碳热还原制备镁铝尖晶石晶须及其形成机理

为制备镁铝尖晶石晶须及探究其生成机理,采用电熔镁砂、活性α-Al_2O_3和石墨为主要原料,在埋碳气氛1 550℃烧制3h合成纤维状镁铝尖晶石晶须,分别使用X射线衍射(XRD)、扫描电子显微镜(SEM)和能量色散光谱(EDS)对产物的物相、形貌和物微区化学成分进行观察分析。结果表明:晶须物相组成为镁铝尖晶石;镁铝尖晶石晶须顶端尖锐,部分晶须有分叉现象,长度可达10mm,直径约为5~20μm;当Al_2O_3与C共存时,镁铝尖晶石晶须生成量较多;镁铝尖晶石晶须的原位生长遵循气-固(VS)机制。

Preparation and Formation Mechanism of Magnesium Aluminate Spinel Whiskers by Carbothermal Reduction Method

Aiming at investigating the preparation and formation mechanism of magnesium aluminate spinel whisker,the present work utilized fused magnesia (≤0.074 mm),α-Al2O3(d50=2.5 μm)and flake graphite (≤0.15 mm)as main raw materials and applied a carbon-embedded heat-treatment process at 1 550 ℃ for 3 h to synthesize fibroid whisker-like MgAl2O4,whose phase composition and microstructure were characterized by X-ray diffraction (XRD),scanning electron microscope (SEM),and energy dispersive X-ray spectroscopy (EDS),respectively.The results confirmed the spinel phase of the resultant whiskers with the length of up to 10 mm and an average diameter ranging from 5 μm to 20 μm.The spinel whiskers exhibit sharp terminals,and some of the whiskers have branches.The mutual presence of alumina and graphite can lead to a relatively large amount of spinel whiskers.It can also be concluded that the vapor-solid (V-S)mechanism dominates the in-situ growth of the magnesium aluminate spinel whiskers.