomer; John Renaud

2010-08-31

It is estimated that by using better and improved high temperature structural materials, the power generation efficiency of the power plants can be increased by 15% resulting in significant cost savings. One such promising material system for future high-temperature structural applications in power plants is Silicon Carbide-Silicon Nitride (SiC-Si{sub 3}N{sub 4}) nanoceramic matrix composites. The described research work focuses on multiscale simulation-based design of these SiC-Si{sub 3}N{sub 4} nanoceramic matrix composites. There were two primary objectives of the research: (1) Development of a multiscale simulation tool and corresponding multiscale analyses of the high-temperature creep and fracture resistance properties of the SiC-Si{sub 3}N{sub 4} nanocomposites at nano-, meso- and continuum length- and timescales; and (2) Development of a simulation-based robust design optimization methodology for application to the multiscale simulations to predict the range of the most suitable phase morphologies for the desired high-temperature properties of the SiC-Si{sub 3}N{sub 4} nanocomposites. The multiscale simulation tool is based on a combination of molecular dynamics (MD), cohesive finite element method (CFEM), and continuum level modeling for characterizing time-dependent material deformation behavior. The material simulation tool is incorporated in a variable fidelity model management based design optimization framework. Material modeling includes development of an experimental verification framework. Using material models based on multiscaling, it was found using molecular simulations that clustering of the SiC particles near Si{sub 3}N{sub 4} grain boundaries leads to significant nanocomposite strengthening and significant rise in fracture resistance. It was found that a control of grain boundary thicknesses by dispersing non-stoichiometric carbide or nitride phases can lead to reduction in strength however significant rise in fracture strength. The

X-ray Raman scattering study of MgSiO₃ glass at high pressure: Implication for triclustered MgSiO₃ melt in Earth's mantle

Energy Technology Data Exchange (ETDEWEB)

Lee, Sung Keun; Lin, Jung-Fu; Cai, Yong Q.; Hiraoka, Nozomu; Eng, Peter J.; Okuchi, Takuo; Mao, Ho-kwang; Meng, Yue; Hu, Michael Y.; Chow, Paul; Shu, Jinfu; Li, Baosheng; Fukui, Hiroshi; Lee, Bum Han; Kim, Hyun Na; Yoo, Choong-Shik [SNU; (LLNL); (NSRRC); (Okayama); (UC); (CIW); (Wash State U); (Nagoya); (SBU)

2015-02-09

Silicate melts at the top of the transition zone and the core-mantle boundary have significant influences on the dynamics and properties of Earth's interior. MgSiO₃-rich silicate melts were among the primary components of the magma ocean and thus played essential roles in the chemical differentiation of the early Earth. Diverse macroscopic properties of silicate melts in Earth's interior, such as density, viscosity, and crystal-melt partitioning, depend on their electronic and short-range local structures at high pressures and temperatures. Despite essential roles of silicate melts in many geophysical and geodynamic problems, little is known about their nature under the conditions of Earth's interior, including the densification mechanisms and the atomistic origins of the macroscopic properties at high pressures. Here, we have probed local electronic structures of MgSiO₃ glass (as a precursor to Mg-silicate melts), using high-pressure x-ray Raman spectroscopy up to 39 GPa, in which high-pressure oxygen K-edge features suggest the formation of tricluster oxygens (oxygen coordinated with three Si frameworks; ^[3]O) between 12 and 20 GPa. Our results indicate that the densification in MgSiO₃ melt is thus likely to be accompanied with the formation of triculster, in addition to a reduction in nonbridging oxygens. The pressure-induced increase in the fraction of oxygen triclusters >20 GPa would result in enhanced density, viscosity, and crystal-melt partitioning, and reduced element diffusivity in the MgSiO₃ melt toward deeper part of the Earth's lower mantle.

Efecto de la microestructura en el comportamiento tribológico de materiales monolíticos de Si3N4 y de compuestos Si3N4–SiC

Directory of Open Access Journals (Sweden)

Silva, R. F.

2000-06-01

Full Text Available The tribological behaviour of various Si3N4 based materials, including Si3N4/SiC composites, has been analysed from room temperature up to 700ºC, and for sliding speeds between 0.5 and 2 m/s. Materials have been prepared by hot pressing at 1750ºC in nitrogen atmosphere, varying α-Si3N4 phase content, microstructure coarseness and shape and size of the SiC particles. Wear tests were performed in self-mated pairs using a pin on disc tribometer, without lubrication and at a fixed load of 5 N. Pin and disc worn surfaces were observed by scanning electron microscopy (SEM-EDS. Debris generated during tests was analysed by SEM-EDS and X-ray diffraction (XRD. Results showed friction, f, and wear coefficients, K, above 0.3 y 10-6 mm3N-1m-1, respectively. Wear mechanism depended on the microstructure and the mechanical properties of the materials.Se ha analizado el comportamiento tribológico de materiales de Si3N4 y de compuestos Si3N4/SiC, desde temperatura ambiente hasta 700ºC y en el rango de velocidades 0.5-2 m/s. Los materiales se han preparado mediante prensado en caliente a 1750ºC en atmósfera de nitrógeno, variando el contenido en fase α-Si3N4, el tamaño medio de grano, y la morfología de las partículas de SiC adicionadas. Los ensayos se han realizado en pares homólogos utilizando un tribómetro del tipo punta sobre disco, sin lubricación y a una carga constante de 5 N. Las superficies de desgaste de las puntas y los discos se observaron en un microscopio electrónico de barrido con capacidad analítica (MEB-EDX. Los residuos generados durante los ensayos se analizaron mediante MEB-EDX y difracción de rayos X (DRX. Los resultados obtenidos en los ensayos daban valores de coeficiente de fricción, f, y de desgaste, K, superiores a 0.3 y 10-6 mm3N-1m-1, respectivamente. El mecanismo de desgaste predominante dependía de la microestructura y de las propiedades mecánicas del material ensayado.

Temperature-dependent photoluminescence from CdS/Si nanoheterojunctions

Energy Technology Data Exchange (ETDEWEB)

Song, Yue Li; Li, Yong; Ji, Peng Fei; Zhou, Feng Qun; Sun, Xiao Jun; Yuan, Shu Qing; Wan, Ming Li [Pingdingshan University, Department of Physics, Solar New Energy Research Center, Pingdingshan (China); Ling, Hong [North China University of Water Resources and Electric Power, Department of Mathematics and Information Science, Zhengzhou (China)

2016-12-15

CdS/Si nanoheterojunctions have been fabricated by growing nanocrystal CdS (nc-CdS) on the silicon nanoporous pillar array (Si-NPA) through using a chemical bath deposition method. The nanoheterojunctions have been constructed by three layers: the upper layer being a nc-CdS thin films, the intermediate layer being the interface region including nc-CdS and nanocrystal silicon (nc-Si), and the bottom layer being nc-Si layer grown on sc-Si substrate. The room temperature and temperature-dependent photoluminescence (PL) have been measured and analyzed to provide some useful information of defect states. Utilizing the Gauss-Newton fitting method, five emission peaks from the temperature-dependent PL spectra can be determined. From the high energy to low energy, these five peaks are ascribed to the some luminescence centers which are formed by the oxygen-related deficiency centers in the silicon oxide layer of Si-NPA, the band gap emission of nc-CdS, the transition from the interstitial cadmium (I{sub Cd}) to the valence band, the recombination from I{sub Cd} to cadmium vacancies (V{sub Cd}), and from sulfur vacancies (V{sub s}) to the valence band, respectively. Understanding of the defect states in the CdS/Si nanoheterojunctions is very meaningful for the performance of devices based on CdS/Si nanoheterojunctions. (orig.)

Electrosynthesis of Ti5Si3, Ti5Si3/TiC, and Ti5Si3/Ti3SiC2 from Ti-Bearing Blast Furnace Slag in Molten CaCl2

Science.gov (United States)

Li, Shangshu; Zou, Xingli; Zheng, Kai; Lu, Xionggang; Chen, Chaoyi; Li, Xin; Xu, Qian; Zhou, Zhongfu

2018-04-01

Ti5Si3, Ti5Si3/TiC, and Ti5Si3/Ti3SiC2 have been electrochemically synthesized from the Ti-bearing blast furnace slag/TiO2 and/or C mixture precursors at a cell voltage of 3.8 V and 1223 K to 1273 K (950 °C to 1000 °C) in molten CaCl2. The pressed porous mixture pellets were used as the cathode, and a solid oxide oxygen-ion-conducting membrane (SOM)-based anode was used as the anode. The phase composition and morphologies of the cathodic products were systematically characterized. The final products possess a porous nodular microstructure due to the interconnection of particles. The variations of impurity elements, i.e., Ca, Mg, and Al, have been analyzed, and the result shows that Ca and Mg can be almost completely removed; however, Al cannot be easily removed from the pellet due to the formation of Ti-Al alloys during the electroreduction process. The electroreduction process has also been investigated by the layer-depended phase composition analysis of the dipped/partially reduced pellets to understand the detailed reaction process. The results indicate that the electroreduction process of the Ti-bearing blast furnace slag/TiO2 and/or C mixture precursors can be typically divided into four periods, i.e., (i) the decomposition of initial Ca(Mg,Al)(Si,Al)2O6, (ii) the reduction of Ti/Si-containing intermediate phases, (iii) the removal of impurity elements, and (iv) the formation of Ti5Si3, TiC, and Ti3SiC2. It is suggested that the SOM-based anode process has great potential to be used for the direct and facile preparation of Ti alloys and composites from cheap Ti-containing ores.

Chemical vapor deposition of NiSi using Ni(PF3)4 and Si3H8

International Nuclear Information System (INIS)

Ishikawa, M.; Muramoto, I.; Machida, H.; Imai, S.; Ogura, A.; Ohshita, Y.

2007-01-01

NiSi x films were deposited using chemical vapor deposition (CVD) with a Ni(PF 3 ) 4 and Si 3 H 8 /H 2 gas system. The step coverage quality of deposited NiSi x was investigated using a horizontal type of hot-wall low pressure CVD reactor, which maintained a constant temperature throughout the deposition area. The step coverage quality improved as a function of the position of the gas flow direction, where PF 3 gas from decomposition of Ni(PF 3 ) 4 increased. By injecting PF 3 gas into the Ni(PF 3 ) 4 and Si 3 H 8 /H 2 gas system, the step coverage quality markedly improved. This improvement in step coverage quality naturally occurred when PF 3 gas was present, indicating a strong relationship. The Si/Ni deposit ratio at 250 deg. C is larger than at 180 deg. C. It caused a decreasing relative deposition rate of Ni to Si. PF 3 molecules appear to be adsorbed on the surface of the deposited film and interfere with faster deposition of active Ni deposition species

C and Si delta doping in Ge by CH_3SiH_3 using reduced pressure chemical vapor deposition

International Nuclear Information System (INIS)

Yamamoto, Yuji; Ueno, Naofumi; Sakuraba, Masao; Murota, Junichi; Mai, Andreas; Tillack, Bernd

2016-01-01

C and Si delta doping in Ge are investigated using a reduced pressure chemical vapor deposition system to establish atomic-order controlled processes. CH_3SiH_3 is exposed at 250 °C to 500 °C to a Ge on Si (100) substrate using H_2 or N_2 carrier gas followed by a Ge cap layer deposition. At 350 °C, C and Si are uniformly adsorbed on the Ge surface and the incorporated C and Si form steep delta profiles below detection limit of SIMS measurement. By using N_2 as carrier gas, the incorporated C and Si doses in Ge are saturated at one mono-layer below 350 °C. At this temperature range, the incorporated C and Si doses are nearly the same, indicating CH_3SiH_3 is adsorbed on the Ge surface without decomposing the C−Si bond. On the other hand, by using H_2 as carrier gas, lower incorporated C is observed in comparison to Si. CH_3SiH_3 injected with H_2 carrier gas is adsorbed on Ge without decomposing the C−Si bond and the adsorbed C is reduced by dissociation of the C−Si bond during temperature ramp up to 550 °C. The adsorbed C is maintained on the Ge surface in N_2 at 550 °C. - Highlights: • C and Si delta doping in Ge is investigated using RPCVD system by CH_3SiH_3 exposure. • Atomically flat C and Si delta layers are fabricated at 350 °C. • Incorporated C and Si doses are saturated at one mono-layer below 350 °C. • CH_3SiH_3 adsorption occurred without decomposing C−Si bond. • Adsorbed C is desorbed due to dissociation by hydrogen during postannealing at 550 °C.

Nuotolinio mokymo(si) elektroninės vizualinės terpės dizainas

OpenAIRE

Cygankova, Daiva

2007-01-01

Nuotolinio mokymo(si) dizainas kaip vizualios informacijos pateikimo forma atlieka svarbų vaidmenį naujos informacinės visuomenės kūrimesi, naujų, netradicinių mokymo(si) formų, būdų atsiradime, jų vystymosi procese. Dalyko mokytojo pamokos atsiranda elektroninės erdvės terpėje. Pedagogui rūpi kaip ir kokiais būdais pateikti tą informaciją, kad sėkmingai vyktų realus ir kokybiškas mokymo(si) procesas. ). Kūrėjui būtina įvertinti būsimo mokinio tiek poreikius, tiek aplinką, tiek tos aplinko...

In situ TEM annealing of ion-amorphized Hi Nicalon S and Tyranno SA3 SiC fibers

Energy Technology Data Exchange (ETDEWEB)

Huguet-Garcia, J., E-mail: juan.huguet-garcia@cea.fr [CEA, DEN, Service de Recherches Métallurgiques Appliquées, F-91191 Gif-sur-Yvette (France); Jankowiak, A. [CEA, DEN, Service de Recherches Métallurgiques Appliquées, F-91191 Gif-sur-Yvette (France); Miro, S. [CEA, DEN, Service de Recherches en Métallurgie Physique, F-91191 Gif-sur-Yvette (France); Meslin, E. [CEA, DEN, Service de Recherches en Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Serruys, Y. [CEA, DEN, Service de Recherches en Métallurgie Physique, F-91191 Gif-sur-Yvette (France); Costantini, J.-M. [CEA, DEN, Service de Recherches Métallurgiques Appliquées, F-91191 Gif-sur-Yvette (France)

2016-05-01

In this work, recrystallization of ion-amorphized Hi Nicalon Type S and Tyranno SA3 SiC fibers (4 MeV Au{sup 3+}, 2 × 10{sup 15} cm{sup −2}) has been studied via in situ TEM annealing. Both fibers show a two-step recovery process of the radiation damage. First recovery stage starts at temperatures as low as 250 °C and implies recovery of the radiation swelling. Eventually the amorphous layer recrystallizes with no signs of polytype change (3C-SiC). Recrystallization temperatures yield 900–920 °C and 930 °C for the HNS and the TSA3 respectively. HNS fiber shows columnar recrystallization perpendicular to the amorphous–crystalline interphase with a grain growth rate of ∼20 nm min{sup −1}. On the other hand, recrystallization of TSA3 fiber is rather “spontaneous” with no preferential growth direction. The different recrystallization is attributed to the different microstructure of the fibers.

In situ TEM annealing of ion-amorphized Hi Nicalon S and Tyranno SA3 SiC fibers

International Nuclear Information System (INIS)

Huguet-Garcia, J.; Jankowiak, A.; Miro, S.; Meslin, E.; Serruys, Y.; Costantini, J.-M.

2016-01-01

In this work, recrystallization of ion-amorphized Hi Nicalon Type S and Tyranno SA3 SiC fibers (4 MeV Au"3"+, 2 × 10"1"5 cm"−"2) has been studied via in situ TEM annealing. Both fibers show a two-step recovery process of the radiation damage. First recovery stage starts at temperatures as low as 250 °C and implies recovery of the radiation swelling. Eventually the amorphous layer recrystallizes with no signs of polytype change (3C-SiC). Recrystallization temperatures yield 900–920 °C and 930 °C for the HNS and the TSA3 respectively. HNS fiber shows columnar recrystallization perpendicular to the amorphous–crystalline interphase with a grain growth rate of ∼20 nm min"−"1. On the other hand, recrystallization of TSA3 fiber is rather “spontaneous” with no preferential growth direction. The different recrystallization is attributed to the different microstructure of the fibers.

Diameter- and Shape-Controlled ZnS/Si Nanocables and Si Nanotubes for SERS and Photocatalytic Applications

OpenAIRE

Chen, Xue; Lee, Chun-Sing; Meng, Xiangmin; Zhang, Wenjun

2011-01-01

ZnS/Si nanocables were synthesized via a simple two-step thermal evaporation method. The shape and diameter of the ZnS/Si nanocables can be controlled by adjusting the morphologies of the ZnS nanostructures (nanowire or nanoribbon) obtained in the first step and the deposition time of the Si shell in the second step, respectively. Furthermore, we obtained polycrystalline Si nanotubes with different shapes and diameters by etching away the inner ZnS core. The as-prepared Si nanotubes were empl...

Hybrid Si/TMD 2D electronic double channels fabricated using solid CVD few-layer-MoS2 stacking for Vth matching and CMOS-compatible 3DFETs

KAUST Repository

Chen, Min Cheng; Lin, Chia Yi; Li, Kai Hsin; Li, Lain-Jong; Chen, Chang Hsiao; Chuang, Cheng Hao; Lee, Ming Dao; Chen, Yi Ju; Hou, Yun Fang; Lin, Chang Hsien; Chen, Chun Chi; Wu, Bo Wei; Wu, Cheng San; Yang, Ivy; Lee, Yao Jen; Yeh, Wen Kuan; Wang, Tahui; Yang, Fu Liang; Hu, Chenming

2014-01-01

Stackable 3DFETs such as FinFET using hybrid Si/MoS2 channels were developed using a fully CMOS-compatible process. Adding several molecular layers (3-16 layers) of the transition-metal dichalcogenide (TMD), MoS2 to Si fin and nanowire resulted in improved (+25%) Ion,n of the FinFET and nanowire FET (NWFET). The PFETs also operated effectively and the N/P device Vth are low and matched perfectly. The proposed heterogeneous Si/TMD 3DFETs can be useful in future electronics. © 2014 IEEE.

Hybrid Si/TMD 2D electronic double channels fabricated using solid CVD few-layer-MoS2 stacking for Vth matching and CMOS-compatible 3DFETs

KAUST Repository

Chen, Min Cheng

2014-12-01

Stackable 3DFETs such as FinFET using hybrid Si/MoS2 channels were developed using a fully CMOS-compatible process. Adding several molecular layers (3-16 layers) of the transition-metal dichalcogenide (TMD), MoS2 to Si fin and nanowire resulted in improved (+25%) Ion,n of the FinFET and nanowire FET (NWFET). The PFETs also operated effectively and the N/P device Vth are low and matched perfectly. The proposed heterogeneous Si/TMD 3DFETs can be useful in future electronics. © 2014 IEEE.

Processing, Microstructure, and Mechanical Properties of Si3N4/SiC Nanocomposites from Precursor Derived Ceramics

Science.gov (United States)

Strong, Kevin Thomas, Jr.

Polymer-derived ceramics (PDCs) provides a unique processing route to create Si3N4/SiC composites. Silazane precursor polyureasilazane (Ceraset PURS20) produce's an amorphous SiCN ceramic at temperatures of ~800 -- 1200 °C and crystallizes to a Si3N4/SiC nanocomposite at temperatures >1500 °C. A novel processing technique was developed where crosslinked polymers were heat-treated in a reactive NH3 atmosphere to control the stoichiometry of the pyrolyzed SiCN ceramic. Using this technique processing parameters were established to produce SiCN powders that resulted in nanocomposites with approximately 0, 5, 10, 20 and 30 vol. % SiC. Lu2O3 was added to these powders as a sintering aid and were densified using Hot Pressing and Field Assisted Sintering. The sintered nanocomposites resulted in microstructures with multiple-length scales. These length-scales included Si3N4 (0.1 -- 5 microm), SiC (10 -- 100 nm) and the intergranular grain boundary phase (<1 nm). Using a combination of SEM and TEM it was possible to quantify some of these microstructural features such as the size and location of the SiC. Hardness and fracture toughness testing was conducted to compared the room temperature mechanical properties of these resultant microstructures. This research was intended to develop robust processing approaches that can be used to control the nanostructures of Si3N4/SiC composites with significant structural features at multiple length scales. The control of their features and the investigation of their affect on the properties of composites can be used to simulate the affect of the structure on properties. These models can then be used to design optimal microstructures for specific applications.

Experimental study and thermodynamic modeling of the phase relation in the Fe-S-Si system with implications for the distribution of S and Si in a partially solidified core

Science.gov (United States)

Tao, R.; Fei, Y.

2017-12-01

Planetary cooling leads to solidification of any initially molten metallic core. Some terrestrial cores (e.g. Mercury) are formed and differentiated under relatively reduced conditions, and they are thought to be composed of Fe-S-Si. However, there are limited understanding of the phase relations in the Fe-S-Si system at high pressure and temperature. In this study, we conducted high-pressure experiments to investigate the phase relations in the Fe-S-Si system up to 25 GPa. Experimental results show that the liquidus and solidus in this study are slightly lower than those in the Fe-S binary system for the same S concentration in liquid at same pressure. The Fe3S, which is supposed to be the stable sub-solidus S-bearing phase in the Fe-S binary system above 17 GPa, is not observed in the Fe-S-Si system at 21 GPa. Almost all S prefers to partition into liquid, while the distribution of Si between solid and liquid depends on experimental P and T conditions. We obtained the partition coefficient log(KDSi) by fitting the experimental data as a function of P, T and S concentration in liquid. At a constant pressure, the log(KDSi) linearly decreases with 1/T(K). With increase of pressure, the slopes of linear correlation between log(KDSi) and 1/T(K) decreases, indicating that more Si partitions into solid at higher pressure. In order to interpolate and extrapolate the phase relations over a wide pressure and temperature range, we established a comprehensive thermodynamic model in the Fe-S-Si system. The results will be used to constrain the distribution of S and Si between solid inner core and liquid outer core for a range of planet sizes. A Si-rich solid inner core and a S-rich liquid outer core are suggested for an iron-rich core.

Characterization of Si3N4-Al interface after corrosion tests Caracterização da interface Si3N4-Al após testes de corrosão

Directory of Open Access Journals (Sweden)

C. dos Santos

2003-12-01

Full Text Available Silicon nitride is a covalent ceramic material of high corrosion resistance and mechanical stability at elevated temperatures. Due to these properties, its use in metallurgical processes, such as the casting of alloys, is increasing. Therefore, the characterization of the interface between Si3N4 and the casted metal is of great importance to investigate possible interactions, which might deteriorate the ceramic mould or contaminate the metal. In this work, the use of Si3N4 as crucible material for Al-casting has been studied, by investigating the corrosion attack of liquid Al at a temperature of 1150 ºC during 30 days in air. The interface was characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. It has been found that due to superficial oxidation two oxide layers form - SiO2 on Si3N4 and Al2O3 on Al - which effectively hinder further reactions under the conditions studied, confering high corrosion resistance to the Si3N4 crucible.Nitreto de silício (Si3N4 é um material cerâmico covalente de elevada resistência à corrosão e estabilidade mecânica em temperaturas elevadas. Devido a essas propriedades, sua utilização em processos metalúrgicos, tais como em fundição de ligas metálicas, é crescente. Desta forma, a caracterização da interface entre Si3N4 e metais fundidos é de grande interesse para investigar possíveis interações as quais poderão deteriorar o material cerâmico e/ou contaminar o metal. Nesse trabalho o uso de Si3N4 como material base de cadinhos para fundição de alumínio foi estudado, pela investigação do ataque corrosivo de Al líquido a 1150 ºC durante 30 dias, ao ar. A interface foi caracterizada por difração de raios X, microscopia eletrônica de varredura e espectroscopia de energia dispersiva. É encontrado que devido à oxidação superficial dois óxidos se formam - SiO2 no Si3N4 e Al2O3 no Al - os quais evitam possíveis reações sob as condi

Synthesis, structural, electronic and linear electro-optical features of new quaternary Ag2Ga2SiS6 compound

Science.gov (United States)

Piasecki, M.; Myronchuk, G. L.; Parasyuk, O. V.; Khyzhun, O. Y.; Fedorchuk, A. O.; Pavlyuk, V. V.; Kozer, V. R.; Sachanyuk, V. P.; El-Naggar, A. M.; Albassam, A. A.; Jedryka, J.; Kityk, I. V.

2017-02-01

For the first time phase equilibria and phase diagram of the AgGaS2-SiS2 system were successfully explored by differential thermal and X-ray phase analysis methods. Crystal structure of low-temperature (LT) modification of Ag2Ga2SiS6 (LT- Ag2Ga2SiS6) was studied by X-ray powder method and it belongs to tetragonal space group I-42d, with unit cell parameters a=5.7164(4) Å, c=9.8023(7) Å, V=320.32(7) Å3. Additional details regarding the crystal structure exploration are available at the web page Fachinformationszentrum Karlsruhe. X-ray photoelectron core-level and valence-band spectra were measured for pristine LT- Ag2Ga2SiS6 crystal surface. In addition, the X-ray photoelectron valence-band spectrum of LT-Ag2Ga2SiS6 was matched on a common energy scale with the X-ray emission S Kβ1,3 and Ga Kβ2 bands, which give information on the energy distribution of the S 3p and Ga 4p states, respectively. The presented X-ray spectroscopy results indicate that the valence S p and Ga p atomic states contribute mainly to the upper and central parts of the valence band of LT-Ag2Ga2SiS6, respectively, with a less significant contribution also to other valence-band regions. Band gap energy was estimated by measuring the quantum energy in the spectral range of the fundamental absorption. We have found that energy gap Eg is equal to 2.35 eV at 300 K. LT-Ag2Ga2SiS6 is a photosensitive material and reveals two spectral maxima on the curve of spectral photoconductivity spectra at λmax1 =590 nm and λmax2 =860 nm. Additionally, linear electro-optical effect of LT-Ag2Ga2SiS6 for the wavelengths of a cw He-Ne laser at 1150 nm was explored.

Fabrication of Si/ZnS radial nanowire heterojunction arrays for white light emitting devices on Si substrates.

Science.gov (United States)

Katiyar, Ajit K; Sinha, Arun Kumar; Manna, Santanu; Ray, Samit K

2014-09-10

Well-separated Si/ZnS radial nanowire heterojunction-based light-emitting devices have been fabricated on large-area substrates by depositing n-ZnS film on p-type nanoporous Si nanowire templates. Vertically oriented porous Si nanowires on p-Si substrates have been grown by metal-assisted chemical etching catalyzed using Au nanoparticles. Isolated Si nanowires with needle-shaped arrays have been made by KOH treatment before ZnS deposition. Electrically driven efficient white light emission from radial heterojunction arrays has been achieved under a low forward bias condition. The observed white light emission is attributed to blue and green emission from the defect-related radiative transition of ZnS and Si/ZnS interface, respectively, while the red arises from the porous surface of the Si nanowire core. The observed white light emission from the Si/ZnS nanowire heterojunction could open up the new possibility to integrate Si-based optical sources on a large scale.

A transmission electron microscopy study of radiation damages to β-dicalcium (Ca{sub 2}SiO{sub 4}) and M3-tricalcium (Ca{sub 3}SiO{sub 5}) orthosilicates

Energy Technology Data Exchange (ETDEWEB)

Noirfontaine, Marie-Noëlle de; Dunstetter, Frédéric [Laboratoire des Solides Irradiés, Ecole Polytechnique, CNRS UMR 7642, CEA-DSM-IRAMIS, Université Paris Saclay, F-91128 Palaiseau Cedex (France); Courtial, Mireille [Laboratoire des Solides Irradiés, Ecole Polytechnique, CNRS UMR 7642, CEA-DSM-IRAMIS, Université Paris Saclay, F-91128 Palaiseau Cedex (France); Université d' Artois, 1230 Rue de l' Université, CS 20819, F-62408 Béthune (France); Signes-Frehel, Marcel [Laboratoire des Solides Irradiés, Ecole Polytechnique, CNRS UMR 7642, CEA-DSM-IRAMIS, Université Paris Saclay, F-91128 Palaiseau Cedex (France); Wang, Guillaume [Laboratoire Matériaux et Phénomènes Quantiques, CNRS UMR 7162, Université Paris Diderot, F-75205 Paris Cedex 13 (France); Gorse-Pomonti, Dominique, E-mail: dominique.gorse-pomonti@polytechnique.edu [Laboratoire des Solides Irradiés, Ecole Polytechnique, CNRS UMR 7642, CEA-DSM-IRAMIS, Université Paris Saclay, F-91128 Palaiseau Cedex (France)

2016-01-15

In this paper, we present results of a first study of electron radiation damages to β-dicalcium silicate (Ca{sub 2}SiO{sub 4}:C{sub 2}S) and M3-tricalcium silicate (Ca{sub 3}SiO{sub 5}:C{sub 3}S) in a Transmission Electron Microscope. Electron irradiation is used here as a means to bring to light a difference of reactivity under the electron beam between these two complex ceramic oxides, keeping in mind that C{sub 3}S reacts faster with water than C{sub 2}S and that this property remains unexplained, owing to the complex structural characteristics of these ceramics which have not yet been fully elucidated. The following results were obtained by coupling TEM imaging and EDS analysis: i) Rapid decomposition of both silicate particles into CaO nano-crystals separated by (presumably SiO{sub 2}-rich) amorphous areas at low flux for both silicates; ii) once reached a threshold electron flux, formation of an amorphous crater in both silicates, fully calcium-depleted in C{sub 3}S but never in C{sub 2}S; iii) significant post-mortem structural evolution of the craters that at least partially recrystallize in C{sub 2}S, to be compared to the quasi frozen damaged area in C{sub 3}S; iv) hole drilling at high flux but only in C{sub 3}S once reached a threshold flux, ϕ{sub th} ∼ 7.9 × 10{sup 21} e{sup −} cm{sup −2} s{sup −1}, of the same order of magnitude than previously estimated in a number of ceramic materials, whereas C{sub 2}S still amorphizes under the electron beam for a flux as high as 2.2 × 10{sup 22} e{sup −} cm{sup −2} s{sup −1}. The radiation damages and their post–mortem evolution differ largely between C{sub 2}S and C{sub 3}S. We attempted to relate the obtained results, and especially the evolution of the Ca content in the damaged areas under the electron beam to the available structural characteristics of these two orthosilicates. - Highlights: • TEM study of electron damages in β-dicalcium (C{sub 2}S), M3-tricalcium silicates

Temperature stability of c-axis oriented LiNbO{sub 3}/SiO{sub 2}/Si thin film layered structures

Energy Technology Data Exchange (ETDEWEB)

Tomar, Monika [Department of Physics and Astrophysics, University of Delhi, Delhi (India)]. E-mail: mtomar@physics.du.ac.in; monikatomar@rediffmail.com; Gupta, Vinay; Mansingh, Abhai; Sreenivas, K. [Department of Physics and Astrophysics, University of Delhi, Delhi (India)

2001-08-07

Theoretical calculations have been performed for the temperature stability of the c-axis oriented LiNbO{sub 3} thin film layered structures on passivated silicon (SiO{sub 2}/Si) substrate with and without a non-piezoelectric SiO{sub 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{sub 2} overlayer on LiNbO{sub 3} film is found to significantly enhance the coupling coefficient. The optimized results reveal that a high coupling coefficient of K{sup 2}=3.45% and a zero TCD can be obtained in the SiO{sub 2}/LiNbO{sub 3}/SiO{sub 2}/Si structure with a 0.235{lambda} thick LiNbO{sub 3} layer sandwiched between 0.1{lambda} thick SiO{sub 2} layers. (author)

Overview of the HIT-SI3 spheromak experiment

Science.gov (United States)

Hossack, A. C.; Jarboe, T. R.; Chandra, R. N.; Morgan, K. D.; Sutherland, D. A.; Everson, C. J.; Penna, J. M.; Nelson, B. A.

2017-10-01

The HIT-SI and HIT-SI3 spheromak experiments (a = 23 cm) study efficient, steady-state current drive for magnetic confinement plasmas using a novel method which is ideal for low aspect ratio, toroidal geometries. Sustained spheromaks show coherent, imposed plasma motion and low plasma-generated mode activity, indicating stability. Analysis of surface magnetic fields in HIT-SI indicates large n = 0 and 1 mode amplitudes and little energy in higher modes. Within measurement uncertainties all the n = 1 energy is imposed by the injectors, rather than being plasma-generated. The fluctuating field imposed by the injectors is sufficient to sustain the toroidal current through dynamo action whereas the plasma-generated field is not (Hossack et al., Phys. Plasmas, 2017). Ion Doppler spectroscopy shows coherent, imposed plasma motion inside r 10 cm in HIT-SI and a smaller volume of coherent motion in HIT-SI3. Coherent motion indicates the spheromak is stable and a lack of plasma-generated n = 1 energy indicates the maximum q is maintained below 1 for stability during sustainment. In HIT-SI3, the imposed mode structure is varied to test the plasma response (Hossack et al., Nucl. Fusion, 2017). Imposing n = 2, n = 3, or large, rotating n = 1 perturbations is correlated with transient plasma-generated activity. Work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, under Award Number DE-FG02-96ER54361.

Synthesis, microstructure and magnetic properties of Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite core

Energy Technology Data Exchange (ETDEWEB)

Wang, Jian, E-mail: snove418562@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Fan, Xi’an, E-mail: groupfxa@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Wu, Zhaoyang, E-mail: wustwuzhaoyang@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Li, Guangqiang [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China)

2015-11-15

Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite core have been synthesized via a modified stöber method combined with following high temperature sintering process. Most of conductive Fe{sub 3}Si{sub 0.7}Al{sub 0.3} particles could be uniformly coated by insulating SiO{sub 2} using the modified stöber method. The Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles exhibited good soft magnetic properties with low coercivity and high saturation magnetization. The reaction 4Al+3SiO{sub 2}=2α-Al{sub 2}O{sub 3}+3Si took place during the sintering process. As a result the new Fe{sub 3}Si/Al{sub 2}O{sub 3} composite was formed. The Fe{sub 3}Si/Al{sub 2}O{sub 3} composite core displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher electrical resistivity and lower core loss than the pure Fe{sub 3}Si{sub 0.7}Al{sub 0.3} core. The method of introducing insulating layers surrounding magnetic particles provides a promising route to develop new and high compact soft magnetic materials with good magnetic and electric properties. - Graphical abstract: In Fe{sub 3}Si/Al{sub 2}O{sub 3} composite, Fe{sub 3}Si phases are separated by Al{sub 2}O{sub 3} layers and the eddy currents are confined in Fe{sub 3}Si phases, thus increasing resistivity and reducing core loss. - Highlights: • Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} cores were prepared. • Fe{sub 3}Si{sub 0.7}Al{sub 0.3} particles could be uniformly coated by nano-sized SiO{sub 2} clusters. • Fe{sub 3}Si{sub 0.7}Al{sub 0.3}@SiO{sub 2} particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} cores showed good soft magnetic properties. • Fe{sub 3}Si/Al{sub 2}O{sub 3} had lower core loss and better frequency stability than Fe{sub 3}Si{sub 0.7}Al{sub 0.3} cores.

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.

Mechanical properties of non-centrosymmetric CePt3Si and CePt3B

Science.gov (United States)

Rogl, G.; Legut, D.; Sýkora, R.; Müller, P.; Müller, H.; Bauer, E.; Puchegger, S.; Zehetbauer, M.; Rogl, P.

2017-05-01

Elastic moduli, hardness (both at room temperature) and thermal expansion (4.2-670 K) have been experimentally determined for polycrystalline CePt3Si and its prototype compound CePt3B as well as for single-crystalline CePt3Si. Resonant ultrasound spectroscopy was used to determine elastic properties (Young’s modulus E and Poisson’s ratio ν) via the eigenfrequencies of the sample and the knowledge of sample mass and dimensions. Bulk and shear moduli were calculated from E and ν, and the respective Debye temperatures were derived. In addition, ab initio DFT calculations were carried out for both compounds. A comparison of parameters evaluated from DFT with those of experiments revealed, in general, satisfactory agreement. Positive and negative thermal expansion values obtained from CePt3Si single crystal data are fairly well explained in terms of the crystalline electric field model, using CEF parameters derived recently from inelastic neutron scattering. DFT calculations, in addition, demonstrate that the atomic vibrations keep almost unaffected by the antisymmetric spin-orbit coupling present in systems with crystal structures having no inversion symmetry. This is opposite to electronic properties, where the antisymmetric spin-orbit interaction has shown to distinctly influence features like the superconducting condensate of CePt3Si.

Sulfur passivation for the formation of Si-terminated Al{sub 2}O{sub 3/}SiGe(0 0 1) interfaces

Energy Technology Data Exchange (ETDEWEB)

Sardashti, Kasra [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA (United States); Hu, Kai-Ting [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA (United States); Tang, Kechao [Department of Materials Science and Engineering, Stanford University, CA (United States); Park, Sangwook; Kim, Hyonwoong [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA (United States); Madisetti, Shailesh [Department of Nanoscale Science and Engineering, University at Albany—State University of New York, Albany, NY (United States); McIntyre, Paul [Department of Materials Science and Engineering, Stanford University, CA (United States); Oktyabrsky, Serge [Department of Nanoscale Science and Engineering, University at Albany—State University of New York, Albany, NY (United States); Siddiqui, Shariq; Sahu, Bhagawan [TD Research, GLOBALFOUNDRIES USA, Inc., Albany, NY (United States); Yoshida, Noami; Kachian, Jessica [Applied Materials, Inc., Santa Clara, CA (United States); Kummel, Andrew, E-mail: akummel@ucsd.edu [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States)

2016-03-15

Graphical abstract: - Highlights: • Effect of wet sulfur passivation on the electrical properties of Al{sub 2}O{sub 3}/SiGe(0 0 1) interfaces has been determined. • EOT of 2.1 nm has been achieved for ALD Al{sub 2}O{sub 3} deposited directly on SiGe(0 0 1) surfaces. • Sulfur passivation has been found to passivate the Al{sub 2}O{sub 3} interface with Si−O−Al bonds. • Sulfur passivation is found to significantly reduce the GeO{sub x} or Ge−O−Al content at the Al{sub 2}O{sub 3}/SiGe interface therefore improving the reliability. • Sulfur passivation extends the surface stability prior to oxide ALD to up to an hour with no dramatic change in D{sub it}, C{sub ox} or V{sub FB} of the resulting devices. - Abstract: Sulfur passivation is used to electrically and chemically passivate the silicon–germanium (SiGe) surfaces before and during the atomic layer deposition (ALD) of aluminum oxide (Al{sub 2}O{sub 3}). The electrical properties of the interfaces were examined by variable frequency capacitance–voltage (C–V) spectroscopy. Interface compositions were determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The sulfur adsorbs to a large fraction of surface sites on the SiGe(0 0 1) surface, protecting the surface from deleterious surface reactions during processing. Sulfur passivation (a) improved the air stability of the cleaned surfaces prior to ALD, (b) increased the stability of the surface during high-temperature deposition, and (c) increased the Al{sub 2}O{sub 3} ALD nucleation density on SiGe, thereby lowering the leakage current. S passivation suppressed formation of Ge−O bonds at the interface, leaving the majority of the Al{sub 2}O{sub 3}–SiGe interface terminated with direct Si−O−Al bonding.

Magnetic properties of two new compounds: Pr2Ni3Si5 and Ho2Ni3Si5

International Nuclear Information System (INIS)

Mazumdar, C.; Padalia, B.D.; Godart, C.

1994-01-01

Formation of two more new materials, Pr 2 Ni 3 Si 5 and Ho 2 Ni 3 Si 5 , of the series, R 2 Ni 3 Si 5 (R = rare earth and Y) and their magnetic properties are reported here. These materials crystallize in the orthorhombic U 2 Co 3 Si 5 -type structure (space group Ibam). Magnetic susceptibility measurement in the temperature range 5 K--300 K show that the compound Pr 2 Ni 3 Si 5 order antiferromagnetically at T N ∼ 8.5 K and Ho 2 Ni 3 Si 5 at ∼ 6 K. Considering T N (Gd 2 Ni 3 Si 5 ) ∼ 15 K, T N (Pr 2 Ni 3 Si 5 ) ∼ 8.5 K is rather high. The magnetic susceptibility of both of the materials, in the paramagnetic state, follows a Curie-Weiss law with effective moment close to that of the corresponding free trivalent rare earth ion

Low-temperature conducting channel switching in hybrid Fe{sub 3}O{sub 4}/SiO{sub 2}/n-Si structures

Energy Technology Data Exchange (ETDEWEB)

Vikulov, V.A., E-mail: vikulov@iacp.dvo.ru [Institute of Automation and Control Processes, FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); Dimitriev, A.A.; Balashev, V.V.; Pisarenko, T.A.; Korobtsov, V.V. [Institute of Automation and Control Processes, FEB RAS, 5 Radio Street, 690041 Vladivostok (Russian Federation); School of Natural Sciences, Far Eastern Federal University, 690950 Vladivostok (Russian Federation)

2016-09-15

Highlights: • Conducting channel switching between the polycrystalline Fe{sub 3}O{sub 4} film and the n-Si substrate takes place in the Fe{sub 3}O{sub 4}/SiO{sub 2}/n-Si structure at temperature below 125 K. • This effect occurs via the field-assisted tunneling through the composite insulating layer that consists of the highly resistive Fe{sub 3}O{sub 4} and the tunnel SiO{sub 2}. • The switching is attended by a change in the shape of the current-voltage characteristics from the linear at 300 K to the S-type at 80 K. - Abstract: The carrier transport properties of the polycrystalline magnetite (Fe{sub 3}O{sub 4}) films grown on an n-type Si substrate with 5 nm-thick SiO{sub 2} have been investigated between 80 and 300 K in current-in-plane geometry. It was established that at temperature decrease to about 120 K, the resistivity of thin Fe{sub 3}O{sub 4} films increases up to a peak value and then abruptly drops. This process is attended by a change in the shape of the current-voltage characteristics from the linear at 300 K to the S-type at 80 K. The observed peculiarities are explained by conducting channel switching from the Fe{sub 3}O{sub 4} film to the Si substrate via the field-assisted tunneling of carriers through the composite insulating layer consisting of highly resistive Fe{sub 3}O{sub 4} and tunnel SiO{sub 2}.

Atomization of U3Si2/U3Si for research reactor fuel

International Nuclear Information System (INIS)

Kuk, Il Hiun

2004-01-01

Instead of comminuting, U 3 Si 2 /U 3 Si powders are produced by atomizating directly from the molten alloys. Many benefits are introduced by applying the atomization technique: reduction of the process, homogeneous alloy composition within a particle and between particles, increase of the thermal conductivity and decrease of the chemical reactivity with aluminium due to particle's spherical shape. (author)

Enhanced saturation magnetization of Fe3Si nanodot-embedded Fe80Si17Nb3 flexible film for efficient wireless power transfer

International Nuclear Information System (INIS)

Pai, Yi-Hao; Yan, Zih-Yu; Fu, Ping-Hao

2013-01-01

An efficient magnetically coupled resonance response is performed using an iron silicide-based nanostructured magnetoelectric material with high saturation magnetization for the wireless charging of battery-powered consumer electronics. With 500 °C annealing, the self-assembled Fe 3 Si nanodots buried in the Fe 80 Si 17 Nb 3 host matrix with (220) lattice spacing of 1.99 Å corresponding to a volume density of 8.96 × 10 16 cm 3 , can be obtained and a maximum saturation magnetization of 244 emu g −1 achieved. The return loss of the antenna will be tuned to match the designed frequency with greater attenuated intensity (−0.39 dB) and a relatively narrow bandwidth (6 kHz) when the Fe 3 Si nanodot-embedded Fe 80 Si 17 Nb 3 sample is placed in a WiTricity system. An efficient wireless power transfer can be created and improved from 47.5% to 97.3%. The associated coil and loop antenna resonators are significantly readjusted to match the power transfer by putting this nanostructured magnetoelectric material in a WiTricity system. - Highlights: • The saturation magnetization is effective enhancement in the presence of Fe 3 Si nanodot buried in the Fe 80 Si 17 Nb 3 . • A saturation magnetization of 244 emu g −1 is proposed for high-efficiency wireless power transfer. • The return loss of the antenna will be tuned to match the designed frequency. • Such a wireless power transfer can be enhanced efficiency up to 97.3%

Study of the nuclear spin-orbit interaction by performing the transfer reaction 36S(d,p)37S and 34Si(d,p)35Si

International Nuclear Information System (INIS)

Burgunder, G.

2011-12-01

The spin-orbit interaction depends on the spin orientation of the nucleons with respect to their angular momenta as well as on the derivative of the nuclear density. Even though this density dependence is used in all mean field model, it has never been tested yet due to the lack of data. We propose an original method to test this density dependence by comparing a bubble nucleus ( 34 Si) to a normal nucleus ( 36 S). The 34 Si exhibits a central density which is depleted by a factor of two which induces a non-zero central density derivative and should change the strength of the spin orbit interaction for the inner orbits such as the p orbits (L=1). By performing (d,p) transfer reactions with 36 S and 34 Si beams, the p(3/2) and p(1/2) spin orbit splitting can be inferred for these nuclei. Depending on the models, the spin-orbit splitting varies from 7% (VlowK interaction) up to 70% (Relativistic mean field approach). Beams of 36 S and 34 Si, produced at the LISE spectrometer at 20 A.MeV, were impinged onto a CD 2 target. Tracking the beam particles was achieved using 2 xy beam tracking gas detectors. Protons emitted were detected by 4 multi-segmented Si detectors (MUST2) placed at backwards angles. Gammas issued from the excited states decay were detected in the 4 EXOGAM segmented Germanium detectors. Transfer like nuclei were identified with an ionization chamber and a plastic detector. The excitation energy spectra of the 37 S and 35 Si are determined up to about 7 MeV. Spectroscopic factors and energies of p and f states are derived for the first time in 35 Si. The two nuclei show strong similarity for the f spin-orbit partners, whereas the p(3/2) - p(1/2) energy gap is reduced by 55%. (author)

Creep/Stress Rupture Behavior of 3D Woven SiC/SiC Composites with Sylramic-iBN, Super Sylramic-iBN and Hi-Nicalon-S Fibers at 2700F in Air

Science.gov (United States)

Bhatt, R. T.

2017-01-01

To determine the influence of fiber types on creep durability, 3D SiC/SiC CMCs were fabricated with Sylramic-iBN, super Sylramic-iBN and Hi-Nicalon-S fibers and the composite specimens were then tested under isothermal tensile creep at 14820C at 69, 103 and 138 MPa for up to 300hrs in air. The failed specimens were examined by scanning electron microscopy (SEM) and computed tomography (CT) for fracture mode analysis. The creep data of these composites are compared with those of other SiC/SiC composites in the literature. The results of this study will be presented.

Synthesis, structures and electroluminescence properties of CdS:In/Si nanoheterostructure array

Energy Technology Data Exchange (ETDEWEB)

Yan, Ling Ling; Cai, Hong Xin; Chen, Liang [Henan Polytechnic University, School of Physics and Electronic Information Engineering, Jiaozuo (China)

2017-10-15

An In-doped CdS/Si nanoheterojunction (CdS:In/Si-NPA) is prepared by depositing an In-doped CdS thin film onto a Si nanoporous pillar array (Si-NPA) via a successive ionic layer adsorption and reaction method. Based on the measured J-V characteristic curve, the nanoheterojunction exhibits a good rectifying behavior with a low forward turn-on voltage (2.2 V), a small leakage current density (0.5 mA/cm{sup 2} at - 3 V) and a high reverse breakdown voltage (> 8 V). The electroluminescence (EL) measurements reveal that a broadband emerges between 400 and 700 nm, and this band is confirmed as a white light emission based on the value of the chromaticity coordinate. The EL properties, including the CIE chromaticity coordinates, Colour Rendering Index and correlated color temperature, can be tuned by the applied voltage. The generation mechanism of the EL can be well interpreted depending on the energy band structure of CdS:In/Si-NPA. The green band should be attributed to the band-edge emission of CdS and the yellow emission may be related to Cd interstitial. These results highlight the potential of CdS:In/Si-NPA as a light source for future white light emitting devices. (orig.)

Application of bias correction methods to improve U{sub 3}Si{sub 2} sample preparation for quantitative analysis by WDXRF

Energy Technology Data Exchange (ETDEWEB)

Scapin, Marcos A.; Guilhen, Sabine N.; Azevedo, Luciana C. de; Cotrim, Marycel E.B.; Pires, Maria Ap. F., E-mail: mascapin@ipen.br, E-mail: snguilhen@ipen.br, E-mail: lvsantana@ipen.br, E-mail: mecotrim@ipen.br, E-mail: mapires@ipen.br [Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP), São Paulo, SP (Brazil)

2017-07-01

The determination of silicon (Si), total uranium (U) and impurities in uranium-silicide (U{sub 3}Si{sub 2}) samples by wavelength dispersion X-ray fluorescence technique (WDXRF) has been already validated and is currently implemented at IPEN's X-Ray Fluorescence Laboratory (IPEN-CNEN/SP) in São Paulo, Brazil. Sample preparation requires the use of approximately 3 g of H{sub 3}BO{sub 3} as sample holder and 1.8 g of U{sub 3}Si{sub 2}. However, because boron is a neutron absorber, this procedure precludes U{sub 3}Si{sub 2} sample's recovery, which, in time, considering routinely analysis, may account for significant unusable uranium waste. An estimated average of 15 samples per month are expected to be analyzed by WDXRF, resulting in approx. 320 g of U{sub 3}Si{sub 2} that would not return to the nuclear fuel cycle. This not only impacts in production losses, but generates another problem: radioactive waste management. The purpose of this paper is to present the mathematical models that may be applied for the correction of systematic errors when H{sub 3}BO{sub 3} sample holder is substituted by cellulose-acetate {[C_6H_7O_2(OH)_3_-_m(OOCCH_3)m], m = 0∼3}, thus enabling U{sub 3}Si{sub 2} sample’s recovery. The results demonstrate that the adopted mathematical model is statistically satisfactory, allowing the optimization of the procedure. (author)

Tunneling magnetoresistance in Fe{sub 3}Si/MgO/Fe{sub 3}Si(001) magnetic tunnel junctions

Energy Technology Data Exchange (ETDEWEB)

Tao, L. L.; Liang, S. H.; Liu, D. P.; Wei, H. X.; Han, X. F., E-mail: xfhan@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, Jian [Department of Physics and the Center of Theoretical and Computational Physics, The University of Hong Kong, Hong Kong (China)

2014-04-28

We present a theoretical study of the tunneling magnetoresistance (TMR) and spin-polarized transport in Fe{sub 3}Si/MgO/Fe{sub 3}Si(001) magnetic tunnel junction (MTJ). It is found that the spin-polarized conductance and bias-dependent TMR ratios are rather sensitive to the structure of Fe{sub 3}Si electrode. From the symmetry analysis of the band structures, we found that there is no spin-polarized Δ{sub 1} symmetry bands crossing the Fermi level for the cubic Fe{sub 3}Si. In contrast, the tetragonal Fe{sub 3}Si driven by in-plane strain reveals half-metal nature in terms of Δ{sub 1} state. The giant TMR ratios are predicted for both MTJs with cubic and tetragonal Fe{sub 3}Si electrodes under zero bias. However, the giant TMR ratio resulting from interface resonant transmission for the former decreases rapidly with the bias. For the latter, the giant TMR ratio can maintain up to larger bias due to coherent transmission through the majority-spin Δ{sub 1} channel.

Sintering behaviour and phase relationships of Si[sub 3]N[sub 4] ceramics in the Si[sub 3]N[sub 4]-SiO[sub 2]-MgO-Y[sub 2]O[sub 3] system. Sinterverhalten und Phasenbeziehungen von Si[sub 3]N[sub 4]-Keramiken im System Si[sub 3]N[sub 4]-SiO[sub 2]-MgO-Y[sub 2]O[sub 3

Energy Technology Data Exchange (ETDEWEB)

Mahoney, F.M.

1992-10-12

The aim of this work is the investigation of the sintering or crystallisation behaviour of Si[sub 3]N[sub 4] ceramics depending on the additive composition in the Si[sub 3]N[sub 4]-SiO[sub 2]-MgO-Y[sub 2]O[sub 3] system. With regard to the complicated manufacturing process of sintered and heat-treated Si[sub 3]N[sub 4] ceramics, one should first determine which additive compositions make complete compression possible. The effect of the composition on the volume and the viscosity of the melting phase should be cleared up, where determining the Si[sub 3]N[sub 4] solubility relative to the additive composition is of special importance. The phase relationships between Si[sub 3]N[sub 4] and the possible crystalline secondary phases should be determined for the crystallisation behaviour. Due to the very fine distribution of only a 5-15% proportion of additive in conventional Si[sub 3]N[sub 4] samples, a characterisation of the secondary phases is difficult to carry out with X-ray or REM/EDX analysis. Therefore, experiments with oxy-nitridic model samples were carried out in this work, which have the same phase relationships as conventional Si[sub 3]N[sub 4] compositions, but with an appreciably higher proportion of additive. The possibility of transferring the results of the model samples were tested on examples of three Si[sub 3]N[sub 4] ceramics. (orig.)

Rare-earth element doped Si3N4/SiC micro/nano-composites-RT and HT mechanical properties

Czech Academy of Sciences Publication Activity Database

Lojanová, Š.; Tatarko, P.; Chlup, Zdeněk; Hnatko, M.; Dusza, J.; Lenčéš, Z.; Šajgalík, P.

2010-01-01

Roč. 30, č. 9 (2010), s. 1931-1944 ISSN 0955-2219 Institutional research plan: CEZ:AV0Z20410507 Keywords : Si3N4 * SiC * Nano-composites * Fracture toughness * Hardness * Strength * Creep Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.574, year: 2010

Anisotropy of single-crystal 3C–SiC during nanometric cutting

International Nuclear Information System (INIS)

Goel, Saurav; Stukowski, Alexander; Luo, Xichun; Agrawal, Anupam; Reuben, Robert L

2013-01-01

3C–SiC (the only polytype of SiC that resides in a diamond cubic lattice structure) is a relatively new material that exhibits most of the desirable engineering properties required for advanced electronic applications. The anisotropy exhibited by 3C–SiC during its nanometric cutting is significant, and the potential for its exploitation has yet to be fully investigated. This paper aims to understand the influence of crystal anisotropy of 3C–SiC on its cutting behaviour. A molecular dynamics simulation model was developed to simulate the nanometric cutting of single-crystal 3C–SiC in nine (9) distinct combinations of crystal orientations and cutting directions, i.e. (1 1 1) 〈−1 1 0〉, (1 1 1) 〈−2 1 1〉, (1 1 0) 〈−1 1 0〉, (1 1 0) 〈0 0 1〉, (1 1 0) 〈1 1 −2〉, (0 0 1) 〈−1 1 0〉, (0 0 1) 〈1 0 0〉, (1 1 −2) 〈1 −1 0〉 and (1 −2 0) 〈2 1 0〉. In order to ensure the reliability of the simulation results, two separate simulation trials were carried out with different machining parameters. In the first trial, a cutting tool rake angle of −25°, d/r (uncut chip thickness/cutting edge radius) ratio of 0.57 and cutting velocity of 10 m s −1 were used whereas a second trial was done using a cutting tool rake angle of −30°, d/r ratio of 1 and cutting velocity of 4 m s −1 . Both the trials showed similar anisotropic variation. The simulated orthogonal components of thrust force in 3C–SiC showed a variation of up to 45%, while the resultant cutting forces showed a variation of 37%. This suggests that 3C–SiC is highly anisotropic in its ease of deformation. These results corroborate with the experimentally observed anisotropic variation of 43.6% in Young's modulus of 3C–SiC. The recently developed dislocation extraction algorithm (DXA) [1, 2] was employed to detect the nucleation of dislocations in the MD simulations of varying cutting orientations

Anisotropy in elastic properties of TiSi2 (C49, C40 and C54), TiSi and Ti5Si3: an ab-initio density functional study

International Nuclear Information System (INIS)

Niranjan, Manish K

2015-01-01

We present a comparative study of the anisotropy in the elastic properties of the C49, C54 and C40 phases of TiSi 2 , as well as orthorhombic TiSi and hexagonal Ti 5 Si 3 . The elastic constants, elastic moduli, Debye temperature and sound velocities are computed within the framework of density functional theory. The computed values of the elastic constants and moduli are found to be in excellent agreement with available experimental values. The average elastic moduli, such as Young’s modulus, shear modulus, bulk modulus and Poisson’s ratio, of polycrystalline aggregates are computed using the computed elastic constants of single crystals. The anisotropy in elastic properties is analyzed using estimates of shear anisotropic factors, bulk modulus anisotropic factors and variations in Young’s and bulk moduli in different crystallographic directions. Among the Ti–Si phases, the computed directional Young’s modulus profiles of C49 TiSi 2 and C40 TiSi 2 are found to be quite similar to those of bulk Si and Ti, respectively. In addition to the elastic properties, the electronic structure of five Ti–Si phases is studied. The density of states and planar charge density profiles reveal mixed covalent–metallic bonding in all Ti–Si phases. (paper)

Reaction of ReH sub 7 (PPh sub 3 ) sub 2 with silanes: Preparation and characterization of the first silyl polyhydride complexes, ReH sub 6 (SiR sub 3 )(PPh sub 3 ) sub 2 (SiR sub 3 = SiPh sub 3 , SiEt sub 3 , SiHEt sub 2 )

Energy Technology Data Exchange (ETDEWEB)

Luo, Xiaoliang; Baudry, D.; Boydell, P.; Charpin, P.; Nierlich, M.; Ephritikhine, M.; Crabtree, R.H. (Yale Univ., New Haven, CT (USA) CEA-CEN Saclay, Gif-sur-Yvette (France))

1990-04-18

Reaction of silanes with ReH{sub 7}(PPh{sub 3}){sub 2} (1) gives the novel rhenium silyl hexahydride complexes ReH{sub 6}(SiR{sub 3})(PPh{sub 3}){sub 2} (SiR{sub 3} = SiPh{sub 3} (2a), SiEt{sub 3} (2b), SiHEt{sub 2} (2c)), which have been fully characterized by IR and {sup 1}H, {sup 31}P, and {sup 13}C NMR spectroscopy and, in the case of 2a, by single-crystal x-ray crystallography. The spectroscopic and x-ray diffraction data suggest that 2a-c probably have a classical nine-coordinate tricapped trigonal-prismatic structure with the two phosphine ligands and the silyl group occupying the three equatorial sites and the six hydride ligands occupying the six axial positions. 2a has been obtained in two crystalline forms, one solvated (CH{sub 2}Cl{sub 2}) and the other unsolvated, and structures were determined on both. The crystal structures of crystals of unsolvated 2a and 2a {times} CH{sub 2} Cl{sub 2} are reported. The Re-Si bond lengths, 2.474 (4) {angstrom} (2a) and 2.475 (4) {angstrom} (2a {times} CH{sub 2}Cl{sub 2}), are shorter than the sum of the covalent radii of the Re and Si atoms (2.65 {angstrom}), which is unusual for a transition-metal silyl complex with a formal d{sup 0} configuration. 35 refs., 2 figs., 4 tabs.

In situ observation of self-propagating high temperature syntheses of Ta5Si3, Ti5Si3 and TiB2 by proton and X-ray radiography

Science.gov (United States)

Bernert, T.; Winkler, B.; Haussühl, E.; Trouw, F.; Vogel, S. C.; Hurd, A. J.; Smilowitz, L.; Henson, B. F.; Merrill, F. E.; Morris, C. L.; Mariam, F. G.; Saunders, A.; Juarez-Arellano, E. A.

2013-08-01

Self-propagating high temperature reactions of tantalum and titanium with silicon and titanium with boron were studied using proton and X-ray radiography, small-angle neutron scattering, neutron time-of-flight, X-ray and neutron diffraction, dilatometry and video recording. We show that radiography allows the observation of the propagation of the flame front in all investigated systems and the determination of the widths of the burning zones. X-ray and neutron diffraction showed that the reaction products consisted of ≈90 wt% of the main phase and one or two secondary phases. For the reaction 5Ti + 3Si → Ti5Si3 flame front velocities of 7.1(3)-34.2(4) mm/s were determined depending on the concentration of a retardant added to the starting material, the geometry and the green density of the samples. The flame front width was determined to be 1.17(4)-1.82(8) mm and depends exponentially on the flame front velocity. Similarly, for the reaction Ti + 2B → TiB2 flame front velocities of 15(2)-26.6(4) mm/s were determined, while for a 5Ta + 3Si → Ta5Si3 reaction the flame front velocity was 7.05(4) mm/s. The micro structure of the product phase Ta5Si3 shows no texture. From SANS measurements the dependence of the specific surface of the product phase on the particle sizes of the starting materials was studied.

Electroless siliconizing Fe-3% Cr-3% Si alloy

International Nuclear Information System (INIS)

Nurlina, Enung; Darmono, Budy; Purwadaria, Sunara

2000-01-01

In this research Fe-3%Cr-3%Mo-3%Si and Fe-3%Cr-3%Cu-3%Si alloys had been coated by silicon metal without electricity current which knows as electroless siliconizing. Coating was conducted by immersed sampler into melt fluoride-chloride salt bath at temperature of 750 o C for certain period. The layer consisted of Fe3Si phase. Observation by microscope optic and EDAX showed that the silicide layer were thick enough, adherent, free for crack and had silicon content on the surface more than 15%. The growth rate of silicide layer followed parabolic rate law, where the process predominantly controlled by interdiffusion rate in the solid phase. Key words : electroless siliconizing, the melt fluoride- chloride salt mix, silicide layer

Oxide Structure Dependence of SiO2/SiOx/3C-SiC/n-Type Si Nonvolatile Resistive Memory on Memory Operation Characteristics

Science.gov (United States)

Yamaguchi, Yuichiro; Shouji, Masatsugu; Suda, Yoshiyuki

2012-11-01

We have investigated the dependence of the oxide layer structure of our previously proposed metal/SiO2/SiOx/3C-SiC/n-Si/metal metal-insulator-semiconductor (MIS) resistive memory device on the memory operation characteristics. The current-voltage (I-V) measurement and X-ray photoemission spectroscopy results suggest that SiOx defect states mainly caused by the oxidation of 3C-SiC at temperatures below 1000 °C are related to the hysteresis memory behavior in the I-V curve. By restricting the SiOx interface region, the number of switching cycles and the on/off current ratio are more enhanced. Compared with a memory device formed by one-step or two-step oxidation of 3C-SiC, a memory device formed by one-step oxidation of Si/3C-SiC exhibits a more restrictive SiOx interface with a more definitive SiO2 layer and higher memory performances for both the endurance switching cycle and on/off current ratio.

Fabrication of highly oriented D0{sub 3}-Fe{sub 3}Si nanocrystals by solid-state dewetting of Si ultrathin layer

Energy Technology Data Exchange (ETDEWEB)

Naito, Muneyuki, E-mail: naito22@center.konan-u.ac.jp [Department of Chemistry, Konan University, Okamoto, Higashinada, Kobe, Hyogo 658-8501 (Japan); Nakagawa, Tatsuhiko; Machida, Nobuya; Shigematsu, Toshihiko [Department of Chemistry, Konan University, Okamoto, Higashinada, Kobe, Hyogo 658-8501 (Japan); Nakao, Motoi [Graduate School of Engineering, Kyushu Institute of Technology, Sensui, Tobata, Kitakyushu, Fukuoka 804-8550 (Japan); Sudoh, Koichi [The Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

2013-07-31

In this paper, highly oriented nanocrystals of Fe{sub 3}Si with a D0{sub 3} structure are fabricated on SiO{sub 2} using ultrathin Si on insulator substrate. First, (001) oriented Si nanocrystals are formed on the SiO{sub 2} layer by solid state dewetting of the top Si layer. Then, Fe addition to the Si nanocrystals is performed by reactive deposition epitaxy and post-deposition annealing at 500 °C. The structures of the Fe–Si nanocrystals are analyzed by cross-sectional transmission electron microscopy and nanobeam electron diffraction. We observe that Fe{sub 3}Si nanocrystals with D0{sub 3}, B2, and A2 structures coexist on the 1-h post-annealed samples. Prolonged annealing at 500 °C is effective in obtaining Fe{sub 3}Si nanocrystals with a D0{sub 3} single phase, thereby promoting structural ordering in the nanocrystals. We discuss the formation process of the highly oriented D0{sub 3}-Fe{sub 3}Si nanocrystals on the basis of the atomistic structural information. - Highlights: • Highly oriented Fe–Si nanocrystals (NCs) are fabricated by reactive deposition. • Si NCs formed by solid state dewetting of Si thin layers are used as seed crystals. • The structures of Fe–Si NCs are analyzed by nanobeam electron diffraction. • Most of Fe–Si NCs possess the D0{sub 3} structure after post-deposition annealing.

Evidence of significant down-conversion in a Si-based solar cell using CuInS2/ZnS core shell quantum dots

Science.gov (United States)

Gardelis, Spiros; Nassiopoulou, Androula G.

2014-05-01

We report on the increase of up to 37.5% in conversion efficiency of a Si-based solar cell after deposition of light-emitting Cd-free, CuInS2/ZnS core shell quantum dots on the active area of the cell due to the combined effect of down-conversion and the anti- reflecting property of the dots. We clearly distinguished the effect of down-conversion from anti-reflection and estimated an enhancement of up to 10.5% in the conversion efficiency due to down-conversion.

Evidence of significant down-conversion in a Si-based solar cell using CuInS2/ZnS core shell quantum dots

International Nuclear Information System (INIS)

Gardelis, Spiros; Nassiopoulou, Androula G.

2014-01-01

We report on the increase of up to 37.5% in conversion efficiency of a Si-based solar cell after deposition of light-emitting Cd-free, CuInS 2 /ZnS core shell quantum dots on the active area of the cell due to the combined effect of down-conversion and the anti- reflecting property of the dots. We clearly distinguished the effect of down-conversion from anti-reflection and estimated an enhancement of up to 10.5% in the conversion efficiency due to down-conversion

3C-SiC nanocrystal growth on 10° miscut Si(001) surface

Energy Technology Data Exchange (ETDEWEB)

Deokar, Geetanjali, E-mail: gitudeo@gmail.com [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); D' Angelo, Marie; Demaille, Dominique [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); Cavellin, Catherine Deville [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); Faculté des Sciences et Technologie UPEC, 61 av. De Gaulle, Créteil F-94010 (France)

2014-04-01

The growth of 3C-SiC nano-crystal (NC) on 10° miscut Si(001) substrate by CO{sub 2} thermal treatment is investigated by scanning and high resolution transmission electron microscopies. The vicinal Si(001) surface was thermally oxidized prior to the annealing at 1100 °C under CO{sub 2} atmosphere. The influence of the atomic steps at the vicinal SiO{sub 2}/Si interface on the SiC NC growth is studied by comparison with the results obtained for fundamental Si(001) substrates in the same conditions. For Si miscut substrate, a substantial enhancement in the density of the SiC NCs and a tendency of preferential alignment of them along the atomic step edges is observed. The SiC/Si interface is abrupt, without any steps and epitaxial growth with full relaxation of 3C-SiC occurs by domain matching epitaxy. The CO{sub 2} pressure and annealing time effect on NC growth is analyzed. The as-prepared SiC NCs can be engineered further for potential application in optoelectronic devices and/or as a seed for homoepitaxial SiC or heteroepitaxial GaN film growth. - Highlights: • Synthesis of 3C-SiC nanocrystals epitaxied on miscut-Si using a simple technique • Evidence of domain matching epitaxy at the SiC/Si interface • SiC growth proceeds along the (001) plane of host Si. • Substantial enhancement of the SiC nanocrystal density due to the miscut • Effect of the process parameters (CO{sub 2} pressure and annealing duration)

Target swapping in PLD: An efficient approach for CdS/SiO2 and CdS:Ag(1%)/SiO2 nanocomposite thin films with enhanced luminescent properties

International Nuclear Information System (INIS)

Saxena, Nupur; Kumar, Pragati; Gupta, Vinay

2017-01-01

A novel synthesis method for luminescent and by-products (like CdO) free CdS/SiO 2 and CdS:Ag(1%)/SiO 2 (i.e. 1%Ag doped CdS/SiO 2 ) nanocomposite thin films at room temperature by pulsed laser deposition is reported. Targets of CdS, CdS:Ag(1%) and SiO 2 are used to deposit CdS/SiO 2 and CdS:Ag(1%)/SiO 2 nanocomposite thin films by swapping them at a frequency ratio of 2:8 laser pulses/sec. X-ray photoelectron spectroscopy analysis ensures the ratio of CdS to SiO 2 in nanocomposite as 21:79 which is nearly same as the ratio of incident pulses/sec (i.e. 2:8) on the two targets. Transmission electron micrographs visualize the formation of CdS/ CdS:Ag(1%) nanocrystals in nanocomposite systems after annealing at 500 °C. Highly intense and broad red emission is achieved from CdS/SiO 2 and CdS:Ag(1%)/SiO 2 nanocomposites. The efficiencies of emission from pristine CdS:SiO 2 and CdS:Ag(1%)/SiO 2 nanocomposites are found to be enhanced by approximately two times as compared to sole nanocrystalline CdS and CdS:Ag(1%) thin films respectively and further enhanced upto 7 times on annealing the nanocomposite systems at 500 °C. - Graphical abstract: A modified synthesis method for luminescent and by-products (like CdO) free undoped &1% Ag doped CdS/SiO 2 (deposit CdS/SiO 2 and CdS:Ag(1%)/SiO 2 ) nanocomposite thin films at room temperature by pulsed laser deposition is reported. Targets of CdS or CdS:Ag(1%) and SiO 2 are used to deposit CdS/SiO 2 and CdS:Ag(1%)/SiO 2 nanocomposite thin films by swapping them at a frequency of 2:8 pulses/sec. X-ray photoelectron spectroscopy analysis ensures the ratio of CdS to SiO 2 in nanocomposite as 21:79 which is nearly same as the ratio of incident pulses/sec (2:8) on the two targets. Transmission electron micrographs visualize the formation of CdS nanocrystals in nanocomposite systems after annealing at 500 °C. Intense and broad red emission is achieved from deposit CdS/SiO 2 and CdS:Ag(1%)/SiO 2 nanocomposites. The efficiency of

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.

Preparation of ZnS microdisks using chemical bath deposition and ZnS/p-Si heterojunction solar cells

Science.gov (United States)

Hsiao, Y. J.; Meen, T. H.; Ji, L. W.; Tsai, J. K.; Wu, Y. S.; Huang, C. J.

2013-10-01

The synthesis and heterojunction solar cell properties of ZnS microdisks prepared by the chemical bath deposition method were investigated. The ZnS deposited on the p-Si blanket substrate exhibits good coverage. The lower reflectance spectra were found as the thickness of the ZnS film increased. The optical absorption spectra of the 80 °C ZnS microdisk exhibited a band-gap energy of 3.4 eV and the power conversion efficiency (PCE) of the AZO/ZnS/p-Si heterojunction solar cell with a 300 nm thick ZnS film was η=2.72%.

Post-irradiation examination of prototype Al-64 wt% U3Si2 fuel rods from NRU

International Nuclear Information System (INIS)

Sears, D.F.; Primeau, M.F.; Buchanan, C.; Rose, D.

1997-01-01

Three prototype fuel rods containing Al-64 wt% U 3 Si 2 (3.15 gU/cm 3 ) have been irradiated to their design burnup in the NRU reactor without incident. The fuel was fabricated using production-scale equipment and processes previously developed for Al-U 3 Si fuel fabrication at Chalk River Laboratories, and special equipment developed for U 3 Si 2 powder production and handling. The rods were irradiated in NRU up to 87 at% U-235 burnup under typical driver fuel conditions; i.e., nominal coolant inlet temperature 37 degrees C, inlet pressure 654 kPa, mass flow 12.4 L/s, and element linear power ratings up to 73 kW/m. Post-irradiation examinations showed that the fuel elements survived the irradiation without defects. Fuel core diametral increases and volumetric swelling were significantly lower than that of Al-61 wt% U 3 Si fuel irradiated under similar conditions. This irradiation demonstrated that the fabrication techniques are adequate for full-scale fuel manufacture, and qualified the fuel for use in AECL's research reactors

C and Si delta doping in Ge by CH{sub 3}SiH{sub 3} using reduced pressure chemical vapor deposition

Energy Technology Data Exchange (ETDEWEB)

Yamamoto, Yuji, E-mail: yamamoto@ihp-microelectronics.com [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Ueno, Naofumi; Sakuraba, Masao [Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, 2-1-1, Katahira, Aoba-Ku, Sendai 980-8577 (Japan); Murota, Junichi [Micro System Integration Center, Tohoku University, 519-1176, Aramaki aza Aoba, Aoba-ku, Sendai 980-0845 (Japan); Mai, Andreas [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Tillack, Bernd [IHP, Im Technologiepark 25, 15236 Frankfurt (Oder) (Germany); Technische Universität Berlin, HFT4, Einsteinufer 25, 10587 Berlin (Germany)

2016-03-01

C and Si delta doping in Ge are investigated using a reduced pressure chemical vapor deposition system to establish atomic-order controlled processes. CH{sub 3}SiH{sub 3} is exposed at 250 °C to 500 °C to a Ge on Si (100) substrate using H{sub 2} or N{sub 2} carrier gas followed by a Ge cap layer deposition. At 350 °C, C and Si are uniformly adsorbed on the Ge surface and the incorporated C and Si form steep delta profiles below detection limit of SIMS measurement. By using N{sub 2} as carrier gas, the incorporated C and Si doses in Ge are saturated at one mono-layer below 350 °C. At this temperature range, the incorporated C and Si doses are nearly the same, indicating CH{sub 3}SiH{sub 3} is adsorbed on the Ge surface without decomposing the C−Si bond. On the other hand, by using H{sub 2} as carrier gas, lower incorporated C is observed in comparison to Si. CH{sub 3}SiH{sub 3} injected with H{sub 2} carrier gas is adsorbed on Ge without decomposing the C−Si bond and the adsorbed C is reduced by dissociation of the C−Si bond during temperature ramp up to 550 °C. The adsorbed C is maintained on the Ge surface in N{sub 2} at 550 °C. - Highlights: • C and Si delta doping in Ge is investigated using RPCVD system by CH{sub 3}SiH{sub 3} exposure. • Atomically flat C and Si delta layers are fabricated at 350 °C. • Incorporated C and Si doses are saturated at one mono-layer below 350 °C. • CH{sub 3}SiH{sub 3} adsorption occurred without decomposing C−Si bond. • Adsorbed C is desorbed due to dissociation by hydrogen during postannealing at 550 °C.

Post-irradiation examination of prototype Al-64 wt% U{sub 3}Si{sub 2} fuel rods from NRU

Energy Technology Data Exchange (ETDEWEB)

Sears, D.F.; Primeau, M.F.; Buchanan, C.; Rose, D. [Chalk River Labs., Ontario (Canada)

1997-08-01

Three prototype fuel rods containing Al-64 wt% U{sub 3}Si{sub 2} (3.15 gU/cm{sup 3}) have been irradiated to their design burnup in the NRU reactor without incident. The fuel was fabricated using production-scale equipment and processes previously developed for Al-U{sub 3}Si fuel fabrication at Chalk River Laboratories, and special equipment developed for U{sub 3}Si{sub 2} powder production and handling. The rods were irradiated in NRU up to 87 at% U-235 burnup under typical driver fuel conditions; i.e., nominal coolant inlet temperature 37{degrees}C, inlet pressure 654 kPa, mass flow 12.4 L/s, and element linear power ratings up to 73 kW/m. Post-irradiation examinations showed that the fuel elements survived the irradiation without defects. Fuel core diametral increases and volumetric swelling were significantly lower than that of Al-61 wt% U{sub 3}Si fuel irradiated under similar conditions. This irradiation demonstrated that the fabrication techniques are adequate for full-scale fuel manufacture, and qualified the fuel for use in AECL`s research reactors.

Au L-shell ionization by Si and S ions

International Nuclear Information System (INIS)

Berinde, A.; Ciortea, C.; Enulescu, A.; Fluerasu, D.; Piticu, I.; Zoran, V.; Trautmann, D.

1984-01-01

We present the following experimental results on Au L-shell ionization: (1) in the bombarding energy range 0.25-2.5 MeV/u, absolute X-ray yields and the L 3 -vacancy integral alignment for Si, and cross section ratios for Si and S as projectiles; (2) at 32 MeV sulphur energy, subshell ionization probability ratios and the components A 20 (b) and A 22 (b) of the statistical tensor describing the L 3 -vacancy for impact parameters b=20-450 fm. A comparison of the data to SCA calcualtions reveals, except perhaps for the differential alignment, important discrepancies relative to the theoretical predictions. (orig./BRB)

Core–shell structured FeSiAl/SiO{sub 2} particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} soft magnetic composite cores with tunable insulating layer thicknesses

Energy Technology Data Exchange (ETDEWEB)

Fan, Xi’an, E-mail: groupfxa@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Wang, Jian, E-mail: snove418562@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Wu, Zhaoyang, E-mail: wustwuzhaoyang@163.com [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Li, Guangqiang, E-mail: ligq-wust@mail.wust.edu.cn [The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China); Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education, Wuhan University of Science and Technology, Wuhan, Hubei 430081 (China)

2015-11-15

Graphical abstract: - Highlights: • FeSiAl/SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores were prepared. • SiO{sub 2} surrounding FeSiAl were replaced by Al{sub 2}O{sub 3} during sintering process. • Fe{sub 3}Si particles were separated by Al{sub 2}O{sub 3} with tunable thickness in composite cores. • Fe{sub 3}Si/Al{sub 2}O{sub 3} had lower core loss and better frequency stability than FeSiAl core. • The insulating layer between ferromagnetic particles can reduce core loss. - Abstract: FeSiAl/SiO{sub 2} core–shell particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores with tunable insulating layer thicknesses have been synthesized via a modified Stöber method combined with following high temperature sintering process. Most of the conductive FeSiAl particles could be coated by insulating SiO{sub 2} using the modified Stöber method. During the sintering process, the reaction 4Al + 3SiO{sub 2} ≣ 2α-Al{sub 2}O{sub 3} + 3Si took place and the new Fe{sub 3}Si/Al{sub 2}O{sub 3} composite was formed. The Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher resistivity and lower core loss than the raw FeSiAl core. Based on this, several types of FeSiAl/SiO{sub 2} particles and Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores with tunable insulating layer thicknesses were selectively prepared by simply varying TEOS contents. The thickness of Al{sub 2}O{sub 3} insulating layer and resistivity of Fe{sub 3}Si/Al{sub 2}O{sub 3} composite cores increased with increasing the TEOS contents, while the permeability and core loss changed in the opposite direction.

PIE of nuclear grade SiC/SiC flexural coupons irradiated to 10 dpa at LWR temperature

Energy Technology Data Exchange (ETDEWEB)

Koyanagi, Takaaki [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Katoh, Yutai [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-03-01

Silicon carbide fiber-reinforced SiC matrix (SiC/SiC) composites are being actively investigated for accident-tolerant core structures of light water reactors (LWRs). Owing to the limited number of irradiation studies previously conducted at LWR-coolant temperature, this study examined SiC/SiC composites following neutron irradiation at 230–340°C to 2.0 and 11.8 dpa in the High Flux Isotope Reactor. The investigated materials are chemical vapor infiltrated (CVI) SiC/SiC composites with three different reinforcement fibers. The fiber materials were monolayer pyrolytic carbon (PyC)-coated Hi-NicalonTM Type-S (HNS), TyrannoTM SA3 (SA3), and SCS-Ultra^TM (SCS) SiC fibers. The irradiation resistance of these composites was investigated based on flexural behavior, dynamic Young’s modulus, swelling, and microstructures. There was no notable mechanical properties degradation of the irradiated HNS and SA3 SiC/SiC composites except for reduction of the Young’s moduli by up to 18%. The microstructural stability of these composites supported the absence of degradation. In addition, no progressive swelling from 2.0 to 11.8 dpa was confirmed for these composites. On the other hand, the SCS composite showed significant mechanical degradation associated with cracking within the fiber. This study determined that SiC/SiC composites with HNS or SA3 SiC/SiC fibers, a PyC interphase, and a CVI SiC matrix retain their properties beyond the lifetime dose for LWR fuel cladding at the relevant temperature.

Energetic prediction on the stability of A2Mg12Si7, A2Mg4Si3, and AMgSi in the A2Si–Mg2Si system (A = Ca, Sr and Ba) and their calculated electronic structures

International Nuclear Information System (INIS)

Imai, Yoji; Mori, Yoshihisa; Nakamura, Shigeyuki; Takarabe, Ken-ichi

2014-01-01

Highlights: • Formation energies of A 2 Mg 4 Si 3 , A 2 Mg 12 Si 7 , and AMgSi (A = Ca,Sr,Ba) were calculated. • All AMgSi are quite stable compared to mixture of A 2 Si and Mg 2 Si. • Ba 2 Mg 4 Si 3 and Sr 2 Mg 4 Si 3 are predicted to be stable, but Ca 2 Mg 4 Si 3 is not. • Ca 2 Mg 12 Si 7 and Sr 2 Mg 12 Si 7 are energetically unstable. • Stability of Ba 2 Mg 12 Si 7 is a tender subject. -- Abstract: In order to evaluate the relative stability of A 2 Mg 4 Si 3 , A 2 Mg 12 Si 7 , and AMgSi (A = Ca, Sr, and Ba) in the A 2 Si–Mg 2 Si system, electronic energy changes in the formation of these compounds were calculated using a density-functional theory with the Perdew–Wang generalized gradient approximations. It was found that (1) AMgSi’s are quite stable compared to equi-molar mixture of A 2 Si and Mg 2 Si, (2) Ba 2 Mg 4 Si 3 and Sr 2 Mg 4 Si 3 are also stable, (3) Ca 2 Mg 4 Si 3 and Ca 2 Mg 12 Si 7 are less stable than the mixture of CaMgSi and Mg 2 Si, and (4) Stability of Ba 2 Mg 12 Si 7 is a tender subject and Sr 2 Mg 12 Si 7 is energetically unstable compared to the mixture of Sr 2 Mg 4 Si 3 (or, SrMgSi) and Mg 2 Si. The presence of Sr 2 Mg 12 Si 7 may be due to the vibrational and/or configurational entropy, which are not treated in the present study. From the calculated electronic densities of state, complex compounds of SrMgSi and Mg 2 Si have both p-type and n-type character, depending on the ratio of SrMgSi and Mg 2 Si in that compound

V3Si multifilamentary superconductor with high overall Jc

International Nuclear Information System (INIS)

Takeuchi, Takao; Inoue, Kiyoshi; Kosuge, Michio; Iijima, Yasuo; Watanabe, Kazuo

1994-01-01

V 3 Si is one of the A15-type superconducting compounds from which single crystals can be quite easily obtained due to the nature of the equilibrium phase diagram. Thus, the fundamental characteristics of A15 compounds (such as electronic structure and cubic-to-tetragonal structural transformation) have been studied with this compound. V 3 Si is, however, also promising in practical use as an alternative to Nb 3 Sn for high field magnets, since the upper critical field H c2 (4.2 K) is more than 20 T. Although the open-quotes bronze process,close quotes the established commercial process to produce Nb 3 Sn conductors, is also available for V 3 Si, the ternary section of the Cu-V-Si phase diagram indicates two diffusion paths are possible: One from the bronze with low Si content (Si 3 Si, and the other from the bronze with higher Si content to V 3 Si via V 5 Si 3 . The high Si bronze is likely to be advantageous in reducing the bronze volume fraction and hence achieving high overall critical current density J c . This is because the initially formed V 5 Si 3 is eventually converted to V 3 Si as long as the total proportion of V to Si in the composite (overall V/Si molar ratio) is kept around 3. However, long times at high temperatures are necessary for appreciable V 3 Si layer growth, thereby yielding grain growth of V 3 Si and lowering the J c of the V 3 Si compound and the overall J c accordingly. In the present study, in order to improve the overall J c , the authors have realized ∼1μm filament diameter by preparing a double-stacked Cu-8.5at.%Si/V composite. The primary bundle is sheathed with a Ta tube. The Si in the bronze inside the Ta is available only for the diffusion reaction, and the overall V/Si ratios is ∼3

Breakdown of coupling dielectrics for Si microstrip detectors

International Nuclear Information System (INIS)

Candelori, A.; Paccagnella, A.; Padova Univ.; Saglimbeni, G.

1999-01-01

Double-layer coupling dielectrics for AC-coupled Si microstrip detectors have been electrically characterized in order to determine their performance in a radiation-harsh environment, with a focus on the dielectric breakdown. Two different dielectric technologies have been investigated: SiO 2 /TEOS and SiO 2 /Si 3 N 4 . Dielectrics have been tested by using a negative gate voltage ramp of 0.2 MV/(cm·s). The metal/insulator/Si I-V characteristics show different behaviours depending on the technology. The extrapolated values of the breakdown field for unirradiated devices are significantly higher for SiO 2 /Si 3 N 4 dielectrics, but the data dispersion is lower for SiO 2 /TEOS devices. No significant variation of the breakdown field has been measured after a 10 Mrad (Si) γ irradiation for SiO 2 /Si 3 N 4 dielectrics. Finally, the SiO 2 /Si 3 N 4 DC conduction is enhanced if a positive gate voltage ramp is applied with respect to the negative one, due to the asymmetric conduction of the double-layer dielectric

Fluorocarbon based atomic layer etching of Si{sub 3}N{sub 4} and etching selectivity of SiO{sub 2} over Si{sub 3}N{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Li, Chen [Department of Physics, and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Metzler, Dominik; Oehrlein, Gottlieb S., E-mail: oehrlein@umd.edu [Department of Materials Science and Engineering, and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Lai, Chiukin Steven; Hudson, Eric A. [Lam Research Corporation, 4400 Cushing Parkway, Fremont, California 94538 (United States)

2016-07-15

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{sub 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{sup +} ion bombardment in a cyclic fashion. Low energy ion bombardment is used to remove the FC layer along with a limited amount of SiO{sub 2} from the surface. In the present article, the authors describe controlled etching of Si{sub 3}N{sub 4} and SiO{sub 2} layers of one to several Angstroms using this cyclic ALE approach. Si{sub 3}N{sub 4} etching and etching selectivity of SiO{sub 2} over Si{sub 3}N{sub 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{sub 3}N{sub 4} were investigated by x-ray photoelectron spectroscopy (XPS) after vacuum transfer at each stage of the ALE process. Since Si{sub 3}N{sub 4} has a lower physical sputtering energy threshold than SiO{sub 2}, Si{sub 3}N{sub 4} physical sputtering can take place after removal of chemical etchant at the end of each cycle for relatively high ion energies. Si{sub 3}N{sub 4} to SiO{sub 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{sub 2} to Si{sub 3}N{sub 4} etching can be achieved for FC accumulation conditions, where FC can be selectively accumulated on Si{sub 3}N{sub 4} surfaces. This highly selective etching is explained by a lower carbon consumption of Si{sub 3}N{sub 4} as compared to Si

Near-surface segregation in irradiated Ni3Si

International Nuclear Information System (INIS)

Wagner, W.; Rehn, L.E.; Wiedersich, H.

1982-01-01

The radiation-induced growth of Ni 3 Si films on the surfaces of Ni(Si) alloys containing = 3 Si phase has been observed. Post-irradiation depth profiling by Auger electron spectroscopy, as well as in situ analysis by high-resolution Rutherford backscattering spectrometry, reveals Si-enrichment at the surfaces of Ni(Si) alloys in excess of stoichiometric Ni 3 Si during irradiation. Thin, near-surface layers with silicon concentrations of 28 to 30 at.% are observed, and even higher Si enrichment is found in the first few atom layers. Transmission electron microscopy and selected area-electron diffraction were employed to characterize these Si-enriched layers. A complex, multiple-spot diffraction pattern is observed superposed on the diffraction pattern of ordered Ni 3 Si. The d-spacings obtained from the extra spots are consistent with those of the orthohexagonal intermetallic compound Ni 5 Si 2 . (author)

Microstructure and properties of MoSi2-MoB and MoSi2-Mo5Si3 molybdenum silicides

International Nuclear Information System (INIS)

Schneibel, J.H.; Sekhar, J.A.

2003-01-01

MoSi 2 -based intermetallics containing different volume fractions of MoB or Mo 5 Si 3 were fabricated by hot-pressing MoSi 2 , MoB, and Mo 5 Si 3 powders in vacuum. Both classes of alloys contained approximately 5 vol.% of dispersed silica phase. Additions of MoB or Mo 5 Si 3 caused the average grain size to decrease. The decrease in the grain size was typically accompanied by an increase in flexure strength, a decrease in the room temperature fracture toughness, and a decrease in the hot strength (compressive creep strength) measured around 1200 deg. C, except when the Mo 5 Si 3 effectively became the major phase. Oxidation measurements on the two classes of alloys were carried out in air. Both classes of alloys were protected from oxidation by an in-situ adherent scale that formed on exposure to high temperature. The scale, although not analyzed in detail, is commonly recognized in MoSi 2 containing materials as consisting mostly of SiO 2 . The MoB containing materials showed an increase in the scale thickness and the cyclic oxidation rate at 1400 deg. C when compared with pure MoSi 2 . However, in contrast with the pure MoSi 2 material, oxidation at 1400 deg. C began with a weight loss followed by a weight gain and the formation of the protective silica layer. The Mo 5 Si 3 containing materials experienced substantial initial weight losses followed by regions of small weight changes. Overall, the MoB and Mo 5 Si 3 additions to MoSi 2 tended to be detrimental for the mechanical and oxidative properties

A note on the Sumerian expression SI-ge4-de3/dam

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Widell, Magnus

2002-12-01

Full Text Available The expression SI-ge4-dam/de3 appears in some of the loan documents of the Ur III period where it was used to establish the interest rate or the loan fee. In addition, it is sometimes preceded by ki-ba 'in its/this place/ground' or, in some cases, ma2 -a 'in the boat'. The regular verb SI.g was closely related, perhaps even synonymous with, the reduplication verb ḡar/ḡa2-ḡa2 'to put' or 'to place'. While it may be concluded that SI-ge4-dam/de3 had nothing to do with the verb si 'to fill' or gi4 'to return', the correct analysis of the expression remains somewhat uncertain. The article proposes that the SI should be read se and understood as a phonetic writing for the regular verb se3.g 'to put', 'to place'. The combination of the verb with the ki-ba may suggest that a more parochial form of keeping products existed side by side with the large centralized granaries and storehouses of the city.La expresión SI-ge4-dam/de3 aparece en algunos contratos de préstamo del período de Ur III, donde se empleaba para determinar el interés de dicho préstamo. Por otra parte, este término se hallaba a veces precedido de ki-ba 'en su/este lugar/suelo', y en algunos casos por ma2 -a 'en la barca'. El verbo regular SI.g está muy relacionado (quizás es incluso sinónimo con el verbo de la clase de la reduplicación ḡar/ḡa2-ḡa2 'poner' o 'colocar'. Mientras que puede concluirse que SI-ge4-dam/de3 no tiene nada que ver con el verbo si 'llenar', ni con gi4 'regresar, devolver', el análisis correcto de la expresión sigue siendo, de algún modo, incierto. En el artículo se propone que SI puede leerse como se , entendiéndolo como una escritura fonética del verbo regular se3.g 'poner', 'colocar'. La combinación del verbo con ki-ba podría indicar que, junto a los grandes graneros y almacenes centrales de la ciudad, había un modo distinto y más modesto de conservar los productos.

Non-condensed (oxo)nitridosilicates: La{sub 3}-[SiN{sub 4}]F and the polymorph o-La{sub 3}-[SiN{sub 3}O]O

Energy Technology Data Exchange (ETDEWEB)

Durach, Dajana; Schnick, Wolfgang [Department of Chemistry, Chair in Inorganic Solid-State Chemistry, University of Munich (LMU) (Germany)

2015-08-15

The isotypic compounds La{sub 3}[SiN{sub 4}]F and La{sub 3}[SiN{sub 3}O]O were synthesized in a radio-frequency furnace at 1600 C. The crystal structures [Pnma (no. 62), Z = 4; La{sub 3}(SiN{sub 4})F: a = 9.970(3), b = 7.697(2), c = 6.897(2) Aa, V = 529.3(3) Aa{sup 3}; La{sub 3}(SiON{sub 3})O: a = 9.950(2), b = 7.6160(15), c = 6.9080(14) Aa, V = 523.48(18) Aa{sup 3}] were elucidated from single-crystal X-ray diffraction data and corroborated by Rietveld refinement, lattice-energy calculations (Madelung part of lattice energy, MAPLE) and Raman/FTIR spectroscopy. Both compounds are homeotypic with Na{sub 2}Pr[GeO{sub 4}]OH forming a network of vertex-sharing FLa{sub 6}/OLa{sub 6} octahedra, whose voids are filled with non-condensed SiN{sub 4}/SiN{sub 3}O tetrahedra. o-La{sub 3}[SiON{sub 3}]O is the orthorhombic polymorph of this compound, which probably represents the high-temperature modification, whereas the tetragonal polymorph t-La{sub 3}[SiON{sub 3}]O represents the low-temperature modification. While the space group of the t-polymorph [I4/mcm (no. 140)] differs from the new La{sub 3}[SiN{sub 4}]F and o-La{sub 3}[SiN{sub 3}O]O, the crystal structure contains the same linking pattern. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Oxidation protection of multilayer CVD SiC/B/SiC coatings for 3D C/SiC composite

International Nuclear Information System (INIS)

Liu Yongsheng; Cheng Laifei; Zhang Litong; Wu Shoujun; Li Duo; Xu Yongdong

2007-01-01

A CVD boron coating was introduced between two CVD SiC coating layers. EDS and XRD results showed that the CVD B coating was a boron crystal without other impurity elements. SEM results indicated that the CVD B coating was a flake-like or column-like crystal with a compact cross-section. The crack width in the CVD SiC coating deposited on CVD B is smaller than that in a CVD SiC coating deposited on CVD SiC coating. After oxidation at 700 deg. C and 1000 deg. C, XRD results indicated that the coating was covered by product B 2 O 3 or B 2 O 3 .xSiO 2 film. The cracks were sealed as observed by SEM. There was a large amount of flake-like material on hybrid coating surface after oxidation at 1300 deg. C. Oxidation weight loss and residual flexural strength results showed that hybrid SiC/B/SiC multilayer coating provided better oxidation protection for C/SiC composite than a three layer CVD SiC coating at temperatures from 700 deg. C to 1000 deg. C for 600 min, but worse oxidation protection above 1000 deg. C due to the large amount of volatilization of B 2 O 3 or B 2 O 3 .xSiO 2

Silicon-incorporated diamond-like coatings for Si3N4 mechanical seals

International Nuclear Information System (INIS)

Camargo, S.S.; Gomes, J.R.; Carrapichano, J.M.; Silva, R.F.; Achete, C.A.

2005-01-01

Amorphous silicon carbide (a-SiC) and silicon-incorporated diamond-like carbon films (DLC-Si) were evaluated as protective and friction reduction coatings onto Si 3 N 4 rings. Unlubricated tribological tests were performed with a pin-on-disk apparatus against stainless steel pins with loads ranging from 3 to 55 N and sliding velocities from 0.2 to 1.0 m/s under ambient air and 50-60% relative humidity. At the lowest loads, a-SiC coatings present a considerable improvement with respect to the behavior of uncoated disks since the friction coefficient is reduced to about 0.2 and the system is able to run stably for thousands of meters. At higher loads, however, a-SiC coatings fail. DLC-Si-coated rings, on the other hand, presented for loads up to 10 N a steady-state friction coefficient below 0.1 and very low wear rates. The lowest steady-state mean friction coefficient value of only 0.055 was obtained with a sliding velocity of 0.5 m/s. For higher loads in the range of 20 N, the friction coefficient drops to values around 0.1 but no steady state is reached. For the highest loads of over 50 N, a catastrophic behavior is observed. Typically, wear rates below 5x10 -6 and 2x10 -7 mm 3 /N m were obtained for the ceramic rings and pins, respectively, with a load of 10 N and a sliding velocity of 0.5 m/s. Analysis of the steel pin contact surface by scanning electron microscopy (SEM)-energy dispersive X-ray spectrometry (EDS) and Auger spectroscopy revealed the formation of an adherent tribo-layer mainly composed by Si, C and O. The unique structure of DLC-Si films is thought to be responsible for the formation of the tribo-layer

Mechanisms and selectivity for etching of HfO2 and Si in BCl3 plasmas

International Nuclear Information System (INIS)

Wang Chunyu; Donnelly, Vincent M.

2008-01-01

The authors have investigated plasma etching of HfO 2 , a high dielectric constant material, and poly-Si in BCl 3 plasmas. Etching rates were measured as a function of substrate temperature (T s ) at several source powers. Activation energies range from 0.2 to 1.0 kcal/mol for HfO 2 and from 0.8 to 1.8 kcal/mol for Si, with little or no dependence on source power (20-200 W). These low activation energies suggest that product removal is limited by chemical sputtering of the chemisorbed Hf or Si-containing layer, with a higher T s only modestly increasing the chemical sputtering rate. The slightly lower activation energy for HfO 2 results in a small improvement in selectivity over Si at low temperature. The surface layers formed on HfO 2 and Si after etching in BCl 3 plasmas were also investigated by vacuum-transfer x-ray photoelectron spectroscopy. A thin boron-containing layer was observed on partially etched HfO 2 and on poly-Si after etching through HfO 2 films. For HfO 2 , a single B(1s) feature at 194 eV was ascribed to a heavily oxidized species with bonding similar to B 2 O 3 . B(1s) features were observed for poly-Si surfaces at 187.6 eV (B bound to Si), 189.8 eV, and 193 eV (both ascribed to BO x Cl y ). In the presence of a deliberately added 0.5% air, the B-containing layer on HfO 2 is largely unaffected, while that on Si converts to a thick layer with a single B(1s) peak at 194 eV and an approximate stoichiometry of B 3 O 4 Cl

Comparison of interfaces for (Ba,Sr)TiO3 films deposited on Si and SiO2/Si substrates

International Nuclear Information System (INIS)

Suvorova, N.A.; Lopez, C.M.; Irene, E.A.; Suvorova, A.A.; Saunders, M.

2004-01-01

(Ba,Sr)TiO 3 (BST) thin films were deposited by ion sputtering on both bare and oxidized Si. Spectroscopic ellipsometry results have shown that a SiO 2 underlayer of nearly the same thickness (2.6 nm in average) is found at the Si interface for BST sputter depositions onto nominally bare Si, 1 nm SiO 2 on Si or 3.5 nm SiO 2 on Si. This result was confirmed by high-resolution electron microscopy analysis of the films, and it is believed to be due to simultaneous subcutaneous oxidation of Si and reaction of the BST layer with SiO 2 . Using the conductance method, capacitance-voltage measurements show a decrease in the interface trap density D it of an order of magnitude for oxidized Si substrates with a thicker SiO 2 underlayer. Further reduction of D it was achieved for the capacitors grown on oxidized Si and annealed in forming gas after metallization

Comparison of interfaces for (Ba,Sr)TiO3 films deposited on Si and SiO2/Si substrates

Science.gov (United States)

Suvorova, N. A.; Lopez, C. M.; Irene, E. A.; Suvorova, A. A.; Saunders, M.

2004-03-01

(Ba,Sr)TiO3(BST) thin films were deposited by ion sputtering on both bare and oxidized Si. Spectroscopic ellipsometry results have shown that a SiO2 underlayer of nearly the same thickness (2.6 nm in average) is found at the Si interface for BST sputter depositions onto nominally bare Si, 1 nm SiO2 on Si or 3.5 nm SiO2 on Si. This result was confirmed by high-resolution electron microscopy analysis of the films, and it is believed to be due to simultaneous subcutaneous oxidation of Si and reaction of the BST layer with SiO2. Using the conductance method, capacitance-voltage measurements show a decrease in the interface trap density Dit of an order of magnitude for oxidized Si substrates with a thicker SiO2 underlayer. Further reduction of Dit was achieved for the capacitors grown on oxidized Si and annealed in forming gas after metallization.

Residual stresses and mechanical properties of Si3N4/SiC multilayered composites with different SiC layers

International Nuclear Information System (INIS)

Liua, S.; Lia, Y.; Chena, P.; Lia, W.; Gaoa, S.; Zhang, B.; Yeb, F.

2017-01-01

The effect of residual stresses on the strength, toughness and work of fracture of Si3N4/SiC multilayered composites with different SiC layers has been investigated. It may be an effective way to design and optimize the mechanical properties of Si3N4/SiC multilayered composites by controlling the properties of SiC layers. Si3N4/SiC multilayered composites with different SiC layers were fabricated by aqueous tape casting and pressureless sintering. Residual stresses were calculated by using ANSYS simulation, the maximum values of tensile and compressive stresses were 553.2MPa and −552.1MPa, respectively. Step-like fracture was observed from the fracture surfaces. Fraction of delamination layers increased with the residual stress, which can improve the reliability of the materials. Tensile residual stress was benefit to improving toughness and work of fracture, but the strength of the composites decreased. [es

On the interplay between Si(110) epilayer atomic roughness and subsequent 3C-SiC growth direction

Science.gov (United States)

Khazaka, Rami; Michaud, Jean-François; Vennéguès, Philippe; Nguyen, Luan; Alquier, Daniel; Portail, Marc

2016-11-01

In this contribution, we performed the growth of a 3C-SiC/Si/3C-SiC layer stack on a Si(001) substrate by means of chemical vapor deposition. We show that, by tuning the growth conditions, the 3C-SiC epilayer can be grown along either the [111] direction or the [110] direction. The key parameter for the growth of the desired 3C-SiC orientation on the Si(110)/3C-SiC(001)/Si(001) heterostructure is highlighted and is linked to the Si epilayer surface morphology. The epitaxial relation between the layers has been identified using X-ray diffraction and transmission electron microscopy (TEM). We showed that, regardless of the top 3C-SiC epilayer orientation, domains rotated by 90° around the growth direction are present in the epilayer. Furthermore, the difference between the two 3C-SiC orientations was investigated by means of high magnification TEM. The results indicate that the faceted Si(110) epilayer surface morphology results in a (110)-oriented 3C-SiC epilayer, whereas a flat hetero-interface has been observed between 3C-SiC(111) and Si(110). The control of the top 3C-SiC growth direction can be advantageous for the development of new micro-electro-mechanical systems.

Residual stresses and mechanical properties of Si3N4/SiC multilayered composites with different SiC layers; Las tensiones residuales y las propiedades mecánicas de compuestos multicapa de Si3N4/SiC con diferentes capas de SiC

Energy Technology Data Exchange (ETDEWEB)

Liua, S.; Lia, Y.; Chena, P.; Lia, W.; Gaoa, S.; Zhang, B.; Yeb, F.

2017-11-01

The effect of residual stresses on the strength, toughness and work of fracture of Si3N4/SiC multilayered composites with different SiC layers has been investigated. It may be an effective way to design and optimize the mechanical properties of Si3N4/SiC multilayered composites by controlling the properties of SiC layers. Si3N4/SiC multilayered composites with different SiC layers were fabricated by aqueous tape casting and pressureless sintering. Residual stresses were calculated by using ANSYS simulation, the maximum values of tensile and compressive stresses were 553.2MPa and −552.1MPa, respectively. Step-like fracture was observed from the fracture surfaces. Fraction of delamination layers increased with the residual stress, which can improve the reliability of the materials. Tensile residual stress was benefit to improving toughness and work of fracture, but the strength of the composites decreased. [Spanish] Se ha investigado el efecto de las tensiones residuales en la resistencia, dureza y trabajo de fractura de los compuestos multicapa de Si3N4/SiC con diferentes capas de SiC. Puede ser una manera eficaz de diseñar y optimizar las propiedades mecánicas de los compuestos multicapa de Si3N4/SiC mediante el control de las propiedades de las capas de SiC. Los compuestos multicapa de Si3N4/SiC con diferentes capas de SiC se fabricaron por medio de colado en cinta en medio acuoso y sinterización sin presión. Las tensiones residuales se calcularon mediante el uso de la simulación ANSYS, los valores máximos de las fuerzas de tracción y compresión fueron 553,2 MPa y −552,1 MPa, respectivamente. Se observó una fractura escalonada a partir de las superficies de fractura. La fracción de capas de deslaminación aumenta con la tensión residual, lo que puede mejorar la fiabilidad de los materiales. La fuerza de tracción residual era beneficiosa para la mejora de la dureza y el trabajo de fractura, pero la resistencia de los compuestos disminuyó.

Tribological Behavior of Si3N4/Ti3SiC2 Contacts Lubricated by Lithium-Based Ionic Liquids

Directory of Open Access Journals (Sweden)

Haizhong Wang

2014-01-01

Full Text Available The tribological performance of Si3N4 ball sliding against Ti3SiC2 disc lubricated by lithium-based ionic liquids (ILs was investigated using an Optimol SRV-IV oscillating reciprocating friction and wear tester at room temperature (RT and elevated temperature (100°C. Glycerol and the conventional imidazolium-based IL 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonylimide (L-F106 were used as references under the same experimental conditions. The results show that the lithium-based ILs had higher thermal stabilities than glycerol and lower costs associated with IL preparation than L-F106. The tribotest results show that the lithium-based ILs were effective in reducing the friction and wear of Si3N4/Ti3SiC2 contacts. [Li(urea]TFSI even produced better tribological properties than glycerol and L-F106 both at RT and 100°C. The SEM/EDS and XPS results reveal that the excellent tribological endurance of Si3N4/Ti3SiC2 contacts lubricated by lithium-based ILs was mainly attributed to the formation of surface protective films composed of various tribochemical products.

Target swapping in PLD: An efficient approach for CdS/SiO{sub 2} and CdS:Ag(1%)/SiO{sub 2} nanocomposite thin films with enhanced luminescent properties

Energy Technology Data Exchange (ETDEWEB)

Saxena, Nupur, E-mail: n1saxena@gmail.com [Department of Physics & Astrophysics, University of Delhi, Delhi 110007 (India); Kumar, Pragati, E-mail: pkumar.phy@gmail.com [Department of Physics & Astrophysics, University of Delhi, Delhi 110007 (India); Department of Nano Sciences and Materials, Central University of Jammu, Rahya-Suchani (Bagla), Samba, 181143 Jammu, J& K (India); Gupta, Vinay [Department of Physics & Astrophysics, University of Delhi, Delhi 110007 (India)

2017-06-15

A novel synthesis method for luminescent and by-products (like CdO) free CdS/SiO{sub 2} and CdS:Ag(1%)/SiO{sub 2} (i.e. 1%Ag doped CdS/SiO{sub 2}) nanocomposite thin films at room temperature by pulsed laser deposition is reported. Targets of CdS, CdS:Ag(1%) and SiO{sub 2} are used to deposit CdS/SiO{sub 2} and CdS:Ag(1%)/SiO{sub 2} nanocomposite thin films by swapping them at a frequency ratio of 2:8 laser pulses/sec. X-ray photoelectron spectroscopy analysis ensures the ratio of CdS to SiO{sub 2} in nanocomposite as 21:79 which is nearly same as the ratio of incident pulses/sec (i.e. 2:8) on the two targets. Transmission electron micrographs visualize the formation of CdS/ CdS:Ag(1%) nanocrystals in nanocomposite systems after annealing at 500 °C. Highly intense and broad red emission is achieved from CdS/SiO{sub 2} and CdS:Ag(1%)/SiO{sub 2} nanocomposites. The efficiencies of emission from pristine CdS:SiO{sub 2} and CdS:Ag(1%)/SiO{sub 2} nanocomposites are found to be enhanced by approximately two times as compared to sole nanocrystalline CdS and CdS:Ag(1%) thin films respectively and further enhanced upto 7 times on annealing the nanocomposite systems at 500 °C. - Graphical abstract: A modified synthesis method for luminescent and by-products (like CdO) free undoped &1% Ag doped CdS/SiO{sub 2} (deposit CdS/SiO{sub 2} and CdS:Ag(1%)/SiO{sub 2}) nanocomposite thin films at room temperature by pulsed laser deposition is reported. Targets of CdS or CdS:Ag(1%) and SiO{sub 2} are used to deposit CdS/SiO{sub 2} and CdS:Ag(1%)/SiO{sub 2} nanocomposite thin films by swapping them at a frequency of 2:8 pulses/sec. X-ray photoelectron spectroscopy analysis ensures the ratio of CdS to SiO{sub 2} in nanocomposite as 21:79 which is nearly same as the ratio of incident pulses/sec (2:8) on the two targets. Transmission electron micrographs visualize the formation of CdS nanocrystals in nanocomposite systems after annealing at 500 °C. Intense and broad red emission is

Effect of ternary additions on the oxidation resistance of Ti5Si3

International Nuclear Information System (INIS)

Thom, A.J.; Akinc, M.; Iowa State Univ., Ames, IA

1995-01-01

Refractory intermetallic silicides are receiving increasing consideration for use as high temperature structural materials. Ti 5 Si 3 -based compositions are attractive due to their ability to incorporate a variety of interstitial ternary additions. These ternary additions present a unique opportunity to potentially tailor physical properties. Previous experimental work has shown that these additions significantly increase the otherwise poor oxidation resistance of undoped Ti 5 Si 3 above 700 C. Recent experimental work by the authors on the oxidation of small atom doped Ti 5 Si 3 is discussed. Interstitial additions of boron, carbon, and oxygen substantially improve the isothermal oxidation resistance of Ti 5 Si 3 at 1,000 C. In contrast, added nitrogen does not provide significant improvement. Even up to 1,306 C, interstitial oxygen imparts excellent oxidation resistance with a mass gain of 1.1 mg/cm 2 after 240 hours

NMR study of CeCoSi3

International Nuclear Information System (INIS)

Iwamoto, Y.

1995-01-01

Low-temperature susceptibility, NMR and NQR of the 59 Co signal in CeCoSi 3 have been measured. CeCoSi 3 showed a superconducting transition at 0.7-1.2K. From NQR measurement, the nuclear quadrupole frequency and the full width at half maximum (FWHM) of 59 Co in CeCoSi 3 were estimated to be about 1.08MHz and 0.08MHz, respectively. The 59 Co nuclear spin-lattice relaxation rate (1/T 1 ) in CeCoSi 3 was proportional to the temperature (T) as the Fermi liquid state above the superconducting transition temperature (T c ), and then rapidly decreased below T c . ((orig.))

Phase relations in the SiC-Al2O3-Pr2O3 system

International Nuclear Information System (INIS)

Pan, W.; Wu, L.; Jiang, Y.; Huang, Z.

2016-01-01

Phase relations in the Si-Al-Pr-O-C system, including the SiC-Al 2 O 3 -Pr 2 O 3 , the Al 2 O 3 -Pr 2 O 3 -SiO 2 and the SiC-Al 2 O 3 -Pr 2 O 3 -SiO 2 subsystems, were determined by means of XRD phase analysis of solid-state-reacted samples fabricated by using SiC, Al 2 O 3 , Pr 2 O 3 and SiO 2 powders as the starting materials. Subsolidus phase diagrams of the systems were presented. Two Pr-aluminates, namely PrAlO 3 (PrAP) and PrAl 11 O 18 (β(Pr) β-Al 2 O 3 type) were formed in the SiC-Al 2 O 3 -Pr 2 O 3 system. SiC was compatible with both of them. Pr-silicates of Pr 2 SiO 5 , Pr 2 Si 2 O 7 and Pr 9.33 Si 6 O 26 (H(Pr) apatite type) were formed owing to presence of SiO 2 impurity in the SiC powder. The presence of the SiO 2 extended the ternary system of SiC-Al 2 O 3 -Pr 2 O 3 into a quaternary system of SiC-Al 2 O 3 -SiO 2 -Pr 2 O 3 (Si-Al-Pr-O-C). SiC was compatible with Al 2 O 3 , Pr 2 O 3 and the Pr-silicates. The effect of SiO 2 on the phase relations and liquid phase sintering of SiC ceramics was discussed.

Thermomagnetic behaviour and compositional irreversibility on (Fe/Si)3 multilayer films

International Nuclear Information System (INIS)

Badía-Romano, L.; Rubín, J.; Magén, C.; Bartolomé, F.; Sesé, J.; Ibarra, M.R.; Bartolomé, J.

2014-01-01

This work presents the correlation between the morphology and magnetic properties of (Fe/Si) 3 multilayers with different Fe layer thicknesses and fixed Si spacer thickness in a broad temperature range (5 R /M S ratios and saturation fields are related to several types of interlayer exchange coupling. 90°-coupling and a superposition of 90° and antiferromagnetic interlayer exchange coupling are found depending on the Fe layer thickness. Magnetization curves were investigated as a function of temperature by in situ annealing. They show an irreversible thermal process as temperature increases from 300 to 450 K that is correlated to the formation of a ferromagnetic silicide phase. At higher temperature this phase transforms into a paramagnetic Fe–Si phase. - Highlights: • A thermomagnetic study on (Fe/Si) 3 multilayers is performed by in situ annealing. • We assess on the Fe layer thickness dependence, while the Si spacer is fixed. • 90° and AF interlayer exchange couplings are found depending on the Fe thickness. • We report an irreversible thermal process, correlated to chemical transformations. • The integrity of these (Fe/Si) 3 films is conserved just till T≈410K

Hot filament-dissociation of (CH3)3SiH and (CH3)4Si, probed by vacuum ultra violet laser time of flight mass spectroscopy.

Science.gov (United States)

Sharma, Ramesh C; Koshi, Mitsuo

2006-11-01

The decomposition of trimethylsilane and tetramethylsilane has been investigated for the first time, using hot wire (catalytic) at various temperatures. Trimethylsilane is catalytic-dissociated in these species SiH(2), CH(3)SiH, CH(3), CH(2)Si. Time of flight mass spectroscopy signal of these species are linearly increasing with increasing catalytic-temperature. Time of flight mass spectroscopy (TOFMS) signals of (CH(3))(3)SiH and photodissociated into (CH(3))(2)SiH are decreasing with increasing hot filament temperature. TOFMS signal of (CH(3))(4)Si is decreasing with increasing hot wire temperature, but (CH(3))(3)Si signal is almost constant with increasing the temperature. We calculated activation energies of dissociated species of the parental molecules for fundamental information of reaction kinetics for the first time. Catalytic-dissociation of trimethylsilane, and tetramethylsilane single source time of flight coupled single photon VUV (118 nm) photoionization collisionless radicals at temperature range of tungsten filament 800-2360 K. The study is focused to understand the fundamental information on reaction kinetics of these molecules at hot wire temperature, and processes of catalytic-chemical vapour deposition (Cat-CVD) technique which could be implemented in amorphous and crystalline SiC semiconductors thin films.

Disorder accumulation and recovery in gold-ion irradiated 3C-SiC

Energy Technology Data Exchange (ETDEWEB)

Jiang, Weilin; Weber, William J.; Lian, Jie; Kalkhoran, N. M.

2009-01-12

A single-crystal 3C-SiC film on the Si/SiO2/Si (SIMOX) substrate was irradiated in different areas at 156 K with Au2+ ions to low fluences. The disorder profiles as a function of dose on both the Si and C sublattices have been determined in situ using a combination of 0.94 MeV D+ Rutherford backscattering spectrometry and nuclear reaction analysis in channeling geometry along the <100>, <110> and <111> axes. The results indicate that for the same damage state, the level of disorder on the Si sublattice in 3C-SiC follows a decreasing order along the <111>, <100> and <110> axes, while that on the C sublattice shows comparable values. Similar levels of Si and C disorder are observed along the <111> axis over the applied dose range. However, the level of C disorder is higher than that of Si disorder along either <100> or <110>. The amount of disorder recovery during thermal annealing processes depends on the sublattice (Si or C) and crystallographic orientation. Room-temperature recovery occurs for both sublattices in 3C-SiC irradiated to a dose of 0.047 dpa or lower. Significant recovery is observed along all directions during thermal annealing at 600 K. The results will be discussed and compared to those for 6H- and 4H-SiC under similar irradiation conditions.

U3Si2 Fabrication and Testing for Implementation into the BISON Fuel Performance Code

Energy Technology Data Exchange (ETDEWEB)

Knight, Travis W.

2018-04-23

A creep test stand was designed and constructed for compressive creep testing of U3Si2 pellets. This is described in Chapter 3.

• Creep testing of U3Si2 pellets was completed. In total, 13 compressive creep tests of U3Si2 pellets was successfully completed. This is reported in Chapter 3.
• Secondary creep model of U3Si2 was developed and implemented in BISON. This is described in Chapter 4.
• Properties of U3Si2 were implemented in BISON. This is described in Chapter 4.
• A resonant frequency and damping analyzer (RFDA) using impulse excitation technique (IET) was setup, tested, and used to analyze U3Si2 samples to measure Young’s and Shear Moduli which were then used to calculate the Poisson ratio for U3Si2. This is described in Chapter 5.
• Characterization of U3Si2 samples was completed. Samples were prepared and analyzed by XRD, SEM, and optical microscopy. Grain size analysis was conducted on images.

Annealing effect and photovoltaic properties of nano-ZnS/textured p-Si heterojunction

Science.gov (United States)

Ji, Liang-Wen; Hsiao, Yu-Jen; Tang, I.-Tseng; Meen, Teen-Hang; Liu, Chien-Hung; Tsai, Jenn-Kai; Wu, Tien-Chuan; Wu, Yue-Sian

2013-11-01

The preparation and characterization of heterojunction solar cell with ZnS nanocrystals synthesized by chemical bath deposition method were studied in this work. The ZnS nanocrystals were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Lower reflectance spectra were found as the annealing temperature of ZnS film increased on the textured p-Si substrate. It was found that the power conversion efficiency (PCE) of the AZO/ZnS/textured p-Si heterojunction solar cell with an annealing temperature of 250°C was η = 3.66%.

Thermal expansion and elastic moduli of the silicide based intermetallic alloys Ti5Si3(X) and Nb5Si3

International Nuclear Information System (INIS)

Zhang, L.; Wu, J.

1997-01-01

Silicides are among those potential candidates for high temperature application because of their high melting temperature, low density and good oxidation resistance. Recent interest is focused on molybdenum silicides and titanium silicides. Extensive investigation has been carried out on MoSi 2 , yet comparatively less work was performed on titanium silicides such as Ti 5 Si 3 and Ti 3 and TiSi 2 which are of lower density than MoSi 2 . Fundamental understanding of the titanium silicides' properties for further evaluation their potential for practical application are thus needed. The thermal expansion coefficients and elastic moduli of intermetallic compounds are two properties important for evaluation as a first step. The thermal expansion determines the possible stress that might arise during cooling for these high melting point compounds, which is crucial to the preparation of defect free specimens; and the elastic moduli are usually reflections of the cohesion in crystal. In Frommeyer's work and some works afterwards, the coefficients of thermal expansion were measured on both polycrystalline and single crystal Ti 5 Si 3 . The elastic modulus of polycrystalline Ti 5 Si 3 was measured by Frommeyer and Rosenkranz. However, in the above works, the referred Ti 5 Si 3 was the binary one, no alloying effect has been reported on this matter. Moreover, the above parameters (coefficient of thermal expansion and elastic modulus) of Nb 5 Si 3 remain unreported so far. In this paper, the authors try to extend the knowledge of alloyed Ti 5 Si 3 compounds with Nb and Cr additions. Results on the coefficients of thermal expansion and elastic moduli of Ti 5 Si 3 compounds and Nb 5 Si 3 are presented and the discussion is focused on the alloying effect

Cross sections and reaction rates for 23Na(p,n) 23Mg, 27Al(p,n) 27Si, 27Al(α,n) 30P, 29Si(α,n) 32S, and 30Si(α,n) 33S

International Nuclear Information System (INIS)

Flynn, D.S.; Sekharan, K.K.; Hiller, B.A.; Laumer, H.; Weil, J.L.; Gabbard, F.

1978-01-01

The total neutron production cross sections for the 23 Na(p,n) 23 Mg, 27 Al(p,n) 27 Si, 27 Al(α,n) 30 P, 29 Si(α,n) 32 S, and 30 Si(α,n) 33 S reactions have been measured for bombarding energies from threshold to 6.3 MeV. The neutron detector was a 60-cm diameter sphere of polyethylene with eight 10 BF 3 counters and was insensitive to the angle and energy of the emitted neutrons. Cross sections for inverse reactions have been obtained using the principle of detailed balance. The data have been used to determine parameters for statistical model calculations to facilitate extrapolation of cross sections to higher bombarding energies. These reactions are relevant to problems of nucleosynthesis and stellar evolution and to studies of radiation damage. Nucleosynthesis reaction rates, N/sub A/(sigmav), were determined for the reactions studied and are tabulated for temperatures ranging from 0.4 x 10 9 to 10.0 x 10 9 K

Delivery Pathway Regulation of 3′,3″-Bis-Peptide-siRNA Conjugate via Nanocarrier Architecture Engineering

Directory of Open Access Journals (Sweden)

Jing Sun

2018-03-01

Full Text Available Small interfering RNA (siRNA has been continuously explored for clinical applications. However, neither nanocarriers nor conjugates have been able to remove the obstacles. In this study, we employed a combined nanochemistry strategy to optimize its delivery dilemma, where different interactions and assembly modes were cooperatively introduced into the forming process of siRNA/lipids nanoplexes. In the nanoplexes, the 3′,3″-bis-peptide-siRNA conjugate (pp-siRNA and gemini-like cationic lipids (CLDs were employed as dual regulators to improve their bio-behavior. We demonstrated that the “cicada pupa”-shaped nanoplexes of MT-pp-siRNA/CLDs (MT represented the mixed two-phase method exhibited more compact multi-sandwich structure (∼25 layers, controllable size (∼150 nm, and lower zeta potential (∼22 mV than other comparable nanoplexes and presented an increased siRNA protection and stability. Significantly, the nanoplex was internalized into melanoma cells by almost caveolae-mediated endocytosis and macropinocytosis (∼99.46%, and later reduced/avoided lysosomal degradation. Finally, the nanoplex facilitated the silencing of mRNA of the mutant B-Raf protein (down by ∼60%. In addition, pp-siRNA had a high intracellular sustainability, a significantly prolonged circulating time, and accumulation in tumor tissues in vivo. Our results have demonstrated that the combined approach can improve the intracellular fate of siRNA, which opens up novel avenues for efficient siRNA delivery.

Interfacial microstructure of Si{sub 3}N{sub 4}/Si{sub 3}N{sub 4} brazing joint with Cu-Zn-Ti filler alloy

Energy Technology Data Exchange (ETDEWEB)

Zhang, J. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)], E-mail: hitzhangjie@hit.edu.cn; Zhang, X.M.; Zhou, Y. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Naka, M. [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Svetlana, Atroshenko [Faculty of Mathematics and Mechanics, Saint-Petersburg State University (Russian Federation)

2008-11-15

In this study, Si{sub 3}N{sub 4} ceramic was jointed by a brazing technique with a Cu-Zn-Ti filler alloy. The interfacial microstructure between Si{sub 3}N{sub 4} ceramic and filler alloy in the Si{sub 3}N{sub 4}/Si{sub 3}N{sub 4} joint was observed and analyzed by using electron-probe microanalysis, X-ray diffraction and transmission electron microscopy. The results indicate that there are two reaction layers at the ceramic/filler interface in the joint, which was obtained by brazing at a temperature and holding time of 1223 K and 15 min, respectively. The layer nearby the Si{sub 3}N{sub 4} ceramic is a TiN layer with an average grain size of 100 nm, and the layer nearby the filler alloy is a Ti{sub 5}Si{sub 3}N{sub x} layer with an average grain size of 1-2 {mu}m. Thickness of the TiN and Ti{sub 5}Si{sub 3}N{sub x} layers is about 1 {mu}m and 10 {mu}m, respectively. The formation mechanism of the reaction layers was discussed. A model showing the microstructure from Si{sub 3}N{sub 4} ceramic to filler alloy in the Si{sub 3}N{sub 4}/Si{sub 3}N{sub 4} joint was provided as: Si{sub 3}N{sub 4} ceramic/TiN reaction layer/Ti{sub 5}Si{sub 3}N{sub x} reaction layer/Cu-Zn solution.

Effects of SiC amount on phase compositions and properties of Ti3SiC2-based composites

Institute of Scientific and Technical Information of China (English)

蔡艳芝; 殷小玮; 尹洪峰

2015-01-01

The phase compositions and properties of Ti3SiC2-based composites with SiC addition of 5%−30% in mass fraction fabricated by in-situ reaction and hot pressing sintering were studied. SiC addition effectively prevented TiC synthesis but facilitated SiC synthesis. The Ti3SiC2/TiC−SiC composite had better oxidation resistance when SiC added quantity reached 20% but poorer oxidation resistance with SiC addition under 15%than Ti3SiC2/TiC composite at higher temperatures. There were more than half of the original SiC and a few Ti3SiC2 remaining in Ti3SiC2/TiC−SiC with 20% SiC addition, but all constituents in Ti3Si2/TiC composite were oxidized after 12 h in air at 1500 °C. The oxidation scale thickness of TS30, 1505.78μm, was near a half of that of T, 2715μm, at 1500 °C for 20 h. Ti3SiC2/TiC composite had a flexural strength of 474 MPa, which was surpassed by Ti3SiC2/TiC−SiC composites when SiC added amount reached 15%. The strength reached the peak of 518 MPa at 20%SiC added amount.

State diagram of U-Al-Si as a basis for analysis of the processes in nuclear fuel compositions based on U(Al, Si)3 and U3Si compounds

International Nuclear Information System (INIS)

Chebotarev, N.T.; Konovalov, L.N.; Zhmak, V.A.; Chebotarev, Ya.N.

1996-01-01

Results of studies into the Al-UAl 3 -USi 3 -Si of the U-Al-Si ternary system are presented. It is established that phase equilibrium between the intermetallic compound U(Al, Si) 3 and the aluminium-silicon alloys may be presented in form of conodes on the isothermal cross-section of the state diagram. It is shown that the U(Al, Si) 3 intermetallic compound, containing up to 6.5 at.% silicon, interacts both with liquid and solid aluminium with the U(Al, Si) 4 phase formation [ru

Enhanced direct-gap light emission from Si-capped n+-Ge epitaxial layers on Si after post-growth rapid cyclic annealing: impact of non-radiative interface recombination toward Ge/Si double heterostructure lasers.

Science.gov (United States)

Higashitarumizu, Naoki; Ishikawa, Yasuhiko

2017-09-04

Enhanced direct-gap light emission is reported for Si-capped n + -Ge layers on Si after post-growth rapid cyclic annealing (RCA), and impact of non-radiative recombination (NRR) at the Ge/Si interface is discussed toward Ge/Si double heterostructure (DH) lasers. P-doped n + -Ge layer (1 × 10 19 cm -3 , 400 nm) is grown on Si by ultra-high vacuum chemical vapor deposition, followed by a growth of Si capping layer (5 nm) to form a Si/Ge/Si DH structure. Post-growth RCA to eliminate defects in Ge is performed in N 2 at temperatures between 900°C and 780°C, where the annealing time is minimized to be 5 s in each RCA cycle to prevent an out-diffusion of P dopants from the Ge surface. Direct-gap photoluminescence (PL) intensity at 1.6 µm increases with the RCA cycles up to 40, although the threading dislocation density in Ge is not reduced after 3 cycles in the present condition. The PL enhancement is ascribed to the suppression of NRR at the Ge/Si interface, where an intermixed SiGe alloy is formed. For Ge/Si DH lasers, NRR at the Ge/Si interface is found to have a significant impact on the threshold current density Jth. In order to achieve Jth on the order of 1 kA/cm 2 , similar to III-V lasers, the interface recombination velocity S is required below 10 3 cm/s in spite of S as large as 10 5 cm/s at the ordinary defect-rich Ge/Si interface.

Van der Waals epitaxial growth of MoS2 on SiO2/Si by chemical vapor deposition

KAUST Repository

Cheng, Yingchun

2013-01-01

Recently, single layer MoS2 with a direct band gap of 1.9 eV has been proposed as a candidate for two dimensional nanoelectronic devices. However, the synthetic approach to obtain high-quality MoS2 atomic thin layers is still problematic. Spectroscopic and microscopic results reveal that both single layers and tetrahedral clusters of MoS2 are deposited directly on the SiO2/Si substrate by chemical vapor deposition. The tetrahedral clusters are mixtures of 2H- and 3R-MoS2. By ex situ optical analysis, both the single layers and tetrahedral clusters can be attributed to van der Waals epitaxial growth. Due to the similar layered structures we expect the same growth mechanism for other transition-metal disulfides by chemical vapor deposition. © 2013 The Royal Society of Chemistry.

Corrosive sliding wear behavior of laser clad Mo2Ni3Si/NiSi intermetallic coating

International Nuclear Information System (INIS)

Lu, X.D.; Wang, H.M.

2005-01-01

Many ternary metal silicides such as W 2 Ni 3 Si, Ti 2 Ni 3 Si and Mo 2 Ni 3 Si with the topologically closed-packed (TCP) hP12 MgZn 2 type Laves phase crystal structure are expected to have outstanding wear and corrosion resistance due to their inherent high hardness and sluggish temperature dependence and strong atomic bonds. In this paper, Mo 2 Ni 3 Si/NiSi intermetallic coating was fabricated on substrate of an austenitic stainless steel AISI321 by laser cladding using Ni-Mo-Si elemental alloy powders. Microstructure of the coating was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). Wear resistance of the coating is evaluated under corrosive sliding wear test condition. Influence of corrosion solutions on the wear resistance of the coating was studied and the wear mechanism was discussed based on observations of worn surface morphology. Results showed that the laser clad Mo 2 Ni 3 Si/NiSi composite coating have a fine microstructure of Mo 2 Ni 3 Si primary dendrites and the interdendritic Mo 2 Ni 3 Si/NiSi eutectics. The coating has excellent corrosive wear resistance compared with austenitic stainless steel AISI321 under acid, alkaline and saline corrosive environments

Modular PbSrS/PbS mid-infrared vertical external cavity surface emitting laser on Si

Science.gov (United States)

Khiar, A.; Rahim, M.; Fill, M.; Felder, F.; Zogg, H.; Cao, D.; Kobayashi, S.; Yokoyama, T.; Ishida, A.

2011-07-01

A mid-infrared vertical external cavity surface emitting laser (VECSEL) based on undoped PbS is described herein. A 200 nm-thick PbS active layer embedded between PbSrS cladding layers forms a double heterostructure. The layers are grown on a lattice and thermal expansion mismatched Si-substrate. The substrate is placed onto a flat bottom Bragg mirror again grown on a Si substrate, and the VECSEL is completed with a curved top mirror. Pumping is done optically with a 1.55 μm laser diode. This leads to an extremely simple modular fabrication process. Lasing wavelengths range from 3-3.8 μm at 100-260 K heat sink temperature. The lowest threshold power is ˜210 mWp and highest output power is ˜250 mWp. The influence of the different recombination mechanism as well as free carrier absorption on the threshold power is modeled.

Fabrication of highly oriented D03-Fe3Si nanocrystals by solid-state dewetting of Si ultrathin layer

International Nuclear Information System (INIS)

Naito, Muneyuki; Nakagawa, Tatsuhiko; Machida, Nobuya; Shigematsu, Toshihiko; Nakao, Motoi; Sudoh, Koichi

2013-01-01

In this paper, highly oriented nanocrystals of Fe 3 Si with a D0 3 structure are fabricated on SiO 2 using ultrathin Si on insulator substrate. First, (001) oriented Si nanocrystals are formed on the SiO 2 layer by solid state dewetting of the top Si layer. Then, Fe addition to the Si nanocrystals is performed by reactive deposition epitaxy and post-deposition annealing at 500 °C. The structures of the Fe–Si nanocrystals are analyzed by cross-sectional transmission electron microscopy and nanobeam electron diffraction. We observe that Fe 3 Si nanocrystals with D0 3 , B2, and A2 structures coexist on the 1-h post-annealed samples. Prolonged annealing at 500 °C is effective in obtaining Fe 3 Si nanocrystals with a D0 3 single phase, thereby promoting structural ordering in the nanocrystals. We discuss the formation process of the highly oriented D0 3 -Fe 3 Si nanocrystals on the basis of the atomistic structural information. - Highlights: • Highly oriented Fe–Si nanocrystals (NCs) are fabricated by reactive deposition. • Si NCs formed by solid state dewetting of Si thin layers are used as seed crystals. • The structures of Fe–Si NCs are analyzed by nanobeam electron diffraction. • Most of Fe–Si NCs possess the D0 3 structure after post-deposition annealing

Magnetic and transport properties of EuNi(Si1-xGex)3 compounds

International Nuclear Information System (INIS)

Uchima, K; Takaesu, Y; Akamine, H; Kakihana, M; Tomori, K; Uejo, T; Teruya, A; Nakamura, A; Hedo, M; Nakama, T; Yagasaki, K; Matsubayashi, K; Uwatoko, Y

2014-01-01

The magnetization M, electrical resistivity ρ, thermopower S and specific heat C of EuNi(Si 1-x Ge x ) 3 compounds have been measured at temperatures from 2 to 300 K. For the compounds of EuNi(Si 1-x Ge x ) 3 , we obtained an effective magnetic moment of μ eff ∼ 7.7 μ B , which is close to the divalent Eu value of μ eff =7.94 μ B . All compounds of EuNi(Si 1-x Ge x ) 3 order antiferromagnetically. The Néel temperature T N decreases monotonously with increasing the Ge concentration x from T N =49 K for EuNiSi 3 to T N =14 K for EuNiGe 3 . In the low temperature region below T N , anomalies corresponding to an additional magnetic phase transition into ferromagnetic state for compounds with x < 0.3, and into another antiferromagnetic for x > 0.3 were observed. The Curie temperature T C rapidly decreases with increasing x and vanishes at x ≈ 0.3. It is found that the magnetic phase transition temperatures of T N and T C in EuNi(Si 1-x Ge x ) 3 are strongly connected with the change of volume induced by the atomic substitution of Si by Ge

Efficient delivery of Notch1 siRNA to SKOV3 cells by cationic cholesterol derivative-based liposome

Directory of Open Access Journals (Sweden)

Zhao Y

2016-10-01

Full Text Available Yun-Chun Zhao,1 Li Zhang,2 Shi-Sen Feng,3 Lu Hong,3 Hai-Li Zheng,3 Li-Li Chen,4 Xiao-Ling Zheng,1 Yi-Qing Ye,1 Meng-Dan Zhao,1 Wen-Xi Wang,3 Cai-Hong Zheng1 1Pharmacy Department, Women’s Hospital, 2Pharmacy Department, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, People’s Republic of China; 3Department of Pharmaceutic Preparation, College of Pharmaceutical Science, Zhejiang University of Technology, Hangzhou, 4Department of Gynecologic Oncology, Women’s Hospital, School of Medicine, Zhejiang University, Hangzhou, People’s Republic of China Abstract: A novel cationic cholesterol derivative-based small interfering RNA (siRNA interference strategy was suggested to inhibit Notch1 activation in SKOV3 cells for the gene therapy of ovarian cancer. The cationic cholesterol derivative, N-(cholesterylhemisuccinoyl-amino-3-propyl-N, N-dimethylamine (DMAPA-chems liposome, was incubated with siRNA at different nitrogen-to-phosphate ratios to form stabilized, near-spherical siRNA/DMAPA-chems nanoparticles with sizes of 100–200 nm and zeta potentials of 40–50 mV. The siRNA/DMAPA-chems nanoparticles protected siRNA from nuclease degradation in 25% fetal bovine serum. The nanoparticles exhibited high cell uptake and Notch1 gene knockdown efficiency in SKOV3 cells at an nitrogen-to-phosphate ratio of 100 and an siRNA concentration of 50 nM. They also inhibited the growth and promoted the apoptosis of SKOV3 cells. These results may provide the potential for using cationic cholesterol derivatives as efficient nonviral siRNA carriers for the suppression of Notch1 activation in ovarian cancer cells. Keywords: siRNA, cationic cholesterol derivative, Notch1, ovarian cancer cells

Enhanced saturation magnetization of Fe{sub 3}Si nanodot-embedded Fe{sub 80}Si{sub 17}Nb{sub 3} flexible film for efficient wireless power transfer

Energy Technology Data Exchange (ETDEWEB)

Pai, Yi-Hao, E-mail: paiyihao@mail.ndhu.edu.tw; Yan, Zih-Yu; Fu, Ping-Hao

2013-07-15

An efficient magnetically coupled resonance response is performed using an iron silicide-based nanostructured magnetoelectric material with high saturation magnetization for the wireless charging of battery-powered consumer electronics. With 500 °C annealing, the self-assembled Fe{sub 3}Si nanodots buried in the Fe{sub 80}Si{sub 17}Nb{sub 3} host matrix with (220) lattice spacing of 1.99 Å corresponding to a volume density of 8.96 × 10{sup 16} cm{sup 3}, can be obtained and a maximum saturation magnetization of 244 emu g{sup −1} achieved. The return loss of the antenna will be tuned to match the designed frequency with greater attenuated intensity (−0.39 dB) and a relatively narrow bandwidth (6 kHz) when the Fe{sub 3}Si nanodot-embedded Fe{sub 80}Si{sub 17}Nb{sub 3} sample is placed in a WiTricity system. An efficient wireless power transfer can be created and improved from 47.5% to 97.3%. The associated coil and loop antenna resonators are significantly readjusted to match the power transfer by putting this nanostructured magnetoelectric material in a WiTricity system. - Highlights: • The saturation magnetization is effective enhancement in the presence of Fe{sub 3}Si nanodot buried in the Fe{sub 80}Si{sub 17}Nb{sub 3}. • A saturation magnetization of 244 emu g{sup −1} is proposed for high-efficiency wireless power transfer. • The return loss of the antenna will be tuned to match the designed frequency. • Such a wireless power transfer can be enhanced efficiency up to 97.3%.

The formal combination of three singlet biradicaloid entities to a singlet hexaradicaloid metalloid Ge14[Si(SiMe3)3]5[Li(THF)2]3 cluster.

Science.gov (United States)

Schenk, Christian; Kracke, Andreas; Fink, Karin; Kubas, Adam; Klopper, Wim; Neumaier, Marco; Schnöckel, Hansgeorg; Schnepf, Andreas

2011-03-02

The reaction of GeBr with LiSi(SiMe(3))(3) leads to the metalloid cluster compound [(THF)(2)Li](3)Ge(14)[Si(SiMe(3))(3)](5) (1). After the introduction of a first cluster of this type, in which 14 germanium atoms form an empty polyhedron, [(THF)(2)Li](3)Ge(14)[Ge(SiMe(3))(3)](5) (2), we present here further investigations on 1 to obtain preliminary insight into its chemical and bonding properties. The molecular structure of 1 is determined via X-ray crystal structure solution using synchrotron radiation. The electronic structure of the Ge(14) polyhedron is further examined by quantum chemical calculations, which indicate that three singlet biradicaloid entities formally combine to yield the singlet hexaradicaloid character of 1. Moreover, the initial reactions of 1 after elimination of the [Li(THF)(2)](+) groups by chelating ligands (e.g., TMEDA or 12-crown-4) are presented. Collision induced dissociation experiments in the gas phase, employing FT-ICR mass spectrometry, lead to the elimination of the singlet biradicaloid Ge(5)H(2)[Si(SiMe(3))(3)](2) cluster. The unique multiradicaloid bonding character of the metalloid cluster 1 might be used as a model for reactions and properties in the field of surface science and nanotechnology.

Temperature dependence of dark current of pSi-n(Si2)1-x(CdS)x structures

International Nuclear Information System (INIS)

Usmonov, Sh.N.

2007-01-01

Full text: The research of influence of isovalent impurity on electric and photo-electric properties of semiconductors where formative with semiconductor continuous solid solutions (CSS) of substitution presents both the fundamental and the applied application interest at the area of material science and photoelectrical properties of semiconductors. In the given work results of experimental researches (Si 2 ) 1-x (CdS) x epitaxial layers grown on c-Si substrates by a method liquid phase epitaxy are presented. The grown layers had thickness and ∼ 10 micron, n-type of conductivity with specific resistance 0,016 Ohm sm. Dependences of the dark current of pSi-n(Si 2 ) 1-x (CdS) x structures have been investigated at various values of a bias voltage. In experiment it was observed anomaly dependence of current. The current with arising of temperature begun monotonously aroused and reached some minimal value at temperature 100 C and then again starts to arise up to temperature 200 C. Arising of dark current is caused of the band-to-band thermal generation of electron-hole pairs. The voltage drop at the temperature 100 C is caused by the recharging of impurity atoms CdS. It is known, that width of the forbidden band of CdS Eg,CdS=2,48 eV more than Eg,Si=1,1 eV. Covalent bond of atoms CdS is stronger than Si-Si bond. However, when the molecule of CdS replaces two atoms of silicon in tetrahedral lattice of silicon the bonds of Cd-S become weak under influence of surrounding atoms of silicon. It causes to occurrence impurity level CdS located on Ei=1,2 eV below a valence band top of silicon. The generation of electron-hole pairs with participation of CdS impurities at the 100 C temperature is occurred under action thermal phonons. However, holes formed on impurity levels are localized and they will be recombination centers. Therefore drop of the dark current caused by dispersion of carriers on impurity centers. (authors)

Direct insight into grains formation in Si layers grown on 3C-SiC by chemical vapor deposition

International Nuclear Information System (INIS)

Khazaka, Rami; Portail, Marc; Vennéguès, Philippe; Alquier, Daniel; Michaud, Jean François

2015-01-01

Graphical abstract: In this contribution, we demonstrated the influence of the 3C-SiC layer on the subsequent growth of Si epilayers. We were able to give a direct evidence that the rotation in the Si epilayer of 90° around the growth direction occurs exactly on the termination of an antiphase boundary in the 3C-SiC layer as shown in the figure above. Thus, increasing the layer thickness of the 3C-SiC leads to a direct improvement of the crystalline quality of the subsequent Si epilayer. (a) Cross-section bright-field TEM image of the Si/3C-SiC layer stack along two 3C-SiC zone axes [1 −1 0] and [1 1 0] (equivalent to [1 −1 1] and [1 1 2] in Si, respectively), (b) dark field image selecting a (2 0 −2) electron diffraction spot indicated by the black circle in the SAED shown as inset, (c) dark field image selecting a (−1 1 −1) electron diffraction spot indicated by the black circle in the SAED shown as inset. The dotted white line in the images show the position of the defect in the 3C-SiC layer. - Abstract: This work presents a structural study of silicon (Si) thin films grown on cubic silicon carbide (3C-SiC) by chemical vapor deposition. The presence of grains rotated by 90° around the growth direction in the Si layer is directly related to the presence of antiphase domains on the 3C-SiC surface. We were able to provide a direct evidence that the 90° rotation of Si grains around the growth direction occurs exactly on the termination of antiphase boundaries (APBs) in 3C-SiC layer. Increasing the 3C-SiC thickness reduces the APBs density on 3C-SiC surface leading to a clear improvement of the uppermost Si film crystal quality. Furthermore, we observed by high resolution plan-view TEM images the presence of hexagonal Si domains limited to few nm in size. These hexagonal Si domains are inclusions in small Si grains enclosed in larger ones rotated by 90°. Finally, we propose a model of grains formation in the Si layer taking into consideration the effect

Bulk superconducting gap of V_3Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

International Nuclear Information System (INIS)

Sato, T.; Souma, S.; Nakayama, K.; Sugawara, K.; Toyota, N.; Takahashi, T.

2016-01-01

Highlights: • We report ultrahigh-resolution photoemission spectroscopy of A15 compound V_3Si. • We found a sharp quasiparticle peak due to superconducting-gap opening. • The surface metallic component is negligibly small in the bulk-sensitive measurement. • We show that V_3Si is a single-gap s-wave superconductor. - Abstract: We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V_3Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (T_c = 15.9 K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30 meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V_3Si is a single-gap s-wave superconductor.

Gas-source molecular beam epitaxy of Si(111) on Si(110) substrates by insertion of 3C-SiC(111) interlayer for hybrid orientation technology

Energy Technology Data Exchange (ETDEWEB)

Bantaculo, Rolando, E-mail: rolandobantaculo@yahoo.com; Saitoh, Eiji; Miyamoto, Yu; Handa, Hiroyuki; Suemitsu, Maki

2011-11-01

A method to realize a novel hybrid orientations of Si surfaces, Si(111) on Si(110), has been developed by use of a Si(111)/3C-SiC(111)/Si(110) trilayer structure. This technology allows us to use the Si(111) portion for the n-type and the Si(110) portion for the p-type channels, providing a solution to the current drive imbalance between the two channels confronted in Si(100)-based complementary metal oxide semiconductor (CMOS) technology. The central idea is to use a rotated heteroepitaxy of 3C-SiC(111) on Si(110) substrate, which occurs when a 3C-SiC film is grown under certain growth conditions. Monomethylsilane (SiH{sub 3}-CH{sub 3}) gas-source molecular beam epitaxy (GSMBE) is used for this 3C-SiC interlayer formation while disilane (Si{sub 2}H{sub 6}) is used for the top Si(111) layer formation. Though the film quality of the Si epilayer leaves a lot of room for betterment, the present results may suffice to prove its potential as a new technology to be used in the next generation CMOS devices.

Karakterisasi Paduan AlMgSi Untuk Kelongsong Bahan Bakar U3Si2/Al Dengan Densitas Uranium 5,2 gU/cm3

Directory of Open Access Journals (Sweden)

Aslina Br. Ginting

2018-03-01

Full Text Available Meningkatnya densitas uranium dari 2,96 gU/cm3 menjadi 5,2 gU/cm3 bahan bakar U3Si2/Al harus diikuti dengan penggunaan kelongsong yang kompatibel. Bahan bakar berdensitas tinggi mempunyai kekerasan yang tinggi, sehingga bila menggunakan paduan AlMg2 sebagai kelongsong dapat menyebabkan terjadi dogbone pada saat perolan. Selain fenomena dogbone, pada saat bahan bakar tersebut digunakan di reaktor dapat terjadi swelling karena meningkatnya hasil fisi maupun burn up. Oleh karena itu, perlu dicari pengganti bahan kelongsong untuk bahan bakar U3Si2/Al densitas tinggi. Pada penelitian ini telah dilakukan karakterisasi paduan AlMgSi sebagai kandidat pengganti kelongsong AlMg2. Karakterisasi yang dilakukan meliputi analisis termal, kekerasan, mikrostruktur dan laju korosi. Analisis termal dilakukan menggunakan DTA (Differential Thermal Analysis dan DSC (Differential Scanning Calorimetry. Analisis kekerasan menggunakan alat uji kekerasan mikro, mikrostruktur menggunakan SEM (Scanning Electron Microscope dan analisis laju korosi dilakukan dengan pemanasan pada temperatur 150 oC selama 77 jam di dalam autoclave. Hasil analisis menunjukkan bahwa kelongsong AlMgSi maupun AlMg2 mempunyai kompatibilitas panas dengan bahan bakar U3Si2/Al cukup stabil hingga temperatur 650 oC. Kelongsong AlMgSi mempunyai kekerasan sebesar 115 HVN dan kelongsong AlMg2 sebesar 70,1 HVN. Sementara itu, analisis mikrostruktur menunjukkan bahwa morfologi ikatan antarmuka (interface bonding kelongsong AlMgSi lebih baik dari kelongsong AlMg2, demikian halnya dengan laju korosi bahwa kelongsong AlMgSi mempunyai laju korosi lebih kecil dibanding kelongsong AlMg2. Hasil karakterisasi termal, kekerasan, mikrostruktur dan laju korosi menunjukkan bahwa PEB U3Si2/Al densitas 5,2 gU/cm3 menggunakan kelongsong AlMgSi lebih baik dibanding PEB U3Si2/Al  densitas 5,2 gU/cm3  menggunakan kelongsong AlMg2. Kata kunci: U3Si2/Al, densitas 5,2 gU/cm3, kelongsong AlMgSi dan AlMg2.

Nanocrystalline SiC and Ti₃SiC₂ Alloys for Reactor Materials: Diffusion of Fission Product Surrogates

Energy Technology Data Exchange (ETDEWEB)

Henager, Charles H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Jiang, Weilin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2014-11-01

MAX phases, such as titanium silicon carbide (Ti₃SiC₂), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti₃SiC₂ has been suggested in the literature as a possible fuel cladding material. Prior to the application, it is necessary to investigate diffusivities of fission products in the ternary compound at elevated temperatures. This study attempts to obtain relevant data and make an initial assessment for Ti₃SiC₂. Ion implantation was used to introduce fission product surrogates (Ag and Cs) and a noble metal (Au) in Ti₃SiC₂, SiC, and a dual-phase nanocomposite of Ti₃SiC₂/SiC synthesized at PNNL. Thermal annealing and in-situ Rutherford backscattering spectrometry (RBS) were employed to study the diffusivity of the various implanted species in the materials. In-situ RBS study of Ti₃SiC₂ implanted with Au ions at various temperatures was also performed. The experimental results indicate that the implanted Ag in SiC is immobile up to the highest temperature (1273 K) applied in this study; in contrast, significant out-diffusion of both Ag and Au in MAX phase Ti₃SiC₂ occurs during ion implantation at 873 K. Cs in Ti₃SiC₂ is found to diffuse during post-irradiation annealing at 973 K, and noticeable Cs release from the sample is observed. This study may suggest caution in using Ti₃SiC₂ as a fuel cladding material for advanced nuclear reactors operating at very high temperatures. Further studies of the related materials are recommended.

Photoelectric characteristics of CH3NH3PbI3/p-Si heterojunction

Science.gov (United States)

Yamei, Wu; Ruixia, Yang; Hanmin, Tian; Shuai, Chen

2016-05-01

Organic-inorganic hybrid perovskite CH3NH3PbI3 film is prepared on p-type silicon substrate using the one-step solution method to form a CH3NH3PbI3/p-Si heterojunction. The film morphology and structure are characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The photoelectric properties of the CH3NH3PbI3/p-Si heterojunction are studied by testing the current-voltage (I-V) with and without illumination and capacitance-voltage (C-V) characteristics. It turns out from the I-V curve without illumination that the CH3NH3PbI3/p-Si heterojunction has a rectifier feature with the rectification ratio over 70 at the bias of ±5 V. Also, there appears a photoelectric conversion phenomenon on this heterojunction with a short circuit current (Isc) of 0.16 μA and an open circuit voltage (Voc) of about 10 mV The high frequency C-V characteristic of the Ag/CH3NH3PbI3/p-Si heterojunction turns out to be similar to that of the metal-insulator-semiconductor (MIS) structure, and a parallel translation of the C-V curve along the forward voltage axis is found. This parallel translation means the existence of defects at the CH3NH3PbI3/p-Si interface and positive fixed charges in the CH3NH3PbI3 layer. The defects at the interface of the CH3NH3PbI3/p-Si heterojunction result in the dramatic decline of the Voc. Besides, the C-V test of CH3NH3PbI3 film shows a non-linear dielectric property and the dielectric value is about 4.64 as calculated. Project supported by the Hebei Province Natural Science Foundation of China (No. F2014202184) and the Tianjin Natural Science Foundation of China (No. 15JCZDJC37800).

Electromagnetic modeling of waveguide amplifier based on Nd3+ Si-rich SiO2 layers by means of the ADE-FDTD method.

Science.gov (United States)

Dufour, Christian; Cardin, Julien; Debieu, Olivier; Fafin, Alexandre; Gourbilleau, Fabrice

2011-04-04

By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a Nd3+ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO2 bottom cladding and a SiO2 rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference Time Domain (FDTD) scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic field in a copropagating scheme of both pumping (λpump = 488 nm) and signal (λsignal = 1064 nm) waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic field ~ 10-15 s and the lifetimes of the electronic levels between ~ 10-10s and ~ 10-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time. We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng) concentrations. A threshold value of 1024 Si-ng m-3 is extracted below which the pump wave can propagate so that a signal amplication is possible.

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 .

Synthesis and fundamental properties of stable Ph(3)SnSiH(3) and Ph(3)SnGeH(3) hydrides: model compounds for the design of Si-Ge-Sn photonic alloys.

Science.gov (United States)

Tice, Jesse B; Chizmeshya, Andrew V G; Groy, Thomas L; Kouvetakis, John

2009-07-06

The compounds Ph(3)SnSiH(3) and Ph(3)SnGeH(3) (Ph = C(6)H(5)) have been synthesized as colorless solids containing Sn-MH(3) (M = Si, Ge) moieties that are stable in air despite the presence of multiple and highly reactive Si-H and Ge-H bonds. These molecules are of interest since they represent potential model compounds for the design of new classes of IR semiconductors in the Si-Ge-Sn system. Their unexpected stability and high solubility also makes them a safe, convenient, and potentially useful delivery source of -SiH(3) and -GeH(3) ligands in molecular synthesis. The structure and composition of both compounds has been determined by chemical analysis and a range of spectroscopic methods including multinuclear NMR. Single crystal X-ray structures were determined and indicated that both compounds condense in a Z = 2 triclinic (P1) space group with lattice parameters (a = 9.7754(4) A, b = 9.8008(4) A, c = 10.4093(5) A, alpha = 73.35(10)(o), beta = 65.39(10)(o), gamma = 73.18(10)(o)) for Ph(3)SnSiH(3) and (a = 9.7927(2) A, b = 9.8005(2) A, c = 10.4224(2) A, alpha = 74.01(3)(o), beta = 65.48(3)(o), gamma = 73.43(3)(o)) for Ph(3)SnGeH(3). First principles density functional theory simulations are used to corroborate the molecular structures of Ph(3)SnSiH(3) and Ph(3)SnGeH(3), gain valuable insight into the relative stability of the two compounds, and provide correlations between the Si-Sn and Ge-Sn bonds in the molecules and those in tetrahedral Si-Ge-Sn solids.

Epitaxial growth of 3C-SiC by using C{sub 60} as a carbon source; Untersuchungen zum epitaktischen Wachstum von 3C-SiC bei Verwendung einer C{sub 60}-Kohlenstoffquelle

Energy Technology Data Exchange (ETDEWEB)

Schreiber, Sascha

2006-01-15

conditions showed the highest crystalline quality within this work. However using a Si:C ratio smaller one in the gas phase during film deposition, i.e. growing under carbon-rich conditions, leads to homoepitaxial 3C-SiC island growth. Films synthesized under these conditions are of significantly lower quality. But despite of the excess supply of carbon during the deposition process they exhibit a Si:C=1:1 stoichiometry. (orig.)

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.

Effect of boron-doping on the luminescent and electrical properties of a CdS/Si heterostructure based on Si nanoporous pillar array

Energy Technology Data Exchange (ETDEWEB)

Yan, Ling Ling [Department of Physics and Laboratory of Material Physics, Zhengzhou University, Zhengzhou 450052 (China); College of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Wang, Xiao Bo [Department of Physics and Laboratory of Material Physics, Zhengzhou University, Zhengzhou 450052 (China); College of Physics and Electrical Engineering, Anyang Normal University, Anyang 455000 (China); Cai, Xiao Jun [Department of Physics and Laboratory of Material Physics, Zhengzhou University, Zhengzhou 450052 (China); Li, Xin Jian, E-mail: lixj@zzu.edu.cn [Department of Physics and Laboratory of Material Physics, Zhengzhou University, Zhengzhou 450052 (China)

2015-05-25

Highlights: • B-doped CdS/Si-NPA heterostructure was prepared by a CBD method. • B-doping does not affect the crystal structure and surface morphology of CdS/Si-NPA. • The optical/electrical properties of CdS/Si-NPA could be tuned by changing [B]/[Cd] ratio. • CdS/Si-NPA with optimal physical properties could be prepared with [B]/[Cd] = 0.01. • The method may find applications in preparing CdS/Si-NPA devices with high device performances. - Abstract: Using silicon nanoporous pillar array (Si-NPA) as substrates and boric acid as dopant source, a series of CdS/Si nanoheterostructures were prepared by growing B-doped CdS thin films on Si-NPA via a chemical bath deposition (CBD) method. The structural, optical and electrical properties of CdS/Si-NPA were studied as a function of the [B]/[Cd] ratio of the initial CBD solutions. Our results disclosed that B concentration could be tuned effectively through changing the ratio of [B]/[Cd], which would bring large variation on the optical and electrical properties of CdS/Si-NPA without affecting its crystal structure and surface morphology. The samples with optimal optical and electrical properties were prepared with [B]/[Cd] = 0.01, in which the physical properties of relatively strong light absorption, small electrical resistivity, low turn-on voltage, small leakage current density and high breakdown voltage could be obtained. These results indicated that B-doping might be an effective path for promoting the performance of the optoelectronic devices based on CdS/Si-NPA.

Effect of 3C-SiC intermediate layer in GaN—based light emitting diodes grown on Si(111) substrate

Science.gov (United States)

Zhu, Youhua; Wang, Meiyu; Li, Yi; Tan, Shuxin; Deng, Honghai; Guo, Xinglong; Yin, Haihong; Egawa, Takashi

2017-03-01

GaN-based light emitting diodes (LEDs) have been grown by metalorganic chemical vapor deposition on Si(111) substrate with and without 3C-SiC intermediate layer (IL). Structural property has been characterized by means of atomic force microscope, X-ray diffraction, and transmission electron microscope measurements. It has been revealed that a significant improvement in crystalline quality of GaN and superlattice epitaxial layers can be achieved by using 3C-SiC as IL. Regarding of electrical and optical characteristics, it is clearly observed that the LEDs with its IL have a smaller leakage current and higher light output power comparing with the LEDs without IL. The better performance of LEDs using 3C-SiC IL can be contributed to both of the improvements in epitaxial layers quality and light extraction efficiency. As a consequence, in terms of optical property, a double enhancement of the light output power and external quantum efficiency has been realized.

A contribution to the kinetic study of the metatectic reaction U+U{sub 3}Si{sub 2}{yields}U{sub 3}Si; Contribucion al Estudio cinetico de la Reaccion Metatectica U+U{sub 3}Si{sub 2} U{sub 3}Si

Energy Technology Data Exchange (ETDEWEB)

Arroyo Ruiperez, J; Esteban Hernandez, J A

1962-07-01

An experimental study has been made to decide upon the advantages and drawbacks of the different methods and reagents employed in the metallography of U-Si alloys. It has been observed that all samples thermally treated to form the epsilon-phase undergo from the beginning a coalescence of the U{sub 3}Si{sub 2} particles, which makes practically useless any fine state of dispersion that might be present originally, as recommended by some authors. The coalescence of the U{sub 3}Si{sub 2} particle decreases the surface available for reaction and consequently the reaction rate. (Author) 7 refs.

Out-of-equilibrium nanocrystalline R1-s(Fe,M)5+2s alloys (R=Sm,Pr; M=Co,Si,Ga)

International Nuclear Information System (INIS)

Bessais, L.; Djega-Mariadassou, C.

2005-01-01

The out-of-equilibrium hexagonal P6/mmm R 1-s (Fe,M) 5+2s (R=Sm,Pr and M=Co, Si or Ga) intermetallics are obtained by controlled nanocrystallization. A model is presented to explain the structure of the hexagonal phases, which stoichiometry is consistent with Sm(Fe,M) 9 and R(Fe,Ti,Co) 10 . The Curie temperatures increase versus Ga, Si, Co content. The analysis of the Moessbauer spectra leads to monotonous variation of the hyperfine parameters. The refinement of the Moessbauer spectra was performed on the basis of the correlation between Wigner-Seitz cell volumes obtained from X-ray diffraction results and isomer shifts. The abundance of each magnetic site was calculated by the multinomial distribution law. For a given substituting Co, Si, Ga content, the sequence for the isomer shift in the hexagonal cell is 2e>3g>6l. With increasing M content, the isomer shift of the 3g site remains quasi-constant. Those approaches lead to the location of Si, Ga, Co in 3g site, Ti in 6l site. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Fundamentals of Passive Oxidation In SiC and Si3N4

Science.gov (United States)

Thomas-Ogbuji, Linus U.

1998-01-01

The very slow oxidation kinetics of silicon carbide and silicon nitride, which derive from their adherent and passivating oxide films, has been explored at length in a broad series of studies utilizing thermogravimetric analysis, electron and optical micrography, energy dispersive spectrometry, x-ray diffractometry, micro-analytical depth profiling, etc. Some interesting microstructural phenomena accompanying the process of oxidation in the two materials will be presented. In Si3N4 the oxide is stratified, with an SiO2 topscale (which is relatively impervious to O2)underlain by a coherent subscale of silicon oxynitride which is even less permeable to O2- Such "defence in depth" endows Si3N4 with what is perhaps the highest oxidation resistance of any material, and results in a unique set of oxidation processes. In SiC the oxidation reactions are much simpler, yet new issues still emerge; for instance, studies involving controlled devitrification of the amorphous silica scale confirmed that the oxidation rate of SiC drops by more than an order of magnitude when the oxide scale fully crystallizes.

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+ .

Effect of germanium concentrations on tunnelling current calculation of Si/Si1-xGex/Si heterojunction bipolar transistor

Science.gov (United States)

Hasanah, L.; Suhendi, E.; Khairrurijal

2018-05-01

Tunelling current calculation on Si/Si1-xGex/Si heterojunction bipolar transistor was carried out by including the coupling between transversal and longitudinal components of electron motion. The calculation results indicated that the coupling between kinetic energy in parallel and perpendicular to S1-xGex barrier surface affected tunneling current significantly when electron velocity was faster than 1x105 m/s. This analytical tunneling current model was then used to study how the germanium concentration in base to Si/Si1-xGex/Si heterojunction bipolar transistor influenced the tunneling current. It is obtained that tunneling current increased as the germanium concentration given in base decreased.

New compounds bearing [M(S{sub 2}O{sub 7}){sub 3}]{sup 2-} anions (M = Si, Ge, Sn): Syntheses and characterization of A{sub 2}[Si(S{sub 2}O{sub 7}){sub 3}] (A = Na, K, Rb), A{sub 2}[Ge(S{sub 2}O{sub 7}){sub 3}] (A = Li, Na, K, Rb, Cs), A{sub 2}[Sn(S{sub 2}O{sub 7}){sub 3}] (A = Na, K), and the unique germanate Hg{sub 2}[Ge(S{sub 2}O{sub 7}){sub 3}]Cl{sub 2} with cationic {sup 1}{sub ∞}[HgCl{sub 2/2}]{sup +} chains

Energy Technology Data Exchange (ETDEWEB)

Logemann, Christian; Witt, Julia; Wickleder, Mathias S. [Universitaet Oldenburg, Institut fuer Reine und Angewandte Chemie (Germany); Gunzelmann, Daniel; Senker, Juergen [Universitaet Bayreuth, Lehrstuhl fuer Anorganische Chemie III (Germany)

2012-10-15

The reaction of the group 14 tetrachlorides MCl{sub 4} (M = Si, Ge, Sn) with oleum (65 % SO{sub 3}) at elevated temperatures led to the unique anionic complexes [M(S{sub 2}O{sub 7}){sub 3}]{sup 2-} that show the central M atoms in coordination of three chelating S{sub 2}O{sub 7}{sup 2-} groups. The mean distances M-O within the complexes increase from 175 pm (M = Si) via 186 pm (M = Ge) up to 200 pm (M = Sn). The charge balance for the [M(S{sub 2}O{sub 7}){sub 3}]{sup 2-} anions is achieved by alkaline metal ions A{sup +} (A = Li, Na, K, Rb, Cs) which were implemented in the syntheses in form of their sulfates. The size of the A{sup +} ions, i.e. their coordination requirement causes the crystallographic differences in the crystal structures, while the structure of the complex [M(S{sub 2}O{sub 7}){sub 3}]{sup 2-} anions remains essentially unaffected. Furthermore, we were able to characterize the unique germanate Hg{sub 2}[Ge(S{sub 2}O{sub 7}){sub 3}]Cl{sub 2} which forms when HgCl{sub 2} is added as a source for the counter cation. The Hg{sup 2+} and the Cl{sup -} ions form infinite cationic chains according to {sup 1}{sub ∞}[HgCl{sub 2/2}]{sup +} which take care for the charge compensation. For selected examples of the compounds the thermal behavior has been monitored by means of thermal analyses and X-ray powder diffraction. For A being an alkaline metal the decomposition product is a mixture of the sulfates A{sub 2}SO{sub 4} and the dioxides MO{sub 2}, whereas Hg{sub 2}[Ge(S{sub 2}O{sub 7}){sub 3}]Cl{sub 2} shows a more complicated decomposition. The tris-(disulfato)-silicate Na{sub 2}[Si(S{sub 2}O{sub 7}){sub 3}] has additionally been examined by solid state {sup 29}Si and {sup 23}Na NMR spectroscopic measurements. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Preparation and characterization of CdS/Si coaxial nanowires

Science.gov (United States)

Fu, X. L.; Li, L. H.; Tang, W. H.

2006-04-01

CdS/Si coaxial nanowires were fabricated via a simple one-step thermal evaporation of CdS powder in mass scale. Their crystallinities, general morphologies and detailed microstructures were characterized by using X-ray diffraction, scanning electron microscope, transmission electron microscope and Raman spectra. The CdS core crystallizes in a hexagonal wurtzite structure with lattice constants of a=0.4140 nm and c=0.6719 nm, and the Si shell is amorphous. Five Raman peaks from the CdS core were observed. They are 1LO at 305 cm -1, 2LO at 601 cm -1, A 1-TO at 212 cm -1, E 1-TO at 234 cm -1, and E 2 at 252 cm -1. Photoluminescence measurements show that the nanowires have two emission bands around 510 and 590 nm, which originate from the intrinsic transitions of CdS cores and the amorphous Si shells, respectively.

Reaction of (carbonylimido)sulfur(IV) derivatives with TAS-fluoride, (Me2N)3S+Me3SiF2-.

Science.gov (United States)

Lork, E; Viets, D; Mews, R; Oberhammer, H

2000-10-16

In the reaction of TAS-fluoride, (Me2N)3S+Me3SiF2-, with carbonyl sulfur difluoride imides RC(O)NSF2 (R = F, CF3), C-N bond, cleavage is observed, and TAS+RC(O)F2- and NSF are the final products. From TASF and RC(O)NS(CF3)F, the salts TAS+RC(O)NS(CF3)F2- (R = F (14), CF3 (15)), with psi-pentacoordinate sulfur centers in the anions, are formed. An X-ray structure investigation of 14 shows that the fluorine atoms occupy axial positions and CF3, NC(O)F, and the sulfur lone pair occupy equatorial positions of the trigonal bipyramid. The -C(O)F group lies in the equatorial plane with the CO bond synperiplanar to the SN bond. According to B3LYP calculations, this structure corresponds to a global minimum and the expected axial orientation of the -C(O)F group represents a transition state. Calculations for the unstable FC(O)NSF3- anion show a different geometry. The -C(O)F group deviates 40 degrees from axial orientation, and the equatorially bonded fluorine is, in contrast to the -CF3 group in 14, syn positioned.

Evolution of 3C-SiC islands nucleated from a liquid phase on Si face α-SiC substrates

International Nuclear Information System (INIS)

Kim-Hak, Olivier; Ferro, Gabriel; Lorenzzi, Jean; Carole, Davy; Dazord, Jacques; Chaudouet, Patrick; Chaussende, Didier; Miele, Philippe

2010-01-01

The contact between α-SiC crystals and Si-Ge based melts provokes the nucleation of 3C-SiC islands on the crystal surface. Evolution of these islands as a function of various parameters was studied. On both 4H and 6H substrates, it was found that, after nucleation, 3C-SiC islands first enlarge and may form a complete 3C layer under certain conditions. The 3C deposit can then be dissolved by the liquid phase at high temperature or for prolonged contact at relatively moderate temperature. The graphite crucible is proposed to play a central role in these enlargement and dissolution mechanisms by providing extra carbon atoms on the seed surface (enlargement) or provoking thermal induced carbon transport toward the sidewall (dissolution). Several differences between the use of 4H and 6H substrates were also observed.

Low silicon U(Al,Si)3 stabilization by Zr addition

International Nuclear Information System (INIS)

Pizarro, L.M.; Alonso, P.R.; Rubiolo, G.H.

2009-01-01

Previous knowledge states that (U,Zr)Al 3 and U(Al,Si) 3 phases with Zr and Si content higher than 6 at.% (7.7 wt%) and 4 at.% (1.4 wt%), respectively, does not partially transform to UAl 4 at 600 o C. In this work, four alloys within the quaternary system U-Al-Si-Zr were made with a fixed nominal 0.18 at.% (0.1 wt%) Si content in order to assess the synergetic effect of both Zr and Si alloying elements to the thermodynamic stability of the (U,Zr)(Al,Si) 3 phase. Heat treatments at 600 deg. C were undertaken and samples were analyzed by means of XRD, EPMA and EDS techniques. A remarkable conclusion is that addition of 0.3 at.% Si in the (U,Zr)(Al,Si) 3 phase reduces in 2.7 at.% the necessary Zr content to inhibit its transformation to U(Al,Si) 4 .

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.

Electromagnetic modeling of waveguide amplifier based on Nd3+ Si-rich SiO2 layers by means of the ADE-FDTD method

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Dufour Christian

2011-01-01

Full Text Available Abstract By means of ADE-FDTD method, this paper investigates the electromagnetic modelling of a rib-loaded waveguide composed of a Nd3+ doped Silicon Rich Silicon Oxide active layer sandwiched between a SiO2 bottom cladding and a SiO2 rib. The Auxilliary Differential Equations are the rate equations which govern the levels populations. The Finite Difference Time Domain (FDTD scheme is used to solve the space and time dependent Maxwell equations which describe the electromagnetic field in a copropagating scheme of both pumping (λ pump = 488 nm and signal (λ signal = 1064 nm waves. Such systems are characterized by extremely different specific times such as the period of electromagnetic field ~ 10-15 s and the lifetimes of the electronic levels between ~ 10-10s and ~ 10-4 s. The time scaling method is used in addition to specific initial conditions in order to decrease the computational time. We show maps of the Poynting vector along the propagation direction as a function of the silicon nanograin (Si-ng concentrations. A threshold value of 1024 Si-ng m-3 is extracted below which the pump wave can propagate so that a signal amplication is possible.

Pós de Al2O3/SiC obtidos a partir de reação de redução carbotérmica Al2O3/SiC powders from carbothermal reduction reaction

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F. M. Spiandorello

1999-12-01

Full Text Available Neste trabalho foram utilizadas matérias-primas naturais para a obtenção de pós Al2O3/SiC através da redução carbotérmica das mesmas por um agente rico em carbono. Os aluminossilicatos estudados foram caulim, cianita e ilita-moscovita, sendo que os mesmos foram reduzidos ou por negro de fumo ou por grafite. Os pós resultantes da reação foram caracterizados por microscopia eletrônica de varredura e transmissão, difração de raios X e picnometria de hélio. Durante a reação, as diferenças existentes tanto na estrutura das matérias-primas quanto na composição química produziram pós com morfologia diversa. Foram encontradas estruturas como grandes aglomerados esféricos, whiskers, partículas e aglomerados fibrosos.In this work natural raw materials were used to obtain Al2O3/SiC powders by carbothermal reduction. The aluminosilicates studied were kaolin, kyanite and illite-muscovite and the reductor agents were carbon black or graphite. The reaction powders were characterized by transmission and scanning electron microscopy, X-ray diffraction and helium picnometry. During the reaction, the differences among the raw materials structures as well as into the chemical composition produced powders with several morphologies. Big spherical agglomerates, whiskers, particles and fibrous clusters were found.

Microstructure and Properties of Porous Si3N4/Dense Si3N4 Joints Bonded Using RE–Si–Al–O–N (RE = Y or Yb Glasses

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Ling Li

2017-11-01

Full Text Available The joining of porous Si3N4 to dense Si3N4 ceramics has been successfully performed using mixed RE2O3 (RE = Y or Yb, Al2O3, SiO2, and α-Si3N4 powders. The results suggested that the α-Si3N4 powders partly transformed into β-SiAlON and partly dissolved into oxide glass to form oxynitride glass. Thus, composites of glass/β-SiAlON-ceramic formed in the seam of joints. Due to the capillary action of the porous Si3N4 ceramic, the molten glass solder infiltrated into the porous Si3N4 ceramic side during the joining process and formed the “infiltration zone” with a thickness of about 400 μm, which contributed to the heterogeneous distribution of the RE–Si–Al–O–N glasses in the porous Si3N4 substrate. In-situ formation of β-SiAlON in the seam resulted in a high bonding strength. The maximum bending strength of 103 MPa and 88 MPa was reached for the porous Si3N4/dense Si3N4 joints using Y–Si–Al–O–N and Yb–Si–Al–O–N glass solders, respectively.

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

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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.

Synthesis, structural, electronic and linear electro-optical features of new quaternary Ag{sub 2}Ga{sub 2}SiS{sub 6} compound

Energy Technology Data Exchange (ETDEWEB)

Piasecki, M., E-mail: m.piasecki@ajd.czest.pl [Institute of Physics, Jan Dlugosz University, Armii Krajowej 13/15, PL-42-201 Czestochowa (Poland); Myronchuk, G.L. [Department of Solid State Physics, Lesya Ukrainka Eastern European National University, 13 Voli Ave., Lutsk 43025 (Ukraine); Parasyuk, O.V. [Department of Inorganic and Physical Chemistry, Lesya Ukrainka Eastern European National University, 13 Voli Ave., Lutsk 43025 (Ukraine); Khyzhun, O.Y. [Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky St., Kyiv 03142 (Ukraine); Fedorchuk, A.O. [Department of Inorganic and Organic Chemistry, Lviv National University of Veterinary Medicine and Biotechnologies, 50 Pekarska Street, Lviv 79010 (Ukraine); Pavlyuk, V.V. [Department of Inorganic Chemistry, Ivan Franko National University of Lviv, 6 Kyryla and Mefodiya St., 79005 Lviv (Ukraine); Institute of Chemistry, Environment Protection and Biotechnology, Jan Dlugosz University, al. Armii Krajowej 13/15, 42-200 Czestochowa (Poland); Kozer, V.R.; Sachanyuk, V.P. [Department of Inorganic and Physical Chemistry, Lesya Ukrainka Eastern European National University, 13 Voli Ave., Lutsk 43025 (Ukraine); El-Naggar, A.M. [Physics Department, Faculty of Science, Ain Shams University, Abassia, Cairo 11566 (Egypt); Research Chair of Exploitation of Renewable Energy Applications in Saudi Arabia, Physics & Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Albassam, A.A. [Research Chair of Exploitation of Renewable Energy Applications in Saudi Arabia, Physics & Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Jedryka, J.; Kityk, I.V. [Faculty of Electrical Engineering, Czestochowa University Technology, Armii Krajowej 17, Czestochowa (Poland)

2017-02-15

For the first time phase equilibria and phase diagram of the AgGaS{sub 2}–SiS{sub 2} system were successfully explored by differential thermal and X-ray phase analysis methods. Crystal structure of low-temperature (LT) modification of Ag{sub 2}Ga{sub 2}SiS{sub 6} (LРў- Ag{sub 2}Ga{sub 2}SiS{sub 6}) was studied by X-ray powder method and it belongs to tetragonal space group I-42d, with unit cell parameters a=5.7164(4) Å, c=9.8023(7) Å, V=320.32(7) Å{sup 3}. Additional details regarding the crystal structure exploration are available at the web page Fachinformationszentrum Karlsruhe. X-ray photoelectron core-level and valence-band spectra were measured for pristine LРў- Ag{sub 2}Ga{sub 2}SiS{sub 6} crystal surface. In addition, the X-ray photoelectron valence-band spectrum of LРў-Ag{sub 2}Ga{sub 2}SiS{sub 6} was matched on a common energy scale with the X-ray emission S Kβ{sub 1,3} and Ga Kβ{sub 2} bands, which give information on the energy distribution of the S 3p and Ga 4p states, respectively. The presented X-ray spectroscopy results indicate that the valence S p and Ga p atomic states contribute mainly to the upper and central parts of the valence band of LРў-Ag{sub 2}Ga{sub 2}SiS{sub 6}, respectively, with a less significant contribution also to other valence-band regions. Band gap energy was estimated by measuring the quantum energy in the spectral range of the fundamental absorption. We have found that energy gap Eg is equal to 2.35 eV at 300 K. LT-Ag{sub 2}Ga{sub 2}SiS{sub 6} is a photosensitive material and reveals two spectral maxima on the curve of spectral photoconductivity spectra at λ{sub max1} =590 nm and λ{sub max2} =860 nm. Additionally, linear electro-optical effect of LT-Ag{sub 2}Ga{sub 2}SiS{sub 6} for the wavelengths of a cw He-Ne laser at 1150 nm was explored. - Graphical abstract: Manuscript present the technology of growth and investigation of properties a new quaternary compound Ag{sub 2}Ga{sub 2}SiS{sub 6

Experimental study of 112 Gb/s short reach transmission employing PAM formats and SiP intensity modulator at 1.3 μm.

Science.gov (United States)

Chagnon, Mathieu; Osman, Mohamed; Poulin, Michel; Latrasse, Christine; Gagné, Jean-Frédéric; Painchaud, Yves; Paquet, Carl; Lessard, Stéphane; Plant, David

2014-08-25

We present a Silicon Photonic (SiP) intensity modulator operating at 1.3 μm with pulse amplitude modulation formats for short reach transmission employing a digital to analog converter for the RF signal generator, enabling pulse shaping and precompensation of the transmitter's frequency response. Details of the SiP Mach-Zehnder interfometer are presented. We study the system performance at various bit rates, PAM orders and propagation distances. To the best of our knowledge, we report the first demonstration of a 112 Gb/s transmission over 10 km of SMF fiber operating below pre-FEC BER threshold of 3.8 × 10(-3) employing PAM-8 at 37.4 Gbaud using a fully packaged SiP modulator. An analytical model for the Q-factor metric applicable for multilevel PAM-N signaling is derived and accurately experimentally verified in the case of Gaussian noise limited detection. System performance is experimentally investigated and it is demonstrated that PAM order selection can be optimally chosen as a function of the desired throughput. We demonstrate the ability of the proposed transmitter to exhibit software-defined transmission for short reach applications by selecting PAM order, symbol rate and pulse shape.

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

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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

Fabrication of FeSi and Fe{sub 3}Si compounds by electron beam induced mixing of [Fe/Si]{sub 2} and [Fe{sub 3}/Si]{sub 2} multilayers grown by focused electron beam induced deposition

Energy Technology Data Exchange (ETDEWEB)

Porrati, F.; Sachser, R.; Huth, M. [Physikalisches Institut, Goethe-Universität, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main (Germany); Gazzadi, G. C. [S3 Center, Nanoscience Institute-CNR, Via Campi 213/a, 41125 Modena (Italy); Frabboni, S. [S3 Center, Nanoscience Institute-CNR, Via Campi 213/a, 41125 Modena (Italy); FIM Department, University of Modena and Reggio Emilia, Via G. Campi 213/a, 41125 Modena (Italy)

2016-06-21

Fe-Si binary compounds have been fabricated by focused electron beam induced deposition by the alternating use of iron pentacarbonyl, Fe(CO){sub 5}, and neopentasilane, Si{sub 5}H{sub 12} as precursor gases. The fabrication procedure consisted in preparing multilayer structures which were treated by low-energy electron irradiation and annealing to induce atomic species intermixing. In this way, we are able to fabricate FeSi and Fe{sub 3}Si binary compounds from [Fe/Si]{sub 2} and [Fe{sub 3}/Si]{sub 2} multilayers, as shown by transmission electron microscopy investigations. This fabrication procedure is useful to obtain nanostructured binary alloys from precursors which compete for adsorption sites during growth and, therefore, cannot be used simultaneously.

Effect of Solids-To-Liquids, Na2SiO3-To-NaOH and Curing Temperature on the Palm Oil Boiler Ash (Si + Ca) Geopolymerisation System

Science.gov (United States)

Yahya, Zarina; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Ismail, Khairul Nizar; Abd Razak, Rafiza; Sandu, Andrei Victor

2015-01-01

This paper investigates the effect of the solids-to-liquids (S/L) and Na2SiO3/NaOH ratios on the production of palm oil boiler ash (POBA) based geopolymer. Sodium silicate and sodium hydroxide (NaOH) solution were used as alkaline activator with a NaOH concentration of 14 M. The geopolymer samples were prepared with different S/L ratios (0.5, 1.0, 1.25, 1.5, and 1.75) and Na2SiO3/NaOH ratios (0.5, 1.0, 1.5, 2.0, 2.5, and 3.0). The main evaluation techniques in this study were compressive strength, X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscope (SEM). The results showed that the maximum compressive strength (11.9 MPa) was obtained at a S/L ratio and Na2SiO3/NaOH ratio of 1.5 and 2.5 at seven days of testing.

Surface Defect Passivation and Reaction of c-Si in H2S.

Science.gov (United States)

Liu, Hsiang-Yu; Das, Ujjwal K; Birkmire, Robert W

2017-12-26

A unique passivation process of Si surface dangling bonds through reaction with hydrogen sulfide (H 2 S) is demonstrated in this paper. A high-level passivation quality with an effective minority carrier lifetime (τ eff ) of >2000 μs corresponding to a surface recombination velocity of passivation by monolayer coverage of S on the Si surface. However, S passivation of the Si surface is highly unstable because of thermodynamically favorable reaction with atmospheric H 2 O and O 2 . This instability can be eliminated by capping the S-passivated Si surface with a protective thin film such as low-temperature-deposited amorphous silicon nitride.

Ablation behavior and mechanism of 3D Cf/ZrC-SiC composites in a plasma wind tunnel environment

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Qinggang Li

2015-12-01

Full Text Available Three-dimensional needle-like Cf/ZrC-SiC composites were successfully fabricated by polymer infiltration and pyrolysis combined with ZrC precursor impregnation. The ablation properties of the composites were tested in a plasma wind tunnel environment at different temperatures and different times. The microstructure and morphology of the composites were examined after ablation by scanning electron microscopy, and their composition was confirmed by energy dispersive spectroscopy. The composites exhibited good configurational stability with a surface temperature of greater than 2273 K over a 300–1000 s period. The formation of ZrSiO4 and SiO2 melts on the surface of the 3D Cf/ZrC-SiC composites contributed significantly to improvement in their ablation properties. However, these composites exhibited serious ablation when the temperature was increased to 2800 K. The 3D Cf/ZrC-SiC composites obtained after ablation showed three different layers attributed to the temperature and pressure gradients: the ablation central region, the ablation transition region, and the unablation region.

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.

Spin injection and magnetoresistance in MoS2-based tunnel junctions using Fe3Si Heusler alloy electrodes.

Science.gov (United States)

Rotjanapittayakul, Worasak; Pijitrojana, Wanchai; Archer, Thomas; Sanvito, Stefano; Prasongkit, Jariyanee

2018-03-19

Recently magnetic tunnel junctions using two-dimensional MoS 2 as nonmagnetic spacer have been fabricated, although their magnetoresistance has been reported to be quite low. This may be attributed to the use of permalloy electrodes, injecting current with a relatively small spin polarization. Here we evaluate the performance of MoS 2 -based tunnel junctions using Fe 3 Si Heusler alloy electrodes. Density functional theory and the non-equilibrium Green's function method are used to investigate the spin injection efficiency (SIE) and the magnetoresistance (MR) ratio as a function of the MoS 2 thickness. We find a maximum MR of ~300% with a SIE of about 80% for spacers comprising between 3 and 5 MoS 2 monolayers. Most importantly, both the SIE and the MR remain robust at finite bias, namely MR > 100% and SIE > 50% at 0.7 V. Our proposed materials stack thus demonstrates the possibility of developing a new generation of performing magnetic tunnel junctions with layered two-dimensional compounds as spacers.

Synthesis and characterization of nanostructured CaSiO3 biomaterial

Science.gov (United States)

Jagadale, Pramod N.; Kulal, Shivaji R.; Joshi, Meghanath G.; Jagtap, Pramod P.; Khetre, Sanjay M.; Bamane, Sambhaji R.

2013-04-01

Here we report a successful preparation of nanostructured calcium silicate by wet chemical approach. The synthesized sample was characterized by various physico-chemical methods. Thermal stability was investigated using thermo-gravimetric and differential thermal analysis (TG-DTA). Structural characterization of the sample was carried out by the X-ray diffraction technique (XRD) which confirmed its single phase hexagonal structure. Transmission electron microscopy (TEM) was used to study the nanostructure of the ceramics while homogeneous grain distribution was revealed by scanning electron microscopy studies (SEM). The elemental analysis data obtained from energy dispersive X-ray spectroscopy (EDAX) were in close agreement with the starting composition used for the synthesis. Superhydrophilic nature of CaSiO3 was investigated at room temperature by sessile drop technique. Effect of porous nanosized CaSiO3 on early adhesion and proliferation of human bone marrow mesenchymal stem cells (BMMSCs) and cord blood mesenchymal stem (CBMSCs) cells was measured in vitro. MTT cytotoxicity test and cell adhesion test showed that the material had good biocompatibility and promoted cell viability and cell proliferation. It has been stated that the cell viability and proliferation are significantly affected by time and concentration of CaSiO3. These findings indicate that the CaSiO3 ceramics has good biocompatibility and that it is promising as a biomaterial.

Fabrication and characterization of 2.5D and 3D SiC{sub f}/SiC composites

Energy Technology Data Exchange (ETDEWEB)

Zhao, Shuang, E-mail: zhsh6007@126.co [Key Laboratory of Advanced Ceramic Fibers and Composites, National University of Defense Technology, Changsha 410073 (China); School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); Zhou, Xingui; Yu, Jinshan [Key Laboratory of Advanced Ceramic Fibers and Composites, National University of Defense Technology, Changsha 410073 (China); Mummery, Paul [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Manchester M13 9PL (United Kingdom)

2013-10-15

Highlights: • 2.5D and 3D KD-I SiC fiber fabrics were used as the reinforcement. • Closed porosity was investigated by X-ray tomographic techniques. • The properties of the composites were improved by the CVD process. -- Abstract: SiC{sub f}/SiC composites are considered promising candidate materials for fusion applications. 2.5D and 3D KD-I SiC fiber fabrics were used as the reinforcement and SiC{sub f}/SiC composites were fabricated via polymer impregnation and pyrolysis (PIP) process and coated with chemical vapor deposited (CVD) SiC. The porosity, thermal conductivity and mechanical property of the composites were characterized. The results indicated that 2.5D and 3D SiC{sub f}/SiC composites fabricated via PIP process exhibited high porosity, and hence low thermal conductivity. After the CVD process, the density, thermal conductivity and mechanical properties of the composites were increased.

Obtenção de substratos cerâmicos no sistema Si-Al-O-N-C empregando polissiloxanos e carga de Si e Al2O3 Ceramic tapes of Si-Al-O-N-C compounds using mixtures of polyssiloxane and Si-Al2O3 fillers

Directory of Open Access Journals (Sweden)

R. M. Rocha

2005-03-01

Full Text Available A técnica de processamento de colagem por fita (tape casting tem sido amplamente utilizada na obtenção de cerâmicas para diferentes aplicações: substratos cerâmicos e estruturas planares em multicamadas para circuitos integrados e capacitores; eletrólitos sólidos para células a combustível e sensores; cerâmicas piezoelétricas para atuadores e transdutores; membranas de separação para micro-filtragem; compósitos estruturais e trocadores de calor. Neste trabalho, a técnica convencional de colagem por fita foi adaptada com a utilização do processo de pirólise controlada de misturas de polímeros e carga, empregando-se polissiloxanos e cargas de silício e alumina nas suspensões. Foram preparadas suspensões com 60% vol. de fase polimérica (polissiloxanos e metil-trietoxi-silano e 40% vol. de carga (Si e Al2O3, com diferentes concentrações dos polímeros e das cargas. As amostras na forma de substratos foram pirolisadas em atmosfera de nitrogênio a 1400 °C/2 h e 1500 °C/2 h, sendo convertidas em materiais cerâmicos no sistema Si-Al-O-N-C. O processo de pirólise foi caracterizado até a temperatura de 1000 ºC por análise termogravimétrica. As cerâmicas foram caracterizadas quanto às fases formadas, microestrutura, massa específica aparente e condutividade térmica. Os substratos cerâmicos apresentaram porosidade relativamente alta (entre 12 e 22% e baixa condutividade térmica (entre 3 e 8 W/m.K, sendo constituídos por fases cristalinas de beta-SiC, Si2ON2, O'-SiAlON, Al2O3, mulita e fase amorfa de SiOC; o Si foi observado nas amostras pirolisadas a 1400 ºC.The tape casting technique has been widely used to prepare ceramic tapes for different applications: ceramic substrates and multilayer planar structures for integrated circuits and capacitors, solid electrolytes for fuel cells and sensors, piezoelectric ceramics for actuators and transducers, membrane systems for micro-filtration, structural composites and

Effect of interstitial nitrogen on magnetism and entropy change of LaFe11.7Si1.3 compound

International Nuclear Information System (INIS)

Balli, M.; Rosca, M.; Fruchart, D.; Gignoux, D.

2009-01-01

Crystal structure, magnetism and magnetocaloric properties of LaFe 11.7 Si 1.3 N y (y=0, 1.3) compounds have been studied by X-ray diffraction and magnetic measurements. The LaFe 11.7 Si 1.3 N y compounds present a cubic NaZn 13 -type structure. Insertion of 1.3 nitrogen atoms per LaFe 11.7 Si 1.3 formula increases the lattice parameter and Curie temperature from 11.467 to 11.733 A and from 190 to ∼230 K, respectively. Besides, the absorption of nitrogen drives drastically the magnetic transition from first to second order and accordingly strongly decreases the magnetocaloric effect compared to the parent alloy. Under an external field change of 5 T, the value of isothermal entropy change -ΔS is about 28 and 3.5 J/kg K for LaFe 11.7 Si 1.3 and LaFe 11.7 Si 1.3 N 1.3 , respectively, close to their Curie temperature. However, the relative cooling power RCP(S) of the nitride is about half that of the parent alloy

Diffusion of Ag, Au and Cs implants in MAX phase Ti3SiC2

Energy Technology Data Exchange (ETDEWEB)

Jiang, Weilin; Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R.; Zhang, Chonghong; Gou, Jie

2015-05-16

MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti3SiC2), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti3SiC2 has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti3SiC2/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including x-ray diffraction, electron backscatter diffraction, energy dispersive x-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti3SiC2 within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti3SiC2 was also observed. Cs out-diffusion and release from Ti3SiC2 occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti3SiC2 as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

Structure of Ti{sub 3}SiC{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Rawn, C.J.; Payzant, E.A.; Hubbard, C.R. [Oak Ridge National Lab., TN (United States); Barsoum, M.W.; El-Raghy, T. [Drexel Univ., Philadelphia, PA (United States). Dept. of Materials Engineering

1998-11-01

Earlier high temperature structure analysis by neutron powder diffraction suggested that Si vacancies were created when Ti{sub 3}SiC{sub 2} was heated. A specimen that was heated to 906 C overnight was later examined at room temperature. For this subsequent room temperature data set refinement of the Si site occupancies in the Ti{sub 3}SiC{sub 2} structure did not support the hypothesis that Si vacancies were being created when the sample was held at elevated temperatures in a vacuum furnace.

Tribological properties of SiC-based MCD films synthesized using different carbon sources when sliding against Si3N4

Science.gov (United States)

Wang, Xinchang; Shen, Xiaotian; Zhao, Tianqi; Sun, Fanghong; Shen, Bin

2016-04-01

Micro-crystalline diamond (MCD) films are deposited on reactive sintering SiC substrates by the bias enhanced hot filament chemical vapor deposition (BE-HFCVD) method, respectively using the methane, acetone, methanol and ethanol as the carbon source. Two sets of standard tribotests are conducted, adopting Si3N4 balls as the counterpart balls, respectively with the purpose of clarifying differences among tribological properties of different MCD films, and studying detailed effects of the carbon source C, normal load Fn and sliding velocity v based on orthogonal analyses. It is clarified that the methane-MCD film presents the lowest growth rate, the highest film quality, the highest hardness and the best adhesion, in consequence, it also performs the best tribological properties, including the lowest coefficient of friction (COF) and wear rate Id, while the opposite is the methanol-MCD film. Under a normal load Fn of 7 N and at a sliding velocity v of 0.4183 m/s, for the methane-MCD film, the maximum COF (MCOF) is 0.524, the average COF during the relatively steady-state regime (ACOF) is 0.144, and the Id is about 1.016 × 10-7 mm3/N m; and for the methanol-MCD film, the MCOF is 0.667, the ACOF is 0.151, and the Id is 1.448 × 10-7 mm3/N m. Moreover, the MCOF, ACOF, Id and the wear rate of the Si3N4 ball Ib will all increase with the Fn, while the v only has significant effect on the ACOF, which shows a monotone increasing trend with the v.

Light emissions from LiNbO sub 3 /SiO sub 2 /Si structures

CERN Document Server

Wu, X L; Tang, N; Deng, S S; Bao, X M

2003-01-01

LiNbO sub 3 (LN) films with a high degree of (006) texture were deposited on Si-based dense SiO sub 2 layers by pulsed laser deposition. After annealing, the LN/SiO sub 2 /Si structures were revealed to have ultraviolet-, green-, and red-emitting properties related to self-trapped excitons and E' defect pairs in the SiO sub 2 surface, which are induced by the photorefractive effect of the LN films. The emission wavelength can be tuned by introducing different dopants into the LN films. Waveguiding properties of the structures were demonstrated. The results obtained indicate that the LN/SiO sub 2 /Si structures could be expected to have important applications in modern optoelectronic integration. (letter to the editor)

The Li–Si–(O)–N system revisited: Structural characterization of Li{sub 21}Si{sub 3}N{sub 11} and Li{sub 7}SiN{sub 3}O

Energy Technology Data Exchange (ETDEWEB)

Casas-Cabanas, M. [CIC energiGUNE, Parque Tecnológico de Álava, Albert Einstein 48, ED.CIC, 01510 Miñano (Spain); Santner, H. [Institut de Ciència de Materials de Barcelona (CSIC) Campus UAB, 08193 Bellaterra, Catalonia (Spain); Palacín, M.R., E-mail: rosa.palacin@icmab.es [Institut de Ciència de Materials de Barcelona (CSIC) Campus UAB, 08193 Bellaterra, Catalonia (Spain)

2014-05-01

A systematic study of the Li–Si–(O)–N system is presented. The synthetic conditions to prepare Li{sub 2}SiN{sub 2}, Li{sub 5}SiN{sub 3}, Li{sub 18}Si{sub 3}N{sub 10}, Li{sub 21}Si{sub 3}N{sub 11} and Li{sub 7}SiN{sub 3}O are described and the structure of the last two compounds has been solved for the first time. While Li{sub 21}Si{sub 3}N{sub 11} crystallizes as a superstructure of the anti-fluorite structure with Li and Si ordering, Li{sub 7}SiN{sub 3}O exhibits the anti-fluorite structure with both anion and cation disorder. - Graphical abstract: A systematic study of the Li–Si–(O)–N system is presented. Li{sub 21}Si{sub 3}N{sub 11} crystallizes as a superstructure of the anti-fluorite structure with Li and Si ordering, Li{sub 7}SiN{sub 3}O exhibits the anti-fluorite structure with both anion and cation disorder. - Highlights: • Li{sub 2}SiN{sub 2}, Li{sub 5}SiN{sub 3}, Li{sub 18}Si{sub 3}N{sub 10}, Li{sub 21}Si{sub 3}N{sub 11} and Li{sub 7}SiN{sub 3}O are prepared. • The structures of Li{sub 21}Si{sub 3}N{sub 11} and Li{sub 7}SiN{sub 3}O are presented. • Li{sub 21}Si{sub 3}N{sub 11} exhibits an anti-fluorite superstructure with Li and Si ordering.

Germanium growth on electron beam lithography patterned Si3N4/Si(001) substrate using molecular beam epitaxy

Science.gov (United States)

Sarkar, Subhendu Sinha; Katiyar, Ajit K.; Sarkar, Arijit; Dhar, Achintya; Rudra, Arun; Khatri, Ravinder K.; Ray, Samit Kumar

2018-04-01

It is important to investigate the growth dynamics of Ge adatoms under different surface stress regimes of the patterned dielectric to control the selective growth of self-assembled Ge nanostructures on silicon. In the present work, we have studied the growth of Ge by molecular beam epitaxy on nanometer scale patterned Si3N4/Si(001) substrates generated using electron beam lithography. The pitch of the patterns has been varied to investigate its effect on the growth of Ge in comparison to un-patterned Si3N4. For the patterned Si3N4 film, Ge did not desorbed completely from the Si3N4 film and hence no site selective growth pattern is observed. Instead, depending upon the pitch, Ge growth has occurred in different growth modes around the openings in the Si3N4. For the un-patterned substrate, the morphology exhibits the occurrence of uniform 3D clustering of Ge adatoms on Si3N4 film. This variation in the growth modes of Ge is attributed to the variation of residual stress in the Si3N4 film for different pitch of holes, which has been confirmed theoretically through Comsol Multiphysics simulation. The variation in stress for different pitches resulted in modulation of surface energy of the Si3N4 film leading to the different growth modes of Ge.

Excitonic Instability and Pseudogap Formation in Nodal Line Semimetal ZrSiS

Science.gov (United States)

Rudenko, A. N.; Stepanov, E. A.; Lichtenstein, A. I.; Katsnelson, M. I.

2018-05-01

Electron correlation effects are studied in ZrSiS using a combination of first-principles and model approaches. We show that basic electronic properties of ZrSiS can be described within a two-dimensional lattice model of two nested square lattices. A high degree of electron-hole symmetry characteristic for ZrSiS is one of the key features of this model. Having determined model parameters from first-principles calculations, we then explicitly take electron-electron interactions into account and show that, at moderately low temperatures, ZrSiS exhibits excitonic instability, leading to the formation of a pseudogap in the electronic spectrum. The results can be understood in terms of Coulomb-interaction-assisted pairing of electrons and holes reminiscent of that of an excitonic insulator. Our finding allows us to provide a physical interpretation of the unusual mass enhancement of charge carriers in ZrSiS recently observed experimentally.

Effect of Si ion irradiation on polycrystalline CdS thin film grown from novel photochemical deposition technique

International Nuclear Information System (INIS)

Soundeswaran, S.; Senthil Kumar, O.; Ramasamy, P.; Kabi Raj, D.; Avasthi, D.K.; Dhanasekaran, R.

2005-01-01

CdS thin films have been deposited from aqueous solution by photochemical reactions. The solution contains Cd(CH 3 COO) 2 and Na 2 S 2 O 3 , and pH is controlled in an acidic region by adding H 2 SO 4 . The solution is illuminated with light from a high-pressure mercury-arc lamp. CdS thin films are formed on a glass substrate by the heterogeneous nucleation and the deposited thin films have been subjected to high-energy Si ion irradiations. Si ion irradiation has been performed with an energy of 80 MeV at fluences of 1x10 11 , 1x10 12 , 1x10 13 and 1x10 14 ions/cm 2 using tandem pelletron accelerator. The irradiation-induced changes in CdS thin films are studied using XRD, Raman spectroscopy and photoluminescence. Broadening of the PL emission peak were observed with increasing irradiation fluence, which could be attributed to the band tailing effect of the Si ion irradiation. The lattice disorder takes place at high Si ion fluences

Excellent Passivation of p-Type Si Surface by Sol-Gel Al2O3 Films

International Nuclear Information System (INIS)

Hai-Qing, Xiao; Chun-Lan, Zhou; Xiao-Ning, Cao; Wen-Jing, Wang; Lei, Zhao; Hai-Ling, Li; Hong-Wei, Diao

2009-01-01

Al 2 O 3 films with a thickness of about 100 nm synthesized by spin coating and thermally treated are applied for field-induced surface passivation of p-type crystalline silicon. The level of surface passivation is determined by techniques based on photoconductance. An effective surface recombination velocity below 100 cm/s is obtained on 10Ω ·cm p-type c-Si wafers (Cz Si). A high density of negative fixed charges in the order of 10 12 cm −2 is detected in the Al 2 O 3 films and its impact on the level of surface passivation is demonstrated experimentally. Furthermore, a comparison between the surface passivation achieved for thermal SiO 2 and plasma enhanced chemical vapor deposition SiN x :H films on the same c-Si is presented. The high negative fixed charge density explains the excellent passivation of p-type c-Si by Al 2 O 3 . (cross-disciplinary physics and related areas of science and technology)

A contribution to the kinetic study of the metatectic reaction U+U3Si2→U3Si

International Nuclear Information System (INIS)

Arroyo Ruiperez, J.; Esteban Hernandez, J. A.

1962-01-01

An experimental study has been made to decide upon the advantages and drawbacks of the different methods and reagents employed in the metallography of U-Si alloys. It has been observed that all samples thermally treated to form the epsilon-phase undergo from the beginning a coalescence of the U 3 Si 2 particles, which makes practically useless any fine state of dispersion that might be present originally, as recommended by some authors. The coalescence of the U 3 Si 2 particle decreases the surface available for reaction and consequently the reaction rate. (Author) 7 refs

Significantly Enhanced Dielectric Performances and High Thermal Conductivity in Poly(vinylidene fluoride)-Based Composites Enabled by SiC@SiO2 Core-Shell Whiskers Alignment.

Science.gov (United States)

He, Dalong; Wang, Yao; Song, Silong; Liu, Song; Deng, Yuan

2017-12-27

Design of composites with ordered fillers arrangement results in anisotropic performances with greatly enhanced properties along a specific direction, which is a powerful tool to optimize physical properties of composites. Well-aligned core-shell SiC@SiO 2 whiskers in poly(vinylidene fluoride) (PVDF) matrix has been achieved via a modified spinning approach. Because of the high aspect ratio of SiC whiskers, strong anisotropy and significant enhancement in dielectric constant were observed with permittivity 854 along the parallel direction versus 71 along the perpendicular direction at 20 vol % SiC@SiO 2 loading, while little increase in dielectric loss was found due to the highly insulating SiO 2 shell. The anisotropic dielectric behavior of the composite is perfectly understood macroscopically to have originated from anisotropic intensity of interfacial polarization based on an equivalent circuit model of two parallel RC circuits connected in series. Furthermore, finite element simulations on the three-dimensional distribution of local electric field, polarization, and leakage current density in oriented SiC@SiO 2 /PVDF composites under different applied electrical field directions unambiguously revealed that aligned core-shell SiC@SiO 2 whiskers with a high aspect ratio significantly improved dielectric performances. Importantly, the thermal conductivity of the composite was synchronously enhanced over 7 times as compared to that of PVDF matrix along the parallel direction at 20 vol % SiC@SiO 2 whiskers loading. This study highlights an effective strategy to achieve excellent comprehensive properties for high-k dielectrics.

Bulk superconducting gap of V{sub 3}Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sato, T., E-mail: t-sato@arpes.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Souma, S. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Nakayama, K. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Sugawara, K. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Toyota, N. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Takahashi, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2016-04-15

Highlights: • We report ultrahigh-resolution photoemission spectroscopy of A15 compound V{sub 3}Si. • We found a sharp quasiparticle peak due to superconducting-gap opening. • The surface metallic component is negligibly small in the bulk-sensitive measurement. • We show that V{sub 3}Si is a single-gap s-wave superconductor. - Abstract: We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V{sub 3}Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (T{sub c} = 15.9 K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30 meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V{sub 3}Si is a single-gap s-wave superconductor.

Angular Magnetoresistance and Hall Measurements in New Dirac Material, ZrSiS

Science.gov (United States)

Ali, Mazhar; Schoop, Leslie; Lotsch, Bettina; Parkin, Stuart

Dirac and Weyl materials have shot to the forefront of condensed matter research in the last few years. Recently, the square-net material, ZrSiS, was theorized and experimentally shown (via ARPES) to host several highly dispersive Dirac cones, including the first Dirac cone demanded by non-symmorphic symmetry in a Si square net. Here we report the magnetoresistance and Hall Effect measurements in this compound. ZrSiS samples with RRR = 40 were found to have MR values up to 6000% at 2 K, be predominantly p-type with a carrier concentration of ~8 x 1019 cm-3 and mobility ~8500 cm2/Vs. Angular magnetoresistance measurements reveal a peculiar behavior with multiple local maxima, depending on field strength, indicating of a sensitive and sensitive Fermi surface. SdH oscillations analysis confirms Hall and angular magnetoresistance measurements. These results, in the context of the theoretical and ARPES results, will be discussed.

Production of Al2O3–SiC nano-composites by spark plasma sintering; Producción de nano-composites – SiC–Al2O3 por spark plasma sinterizado

Energy Technology Data Exchange (ETDEWEB)

Mansour Razavi; Ali Reza Farajipour; Mohammad Zakeri; Mohammad Reza Rahimipour; Ali Reza Firouzbakht

2017-11-01

In this paper, Al2O3–SiC composites were produced by SPS at temperatures of 1600°C for 10min under vacuum atmosphere. For preparing samples, Al2O3 with the second phase including of micro and nano-sized SiC powder were milled for 5h. The milled powders were sintered in a SPS machine. After sintering process, phase studies, densification and mechanical properties of Al2O3–SiC composites were examined. Results showed that the specimens containing micro-sized SiC have an important effect on bulk density, hardness and strength. The highest relative density, hardness and strength were 99.7%, 324.6 HV and 2329MPa, respectively, in Al2O3–20wt% SiCmicro composite. Due to short time sintering, the growth was limited and grains still remained in nano-meter scale. [Spanish] En este trabajo se muestran compuestos de Al2O3-SiC producidos por SPS, en vacío, a 1.600 °C durante 10 min. Para la preparación de muestras, se molieron polvos de Al2O3 durante 5 h con la segunda fase de micro-y-nano polvo de SiC. Posteriormente, estos polvos molidos se sinterizaron mediante SPS. Después del proceso de sinterización, se realizaron estudios de fase, densificación y propiedades mecánicas de los compuestos de Al2O3-SiC obtenidos. Los resultados mostraron que micro-SiC en las muestras tiene un efecto importante en su densidad aparente, dureza y resistencia. La mayor densidad relativa, dureza y resistencia fueron respectivamente del 99,7%, 324,6 HV y 2.329 MPa para Al2O3 con un 20% en peso micro-SiC. Debido al corto tiempo de sinterización, el crecimiento los granos fue limitado y se mantuvieron en escala nanométrica.

(FeCo)3Si-SiOx core-shell nanoparticles fabricated in the gas phase

International Nuclear Information System (INIS)

Bai Jianmin; Xu Yunhao; Thomas, John; Wang Jianping

2007-01-01

A method of fabricating core-shell nanoparticles by using an integrated nanoparticle deposition technique in the gas phase is reported. The principle of the method is based on nanoparticle growth from the vapour phase, during which elements showing lower surface energies prefer to form the shells and elements showing higher surface energies prefer to stay in the cores. This method was applied successfully to the Fe-Co-Si ternary system to fabricate core-shell-type nanoparticles. The nanoparticles were exposed in air after collection to achieve oxidation. The analysis results based on transmission electron microscopy (TEM), Auger electron spectroscopy (AES), x-ray diffraction (XRD), and a superconducting quantum interference device (SQUID) showed that the core parts are magnetic materials of body-centred cubic (bcc) structured (FeCo) 3 Si of 15 nm in diameter, and the shell parts are amorphous SiO x of 2 nm in thickness. These core-shell-type nanoparticles show a magnetic anisotropy constant of about 7 x 10 5 erg cm -3 and a saturation magnetization of around 1160 emu cm -3 , which is much higher than that of iron oxide. After annealing at 300 deg. C in air (FeCo) 3 Si-SiO x core-shell-type nanoparticles showed a little bit of a drop in magnetic moment, while pure FeCo nanopariticles totally lost their magnetic moment. This means that the shells of SiO x are dense enough to prevent the magnetic cores from oxidation

Structural and electronic properties of Si/SiO2 MOS structures with aligned 3C-SiC nanocrystals in the oxide

International Nuclear Information System (INIS)

Pongracz, A.; Battistig, G.; Duecso, Cs.; Josepovits, K.V.; Deak, P.

2007-01-01

Our group previously proved that a simple reactive annealing in CO containing gas produces 3C-SiC nanocrystals, which are epitaxially and void-free aligned in the Si substrate. By a further thermal oxidation step, these nanocrystals can be lifted from the Si and incorporated into the SiO 2 matrix, thereby creating a promising structure for charge storage. In this work the structural and electrical properties of such systems with nanocrystalline SiC will be presented. Prototype MOS structures with 3C-SiC nanocrystals were produced for current-voltage and capacitance-voltage measurements. The results indicate that the high-temperature annealing did not damage the MOS structure, despite the fact that the CO annealing changed the electrical properties of the system. There was a positive charge accumulation and a reversible carrier injection observed in the structure. We assume that the positive charges originated from oxygen vacancies and the charge injection is related to the presence of SiC nanocrystals

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

2017-02-28

Yb 3+ -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 ²F 7/2 level (781 cm -1 ), and the largest scalar crystal-field N J and Yb 3+ 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 29 Si 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 Yb 3+ -doped gain medium for solid-state lasers and optical fiber amplifiers.

The effect of pH on the corrosion behavior of intermetallic compounds Ni{sub 3}(Si,Ti) and Ni{sub 3}(Si,Ti) + 2Mo in sodium chloride solutions

Energy Technology Data Exchange (ETDEWEB)

Priyotomo, Gadang, E-mail: gada001@lipi.go.id; Nuraini, Lutviasari, E-mail: Lutviasari@gmail.com [Research Center for Metallurgy and Material, Indonesian Institute of Sciences, Kawasan PUSPIPTEK Gd.474, Setu, Tangerang Selatan, Banten 15314 (Indonesia); Kaneno, Yasuyuki, E-mail: kaneno@mtr.osakafu-u.ac.id [Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531 (Japan)

2015-12-29

The corrosion behavior of the intermetallic compounds, Ni{sub 3}(Si,Ti) (L1{sub 2}: single phase) and Ni{sub 3}(Si,Ti) + 2Mo (L1{sub 2} and (L12 + Ni{sub ss}) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m{sup 3} NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni{sub 3}(Si,Ti) for the immersion test at lower pH, while the pitting attack was observed on this compound for this test at neutral solution. Furthermore, Ni{sub 3}(Si,Ti)+2Mo had the preferential dissolution of L1{sub 2} compared to (L1{sub 2} + Ni{sub ss}) mixture region at lower pH, while pitting attack occurred in (L1{sub 2} + Ni{sub ss}) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni{sub 3}(Si,Ti)+2Mo is lower than that of Ni{sub 3}(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.

Investigation of 3C-SiC/SiO2 interfacial point defects from ab initio g-tensor calculations and electron paramagnetic resonance measurements

Science.gov (United States)

Nugraha, T. A.; Rohrmueller, M.; Gerstmann, U.; Greulich-Weber, S.; Stellhorn, A.; Cantin, J. L.; von Bardeleben, J.; Schmidt, W. G.; Wippermann, S.

SiC is widely used in high-power, high-frequency electronic devices. Recently, it has also been employed as a building block in nanocomposites used as light absorbers in solar energy conversion devices. Analogous to Si, SiC features SiO2 as native oxide that can be used for passivation and insulating layers. However, a significant number of defect states are reported to form at SiC/SiO2 interfaces, limiting mobility and increasing recombination of free charge carriers. We investigated the growth of oxide on different 3C-SiC surfaces from first principles. Carbon antisite Csi defects are found to be strongly stabilized in particular at the interface, because carbon changes its hybridization from sp3 in the SiC-bulk to sp2 at the interface, creating a dangling bond inside a porous region of the SiO2 passivating layer. Combining ab initio g-tensor calculations and electron paramagnetic resonance (EPR) measurements, we show that Csi defects explain the measured EPR signatures, while the hyperfine structure allows to obtain local structural information of the oxide layer. Financial support from BMBF NanoMatFutur Grant 13N12972 and DFG priority program SPP-1601 is gratefully acknowledged.

Irradiation damages in Ti3SiC2

International Nuclear Information System (INIS)

Nappe, J.C.; Grosseau, Ph.; Guilhot, B.; Audubert, F.; Beauvy, M.

2007-01-01

Carbides, by their remarkable properties, are considered as possible materials (fuel cans) in reactor of generation IV. Among those studied, Ti 3 SiC 2 is particularly considered because it joins both the ceramics and metals properties. Nevertheless, its behaviour under irradiation is not known. Characterizations have been carried out on samples irradiated at 75 MeV krypton ions. They have revealed that TiO 2 (formed at the surface of Ti 3 SiC 2 ) is pulverized by the irradiation and that the crystal lattice of Ti 3 SiC 2 dilates with c. (O.M.)

Enhancement of CdSiO3: Tb3+ green long-lasting phosphors by co-doping with Re3+ (Re3+=Gd3+, Y3+, La3+) ions

International Nuclear Information System (INIS)

Zeng, Wei; Wang, Yuhua; Han, Shaochun; Chen, Wenbo; Li, Gen

2014-01-01

CdSiO 3 : Tb 3+ , Re 3+ long-lasting phosphors were synthesized by the conventional high temperature solid-state method. A green-light phosphorescence phenomenon, which was associated with the 5 D 4 → 7 F J (J=6, 5, 4, 3) transitions of the Tb 3+ ion, was observed. Introduction of Re 3+ (Re 3+ =Gd 3+ , Y 3+ , La 3+ ) ions, which deepens the depth (E t ) or/and increases the density (n 0 ) of traps, greatly improved the afterglow properties of CdSiO 3 : Tb 3+ . Possible mechanism of CdSiO 3 : Tb 3+ , Re 3+ was discussed in this work. - Highlights: • CdSiO 3 : Tb 3+ , Re 3+ samples enrich the color of long-lasting afterglow phosphors in CdSiO 3 host. • Both the afterglow intensity and the lasting time are greatly enhanced for the co-doped samples, especially for Cd 0.96 SiO 3 : Tb 0.03 3+ , La 0.01 3+ . • Introduction of Re 3+ (Re 3+ =Gd 3+ , Y 3+ , La 3+ ) ions, which deepens the depth (E t ) or increase density(n 0 ) of traps, greatly improved the afterglow properties of CdSiO 3 : Tb 3+

Sonoporation-mediated transduction of siRNA ameliorated experimental arthritis using 3 MHz pulsed ultrasound.

Science.gov (United States)

Inoue, Hiroaki; Arai, Yuji; Kishida, Tsunao; Shin-Ya, Masaharu; Terauchi, Ryu; Nakagawa, Shuji; Saito, Masazumi; Tsuchida, Shinji; Inoue, Atsuo; Shirai, Toshiharu; Fujiwara, Hiroyoshi; Mazda, Osam; Kubo, Toshikazu

2014-03-01

The goal of this feasibility study was to examine whether sonoporation assisted transduction of siRNA could be used to ameliorate arthritis locally. If successful, such approach could provide an alternative treatment for the patients that have or gradually develop adverse response to chemical drugs. Tumor necrosis factor alpha (TNF-α) produced by synovial fibroblasts has an important role in the pathology of rheumatoid arthritis, inducing inflammation and bone destruction. In this study, we injected a mixture of microbubbles and siRNA targeting TNF-α (siTNF) into the articular joints of rats, and transduced siTNF into synovial tissue by exposure to a collimated ultrasound beam, applied through a probe 6mm in diameter with an input frequency of 3.0 MHz, an output intensity of 2.0 W/cm(2) (spatial average temporary peak; SATP), a pulse duty ratio of 50%, and a duration of 1 min. Sonoporation increased skin temperature from 26.8 °C to 27.3 °C, but there were no adverse effect such as burns. The mean level of TNF-α expression in siTNF-treated knee joints was 55% of those in controls. Delivery of siTNF into the knee joints every 3 days (i.e., 7, 10, 13, and 16 days after immunization) by in vivo sonoporation significantly reduced paw swelling on days 20-23 after immunization. Radiographic scores in the siTNF group were 56% of those in the CIA group and 61% of those in the siNeg group. Histological examination showed that the number of TNF-α positive cells was significantly lower in areas of pannus invasion into the ankle joints of siTNF- than of siNeg-treated rats. These results indicate that transduction of siTNF into articular synovium using sonoporation may be an effective local therapy for arthritis. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

ILD SiW ECAL and sDHCAL dimension-performance optimisation

CERN Document Server

Tran, T.H

2015-01-01

The ILD, International Large Detector, is one of the detector concepts for a future linear collider. Its performance is investigated using Monte-Carlo full simulation and PandoraPFA. Among several options, a combination of the silicon-tungsten electromagnetic calorimeter (SiW ECAL) and the semi-digital hadronic calorimeter (sDHCAL) presenting the highest granularity calorimeters, is here investigated. It is shown that by reducing the radius and length of the entire detector by a factor of ∼ 1.3 with respect to the baseline dimensions, the jet energy resolution is degraded by 8 to 19% in the range of 45 and 250 GeV. The price of ILD which scales roughly quadratically with the ILD dimensions may be reduced by a factor of nearly two. A similar study made with the SiW ECAL and the analog hadronic calorimeter (AHCAL) shows that for an inner radius of ECAL of about 1.4 m, the performance is comparable between sDHCAL and AHCAL.

Preparation and oxidation protection of CVD SiC/a-BC/SiC coatings for 3D C/SiC composites

International Nuclear Information System (INIS)

Liu Yongsheng; Zhang Litong; Cheng Laifei; Yang Wenbin; Zhang Weihua; Xu Yongdong

2009-01-01

An amorphous boron carbide (a-BC) coating was prepared by LPCVD process from BCl 3 -CH 4 -H 2 -Ar system. XPS result showed that the boron concentration was 15.0 at.%, and carbon was 82.0 at.%. One third of boron was distributed to a bonding with carbon and 37.0 at.% was dissolved in graphite lattice. A multiple-layered structure of CVD SiC/a-BC/SiC was coated on 3D C/SiC composites. Oxidation tests were conducted at 700, 1000, and 1200 deg. C in 14 vol.% H 2 O/8 vol.% O 2 /78 vol.% Ar atmosphere up to 100 h. The 3D C/SiC composites with the modified coating system had a good oxidation resistance. This resulted in the high strength retained ratio of the composites even after the oxidation.

Fabrication and characterization of Al2O3 /Si composite nanodome structures for high efficiency crystalline Si thin film solar cells

Directory of Open Access Journals (Sweden)

Ruiying Zhang

2015-12-01

Full Text Available We report on our fabrication and characterization of Al2O3/Si composite nanodome (CND structures, which is composed of Si nanodome structures with a conformal cladding Al2O3 layer to evaluate its optical and electrical performance when it is applied to thin film solar cells. It has been observed that by application of Al2O3thin film coating using atomic layer deposition (ALD to the Si nanodome structures, both optical and electrical performances are greatly improved. The reflectivity of less than 3% over the wavelength range of from 200 nm to 2000 nm at an incident angle from 0° to 45° is achieved when the Al2O3 film is 90 nm thick. The ultimate efficiency of around 27% is obtained on the CND textured 2 μm-thick Si solar cells, which is compared to the efficiency of around 25.75% and 15% for the 2 μm-thick Si nanodome surface-decorated and planar samples respectively. Electrical characterization was made by using CND-decorated MOS devices to measure device’s leakage current and capacitance dispersion. It is found the electrical performance is sensitive to the thickness of the Al2O3 film, and the performance is remarkably improved when the dielectric layer thickness is 90 nm thick. The leakage current, which is less than 4x10−9 A/cm2 over voltage range of from -3 V to 3 V, is reduced by several orders of magnitude. C-V measurements also shows as small as 0.3% of variation in the capacitance over the frequency range from 10 kHz to 500 kHz, which is a strong indication of surface states being fully passivated. TEM examination of CND-decorated samples also reveals the occurrence of SiOx layer formed between the interface of Si and the Al2O3 film, which is thin enough that ensures the presence of field-effect passivation, From our theoretical and experimental study, we believe Al2O3 coated CND structures is a truly viable approach to achieving higher device efficiency.

Broadband Luminescence in Rare Earth Doped Sr2SiS4: Relating Energy Levels of Ce3+ and Eu2+

Directory of Open Access Journals (Sweden)

Anthony B. Parmentier

2013-08-01

Full Text Available Sr2SiS4:Ce3+ is an efficient blue-emitting (460 nm phosphor, excitable with light of wavelengths up to 420 nm. From the excitation spectrum, we construct the energy level scheme and use it to check the predictive power of the Dorenbos model, relating the positions of the Ce3+ energy levels with those of Eu2+ in the same host. For strontium thiosilicate, this method gives excellent results and allows us to determine which of two available crystallographic sites is occupied by cerium. We use the Dorenbos method for extracting information on the coordination of Ce3+ from the observed crystal field splitting.

Insights into Mercury's Core Evolution from the Thermodynamic Properties of Fe-S-Si

Science.gov (United States)

Edgington, A.; Vocadlo, L.; Stixrude, L. P.; Wood, I. G.; Lord, O. T.

2015-12-01

The structure, composition and evolution of Mercury, the innermost planet, are puzzling, as its high uncompressed density implies a body highly enriched in metallic iron, whilst the existence of Mercury's magnetic field and observations of its longitude librations [1] suggest at least a partially molten core. This study uses a combination of experimental and ab-initio computer simulation techniques to determine the properties of Fe-S-Si (relative atomic percentages, 80:10:10) throughout the conditions of the interior of the planet Mercury, and evaluates the implications of this material for the structure and evolution of the planet's core. Previous studies have considered the addition of sulphur to the pure iron system, as this can significantly depress the melting curve of iron, and so may possibly allow Mercury's core to remain molten to the present day [2]. However, important constraints placed by the MESSENGER spacecraft on Mercury's surface abundance of iron [3] suggest that the planet formed in highly reduced conditions, in which significant amounts of silicon could have also dissolved into the core [4]. First-principles molecular dynamics simulations of the thermodynamic properties of liquid Fe-S-Si, alongside laser-heated diamond-anvil-cell experiments to determine the melting behaviour of the same composition, reveal the slopes of the adiabatic gradient and melting curve respectively, which together may allow insight into the evolution of our solar system's smallest planet. [1] Margot, J. L. et al. (2007) Science, 316: 710-714[2] Schubert, G. et al. (1988) in 'Mercury' 429-460[3] Nittler, L. R. et al. (2011) Science, 333, 1847-1850[4] Malavergne, V. et al. (2010) Icarus, 206:199-209

The impact of Ti and temperature on the stability of Nb5Si3 phases: a first-principles study.

Science.gov (United States)

Papadimitriou, Ioannis; Utton, Claire; Tsakiropoulos, Panos

2017-01-01

Nb-silicide based alloys could be used at T > 1423 K in future aero-engines. Titanium is an important additive to these new alloys where it improves oxidation, fracture toughness and reduces density. The microstructures of the new alloys consist of an Nb solid solution, and silicides and other intermetallics can be present. Three Nb 5 Si 3 polymorphs are known, namely αNb 5 Si 3 ( tI 32 Cr 5 B 3 -type, D8 l ), βNb 5 Si 3 ( tI 32 W 5 Si 3 -type, D8 m ) and γNb 5 Si 3 ( hP 16 Mn 5 Si 3 -type, D8 8 ). In these 5-3 silicides Nb atoms can be substituted by Ti atoms. The type of stable Nb 5 Si 3 depends on temperature and concentration of Ti addition and is important for the stability and properties of the alloys. The effect of increasing concentration of Ti on the transition temperature between the polymorphs has not been studied. In this work first-principles calculations were used to predict the stability and physical properties of the various Nb 5 Si 3 silicides alloyed with Ti. Temperature-dependent enthalpies of formation were computed, and the transition temperature between the low (α) and high (β) temperature polymorphs of Nb 5 Si 3 was found to decrease significantly with increasing Ti content. The γNb 5 Si 3 was found to be stable only at high Ti concentrations, above approximately 50 at. % Ti. Calculation of physical properties and the Cauchy pressures, Pugh's index of ductility and Poisson ratio showed that as the Ti content increased, the bulk moduli of all silicides decreased, while the shear and elastic moduli and the Debye temperature increased for the αNb 5 Si 3 and γNb 5 Si 3 and decreased for βNb 5 Si 3 . With the addition of Ti the αNb 5 Si 3 and γNb 5 Si 3 became less ductile, whereas the βNb 5 Si 3 became more ductile. When Ti was added in the αNb 5 Si 3 and βNb 5 Si 3 the linear thermal expansion coefficients of the silicides decreased, but the anisotropy of coefficient of thermal expansion did not change significantly.

Metallographic analysis of irradiated U3Si2/Al fuel element plate of 2.96 gU/cm3 density

International Nuclear Information System (INIS)

Maman Kartaman Ajiriyanto; Aslina Br Ginting; Junaedi

2018-01-01

Metallographic analysis of U 3 Si 2 /Al fuel element plate has been performed in hot cell. The purpose of metallographic analysis is to study changes in PEB U 3 Si 2 /Al microstructure and AlMg 2 cladding thickness after irradiation in reactor until burn up of 56 %. The fuel element plate of irradiated U 3 Si 2 /Al was cut in top, middle and bottom positions with each size around 5 x 5 x 1.37 mm. Metallographic preparation starts from sample cutting using cutting machine with low speed and sample mounting, grinding and polishing in hot cell 104–105. Sample mounting was done by using resin for more than 10 hours followed by grinding with sand papers up to grit size of 2400 and polishing with diamond paste of size 3 to 1 micron at a rotational speed of 150 rpm for 5 minutes. Microstructure observation was performed with optical microscope in hot cell 107 at 200 times magnification. Microstructure examination reveals U 3 Si 2 particles with inverse forms and sizes, Al matrix and AlMg 2 cladding were spread along the U 3 Si 2 /Al side. Microstructure observation of irradiated U 3 Si 2 /Al has not shown good result because only topography observation of U 3 Si 2 /Al meat, Al matrix and AlMg 2 cladding can be done due to limited capability of the optical microscope in hot cell, where maximum magnification can be attained only at 200 times so that the phenomenon of interaction layer and small gas bubble can not be observed. However, U 3 Si 2 /Al microstructure of 56 % burnup, if compared to the microstructure of U 3 Si 2 /Al fuel element plate of 60 % burnup from previous researcher, shows interaction between U 3 Si 2 meat with Al matrix and the existence of layers with a thickness about 5 up to 20 microns. Meanwhile, the observed thickness of AlMg 2 cladding is greater than 0.25 mm, which indicates that irradiation does not significantly change the thickness of AlMg 2 cladding so that the overall irradiated U 3 Si 2 -Al still has good integrity and stability. (author)

Thermophysical properties of U3Si to 1150 K

International Nuclear Information System (INIS)

White, J.T.; Nelson, A.T.; Byler, D.D.; Valdez, J.A.; McClellan, K.J.

2014-01-01

U 3 Si has the highest uranium density of the U–Si compounds, making it an attractive option for specialized reactor applications. Although the compound has been used in research and test reactors for nearly six decades, little data has been published in the literature which characterizes the thermophysical properties at elevated temperatures. A systematic study was conducted on U 3 Si to characterize thermal expansion, heat capacity, thermal diffusivity, and thermal conductivity as a function of temperature to 1150 K. Thermophysical properties were also tabulated for the high temperature δ ′ -U 3 Si phase as a function of temperature, which has not been reported previously

Magnetism and superconductivity of CePt3Si and Ce1+xPt3+ySi1+z

International Nuclear Information System (INIS)

Motoyama, Gaku; Yamamoto, Suguru; Takezoe, Hiroaki; Oda, Yasukage; Ueda, Ko-ichi; Kohara, Takao

2006-01-01

We measured the dc magnetization, electrical resistivity, and ac magnetic susceptibility of a series of polycrystalline CePt 3 Si samples whose compositions vary slightly from the stoichiometric composition. The sample that showed the most distinct anitiferromagnetic transition at 2.2K was found to be Ce 1.01 Pt 3 Si annealed. This sample showed a clear bulk antiferromagnetic order at 2.2 K even in both electrical resistivity and dc magnetization measurements, although the characteristic change in dc magnetization at 2.2 K was found to be small and to be easily masked in other magnetic anomalies if they exist. Moreover, it had the largest residual resistivity ratio. We concluded that Ce 1.01 Pt 3 Si annealed has the intrinsic bulk properties of ideal CePt 3 Si. In addition, we revealed that some anomalies arise as a result of the variation in composition. One is a ferromagnetic anomaly at 3.0 K in the Pt-rich samples, and the other is an antiferromagnetic anomaly at 4.0 K in the Pt-poor samples. The two magnetic anomalies seemed to appear in small domains in the samples that exhibited an antiferromagnetic order at 2.2 K. To reveal the relationship between these magnetisms and superconductivity, we measured ac magnetic susceptibility down to ∼14mK. We found that the superconducting transition temperature is suppressed by the ferromagnetic anomaly. (author)

Observing the semiconducting band-gap alignment of MoS2 layers of different atomic thicknesses using a MoS2/SiO2/Si heterojunction tunnel diode

NARCIS (Netherlands)

Nishiguchi, K.; Castellanos-Gomez, A.; Yamaguchi, H.; Fujiwara, A.; Van der Zant, H.S.J.; Steele, G.A.

2015-01-01

We demonstrate a tunnel diode composed of a vertical MoS2/SiO2/Si heterostructure. A MoS2 flake consisting four areas of different thicknesses functions as a gate terminal of a silicon field-effect transistor. A thin gate oxide allows tunneling current to flow between the n-type MoS2 layers and

Angular distributions of fast neutrons scattered by Al, Si, P, S and Zn; Distributions angulaires des neutrons rapides diffuses par Al, Si, P, S et Zn; Usloviya raspredeleniya bystrykh nejtronov, rasseyannykh alyuminiem, kremniem, fosforom i tsinkom; Distribuciones angulares de neutrones rapidos dispersados por Al, Si, P, S y Zn

Energy Technology Data Exchange (ETDEWEB)

Tstjkaija, K; Tanaka, S; Maeuyama, M; Tomita, Y [Japan Atomic Energy Research Institute, Tokai-Mtjea (Japan)

1962-03-15

Differential scattering cross-sections of Al, Si, P, S and Zn for fast neutrons have been measured in an energy range of 3.4 to 4.6 MeV by using the time-of-flight method. Angular distributions of the inelastically scattered neutrons are nearly isotropic in all cases. These results are discussed on the basis of the Hauser-Feshbach theory. (author) [French] Les sections efficaces differentielles de diffusion de Al, Si, P, S et Zn pour des neutrons rapides ont ete mesurees dans la gamme d'energies de 3,4 a 4,6 MeV, en employant la methode du temps de vol. Les distributions angulaires des neutrons diffuses inelastiquement sont presque isotropes dans tous les cas. Les auteurs analysent ces resultats en se fondant sur la theorie de Hauser-Feshbach. (author) [Spanish] Los autores han medido por el metodo del tiempo de vuelo las secciones eficaces diferenciales de dispersion del Al, Si, P, S y Zn para neutrones rapidos de energia comprendida entre 3,4 y 4,6 MeV. Las distribuciones angulares de los neutrones dispersados inelasticamente son casi isotropicas en todos los casos. Los autores analizan los resultados obtenidos basandose en la teoria de Hauser-Feshbach . (author) [Russian] Differentsial'no e sechenie rasseyaniya alyuminiya, kremniya, fosfora, sery i tsinka dlya bystrykh nejtronov izmereno v diapazone ehnergii ot 3,4 do 4,6 Megaehlektronvol't ispol'zovanie m metoda vremeni proleta. Uglovye raspredeleniya neuprugo rasseyannykh nejtronov yavlyayutsya pochti vo vsekh sluchayakh izotropnymi. Jeti rezul'taty obsuzhdayutsya na osnove teorii Hauzera-Feshbakha. (author)

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

Ni3Si(Al)/a-SiOx core shell nanoparticles: characterization, shell formation, and stability

Science.gov (United States)

Pigozzi, G.; Mukherji, D.; Gilles, R.; Barbier, B.; Kostorz, G.

2006-08-01

We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni3Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni3Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiOx). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

Effect of fiber directionality on the static and dynamic mechanical properties of 3D SiCf/SiC composites

International Nuclear Information System (INIS)

Hou, Zhenhua; Luo, Ruiying; Yang, Wei; Xu, Huaizhe; Han, Tao

2016-01-01

The static and dynamic mechanical properties of three-dimensional (3D) 4-directional and 3D 5-directional braided SiC f /SiC composites fabricated by polymer infiltration and pyrolysis (PIP) were investigated using static and dynamic bending tests, as well as microstructural characterization. X-ray diffraction revealed that polycarbosilane was converted into a matrix of crystalline β-SiC after PIP cycling. Test results indicated that the density, flexural strength, elastic modulus, fracture toughness, and storage modulus of 3D 5-directional SiC f /SiC composites were superior to those of 3D 4-directional braided SiC f /SiC composites; the former also showed a smaller internal friction than the latter. Results from Weibull statistical analysis indicated that the scale parameter σ 0 (736.9 MPa) and Weibull modulus m (21.7) of the 3D 5-directional specimen were higher than those of 3D 4-directional braided SiC f /SiC composites (629.6 MPa, 14.7). Both 3D braided composites demonstrated good toughness and avoided catastrophic brittle fractures under loading because of the effective crack energy dissipating mechanisms of crack deflection, interface debonding, and fiber pull-out. The internal friction and storage modulus of the 3D braided composites were sensitive to temperature. The cross angle of fiber placement in the preform and the direction of the applied force, as well as the pre-crack propagation remarkably influenced the static mechanical properties and failure behavior of the 3D braided SiC f /SiC composites. The dynamic mechanical properties of the 3D braided composites, including internal friction and storage modulus, were also considerably affected by fiber directionality in their preforms.

SAW propagation characteristics of TeO3/3C-SiC/LiNbO3 layered structure

Science.gov (United States)

Soni, Namrata D.

2018-04-01

Surface acoustic wave (SAW) devices based on Lithium Niobate (LiNbO3) single crystal are advantageous because of its high SAW phase velocity, electromechanical coupling coefficient and cost effectiveness. In the present work a new multi-layered TeO3/3C-SiC/128° Y-X LiNbO3 SAW device has been proposed. SAW propagation properties such as phase velocity, coupling coefficient and temperature coefficient of delay (TCD) of the TeO3/SiC/128° Y-X LiNbO3 multi layered structure is examined using theoretical calculations. It is found that the integration of 0.09λ thick 3C-SiC over layer on 128° Y-X LiNbO3 increases its electromechanical coupling coefficient from 5.3% to 9.77% and SAW velocity from 3800 ms‑1 to 4394 ms‑1. The SiC/128° Y-X LiNbO3 bilayer SAW structure exhibits a high positive TCD value. A temperature stable layered SAW device could be obtained with introduction of 0.007λ TeO3 over layer on SiC/128° Y-X LiNbO3 bilayer structure without sacrificing the efficiency of the device. The proposed TeO3/3C-SiC/128° Y-X LiNbO3 multi-layered SAW structure is found to be cost effective, efficient, temperature stable and suitable for high frequency application in harsh environment.

Effect of Pressurizing during Compaction and Sintering on the Formation of Reaction-Bonded SiC–Ti{sub 3}SiC{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Kim, Sun-Han; Jung, Yang-Il; Rhee, Young-Woo; Park, Dong-Jun; Park, Jung-Hwan; Park, Jeong-Yong; Kim, Hyun-Gil; Koo, Yang-Hyun [LWR Fuel Technology Division, KAERI, Daejeon (Korea, Republic of)

2016-05-15

A reaction-bonded SiC-Ti{sub 3}SiC{sub 2} ceramic composite was produced for use in a ceramic-metal composite cladding tube. The diffusion reaction between TiC and Si was investigated with respect to process pressure. The mole-fraction of TiC and Si was controlled to be 3:2 to obtain a Ti{sub 3}SiC{sub 2} phase in the ceramic composite. Sintering was conducted at 1450 °C where TiC particles could react with melted Si. SiC ceramic composites consisting of Ti{sub 3}SiC{sub 2} and TiSi{sub 2} matrix phases were obtained. The formation of the constituent phases was strongly related to the processing pressure. The number of second phases in the SiC-Ti{sub 3}SiC{sub 2} composite was controlled by adjusting the processing pressure. When the powder compacts were not pressurized, no Ti{sub 3}SiC{sub 2} phase was formed. However, the Ti{sub 3}SiC{sub 2} phase was formed under pressurizing during compaction and/or sintering. The higher the pressure the higher the purity of SiC-Ti{sub 3}SiC{sub 2}. The dual-phased SiC-Ti{sub 3}SiC{sub 2} composite, however, revealed the decreased resistance to high-temperature oxidation. It is suggested that the incorporation of TiSi{sub 2} in the composite increases the oxidation resistance as well as mechanical property.

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.

Oxidation precursor dependence of atomic layer deposited Al2O3 films in a-Si:H(i)/Al2O3 surface passivation stacks.

Science.gov (United States)

Xiang, Yuren; Zhou, Chunlan; Jia, Endong; Wang, Wenjing

2015-01-01

In order to obtain a good passivation of a silicon surface, more and more stack passivation schemes have been used in high-efficiency silicon solar cell fabrication. In this work, we prepared a-Si:H(i)/Al2O3 stacks on KOH solution-polished n-type solar grade mono-silicon(100) wafers. For the Al2O3 film deposition, both thermal atomic layer deposition (T-ALD) and plasma enhanced atomic layer deposition (PE-ALD) were used. Interface trap density spectra were obtained for Si passivation with a-Si films and a-Si:H(i)/Al2O3 stacks by a non-contact corona C-V technique. After the fabrication of a-Si:H(i)/Al2O3 stacks, the minimum interface trap density was reduced from original 3 × 10(12) to 1 × 10(12) cm(-2) eV(-1), the surface total charge density increased by nearly one order of magnitude for PE-ALD samples and about 0.4 × 10(12) cm(-2) for a T-ALD sample, and the carrier lifetimes increased by a factor of three (from about 10 μs to about 30 μs). Combining these results with an X-ray photoelectron spectroscopy analysis, we discussed the influence of an oxidation precursor for ALD Al2O3 deposition on Al2O3 single layers and a-Si:H(i)/Al2O3 stack surface passivation from field-effect passivation and chemical passivation perspectives. In addition, the influence of the stack fabrication process on the a-Si film structure was also discussed in this study.

Effect of hydrogen on passivation quality of SiNx/Si-rich SiNx stacked layers deposited by catalytic chemical vapor deposition on c-Si wafers

International Nuclear Information System (INIS)

Thi, Trinh Cham; Koyama, Koichi; Ohdaira, Keisuke; Matsumura, Hideki

2015-01-01

We investigate the role of hydrogen content and fixed charges of catalytic chemical vapor deposited (Cat-CVD) SiN x /Si-rich SiN x stacked layers on the quality of crystalline silicon (c-Si) surface passivation. Calculated density of fixed charges is on the order of 10 12 cm −2 , which is high enough for effective field effect passivation. Hydrogen content in the films is also found to contribute significantly to improvement in passivation quality of the stacked layers. Furthermore, Si-rich SiN x films deposited with H 2 dilution show better passivation quality of SiN x /Si-rich SiN x stacked layers than those prepared without H 2 dilution. Effective minority carrier lifetime (τ eff ) in c-Si passivated by SiN x /Si-rich SiN x stacked layers is as high as 5.1 ms when H 2 is added during Si-rich SiN x deposition, which is much higher than the case of using Si-rich SiN x films prepared without H 2 dilution showing τ eff of 3.3 ms. - Highlights: • Passivation mechanism of Si-rich SiN x /SiN x stacked layers is investigated. • H atoms play important role in passivation quality of the stacked layer. • Addition of H 2 gas during Si-rich SiN x film deposition greatly enhances effective minority carrier lifetime (τ eff ). • For a Si-rich SiN x film with refractive index of 2.92, τ eff improves from 3.3 to 5.1 ms by H 2 addition

Sub-barrier fusion of Si+Si systems

Science.gov (United States)

Colucci, G.; Montagnoli, G.; Stefanini, A. M.; Bourgin, D.; Čolović, P.; Corradi, L.; Courtin, S.; Faggian, M.; Fioretto, E.; Galtarossa, F.; Goasduff, A.; Haas, F.; Mazzocco, M.; Scarlassara, F.; Stefanini, C.; Strano, E.; Urbani, M.; Szilner, S.; Zhang, G. L.

2017-11-01

The near- and sub-barrier fusion excitation function has been measured for the system 30Si+30Si at the Laboratori Nazionali di Legnaro of INFN, using the 30Si beam of the XTU Tandem accelerator in the energy range 47 - 90 MeV. A set-up based on a beam electrostatic deflector was used for detecting fusion evaporation residues. The measured cross sections have been compared to previous data on 28Si+28Si and Coupled Channels (CC) calculations have been performed using M3Y+repulsion and Woods-Saxon potentials, where the lowlying 2+ and 3- excitations have been included. A weak imaginary potential was found to be necessary to reproduce the low energy 28Si+28Si data. This probably simulates the effect of the oblate deformation of this nucleus. On the contrary, 30Si is a spherical nucleus, 30Si+30Si is nicely fit by CC calculations and no imaginary potential is needed. For this system, no maximum shows up for the astrophysical S-factor so that we have no evidence for hindrance, as confirmed by the comparison with CC calculations. The logarithmic derivative of the two symmetric systems highlights their different low energy trend. A difference can also be noted in the two barrier distributions, where the high-energy peak present in 28Si+28Si is not observed for 30Si+30Si, probably due to the weaker couplings in last case.

Sub-barrier fusion of Si+Si systems

Directory of Open Access Journals (Sweden)

Colucci G.

2017-01-01

Full Text Available The near- and sub-barrier fusion excitation function has been measured for the system 30Si+30Si at the Laboratori Nazionali di Legnaro of INFN, using the 30Si beam of the XTU Tandem accelerator in the energy range 47 - 90 MeV. A set-up based on a beam electrostatic deflector was used for detecting fusion evaporation residues. The measured cross sections have been compared to previous data on 28Si+28Si and Coupled Channels (CC calculations have been performed using M3Y+repulsion and Woods-Saxon potentials, where the lowlying 2+ and 3− excitations have been included. A weak imaginary potential was found to be necessary to reproduce the low energy 28Si+28Si data. This probably simulates the effect of the oblate deformation of this nucleus. On the contrary, 30Si is a spherical nucleus, 30Si+30Si is nicely fit by CC calculations and no imaginary potential is needed. For this system, no maximum shows up for the astrophysical S-factor so that we have no evidence for hindrance, as confirmed by the comparison with CC calculations. The logarithmic derivative of the two symmetric systems highlights their different low energy trend. A difference can also be noted in the two barrier distributions, where the high-energy peak present in 28Si+28Si is not observed for 30Si+30Si, probably due to the weaker couplings in last case.

Temporal correlation of blinking events in CdSe/ZnS and Si/SiO{sub 2} nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Bruhn, Benjamin, E-mail: b.bruhn@uva.nl [Materials and Nanophysics, KTH Royal Institute of Technology, 164 40 Kista (Sweden); Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Qejvanaj, Fatjon [Materials and Nanophysics, KTH Royal Institute of Technology, 164 40 Kista (Sweden); Gregorkiewicz, Tom [Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Linnros, Jan [Materials and Nanophysics, KTH Royal Institute of Technology, 164 40 Kista (Sweden)

2014-11-15

Well passivated single Si/SiO{sub 2} nanoparticles obey mono-exponential blinking statistics, whereas CdSe/ZnS quantum dots follow an apparent (truncated) power-law. Log-normal distributions are found to describe the interval length histograms at least as well as power-laws, while at the same time being more physically feasible and significantly easing the determination of the exponential cutoff in the ON-time distribution. The correlation of an ON- (OFF-)interval with its temporally displaced ON (OFF) neighbors, as well as that of intermixed intervals (ON with OFF and OFF with ON neighbors) has been studied. As expected from purely random processes, the correlation coefficients for events in silicon nanocrystals equal zero, whereas positive correlations between the pure and negative correlations between the mixed states in CdSe quantum dots hint at a switching process between two distinct blinking regimes that are slower than the blinking itself.

Radiation emission from wrinkled SiGe/SiGe nanostructure

Czech Academy of Sciences Publication Activity Database

Fedorchenko, Alexander I.; Cheng, H. H.; Sun, G.; Soref, R. A.

2010-01-01

Roč. 96, č. 11 (2010), s. 113104-113107 ISSN 0003-6951 Institutional research plan: CEZ:AV0Z20760514 Keywords : SiGe wrinkled nanostructures * si-based optical emitter * synchrotron radiation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.820, year: 2010 http://apl.aip.org/resource/1/applab/v96/i11/p113104_s1?isAuthorized=no

XPS and EELS characterization of Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Grosvenor, A.P., E-mail: andrew.grosvenor@usask.ca [Department of Chemistry, University of Saskatchewan, Saskatoon, SK S7N 5C9 (Canada); Bellhouse, E.M., E-mail: erika.bellhouse@arcelormittal.com [Global R & D—Hamilton, ArcelorMittal Dofasco, 1330 Burlington St. E, Hamilton, ON L8N 3J5 (Canada); Korinek, A., E-mail: korinek@mcmaster.ca [Canadian Centre for Electron Microscopy, Brockhouse Institute for Materials Research, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada); Bugnet, M., E-mail: bugnetm@mcmaster.ca [Canadian Centre for Electron Microscopy, Brockhouse Institute for Materials Research, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada); McDermid, J.R., E-mail: mcdermid@mcmaster.ca [Steel Research Centre, McMaster University, 1280 Main St. W., Hamilton, ON L8S 4M1 (Canada)

2016-08-30

Graphical abstract: XPS and EELS spectra were acquired from Mn2Al2O4, MnSiO3 and Mn2SiO4 standards and unique features identified that will allow unambiguous identification of these compounds when studying the selective oxidation of advanced steels. - Highlights: • Mn2Al2O4, MnSiO3 and Mn2SiO4 standards were synthesized and characterized using both XPS and EELS. • Unique features in both the XPS high resolution and EELS spectra were identified for all compounds. • The spectra can be used to identify these compounds when studying the selective oxidation of steels. - Abstract: X-ray Photoelectron Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS) are strong candidate techniques for characterizing steel surfaces and substrate-coating interfaces when investigating the selective oxidation and reactive wetting of advanced high strength steels (AHSS) during the continuous galvanizing process. However, unambiguous identification of ternary oxides such as Mn{sub 2}SiO{sub 4}, MnSiO{sub 3}, and MnAl{sub 2}O{sub 4} by XPS or EELS, which can play a significant role in substrate reactive wetting, is difficult due to the lack of fully characterized standards in the literature. To resolve this issue, samples of Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4} were synthesized and characterized by XPS and EELS. The unique features of the XPS and EELS spectra for the Mn{sub 2}SiO{sub 4}, MnSiO{sub 3} and MnAl{sub 2}O{sub 4} standards were successfully derived, thereby allowing investigators to fully differentiate and identify these oxides at the surface and subsurface of Mn, Si and Al alloyed AHSS using these techniques.

Study on the preparation of the SiCp/Al-20Si-3Cu functionally graded material using spray deposition

International Nuclear Information System (INIS)

Su, B.; Yan, H.G.; Chen, G.; Shi, J.L.; Chen, J.H.; Zeng, P.L.

2010-01-01

Research highlights: → The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. → The SiCp/Al-20Si-3Cu functionally gradient material (FGM) was successfully prepared via the spray deposition technique. → In the experimental setup, the novel devices play an important role in adjusting the output of SiCp to prepare the FGM. → The experiment results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. → The fraction of SiC particles has no obvious influence on the phase constitutions of the SiCp/Al-20Si-3Cu FGM. - Abstract: The SiCp/Al-20Si-3Cu functionally gradient material (FGMs) was successfully prepared via the spray deposition technique accompanied with an automatic control system. The results reveal that the SiCp weight fraction of the as-deposited preform from the top to the bottom ranges almost continuously from 0% to 30%. The part with the higher SiCp weight fraction exhibits a relatively smaller density than that with the lower SiCp weight fraction. However, the microhardness and the porosity increase with the increasing SiCp weight fraction in the as-deposited preform. The X-ray diffraction results exhibit that the secondary phases in the regions with the different amount of SiC particles are the same such as Al 2 Cu and AlCuMg. The spray deposition technology is promising to produce a wide range of other FGMs.

Si te sobreprotejo, no aprenderás a volar

OpenAIRE

Ortega Delgado, Juan Carlos; Enríquez Lara, Mónica Mercedes

2013-01-01

Tesis (Maestría en Educación desde la Diversidad). Universidad de Manizales. Facultad de Ciencias Sociales y Humanas, 2013 RESUMEN 1. Mónica Enríquez 2. Juan Carlos Ortega SI TE SOBREPROTEJO, NO APRENDERÁS A VOLAR El presente artículo se basa en la investigación denominada SI TE SOBREPROTEJO, NO APRENDERÁS A VOLAR, realizada acerca de la sobreprotección vista como otra forma de maltrato, la cual se ubica en el macroproyecto de Desarrollo Humano, Sujeto y diversidad, de...

Irradiation mixing of Al into U3Si

International Nuclear Information System (INIS)

Birtcher, R.C.; Ding, F.R.; Kestel, B.J.; Baldo, P.M.; Zaluzec, N.J.

1995-11-01

Thermal and irradiation induced intermixing of uranium silicide reactor fuels with the aluminum cladding is an important consideration in understanding their fission gas and fuel swelling behavior. The authors have used Rutherford backscattering to follow the behavior of an Al thin film on U 3 Si and U 3 Si 2 during 1.5 MeV Kr ion irradiation at temperatures of 30 and 350 C. After an initial dose during which no intermixing occurs, the Al mixes quickly into U 3 Si. The threshold dose is believed to be associated with an oxide layer between the Al and the uranium silicide. At 300 C and doses greater than threshold, rates of mixing and aluminide phase growth are extracted

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

Actinide-carbon bonds: insertion reactions of carbon monoxide, tert-butyl isocyanide, and tert-butyl cyanide into [(Me3Si)2N]2MCH2Si(Me)2NSiMe3

International Nuclear Information System (INIS)

Simpson, S.J.; Andersen, R.A.

1981-01-01

The thorium or uranium metallacycles [(Me 2 Si) 2 N] 2 MCH 2 Si(Me) 2 NSiMe 3 (I) react with tert-butyl cyanide to give the six-membered ring compounds [(Me 3 Si) 2 N] 2 MN = C(t-Bu)CH 2 Si(Me) 2 NSiMe 3 . The metallacycles (I) also react with the isoelectronic molecules tert-butyl isocyanide and carbon monoxide to give the unique five-membered ring compounds with exocyclic carbon-carbon double bonds, [(Me 3 Si) 2 N] 2 MXC(=CH 2 )Si(Me) 2 NSiMe 3 , where X is t-BuN or oxygen. The four-membered ring metallacycles (I) give simple coordination complexes of the type [(Me 3 Si) 2 N] 2 MCH 2 Si-(Me) 2 NSiMe 3 (N 3 SiMe 3 ) with trimethylsilyl azide

Slow Collisions of Si3+ with Atomic Hydrogen

Science.gov (United States)

Joseph, D. C.; Gu, J.-P.; Saha, B. C.; Liebermann, H. P.; Funke, P.; Buenker, R. J.

2010-03-01

Low energy electron capture from hydrogen atom by multi-charged ions continues to be of interest and applications include both magnetically confined fusion and astrophysical plasmas. The charge exchange process reported here, Si^3+ + H -> Si^2+ + H^+ is an important destruction mechanism of Si^3+ in photo-ionized gas. The soft X-ray emission from comets has been explained by charge transfer of solar wind ions, among them Si^3+, with neutrals in the cometary gas vapor. The state selective cross sections are evaluated using the full quantum [1] and semi-classical molecular orbital close coupling (MOCC) [2] methods. Adiabatic potentials and wave functions for a number of low-lying singlet and triplet states of and symmetry are calculated wing the MRD-CI package [3]. Details will be presented at the conference. [4pt] [1] L. B. Zhao, D. C. Joseph, B. C. Saha, H. P. Liebermann, P. Funke and R. J. Buenker, Phys. Rev A, 79, 034701 (1009).[0pt] [2] M. Kimura and N. F. Lane, At. Mol. Opt. Phys 26, 79 (1990).[0pt] [3] R. J. Buenker, ``Current Aspects of Quantum Chemistry 1981, Vol 21, edited by R. Carbo (Elsevier, Amsterdam) p 17.

Raman spectra of MgSiO3 . 10% Al2O3-perovskite at various pressures and temperatures

International Nuclear Information System (INIS)

Liu Lingun; Irifune, T.

1995-01-01

Variations of Raman spectra of MgSiO 3 . 10% Al 2 O 3 -perovskite were investigated up to about 270 kbar at room temperature and in the range 108-425 K at atmospheric pressure. Like MgSiO 3 -perovskite, the Raman frequencies of MgSiO 3 . 10% Al 2 O 3 -perovskite increase nonlinearly with increasing pressure and decrease linearly with increasing temperature within the experimental uncertainties and the range investigated. A comparison of these data with those of MgSiO 3 -perovskite suggests that MgSiO 3 . 10% Al 2 O 3 -perovskite is slightly more compressible than MgSiO 3 -perovskite, and that the volume thermal expansion for MgSiO 3 . 10% Al 2 O 3 -perovskite is also slightly greater than that for MgSiO 3 -perovskite. (orig.)

Facile and efficient synthesis of the surface tantalum hydride (≡SiO)2TaIIIH and tris-siloxy tantalum (≡SiO)3TaIII starting from novel tantalum surface species (≡SiO)TaMe4 and (≡SiO)2TaMe 3

KAUST Repository

Chen, Yin

2014-03-10

By grafting of TaMe5 (1) on the surface of silica partially dehydroxylated at 500 C (silica500), a mixture of (≡SiO)TaMe4 (2a; major, 65 ± 5%) and (≡SiO) 2TaMe3 (2b; minor, 35 ± 5%) was produced, which has been characterized by microanalysis, IR, and SS NMR (1H, 13C, 1H-13C HETCOR, proton double and triple quantum). After grafting, these surface organometallic compounds are more stable than the precursor TaMe5. Treatment of 2a,b with water and H 2 resulted in the formation of methane in amount of 3.6 ± 0.2 and 3.4 ± 0.2 mol/grafted Ta, respectively. 2a,b react with H2 (800 mbar) to form (≡SiO)2TaH. After (≡SiO) 2TaH was heated to 500 C under hydrogen or vacuum, [(≡SiO) 3Ta][≡SiH] was produced, and the structure was confirmed by IR, NMR, and EXAFS. Considering the difficulty of the previous preparation method, these syntheses represent a facile and convenient way to prepare tantalum surface species (≡SiO)2TaH and (≡SiO)3Ta via the intermediate of the new surface organometallic precursors: (≡SiO)TaMe4/(≡SiO)2TaMe3. (≡SiO)2TaH and (≡SiO)3Ta exhibit equal reactivities in alkane metathesis and ethylene polymerization in comparison to those in previous reports. © 2014 American Chemical Society.

Facile and efficient synthesis of the surface tantalum hydride (≡SiO)2TaIIIH and tris-siloxy tantalum (≡SiO)3TaIII starting from novel tantalum surface species (≡SiO)TaMe4 and (≡SiO)2TaMe 3

KAUST Repository

Chen, Yin; Ould-Chikh, Samy; Abou-Hamad, Edy; Callens, Emmanuel; Mohandas, Janet Chakkamadathil; Khalid, Syed M.; Basset, Jean-Marie

2014-01-01

By grafting of TaMe5 (1) on the surface of silica partially dehydroxylated at 500 C (silica500), a mixture of (≡SiO)TaMe4 (2a; major, 65 ± 5%) and (≡SiO) 2TaMe3 (2b; minor, 35 ± 5%) was produced, which has been characterized by microanalysis, IR, and SS NMR (1H, 13C, 1H-13C HETCOR, proton double and triple quantum). After grafting, these surface organometallic compounds are more stable than the precursor TaMe5. Treatment of 2a,b with water and H 2 resulted in the formation of methane in amount of 3.6 ± 0.2 and 3.4 ± 0.2 mol/grafted Ta, respectively. 2a,b react with H2 (800 mbar) to form (≡SiO)2TaH. After (≡SiO) 2TaH was heated to 500 C under hydrogen or vacuum, [(≡SiO) 3Ta][≡SiH] was produced, and the structure was confirmed by IR, NMR, and EXAFS. Considering the difficulty of the previous preparation method, these syntheses represent a facile and convenient way to prepare tantalum surface species (≡SiO)2TaH and (≡SiO)3Ta via the intermediate of the new surface organometallic precursors: (≡SiO)TaMe4/(≡SiO)2TaMe3. (≡SiO)2TaH and (≡SiO)3Ta exhibit equal reactivities in alkane metathesis and ethylene polymerization in comparison to those in previous reports. © 2014 American Chemical Society.

Investigation of passivity and its breakdown on Fe3Al–Si and Fe3Al–Ge intermetallics in chloride-containing solution

International Nuclear Information System (INIS)

Rosalbino, F.; Carlini, R.; Parodi, R.; Zanicchi, G.; Scavino, G.

2014-01-01

Highlights: • Passivity and its breakdown on Fe 3 Al–Si and Fe 3 Al–Ge iron aluminides was investigated. • Investigation was performed in borate buffer solution with and without 100 mM KCl. • Polarization, potentiostatic transients and impedance measurements have been employed. • Results have been compared with those obtained on Fe 3 Al intermetallic. • Si and Ge improve the resistance to localized corrosion of Fe 3 Al. - Abstract: The passivity and passivity breakdown of Fe 3 Al–Si and Fe 3 Al–Ge iron aluminides were studied in borate buffer solution (pH 8.4) in the absence and presence of 100 mM KCl, performing potentiodynamic polarization, potentiostatic transients and electrochemical impedance spectroscopy (EIS) measurements complemented with scanning electron microscopy (SEM). In the absence of chloride ions Si and Ge exercise a beneficial role in the passivating characteristics of Fe 3 Al intermetallic. Addition of Si or Ge significantly modifies the electrochemical response of iron aluminide Fe 3 Al resulting in a more stable passive film. In the presence of chloride ions all the intermetallic compounds experience localized corrosion (pitting). However, Si and Ge alloying additions increase the breakdown potential and the extent of passivation domain, indicating improved resistance to initiation of pitting corrosion. Furthermore, EIS measurements performed at the breakdown state evidenced higher R ct and lower depression angle values for Fe 3 Al–Si and Fe 3 Al–Ge iron aluminides compared to Fe 3 Al intermetallic, confirming their better localized corrosion behavior. The improved resistance to pitting corrosion results from the enhanced protective function of passive film due to the presence of Si or Ge that inhibit pit initiation by hindering the adsorption of Cl − ions at the metal surface

SiO 2/SiC interface proved by positron annihilation

Science.gov (United States)

Maekawa, M.; Kawasuso, A.; Yoshikawa, M.; Itoh, H.

2003-06-01

We have studied positron annihilation in a Silicon carbide (SiC)-metal/oxide/semiconductor (MOS) structure using a monoenergetic positron beam. The Doppler broadening of annihilation quanta were measured as functions of the incident positron energy and the gate bias. Applying negative gate bias, significant increases in S-parameters were observed. This indicates the migration of implanted positrons towards SiO 2/SiC interface and annihilation at open-volume type defects. The behavior of S-parameters depending on the bias voltage was well correlated with the capacitance-voltage ( C- V) characteristics. We observed higher S-parameters and the interfacial trap density in MOS structures fabricated using the dry oxidation method as compared to those by pyrogenic oxidation method.

SiO2/SiC interface proved by positron annihilation

International Nuclear Information System (INIS)

Maekawa, M.; Kawasuso, A.; Yoshikawa, M.; Itoh, H.

2003-01-01

We have studied positron annihilation in a Silicon carbide (SiC)-metal/oxide/semiconductor (MOS) structure using a monoenergetic positron beam. The Doppler broadening of annihilation quanta were measured as functions of the incident positron energy and the gate bias. Applying negative gate bias, significant increases in S-parameters were observed. This indicates the migration of implanted positrons towards SiO 2 /SiC interface and annihilation at open-volume type defects. The behavior of S-parameters depending on the bias voltage was well correlated with the capacitance-voltage (C-V) characteristics. We observed higher S-parameters and the interfacial trap density in MOS structures fabricated using the dry oxidation method as compared to those by pyrogenic oxidation method

Metallization of ion beam synthesized Si/3C-SiC/Si layer systems by high-dose implantation of transition metal ions

International Nuclear Information System (INIS)

Lindner, J.K.N.; Wenzel, S.; Stritzker, B.

2001-01-01

The formation of metal silicide layers contacting an ion beam synthesized buried 3C-SiC layer in silicon by means of high-dose titanium and molybdenum implantations is reported. Two different strategies to form such contact layers are explored. The titanium implantation aims to convert the Si top layer of an epitaxial Si/SiC/Si layer sequence into TiSi 2 , while Mo implantations were performed directly into the SiC layer after selectively etching off all capping layers. Textured and high-temperature stable C54-TiSi 2 layers with small additions of more metal-rich silicides are obtained in the case of the Ti implantations. Mo implantations result in the formation of the high-temperature phase β-MoSi 2 , which also grows textured on the substrate. The formation of cavities in the silicon substrate at the lower SiC/Si interface due to the Si consumption by the growing silicide phase is observed in both cases. It probably constitutes a problem, occurring whenever thin SiC films on silicon have to be contacted by silicide forming metals independent of the deposition technique used. It is shown that this problem can be solved with ion beam synthesized contact layers by proper adjustment of the metal ion dose

Effects of Si content on microstructure and mechanical properties of TiAlN/Si3N4-Cu nanocomposite coatings

Science.gov (United States)

Feng, Changjie; Hu, Shuilian; Jiang, Yuanfei; Wu, Namei; Li, Mingsheng; Xin, Li; Zhu, Shenglong; Wang, Fuhui

2014-11-01

TiAlN/Si3N4-Cu nanocomposite coatings of various Si content (0-5.09 at.%) were deposited on AISI-304 stainless steel by DC reactive magnetron sputtering technique. The chemical composition, microstructure, mechanical and tribological properties of these coatings were systematically investigated by means of X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), nanoindentation tester, a home-made indentation system, a scratch tester and a wear tester. Results indicated that with increasing Si content in these coatings, a reduction of grain size and surface roughness, a transformation of the (1 1 1) preferred orientation was detected by XRD and FESEM. Furthermore the hardness of these coatings increase from 9.672 GPa to 18.628 GPa, and the elastic modulus reveal the rising trend that increase from 224.654 GPa to 251.933 GPa. However, the elastic modulus of TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content dropped rapidly and changed to about 180.775 GPa. The H3/E2 ratio is proportional to the film resistance to plastic deformation. The H3/E2 ratio of the TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content possess of the maximum of 0.11 GPa, and the indentation test indicate that few and fine cracks were observed from its indentation morphologies. The growth pattern of cracks is mainly bending growing. The present results show that the best toughness is obtained for TiAlN/Si3N4-Cu nanocomposite coating containing 3.39 at.% Si content. In addition, the TiAlN/Si3N4-Cu coating containing 3.39 at.% Si content also has good adhesion property and superior wear resistance, and the wear mechanism is mainly adhesion wear.

UV and IR laser induced ablation of Al2O3/SiN:H and a-Si:H/SiN:H

Directory of Open Access Journals (Sweden)

Schutz-Kuchly T.

2014-01-01

Full Text Available Experimental work on laser induced ablation of thin Al2O3(20 nm/SiN:H (70 nm and a-Si:H (20 nm/SiN:H (70 nm stacks acting, respectively, as p-type and n-type silicon surface passivation layers is reported. Results obtained using two different laser sources are compared. The stacks are efficiently removed using a femtosecond infra-red laser (1030 nm wavelength, 300 fs pulse duration but the underlying silicon surface is highly damaged in a ripple-like pattern. This collateral effect is almost completely avoided using a nanosecond ultra-violet laser (248 nm wavelength, 50 ns pulse duration, however a-Si:H flakes and Al2O3 lace remain after ablation process.

Crystalline and lattice matched Ba0.7Si0.3O layers on plane and vicinal Si(001) surfaces

International Nuclear Information System (INIS)

Zachariae, J.

2006-01-01

In this work the low temperature growth conditions of epitaxial and lattice-matched Ba 0.7 Sr 0.3 O layers on Si(100) were investigated using the combination of low energy electron diffraction (LEED), x-ray photoemission (XPS) and electron energy loss spectroscopy (EELS). With these methods crystallinity, stoichiometry and electronic structure of both occupied and unoccupied levels were studied as a function of layer thickness. Oxide layers were generated by evaporating the metals in oxygen ambient pressure with the sample at room temperature. Perfect crystallinity and lattice matching was only obtained starting with a preadsorbed monolayer (ML) of Sr or Ba at a concentration close to one monolayer. The XPS analysis shows that Ba 0.7 Sr 0.3 O as a high-K gate dielectric offers an adequate band gap, an appropriate band alignment and a atomically sharp interface to the Si(001) substrate. No silicide and silicate species, or SiO 2 formation at the interface after oxidation were found. To show that Ba 0.7 Sr 0.3 O is really appropriate to replace SiO 2 as a gate dielectric, first C-V and I-V curves of MOS-diodes with SrO, BaO and Ba 0.7 Sr 0.3 O as gateoxide were measured under ambient conditions. Besides other results, it turns out that the measured dielectric constant of Ba 0.7 Sr 0.3 O conforms with the expected value of ε ∼ 25 - 30. Exploring ways for self-organized structuring of insulating films, the possibility to produce replicas of step trains, given by a vicinal Si(001)-4 [110] surface, in layers of crystalline and perfectly lattice matched Ba 0.7 Sr 0.3 O were investigated. For this purpose high-resolution spot profile analyses in low-energy electron diffraction (SPA-LEED) both on flat Si(001) and on vicinal Si(001)-4 [110] were carried out. The G(S) analysis of these mixed oxide layers reveals a strong influence of local compositional fluctuations of Sr and Ba ions and their respective scattering phases, which appears as an unphysically large variation

Novel targeted therapy for neuroblastoma: silencing the MXD3 gene using siRNA.

Science.gov (United States)

Duong, Connie; Yoshida, Sakiko; Chen, Cathy; Barisone, Gustavo; Diaz, Elva; Li, Yueju; Beckett, Laurel; Chung, Jong; Antony, Reuben; Nolta, Jan; Nitin, Nitin; Satake, Noriko

2017-09-01

BackgroundNeuroblastoma is the second most common extracranial cancer in children. Current therapies for neuroblastoma, which use a combination of chemotherapy drugs, have limitations for high-risk subtypes and can cause significant long-term adverse effects in young patients. Therefore, a new therapy is needed. In this study, we investigated the transcription factor MXD3 as a potential therapeutic target in neuroblastoma.MethodsMXD3 expression was analyzed in five neuroblastoma cell lines by immunocytochemistry and quantitative real-time reverse transcription PCR, and in 18 primary patient tumor samples by immunohistochemistry. We developed nanocomplexes using siRNA and superparamagnetic iron oxide nanoparticles to target MXD3 in neuroblastoma cell lines in vitro as a single-agent therapeutic and in combination with doxorubicin, vincristine, cisplatin, or maphosphamide-common drugs used in current neuroblastoma treatment.ResultsMXD3 was highly expressed in neuroblastoma cell lines and in patient tumors that had high-risk features. Neuroblastoma cells treated in vitro with the MXD3 siRNA nanocomplexes showed MXD3 protein knockdown and resulted in cell apoptosis. Furthermore, on combining MXD3 siRNA nanocomplexes with each of the four drugs, all showed additive efficacy.ConclusionThese results indicate that MXD3 is a potential new target and that the use of MXD3 siRNA nanocomplexes is a novel therapeutic approach for neuroblastoma.

Sulfide and Oxide Heterostructures For the SrTiO3 Thin Film Growth on Si and Their Structural and Interfacial Stabilities

Science.gov (United States)

Yoo, Young‑Zo; Song, Jeong‑Hwan; Konishi, Yoshinori; Kawasaki, Masashi; Koinuma, Hideomi; Chikyow, Toyohiro

2006-03-01

Epitaxial SrTiO3 (STO) thin films with high electrical properties were grown on Si using ZnS single- and SrS/MnS hetero-buffer layers. STO films on both ZnS-buffered and SrS/MnS-buffered Si showed two growth orientations, (100) and (110). The temperature dependence of the growth orientation for STO films was different for the ZnS single-buffer layer in comparison with the SrS/MnS heterobuffer layers. (100) growth of STO films on SrS/MnS-buffered Si became dominant at high temperatures about 700 °C, while (100) growth of STO films on ZnS-buffered Si became dominant at a relatively low growth temperature of 550 °C. STO(100) films on ZnS-buffered and SrS/MnS-buffered Si showed lattice and domain matches for epitaxial relationships with [001]ZnS\\parallel[011]STO and SrS[001]\\parallel[011]STO, respectively via 45° in-plane rotation of STO films relative to both ZnS and SrS layers. The ZnS buffer layer contained many stacking faults because of the mismatch between ZnS and Si, however, those defects were terminated at the ZnS/STO interface. In contrast, the MnS buffer was very stable against stacking defect formation. Transmission electron microscopy measurements revealed the presence of a disordered region at the ZnS/Si and MnS/Si interfaces. Auger electron spectroscopy and transmission electron microscopy results showed that a good MnS/Si interface at the initial growth stage degraded to a SiS2-x-rich phase during MnS deposition and again into a SiO2-x-rich phase during STO deposition at the high growth temperature of 700 °C. It was also observed that STO on SrS/MnS-buffered Si showed a markedly high dielectric constant compared with that of STO on ZnS-buffered Si.

Irradiation damages in Ti{sub 3}SiC{sub 2}; Dommages d'irradiation dans Ti{sub 3}SiC{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Nappe, J.C.; Grosseau, Ph. [Ecole Nationale Superieure des Mines, Centre SPIN, Lab. PMMC et LPMG UMR CNRS 5148, 42 - Saint-Etienne (France); Guilhot, B. [Ecole Nationale Superieure des Mines, Centre CIS, 42 - Saint-Etienne (France); Audubert, F.; Beauvy, M. [CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. d' Etudes des Combustibles; Iacconi, Ph.; Benabdesselam, M. [Nice Univ. - Sophia Antipolis, Lab. LPES-CRESA, 06 (France)

2007-07-01

Carbides, by their remarkable properties, are considered as possible materials (fuel cans) in reactor of generation IV. Among those studied, Ti{sub 3}SiC{sub 2} is particularly considered because it joins both the ceramics and metals properties. Nevertheless, its behaviour under irradiation is not known. Characterizations have been carried out on samples irradiated at 75 MeV krypton ions. They have revealed that TiO{sub 2} (formed at the surface of Ti{sub 3}SiC{sub 2}) is pulverized by the irradiation and that the crystal lattice of Ti{sub 3}SiC{sub 2} dilates with c. (O.M.)

Fabrication of SiC Composites with Synergistic Toughening of Carbon Whisker and In Situ 3C-SiC Nanowire

Directory of Open Access Journals (Sweden)

Zhang Yunlong

2016-01-01

Full Text Available The SiC composites with synergistic toughening of carbon whisker and in situ 3C-SiC nanowire have been fabricated by hot press sinter technology and annealed treatment technology. Effect of annealed time on the morphology of SiC nanowires and mechanical properties of the Cw/SiC composites was surveyed in detail. The appropriate annealed time improved mechanical properties of the Cw/SiC composites. The synergistic effect of carbon whisker and SiC nanowire can improve the fracture toughness for Cw/SiC composites. The vapor-liquid-solid growth (VLS mechanism was proposed. TEM photo showed that 3C-SiC nanowire can be obtained with preferential growth plane ({111}, which corresponded to interplanar spacing about 0.25 nm.

Ni(3)Si(Al)/a-SiO(x) core-shell nanoparticles: characterization, shell formation, and stability.

Science.gov (United States)

Pigozzi, G; Mukherji, D; Gilles, R; Barbier, B; Kostorz, G

2006-08-28

We have used an electrochemical selective phase dissolution method to extract nanoprecipitates of the Ni(3)Si-type intermetallic phase from two-phase Ni-Si and Ni-Si-Al alloys by dissolving the matrix phase. The extracted nanoparticles are characterized by transmission electron microscopy, energy-dispersive x-ray spectrometry, x-ray powder diffraction, and electron powder diffraction. It is found that the Ni(3)Si-type nanoparticles have a core-shell structure. The core maintains the size, the shape, and the crystal structure of the precipitates that existed in the bulk alloys, while the shell is an amorphous phase, containing only Si and O (SiO(x)). The shell forms around the precipitates during the extraction process. After annealing the nanoparticles in nitrogen at 700 °C, the tridymite phase recrystallizes within the shell, which remains partially amorphous. In contrast, on annealing in air at 1000 °C, no changes in the composition or the structure of the nanoparticles occur. It is suggested that the shell forms after dealloying of the matrix phase, where Si atoms, the main constituents of the shell, migrate to the surface of the precipitates.

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.

Infrared Spectra and Structures of SiH{sub 2}-(CH{sub 2}){sub 2} and CH{sub 2}=CH-SiH{sub 3} Intermediates Prepared in Reactions of Laser-ablated Silicon Atoms with Ethane

Energy Technology Data Exchange (ETDEWEB)

Cho, Han-Gook [Incheon National University, Incheon (Korea, Republic of); Andrews, Lester [University of Virginia, Charlottesville (United States)

2016-03-15

SiH{sub 2}-(CH{sub 2}){sub 2} and CH{sub 2}=CH-SiH{sub 3} were observed in the matrix IR spectra following reactions of laser-ablated Si atoms with ethane on the basis of correlation with computed frequencies. Evidently photon energy is required for the formation of the cyclic Si compound. These Si complexes are similar to the primary products in the previous studies of group 4 metals, in line with the previous results that s{sup 2}p{sup 2} and s{sup 2}d{sup 2} electronic configurations yield similar products. The relatively long C–C bond in the cyclic Si product reflects the structural strain, and the short C-Si and C-C bonds of CH{sub 3}CH=SiH{sub 2} and CH{sub 2}=CH-SiH{sub 3} show that they are true double bonds in line with the natural bond orders. Reactions of transition-metal atoms with small alkanes and halomethanes have been studied in a series of recent investigations. High oxidation-state products (methylidenes and methylidynes) along with insertion complexes were identified in the matrix spectra. It is interesting whether or not Si, a group 14 metalloid, undergoes similar reactions with larger hydrocarbons to provide higher oxidation-state compounds.

The structure of well defined SiO2 supported MoO3 clusters during sulfidation : an in situ EXAFS-study

NARCIS (Netherlands)

Boer, de M.; Dillen, van A.J.; Koningsberger, D.C.; Geus, J.W.; Kuroda, H.; Ohta, T.

1993-01-01

The sulfidation of a well defined MoO3/SiO2 catalyst has been examd. by means of TPS, EXAFS, and TEM. The oxidic clusters in a 5.6 wt% MoO3/SiO2 catalyst are transformed into almost completely sulfided particles (MoOxSy) by O-S exchange at RT. A molybdenum-sulfido particle that resembles the MoS3

Excitation mechanism of Er{sup 3+} in a-Si:H; Anregungsmechanismus von Er{sup 3+} in a-Si:H

Energy Technology Data Exchange (ETDEWEB)

Kuehne, H.

2004-07-01

The aim of this work is the examination of the optoelectronical material a-Si:H (Er). It is characterised in the good electronic properties of the a-Si:H and the emission wavelength of 1.5 micrometer of erbium which coincides with the absorbtion minimum of glasfibres. Photoluminescence measurements confirm the assumption that oxigen is necessary for the optical activation of Er{sup 3+} in addition to the symmetrical breaking of the crystal field. The flexible lattice of a-Si:H enables a high concentration of Erbium up to 5.10{sup 21}/cm{sup 3} with a quantum efficiency of the luminescence of 0.5-1.5.10{sup -4} at room temperature. Photoluminescence excitation and absorption measurements of a-Si:H (Er) show, that there is no direct excitation of the erbium ions because the absorption of the Er{sup 3+} ions is two orders of magnitude below the absorption of silicon. The excitation or the Er{sup 3+} ions takes place through the absorption in silicon with additional energy transfer to Erbium. Photoluminescence measurements are done in order to differentiate between the possible excitation channels, the intrinsic bond-bond channel and the excitation through defects. The different temperature dependence of the intensity of the intrinsic luminescence (77 K - 300 K >3 orders of magnitude) in comparison with the defect luminescence and the Erbium luminescence (both 1-1.5 orders of magnitude) shows that the energy transfer takes place over defects. Luminescence and absorption measurements with boron doped a-Si:H (Er) show no dependence of the Erbium luminescence in dependence of defect density or the electrical charge of the defects. The luminescence spectra show a break in the defect luminescence at 0.84 eV. This agrees with the first excited state of the Er{sup 3+} ion combined with a clearly smaller line width of the defect luminescence (0.18 eV in comparision with >0.3 eV in erbium free a-Si:H). This result shows the resonance of the energy transfer. The resonance is

Channeling effect studies in V3Si single crystals

International Nuclear Information System (INIS)

Meyer, O.

1978-01-01

Angular scans through the [100] and [110] channeling directions in V 3 Si have been performed using elastically scattered He ions for the V-rows and the 28 Si(d,p 8 ) 29 Si reaction for the Si-rows. The amplitude of thermal vibration perpendicular to the V-chains was found to be larger than that at 45 0 to them. The Si atoms however vibrate isotropically. The use of multi-row potentials instead of single-row potentials leads to better overall agreement between measured and calculated critical angles. (Auth.)

Construction of MoS2/Si nanowire array heterojunction for ultrahigh-sensitivity gas sensor

Science.gov (United States)

Wu, Di; Lou, Zhenhua; Wang, Yuange; Xu, Tingting; Shi, Zhifeng; Xu, Junmin; Tian, Yongtao; Li, Xinjian

2017-10-01

Few-layer MoS2 thin films were synthesized by a two-step thermal decomposition process. In addition, MoS2/Si nanowire array (SiNWA) heterojunctions exhibiting excellent gas sensing properties were constructed and investigated. Further analysis reveals that such MoS2/SiNWA heterojunction devices are highly sensitive to nitric oxide (NO) gas under reverse voltages at room temperature (RT). The gas sensor demonstrated a minimum detection limit of 10 ppb, which represents the lowest value obtained for MoS2-based sensors, as well as an ultrahigh response of 3518% (50 ppm NO, ˜50% RH), with good repeatability and selectivity of the MoS2/SiNWA heterojunction. The sensing mechanisms were also discussed. The performance of the MoS2/SiNWA heterojunction gas sensors is superior to previous results, revealing that they have great potential in applications relating to highly sensitive gas sensors.

Unidirectional solidification of a Nbss/Nb5Si3 in-situ composite

International Nuclear Information System (INIS)

Guo, X.P.; Ding, X.; Zhang, J.; Fu, H.Z.; Guan, P.; Kusabiraki, K.

2005-01-01

The directionally solidified specimens of Nb-13.52 Si-22.60 Ti-6.88 Hf-2.54 Cr-2.24 Al alloy were prepared in an electron beam floating zone melting furnace at the withdrawing rate of 0.1, 0.3, 0.6, 1.0, 2.4 and 6.0 mm/min. All the primary Nb solid solution (Nb ss ) columns, Nb ss + (Nb) 3 Si/(Nb) 5 Si 3 eutectic colonies and divorced (Nb) 3 Si/(Nb) 5 Si 3 plates or chains align well along the longitudinal axis of the specimens. With increasing of the withdrawing rate, the microstructure is gradually refined, and the amount of Nb ss + (Nb) 3 Si/(Nb) 5 Si 3 eutectic colonies increases. Both the room temperature ultimate tensile strength σ b and fracture toughness K Q are improved for the directionally solidified specimens. The tensile fracture occurs in a cleavage way. (orig.)

Incorporating Si3 N4 into PEEK to Produce Antibacterial, Osteocondutive, and Radiolucent Spinal Implants.

Science.gov (United States)

Pezzotti, Giuseppe; Marin, Elia; Adachi, Tetsuya; Lerussi, Federica; Rondinella, Alfredo; Boschetto, Francesco; Zhu, Wenliang; Kitajima, Takashi; Inada, Kosuke; McEntire, Bryan J; Bock, Ryan M; Bal, B Sonny; Mazda, Osam

2018-04-24

Polyetheretherketone (PEEK) is a popular polymeric biomaterial which is primarily used as an intervertebral spacer in spinal fusion surgery; but it is developed for trauma, prosthodontics, maxillofacial, and cranial implants. It has the purported advantages of an elastic modulus which is similar to native bone and it can be easily formed into custom 3D shapes. Nevertheless, PEEK's disadvantages include its poor antibacterial resistance, lack of bioactivity, and radiographic transparency. This study presents a simple approach to correcting these three shortcomings while preserving the base polymer's biocompatibility, chemical stability, and elastic modulus. The proposed strategy consists of preparing a PEEK composite by dispersing a minor fraction (i.e., 15 vol%) of a silicon nitride (Si 3 N 4 ) powder within its matrix. In vitro tests of PEEK composites with three Si 3 N 4 variants-β-Si 3 N 4 , α-Si 3 N 4 , and β-SiYAlON-demonstrate significant improvements in the polymer's osteoconductive versus SaOS-2 cells and bacteriostatic properties versus gram-positive Staphylococcus epidermidis bacteria. These properties are clearly a consequence of adding the bioceramic dispersoids, according to chemistry similar to that previously demonstrated for bulk Si 3 N 4 ceramics in terms of osteogenic behavior (vs both osteosarcoma and mesenchymal progenitor cells) and antibacterial properties (vs both gram-positive and gram-negative bacteria). © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Structural stability and fission product behaviour in U{sub 3}Si

Energy Technology Data Exchange (ETDEWEB)

Middleburgh, S.C., E-mail: simon.middleburgh@hotmail.co.uk [IME, Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales (Australia); Westinghouse Electric Sweden AB, SE-72163 Västerås (Sweden); Burr, P.A. [Department of Materials, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); King, D.J.M.; Edwards, L.; Lumpkin, G.R. [IME, Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales (Australia); Grimes, R.W. [Department of Materials, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom)

2015-11-15

The crystalline and amorphous structures of U{sub 3}Si have been investigated using density functional theory techniques for the first time. The effects of disorder and the impact of fission products has been separated to understand the swelling characteristics of U{sub 3}Si in both crystalline and amorphous U{sub 3}Si. Initially, the stability of the three experimentally observed polymorphs of U{sub 3}Si were explored. Subsequently, we modelled the amorphous U{sub 3}Si system and conclude that initial increase in volume observed experimentally at low temperature corresponds well with the volume change that occurs with the observed amorphisation of the material. The solubility of Xe and Zr into both the crystalline and amorphous systems was subsequently investigated.

Specific heat measurements of CePt{sub 3}Si and Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z}

Energy Technology Data Exchange (ETDEWEB)

Motoyama, G. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)]. E-mail: motoyama@sci.u-hyogo.ac.jp; Watanabe, M. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Maeda, K. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Oda, Y. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Ueda, K. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan); Kohara, T. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)

2007-03-15

We have measured the specific heat of a series of polycrystalline CePt{sub 3}Si and Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z} samples whose compositions vary slightly from the stoichiometric composition. We observed two peaks derived from magnetic anomalies on the specific heat measurements of the Ce{sub 1+x}Pt{sub 3+y}Si{sub 1+z} samples. One of the peaks relates to the antiferromagnetic phase transition at T{sub N}=2.2K. The other is a large peak at 2.7K observed for the sample that showed a ferromagnetic anomaly at 3.0K on the temperature dependence of the magnetization. Heat treatment had different effects between these anomalies.

3C-SiC epitaxial films deposited by reactive magnetron sputtering: Growth, characterization and device development

Energy Technology Data Exchange (ETDEWEB)

Wahab, Qamar ul.

1994-01-01

Epitaxial 3C-SiC films were grown on silicon substrates by reactive magnetron sputtering of pure Si target in a mixed Ar-CH[sub 4] discharges. Films were grown on Si(001), and 4 degrees off-oriented (001) substrates. Epitaxial 3C-SiC films with sharp interface to Si substrates have been grown at substrate temperatures [<=] 900 degrees C. Above 900 degrees C interfacial reaction starts resulting in a rough SiC/Si interface. The carbon content as well as the crystalline structure was also found to be strongly dependent on CH[sub 4] partial pressure (PCH[sub 4]) and stoichiometric composition can only be obtained in a narrow PCH[sub 4] range. Films grown on Si(001) substrates contained anti domain boundaries as evident by cross-sectional transmission electron microscopy (XTEM). Films grown on (111)-oriented substrates were epitaxial at 850 degrees C but contained double positioning domains as determined by X-ray diffraction analysis and XTEM. High quality films were obtained on 4 degrees off-oriented Si(001) substrates at T[sub s]=850 degrees C and PCH[sub 4]=0.6 mTorr. Films grown on off-oriented substrates showed atomically sharp interface to Si and also a smooth top surface. SiO[sub 2] layer grown on such films showed atomically sharp oxide/film interface. Also the growth of epitaxial Si films on top of SiC films was realized. Au-Schottky diodes fabricated on (001)-oriented 3C-SiC films showed good rectification with a leakage current density = 4 [mu]A cm[sup -2], a breakdown voltage of -15 V, an ideality factor of 1.27 and a barrier height of 1.04 eV. Metal oxide semiconductor structures were fabricated by thermally grown SiO[sub 2] on (111)-oriented SiC films. The capacitance-voltage measurements showed the accumulation, depletion and deep depletion region in the C-V curve. The interface trap densities were 3-7 x 10[sup 11] cm[sup -2] eV[sup -1]. Finally 3C-SiC/Si heterojunction diodes processed showed good rectification and the diode had a breakdown at -110 V.

3C-SiC epitaxial films deposited by reactive magnetron sputtering: Growth, characterization and device development

International Nuclear Information System (INIS)

Wahab, Qamar ul.

1994-01-01

Epitaxial 3C-SiC films were grown on silicon substrates by reactive magnetron sputtering of pure Si target in a mixed Ar-CH 4 discharges. Films were grown on Si(001), and 4 degrees off-oriented (001) substrates. Epitaxial 3C-SiC films with sharp interface to Si substrates have been grown at substrate temperatures ≤ 900 degrees C. Above 900 degrees C interfacial reaction starts resulting in a rough SiC/Si interface. The carbon content as well as the crystalline structure was also found to be strongly dependent on CH 4 partial pressure (PCH 4 ) and stoichiometric composition can only be obtained in a narrow PCH 4 range. Films grown on Si(001) substrates contained anti domain boundaries as evident by cross-sectional transmission electron microscopy (XTEM). Films grown on (111)-oriented substrates were epitaxial at 850 degrees C but contained double positioning domains as determined by X-ray diffraction analysis and XTEM. High quality films were obtained on 4 degrees off-oriented Si(001) substrates at T s =850 degrees C and PCH 4 =0.6 mTorr. Films grown on off-oriented substrates showed atomically sharp interface to Si and also a smooth top surface. SiO 2 layer grown on such films showed atomically sharp oxide/film interface. Also the growth of epitaxial Si films on top of SiC films was realized. Au-Schottky diodes fabricated on (001)-oriented 3C-SiC films showed good rectification with a leakage current density = 4 μA cm -2 , a breakdown voltage of -15 V, an ideality factor of 1.27 and a barrier height of 1.04 eV. Metal oxide semiconductor (MOS) structures were fabricated by thermally grown SiO 2 on (111)-oriented SiC films. The capacitance-voltage measurements showed the accumulation, depletion and deep depletion region in the C-V curve. The interface trap densities were 3-7 x 10 11 cm -2 eV -1 . Finally 3C-SiC/Si heterojunction diodes processed showed good rectification and the diode had a breakdown at -110 V. 59 refs, figs, tabs

X-ray photoelectron spectrometry and binding energies of Be 1s and O 1s core levels in clinobarylite, BaBe2Si2O7, from Khibiny massif, Kola peninsula

International Nuclear Information System (INIS)

Atuchin, V.V.; Kesler, V.G.; Sapozhnikov, V.K.; Yakovenchuk, V.N.

2008-01-01

The electronic structure of BaBe 2 Si 2 O 7 , clinobarylite, has been investigated by means of X-ray photoelectron spectroscopy (XPS). The valence band of the crystal is mainly formed by Ba 5p, Ba 3s and O 2s states. At higher binding energies the emission lines related to the Si 2p, Be 1s, Si 2s, O 1s and numerous Ba-related states were analyzed in the photoemission spectrum. The Si KLL Auger line has been measured under excitation by the bremsstrahlung X-rays from the Al anode. Chemical bonding effects for Be 1s core level have been considered by comparison with electronic parameters measured for other beryllium containing oxides

Thermal Stability of siRNA Modulates Aptamer- conjugated siRNA Inhibition

Directory of Open Access Journals (Sweden)

Alexey Berezhnoy

2012-01-01

Full Text Available Oligonucleotide aptamer-mediated in vivo cell targeting of small interfering RNAs (siRNAs is emerging as a useful approach to enhance the efficacy and reduce the adverse effects resulting from siRNA-mediated genetic interference. A current main impediment in aptamer-mediated siRNA targeting is that the activity of the siRNA is often compromised when conjugated to an aptamer, often requiring labor intensive and time consuming design and testing of multiple configurations to identify a conjugate in which the siRNA activity has not been significantly reduced. Here, we show that the thermal stability of the siRNA is an important parameter of siRNA activity in its conjugated form, and that siRNAs with lower melting temperature (Tm are not or are minimally affected when conjugated to the 3′ end of 2′F-pyrimidine-modified aptamers. In addition, the configuration of the aptamer-siRNA conjugate retains activity comparable with the free siRNA duplex when the passenger strand is co-transcribed with the aptamer and 3′ overhangs on the passenger strand are removed. The approach described in this paper significantly reduces the time and effort necessary to screening siRNA sequences that retain biological activity upon aptamer conjugation, facilitating the process of identifying candidate aptamer-siRNA conjugates suitable for in vivo testing.

Improvement of photoluminescence intensity of Ce-doped Y{sub 3}Al{sub 5}O{sub 12} phosphor by Si{sub 3}N{sub 4} addition

Energy Technology Data Exchange (ETDEWEB)

Shyu, Jiin-Jyh, E-mail: jjshyu@ttu.edu.tw; Yang, Chia-Wei

2017-06-01

Yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}, YAG) has been widely used as a host for luminescent ions. The present paper describes the effects of Si{sub 3}N{sub 4} addition on the formation and photoluminescence properties of the Ce-doped YAG yellow phosphors. Phosphor powders with the nominal compositions of Y{sub 2.95}Ce{sub 0.05}Al{sub 5-m}Si{sub m}O{sub 12-m}N{sub m} (m = 0–0.6) were prepared by calcining the mixed raw materials at 1500 °C in nitrogen atmosphere. X-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscope, and transmission electron microscopy equipped with an energy dispersive x-ray spectrometer were used to characterize the structure of the calcined powders. The photoluminescence properties were measured with fluorescence spectrophotometry. It was found that in the range of m = 0–0.27, single phase YAG solid solution (s.s.) in which the Y, Al, and O sites are partially occupied by Ce, Si, and N ions, respectively. The nitrogen ions do not distribute homogeneously over the YAG lattice. The tendency to bond with nitrogen ion for the cations is (Y, Ce) > Si > Al. With the increase in the Si{sub 3}N{sub 4} content, the increase in both the Ce{sup 3+}/(Ce{sup 3+} + Ce{sup 4+}) ratio and the Ce-N bonds improve the intensity of the photoluminescent emission. At m = 0.27, the emission intensity reaches a maximum which is about 2.5 and 1.6 times of that for the Si{sub 3}N{sub 4}-free composition (m = 0) calcined in air and nitrogen, respectively. When the Si{sub 3}N{sub 4} content (m) is higher than 0.27, the emission intensity decreases due to the existence of residual Si{sub 3}N{sub 4} phase. - Highlights: • Addition of Si{sub 3}N{sub 4} can increase the emission intensity of YAG:Ce up to 2.5 times. • Increase in the Ce{sup 3+}/Ce{sup 4+} ratio and the number of Ce-N bonds improve the emission. • The tendency to bond with nitrogen ion for cations in YAG:Ce is (Y, Ce) > Si > Al. • The incomplete dissolution

Fabrication and characterization of Al{sub 2}O{sub 3} /Si composite nanodome structures for high efficiency crystalline Si thin film solar cells

Energy Technology Data Exchange (ETDEWEB)

Zhang, Ruiying, E-mail: ryzhang2008@sinano.ac.cn [Key lab of nanodevices and applications, Chinese Academy of Sciences, Division of nano-devices and related materials, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou, 215123 (China); State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai 200050 China (China); Zhu, Jian; Zhang, Zhen; Wang, Yanyan; Qiu, Bocang [Key lab of nanodevices and applications, Chinese Academy of Sciences, Division of nano-devices and related materials, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou, 215123 (China); Liu, Xuehua; Zhang, Jinping; Zhang, Yi [Platform for Characterization & Test, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou, 215123 (China); Fang, Qi; Ren, Zhong [Oxford Instruments Plasma Technology, Yatton, Bristol, BS49 4AP (United Kingdom); Bai, Yu [School of Nano-Science and Nano-Engineering, Xi’an Jiaotong University, Suzhou, 215123 (China)

2015-12-15

We report on our fabrication and characterization of Al{sub 2}O{sub 3}/Si composite nanodome (CND) structures, which is composed of Si nanodome structures with a conformal cladding Al{sub 2}O{sub 3} layer to evaluate its optical and electrical performance when it is applied to thin film solar cells. It has been observed that by application of Al{sub 2}O{sub 3}thin film coating using atomic layer deposition (ALD) to the Si nanodome structures, both optical and electrical performances are greatly improved. The reflectivity of less than 3% over the wavelength range of from 200 nm to 2000 nm at an incident angle from 0° to 45° is achieved when the Al{sub 2}O{sub 3} film is 90 nm thick. The ultimate efficiency of around 27% is obtained on the CND textured 2 μm-thick Si solar cells, which is compared to the efficiency of around 25.75% and 15% for the 2 μm-thick Si nanodome surface-decorated and planar samples respectively. Electrical characterization was made by using CND-decorated MOS devices to measure device’s leakage current and capacitance dispersion. It is found the electrical performance is sensitive to the thickness of the Al{sub 2}O{sub 3} film, and the performance is remarkably improved when the dielectric layer thickness is 90 nm thick. The leakage current, which is less than 4x10{sup −9} A/cm{sup 2} over voltage range of from -3 V to 3 V, is reduced by several orders of magnitude. C-V measurements also shows as small as 0.3% of variation in the capacitance over the frequency range from 10 kHz to 500 kHz, which is a strong indication of surface states being fully passivated. TEM examination of CND-decorated samples also reveals the occurrence of SiO{sub x} layer formed between the interface of Si and the Al{sub 2}O{sub 3} film, which is thin enough that ensures the presence of field-effect passivation, From our theoretical and experimental study, we believe Al{sub 2}O{sub 3} coated CND structures is a truly viable approach to achieving higher device

Diffusion of Ag, Au and Cs implants in MAX phase Ti{sub 3}SiC{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Jiang, Weilin, E-mail: weilin.jiang@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA (United States); Henager, Charles H.; Varga, Tamas; Jung, Hee Joon; Overman, Nicole R. [Pacific Northwest National Laboratory, Richland, WA (United States); Zhang, Chonghong; Gou, Jie [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China)

2015-07-15

MAX phases (M: early transition metal; A: elements in group 13 or 14; X: C or N), such as titanium silicon carbide (Ti{sub 3}SiC{sub 2}), have a unique combination of both metallic and ceramic properties, which make them attractive for potential nuclear applications. Ti{sub 3}SiC{sub 2} has been considered as a possible fuel cladding material. This study reports on the diffusivities of fission product surrogates (Ag and Cs) and a noble metal Au (with diffusion behavior similar to Ag) in this ternary compound at elevated temperatures, as well as in dual-phase nanocomposite of Ti{sub 3}SiC{sub 2}/3C-SiC and polycrystalline CVD 3C-SiC for behavior comparisons. Samples were implanted with Ag, Au or Cs ions and characterized with various methods, including X-ray diffraction, electron backscatter diffraction, energy dispersive X-ray spectroscopy, Rutherford backscattering spectrometry, helium ion microscopy, and transmission electron microscopy. The results show that in contrast to immobile Ag in 3C-SiC, there is a significant outward diffusion of Ag in Ti{sub 3}SiC{sub 2} within the dual-phase nanocomposite during Ag ion implantation at 873 K. Similar behavior of Au in polycrystalline Ti{sub 3}SiC{sub 2} was also observed. Cs out-diffusion and release from Ti{sub 3}SiC{sub 2} occurred during post-implantation thermal annealing at 973 K. This study suggests caution and further studies in consideration of Ti{sub 3}SiC{sub 2} as a fuel cladding material for advanced nuclear reactors operating at very high temperatures.

Structure and physical properties of Cr_5B_3-type Ta_5Si_3 and Ta_5Ge_3

International Nuclear Information System (INIS)

Yuan, Fang; Forbes, Scott; Ramachandran, Krishna Kumar; Mozharivskyj, Yurij

2015-01-01

The Cr_5B_3-type Ta_5Si_3 phase was prepared by arc-melting, while the Cr_5B_3-type Ta_5Ge_3 one was synthesized through sintering at 1000 °C. X-ray single crystal diffraction was employed to elucidate their structure. According to the magnetization measurements, both Ta_5Si_3 and Ta_5Ge_3 are Pauli paramagnets, with Ta_5Ge_3 showing a Curie-Weiss-like paramagnetic behavior at low temperatures likely due to presence of paramagnetic impurity. Both Ta_5Si_3 and Ta_5Ge_3 display a very low electrical resistivity from 2 to 300 K. The resistivity is constant below 20 K, but displays a positive temperature coefficient above 20 K. Electronic structure calculations with the TB-LMTO-ASA method support the metallic character of the two phases and suggest that the bonding is optimized in both phases. - Highlights: • Synthesis of Cr_5B_3-type Ta_5Si_3 and Ta_5Ge_3 phases with high purity by arc-melting and sintering, respectively. • Magnetization data and electrical resistivity of the Cr_5B_3-type Ta_5Si_3 and Ta_5Ge_3 phases. • Crystal and electronic structure analysis for Ta_5Si_3 and Ta_5Ge_3 phase by X-ray diffraction and TB-LMTO-ASA calculations.

Structure-Dependent Spectroscopic Properties of Yb3+-Doped Phosphosilicate Glasses Modified by SiO2

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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.

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