【作者】 黄军同；

【导师】 黄朝晖； 刘艳改；

【作者基本信息】 中国地质大学（北京） ， 岩石矿物材料学， 2012， 博士

【摘要】 为应对天然高品质高铝矾土矿物资源的匮乏对铝硅体系耐高温材料带来的严重挑战,针对目前非氧化物复相耐火材料Si3N4/Sialon基质存在合成原料成本高以及非氧化物复相耐火材料的高温烧成过程存在耗能高的突出问题,本论文利用天然铝硅矿物(特别是中低品位的铝矾土和高铝含量固废资源)通过碳热/铝热还原氮化等技术转型为非氧化物耐火原料,进行合成的非氧化物复合SiC系耐火材料免烧成技术和性能优化的研究,并利用过渡金属原位催化氮化反应制备新一代高性能Si3N4/Sialon结合SiC复相耐火材料,取得了一些重要的研究成果。论文系统研究了天然铝硅矿物原料配比、合成温度和还原剂加入量等工艺参数对非氧化物转型后材料物相组成、显微结构的影响规律。以天然石英、中低品位的铝矾土和菱镁矿等铝硅矿物以及煤矸石、高铝粉煤灰和铝灰等工业固体废弃物为原料,在1400℃-1600-C通过碳热/铝热还原氮化非氧化物转型合成得至β-Si3N4、β-Sialon、Ca-α-Sialon、镁铝尖晶石-刚玉-Sialon等材料；对比研究的化学纯原料在高温1700℃下非氧化物转型合成得至Ca-Dy-α-Sialon和Li-α-Sialon,为矿物转型后的非氧化物在耐火材料中的应用奠定了技术依据。过渡金属Fe、Co、Ni能够促进Si粉、Si-Al-Al2O3粉氮化形成Si3N4/β-Sialon及提高其纳米纤维含量,通过催化热化学气相沉积法制备得到一维α-Si3N4、Sialon纳米线/带。在1400℃氮化烧结后,当Co加入量为0.5%-1.0%时,制备的Si3N4/Sialon结合SiC试样的抗折强度能够提高50%-80%,达到60MPa。催化剂促进氮化反应结合Si3N4/Sialon-SiC复相材料强度提高的机制为“催化剂促进液相烧结”和“原位自生纤维(晶须)强化”机制,为免烧成耐火材料在高温使用条件下的高温在线烧结和强度获得提供理论基础。研究了低品位铝矾土和锆英石非氧化物转型后在免烧成耐火材料的应用,讨论了材料组成、结构、力学性能与高温抗渣侵蚀性能之间的关系,借鉴结晶学和矿物学理论探讨其抗渣侵蚀机理。低品位铝矾土和锆英石在1600℃非氧化物转型为Sialon-ZrN及其作为基质以酚醛树脂为结合剂制备获得Sialon-ZrN-SiC复相非氧化物免烧成耐火材料,常温强度由树脂提供,高温强度由材料的烧结而获得,基质中的Sialon柱状晶呈穿晶断裂有助于强度的提高。高炉渣对免烧成Sialon-ZrN-SiC复相耐火材料的侵蚀存在两个方面：耐火材料熔蚀到渣中的溶解以及熔渣在耐火材料内的渗透。本研究工作制备的免烧成的Sialon-ZrN-SiC耐火材料中ZrN氧化后形成的ZrO2,不与渣中的其他氧化物反应形成低熔点的物质,能够起到抵抗渣侵蚀的作用。更多还原

【Abstract】 In oder to cope with the serious challeges of the scarcity of the high-quality bauxite mineral resources on alumina-silica system refractories and aim at the problems of Si3N4/Sialon matrix in traditional non-oxide composite refractories (i.e., high cost of synthetic raw materials) and the problems raised during the firing process of non-oxide composite refractories at high temperature (e.g., high energy consumption, unstable quality and high cost), in this doctoral dissertation, we advanced an idea, namely, the oxynitride transformation of natural minerals with high Al2O3/SiO2(including high-alumina-content solid waste resources) by carbothermal/aluminothermic reduction-nitridation technologies. The studies on firing-free technologies and performance optimization of the as-synthesized oxynitride composite SiC refractories were performed. Meanwhile, a new generation high-performance Si3N4/Sialon bonded SiC composite refractories by in-situ transition metal-catalytic nitride reaction was investigated. Many important researches were made.The process parameters effects, such as the raw materials components, synthesis temperature and reductant amount, on the phase compositions, morphologies/microstructures of the transformed products were analyzed systematically.The natural minerals, i.e., quartz, low-grade bauxite and magnesite, as well as industrial solid wastes, i.e., fly ash, coal gangue, aluminum ash were transformed to β-Si3N4, P-Sialon, Ca-a-Sialon and spinel-corundum-Sialon composite materials via CRN/ARN at1400℃-1600℃.The chemically pure raw materials for comparative study were transformed to Ca-Dy-a-Sialon and Li-a-Sialon at higher temperature of1700℃. The above results provided technical and theoretical basis for the application of the related non-oxides transformation of minerals in refractories.Transition metals Fe, Co and Ni could promote the nitridation of Si powders as well as Si-Al-Al2O3powders to form Si3N4/β-Sialon and improve their nano-fibers contents. One-dimensional α-Si3N4,β-Sialon nanowire/nanobelts were synthesized by catalytic thermal chemical vapor deposition method. Si3N4/Sialon bonded SiC composites were prepared by in-situ Co-catalytic nitridation reaction at1350-1450℃.When the added amount of Co is0.5%-1.0%, the bending strength of the composites fired at1400℃could be improved by50%-80%(reaching60MPa) compared to that without Co.The mechanisms of strength improvement in the Si3N4/Sialon bonded SiC composites through in-situ Co-catalytic nitridation reaction are proposed to be co-dominated by "catalyst promoting liquid phase sintering " and "strengthen via in-situ fibers (whiskers)" mechanisms.The oxynitride transformed from the natural minerals was applied in the firing-free refractories. The relationships among the material compositions, microstructure, mechanical properties and high temperature slag-resistance properties was discussed, and the slag erosion mechanism of prepared firing-free refractories also discussed by means of crystallography and mineralogy theory. Sialon-ZrN composites were synthesized from low-grade bauxite and zircon by CRN at1600℃, and the Sialon-ZrN-SiC firing-free composite refractories were prepared by using phenolic resin as the binder. The room-temperature strength of the as-prepared samples was provided by the resin, and the high-temperature strength is obtained by the sintering of the materials. The long-columnar Sialon grains with transgranular fracture are benefit to the strength improvement. There are two aspects erosion of blast furnace slag to firing-free Sialon-ZrN-SiC composite refractories:the refractories dissolved in the slag and slag penetrated into the refractories. In this work, the as-prepared Sialon-ZrN-SiC firing-free refractories have good slag erosion resistance, resulted from the ZrO2which was oxidated from ZrN and didn’t react with the oxides in the slag to the formation of low-melting substances, consequently play a key role in resistance to slag erosion.更多还原