MgO-C材料在氮气气氛下的物相演化及其力学性能研究

以电熔镁砂、天然鳞片石墨、煤沥青、Al粉及Si粉为主要原料,以热固性酚醛树脂为结合剂,混匀后压制成MgO-C材料试样。将试样在氮气气氛下分别经1000℃×3h、1200℃×3h、1400℃×3h热处理,研究热处理温度对材料物相组成、显微结构及力学性能的影响。结果表明,1000℃热处理后,试样中Al消失,反应生成了柱状AlN和八面体状MgAl2O4,此温度下Si尚未参与反应;1200℃热处理后,Si开始反应生成六边形板状的SiC,镶嵌在镁砂基体中,提高了试样的高温抗折强度和热震后残余抗折强度;1400℃热处理后,试样中除有柱状AlN和八面体状MgAl2O4生成外,还有较多晶须状SiC和针状β-Si3N4生成,形成了良好的非氧化物结合,使得材料具有优良的高温力学性能和抗热震性能。

Phase evolution and mechanical properties of MgO-C material under nitrogen atmosphere

With fused magnesia ,flake graphite and coal tar pitch as main raw materials ,metallic Al and Si powders as additives ,and phenolic resin as binder ,MgO-C refractory specimens were prepared and then heat-treated at 1000 ℃ ,1200 ℃ ,1400 ℃ × 3h respectively under nitrogen atmosphere to study the characteristics of the specimens in phase composition , microstructure and mechanical strength .The results show that after 1000 ℃ heating treatment ,the metallic Al has reacted with C （CO） or N2 ,resulting in the formation of strip-like AlN and octahedral MgAl2 O4 .It is also found that the metallic Si has not taken part in any reaction at this stage .After 1200 ℃ heating treatment , the reaction between Si and C or CO leads to the formation of platelike SiC which is then interlocked into magnesia matrix ,raising the specimen’s modulus of rupture and residual strength after thermal shock test .After 1400 ℃ heating treatment ,besides strip-like AlN and octahedral MgAl2 O4 ,a large amount of SiC whiskers and needlelike β-Si3 N4 are formed within the skeleton structure ,giving the specimen excellent hot modulus of rupture and thermal shock resistance .