非氧化物复合浇注料结合体系与热态强度演变关系及相关机理的研究

Incorporation of in situ nonoxide bonding through carbonization or nitridation is of an improtant approach to realizing high performance of oxide-nonoxide composited refractories. It becomes increasingly popular to adopt precast shapes of castables, which can be large in size, complex in shape and thin in thickness, to compensate the unsatisfactions of pressed oxide-nonoxide composited refractory products with plain shape, limited demension and top size of aggregate. However, the matrix composition becomes more complex due to unavoidable binding component in the castable, leading to distiguished changes from the pressed counterparts in phase composition, microstructure and properties after nitridization or carbonization, e.g., an abrupt decline in hot modulus of rupture (HMOR) occurs after a certain temperature, and its mechanism remains unclear. Choosing widely applicable silicon carbide and alumina based castables as subjects, this proposal puts forward a new research appraoch by investigating the deformation under load during heating and stain-stress behavior at specific temperature in leiu of simply testing HMOR to investigate hot strength evolution and its interconnection with binding system and reveal how phase composition and microstructure change with temeprature, time and atmosphere, when subjecting to reheating, and their effect on HMOR of the castables using different binding system, ultralow cement vs non-cement, after nitridation or carbonization. This project, with good acdemic and practical values behind, holds realistic meaningfulness to solve techninal problems encountered in realizing high performace of such in situ nonoxide composited castables and promote their applications.

通过碳化或氮化原位形成非氧化物结合相是氧化物-非氧化物复合耐火材料实现高性能的重要技术途径。针对目前采用机压成形的这类制品存在形状简单、尺寸小、骨料临界尺度有限等不足，采用浇注料预制成大、异、薄形制品日益流行。然而，浇注料必需的常温结合剂使其基质组分变复杂，导致氮化或碳化后制品的相组成、显微结构和性能出现与机压制品不同的变化，如达一定温度后热态抗折强度会急剧衰减，其机理不明。本项目以用途广泛的SiC基和Al2O3基浇注料为研究对象，提出了考察热态抗折强度的同时还考察荷重变形和一定温度下应力-应变行为的研究方法，用以更好地揭示热态强度变化机理及其与结合体系的关联，探明超低水泥、无水泥不同结合体系的这类浇注料氮化、碳化后再受热时相组成、显微结构随温度、时间和气氛的演变及其对热态抗折强度的影响。本工作对原位非氧化物复合浇注料实现高性能遇到技术难题的解决和指导应用有现实意义，有较高学术和实用价值。

以用途广泛的SiC基和Al2O3基浇注料为研究对象，通过原位碳化或氮化技术制备了以非氧化物为结合相的浇注料。通过热力学计算与分析，得到了Al-Si-C-N-O体系的优势区相图，实现了基质部分物相组成的设计与控制。.为揭示结合系统对浇注料热态抗折强度-温度演变关系的影响，通过改变基质中水泥的加入量，分别制备了非氧化物结合的低水泥、超低水泥和无水泥刚玉基浇注料，综合浇注料的热态应力-应变行为、玻璃相含量、物相组成和显微结构分析等结果，揭示了浇注料的热态强度衰减机理。.对非氧化物结合Al2O3基浇注料而言，水泥的引入会显著降低1400℃时试样的热态强度，其值由无水泥时的21.6MPa降至水泥加入量5%时的0.64MPa。加入水泥的试样，1200℃开始出现塑性变形；1400℃时出现粘滞变形；而无水泥试样，1400℃仅有少量塑性变形。随水泥加入量的增加，试样中玻璃相含量呈线性增多。除β-SiAlON、O’-SiAlON等非氧化物结合相外，含水泥的浇注料中还会形成钙长石相和玻璃相，且SiAlON呈粒状，为不连续相；玻璃相多且呈连续分布。无水泥试样中，SiAlON为柱状或纤维状，相交织成连续网状；玻璃相少，呈孤立状分布，有利于热态强度的保持。粘滞变形是含水泥试样热态强度衰减的主因，而玻璃相的存在和软化则是产生粘滞变形的主因。.采用楔入劈拉法研究了浇注料结合系统与常温断裂行为间的关联。发现结合体系会显著影响浇注料的断裂行为。低水泥和超低水泥刚玉基浇注料的载荷-位移曲线呈线性，属典型的脆性断裂，表明浇注料的韧性差；无水泥刚玉基浇注料的载荷-位移曲线呈非线性，属准稳态断裂，说明浇注料的韧性高。.非氧化物结合浇注料再受热时性能及结构演变规律研究发现，在埋碳和空气气氛下再受热时，虽常温强度有一定提高，但关键性能如热态强度和热震稳定性均会降低，无水泥或硅溶胶作结合体系时浇注料性能降低幅度最小。.本项目研究成果可为此类浇注料结合体系的选择、优化和高性能化提供理论依据和技术参考，对高性能不定形耐火材料的发展和应用有重要学术价值和现实意义。