化学输运法制备钨单晶涂层的微观组织分析

发布时间：2018-02-16 23:32

本文关键词： 化学输运法钨单晶涂层位错密度异常生长　出处：《北京理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：热离子能量转换器发射极材料需要长时间工作于1500°C以上的高温环境,采用W-WClx-Cl体系的化学输运法能够制备满足热离子能量转换器使用要求的钨单晶涂层。根据目前所掌握的文献资料,尽管国内外学者对于化学输运法制备钨单晶涂层进行了多方面的研究,但对其微观组织研究甚少。本文采用化学输运法在不同基体温度下制备钨单晶涂层,通过对涂层的宏观生长形貌进行研究,分析了其生长机制;通过采用蚀坑技术、常规高分辨X射线衍射技术和同步辐射高能X射线衍射技术对钨单晶涂层的微观生长习性进行深入探讨,定性、定量的分析了晶体中的位错;通过采用扫描电子显微镜和电子背散射衍射技术对钨单晶涂层的表面异常生长形貌进行分析,明确了其产生原因。主要研究成果如下:1.化学输运法制备的钨单晶涂层宏观上为明显的六面体或十二面体形态,且具有交替排列的{110}和{112}表面。其生长习性的差异主要是由钨原子在两表面的迁移能力不同导致的。2.当沉积体系压力为15.77Pa,基体温度处于1300°C~1400°C时,采用化学输运法制备的钨单晶涂层:根据蚀坑技术得到的位错密度在106量级,{110}表面的位错密度均小于{112}表面的位错密度,位错密度均随着基体温度的升高而呈降低的趋势。3.采用化学输运法制备的钨单晶涂层表面可能会出现以下异常生长的形貌:(1)钨单晶涂层表面存在单一生长丘、生长丘群和顶部具有针刺状结构的带状生长丘。不同形貌的生长丘产生的原因是基体表面排列不同、能量有差异的位错。(2)钨单晶涂层生长丘表面存在大小不一、形状各异的不规则突起。其产生的原因在于沉积结束后降温过早,沉积室内残余气相物质在涂层表面重新吸附,成为非均匀形核中心,钨原子于其上异常形核和长大。(3)钨单晶涂层的表面存在簇状结构,该簇状结构的截面及表面存在大量的晶界。其产生的原因可能是由于基体表面处理时残留的杂质或测量基体尺寸时遗留下的划痕所导致的。
[Abstract]:The emitter material of thermionic energy converter needs a high temperature environment above 1500 掳C for a long time. Tungsten single crystal coatings can be prepared by chemical transport of W-WClx-Cl system to meet the requirements of thermionic energy converters. Although many researches have been done on the preparation of tungsten single crystal coating by chemical transport method, the microstructure of tungsten single crystal coating has been studied very little. In this paper, tungsten single crystal coating was prepared by chemical transport method at different substrate temperatures. The growth mechanism of the coating was analyzed by studying the macroscopic growth morphology of the coating. Conventional high-resolution X-ray diffraction technique and synchrotron radiation high-energy X-ray diffraction technique were used to study the microcosmic growth habit of tungsten single crystal coating. The dislocation in the crystal was analyzed qualitatively and quantitatively. The abnormal growth morphology of tungsten single crystal coating was analyzed by scanning electron microscope (SEM) and electron backscattering diffraction (EBSD). The main research results are as follows: 1. The tungsten single crystal coating prepared by chemical transport method has obvious hexahedron or 12 hedron morphology. The difference in growth habits of {110} and {112} surfaces is mainly caused by the different mobility of tungsten atoms on the two surfaces. When the deposition pressure is 15.77 Paand the substrate temperature is 1300 掳C ~ (1400 掳C), Tungsten single crystal coating prepared by chemical transport method: the dislocation density of {110} surface is lower than that of {112} surface, and the dislocation density of {110} surface is less than that of {112} surface. Dislocation density decreased with the increase of substrate temperature. 3. The surface of tungsten single crystal coating prepared by chemical transport method may have the following abnormal growth morphology: 1) there is a single growth mound on the surface of tungsten single crystal coating. The growth mounds with different morphologies are due to the different surface arrangement of the substrate and the dislocations with different energy. 2) the surface size of the monocrystalline tungsten coated monocrystalline monocrystalline monocrystalline coated mounds is not the same as that of the monocrystalline monocrystalline monocrystalline coatings. Irregular protuberances of various shapes. The reason is that the temperature is too early after the deposition, and the residual vapor material in the deposition room readsorbs on the surface of the coating and becomes the center of heterogeneous nucleation. There are cluster structures on the surface of tungsten monocrystalline coating with abnormal nucleation of tungsten atom and growth of tungsten single crystal coating. There are a large number of grain boundaries on the cross section and surface of the cluster structure, which may be due to the residual impurities in the surface treatment of the substrate or the scratches left over when measuring the size of the matrix.
【学位授予单位】：北京理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TB306

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