本文選題：超臨界流體　切入點：石墨烯　出處：《上海交通大學(xué)》2015年博士論文　論文類型：學(xué)位論文

【摘要】：石墨烯、氧化鈦納米薄層具備許多優(yōu)異的性能,如何實現(xiàn)大規(guī)�；苽淙匀皇且淮筇魬�(zhàn)。探索新途徑制備納米薄層材料具有十分重要的實際意義。超臨界流體具有獨特的特性,如低表面張力、高擴(kuò)散系數(shù)、低粘度系數(shù)、優(yōu)異的表面濕潤能力。因此,可以充分利用超臨界流體的優(yōu)點剝離層狀材料制備納米薄層材料。本文針對超臨界流體制備過程中的關(guān)鍵技術(shù)問題、熱性能方面展開深入研究。超臨界流體操作參數(shù)、初始原料、再循環(huán)處理工藝極大地影響到石墨烯的產(chǎn)率,通過實驗研究,得到最佳實驗操作參數(shù)。天然石墨作為原料時,石墨烯的產(chǎn)率比較低,天然石墨經(jīng)過硝酸預(yù)處理后,表面附著少量的極性官能團(tuán),通過雙極性作用吸附大量的DMF分子,提高了石墨烯的產(chǎn)率,極性官能團(tuán)在高溫高壓環(huán)境中會還原,因此,基本保留石墨烯的本征特性。利用超(亞)臨界水還原氧化石墨烯制備還原石墨烯。并通過超(亞)臨界水和DMF對比實驗,澄清了超(亞)臨界水中H~+對氧化石墨烯的高效催化還原作用。氧化石墨烯水相分散液在密閉反應(yīng)器中進(jìn)行熱處理(200℃-400℃),該方法綠色、簡單、快速、高效。同時,將氧化石墨分散在二甲基甲酰胺溶劑中進(jìn)行同樣的熱處理(200℃-400℃),作為對比試驗探索超(亞)臨界水還原氧化石墨烯的過程。結(jié)果發(fā)現(xiàn),水是一種典型的質(zhì)子性溶劑,在200℃-400℃溫度范圍內(nèi),能夠產(chǎn)生大量的H~+,并快速催化氧化石墨烯的脫水還原反應(yīng),得到還原石墨烯,大大提高了石墨烯的還原程度和還原速率。提出超臨界流體法剝離層狀鈦酸制備氧化鈦納米薄層材料,如何選擇溶劑是超臨界流體制備技術(shù)中最重要的問題。通過合理設(shè)計實驗探索其中規(guī)律,結(jié)果表明,以典型的非質(zhì)子性溶劑如二甲基甲酰胺為超臨界流體時,僅有剝離過程發(fā)生。而以典型的質(zhì)子性溶劑如水為超臨界流體時,水是一種典型的質(zhì)子性溶劑,在這一溫度范圍內(nèi),能夠產(chǎn)生大量H~+,在H~+存在的情況下,層狀材料不但有剝離發(fā)生,同時還伴隨晶型相變發(fā)生,并進(jìn)一步探索相變過程。XRD和SEM結(jié)果證明層狀鈦酸通過溶解和再結(jié)晶過程相變成銳鈦礦。電子工業(yè)向高集成化、大功率化方向迅猛發(fā)展,對高效熱界面材料的需求突顯得尤為重要。石墨烯具有高導(dǎo)熱率、低皮卡爾熱阻,是環(huán)氧樹脂基復(fù)合材料最理想的填充材料。將超臨界流體法以及水熱還原法得到的石墨烯作為熱界面材料中的納米添加劑,所有的石墨烯都按體積分?jǐn)?shù)(2%、4%、6%、8%、10%)填充制備石墨烯-環(huán)氧樹脂復(fù)合物,研究熱界面材料的熱性能,發(fā)現(xiàn)導(dǎo)熱率明顯提高。同時,通過導(dǎo)熱理論模型對復(fù)合物的熱導(dǎo)率進(jìn)行計算,并與實驗結(jié)果對比,發(fā)現(xiàn)理論計算值與實驗規(guī)律相一致。
[Abstract]:There are many excellent properties of graphene and titanium oxide nanocrystalline, how to achieve large-scale preparation is still a big challenge. It is of great practical significance to explore new ways to prepare nano-thin layer material. Supercritical fluid has unique properties. Such as low surface tension, high diffusion coefficient, low viscosity coefficient, excellent surface wetting ability. The advantages of supercritical fluid can be fully utilized to peel off layered materials to prepare nano-thin layer materials. In this paper, the thermal properties of supercritical fluids are studied in detail in view of the key technical problems in the preparation process. The operating parameters of supercritical fluids, The yield of graphene is greatly affected by the process of initial raw material and recycling treatment. The optimum operating parameters are obtained through experimental study. When natural graphite is used as raw material, the yield of graphene is relatively low, and the natural graphite is pretreated with nitric acid. A small amount of polar functional groups were attached to the surface, and a large number of DMF molecules were adsorbed by bipolar interaction, which increased the yield of graphene, and the polar functional groups would be reduced under high temperature and high pressure. The basic intrinsic properties of graphene were preserved. Reduction of graphene by supercritical water was used to prepare reduced graphene. The experiments of supercritical water and DMF were carried out. The catalytic reduction of graphene oxide by H ~ in supercritical water was clarified. The aqueous dispersion of graphene oxide was heat-treated in a closed reactor at 200 鈩，

本文編號：1604998