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研究了1—76毫米汞柱氧压和350—500℃温度范围内钼的氧化过程。结果表明,钼的氧化是首先在表面生成MoO_2,MoO_2生长到某种厚度以后才出现MoO_3,这种厚度与温度和氧压有关。 MoO_2的生长服从抛物线规律。MoO_3的出现虽使钼的氧化速率略为增大,但并不意味着MoO_2停止了生长。在MoO_3与MoO_2同时生长的情况下,钼的氧化仍然遵从抛物线规律。 氧化后表面的MoO_3晶粒随氧化时间的延长而变大,长大到一定程度的晶粒往往容易从表面脱落,困而是氧化层出现疏松的象征。这种疏松可能使钼的氧化偏离抛物线开始向直线规律过渡。 在450℃1—76毫米汞柱氧压范围内,钼的氧化速率与氧压的2/3次方成正比,即K∝P_(O_2)~(2/3)。因此有理由认为,在上述条件下表面吸附层中的氧分子浓度对钼的氧化速率起着控制作用。

An investigation on the oxidation of molybdenum at 350-500℃ was carried outwithin the range of 1-76 mm Hg oxygen pressure. It is shown that MoO_2 was formedfrom the very beginning directly on the molybdenum surface at all temperatures. MoO_3came to appearance later when the first-formed MoO_2 layer had attained a certain thick-ness which seems to vary with temperature and oxygen pressure. The growth of MoO_2 on molybdenum was found to obey a parabolic rate law. Itwas continued at a later stage along with the growth of MoO_3 which was confined tothe outer layer of the surface oxide. The presence of MoO_3 increased the over-all rateof oxidation somewhat, but the growth law, being parabolic, was apparently unaltered. The grain-size of MoO_3 as observed at the outer surface increased with the increasedtime of oxidation. Coarse grains of MoO_3 were prone to detachment from the oxidizedsurface, thus suggesting a kind of loosening grain-structure which may have connectionswith the departure from the parabolic towards a linear rate law of oxidation at 450℃. The rate of oxidation of molybdenum at 450℃ was found to vary with the oxygenpressure in such a way that K_P∝Po_2~(2/3). In view of this, it is suggested that theconcentration of oxygen molecules in the adsorbed surface layer may play a controllingrole upon the oxidation of molybdenum.