高温烟尘过滤用碳化硅多孔陶瓷的制备及性能研究

The porous ceramics with micron holes have a wide application prospect at hot gas filtration, heat insulation materials, catalyst supports, and other fields. The emulsion template method combined with sol-gel has been successfully used for the preparation of porous oxide ceramics, and the microstructure of the porous ceramics can be easily controlled. For the problem that emulsion template method combined with sol-gel is not applicable for the preparation of non-oxide porous ceramics, the emulsion template method combined with gelcasting is selected to prepare porous silicon carbide ceramics for the first time in this project. Mixing ceramic slurry contaning oil-in-water emulsion, SiC particles, monomer and crosslinker was prepared firstly. Then, polymerization was initiated in the slurry and the oil drops were fixed in the green body. Subsequently, the green body was dried and the oil drops were exhausted to form the porous structure. In the end, porous ceramics were sintered in an inert atmosphere. In this project, the appropriate raw materials were firstly explored and the rational process was established. Then the microstructure was adjusted by changing the type and amount of raw materials and the process parameters. The relationship of the microstructure and properties (thermal conductivity, compressive strength, specific surface area, transportation ratio and adsorption ratio for the hot dust) was built. The project was of great meaning for the design and preparation of the silicon carbide porous ceramics with high performances.

微米孔多孔陶瓷在高温气体过滤、隔热材料、催化剂载体等领域有着广泛的应用前景。乳状液模板法结合溶胶-凝胶方法已成功用来制备氧化物微米孔陶瓷方面，且所制备多孔陶瓷的微结构均匀可控。针对乳状液模板法结合溶胶凝胶方法尚不适用于非氧化物多孔陶瓷制备的问题，本项目首次采用乳状液模板法结合凝胶注模成型的方法制备碳化硅多孔陶瓷：先制备出水包油的乳状液陶瓷浆料，水相中含陶瓷颗粒和单体、交联剂；然后引发水相中聚合反应，浆料凝胶固化成型，油滴被固定；最后干燥、排油、排胶得到多孔坯体，在惰性气氛下烧结得到多孔陶瓷。项目首先探寻合适原料体系并建立合理的工艺，然后利用原料种类与用量的改变和工艺参数的调整对微结构进行调控，建立起微结构与性能（热导率、耐压强度、比表面积、透过率和对烟尘的吸附率）间的关系模型，揭示出微结构对性能的影响规律，为设计和制备高性能碳化硅多孔陶瓷材料奠定基础。

我国空气污染状况堪忧，每当冬季来临，雾霾和PM2.5总能成为人们关注的话题。要从根本上解决这个问题，需要工业用高温烟尘过滤器的研制和推广应用。碳化硅多孔陶瓷是过滤元件的重要候选材料。要实现PM2.5的有效去除，多孔陶瓷孔与孔之间的通道尺寸要小于或接近2.5um。多孔陶瓷的造孔机制有模板复刻法、直接发泡法、添加造孔剂法等。仅添加造孔剂法有可能制备孔径在如此小尺寸的碳化硅多孔陶瓷。造孔剂通常需要在中温阶段缓慢升温才能排出。该过程效率低，能耗大，且会对环境造成不利影响。. 本项目提出了采用液态造孔剂的研究思路，以平均粒径为1μm的碳化硅粉为原料，以环己烷形成的乳状油滴作为模板，通过凝胶注模成型将粒径为微米级的油滴原位固定在坯体内部，通过低温烘干即可使其挥发，再进行高温烧结得到碳化硅多孔陶瓷材料。项目实施期间，开展了关于碳化硅水基浆料与乳状液稳定共存的研究，乳状液浆料的凝胶过程研究，坯体的干燥及烧结参数研究，不同参数制备样品的性能测试和微观结构表征等一系列工作。浆料制备阶段通过改变油水体积比以及油乳质量比来控制乳状液体系；固化成型阶段利用催化剂和引发剂的加入量控制固化速率；干燥阶段采用控温控湿的方式避免开裂；烧成阶段的温度根据烧结试样微结构与强度确定为2100°C。. 多孔陶瓷的微结构为贯通的球形多孔结构。相组成除碳化硅外还包含有少量的石墨相。多孔陶瓷的气孔率、孔径尺寸等微观结构可以通过油水体积比、油乳质量比的改变进行调控。多孔陶瓷的气孔率主要分布在38.02-62.17%之间，其体积密度主要分布在1.18-1.87g/cm3。多孔陶瓷的耐压强度为58.89-231.03MPa，且其与体积密度具有正相关性。抗氧化性同样与油水体积比、油乳质量比有关，在同等氧化条件下其氧化率分布在4.55-14.55%。典型试样SC3-65-50的透气率为4.1*10-13m2，此外还具有良好抗热震性，其中试样SC1-65-50可经受4-5次水冷。. 在制备孔径尺寸在几到几十微米的多孔陶瓷时，乳状液模板结合凝胶注模工艺更具方法的优势。本项目中采用乳状液模板法制备的碳化硅多孔材料气孔更为均匀且孔壁致密化情况更好，尤其在高气孔率时更为明显。所制备碳化硅多孔陶瓷具有较好的力学强度、抗热震性、气孔分布及透气率，可以用于高温烟尘的过滤装置。