微波法制备还原氧化石墨烯及其在锂硫电池中的应用

采用改进的Hummers法制备了氧化石墨（GO）,对GO进行碳酸浸渍后,通过微波固相法剥离其为少层的还原氧化石墨烯（MRGO）。并采用低温原位化学沉积法制备微波还原氧化石墨烯/纳米硫（MRGO/NS）锂硫电池正极复合材料。通过FT-IR、XRD、SEM、TEM、BET对所制备的MRGO和MRGO/NS的微观结构、形貌等进行表征,采用恒流充放电测试和交流阻抗测试对复合材料的电化学性能进行研究。结果表明,通过微波固相法剥离碳酸浸渍后的GO所制备的MRGO为少层的折扇状还原氧化石墨烯,可为锂硫电池的硫和多硫化物提供足够的容纳空间,从而缓解穿梭效应,提高了电极材料的循环性能和倍率性能。     

石墨烯制备及应用研究进展

石墨烯是近几年发展起来的一种非常有潜力的新型碳材料,具有优异的物理和化学性能,在物理、化学、电子器件、能源以及材料等领域具有广泛的应用。综述了目前制备石墨烯的几种方法:机械剥离法、氧化还原法、液相剥离法、电化学剥离法、超临界流体剥离法、化学气相沉积法和外延生长法等,对比了各种制备方法的优缺点,分析了石墨烯制备方法的发展趋势,并对石墨烯行业的应用前景与发展趋势进行了展望。     

微波法制备还原氧化石墨烯及其在锂硫电池中的应用

采用改进的Hummers法制备了氧化石墨(GO),对GO进行碳酸浸渍后,通过微波固相法剥离其为少层的还原氧化石墨烯(MRGO)。并采用低温原位化学沉积法制备微波还原氧化石墨烯/纳米硫(MRGO/NS)锂硫电池正极复合材料。通过FT-IR、XRD、SEM、TEM、BET对所制备的MRGO和MRGO/NS的微观结构、形貌等进行表征,采用恒流充放电测试和交流阻抗测试对复合材料的电化学性能进行研究。结果表明,通过微波固相法剥离碳酸浸渍后的GO所制备的MRGO为少层的折扇状还原氧化石墨烯,可为锂硫电池的硫和多硫化物提供足够的容纳空间,从而缓解穿梭效应,提高了电极材料的循环性能和倍率性能。     

石墨烯掺杂聚丙烯复合材料的制备、性能及应用研究进展

综述了石墨烯及其掺杂聚丙烯(PP)复合材料的常见制备方法。机械剥离法制备效率低,适合实验室发现性制备;化学气相沉积法对设备要求苛刻、成本高,只适合实验室制备或特殊条件使用的定向制备;化学剥离法和碳纳米管剖开法不适合大规模工业化生产;氧化石墨烯还原法是工业化生产石墨烯的最有效方法;熔融共混法有望成为PP/石墨烯复合材料的工业化制备方法。简要说明了工业化生产PP/石墨烯复合材料的力学、电学、热学性能及其应用领域,最后,展望了PP/石墨烯复合材料的发展前景。     

剥离法制备石墨烯的研究进展

石墨烯具有载流子迁移率高、热导率大、比表面积大等优点，被广泛应用在光学、电学、材料学以及生物医学等领域。当前，寻求一种低成本、高效率且可大规模工业化生产石墨烯的方法仍然是一个挑战。从剥离机制出发，综述了机械剥离法和液相剥离法制备石墨烯的研究现状，总结了这两种方法的优点及存在的主要问题，并对石墨烯剥离制备技术的发展方向进行了展望。     

聚丙烯/石墨烯复合材料的制备及性能研究进展

介绍了几种石墨烯的制备方法,包括微机械剥离法、液相或气相直接剥离法（物理方法）,化学气相沉积法、碳纳米管剖开法、外延生长法、还原氧化石墨法（化学方法）,并阐述了这几种方法的优缺点。其次总结了聚丙烯/石墨烯纳米复合材料的制备方法,重点讨论了石墨烯对不同方法制备的复合材料电学、力学、热学、结晶及流变性能的影响,最后展望了石墨烯在聚丙烯材料改性中所面临的问题及其聚丙烯/石墨烯复合材料的应用前景。     

石墨剥离制备石墨烯的研究进展

石墨烯是一种具有二维平面结构的碳纳米材料,特殊的结构决定了它具有许多优异的物化性能。近年来,人们在以石墨为原料制备石墨烯方面取得了积极的进展,为石墨烯的基础研究和下游应用开发提供了原料保障。以石墨为原料制备石墨烯是最为经济简单的方法。本文对近3年来以石墨为原料制备石墨烯的6种方法(化学氧化-还原法、溶剂热法、液相剥离法、电化学剥离法、球磨法以及超临界流体剥离法)作了综述并讨论了各方法的优缺点。     

超临界CO2剥离法制备石墨烯的过程强化研究

石墨烯因其独特的二维结构和优异的物理性能在众多领域中引起了广泛的关注,高质量石墨烯的制备是实现其应用价值的前提。尽管目前石墨烯的制备方法较多,但是开发绿色、低成本、规模化制备方法的道路仍然充满挑战。物理法剥离石墨能够实现高结晶石墨烯的制备,特别是超临界CO₂流体具有廉价、绿色、稳定、易分离且可重复利用的优势,在石墨烯制备上展现出巨大的应用潜力。以超临界CO₂制备石墨烯为出发点,梳理了近年来超临界CO₂法剥离石墨制备石墨烯的研究进展,重点阐述了制备过程中的强化剥离手段,期望对未来石墨烯材料的制备提供思路。     

石墨烯制备方法的研究进展

近年来,石墨烯以其独特的结构和优异的性能,在化学、物理和材料学界引起了广泛的研究兴趣。人们已经在石墨烯的制备方面取得了积极的进展。本文总结了一些石墨烯的制备方法,如微机械剥离法、液相或气相直接剥离法、化学气相沉积法和氧化石墨还原法等,并简单分析了各类制备方法的优缺点。     

氧化石墨烯剥离方法的研究进展

用石墨制备氧化石墨是大规模合成石墨烯的起点,也是实现石墨烯大量制备的有效方法之一。目前。制备氧化石墨的工艺相对成熟,而有效剥离出不同尺寸的石墨烯以满足不同的需求,还存在诸多技术难点需要突破。本文着重介绍了氧化石墨烯剥离方法的研究进展,包括热膨胀剥离、超声剥离、机械剥离、静电剥离、低温剥离等方法;最后展望了氧化石墨烯研究工作的发展前景。     

Exfoliation of graphene nanosheets in aqueous media

Graphene has attracted much attention and holds great promise in various applications due to its extraordinary properties. To realize applications of graphene in large scale, developing a facile, green and cost-effective method for mass production of high-quality graphene is highly desired. Relative to expensive and complicated bottom-up approaches, top-down methods for graphene production are promising owing to their low cost and simplicity. Specifically, exfoliation of graphene nanosheets in liquid phase is favorable for their dispersion, functionalization and processing. Instead of highly toxic organic solvents, using water as the liquid medium makes exfoliation process eco-friendly and sustainable. In this review, recent progress on exfoliation of graphene nanosheets in water is discussed, with a particular focus on exfoliation and stabilizing mechanism in various aqueous media. Different water-based exfoliation methods, such as liquid-phase exfoliation and electrochemical exfoliation, are surveyed.     

The production of graphene by direct liquid phase exfoliation of graphite at moderate sonication power by using low boiling liquid media: The effect of liquid media on yield and optimization

There are many production methods for graphene production. One of the most successful production methods in terms of scale-up is liquid phase exfoliation (LPE) method. In this study, after optimizing the sonication time and sonication power that are effective in the production to increase the efficiency of the LPE method, the experiments were continued at moderate sonication powers and the effect of liquid media, another important parameter, was examined. In this study, hexagonal graphite powders were subjected to direct liquid phase exfoliation process by using different liquid media (N-Methyl-2-Pyrrolidone (NMP), N,N-Dimethylformamide (DMF), ethanol, 2-propanol, acetone, methanesulfonic acid, ethanol + Sodium dodecyl sulphate (SDS), 2-propanol + SDS) and the obtained samples were characterized. As a result of the characterization, the liquid media with the highest efficiency was determined to be NMP. Besides, it was observed that a new hybrid solvent obtained by adding a surfactant such as SDS into low-cost and environmentally friendly liquid media such as ethanol and 2-propanol showed a higher efficiency than NMP. It was observed that 3–5 layer graphene ranged between 15 and 19 wt% in either graphene produced by using hybrid solvents containing NMP or SDS. The amount of double or single-layer graphene was negligibly small. The production with the lowest efficiency was observed in the use of acetone. The produced graphenes were dispersed in the liquid and their sedimentation time was observed. The sedimentation time of graphenes, produced using NMP and SDS-doped hybrid solvents, in liquid was more than 120 days. The sedimentation time of graphene produced using acetone was less than 20 days. In the use of graphene as a reinforcing material or adsorbent, large amounts of graphene are needed. In such applications, mass production of graphene is important rather than the number or quality of sheets of graphene. Therefore, optimization of production parameters of LPE method, which is suitable for mass production, is significance.     

Vacuum-assisted microwave reduction/exfoliation of graphite oxide and the influence of precursor graphite oxide

One-step synthesis of high quality graphene at gram-scale quantities is important for industrial applications, e.g. in electrochemistry for sensing and energy storage. Currently, thermal reduction/exfoliation of graphite oxide (GO) is a typical method of choice. However, it has the drawback of requiring specialized equipment for rapid thermal shock. A recent alternative method, microwave-assisted exfoliation, usually suffers from poor reduction of graphite oxide and thus low C/O ratios. Herein we show that vacuum-assisted microwave reduction/exfoliation of graphite oxide in a closed system leads to high C/O ratios and partial hydrogenation of graphene (2.6 at.% of H). Microwave irradiation of graphite oxide in vacuum leads to outgassing from GO and the creation of plasma which aids temperature distribution and hydrogenation. This plasma is quickly extinguished by further dramatic evolution of gases from GO and consequent pressure increase. We assess the influence of precursor graphite oxide, prepared by Hummers, Staudenmaier, and Hofmann methods, upon the materials properties of microwave exfoliated graphene. We show that microwave-exfoliated graphenes prepared from different graphite oxides show very fast heterogeneous electron transfer rates, with similar electrochemical behaviour to thermally reduced graphene oxide.     

Effect of synthesis method on solvation and exfoliation of graphite oxide

Graphite oxides (GOs) synthesized by Brodie’s and Hummers’ methods are significantly different with respect to hydration, solvation and exfoliation properties. Hummers GO is more easily intercalated by liquid water and alcohols, exhibiting osmotic type of swelling. In contrast, Brodie GO shows crystalline swelling in alcohol solvents with step-like insertion of methanol or ethanol monolayers. However, the stronger hydration and easier dispersion in water observed for Hummers GO do not correlate with better dispersion of graphene powder obtained by thermal exfoliation. Higher surface area graphene powder was obtained by exfoliation of Brodie GO, while the temperature of its exfoliation is about 75 °C higher than that for the studied sample of Hummers GO. It is suggested that higher exfoliation temperature and better crystallinity of GO are important factors for preparation of graphene powder using thermal exfoliation.     

应用于固体推进剂的石墨烯及其复合材料制备技术研究进展

系统介绍了多种石墨烯的制备、改性和复合方法,制备方法主要有机械剥离和湿法剥离,改性方法主要有非共价改性和共价改性,复合方法主要有非原位合成和原位合成。从石墨烯在固体推进剂中应用的角度分析比较了不同制备方法的优缺点,指出今后用作燃烧催化剂的石墨烯及其复合材料的制备技术重点应集中在如下几方面:(1)将微乳液法等纳米材料制备方法应用于石墨烯复合材料制备中;(2)应加强负载有机金属盐和含能催化剂的石墨烯负载型燃烧催化剂的研究;(3)开展石墨烯负载物的晶体生长研究。附参考文献57篇。     

氧化石墨烯还原方法的研究进展

石墨烯的制备对于石墨烯的理论研究和应用研究起着重要的作用,化学氧化还原法是制备石墨烯最为重要的方法之一。综述了近年来氧化石墨烯的还原剂还原法、高温热处理还原法、电化学还原法、溶剂热还原法、催化还原法、微波还原法等多种还原方法,分析了目前各种常用还原方法的优缺点,并进一步提出氧化石墨烯还原方法未来的几个研究方向：还原前后原子结构变化及还原机理研究;新型还原方法或多种还原方法联用的研究;还原氧化石墨烯和制备复合物同时进行的研究。     

On the Consistency of the Exfoliation Free Energy of Graphenes by Molecular Simulations

Monolayer graphene is now produced at significant yields, by liquid phase exfoliation of graphites in solvents. This has increased the interest in molecular simulation studies to give new insights in the field. We use decoupling simulations to compute the exfoliation free energy of graphenes in a liquid environment. Starting from a bilayer graphene configuration, we decouple the Van der Waals interactions of a graphene monolayer in the presence of saline water. Then, we introduce the monolayer back into water by coupling its interactions with water molecules and ions. A different approach to compute the graphene exfoliation free energy is to use umbrella sampling. We apply umbrella sampling after pulling the graphene monolayer on the shear direction up to a distance from a bilayer. We show that the decoupling and umbrella methods give highly consistent free energy results for three bilayer graphene samples with different size. This strongly suggests that the systems in both methods remain closely in equilibrium as we move between the states before and after the exfoliation. Therefore, the amount of nonequilibrium work needed to peel the two layers apart is minimized efficiently.     

A note on using expanded graphite for achieving energy- and time-efficient production of graphene nanoplatelets via liquid phase exfoliation

Although easily scalable, the production of graphene nanoplatelets (GNP) by the means of liquid-phase exfoliation of graphite flakes (GF) remains an energy- and time-intensive process. In this work, we demonstrate that significant time and energy can be saved in GNP production when employing expanded graphite (EG) in a surfactant-assisted liquid phase exfoliation process. Owing to its increased interlayer distance, the exfoliation of EG can be accomplished in a much shorter time (<30 min) compared to GF (approximately 7 h in the present case). Moreover, the energy required for the EG exfoliation is close to 80-fold lower than that for GF exfoliation. Monitoring of the mean lateral dimension, specific surface area, and graphite flake-to-GNP transition during exfoliation was performed experimentally using several analytical techniques. The EG-derived GNPs are produced much faster and require less energy for exfoliation compared to GF, thus making it a more efficient alternative technique.