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（SE...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.展开更多
Great achievements were made in the 12th Five-Year Plan period （2011-2015） in such areas as economic growth, living standards, industrial restructuring, innovation- driven growth, new-type urbanization and ecologica...Great achievements were made in the 12th Five-Year Plan period （2011-2015） in such areas as economic growth, living standards, industrial restructuring, innovation- driven growth, new-type urbanization and ecological civilization, trade and investment, and reform. These achievements have paved the way for China to enhance the quality and efficiency of growth in the new normal. China＇s future growth prospects are highly correlated with the 13th Five-Year Plan （2016-2020）. For the 13th Five-Year Plan period, China is committed to maintaining an annual growth rate of no less than 6.5%, which is both necessary for China to build an all-round, well-off society before 2020 and consistent with the characteristics of China＇s current economic development stage. Meanwhile, efforts must be made to give prominence to consumption, investment, and export as drivers of growth while continuing to improve labor and capital input and efficiency which is vital to mid- and long- term economic development.展开更多
基金Projects(51301211,21271188)supported by the National Natural Science Foundation of ChinaProject(2012M521540)supported by the China Postdoctoral Science Foundation+2 种基金Project(2013RS4027)supported by the Postdoctoral Science Foundation of Hunan Province,ChinaProject(20110933K)supported by the Open Foundation of the State Key Laboratory of Powder Metallurgy,ChinaProject supported by the Open-End Fund for Valuable and Precision Instruments of Central South University,China
文摘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.
文摘Great achievements were made in the 12th Five-Year Plan period （2011-2015） in such areas as economic growth, living standards, industrial restructuring, innovation- driven growth, new-type urbanization and ecological civilization, trade and investment, and reform. These achievements have paved the way for China to enhance the quality and efficiency of growth in the new normal. China＇s future growth prospects are highly correlated with the 13th Five-Year Plan （2016-2020）. For the 13th Five-Year Plan period, China is committed to maintaining an annual growth rate of no less than 6.5%, which is both necessary for China to build an all-round, well-off society before 2020 and consistent with the characteristics of China＇s current economic development stage. Meanwhile, efforts must be made to give prominence to consumption, investment, and export as drivers of growth while continuing to improve labor and capital input and efficiency which is vital to mid- and long- term economic development.
