超临界流体体系中石墨烯的制备研究

发布时间：2018-04-08 13:22

本文选题：石墨烯　切入点：超临界流体　出处：《昆明理工大学》2017年硕士论文

【摘要】：石墨烯是由sp2碳原子以蜂巢晶格构成的准二维单原子层结构。由于石墨烯独特的结构,其拥有特殊的电学、光学、力学、热学性质,在电子、航天、军工、生物、新能源、半导体等领域显示出广阔的应用前景。石墨烯具有的特殊性质使其在环境污染治理中也表现出非凡的能力。本论文对目前石墨烯主要的制备方法进行了简要的介绍,包括机械剥离法、气相沉积法、氧化还原法、SiC外延生长法等,但这些方法不能同时满足大规模、低成本以及高质量制备的要求。本论文利用超临界流体插层-剥离石墨制备石墨烯。研究了石墨原料种类对产物的影响。在超临界CO2体系中,研究了反应温度、反应压强、反应时间、表面活性剂的种类和初始石墨用量对所制备石墨烯溶液浓度的影响;研究了对石墨进行重复多次剥离的效果。在其它超临界流体的实验中,研究了超临界甲醇、乙醇、异丙醇、丙酮和水等对石墨进行剥离的效果;探索了利用两种超临界流体同时对石墨进行剥离。对利用各种流体制备的产物进行了 SEM、TEM、Raman、AFM、XRD等表征分析。本论文的主要工作及成果如下:1、石墨原料种类的影响本实验所选用的天然鳞片石墨和可膨胀石墨都具有比较明显的层状结构,天然鳞片石墨的尺寸大部分为几微米,可膨胀石墨的尺寸集中在十到二十微米之间。尺寸的差异也会反映在产物石墨烯上面,即利用天然石墨制备的石墨烯尺寸比较小,用可膨胀石墨制备的石墨烯尺寸比较大。综合考虑,本研究使用可膨胀石墨作为原料。2、超临界CO2体系中,实验条件的影响在不同的条件下,超临界CO2的密度、粘度和扩散系数有着很大变化。在超临界CO2体系中,利用控制变量法考察了反应温度、压强、时间、表面活性剂种类及石墨用量对剥离结果的影响,选出的最佳反应条件为80℃、15MPa、反应时间2h、表面活性剂种类为PVP、原料用量50mg。在最佳反应条件下制备的石墨烯层数大概为8层,重复三次剥离后石墨烯层数减小为3～4层。3、利用其他超临界流体进行剥离本论文利用超临界甲醇、乙醇、异丙醇、丙酮和水等溶剂对石墨进行了剥离,剥离效果最好的为乙醇,层数最少为3～4层。探索了两种超临界流体(乙醇+氦气)同时对石墨进行剥离,TEM和AFM表征结果显示超临界乙醇和氦气可以制备出层数为2～3层的石墨烯。4、表征分析对各种流体剥离后的产品进行了 SEM、TEM、Raman、AFM、XRD等表征分析。SEM的图像显示剥离后样品的分布和尺寸更加均匀,伴有许多褶皱和重叠,颜色变浅。AFM的测试结果显示利用超临界CO2制备的石墨烯厚度大概为8层,利用超临界CO2重复三次剥离和超临界乙醇一次剥离的效果相当,层数都为3～4层。利用超临界乙醇和氦气同时作用制备的石墨烯层数最少为2～3层。在HR-TEM图像下可以看出片层折叠边缘的暗线,暗线数目代表了石墨烯的层数,利用超临界CO2制备的石墨烯层数最少为3～5层,利用超临界乙醇制备的石墨烯最少层数为2～4层。Raman光谱测试结果显示反应前后G峰和2D峰的比值有所减小,说明层数有所减少,利用超临界乙醇制备的石墨烯其比值减小的更为明显,说明超临界乙醇的剥离效果更佳。剥离后样品的XRD衍射图谱没有石墨那么完整,表明剥离后石墨的长程有序性被破坏,剥离有一定的效果。
[Abstract]:Graphene is composed of SP2 carbon atoms in the honeycomb lattice of quasi two dimensional single atomic layer structure. Because of its unique structure of graphene, have special optical, electrical, mechanical, thermal properties, in the electronic, aerospace, military, biology, new energy, semiconductor and other areas show a broad application prospect. The special nature graphene has in the environmental pollution control also showed remarkable ability. This paper gives a brief introduction to the main preparation methods of graphene, including mechanical stripping method, vapor deposition method, oxidation reduction method, SiC epitaxial growth method, but these methods can not meet the large-scale. Low cost and high quality preparation. The preparation of graphite intercalation exfoliation of graphene using supercritical fluid. The effect of graphite on the product. The types of raw materials in supercritical CO2 system, studied the reaction temperature, reaction pressure, reaction The time, type and amount of the initial graphite surface active agent on the effect of preparing the concentration of graphene solution; Study on the effect of repeated stripping graphite. In other supercritical fluid experiments of supercritical methanol, ethanol, isopropanol, acetone and water to remove the effect of graphite; at the same time to explore the stripping of graphite by using two kinds of supercritical fluid. The products use a variety of fluid prepared by SEM, TEM, Raman, AFM, XRD analysis techniques. The main work of this paper are as follows: 1. The effect of graphite material types of the natural flake graphite used in this experiment and the expandable graphite has obvious layered structure, size of natural flake graphite is mostly a few microns, expandable graphite size from ten to twenty microns. The size of the difference will be reflected in the above product of graphene, namely, The size of graphene with natural graphite preparation is relatively small, with expandable graphite prepared graphene size is relatively large. Comprehensive consideration, this study using expandable graphite as raw material.2, supercritical CO2 system, experimental conditions under different conditions, supercritical CO2 density, viscosity and diffusion coefficient there are great changes. In the supercritical CO2 system, the effects of reaction temperature, time, pressure control variable method, effects of surfactants and graphite dosage on the stripping results, the optimum reaction conditions were selected as 80 DEG C, 15MPa, reaction time 2h, the type of surfactant is PVP, amount of raw materials in 50mg. under the optimum reaction conditions for the preparation of graphene layers or 8 layers, repeated three times after the peeling graphene layers decreases to 3~4 layer.3, the use of other supercritical fluid stripping in supercritical methanol, using the ethanol, isopropanol, acetone and water. Solvent stripped of graphite, stripping the best ethanol, layers of at least 3~4. Explored two supercritical fluid (ethanol + helium) and stripping of graphite, TEM and AFM showed that the ethanol and supercritical helium can be prepared by 2~3 layers of graphene.4, characterization analysis of various fluid after stripping the products were analyzed by SEM, TEM, Raman, AFM, XRD characterization analysis of.SEM image display after peeling off the distribution and size of the samples is more uniform, with many folds and overlap, test results color.AFM display by using graphene thickness of supercritical CO2 prepared about 8 layers rather, the use of supercritical CO2 was repeated three times and a supercritical ethanol stripping stripping effect, layers are 3~4 layers. By using supercritical helium and ethanol and graphene layers prepared at least 2~3 layer in HR-TEM image can be. The folded edge of the dark, dark line represents the number of graphene layers, using graphene layers of supercritical CO2 prepared at least 3~5 layers of graphene using supercritical ethanol prepared at least 2~4 layer.Raman spectroscopy results show that before and after the reaction ratio of G and 2D peaks decreased, indicating the number has decreased, decreased by using graphene prepared by the supercritical ethanol ratio is more obvious, indicating better stripping effect in supercritical ethanol. After stripping the XRD diffraction patterns of the samples without graphite so complete, indicating that the long-range ordered graphite after stripping was destroyed, peel have a certain effect.

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ127.11

【相似文献】