Ti3SiC2、Al2O3和Y2SiO5多孔陶瓷的制备和性能表征

IMR OpenIR

	Ti3SiC2、Al2O3和Y2SiO5多孔陶瓷的制备和性能表征
	李端阳
学位类型	博士
导师	周延春
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料学
关键词	多孔陶瓷冷冻升华法 Ti3sic2 Y2sio5 Al2o3 Porous Ceramic Freeze Casting Ti3sic2 Y2sio5 Al2o3
摘要	"通过系统的研究工作，论文得到的主要结论如下：通过水解、电动力学实验研究了Ti3SiC2水基浆料的水解程度及其在水溶液中的分散性质。没有添加分散剂的悬浮液在 pH 4~11范围内很难保持浆料的稳定性。聚乙烯亚胺（PEI）是一种有效的分散剂，添加1 dwb% 和1.5 dwb%的PEI的悬浮液在pH 4~8范围内具有很高的稳定性。在得到稳定的浆料基础上，针对不同湿法成型工艺要求，通过调整相应的参数来配置合理的浆料。选择合适的贫氧气氛，采用有机浸渍法制备出多孔网状Ti3SiC2陶瓷。由于多孔网状Ti3SiC2陶瓷比表面积大，热稳定性远低于块体材料，在1100ºC下即开始出现分解。 Y2SiO5具有优良的力学性能和突出的热学性能，比如具有低的热导率，是一种潜在的隔热材料。在1550ºC,不添加任何烧结助剂的条件下,通过固相直接反应法制备出高纯Y2SiO5材料。将所制备的高纯Y2SiO5材料研磨成细粉。表明，单纯的用Y2SiO5粉末难以配置成稳定的悬浮液。而选用PEI作为分散剂后，只要添加1.5dwb.%的PEI，可以配置得到稳定的Y2SiO5浆料。利用有机浸渍法，在固含量为35vol.%的条件下制备出开孔率为73%多孔网状Y2SiO5陶瓷。利用冷冻升华法，并采用叔丁醇作为溶剂，成功的制备出高孔隙率的具有定向排列的长直孔的多孔氧化铝陶瓷。这种定向排列的长直孔形貌是由叔丁醇在定向凝固条件下的结晶状态所决定。该种孔结构在垂直于冷冻方向呈尺寸约为100 μm左右的多边形孔，而在平行于冷冻方向为长度可达到毫米级别的、非枝晶状直孔，且各个方向孔的分布均匀有序。该种孔结构同以水或者莰烯作为溶剂得到的孔迥异，后二者更容易形成片层状结构或者枝晶状结构的孔。由于这种结构相对于含枝晶状结构的多孔材料发生更少的热交换，预期热导率更低。以叔丁醇为溶剂采用冷冻升华法所制备的多孔氧化铝的孔隙率与初始固含量密切相关。随着固含量从20 vol.%降到10 vol.%，孔隙率从65%线性地上升到82%。在固含量为10 vol.%时，可以得到高孔隙率的氧化铝陶瓷，其体密度仅为0.68 g×cm-3，甚至低于水的密度。与孔隙率的变化相反，随着固含量从20 vol.%降到10 vol.%，压缩强度却从37.0 MPa降到2.6MPa。表明，对孔隙率为65%的多孔氧化铝，其断裂符合伸展结构模式（stretch-dominated structures）；而对具有孔隙率为82%的多孔氧化铝，其断裂符合弯曲结构模式（bending-dominated structures）。采用以叔丁醇为溶剂的冷冻升华法，在1300ºC时，制备出具有单一取向孔结构的新型多孔材料Y2SiO5陶瓷。当固含量从20 vol.%变化到10 vol.%，其孔径变大，孔壁变薄，但孔都具有直孔状形貌，且孔尺寸分布比较均一。多孔Y2SiO5陶瓷的孔隙率与固含量间呈线性关系。随着固含量的下降，孔隙率升高，而样品的压缩强度下降。该样品在径向方向的热导率显著低于其致密体的热导率。而当固含量为15vol.%时，其热导率有仅为0.05 W/mK，此固含量下样品的压缩强度也可达近20 MPa。"
其他摘要	"The main conclusions of this dissertation have been drawn as followings： The suspension of Ti3SiC2 has been investigated by hydrolysis and electroacoustic experiments. When the pH value of Ti3SiC2 suspension was in the range from 4 to 11, the stability of the suspension was poor. PEI is an effective dispersing agent for the suspension. In the range of pH from 4 to 8, the stability of suspension has been improved remarkably by adding 1 dwb% or 1.5 dwb% PEI. Reticulated porous Ti3SiC2 ceramic was successfully fabricated via polymeric foam replication. Because of high specific surface area, the as-fabricated porous Ti3SiC2 decomposed much easily than the dense Ti3SiC2. The decomposition temperature of the as-fabricated porous Ti3SiC2 ceramic was even as low as 1100ºC. Due to the excellent high-temperature and mechanical properties, yttrium silicate (Y2SiO5) is a promising candidate for high-temperature structural materials. Y2SiO5 was synthesized by solid reaction method without any sintering additive at 1550ºC. The suspension of Y2SiO5 was not stable. However, when the amount of 1.5 dwb.% PEI was added, the suspension of Y2SiO5 became stable. Reticulated porous Y2SiO5 ceramic could been fabricated with the porosity of 73%, when the solid loading was 35 vol.%. Using tert-butyl alcohol (TBA)-based freeze casting, porous alumina ceramic with long, straight pores and high porosity has been fabricated. The morphology of the pore was replica of the structure of TBA. In the direction vertical to the freezing, the pore size was about 100 μm and the shape of the pore was polygon. And along the freezing direction, the pores presented a form of long straight prisms without any branch. The length of the pores was in the order of millimeters. The size distribution of the pores was very uniform. This pore feature was quite different from the lamellar porous structure or dendritic channels obtained by using water or camphene as solvent, respectively. The non-dendritic structure may be more suitable for thermal insulation due to less heat exchange. The porosity of porous alumina ceramic prepared using TBA-based freeze casting was closely related to the initial solid loading. When the solid loading decreased from 20 vol.% to 10 vol.%, the porosity increased linearly from 65% to 82%. However, as the porosity increased, the compressive strength declined from 37.0 MPa to 2.6 MPa. When the porosity was 65%, the porous alumina ceramic became stretch-dominated structure. When the porosity was 82%, the porous alumina ceramic had bending-dominated structure. In addition, when the solid loading was 10 vol.%, the bulk density of the as-fabricated porous alumina ceramic with the porosity of 82% was only 0.68 g×cm-3. A novel porous ceramic, Y2SiO5, was fabricated by freeze casting using TBA as solvent at 1300ºC. When the solid loading decreased from 20 vol.% to 10 vol.%, the pore size increased linearly, and the ceramic wall thickness declined. The pores were still long and straight, the pore size was uniform. As the solid loading decreased, the porosity increased, while the compressive strength declined obviously. Along the freezing direction, the thermal conductivity of the porous Y2SiO5 ceramic was determined. When the solid loading was 15vol.%, the thermal conductivity was only 0.05 W/mK, while the compressive strength was about 20 MPa. "
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64452
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	李端阳. Ti3SiC2、Al2O3和Y2SiO5多孔陶瓷的制备和性能表征[D]. 北京. 中国科学院金属研究所,2012.