材料期刊网

研究了钢在200—900℃和76毫米汞柱氧压下的氧化行为。 结果表明,在200—350℃铜的氧化符合立方规律;400—550℃的氧化初期为抛物线,但超过一定时间即明显地向愈来愈慢的氧化速率偏离;600—900℃的氧化则自始至终遵从抛物线规律。根据上述结果,求得铜在600—900℃的氧化激活能为30,700卡/克分子。 铜表面氧化层的外部是由晶粒细小的CuO组成,内部则为Cu_2O,其晶粒较为粗大组织较为疏松。从300—550℃在氧化层表面可以观察到起伏不平的褶鄒,这种褶鄒随氧化时间的增长和温度的升高而加剧。在600和650℃上述褶鄒已不明显,但在氧化层表面却出现一层稠密的CuO胡须。这种胡须大多数不受电子显微镜观察的影响,但也有少数在电子束的作用下立即由挺直状态变成如弯曲枯萎的草木。由此可认为,并非所有的胡须都是结构完整的CuO单晶。 文中结合氧化层的结构、表面形态和宏观缺陷对铜在上述不同温度下的氧化行为进行了讨论。并根据Frank的胡须生长机制对铜氧化层表面可能同时出现结构完整与结构不完整的CuO胡须提出了解释。

An investigation on the oxidation of copper under an oxygen pressure of 76 mm Hgat 200-900℃ has been carried out. It is shown that, the oxidation of copper at 200-350℃ obeys a cubic law; at 400-550℃ the initial growth of the oxide layer is para-bolic, but departure from this law is evident at a later stage and the rate of oxidationbecomes increasingly smaller; in the temperature range of 600-900℃, however, the para-bolic rate law applies for the whole period of oxidation. From the results obtained be-tween 600℃ and 900℃, an activation energy of oxidation of 30,700 cal/mol has beenfound. The surface scale of copper is shown to be consisted of two layers, the outer layeris made of small-grained CuO whereas the inner one is composed of coarse-grained Cu_2Owith a somewhat open texture. From 300℃ to 550℃, the surface scaling exhibits arugged appearance, with the degree of ruggedness increasing with increased time andtemperature of oxidation. At 600℃ and 650℃, the scaling surface has been observedto be covered with rather dense CuO whiskers. Under the examination of electronmicroscope the oxide whiskers generally remain erect and straight, but a few of themappear to fall suddenly into a tangled bush under the action of the electron beam. Itwould appear that not all of the oxide whiskers are as perfect as is generally believed tobe dislocation-free single crystals. The different oxidation behaviors of copper at the different temperatures as observedare discussed in the light of surface morphology and gross defects such as cracks andcavities which may be present in the oxide layer. Moreover, on the assumption of Frank'smechanism of whisker growth, an explanation of the possibility of the presence of imper-fectly structured CuO whiskers is given.