烧成低碳铝碳耐火材料中Ti3AlC2相与原位次生相的协同强韧化及材料抗煤灰渣侵蚀机理研究

High-temperature gasification technology is one of the important ways for efficient utilization of coal resources. The conventional high-chrome refractories used in gasifier have poor penetration resistance, spalling problem, short service life and may cause pollution due to the formation of Cr6+. Based on the non-wetting characteristics of carbon materials to slag and high toughness and self-healing anti-oxidation properties of Ti3AlC2, this project will use Ti3AlC2 composite powder-synthetised by aluminothermic reduction method, graphite, CNTs and other materials to fabricate fired Al2O3-C refractories as substitute for the conventional high-chrome refractories. Further improvement of thermal shock resistance and corrosion resistance can be achieved by optimizing the interfacial properties between Ti3AlC2 and the in-situ secondary phases, increasing the rate of micropore and enhancing the formation of dense protective layer on the surface of the materials. This project intends to systematically study the physical and chemical conditions of synthesizing Ti3AlC2 composite powder by aluminothermic reduction method, formation rules of secondary phases such as CNTs and SiC whiskers and their interfacial properties with Ti3AlC2, get a better understanding of fracture behavior and strengthening and toughening mechanism. Stability and anti-slag corrosion process of the Ti3AlC2-containing Al2O3-C refractories under complex atmosphere will be studied to reveal the mechanism of corrosion resistance. All these will provide a theoretical basis for the preparation of low-carbon Al2O3-C refractories with excellent thermal shock resistance and corrosion resistance.

高温气化技术是煤资源高效利用的重要途径之一。针对目前水煤浆气化炉用高铬耐火材料抗煤渣渗透性差、易剥落、寿命短及可能产生六价铬污染环境的问题，本项目基于炭素原料对渣不润湿的特性和利用Ti3AlC2高韧性和自修复抗氧化能力强的特点，拟采用铝热还原法制备的Ti3AlC2复合粉体和石墨、碳纳米管等为原料制备烧成低碳铝碳耐火材料，取代高铬耐火材料，并通过优化Ti3AlC2与原位次生相界面特性，提高材料微孔化率，控制材料表面形成致密保护层等措施，提高材料的抗热震性和抗渣渗透侵蚀性。本项目拟系统研究铝热还原法合成Ti3AlC2复合粉体物理化学条件；研究次生碳纳米管和碳化硅晶须形成规律及其与Ti3AlC2相界面特性，探明材料断裂行为和强韧化机理；研究高温多气氛下含Ti3AlC2低碳铝碳材料的稳定性及抗渣侵蚀过程，揭示材料抗渣侵蚀机理，为制备兼具热震稳定性和抗渣渗透侵蚀性优异的低碳铝碳耐火材料提供理论基础。

针对水煤浆气化炉用高铬耐火材料抗煤渣渗透性差、易剥落、寿命短及可能产生六价铬污染环境的问题，本项目基于Ti3AlC2高韧性和自修复抗氧化能力强的特点，开发了新型低碳铝碳耐火材料。主要研究了铝热还原法可控合成Ti3AlC2-Al2O3复合粉体的制备技术；研究了Ti3AlC2的结构演变以及原位形成碳纳米管和碳化硅晶须与材料的强韧化的关联性，揭示材料的强韧化机理；研究了高温多气氛下的氧化动力学行为，揭示了材料表面致密保护层形成的机理，为制备兼具热震稳定性和抗渣渗透侵蚀性优异的低碳铝碳耐火材料提供理论基础。项目研究工作具有重要的学术价值和工程应用前景。通过开展上述研究工作，得到如下主要结论：.1. 合成Ti3AlC2时1000℃保温促进形成中间相Al3Ti和TiC，大幅提高1400℃合成产物中Ti3AlC2的转化率。同时，控制原料中的铝过量也有利于提高Ti3AlC2的转化率。.2. Ti3AlC2在800~1400℃下会蚀变形成TiC-Al2O3核壳结构，1600℃时进一步反应形成TiC-Al2TiO5-Mullite多层核壳结构。正是由于上述结构演变以及原位形成碳化硅晶须和碳纳米管在材料断裂的过程中起到裂纹偏转的作用，有利于提高材料的热震稳定性。.3. 由于处理过程中形成TiC-Al2TiO5-Mullite核壳结构，抑制了高温氧化气氛向试样内部扩散；此外，氧化时核壳结构中TiC还会继续氧化形成Al2TiO5，与周围莫来石共同促进脱碳层的致密化，提高抗氧化。