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)

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

Science.gov (United States)

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.

Preparación y propiedades de materiales cerámicos bioinertes en el sistema Al2O3-TiO2-SiO2

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Boccaccini, A. R.

1998-12-01

Full Text Available Very fine and sinterable ceramic powders (100-600 nm in the system Al2O3-TiO2-SiO2 were obtained by the method of cohydrolisis from organo-metallic precursors. Isostatically pressed powder compacts could be densified to a relative high density (~ 92 % th. density at relative low temperatures (1320-1380ºC. The technical coefficient of thermal expansion was measured by dilatometry. The value obtained (8.8 10-6 1/ºC corresponds closely to that of Ti, opening the possibility to use Al2O3-TiO2-SiO2 ceramics to fabricate metal/ceramic composite implants. The measured mechanical properties of dense sintered Al2O3-TiO2-SiO2 material: Young´s modulus, flexure strength and compression strength, are higher than those of pure TiO2. Highly porous Al2O3-TiO2-SiO2 ceramics (P~ 65% were obtained by the method of evaporation of hydrogen peroxide. These materials exhibited interconnected porosity and their properties, particularly the Young´s modulus, resulted very similar to those of bone, which is an important pre-requisite for the design of quirurgical implants.Se han obtenido polvos cerámicos muy finos (100- 600 nm y de alta sinterabilidad, en el sistema Al2O3-TiO2-SiO2, por el método de co-hidrólisis controlada a partir de precursores organo-metálicos. Los compactos fabricados a partir del polvo de cohidrólisis calcinado fueron sinterizados en el rango de temperaturas 1320-1380 ºC, obteniéndose densidades elevadas (~ 92% D.T.. El coeficiente de expansión térmica técnico del material cerámico sinterizado fue medido por dilatometría. El valor obtenido, 8.8 10-6 ºC-1, es muy similar al de titanio metálico y por lo tanto el material cerámico Al2O3-TiO2-SiO2 puede ser candidato para la fabricación de implantes compuestos cerámico/metal. Las propiedades mecánicas: módulo de elasticidad, resistencia a la flexión y resistencia a la compresión, del material denso sinterizado, fueron determinadas, resultando muy superiores a las de TiO2 puro

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)

Vitrocerâmicas do sistema Li2O Al2O3 SiO2 (LAS) via siterização com cristalização corrente.

OpenAIRE

Viviane Oliveira Soares

2007-01-01

Os vidros do sistema LAS (Li2O-Al2O3-SiO2) vêm sendo estudados para obtenção de vitrocerâmicas com coeficiente de expansão térmica próximo de zero, que são necessárias em aplicações que requerem elevada resistência ao choque térmico. No entanto a obtenção destas vitrocerâmicas ainda está muito limitada à utilização de técnicas tradicionais de fusão e conformação seguida por nucleação (induzida pela adição de catalisadores) e crescimento de cristais no volume de peças monolít...

Síntesis de pigmentos basados en el sistema ZRO2 - SIO2 - V2O5 mediante Silicato de Zirconio

OpenAIRE

ZHANG, HONGQUAN; WANG, LIRONG; ZHANG, QIMIN

2003-01-01

El pigmento basado en el sistema óxido de zirconioóxido de silicio ( ZrO2-SiO2) es de una clase importante que se utiliza ampliamente en la preparación de cerámicas vidriadas y en la producción de esmaltes cerámicos. En este artículo se expone una nueva tecnología de síntesis, mediante la cual se ha obtenido el pigmento azul de zirconio–vanadio, a partir de un mineral de silicato de zirconio(ZrSiO4). Se discute acerca de los factores que influyen en la tonalidad del...

Reduction Mechanisms of Cu2+-Doped Na2O-Al2O3-SiO2 Glasses during Heating in H2 Gas.

Science.gov (United States)

Nogami, Masayuki; Quang, Vu Xuan; Ohki, Shinobu; Deguchi, Kenzo; Shimizu, Tadashi

2018-01-25

Controlling valence state of metal ions that are doped in materials has been widely applied for turning optical properties. Even though hydrogen has been proven effective to reduce metal ions because of its strong reducing capability, few comprehensive studies focus on practical applications because of the low diffusion rate of hydrogen in solids and the limited reaction near sample surfaces. Here, we investigated the reactions of hydrogen with Cu 2+ -doped Na 2 O-Al 2 O 3 -SiO 2 glass and found that a completely different reduction from results reported so far occurs, which is dominated by the Al/Na concentration ratio. For Al/Na glass body. For Al/Na > 1, on the other hand, the reduction of Cu 2+ ions occurred simultaneously with the formation of OH bonds, whereas the reduced Cu metal moved outward and formed a metallic film on glass surface. The NMR and Fourier transform infrared results indicated that the Cu 2+ ions were surrounded by Al 3+ ions that formed AlO 4 , distorted AlO 4 , and AlO 5 units. The diffused H 2 gas reacted with the Al-O - ···Cu + units, forming Al-OH and metallic Cu, the latter of which moved freely toward glass surface and in return enhanced H 2 diffusion.

Investigating the influence of Na+ and Sr2+ on the structure and solubility of SiO2-TiO2-CaO-Na2O/SrO bioactive glass.

Science.gov (United States)

Li, Y; Placek, L M; Coughlan, A; Laffir, F R; Pradhan, D; Mellott, N P; Wren, A W

2015-02-01

This study was conducted to determine the influence that network modifiers, sodium (Na+) and strontium (Sr2+), have on the solubility of a SiO2-TiO2-CaO-Na2O/SrO bioactive glass. Glass characterization determined each composition had a similar structure, i.e. bridging to non-bridging oxygen ratio determined by X-ray photoelectron spectroscopy. Magic angle spinning nuclear magnetic resonance (MAS-NMR) confirmed structural similarities as each glass presented spectral shifts between -84 and -85 ppm. Differential thermal analysis and hardness testing revealed higher glass transition temperatures (Tg 591-760 °C) and hardness values (2.4-6.1 GPa) for the Sr2+ containing glasses. Additionally the Sr2+ (~250 mg/L) containing glasses displayed much lower ion release rates than the Na+ (~1,200 mg/L) containing glass analogues. With the reduction in ion release there was an associated reduction in solution pH. Cytotoxicity and cell adhesion studies were conducted using MC3T3 Osteoblasts. Each glass did not significantly reduce cell numbers and osteoblasts were found to adhere to each glass surface.

Crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses; Li2O-SiO2, Na2O-SiO2, Na2O-CaO-SiO2 kei glass no kessho sekishutsu kyodo

Energy Technology Data Exchange (ETDEWEB)

Tsutsumi, K.; Otake, J.; Nagasaka, T.; Hino, M. [Tohoku University, Sendai (Japan)

1998-06-01

It has been known that crystallization of mold powder is effective on the disturbance of heat transfer between mold and solidified shell in production of middle carbon steel slabs in continuous casting process. But it has not yet been made clear which composition of mold powder is the most suitable for crystallization. The crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses was observed by differential thermal analysis (DTA) and hot-thermocouple methods with DTA in the present work. As a result, addition of alkaline metal and alkaline earth metal oxides to SiO2 increased the critical cooling rate for glass formation in binary system of Li2O-SiO2 and Na2O-SiO2 and Li2O-SiO2 system crystallized easier than Na2O-SiO2 system. In ternary system of Na2O-CaO-SiO2, addition of Na2O hurried the critical cooling rate at CaO/SiO2=0.93 mass ratio, but the rate was almost constant in the composition range of more than 15 mass% Na2O. The slag of CaO/SiO2=0.93 made the rate faster than the slag of CaO/SiO2=0.47 at constant content of 10mass% Na2O. 17 refs., 10 figs., 3 tabs.

Crystallization and chemical durability of glasses in the system Bi2O3-SiO2

International Nuclear Information System (INIS)

Fredericci, C.

2011-01-01

The crystallization of the Bi 2 O 3 -SiO 2 -TiO 2 -Al 2 O 3 -Na 2 O-K 2 O and Bi 2 O 3 -SiO 2 -ZnO-Al 2 O 3 -B 2 O 3 -Na 2 O glasses was studied using glass samples prepared by traditional melt-quench method. Differential thermal analysis (DTA) curves suggested that surface crystallization played a major role in the crystallization of the glass samples. X-ray diffraction (XRD) analysis revealed the crystallization of bismuth silicate for both glasses and bismuth silicate and zinc silicate for the glass containing ZnO. Through scanning electron microscopy (MEV) and energy dispersive spectroscopy (EDS), it was possible to observe that the crystals of zinc silicate (Zn 2 SiO 4 ) were readily attacked by hot 0,1 N sulfuric acid, whereas bismuth silicate crystals were more resistant to acidic attack etching. (author)

Nanocomposite dielectrics in PbO-BaO-Na2O-Nb2O5-SiO2 system with high breakdown strength for high voltage capacitor applications.

Science.gov (United States)

Zhang, Qingmeng; Luo, Jun; Tang, Qun; Han, Dongfang; Zhou, Yi; Du, Jun

2012-11-01

Nanocomposite dielectrics in 6PbO-4BaO-20Na2O-40Nb2O5-30SiO2 system were prepared via melt-quenching followed by controlled crystallization. X-ray diffraction studies reveal that Pb2Nb2O7, Ba,NaNb5O15, NaNbO3 and PbNb2O6 phases are formed from the as-quenched glass annealed in temperature range from 700 degrees C to 850 degrees C. Ba2NaNb5O15, Pb2Nb2O7 crystallizes at 700 degrees C and then Pb2Nb2O7 disappears at 850 degrees C, while PbNb2O6 and NaNbO3 are formed at 850 degrees C. Microstructural observation shows that the crystallized particles are nanometer-sized and randomly distributed with glass matrix being often found at grain boundaries. The dielectric constant of the nanocomposites formed at different crystallization temperatures shows good frequency and electric field stability. The breakdown strength is slightly decreased when the glass-ceramics thickness is varied from 1 mm to 4 mm. The corresponding energy density could reach 2.96 J/cm3 with a breakdown strength of 58 kV/mm for thickness of 1 mm.

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...

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

International Nuclear Information System (INIS)

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

2017-01-01

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

Gels and gel-derived glasses in the system Na2O-B2O3-SiO2

Science.gov (United States)

Mukherjee, S. P.

1983-01-01

The containerless melting of high-purity multicomponent homogeneous gels and gel monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the system Na2O-B2O3-SiO2 are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures was found to be significantly different. Infrared absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel monoliths to transparent 'glass' without melting are described.

A Structural Molar Volume Model for Oxide Melts Part I: Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 Melts—Binary Systems

Science.gov (United States)

Thibodeau, Eric; Gheribi, Aimen E.; Jung, In-Ho

2016-04-01

A structural molar volume model was developed to accurately reproduce the molar volume of molten oxides. As the non-linearity of molar volume is related to the change in structure of molten oxides, the silicate tetrahedral Q-species, calculated from the modified quasichemical model with an optimized thermodynamic database, were used as basic structural units in the present model. Experimental molar volume data for unary and binary melts in the Li2O-Na2O-K2O-MgO-CaO-MnO-PbO-Al2O3-SiO2 system were critically evaluated. The molar volumes of unary oxide components and binary Q-species, which are model parameters of the present structural model, were determined to accurately reproduce the experimental data across the entire binary composition in a wide range of temperatures. The non-linear behavior of molar volume and thermal expansivity of binary melt depending on SiO2 content are well reproduced by the present model.

Bioactivity of gel-glass powders in the CaO-SiO2 system: a comparison with ternary (CaO-P2O5-SiO2) and quaternary glasses (SiO2-CaO-P2O5-Na2O).

Science.gov (United States)

Saravanapavan, Priya; Jones, Julian R; Pryce, Russell S; Hench, Larry L

2003-07-01

Bioactive glasses react chemically with body fluids in a manner that is compatible with the repair processes of the tissues. This results in the formation of an interfacial bond between the glasses and living tissue. Bioactive glasses also stimulate bone-cell proliferation. This behavior is dependent on the chemical composition as well as the surface texture of the glasses. It has been recently reported that gel-derived monolith specimens in the binary SiO2 - CaO are bioactive over a similar molar range of SiO2 content as the previously studied ternary CaO-P2O5-SiO2 system. In this report, the preparation and bioactivity of the binary gel-glass powder with 70 mol % SiO2 is discussed and its bioactivity is compared with the melt-derived 45S5 (quaternary) Bioglass and sol-gel-derived 58S (ternary) bioactive gel-glass compositions. Dissolution kinetic parameters K(1) and K(2) were also computed based on the silicon release for all glass powders. It was shown that the simple two-component SiO2-CaO gel-glass powder is bioactive with comparable dissolution rates as the clinically used melt-derived 45S5 Bioglass powder and extensively studied sol-gel-derived 58S gel-glass powder. Copyright 2003 Wiley Periodicals, Inc.

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 .

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.

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

Science.gov (United States)

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

2015-01-01

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

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

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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

Effect of calcium fluoride on sintering behaviour of SiO2-CaO-Na2O-MgO glass-ceramic system

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Bahman Mirhadi

2012-09-01

Full Text Available The crystallization characteristics of glasses based on the SiO2-CaO-Na2O-MgO (SCNM system containing calcium fluoride (CaF2 have been investigated by differential thermal analysis (DTA, X-ray diffraction (XRD and scanning electron microscopy (SEM. The partial replacement of CaO by CaF2 in the studied glass-ceramics led to the development of different crystalline phase assemblages, including wollastonite and diopside using various heat-treatment processes. With the increase of CaF2 content, the crystallization temperature of the glass and the strength of the crystallization peak temperature decreases. Addition of CaF2 up to 6.0 mol%, as expected, improved the sinterability. This sample reached to maximum density by sintering at 950 °C.

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

International Nuclear Information System (INIS)

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

2004-01-01

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

Phase Equilibria Study in the TeO2-Na2O-SiO2 System in Air Between 723 K (500 °C) and 1473 K (1200 °C)

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Santoso, Imam; Taskinen, Pekka

2016-08-01

Knowledge of phase equilibria in the TeO2-Na2O-SiO2 system at elevated temperatures is important for ceramic and glass industries and for improving the operation of the smelting process of tellurium-containing materials. A review of previous investigations has indicated, however, that there are omissions in the available datasets on the liquidus temperatures of the molten TeO2-Na2O-SiO2 mixtures. The employed experimental method included equilibration of mixtures made from high purity oxides, rapid quenching of the equilibrated samples in water and followed by compositional analysis of the phases using an electron probe X-ray microanalyzer. The liquidus and phase equilibria in the TeO2-SiO2, TeO2-Na2O, and SiO2-TeO2-Na2O systems have been studied for a wide range of compositions between 723 K (500 °C) and 1473 K (1200 °C) at TeO2, SiO2, and Na2SiO3 saturations. New data have been generated in the SiO2-TeO2-Na2O system at SiO2 saturation. The liquidus compositions in the TeO2-Na2O system at TeO2 saturation have been compared with the previous data and an assessed phase diagram.

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.

Structural study of Na2O-B2O3-SiO2 glasses from molecular simulations using a polarizable force field.

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Pacaud, Fabien; Delaye, Jean-Marc; Charpentier, Thibault; Cormier, Laurent; Salanne, Mathieu

2017-10-28

Sodium borosilicate glasses Na 2 O-B 2 O 3 -SiO 2 (NBS) are complex systems from a structural point of view. Three main building units are present: tetrahedral SiO 4 and BO 4 (B IV ) and triangular BO 3 (B III ). One of the salient features of these compounds is the change of the B III /B IV ratio with the alkali concentration, which is very difficult to capture in force fields-based molecular dynamics simulations. In this work, we develop a polarizable force field that is able to reproduce the boron coordination and more generally the structure of several NBS systems in the glass and in the melt. The parameters of the potential are fitted from density functional theory calculations only, in contrast with the existing empirical potentials for NBS systems. This ensures a strong improvement on the transferability of the parameters from one composition to another. Using this new force field, the structure of NBS systems is validated against neutron diffraction and nuclear magnetic resonance experiments. A special focus is given to the distribution of B III /B IV with respect to the composition and the temperature.

Effect of Na2SiO3 on heavy metal uptake by field grown Basella alba L. in Matara, Sri Lanka

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Samanthika R. Hettiarachchi

2016-12-01

Full Text Available In this study, we investigated heavy metal uptake and the effects of Na2SiO3 on heavy metal absorption by field grown Basella alba L (Basellaceae. The concentrations of Fe, Cr, Pb and Cd in the field soils were 29755.30 ± 292.02, 32.99 ± 0.97, 26.01 ± 1.02, 0.13 ± 0.004 µg/g, respectively. These concentrations are significantly below the maximum permissible limits reported by FAO/WHO. Although Fe, Cr, Pb and Cd were present in the soil, only Fe was absorbed by B. alba; the tissue concentrations of other heavy metals were below the detection limit. The distribution of Fe from soil to different plant parts was investigated by calculating transfer factors. Low transfer factors indicated low absorption and translocation of Fe from soil to plant tissue. We also investigated the effects of Na2SiO3 on metal absorption by applying two different concentrations of Na2SiO3 (Si-100 mg/L and Si-50 mg/L alongside a control. There was a significant reduction of Fe absorption in B. alba treated with Si-100mg/L of Na2SiO3 compared to that of plants treated with Si-50 mg/L of Na2SiO3 and the control.

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.

Bioactivity of Y2O3 and CeO2 doped SiO2-SrO-Na2O glass-ceramics.

Science.gov (United States)

Placek, L M; Keenan, T J; Wren, A W

2016-08-01

The bioactivity of yttrium and cerium are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24-xNa2O-xMO glass-ceramics (where x = 0.08 and MO = Y2O3 or CeO2). Bioactivity is monitored through pH and inductively coupled plasma-optical emission spectrometry where pH of simulated body fluid ranged from 7.5 to 7.6 and increased between 8.2 and 10.0 after 14-day incubation with the glass-ceramic disks. Calcium (Ca) and phosphorus (P) levels in simulated body fluid after incubation with yttrium and cerium containing disks show a continual decline over the 14-day period. In contrast, Con disks (not containing yttrium or cerium) caused the elimination of Ca in solution after 1 day and throughout the incubation period, and initially showed a decline in P levels followed by an increase at 14 days. Scanning electron microscopy and energy dispersive spectroscopy confirmed the presence of Ca and P on the surface of the simulated body fluid-incubated disks and showed precipitates on Con and HCe (8 mol% cerium) samples. Cell viability of MC3T3 osteoblasts was not significantly affected at a 9% extract concentration. Optical microscopy after 24 h cell incubation with disks showed that Con samples do not support osteoblast or Schwann cell growth, while all yttrium and cerium containing disks have direct contact with osteoblasts spread across the wells. Schwann cells attached in all wells, but only showed spreading with the HY-S (8 mol% yttrium, heated to sintering temperature) and YCe (4 mol% yttrium and cerium) disks. Scanning electron microscopy of the compatible disks shows osteoblast and sNF96.2 Schwann cells attachment and spreading directly on the disk surfaces. © The Author(s) 2016.

Preparation and Characterization of PbO-SrO-Na2O-Nb2O5-SiO2 Glass Ceramics Thin Film for High-Energy Storage Application

Science.gov (United States)

Tan, Feihu; Zhang, Qingmeng; Zhao, Hongbin; Wei, Feng; Du, Jun

2018-03-01

PbO-SrO-Na2O-Nb2O5-SiO2 (PSNNS) glass ceramic thin films were prepared by pulsed laser deposition technology on heavily doped silicon substrates. The influence of annealing temperatures on microstructures, dielectric properties and energy storage performances of the as-prepared films were investigated in detail. X-ray diffraction studies indicate that Pb2Nb2O7 crystallizes at 800°C and disappears at 900°C, while NaNbO3 and PbNb2O6 are formed at the higher temperature of 900°C. The dielectric properties of the glass ceramics thin films have a strong dependence on the phase assemblages that are developed during heat treatment. The maximum dielectric constant value of 171 was obtained for the film annealed at 800°C, owing to the high electric breakdown field strength, The energy storage densities of the PSNNS films annealed at 800°C were as large as 36.9 J/cm3, These results suggest that PSNNS thin films are promising for energy storage applications.

Thermodynamics of Bi2O3-SiO2 system

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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.

High Energy Ion Beam Studies of Ion Exchange in a Na2O-Al2O3-SiO2 Glass

International Nuclear Information System (INIS)

Shutthanadan, Vaithiyalingam; Baer, Donald R.; Thevuthasan, Suntharampillai; Adams, Evan M.; Maheswaran, Saravanamuthu; Engelhard, Mark H.; Icenhower, Jonathan P.; McGrail, Bernard P.

2002-01-01

As part of understanding the processes leading to sodium release and ion exchange, the surface and near surface reaction regions on several specimens of a Na2O-Al2O3-SiO2 glass have been examined after exposures to isotopically labeled aqueous solutions. The majority of the analyses describe here have been carried out using energetic ion beam analysis. Rutherford backscattering spectrometry (RBS) has been used to measure the overall glass composition and to determine the profiles and amounts of Na released from the surface. An important part of the ion exchange process is the uptake and incorporation of hydrogen and oxygen in the glass from the solution. To facilitate this analysis, the glasses were exposed to a solution containing 18O and deuterium and analyzed by accelerator based nuclear reaction analysis (NRA). To confirm some of the RBS depth profile data very near the surface, XPS depth profiles were collected on some samples. Although the Na concentration is decreased in the near surface region, it is not totally removed from the outer surface. In this same region, there is also a significant amount of 18O incorporated demonstrating considerable interaction between the water and the glass. Deeper into the material the amounts of deuterium and 18O are more consistent with water or H3O+ diffusion. These results suggest that there exist an outer reaction layer and an inner diffusion controlled layer in the surface region of the reacted glass

Structural Evaluation of 5,5′-Bis(naphth-2-yl)-2,2′-bithiophene in Organic Field-Effect Transistors with n-Octadecyltrichlorosilane Coated SiO2 Gate Dielectric

DEFF Research Database (Denmark)

Lauritzen, Andreas E.; Torkkeli, Mika; Bikondoa, Oier

2018-01-01

We report on the structure and morphology of 5,5′-bis(naphth-2-yl)-2,2′-bithiophene (NaT2) films in bottom-contact organic field-effect transistors (OFETs) with octadecyltrichlorosilane (OTS) coated SiO2 gate dielectric, characterized by atomic force microscopy (AFM), grazing-incidence X......-ray diffraction (GIXRD), and electrical transport measurements. Three types of devices were investigated with the NaT2 thin-film deposited either on (1) pristine SiO2 (corresponding to higher surface energy, 47 mJ/m2) or on OTS deposited on SiO2 under (2) anhydrous or (3) humid conditions (corresponding to lower...... surface energies, 20–25 mJ/m2). NaT2 films grown on pristine SiO2 form nearly featureless three-dimensional islands. NaT2 films grown on OTS/SiO2 deposited under anhydrous conditions form staggered pyramid islands where the interlayer spacing corresponds to the size of the NaT2 unit cell. At the same time...

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

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Karim OMRI

2014-05-01

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

Thermodynamic optimization of the (Na2O + SiO2 + NaF + SiF4) reciprocal system using the Modified Quasichemical Model in the Quadruplet Approximation

International Nuclear Information System (INIS)

Lambotte, Guillaume; Chartrand, Patrice

2011-01-01

Highlights: → We model the Na 2 O-SiO 2 -NaF-SiF 4 reciprocal system based on a comprehensive review of all available experimental data. → The assessment includes Na 2 O-SiO 2 and NaF-SiF 4 binary systems. → Improvements to the Modified Quasichemical Model in the Quadruplet Approximation are presented. → The very strong short-range ordering among first-nearest and second-nearest neighbors in this system is reproduced. → This work constitutes the first assessment for all compositions and temperatures of a reciprocal oxyfluoride system. - Abstract: All available thermodynamic and phase diagram data for the condensed phases of the ternary reciprocal system (NaF + SiF 4 + Na 2 O + SiO 2 ) have been critically assessed. Model parameters for the unary (SiF 4 ), the binary systems and the ternary reciprocal system have been found, which permit to reproduce the most reliable experimental data. The Modified Quasichemical Model in the Quadruplet Approximation was used for the oxyfluoride liquid solution, which exhibits strong first-nearest-neighbor and second-nearest-neighbor short-range ordering. This thermodynamic model takes into account both types of short-range ordering as well as the coupling between them. Model parameters have been estimated for the hypothetical high-temperature liquid SiF 4 .

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.

Gels and gel-derived glasses in the Na2O-B2O3-SiO2 system. [containerless melting in space

Science.gov (United States)

Mukherjee, S. P.

1982-01-01

The containerless melting of high-purity multicomponent homogeneous gels and gel-monoliths offers a unique approach to making ultrapure multicomponent optical glasses in the reduced gravity environment of space. Procedures for preparing and characterizing gels and gel-derived glasses in the Na2O-B2O3-SiO2 system are described. Preparation is based on the polymerization reactions of alkoxysilane with trimethyl borate or boric acid and a suitable sodium compound. The chemistry of the gelling process is discussed in terms of process parameters and the gel compositions. The physicochemical nature of gels prepared by three different procedures were found to be significantly different. IR absorption spectra indicate finite differences in the molecular structures of the different gels. The melting of the gel powders and the transformation of porous gel-monoliths to transparent 'glass' without melting are described.

Investigating the effect of SiO2-TiO 2-CaO-Na 2O-ZnO bioactive glass doped hydroxyapatite: characterisation and structural evaluation.

Science.gov (United States)

Yatongchai, Chokchai; Wren, Anthony W; Curran, Declan J; Hampshire, Stuart; Towler, Mark R

2014-07-01

The effects of increasing bioactive glass additions, SiO2-TiO2-CaO-Na2O-ZnO up to 25 wt% in increments of 5 wt%, on the physical and mechanical properties of hydroxyapatite (HA) sintered at 900, 1000, 1100 and 1200 °C for 2 h was investigated. Increasing both the glass content and the temperature resulted in increased HA decomposition. This resulted in the formation of a number of bioactive phases. However the presence of the liquidus glass phase did not result in increased densification levels. At 1000 and 1100 °C the additions of 5 wt% glass resulted in a decrease in density which never recovered with increasing glass content. At 1200 °C a cyclic pattern resulted from increasing glass content. There was no direct relationship between strength and density with all samples experiencing no change or a decrease in strength with increasing glass content. Weibull statistics displayed no pattern with increasing glass content.

Heat treatment of Na2O-CaO-P2O5-SiO2 bioactive glasses: densification processes and postsintering bioactivity.

Science.gov (United States)

Sola, A; Bellucci, D; Raucci, M G; Zeppetelli, S; Ambrosio, L; Cannillo, V

2012-02-01

Because of their excellent bioactivity, bioactive glasses are increasingly diffused to produce biomedical devices for bone prostheses, to face the dysfunctions that may be caused by traumatic events, diseases, or even natural aging. However, several processing routes, such as the production of scaffolds or the deposition of coatings, include a thermal treatment to apply or sinter the glass. The exposure to high temperature may induce a devetrification phenomenon, altering the properties and, in particular, the bioactivity of the glass. The present contribution offers an overview of the thermal behavior and properties of two glasses belonging to the Na2O-CaO-P2O5-SiO2 system, to be compared to the standard 45S5 Bioglass(®). The basic goal is to understand the effect of both the original composition and the thermal treatment on the performance of the sintered glasses. The new glasses, the one (BG_Na) with a high content of Na2O, the other (BG_Ca) with a high content of CaO, were fully characterized and sintering tests were performed to define the most interesting firing cycles. The sintered samples, treated at 880°C and 800°C respectively, were investigated from a microstructural point of view and their mechanical properties were compared to those of the bulk (not sintered) glass counterparts. The effect of sintering was especially striking on the BG_Ca material, whose Vickers hardness increased from 598.9 ± 46.7 HV to 1053.4 ± 35.0 HV. The in vitro tests confirmed the ability of the glasses, both in bulk and sintered form, of generating a hydroxyapatite surface layer when immersed in a simulated body fluid. More accurate biological tests performed on the sintered glasses proved the high bioactivity of the CaO-rich composition even after a heat treatment. Copyright © 2011 Wiley Periodicals, Inc.

Photocatalytic Removal of Phenol under Natural Sunlight over N-TiO2-SiO2 Catalyst: The Effect of Nitrogen Composition in TiO2-SiO2

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Viet-Cuong Nguyen

2009-01-01

Full Text Available In this present work, high specific surface area and strong visible light absorption nitrogen doped TiO2-SiO2 photocatalyst was synthesized by using sol-gel coupled with hydrothermal treatment method. Nitrogen was found to improve the specific surface area while it also distorted the crystal phase of the resulting N-TiO2-SiO2 catalyst. As the N/ (TiO2-SiO2 molar ratio was more than 10%, the derived catalyst presented the superior specific surface area up to 260 m2/g. Nevertheless, its photoactivity towards phenol removal was observed to significantly decrease, which could results from the too low crystallinity. The nitrogen content in N-TiO2-SiO2 catalyst was therefore necessary to be optimized in terms of phenol removal efficiency and found at ca. 5%. Under UVA light and natural sunlight irradiation of 80 min, N(5%-TiO2-SiO2 catalyst presented the phenol decomposition efficiencies of 68 and 100%, respectively. It was also interestingly found in this study that the reaction rate was successfully expressed using a Langmuir-Hinshelwood (L-H model, indicating the L-H nature of photocatalytic phenol decomposition reaction on the N-TiO2-SiO2 catalyst.

Investigating the Effect of Glass Ion Release on the Cytocompatibility, Antibacterial Eflcacy and Antioxidant Activity of Y2O3 / CeO2 doped SiO2-SrO-Na2O glasses

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Placek L. M.

2018-02-01

Full Text Available The effect on ion release and cytocompatibility of Yttrium (Y and Cerium (Ce are investigated when substituted for Sodium (Na in a 0.52SiO2-0.24SrO-0.24-Na2OMOglass series (where MO= Y2O3 or CeO2. Glass leaching was evaluated through pH measurements and Inductive Coupled Plasma-Optical Emission Spectrometry (ICP-OES analysiswhere the extract pH increased during incubation (11.2 - 12.5. Ion release of Silicon (Si, Na and Strontium (Sr from the Con glass was at higher than that of glasses containing Y or Ce, and reached a limit after 1 day. Ion release from Y and Ce containing glasses reached a maximum of 1800 μg/mL, 1800 μg/mL, and 10 μg/mL for Si, Na, and Sr, respectively. Release of Y and Cewas below the ICP- OES detection limit 75% of bacteria at a 9% extract concentration. Antioxidant capacity (mechanism for neuroprotection was evaluated using the ABTS assay. All glasses had inherent radical oxygen species (ROS scavenging capability with Con reaching 9.5 mMTE.

The effect on phase separation of the oxidation state of molybdenum in a Na2O-B2O3-SiO2 glass

International Nuclear Information System (INIS)

Kawamoto, Y.; Clemens, K.; Tomozawa, M.; Warden, J.T.

1981-01-01

The effect of oxidation state on phase separation was studied for 13Na 2 O, 49B 2 O 3 , 38SiO 2 (mol%) glasses containing 1 mol% Mo oxide. The glasses were melted under various conditions to vary the oxidation states of Mo ions. The oxidation states of Mo ions were determined by chemical analysis and ESR. The crystallisation tendency, the immiscibility temperature, and the phase separation morphology of the glasses were examined by DTA, x-ray diffraction, opalescence method, and replica electron microscopy. Glasses containing Mo 4+ ions have a great tendency to precipitate MoO 2 crystals. The immiscibility temperature of glass goes through a minimum when the oxidation states of Mo ions are changed. It was suggested that there is an optimum oxidation state to prevent crystallisation and to suppress the phase separation tendency of this system. (author)

Crystallization kinetics of bioactive glasses in the ZnO-Na2O-CaO-SiO2 system.

Science.gov (United States)

Malavasi, Gianluca; Lusvardi, Gigliola; Pedone, Alfonso; Menziani, Maria Cristina; Dappiaggi, Monica; Gualtieri, Alessandro; Menabue, Ledi

2007-08-30

The crystallization kinetics of Na(2)O.CaO.2SiO(2) (x = 0) and 0.68ZnO.Na(2)O.CaO.2SiO(2) (x = 0.68, where x is the ZnO stoichiometric coefficient in the glass formula) bioactive glasses have been studied using both nonisothermal and isothermal methods. The results obtained from isothermal XRPD analyses have showed that the first glass crystallizes into the isochemical Na(2)CaSi(2)O(6) phase, whereas the Na(2)ZnSiO(4) crystalline phase is obtained from the Zn-rich glass, in addition to Na(2)CaSi(2)O(6). The activation energy (Ea) for the crystallization of the Na(2)O.CaO.2SiO(2) glass is 193 +/- 10 and 203 +/- 5 kJ/mol from the isothermal in situ XRPD and nonisothermal DSC experiments, respectively. The Avrami exponent n determined from the isothermal method is 1 at low temperature (530 degrees C), and its value increases linearly with temperature increase up to 2 at 607 degrees C. For the crystallization of Na(2)CaSi(2)O(6) from the Zn-containing glass, higher values of both the crystallization temperature (667 and 661 degrees C) and Ea (223 +/- 10 and 211 +/- 5 kJ/mol) have been found from the isothermal and nonisothermal methods, respectively. The Na(2)ZnSiO(4) crystalline phase crystallizes at lower temperature with respect to Na(2)CaSi(2)O(6), and the Ea value is 266 +/- 20 and 245 +/- 15 kJ/mol from the isothermal and nonisothermal methods, respectively. The results of this work show that the addition of Zn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass. In fact, it causes an increase of Ea for the Na diffusion process, determined using MD simulations, and consequently an overall increase of Ea for the crystallization process of Na(2)CaSi(2)O(6). Our results show good agreement between the Ea and n values obtained with the two different methods and confirm the reliability of the nonisothermal method applied to kinetic crystallization of glassy systems. This study allows the determination of the temperature

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

International Nuclear Information System (INIS)

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

2009-01-01

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

SiO2@TiO2 Coating: Synthesis, Physical Characterization and Photocatalytic Evaluation

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A. Rosales

2018-03-01

Full Text Available Use of silicon dioxide (SiO2 and titanium dioxide (TiO2 have been widely investigated individually in coatings technology, but their combined properties promote compatibility for different innovative applications. For example, the photocatalytic properties of TiO2 coatings, when exposed to UV light, have interesting environmental applications, such as air purification, self-cleaning and antibacterial properties. However, as reported in different pilot projects, serious durability problems, associated with the adhesion between the substrate and TiO2, have been evidenced. Thus, the aim of this work is to synthesize SiO2 together with TiO2 to increase the durability of the photocatalytic coating without affecting its photocatalytic potential. Therefore, synthesis using sonochemistry, synthesis without sonochemistry, physical characterization, photocatalytic evaluation, and durability of the SiO2, SiO2@TiO2 and TiO2 coatings are presented. Results indicate that using SiO2 improved the durability of the TiO2 coating without affecting its photocatalytic properties. Thus, this novel SiO2@TiO2 coating shows potential for developing long-lasting, self-cleaning and air-purifying construction materials.

Emission analysis of Tb3+ -and Sm3+ -ion-doped (Li2 O/Na2 O/K2 O) and (Li2 O + Na2 O/Li2 O + K2 O/K2 O + Na2 O)-modified borosilicate glasses.

Science.gov (United States)

Naveen Kumar Reddy, B; Sailaja, S; Thyagarajan, K; Jho, Young Dahl; Sudhakar Reddy, B

2018-05-01

Four series of borosilicate glasses modified by alkali oxides and doped with Tb 3+ and Sm 3+ ions were prepared using the conventional melt quenching technique, with the chemical composition 74.5B 2 O 3 + 10SiO 2 + 5MgO + R + 0.5(Tb 2 O 3 /Sm 2 O 3 ) [where R = 10(Li 2 O /Na 2 O/K 2 O) for series A and C, and R = 5(Li 2 O + Na 2 O/Li 2 O + K 2 O/K 2 O + Na 2 O) for series B and D]. The X-ray diffraction (XRD) patterns of all the prepared glasses indicate their amorphous nature. The spectroscopic properties of the prepared glasses were studied by optical absorption analysis, photoluminescence excitation (PLE) and photoluminescence (PL) analysis. A green emission corresponding to the 5 D 4 → 7 F 5 (543 nm) transition of the Tb 3+ ions was registered under excitation at 379 nm for series A and B glasses. The emission spectra of the Sm 3+ ions with the series C and D glasses showed strong reddish-orange emission at 600 nm ( 4 G 5/2 → 6 H 7/2 ) with an excitation wavelength λ exci = 404 nm ( 6 H 5/2 → 4 F 7/2 ). Furthermore, the change in the luminescence intensity with the addition of an alkali oxide and combinations of these alkali oxides to borosilicate glasses doped with Tb 3+ and Sm 3+ ions was studied to optimize the potential alkali-oxide-modified borosilicate glass. Copyright © 2017 John Wiley & Sons, Ltd.

PAC study in the HfO2-SiO2 system

International Nuclear Information System (INIS)

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

2010-01-01

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

In vitro evaluation of bioactivity of SiO2-CaO-P2O5-Na2O-CaF2-ZnO glass-ceramics

Science.gov (United States)

Riaz, Madeeha; Zia, Rehana; Saleemi, Farhat; Bashir, Farooq; Hossain, Tousif; Kayani, Zohra

2014-09-01

Zinc is an essential trace element that stimulates bone formation but it is also known as an inhibitor of apatite crystal growth. In this work addition of ZnO to SiO2-CaO-P2O5-Na2O-CaF2 glass-ceramic system was made by conventional melt-quenching technique. DSC curves showed that the addition of ZnO moved the endothermic and exothermic peaks to lower temperatures. X-ray diffraction analysis did not reveal any additional phase caused by ZnO addition and showed the presence of wollastonite and hydroxyapatite crystalline phases only in all the glass-ceramic samples. As bio-implant apatite forming ability is an essential condition, the surface reactivity of the prepared glass-ceramic specimens was studied in vitro in Kokubo's simulated body fluid (SBF) [1] with ion concentration nearly equal to human blood plasma for 30 days at 37 °C under static condition. Atomic absorption spectroscopy (AAS) was used to study the changes in element concentrations in soaking solutions and XRD, FT-IR and SEM were used to elucidate surface properties of prepared glass-ceramics, which confirmed the formation of HCAp on the surface of all glass-ceramics. It was found that the addition of ZnO had a positive effect on bioactivity of glass-ceramics and made it a potential candidate for restoration of damaged bones.

Dependence of Photocatalytic Activity of TiO2-SiO2 Nanopowders

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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.

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

Science.gov (United States)

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

2009-01-01

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

Investigating the solubility and cytocompatibility of CaO-Na2 O-SiO2 /TiO2 bioactive glasses.

Science.gov (United States)

Wren, Anthony W; Coughlan, Aisling; Smith, Courtney M; Hudson, Sarah P; Laffir, Fathima R; Towler, Mark R

2015-02-01

This study aims to investigate the solubility of a series of titanium (TiO2 )-containing bioactive glasses and their subsequent effect on cell viability. Five glasses were synthesized in the composition range SiO2 -Na2 O-CaO with 5 mol % of increments TiO2 substituted for SiO2 . Glass solubility was investigated with respect to (1) exposed surface area, (2) particle size, (3) incubation time, and (4) compositional effects. Ion release profiles showed that sodium (Na(+) ) presented high release rates after 1 day and were unchanged between 7 and 14 days. Calcium (Ca(2+) ) release presented a significant change at each time period and was also composition dependent, where a reduction in Ca(2+) release is observed with an increase in TiO2 concentration. Silica (Si(4+) ) release did not present any clear trends while no titanium (Ti(4+) ) was released. Cell numbers were found to increase up to 44%, compared to the growing control population, with a reduction in particle size and with the inclusion of TiO2 in the glass composition. © 2014 Wiley Periodicals, Inc.

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....

The electrorheological properties of nano-sized SiO2 particle materials doped with rare earths

International Nuclear Information System (INIS)

Liu Yang; Liao Fuhui; Li Junran; Zhang Shaohua; Chen Shumei; Wei Chenguan; Gao Song

2006-01-01

Electrorheological (ER) materials of pure SiO 2 and SiO 2 doped with rare earths (RE = Ce, Gd, Y) (non-metallic glasses (silicates)) were prepared using Na 2 SiO 3 and RECl 3 as starting materials. The electrorheological properties are not enhanced by all rare earth additions. The material doped with Ce exhibits the best ER performance

Liquidus Temperature of SrO-Al2O3-SiO2 Glass-Forming Compositions

DEFF Research Database (Denmark)

Abel, Brett M.; Morgan, James M.; Mauro, John C.

2013-01-01

. In the composition range of interest for industrial glasses, Tliq tends to decrease with increasing strontium-to-alumina ratio. We find that cristobalite, mullite, and slawsonite are the dominant devitrification phases for the compositions with high SiO2, SiO2+Al2O3, and SrO contents, respectively. By comparison...... with the phase diagrams for CaO-Al2O3-SiO2 and MgO-Al2O3-SiO2 systems, we have found that for the highest [RO]/[Al2O3] ratios, Tliq exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging...... to the SrO-Al2O3-SiO2 family may be designed with a more exact control of the glass-forming ability by avoiding the regions of high liquidus temperature....

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

Science.gov (United States)

Ohta, Hiromichi; Watanabe, Takanobu; Ohdomari, Iwao

2008-10-01

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

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.

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

International Nuclear Information System (INIS)

Degueldre, C.; Wernli, B.

1993-01-01

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

Optimization of NaOH Molarity, LUSI Mud/Alkaline Activator, and Na2SiO3/NaOH Ratio to Produce Lightweight Aggregate-Based Geopolymer

Directory of Open Access Journals (Sweden)

Rafiza Abdul Razak

2015-05-01

Full Text Available This paper presents the mechanical function and characterization of an artificial lightweight geopolymer aggregate (ALGA using LUSI (Sidoarjo mud and alkaline activator as source materials. LUSI stands for LU-Lumpur and SI-Sidoarjo, meaning mud from Sidoarjo which erupted near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia on 27 May 2006. The effect of NaOH molarity, LUSI mud/Alkaline activator (LM/AA ratio, and Na2SiO3/NaOH ratio to the ALGA are investigated at a sintering temperature of 950 °C. The results show that the optimum NaOH molarity found in this study is 12 M due to the highest strength (lowest AIV value of 15.79% with lower water absorption and specific gravity. The optimum LUSI mud/Alkaline activator (LM/AA ratio of 1.7 and the Na2SiO3/NaOH ratio of 0.4 gives the highest strength with AIV value of 15.42% with specific gravity of 1.10 g/cm3 and water absorption of 4.7%. The major synthesized crystalline phases were identified as sodalite, quartz and albite. Scanning Electron Microscope (SEM image showed more complete geopolymer matrix which contributes to highest strength of ALGA produced.

Optimization of NaOH Molarity, LUSI Mud/Alkaline Activator, and Na2SiO3/NaOH Ratio to Produce Lightweight Aggregate-Based Geopolymer

Science.gov (United States)

Abdul Razak, Rafiza; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Ismail, Khairul Nizar; Hardjito, Djwantoro; Yahya, Zarina

2015-01-01

This paper presents the mechanical function and characterization of an artificial lightweight geopolymer aggregate (ALGA) using LUSI (Sidoarjo mud) and alkaline activator as source materials. LUSI stands for LU-Lumpur and SI-Sidoarjo, meaning mud from Sidoarjo which erupted near the Banjarpanji-1 exploration well in Sidoarjo, East Java, Indonesia on 27 May 2006. The effect of NaOH molarity, LUSI mud/Alkaline activator (LM/AA) ratio, and Na2SiO3/NaOH ratio to the ALGA are investigated at a sintering temperature of 950 °C. The results show that the optimum NaOH molarity found in this study is 12 M due to the highest strength (lowest AIV value) of 15.79% with lower water absorption and specific gravity. The optimum LUSI mud/Alkaline activator (LM/AA) ratio of 1.7 and the Na2SiO3/NaOH ratio of 0.4 gives the highest strength with AIV value of 15.42% with specific gravity of 1.10 g/cm3 and water absorption of 4.7%. The major synthesized crystalline phases were identified as sodalite, quartz and albite. Scanning Electron Microscope (SEM) image showed more complete geopolymer matrix which contributes to highest strength of ALGA produced. PMID:26006238

Comparisons between TiO2- and SiO2-flux assisted TIG welding processes.

Science.gov (United States)

Tseng, Kuang-Hung; Chen, Kuan-Lung

2012-08-01

This study investigates the effects of flux compounds on the weld shape, ferrite content, and hardness profile in the tungsten inert gas (TIG) welding of 6 mm-thick austenitic 316 L stainless steel plates, using TiO2 and SiO2 powders as the activated fluxes. The metallurgical characterizations of weld metal produced with the oxide powders were evaluated using ferritoscope, optical microscopy, and Vickers microhardness test. Under the same welding parameters, the penetration capability of TIG welding with TiO2 and SiO2 fluxes was approximately 240% and 292%, respectively. A plasma column made with SiO2 flux exhibited greater constriction than that made with TiO2 flux. In addition, an anode root made with SiO2 flux exhibited more condensation than that made with TiO2 flux. Results indicate that energy density of SiO2-flux assisted TIG welding is higher than that of TiO2-flux assisted TIG welding.

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.

Magnetic SiO2/Fe3O4 colloidal crystals

International Nuclear Information System (INIS)

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

2008-01-01

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

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...

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

Directory of Open Access Journals (Sweden)

Laleh Enayati Ahangar

2016-01-01

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

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

Institute of Scientific and Technical Information of China (English)

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

2009-01-01

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

Bioactivity analysis of the Ta (V doped SiO2–CaO–Na2O–P2O5 ceramics prepared by solid state sintering method

Directory of Open Access Journals (Sweden)

Rehana Zia

2016-02-01

Full Text Available The main objective of the study was to control the degradation rate of material at a higher degradation rate improving the chemical stability of the material. Ta is known to have good chemical resistance, biocompatibility and show no adverse biological response. In the present study, SiO2–Na2O–CaO–P2O5 bioceramics with different Ta2O5 contents was prepared by solid state sintering method at 1000 °C. The as-sintered ceramics were subjected to immersion studies in stimulated body fluid (SBF for 21 days under static condition and characterized by XRD, FTIR, SEM, and AAS. The findings of the research indicate that the addition of Ta2O5 controlled degradability, and all samples showed sufficient bioactivity.

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

Science.gov (United States)

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

2011-05-01

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

Enhanced Photocatalytic Activity of ZrO2-SiO2 Nanoparticles by Platinum Doping

Directory of Open Access Journals (Sweden)

Mohammad W. Kadi

2013-01-01

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

Mineral-solution equilibria—III. The system Na 2OAl 2O 3SiO 2H 2OHCl

Science.gov (United States)

Popp, Robert K.; Frantz, John D.

1980-07-01

Chemical equilibrium between sodium-aluminum silicate minerals and chloride bearing fluid has been experimentally determined in the range 500-700°C at 1 kbar, using rapid-quench hydrothermal methods and two modifications of the Ag + AgCl acid buffer technique. The temperature dependence of the thermodynamic equilibrium constant ( K) for the reaction NaAlSi 3O 8 + HCl o = NaCl o + 1/2Al 2SiO 5, + 5/2SiO 2 + 1/2H 2O Albite Andalusite Qtz. K = (a NaCl o) /(a H 2O ) 1/2/(a HCl o) can be described by the following equation: log k = -4.437 + 5205.6/ T( K) The data from this study are consistent with experimental results reported by MONTOYA and HEMLEY (1975) for lower temperature equilibria defined by the assemblages albite + paragonite + quartz + fluid and paragonite + andalusite + quartz + fluid. Values of the equilibrium constants for the above reactions were used to estimate the difference in Gibbs free energy of formation between NaCl o and HCl o in the range 400-700°C and 1-2 kbar. Similar calculations using data from phase equilibrium studies reported in the literature were made to determine the difference in Gibbs free energy of formation between KCl o and HCl o. These data permit modelling of the chemical interaction between muscovite + kspar + paragonite + albite + quartz assemblages and chloride-bearing hydrothermal fluids.

CoFe2O4-SiO2 Composites: Preparation and Magnetodielectric Properties

Directory of Open Access Journals (Sweden)

T. Ramesh

2016-01-01

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

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.

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.

Origin of the n -type and p -type conductivity of MoS 2 monolayers on a SiO 2 substrate

KAUST Repository

Dolui, Kapildeb

2013-04-02

Ab initio density functional theory calculations are performed to study the electronic properties of a MoS2 monolayer deposited over a SiO 2 substrate in the presence of interface impurities and defects. When MoS2 is placed on a defect-free substrate, the oxide plays an insignificant role since the conduction band top and the valence band minimum of MoS2 are located approximately in the middle of the SiO2 band gap. However, if Na impurities and O dangling bonds are introduced at the SiO2 surface, these lead to localized states, which modulate the conductivity of the MoS2 monolayer from n- to p-type. Our results show that the conductive properties of MoS2 deposited on SiO 2 are mainly determined by the detailed structure of the MoS 2/SiO2 interface, and suggest that doping the substrate can represent a viable strategy for engineering MoS2-based devices. © 2013 American Physical Society.

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.

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.

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-.

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.

Adsorption of uranyl in SiO2 porous glass

International Nuclear Information System (INIS)

Benedetto, F. E.; Prado, M. O.

2013-01-01

Vitreous SiO 2 porous matrices can be used in many applications involving the uptake of chemical species on its solid surface. In this work, vitreous silica sponges were prepared from a sodium borosilicate glass manufactured in our laboratory. The product obtained was then separated into phases with subsequent leaching of the soluble phase rich in B and Na. The resulting porous matrices have a specific surface of 35 m2/gr. Adsorption of uranyl ions onto the SiO 2 porous surface was studied to evaluate the use of this material as a filter for treatment of uranium containing water. The effects of contact time, adsorbent mass and equilibrium concentration of solution were studied. The porous adsorbent exhibits a pseudo-second-order kinetic behavior. The sponges with adsorbed uranium were thermally sealed as a way of U immobilization. Retention of uranium was confirmed during the matrix sealing by TGA. Uranium concentration before and after adsorption tests were made by means of ICP-OES. For uranium concentration of 800 ppm, 72 hours contact time and pH of 3.5, the amount of uranium adsorbed was 21.06 ± 0.02 mg U per gram of vitreous porous SiO 2 . (author)

Effect of alkali earth oxides on hydroxy-carbonated apatite nano layer formation for SiO2-BaO-CaO-Na2O-P2O5 glass system

Science.gov (United States)

Kiran, P.; Ramakrishna, V.; Shashikala, H. D.; Udayashankar, N. K.

2017-11-01

Barium soda lime phosphosilicate [(58SiO2-(32 - x)BaO- xCao-6Na2O-4P2O5 (where x = 15, 20, 25 and 30 mol%)] samples were synthesised using conventional sol-gel method at 700 °C sintering temperature. Thermal, structural properties were studied using thermo gravimetric analysis and differential thermal analysis, X-ray diffraction, scanning electron microscopy, fourier transform infrared and Raman spectroscopy. Using Raman spectra non-bridging oxygen concentrations were estimated. The hydroxy-carbonated apatite (HCA) layer formation on samples was analysed for 7 days using simulated body fluid (SBF) soaked samples. The growth of HCA layers self-assembled on the sample surface was discussed as a function of NBO/BO ratio. Results indicated that the number of Ca2+ ions released into SBF solution in dissolution process and weight loss of SB-treated samples vary with NBO/BO ratio. The changes in NBO/BO ratios were observed to be proportional to HCA forming ability of barium soda lime phosphosilicate glasses.

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.)

A study of low threshold and high gain Nd3+ ions doped SiO2-B2O3-Na2CO3-NaF-CaF2 glasses for NIR laser applications

Science.gov (United States)

Megala, Rajesh; Gowthami, T.; John Sushma, N.; Kamala, S.; Deva Prasad Raju, B.

2018-05-01

Fluoroborosilicate glasses of composition 35SiO2-25B2O3-10Na2CO3-15NaF-15CaF2-xNd2O3 (where x = 0.1, 0.5. 1.0, 2.0 mol%) were prepared by melt quenching technique and various physical properties have been calculated. From the absorption spectra J-O Intensity parameters Ωλ (λ = 2, 4, 6) and radiative properties are evaluated by using J-O theory. The high values of Ω2 = 4.213 × 10-20 cm2, Ω4 = 5.345 × 10-20 cm2, Ω6 = 5.526 × 10-20 cm2 suggest that among the prepared glasses 0.5 mol% Nd glass is more asymmetric, more covalent and rigid in nature. The emission spectra were recorded with 808 nm laser as excitation source. The strong NIR emissions were observed at 876 nm, 1056 nm, 1328 nm corresponding to the transitions 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, 4F3/2 → 4I13/2 respectively. Stimulated emission cross -section (σemi) and Gain bandwidth (σemi × Δλeff) were calculated. For 0.5 mol% Nd these values are found to be 3.30 × 10-20 cm2, 11 × 10-26 cm2. From the decay curve analysis the lifetime values for 4F3/2 level have been determined and these values are decreased with increase in Nd3+ ions concentration. These results may suggest that the prepared SBNCNd05 (Nd = 0.5 mol%) glass could be useful for 1056 nm laser applications.

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)

Sol–gel hybrid membranes loaded with meso/macroporous SiO2, TiO2–P2O5 and SiO2–TiO2–P2O5 materials with high proton conductivity

International Nuclear Information System (INIS)

Castro, Yolanda; Mosa, Jadra; Aparicio, Mario; Pérez-Carrillo, Lourdes A.; Vílchez, Susana; Esquena, Jordi; Durán, Alicia

2015-01-01

In this work, highly conductive hybrid organic–inorganic membranes loaded with SiO 2 , TiO 2 –P 2 O 5 and SiO 2 –TiO 2 –P 2 O 5 meso/macroporous particles were prepared via a sol–gel process. Meso/macroporous particles were incorporated to hybrid membranes, for improving water retention and enhancing electrochemical performance. These particles with a polymodal pore size distribution were prepared by templating in highly concentrated emulsions, the particles showed a specific surface area between 50 m 2 /g (TiO 2 –P 2 O 5 ) and 300 m 2 /g (SiO 2 –TiO 2 –P 2 O 5 ). The particles were dispersed in a hybrid silica sol and further sprayed onto glass paper. The films were polymerized and sintered; those loaded with meso/macroporous particles had a homogenous distribution. High temperature proton conductivity measurements confirmed a high water retention. Conductivity of these materials is higher than that of Nafion ® at higher temperatures (120 °C) (2·10 −2  S/cm). This study provides processing guideline to achieve hybrid electrolytes for efficient conduction of protons due to their high surface area and porous structure. - Highlights: • Hybrid electrolyte with meso/macroporous particles were synthesized by sol–gel. • Depositions of hybrid solutions by spraying onto glass substrates were performed. • Proton conductivity was evaluated as a function of composition and porous structure

The Effect of SiO2 Shell on the Suppression of Photocatalytic Activity of TiO2 and ZnO Nanoparticles

International Nuclear Information System (INIS)

Lee, Min Hee; Lee, Choon Soo; Patil, Umakant Mahadev; Kochuveedu, Saji Thomas

2012-01-01

In this study, we investigate the potential use of TiO 2 SiO 2 and ZnO SiO 2 core/shell nanoparticles (NPs) as effective UV shielding agent. In the typical synthesis, SiO 2 was coated over different types of TiO 2 (anatase and rutile) and ZnO by sol-gel method. The synthesized TiO 2 SiO 2 and ZnO SiO 2 Nps were characterized by UV-Vis, XRD, Sem and TEM. The UV-vis absorbance and transmittance spectra of core shell NPs showed an efficient blocking effect in the UV region and more than 90% transmittance in the visible region. XRD and SAED studies confirmed the formation of amorphous SiO 2 coated over the TiO 2 and ZnO NPs. The FESEM and TEM images shows that coating of SiO 2 over the surface of anatase, rutile TiO 2 and ZnO NPs resulted in the increase in particle size by ∼30 nm. In order to study the UV light shielding capability of the samples, photocatalytic degradation of methylene blue dye on TiO 2 SiO 2 and ZnO SiO 2 NPs was performed. Photocatalytic activity for both types of TiO 2 NPs was partially suppressed. In comparison, the photocatalytic activity of ZnO almost vanished after the SiO 2 coating

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.

Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

Science.gov (United States)

Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

2015-12-30

This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions. Copyright © 2015 Elsevier B.V. All rights reserved.

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

Directory of Open Access Journals (Sweden)

Yuan Xiao

2018-03-01

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

Enhancement of photocatalytic properties of TiO2 nanoparticles doped with CeO2 and supported on SiO2 for phenol degradation

International Nuclear Information System (INIS)

Hao, Chunjing; Li, Jing; Zhang, Zailei; Ji, Yongjun; Zhan, Hanhui; Xiao, Fangxing; Wang, Dan; Liu, Bin; Su, Fabing

2015-01-01

Highlights: • CeO 2 -TiO 2 /SiO 2 composites were prepared via a facile co-precipitation method. • Introduction of SiO 2 support increases the dispersion of CeO 2 -TiO 2 . • CeO 2 -TiO 2 /SiO 2 exhibits an enhanced photocatalytic efficiency for phenol degradation. • Ce 3+ /Ce 4+ pair coexisting in CeO 2 improves electron–hole pairs separation efficiency. - Abstract: A series of CeO 2 -TiO 2 and CeO 2 -TiO 2 /SiO 2 composites were prepared with TiCl 4 and Ce (NO 3 ) 3 ·6H 2 O as precursors via a facile co-precipitation method. The obtained samples were characterized by various techniques such as X-ray diffraction (XRD), nitrogen adsorption (N 2 -BET), Fourier transformation infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis spectroscopy measurements. The results indicated that TiO 2 doped with CeO 2 and supported on SiO 2 could reduce the crystallite size, inhibit the phase transformation, enhance the thermal stability, and effectively extend the spectral response from UV to visible range. When applied to the phenol photodegradation on a homemade batch reactor with an external cooling jacket, the CeO 2 -TiO 2 /SiO 2 catalysts exhibited significantly enhanced photodegradation efficiency in comparison with commercial Degussa P25 and CeO 2 -TiO 2 . The unique catalytic properties of CeO 2 -TiO 2 /SiO 2 were ascribed to improved electron–hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce 3+ /Ce 4+ , as well as high dispersion of active component of CeO 2 -TiO 2 as a result of the introduction of SiO 2 support. Furthermore, the catalysts can be easily recovered from the reaction solution by centrifugation and reused for four cycles without significant loss of activity

Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values

Science.gov (United States)

Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

2017-06-01

We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

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.

Stability analysis of SiO2/SiC multilayer coatings

International Nuclear Information System (INIS)

Fu Zhiqiang; Jean-Charles, R.

2006-01-01

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

Apatite formation on organic polymers by biomimetic process using Na2O-SiO2 glasses as nucleating agent

Energy Technology Data Exchange (ETDEWEB)

Tanahashi, M; Yao, t; Kokubo, T [Kyoto University, Kyoto (Japan). Faculty of Engineering; Minoda, M; Miyamoto, T [Kyoto University, Kyoto (Japan). Institute for Chemical Research; Nakamura, T [Kyoto University, Kyoto (Japan). Research Center for Biomedical Engineering; Yamamuro, T [Kyoto University, Kyoto (Japan). Faculty of Medicine

1994-09-01

In this investigation, CaO-SiO2-based glass, which was previously used as the nucleating agent, was replaced by Na2O-SiO2 glasses, SiO2 glass, and SiO2 gel. The induction period for the apatite nucleation on various organic polymer substrates and the adhesive strength of the apatite layer to the substrates were examined. It was considered that the short induction period for the glasses with high Na2O contents was attributed to high dissolution rates of sodium and silicate ions from them. It was also considered that highly polar carboxyl or sulfinyl groups were formed on the polymer surfaces by the hydrolysis of their ester, amide or sulfonyl group in simulated body fluid with its pH increased by the Na{sup +} dissolution from the glass, and that these polar groups formed a strong bond with the apatite. It is suggested that thus formed apatite-organic polymer composites are useful as the bone-repairing as well as soft tissue-repairing materials. 11 refs., 13 figs., 3 tabs.

Electronic states of SiO2-MxOy (MxOy=P205, TiO2 and ZrO2) glasses

Energy Technology Data Exchange (ETDEWEB)

Kowada, Y [Hyogo Univ. of Teacher Education, Hyogo (Japan); Adachi, H [Kyoto Univ. (Japan). Faculty of Engineering; Minami, T [Univ. of Osaka Prefecture, Osaka (Japan). Faculty of Engineering

1993-12-01

Using the sol-gel method the surface of metal and glass substrates can be modified. For example, stainless steel sheets coated with the SiO2-ZrO2 glass films have higher resistance to corrosion and oxidation. The coating films contain high concentration of alkali ions diffusing from the glass substrates. It suggests that the sodium ions are trapped strongly within the coating films and are blocked to further diffuse to the surface. This behavior must be associated with the chemical bonding around the sodium ions in the SiO2-TiO2 and SiO2-ZrO2 films. For better understanding of the chemical bonding in the glasses, the electronic states of the SiO2-MxOy glasses were calculated by means of the DV-Xa cluster method. In this paper, the calculation method is explained, the results are discussed and the conclusion is stated. 17 refs., 6 figs.

Effect of interfacial SiO2- y layer and defect in HfO2- x film on flat-band voltage of HfO2- x /SiO2- y stacks for backside-illuminated CMOS image sensors

Science.gov (United States)

Na, Heedo; Lee, Jimin; Jeong, Juyoung; Kim, Taeho; Sohn, Hyunchul

2018-03-01

In this study, the effect of oxygen gas fraction during deposition of a hafnium oxide (HfO2- x ) film and the influence of the quality of the SiO2- y interlayer on the nature of flat-band voltage ( V fb) in TiN/HfO/SiO2- y /p-Si structures were investigated. X-ray photoemission spectroscopy analysis showed that the non-lattice oxygen peak, indicating an existing oxygen vacancy, increased as the oxygen gas fraction decreased during sputtering. From C- V and J- E analyses, the V fb behavior was significantly affected by the characteristics of the SiO2- y interlayer and the non-lattice oxygen fraction in the HfO2- x films. The HfO2- x /native SiO2- y stack presented a V fb of - 1.01 V for HfO2- x films with an oxygen gas fraction of 5% during sputtering. Additionally, the V fb of the HfO2- x /native SiO2- y stack could be controlled from - 1.01 to - 0.56 V by changing the deposition conditions of the HfO2- x film with the native SiO2- y interlayer. The findings of this study can be useful to fabricate charge-accumulating layers for backside-illuminated image sensor devices.

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

International Nuclear Information System (INIS)

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

2008-01-01

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

Hazards of TiO2 and amorphous SiO2 nanoparticles

NARCIS (Netherlands)

Reijnders, L.; Kahn, H.A.; Arif, I.A.

2012-01-01

TiO2 and amorphous SiO2 nanoparticles have been described as ‘safe’, ‘non-toxic’ and ‘environment friendly’ in scientific literature. However, though toxicity data are far from complete, there is evidence that these nanoparticles are hazardous. TiO2 nanoparticles have been found hazardous to humans

SIMULTANEOUS OBSERVATIONS OF SiO AND H{sub 2}O MASERS TOWARD KNOWN STELLAR H{sub 2}O MASER SOURCES

Energy Technology Data Exchange (ETDEWEB)

Kim, Jaeheon [Yonsei University Observatory, Seongsan-ro 262, Seodaemun, Seoul 120-749 (Korea, Republic of); Cho, Se-Hyung [Korean VLBI Network Yonsei Radio Astronomy Observatory, Yonsei University, Seongsan-ro 262, Seodaemun, Seoul 120-749 (Korea, Republic of); Kim, Sang Joon, E-mail: jhkim@kasi.re.kr, E-mail: cho@kasi.re.kr, E-mail: sjkim1@khu.ac.kr [Department of Astronomy and Space Science, Kyung Hee University, Seocheon-Dong, Giheung-Gu, Yongin, Gyeonggi-Do 446-701 (Korea, Republic of)

2013-01-01

We present the results of simultaneous observations of SiO v = 1, 2, {sup 29}SiO v = 0, J = 1-0, and H{sub 2}O 6{sub 16}-5{sub 23} maser lines toward 152 known stellar H{sub 2}O maser sources using the Yonsei 21 m radio telescope of the Korean VLBI Network from 2009 June to 2011 January. Both SiO and H{sub 2}O masers were detected from 62 sources with a detection rate of 40.8%. The SiO-only maser emission without H{sub 2}O maser detection was detected from 27 sources, while the H{sub 2}O-only maser without SiO maser detection was detected from 22 sources. Therefore, the overall SiO maser emission was detected from 89 sources, resulting in a detection rate of 58.6%. We have identified 70 new detections of the SiO maser emission. For both H{sub 2}O and SiO maser detected sources, the peak and integrated antenna temperatures of SiO masers are stronger than those of H{sub 2}O masers in both Mira variables and OH/IR stars and the relative intensity ratios of H{sub 2}O to SiO masers in OH/IR stars are larger than those in Mira variables. In addition, distributions of 152 observed sources were investigated in the IRAS two-color diagram.

Synthesis and thermal stability of the sodalite Na6Zn2[Al6Si6O24](SO4)2 and its reaction with hydrogen

DEFF Research Database (Denmark)

Heiden, Frank; Nielsen, Ulla Gro; Warner, Terence Edwin

2012-01-01

Ca2[Al6Si6O24](SO4)2. Na6Zn2[Al6Si6O24](SO4)2 was shown to be largely immiscible with nosean, Na8[Al6Si6O24]SO4 in the solid-state. Na6Zn2[Al6Si6O24](SO4)2 decomposes above 700 °C, yielding nosean, Na8[Al6Si6O24]SO4; willemite, Zn2SiO4; gahnite, ZnAl2O4; and presumably a glass phase, 2Na2O•9SiO2...

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

Directory of Open Access Journals (Sweden)

Eko Sri Kunarti

2009-03-01

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

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

Science.gov (United States)

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

2018-01-01

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

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

Science.gov (United States)

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

2017-09-01

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

Precipitation of amorphous SiO2 particles and their properties

Directory of Open Access Journals (Sweden)

S. Musić

2011-03-01

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

Coupling between Ge-nanocrystals and defects in SiO2

International Nuclear Information System (INIS)

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

2006-01-01

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

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).

Effects of four step sintering on Y2O3: SiO2 nanocomposite

International Nuclear Information System (INIS)

Ahlawat, Rachna

2015-01-01

Need for high performance materials for advanced applications have led to the development of new concepts in materials design processing and their fabrication. The development of nanocrystalline materials with improved and novel properties is an important turning point in materials research. In present work, we report synthesis and structural characterization of Y 2 O 3 : SiO 2 nanocomposite. Sol-gel technique is being used to prepare-Y 2 O 3 SiO 2 nanocomposite due to its effectiveness in preparing samples with good mixing of starting materials and at relatively low reaction temperature. We have used Y(NO 3 ) 3 .4H 2 O and TEOS as precursors and followed usual approach of sol-gel technique, the final product of Y 2 O 3 : SiO 2 nanocomposite is obtained in the form of powder. The powder samples were sintered at different temperature for different time durations in programmable muffle furnace. The samples were characterized by complementary techniques as X-Ray Diffraction (XRD), Fourier Transforms Infrared Spectroscopy (FTIR) and Transmission Electron Microscopy (TEM). (author)

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

Surface properties of SiO2 with and without H2O2 treatment as gate dielectrics for pentacene thin-film transistor applications

Science.gov (United States)

Hung, Cheng-Chun; Lin, Yow-Jon

2018-01-01

The effect of H2O2 treatment on the surface properties of SiO2 is studied. H2O2 treatment leads to the formation of Si(sbnd OH)x at the SiO2 surface that serves to reduce the number of trap states, inducing the shift of the Fermi level toward the conduction band minimum. H2O2 treatment also leads to a noticeable reduction in the value of the SiO2 capacitance per unit area. The effect of SiO2 layers with H2O2 treatment on the behavior of carrier transports for the pentacene/SiO2-based organic thin-film transistor (OTFT) is also studied. Experimental identification confirms that the shift of the threshold voltage towards negative gate-source voltages is due to the reduced number of trap states in SiO2 near the pentacene/SiO2 interface. The existence of a hydrogenated layer between pentacene and SiO2 leads to a change in the pentacene-SiO2 interaction, increasing the value of the carrier mobility.

Potentiodynamical deposition of nanostructured MnO2 film at the assist of electrodeposited SiO2 as template

International Nuclear Information System (INIS)

Wu, Lian-Kui; Xia, Jie; Hou, Guang-Ya; Cao, Hua-Zhen; Tang, Yi-Ping; Zheng, Guo-Qu

2016-01-01

Highlights: • MnO 2 -SiO 2 composite film is prepared by potentiodynamical deposition. • Hierarchical porous MnO 2 films is obtained after the etching of SiO 2 . • The obtained MnO 2 film electrode exhibit high specific capacitance. - Abstract: We report a novel silica co-electrodeposition route to prepare nanostructured MnO 2 films. Firstly, MnO 2 -SiO 2 composite film was fabricated on a stainless steel substrate by potentiodynamical deposition, i.e. cyclic deposition, and then the SiO 2 template was removed by simple immersion in concentrated alkaline solution, leading to the formation of a porous MnO 2 (po-MnO 2 ) matrix. The structure and morphology of the obtained films were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical properties of the po-MnO 2 film were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). Results showed that this porous MnO 2 derived from the MnO 2 -SiO 2 composite film exhibits good electrochemical performance for potential use as a supercapacitor material.

Viscosity of SiO2-"FeO"-Al2O3 System in Equilibrium with Metallic Fe

Science.gov (United States)

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2013-08-01

The present study delivered the measurements of viscosities in SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe. The rotational spindle technique was used in the measurements at the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The Fe saturation condition was maintained by an iron plate placed at the bottom of the crucible. The equilibrium compositions of the slags were measured by EPMA after the viscosity measurements. The effect of up to 20 mol. pct Al2O3 on the viscosity of the SiO2-"FeO" slag was investigated. The "charge compensation effect" of the Al2O3 and FeO association has been discussed. The modified quasi-chemical viscosity model has been optimized in the SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe to describe the viscosity measurements of the present study.

PECVD SiO2 dielectric for niobium Josephson IC process

International Nuclear Information System (INIS)

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

1991-01-01

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

Silicate liquid immiscibility in magmas and in the system K2O-FeO-AI2O3-SiO2: an example of serendipity

Science.gov (United States)

Roedder, E.

1978-01-01

The concept of silicate liquid immiscibility was invoked early in the history of petrology to explain certain pairs of compositionally divergent rocks, but. as a result of papers by Greig (Am. J. Sci. 13, 1-44, 133-154) and Bowen (The Evolution of the Igneous Rocks), it fell into disfavor for many years. The discovery of immiscibility in geologically reasonable temperature ranges and compositions in experimental work on the system K2O-FeO-Al2O3-SiO2, and of evidence for immiscibility in a variety of lunar and terrestrial rocks, has reinstated the process. Phase equilibria in the high-silica corner of the tetrahedron representing the system K2O- FeO-Al2O3-SiO2 are presented, in the form of constant FeO sections through the tetrahedron, at 10% increments. Those sections, showing the tentative relationships of the primary phase volumes, are based on 5631 quenching runs on 519 compositions, made in metallic iron containers in pure nitrogen. Thirteen crystalline compounds are involved, of which at least six show two or more crystal modifica-tions. Two separate phase volumes, in each of which two immiscible liquids, one iron-rich and the other iron-poor, are present at the liquidus. One of these volumes is entirely within the quaternary system, astride the 1:1 K2O:Al2O3 plane. No quaternary compounds as such have been found, but evidence does point toward at least partial quaternary solid solution, with rapidly lowering liquidus temperatures, from K2O??Al2O3?? 2SiO2 ('potash nepheline', kalsilite. kaliophilite) to the isostructural compound K2O??FeO??3SiO2, and from K2O??Al2O3??4SiO2 (leucite) to the isostructural compound K2O??FeO??5SiO2, Both of these series apparently involve substitution, in tetrahedral coordination. of a ferrous iron and a silicon ion for two aluminum ions. Some of the 'impurities' found in analyses of the natural phases may reflect these substitutions. As a result of the geometry of the immiscibility volume located entirely within the quaternary

Theory of Al2O3 incorporation in SiO2

DEFF Research Database (Denmark)

Lægsgaard, Jesper

2002-01-01

Different possible forms of Al2O3 units in a SiO2 network are studied theoretically within the framework of density-functional theory. Total-energy differences between the various configurations are obtained, and simple thermodynamical arguments are used to provide an estimate of their relative...

SIMULTANEOUS OBSERVATIONS OF SiO AND H2O MASERS TOWARD SYMBIOTIC STARS

International Nuclear Information System (INIS)

Cho, Se-Hyung; Kim, Jaeheon

2010-01-01

We present the results of simultaneous observations of SiO v = 1, 2, J = 1-0, 29 SiO v = 0, J = 1-0, and H 2 O 6 16 -5 23 maser lines performed with the KVN Yonsei 21 m radio telescope from 2009 November to 2010 January. We searched for these masers in 47 symbiotic stars and detected maser emission from 21 stars, giving the first time detection from 19 stars. Both SiO and H 2 O masers were detected from seven stars of which six were D-type symbiotic stars and one was an S-type star, WRAY 15-1470. In the SiO maser emission, the 28 SiO v = 1 maser was detected from 10 stars, while the v = 2 maser was detected from 15 stars. In particular, the 28 SiO v = 2 maser emission without the v = 1 maser detection was detected from nine stars with a detection rate of 60%, which is much higher than that of isolated Miras/red giants. The 29 SiO v = 0 maser emission was also detected from two stars, H 2-38 and BF Cyg, together with the 28 SiO v = 2 maser. We conclude that these different observational results between isolated Miras/red giants and symbiotic stars may be related with the presence of hot companions in a symbiotic binary system.

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

Science.gov (United States)

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

2017-05-01

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

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 .

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

International Nuclear Information System (INIS)

Fukuda, Koichiro; Asaka, Toru; Uchida, Tomohiro

2012-01-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Cristalización de Cordierita en vidrios derivados del sistema cuaternario CaO-MgO-Al2O3-SiO2. Influencia de la composición del vidrio

Directory of Open Access Journals (Sweden)

Alarcón, J.

1998-10-01

Full Text Available It has been studied the calcium effect on the crystallization of cordierite for obtaining a glassceramic material into the CaOáMgOáAl2O3áSiO2 quaternary system. With this propose it has been selected six compositions into de cordierite primary field of crystallization and obtained the original glasses. The obtained samples have been analysed after a thermal treatment in three steps (glass transformation, nucleation and growth by X-ray diffraction (XRD. The composition of phases in microstructures have been analysed by scanning electron microscopy (SEM. The microstructures have been related with the crystalline phases by energy dispersive X-ray microanalysis (EDX. The amount of CaO in glasses is directly related with the anorthite crystallization, suggesting that the great amount of crystallized anorthite in relation with the low amount of CaO in the original glasses is due to the formation of one anorthite-diopside solid solution, what was tested by EDX. At growth temperature almost every samples partly crystallized, as primary or secondary cordierite phase. The anorthite microstructure was very particulated in spherulites forms of radius near to 250 nm, while the cordierite phase showed different morphologies, from almost-spherulitic crystallization nucleus ("rosettes" of μ-cordierite for direct crystallization from glass, to dense dendrites coming from μ transformation. Finally it can be found homogeneous blocks of α-cordierite with dimension of 10 x 10 μm2.Se ha estudiado el efecto del calcio en la cristalización de cordierita para la obtención de un material vitrocerámico dentro del sistema cuaternario CaO-MgO-Al2O3-SiO2. Con este objetivo se han seleccionado seis composiciones dentro del campo primario de cristalización de la cordierita y se han obtenido por fusión sus correspondientes vidrios. Se han analizado las muestras obtenidas tras un tratamiento térmico en tres etapas (transformación vítrea, nucleación y crecimiento

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.

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

Science.gov (United States)

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

2015-12-09

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

Efeito da adição de Na2O na viscosidade e devitrificação do vidro obtido a partir de cinzas volantes e Li2O Influence of Na2O on the viscosity and devitrification behavior of glasses obtained from fly ashes and Li2O

Directory of Open Access Journals (Sweden)

Etney Neves

1998-07-01

Full Text Available Glass-ceramic materials can be produced by the addition of LiO2 to fly ashes disposible in Southern Brazil. These glass-ceramics are based on the Al2O3-SiO2-Li 2O system. The high viscosity of the obtained glasses, however, makes forming useful articles with these materials difficult. In this study we investigate the effect of adding low cost Na2CO3 on the melt viscosity and on the nature of the developed crystalline phases. It was intended that the ultimate crystalline phase (LiAlSi3O8 should not be altered. With additions up to 3 wt. % Na2CO3, the viscosity was apparently lowered and no new crystalline phase were detected.

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...

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

International Nuclear Information System (INIS)

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

2009-01-01

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

SiO2 Glass Density to Lower-Mantle Pressures

DEFF Research Database (Denmark)

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

2017-01-01

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

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

Visible Light Excited Catalysis and Reusability Performances of TiO2@Pr:Y2SiO5 Upconversion Materials

Directory of Open Access Journals (Sweden)

Yan Jiao

2017-01-01

Full Text Available To get high efficiency photodegradation on pollutants under visible light, Pr(III doped Y2SiO5 upconversion materials and anatase TiO2 nanofilm coated Pr:Y2SiO5 composite have been prepared by using a sol-gel method. XRD and SEM test results indicated that TiO2 nanofilm was well coated on Pr:Y2SiO5 to form TiO2@Pr:Y2SiO5 composite particles with the sizes of 0.5–1.0 μm. To avoid secondary pollution resulting from incomplete recovery of catalyst particles, TiO2@Pr:Y2SiO5 was loaded on the glass fiber filters by using a dip-coating method. It is found that the catalyst particles were embedded into the carrier firmly, even after having been reused for 6 times. The luminescence intensities of TiO2@Pr:Y2SiO5 were getting down sharply with the coating contents of TiO2 increased, which was attributed to the adsorption of the luminescence by the TiO2 film in situ. As a result, TiO2@Pr:Y2SiO5 with 4% TiO2, which presented lowest luminescence intensity, showed the highest efficiency on the photodegradation of nitrobenzene wastewater. The catalysts loaded on glass fiber filters showed excellent reusability on the photodegradation of nitrobenzene and presented a photodegradation rate of 95% at the first time and up to 75.9% even after 6 times of reusing by the treatment time of 12 h.

Catalytic combustion of trichloroethylene over TiO2-SiO2 supported catalysts

NARCIS (Netherlands)

Kulazynski, M.; van Ommen, J.G.; Trawczynski, J.; Walendziewski, J.

2002-01-01

Combustion of trichloroethylene (TCE) on Cr2O3, V2O5, Pt or Pd catalysts supported on TiO2-SiO2 as a carrier has been investigated. It was found that oxide catalysts are very active but their activity quickly diminishes due to loss of the active component, especially at higher reaction temperatures

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

Science.gov (United States)

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.

Structure of Na2O·MO·SiO2·CaF2 (M=Mg, Ca) oxyfluoride glasses

International Nuclear Information System (INIS)

Cheng Jinshu; Deng Wei; Wang Mitang

2012-01-01

(9-x)CaO·xMgO·15Na 2 O·60SiO 2 ·16CaF 2 (x=0, 2, 4, 6, and 9) oxyfluoride glasses were prepared. Utilizing the Raman scattering technique together with 29 Si and 19 F MAS NMR, the effect of alkaline metal oxides on the Q species of glass was characterized. Raman results show that as magnesia is added at the expense of calcium oxide, the disproportional reaction Q 3 →Q 4 +Q 2 (Q n is a SiO 4 tetrahedron with n bridging oxygens) prompted due to the high ionic field strength of magnesia, magnesium oxide entered into the silicate network as tetrahedral MgO 4 , and removed other modifying ions for charge compensation. This reaction was confirmed by 29 Si MAS NMR. 19 F MAS NMR results show that fluorine exists in the form of mixed calcium sodium fluoride species in all glasses and no Si-F bonds were formed. As CaO is gradually replaced by MgO (x=6, 9), a proportion of the magnesium ions combines with fluorine to form the MgF + species. Meanwhile, some part of Na + ions complex F - in the form of F-Na(6).

UV-VUV laser induced phenomena in SiO2 glass

International Nuclear Information System (INIS)

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

2004-01-01

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

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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.

Co-electrospinning fabrication and photocatalytic performance of TiO2/SiO2 core/sheath nanofibers with tunable sheath thickness

International Nuclear Information System (INIS)

Cao, Houbao; Du, Pingfan; Song, Lixin; Xiong, Jie; Yang, Junjie; Xing, Tonghai; Liu, Xin; Wu, Rongrong; Wang, Minchao; Shao, Xiaoli

2013-01-01

Graphical abstract: - Highlights: • The core–sheath TiO 2 /SiO 2 nanofibers were fabricated by co-electrospinning technique. • The catalytic property of nanofibers with different sheath thickness was studied. • The potential methods of improving catalytic efficiency are suggested. - Abstract: In this paper, core/sheath TiO 2 /SiO 2 nanofibers with tunable sheath thickness were directly fabricated via a facile co-electrospinning technique with subsequent calcination at 500 °C. The morphologies and structures of core/sheath TiO 2 /SiO 2 nanofibers were characterized by TGA, FESEM, TEM, FTIR, XPS and BET. It was found that the 1D core/sheath nanofibers are made up of anatase–rutile TiO 2 core and amorphous SiO 2 sheath. The influences of SiO 2 sheath and its thickness on the photoreactivity were evaluated by observing photo-degradation of methylene blue aqueous solution under the irradiation of UV light. Compared with pure TiO 2 nanofibers, the core/sheath TiO 2 /SiO 2 nanofibers performed a better catalytic performance. That was attributed to not only efficient separation of hole–electron pairs resulting from the formation of heterojunction but also larger surface area and surface silanol group which will be useful to provide higher capacity for oxygen adsorption to generate more hydroxyl radicals. And the optimized core/sheath TiO 2 /SiO 2 nanofibers with a sheath thickness of 37 nm exhibited the best photocatalytic performance

Sol-gel synthesis of TiO2-SiO2 photocatalyst for β-naphthol photodegradation

International Nuclear Information System (INIS)

Qourzal, S.; Barka, N.; Tamimi, M.; Assabbane, A.; Nounah, A.; Ihlal, A.; Ait-Ichou, Y.

2009-01-01

Silica gel supported titanium dioxide particles (TiO 2 -SiO 2 ) prepared by sol-gel method was as photocatalyst in the degradation of β-naphthol in water under UV-illumination. The prepared sample has been characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The supported catalyst had large surface area and good sedimentation ability. The photodegradation rate of β-naphthol under UV-irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The experiments were measured by high performance liquid chromatography (HPLC). The photodegradation rate of β-naphthol using 60% TiO 2 -SiO 2 particles was faster than that using TiO 2 'Degussa P-25', TiO 2 'PC-50' and TiO 2 'Aldrich' as photocatalyst by 2.7, 4 and 7.8 times, respectively. The kinetics of photocatalytic β-naphthol degradation was found to follow a pseudo-first-order rate law. The effect of the TiO 2 loading on the photoactivity of TiO 2 -SiO 2 particles was also discussed. With good photocatalytic activity under UV-irradiation and the ability to be readily separated from the reaction system, this novel kind of catalyst exhibited the potential effective in the treatment of organic pollutants in aqueous systems.

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 polyethylenimine-tannins coated SiO2 hybrid materials for Cu2+ removal

Science.gov (United States)

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

2018-01-01

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

Adsorption of cationic dye on a biohybrid SiO2-alginate

International Nuclear Information System (INIS)

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

2013-01-01

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

Effects of H2O/Na2O molar ratio on the strength of alkaline activated ground blast furnace slag-ultrafine palm oil fuel ash based concrete

International Nuclear Information System (INIS)

Yusuf, Moruf Olalekan; Megat Johari, Megat Azmi; Ahmad, Zainal Arifin; Maslehuddin, Mohammed

2014-01-01

Highlights: • Effects of H 2 O/Na 2 O on GBFS-POFA alkaline activated concrete are investigated. • High H 2 O/Na 2 O contents enhance dissolutions/workability at the expense of strength. • Lower H 2 O/Na 2 O molar ratios aid compressive strength of the products. • Increase in H 2 O/Na 2 O favours the reactivity of Ca and the products molecular bonds. • Low H 2 O/Na 2 O positively affects the microstructural density of the products. - Abstract: Effects of H 2 O/Na 2 O molar ratios (MRs) on the developed alkaline activated pozzolanic solid wastes (PMs)-ultrafine palm oil fuel ash (UPOFA) and ground blast furnace slag (GBFS)-were studied by using the constant mass of combined activators (10 M NaOH aq + Na 2 SiO 3aq of silica-modulus (Ms = SiO 2 /Na 2 O) of 3.3).The free water content (FWC) expressed as FWC/(PMs) varied from 0.02 to 0.1 by mass while the total H 2 O/Na 2 O MRs ranged from 18.9 to 23.1 The findings revealed that increase in H 2 O/Na 2 O MRs negatively affects the strength but positively impact the mixture workability (consistency). The microstructural morphology examination using Scanning Electron Microscope coupled with Energy dispersive spectroscopy (SEM + EDS) reveals the contribution of H 2 O/Na 2 O MRs to the product nature, compactness, and the reactivity of Ca 2+ and Al 3+ while Fourier transform infra-red (FTIR) spectroscopy indicates that H 2 O/Na 2 O ratios contributed to the product amorphousity and carbonation process but sparingly affected its formed polymerized structural units (SiQ n (mAl), n = 2 and 3)

Preparação do sistema Fe2O3/ZSM-5 para uso como catalisador na reação foto-Fenton

Directory of Open Access Journals (Sweden)

J. S. de Oliveira

Full Text Available Resumo Este trabalho objetivou a preparação da zeólita ZSM-5 suportada com nanopartículas de óxido de ferro para uso como catalisador na degradação de um poluente orgânico em solução aquosa a partir do processo foto-Fenton. A zeólita foi preparada usando gel nucleante como indutor de formação da estrutura tipo MFI. Nanopartículas de óxido de ferro foram suportadas sobre a zeólita através da técnica de impregnação incipiente. Além disso, nanopartículas de óxido de ferro foram preparadas para fins de comparação entre as atividades catalíticas na reação foto-Fenton. Os materiais produzidos foram caracterizados por difração de raios X, microscopia eletrônica de varredura e análise de adsorção/dessorção de nitrogênio. Os resultados revelaram a formação do sistema Fe2O3/ZSM-5 com propriedades intrínsecas que resultaram em satisfatória atividade catalítica, sendo superior ao óxido de ferro. Além disso, esse sistema apresentou excelente atividade e estabilidade após três ciclos de reuso. O material Fe2O3/ZSM-5 produzido neste trabalho apresenta-se como um catalisador promissor para uso na reação foto-Fenton para a degradação de poluentes orgânicos em soluções aquosas.

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

Directory of Open Access Journals (Sweden)

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.

Design and Synthesis of Hierarchical SiO2@C/TiO2 Hollow Spheres for High-Performance Supercapacitors.

Science.gov (United States)

Zhang, Ying; Zhao, Yan; Cao, Shunsheng; Yin, Zhengliang; Cheng, Li; Wu, Limin

2017-09-06

TiO 2 has been widely investigated as an electrode material because of its long cycle life and good durability, but the relatively low theoretical capacity restricts its practical application. Herein, we design and synthesize novel hierarchical SiO 2 @C/TiO 2 (HSCT) hollow spheres via a template-directed method. These unique HSCT hollow spheres combine advantages from both TiO 2 such as cycle stability and SiO 2 with a high accessible area and ionic transport. In particular, the existence of a C layer is able to enhance the electrical conductivity. The SiO 2 layer with a porous structure can increase the ion diffusion channels and accelerate the ion transfer from the outer to the inner layers. The electrochemical measurements demonstrate that the HSCT-hollow-sphere-based electrode manifests a high specific capacitance of 1018 F g -1 at 1 A g -1 which is higher than those for hollow TiO 2 (113 F g -1 ) and SiO 2 /TiO 2 (252 F g -1 ) electrodes, and substantially higher than those of all the previously reported TiO 2 -based electrodes.

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

Science.gov (United States)

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

2017-07-01

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

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

Directory of Open Access Journals (Sweden)

Yu Ri

2015-06-01

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

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

Science.gov (United States)

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

2010-05-01

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

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 .

Pseudo-ternary phase diagram in the Na2O-Na2O2-NaOH system

International Nuclear Information System (INIS)

Saito, Jun-ichi; Tendo, Masayuki; Aoto, Kazumi

1997-10-01

Generally, the phase diagrams are always used to understand the present state of compounds at certain temperature. In order to understand the corrosion behavior of structural material for FBR by main sodium compounds (Na 2 O, Na 2 O 2 and NaOH), it is very important to comprehend the phase diagrams of their compounds. However, only Na 2 O-NaOH pseudo-binary phase diagram had been investigated previously in this system. There is no study of other pseudo-binary or ternary phase diagrams in the Na 2 O-Na 2 O 2 -NaOH system. In this study, in order to clarify the present states of their compounds at certain temperatures, the pseudo-binary and ternary phase diagrams in the Na 2 O-Na 2 O 2 -NaOH system were prepared. A series of thermal analyses with binary and ternary component system has been carried out using the differential scanning calorimetry (DSC). The liquidus temperature and ternary eutectic temperatures were confirmed by these measurements. The beneficial indications for constructing phase diagrams were obtained from these experiments. On the basis of these results, the interaction parameters between compounds which were utilized for the Thermo-Calc calculation were optimized. Thermo-Calc is one of thermodynamic calculation software. Consequently the accurate pseudo-binary and ternary phase diagrams were indicated using the optimized parameters. (author)

Fast detoxication of 2-chloro ethyl ethyl sulfide by p-type Ag_2O semiconductor nanoparticle-loaded Al_2O_3-based supports

International Nuclear Information System (INIS)

Ma, Meng-Wei; Kuo, Dong-Hau

2016-01-01

Highlights: • Detoxication of CWA surrogate of 2-chloro ethyl ethyl sulfide is investigated. • A small amount of Ag_2O on Al_2O_3-base support is sufficient to degrade 2-CEES. • Detoxication conversion >82% in 15 min is achieved for >2.5% Ag_2O/Na_2SiO_3/Al_2O_3. • Na_2SiO_3 modified Al_2O_3 to have the valley-like line pattern for depositing Ag_2O. • 2-CEES oxidation is initiated from the dominant electronic holes in p-type Ag_2O. - Abstract: p-type Ag_2O semiconductor nanoparticle-loaded Al_2O_3 or Na_2SiO_3/Al_2O_3 powders used for detoxicating the surrogate of sulfur mustard of 2-chloro ethyl ethyl sulfide (C_2H_5SCH_2CH_2Cl, 2-CEES) were investigated. Different amounts of Ag_2O and Na_2SiO_3 on catalyst supports were evaluated. Gas chromatography with a pulsed flame photometric detector (GC–PFPD) and gas chromatography coupled with a mass spectroscopy (GC–MS) were used to monitor and identify the catalytic reactions, together with reaction products analysis. The GC analyses showed that the decontamination of 2-CEES in isopropanol solvent for 15 min was above 82% efficiency for the 0.5% Na_2SiO_3/Al_2O_3 support deposited with a Ag_2O content above 2.5%. 2-(ethylthio)ethanol and 2-(ethylthio)ethanoic acid were identified as the major products after catalytic reactions. The electronic holes dominating in p-type Ag_2O is proposed to provide the key component and to initiate the catalytic reactions. The electronic hole-based detoxication mechanism is proposed.

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+ .

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

Science.gov (United States)

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

2010-04-01

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

Análisis de la adhesión de recubrimientos del sistema Y2O3-Al2O3-SiO2 sobre sustratos de interés para la industria aeroespacial

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Cinta Marraco-Borderas

2016-07-01

Full Text Available En la industria aeroespacial se necesitan materiales ligeros que tengan unas altas prestaciones mecánicas combinadas con una baja densidad. El carburo de silicio, el carbono reforzado con fibra de carbono y el carburo de silicio reforzado con fibra de carbono son materiales que cumplen con estos requisitos, pero a altas temperaturas presentan problemas de oxidación. Una de las formas más efectivas de prevenir este fenómeno es la utilización de recubrimientos cerámicos, cuya correcta adhesión sobre los distintos sustratos es fundamental para garantizar su funcionamiento. En el caso del presente trabajo, se analiza la adhesión de recubrimientos vítreos del sistema Y2O3-Al2O3-SiO2 obtenidos mediante proyección térmica por llama oxiacetilénica. Para ello, se realizan ensayos de rayado a carga creciente analizando el tipo y la carga de fallo y su relación con las propiedades elásticas y mecánicas de los recubrimientos. Los resultados indican que la adhesión sobre los sustratos carburo de silicio y carburo de silicio reforzado con fibra de carbono es buena, mientras que el carbono reforzado con fibra de carbono no es un material adecuado para recubrir.

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

International Nuclear Information System (INIS)

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

2009-01-01

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

Laser conditioning effect on HfO2/SiO2 film

International Nuclear Information System (INIS)

Wei Yaowei; Zhang Zhe; Liu Hao; Ouyang Sheng; Zheng Yi; Tang Gengyu; Chen Songlin; Ma Ping

2013-01-01

Laser conditioning is one of the important methods to improve the laser damage threshold of film optics. Firstly, a large aperture laser was used to irradiate the HfO 2 /SiO 2 reflectors, which were evaporated from hafnia and silica by e-beam. Secondly, a laser calorimeter was used to test the film absorption before and after laser irradiation. Focused ion beam (FIB) was few reported using on laser film, it was used to study the damage morphology and explore the cause of damage. The shooting of the partial ejection on nodule was obtained for the first time, which provided the basis for study the damage process. The results show that film absorption was decreased obviously after the laser irradiation, laser conditioning can raise the laser damage threshold by the 'cleaning mechanism'. For the HfO 2 /SiO 2 reflectors, laser conditioning was effective to eject the nodules on substrate. It resulted from the nodule residue not to affect the subsequent laser. In addition, laser conditioning was not effective to the nodule in the film, which might be from the material spatter in coating process. In this case, other method could be used to get rid of the nodules. (authors)

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.

Na2MoO2As2O7

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Raja Jouini

2012-12-01

Full Text Available Disodium molybdenum dioxide diarsenate, Na2MoO2As2O7, has been synthesized by a solid-state reaction. The structure is built up from MoAs2O12 linear units sharing corners to form a three-dimensional framework containing tunnels running along the a-axis direction in which the Na+ cations are located. In this framework, the AsV atoms are tetrahedrally coordinated and form an As2O7 group. The MoVI atom is displaced from the center of an octahedron of O atoms. Two Na+ cations are disordered about inversion centres. Structural relationships between different compounds: A2MoO2As2O7 (A = K, Rb, AMOP2O7 (A = Na, K, Rb; M = Mo, Nb and MoP2O7 are discussed.

Alkali passivation mechanism of sol-gel derived TiO2-SiO2 films coated on soda-lime-silica glass substrates

Energy Technology Data Exchange (ETDEWEB)

Matsuda, A; Matsuno, Y; Katayama, S; Tsuno, T [Nippon Steel Glass Co. Ltd., Tokyo (Japan); Toge, N; Minami, T [University of Osaka Prefecture, Osaka (Japan). College of Engineering

1992-09-01

TiO2-SiO2 films prepared by the sol-gel method serves as an effective alkali passivation layer on a soda-lime-silica glass substrate and the film is superior to a sol-gel derived pure SiO2 film from the view point of weathering resistance improvement. To clarify the reason, alkali passivation mechanism of sol-gel derived TiO2-SiO2 glass films with different TiO2 contents coated on a soda-lime-silica glass substrate was studied by SIMS (secondary ion mass spectroscopy) and XPS (X-ray photoelectron spectroscopy) analyses, and compared with the results of a sol-gel derived pure SiO2 film. As a result, the following conclusions were obtained: An increase in TiO2 content in the TiO2 SiO2 film increases the sodium concentration in the film, which was induced by sodium migration from the glass substrate during the heat-treatment. Because of the presence of sodium the TiO2 -SiO2 films serve not as a barrier but as an effective getter of alkali ions and thereby effectively improve the weathering resistance Of the glass substrate. 10 refs., 6 figs.

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

Science.gov (United States)

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

2007-03-01

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

Metabolomic effects of CeO2, SiO2 and CuO metal oxide nanomaterials on HepG2 cells

Data.gov (United States)

U.S. Environmental Protection Agency — The data set is a matrix of cellular biochemical (metabolites) in HepG2 cells treated with various metal oxide nanomaterials composed of CeO2, SiO2 and CuO. This...

Resistencia al desgaste de recubrimientos sol-gel de SiO2 y SiO2 - ZrO2 sobre materiales vitrocerámicos obtenidos por sinterización

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Soares, V. O.

2013-10-01

Full Text Available The sol-gel process is widely used to obtain coatings on glass-ceramic substrates in order to improve the scratch and abrasion resistance, also providing a bright and homogeneous appearance of a glaze avoiding expensive final polishing treatments. This paper describes the preparation of silica and silica / zirconia coatings by sol-gel method on Li2O-Al2O3-SiO2 (LAS glassceramic substrates produced by sintering. The coatings were deposited by dip-coating on LAS substrates and characterized by optical microscopy and spectral ellipsometry. On the other hand, hardness and elastic modulus, coefficient of friction and abrasion and scratch resistance of the coatings were determined and compared with the substrate properties. Coatings deposited on LAS glass-ceramic confere the substrate a bright and homogeneous aspect, similar to a glaze, improving the appearance and avoiding the final polishing. However these coatings do not increase the scratch resistance of the substrate only equaling the properties of the glass-ceramic.El proceso sol-gel es un método interesante para la producción de recubrimientos vítreos sobre sustratos vitrocerámicos con el fin de mejorar su resistencia al rayado y al desgaste, y proporcionando además un aspecto homogéneo, vidriado y brillante que evite los costosos tratamientos finales de pulido. Este trabajo describe la preparación de recubrimientos de sílice y sílice/ circona por el método sol-gel sobre sustratos vitrocerámicos del sistema Li2O-Al2O3-SiO2 (LAS producidos por sinterización. Los recubrimientos se depositaron por la técnica de inmersión y se caracterizaron mediante microscopía óptica de luz reflejada y elipsometría espectral. Por otro lado, se determinó la dureza y el módulo de elasticidad, además del coeficiente de fricción, la resistencia al desgaste y al rayado de los recubrimientos. Estos resultados se compararon con las propiedades del sustrato sin recubrir. Las capas depositadas

Assembly of Fe3O4 nanoparticles on SiO2 monodisperse spheres

Indian Academy of Sciences (India)

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

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

Science.gov (United States)

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.

Atmospheric Plasma Deposition of SiO2 Films for Adhesion Promoting Layers on Titanium

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Liliana Kotte

2014-12-01

Full Text Available This paper evaluates the deposition of silica layers at atmospheric pressure as a pretreatment for the structural bonding of titanium (Ti6Al4V, Ti15V3Cr3Sn3Al in comparison to an anodizing process (NaTESi process. The SiO2 film was deposited using the LARGE plasma source, a linearly extended DC arc plasma source and applying hexamethyldisiloxane (HMDSO as a precursor. The morphology of the surface was analyzed by means of SEM, while the characterization of the chemical composition of deposited plasma layers was done by XPS and FTIR. The long-term durability of bonded samples was evaluated by means of a wedge test in hot/wet condition. The almost stoichiometric SiO2 film features a good long-term stability and a high bonding strength compared to the films produced with the wet-chemical NaTESi process.

Influence of ionic strength in the adsorption and during photocatalysis of reactive black 5 azo dye on TiO2 coated on non woven paper with SiO2 as a binder

International Nuclear Information System (INIS)

Aguedach, Abdelkahhar; Brosillon, Stephan; Morvan, Jean; Lhadi, El Kbir

2008-01-01

Reactive black 5 (RB5), an azo dye, was degraded by using UV-irradiated TiO 2 coated on non woven paper with SiO 2 as a binder. The adsorption capacity of the photocatalyst was studied at natural pH, superior to pH pzc of the binder, for various ionic strengths. Different salts such as NaCl, KCl, CaCl 2 , LiCl, Ca(NO 3 ) 2 were used to increase the ionic strength. The presence of salt increased the adsorption capacity. The electrostatic interactions between dye and oxide surface charges (TiO 2 /SiO 2 ) is very important in the adsorption phenomena. The effect of the ionic strength of the solution on photocatalyst degradation was studied. The rate of degradation was increased by the presence of salts in the range of the experimental conditions. The increase of the initial decolorization rate was observed in the following order: Ca 2+ > K + > Na + > Li + . Experiments with different anions (Cl - , NO 3 - ) had shown that nitrate was an indifferent electrolyte for the adsorption and photodegradation of the dye on SiO 2 /TiO 2

Luminescence properties of Ca2 Ga2 SiO7 :RE phosphors for UV white-light-emitting diodes.

Science.gov (United States)

Jiao, Mengmeng; Lv, Wenzhen; Lü, Wei; Zhao, Qi; Shao, Baiqi; You, Hongpeng

2015-03-16

A series of Eu(2+) -, Ce(3+) -, and Tb(3+) -doped Ca2 Ga2 SiO7 phosphors is synthesized by using a high-temperature solid-state reaction. The powder X-ray diffraction and structure refinement data indicate that our prepared phosphors are single phased and the phosphor crystalizes in a tetrahedral system with the ${P\\bar 42m}$ (113) space group. The Eu(2+) - and Ce(3+) -doped phosphors both have broad excitation bands, which match well with the UV light-emitting diodes chips. Under irradiation of λ=350 nm, Ca2 Ga2 SiO7 :Eu(2+) and Ca2 Ga2 SiO7 :Ce(3+) , Li(+) have green and blue emissions, respectively. Luminescence of Ca2 Ga2 SiO7 :Tb(3+) , Li(+) phosphor varies with the different Tb(3+) contents. The thermal stability and energy-migration mechanism of Ca2 Ga2 SiO7 :Eu(2+) are also studied. The investigation results indicate that the prepared Ca2 Ga2 SiO7 :Eu(2+) and Ca2 Ga2 SiO7 :Ce(3+) , Li(+) samples show potential as green and blue phosphors, respectively, for UV-excited white-light-emitting diodes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

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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.

Thermally tunable VO2-SiO2 nanocomposite thin-film capacitors

Science.gov (United States)

Sun, Yifei; Narayanachari, K. V. L. V.; Wan, Chenghao; Sun, Xing; Wang, Haiyan; Cooley, Kayla A.; Mohney, Suzanne E.; White, Doug; Duwel, Amy; Kats, Mikhail A.; Ramanathan, Shriram

2018-03-01

We present a study of co-sputtered VO2-SiO2 nanocomposite dielectric thin-film media possessing continuous temperature tunability of the dielectric constant. The smooth thermal tunability is a result of the insulator-metal transition in the VO2 inclusions dispersed within an insulating matrix. We present a detailed comparison of the dielectric characteristics of this nanocomposite with those of a VO2 control layer and of VO2/SiO2 laminate multilayers of comparable overall thickness. We demonstrated a nanocomposite capacitor that has a thermal capacitance tunability of ˜60% between 25 °C and 100 °C at 1 MHz, with low leakage current. Such thermally tunable capacitors could find potential use in applications such as sensing, thermal cloaks, and phase-change energy storage devices.

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

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ZHANG Hai-yuan

2017-05-01

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

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%.

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.

Crystallization and characterization of Y2O3-SiO2 glasses

Science.gov (United States)

Drummond, Charles H., III; Lee, William E.; Sanders, W. A.; Kiser, J. D.

1991-01-01

Glasses in the yttria-silica system with 20 to 40 mol pct Y2O3 were subjected to recrystallization studies after melting at 1900 to 2100 C in W crucibles in 1 and 50 atm N2. The TEM and XRD results obtained indicate the presence of the delta, gamma, gamma prime, and beta-Y2Si2O7 crystalline phases, depending on melting and quenching conditions. Heat treatment in air at 1100 to 1600 C increased the amount of crystallization, and led to the formation of Y2SiO5, cristabalite, and polymorphs of Y2Si2O7. Also investigated were the effects of 5 and 10 wt pct zirconia additions.

The effect of rare earth dopants on the structure, surface texture and photocatalytic properties of TiO2-SiO2 prepared by sol-gel method

International Nuclear Information System (INIS)

Mohamed, R.M.; Mkhalid, I.A.

2010-01-01

The sol-gel method was successfully used to prepare a series of TiO 2 -SiO 2 and rare earth (RE) (La 3+ , Nd 3+ , Sm 3+ , Gd 3+ )-doped TiO 2 -SiO 2 nanoparticles at a doping level of 3 atomic percent. The structural features of parent TiO 2 -SiO 2 and RE-TiO 2 -SiO 2 fired at 550 o C have been investigated by XRD, UV-diffuse reflection, SEM and nitrogen adsorption measurements at -196 o C. XRD data verified the formation of typical characteristic anatase form in all the prepared RE-doped TiO 2 -SiO 2 samples. In comparison with the pure TiO 2 -SiO 2 samples (ca. 35 nm in diameter), the RE-TiO 2 -SiO 2 samples have relatively small particle size indicating that the doping with RE metal ions can improve the particle morphology, and retard the grain growth of TiO 2 -SiO 2 during heat treatment. The results indicated that Gd 3+ doped TiO 2 -SiO 2 has the lowest bandgap and particle size compared with pure TiO 2 -SiO 2 and other nanoparticles of RE-doped TiO 2 -SiO 2 . The highest surface area (S BET ) and pore volume (V p ) values were recorded for Gd-TiO 2 -SiO 2 as well. The effect of doping on the photoactivity was evaluated by the photocatalytic degradation of EDTA as a probe reaction. Among all the pure and RE-doped TiO 2 -SiO 2 , Gd 3+ -TiO 2 -SiO 2 performed the highest catalytic activity towards the tested reaction. That might be due to its special characteristics of particle size, surface texture and bandgap properties. Details of the synthesis procedure and results of the characterization studies of the produced RE-TiO 2 -SiO 2 are presented in this paper.

Temperature-dependent field-effect carrier mobility in organic thin-film transistors with a gate SiO2 dielectric modified by H2O2 treatment

Science.gov (United States)

Lin, Yow-Jon; Hung, Cheng-Chun

2018-02-01

The effect of the modification of a gate SiO2 dielectric using an H2O2 solution on the temperature-dependent behavior of carrier transport for pentacene-based organic thin-film transistors (OTFTs) is studied. H2O2 treatment leads to the formation of Si(-OH) x (i.e., the formation of a hydroxylated layer) on the SiO2 surface that serves to reduce the SiO2 capacitance and weaken the pentacene-SiO2 interaction, thus increasing the field-effect carrier mobility ( µ) in OTFTs. The temperature-dependent behavior of carrier transport is dominated by the multiple trapping model. Note that H2O2 treatment leads to a reduction in the activation energy. The increased value of µ is also attributed to the weakening of the interactions of the charge carriers with the SiO2 dielectric that serves to reduce the activation energy.

Diffusive charge transport in graphene on SiO 2

Science.gov (United States)

Chen, J.-H.; Jang, C.; Ishigami, M.; Xiao, S.; Cullen, W. G.; Williams, E. D.; Fuhrer, M. S.

2009-07-01

We review our recent work on the physical mechanisms limiting the mobility of graphene on SiO 2. We have used intentional addition of charged scattering impurities and systematic variation of the dielectric environment to differentiate the effects of charged impurities and short-range scatterers. The results show that charged impurities indeed lead to a conductivity linear in density ( σ(n)∝n) in graphene, with a scattering magnitude that agrees quantitatively with theoretical estimates; increased dielectric screening reduces the scattering from charged impurities, but increases the scattering from short-range scatterers. We evaluate the effects of the corrugations (ripples) of graphene on SiO 2 on transport by measuring the height-height correlation function. The results show that the corrugations cannot mimic long-range (charged impurity) scattering effects, and have too small an amplitude-to-wavelength ratio to significantly affect the observed mobility via short-range scattering. Temperature-dependent measurements show that longitudinal acoustic phonons in graphene produce a resistivity that is linear in temperature and independent of carrier density; at higher temperatures, polar optical phonons of the SiO 2 substrate give rise to an activated, carrier density-dependent resistivity. Together the results paint a complete picture of charge carrier transport in graphene on SiO 2 in the diffusive regime.

Stability of trapped electrons in SiO2

International Nuclear Information System (INIS)

Fleetwood, D.M.; Winokur, P.S.; Flament, O.; Leray, J.L.

1998-01-01

Electron trapping near the Si/SiO 2 interface plays a crucial role in mitigating the response of MOS devices to ionizing radiation or high-field stress. These electrons offset positive charge due to trapped holes, and can be present at densities exceeding 10 12 cm -2 in the presence of a similar density of trapped positive charge. The nature of the defects that serve as hosts for trapped electrons in the near-interfacial SiO 2 is presently unknown, although there is compelling evidence that these defects are often intimately associated with trapped holes. This association is depicted most directly in the model of Lelis et al., which suggests that trapped electrons and holes occupy opposite sides of a compensated E center in SiO 2 . Charge exchange between electron traps and the Si can occur over a wide range of time scales, depending on the trap depth and location relative to the Si/SiO 2 interface. Here the authors report a detailed study of the stability of electron traps associated with trapped holes near the Si/SiO 2 interface

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Metabolomic effects in HepG2 cells exposed to CeO2, SiO2 and CuO nanomaterials.

Science.gov (United States)

To better assess potential hepatotoxicity of nanomaterials, human liver HepG2 cells were exposed for three days to 5 different CeO2 (either 30 or 100 ug/ml), 3 SiO2 based (30 ug/ml) or 1 CuO (3 ug/ml) nanomaterials with dry primary particle sizes ranging from 15 to 213 nm. Metab...

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

International Nuclear Information System (INIS)

Nakano, Shinsuke; Muto, Shunsuke; Tanabe, Tetsuo

2005-01-01

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

Theoretical prediction of Grüneisen parameter for SiO_2.TiO_2 bulk metallic glasses

International Nuclear Information System (INIS)

Singh, Chandra K.; Pandey, Brijesh K.; Pandey, Anjani K.

2016-01-01

The Grüneisen parameter (γ) is very important to decide the limitations for the prediction of thermoelastic properties of bulk metallic glasses. It can be defined in terms of microscopic and macroscopic parameters of the material in which former is based on vibrational frequencies of atoms in the material while later is closely related to its thermodynamic properties. Different formulation and equation of states are used by the pioneer researchers of this field to predict the true sense of Gruneisen parameter for BMG but for SiO_2.TiO_2 very few and insufficient information is available till now. In the present work we have tested the validity of two different isothermal EOS viz. Poirrior-Tarantola EOS and Usual-Tait EOS to predict the true value of Gruneisen parameter for SiO_2.TiO_2 as a function of compression. Using different thermodynamic limitations related to the material constraints and analyzing obtained result it is concluded that the Poirrior-Tarantola EOS gives better numeric values of Grüneisen parameter (γ) for SiO_2.TiO_2 BMG.

Determination and modeling for the solubility of Na_2WO_4·2H_2O and Na_2MoO_4·2H_2O in the (Na"+ + MoO_4"2"− + WO_4"2"− + SO_4"2"− + H_2O) system

International Nuclear Information System (INIS)

Ning, Pengge; Xu, Weifeng; Cao, Hongbin; Xu, Hongbin

2016-01-01

Highlights: • The solubility of Na_2MoO_4·2H_2O and Na_2WO_4·2H_2O in Na_2MoO_4–Na_2WO_4–Na_2SO_4–H_2O were performed. • The solubility of sodium tungstate dihydrate in Na_2WO_4–Na_2SO_4–H_2O was determined. • The new model was established via regressing the published and the determined data. • The Pitzer parameter and the solubility product constant of the salt in solution were calculated. • The model was used to estimate the solubility of the sodium molybdate and sodium tungstate. - Abstract: The solubility of sodium tungstate dihydrate and sodium molybdate dihydrate in the (Na_2MoO_4 + Na_2WO_4 + Na_2SO_4 + H_2O) system was studied using experimental and calculated methods. The osmotic coefficient of sodium tungstate was fitted to calculate the thermodynamics parameters of (Na_2WO_4 + H_2O) system. The solubility of sodium tungstate dihydrate was determined using the dynamic method in Na_2WO_4–Na_2SO_4–H_2O to establish the new model which can provide an estimate the solubility of sodium tungstate dihydrate in various conditions, combined with the data published, the solubility of sodium tungstate dihydrate and the sodium molybdate dihydrate in quaternary system of (Na_2MoO_4 + Na_2WO_4 + Na_2SO_4 + H_2O) was estimated using the parameters of the two ternary systems of (Na_2WO_4 + Na_2SO_4 + H_2O) and (Na_2MoO_4 + Na_2SO_4 + H_2O). The results show that the AARD is always small and the calculated value is basically consistent with the experimental values for the system studied.

Comparative study of neurologic effects of nano-TiO2 versus SiO2 after direct intracerebral exposure in mice

International Nuclear Information System (INIS)

Balvay, A; Bencsik, A; Thieriet, N; Lakhdar, L

2013-01-01

Titanium and silicon dioxide nanoparticles (TiO 2 and SiO 2 NPs) are now in daily use in many commercial products of which food, sunscreens, toothpastes or cosmetics. However, their effects on human body, especially on the central nervous system, are still unclear. The aim of this study was to determine whether direct exposition of the brain to TiO 2 and SiO 2 NPs results in alternations in nervous system function. C57Bl6 mice were exposed to 5 and 10 μg doses of TiO 2 and SiO 2 NPs through intracerebroventricular administration using a stereotaxic approach. Then the neurologic effects were investigated using motor performance parameters, measured on a rotarod at 20 rpm or at an accelerating rod (from 4 to 40 rpm). Before and after injection, motor activity is registered individually for each mouse exposed, once a week, for 8 weeks. Besides, a group of 3 mice is culled at 1, 2, 3, 4 and 8 weeks after exposure in order to study the time dependant effect on the histopathology of the brain (gliosis, inflammatory process...). Both rotarod tests (accelerating and at 20 rpm) showed that TiO 2 and SiO 2 NPs exposure could significantly impair the motor performances, even several weeks after initial acute exposure. The first examination of the brain histopathology revealed microglial activation. As it appeared to grow throughout the brain in a time dependant manner this suggests the induction of a long lasting neuroinflammation. These primary findings indicated that exposure to TiO 2 and SiO 2 NPs could possibly impair the locomotor ability and this deficit may be possibly attributed at least to an inflammatory process maintained till 8 weeks after exposure in the mouse brain. To fully investigate the neurotoxicological consequences of TiO 2 and SiO 2 NPs exposure, brain contents in these NPs will be also investigated as well as other alterations like neurotransmitter levels. These preliminary data already underline the necessity of more in vivo studies to better

Comparative study of neurologic effects of nano-TiO2 versus SiO2 after direct intracerebral exposure in mice

Science.gov (United States)

Balvay, A.; Thieriet, N.; Lakhdar, L.; Bencsik, A.

2013-04-01

Titanium and silicon dioxide nanoparticles (TiO2 and SiO2 NPs) are now in daily use in many commercial products of which food, sunscreens, toothpastes or cosmetics. However, their effects on human body, especially on the central nervous system, are still unclear. The aim of this study was to determine whether direct exposition of the brain to TiO2 and SiO2 NPs results in alternations in nervous system function. C57Bl6 mice were exposed to 5 and 10 μg doses of TiO2 and SiO2 NPs through intracerebroventricular administration using a stereotaxic approach. Then the neurologic effects were investigated using motor performance parameters, measured on a rotarod at 20 rpm or at an accelerating rod (from 4 to 40 rpm). Before and after injection, motor activity is registered individually for each mouse exposed, once a week, for 8 weeks. Besides, a group of 3 mice is culled at 1, 2, 3, 4 and 8 weeks after exposure in order to study the time dependant effect on the histopathology of the brain (gliosis, inflammatory process...). Both rotarod tests (accelerating and at 20 rpm) showed that TiO2 and SiO2 NPs exposure could significantly impair the motor performances, even several weeks after initial acute exposure. The first examination of the brain histopathology revealed microglial activation. As it appeared to grow throughout the brain in a time dependant manner this suggests the induction of a long lasting neuroinflammation. These primary findings indicated that exposure to TiO2 and SiO2 NPs could possibly impair the locomotor ability and this deficit may be possibly attributed at least to an inflammatory process maintained till 8 weeks after exposure in the mouse brain. To fully investigate the neurotoxicological consequences of TiO2 and SiO2 NPs exposure, brain contents in these NPs will be also investigated as well as other alterations like neurotransmitter levels. These preliminary data already underline the necessity of more in vivo studies to better characterize TiO2

Multifunctional Roles of TiO 2 Nanoparticles for Architecture of Complex Core−Shells and Hollow Spheres of SiO 2 −TiO 2 −Polyaniline System

KAUST Repository

Wang, Dan Ping

2009-10-27

Nanoparticles are often used as seeds to grow one-dimensional nanomaterials or as core materials to prepare core-shell nanostructures. On the other hand, the presynthesized inorganic nanoparticles can also be used as starting building blocks to prepare inorganic-polymer nanocomposites. In this work, we explore the roles of metal-oxide nanoparticles (anatase TiO2) in the area of constructional synthesis of highly complex core-shell and hollow sphere nanostructures comprising SiO2, TiO2, and polyaniline (PAN). In particular, multifunctional roles of oleate-surfactant-protected TiO2 nanoparticles have been revealed in this study: they provide starting sites for polymerization of aniline on the surface of SiO2 mesospheres; they land on the inner surface of polyaniline shell to form a secondary material phase; they work as initial crystalline seeds for homogeneous growth of interior TiO2 shell; and they serve as primary nanobuilding blocks to form exterior TiO2 shell on the polyaniline via self-assembly. With the assistance of the TiO2 nanoparticles, a total of six complex core-shell and hollow sphere nanocomposites (SiO 2/TiO2, SiO2/TiO2/PAN, SiO 2/TiO2/PAN/TiO2, TiO2/PAN, TiO 2/PAN/TiO2, and TiO2/TiO2) have been made in this work through controlled self-assembly, templating growth, polymerization, and homogeneous seeded growth. Applicability of these nanostructures in photocatalytic applications has also been demonstrated by our preliminary investigations. The easy separation of used catalysts after reaction seems to be advantageous because of relatively large external diameters of the lightweight nanocomposites. © 2009 American Chemical Society.

Synthesis And Characterization Of SiO2, SnO2 And TiO2 Metal Oxide Shells Covering Cu2O Particles

Directory of Open Access Journals (Sweden)

Yu Ri

2015-06-01

Full Text Available In this work is described a means of improving the chemical stability of Cu2O@SiO2, Cu2O@SnO2 and Cu2O@TiO2 materials. The SiO2, SnO2 and TiO2 coated samples were stable from pH 3 to pH 10 for up to seven days. To determine the stability of the coated nanoparticles, and their colloidal solutions under acidic and basic conditions, colloidal nanoparticle solutions with various pH values were prepared and monitored over time. Details of the effect of variations in pH on the phase stability of core-shell type Cu2O were characterized using transmission electron microscopy and X-ray diffraction.

Effect of SiO 2-ZrO 2 supports prepared by a grafting method on hydrogen production by steam reforming of liquefied natural gas over Ni/SiO 2-ZrO 2 catalysts

Science.gov (United States)

Seo, Jeong Gil; Youn, Min Hye; Song, In Kyu

SiO 2-ZrO 2 supports with various zirconium contents are prepared by grafting a zirconium precursor onto the surface of commercial Carbosil silica. Ni(20 wt.%)/SiO 2-ZrO 2 catalysts are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of SiO 2-ZrO 2 supports on the performance of the Ni(20 wt.%)/SiO 2-ZrO 2 catalysts is investigated. SiO 2-ZrO 2 prepared by a grafting method serves as an efficient support for the nickel catalyst in the steam reforming of LNG. Zirconia enhances the resistance of silica to steam significantly and increases the interaction between nickel and the support, and furthermore, prevents the growth of nickel oxide species during the calcination process through the formation of a ZrO 2-SiO 2 composite structure. The crystalline structures and catalytic activities of the Ni(20 wt.%)/SiO 2-ZrO 2 catalysts are strongly influenced by the amount of zirconium grafted. The conversion of LNG and the yield of hydrogen show volcano-shaped curves with respect to zirconium content. Among the catalysts tested, the Ni(20 wt.%)/SiO 2-ZrO 2 (Zr/Si = 0.54) sample shows the best catalytic performance in terms of both LNG conversion and hydrogen yield. The well-developed and pure tetragonal phase of ZrO 2-SiO 2 (Zr/Si = 0.54) appears to play an important role in the adsorption of steam and subsequent spillover of steam from the support to the active nickel. The small particle size of the metallic nickel in the Ni(20 wt.%)/SiO 2-ZrO 2 (Zr/Si = 0.54) catalyst is also responsible for its high performance.

Non-isothermal crystallization kinetics and phase transformation of Bi2O3-SiO2 glass-ceramics

Directory of Open Access Journals (Sweden)

Guo H.W.

2011-01-01

Full Text Available The Bi2O3-SiO2 (BS glass-ceramics were prepared by melt-quench technique, and the crystallization kinetics and phase transformation behavior were investigated in accordance with Kissinger and Johson-Mehl-Avrami equation, DSC, XRD and SEM. The results show that in the heat treatment process (or termed as re-crystallizing process Bi2SiO5 and Bi4Si3O12 crystals were found consequently. Respectively, the crystallization activation energies of the two crystals are Ep1=14.8kJ/mol and Ep2=34.1kJ/mol. And the average crystallization index of n1=1.73 and n2=1.38 suggested volume nucleation, one-dimensional growth and surface nucleation, one-dimensional growth from surface to the inside respectively. The meta-stable needle-like Bi2SiO5 crystals are easily to be transformed into stable prismatic Bi4Si3O12 crystals. By quenching the melt and hold in 850°C for 1h, the homogenous single Bi4Si3O12 crystals were found in the polycrystalline phase of the BS glassceramics system.

The application of Cu/SiO2 catalytic system in chemical mechanical planarization based on the stability of SiO2 sol

International Nuclear Information System (INIS)

Li Yan; Liu Yuling; Wang Aochen; Yang Zhixin; Sun Mingbin; Cheng Chuan; Zhang Yufeng; Zhang Nannan

2014-01-01

There is a lot of hydroxyl on the surface of nano SiO 2 sol used as an abrasive in the chemical mechanical planarization (CMP) process, and the chemical reaction activity of the hydroxyl is very strong due to the nano effect. In addition to providing a mechanical polishing effect, SiO 2 sol is also directly involved in the chemical reaction. The stability of SiO 2 sol was characterized through particle size distribution, zeta potential, viscosity, surface charge and other parameters in order to ensure that the chemical reaction rate in the CMP process, and the surface state of the copper film after CMP was not affected by the SiO 2 sol. Polarization curves and corrosion potential of different concentrations of SiO 2 sol showed that trace SiO 2 sol can effectively weaken the passivation film thickness. In other words, SiO 2 sol accelerated the decomposition rate of passive film. It was confirmed that the SiO 2 sol as reactant had been involved in the CMP process of copper film as reactant by the effect of trace SiO 2 sol on the removal rate of copper film in the CMP process under different conditions. In the CMP process, a small amount of SiO 2 sol can drastically alter the chemical reaction rate of the copper film, therefore, the possibility that Cu/SiO 2 as a catalytic system catalytically accelerated the chemical reaction in the CMP process was proposed. According to the van't Hoff isotherm formula and the characteristics of a catalyst which only changes the chemical reaction rate with out changing the total reaction standard Gibbs free energy, factors affecting the Cu/SiO 2 catalytic reaction were derived from the decomposition rate of Cu (OH) 2 and the pH value of the system, and then it was concluded that the CuSiO 3 as intermediates of Cu/SiO 2 catalytic reaction accelerated the chemical reaction rate in the CMP process. It was confirmed that the Cu/SiO 2 catalytic system generated the intermediate of the catalytic reaction (CuSiO 3 ) in the CMP process

Regulating effect of SiO2 interlayer on optical properties of ZnO thin films

International Nuclear Information System (INIS)

Xu, Linhua; Zheng, Gaige; Miao, Juhong; Su, Jing; Zhang, Chengyi; Shen, Hua; Zhao, Lilong

2013-01-01

ZnO/SiO 2 nanocomposite films with periodic structure were prepared by electron beam evaporation technique. Regulating effect of SiO 2 interlayer with various thicknesses on the optical properties of ZnO/SiO 2 thin films was investigated deeply. The analyses of X-ray diffraction show that the ZnO layers in ZnO/SiO 2 nanocomposite films have a wurtzite structure and are preferentially oriented along the c-axis while the SiO 2 layers are amorphous. The scanning electron microscope images display that the ZnO layers are composed of columnar grains and the thicknesses of ZnO and SiO 2 layers are all very uniform. The SiO 2 interlayer presents a significant modulation effect on the optical properties of ZnO thin films, which is reflected in the following two aspects: (1) the transmittance of ZnO/SiO 2 nanocomposite films is increased; (2) the photoluminescence (PL) of ZnO/SiO 2 nanocomposite films is largely enhanced compared with that of pure ZnO thin films. The ZnO/SiO 2 nanocomposite films have potential applications in light-emitting devices and flat panel displays. -- Highlights: ► ZnO/SiO 2 nanocomposite films with periodic structure were prepared by electron beam evaporation technique. ► The SiO 2 interlayer presents a significant modulation effect on the optical properties of ZnO thin films. ► The photoluminescence of ZnO/SiO 2 nanocomposite films is largely enhanced compared with that of pure ZnO thin films. ► The ZnO/SiO 2 nanocomposite films have potential applications in light-emitting devices and flat panel displays

Processing of SiO2 protective layer using HMDS precursor by combustion CVD.

Science.gov (United States)

Park, Kyoung-Soo; Kim, Youngman

2011-08-01

Hexamethyldisilazane (HMDS, [(CH3)3Si]2NH) was used as a precursor to form SiO2 protective coatings on IN738LC alloys by combustion chemical vapor deposition (CCVD). SEM and XPS showed that the processed coatings were composed mainly of SiO2. The amount of HMDS had the largest effect on the size of the SiO2 agglomerates and the thickness of the deposited coatings. The specimens coated with SiO2 using the 0.05 mol/l HMDS solution showed a significantly higher temperature oxidation resistance than those deposited under other conditions.

SiO2-induced release of sVEGFRs from pulmonary macrophages.

Science.gov (United States)

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

2018-01-01

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

HfO2 and SiO2 as barriers in magnetic tunneling junctions

Science.gov (United States)

Shukla, Gokaran; Archer, Thomas; Sanvito, Stefano

2017-05-01

SiO2 and HfO2 are both high-k, wide-gap semiconductors, currently used in the microelectronic industry as gate barriers. Here we investigate whether the same materials can be employed to make magnetic tunnel junctions, which in principle can be amenable for integration in conventional Si technology. By using a combination of density functional theory and the nonequilibrium Green's functions method for quantum transport we have studied the transport properties of Co [0001 ] /SiO2[001 ] /Co [0001 ] and Fe [001 ] /HfO2[001 ] /Fe [001 ] junctions. In both cases we found a quite large magnetoresistance, which is explained through the analysis of the real band structure of the magnets and the complex one of the insulator. We find that there is no symmetry spin filtering for the Co-based junction since the high transmission Δ2' band crosses the Fermi level, EF, for both spin directions. However, the fact that Co is a strong ferromagnet makes the orbital contribution to the two Δ2' spin subbands different, yielding magnetoresistance. In contrast for the Fe-based junction symmetry filtering is active for an energy window spanning between the Fermi level and 1 eV below EF, with Δ1 symmetry contributing to the transmission.

Compositional and microstructural design of highly bioactive P2O5-Na2O-CaO-SiO2 glass-ceramics.

Science.gov (United States)

Peitl, Oscar; Zanotto, Edgar D; Serbena, Francisco C; Hench, Larry L

2012-01-01

Bioactive glasses having chemical compositions between 1Na(2)O-2CaO-3SiO(2) (1N2C3S) and 1.5Na(2)O-1.5CaO-3SiO(2) (1N1C2S) containing 0, 4 and 6 wt.% P(2)O(5) were crystallized through two stage thermal treatments. By carefully controlling these treatments we separately studied the effects on the mechanical properties of two important microstructural features not studied before, crystallized volume fraction and crystal size. Fracture strength, elastic modulus and indentation fracture toughness were measured as a function of crystallized volume fraction for a constant crystal size. Glass-ceramics with a crystalline volume fraction between 34% and 60% exhibited a three-fold improvement in fracture strength and an increase of 40% in indentation fracture toughness compared with the parent glass. For the optimal crystalline concentration (34% and 60%) these mechanical properties were then measured for different grain sizes, from 5 to 21 μm. The glass-ceramic with the highest fracture strength and indentation fracture toughness was that with 34% crystallized volume fracture and 13 μm crystals. Compared with the parent glass, the average fracture strength of this glass-ceramic was increased from 80 to 210 MPa, and the fracture toughness from 0.60 to 0.95 MPa.m(1/2). The increase in indentation fracture toughness was analyzed using different theoretical models, which demonstrated that it is due to crack deflection. Fortunately, the elastic modulus E increased only slightly; from 60 to 70 GPa (the elastic modulus of biomaterials should be as close as possible to that of cortical bone). In summary, the flexural strength of our best material (215 MPa) is significantly greater than that of cortical bone and comparable with that of apatite-wollastonite (A/W) bioglass ceramics, with the advantage that it shows a much lower elastic modulus. These results thus provide a relevant guide for the design of bioactive glass-ceramics with improved microstructure. Copyright © 2011 Acta

The principal Hugoniot of Mg2SiO4 to 950 GPa

Science.gov (United States)

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

2017-12-01

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

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

Science.gov (United States)

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

2015-01-01

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

Energy stored in BeO, MgO, Al2O3 and SiO2 oxides irradiated with neutrons

International Nuclear Information System (INIS)

Roux, Andre

1969-01-01

Within the field of researches on refractory oxides which may be used in structure materials in atomic pile, the objective of this research thesis has been the measurement of the energy stored in some specific oxides (BeO, MgO, Al 2 O 3 and SiO 2 ) after their irradiation in a nuclear reactor. This measurement is performed by 'healing' the irradiated substance by means of thermal treatments during which sample initial mass and morphologies are preserved. The measurement of the Wigner energy is then performed by differential enthalpy analysis. The first part reports the experimental determination of Wigner energies (measurement apparatus, method of ballistic differential enthalpy analysis, thermo-gram compensation). The second part presents the Wigner energies obtained for the sintered BeO, the sintered MgO, the sintered Al 2 O 3 , and the vitreous SiO 2 . The third part reports the result interpretation

Efficient photocatalytic activity with carbon-doped SiO2 nanoparticles

KAUST Repository

Zhang, Dongen

2013-01-01

Photocatalysis provides a \\'green\\' approach to completely eliminate various kinds of contaminants that are fatal for current environmental and energy issues. Semiconductors are one of the most frequently used photocatalysts as they can absorb light over a wide spectral range. However, it is also well known that naked SiO2 is not an efficient photocatalyst due to its relatively large band gap, which could only absorb shortwave ultraviolet light. In this report, nanoscale particles of carbon-doped silicon dioxide (C-doped SiO2) for use in photocatalysis were successfully prepared by a facile one-pot thermal process using tetraethylorthosilicate (TEOS) as the source of both silicon and carbon. These particles were subsequently characterized by thermogravimetric analysis, X-ray diffraction, standard and high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The C-doped SiO2 displayed outstanding photocatalytic properties, as evidenced by its catalysis of Rhodamine B degradation under near-UV irradiation. We propose that carbon doping of the SiO2 lattice creates new energy states between the bottom of the conduction band and the top of the valence band, which narrows the band gap of the material. As a result, the C-doped SiO2 nanoparticles exhibit excellent photocatalytic activities in a neutral environment. The novel synthesis reported herein for this material is both energy efficient and environmentally friendly and as such shows promise as a technique for low-cost, readily scalable industrial production. © 2013 The Royal Society of Chemistry.

Phase formation in the systems ZrO2-H2SO4-Na2SO4 (NaCl)-H2O

International Nuclear Information System (INIS)

Sozinova, Yu.P.; Motov, D.L.; Rys'kina, M.P.

1988-01-01

Formation of solid phases in the systems ZrO 2 - H 2 SO 4 - Na 2 SO 4 (NaCl) - H 2 O at 25 and 75 deg C is studied. Three basic Na 2 Zr(OH) 2 (SO 4 ) 2 x (0.2 - 0.4)H 2 O, NaZrOH(SO 4 ) 2 x H 2 O, NaZrO 0.5 (OH) 2 SO 4 x 2H 2 O and three normal sodium sulfatozirconates Na 2 Zr(SO 4 ) 3 x 3H 2 O, Na 4 Zr(SO 4 ) 4 x 3H 2 O, Na 6 Zr(SO 4 ) 5 x 4H 2 O have been isolated, their solubility and crystal optical properties are determined

Semiconductor nanocrystals formed in SiO2 by ion implantation

International Nuclear Information System (INIS)

Zhu, J.G.; White, C.W.; Budai, J.D.; Withrow, S.P.; Chen, Y.

1994-11-01

Nanocrystals of group IV (Si, Ge and SiGe), III-V (GaAs), and II-VI (CdSe) semiconductor materials have been fabricated inside SiO 2 by ion implantation and subsequent thermal annealing. The microstructure of these nanocrystalline semiconductor materials has been studied by transmission electron microscopy (TEM). The nanocrystals form in near-spherical shape with random crystal orientations in amorphous SiO 2 . Extensive studies on the nanocrystal size distributions have been carried out for the Ge nanocrystals by changing the implantation doses and the annealing temperatures. Remarkable roughening of the nanocrystals occurs when the annealing temperature is raised over the melting temperature of the implanted semiconductor material. Strong red photoluminescence peaked around 1.67 eV has been achieved in samples with Si nanocrystals in SiO 2

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

Science.gov (United States)

Masjedi-Arani, Maryam; Salavati-Niasari, Masoud

2018-05-01

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