Effect of Nano-CaCo_3 on Properties and Microstructure of Corundum Based Castables

The chrome-containing corundum castables specimens with different nano-CaCO3 additions （0-1.6 wt%） were prepared using tabular corundum,alumina powder,chrome oxide micropowder （average particle size 〈 5 μm）,calcium aluminate cement （Secar71）,commercial nano-CaCO3 （average particle size 〈100 nm） as main starting materials and FS10 as water reducer. The specimens heat treated at 1 000 ℃ and 1 600 ℃ were characterized in terms of apparent porosity,bulk density,cold and hot strengths,and microstructure. The results show that,when the nano-CaCO3 addition is no more than 1.0 wt%,the apparent porosity of the castables increases with nano-CaCO3 addition increasing,both the cold and hot strengths are enhanced; however,when the nano-CaCO3 addition excesses 1.0 wt%,both the cold and hot strengths go down remarkably with nano-CaCO3 addition increasing; the thermal shock resistance is gradually improved with nano-CaCO3 addition increasing in chosen range.

加入纳米碳酸钙对铬刚玉浇注料力学性能的影响

以板状刚玉、氧化铝微粉、氧化铬微粉(平均粒径<5μm)、铝酸钙水泥(Secar 71)、商品纳米碳酸钙(平均粒径<100 nm)为主要原料,FS10为减水剂,制备了不同纳米碳酸钙加入量(0、0.2%、0.4%、0.6%、0.8%、1%)的铬刚玉浇注料试样,测定了其经1 000及1 600℃热处理后的显气孔率、体积密度和强度,并用扫描电子显微镜(SEM)观察了材料的微观结构。结果表明,在减水剂加入量一定时,随纳米碳酸钙加入量的增大,浇注料的流动性显著下降,显气孔率逐渐升高,冷态和热态强度逐渐降低;在浇注料流动值基本一致的情况下,随纳米碳酸钙加入量的增大,浇注料的显气孔率明显增大,但其冷态和热态强度皆逐渐提高,这主要是由于纳米碳酸钙在高温下分解产生的CaO和结构中的A l2O3原位反应形成铝酸钙物相的缘故。