【作者】 郑友进；

【导师】 贾晓鹏；

【作者基本信息】 吉林大学 ， 凝聚态物理， 2010， 博士

【摘要】 本文以溶剂理论为指导,首次研究了Fe（Ni）基触媒-石墨体系中添加氟化物（氟化三铁、氟化锂）及硅粉,对合成金刚石的影响以及相关的物理机制。通过对比Fe（Ni）基触媒-石墨体系合成金刚石的实验,发现在4.5-6.0GPa,1300-1600℃的条件下,添加剂对Fe（Ni）基触媒-石墨体系合成金刚石的生长条件、成核、生长速度、形貌等具有较大的影响。首先,利用氟化物作为添加剂合成工业金刚石,可在一定程度上抑制金刚石的成核,降低了金刚石的生长速度。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,提高了晶体品质,同时,增大了金刚石P-T相图中V型区的六-八体晶体生长区间,使优晶产率大幅度提高;并且,合成出表面粗糙、具有{311}的高指数晶面的晶体,这种晶体理论上有利于增加晶体与胎体的把持力。其次,利用硅粉添加剂合成工业金刚石,可以降低金刚石合成条件。如在Fe+C+Si系中,金刚石最低压力温度分别降低了0.3GPa和100℃左右,在相对高温区,可增加金刚石晶体的成核量。再次,利用Fe+C+FeF₃+Si系成功合成出高品级六-八面体金刚石,增大了金刚石P-T相图中V型区的六-八体晶体生长区间,使优晶产率大幅度提高。这一结果为开发价格低廉的纯铁触媒提供了重要的实验数据。更多还原

【Abstract】 Diamond is a functional material with many excellent properties. Now, it has been applied in many fields such as industry, scientific research, national defense, medical treatment etc. It plays an important part in the development of industry.The diamond synthesis technique has been greatly improved due to its extensive application. In the late 1980s, the technique for the high-strength coarse grain diamond crystal synthesized by powder catalyst in a belt apparatus was successfully exploited by Winter Company, Germany, which made a great breakthrough in synthesis of high grade diamond using powder materials. This method had many merits such as increasing the output, decreasing the consumption of raw materials and improving the crystal quality. Therefore, almost all the famous diamond companies in the world employed the method to synthesize high-strength coarse grain diamond and cornered chronically the high grade diamond market since the end of 90’s.In the industrial production of diamond, the cost of catalyst and tungsten carbide anvil occupies very large proportion in the total production cost. So it is of great significance to develop cheap catalyst and reduce the cost of anvil in the synthesis of diamond.Strong indicated that the advantages of using metal alloy as catalyst were that the synthesis temperature and pressure were lower than pure metal. The synthesis pressure could be dropped to 5GPa from 7Gpa. The scientific researchers of our country have done a large amount of work on iron-base catalyst too, and have get some comparatively prominent achievement. Now, almost all the domestic producers are using iron-base catalyst to synthesize industrial diamond. However, compared with NiMnCo, the synthesis pressure and temperature of iron-base catalyst are still higher. This undoubtedly lead to the higher anvil consumption in industrialization and higher production cost. So it is necessary to develop new catalyst material to solve the problem described above. XiaoPeng Jia Professor has proposed to develop cheap pure iron catalyst for industrial diamond synthesis, only that it still has following problems: firstly, needing higher pressure and temperature; secondly, the growth region of {100}is narrow, and the crystal is mostly octahedral; thirdly, there is more inclusions in the crystal. So pure iron is unsuitable to be used for synthsizing high grade diamond. Even so, because of the low price of pure iron powder catalyst, numerous scientific research workers are still devoted to research and develop on this respect.In this paper, using china-made cubic high-pressure apparatus, the growth characteristic of industrial diamond in the five different powder systems （NiMnCo+C+FeF₃, Fe+C+FeF₃, FeNi+C+FeF₃, FeNi+C+LiF, Fe+C+Si+FeF₃） were investigated separately under high pressure and high temperature conditions. And the effect of additive FeF₃, Si on the synthesis was also studied. It is found that the introduction of FeF₃ has inhibited the nucleation of diamond to a certain extent, and reduced the growth rate, and expanded the growth region of cubo-octahedral diamond. On the other hand, the introduction of Si has largely reduced the synthesis conditions for pure iron catalyst. There are also some other obvious effects of additive FeF₃ and Si on synthesis, such as the surface morphology, crystal shape and growth rate of diamonds. In this paper, optical microscope, SEM, XRD, Raman, etc. have been used to carry on relevant test and characteristics.In this paper, the growth region of cubo-octahedral diamond crystal was expanded in Fe+C+FeF₃, FeNi+C+FeF₃ system, and the growth rate of diamond was reduced. So the operability of synthesis in the actual course was enhanced, and the quality of crystal could be improved. The crystal with coarse surface and high index crystal surface {311} was successfully synthesized, which probably has some advantage on preparing diamond tools by enhancing the holding ability of the carcass to diamond, lengthening the service life of diamond tools, etc. And the temperature ranges for the synthesis of this crystal in every system was investigated and confirmed under certain pressure conditions for the first time.It is reasonably explained that the effect of additive FeF₃ on catalyst characteristic and its inhibition function on the nucleation. On one hand, the iron in FeF₃ had entered into metal catalyst, changed the already existing catalyst matching, which should lead to the change of the catalyst characteristics, such as melting point, flow ability, surface tension of metal liquid, and dissolving carbon ability of catalyst, etc. That is to say, the catalyst was poisoned. On the other hand, there was CF_x compound in the metal catalyst, so the carbon in diamond must react with CF_x during diamond nucleation and growth. Only if CF_x was excessive, the nucleation will be destroyed, and diamond will be graphitized, forming other compound of fluorum or carbon. These have inhibited the nucleation of diamond in the synthesis using iron, nickel alloy as catalyst.In the Fe-C-Si system, the introduction of Si has reduced the minimum synthesis pressure and temperature. So the growth range of cubo-octahedral diamond was expanded, and then high-quality cubo-octahedral diamonds were synthesized successfully. This takes an important step to develop the cheap pure iron catalyst.更多还原