二元凝胶法制备Al2O3多孔陶瓷及其表面强化层

Preparation of Porous Al2O3 Ceramics with Surface Reinforcement Layers by Binary Gel System

采用发泡注凝法制备Al2O3多孔陶瓷,研究了丙烯酰胺与明胶所组成的二元凝胶体系对陶瓷浆料黏度、发泡效果、坯体强度及陶瓷显微结构的影响,并对烧结陶瓷体的显气孔率、强度等进行了表征。结果表明:丙烯酰胺具有辅助分散作用,可降低明胶对浆料黏度的影响并改善浆料发泡效果;采用二元凝胶体系可制备具有均匀孔径分布的可适当机械加工陶瓷坯体;经1 600℃烧结2 h,可获得显气孔率为70%~90%的Al2O3多孔陶瓷,其中显气孔率最高为90.8%的多孔陶瓷其抗压强度高达3.3 MPa。在此基础上,对其进行了表面强化的研究。通过在其表面流延一层高强度多孔薄层,不仅使材料整体抗弯强度从6.4 MPa提高到10.8 MPa,而且可以有效降低高温气流对材料表面的烧蚀程度。

Porous alumina ceramics were fabricated by a foam–gelcasting technology with acrylamide system and gelatin as binary gelling agents.The effects of acrylamide system and gelatin content on the viscosity of the slurries,foaming,green strength and microstructures were investigated.Also,the apparent porosities and mechanical properties of porous alumina ceramics were characterized.The results show that the use of acrylamide can decrease the viscosity of the slurries and increase the foaming volumes.The porous green bodies prepared by the binary gel system have an uniform pore size distribution and a good strength for simple machining.The porous alumina ceramics with high porosities ranging from 70%to 90%are obtained after the green samples are sintered at 1 600℃for 2 h.For the sample with an apparent porosity of 90.8%,its compressive strength is 3.3 MPa.Moreover,the surface reinforcement layers of porous ceramics were obtained by a tape–casting method.The porous layers with a relatively high strength increase the bending strength of the whole porous alumina ceramics from 6.4 to 10.8 MPa,and improve the surface strength and the thermal ablation resistance of the porous materials.