新金刚石的实验制备及其晶体结构的第一性原理研究

发布时间：2018-04-09 22:31

  本文选题：新金刚石　切入点：高温　出处：《燕山大学》2015年硕士论文

【摘要】：作为一种新型的碳同素异形体,由于其巨大的科研价值和潜在的应用价值,新金刚石引起了研究者的广泛关注。目前已提出了多种制备新金刚石的方法,但这些方法制备出的新金刚石产量和纯度都不高,严重制约了对新金刚石的进一步研究。此外,也有多种理论模型解释新金刚石的晶体结构,但大部分理论模型在动力学上并不稳定,而动力学稳定理论模型的电子衍射图谱与实验的新金刚石电子衍射图谱并不匹配。因此,新金刚石的晶体结构至今是一个未解之谜。针对上述存在的问题,本文对新金刚石晶体结构进行了实验和理论两方面的研究。实验方面是以炭黑催化法进行的,即以炭黑为碳源,纳米铁为催化剂,在氩气高温条件下制备新金刚石。此外,对实验产物还进行了提纯;理论方面是以新金刚石是一种三维金属碳这一实验结果为出发点,利用第一性原理预测其晶体结构。以炭黑为碳源、纳米铁为催化剂,配制碳铁摩尔比为4:1的混合粉末。在管式高温炉内,对混合粉末进行加热,并在1100℃温度下保温一小时。冷却后,混合粉末的XRD结果表明:本实验条件下获得了含有新金刚石的粉体材料。提纯过程中发现酸洗会使新金刚石分解,本文采用了磁铁吸附法去除了新金刚石粉体中的催化剂纳米铁。结合上述实验制备和提纯方法,可以大量制备高纯度的新金刚石粉体,这将为新金刚石后续的研究工作提供强有利的帮助。通过第一性原理计算,提出了两种三维金属碳的结构模型,它们分别是聚合富勒烯模型(sc-C96)和扭曲sp3杂化碳模型(Tri-C9)。计算结果表明:这两个模型均是动力学稳定的亚稳相,而且都具有金属性。sc-C96是一种三维拓扑nodal line半金属碳,它可以通过C96富勒烯分子聚合的方式得到。但可惜的是,模拟的XRD衍射结果表明sc-C96结构并不是新金刚石晶体结构。而Tri-C9是一种sp3杂化的金属碳,其密度与金刚石接近,维氏硬度为35 GPa。在压力70 GPa条件下压缩石墨,可能会获得Tri-C9。模拟的XRD结果表明Tri-C9将对确定实验合成的新金刚石晶体结构非常有帮助。
[Abstract]:As a new type of carbon isomorphism, new diamond has attracted wide attention due to its great scientific research value and potential application value.At present, a variety of new diamond preparation methods have been proposed, but the production and purity of new diamond produced by these methods are not high, which seriously restricts the further research of new diamond.In addition, there are many theoretical models to explain the crystal structure of new diamond, but most of the theoretical models are not stable in kinetics, and the electron diffraction patterns of the kinetic stability theory model do not match the experimental new diamond electron diffraction patterns.Therefore, the crystal structure of new diamond is still a mystery.In view of the above problems, the crystal structure of new diamond has been studied experimentally and theoretically.The experiment was carried out by carbon black catalytic method, that is, using carbon black as carbon source and nanometer iron as catalyst, new diamond was prepared in argon atmosphere at high temperature.In addition, the experimental product was purified, and the crystal structure of the new diamond was predicted by first principles based on the experimental results that the new diamond is a three-dimensional metal carbon.Using carbon black as carbon source and nanometer iron as catalyst, the mixed powder with C / Fe molar ratio of 4:1 was prepared.In the tube furnace, the mixed powder is heated and kept at 1100 鈩，

本文编号：1728474