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利用X射线衍射对鳞片石墨、可膨胀石墨、膨胀石墨和纳米石墨薄片以及石墨 /双马来酰亚胺、纳米石墨薄片 /双马来酰亚胺减摩复合材料进行了研究,探讨它们之间在结构上的关系以及以复合材料中双马来酰亚胺预聚体对石墨层间距的影响.实验结果表明:可膨胀石墨中插层剂的插入除了增大石墨层间距外,还减小相邻插层剂未插入的石墨层间距;膨胀石墨的结构除了保留强度很弱的石墨特征峰外,还有大量强度极其微弱、层间距大小不一的峰;超声波对膨胀石墨的结构有整合、均匀化作用;双马来酰亚胺预聚体不能插入鳞片石墨层间,而能插入纳米石墨薄片的层间. 相似文献
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A facile process for the synthesis of exfoliated graphite and polyaniline/graphite (PANI/graphite) nanocomposite was developed. Graphite nanosheets were prepared via the microwave irradiation and sonication from synthesized expandable graphite. The nanocomposites were fabricated via in situ polymerization of aniline monomer in the presence of graphite nanosheets. The nanoscale dispersion of graphite sheets was evidenced by the SEM and TEM examinations. According to the electrical conductivity test, the conductivity of the final PANI/graphite nanocomposites were dramatically increased compared with pristine PANI. From the thermogravimetric analysis, the introduction of graphite exhibits a beneficial effect on the thermal stability of PANI. 相似文献
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A new method for the synthesis of exfoliated graphite and polyaniline (PANI)/graphite nanocomposites was developed. Exfoliated graphite nanosheets were prepared through the microwave irradiation and sonication of synthesized expandable graphite. The nanocomposites were fabricated via the in situ polymerization of the monomer at the presence of graphite nanosheets. The as-synthesized graphite nanosheets and PANI/graphite nanocomposite materials were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis (TGA). The conductivity of the PANI/graphite nanocomposites was dramatically increased over that of pure PANI. TGA indicated that the incorporation of graphite greatly improved the thermal stability of PANI. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1972–1978, 2004 相似文献
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Insertion of sheet-type platinum particles (platinum nanosheets) between graphite layers was achieved by a thermal treatment of a mixture of platinum chloride (IV) and graphite powder (natural graphite or artificial graphite) under 0.3 MPa of chlorine at 723 K, followed by the treatment under 40 kPa of hydrogen pressure. Similar platinum nanosheets, which were 1–3 nm in thickness and 100–500 nm in width and had a number of hexagonal holes and edges with 120° angle, were formed between the layers of both natural graphite or artificial graphite; however, their location in the graphite layers depended on the type of graphite used. A number of platinum nanosheets were observed in the edge region of natural graphite particles which have flat surface. On the other hand, a number of platinum nanosheets were found inside and away from the edge of the artificial graphite particles especially in the vicinity of the cracks. Both the platinum nanosheet-containing artificial and natural graphite samples showed high selectivity to cinnamyl alcohol in cinnamaldehyde hydrogenation under supercritical carbon dioxide conditions, while spherical platinum particles, which were located on the surface of natural and artificial graphite, showed lower selectivity. 相似文献
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Effects of traces of water on the graphite anode reaction have been investigated in the KF2HF melt at 100 °C. Cyclic voltammetry shows that with increasing water content from 0.01% to 0.05%, anode potentials for the formation of graphite oxide and graphite fluoride films on graphite electrodes are shifted to lower potentials. This may be ascribed to increase in the reaction of discharged oxygen with graphite and the subsequent decomposition of graphite oxide film by attack of discharged fluorine, which gives ultimately graphite fluoride film on a graphite electrode. When the water content is 0.05 %, the anode effect is thus caused in a short time by graphite fluoride film with a low surface energy. However, when it is 0.01-0.02%, a stage 4 intercalation compound of graphite, Cn+HF2- was prepared. Addition of 3-6 wt% LiF to the melt gave a stage 3 CXF(HF)y without occurrence of anode effect. 相似文献
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Graphite is the most widely used anode material for lithium ion batteries (LIBs). However, the performance of graphite is limited by its slow charging rates. In this work, porous graphite was successfully prepared by nickel-catalyzed gasification. The existence of the pores and channels in graphite particles can greatly increase the number of sites for Li-ion intercalation-deintercalation in graphite lattice and reduce the Li-ion diffusion distance, which can greatly facilitate the rapid diffusion of lithium ions; meanwhile, the pores and channels can act as buffers for the volume change of the graphite in charging-discharging processes. As a result, the prepared graphite with pores and channels exhibits excellent cycling stability at high rate as anode materials for LIBs. The porous graphite offers better cycling performance than pristine graphite, retaining 81.4 % of its initial reversible capacity after 1500 cycles at 5 C rates. The effective synthesis strategy might open new avenues for the design of high-performance graphite materials. The porous graphite anode material is proposed in applications of high rate charging Li-ion batteries for electric vehicles. 相似文献
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以可膨化石墨为原料,高温处理得到膨化石墨,再经过超声处理,得到纳米薄片石墨。将得到的纳米薄片石墨与甲基丙烯酸甲酯单体在超声作用下预聚,灌模,得到块状的聚甲基丙烯酸甲酯(PMMA)/石墨复合材料。用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、选区电子衍射SAD、红外、热重等分析仪器表征了纳米石墨薄片及PMMA/石墨复合材料。测试了复合材料的力学、电学性能,发现在室温下该复合材料的渗滤阀值为1.3%(wt),且保证石墨含量在1.4%(wt)时,即可保证复合材料具有良好的电学和力学性能。 相似文献
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Ali Eftekhari Bahareh Yazdani 《Journal of polymer science. Part A, Polymer chemistry》2010,48(10):2204-2213
Because of its special chemical composition, graphite oxide has peculiar influences on electrochemical processes. The existence of various functional groups significantly affects electropolymerization processes and the formation of conductive polymers. Electrochemical synthesis of polyaniline (as a prototype of conductive polymers) on a paste‐based substrate of graphite oxide was investigated. In this case, the electropolymerization is significantly different from conventional cases, and the polymer is generated just during the first potential cycle. This can be attributed to the fact that graphite oxide can assist the monomer oxidation. Alternatively, electropolymerization was successfully performed inside the graphite oxide layers via electrochemical treatment of aniline‐intercalated graphite oxide in the supporting electrolyte. Although these phenomena are related to the chemical composition of graphite oxide, the graphite prepared by the reduction of graphite oxide also displayed some advantages for the electropolymerization (over natural graphite). There is an emphasis on the morphological investigations throughout this study, because novel morphologies were observed in the system under investigation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2204–2213, 2010 相似文献
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Models, mechanisms, and criteria of formation of protective coatings on graphite by a microspark oxidation method (MSO) are considered. It is established that a prerequisite for the graphite MSO is the deposition of a barrier film of a valve metal oxide at the graphite surface. Optimum regimes of the graphite MSO in aqueous solutions of sodium aluminate are determined. Protective coatings on graphite comprising α-phase aluminum oxide are obtained. It is concluded that the graphite MSO should be viewed as a version of MSO of metals, which involves the electrochemical deposition (at high voltages that cause the anode to microspark) of oxide films consisting of electrolyte components on graphite, as opposed to a version of MSO of metals, which involves the formation of an anodic film consisting of electrolyte components and the intrinsic oxide. 相似文献
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Improved polyvinylpyrrolidone (PVP)/graphite nanocomposites by solution compounding and spray drying
In order to evaluate the roles of graphite dispersion on the functional properties of the composites, PVP/graphite nanocomposites were prepared by blending the aqueous suspension of expanded graphite sheets and polyvinylpyrrolidone (PVP) aqueous solution by ultrasonic treatment, followed by spray drying and direct drying as a comparison individually. The effects of graphite loading and drying method on the dispersion of graphite and the resultant properties of the composites such as electrical and thermal conductivity, friction, and dynamic mechanical properties were studied. The results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X‐ray diffraction showed that the composites prepared by fast spray drying exhibited a higher degree of exfoliation and a better dispersion of graphite sheets in the PVP matrix than the corresponding composites prepared by direct drying, leading to a conclusion that fast spray drying can effectively prevent from re‐stacking of the exfoliated graphite sheets as illustrated. As a result, dynamic mechanical thermal analysis showed significant increases in the storage modulus and glass transition temperature for the composites prepared by spray drying. Besides, the spray drying as well greatly improved the electrical and thermal conductivity of the composites. It was also found that the electrical and thermal conductivity of the composites strongly depended on the graphite dispersion, while the friction coefficient unexpectedly does not. Increasing graphite loading level might enhance the probability of graphite sheets re‐stacking, resulting in poor graphite dispersion. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Keun-il Kim Qiubo Guo Longteng Tang Liangdong Zhu Changqing Pan Prof. Chih-hung Chang Joshua Razink Prof. Michael M. Lerner Prof. Chong Fang Prof. Xiulei Ji 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):20096-20100
Oxidative anion insertion into graphite in an aqueous environment represents a significant challenge in the construction of aqueous dual-ion batteries. In dilute aqueous electrolytes, the oxygen evolution reaction (OER) dominates the anodic current before anions can be inserted into the graphite gallery. Herein, we report that the reversible insertion of Mg-Cl superhalides in graphite delivers a record-high reversible capacity of 150 mAh g−1 from an aqueous deep eutectic solvent comprising magnesium chloride and choline chloride. The insertion of Mg-Cl superhalides in graphite does not form staged graphite intercalation compounds; instead, the insertion of Mg-Cl superhalides makes the graphite partially turbostratic. 相似文献
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高温气冷堆燃料元件的基体石墨是一种多孔复合材料,是燃料元件的主要组成部分,其结构影响燃料元件的性能和裂变产物在燃料元件中的扩散。 本文利用压汞法表征基体石墨的孔隙结构,并讨论了基体石墨制备工艺中最大压制压强与热处理过程对孔隙结构的影响。 结果表明,基体石墨大孔孔径分布为6001900 nm,高温热处理使基体石墨的总孔隙率、中值孔径、大孔孔容均减小;基体石墨热处理样品的大孔孔容随最大压制压强的增加而呈线性减少,热处理过程单质Ag在石墨基体中的扩散速度与大孔孔容变化具有正相关性。 相似文献
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粒度对石墨负极材料嵌锂性能的影响 总被引:2,自引:0,他引:2
研究了不同粒径(13~80 μm)石墨材料作为锂离子电池负极材料的嵌锂性能.结果表明,石墨粒度大小对嵌锂性能有明显影响,石墨的不可逆容量随着粒径的减小而逐渐增大,当粒径从80 μm减小到13 μm时,其不可逆容量增大了10%.而对可逆容量来说,随着粒径的减小,可逆容量逐渐增大;当粒径减小到20 μm时,可逆容量达到最大;再进一步减小石墨颗粒的粒径,可逆容量则随之减小.这表明石墨颗粒过大或过小都不利于锂离子的可逆脱嵌,只有合适的粒度才能最大限度地可逆脱嵌锂离子.根据不同粒度石墨的比表面的变化趋势,阐述了嵌锂性能随粒度变化的原因. 相似文献
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Electrochemical investigation of lithium intercalation into graphite from molten lithium chloride 总被引:1,自引:0,他引:1
Qian Xu Carsten Schwandt George Z. Chen Derek J. Fray 《Journal of Electroanalytical Chemistry》2002,530(1-2)
Lithium reduction at a graphite electrode in molten lithium chloride was studied at temperatures from 650 to 900 °C using cyclic voltammetry and chronoamperometry. It was found that, during cathodic polarization, lithium intercalation into graphite occurred before deposition of metallic lithium started. This process was confirmed to be rate-controlled by the diffusion of lithium in the graphite. When the cathodic polarization potential was more negative than that for metallic lithium deposition, exfoliation of graphite particles from the electrode surface was observed. This was caused by fast and excessive accumulation of lithium intercalated into the graphite, which produced mechanical stress too high for the graphite matrix to accommodate. The erosion process was abated once the graphite surface was covered by a continuous layer of liquid lithium. These results are of relevance to the mechanism of carbon nanotube and nanoparticle formation by electrochemical synthesis in molten lithium chloride. 相似文献
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Graphite fluoride is classified into (C2F)n and (CF)n types from the structure and composition. Both compounds have such unique physicochemical properties as low surface energy, solid lubricating characteristics, and oxidizing ability. However, a long reaction time is required to completely fluorinate graphite and moreover, the decomposition reaction of the product causes the lowering of the yields.In this paper, the effect of the pretreatments of the starting material on the fluorination will be reported on the following methods.1) Fluorination of Exfoliated Graphite Obtained by Heat-treatment of Graphite Lamellar Compound.The exfoliated graphite was obtained by the immersion of graphite into the mixed solution of sulfuric acid and hydrogen peroxide and subsequent heat-treatment. It has both much large surface area and larger lattice strain than that of the original graphite.The exfoliated graphite was much faster fluorinated than the original graphite. The dissociation of fluorine molecules to atoms was found to be a rate-determining step in the formation of graphite fluoride from the exfoliated graphite, whereas the process of diffusion of fluorine molecules was the rate-determining step in the fluorination of the original graphite.2) Fluorination of Residual Carbon Formed upon Pyrolysis of Graphite Fluoride.Graphite fluoride decomposes to carbon and some perfluorocarbons of low molecular weight at high temperature above 600 °C. The residual carbon was amorphous in analogy with petroleum coke or carbon black, but had smaller interlayer spacing and larger specific surface area due to its microporous structure than these amorphous carbonsThe rate of the direct fluorination of residual carbon at a room temperature was comparable to that of active carbon, and the graphite fluoride obtained from the residual carbon has a similar high thermostability to that of graphite fluoride obtained from graphite at a high temperature under an atmosphere of fluorine gas. Upon direct fluorination of the residual carbon a more crystalline graphite fluoride was obtained even at a low temperature than the case of petroleum coke and carbon black. It is interesting that the fluorination of the residual carbon leads to the formation of crystalline graphite fluoride in high yield. 相似文献
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