| Preparation of bauxite based p-Sialon bonded corundum composite(BSC) through reactive sintering were investigated, using bauxite, silicon, fused white corundum grains, and additives as the raw materials. XRD results showed that the main crystal phase was corundum in the specimens sintered at ISOO? for 5 hours under flowing nitrogen atmosphere, and the other phase was P-Sialon phase. Stepwise regress method were used to investigate relationship between grain size gradient and sintering properties of BSC, and functions were established. The functions fit close well with the experimental results and can be used for forecasting properties of BSC at room temperature. Suitable grain size gradient for preparation of BSC was 45wt% coarse-grain corundum, 10% middle size corundum, and 45% powders(include 25% corundum powder and 20% powders for the synthesis of P-Sialon involved). Interwoven structure could be found in cracked surface of BSC by scanning electronic microscope, when using bakelite as temporary bonder. According to the process above, BSC were got with bulk density >2.9g/cm3, and apparent porosity <21%, and modulus of rupture(MOR, at room temperature) 15MPa or so.Relationship of HT-MOR P-Sialon bonded corundum composites with temperature increasing from room temperature up to 1400癈 were studied. Results showed that when temperature rised from room temperature to 800 ?, MOR of the composites increased to the top at 20MPa. When it was in range of 800 癈 to 1400癈, MOR holding almostly the same value as that at 800 for 25% and 30% p-Sialon-contained specimens. In case of the composite with 20% p-Sialon, MOR reduced slightly with the rise of temperature after 800 However, which still higher at 1400 than that at room temperature.From room temperature to 800 , stress-strain curves of p-Sialon bonded corundum exhibited elastic deformation character. When testing temperature is between 1000 to 1400, pamernent deformation were detected. It means that the composites were in plastic flow range. These also proved that the compositescontained just little liquid phase, and crystal effect was the main factor for high temperature strength.P-Sialon bonded corundum composites displayed good thermal shock resistance(TSR) properties. When p-Sialon-containing percentage was 25%, critical temperature difference for BSC was 600癈, and ASC, 800癈. But when the temperature difference was 1350癈, residual strength ratio of BSC was 65%, however it was 55% for ASC.Oxidation behavior of p-Sialon bonded corundum composites were studied. Oxidation process of BSC was a protective one. Oxidation kinetic could be divided into two range. That is, when oxidation time is under 60 minutes, quadratic polynomial of weight gain per unit area exhibited a straight line relationship with time in minute. When oxidation time is longer than 60 minutes, parabolic relation between square of weight gain per unit area and time was discovered. Constant rates of the kinetic model were evaluated from the curves. Oxidation speed decrease with the ascending of temperature for BSC when testing temperature is 1250癈 to 1350 癈, and opposite result was got for ASC. Oxidation models were deduced.Comparing with high alumina brick and corundum brick, BSC displayed much better property of COerosion resistance at 1300... |
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