【作者】 周林；

【导师】 贾晓鹏；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2008， 博士

【摘要】 本文以溶剂理论为指导,在5.0-5.7GPa,1300-1650℃的条件下,用镍锰钴、纯铁和铁镍作触媒,硫(硫化亚铁)作添加剂,在四种不同掺硫粉末体系中合成工业金刚石,考察了添加剂S(FeS)对金刚石生长特性的影响,包括合成条件、成核、合成工艺、生长速度、形貌等方面。研究发现,硫(硫化亚铁)的添加,使金刚石的合成条件(温度、压力)升高,并在一定程度上抑制了金刚石的成核与生长。利用这个特性,成功地降低了纯铁触媒中金刚石的生长速度,增加了晶体生长的可控性,提高了晶体品质。对铁基粉末体系来说,利用添加剂硫的抑制成核作用,采用一次升压工艺,即可实现对成核的有效控制,合成优质金刚石。节省了二次升压工艺中台阶压力处对石墨的处理时间(3-5min),缩短了合成周期,提高了生产效率。在FeNi+C+S系中,成功地合成出高品级的金黄色八面体工业金刚石,粒度均一,透明度高,优晶率可达90%以上,该产品具有很好的应用前景。本文也对金刚石的生长机制进行了初步的探讨,发现添加剂电负性大小和金刚石合成条件变化之间有一定的对应关系。利用“表面悬键”模型,合理地解释了金刚石{100}面粗糙和出现凹坑的实验现象。更多还原

【Abstract】 Diamond is a representative production of superhard materials. It is a limiting functional material with many exceptional physical and chemical properties. Now, it has been applied in many fields such as industry, scientific research, national defense, medical treatment etc. Diamond plays an important part in the development of industry. China is not rich in natural diamond, so that independently holding high-level diamond synthesis technique is of realistic strategic significance.Recently, in the field of diamond synthesis, powder catalyst technique has gradually replaced the traditional slice catalyst depending on its advantages of high unit yield, low raw material consumption and good synthesis quality. Especially, with the extensive application and popularization of the large-scale cubic high pressure apparatus and indirect heating technique, the level of Chinese diamond synthesis using powder catalyst has made a great step forward in, and china is gradually stepping in the ranks of strong country on diamond synthesis.Natural diamonds are usually hosted by kimberlites and lamproites, which contain sulfur. Sulphides are the most common syngenetic inclusions in natural diamonds. Study on the influence of sulfur on diamond growth will contribute to understanding the formation of natural diamonds. This research will also be helpful to explore new type catalyst, and synthesize special type diamond.In this paper, the uniformly mixed technique for catalyst-graphite powder system was improved. For several important assembling departments(heating cube, insulating cube, etc.), the selection of raw materials and the preparation were studied and improved. And then the stable growth of industrial diamond single crystal was realized. Regard solvent theory as guidelines, the diamond synthesis craft was further improved.We have respectively investigated the growth characteristics of industrial diamonds in four kinds of sulfur-added powder system (NiMnCo-C-FeS, NiMnCo-C-S, Fe-C-S, FeNi-C-S). The influences of additive sulfur on the synthesis have been studied. It was found that the introduction of additive sulfur have made the diamond forming condition rise, and inhibited the spontaneous nucleation with a certain degree. Additive sulfur has obviously influenced the growth of diamond from several aspects such as surface morphology, growth rate and inclusions. Optical microscope, SEM, XRD and XPS were used for detection and characterization.In our research, high-quality golden octahedral industrial diamonds have been successfully synthesized. The granularity of the crystals are uniform, transparency is high, and the excellent crystal ratio can be more than 90%. This product has very good application prospect, and has been approved in the trade. Utilize the inhibitory nucleation character of additive sulfur, we have further improved the diamond synthesis craft, made the synthesis cycle shorten, improved the production efficiency.In the end of this paper, the experimental phenomenon and the growth mechanism of industrial diamond was discussed in light of the solvent theory. It was found that there was certain correlation between diamond synthesis conditions and the electronegativity value of additive. This has some important guiding significance for the selection of additive for diamond synthesis. We also investigated the effect of diamond surface dangling bond on the morphology of diamond, and crystal growth rate on inclusion distribution. Using these mechanism, the correlative experimental phenomenon was explained rationally.更多还原