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超微粉(粒度在100钠米以下)的使用在微晶陶瓷及功能材料中日益受到得视。由于超微粉很细小,选区电子衍射实验难以对其作物相鉴定。在一定条件下,如分散得当,利用高分辩电子显微镜直接显示超微粉的原子排列规律可成为其结构及物相鉴定的有力手段。本文所用超微粉是由金属所以公斤级生产的,其平均尺寸在20nm左右。图1为激光法制备的Si—B—C合超微粉的高分辩像。高分辩像观察表明此种复合粉主要为SiC超微粉,其次为SiB_6微粉。SiB_6的晶体结构尚有争议,有人认为是立方晶系,CaB_6型,有人认为是正交晶系。近来的研究趋于后者,确定SiB_6属正交晶系,空间群为Pnnm,点阵常数为a=14.397埃,b=18.138埃,c=9.911
The use of ultrafine powder (particle size below 100 nanometers) is gaining popularity in microcrystalline ceramics and functional materials. As the ultrafine powder is very small, the selection of electron diffraction experiments difficult to identify the crop phase. Under certain conditions, such as decentralized, the use of high resolution electron microscopy direct atomic arrangement of ultrafine powder can become a powerful means of identification of its structure and phase. Superfine powder used in this article is produced by the kilogram of metal, the average size of about 20nm. Figure 1 shows the high-resolution image of ultra-fine Si-B-C powders prepared by laser method. High-resolution observations show that the composite powder is mainly SiC ultrafine powder, followed by SiB_6 micronized powder. SiB_6 crystal structure is still controversial, some people think that is cubic crystal, CaB_6 type, some people think that is orthogonal crystal system. Recent research tends to the latter, to determine the orthorhombic SiB_6 crystal space group Pnnm, lattice constant a = 14.397 angstroms, b = 18.138 angstroms, c = 9.911