【作者】 陈凯；

【导师】 黄朝晖； 房明浩；

【作者基本信息】 中国地质大学（北京） ， 岩石矿物材料学， 2014， 博士

【摘要】 针对目前Si3N4-SiC复相耐火材料高温烧成过程中存在的成本高、能耗高、质量不稳定等突出问题，本论文利用石英和金红石经碳热还原氮化工艺合成Si3N4、TiCN等非氧化物原料，并进行SiC-Si3N4耐火材料的免烧成制备技术与性能优化的研究，探讨了免烧成耐火材料强度获得的机制，取得了一些重要研究成果。分析了石英和金红石碳热还原氮化低成本合成TiCN和Si3N4耐火原料的物相行为，获得了优化的工艺参数。以石英为原料，焦炭添加量为理论量，Fe2O3添加量为5%，在1600℃保温3h碳热还原氮化，可合成晶粒尺寸2~4μm的β-Si3N4粉体。以金红石和石英为原料，金红石和石英比例为1∶9，焦炭添加量为理论量，在1600℃保温3h碳热还原氮化，可合成TiCN-Si3N4复相粉体。研究结果为矿物合成非氧化物在耐火材料中的应用奠定了基础。对SiC-Si3N4耐火材料的免烧成制备技术和性能优化工艺进行了研究。发现Si3N4加入50%的免烧成SiC-Si3N4耐火材料具有最佳的综合性能，其体积密度2.31g·cm-3，常温抗折强度7.41MPa，抗冰晶石侵蚀性能优良，常温和1100℃的体积冲蚀磨损率分别为24.17mm3·g-1和43.97mm3·g-1。随着TiCN-Si3N4添加量增加，免烧成SiC-TiCN-Si3N4耐火材料的侵蚀分形维数由1.0568减小到1.0105，抗高炉渣侵蚀性能提高。分析其作用机理是TiCN增大了高炉渣的粘度，降低了渣的渗透能力，可与渣反应生成高粘度相富集在熔渣与基质的反应层中，阻挡熔渣的侵入，提高了抗渣侵蚀性能。硅粉/酚醛树脂结合的免烧成SiC-Si3N4耐火材料150℃以下通过树脂的交联硬化获得强度。随着温度的升高，致密度降低，600~700℃，酚醛树脂的热解和氧化造成材料的强度下降，800℃的抗折强度最小。900~1400℃，材料内部的氧化烧结作用加强，高温抗折强度增大。1400℃时晶粒间相互交错、重叠，形成强度较高的结晶联生体，抗折强度达最大为15.64MPa。铝酸盐水泥/酚醛树脂结合的免烧成SiC-Si3N4耐火材料常温下通过水泥的水化以及酚醛树脂的交联固化使材料获得高的强度。升温过程中，低温水化矿物逐渐转化成高温水化矿物，强度下降，800℃时由于水化铝酸钙全部转变为二次CA和CA2，水泥失去胶结作用并形成内部气孔，材料的强度降至最低。1100℃以上，由于液相烧结和原位莫来石晶须增强，起到原位自修复/自强化的作用，材料强度显著增大，1400℃时高温抗折强度最大为48.83MPa。揭示了免烧成SiC-Si3N4耐火材料分别在150~800℃和800~1600℃下抗折强度与温度的关系。液相烧结和原位晶须增强机制为免烧成耐火材料在高温使用条件下的动态烧结和强度获得提供了理论依据。本论文研究成果能够为开发具有自主知识产权的高性能低成本免烧成SiC-Si3N4复相耐火材料提供相应理论基础和技术依据，对节能减排、矿物资源高效利用和推动新一代高性能耐火材料的研究和发展具有重要意义。更多还原

【Abstract】 In this doctoral dissertation, we aimed at coping with the critical problems (e.g.,high cost, high energy consumption and unstable quality) which were raised during thepreparation process and the high temperature sintering process in the traditionalpreparation technique of the widely used Si3N4-SiC composite refractories. Quartz andrutile were used as the raw materials to synthesize the non-oxide composite powdersincluding Si3N4and TiCN. We advanced a novel unfired technology to prepare theSiC-Si3N4composite refractories using the synthesized TiCN, Si3N4and SiC as thestarting materials. The preparation parameters and the properties optimization of theunfired SiC-Si3N4composite refractories were investigated in detail.The phase transformation of quartz and rutile during the carbothermal reductionnitridation (CRN) process were studied. The optimal experimental parameters forsynthesizing high purity β-Si3N4powder were carbon content of stoichiometric content,temperature of1600°C for3h and Fe2O3content of5%. The optimum parameters forsynthesizing TiCN-Si3N4by CRN process were the mass ratio between rutile and quartzof1∶9, carbon addition of stoichiometric content and temperature of1600°C for3h.The preparation parameters and the properties optimization of the unfiredSiC-Si3N4composite refractories were studied. The unfired SiC-Si3N4refractories with50wt%Si3N4had best comprehensive properties, with density of2.31g·cm-3, roomtemperature flexural strength of7.41MPa, good cryolite erosion resistance and gooderosion wear resistance. The erosion fractal dimensions of the unfired refractoriesdecreased from1.0568to1.0105with the increase of the TiCN-Si3N4content, so theslag erosion resistance of the unfired SiC-TiCN-Si3N4refractories was improvedobviously. On the one hand, TiCN increased the viscosity of slag and reduced thepenetration of slag. On the other hand, the oxidation products of TiCN and Si3N4wereTiO2and SiO2, which could react with slag to generate a high viscosity phase. The highviscosity phase concentrated in the reaction layer between the slag and the refractory,could block the invasion of the slag effectively.The mechanism for acquiring high strength of the unfired SiC-Si3N4composite refractories was also investigated. Below150°C, the strength of the unfired refractoriescombined with silicon powder-phenolic resin was obtained through the cross-linkinghardening of phenolic resin. With the increase of temperature, the density of the unfiredrefractories decreased.600~700°C, the high temperature pyrolysis and oxidation of thephenolic resin caused the loss of the strength of the unfired refractories. At800°C, aminimum flexural strength was obtained.900~1400°C, the internal oxidation sinteringrole of the unfired refractories was strengthened, so the flexural strength increased. At1400°C, the grains in the unfired refractories interlocked and overlapped each other toform the crystallization body with high strength, so flexural strength increased.At room temperature, the high strength of the unfired refractories combined withaluminate cement-phenolic resin was obtained through the hydration of cement and thecross-linking hardening of phenolic resin. With the increase of temperature, the lowtemperature hydration mineral gradually transformed into high temperature hydrationmineral, so the strength decreased. At800°C, the hydration calcium aluminatetransformed into secondary CA and CA2completely, the cementation of cement got lostand caused the formation of the pore, so a minimum flexural strength was obtained.Above1100°C, the flexural strength of the unfired refractories increased remarkablydue to the liquid phase sintering and in-situ formation of mullite whisker, which hadeffect of in situ self-healing/self strengthening and toughening. At1400°C, hightemperature flexural strength of the unfired refractories was up to48.83MPa. We foundthe relationship between flexural strength and temperature at150~800°C and800~1600°C.The above research results can provide theoretical basis and technical support todevelop high performance unfired SiC-Si3N4refractories with low cost and independentintellectual property rights. They also have important significance for promoting theresearch and development of a new generation of high performance refractory materials.更多还原