湖南金刚石的显微塑性变形特征

湖南金刚石主要产自沅江流域.金刚石表面普遍遭受了强烈的熔蚀, 与位错相关的熔蚀特征主要为熔蚀线和熔蚀孔道.熔蚀线常见的为一组和二组, 有时为三组, 组内相互平行, 组间相互交切.熔蚀孔道则沿主滑移面成排分布, 孔道圆而直, 其形成的原因与主滑移面和另一强滑移面交切形成的应力虚脱区有关.将金刚石沿生长中心磨成薄片, 在阴极发光(CL)、正交偏光和显微放大观察发现, 金刚石的主滑移面方向常表现为平行消光条带, 一组条带相互平行, 二组相互交切, 三组形成六方环, 四组构成应力幻影.消光条带与褐色色带的形成密切相关, 有褐色色带必有消光条带与之对应, 但有消光条带则不一定有褐色色带与之对应.透射电镜(TEM) 资料显示: 金刚石中刃型位错与螺旋位错均有发育, 位错缠结十分明显, 位错密度分布不均, 在位错缠结的带内位错密度明显高于带间.从生长与变形特征的关系来看, 金刚石的塑性变形发生于生长完成之后. 

Characters of Plastic Deformation on Diamonds from Hunan Province, China

The studied diamonds come from the Yuanjiang River in Hunan Province, China. The diamonds were etched strongly, the etched lines and etched dislocation channels can be seen on the surface of diamond. The most commons are two sets lines, up to four sets occasionally. The line parallels each other in the same set, but across between two sets. Rows etched dislocation channels that represent zones of weakness in the crystal structure distribute along main deformed faces. Studies on the chosen polished slab specimens for micro-characters by gem microscope and polarizering microscope, cathodoluminescence (CL) show that the parallel extinctions caused by the main plastic deformation planes are clear under crossed polarizers, with two sets of parallel extinctions intersecting, three sets forming ring, four sets forming a strain phantom. The brown bands are closely related to the parallel extinctions; the brown bands are surely accompanied by the parallel extinctions, but the parallel extinctions do not guarantee to be accompanied by the brown bands. TEM shows both screw and knife dislocation can be seen and dislocation tangle is very clear; the dislocation density is uneven distribution: the density in tangle belt is clearly higher than that in the zone between two belts. The plastic deformation occurred after the growth stage of diamond.