Nano-structure formation of Fe-Pt perpendicular magnetic recording media co-deposited with MgO, Al2O3 and SiO2 additives

International Nuclear Information System (INIS)

Safran, G.; Suzuki, T.; Ouchi, K.; Barna, P.B.; Radnoczi, G.

2006-01-01

Perpendicular magnetic recording media samples were prepared by sputter deposition on sapphire with a layer sequence of MgO seed-layer/Cr under-layer/FeSi soft magnetic under-layer/MgO intermediate layer/FePt-oxide recording layer. The effects of MgO, Al 2 O 3 and SiO 2 additives on the morphology and orientation of the FePt layer were investigated by transmission electron microscopy. The samples exhibited (001) orientation of the L1 FePt phase with the mutual orientations of sapphire substrate//MgO(100)[001]//Cr(100)[11-bar0]//FeSi(100)[11-bar0]//MgO(100) [001]//FePt(001)[100]. The morphology of the FePt films varied due to the co-deposited oxides: The FePt layers were continuous and segmented by stacking faults aligned at 54 o to the surface. Films with SiO 2 addition, beside the oriented columnar FePt grains, exhibited a fraction of misoriented crystallites due to random repeated nucleation. Al 2 O 3 addition resulted in a layered structure, i.e. an initial continuous epitaxial FePt layer covered by a secondary layer of FePt-Al 2 O 3 composite. Both components (FePt and MgO) of the MgO-added samples were grown epitaxially on the MgO intermediate layer, so that a nano-composite of intercalated (001) FePt and (001) MgO was formed. The revealed microstructures and formation mechanisms may facilitate the improvement of the structural and magnetic properties of the FePt-oxide composite perpendicular magnetic recording media

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

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

2018-04-01

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

Composition and crystallization kinetics of R2O-Al2O3-SiO2 glass-ceramics

International Nuclear Information System (INIS)

Xiong, Dehua; Cheng, Jinshu; Li, Hong

2010-01-01

The crystallization behavior and microstructure of R 2 O-Al 2 O 3 -SiO 2 (R means K, Na and Li) glass were investigated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallization kinetic parameters including the crystallization apparent activation energy (E a ), the Avrami parameter (n), glass transition temperature (T g ) and the activity energy of glass transition (E t ) were also measured with different methods. The results have shown that: the DSC traces of composition A parent glass have two different precipitation crystallization peaks corresponding to E a1 (A) = 151.4 kJ/mol (Li 2 SiO 3 ) and E a2 (A) = 623.1 kJ/mol (Li 2 Si 2 O 5 ), the average value of n = 1.70 (Li 2 Si 2 O 5 ) for the surface crystallization and E t (A) = 202.8 kJ/mol. And E a (B) = 50.7 kJ/mol (Li 2 SiO 3 ), the average value of n = 3.89 (Li 2 SiO 3 ) for the bulk crystallization and E t (B) = 220.4 kJ/mol for the composition B parent glass. Because of the content of R 2 O is bigger than composition A, composition B parent glass has a lower E a , T g and a larger n, E t .

Moessbauer studies of magnetic Fe2O3/SiO2 nanocomposite

International Nuclear Information System (INIS)

Lancok, A.; Zaveta, K.; Savii, C.; Barcova, K.

2006-01-01

Fe 2 O 3 /SiO 2 magnetic nanocomposites rich in Fe 2 O 3 have been obtained by annealing at 1000 grad C the xerogel samples, prepared under various conditions. The target concentrations of iron oxide in inert matrix were 20% and 30%. As mesoporous matrices both silica and polyvinyl alcohol - silica hybrid ones were used. The xerogel nanocomposite samples were obtained in situ and by impregnation under ultrasonic activation. All obtained samples were annealed under moderate oxidation conditions (air) and inert atmosphere such as vacuum or nitrogen. Moessbauer spectra were obtained using a conventional Moessbauer spectrometer with a 57 Co/Rh source and constant acceleration. Velocity calibration was done using α-iron, and the Moessbauer parameters are given relative to this standard at room temperature. The Moessbauer spectra contained the sextets of ε-Fe 2 O 3 , hematite, and superparamagnetic component. The content of various phases in the samples depends on the conditions of preparation. In one of the samples also magnetite was present. The ranges of the ε-Fe 2 O 3 area of the samples are 39-76%. The hematite phase is only residual, after transformation due to heat treatment. (authors)

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

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Chenyang Xue

2013-01-01

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

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

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

2016-08-01

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

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Nuryono Nuryono

2016-08-01

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

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

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Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2014-01-01

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

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

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Chao Li

2016-01-01

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Synthesis of Fe3O4@SiO2@OSi(CH2)3NHRN(CH2PPh2)2PdCl2 type nanocomposite complexes: Highly efficient and magnetically-recoverable catalysts in vitamin K3 synthesis.

Science.gov (United States)

Uruş, Serhan

2016-12-15

The synthesis of aminomethylphosphine-metal complexes have opened a new perspective to the catalytic applications of organic compounds. Magnetic Fe3O4 nano-core was synthesized using the closed quartz tube with Teflon cover and microwaved 200°C for 1h with power controlled instrument set to max. 600W. Novel nano-composite supported; Fe3O4@SiO2(CH2)3NHArN(CH2PPh2)2 and Fe3O4@SiO2(CH2)3N(CH2PPh2)2 type bis(diphenylphosphinomethyl)amino ligands and their Pd(II) complexes have been synthesized and characterized with FT-IR, SEM, EDX, TEM, UV-Visible, XRD and TG/DTA techniques. All the complexes were used as heterogeneous catalysts in the oxidation of 2-methyl naphthalene (2MN) to 2-methyl-1, 4-naphthoquinone (vitamin K3, menadione, 2MNQ) in the presence of hydrogen peroxide and acetic acid. Selectivity reached about 55-60% with a conversion of 90-96% using the nano-magnetite supported aminomethylphosphine-Pd(II) complexes. The complexes were very active in three times in the catalytic recycling experiments in five catalytic cycles. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

International Nuclear Information System (INIS)

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

2007-01-01

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

High performance GaN-based LEDs on patterned sapphire substrate with patterned composite SiO2/Al2O3 passivation layers and TiO2/Al2O3 DBR backside reflector.

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Guo, Hao; Zhang, Xiong; Chen, Hongjun; Zhang, Peiyuan; Liu, Honggang; Chang, Hudong; Zhao, Wei; Liao, Qinghua; Cui, Yiping

2013-09-09

GaN-based light-emitting diodes (LEDs) on patterned sapphire substrate (PSS) with patterned composite SiO(2)/Al(2)O(3) passivation layers and TiO(2)/Al(2)O(3) distributed Bragg reflector (DBR) backside reflector have been proposed and fabricated. Highly passivated Al(2)O(3) layer deposited on indium tin oxide (ITO) layer with excellent uniformity and quality has been achieved with atomic layer deposition (ALD) technology. With a 60 mA current injection, an enhancement of 21.6%, 59.7%, and 63.4% in the light output power (LOP) at 460 nm wavelength was realized for the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layers, the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layers and Ag mirror + 3-pair TiO(2)/SiO(2) DBR backside reflector, and the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layer and Ag mirror + 3-pair ALD-grown TiO(2)/Al(2)O(3) DBR backside reflector as compared with the conventional LED only with a single SiO(2) passivation layer, respectively.

Synthesis of Y2O3-ZrO2-SiO2 composite coatings on carbon fiber reinforced resin matrix composite by an electro-plasma process

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Zhang, Yuping; Lin, Xiang; Chen, Weiwei; Cheng, Huanwu; Wang, Lu

2016-05-01

In the present paper the Y2O3-ZrO2-SiO2 composite coating was successfully synthesized on carbon fiber reinforced resin matrix composite by an electro-plasma process. The deposition process, microstructures and oxidation resistance of the coatings with different SiO2 concentrations were systematically investigated. A relatively dense microstructure was observed for the Y2O3-ZrO2-SiO2 composite coating with the SiO2 concentration above 5 g/L. The coating exhibited very good oxidation resistance at 1273 K with the mass loss rate as low as ∼30 wt.%, compared to 100 wt.% of the substrate. The formation of the ceramic composites was discussed in detail based on the electrochemical mechanism and the deposition dynamics in order to explain the effect of the plasma discharge. We believe that the electro-plasma process will find wide applications in preparing ceramics and coatings in industries.

Physicochemical characterization of Fe3O4/SiO2/Au multilayer nanostructure

International Nuclear Information System (INIS)

Khosroshahi, Mohammad E.; Ghazanfari, Lida

2012-01-01

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

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

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

2017-10-01

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

The photodeposition of surface plasmon Ag metal on SiO2@α-Fe2O3 nanocomposites sphere for enhancement of the photo-Fenton behavior

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Uma, Kasimayan; Arjun, Nadarajan; Pan, Guan-Ting; Yang, Thomas C.-K.

2017-12-01

In this study, a simple sol-gel method was used for the synthesis of a core-shell structure of SiO2@α-Fe2O3 nanocomposites for employment as a visible light photocatalyst. It was observed that Ag nanoparticles about 20 nm in size were successfully deposited on the surface of the SiO2@α-Fe2O3 nanocomposites. The photocatalytic activity of the Ag-SiO2@α-Fe2O3 nanocomposites catalyst was investigated by observing the degradation of methylene blue (MB) dye in a photo-Fenton process. The results showed that the Ag nanoparticles acted as centers for photo induced electron transfer. The catalytic activity in the SiO2@α-Fe2O3 nanocomposites were enhanced due to the plasmoni c effect of Ag metal under visible light irradiation. The addition of H2O2 played an important role, generating more OH radicals which improved the photo-Fenton catalytic activity, resulting in quicker degradation of the MB dye using the Ag-SiO2@α-Fe2O3 nanocomposite catalyst.

Crystallization kinetics of BaO-Al2O3-SiO2 glasses

Science.gov (United States)

Bansal, Narottam P.; Hyatt, Mark J.

1989-01-01

Barium aluminosilicate glasses are being investigated as matrix materials in high-temperature ceramic composites for structural applications. Kinetics of crystallization of two refractory glass compositions in the barium aluminosilicate system were studied by differential thermal analysis (DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). From variable heating rate DTA, the crystallization activation energies for glass compositions (wt percent) 10BaO-38Al2O3-51SiO2-1MoO3 (glass A) and 39BaO-25Al2O3-35SiO2-1MoO3 (glass B) were determined to be 553 and 558 kJ/mol, respectively. On thermal treatment, the crystalline phases in glasses A and B were identified as mullite (3Al2O3-2SiO2) and hexacelsian (BaO-Al2O3-2SiO2), respectively. Hexacelsian is a high-temperature polymorph which is metastable below 1590 C. It undergoes structural transformation into the orthorhombic form at approximately 300 C accompanied by a large volume change which is undesirable for structural applications. A process needs to be developed where stable monoclinic celsian, rather than hexacelsian, precipitates out as the crystal phase in glass B.

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

Science.gov (United States)

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

Melts in the Deep Earth: Calculating the Densities of CaO-FeO-MgO-Al2O3-SiO2 Liquids

Science.gov (United States)

Thomas, C.; Guo, X.; Agee, C. B.; Asimow, P. D.; Lange, R. A.

2012-12-01

We present new equation of state (EOS) measurements for hedenbergite (Hd, CaFeSi2O6) and forsterite (Fo, Mg2SiO4) liquids. These liquid EOS add to the basis set in the CaO-FeO-MgO-Al2O3-SiO2 (CMASF) oxide space at elevated temperatures and pressures; other liquids include: enstatite (En, MgSiO3), anorthite (An, CaAl2Si2O8), diopside (Di, CaMgSi2O6), and fayalite (Fa, Fe2SiO4). The Hd EOS measurement was a multi-technique collaboration using 1-atm double-bob Archimedean, ultrasonic, sink/float, and shock wave techniques. Un-weighted linear fitting of the shock data in shock velocity (US)-particle velocity (up) space defines a pre-heated (1400 °C) Hugoniot US = 2.628(0.024) + 1.54(0.01)up km/s. The slope corresponds to a K' of 5.16(0.04), consistent with piston-cylinder and multi-anvil sink/float experiments. The intercept is fixed at the ultrasonic sound speed (Co) since the unconstrained intercept is within the stated error. This behavior demonstrates consistency across methods and that the liquid is relaxed during shock compression. Shock compression of pre-heated (2000°C) single crystal Fo gives an un-weighted linear Hugoniot of US = 2.674(0.188) + 1.64(0.06)up km/s. The unconstrained Co falls below estimates based on extrapolation in both temperature and composition from two published partial molar sound speed models, 3.195m/s [1] and 3.126 m/s [2]. The shock-derived Co indicates that dC/dT is negative for Fo liquid, contrary to the positive [1] and zero [2] temperature dependences derived over relatively narrow temperature intervals. CMASF liquid isentropes were calculated using five end-members (En, Fo, Fa, An, Di). For modeling crystallization of a fictive magma ocean, we examined two liquids: peridotite [3] (P=.33En+.56Fo+.07Fa+.03An+.007Di) and simplified chondrite [4] (Ch=.62En+.24Fo+.08Fa+.04An+.02Di). Each end-member is defined by a 3rd or 4th order Birch-Murnaghan isentrope, Mie-Grüneisen thermal pressure and a constant heat capacity. The volumes are

Dependence of Photocatalytic Activity of TiO2-SiO2 Nanopowders

Directory of Open Access Journals (Sweden)

M. Riazian

2014-10-01

Full Text Available Structural properties and chemical composition change the photocatalytic activity in TiO2-SiO2 nanopowder composite. The SiO2-TiO2 nanostructure is synthesized based on sol–gel method. The nanoparticles are characterized by x-ray fluorescents (XRF, x- ray diffraction (XRD, tunneling electron microscopy (TEM, field emission scanning electron microscopy (FE-SEM, UV-vis. Spectrophotometer and furrier transmission create infrared absorption (FTIR techniques. The rate constant k for the degradation of methylen blue in its aqueous solution under UV irradiation is determined as a measure of photocatalytic activity. Dependence between photocatalytic activity and SiO2 content in the composite is determined. Rate constant k is found dependent on the content of SiO2 in the composite that calcined at 900 oC. The addition of low composition SiO2 to the TiO2 matrix (lower than 45% enhances the photocatalytic activity due to thermal stability and increasing in the surface area. The effects of chemical compositions on the surface topography and the crystallization of phases are studied.

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

Science.gov (United States)

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

2018-04-01

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

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

Directory of Open Access Journals (Sweden)

Mostafa Karimkoshteh

2016-01-01

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

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

Science.gov (United States)

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

2017-11-01

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

Nanotextured Spikes of α-Fe2O3/NiFe2O4 Composite for Efficient Photoelectrochemical Oxidation of Water.

Science.gov (United States)

Hussain, Shabeeb; Tavakoli, Mohammad Mahdi; Waleed, Aashir; Virk, Umar Siddique; Yang, Shihe; Waseem, Amir; Fan, Zhiyong; Nadeem, Muhammad Arif

2018-03-27

We demonstrate for the first time the application of p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin films as anode materials for light-assisted electrolysis of water. The p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin films were deposited on planar fluorinated tin oxide (FTO)-coated glass as well as on 3D array of nanospike (NSP) substrates. The effect of substrate (planar FTO and 3D-NSP) and percentage change of each component (i.e., NiFe 2 O 4 and Fe 2 O 3 ) of composite was studied on photoelectrochemical (PEC) water oxidation reaction. This work also includes the performance comparison of p-NiFe 2 O 4 /n-Fe 2 O 3 composite (planar and NSP) devices with pure hematite for PEC water oxidation. Overall, the nanostructured p-NiFe 2 O 4 /n-Fe 2 O 3 device with equal molar 1:1 ratio of NiFe 2 O 4 and Fe 2 O 3 was found to be highly efficient for PEC water oxidation as compared with pure hematite, 1:2 and 1:3 molar ratios of composite. The photocurrent density of 1:1 composite thin film on planar substrate was equal to 1.07 mA/cm 2 at 1.23 V RHE , which was 1.7 times higher current density as compared with pure hematite device (0.63 mA/cm 2 at 1.23 V RHE ). The performance of p-NiFe 2 O 4 /n-Fe 2 O 3 composites in PEC water oxidation was further enhanced by their deposition over 3D-NSP substrate. The highest photocurrent density of 2.1 mA/cm 2 at 1.23 V RHE was obtained for the 1:1 molar ratio p-NiFe 2 O 4 /n-Fe 2 O 3 composite on NSP (NF1-NSP), which was 3.3 times more photocurrent density than pure hematite. The measured applied bias photon-to-current efficiency (ABPE) value of NF1-NSP (0.206%) was found to be 1.87 times higher than that of NF1-P (0.11%) and 4.7 times higher than that of pure hematite deposited on FTO-coated glass (0.044%). The higher PEC water oxidation activity of p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin film as compared with pure hematite is attributed to the Z-path scheme and better separation of electrons and holes. The increased surface area and greater light

Fe-N co-doped SiO2@TiO2 yolk-shell hollow nanospheres with enhanced visible light photocatalytic degradation

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Wan, Hengcheng; Yao, Weitang; Zhu, Wenkun; Tang, Yi; Ge, Huilin; Shi, Xiaozhong; Duan, Tao

2018-06-01

SiO2@TiO2 yolk@shell hollow nanospheres (STNSs) is considered as an outstanding photocatalyst due to its tunable structure and composition. Based on this point, we present an unprecedentedly excellent photocatalytic property of STNSs toward tannic acid via a Fe-N co-doped strategy. Their morphologies, compositions, structure and properties are characterized. The Fe-N co-doped STNSs formed good hollow yolk@shell structure. The results show that the energy gap of the composites can be downgraded to 2.82 eV (pure TiO2 = 3.2 eV). Photocatalytic degradation of tannic acid (TA, 30 mg L-1) under visible light (380 nm TiO2 nanospheres, non-doped STNSs and N-doped STNSs, the Fe-N co-doped STNSs exhibits the highest activity, which can degrade 99.5% TA into CO2 and H2O in 80 min. The probable degradation mechanism of the composites is simultaneously proposed, the band gap of STNSs becomes narrow by co-doping Fe-N, so that the TiO2 shell can stimulate electrons under visible light exposure, generate the ions of radOH and radO2- with a strong oxidizing property. Therefore this approach works is much desired for radioactive organic wastewater photocatalytic degradation.

First Measurements of Time-Dependent Nucleation as a Function of Composition in Na2O.2CaO.3SiO2 Glasses

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Kelton, K. F.; Narayan, K. Lakshmi

1996-01-01

The first measurements in any system of the composition dependence of the time-dependent nucleation rate are presented Nucleation rates of the stoichiometric crystalline phase, Na2O.2CaO.3SiO2, from quenched glasses made with different SiO2 concentrations were determined as a function of temperature and glass composition. A strong compositional dependence of the nucleation rates and a weak dependence for the induction times are observed. Using measured values of the liquidus temperatures and growth velocities as a function of glass composition, these data are shown to be consistent with predictions from the classical theory of nucleation, assuming a composition-dependent interfacial energy.

Stabilization/Solidification of Radioactive LiCl-KCl Waste Salt by Using SiO2-Al2O3-P2O5(SAP) Inorganic Composite: Part 2. The Effect of SAP Composition on Stabilization/Solidification

International Nuclear Information System (INIS)

Ahn, Soo Na; Park, Hwan Seo; Cho, In Hak; Kim, In Tae; Cho, Yong Zun

2012-01-01

Metal chloride waste is generated as a main waste streams in a series of electrolytic processes of a pyrochemical process. Different from carbonate or nitrate salt, metal chloride is not decomposed into oxide and chlorine but it is just vaporized. Also, it has low compatibility with conventional silicate glasses. Our research group adapted the dechlorination approach for the immobilization of waste salt. In this study, the composition of SAP (SiO 2 -Al 2 O 3 -P 2 O 5 ) was adjusted to enhance the reactivity and to simplify the solidification process as a subsequent research. The addition of Fe 2 O 3 into the basic SAP decreased the SAP/Salt ratio in weight from 3 for SAP 1071 to 2.25 for M-SAP(Fe=0.1). The experimental results indicated that the addition of Fe 2 O 3 increased the reactivity of M-SAP with LiCl-KCl but the reactivity gradually decreased above Fe=0.1. Also, introducing B 2 O 3 into M-SAP requires no glass binder for the consolidation of reaction products. U-SAP (SiO 2 -Al 2 O 3 -P 2 O 5 ) could effectively dechlorinate the LiCl-KCl waste and its reaction product could be consolidated as a monolithic form without a glass binder. The leaching test result indicated that U-SAP 1071 was more durable than other SAPs wasteform. By using U-SAP, 1 g of waste salt could generated 3 - 4 g of wasteform for final disposal. The final volume would be about 3 - 4 times lower than the glass-bonded sodalite. From these results, it could be concluded that the dechlorination approach using U-SAP would be one of prospective methods to manage the volatile waste salt.

Crack-resistant Al2O3-SiO2 glasses.

Science.gov (United States)

Rosales-Sosa, Gustavo A; Masuno, Atsunobu; Higo, Yuji; Inoue, Hiroyuki

2016-04-07

Obtaining "hard" and "crack-resistant" glasses have always been of great important in glass science and glass technology. However, in most commercial glasses both properties are not compatible. In this work, colorless and transparent xAl2O3-(100-x)SiO2 glasses (30 ≤ x ≤ 60) were fabricated by the aerodynamic levitation technique. The elastic moduli and Vickers hardness monotonically increased with an increase in the atomic packing density as the Al2O3 content increased. Although a higher atomic packing density generally enhances crack formation in conventional oxide glasses, the indentation cracking resistance increased by approximately seven times with an increase in atomic packing density in binary Al2O3-SiO2 glasses. In particular, the composition of 60Al2O3 • 40SiO2 glass, which is identical to that of mullite, has extraordinary high cracking resistance with high elastic moduli and Vickers hardness. The results indicate that there exist aluminosilicate compositions that can produce hard and damage-tolerant glasses.

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

Science.gov (United States)

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

2017-06-15

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

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

Science.gov (United States)

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

2011-02-01

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

Nonstoichiometric Zn Ferrite and ZnFe2O4/Fe2O3 Composite Spheres: Preparation, Magnetic Properties, and Chromium Removal

Science.gov (United States)

Hang, Chun-Liang; Yang, Li-Xia; Sun, Chang-Mei; Liang, Ying

2018-03-01

Monodisperse and porous nonstoichiometric Zn ferrite can be prepared by a solvothermal method. Such non-Zn ferrite was used to be the precursor for synthesis of ZnFe2O4/Fe2O3 composite via calcination at 600°C for 3 h in air. X-ray powder diffractometer (XRD) and Energy Dispersive Spectrometer (EDS) proved the nonstoichiometry of Zn ferrite synthesized by solvothermal method and the formation of ZnFe2O4/Fe2O3 composite via calcination. TEM image showed that non-Zn ferrite spheres with wormlike nanopore structure were made of primary nanocrystals. BET surface area of non-Zn ferrite was much higher than that of ZnFe2O4/Fe2O3 composite. Saturation magnetization of non-Zn ferrites was significantly higher than that of ZnFe2O4/Fe2O3 composites. Calcination of non-Zn ferrite resulted in the formation of large amount of non-magnetic Fe2O3,which caused a low magnetization of composite. Because of higher BET surface area and higher saturation magnetization, non-Zn ferrite presented better Cr6+ adsorption property than ZnFe2O4/Fe2O3 composites.

CHARACTERIZATION OF COMMERCIALLY AVAILABLE ALKALI RESISTANT GLASS FIBER FOR CONCRETE REINFORCEMENT AND CHEMICAL DURABILITY COMPARISON WITH SrO-Mn2O3-Fe2O3-MgO-ZrO2-SiO2 (SMFMZS SYSTEM GLASSES

Directory of Open Access Journals (Sweden)

Göktuğ GÜNKAYA

2012-12-01

Full Text Available According to the relevant literature, the utilization of different kind of glass fibers in concrete introduces positive effect on the mechanical behavior, especially toughness. There are many glassfibers available to reinforce concretes. Glass fiber composition is so important because it may change the properties such as strength, elastic modulus and alkali resistance. Its most important property to be used in concrete is the alkali resistance. Some glasses of SrO–MgO–ZrO2–SiO2 (SMZS quaternary system, such as 26SrO, 20MgO, 14ZrO2, 40SiO2 (Zrn glass, have been found to be highly alkali resistant thanks to their high ZrO2 and MgO contents. Previous researches on these glasses with MnO and/or Fe2O3 partially replacing SrO have been made with the aim of improving the chemical resistance and decreasing the production cost.The main target of the present study, first of all, was to characterize commercially available alkali resistant glass fiber for concrete reinforcement and then to compare its alkali durability with those of the SrO-Mn2O3-Fe2O3-MgO-ZrO2-SiO2 (SMFMZS system glasses. For such purposes, XRF, Tg-DTA, alkali resistance tests and SEM analysis conducted with EDX were employed. According tothe alkali endurance test results it was revealed that some of the SMFMZS system glass powders are 10 times resistant to alkali environments than the commercial glass fibers used in this study.Therefore, they can be considered as alternative filling materials on the evolution of chemically resistant concrete structures.

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

Science.gov (United States)

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

2017-12-01

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

Photoluminescence of the Mg2Al4Si5O18-Al2O3-MgAl2O4-SiO2 ceramic system containing Fe3+ and Cr3+ as impurity ions

Science.gov (United States)

Sosman, L. P.; López, A.; Pedro, S. S.; Papa, A. R. R.

2018-02-01

This work presents the results of photoluminescence, excitation and radiative decay time for a ceramic system containing Mg2Al4Si5O18-Al2O3-MgAl2O4-SiO2 with Fe3+ and Cr3+ as impurity ions. Emission data were obtained using several excitation wavelengths and the excitation data were acquired for the most intense emission bands. The optical results were analyzed according to the Tanabe-Sugano (TS) theory from which the crystalline field parameter Dq and Racah parameters B and C were obtained for the Fe3+ and Cr3+ sites. The results indicate that the Fe3+ and Cr3+ ions occupy tetrahedral and octahedral sites, respectively. The emission from Fe3+ and Cr3+ ions causes an intense and broad band ranging between 350 nm and 850 nm, showing that this material is a potential tunable radiation source at room temperature.

Effect of Fe{sub 2}O{sub 3} in Fe{sub 2}O{sub 3}/AP composite particles on thermal decomposition of AP and on burning rate of the composite propellant

Energy Technology Data Exchange (ETDEWEB)

Ma, Zhenye [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing, 210094 (China); Nanjing University of Technology, Nanjing (China); Li, Fengsheng; Bai, Huaping [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing, 210094 (China)

2006-12-15

A technique of composite processing of Fe{sub 2}O{sub 3} and ammonium perchlorate (AP) was employed in making the propellant. The effects of composite processing of Fe{sub 2}O{sub 3} on catalytic activity, on the thermal decomposition of AP, and on the burning rate of the composite propellant were investigated in this paper. Fe{sub 2}O{sub 3}/AP composite particles were prepared by a novel solvent-nonsolvent method. The results show that AP is successfully coated on the surface of Fe{sub 2}O{sub 3}. Composite processing of Fe{sub 2}O{sub 3} and AP can improve the catalytic activity of Fe{sub 2}O{sub 3}. Fe{sub 2}O{sub 3} exhibits better catalytic effect with increasing Fe{sub 2}O{sub 3} content. The larger interface between Fe{sub 2}O{sub 3} and AP and lower density of composite propellant (with the added Fe{sub 2}O{sub 3}/AP composite particles) are responsible for the enhancement of the catalytic activity of Fe{sub 2}O{sub 3}. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

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

Science.gov (United States)

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

2018-04-01

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

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

Science.gov (United States)

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

2013-03-28

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

Influence of SiO2 Addition on Properties of PTFE/TiO2 Microwave Composites

Science.gov (United States)

Yuan, Ying; Wang, Jie; Yao, Minghao; Tang, Bin; Li, Enzhu; Zhang, Shuren

2018-01-01

Composite substrates for microwave circuit applications have been fabricated by filling polytetrafluoroethylene (PTFE) polymer matrix with ceramic powder consisting of rutile TiO2 ( D 50 ≈ 5 μm) partially substituted with fused amorphous SiO2 ( D 50 ≈ 8 μm) with composition x vol.% SiO2 + (50 - x) vol.% TiO2 ( x = 0, 3, 6, 9, 12), and the effects of SiO2 addition on characteristics such as the density, moisture absorption, microwave dielectric properties, and thermal properties systematically investigated. The results show that the filler was well distributed throughout the matrix. High dielectric constant ( ɛ r > 7.19) and extremely low moisture absorption (ceramic particles served as barriers and improved the thermal stability of the PTFE polymer, retarding its decomposition. The temperature coefficient of dielectric constant ( τ ɛ ) of the composites shifted toward the positive direction (from - 309 ppm/°C to - 179 ppm/°C) as the SiO2 content was increased, while the coefficient of thermal expansion remained almost unchanged (˜ 35 ppm/°C).

FeCl3.nano SiO2: An Efficient Heterogeneous Nano Catalyst for the ...

African Journals Online (AJOL)

NICO

2012-05-28

May 28, 2012 ... low cost, ease of preparation, and catalyst recycling.3,4 Among various solid .... FeCl3-SiO2 (np) to produce 1,8-dioxo-octahydro-xanthenes. RESEARCH ..... 38 G. Song, B. Wang, H. Luo and L. Yang, Catal. Commun., 2007, 8 ...

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.

Air Plasma-Sprayed La2Zr2O7-SrZrO3 Composite Thermal Barrier Coating Subjected to CaO-MgO-Al2O3-SiO2 (CMAS)

Science.gov (United States)

Cai, Lili; Ma, Wen; Ma, Bole; Guo, Feng; Chen, Weidong; Dong, Hongying; Shuang, Yingchai

2017-08-01

La2Zr2O7-SrZrO3 composite thermal barrier coatings (TBCs) were prepared by air plasma spray (APS). The La2Zr2O7-SrZrO3 composite TBCs covered with calcium-magnesium-aluminum-silicate (CMAS) powder, as well as the powder mixture of CMAS and spray-dried La2Zr2O7-SrZrO3 composite powder, were heat-treated at 1250 °C in air for 1, 4, 8, and 12 h. The phase constituents and microstructures of the reaction products were characterized by x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. Experimental results showed that the La2Zr2O7-SrZrO3 composite TBCs had higher CMAS resistance than 8YSZ coating. A dense new layer developed between CMAS and La2Zr2O7-SrZrO3 composite TBCs during interaction, and this new layer consisted mostly of apatite (Ca2La8(SiO4)6O2) and c-ZrO2. The newly developed layer effectively protected the La2Zr2O7-SrZrO3 composite TBCs from further CMAS attack.

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.

Enhanced the hydrophobic surface and the photo-activity of TiO2-SiO2 composites

Science.gov (United States)

Wahyuni, S.; Prasetya, A. T.

2017-02-01

The aim of this research is to develop nanomaterials for coating applications. This research studied the effect of various TiO2-SiO2 composites in acrylic paint to enhance the hydrophobic properties of the substrate. Titanium dioxide containing silica in the range 20-35 mol% has been synthesized using sol-gel route. The XRD’s spectra show that increasing SiO2 content in the composite, decreasing its crystalline properties but increasing the surface area. TiO2-SiO2 composite was dispersed in acrylic paint in 2% composition by weight. The largest contact angle was 70, which produced by the substrate coated with TS-35-modified acrylic paint. This study also investigated the enhanced photo-activity of TiO2-SiO2 modified with poly-aniline. The XRD spectra show that the treatment does not change the crystal structure of TiO2. The photo-activity of the composite was evaluated by degradation of Rhodamine-B with visible light. The best performance of the degradation process was handled by the composite treated with 0.1mL anilines per gram of TiO2-SiO2 composite (TSP-A). On the other side, the contact angle 70 has not shown an excellent hydrophobic activity. However, the AFM spectra showed that nanoroughness has started to form on the surface of acrylic paint modified with TiO2-SiO2 than acrylic alone.

Effect of Fe2O3 and Binder on the Electrochemical Properties of Fe2O3/AB (Acetylene Black) Composite Electrodes

Science.gov (United States)

Anh, Trinh Tuan; Thuan, Vu Manh; Thang, Doan Ha; Hang, Bui Thi

2017-06-01

In an effort to find the best anode material for Fe/air batteries, a Fe2O3/AB (Acetylene Black) composite was prepared by dry-type ball milling using Fe2O3 nanoparticles and AB as the active and additive materials, respectively. The effects of various binders and Fe2O3 content on the electrochemical properties of Fe2O3/AB electrodes in alkaline solution were investigated. It was found that the content of Fe2O3 strongly affected the electrochemical behavior of Fe2O3/AB electrodes; with Fe2O3 nanopowder content reaching 70 wt.% for the electrode and showing improvement of the cyclability. When the electrode binder polytetrafluoroethylene (PTFE) was used, clear redox peaks were observed via cyclic voltammetry (CV), while polyvinylidene fluoride-containing electrodes provided CV curves with unobservable redox peaks. Increasing either binder content in the electrode showed a negative effect in terms of the cyclability of the Fe2O3/AB electrode.

Facile synthesis and characterization of ZnFe{sub 2}O{sub 4}/{alpha}-Fe{sub 2}O{sub 3} composite hollow nanospheres

Energy Technology Data Exchange (ETDEWEB)

Shen, Yu [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); School of Environmental and Chemical Engineering, Dalian Jiaotong University, Dalian 116028 (China); Li, Xinyong, E-mail: xyli@dlut.edu.cn [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Department of Chemical Engineering, Curtin University, Perth, WA 6845 (Australia); Zhao, Qidong; Hou, Yang [Key Laboratory of Industrial Ecology and Environmental Engineering and State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024 (China); Tade, Moses [Department of Chemical Engineering, Curtin University, Perth, WA 6845 (Australia); Liu, Shaomin, E-mail: Shaomin.Liu@curtin.edu.au [Department of Chemical Engineering, Curtin University, Perth, WA 6845 (Australia)

2011-12-15

Highlights: Black-Right-Pointing-Pointer ZnFe{sub 2}O{sub 4}/{alpha}-Fe{sub 2}O{sub 3} composite hollow nanospheres were successfully synthesized via a facile method. Black-Right-Pointing-Pointer Detailed structural, morphology and the phase composition were studied. Black-Right-Pointing-Pointer The incorporation of ZnFe{sub 2}O{sub 4} and {alpha}-Fe{sub 2}O{sub 3} gives an appropriate band gap value to utilize solar energy. -- Abstract: ZnFe{sub 2}O{sub 4}/{alpha}-Fe{sub 2}O{sub 3} composite hollow nanospheres were successfully fabricated via a facile one-pot solvothermal method, utilizing polyethylene glycol as soft template. X-ray diffraction and scanning electron microscopy analysis revealed that the prepared nanospheres with cubic spinel and rhombohedra composite structure had a uniform diameter of about 370 nm, and the hollow structure could be further confirmed by transmission electron microscopy. Energy dispersive X-ray, X-ray photoelectron spectroscopy and Fourier transform infrared techniques were also applied to characterize the elemental composition and chemical bonds in the hollow nanospheres. The ZnFe{sub 2}O{sub 4}/{alpha}-Fe{sub 2}O{sub 3} composite hollow nanospheres show attractive light absorption property for potential applications in electronics, optics, and catalysis.

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

Directory of Open Access Journals (Sweden)

В. Судавцова

2012-04-01

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

Synthesis of TiO2-doped SiO2 composite films and its applications

Indian Academy of Sciences (India)

Wintec

structure of the titanium oxide species in the TiO2-doped SiO2 composite films and the photocatalytic reactiv- ity in order to ... gaku D-max γA diffractometer with graphite mono- chromized ... FT–IR absorption spectra of TiO2-doped SiO2 com-.

Microstructure and Transparent Super-Hydrophobic Performance of Vacuum Cold-Sprayed Al2O3 and SiO2 Aerogel Composite Coating

Science.gov (United States)

Li, Jie; Zhang, Yu; Ma, Kai; Pan, Xi-De; Li, Cheng-Xin; Yang, Guan-Jun; Li, Chang-Jiu

2018-02-01

In this study, vacuum cold spraying was used as a simple and fast way to prepare transparent super-hydrophobic coatings. Submicrometer-sized Al2O3 powder modified by 1,1,2,2-tetrahydroperfluorodecyltriethoxysilane and mixed with hydrophobic SiO2 aerogel was employed for the coating deposition. The deposition mechanisms of pure Al2O3 powder and Al2O3-SiO2 mixed powder were examined, and the effects of powder structure on the hydrophobicity and light transmittance of the coatings were evaluated. The results showed that appropriate contents of SiO2 aerogel in the mixed powder could provide sufficient cushioning to the deposition of submicrometer Al2O3 powder during spraying. The prepared composite coating surface showed rough structures with a large number of submicrometer convex deposited particles, characterized by being super-hydrophobic. Also, the transmittance of the obtained coating was higher than 80% in the range of visible light.

Preparation and photocatalytic activity of ZnO/Fe{sub 2}O{sub 3} nanotube composites

Energy Technology Data Exchange (ETDEWEB)

Liu, Yanjun; Sun, Li; Wu, Jiagen; Fang, Ting; Cai, Ran; Wei, Ang, E-mail: wei1177@126.com

2015-04-15

Highlights: • ZnO/Fe{sub 2}O{sub 3} tubular structure was prepared via photochemical deposition at RT. • The composites show a great improvement in photocatalytic characteristics. • The possible reasons of photocatalytic performance of composites were researched. • The formation mechanism of ZnO/Fe{sub 2}O{sub 3} tubular structure was discussed. - Abstract: Fe{sub 2}O{sub 3} nanoparticles were grown on ZnO nanorods (NRs) to form ZnO/Fe{sub 2}O{sub 3} nanotube (NT) composites via photochemical deposition under ultraviolet light irradiation at a room temperature. Fe{sup 3+} ions in the solution preferentially adhere to the metastable Zn-rich (0 0 0 1) polar surfaces in ZnO NRs, which leading to the formation of ZnO/Fe{sub 2}O{sub 3} NTs. ZnO/Fe{sub 2}O{sub 3} NT nanocomposites show a great improvement in photocatalytic characteristics compared with the bare ZnO NRs. It can be inferred that the enhanced photocatalytic performance of ZnO/Fe{sub 2}O{sub 3} is benefit from the synergistic effect of ZnO and Fe{sub 2}O{sub 3} semiconductors.

Magnetic nanoparticles induced dielectric enhancement in (La, Gd)2O3: SiO2 composite systems

Science.gov (United States)

Kao, T. H.; Mukherjee, S.; Yang, H. D.

2013-11-01

Magnetic Gd2O3 and non-magnetic La2O3 nanoparticles (NPs) have been synthesized together with different doping concentrations in SiO2 matrix via sol-gel route calcination at 700 °C and above. Properly annealed NP-glass composite systems show enhancement of dielectric constant and magnetodielectric effect (MDE) near room temperature, depending on superparamagnetic NPs concentrations. From application point of view, the enhancement of dielectric constant along with MDE can be achieved by tuning the NPs size through varying calcination temperature and/or increasing the doping concentration of magnetic rare earth oxide.

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

Science.gov (United States)

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

2018-06-01

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

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

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Zohreh Akbari Jonoosh

2016-09-01

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

Refractories in the Al2O3-ZrO2-SiO2 system

International Nuclear Information System (INIS)

Banerjee, S.P.; Bhadra, A.K.; Sircar, N.R.

1978-01-01

The effect of addition of ZrO 2 in different proportions in the refractories of the Al 2 O 3 -SiO 2 system was studied. The investigation was confined to two broad ranges of compositions incorporating zirconia (15-30 percent and 80-85 percent) in the Al 2 O 3 -ZrO 2 -SiO 2 system. The overall attainment of properties is dependent upon the mode of fabrication and firing, and bears a relationship with the phase assemblages and the relative proportion thereof. Of the different characteristics, the trend of dissociation of zircon has been found to be specially significant vis-a-vis the temperature of firing and thermal shock resistance. Reassociation of the dissociated products has been ascribed to bring forth improved resistance to thermal spalling. The different products developed during this investigation are considered to be very promising which find useful applications in view of the properties attained by them. (auth.)

The influence of SiO2 Addition on 2MgO-Al2O3-3.3P2O5 Glass

DEFF Research Database (Denmark)

Larsen, P.H.; Poulsen, F.W.; Berg, Rolf W.

1999-01-01

2MgO-Al2O3-3.3P2O5 glasses with increasing amounts of SiO2 are considered for sealing applications in Solid Oxide Fuel Cells (SOFC). The change in chemical durability under SOFC anode conditions and the linear thermal expansion is measured as functions of the SiO2 concentration. Raman spectroscopy...... analysis of the glasses reveals no sign of important changes in the glass structure upon SiO2 addition. Some increase in glass durability with SiO2 concentration is reported and its cause is discussed....

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

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Mohammad Ali Ghasemzadeh

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

Viscosity Measurements of "FeO"-SiO2 Slag in Equilibrium with Metallic Fe

Science.gov (United States)

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2013-06-01

The current study delivered the measurements of viscosities in the system "FeO"-SiO2 in equilibrium with metallic Fe in the composition range between 15 and 40 wt pct SiO2. The experiments were carried out in the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C) using a rotational spindle technique. An analysis of the quenched sample by electron probe X-ray microanalysis (EPMA) after the viscosity measurement enables the composition and microstructure of the slag to be directly linked with the viscosity. The current results are compared with available literature data. The significant discrepancies of the viscosity measurements in this system have been clarified. The possible reasons affecting the accuracy of the viscosity measurement have been discussed. The activation energies derived from the experimental data have a sharp increase at about 33 wt pct SiO2, which corresponds to the composition of fayalite (Fe2SiO4). The modified quasi-chemical model was constructed in the system "FeO"-SiO2 to describe the current viscosity data.

Understanding the magnetic behavior of heat treated CaO-P2O5-Na2O-Fe2O3-SiO2 bioactive glass using electron paramagnetic resonance studies

Science.gov (United States)

Shankhwar, Nisha; Kothiyal, G. P.; Srinivasan, A.

2014-09-01

Bioactive glass of composition 41CaO-44SiO2-4P2O5-8Fe2O3-3Na2O has been heat treated in the temperature (TA) range of 750-1150 °C for time periods (tA) ranging from 1 h to 3 h to yield magnetic bioactive glass ceramics (MBCs). X-ray diffraction studies indicate the presence of bone mineral (hydroxyapatite and wollastonite) and magnetic (magnetite and α-hematite) phases in nanocrystalline form in the MBCs. Electron paramagnetic resonance (EPR) study was carried out to understand the variation in saturation magnetization and coercivity of the MBCs with TA and tA. These studies reveal the nature and amount of iron ions present in the MBCs and their interaction in the glassy oxide matrix as a function of annealing parameters. The deterioration in the magnetic properties of the glass heat treated above 1050 °C is attributed to the crystallization of the non-magnetic α-hematite phase. These results are expected to be useful in the application of these MBCs as thermoseeds in hyperthermia treatment of cancer.

Immobilization of glucose oxidase using CoFe2O4/SiO2 nanoparticles as carrier

Science.gov (United States)

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

2011-04-01

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

Dependence of glass-forming ability on starting compositions in Y2O3–Al2O3–SiO2 system

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Yixiang Chen

2011-09-01

Full Text Available The dependence of glass-forming ability on starting compositions in Y2O3–Al2O3–SiO2 (YAS system has been investigated by melting experiment. Transparent YAS glasses have been prepared under the condition of furnace cooling instead of quenching. It is found that, in the YAS ternary phase diagram, the compositions on the Y3Al5O12–SiO2 line and with 52-68 mol% SiO2 have a higher glass-forming ability to produce pure glass. For the compositions with too much or less SiO2 or with Y/Al = 5/3, 1/1, or 1/3, crystallization occurs with the formation of Y3Al5O12, Y2Si2O7, Al6Si2O13, or SiO2. The densities of the YAS glasses increase with decreasing SiO2 contents and increasing Y/Al ratios, and for the samples with Y/Al = 3/5 there is a good linear relationship between the density and SiO2 content.

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

Science.gov (United States)

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

2013-12-01

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

Fabrication of cube-like Fe3O4@SiO2@Ag nanocomposites with high SERS activity and their application in pesticide detection

International Nuclear Information System (INIS)

Li, Lei; Zhao, Aiwu; Wang, Dapeng; Guo, Hongyan; Sun, Henghui; He, Qinye

2016-01-01

The cube-like Fe 3 O 4 @SiO 2 @Ag (FSA) nanocomposites with great SERS activity have been successfully synthesized by a layer-by-layer procedure in this paper. The cube-like Fe 3 O 4 @SiO 2 core–shell structures were prepared via a new route and Ag nanoparticles were introduced onto their surface through a one-pot hydrothermal reaction. By controlling the reaction time, the coverage rate of Ag on the FSA surface could be tuned, and then a series of FSA composites were obtained. The SERS properties of these FSA composites were investigated using p-aminothiophenol (p-ATP) as the probe molecule. It was found that the FSA composites synthesized with a reaction time of 6 h showed the best SERS performance, and the detection limit for p-ATP could reach 1 × 10 −7 M. For practical application, the FSA composites were also used to detect thiram, one of the dithiocarbamate fungicides that has been widely used as a pesticide in agriculture. The detection limit is as low as 1 × 10 −6 M (0.24 ppm), lower than the maximal residue limit of 7 ppm in fruit prescribed by the US Environmental Protection Agency. The resulting substrate with high SERS activity, stability and strong magnetic responsivity makes the FSA composite a perfect choice for practical SERS detection applications.

B2O3/SiO2 substitution effect on structure and properties of Na2O-CaO-SrO-P2O5-SiO2 bioactive glasses from molecular dynamics simulations.

Science.gov (United States)

Ren, Mengguo; Lu, Xiaonan; Deng, Lu; Kuo, Po-Hsuen; Du, Jincheng

2018-05-23

The effect of B2O3/SiO2 substitution in SrO-containing 55S4.3 bioactive glasses on glass structure and properties, such as ionic diffusion and glass transition temperature, was investigated by combining experiments and molecular dynamics simulations with newly developed potentials. Both short-range (such as bond length and bond angle) and medium-range (such as polyhedral connection and ring size distribution) structures were determined as a function of glass composition. The simulation results were used to explain the experimental results for glass properties such as glass transition temperature and bioactivity. The fraction of bridging oxygen increased linearly with increasing B2O3 content, resulting in an increase in overall glass network connectivity. Ion diffusion behavior was found to be sensitive to changes in glass composition and the trend of the change with the level of substitution is also temperature dependent. The differential scanning calorimetry (DSC) results show a decrease in glass transition temperature (Tg) with increasing B2O3 content. This is explained by the increase in ion diffusion coefficient and decrease in ion diffusion energy barrier in glass melts, as suggested by high-temperature range (above Tg) ion diffusion calculations as B2O3/SiO2 substitution increases. In the low-temperature range (below Tg), the Ea for modifier ions increased with B2O3/SiO2 substitution, which can be explained by the increase in glass network connectivity. Vibrational density of states (VDOS) were calculated and show spectral feature changes as a result of the substitution. The change in bioactivity with B2O3/SiO2 substitution is discussed with the change in pH value and release of boric acid into the solution.

Integrated nanophotonic hubs based on ZnO-Tb(OH3/SiO2 nanocomposites

Directory of Open Access Journals (Sweden)

Lin Yu

2011-01-01

Full Text Available Abstract Optical integration is essential for practical application, but it remains unexplored for nanoscale devices. A newly designed nanocomposite based on ZnO semiconductor nanowires and Tb(OH3/SiO2 core/shell nanospheres has been synthesized and studied. The unique sea urchin-type morphology, bright and sharply visible emission bands of lanthanide, and large aspect ratio of ZnO crystalline nanotips make this novel composite an excellent signal receiver, waveguide, and emitter. The multifunctional composite of ZnO nanotips and Tb(OH3/SiO2 nanoparticles therefore can serve as an integrated nanophotonics hub. Moreover, the composite of ZnO nanotips deposited on a Tb(OH3/SiO2 photonic crystal can act as a directional light fountain, in which the confined radiation from Tb ions inside the photonic crystal can be well guided and escape through the ZnO nanotips. Therefore, the output emission arising from Tb ions is truly directional, and its intensity can be greatly enhanced. With highly enhanced lasing emissions in ZnO-Tb(OH3/SiO2 as well as SnO2-Tb(OH3/SiO2 nanocomposites, we demonstrate that our approach is extremely beneficial for the creation of low threshold and high-power nanolaser.

Magnetocapacidad en nanopartículas de Fe3O4 y NiFe2O4

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Mira, J.

2010-02-01

Full Text Available We have synthesized NiFe2O4 (φ∼ 6 nm and Fe3O4 (φ∼ 30 nm magnetic nanoparticles by solvothermal synthesis; furthermore the Fe3O4 nanoparticles have been coated with a SiO2 shell of approximately 5 nm of thickness by the Stöber method. In the study of the dielectric properties as a function of the frequency, temperature and applied magnetic field, we observe a magnetocapacitive behavior (MC at room temperature and under a moderate magnetic field (H=0.5T, that is specially important in the case of the Fe3O4, nanoparticles (MC≈ 6%. On the other hand, the NiFe2O4 and Fe3O4@SiO2 samples present smaller magnetocapacitive effects: MC≈ 2% y MC≈ 1%, respectively. These MC values, that are higher than those reported in the literature for other related magnetic nanoparticles, corroborate the theoretical model proposed by Catalán in which the combination of Maxwell-Wagner effects and magnetoresistance promote the appearance of stronger magnetocapacitive effects.Hemos preparado nanopartículas magnéticas de NiFe2O4 (φ∼ 6 nm y Fe3O4 (φ∼ 30 nm mediante el método de síntesis solvotermal; además estas últimas han sido recubiertas con una capa de SiO2 de unos 5 nm de espesor mediante el método de Stöber. Al estudiar el comportamiento dieléctrico en función de la frecuencia, temperatura y campo magnético aplicado, observamos un comportamiento magnetocapacitivo (MC a temperatura ambiente y bajo un campo magnético moderado (H= 0.5 T que es especialmente importante en el caso de las nanopartículas de Fe3O4 (MC≈ 6%. Por su parte las muestras de NiFe2O4 y Fe3O4@SiO2 presentan efectos magnetocapacitivos menores: MC≈ 2% y MC≈ 1%, respectivamente. Estos valores de MC, que son considerablemente superiores a los descritos hasta el momento para otras nanopartículas magnéticas, corroboran la predicción teórica de Catalán de que la combinación de efecto Maxwell-Wagner con efectos magnetorresitivos potencian la aparición de fen

TiO2-BASED Composite Films for the Photodegradation of Oxytetracycline

Science.gov (United States)

Li, Hui; Guan, Ling-Xiao; Feng, Ji-Jun; Li, Fang; Yao, Ming-Ming

2015-02-01

The spread of the antibiotic oxytetracycline (OTC) has been thought as a threat to the safety of drinking water. In this paper, the photocatalytic activity of the nanocrystalline Fe/Ca co-doped TiO2-SiO2 composite film for the degradation of OTC was studied. The films were characterized by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), N2 adsorption/desorption isotherms, photoluminescence (PL) spectra, and UV-Vis diffraction reflectance absorption spectra (DRS). The FE-SEM results indicated that the Fe/Ca co-doped TiO2-SiO2 film was composed of smaller nanoparticles compared to pure TiO2 or TiO2-SiO2 film. The BET surface area results showed that the specific surface area of the pure TiO2, TiO2-SiO2 and Ca2+/Fe3+ co-doped TiO2-SiO2 is 118.3 m2g-1, 294.3 m2g-1 and 393.7 m2g-1, respectively. The DRS and PL spectra revealed that the Fe/Ca co-doped TiO2-SiO2 film had strong visible light adsorption and diminished electrons/holes recombination. Experimental results showed that the Fe/Ca co-doped TiO2-SiO2 film is effective in the degradation of OTC under both UV and visible light irradiation.

Preparation and encapsulation performance of Al_2O_3-SiO_2-B_2O_3 glass-ceramic for high temperature thermal storage

International Nuclear Information System (INIS)

Li, Ruguang; Zhu, Jiaoqun; Zhou, Weibing; Cheng, Xiaomin; Liu, Fengli

2017-01-01

Highlights: • Al_2O_3-B_2O_3-SiO_2 has good chemical durability, corrosion resistance and dense structure. • The material rarely used in high temperature thermal storage. • The material was prepared and characterized in the paper. - Abstract: In this paper, Al_2O_3-SiO_2-B_2O_3 glass-ceramic was prepared and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), further, the porosity was detected by Archimedes principle, thermo physical properties were investigated by differential scanning calorimeter (DSC), respectively. The phase composition was detected by XRD, and the morphology was observed by SEM. The results indicated that the thermal conductivities of the Al_2O_3-SiO_2-B_2O_3 glass-ceramic were between 1.3 and 1.5 W·(m·K)"−"1, and the material had good thermal stability in the range of 300–900 °C. The porosity and apparent density were increased with the temperature. The porosity of Al_2O_3-SiO_2-B_2O_3 glass-ceramic in ranging from 1.2 to 9.6%, the apparent density were between 2.12 and 2.67 g·cm"−"3, and heat capacities were between 0.64 and 0.79 kJ/(kg·K). All the results indicated that the Al_2O_3-SiO_2-B_2O_3 glass-ceramic can be applied as encapsulation material in high temperature latent thermal energy storage.

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

Science.gov (United States)

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

2015-07-01

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

Fabrication, characterization, and photocatalytic property of α-Fe2O3/graphene oxide composite

International Nuclear Information System (INIS)

Li Hong; Zhao Qidong; Li Xinyong; Zhu Zhengru; Tade, Moses; Liu Shaomin

2013-01-01

Spindle-shaped microstructure of α-Fe 2 O 3 was successfully synthesized by a simple hydrothermal method. The α-Fe 2 O 3 /graphene oxide (GO) composites was prepared using a modified Hummers’ strategy. The properties of the samples were systematically investigated by X-ray powder diffraction (XRD), UV–Vis diffuse reflectance spectrophotometer, transmission electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy (Raman) techniques. GO nanosheets act as supporting materials for anchoring the α-Fe 2 O 3 particles. The average crystallite sizes of the α-Fe 2 O 3 and α-Fe 2 O 3 /GO samples are ca. 27 and 24 nm, respectively. The possible growth of α-Fe 2 O 3 onto GO layers led to a higher absorbance capacity for visible light by α-Fe 2 O 3 /GO than α-Fe 2 O 3 composite. The photocatalytic degradation of toluene over the α-Fe 2 O 3 and α-Fe 2 O 3 /GO samples under xenon-lamp irradiation was comparatively studied by in situ FTIR technique. The results indicate that the α-Fe 2 O 3 /GO sample synthesized exhibited a higher capacity for the degradation of toluene. The composite of α-Fe 2 O 3 /GO could be promisingly applied in photo-driven air purification.

Fabrication, characterization, and photocatalytic property of α-Fe2O3/graphene oxide composite

Science.gov (United States)

Li, Hong; Zhao, Qidong; Li, Xinyong; Zhu, Zhengru; Tade, Moses; Liu, Shaomin

2013-06-01

Spindle-shaped microstructure of α-Fe2O3 was successfully synthesized by a simple hydrothermal method. The α-Fe2O3/graphene oxide (GO) composites was prepared using a modified Hummers' strategy. The properties of the samples were systematically investigated by X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectrophotometer, transmission electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy (Raman) techniques. GO nanosheets act as supporting materials for anchoring the α-Fe2O3 particles. The average crystallite sizes of the α-Fe2O3 and α-Fe2O3/GO samples are ca. 27 and 24 nm, respectively. The possible growth of α-Fe2O3 onto GO layers led to a higher absorbance capacity for visible light by α-Fe2O3/GO than α-Fe2O3 composite. The photocatalytic degradation of toluene over the α-Fe2O3 and α-Fe2O3/GO samples under xenon-lamp irradiation was comparatively studied by in situ FTIR technique. The results indicate that the α-Fe2O3/GO sample synthesized exhibited a higher capacity for the degradation of toluene. The composite of α-Fe2O3/GO could be promisingly applied in photo-driven air purification.

Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

Science.gov (United States)

Xu, J. L.; Xiao, Q. F.; Mei, D. D.; Zhong, Z. C.; Tong, Y. X.; Zheng, Y. F.; Li, L.

2017-03-01

Amorphous SiO2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the "coral reef" like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 μm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO2 and a few amorphous Fe2O3 and Nd2O3. The amorphous SiO2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees.

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

Directory of Open Access Journals (Sweden)

Li T

2015-07-01

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

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

Directory of Open Access Journals (Sweden)

Mike O. Ojemaye

2017-01-01

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

Synthesis of Fe2O3/TiO2 nanorod-nanotube arrays by filling TiO2 nanotubes with Fe

International Nuclear Information System (INIS)

Mohapatra, Susanta K; Banerjee, Subarna; Misra, Mano

2008-01-01

Synthesis of hematite (α-Fe 2 O 3 ) nanostructures on a titania (TiO 2 ) nanotubular template is carried out using a pulsed electrodeposition technique. The TiO 2 nanotubes are prepared by the sonoelectrochemical anodization method and are filled with iron (Fe) by pulsed electrodeposition. The Fe/TiO 2 composite is then annealed in an O 2 atmosphere to convert it to Fe 2 O 3 /TiO 2 nanorod-nanotube arrays. The length of the Fe 2 O 3 inside the TiO 2 nanotubes can be tuned from 50 to 550 nm by changing the deposition time. The composite material is characterized by scanning electron microscopy, transmission electron microscopy and diffuse reflectance ultraviolet-visible studies to confirm the formation of one-dimensional Fe 2 O 3 /TiO 2 nanorod-nanotube arrays. The present approach can be used for designing variable one-dimensional metal oxide heterostructures

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

OpenAIRE

Ziemath, Ervino C.; Aegerter, Michel A.

1994-01-01

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

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

Science.gov (United States)

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

2017-12-01

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

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.

The Partial Molar Volume and Thermal Expansivity of Fe2O3 in Alkali Silicate Liquids: Evidence for the Average Coordination of Fe3+

Science.gov (United States)

Liu, Q.; Lange, R.

2003-12-01

Ferric iron is an important component in magmatic liquids, especially in those formed at subduction zones. Although it has long been known that Fe3+ occurs in four-, five- and six-fold coordination in crystalline compounds, only recently have all three Fe3+ coordination sites been confirmed in silicate glasses utilizing XANES spectroscopy at the Fe K-edge (Farges et al., 2003). Because the density of a magmatic liquid is largely determined by the geometrical packing of its network-forming cations (e.g., Si4+, Al3+, Ti4+, and Fe3+), the capacity of Fe3+ to undergo composition-induced coordination change affects the partial molar volume of the Fe2O3 component, which must be known to calculate how the ferric-ferrous ratio in magmatic liquids changes with pressure. Previous work has shown that the partial molar volume of Fe2O3 (VFe2O3) varies between calcic vs. sodic silicate melts (Mo et al., 1982; Dingwell and Brearley, 1988; Dingwell et al., 1988). The purpose of this study is to extend the data set in order to search for systematic variations in VFe2O3 with melt composition. High temperature (867-1534° C) density measurements were performed on eleven liquids in the Na2O-Fe2O3-FeO-SiO2 (NFS) system and five liquids in the K2O-Fe2O3-FeO-SiO2 (KFS) system using Pt double-bob Archimedean method. The ferric-ferrous ratio in the sodic and potassic liquids at each temperature of density measurement were calculated from the experimentally calibrated models of Lange and Carmichael (1989) and Tangeman et al. (2001) respectively. Compositions range (in mol%) from 4-18 Fe2O3, 0-3 FeO, 12-39 Na2O, 25-37 K2O, and 43-78 SiO2. Our density data are consistent with those of Dingwell et al. (1988) on similar sodic liquids. Our results indicate that for all five KFS liquids and for eight of eleven NFS liquids, the partial molar volume of the Fe2O3 component is a constant (41.57 ñ 0.14 cm3/mol) and exhibits zero thermal expansivity (similar to that for the SiO2 component). This value

Manufacturing and investigation of surface morphology and optical properties of composite thin films reinforced by TiO2, Bi2O3 and SiO2 nanoparticles

Science.gov (United States)

Jarka, Paweł; Tański, Tomasz; Matysiak, Wiktor; Krzemiński, Łukasz; Hajduk, Barbara; Bilewicz, Marcin

2017-12-01

The aim of submitted paper is to present influence of manufacturing parameters on optical properties and surface morphology of composite materials with a polymer matrix reinforced by TiO2 and SiO2 and Bi2O3 nanoparticles. The novelty proposed by the authors is the use of TiO2 and SiO2 and Bi2O3 nanoparticles simultaneously in polymeric matrix. This allows using the combined effect of nanoparticles to a result composite material. The thin films of composite material were prepared by using spin-coating method with various spinning rates from solutions of different concentration of nanoparticles. In order to prepare the spinning solution polymer, Poly(methyl methacrylate) (PMMA) was used as a matrix. The reinforcing phase was the mixture of the nanoparticles of SiO2, TiO2 and B2O3. In order to identify the surface morphology of using thin films and arrangement of the reinforcing phase Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) were used. In order to study the optical properties of the obtained thin films, the thin films of composites was subjected to an ellipsometry analysis. The measurements of absorbance of the obtained materials, from which the value of the band gap width was specified, were carried out using the UV/VIS spectroscopy. The optical properties of obtain composite thin films depend not only on the individual components used, but also on the morphology and the interfacial characteristics. Controlling the participation of three kinds of nanoparticles of different sizes and optical parameters allows to obtaining the most optimal optical properties of nanocomposites and also controlling the deposition parameters allows to obtaining the most optimal surface morphology of nanocomposites.

Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

International Nuclear Information System (INIS)

Xu, J.L.; Xiao, Q.F.; Mei, D.D.; Zhong, Z.C.; Tong, Y.X.; Zheng, Y.F.; Li, L.

2017-01-01

Amorphous SiO 2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the “coral reef” like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 µm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO 2 and a few amorphous Fe 2 O 3 and Nd 2 O 3 . The amorphous SiO 2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees. - Highlights: • Amorphous SiO 2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation. • The coatings presented excellent thermal shock resistance. • The corrosion resistance could be enhanced by one order of magnitude. • The MAO coatings slightly decreased the magnetic properties of the NdFeB samples.

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

Directory of Open Access Journals (Sweden)

Huan Liu

2013-11-01

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

Preparation of TiO2-SiO2 composite photocatalysts for environmental applications

Czech Academy of Sciences Publication Activity Database

Paušová, Š.; Krýsa, J.; Jirkovský, Jaromír; Prevot, V.; Mailhot, G.

2014-01-01

Roč. 89, č. 8 (2014), s. 1129-1135 ISSN 0268-2575 Institutional support: RVO:61388955 Keywords : photocatalysis * TiO2/SiO2 * composite Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.349, year: 2014

TiO2 nanoparticles supported on the Fe3O4@SiO2 nanocomposites: a novel magnetic nanocatalyst for the synthesis of 2-aminothiazoles

International Nuclear Information System (INIS)

Safari, Javad; Abedi-Jazini, Zahra; Zarnegar, Zohre; Sadeghi, Masoud

2015-01-01

Nano TiO 2 supported on the Fe 3 O 4 @SiO 2 nanocomposites is introduced as a novel catalyst for the environmental synthesis of 2-aminothiazoles in PEG-200 as a green medium at room temperature. In this reaction, thiourea and N-bromosuccinimide were reacted with various ketones affording the desired 2-aminothiazole compounds. This green protocol has promising features for the reaction response such as simple procedure, high yields, and the ease of separation of pure product, short reaction time, and convenient manipulation. This catalyst was easily separated by an external magnet, and the recovered catalyst was reused several times without any significant loss of activity.Graphical abstract

Nanocrystal in Er3+-doped SiO2-ZrO2 Planar Waveguide with Yb3+ Sensitizer

International Nuclear Information System (INIS)

Razaki, N. Iznie; Jais, U. Sarah; Abd-Rahman, M. Kamil; Bhaktha, S. N. B.; Chiasera, A.; Ferrari, M.

2010-01-01

Higher doping of Er 3+ in glass ceramic waveguides would cause concentration and pair-induced quenching which lead to inhomogeneous line-width of luminescence spectrum thus reduce output intensity. Concentration quenching can be overcome by introducing ZrO 2 in the glass matrix while co-doping with Yb 3+ which acts as sensitizer would improve the excitation efficiency of Er 3+ . In this study, SiO 2 -ZrO 2 planar waveguides having composition in mol percent of 70SiO 2 -30ZrO 2 doped with Er 3+ and co-doped with Yb 3+ , were prepared via sol-gel route. Narrower and shaper peaks of PL and XRD shows the formation of nanocrystals. Intensity is increase with addition amount of Yb 3+ shows sensitizing effect on Er 3+ .

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

Science.gov (United States)

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

2017-04-01

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

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

International Nuclear Information System (INIS)

Huh, Nam Jung; Yang, Joong Sik

1991-01-01

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

One-step facile hydrothermal synthesis of Fe2O3@LiCoO2 composite as excellent supercapacitor electrode materials

Science.gov (United States)

Gopi, Chandu V. V. Muralee; Somasekha, A.; Reddy, Araveeti Eswar; Kim, Soo-Kyoung; Kim, Hee-Je

2018-03-01

Herein, for the first time, we demonstrate the fabrication of Fe2O3@LiCoO2 hybrid nanostructures on Ni foam substrate by facile one-step hydrothermal technique. Morphological studies reveal that aggregated Fe2O3 nanoflakes anchored on the surface of sphere-like LiCoO2 nanoflakes. Electrochemical studies are used to examine the performance of the supercapacitor electrodes. The composite Fe2O3@LiCoO2 electrode exhibited excellent electrochemical performance than Fe2O3 and LiCoO2 electrodes, such as a low charge transfer resistance, a high specific capacitance of 489 F g-1 at 5 mA cm-2 and an enhanced capacity retention of 108% over 3000 cycles at 15 mA cm-2. The composite Fe2O3@LiCoO2 holds great promise for electrochemical applications due to well-defined hierarchical morphology, synergetic effect of Fe2O3 and LiCoO2, enhanced electrical conductivity, efficient electrolyte penetration and fast electron transfer.

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

Science.gov (United States)

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

2018-04-01

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

INVESTIGATION ON PHYSICAL AND ELECTRICAL PROPERTIES OF THE SiO2-ZnO NANOCOMPOSITE AT DIFFERENT COMPOSITION MIXINGS

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Moh. Sinol

2018-01-01

Full Text Available Physical and electrical properties of The SiO2-ZnO mixing at different compositions were investigated. The experiment used simple mixing method at the sintering temperature 600oC. It was used the composition mixing ratio of SiO2:ZnO ie. 0:10; 7:3; 5:5; 3:7; and 10:0 (%Wt. Based on X-Ray Diffraction (XRD results, it obtained that a new phase in each sample was not formed even though having different diffraction peak. The mixing ratio of SiO2: ZnO nanocomposite (7:3 %wt had the biggest grain size (77,92 nm, the highest dielectric constant (3.00E+05 and the smallest conductivity (0,726549 (Ωm-1. On the other side, the mixing ratio of SiO2: ZnO nanocomposite (5:5 %wt had the smallest grain size (35.42nm, dielectric constant (3.00E+2 and the highest conductivity (25.36729  (Ωm-1. It can be concluded that the difference of composition ratio offered the change on both physical and electrical properties of SiO2-ZnO nanocomposite.

Incorporation of Fe2O3, FeO and Al2O3 in silicate glasses and its effect on their structure and chemical stability

Energy Technology Data Exchange (ETDEWEB)

Van Iseghem, P; De Grave, E; Peters, L; De Batist, R

1983-09-01

Large amounts of the glass intermediates Al2O3, Fe2O3 and FeO are present in the amorphous silicate slags developed at the S.C.K./C.E.N. for the conditioning of Pu contaminated radioactive waste. Strong ambiguity exists in literature about both the structural incorporation and the effect on the chemical stability of Fe2O3 and FeO. The chemical stability and its relationship to the glass structure therefore was investigated for a number of silicate base glasses, taking into consideration the following parameters (the amount of glass modifiers was kept constant at 16 mole %, equimolarly spread over Li2O, K2O, MgO and CaO): 1) Fe2Ox concentrations (x = 2 or 3) varying between 2.5 and 30 mole % (compensated by changes in SiO2 concentration); 2)Equimolar replacement of Fe2Ox by Al2O3 and Fe2Ox in all glasses listed in 1. The structural incorporation of Fe2Ox was investigated by 57 Fe Mossbauer Spectroscopy, the chemical stability by the Soxhlet corrosion test. The sample weight was measured after 14 days of corrosion, after drying and removal of the weakly bounded surface layer.

Fabrication of Nano-CeO2 and Application of Nano-CeO2 in Fe Matrix Composites

International Nuclear Information System (INIS)

Tiebao, W.; Chunxiang, C.; Xiaodong, W.; Guobin, L.

2010-01-01

It is expatiated that nano-CeO2 is fabricated by the direct sedimentation method. The components and particles diameter of nano-CeO2 powders are analyzed by XRD and SEM . The thermodynamic analysis and acting mechanism of nano-CeO2 with Al in Fe matrix composites are researched, which shows that the reaction is generated between CeO2 and Al in the composite, that is, 3CeO2+4Al - 2Al2O3+3[Ce], which obtains Al2O3 and active [Ce] during the sintering process. The active [Ce] can improve the performance of CeO2/Fe matrix composites. The suitable amount of CeO2 is about 0.05% in CeO2/Fe matrix composites. SEM fracture analysis shows that the toughness sockets in nano-CeO2/Fe matrix composites are more than those in no-added nano-CeO2 composites, which can explain that adding nano-CeO2 into Fe matrix composite, the toughness of the composite is improved significantly. Applied nano-CeO2 to Fe matrix diamond saw blades shows that Fe matrix diamond saw blade is sharper and of longer cutting life than that with no-added nano-CeO2.

Dependence of glass-forming ability on starting compositions in Y2O3–Al2O3–SiO2 system

OpenAIRE

Yixiang Chen; Zengchao Yang; Bin He; Guanghua Liu; Jiangtao Li; Liang Wu

2011-01-01

The dependence of glass-forming ability on starting compositions in Y2O3–Al2O3–SiO2 (YAS) system has been investigated by melting experiment. Transparent YAS glasses have been prepared under the condition of furnace cooling instead of quenching. It is found that, in the YAS ternary phase diagram, the compositions on the Y3Al5O12–SiO2 line and with 52-68 mol% SiO2 have a higher glass-forming ability to produce pure glass. For the compositions with too much or less SiO2 or with Y/Al = 5/3, 1/1,...

Heterogeneous Ag-TiO2-SiO2 composite materials as novel catalytic systems for selective epoxidation of cyclohexene by H2O2.

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Xin Wang

Full Text Available TiO2-SiO2 composites were synthesized using cetyl trimethyl ammonium bromide (CTAB as the structure directing template. Self-assembly hexadecyltrimethyl- ammonium bromide TiO2-SiO2/(CTAB were soaked into silver nitrate (AgNO3 aqueous solution. The Ag-TiO2-SiO2(Ag-TS composite were prepared via a precipitation of AgBr in soaking process and its decomposition at calcination stage. Structural characterization of the materials was carried out by various techniques including X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscopy (TEM, N2 adsorption-desorption and ultraviolet visible spectroscopy (UV-Vis. Characterization results revealed that Ag particles were incorporated into hierarchical TiO2-SiO2 without significantly affecting the structures of the supports. Further heating-treatment at 723 K was more favorable for enhancing the stability of the Ag-TS composite. The cyclohexene oxide was the major product in the epoxidation using H2O2 as the oxidant over the Ag-TS catalysts. Besides, the optimum catalytic activity and stability of Ag-TS catalysts were obtained under operational conditions of calcined at 723 K for 2 h, reaction time of 120 min, reaction temperature of 353 K, catalyst amount of 80 mg, aqueous H2O2 (30 wt.% as oxidant and chloroform as solvent. High catalytic activity with conversion rate up to 99.2% of cyclohexene oxide could be obtainable in water-bathing. The catalyst was found to be stable and could be reused three times without significant loss of catalytic activity under the optimized reaction conditions.

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

International Nuclear Information System (INIS)

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

1998-01-01

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

Optical properties of ZrO2, SiO2 and TiO2-SiO2 xerogels and coatings doped with Eu3+ and Eu2+

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Gonçalves Rogéria R.

1999-01-01

Full Text Available Eu3+ doped bulk monoliths and thin films were obtained by sol-gel methods in the ZrO2, SiO2 and SiO2-TiO2 systems. Eu3+ 5D0 ® 7FJ emission and decay time characteristics were measured during the entire experimental preparation route from the initial sol to the final xerogels. The crystalline phases identified were tetragonal ZrO2 and mixtures of rutile and anatase TiO2 at high temperature treatments in bulk samples. Good quality thin films were obtained for all systems by dip-coating optical glasses (Schott BK270. The same spectroscopic features were observed either for the bulk monoliths or the films. By appropriate heat treatments under H2 atmosphere Eu2+ containing samples could be obtained in the SiO2-TiO2 system.

Synthesis and electrochemical characterization of LiCo_1_/_3Fe_2_/_3PO_4/C composite using nano CoFe_2O_4 as precursor

International Nuclear Information System (INIS)

Wu, Kaipeng; Hu, Guorong; Du, Ke; Peng, Zhongdong; Cao, Yanbing

2015-01-01

LiCo_1_/_3Fe_2_/_3PO_4/C composite was synthesized by a solid state method with CoFe_2O_4 as the precursor and glucose as the carbon source. The composite consists of homogeneous Co–Fe distributed LiCo_1_/_3Fe_2_/_3PO_4 with its particles covered by nano-carbon layers, which could prevent the growth of the particles as well as form a fast path for electronic transmission during charging and discharging process. It shows excellent electrochemical performance as the cathode for lithium-ion batteries, which delivers discharge capacities of 154.6, 152.9, 135.4, 122.3, 105.2 and 91.3 mAh g"−"1 at 0.05, 0.1, 0.5, 1, 2 and 5 C, respectively, and retains 94.6% of its initial discharge capacity after 30 cycles at 5 C. - Highlights: • Nano CoFe_2O_4 was prepared by a co-precipitation method. • LiCo_1_/_3Fe_2_/_3PO_4/C composite was synthesized using nano CoFe_2O_4 as a precursor. • Homogeneous Co–Fe distributed LiCo_1_/_3Fe_2_/_3PO_4 is obtained. • LiCo_1_/_3Fe_2_/_3PO_4/C composite exhibits a quite good electrochemical performance.

Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

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Jingbin Yang

2017-06-01

Full Text Available C-A-S-H (CaO-Al2O3-SiO2-H2O and N-A-S-H (Na2O-Al2O3-SiO2-H2O have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na2O/SiO2 ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO2 ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO2 ratio, an excess of Ca(OH2 was observed at room temperature, while in a high-temperature reaction system, katoite, C4AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH2 and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na2O/SiO2 ratio resulted in more non-bridging oxygen and the TO4 was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali

More accurate definition of liquation dome in Na2O-B2O3-SiO2 system

International Nuclear Information System (INIS)

Alekseeva, Z.D.; Mazurin, O.V.; Aver'yanov, V.I.; Galakhov, F.Ya.

1977-01-01

The liquation region in the system Na 2 O-B 2 O 3 -SiO 2 was investigated. The liquation temperatures were determined by the boundary of disappearance of opalescence in specimens with pre-induced opalescence. Extrapolation of the concentration dependences of the liquation temperature along sections with a constant SiO 2 content to a point indicates that with a SiO 2 content of 20-40% the liquation boundary in the system B 2 O 3 -SiO 2 hardly lies above 450 deg C

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

Science.gov (United States)

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

2017-09-27

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

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.

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...

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

Science.gov (United States)

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

2018-04-01

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

Microstructure and Mechanical Properties of Multiphase Strengthened Al/Si/Al_2O_3/SiO_2/MWCNTs Nano composites Sintered by In Situ Vacuum Hot Pressing

International Nuclear Information System (INIS)

Li, J.; Jiang, X.; Zhu, D.; Zhu, M.; Shao, Z.; Johnson, S.; Luo, Z.

2015-01-01

Eutectic Al/Si binary alloy is technically one of the most important Al casting alloys due to its high corrosion resistance, evident shrinkage reduction, low thermal expansion coefficient, high fluidity, and good weldability. In this work, multi phased Al/Si matrix nano composites reinforced with Al_2O_3 and multi walled carbon nano tubes (MWCNTs) have been sintered by an in situ vacuum hot-pressing method. The alumina Al_2O_3 nanoparticles were introduced by an in situ reaction of Al with SiO_2. Microstructure and mechanical properties of the sintered Al/Si/Al_2O_3/SiO_2/MWCNTs nano composites with different alumina contents were investigated. The mechanical properties were determined by micro-Vickers hardness and compressive and shear strength tests. The results demonstrated that in situ alumina and MWCNTs had impacts on microstructure and mechanical properties of the nano composites. Based on the mechanical properties and microstructure of the nano composites, strengthening and fracture mechanisms by multiple reinforcements were analyzed

Investigation of 70SiO2-15CaO-10P2O5-5Na2O Glass Composition for Bone Regeneration Applications

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Vikas Anand

2014-11-01

Full Text Available Glass with the composition 70SiO2-15CaO -10P2O5-5Na2O has been prepared by using sol gel technique. Bioactive behavior of the glass sample has been checked by in vitro study using TRIS simulated body fluid. Bioactive properties of the sample has been analyzed by using XRD, Raman, FE-SEM, EDX and Brunauer Emmett Teller studies. pH study has been conducted to check the non- acidic nature of the glass sample. Drug delivery behavior of the sample has been estimated by using gentamicin as an antibiotic. Reported sample has been found to be potential candidate for bone regeneration applications.

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

International Nuclear Information System (INIS)

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

2011-01-01

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

Self assembly of SiO2-encapsulated carbon microsphere composites

International Nuclear Information System (INIS)

Yang Yongzhen; Song Jingjing; Han Yanxing; Guo Xingmei; Liu Xuguang; Xu Bingshe

2011-01-01

SiO 2 was firstly coated onto the surface of carbon microspheres (CMSs) using tetraethyl orthosilicate (TEOS) as precursor by Stoeber method. Then SiO 2 -encapsulated CMS (CMS-SiO 2 ) composites were self-assembled by vertical deposition, in which the effects of deposition temperature and suspension concentration on the quality of self-assembling film were investigated. Morphologies and structures of the samples were characterized by field emission scanning electron microscopy, Fourier transformation infrared spectrometry, X-ray diffraction and thermogravimetry. The results show that uniform CMS-SiO 2 composites with good mono-dispersion were prepared by Stober method with 0.5 g of CMSs, 2 mL of TEOS, 30 mL of ammonia and 12 h of reaction time, the CMSs-based films with ordered and denser structure were prepared by vertical deposition using CMS-SiO 2 composites as monodipersion spheres under suspension concentration of 1 wt% and deposition temperature of 50 deg. C. The ultraviolet-visible absorption measurement shows that the absorbance of CMS-SiO 2 composite films grew steadily with increasing suspension concentration.

Fabrication, characterization, and photocatalytic property of {alpha}-Fe{sub 2}O{sub 3}/graphene oxide composite

Energy Technology Data Exchange (ETDEWEB)

Li Hong; Zhao Qidong; Li Xinyong, E-mail: xinyongli@hotmail.com [School of Environmental Science and Technology, Dalian University of Technology, State Key Laboratory of Fine Chemical, Key Laboratory of Industrial Ecology and Environmental Engineering (MOE) (China); Zhu Zhengru [Research Center of Hydrology and Engineering, Academy of City and Environment, Liaoning Normal University (China); Tade, Moses; Liu Shaomin, E-mail: shaomin.liu@curtin.edu.au [Curtin University, Department of Chemical Engineering (Australia)

2013-06-15

Spindle-shaped microstructure of {alpha}-Fe{sub 2}O{sub 3} was successfully synthesized by a simple hydrothermal method. The {alpha}-Fe{sub 2}O{sub 3}/graphene oxide (GO) composites was prepared using a modified Hummers' strategy. The properties of the samples were systematically investigated by X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectrophotometer, transmission electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy (Raman) techniques. GO nanosheets act as supporting materials for anchoring the {alpha}-Fe{sub 2}O{sub 3} particles. The average crystallite sizes of the {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}/GO samples are ca. 27 and 24 nm, respectively. The possible growth of {alpha}-Fe{sub 2}O{sub 3} onto GO layers led to a higher absorbance capacity for visible light by {alpha}-Fe{sub 2}O{sub 3}/GO than {alpha}-Fe{sub 2}O{sub 3} composite. The photocatalytic degradation of toluene over the {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}/GO samples under xenon-lamp irradiation was comparatively studied by in situ FTIR technique. The results indicate that the {alpha}-Fe{sub 2}O{sub 3}/GO sample synthesized exhibited a higher capacity for the degradation of toluene. The composite of {alpha}-Fe{sub 2}O{sub 3}/GO could be promisingly applied in photo-driven air purification.

Development ceramic composites based on Al2O3, SiO2 and IG-017 additive

Science.gov (United States)

Kurovics, E.; Shmakova, A.; Kanev, B.; Gömze, L. A.

2017-02-01

Based on high purity alumina and quartz powders and IG-017 bio-original additives the authors have developed new ceramic composite materials for different industrial purposes. The main goal was to fine a material and morphological structures of high performance ceramic composites as frames for development complex materials for extreme consumptions in the future. For this the mixed powders of Al2O3 , SiO2 and IG-017 bio-original additive were uniaxially pressed at different compaction pressures into disc shapes and were sintered in electric kiln under air (1) and nitrogrn (2) atmosphere. The grain size distributions of the raw materials were determined by laser granulometry. There thermo-physical properties were also determined by derivatography. The prepared and sintered specimens were tested on geometrical sizes, microstructure and morphology by scanning electron microscopy, porosity and water absorption. In this work the authors present the results of their research and investigation.

Preparation and Characterization of Fluorescent SiO2 Microspheres

Science.gov (United States)

Xu, Cui; Zhang, Hao; Guan, Ruifang

2018-01-01

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

Glass-ceramic enamels derived from the Li2O-Na2O-Al2O3-TiO2-SiO2 system

Directory of Open Access Journals (Sweden)

SNEZANA R. GRUJIC

2002-02-01

Full Text Available The results of research on the conditions for obtaining model glass-ceramic enamels, derived from the basic Li2O-Na2O-Al2O3-TiO2-SiO2 system, by varying the initial composition and thermal treatment conditions, are presented in this paper. Segregation of the crystal phases in the glassy-matrix was carried out during subsequent thermal treatment. The formation of different crystal phases was evidenced through the results of differential-thermal analysis and X-ray powder diffraction analysis.

Effect of MgO on compositions of the system CaO-Al2O3-Fe2O3. Solubility

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Palomo, Ángel

1986-12-01

Full Text Available Five different compositions belonging to the equilibrium system CaO-Al2O3-Fe2O3 were dopep with a fixed quantity of MgO (6,5% wt. The compositions, which lie in different primary fields of crystallization and in different triangles of compatibility, were submitted to several thermal treatments. Each composition, which had previously been melted, originates in its solidification the aluminates and ferrites which are usual in the interstitial phase of clinker Portland, although they are in different microstructural arrangements. The effect of MgO on the generated microstructures has been shown. Also, the solubility of MgO on the aluminic and ferritic phases has been measured.CCinco composiciones diferentes pertenecientes al sistema de equilibrio CaO-Al2O3-Fe2O3 fueron dopadas con una cantidad fija de MgO (6,5%. Las cinco composiciones, que están situadas sobre diferentes campos primarios de cristalización y/o sobre diferentes triángulos de compatibilidad, fueron sometidas a varios tratamientos térmicos. Cada composición (previamente fundida origina en su solidificación los aluminatos y ferritos habituales en la fase intersticial del clinker portland, aunque ordenados en microestructuras diferentes. Se ha comprobado el efecto del MgO sobre las microestructuras generadas, así como su solubilidad en las fases alumínicas y ferríticas.

Magnetic ordered mesoporous Fe3O4/CeO2 composites with synergy of adsorption and Fenton catalysis

Science.gov (United States)

Li, Keyan; Zhao, Yongqin; Song, Chunshan; Guo, Xinwen

2017-12-01

Magnetic Fe3O4/CeO2 composites with highly ordered mesoporous structure and large surface area were synthesized by impregnation-calcination method, and the mesoporous CeO2 as support was synthesized via the hard template approach. The composition, morphology and physicochemical properties of the materials were characterized by XRD, SEM, TEM, XPS, Raman spectra and N2 adsorption/desorption analysis. The mesoporous Fe3O4/CeO2 composite played a dual-function role as both adsorbent and Fenton-like catalyst for removal of organic dye. The methylene blue (MB) removal efficiency of mesoporous Fe3O4/CeO2 was much higher than that of irregular porous Fe3O4/CeO2. The superior adsorption ability of mesoporous materials was attributed to the abundant oxygen vacancies on the surface of CeO2, high surface area and ordered mesoporous channels. The good oxidative degradation resulted from high Ce3+ content and the synergistic effect between Fe and Ce. The mesoporous Fe3O4/CeO2 composite presented low metal leaching (iron 0.22 mg L-1 and cerium 0.63 mg L-1), which could be ascribed to the strong metal-support interactions for dispersion and stabilization of Fe species. In addition, the composite can be easily separated from reaction solution with an external magnetic field due to its magnetic property, which is important to its practical applications.

Surface spins disorder in uncoated and SiO2 coated maghemite nanoparticles

International Nuclear Information System (INIS)

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

2017-01-01

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

Study of magnetization and magnetoelectricity in CoFe2O4/BiFeO3 core-shell composites

Science.gov (United States)

Kuila, S.; Tiwary, Sweta; Sahoo, M. R.; Barik, A.; Babu, P. D.; Siruguri, V.; Birajdar, B.; Vishwakarma, P. N.

2018-02-01

CoFe2O4 (core)/BiFeO3 (shell) nanoparticles are prepared by varying the relative molar concentration of core and shell materials (40%CoFe2O4-60%BiFeO3, 50%CoFe2O4-50%BiFeO3, and 60%CoFe2O4-40%BiFeO3). The core-shell nature is confirmed from transmission electron microscopy on these samples. A plot of ΔM (=MFC-MZFC) vs temperature suggests the presence of two types of spin dynamics: (a) particle size dependent spin blocking and (b) spin-disorder. These two spin dynamic processes are found to contribute independently to the generation of magnetoelectric voltage. Very clear first order and second order magnetoelectric voltages are recorded. The resemblance of the first order magnetoelectric coefficient vs temperature plot to that of building up of order parameters in the mean field theory suggests that spin disorder can act like one of the essential ingredients in building the magnetoelectric coupling. The best result is obtained for the 50-50 composition sample, which may be due to better coupling of magnetostrictive CoFe2O4, and piezoelectric BiFeO3, because of the optimum thickness of shell and core.

Non-stoichiometric mullites from Al2O3-SiO2-ZrO2 amorphous materials by rapid quenching

International Nuclear Information System (INIS)

Yoshimura, M.; Hanaue, Y.; Somiya, S.

1990-01-01

In order to study the formation of zirconia dispersed mullite ceramics from homogeneous starting materials hot-pressing and heat-treatments have been carried out for rapidly quenched amorphous materials with 0 to 20 wt% ZrO 2 mullite compositions. These amorphous materials crystallized directly to mullite for 0-10 wt% ZrO 2 samples or mullite + t-ZrO 2 for 20 wt% ZrO 2 at about 970 degrees C. An A1 2 O 3 - rich composition (82 wt% A1 2 O 3 ) and also a significant solid solubility of ZrO 2 (>10 wt%) were estimated for these mullites by XRD studies. Amorphous speres of 10 nm which were considered to be SiO 2 - rich phase were produced by a phase separation in mullite grains

Luminescence and energy transfer of Tb3+-doped BaO-Gd2O3-Al2O3-B2O3-SiO2 glasses.

Science.gov (United States)

Zuo, Chenggang; Huang, Jinze; Liu, Shaoyou; Xiao, Anguo; Shen, Youming; Zhang, Xiangyang; Zhou, Zhihua; Zhu, Ligang

2017-12-05

Transparent Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses with the greater than 4g/cm 3 were prepared by high temperature melting method and its luminescent properties have been investigated by measured UV-vis transmission, excitation, emission and luminescence decay spectra. The transmission spectrum shows there are three weak absorption bands locate at about 312, 378 and 484nm in the glasses and it has good transmittance in the visible spectrum region. Intense green emission can be observed under UV excitation. The effective energy transfer from Gd 3+ ion to Tb 3+ ion could occur and sensitize the luminescence of Tb 3+ ion. The green emission intensity of Tb 3+ ion could change with the increasing SiO 2 /B 2 O 3 ratio in the borosilicate glass matrix. With the increasing concentration of Tb 3+ ion, 5 D 4 → 7 F J transitions could be enhanced through the cross relaxation between the two nearby Tb 3+ ions. Luminescence decay time of 2.12ms from 546nm emission is obtained. The results indicate that Tb 3+ -doped BaO-Gd 2 O 3 -Al 2 O 3 -B 2 O 3 -SiO 2 glasses would be potential scintillating material for applications in X-ray imaging. Copyright © 2017 Elsevier B.V. All rights reserved.

Facile preparation of large-scale α-Fe{sub 2}O{sub 3} nanorod/SnO{sub 2} nanorod composites and their LPG-sensing properties

Energy Technology Data Exchange (ETDEWEB)

Vuong, Dang Duc [School of Engineering Physics, Hanoi University of Science and Technology, No. 1, Dai Co Viet Road, Hai Ba Trung District, Hanoi (Viet Nam); Trung, Khuc Quang [University of Fire Fighting and Protection, No. 243, Khuat Duy Tien Street, Thanh Xuan District, Hanoi (Viet Nam); Hung, Nguyen Hoang [School of Engineering Physics, Hanoi University of Science and Technology, No. 1, Dai Co Viet Road, Hai Ba Trung District, Hanoi (Viet Nam); Hieu, Nguyen Van [International Training Institute for Materials Science, Hanoi University of Science and Technology (Viet Nam); Chien, Nguyen Duc, E-mail: chien.nguyenduc@hust.edu.vn [School of Engineering Physics, Hanoi University of Science and Technology, No. 1, Dai Co Viet Road, Hai Ba Trung District, Hanoi (Viet Nam)

2014-06-25

Highlights: • A simple method was used for synthesis of α-Fe{sub 2}O{sub 3} nanorod/SnO{sub 2} nanorod composites. • LPG-sensing properties of the composites were studied and explained consistently. • The results demonstrate a potential method for the mass production of gas sensors. - Abstract: α-Fe{sub 2}O{sub 3} nanorods (NRs) with length and diameter of 300 and 50 nm, and SnO{sub 2} NRs with length and diameter of 30 and 10 nm, respectively, were prepared through hydrothermal treatment method. Morphologies of α-Fe{sub 2}O{sub 3} and SnO{sub 2} NRs and their composites with different weight ratios were studied by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The SEM and TEM images showed SnO{sub 2} NRs attached on (branch onto) the surface of the α-Fe{sub 2}O{sub 3} NRs. Liquefied petroleum gas (LPG)-sensing properties of films with bare α-Fe{sub 2}O{sub 3}, SnO{sub 2} NRs, and their composite NRs were investigated. The composite of 75 wt% α-Fe{sub 2}O{sub 3}/25 wt% SnO{sub 2} exhibits the highest response to LPG at optimum operating temperature of 370 °C. The improvement in the gas-sensing characteristics of the composite NRs compared with bare NRs is attributed to the formation of hetero-junctions in α-Fe{sub 2}O{sub 3} NRs/SnO{sub 2} NRs and to their porous structure.

Characterisation and Properties of Lithium Disilicate Glass Ceramics in the SiO2-Li2O-K2O-Al2O3 System for Dental Applications

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Naruporn Monmaturapoj

2013-01-01

Full Text Available This work proposes four different glass formulas derived from the SiO2-Li2O-K2O-Al2O3 system to investigate the effect of glass composition on their crystal formations and properties. Glass LD1 was SiO2-Li2O-K2O-Al2O3 system with the addition of P2O5 and CaF2 as nucleating agents. In Glass LD2, a slight amount of MgO was mixed in order to increase the viscosity of the melting glass. Finally, the important factor of Si : Li ratio was increased in Glasses LD3 and LD4 with compositions otherwise the same as LD1 and LD2. The results found that P2O5 and CaF2 served as a nucleating site for lithium phosphate and fluorapatite to encourage heterogenous nucleation and produce a fine-grained interlocking microstructure of lithium disilicate glass ceramics. MgO content in this system seemed to increase the viscosity of the melting glass and thermal expansion coefficient including the chemical solubility. Increasing the Si : Li ratio in glass compositions resulted in the change of the microstructure of Li2Si2O5 crystals.

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

International Nuclear Information System (INIS)

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

2016-01-01

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

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

Science.gov (United States)

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

2015-02-01

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

Homogeneity of peraluminous SiO2-B2O3-Al2O3-Na2O-CaO-Nd2O3 glasses: Effect of neodymium content

International Nuclear Information System (INIS)

Gasnier, E.; Bardez-Giboire, I.; Massoni, N.; Montouillout, V.; Pellerin, N.; Allix, M.; Ory, S.; Cabie, M.; Poissonnet, S.; Massiot, D.

2014-01-01

Considering the interest of developing new glass matrices able to immobilize higher concentration of high level nuclear wastes than currently used nuclear borosilicate compositions, glasses containing high rare earth contents are of particular interest. This study focuses on a peraluminous alumino borosilicate system SiO 2 -B 2 O 3 -Al 2 O 3 -Na 2 O-CaO-Nd 2 O 3 defined by a per-alkaline/peraluminous ratio RP = ([Na 2 O] + [CaO])/ ([Na 2 O] + [CaO] + [Al 2 O 3 ]) ≤ 0.5. Samples with various contents of Nd 2 O 3 from 0 to 10 mol% were studied using DSC, XRD, SEM, TEM, STEM and EMPA methods. The glasses present a high thermal stability even after a slow cooling treatment from the melt. Only a slight mullite crystallization is detected for low Nd 2 O 3 content (≤2.3 mol%) and crystallization of a neodymium borosilicate crystalline phase combined to a phase separation occurred at high Nd 2 O 3 content (≥8 mol%). The solubility of neodymium in the presence of aluminum is demonstrated, with higher neodymium incorporation amounts than in per-alkaline glasses. (authors)

Facile synthesis of nanorod-type graphitic carbon nitride/Fe2O3 composite with enhanced photocatalytic performance

International Nuclear Information System (INIS)

Wang, Jiangpeng; Li, Changqing; Cong, Jingkun; Liu, Ziwei; Zhang, Hanzhuo; Liang, Mei; Gao, Junkuo; Wang, Shunli; Yao, Juming

2016-01-01

Here we report a facile synthesis of nanorod-type graphitic carbon nitride/Fe 2 O 3 composite (Fe 2 O 3 -g-C 3 N 4 ) by using Fe-melamine supramolecular framework as precursor. The chemical and optical properties of the nanocomposites are well-characterized. The Fe 2 O 3 -g-C 3 N 4 nanocomposite demonstrated excellent photocatalytic activities under visible light due to the efficient utilization of sunlight and the construction of Z-scheme electron transfer pathway. The results indicated that it could be a promising approach for the preparation of efficient g-C 3 N 4 nanocomposites photocatalysts by using metal-melamine supramolecular framework as precursors. - Graphical abstract: Nanorod-type graphitic carbon nitride/Fe 2 O 3 composite (Fe 2 O 3 -g-C 3 N 4 ) was synthesized by using Fe-melamine supramolecular framework as precursor. The Fe 2 O 3 -g-C 3 N 4 nanocomposite demonstrated excellent photocatalytic activities under visible light. Display Omitted - Highlights: • Nanorod-type graphitic carbon nitride/Fe 2 O 3 composite (Fe 2 O 3 -g-C 3 N 4 ) was synthesized. • Fe 2 O 3 -g-C 3 N 4 showed strong optical absorption in the visible-light region. • The Fe 2 O 3 -g-C 3 N 4 nanocomposite demonstrated excellent photocatalytic activities.

Synthesis, structural characterization and dielectric properties of Nb doped BaTiO3/SiO2 core–shell heterostructure

International Nuclear Information System (INIS)

Cernea, M.; Vasile, B.S.; Boni, A.; Iuga, A.

2014-01-01

Highlights: • Optimal parameters for preparation by sol–gel of core–shell (BT-Nb 0.005 )/SiO 2 are presented in this paper. • Single crystalline BT-Nb 0.005 /SiO 2 core–shell composite with ∼34 nm shell thick was prepared. • The core–shell ceramic exhibits good dielectric properties and ferroelectric characteristics. -- Abstract: Perovskite complex ceramic oxides, BaTiO 3 doped with 0.5 mol%Nb 2 O 5 and then nanocoated with SiO 2 (abbreviated as BT-Nb 0.005 /SiO 2 ) was successful prepared using conventional sol–gel processing. Phase composition, particle morphology, structure, and electric properties of BT-Nb 0.005 core and BT-Nb 0.005 /SiO 2 core–shell were examined and compared, using X-ray diffraction, transmission electron microscopy and, dielectric and ferroelectric measurements. Core–shell composite with well-defined perovskite tetragonal phase of BaTiO 3 was achieved. Furthermore, single crystalline BT-Nb 0.005 /SiO 2 core–nanoshell heterostructure with ∼34 nm shell thick was prepared, which is a novelty in ferroelectrics field. The ferroelectric quality of BT-Nb 0.005 has suffered an alteration when the (BT-Nb 0.005 )/SiO 2 core–shell heterostructure was realized. One-dimensional BT-Nb 0.005 /SiO 2 core–shell heterostructure exhibits an improvement of dielectric losses and a decrease of dielectric constant, compared to uncoated BT-Nb 0.005 . The (BT-Nb 0.005 )/SiO 2 core–shell material could be interesting for application in the composite capacitors

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

Science.gov (United States)

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

2017-04-01

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

Novel ZnO/MgO/Fe2O3 composite optomagnetic nanoparticles

International Nuclear Information System (INIS)

Kamińska, I; Sikora, B; Fronc, K; Dziawa, P; Sobczak, K; Minikayev, R; Paszkowicz, W; Elbaum, D

2013-01-01

A facile sol–gel synthesis of novel ZnO/MgO/Fe 2 O 3 nanoparticles (NPs) is reported and their performance is compared to that of ZnO/MgO. Powder x-ray diffraction (XRD) patterns reveal the crystal structure of the prepared samples. The average particle size of the sample was found to be 4.8 nm. The optical properties were determined by UV–vis absorption and fluorescence measurements. The NPs are stable in biologically relevant solutions (phosphate buffered saline (PBS), 20 mM, pH = 7.0) contrary to ZnO/MgO NPs which degrade in the presence of inorganic phosphate. Superparamagnetic properties were determined with a superconducting quantum interference device (SQUID). Biocompatible and stable in PBS ZnO/MgO/Fe 2 O 3 core/shell composite nanocrystals show luminescent and magnetic properties confined to a single NP at room temperature (19–24 ° C), which may render the material to be potentially useful for biomedical applications. (paper)

Optical Properties of Malachite Green Dye Doped SiO2 Glasses: Effect of Transition Metal (Fe-I Used as a Codopant

Directory of Open Access Journals (Sweden)

Dulen Bora

2014-01-01

Full Text Available Enhanced luminescence properties of Malachite Green (MG (oxalate in Fe-MG codoped SiO2 glasses compared to its values in MG doped SiO2 glasses are reported here. The enhancement is chiefly attributed to a resonance nonradiative energy transfer between Fe and MG. The quantum yield of Malachite Green (MG, in presence of Iron, trapped in sol-gel derived SiO2 glass increases by an order of ~103 compared to that in low viscous solvent while a lifetime of 3.29 ns is reported.

Photocatalytic Property of Fe3O4/SiO2/TiO2 Core-Shell Nanoparticle with Different Functional Layer Thicknesses

Directory of Open Access Journals (Sweden)

Junyang Li

2014-01-01

Full Text Available This study examined the different properties of Fe3O4/SiO2/TiO2 (FST core-shell nanoparticles encapsulated for one to five different times, represented as FST1 to FST5, respectively. These FST nanoparticles were obtained using the carbon reduction and sol-gel methods, and their properties were characterized by various tools, such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, vibratory sample magnetometer, laser granularity apparatus, and specific surface area analyzer. The relationship between irradiation time and decoloration ratio indicates that FST2 demonstrated significant efficiency in the decolorization of methyl orange (MO under UV light. Further study on recycle activity showed that FST2 had a high decoloration rate after four cycles of photocatalysis, and its degradation of MO was well aligned with the apparent first-order kinetic equation. Furthermore, FST2 exhibited the highest apparent rate in the first cycle. All these results demonstrate that the recoverable FST2 possessed excellent photocatalytic activity while maintaining outstanding stability for further applications, such as managing environmental pollution.

alpha-Fe2O3 versus beta-Fe2O3: Controlling the Phase of the Transformation Product of epsilon-Fe2O3 in the Fe2O3/SiO2 System

Czech Academy of Sciences Publication Activity Database

Brázda, Petr; Kohout, J.; Bezdička, Petr; Kmjec, T.

2014-01-01

Roč. 14, č. 3 (2014), s. 1039-1046 ISSN 1528-7483 R&D Projects: GA ČR GAP204/10/0035 Institutional support: RVO:61388980 Keywords : CHEMICAL-VAPOR-DEPOSITION * OXIDE THIN-FILMS * X-RAY * GAMMA-FE2O3 NANOPARTICLES * THERMAL-DECOMPOSITION Subject RIV: CA - Inorganic Chemistry Impact factor: 4.891, year: 2014

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

International Nuclear Information System (INIS)

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

2011-01-01

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

High-temperature mass spectrometric study of the vaporization processes and thermodynamic properties of melts in the PbO-B2O3-SiO2 system.

Science.gov (United States)

Stolyarova, V L; Lopatin, S I; Shilov, A L; Shugurov, S M

2013-07-15

The unique properties of the PbO-B2O3-SiO2 system, especially its extensive range of glass-forming compositions, make it valuable for various practical applications. The thermodynamic properties and vaporization of PbO-B2O3-SiO2 melts are not well established so far and the data obtained on these will be useful for optimization of technology and thermodynamic modeling of glasses. High-temperature Knudsen effusion mass spectrometry was used to study vaporization processes and to determine the partial pressures of components of the PbO-B2O3-SiO2 melts. Measurements were performed with a MS-1301 mass spectrometer. Vaporization was carried out using two quartz effusion cells containing the sample under study and pure PbO (reference substance). Ions were produced by electron ionization at an energy of 25 eV. To facilitate interpretation of the mass spectra, the appearance energies of ions were also measured. Pb, PbO and O2 were found to be the main vapor species over the samples studied at 1100 K. The PbO activities as a function of the composition of the system were derived from the measured PbO partial pressures. The B2O3 and SiO2 activities, the Gibbs energy of formation, the excess Gibbs energy of formation and mass losses in the samples studied were calculated. Partial pressures of the vapor species over PbO-B2O3-SiO2 melts were measured at 1100 K in the wide range of compositions using the Knudsen mass spectrometric method. The data enabled the PbO, B2O3, and SiO2 activities in these melts to be derived and provided evidence of their negative deviations from ideal behavior. Copyright © 2013 John Wiley & Sons, Ltd.

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

Science.gov (United States)

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

2013-11-01

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Preparation and photoelectric properties of p-CaFe2O4/n-WO3 composites

International Nuclear Information System (INIS)

Wan, Ruiqin; Jia, Caihong; Zhang, Weifeng

2012-01-01

Highlights: ► Surface photovoltage spectroscopy investigation on p-CaFe 2 O 4 /n-WO 3 composites. ► The photovoltaic response is enhanced in p-CaFe 2 O 4 /n-WO 3 composites. ► The multielectron process and high rate of carrier migration in WO 3 . - Abstract: Composites of p-CaFe 2 O 4 /n-WO 3 are prepared via a sol–gel technique. Their structures and optical properties are characterized with X-ray diffraction, scanning electron microscopy and UV–vis absorption spectroscopy. The photoelectric characteristics are investigated by surface photovoltage spectroscopy combined with electric field induced surface photovoltage spectroscopy. The results indicate that CaFe 2 O 4 can well form a p–n type composite with WO 3 , and the intensity and spectral region of surface photovoltaic response for the composites are strongly dependent on the molar ratio of two components. The enhancement in photoelectric properties and the effective separation of photogenerated carriers could be attributed to the energy level matching between the two components, multielectron process and the high migration rate in WO 3 .

Natural CaO-TiO2-SiO2 based ceramics

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Jelena Pantić

2011-06-01

Full Text Available Lešnica river deposits consist of a large number of minerals of different grain sizes including sphene. Since it is very difficult to obtain pure monophase titanite by different synthetic routes (sol-gel, coprecipitation, combustion, spray pyrolysis and hydrothermal method, the aim of this work was to study the structure of the sphene from the Lešnica river deposits and possibility of using it as a natural precursor for CaO-TiO2-SiO2 based ceramics. The sphene from Lešnica was analyzed by different methods: tristimulus colorimetry, infrared spectroscopy, electron microprobe and X-ray single crystal diffraction. It was confirmed that Al, Fe, Mn and P are present in the sphene structure and proposed that corresponding structural formula could be: (Ca2+1.008 Mn2+0.0021.010(Ti4+0.901 Fe3+0.033 Al3+0.060 P5+0.0010.995 Si4+1.024 O2-5.

CuO, MnO2 and Fe2O3 doped biomass ash as silica source for glass production in Thailand

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N. Srisittipokakun

Full Text Available In this research, glass productions from rice husk ash (RHA and the effect of BaO, CuO, MnO2 and Fe2O3 on physical and optical properties were investigated. All properties were compared with glass made from SiO2 using same preparations. The results show that a higher density and refractive index of BaO, CuO, MnO2 and Fe2O3 doped in RHA glasses were obtained, compared with SiO2 glasses. The optical spectra show no significant difference between both glasses. The color of CuO glasses show blue from the absorption band near 800 nm (2B1g → 2B2g due to Cu2+ ion in octahedral coordination with a strong tetragonal distortion. The color of MnO2 glasses shows brown from broad band absorption at around 500 nm. This absorption band is assigned to a single allowed 5Eg → 5T2g transition which arises from the Mn3+ ions (3d4 configuration in octahedral symmetry. The yellow color derives from F2O3 glass due to the homogeneous distribution of Fe3+ (460 nm and Fe2+ (1050 nm ions in the glass matrices. Glass production from RHA is possible and is a new option for recycling waste from biomass power plant systems and air pollution reduction. Keywords: Rice husk ash, Glass, Optical, Physical

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 .

Characterisation of a tertiary mixture of {alpha}-Fe{sub 2}O{sub 3}, {gamma}-Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Srinivasan, M.P.; Narasimhan, S.V. [Water and Steam Chemistry Laboratory (Chemistry Group, BARC) BARC Facilities, Kalpakkam, Tamil Nadu 603 102. (India)

1998-12-31

A method has been developed to quantify the individual components of a ternary mixture containing {alpha}-Fe{sub 2}O{sub 3}, {gamma}- Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} based on the preferential dissolution of the components at a fixed time (fixed time - depending on the strength of the chelating agent) in a dilute chemical formulation (containing a chelant and an organic acid) both in presence and absence of reductant. A ternary component diagram was constructed based on the percentage dissolution of the individual components in 2,6-Pyridine dicarboxylic acid (PDCA), Nitrilo triacetic acid (NTA) and EDTA based formulation at 60degC both in presence and absence of reductant. In these formulations, the observed behaviour that the {alpha}-Fe{sub 2}O{sub 3} dissolved very little both in presence and absence of reductant and {gamma}-Fe{sub 2}O{sub 3} dissolved very little in absence of reductant were used for resolving the ternary physical mixture composition. Physical mixtures of Fe{sub 3}O{sub 4}, {alpha}-Fe{sub 2}O{sub 3} and {gamma}-Fe{sub 2}O{sub 3} based on mole ratio were taken such that the total quantity of Fe present would be 1.37 mM for complete dissolution. In presence and absence of reductant, dissolution percentage of Fe observed at fixed time in these formulations, when fit into the already constructed three component phase diagram for each formulation at the same fixed duration, the experimentally resolved composition showed good agreement with that based on individual components. This method is useful to resolve different polymorphs of metal oxides having the metal ions in single and/or multiple oxidation states. (author)

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.

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

International Nuclear Information System (INIS)

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

2002-01-01

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

Study on adsorption of rhodamine B onto Beta zeolites by tuning SiO2/Al2O3 ratio.

Science.gov (United States)

Cheng, Zhi-Lin; Li, Yan-Xiang; Liu, Zan

2018-02-01

The exploration of the relationship between zeolite composition and adsorption performance favored to facilitate its better application in removal of the hazardous substances from water. The adsorption capacity of rhodamine B (RB) onto Beta zeolite from aqueous solution was reported. The relationship between SiO 2 /Al 2 O 3 ratio and adsorption capacity of Beta zeolite for RB was explored. The structure and physical properties of Beta zeolites with various SiO 2 /Al 2 O 3 ratios were determined by XRD, FTIR, TEM, BET, UV-vis and so on characterizations. The adsorption behavior of rhodamine B onto Beta zeolite matched to Langmuir adsorption isotherm and more suitable description for the adsorption kinetics was a pseudo-second-order reaction model. The maximum adsorption capacity of the as-prepared Beta zeolite with SiO 2 /Al 2 O 3 = 18.4 was up to 27.97mg/g. Copyright © 2017 Elsevier Inc. All rights reserved.

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

International Nuclear Information System (INIS)

Lai, Chunyan; Wu, Tingting; Wang, Zhen

2016-01-01

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

Magneto electric effects in BaTiO3-CoFe2O4 bulk composites

Science.gov (United States)

Agarwal, Shivani; Caltun, O. F.; Sreenivas, K.

2012-11-01

Influence of a static magnetic field (HDC) on the hysteresis and remanence in the longitudinal and transverse magneto electric voltage coefficients (MEVC) observed in [BaTiO3]1-x-[CoFe2O4]x bulk composites are analyzed. Remanence in MEVC at zero bias (HDC=0) is stronger in the transverse configuration over the longitudinal case. The observed hysteretic behavior in MEVC vs. HDC is correlated with the changes observed in the magnetostriction characteristics (λ and dλ/dH) reported for [BaTiO3]1-x-[CoFe2O4]x bulk composites.

Effects of additives on the sintering of UO2.Gd2O3 nuclear fuel

International Nuclear Information System (INIS)

Pagano Junior, Luciano

2009-01-01

The addition of 0.5wt% TiO 2 , Nb 2 O 5 , SiO 2 , Fe 2 O 3 and Al(OH) 3 in the UO 2 ·7%Gd 2 O 3 nuclear fuel and the effect on its sintering kinetics under a 99.999% H 2 atmosphere were investigated by stepwise isothermal dilatometry. This fuel, used as burnable poison in nuclear power plants, presents a diffusion barrier around 1573 K that impairs densification. The aid of the sintering additives TiO 2 , Al(OH) 3 , Nb 2 O 5 and Fe 2 O 3 turned out to be effective to obtain the required final density, unlike the effect observed for the SiO 2 -doped composition. The activation energy for the intermediate sintering stage was calculated by stepwise isothermal dilatometry method and a positive correlation with the sintered body density was found. The method was valid for part of the intermediate sintering stage, in the range from 1200 K to 1700 K for the doped compositions and with no additive, except for the SiO 2 -doped one, whose validity range was between 1500 K and 1900 K. The energy-density correlation was not valid for the SiO 2 -doped composition, whose effect was to reduce the final density. This anomalous behavior may be attributed to the intense loss of Si mass, probably due to lower oxides volatilization, during the initial sintering stage at temperatures lower than 1173 K. Similar loss, but no so intense, was observed for the Al(OH) 3 -doped composition in the temperature interval from 1173 K to 1573 K. The Si concentration decrease to residual values of dozens of parts per million may explain its anomalous behavior. The positive correlation between activation energy and sintered body density may be explained by the inhibitor role played by the TiO 2 , Nb 2 O 5 , Fe 2 O 3 and Al(OH) 3 additives on the diffusion mechanisms that enhance the coarsening regime. As a consequence, the densification mechanisms are favored in the competition for the surface free energy. The coarsening-densification transition temperature model, originally suggested for the UO 2

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

International Nuclear Information System (INIS)

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

2010-01-01

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

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

Science.gov (United States)

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

2014-01-10

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

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+ .

Hydrothermal synthesis of reduced graphene sheets/Fe2O3 nanorods composites and their enhanced electrochemical performance for supercapacitors

Science.gov (United States)

Yang, Wanlu; Gao, Zan; Wang, Jun; Wang, Bin; Liu, Lianhe

2013-06-01

Reduced graphene nanosheets/Fe2O3 nanorods (GNS/Fe2O3) composite has been fabricated by a hydrothermal route for supercapacitor electrode materials. The obtained GNS/Fe2O3 composite formed a uniform structure with the Fe2O3 nanorods grew on the graphene surface and/or filled between the graphene sheets. The electrochemical performances of the GNS/Fe2O3 hybrid supercapacitor were tested by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge tests in 6 M KOH electrolyte. Comparing with the pure Fe2O3 electrode, GNS/Fe2O3 composite electrode exhibits an enhanced specific capacitance of 320 F g-1 at 10 mA cm-2 and an excellent cycle-ability with capacity retention of about 97% after 500 cycles. The simple and cost-effective preparation technique of this composite with good capacitive behavior encourages its potential commercial application.

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.

Synthesis of graphene supported Li2SiO3 as a high performance anode material for lithium-ion batteries

Science.gov (United States)

Yang, Shuai; Wang, Qiufen; Miao, Juan; Zhang, Jingyang; Zhang, Dafeng; Chen, Yumei; Yang, Hong

2018-06-01

The Li2SiO3-graphene composite is successfully synthesized through an easy hydrothermal method. The structures and morphologies of the produced samples are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrum, Brunauer-Emmett-Teller formalism, scanning electron microscope, transmission electron microscope, and electrochemistry methods. The result shows a well crystalline of the Li2SiO3-GE composite. The existence of graphene doesn't change the crystalline of Li2SiO3. In addition, the Li2SiO3 compound with an average diameter of 20 nm can be seen on the surface of graphene with uniform distribution. After the composite with graphene, the composite displays large surface area which ensures the well electrochemistry of the composite. Finally, the Li2SiO3-graphene composite delivers a high initial capacity of 878.3 mAh g-1 at 1C as well as a high recovery capacity of 400 mAh g-1 after 200 cycles. When charged and discharged at high rate, the Li2SiO3-doping graphene composite still exhibits a high specific capacity of 748.3 mAh g-1 (at 2C, and 576 mAh g-1 at 5C) and well cycling performance. The well synthesized composite possesses well structure and well electrochemistry performance.

Core-shelled mesoporous CoFe2O4-SiO2 material with good adsorption and high-temperature magnetic recycling capabilities

Science.gov (United States)

Li, Zhi'ang; Wang, Jianlin; Liu, Min; Chen, Tong; Chen, Jifang; Ge, Wen; Fu, Zhengping; Peng, Ranran; Zhai, Xiaofang; Lu, Yalin

2018-04-01

Residues of organic dye in industrial effluents cause severe water system pollution. Although several methods, such as biodegradation and activated carbon adsorption, are available for treating these effluents before their discharge into waterbodies, secondary pollution by adsorbents and degrading products remains an issue. Therefore, new materials should be identified to solve this problem. In this work, CoFe2O4-SiO2 core-shell structures were synthesized using an improved Stöber method by coating mesoporous silica onto CoFe2O4 nanoparticles. The specific surface areas of the synthesized particles range from 30 m2/g to 150 m2/g and vary according to the dosage amount of tetraethoxysilane. Such core-shelled nanoparticles have the following advantages for treating industrial effluents mixed with dye: good adsorption capability, above-room-temperature magnetic recycling capability, and heat-enduring stability. Through adsorption of methylene blue, a typical dyeing material, the core-shell-structured particles show a good adsorption capability of approximately 33 mg/L. The particles are easily and completely collected by magnets, which is possible due to the magnetic property of core CoFe2O4. Heat treatment can burn out the adsorbed dyes and good adsorption performance is sustained even after several heat-treating loops. This property overcomes the common problem of particles with Fe3O4 as a core, by which Fe3O4 is oxidized to nonmagnetic α-Fe2O3 at the burning temperature. We also designed a miniature of effluent-treating pipeline, which demonstrates the potential of the application.

Glass-ceramic materials of system MgO-Al2O3-SiO2 from rice husk ash

OpenAIRE

Martín Hernández, María Isabel; Rincón López, Jesús María; Andreola, F.; Barbieri, L.; Bondioli, F.; Lancellotti, I.; Romero, Maximina

2011-01-01

This wok shows the results of a valorisation study to use rice husk ash as raw material to develop glass-ceramic materials. An original glass has been formulated in the base system MgO-Al2O3-SiO2 with addition of B2O3 and Na2O to facilitate the melting and poring processes. Glass characterization was carried out by determining its chemical composition. Sintering behaviour has been examined by Hot Stage Microscopy (HSM). Thermal stability and crystallization mechanism have been studied by Diff...

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

Directory of Open Access Journals (Sweden)

Tursunov Obid

2017-11-01

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