The Synthesis of β-Sialon Bonded Corundum Bricks from Al-Si Alloy

The paper presents a new method to synthesize β-Sialon bonded corundum brick(β-SBCB) from Al-Si alloy directly and easily under 1430℃,the volume expansion of reaction between Al powder and Nitrogen can help to establish the fast diffusion channel in Al-Si alloy;the suitable crystal seed of Si3N4 is helpful to the fast synthesis of β-Sialon.     

Improvement of FeO Corrosion Resistance by Addition of β－Sialion in Matrix of Corundum Castable

Silicon aluminum oxynitride (β-Si4Al2O2N6) powder was added into corundum castable and its FeO corrosion resistance was tested in crucible method.It was found that FeO corrosion resistance of sialon containing corundum castables was better than that of no sialon powder added ,The optimum content of the sialon powder in castables was higher than mass of the sialon powder in castables was higher than mass 15%.Moreover,O‘-sialon phase,together with β-sialon phase occurred in corundum castables heated in coke bed at 1500℃,although β-sialon powder was initially admixed into the matrix of castables.The EPMA results showed these nitrogen-containing phases located in the matrix of castables were favorable to hinder the penetration of FeO melt at high temperature in comparison with pure corundum castable.However,the flowability of corundum castable became worse originated from the sialon powder added.     

Thermomechanical Properties of Corundum—Mullite—Zirconia Materials

The mechanical properties at elevated tempera-tures of corundum-mullite materials and the effects of zirconia and titania additions have been investi-gated.The results are correlated with changes in microstructure,Based on the results of these investi-gations ,reaction-sintered corundum-mullite-zirco-nia materials with improved hot strength and ther-mal shock resistance have been developed for refractor-ries usage.     

Slag Corrosion Resistance of β－Sialon－Al2O3 Composites－Part Ⅱ.Kinetics

The kinetic process of slag corrosion for β－Sialon and β-Sialon-Al2O3 composites has been studied by means of dip method (static and self-rotating),The corrosion model is buitl and the formula of corrosion rate is deduced,which are in accordance with experimental results.     

Reaction Sintering of β-sialon／Al2O3／SiO2 Mixtures in Flowing Nitrogen at High Temperatures

β-sialon/alumina/silica mixtures were sintered in flowing nitrogen at 1500℃ and 1600℃ respectively.The sintering properties and morphology of samples were investigated by SEM, EDS and XRD. Results show that sintered properties of the samples are influenced by soaking temperatures and compositions. Bulk densities of samples are increased with the increase of the soaking temperature, whereas the apparent porosities are decreased. Mass loss of the sintered samples at 1500℃ is lower than that at 1600℃, but all the mass loss remains approximately constant with the increase of sialon content. From the point of thermodynamic analysis,Complex chemical reactions take place in samples during sintering process and the volatile of SiO (g) is responsible for the mass loss of samples. Compared to cross section microstructure of β-sialon/Al2O3/SiO2 mixtures sintered in coke powder bed consisting of the dense center with well-developed column of sialon phase, the transitional part with needle like grain nitrogen-containing phase and the loose part with short granular Al2 O3 phase, those of mixtures sintered in flowing nitrogen is of well-developed sialon in dense center and slightly loose part with sialon debris.     

Synthesis of β‘—SIALON Powder from Clay

The synthesis of β‘-sialon powder by carbothermic reduction of clay followed by nitridation has been carried out.The effect of charge mixture,temperature,holding time and nitrogen flow rate on synthesis was examined.The fired sample was identified by XRD and the nitrogen content of fired sample was measured.The synthesis process of sialon powder was described.     

Carbonthermal Reduction—Nitridation Method for Preparation of O‘—Sialon—SiC—ZrO Composites

Based on thermodynamic analysis,O‘-Sialon-SiC-ZrO2 composites have been prepared by carbonthermal reduction-nitriation from natural kaolin and zircon with certain additives,The modulus of racture of well sintered specimen may reach 110 MPa,The process of reaction-sintering has been discussed,The formation temperature of O‘-Sialon is 1718 K by calcuation.     

Fractal Calculation of Mo／β‘—Sialon Functionally Gradient Materials by Powder Metalurgy

The preparation of disk shaped Mo/β‘-sialon functionally gradient material(FGM) is studied.Random fractal of diffusion interface in Mo/β‘－sialon FGM is also studied by variation method.     

Development of Sialon Bonded Corundum Bricks

Influence of additives and composition of the matrix on mecharical properties of Sialon bonded corundum brick with appropriate nitridation sintering curve was investigated in present paper.The phase composition and microstructure of the sintered specimen were analyzed by means of SEM and XRD.The results indicate that with appropriate content of ultra-fine alumina powder and aditive A,both cold and hot mechanical properties of speimens are notably enhanced.The microstructure of specimen is dense and with less porosity,Main phase of the specimen is corundum, β－sialon is also observed as the bonding phase, little impurity is observed.     

Effect of Sintering Additive on the Properties of Sialon-SiC by Gelcasting

Sintering additivesto gelcasting Sialon‘SiC were decided by the optimizing experiments , The resuhs show that Sialon-SiC can be sintered under 1450℃ and sintering temperature dcreases by 100℃，when 2%～3% TiO2 or Guangxi clay is used as sintering additive.     

Development of Thermal Low Creep Bricks for Shock Resistant and Hot Blast Stove

The paper describes the ries with high thermal shock development of brick seresistance and low creep rate for hot blast stove, including research target and research plan on the basis of analysis on how to enhance the thermal shock resistance and to lower creep rate of the bricks. Efforts have been made on the selection of starting materials such as corundum, mullite, andalusite and sillimanite etc., together with some measures taken on multi-grade formulation, homogenizing of the matrix of bricks and addition of some special additives. The results indicated that the bricks were with characteristics such as higher thermal shock resistance of 〉 30 cycles under quenching in water from 1000℃, and creep rate of 0. 2 under 1400℃ for 20 -50hrs with load of 0.2 MPa. Now a series of products of this kind have been developed and produced. The application of the products in Wuhan Iron and Steel Co. showed very prospective results. Now most of domestic large sized blast furnaces say ≥- 1000m^3, including those of Baoshan Iron and Steel Co. , have selected the series products made by Gongyi No. 5 Refractories Head Factory（GYWN） for their hot blast stoves.     

Thermodynamic Investigation of Synthesizaing Metastable β—Sialon—Alon Composite Ceramic

Based on its thermodynamic analysis ,β-Sialon-Alon metastable composite ceramic has been prepared by hot pressing sintering,XRD results indicate that the product of hot pressing singering is indeed Sialon-Alon metastable omposite ceramic ,which is in accordance with thermodynamic analysis     

Preparation and Microstructure of Bauxite-Based Sialon by Reduction Nitridation

The phase composition and microstructure of Sialon prepared from Chinese bauxite have been studied. The use of Si powder is more effective than that of activated carbon for reduction-nitridation. For bauxite specimens with 40～50% Si addition, more than 90% of Sialon may be obtained when nitrided at 1450～1500℃ ; the main crystalline phase is O‘-Sialon ( Z =0.2).     

Study on the Microstructure of β‘—Sialon／SiC（w） Composites

The phase composition and microstructure of β‘-Sialon/SiC whisker compostie materials were studied by means of XRD ,SEM,EDAX and HREM.Besides β‘-Sialon and β-SiC as main crys-talline phases,15R AIN polytypoids presented in the materials,Yttrium,added in Y2O3 as sintering aid,was concetrated mainly in glassy phase,A mosaic structure of SiC whisker in β‘-Sialon grains was observed,Two kinds of grain boundaries were also observed:one was a direct-contact grain boundry between β‘-Sialon and β-SiC,while the other was a boundary between β‘-Sialon grains wqith glassy phases.     

Estimation of Gibbs Free Energy of Formation of Sialon （O‘—and X—Phases

Based on introducing the quasi-parabolid rule,which indicates the relation of Gibbs free energy of formation of compounds and its compostitions,the Gibbs free energes of formation of Sialons (O‘-and X-phases) were estimated.     

The Improvement of the Slag Resistance of Corundum—Spinel Castable with Addition of Aluminum Oxynitride （AlON）

The slag corrosion resisance of corundum-spinel castable has been increased by adding aluminum oxynitride spinel (AlON) powder ,Its results show that corrosion resistance of this castable is remarkably imroved when 3 wt% of the AlON powder added ,It was assumed that solid solution between aluminum oxynitride and magnesium aluminate spinel occurred to prevent the slag penetration into castable and increase the corrosion resistance of the corundum-spinel castable However,the experimental resultsd suggest such castable containing AlON powder be much more appropriate to be used in non-oxidation condition rather than in oxidation atmosphere.     

Effect of Water Addition on Rheological Behaviour of Bauxite Based Low-cement Castables

Water addition has direct impact on castables and needs to be under control placement and properties, In this work, two rheological properties, flow resistance and torque viscosity, have been measured against time, with different water addition in the same bauxile-based LC Castable mix. The flow resistance indicates the mobility, whereas the torque viscosity dictates the stability of a castable during installation. It has been observed that with 6.0 wt% water addition, such a mix possesses good vibration castable characteristics; with 6. 5 wt% , it shows good self-flow castable characteristics; and with 7.0wt%, it can be a good pumpable castable, in every case with comparable mechanical properties. While with 7.5wt% water addition, the properties of such castable ared efinitively impaired.     

Application Study onβ—Sialon—Al2O3 Brick in Iron Ladle

The microstructure and slag erosion fractal dimension of reaction interface of β-Sialon-Al2O3 brick used in 300 Mt iron ladle of Baosteel have been studied by SEM and XRD.The results indicated that β-Sialon-Al2O3 brick exhibited excellent slag resistance.The main wear mechanism of β-Sialon-Al2O3 brick is mainly from the spalling caused by thermal mechanical stress and attacked by slag secondly.     

Investigation on Reaction Synthesis of Sialon Multiphase Refractory from Clay and Additive TiO2

Sialon multiphase composites containting titanium-carbon or titanium-nitrogen have been synthesized from clay nd additive titania through different sintering processes,The experimental results indicated that there was a great change of crystal phase in the similar-composition specimens singtering in air ,nitrogen and bedding protecive poder respectively,determined by XRD analysis,The subsequent evidences were also supplied by SEM.The improvement in mehanical properties of multiphase refracto-ries was observed as the amount of titania changing from 0 to 16%,The main causes maybe come from the excellent properties of high hardness and in-situ strengthening effects of the in-situ formed secondary phase,TiC or TiN.     

Slag Corrosion Resistace of β－Sialon－Al2O3 Composites－Part I. Thermodynamics and Mechanism

Slag corrosion resistance of β－Sialon and β－Sialon-Al2O3 composites has been studied .The effects of FeO content and temperature on corrosion rate have been investi-gated by mens of dip method(static and self-rotating).The corrosion process and microstructural analysis.It is shown that FeO preferentially attacks β-Sialon in the composite and the protruded corundum grains would gradualy fall off into the slag.