二十面体金刚石和其他五重对称金刚石晶体的生长机制

二十面体金刚石和其他五重对称金刚石晶体的生长机制

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Bibliographic Details
Published in:中国有色金属学报：英文版 Vol. 25; no. 5; pp. 1587 - 1598
Main Author: 魏秋平 马莉 叶浚 余志明
Format: Journal Article
Language:English
Published: 2015
Subjects:
二十面体
五重对称
十二面体
缺陷
金刚石
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Bibliography:43-1239/TG
Five-fold symmetric diamond crystals（FSDCs） were synthesized by hot filament chemical vapour deposition（HFCVD） methods. Their surface morphologies and defects were characterised by scanning electron microscopy（SEM）. From the perspective of nucleation-growth, a growth mechanism for icosahedral and other five-fold symmetric diamond crystals was discussed. Computer modelling was also carried out. The results show that the dodecahedrane（C20H20） molecule is proposed as a nucleus for the growth of icosahedral diamond crystals（IDCs）, wherein the 20 {111} surface planes develop orthogonal to the direction of the original 20 C—H bonds by sequential H abstraction and CH3 addition reactions. IDC can be pictured as an assembly of isosceles tetrahedra, with each tetrahedron contributing a {111} plane to the surface of the IDC and the remainder of the tetrahedral surfaces forming twin planes with neighbouring tetrahedra. The small mismatch（1.44°） between the {111} surface dihedral angle of a perfect icosahedron and that of a twinned icosahedron reveals itself via twin planes in the IDC grain. The modelling suggests how the relief of strain induced by this distortion could lead to the formation of defects such as concave pentagonal cavities at vertices and grooves along the grain edges that accord well with those observed experimentally. Similar arguments based on growth from the hexacyclo pentadecane（C15H20） nucleus can also account for the observed formation of star and rod shaped FSDCs, and some of their more obvious morphological defects.
diamond; five-fold symmetry; icosahedron; dodecahedrane; defect
Qiu-ping WEI,Li MA,Jun YE,Zhi-ming YU（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China; 2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China; 3. School of Metallurgy and Environment, Central South University, Changsha 410083, China; 4. School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore）
ISSN:1003-6326