CoO对菱镁矿制备镁砂性能的影响

通过添加CoO到天然菱镁矿中，采用二步煅烧法制备了镁砂。利用X射线衍射仪和扫描电子显微镜表征了样品的物相构成和显微组织。结果表明，在1600℃烧结保温3 h，未添加CoO试样烧结前后线变化率为8.8%，制备镁砂的体积密度为3.02 g·cm-3，显气孔率为17.8%，MgO晶粒尺寸为3.66 μm；在相同烧结条件下，添加质量分数为0.75% CoO试样烧结前后线变化率为18.1%，镁砂的体积密度为3.28 g·cm-3，显气孔率为9.4%，MgO晶粒尺寸为5.31 μm。经高温烧结后，添加到菱镁矿中的CoO完全固溶到MgO晶格中，改变了MgO晶格常数，导致MgO发生晶格畸变，降低了MgO生长活化能，促进菱镁矿的烧结。

Effect of CoO addition on the preparation of magnesia by magnesite

The magnesia was prepared by using CoO-doped natural magnesite as raw material through two steps calcining process in this paper. Phase components and microstructures of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The results show that, the bulk density and apparent porosity of magnesia prepared by magnesite without CoO addition sintered at 1600℃ are 3.02 g·cm-3 and 17.8%, respectively, and the particle size of MgO only is 3.66 μm. In the same sintering conditions, the bulk density and apparent porosity of magnesia prepared by magnesite doped with 0.75% CoO by mass are 3.28 g·cm-3 and 9.4%, respectively, and the particle size of MgO reaches to 5.31 μm. After the high temperature sintering, the CoO-doped natural magnesite changes the lattice constants of MgO and makes the MgO lattice distortion, which consequentially reduces the activation energy of grain growth and promotes the sintering of natural magnesite.