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摘要: 通过两段氢气还原实验研究球形三氧化钼还原得到MoO2和Mo粉的显微形貌。结果表明：经一段还原后球形三氧化钼（β-MoO3）先变成α-MoO3，再生成立方形的γ-Mo4O11，最后形成α-MoO2；经二段还原得到Mo粉。MoO2形貌受还原温度和还原气氛影响较大，还原温度较低或者在还原气氛中引入水分时，MoO2为松散、细小的不规则形貌；还原温度较高或者还原气氛为大流量的干氢时，MoO2为薄片状，易板结。超细Mo粉的形貌主要受还原温度、水蒸汽分压和氢气分压的影响，还原温度低或者氢气流量较小，应尽量使水蒸汽分压和氢气分压的比值接近平衡常数，可得到大小均匀、分散的超细钼粉。Abstract: The morphology of MoO2 and Mo powders prepared by the two-stage hydrogen reduction experiment of the spherical molybdenum trioxide powders was studied. The results show that, the spherical molybdenum trioxide (β-MoO3) is transformed into α-MoO3 firstly, and then the square γ-Mo4O11 is regenerated to form α-MoO2 in first stage hydrogen reduction; Molybdenum powders are obtained in second stage hydrogen reduction. The morphology of MoO2 is greatly affected by the reduction temperature and reduction atmosphere, the MoO2 powders with fine and loose irregular morphology are obtained at low reduction temperature or by importing the water vapor into the reduction atmosphere; the MoO2 powders with flake and hardened are formed at the higher reduction temperature or in the dry hydrogen with large flow. The morphology of ultrafine Mo powders is mainly affected by the reduction temperature, the water vapor partial pressure, and the hydrogen partial pressure. When the reduction temperature is low or the hydrogen flow rate is small, the ratio of the water vapor partial pressure and the hydrogen partial pressure should be close to the equilibrium constant as far as possible, and the uniform and dispersed ultra-fine molybdenum powders can be obtained.
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图 2 以球形MoO3为原料的不同还原率还原产物X射线衍射图谱
Figure 2. XRD patterns of the reduction products in the different reduction ratio using the spherical MoO3 powders ae the raw materials
图 3 还原率为16%的还原产物显微形貌：（a）γ-Mo4O11；（b）α-Mo4O11
Figure 3. SEM images of the reduction products with the reduction rate of 16%: (a) γ-Mo4O11; (b) α-Mo4O11
图 4 不同还原温度制备的MoO2还原产物扫描电子显微形貌：（a）400 ℃；（b）450 ℃；（c）500 ℃；（d）550 ℃
Figure 4. SEM images of the MoO2 reduction products at the different reduction temperatures: (a) 400 ℃; (b) 450 ℃; (c) 500 ℃; (d) 550 ℃
图 5 不同H2流量条件下制备的MoO2扫描电子显微形貌：（a）0.2 m3·h−1，湿氢；（b）0.2 m3·h−1；（c）1.0 m3·h−1；（d）2.0 m3·h−1
Figure 5. SEM images of MoO2 at the different H2 flow rates: (a) 0.2 m3·h−1, wet hydrogen; (b) 0.2 m3·h−1; (c) 1.0 m3·h−1; (d) 2.0 m3·h−1
图 6 不同还原温度制备的Mo粉显微形貌：（a）700 ℃；（b）750 ℃；（c）850 ℃；（d）950 ℃
Figure 6. SEM images of the molybdenum powders at the different reduction temperatures: (a) 700 ℃; (b) 750 ℃; (c) 850 ℃; (d) 950 ℃
图 7 在850 ℃还原时不同氢气流量得到的Mo粉形貌：（a）0.5 m3·h−1，（湿氢+25 ℃）；（b）0.1 m3·h−1；（c）0.5 m3·h−1（干氢−60 ℃）；（d）2.0 m3·h−1
Figure 7. SEM images of the Mo powders reduced at 850 ℃ with the different H2 flow rates: (a) 0.5 m3·h−1, (wet hydrogen +25 ℃); (b) 0.1 m3·h−1; (c) 0.5 m3·h−1, (dry hydrogen −60 ℃); (d) 2.0 m3·h−1
表 1 原料MoO3粉末化学成分（质量分数）
Table 1. Chemical composition of the raw MoO3 powders
% MoO3 Ca Al Si Fe S K C Cr ≥99.50 0.0015 0.0008 0.008 0.0048 0.0026 0.0029 0.0089 0.0011 
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