矾土基β-Sialon结合刚玉复合材料的制备、结构及性能研究

【作者】 刘战杰；

【导师】 钟香崇； 张海军；

【作者基本信息】 郑州大学 ， 材料学， 2004， 硕士

【摘要】 本文研究了以高铝矾土、Si、电熔白刚玉颗粒及细粉和部分添加剂为原料，氮气气氛下通过反应烧结的方法一步制备矾土基β-Sialon结合刚玉复合材料的工艺。研究结果表明，流动氮气气氛下1500℃／5h反应烧结可以得到主晶相为刚玉、次晶相为β-Sialon的矾土基β-Sialon结合刚玉复合材料，无其他晶相生成。用逐次回归的方法得到了常温抗折强度、体积密度及显气孔率与与颗粒级配间的函数式，其回归效果良好，可信度高，可用于预报反应烧结法制备矾土基β-Sialon结合刚玉复合材料的常温物理性能。得到了较理想的颗粒级配：刚玉粗颗粒45％、中颗粒10％、细粉45％(其中刚玉细粉25％，合成矾土基β-Sialon的细粉为20％)。用酚醛树脂作结合剂，显微结构表明，复合材料中生成大量矾土基β-Sialon晶须，并互相编织成网络结构。根据前面的工艺得到的矾土基β-Sialon结合刚玉复合材料的常温性能为：体积密度＞2.9g／cm3，显气孔率＜21％，抗折强度～15MPa。 矾土基β-Sialon结合刚玉复合材料的高温力学性能研究结果表明：矾土基β-Sialon含量在25％和30％时，复合材料的强度在800℃以前逐渐增加，800-1400℃基本保持不变。应力-应变关系随温度的变化规律表明800℃以前为弹性变形阶段，1400℃以前没有出现快速流动，说明复合材料中结晶效应占主导地位。 矾土基β-Sialon结合刚玉复合材料的抗热震性能较好，矾土基β-Sialon含量为25％时，其热震临界温度为600℃，热震温差为1350℃时其残余强度保持率仍然有65％；而相同条件的氧化铝基β-Sialon结合刚玉复合材料的临界温差为800℃，但温差为1350℃时的强度保持率比矾土基β-Sialon结合刚玉复合材料的低10个百分点。 矾土基β-Sialon结合刚玉复合材料的氧化属保护性氧化。实验条件下，矾土基β-Sialon结合刚玉复合材料的氧化动力学可分为两个阶段：60分钟以前，单位面积氧化增重与时间呈线性关系，属于化学反应与扩散过程共同控速。60分钟以后，单位面积氧化增重的平方与时间呈线性关系，属于扩散控速阶段。1250-1350℃范围内温度上升，矾土基β-Sialon结合刚玉复合材料的氧化速率减小。而同样条件下氧化铝基β-Sialon结合刚玉复合材料的变化趋势正好相反。推郑州大学硕士学位论文.，.闷月~.电口...，..口................................ 一‘.........两.州......‘月曰..卜‘~导了各阶段的氧化动力学模型。 与高铝砖和刚玉砖相比，矾土基p一Sialon结合刚玉复合材料的抗从C03侵蚀性能优异。更多还原

【Abstract】 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更多还原