Abstract: To improve the utilization rate and application value of magnesite tailings,magnesia composites were prepared using light burnt powder of magnesite tailings as the raw material,silicon powder and 95-graphite as additives and phenolic resin as the binder by the solid-state reaction pressureless sintering method.The effects of the Si powder and graphite powder additions on the cold modulus of rupture,density,linear change rate,thermal shock resistance,microstructure and phase composition of the composites were studied in the carbon embedded atmosphere.The results show that with the increasing additions of silicon powder and graphite powder,the contents of forsterite (M₂S) and SiC in the materials increase,finally forming an M₂S-SiC-C multiphase material with M₂S as the main crystal phase.The CO and SiO gases produced during reaction are not conducive to material sintering,leading to the decrease of the cold modulus of rupture,bulk density and linear shrinkage,and the increase of the porosity.After thermal shock,the strength retention ratio of the materials increases significantly compared with that of the sample without additives,because both the increased M₂S content and the generation of SiC whiskers in the materials are beneficial to improving the thermal shock resistance.

Key words: magnesite tailings, magnesia composites, silicon carbide, thermal shock resistance

摘要： 为提高菱镁矿尾矿的利用率和使用价值,以菱镁矿尾矿轻烧粉为原料,单质硅粉和95-石墨为添加剂,酚醛树脂为结合剂,利用固相反应无压烧结法制备镁质复合材料。研究了在埋碳气氛下,硅粉和石墨加入量对镁质复合材料常温抗折强度、致密度、线变化率、抗热震性能、显微结构以及物相组成的影响。结果表明:随着Si粉和石墨粉添加量的增加,材料中的镁橄榄石(M₂S)和SiC含量增加,最终形成了以M₂S为主晶相的M₂S-SiC-C的复相材料;反应过程中产生的CO和SiO气体,不利于材料的烧结,造成材料的常温抗折强度和体积密度下降,气孔率上升,线收缩率减小;材料热震后的强度保持率均比未添加添加剂的试样明显的增加,因为材料中M₂S的增加和SiC晶须的生成均对材料的抗热震性提高有利。

关键词: 菱镁矿尾矿, 镁质复合材料, 碳化硅, 抗热震性