Recent anvanceincnts of research on Self-Toughening Si₃N₄ ceramics were reviewed. The growth nleclla1nsin and all kinds of effect factors on Self-Toughening Si₃N₄ ceramics, as well as mechanical and physical properties, snch as the fracture toughness, strength, Weiball modulus, R-curve behavior, fatigue behavior, creepbehavior, oxidation behavior, thermal shock resistance, thermal conductivity were discusscd and analyzed. The key technologies of toughening for Self-Toughening Si₃N₄ ceramics are the control of the size of elougated Si₃N₄ grains and the proper choice of galss phase.

The relationship between the orientation of tetrahedral [SO₄]^2- in sulfate crystals such as barite,anhydrite, epsomite and jarosite and their morphology was studied from the standpoint of crystal chemistry,and the formation inechanisin of their morphology was analysed according to the structural orientation of tetrahedral [SO₄]^2- and the bonding energy between [SO₄]^2- and metal ions [M²⁺] during growth. It was found that the inorphology ofsulfates is related to the orientation of tetrahedral [SO₄]^2- in the crystal, i.e., the faces, the edges and faees of the tetrahedra normal to, are expected to grow slowly and observed in final form; in contrast, the faces, the vextices of the tetrahedra pointing to, usually grow fast, and will disappear.

The doped Li ion has aneffect on both the crystal structure and property of SrB₄O₇. The crystal structure and microstructure of doped SrB₄O₇ was studied in detail from X-ray powder diffraction data. Its space group is Pmn21, cell parameters: a=1O.741(5)A, b=4.245(1)A, c=4.437(1)A, a little bigger than those of SrB₄O₇. Reasons for thesc changes were presented. In the cel1, Li ions occupy part of the vacancy between B-O layers; such a structure can improve the nonlinear optical coefficicnts. The errors of crystal data from references were also analyzed.

The effects of T1 distributioll, geometric shapc and surfacc condition of the crystal on the uniformity of CsI(Tl) crystals were investigated. Measurcs for improving the uniformity 0f large size taped CsI(Tl) crystals were proposed.

The glass formation bellavior of PbI₂-PbCl₂-KCl system was discussed in the view of coordination number and characteristics of chemical bonds. The crystallization behavior of 50PbI₂·30PbCl₂·20KC1(mol%) glass was investigated by means of DSC, SEM and XRD. The kinetic parameters of crystallization of the glass wcrc deternnnnned by nonisothermal methods. The results showed that the crystallization mechanisms corresponding respectively to two crystallization peaks in the DSC curve were different. The low crystallization rates at crystallization temperatures were attributed to high apparent activation energies, closing to the values obtained from the relatively stable fluorozirconate glass. It was found that the IR transmitting property of the glass-ceramic obtained under suitable heat treatment conditions was consistert with that of the original glass. The microhardness of the glass-ceramic could also be greatly improved. Moreover, the glass synthesized in this work had good chemical durability and excellent IR transmitting properties, so multicomponent galss based on our ternary system could be developed as one of promising materials for IR transmission.

The rheological properties of slurry formed by nano-sized Y-TZP were studied. With the adding of dispersant NaPAA or NH₄PAA, the optimum pH range for the stable slurry is between 8 to 12. The relationship of the solid loading and the amount of dispersant was obtained. The slurry dispersed with NH₄PAA has lower viscosity comparing to tkat of NaPAA. The variation of viscosity with the specific surface area (SSA) of powders was discussed. The viscosity does not change greatly witk SSA if the solid coltent is less than 50wt%. When the solid content is 65wt%, the viscosity increases with SSA exponentially, the finer particles need more dispersant to adsorb to be flowable.

β-Si₃N₄ inaterial prepared by self-propagating high-teinperature synthesis from silcon powder and nitrogen was studied by gas pressure sintering process. The effects of different ainounts of YAG additive and holding time on the properties were investigated. The results show that this β-Si₃N₄ powder can be sintered to>99% of the theoretical density with high fracture toughness under the sintering conditions of 1.2MPa Ar pressure 1940℃ and ho1ding 1 hour.

SiO₂-Si₃N₄ composites were prepared by hot pressing process. Their flexural strength and fracture toughness obtained are 143MPa and 1.7MPa.m^1/2, which are 107% and 70% higherthan those of the SiO₂ matrix material respectively. The addition of higher elastic modulus Si₃N₄ particulates and the residual stress caused by the difference in thermal expansion coefficient of Si3N4 and SiO₂ are the main reason responsible for the improvement of mechanical properties of the composites.

The ferric oaide system with transition metal oxides such as CuO-Fe₂O₃ and ZnO-Fe₂O₃, were Sintered at different temperatures and formed a porous ceramic with a-Fe₂O₃ and spinel crystal phases. This ceramic possesses a remarked sensitivity to reductive gases. The special property is considered to relate to the ferric vacancy coccentration in a spinel phase. The ferric vacancy concentration varies with composition and heating temperature. The gas sensitivity can be improved by the increment of the ferric vacancy concentration.

SnO₂(ZrO₂) thin films with different dopant concentrations were deposited on soda-glass sheets by the Sol-Gel technique, using non-alkoxide SnCl₂.2H₂O as main precursor, Zr(OC₃H₇)₄ as dopant, ethanol as solvent. The effect of ZrO₂ dopant concentration on the efectrical and gas sensing was studicd. We found that the ZrO₂-SnO₂ thin films prepared by this method havc very good gas sensitivity, excellent selectivity, rapid rcspionse and recovery behaviour to H₂S at room temperature

Film Humidity sensors of Cu, Zn, Fe, Sb, Ti and so on sulfide systenis were prepared by the Sol-gel mcthod aceording to the idea of developing a kind of pure physisorbed surface (without chemisorption). It was found that the filmhumidity sensors of sulfide systems possess the properties of high sensitivity, small hysterisis, and rapid responsc, and the sensors made of sulfide films of metal cations with Large charge-radius ratio have all excellent durability, these agree with our cxpectant results.

Si₃N₄－based ceramics were recently used for machining cast iron at very high speeds.However，they were found to be unsuitable for machiningsteels because of the severe wear ofthe ceramic. In sliding contacts.The tests were carried out on a pin－on－disk tribometer. The test results showed that the lubricants containing additives could effectively reduce the friction and wear of Si₃N₄ ceramics. The between the rubbing surfaces. The element interdiffusion and adhesion between the rubbing surfaces were prevented or greatly reduced.

Friction and wear behaviors were studied for Sialon, Al₂O₃ and SiC unlubricated sliding against themselves with block-ring apparatus at 5ON normal load and 0.9m/s sliding velocity. All materich and worn surfaces as well as debris were extensively characterized by means of SEM, TEM and XPS. The results obtained indicated that: Wear of Sialon is interpreted in terms of delamination. In the processing, the oxidation and its formation appeared. Mixed surface film of SiO₂ and Al₂O₃ improved the wear of Sialon. Wear of Al₂O₃ is explained in terms of the grain fracture. wear of SiC is caused by the formation of powders and loose wear debris which was due to the oxidation of Sic.

Based on the relation between the phase contents in a multiphase powder and their corresponding scale factors in Rietveld refinements, the phase abundance of multiphase material could be quantitatively obtained^[1]. The results of quantitative phase analysis of Y₂O₃-doped ZrO₂ specimens using Rietveld technique and X-ray diffraction data of profile intensities were given. The effect of grinding on the transformation of tetragonal to monoclinic ZrO₂ was a1so confirmed.

ZrO₂ powder doped with 8mol% MgO, CaO or Y₂O₃ was prepared by co-precipitation technique. The densified and partially or fully stabilized ZrO₂ ceramics were obtained by sintering the powder under 1550℃. The quantitative analyscs of phase compositions of ZrO₂ ceramics were performed based on X-ray profile diffraction data and Rietveld inethod. The results show that ZrO₂ ceramics stabilized by MgO, CaO or Y₂O₃ with the same starting composition possess the different phase contents. MgO partially stabilized ZrO₂ consists of cubic, tetragonal and monoclinic phases with the weight ratio of 17:57:26, CaO partially stabilized ZrO₂ contains cubic and monoclinic phases with the weight ration of 68:32, Y₂O₃-doped ZrO₂ shows almost a pure cubic phase with only 3wt% tetragonal one, however. In the paper, the influence of grain size on phase transformation of tetragonal to monodlinic of ZrO₂ is also discussed.

Mass transfer model and equation were established according to the characteristics of nitridation reactions of molten Al-Si-Mg alloys. It shows that nitridation rocess is divided into two stages: stage Ⅰ－AlN crystal growth with Si-enrichment; stage Ⅱ- co-growth of binary crystal AlN and Si_cry. The rate of N atom diffusion is the key factor of controlling whole nitridation rate.

The growth process of AlN synthesized by Lanxide method was studied. XRD analysis shows that AlN crystal grows in a specific direction [0001]. During nitridation, AlN crystal grew from the metal base surface toward atmosphere, then formed a parallel and rod-like microstructure. Durillg initia1 reaction, there was a significant Mg-evaporation phenomenon, and magnesium gas reacted with nitrogen or oxygen to form a porous and loosen surface layer. It was also found that there was a Si-rich process during nitridation which caused composition unhomogenity in product.

The preparation of TiO₂ particles from H₃TiO₃ by using hydrothermal method was reported. The effects of H₃TiO₃, H₄TiO₄ and ions, for example: PO^-₄, Ac^-, Zn²⁺, NH⁺₄ and so on were studied. The results indicated that the phases and partical morphology of TiO₂ were intimate relative to the structure of H₃TiO₃, PO^-₄ and other high valence or big anions could accelerate anatase formation of TiO₂ and Zn²⁺, NH⁺₄ or H₄TiO₄ were the promoter of rutile phase.

The concept of the equivalent thermal conductivity of Functionally Gradient Materials (FGM) was firstly presented, a kind of calculating method of the equivalent thermal conductivity was introduced. Its introduction with the theoretical importance and practical value not only guides the componental and structural designing of FGM, but also accelerates its utilization.

The dependence of K_ic on the notch-root radius was tested with the notch radius as small as a few micrometers in a polycrystalline alumina ceramics. The results show that the fracture toughness decreases as the notch radius decreases, when the notch radius approximately equal, to or lowcr than the average grain diameter, the fracturc tonghness becomes constant, this implies that the critical notch tip radius has the same sizc as the average grain diameter. The fracture toughness of a same alumina was also tested by seven different methods, ie.e. bridge indentation, compressive cyclic fatigue, precrack before sintered and polished sharp notch methods with the SENB specimens; wedge press and precrack before sintered methods with DCB specimens; indentation method with disc. the results show that SENB specimens with polished sharp notch or compressive cyclic fatigue precrack yield the true K_ic value.

PbO₂-MnO₂ mixed metal oxide electrodes were prepared by the thermo-decomposition method. The electroded were tested by means of EDS, SEM aud XRD. The lifetime and the kinetic parameters of the electrodes were measured in lmol/L H₂SO₄ solution. The results showed that the prepared electrodes had better electrocatalytic activity and electrochemical stability.