用XPS研究了金属Ni在不同温度下在空气和水中的氧化行为及生成的表面氧化物的热稳定性。结果表明氧化物除NiO以外还存在Ni_2O_3。在室温下长期暴露空气后Ni表面生成Ni_2O_3更明显。金属Ni在纯水中氧化比空气中慢得多。研究结果还表明:Ni表面氧化物的热稳定性与其生成时的温度密切有关。金属Ni在室温暴露空气生成的NiO在10~(-6)Pa真空中在300℃加热10min即可使其还原成金属Ni。该还原作用是NiO与表面碳氢化合物污染物之间的反应。然而,在200℃以上在空气中加热生成的NiO在相同条件下作真空热处理时不能使其还原成金属。最后本文对不同温度下生成的NiO有不同的热稳定性的原因进行了讨论。
Surface oxidation of polycrystalline nickel foil in air and purewater at different temperatures and the thermal stability of the surface oxides havebeen investigated by means of XPS. In addition to NiO, Ni_2O_3 is formed especiallyafter long periods of air exposure. Nickel surfaces are much less reactive to purewater than to air. The thermal stability of the surface oxides is related to oxidativetemperature. The surface species of oxides formed by air exposure at temperaturesbelow 120℃ can be reduced into nickel metal after heating the sample in vacuumat 300℃ for only 10 minutes (in the case of room temperature) to 1 hour (in thecase of 120℃). This reduction is caused by reaction with surface carbon contami-nants. However, the surface species of nickel oxides formed by air exposure withheating at temperatures above 200℃ can not be reduced into metal after heatingthe sample in vacuum at 300℃ for 1 hour.
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