SiC泡沫陶瓷的凝胶注模制备与表征

Preparation and Characterization of SiC Foam Ceramic by Gelcasting

以高分子多糖明胶为胶凝剂，采用凝胶注模工艺制备SiC泡沫陶瓷。测量了分散剂加入前后浆料的f电位的变化。研究了分散剂四甲基氢氧化铵（TMAH）、明胶加入量、固含量等对SiC浆料流变性能的影响。结果表明：分散剂的加入对SiC颗粒的动力学行为有显著影响。在碱性范围内，ζ电位绝对值随TMAH加入量的增加而增大；明胶的加入明显提高了浆料的粘度；固含量为65％～74％时，为使浆料具有好的稳定性和流动性，同时保证明胶的成胶性能，TMAH和明胶的加入量应分别控制在2．5％左右及5％～7％为宜。制备的泡沫陶瓷由相互贯通的球形孔室构成，孔隙率最高可达到92％，其孔径分布取决于泡沫体孔隙率，对于孔隙率为76％和90％的样品，其孔径分别达到120μm和200μm。泡沫陶瓷的抗弯强度随相对密度增大而提高，相对密度达到25％时，其抗弯强度可达到25．2MPa。

SiC ceramic foams were fabricated by gelcasting, using gelatine as gelling agent and TMAH as dispersant. The effects of gelatine and TMAH addition and solid load on the slurries dispersity were investigated. The results show that the addition of TMAH pronouncedly raised the absolute zeta potential value（ζ）, and it increases with TMAH increasing at basic pH, and meanwhile, the viscosity of SiC suspensions was elevated apparently with gelatine adding. For slurries with solid load ranging from 65% 74%, the addition of about 2.5% TMAH and 5% - 7% gelatine is appropriate in order to obtain good gelling performance of gelatine and good stability, flowability of the suspensions. The resulting ceramic foams consisted of a highly interconnected network of spherical cells and the distribution of cell size was dependent on the porosity of the specimen produced. The flexural strength of the prepared foam ceramics increased with the relative bulk density of the sinters, which was up to 25.2 MPa with a density of 25% resulted form highly densified struts.