The adsorption of metal atoms, Ni, Pd, Pt, Cu, Ag and Au, at low-coordinated edge and corner oxygen sites of MgO (001) surface has been studied theoretically by using density functional method with cluster models embe...The adsorption of metal atoms, Ni, Pd, Pt, Cu, Ag and Au, at low-coordinated edge and corner oxygen sites of MgO (001) surface has been studied theoretically by using density functional method with cluster models embedded in a large array of point charges. For comparison, the interaction of metal atoms with perfect regular oxygen site of MgO (001) surface was also calculated. As regards these metal atoms adsorbed at perfect oxygen sites of MgO (001) surface, Cu, Ag and Au are very weakly bonded to the surface of MgO; Ni, Pd and Pt, on the other hand, exhibit strong interactions with perfect oxygen sites of MgO (001) surface; the large adsorption energy shows that there exist strong bonds formed between these metal atoms with surface oxygen sites. For the metal atoms adsorbed at edge and corner sites, the adsorption energy is much increased, consistent with our previous study of CO and Cl2 adsorption on MgO (001) surface. This illustrates that the low-coordinated sites, especially corner site, are more advantageous positions for those metal atoms adsorbed on MgO (001) surface. The Mulliken population analysis indicates that the electron transferred from MgO to the metal atoms were increased with the decrease of the coordination numbers, which may be one of the reasons for changing catalytic efficiency and selectivity of the metal particles supported by MgO.展开更多
The effects of rare earth metal salts (REMs), cerium(IV) salt and lanthanum (III) salt, on the property of anodized coating of LD10 aluminum alloy are studied by corrosion tests including neutral salt spray test and c...The effects of rare earth metal salts (REMs), cerium(IV) salt and lanthanum (III) salt, on the property of anodized coating of LD10 aluminum alloy are studied by corrosion tests including neutral salt spray test and copper accelerated acetic acid immersion test, polarization curves measurement, energy dispersion analyzer of X-Ray(EDAX) analysis, and in situ ellipsometry. The results show that the addition of either of the two REMs in anodizing solution hardly changes the composition of an anodized coating, while increases the thickness of barrier part and reduces the porosity of porous part, which contributed to the improvement of the corrosion resistance of the anodized coating. The results also demonstrate that the effect of cerium salt was better than that of lanthanum salt.展开更多
A novel light scattering technique for mapping metal surface corrosion is presented and its results on copper exposed to atmosphere are reported. The front end of the instrument is made up of a sensor module comprisin...A novel light scattering technique for mapping metal surface corrosion is presented and its results on copper exposed to atmosphere are reported. The front end of the instrument is made up of a sensor module comprising a thin beam light emitting diode (LED) illuminating a small spot on the metal surface, and a matched pair of photodetectors, one for capturing the reflected light and the other for sampling the scattered light. The analog photocurrent signals are digitized and processed online by a personal computer (PC) to determine the corrosion factor defined in terms of the two current values. By scanning the sample surface using the light beam and by computing the corrosion factor values simultaneously, a three dimensional graph and a two dimensional contour map are generated in the PC using Matlab tools. The values of the corrosion factor measured in different durations of exposure to atmosphere, which obey a bilogarithmic law, testify to the validity of our mathematical model.展开更多
基金This research has been supported by the Foundation of State Key Laboratory of Structural Chemistry the National Natural+3 种基金Science Foundation of China (29973006) and Administration of Science and Technology of Fujian province (2001J018)
文摘The adsorption of metal atoms, Ni, Pd, Pt, Cu, Ag and Au, at low-coordinated edge and corner oxygen sites of MgO (001) surface has been studied theoretically by using density functional method with cluster models embedded in a large array of point charges. For comparison, the interaction of metal atoms with perfect regular oxygen site of MgO (001) surface was also calculated. As regards these metal atoms adsorbed at perfect oxygen sites of MgO (001) surface, Cu, Ag and Au are very weakly bonded to the surface of MgO; Ni, Pd and Pt, on the other hand, exhibit strong interactions with perfect oxygen sites of MgO (001) surface; the large adsorption energy shows that there exist strong bonds formed between these metal atoms with surface oxygen sites. For the metal atoms adsorbed at edge and corner sites, the adsorption energy is much increased, consistent with our previous study of CO and Cl2 adsorption on MgO (001) surface. This illustrates that the low-coordinated sites, especially corner site, are more advantageous positions for those metal atoms adsorbed on MgO (001) surface. The Mulliken population analysis indicates that the electron transferred from MgO to the metal atoms were increased with the decrease of the coordination numbers, which may be one of the reasons for changing catalytic efficiency and selectivity of the metal particles supported by MgO.
文摘The effects of rare earth metal salts (REMs), cerium(IV) salt and lanthanum (III) salt, on the property of anodized coating of LD10 aluminum alloy are studied by corrosion tests including neutral salt spray test and copper accelerated acetic acid immersion test, polarization curves measurement, energy dispersion analyzer of X-Ray(EDAX) analysis, and in situ ellipsometry. The results show that the addition of either of the two REMs in anodizing solution hardly changes the composition of an anodized coating, while increases the thickness of barrier part and reduces the porosity of porous part, which contributed to the improvement of the corrosion resistance of the anodized coating. The results also demonstrate that the effect of cerium salt was better than that of lanthanum salt.
文摘A novel light scattering technique for mapping metal surface corrosion is presented and its results on copper exposed to atmosphere are reported. The front end of the instrument is made up of a sensor module comprising a thin beam light emitting diode (LED) illuminating a small spot on the metal surface, and a matched pair of photodetectors, one for capturing the reflected light and the other for sampling the scattered light. The analog photocurrent signals are digitized and processed online by a personal computer (PC) to determine the corrosion factor defined in terms of the two current values. By scanning the sample surface using the light beam and by computing the corrosion factor values simultaneously, a three dimensional graph and a two dimensional contour map are generated in the PC using Matlab tools. The values of the corrosion factor measured in different durations of exposure to atmosphere, which obey a bilogarithmic law, testify to the validity of our mathematical model.
