本文選題：新金剛石　切入點：高溫　出處：《燕山大學》2015年碩士論文

【摘要】：作為一種新型的碳同素異形體,由于其巨大的科研價值和潛在的應用價值,新金剛石引起了研究者的廣泛關注。目前已提出了多種制備新金剛石的方法,但這些方法制備出的新金剛石產(chǎn)量和純度都不高,嚴重制約了對新金剛石的進一步研究。此外,也有多種理論模型解釋新金剛石的晶體結構,但大部分理論模型在動力學上并不穩(wěn)定,而動力學穩(wěn)定理論模型的電子衍射圖譜與實驗的新金剛石電子衍射圖譜并不匹配。因此,新金剛石的晶體結構至今是一個未解之謎。針對上述存在的問題,本文對新金剛石晶體結構進行了實驗和理論兩方面的研究。實驗方面是以炭黑催化法進行的,即以炭黑為碳源,納米鐵為催化劑,在氬氣高溫條件下制備新金剛石。此外,對實驗產(chǎn)物還進行了提純;理論方面是以新金剛石是一種三維金屬碳這一實驗結果為出發(fā)點,利用第一性原理預測其晶體結構。以炭黑為碳源、納米鐵為催化劑,配制碳鐵摩爾比為4:1的混合粉末。在管式高溫爐內(nèi),對混合粉末進行加熱,并在1100℃溫度下保溫一小時。冷卻后,混合粉末的XRD結果表明:本實驗條件下獲得了含有新金剛石的粉體材料。提純過程中發(fā)現(xiàn)酸洗會使新金剛石分解,本文采用了磁鐵吸附法去除了新金剛石粉體中的催化劑納米鐵。結合上述實驗制備和提純方法,可以大量制備高純度的新金剛石粉體,這將為新金剛石后續(xù)的研究工作提供強有利的幫助。通過第一性原理計算,提出了兩種三維金屬碳的結構模型,它們分別是聚合富勒烯模型(sc-C96)和扭曲sp3雜化碳模型(Tri-C9)。計算結果表明:這兩個模型均是動力學穩(wěn)定的亞穩(wěn)相,而且都具有金屬性。sc-C96是一種三維拓撲nodal line半金屬碳,它可以通過C96富勒烯分子聚合的方式得到。但可惜的是,模擬的XRD衍射結果表明sc-C96結構并不是新金剛石晶體結構。而Tri-C9是一種sp3雜化的金屬碳,其密度與金剛石接近,維氏硬度為35 GPa。在壓力70 GPa條件下壓縮石墨,可能會獲得Tri-C9。模擬的XRD結果表明Tri-C9將對確定實驗合成的新金剛石晶體結構非常有幫助。
[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，

本文編號：1728474