以MoO3为前体, CH4/H2为还原碳化气, 经程序升温还原碳化反应制备了Mo2C样品, 并用TG-DTA、XRD、BET、SEM、XPS进行了表征. 结果表明, MoO3在CH4/H2气氛中的还原碳化历程为MoO3→MoO2→MoOxCy→Mo2C, 适宜的还原碳化温度为675℃. 实验条件下制得的碳化钼晶相为β-Mo2C, 表面呈现出形状规整、大小相对均一的片状颗粒, 平均粒径约3.9μm. 碳化钼表面有两种不同价态的钼原子, 分别归属于Mo--C 物种的Mo2+和Mo--O物种的Moδ+ , 以前者为主; 碳物种由四种不同价态的碳原子组成, 分别归属于C--Mo、C--C、C--H和C--O物种, 以前者为主. 随还原碳化反应温度的升高, 制备的碳化钼颗粒增大, 比表面积下降, C--C物种和C--H物种增加, 表面积炭增多. 由于积炭的覆盖和保护作用, 碳化钼表面的Mo原子主要以Mo2+ 的Mo--C物种存在, 只有少部分被氧钝化.
Molybdenum carbide, prepared by temperature-programmed reaction(TPR), using CH4/H2 gas mixture to carburize molybdenum trioxide, was characterized by TG-DTA, XRD, BET, SEM and XPS techniques. The results indicate that molybdenum carbide can be prepared by the pathway of MoO3→MoO2→MoOxCy→Mo2C in CH4/H2 mixture to carburize molybdenum trioxide by TPR, and the proper carburizing temperature is about 675℃. The phase of molybdenum carbide is β--Mo 2C, the particles with the dimension of about 3.9μm are orderly and uniform. It is found that the XPS spectra of Mo3d included two peaks, one is due to Mo--C identified to Mo 2+ which is the dominant species and the other is due to Mo--O identified to Mo δ+ . The four peaks of C1s spectra are corresponding to C--Mo, C--C, C--H and C--O species respectively, and the C-- Mo is the dominant species. The particle size of Mo2C is aggrandized, the BET area decreased, and free carbon of the surface increased with the increase of carburizing temperature, furthermore the Mo atoms on the surface are mainly in the form of Mo--C identified to Mo 2+ , and only a small part is passivated by oxygen, because of the cover and
protection of free carbon.
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