本文關(guān)鍵詞： 激光液相輻照法 納米金剛石 石墨烯納米帶 生長(zhǎng)機(jī)理 影響因素　出處：《江蘇大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：與宏觀金剛石相比,納米金剛石具有特殊機(jī)械、光電、熱、磁性能,在各領(lǐng)域都有廣泛的應(yīng)用價(jià)值。與傳統(tǒng)制備方法相比,激光液相輻照法綠色無(wú)污染、操作靈活、參數(shù)可控,在新型納米材料的制備方面效果顯著。本文以傳統(tǒng)碳材料(鱗片石墨)為研究對(duì)象,采用高能脈沖激光輻照石墨懸浮液實(shí)驗(yàn)研究,討論了納米金剛石、石墨烯納米帶的形成機(jī)理及其產(chǎn)率的影響因素。論文的主要研究?jī)?nèi)容和結(jié)論如下:(1)高功率密度(109~1011W/cm2)、短脈沖(10ns)的激光輻照循環(huán)流動(dòng)的石墨懸浮液后,石墨轉(zhuǎn)變成不同的納米結(jié)構(gòu):納米金剛石、石墨烯納米帶、球狀無(wú)定型納米碳團(tuán)簇、類(lèi)碳納米管狀物、亂層碳組織團(tuán)簇。在石墨粒度相同而能量不同的情況下,石墨烯結(jié)構(gòu)層數(shù)各不相同,層數(shù)范圍在單層到14層之間。在激光熱應(yīng)力和沖擊波的復(fù)合作用下,少數(shù)層的短而有序的石墨烯片段也會(huì)單獨(dú)從石墨表層剝離開(kāi)來(lái)。隨著能量的增加,石墨烯納米帶的層數(shù)越多,且無(wú)序度也越來(lái)越高。(2)脈沖激光液相輻照法連續(xù)合成了納米金剛石,并對(duì)其晶體學(xué)形態(tài)、微觀組織結(jié)構(gòu)、微應(yīng)力及各類(lèi)缺陷進(jìn)行了分析。實(shí)驗(yàn)發(fā)現(xiàn)粒度相同而激光能量不同的情況下,隨著能量的增加,金剛石產(chǎn)量并沒(méi)有明顯的變化,表面形貌基本呈現(xiàn)球狀或橢圓狀,尺寸在2~10nm,平均尺寸在5nm左右。與宏觀金剛石相比,生成物發(fā)生了細(xì)化,并且晶粒內(nèi)部有殘余應(yīng)力,Raman光譜中的金剛石特征峰發(fā)生了寬化并向低頻段位移。(3)從熱力學(xué)和動(dòng)力學(xué)角度提出了納米金剛石的生長(zhǎng)機(jī)理:在石墨顆粒升溫過(guò)程中,石墨表面形成的等離子體潰滅形成液態(tài)碳液滴,此時(shí)液態(tài)碳液滴在熱力學(xué)條件下進(jìn)入石墨亞穩(wěn)定金剛石穩(wěn)定區(qū)域,碳原子開(kāi)始重組形成金剛石晶核并迅速長(zhǎng)大。結(jié)合碳的溫度-壓力相圖,在等離子體冷卻降溫過(guò)程中,逼近三相共存點(diǎn),由互相纏繞的帶狀石墨烯納米管狀物形成封閉的納米級(jí)空間,金剛石可能在其內(nèi)部形核長(zhǎng)大。石墨的相變過(guò)程遵循固態(tài)-氣態(tài)-液態(tài)-固態(tài)和固態(tài)-氣態(tài)-等離子體態(tài)-液態(tài)-三相共存態(tài)-固態(tài)路徑發(fā)展�？偨Y(jié)了金剛石納米晶尺寸細(xì)小的原因:從金剛石納米晶的生長(zhǎng)限制機(jī)制角度考慮,高的過(guò)冷度及短暫的生長(zhǎng)時(shí)間制約了納米金剛石的長(zhǎng)大。(4)在激光能量相同而粒度不同的情況下,小粒徑(2μm、5μm)石墨更易于相變形成納米金剛石,小粒徑石墨的形成熱大于大粒徑石墨,更不穩(wěn)定,更易發(fā)生金剛石相變。通過(guò)優(yōu)化改進(jìn)實(shí)驗(yàn)裝置,在雙光束脈沖激光的共同作用下,增加了激光與石墨的作用面積,大大提高了納米金剛石的合成效率。此時(shí)石墨的相變過(guò)程遵循固態(tài)-氣態(tài)-等離子體態(tài)-液態(tài)-三相共存態(tài)-固態(tài)及固態(tài)-液態(tài)-固態(tài)兩種路徑生長(zhǎng),另外非晶碳團(tuán)簇內(nèi)部及亂層碳團(tuán)簇邊緣發(fā)現(xiàn)了金剛石相的存在,進(jìn)一步證明了納米金剛石的形成遵循液化機(jī)制。納米尺寸效應(yīng)導(dǎo)致的熔點(diǎn)降低是合成超細(xì)納米金剛石的另一機(jī)制也是納米金剛石表層自發(fā)重組形成類(lèi)似Bucky-diamond的形狀的重要原因。
[Abstract]:Compared with the macro nano diamond, diamond has special mechanical, optical, thermal and magnetic properties, are widely used in various fields. Compared with the traditional preparation method, laser irradiation method, liquid green pollution-free, flexible operation, controllable parameters, significant effect in the preparation of new nano materials based on the traditional. Carbon materials (graphite) as the research object, using the graphite suspension irradiated by laser experiment of high energy pulse, discusses the factors influencing the formation mechanism of nano diamond, and the yield of the graphene nanoribbons. The main research contents and conclusions are as follows: (1) high power density (109~1011W/cm2), short pulse (10ns) graphite suspension flow after laser irradiation, graphite into different nanostructures: nano diamond, graphene nanoribbons, spherical amorphous carbon clusters, carbon nano tube, disordered carbon clusters in the organization. The same energy while the graphite particle size under the condition of different graphene layers vary in scope of layers to 14 layers. Between the monolayer composite action force and impact wave in laser heat, a layer of short fragments will be ordered graphene from graphite surface alone to peel off. With the increase of the energy, the more layers of the graphene nanoribbons, and the degree of disorder is more and more high. (2) pulsed laser irradiation of continuous liquid phase synthesis of nano diamond, and the crystal morphology, microstructure, micro stress and all kinds of defects are analyzed. The experimental results showed that the same size and different laser energy situation, with the the increase of the energy, diamond production and no significant change in surface morphology showed spherical or oval shape, size in 2~10nm, the average size is about 5nm. Compared with the macro diamond, the refinement of product, and the grains Residual stress, characteristic of Diamond Peak in the Raman spectrum are broadened and shifted to low frequency. (3) the growth mechanism of nano diamond is put forward from the view of thermodynamics and dynamics: the graphite particles in the heating process, the formation of graphite surface plasma collapse to form liquid carbon droplets, the liquid droplets in the thermodynamics of carbon under the condition of graphite into the metastable diamond stable region, carbon atoms begin to recombine to form diamond nucleation and grow rapidly. The carbon temperature pressure phase diagram in the plasma cooling process approximation of three phase coexistence, to form a closed space by nano tube shaped graphene nano diamond may be intertwined, grew up in the the internal phase change process of graphite nucleation. Follow the solid - gas - liquid - solid and solid - liquid - gas - plasma - three-phase coexistence of solid gold total node development path. The reason of diamond nanocrystal size: from small diamond nanocrystal growth limiting mechanism into consideration, the undercooling and the short time high growth restricted grow the nanodiamond. (4) in the same laser energy and particle size under the condition of different particle size (2 m, 5 m) graphite more easily the formation of nano diamond phase transition, the formation of more heat than large size graphite particle size of graphite, more unstable, more prone to diamond. Through the improvement of device optimization, interaction of the double beam pulse laser, laser and graphite increases the area of effect, greatly improve the efficiency of the synthesis of nano diamond. The phase change follow the process of graphite solid gas - liquid phase plasma - coexistence of solid and solid - liquid - solid - two growth path, another non internal amorphous carbon clusters and turbostratic carbon cluster edge found the diamond phase into existence One step proves that the formation of nanocrystalline diamond follows the liquefaction mechanism. The reduction of melting point caused by nanometer size effect is another mechanism of synthesizing ultrafine nano diamond. It is also an important reason for the formation of Bucky-diamond like diamond on the surface of nano diamond.

【學(xué)位授予單位】：江蘇大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TQ163;TB383.1

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