造孔剂对无压熔渗SiC_p/Al复合材料的组织和导热性能的影响

Effect of pore-forming agent on microstructure and thermal conductivity of SiC_p/Al composites prepared by pressureless infiltration

利用无压浸渗法制备高体积分数的SiCp/Al复合材料,采用X射线衍射(XRD)、扫描电镜(SEM)和能谱(EDS)对预制块和复合材料的相组成及微观组织进行分析,研究不同造孔剂对复合材料导热性能的影响。结果表明:在900℃时,以Fe(NO3)3.9H2O为造孔剂制备的复合材料组织均匀,致密度好,无明显气孔缺陷,界面反应产物为Mg2Si、MgAl2O4和Fe;以Ni(NO3)2.6H2O为造孔剂制备的复合材料致密度差,有明显气孔缺陷,界面反应产物为Mg2Si、MgAl2O4和NiO,且热导率和相对密度均低于以Fe(NO3)3.9H2O为造孔剂制备的复合材料的,其原因是Fe2O3和铝液发生铝热反应改善基体和SiC的润湿性,从而提高复合材料的致密度。

The high volume fraction SiCp/Al composites were prepared by pressureless infiltration,and the effects of Fe（NO3）3·9H2O and Ni（NO3）2·6H2O on thermal conductivity of the composites were studied.The microstructures of the SiC porous preforms and the composites sintered at 900 ℃ were characterized by XRD,SEM and EDS.The results show that the microstructures of SiCp/Al-10Si-8Mg composite with Fe（NO3）3·9H2O as pore-forming agent are more homogeneous than those with Ni（NO3）2·6H2O pore-forming agent,and the compactness of the former is higher than that of the latter.The interfacial reactive products are Mg2Si,MgAl2O4 and Fe for the former whereas are Mg2Si,MgAl2O4 and NiO obtained for the latter.Moreover,the thermal conductivity and relative density of the composite with Ni（NO3）2·6H2O as pore-forming agent are lower than those with Fe（NO3）3·9H2O.The reason of these differences may be the thermite reaction in Fe2O3 and Al system occurred,which improves the wetting property,and therefore higher density composite can be achieved.