纳米结构在刚玉质致密浇注料中形成机理及对高温性能的改善机制

Nano bonded phases with high specific surface area and high surface energy can significantly improve the bonding strength and thermal shock resistance of refractory castables. Nano-scale pore structure can also form the high potential barrier of solid-liquid and greatly enhance the resistance of the castables to slag penetration and corrosion. So the generation of the aboved nano-structures in refractory castables will give rise to the materials with excellent comprehensive properties at elevated temperature. Through optimization of packing model of micro-nano powders, surface modification of nano particles and interfacial adjustability of solid-liquid, the nano structures in the castables from room to high temperature will be realized successfully. The evolution and adjustable model of nano structures in the castables will be established from the aspects of interfacial reaction(micro-nano powders), certain migration and diffusion, limited interfacial solution at elevated temperature. Furthermore, the influence regulation of critical size, morphology, content and distribution of nano structures on the bonding strength, fracture toughness and thermal shock resistance of the castables will be investigated. The impact mechanism of nano structures with different critical size and morphology on the distortion, shielding and deformation of microcracks will be revealed. At the same time, the effect of high potential barrier of solid-liquid, originated from nano pore, on slag diffusion, composition attachment, interfacial reaction of liquid-gas-solid will be explored. The obvious improvement mechanism of high temperature comprehensive properties of refractory castables with nano structures will also be illustrated. The result of this project research will enrich the theory of the bonding system and performance design for refractory castables. It is believed that this project research will significantly facilitate the service life lengthening of refractory castables with cement free, clean steelmaking, environment protection and energy saving of high temperature industries.

纳米结合相高比表面积和高表面能可显著提高耐火浇注料结合强度和热震稳定性，纳米气孔形成的液固势垒能急剧降低熔渣对耐火浇注料渗透和侵蚀。因此，纳米固-气结构有利于耐火浇注料高温性能的显著提升。本项目通过微纳米颗粒密堆模型优化、纳米粒子表面修饰和液固界面控制，在刚玉质致密浇注料中实现纳米结合相和纳米气孔的基质结构；从微纳米多尺度界面作用、物质可控迁移与扩散、界面有限固溶反应等方面，来构建浇注料中纳米结构高温下演化和调控模型。研究纳米结构尺寸、形貌、含量和分布等对浇注料结合强度、断裂韧性和热震稳定性的影响规律，揭示纳米结构对材料中微裂纹扭曲、屏蔽和形变的作用机理；研究纳米气孔形成的液固高势垒对熔渣扩散、成分吸附、液固气界面反应等的影响规律，阐明纳米结构对浇注料高温性能的显著改善机制。相关研究成果可丰富耐火浇注料结合体系及性能设计理论，亦有利于无水泥耐火浇注料长寿化、洁净钢冶炼和高温工业节能降耗。

纳米结合相高比表面积和高表面能可显著提高耐火浇注料结合强度和热震稳定性，纳米气孔的形成能急剧降低熔渣对耐火浇注料渗透和侵蚀。因此，纳米固-气结构有利于耐火浇注料高温性能的显著提升。本项目以刚玉质耐火浇注料为对象，通过微纳米颗粒密堆模型优化，探索纳米粒子的添加对刚玉质浇注料孔径分布和高温性能的影响规律，取得如下成果：（1）从理论上构建了耐火浇注料气孔向微纳米尺度转变的结构演化模型，微纳米颗粒密堆积结构模型的优化，有利于体系堆积密度的提高，且微纳米粉的加入促进了堆积模型中孔径的进一步细化。纳米粉体的添加有利于体系的烧结驱动力的增强，加快晶界迁移速度，促进添加纳米相结合体系的烧结作用。（2）探究了纳米粒子对致密浇注料的显微结构的影响。Al2O3-SiO2凝胶粉溶于水会形成直径为1-100nm的溶胶，一方面可填充微小孔隙，另一方面也可以封闭部分较小的显气孔，Al2O3-SiO2凝胶粉中纳米级溶胶粒子的填充作用和较高的表面能使浇注料基质中气孔的孔径从微米级向亚微米级和纳米级转化。（3）发现了较小的气孔能减少应力集中，限制裂纹的扩展，从而提高浇注料的热震稳定性。故添加2%纳米SiO2的浇注料中具有较多孔径较小的气孔。这些微小气孔有助于缓解浇注料内部的应力集中，限制裂纹的扩展，从而提高浇注料的抗热震性。此外，添加2%纳米SiO2的浇注料中生成了较多交错分布的柱状莫来石，莫来石间形成连续的互锁网络结构，有助于限制裂纹的扩展，使浇注料的抗热震性有所提升。（4）说明了添加适量的纳米ZrO2可以减小气孔尺寸，使气孔朝着微纳米尺寸转化，并分布在一个小范围内，这种气孔分布情况减少了渣向四周扩散的可能性，不利于渣向内部渗透。与此同时纳米ZrO2可以降低熔渣的表面张力、形成保护层并增加熔渣的黏度来阻碍熔渣向浇注料中渗透，因此，纳米ZrO2粒子的增加使浇注料的抗渣侵蚀性能提高。