S.Q.Wang1
,
2) and H.Q.Ye1) 1) Laboratory of Atomic Imaging of Solids
,
Institute of Metal Research
,
The Chinese Academy of Sciences
,
Shenyang 110015
,
China 2)Department of Materials Science and Metallurgy
,
University of Cambridge
,
Cambridge CB2 3QZ
,
UK
金属学报(英文版)
Apeculiar crystal defect was observed by experiment of high resolution electron microscopy( HREM) .It wasidentifiedtoformed bytwothreading dislocationsand asegmentof(11 20) domain boundary. An atomicstructure model was proposed for the anomalous defect. Theresultofthe weak beam experimentofelectron microscopeaffirmedthesuggested model.Thestructuralpropertiesofseveral GaN(11 2 0) domain boundaries werestudied by Molec ular Dynamicscalculations. Thetheoreticalresultsshowedthatthelike atom bonding domain boundary, whichcomposesthe main partofthe peculiar defect, has much higher formationenergy than itcounterpartof unlike atom bonding domain boundary. Theoutcome providesanotherevidenceforthesuggested model.
关键词:
HREM
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C. Liu and G.T. Burstein (Department of MateriaIs Science and Metallurgy
,
University of Cambridge
,
Pembroke Street
,
Cambridge CB2 3QZ
,
United Kingdom)
金属学报(英文版)
The passivity of guillotined aluminium electrode is enhanced in alkaline electrolytes by SiO32-. It is proposed that the formation of a complete aluminosilicate gel is responsible for this phenomenon. Dissolution of the metal proceeds via the existing film and the dissolution product reacts with SiO_3~2- ions to form the gel. Under galvanostatic polarisation, significant amount of the gel is formed when the applied anodic i > 10mA cm-2. This gel layer can then be transformed into barrier-type of oxide film, thus contributing to the initial stage of the high voltage anodisation.
关键词:
passivity
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