SURFACE-ANALYSIS OF OXIDIZED ALUMINUM .1. HYDRATION OF AL2O3 AND DECOMPOSITION OF AL(OH)3 IN A VACUUM AS STUDIED BY ESCA

被引:180
作者
NYLUND, A [1 ]
OLEFJORD, I [1 ]
机构
[1] CHALMERS UNIV TECHNOL,DEPT ENGN MET,S-41296 GOTHENBURG,SWEDEN
关键词
D O I
10.1002/sia.740210504
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Pure polycrystalline Al (99.998%) was oxidized in dry oxygen and water. The surface products formed were analysed by ESCA. The thicknesses of the amorphous Al2O3 formed during oxidation for 1 h in dry oxygen at 25-degrees-C and 250-degrees-C are 14 and 20 angstrom, respectively. During exposure of the oxidized sample to water a surface layer of amorphous Al2O3 is hydrated and Al(OH)3 is formed by the reaction: Al2O3 + 3H2O reversible 2Al(OH)3. The hydroxide is not stable in a vacuum. During analysis in the ESCA instrument. Al(OH)3 is decomposed to Al2O3 and H2O because the equilibrium pressure of H2O is higher than the partial pressure of water in the vacuum system. It is found that a 7 angstrom thick layer of Al2O3 is formed on the surface of Al(OH)3. The binding energies of the Al3+(2p) and O2-(1s) signals recorded from Al2O3 formed on Al at 22-degrees-C and at 250-degrees-C are 75.8 and 532.7 eV, respectively. The binding energies of these peaks are 0.6 eV lower for a sample preoxidized at 250-degrees-C and then exposed to a humid atmosphere and immediately analysed. It is suggested that the change of the binding energy is due to set up of a space charge during exposure to a humid atmosphere. After exposure for a long time to a humid atmosphere the charging decays and the binding energies approach their normal values.
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页码:283 / 289
页数:7
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