添加TiO_2对铁铝尖晶石合成和烧结的影响

Effect of TiO_2 on synthesis and sintering of hercynite

以氧化铁粉、α-Al2O3粉、石墨为主要原料,分别外加质量分数为0、2%、5%和8%的钛白粉,以亚硫酸纸浆废液为结合剂混练均匀后,压制成型为50 mm×50 mm的试样,于100℃干燥24 h,在氮气气氛中分别于1400、1450、1500和1550℃保温4 h煅烧,然后检测烧后试样的体积密度,并分析其物相组成和显微结构。结果表明:在氮气气氛下,TiO2的引入能降低铁铝尖晶石的合成温度,1450℃煅烧后铁源几乎完全转化为铁铝尖晶石;TiO2的引入能明显促进铁铝尖晶石的烧结,引入2%质量分数的钛白粉的试样体积密度最高,物相组成最好;引入多于2%质量分数的钛白粉的试样中有一定量的Fe2TiO5-Al2TiO5固溶相生成,试样体积密度下降,而且随着温度升高,Ti4+更容易被还原而抑制Fe3+还原,从而阻碍铁铝尖晶石的合成。

The specimens with the size of 50 mm×50 mm were prepared using Fe2O3,α-Al2O3,and graphite powders as main starting materials,lignosulfite as binder,extra-adding TiO2 powder（0,2%,5%,and 8%）,mixing well,pressing,drying at 100 ℃ for 24 h,and firing at 1 400,1 450,1 500,and 1 550 ℃ for 4 h in N2 atmosphere,respectively.The bulk density was determined,and the phase composition and the microstructure were analyzed.The result shows that：（1）in N2 atmosphere TiO2 can apparently decrease the synthesis temperature of hercynite,and nearly all iron oxides can transform into hercynite at 1 450 ℃;（2）TiO2 can apparently accelerate the sintering of the specimens;the specimen with 2% TiO2 has the highest bulk density and the optimum phase composition;（3）for the specimen with over 2% TiO2,some Fe2TiO5-Al2TiO5 solid solution forms,the bulk density decreases,and with the temperature rising,Ti4＋ is easier reduced which limits the reduction of Fe3＋,so the synthesis of hercynite is inhibited.