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摘要: 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。Abstract: 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.
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Key words:
- magnesite /
- CoO /
- magnesia /
- sintering /
- lattice distortion /
- activation energy
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图 1 线收缩率与CoO质量分数的关系
Figure 1. Relationship between the shrinkage and CoO content by mass of samples
图 2 试样体积密度和显气孔率与CoO质量分数的关系
Figure 2. Relationship of the bulk density, apparent porosity, and CoO content by mass of samples
图 3 添加不同质量分数CoO对烧结镁砂显微结构的影响：（a）0%；（b）0.25%；（c）0.50%；（d）0.75%；（e）1.00%
Figure 3. Microstructures of magnesite clinker doped with different CoO contents by mass: (a) 0; (b) 0.25%; (c) 0.50%; (d) 0.75%; (e) 1.00%
图 5 添加不同质量分数CoO烧结镁砂X射线衍射图谱
Figure 5. XRD pattern of magnesite clinker doped with different CoO contents by mass
表 1 天然菱镁矿石的化学成分（质量分数）
Table 1. Chemical component of natural magnesite
% MgCO3 CaCO3 Fe2O3 SiO2 H2O 95.010 3.020 0.840 1.030 0.013 
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表 2 添加CoO质量分数与MgO晶粒尺寸的关系
Table 2. Relationship between the CoO content by mass and MgO grain size of magnesite clinker
CoO质量分数/ % MgO晶粒尺寸/ μm 0 3.66 0.25 4.58 0.50 5.19 0.75 5.31 1.00 5.25
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表 3 添加不同质量分数CoO的烧结镁砂中MgO晶格常数
Table 3. Lattice constants of MgO in magnesia clinke doped with different CoO contents by mass
CoO质量分数/ % MgO晶格常数/ nm 0 0.420215 0.25 0.420375 0.50 0.420431 0.75 0.420658 1.00 0.420580
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