Fabrication and Property Control of Ceramic Composites for High Temperature Filtration

采用凝胶注模成型法制备了堇青石/莫来石（C/M）多孔复合材料和堇青石陶瓷。为了控制C/M复合材料中孔的形貌，增加孔隙率，在一定量的复合粉末、有机单体和分散剂的浆料中加入直径为10μm的球形玉米淀粉颗粒。将浆料在模具中原位固化（单体聚合）后，将绿色坯体加热至700℃（粘结剂析出），在空气中于1350℃烧结10 h，制得孔隙率为54%的多孔C/M复合材料。虽然随着烧结温度的升高，烧结复合材料的孔隙率显著降低，但初始复合材料颗粒之间形成的一次孔的平均尺寸（0.4 ~ 0.6 μm）变化很小。对于玉米淀粉颗粒的次生孔，直径约为10 μ m的球形孔 关于我们 在1350℃下制备的C/M复合材料中，观察到与加入淀粉粉末的初始形状和尺寸相对应的粒径为2.5 μ m。在高温烧结时，二次气孔变形为不规则形状和较小的气孔。采用氮气鼓泡法制备了高孔率的堇青石陶瓷。在聚合固化之前，向浆料中通入恒定流量的N_2气体。该过程产生具有75 - 83%孔隙率的极多孔氧化铝陶瓷。这些样品的抗弯强度在3 - 10 MPa之间，高于使用有机成孔剂制备的堇青石陶瓷。这种强度的提高可能是由于N_2气鼓泡形成的球形孔相互连通的特征孔结构所致。研究了以球形中空玻璃、聚乙烯醇和各种淀粉为造孔剂的多孔陶瓷的孔结构与力学性能和热性能的关系。少

Porous cordierite/mullite (C/M) composite and cordierite ceramics were fabricated using gel-casting as forming method. In order to control the morphology of pores and increase the porosity in the C/M composite bodies, spherical corn starch particles with 10μm in diameter was added to a slurry containing fixed amounts of the composite powder, organic monomer and dispersant. After in-situ solidification of the slurry (polymerization of the monomer added) in a mold, a green body was heated up to 700℃ (binder born-out) and successively sintered at 1350℃ for 10 h in air, which produced a Porous C/M composite having 54 % porosity. Although the porosity of the sintered composites was considerably decreased with an increasing sintering temperature, only a subtle change was detected in the average size of the primary pores (0.4 - 0.6 μm) formed between starting composite particles. Concerning the secondary pores derived from corn starch particles, spherical pores with the diameter of about 10 μ … More m corresponding to the original shape and size of the starch powder added were observed in C/M composites obtained at 1350℃. At elevated sintering temperatures, the secondary pores were deformed into irregularly shaped and smaller ones. Therefore, an optimum sintering temperature to control the resulting pore structure was found to be 1350℃ for the present composite powders.N_2 gas bubbling procedure was employed to produce highly porous cordierite ceramics from a commercial powder. Prior to the solidification due to polymerization, a constant flow of N_2 gas was introduced into a slurry. This procedure yielded extremely porous alumina ceramics with 75 - 83 % porosity. Bending strength of these samples ranged between 3 - 10 MPa, which were higher than those of cordierite ceramics fabricated using organic pore-forming agents. The enhanced strength might be due to the characteristic pore structure in which largely spherical pores derived from N_2 gas bubbling were interconnected.Porous alumina ceramics were also fabricated using some forming procedure other than gel-casting. Relationships between pore structures and mechanical or thermal properties were examined for samples that particles of spherical hollow glass, PVA or various kinds of starches were added as pore-forming agent. Less