高导电聚苯胺/纳米石墨微片复合材料的结构与性能

以天然可膨胀石墨(GN)为原材料,采用酸及快速热处理制备了膨胀石墨(EG),再将膨胀石墨置于超声波中制得了纳米石墨微片(NanoG),最后采用原位聚合法制备了聚苯胺/纳米石墨微片(PANI/NanoG)导电复合物。扫描电镜(SEM)显示纳米石墨微片长径为0.8μm～20μm,厚度为30nm～90nm。聚苯胺均匀覆盖在纳米石墨微片表面;透射电镜(TEM)揭示了纳米石墨微片的片层分散在复合物中并形成了导电网络;电性能测试表明,当纳米石墨微片含量为0.5%(质量分数,下同)时,复合物电导率达到107.3S/cm,其渗滤阈值达到0.1%,纳米石墨微片独特的结构(宽度/厚度的高比值)及在聚苯胺中的分散造就了复合物良好的导电性能。     

HClO_4-CrO_3-石墨层间化合物的制备及其性能

以天然鳞片石墨、CrO3、HClO4为原料,采用化学氧化法制备石墨层间化合物(GIC);研究了反应物用量、反应时间、反应温度对石墨层间化合物膨胀容积的影响。结果表明:按石墨∶三氧化铬∶高氯酸(质量比)=1∶0.3∶5,反应温度30℃,反应时间60min的条件,可制得膨胀容积为555mL.g-1的石墨层间化合物。采用FTIR、XRD、TG等技术对石墨层间化合物的组成、结构进行表征和分析得知:石墨层间的插入物为ClO4-、Cr2O72-。GIC性能特点测试结果说明:所制GIC具有低能耗性能、良好的真空安定性、较好的8毫米波动态衰减效果。     

膨胀石墨对重油和生物体液的吸附-来自中国的研究

膨胀石墨(简称EG)是通过将残留石墨层间化合物(简称GIC)快速加热到约1000℃而分解、膨胀制得的。这种材料具有较大比表面积和较强表面活性,因此,EG可以吸附重油和粘稠性有机液体。本文综述了清华大学研究组近年来所进行的膨胀石墨吸附重油和生物体液的研究成果。     

石墨层间化合物和膨胀石墨

石墨是一种典型的层状结构炭材料 ,其各层面间由较弱的范德华力连接 ,所以人们可以用物理或化学的方法将其它异类粒子如原子、分子、离子甚至原子团插入到晶体石墨的层间 ,生成一种新的层状化合物 ,这种材料被称做石墨层间化合物 (GraphiteIntercalation Compound,简称 GIC)。实验室常用的合层方法有加热法、化学法、电化学法、光化学法等。不同种类的插入物将导致不同的插层结构 ,使其既不同于母体石墨 ,也不同于客体材料 ,而赋予了石墨层间化合物独特的物理和化学性能 ,如高导电性 ,超导特性 ,电池性能 ,催化特性 ,膨胀性能等。天然鳞…     

分步插层法制备硝酸盐-硫酸-GIC

通过硫酸、硝酸或硝酸盐分步插层的方法,成功制备了硝酸/硝酸盐-硫酸-GIC三元石墨层间化合物.采用XRD、SEM和EDS对GIC的结构进行了研究.结果表明:与直接插层法相比,分步插层法有利于插层物质的插层反应,充分扩大石墨层间距,形成低阶石墨层间化合物,使膨胀效果更优,膨胀体积高达450mL/g以上;膨胀后GIC的孔结构均匀,层壁较薄,片层结构清晰,膨胀充分.同时,分步插层法能够降低实验操作的危险性,污染小,反应易于控制.     

水交换法制备低温可膨胀石墨的研究

采用一种新型的水交换法制备工艺,以天然石墨、高锰酸钾、浓硫酸为原料,制得了在160℃时即可发生膨胀的低温可膨胀石墨.采用热失重分析(TGA)、傅立叶转换红外光谱分析(FT-IR)、X射线衍射(XRD)和扫描电镜(SEM)对其结构进行了表征与分析.结果表明,通过水交换法使得插入石墨层间的主要物质为水,水在低温下瞬间汽化对石墨片层产生张力,导致石墨低温膨胀.因此,石墨发生膨胀时无有害小分子释放,对环境友好.     

HClO4-GIC的制备及其柔性石墨的性能

以天然鳞片石墨、高氯酸、硝酸为原料，采用化学法经插层、水洗、干燥、膨化等工艺过程制备膨胀石墨；以石墨蠕虫的膨胀体积为判据，采用正交实验方法确定工艺参数对石墨蠕虫膨胀体积的影响大小：探讨了反应温度、时间、膨化温度，GIC的挥发分对膨胀体积的影响；利用XRD表征了天然鳞片石墨、酸化石墨、柔性石墨的微观结构；利用EDS确定了插入物为HClO4；并对制备的柔性石墨的力学、电／热性能进行了测试。结果表明：工艺参数影响大小依次为反应温度、高氯酸／硝酸间的配比及反应时间、鳞片石墨／高氯酸间的配比。在较宽的温度范围内（室温～100℃），可容易地制备出GIC，且能在低温200℃下膨化。以最佳工艺条件：鳞片石墨：高氯酸：硝酸=1：4：0．15（质量比）制备的GIC，在200℃下膨化，可以制备出膨胀体积达360mL/g的膨胀石墨；在高温900℃下膨化，可以制备出膨胀体积达540mL/g的高倍膨胀石墨。石墨蠕虫经压制成型制备的柔性石墨的抗拉强度、电阻率同其表观体积密度存在密切的相关性，密度增加，抗拉强度增加，电阻率下降；其电阻率与导热率间也存在密切的相关性，电阻率下降，导热率提高，且其导热率高于同电阻率的人造炭／石墨材料的导热率。     

三元乙丙橡胶/膨胀石墨复合材料的制备及其性能研究

为寻求密封性能优异的新型橡胶密封材料,借助微波技术、超声波技术以及相容性改进技术,采用熔融插层复合方法制备三元乙丙橡胶/膨胀石墨(EPDM/EG)复合材料,利用扫描电镜、X射线衍射、红外光谱等分析EG及其复合材料的微观结构,并初步研究复合材料气体阻隔性能与相关力学性能.研究表明:通过EPDM与EG的熔融插层复合,聚合物分子插入石墨片层间隙形成插层型复合材料,其气体阻隔性能显著提高,相关力学性能得以改善.     

再次插入法制备超大膨胀体积石墨层间化合物(英文)

为进一步增大膨胀石墨的膨胀体积,用二次插入的方法制备了石墨层间化合物。首先用化学氧化法制备了膨胀体积为250mL/g的可膨胀石墨,然后以膨胀体积为250mL/g的可膨胀石墨为原料,用二次插入的方法制备了膨胀体积为380mL/g的膨胀石墨。讨论了各种反应物比率、反应温度和反应时间对膨胀体积的影响。对制得的膨胀石墨进行了各种表征,XRD谱显示产物保持了天然石墨的层状晶体结构,但是产物的石墨层间距离增大。扫描电镜照片显示通过二次插入石墨层间确实被进一步打开。结果显示这种新的制备方法是可行的,它为纳米石墨材料的研究提供了新的思路。     

NanoG/BMI纳米减摩复合材料的制备及其性能

利用扫描电子显微镜(SEM)和X射线衍射(XRD)手段研究纳米石墨薄片(NanoG)制备条件对层间结构与润滑性能影响,首次以NanoG为润滑剂制备的NanoG/BMI纳米减摩复合材料,研究其减摩性能和耐热性能及力学性能.研究表明:NanoG主要是由具有石墨的标准002特征峰的多层碳-碳六方平面结构的“亚结构单元“构成,其润滑性能主要是由于这些多层“亚结构单元“之间易相对滑动的结果;3%～5%NanoG或NanoG MoS2制备的NanoG/BMI或NanoG MoS2/BMI纳米减摩复合材料减摩性能优于20%石墨粉制备的传统减摩复合材料或与其相当,而前者的力学性能远优于后者,且均具有较好的耐热性能.     

超声波和修饰剂及预聚体对石墨层间结构的影响

利用X射线衍射(XRD)、扫描电镜(SEM)和傅立叶红外光谱仪(FT-IR)研究修饰剂、超声波和双马来酰亚胺(BMI)预聚体对纳米石墨薄片的石墨层间结构的影响,结果表明:超声波对膨胀石墨层间距结构的影响,因石墨层间距大小而不同,且超声波并没有破坏膨胀石墨的层状结构;修饰剂和双马来酰亚胺的预聚体可插入纳米石墨薄片中层间距较大的层间,但此层间距的石墨薄片较少,因此插入量也较少,可认为修饰剂或树脂的"插层"主要是插入纳米石墨薄片的网状孔隙内部.     

Surface modified graphite nanosheets used as adsorbent to remove 1,2-dichlorobenzene from water

The surface of graphite nanosheets (GNs) prepared by wet ball milling from expanded graphite (EG) was surface modified during the preparation process. The SEM images shown were employed to analyze the morphology of surface modified graphite nanosheets. The XPS date and Raman spectroscopy show that the milling process gives graphene surface more defects and phenolic groups compared to that of expanded graphite and graphite nanosheets. It was found that after ball milling, the surface modified GNs can be used as an effective adsorbent to remove 1,2-dichlorobenzene from water. Their adsorption capacity reaches 28.3 mg/g, which is comparable to that of carbon nanotubes (CNTs).     

石墨烯/碳纳米管复合粉体制备工艺的研究

研究了利用膨化石墨制备石墨烯/碳纳米管复合粉体技术。以膨胀石墨为基体,利用硝酸铁、碳酸铵等对其进行修饰,结合化学气相沉积工艺,原位制备出石墨烯/碳纳米管复合粉体材料;研究了不同的修饰液相、不同沉积工艺对复合粉体比例、微观形貌的影响。利用扫描电镜对复合粉体进行了表征。结果表明,实现了石墨烯/碳纳米管复合粉体材料的批量制备;其中石墨烯为透明薄片,其厚度最小可达到10nm;通过控制工艺参数,可以实现碳纳米管/石墨烯的质量比在0.625～8.250之间变化;并初步获得了最佳修饰液相和最佳工艺。研究结果表明该方法可以制备出性能优异的石墨烯/碳纳米管复合粉体材料。     

Production of graphene layer by liquid-phase exfoliation with low sonication power and sonication time from synthesized expanded graphite

Multi-layer graphene was produced through synthesized expanded graphite (EG) liquid exfoliation using organic solvent. Hexagonal graphite (HG) was used as a starting material. HG was mixed with an acidic mixture, dried, rand subjected to thermal treatment. After this process, EG was obtained. This obtained EG was sonicated for 1 h via an ultrasonic homogenizer by blending an organic solvent. Samples were subjected to SEM, TEM, FTIR, and UV-Vis/NIR spectroscopy investigations. After the investigations, it was shown that nano-size graphene sheets were obtained.     

High conductivity and low percolation threshold in polyaniline/graphite nanosheets composites

An easy process for the synthesis of polyaniline/graphite nanosheets (PANI/NanoG) composites was developed. NanoG were prepared by treating the expanded graphite with sonication in aqueous alcohol solution. Scanning electron microscopy (SEM), X-ray diffraction techniques (XRD), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) were used to characterize the structures of NanoG and PANI/NanoG conducting composites. Electrical conductivity measurements indicated that the percolation threshold of PANI/NanoG composites at room temperature was as low as 0.32 vol.% and the conductivity of PANI/NanoG composites was 420 S/cm. The percolation theory, mean-field theory, and excluded volume theory were applied to interpret the conducting properties. Results showed that the low value of percolation threshold may be mainly attributed to nanoscale structure of NanoG forming conducting bridge in PANI matrix and there exists contact resistance in the percolation network formed within PANI/NanoG composites.     

Large reversible Li storage of graphene nanosheet families for use in rechargeable lithium ion batteries

The lithium storage properties of graphene nanosheet (GNS) materials as high capacity anode materials for rechargeable lithium secondary batteries (LIB) were investigated. Graphite is a practical anode material used for LIB, because of its capability for reversible lithium ion intercalation in the layered crystals, and the structural similarities of GNS to graphite may provide another type of intercalation anode compound. While the accommodation of lithium in these layered compounds is influenced by the layer spacing between the graphene nanosheets, control of the intergraphene sheet distance through interacting molecules such as carbon nanotubes (CNT) or fullerenes (C60) might be crucial for enhancement of the storage capacity. The specific capacity of GNS was found to be 540 mAh/g, which is much larger than that of graphite, and this was increased up to 730 mAh/g and 784 mAh/g, respectively, by the incorporation of macromolecules of CNT and C60 to the GNS.     

膨胀石墨的形貌结构与表面功能基团的XPS研究

膨胀石墨的孔结构和表面化学组成对其物化性能有着很大影响,利用扫描电镜（SEM）和X射线光电子能谱（XPS）对550～920℃制备的膨胀石墨形态结构和表面功能基团进行了表征,结果表明：在蠕虫状的膨胀石墨粒子表面和内部存在大量的网状孔洞,这些网络状孔洞是由10～50nm厚的石墨片叠合而成的平行塌陷片层构成;膨胀石墨表面化学组成以C、O元素为主,其它元素含量较低,其表面存在有-C=O、-C-O和-O-O-（过氧基团）等功能基团.     

石蜡/膨胀石墨复合相变储热材材料的性能研究

以石蜡为相变材料、膨胀石墨为支撑结构,利用膨胀石墨的多孔吸附特性,制备出了石蜡含量90%(质量分数)的石蜡/膨胀石墨复合相变储热材料.采用扫描电镜(SEM)、偏光显微镜(PM)、X射线衍射(XRD)及差示扫描量热分析(DSC)对复合相变储热材料的结构和性能进行了表征.结果表明,膨胀石墨吸附石蜡后仍然保持了原来疏松多孔的蠕虫状形态,石蜡被膨胀石墨微孔所吸附,在石蜡质量含量为90%时仍保持定型特性;复合相变储热材料没有形成新物质,其相变温度与石蜡相似,相变焓与基于复合材料中石蜡含量的相变焓计算值相当.     

Deformation and fracture in graphene nanosheets

Graphene nanosheets (GNSs) are flake-like materials composed of few-layer graphene sheets. GNSs are similar to multi-walled carbon nanotubes (CNTs) in graphene structures and in layer numbers. However, GNSs and CNTs behave very differently in deformation and fracture. In this study, natural graphite flakes were employed to make expanded graphite (EG), which is composed of partially connected GNSs. Both sonication and three-roll milling were used to separate the GNSs and to disperse them into an epoxy resin. By compacting EG, the GNSs inside were compressed and deformed. By breaking the GNS/epoxy composite, most GNSs on the cracked surfaces were fractured. Both SEM and TEM have been used for microscopic observations. The micrographs revealed that folding and wrinkling are the major modes of deformation, while tearing and peeling are the dominant modes of fracture. These modes are virtually non-existent in CNTs. The factors to cause the different behavior are discussed.