悬浮石墨烯的制备、性能及应用研究

作为一种新型二维材料,石墨烯在电学、光学、传热学及力学性能等方面均表现出极其优异的特性,对石墨烯的研究也得到众多研究者的关注.同时,拥有桥状悬浮结构的悬浮石墨烯(Suspended graphene)以其杂质少、受外界干扰小等优点使得石墨烯的本征特性得到最大化施展.在研究石墨烯的电子迁移率、传热性、力学性能等方面,悬浮石墨烯有着独特的优势,并且对提升微电子器件的性能作用显著.综述了悬浮石墨烯的制备与性质研究及其在微电子领域的应用进展,并展望了悬浮石墨烯的应用前景.     

悬浮石墨烯的制备、性能及应用研究

作为一种新型二维材料,石墨烯在电学、光学、传热学及力学性能等方面均表现出极其优异的特性,对石墨烯的研究也得到众多研究者的关注。同时,拥有桥状悬浮结构的悬浮石墨烯(Suspended graphene)以其杂质少、受外界干扰小等优点使得石墨烯的本征特性得到最大化施展。在研究石墨烯的电子迁移率、传热性、力学性能等方面,悬浮石墨烯有着独特的优势,并且对提升微电子器件的性能作用显著。综述了悬浮石墨烯的制备与性质研究及其在微电子领域的应用进展,并展望了悬浮石墨烯的应用前景。     

石墨烯复合纤维材料研究进展

石墨烯具有优越的力学、电学、热学等性能。石墨烯纳米片组装成石墨烯纤维,将石墨烯优异的性能应用到先进的宏观材料中,石墨烯纤维可用于组装柔性电极、导电织物等智能器件。不同的制备方法赋予石墨烯纤维不同的功能化性能,比如高温石墨化处理会大大减少纤维的缺陷,从而获得很高的力学性能;通过掺杂不同元素,可以使石墨烯纤维具有非常好的导电性和导热性;通过界面协同作用增强石墨烯片层间的界面强度,使石墨烯纤维在提高力学性能的同时,保证较高的导电性;限域水热法制备,可以通过控制玻璃毛细管的形状来获得不同宏观形状的石墨烯纤维。综述了石墨烯纤维研究的最新进展,主要关注不同的制备方法以及后处理过程对石墨烯纤维的力学性能、电学性能以及功能化应用的影响。     

自组装液晶性石墨烯功能材料的研究进展

目的分析液晶性石墨烯功能材料的研究现状及在电子器件中的应用前景。方法分别从热致液晶性石墨烯和溶致液晶性石墨烯材料的制备、表征和自组装特性等方面对目前的功能性石墨烯材料进行综述,并系统分析石墨烯的自组装性能对其在电子器件中电学性能的影响。结果石墨烯的结构对其电学性能有着重要的影响,自组装技术实现了石墨烯的高度有序性,提升了石墨烯的电学性能。结论自组装液晶性石墨烯材料能够实现高性能的电子器件的制备,有助于石墨烯在电子器件中的广泛应用。     

石墨烯在涂料领域的应用

石墨烯作为战略性新兴材料,凭借其优异的热性能、力学性能以及电学性能,已在各种功能涂料中得到了广泛应用,并在涂料领域表现出其独特的作用。本文主要介绍了石墨烯在防腐涂料、导电涂料、防火涂料、抗静电涂料及其他功能性涂料中的应用及效果,最后指出了目前将石墨烯应用到涂料中所遇到的问题。     

氧化还原法制备石墨烯及其在陶瓷材料中应用研究现状

氧化还原法制备石墨烯因原材料价格低廉、制备工艺简单,被认为是一种适应大规模制备石墨烯的途径,其中氧化石墨的还原是制备电学性能、力学性能与热稳定性优异的石墨烯的关键,而不同的还原方法对石墨烯的结构和性能影响较大。综述了氧化还原法制备石墨烯的还原方法,以及将石墨烯引入到陶瓷材料中所存在的问题和相应的解决方法。探讨了石墨烯对耐火材料在改善材料的强度和热震性的应用前景,并且指出了今后石墨烯在耐火材料中的应用需要重视的几个关键性问题。     

石墨烯电输运特性的研究进展

二维蜂巢状结构的石墨烯拥有独特的电学特性,其极高的电子迁移率、异常的量子霍尔效应、室温下亚微米尺度的弹道输运特性使之成为电子元器件研究的热点。简要介绍了近年来石墨烯电学方面的发展概况,其中包括晶界、晶畴对电学性能的影响,石墨烯场效应晶体管,石墨烯量子点,石墨烯pn结,石墨烯电学性能在磁场中的应用和石墨烯相关衍生物的电学性质。     

石墨烯/聚合物导电复合材料的研究

石墨烯以其独特的二维结构和优异的性能成为材料领域的研究热点。它在改善聚合物复合材料的电学性能、热学性能和力学性能等方面具有很大的潜力。综述了近些年石墨烯/聚合物导电复合材料制备与应用领域的研究,并对石墨烯/聚合物导电复合材料的发展前景进行了展望。     

空气吸附对石墨烯电学性能的影响

研究了空气掺杂对化学气相沉积(CVD)法制备的双层石墨烯底栅型场效应管电输运性能的影响。分别在大气、真空(<1Pa)、氮气以及不同湿度环境中测试了石墨烯场效应管的电学性能,测试结果表明大气中水分子和氧气分子的吸附导致的空穴掺杂作用使石墨烯的电学性能发生了严重退化,随着石墨烯表面吸附水分子和氧气分子的增多,狄拉克转变点电压向正方向的偏移量逐渐增大,空穴掺杂浓度增大,载流子迁移率减小。     

石墨烯增强铜基复合材料研究进展

铜(Cu)基复合材料具有优异的力学、热学、电学及耐磨和耐腐蚀等性能,广泛应用于各种工业技术领域。石墨烯(Graphene,Gr)具有二维平面结构和优异的综合性能,是金属基复合材料理想的增强相。石墨烯增强铜基复合材料拓展了铜及其合金的应用范围,适当的制备方法可以使其在保持优异导电导热性能的同时拥有更好的力学性能。石墨烯在铜基体中的存在形式主要以还原氧化石墨烯、石墨烯纳米片或与金属氧化物/碳化物纳米颗粒连接,旨在增强两者之间的界面结合。因此,石墨烯在铜基体中的结构完整性及存在形式直接影响了其性能的优劣。本文综述了Cu/Gr复合材料的制备及模拟方法、复合材料的性能评价及力学性能与功能特性的相互影响规律。指明Cu/Gr复合材料的发展关键在于：(1)分散性与界面结合;(2)三维石墨烯结构的构建;(3)界面结合对力学性能与功能特性的影响及两者间的相互协调。     

Consideration of bending and buckling behaviors of monolayer and multilayer graphene sheets

Graphene is a two-dimensional carbon based material. Remarkable mechanical, thermal and electrical properties of graphene make it as promising material for advanced applications; nevertheless, majority of its mechanical properties are still unknown. This research investigates buckling and bending behaviors of monolayer and multilayer armchair and zigzag graphene sheets. Bending stiffness, critical buckling force per unit length and critical strain of graphene sheets have been measured by molecular dynamic simulation method. Zigzag graphene sheet shows higher bending stiffness than armchair sheet. Van der Waals interaction between graphene sheets has an improving effect on the stability of middle layers. Cross-linkages reduce the buckling force per unit length and the buckling strain of multi layer graphene sheets.     

Plasmons in graphene: Recent progress and applications

Owing to its excellent electrical, mechanical, thermal and optical properties, graphene has attracted great interests since it was successfully exfoliated in 2004. Its two dimensional nature and superior properties meet the need of surface plasmons and greatly enrich the field of plasmonics. Recent progress and applications of graphene plasmonics will be reviewed, including the theoretical mechanisms, experimental observations, and meaningful applications. With relatively low loss, high confinement, flexible feature, and good tunability, graphene can be a promising plasmonic material alternative to the noble metals. Optics transformation, plasmonic metamaterials, light harvesting etc. are realized in graphene based devices, which are useful for applications in electronics, optics, energy storage, THz technology and so on. Moreover, the fine biocompatibility of graphene makes it a very well candidate for applications in biotechnology and medical science.     

Graphene-based atomic-scale switches

Graphene's remarkable mechanical and electrical properties, combined with its compatibility with existing planar silicon-based technology, make it an attractive material for novel computing devices. We report the development of a nonvolatile memory element based on graphene break junctions. Our devices have demonstrated thousands of writing cycles and long retention times. We propose a model for device operation based on the formation and breaking of carbon atomic chains that bridge the junctions. We demonstrate information storage based on the concept of rank coding, in which information is stored in the relative conductance of graphene switches in a memory cell.     

Unusually High Optical Transparency in Hexagonal Nanopatterned Graphene with Enhanced Conductivity by Chemical Doping

Graphene has received appreciable attention for its potential applications in flexible conducting film due to its exceptional optical, mechanical, and electrical properties. However increasing transmittance of graphene without sacrificing the electrical conductivity has been difficult. The fabrication of optically highly transparent (≈98%) graphene layer with a reasonable electrical conductivity is demonstrated here by nanopatterning and doping. Anodized aluminium oxide nanomask prepared by facile and simple self‐assembly technique is utilized to produce an essentially hexagonally nanopatterned graphene. The electrical resistance of the graphene increases significantly by a factor of ≈15 by removal of substantial graphene regions via nanopatterning into hexagonal array pores. However, the use of chemical doping on the nanopatterned graphene almost completely recovers the lost electrical conductivity, thus leading to a desirably much more optically transparent conductor having ≈6.9 times reduced light blockage by graphene material without much loss of electrical conductivity. It is likely that the availability of large number of edges created in the nanopatterned graphene provides ideal sites for chemical dopant attachment, leading to a significant reduction of the sheet resistance. The results indicate that the nanopatterned graphene approach can be a promising route for simultaneously tuning the optical and electrical properties of graphene to make it more light‐transmissible and suitable as a flexible transparent conductor.     

石墨烯及复合材料作锂离子电池电极的进展

石墨烯是一种单原子层厚度的石墨材料,具有独特的二维结构和优异的电学、力学及化学稳定性。此外,石墨烯还具有特殊sp^2结构,易于与其它材料复合。利用石墨烯获得具有特殊形貌和微观结构的电极材料,能有效改善材料的各项电化学性能,作为锂离子电池的电极材料具有潜在的应用前景。总结了近些年对石墨烯及复合材料作为锂离子电池电极材料的研究,重点阐述了材料的制备、电学性质及基本原理,为其作为锂离子电极材料的应用提供相应的理论依据。     

石墨烯增强铜基复合材料研究进展

石墨烯是一种新兴的二维碳纳米材料,具有良好的力学、导电以及润滑性能,是铜基复合材料中最具潜力的增强体.本文综述了石墨烯增强铜基复合材料的制备工艺,详细分析并归纳了石墨烯增强铜基复合材料的界面结构对于复合材料力学性能的影响及增强机制,总结了石墨烯增强铜基复合材料摩擦学行为研究的最新进展,并深入阐述了石墨烯增强铜基复合材料...     

Thermoresponsive Conductivity of Graphene-Based Fibers

Smart materials are versatile material systems which exhibit a measurable response to external stimuli. Recently, smart material systems have been developed which incorporate graphene in order to share on its various advantageous properties, such as mechanical strength, electrical conductivity, and thermal conductivity as well as to achieve unique stimuli-dependent responses. Here, a graphene fiber-based smart material that exhibits reversible electrical conductivity switching at a relatively low temperature (60 °C), is reported. Using molecular dynamics (MD) simulation and density functional theory-based non-equilibrium Green's function (DFT-NEGF) approach, it is revealed that this thermo-response behavior is due to the change in configuration of amphiphilic triblock dispersant molecules occurring in the graphene fiber during heating or cooling. These conformational changes alter the total number of graphene-graphene contacts within the composite material system, and thus the electrical conductivity as well. Additionally, this graphene fiber fabrication approach uses a scalable, facile, water-based method, that makes it easy to modify material composition ratios. In all, this work represents an important step forward to enable complete functional tuning of graphene-based smart materials at the nanoscale while increasing commercialization viability.     

Charge Transport in Polycrystalline Graphene: Challenges and Opportunities

Graphene has attracted significant interest both for exploring fundamental science and for a wide range of technological applications. Chemical vapor deposition (CVD) is currently the only working approach to grow graphene at wafer scale, which is required for industrial applications. Unfortunately, CVD graphene is intrinsically polycrystalline, with pristine graphene grains stitched together by disordered grain boundaries, which can be either a blessing or a curse. On the one hand, grain boundaries are expected to degrade the electrical and mechanical properties of polycrystalline graphene, rendering the material undesirable for many applications. On the other hand, they exhibit an increased chemical reactivity, suggesting their potential application to sensing or as templates for synthesis of one‐dimensional materials. Therefore, it is important to gain a deeper understanding of the structure and properties of graphene grain boundaries. Here, we review experimental progress on identification and electrical and chemical characterization of graphene grain boundaries. We use numerical simulations and transport measurements to demonstrate that electrical properties and chemical modification of graphene grain boundaries are strongly correlated. This not only provides guidelines for the improvement of graphene devices, but also opens a new research area of engineering graphene grain boundaries for highly sensitive electro‐biochemical devices.     

Hysteresis I–V nature of mechanically exfoliated graphene FET

Graphene is an attractive material for device applications due to its excellent electrical and mechanical properties. The mechanical exfoliation is an attractive method to fabricate graphene devices using mono and multilayer graphene flakes. As the graphene is very sensitive to atmosphere the occurrence of hysteresis and p-doping is common. This paper reports electrical characterization and hysteresis effect of graphene field effect transistor (FET) fabricated using mechanically exfoliated graphene flakes. Raman spectra and atomic force microscopy techniques have been used to examine the quality and thickness of the exfoliated graphene. This fabricated graphene FET has shown hysteresis nature with p-type doping. The possible reason for the observed hysteresis and p-doping has been explained.