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半个世纪以来,从NaCl的蒸汽生长其单晶体的企图并没有得到正面的结果,解理面上的取向性结晶也尚未有超过数个分子层者。对于从溶液结晶出来时NaCl晶面发展的顺序,或者相对的重要性的研究已有肯定的结果。关于晶核或生长驼峰发端的位置从几率上看应在晶面何处的时尚理论未能从NaCl自溶液中结晶出来的实验加以证实或否定。为探索从蒸汽相生长NaCl单晶体的规律,本实验初步获得较大尺度的单晶体,并同时使取向性晶面上结晶达到1毫米以上的厚度。升华蒸汽来源于高纯度的从熔融体结晶出来的单晶体,并使母晶和结晶基面保持在近于NaCBy sublimation of NaCl crystals of high purity in vacuum at a temperature near its melting point single NaCl crystals of macroscopic size were grown at zones of somewhat lower temperatures. Oriented overgrowths up to 1 mm thick were obtained over the whole cleavage faces of the crystals, but the deposition was muchmore effective on the faees normal to the temperature gradient.The influence of zonal temperature differences and the geometric form of the substrate upon the size and orientation of the crystals have been investigated. The relative importance of faces observed was found of the following sequence: 100> 111>120>122>110. of these the form 122 has not been reported for NaCl crystals growing from the solution. But there is ample evidence from the present experiment that the dominance of 111 over 120 may not be as certain as obsreved for the crystals prepared from solution.In accord with the theory generally held, initial deposition was found to take place statistically more often at the corners of cube faces than elsewhere. New patterns of interpenetration growth and surface structures have been observed and there are features indicating layer growth and screw dislocation.Preliminary experiment was also made on evaporation of a cylindrical NaCl crystal resulting in the exposition of the faces (100) and (120).
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