等离子体垃圾焚烧条件下CA6-SiC复合材料烧结机理与服役行为

The disposal of high-risk waste could realize harmlessness through plasma gasification process, by which instant high temperature of 3000℃~10000℃ occurred during the air ionization in the plasma gasifier. Lacking of application basis research and theoretical guidance is one of the main reasons that the plasma technology is not mature in China at present. In this project, CA6 particles were used as aggregate, SiC powders were used as matrix, by controlling the addition amount of Zr, Ti, Si and C powders to form ZrC and TiC through in situ reaction by adopting spark plasma sintering (SPS) technology, in which to realize the sintering densification of the materials at low temperature to improve the oxidation resistance. On the other hand, the formation of SiC whisker could enhance the mechanical behavior at high temperature and further improve the oxidation resistance through blocking the pores. Finally, penetration and erosion models at high temperature were built through numerical simulation combined with experiments to verify the gaseous (HCl, H2O and CO) erosion resistance mechanism of CA6-SiC composites. Microstructure evolution and erosion resistance mechanism of CA6-SiC composites under the condition of plasma were revealed to obtain the preparation method of CA6-SiC lining refractories with outstanding gaseous erosion resistance and mechanical properties for plasma gasifier.

等离子体气化炉通过对空气进行电离瞬间产生3000℃~10000℃的高温，高危废物经过等离子体气化炉处理能实现无害化。国内等离子体技术尚不成熟，难题之一是缺乏对等离子体气化炉用耐火材料的应用基础研究及理论指导。项目以CA6颗粒为骨料，SiC细粉为基质，一方面通过添加Zr、Ti、Si、C细粉，控制添加量，采用等离子烧结（SPS）技术，原位反应生成ZrC、TiC，实现材料的低温烧结致密化，提高基质部分SiC的抗氧化性。另一方面，控制合适条件促进原位反应生成SiC晶须，增强材料的高温力学性能，同时通过晶须的形成来堵塞气孔，进一步提高抗氧化性。最后，构建CA6-SiC复合材料高温下的气体渗透和腐蚀模型，探明CA6-SiC复合材料耐高温气体（HCl、CO、H2O等）腐蚀机理；揭示CA6-SiC复合材料在等离子体条件下显微结构演变规律。

等离子体气化炉通过对空气进行电离瞬间产生3000℃~10000℃的高温，高危废物经过等离子体气化炉处理能实现无害化。国内等离子体技术尚不成熟，难题之一是缺乏对等离子体气化炉用耐火材料的应用基础研究及理论指导。本项目以SiC浇注料为研究对象，首先制备性能优异的SiC晶须增强SiC质耐火材料。接着引入金属Zr和Ti，研究不同金属及其含量对SiC浇注料抗氧化性能的影响；同时模拟等离子体气化炉实际工况条件，采用放电等离子烧结(SPS)技术对材料进行烧结，探明等离子条件下含不同添加剂的SiC浇注料显微结构与性能的变化规律。然后以致密CA6骨料取代SiC颗粒，研究CA6骨料对SiC浇注料常温物理性能的影响。最后，对比研究CA6-SiC、SiC、MgAl2O4-Cr2O3质耐火材料抗高温湿空气腐蚀性能，探明不同耐火材料高温湿空气腐蚀机理，建立高温湿空气腐蚀模型，为等离子体气化炉衬材料选择提供指导。通过上述研究，得到以下结论：.（1）1500℃下，SiO与CO反应原位形成SiC晶须，显著提高了断裂能，比MgAl2O4-Cr2O3浇注料显示出更高的抗热应力损伤因子，1700℃处理的SiC浇注料原位形成大量SiC晶须，显著提高了强度。.（2）添加Zr/Ti能够提高SiC浇注料的高温抗氧化性能。1500℃下，Zr/Ti优先氧化产生体积膨胀，堵塞气孔，降低氧分压，促进生成SiC晶须与石墨化碳，使SiC浇注料达到自修复功能并显著增强材料高温力学性能。在SPS系统高频脉冲电场的作用下，Ti与Si及炭黑发生反应生成片状Ti3SiC2（MAX相），最终生成片状Ti3SiC2包裹SiC颗粒的结构，显著提高了试样的力学性能和抗氧化性。.（3） 以CA6骨料取代SiC颗粒制备的CA6-SiC浇注料具有较高的烘后强度。且CA6在1000℃的高温湿空气条件下稳定性较好，而SiC和Cr2O3会与高温湿空气发生反应。SiC在高温湿空气条件下首先被O2氧化形成SiO2，随着湿空气持续腐蚀，硅氧网络结构（Si-O-Si）与水蒸气反应形成硅醇基（Si-OH）造成SiO2保护膜破坏，形成不规则多孔状SiO2膜；Cr2O3高温条件下与H2O (g)和O2 (g)反应形成气相产物CrO2(OH)2 (g)。相比于SiC浇注料和MgAl2O4-Cr2O3浇注料，CA6-SiC浇注料具有较好的抗高温湿空气腐蚀性能。