Effect of Electron Beam on the Structure and Crystallization Features of BaO-SrO-TiO_2-SiO_2 Glass

Glasses of BaO-SrO-TiO2-SiO2 after electronic radiation treatment of 50 - 1000 kgy were studied by means of IR spectra, DTA and visible light absorption method. The result shows that the glass structure is changed due to the formation of structure defect from oxygen vacancy and E' color center, which resultsd in the crystallization process and new precursors, and decreasement of Tg temperature and crystallization peaks by 20 -50℃.     

Structure and mechanical properties of ZrO2-mullite nano-ceramics in SiO2-Al2O3-ZrO2 system

ZrO2-mullite nano-ceramics were fabricated by in-situ controlled crystallizing from SiO2-Al2O3-ZrO2 amorphous bulk. The thermal transformation sequences of the SiO2-Al2O3-ZrO2 amorphous bulk were investigated by X-ray diffraction, infrared spectrum, scanning electron microscope and differential scanning calorimetric. And the mechanical properties of the nano-ceramics were studied. The results show that the bulks are still in amorphous state at 900 ℃ and the t-ZrO2 forms at about 950 ℃ with a faint spinel-like phase which changes into mullite on further heating. ZrO2 and mullite become major phases at 1 100 ℃ and an amount of m-ZrO2 occur at the same time. The sample heated at 950 ℃ for 2 h and then at 1 100 ℃ for 1 h shows very dense and homogenous microstructure with ball-like grains in size of 20-50 nm. With the increase of crystallization temperature up to 1 350 ℃, the grains grow quickly and some grow into lath-shaped grains with major diameter of 5 μm. After two-step treatment the highest micro-hardness, flexural strength and fracture toughness of the samples are 13.72 GPa, 520 MPa and 5.13 MPa·m1/2, respectively.     

The Mechanism of Sol-Gel Synthesis of Normal Spinel LiMn2O4 with Chelation of Citric Acid

The sol-gel process of citric acid chelating with metal cations for the synthesis of normol spinel LiMn2O4 and the reaction mechanion mechavism were investigated by means of XRD,TG-DTA,and SEM ,the results show that at the beginning lithium citrate and chelate compound of citic acid with manganese ions formed ,and then with heating the esterification and condensation reacions occured between them and glyol ,The products obtained are polymers in which metal cations are distibuted homogeneously on atomic scale that ensur hight reacivity to cations of Li^ and Mn^2 ,Firing the gel grepared by this process ,the lattice diffusions of solid reactant ions caused by non-homogeneity of reactants are elinimated and avoided .At 400℃ phase-pure LiMn2O4 with nanometer scale crystallization having precise stoichiometry and perfect crystallization can be obtained ,The model of chelate coordinated of double -molecule between citric acid and Mn^2 in the gel network is proosed ,It is important for explaining the dispersion state of Mn^2 and the formaiton process of gel by this model.     

Influence of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass-ceramics

ZrO2 was added into CaO-Al2O3-SiO2 glass-ceramics and the effect of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass ceramics was investigated. The results show that the sintering shrinkage ratio of glass particles decreases with the increase of the content of ZrO2. ZrO2 has an unfavourable effect on sintering shrinkage ratio of glass particles. The sintering shrinkage ratio of glass particles increases with the increase of sintering temperature. The increase of sintering temperature favors the decrease of the liquid phase viscosity of glass particles. ZrO2 has little effect on crystallization of main crystalline phase （β-wollastonite）. However, it promotes the crystallization at relatively low temperature.     

A study of the crystallization kinetics of Ge-Te amorphous systems

The glass-forming ability of binary GexTe100-x (x=15, 20, 30) alloys was investigated. The crystallization mechanism of these amorphous bulks was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calo- rimetry (DSC). The temperature of glass transition, the temperature of crystallization, the activation energy for glass transition and crystallization, and the order of the crystallization mechanism were calculated from the different heating-rates.     

Preparation of Al2O3-SiO2-TiO2-ZrO2 Composite Ceramic Membranes by Sol-Gel Method

Al2O3-SiO2- TiO2-ZrO2 supported membranes were prepared by Sol-Gel method. These composite ceramic membranes are level, even and no macro crack. There exist several crystalline phases such as Al2O3, TiO2 ( anatase ), Al2 SiO5 , and ZrO2 in these membranes. Changing the molar ratio of Al:Si: Ti : Zr ,the kinds and content of crystal phases of composite membranes could be different, which may lend to a variety of microstructure of membranes. The surface nanoscale topography and microstructure of membranes were investigated by XRD, SEM, AFM, EPMA. The effects of additives and heat treatments on the surface nanoscale topography and microstracture of composite ceramic membranes were also analyzed.     

Al-induced Lateral Crystallization of Amorphous Si Thin Films by Microwave Annealing

Al-induced lateral crystallization of amorphous silicon thin films by micr owave annealing is investigated,The erystallized Si films are examined by optical microscopy,Raman spectroscopy ,transimission electron microscopy and transmission electron diffraction micrography.After microwave annealing at 480 ℃ for 50min the amorphous Si is completely cystallized with lagrge grains of main (111) orientation,The rate of lateral crystallization is 0.04μm/min,This process,labeled MILC-MA ,not only lowers the temperature but also reduces the time of crystallization.The crystallization.mechanism during microwave annealing and the electrical properies of polycrystalline Si thin films are analyzed.This MILC-MA process has potentila application in large area electronics.     

Crystallization kinetics of amorphous Nd3.6 Pr5.4 Fe83Co3B5 and preparation of α-Fe/Nd2Fe14B nanocomposite magnets by controlled melt-solidification technique

The crystallization kinetics of amorphous Nd3. 6 Pr5.4 Fe83 Co3 B5 and the preparation of α-Fe/Nd2 Fe14 B nanocomposite magnets by controlled melt-solidification of Nd3.6Pr5.4Fe83Co3B5 was investigated by employing DTA, XRD, and TEM. The results show that a metastable intermediate phase Nd8Fe27B24 prior to α-Fe and Nd2 Fe14 B phases is crystallized as the amorphous Nd3.6 Pr5.4 Fe83 Co3 B5 is heated to 1 223 K. The crystallization activation energy of α-Fe and Nd8 Fe27324 phases is larger at the beginning stage of crystallization, and then it decreases with crystallized fraction x for the former and has little change when x is below 70% for the latter, which essentially results in an α-Fe/Nd2 Fe14 B microstructure with a relatively coarse grain size about 20-60 nm and a non-uniform distribution of grain size in the annealed alloy. The a-Fe/Nd2 Fe14 B nanocomposite magnets with a small average grain size about 14 nm and a quite uniform grain size distribution were prepared by controlled melt-solidification of nealing the amorphous Nd3. 6 Pr5. 4 Fe83 Co3 B5 precursor alloy.     

Effect of Rare Earth on the Crystallization Behavior of Li₂O-Al₂O₃-SiO₂ Glass-ceramic

X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of different heat-treatment temperatures and with various amounts.The powders were derived from the polyacrylamide gel method.The results show that,the wet gels prepared by polyacrylamide perform a unique crystallization behavior in the process of drying,comparing with some customary preparation such as melt processing.The main crystal phase and crystallization sequence of Li2O-Al2O3-SiO2 micro-powders have no distinct with addition of Eu2O3,Gd2O3 or Er2O3,while the crystallization temperature of the β-spodumene decreased and the amount of the β-spodumene increased.     

Preparation of BN／SiO2 ceramics by PIP method

The precursor infiltration and pyrolysis(PIP) method for preparation of BN/SiO2 composites was used to improve mechanical properties, dielectric properties and feasibility of high temperature dielectric parts with large dimensions and complex shapes. In the processing procedure, the porous BN ceramic matrix was first successfully prepared by compacting the mixed powders of B and BN and then sintering them at a certain temperature under normal pressure of N2. The polycarbosilane(PCS) solution was vacuum infiltrated into porous BN ceramics at the room temperature and then at 800℃ in the air to depolimerize out amorphous SiO2, and sintered further at 1 300℃ in N2 to get BN/SiO2 composites. The microstructure of materials was studied by means of X-ray diffraction and electron probe micro analysis. The thermo-decomposition mechanism of PCS was investigated by a TG-DTA and infrared (IR) spectrum analysis. The flexural strengths were measured by the three-point bending method. The dielectric constant and the loss tangent were measured by the wave-guide method. The results show BN/SiO2 composites were fabricated. The obtained composites posses a flexural strength of 61.96 - 93.31 MPa, the dielectric constant in the range of 3.50 - 3.78 and the order of magnitude of the loss tangent at 10^-3 , which are good for the high tempera turedielectric parts with large size and complex shapes.     

Preparation and characteristics of Cu/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/MgF<Subscript>2</Subscript>/Au tunnel junction

The fabrication process of Cu/Al₂O₃/MgF₂/Au double-barrier metal/insulator/metal junction (DMIMJ) was introduced, and more stable light emission from this junction was successfully observed. The light emission physical mechanism of the junction was discussed. Results show that light emission spectrum of this structure locates at wavelength of 250–700 nm with two peaks at around 460 nm and 640 nm, which moves towards shorter wavelength region in comparison with that of the Al/Al₂O₃/Au junction. The light emission efficiency of this junction ranges from 0.7×10⁻⁵–2.0×10⁻⁵, which is 1 to 2 orders higher than that of the single-barrier Al/Al₂O₃/Au junction. The improved properties of this structure should be due to the electrons resonant tunneling effect in the double-barrier.     

Erosion Resistance of CaO-AI203-SiO2 System Glass-Ceramics

The erosion resistance tests were used to research the erosion wear behavior of CaO-Al2O3-SiO2 system glass-ceramic. With the orthogonal test method, the factors thai affect the erosion wear of CaO-Al2O3-SiO2 system galss-ceramic such as pacticles property, impact angle, impact time, size of particles were discussed. The results show that erosion rate rises along a straight line at the early period of erosion wear. With the impact time increased, the erosion rate deviates from original staight line, tendency of the erosion rate increases, With the size of paricle increased , it will have more kinetic energy, the erosion rate of the surface of glass-ceramics ploate rises.     

Synthesis and Characterization of LiCoxMn2-xO4 Cathode Materials

LiCoxMn2.04 cathode materials for lithium ion batteries were synthesized by mechanical activation-solid state reaction at 750 ℃ for 24 h in air atmosphere, and their crystal structure, morphology, element composition and electrochemical performance were characterized with XRD, SEM, ICP-AES and charge-discharge test. The experimental results show that all samples have a single spinel structure, well formed crystal shape and uniformly particle size distribution. The lattice parameters of LiCo Mn2-xO4 decrease and the average oxidation states of manganese ions increase with an increase in Co content. Compared with pure LiMn2O4, the LiCo Mn2xO4 （x=0.03-0.12） samples show a lower special capacity, but their cycling life are improved. The capacity loss of LiCo009Mn191O4 and LiCo0.1Mn1.88O4 is only 1.85% and 0.95%, respectively, after the 20th cycle. The improvement of the cycle performance is attributed to the substitution of Co at the Mn sites in the spinel structure, which suppresses the Jahn-Teller distortion and improves the structural stability.     

Nanocomposite films of V<Subscript>2</Subscript>O<Subscript>5</Subscript>−MoO<Subscript>3</Subscript> xerogel with poly ethylene oxide intercalation

Poly ethylene oxide (PEO)_x−V₂O₅−V₂O₅−MoO₃ (x=0, 0.5, 1) films were prepared by the sol-gel method. The synthesis and structure of the films were investigated by XRD, TG-DTA, FTIR, etc. The results show that V₂O₅−MoO₃ xerogel has a layered structure and its interlayer space increased from 1.3181 nm at x=0 to 1. 7898 nm at x=1 after the nanocomposite films were dried, and PEO in the interlayer changes the interface structure by forming hydrogen bonds with V=0 bands. CV measurement indicates that the intercalation of PEO improves insertion/extration properties of Li⁺ ions in the interlayer. ZHENG Jin-xia: Born in 1976 Funded by the National Natural Science Foundation of China (No. 50172036) and Natural Science Foundation of Hubei Province(No. 2001ABB083)     

Structure and Electric Properties of （1-x）（Bi1/2Na1/2） TiO3-xBaTiO3 Systems

The structural, dielectric and piezoelectric properties of （1-x）（Bi1/2Na1/2） TiO3-xBaTiO3 ceramics were investigated for the compositional range, x=0.02, 0.04, 0.06, 0.08, 0.10. The samples were synthesized by a conventional solid-state reaction technique. All compositions show a single perovskite structure, and X-ray powder diffraction patterns can be indexed using a rhombohedral structure. Lattice constants and lattice distortion increase while the amount of BaTiO3 increases. The X-ray diffraction results show the morphotropic phase boundary （MPB） of （1-x）（Bi1/2Na12） TiO3-xBaTiO3 exists in near x=0.06-0.08. Temperature dependence of dielectric constant eT33/ε0 measurement reveals that all compositions experience one structural phase and two ferroelectric phases transition below 400℃： rhombohedral （or rhombohedral plus tetragonal） ferroelectric phase ←→ tetragonal antiferroelectric phase ←→ tetragonal paraelectric phase. Relaxor behaviors exist in the course of ferroelectric to antiferroelectric phase transition. Dielectric and piezoelectric properties are enhanced in the MPB range for （ 1-x）（Bi1/2Na1/2）TiO3-xBaTiO3.     

Chemial Bond and Stability of Adsorption of [Au（ AsS3 ）]^2- on the Surface of Kaolinite

Density function theory and discrete variation method (DFT-DVM) were used to study the adsorption of [Au( AsS3 )]^2- on the surface of kaolinite. The correlation among structure, chemical bond and stability was discussed. Several models were selected with [ Au( AsS3)]^2- in different directions and sites. The results show that the models with gold on the edge of kaolinite basal layer contain pincerlike bond among gold and several oxygen atoms and form strong Au - 0 covalent bond, so these models are more stable than those with gold above or under the layer. The models with gold near to [ AlO2(OH)4] octahedra are more stable than those with gold near to the vacancy withont aluminium. These two stable tendencies in kaolinite- [ Au( AsS3)]^2- are stronger than that in kaolinite-Au systems. The interaction between [ Au( AsS3 )]^2- and kaolinite is stronger than that between gold and kaolinite, and this interaction is strong enough to form the surface complexes.     

Microstructure and Thermal Properties Analysis of （1-x）As2S3-x CdBr2 Glass System

The homogeneous glass sample for the ( 1 - x ) As2S3-xCdBr2, where x=0. 015,0. 035,0.05, was prepared by the conventional melt-quenched method. Amorphoas ( 1 - x ) As2S3-xCdBr2 alloys were determined by X-ray diffraction, thermal compreheasive analysis and Raman scattering. The glass transittion temperature (TR) deereases a bit with the addition of CdBr2 . Based on the experimental data, the microstrtucture is considered to be the discrete molecule species of AsBr3 and Cd - S atomic bonds or clusters are honigeneously dispersed in a disordered polymer network formed by AsS3 pyramids interlinked by sulfur bridges.     

Preparation of Ti3SiC2 with Aluminum by Means of Spark Plasma Sintering

Polycrystalline bulk Ti3SiC2 material with a high purity and density was fabricated by spark plasma sintering from the elemental powder mixture with starting composition of Ti3Si3Si1-xAlxC2 , where x = 0. 05 -0.2. X-ray diffraction patterns and scanning electron microscopy photographs of the fully dense samples show that a proper addition of aluminum promotes the formation, and accelerates the crystal growth rate of Ti3SIC2, conse-quently results in a high purity of the prepared samples. The synthesized Ti3 SiC2 is in plane-shape with a size of about 10- 25μm in the elongated dimension. Solid solution of aluminum decreases the thermal stability of Ti3SiC2, and lowers the temperature of Ti3SiC2 decomposeing to be 1300 ℃ .     

Influence of thickness on the properties of solution-derived LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> thin films

LiMn₂O₄ thin films of different thickness were derived from solution deposition and heat treated by rapid thermal annealing. The phase identification and surface morphology were studied by X-ray diffraction and scanning electron microscopy. The electrochemical properties of the films were examined by galvanostatic charge-discharge experiments and electrochemical impedance spectroscopy. LiMn₂O₄ thin films of different thickness derived from solution deposition and rapid thermal annealing are homogeneous and crack free with the grain size between 20 nm and 50 nm. The specific capacity of these films is between 42 and 47 μAh·cm²·μm⁻¹. The capacity decreases with the increase of discharge current density. The capacity loss per cycle increases from 0.012% to 0.16% after being cycled 50 times as the film thickness increases from 0.18 μm to 1.04 μm. The lithium diffusion coefficients of these films are in the same order of 10⁻¹¹ cm²·s⁻¹.     

Microstructure and thermal properties of (1−<Emphasis Type="Italic">x</Emphasis>) As<Subscript>2</Subscript>S<Subscript>3</Subscript>−<Emphasis Type="Italic">x</Emphasis>CdCl<Subscript>2</Subscript> glassy system

The homogenous glass samples of the (1−x) As₂S₃−xCdCl₂ where x=0 and 0.05 were prepared by the conventional melt-quenched method. The addition of 5 mol% CdCl₂ enhanced the glass transition temperature of pure As₂S₃ glass sample by about 30°C. Based on the experimental data, the microstructure is considered to be that the discrete molecule species of AsCl₃ and nanocrystal CdS is homogeneously dispersed in the disordered polymer network formed by AsS₃ pyramids interconnected by sulfur bridges. TAO Hai-zheng : Born in 1973 Funded by the Foundation for Excellent Youth of China.