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1.
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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Thermal
conductivity of exfoliated graphite nanocomposites 总被引:1,自引:0,他引:1
H. Fukushima L. T. Drzal B. P. Rook M. J. Rich 《Journal of Thermal Analysis and Calorimetry》2006,85(1):235-238
Since the late 1990’s, research has been reported where intercalated,
expanded, and/or exfoliated graphite nanoflakes could also be used as reinforcements
in polymer systems. The key point to utilizing graphite as a platelet nanoreinforcement
is in the ability to exfoliate graphite using Graphite Intercalated Compounds
(GICs). Natural graphite is still abundant and its cost is quite low compared
to the other nano–size carbon materials, the cost of producing graphite
nanoplatelets is expected to be ~$5/lb. This is significantly less expensive
than single wall nanotubes (SWNT) (>$45000/lb) or vapor grown carbon fiber
(VGCF) ($40–50/lb), yet the mechanical, electrical, and thermal properties
of crystalline graphite flakes are comparable to those of SWNT and VGCF. The
use of exfoliated graphite flakes (xGnP) opens up many new applications where
electromagnetic shielding, high thermal conductivity, gas barrier resistance
or low flammability are required.
A special
thermal treatment was developed to exfoliate graphite flakes for the production
of nylon and high density polypropylene nanocomposites. X-ray diffraction
(XRD), scanning electron microscopy (SEM) and transmission electron microscopy
(TEM) were used to assess the degree of exfoliation of the graphite platelets
and the morphology of the nanocomposites. The thermal conductivity of these
composites was investigated by three different methods, namely, by DSC, modified
hot wire, and halogen flash lamp methods. The addition of small amounts of
exfoliated graphite flakes showed a marked improvement in thermal and electrical
conductivity of the composites. 相似文献
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Cross-sections cut from rectangular plates injection or compression-molded from composites of isotactic polypropylene and varying amounts (up to 40 mass%) of different grades of graphite were investigated by site-resolved wide-angle X-ray scattering (WAXS), using a two-circle goniometer and a specially adapted Kratky camera, respectively. The measurements yielded detailed information about the orientation of both the filler particles and the PP crystallites, in dependence on the position in the cross-sections. In the plates molded from composites, the graphite particles are preferentially oriented with their (002) planes parallel to the surface of the plates and the α-PP crystallites prefer the same orientation for their (040) planes. In plates devoid of graphite, the PP crystallites show a different orientation behavior, however, the presence of 0.2% graphite is already sufficient to change the orientation to the afore-mentioned mode. The observed parallelism in the preferential orientation of the graphite particles and the PP matrix suggests the assumption of hetero-epitaxial growth of α-PP crystallites on the (002) surface of oriented graphite particles. According to our results, the effects of the PP-graphite interaction are dependent on the nature and properties of the graphite particles and may be modulated by treating the graphite surface with different coatings. 相似文献
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The properties, interactions, and reactions of cyclic water clusters (H(2)O)(n=1-5) on model systems for a graphite surface have been studied using pure B3LYP, dispersion-augmented density functional tight binding (DFTB-D), and integrated ONIOM(B3LYP:DFTB-D) methods. Coronene C(24)H(12) as well as polycircumcoronenes C(96)H(24) and C(216)H(36) in monolayer, bilayer, and trilayer arrangements were used as model systems to simulate ABA bulk graphite. Structures, binding energies, and vibrational frequencies of water clusters on mono- and bilayer graphite models have been calculated, and structural changes and frequency shifts due to the water cluster-graphite interactions are discussed. ONIOM(B3LYP:DFTB-D) with coronene and water in the high level and C(96)H(24) in the low level mimics the effect of extended graphite pi-conjugation on the water-graphite interaction very reasonably and suggests that water clusters only weakly interact with graphite surfaces, as suggested by the fact that water is an excellent graphite lubricant. We use the ONIOM(B3LYP:DFTB-D) method to predict rate constants for model pathways of water dissociative adsorption on graphite. Quantum chemical molecular dynamics (QM/MD) simulations of water clusters and water addition products on the C(96)H(24) graphite model are presented using the DFTB-D method. A three-stage strategy is devised for a priori investigations of high temperature corrosion processes of graphite surfaces due to interaction with water molecules and fragments. 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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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
10.
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
11.
Toshihiro Arai Yoichi Tominaga Shigeo Asai Masao Sumita 《Journal of Polymer Science.Polymer Physics》2005,43(18):2568-2577
Highly loaded graphite–polymer composites for a bipolar plate of polymer electrolyte fuel cell are studied. One of the composites contains of polypropylene (PP), and graphite powder and the other contains of poly(vinylidene fluoride) (PVDF) and the graphite, respectively. The electrical and physical properties for the composites are determined. Inverse gas chromatography (IGC) measurements are carried out to characterize the surface of the graphite and the interface between the graphite and each polymer, following the Fowkes scheme. The IGC measurements show that the surface of graphite is nucleophilic and strongly attracts electrophiles by acid–base interaction. It is considered to be reasonable that the main chain carbon atoms to which electronegative fluorine atoms bond in PVDF are nucleophilic and has strong acid–base interaction with graphite. Such strong interaction causes high electric resistivity, high flexural properties, and high melt viscosity of the composite. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2568–2577, 2005 相似文献
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Zhoutong He Can Zhang Hui Tang Ming Liu Barry J. Marsden Xingtai Zhou 《Surface and interface analysis : SIA》2021,53(1):90-99
Knowledge about the microstructure of nuclear graphite is critical to the understanding of its irradiation behavior in the reactor. Using micro X‐ray diffraction (μXRD) two‐dimensional (2D) maps, the crystallite character of IG110 and reactor pebble graphite was characterized at the submillimeter range with a spatial resolution of about 5 μm. Various structures in the nuclear graphite were identified by comparing the X‐ray diffraction peak intensity, position, and full width at half maximum (FWHM) 2D maps. The two‐peak feature of the FWHM histograms seen in pebble graphite may be related to the raw coke and natural graphite used as raw materials. With these results, it can be concluded that the μXRD 2D map is an effective method to characterize the microstructure of nuclear graphite. 相似文献
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锂离子在石墨负极材料中扩散系数的测定 总被引:5,自引:0,他引:5
锂离子电池是以各种碳材料为负极而起来的一 种新型电池,成功地解决了以 为负极瓣锂可充电电池的安全性问题,已经应用于锂离子电池的负极材料有石墨和石油焦炭,正在研究的负极材料有热解碳,石墨化碳纤维,硼炭或硼炭氮化合物以及锡基氧化物等[1],石墨的比容量要比石油焦炭的比容量高一倍左右,其理论比容量372mA.h.g^-1,但锂离子在石墨材料中的扩散系数比较低,限制了以其为负极材料的电池的大电流充放电能力,锂离子在电极材料中的扩散系数可以用多种电化学方法测量得到,主要有:电位间歇滴定方法(PITT)(Potentiostatic Intermittent Titratiobn Technique)^[2,3,4,6],恒电流间歇滴定法(GITT)(Galvanostatic Intermittent Titration Technology)^[6],电流脉冲松弛法(CPR)(Current Pulse Relaxation Method)^[3,6]和交流阻抗法(A-C Technology)^[4,5,6],GITT,CPR,A-C等方法测定锂离子扩散系数时,由于相变发生处dE/dy值不容易准确得到(相变时,dE/dy→0),此时测得的扩散系数误差比较大,PITT方法测定锂离子扩展系统,不存在这个问题,能比较准确地测定整个嵌入组成范围内的锂离子扩散系数。 相似文献
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The metnoas or rotating ring-disc electrode(RRDE) ana cyclic voltammetry were used to study the oxidation of cgsteine on heat-treated cobalt tetramethoxyphenyl porphyrin adsorbed on graphite(Co-TMPP/graphite) in solutions of various pH.Experimental results showed that Co-TMPP/graphite exhibits significant catalytic activity for cysteine oxidation in solutions with various pH.The current efficiency of cysteine oxidation on Co-TMPP/graphite in basic media is more than 90%.It was found that the kinetics of cysteine oxidation on Co-TMPP/graphite is a simple irreversible reaction controlled by rate of charge transfer.The standard rate,constants(k) of cysteine oxidation were calculated and the reaction mechanism of this reaction in solutions of various pH wes discussed. 相似文献
16.
Anionic graft polymerizations of methyl methacrylate (MMA) and styrene from graphite powder initiated by metallized aromatic rings on the surface were investigated. Metalation of the surface was achieved by the reaction of polycondensed aromatic rings of graphite withn-butyllithium (BuLi) in N,N,N,N-tetramethylethylenediamine (TMEDA) or hexamethylphosphorous triamide (HMPT) at 0 °C., Anionic polymerizations of MMA and styrene were initiated by metallized graphite, and these polymers were grafted onto the surface. The conversion and percentage of grafting increased by increasing the amount of BuLi used for metalation. When 0.20 g of graphite was treated with 0.4–0.5 mmol of BuLi in TMEDA, the percentage of grafting of PMMA and polystyrene reached the maximum value: PMMA 52.8% (PMMA/graphite =0.528 g/1.0 g) and polystyrene 37.2% (polystyrene/graphite=0.372 g/1.0 g). Grafting of polymers was also confirmed by infrared spectra. Although no metalation of graphite proceeded in toluene, graphite could be metallized even in toluene by the addition of crown ether as a complexing cation agent. The stability of graphite powder in organic solvent dispersion was found to be improved remarkably by grafting of polymer onto the surface. 相似文献
17.
Phillips J Shiina T Nemer M Lester K 《Langmuir : the ACS journal of surfaces and colloids》2006,22(23):9694-9703
It is shown that self-supporting graphitic structures of specific shape can be grown in a variety of forms, from nanoscale to macroscale, on metal templates, in a fuel-rich mixture of ethylene and oxygen at temperatures between 750 and 900 K. The evidence presented suggests graphite can be grown in any shape created from catalytic metals (e.g., Ni) under the proper conditions of temperature and gas composition. Structures produced include macroscale bodies, centimeters in dimension, composed of micrometer-scale graphite elements such as graphite "foam" and regular graphite "lattices". Nanoscale hollow graphite spheres were also produced. The production rate in the apparatus employed was roughly shown to be 1 layer/s and was steady with time over several hours. The process of producing self-supporting bodies generally produces hollow graphite structures, as the underlying metal template must be removed by acid following the completion of graphite growth. The process is believed to be possible only in an environment, such as combustion, in which a high concentration of particular radical species is present in the vicinity of the template surface. The following process is postulated: (i) a single layer of graphite is formed from gas-phase radicals by the catalytic action of the metal template, (ii) additional graphite growth is "autocatalytic" and occurs via the decomposition of radicals on the surface and the incorporation of "free" carbon atoms, or other radical fragments, into "edge sites" on the graphite surface. 相似文献
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三元脂肪酸/膨胀石墨复合相变材料的制备、包覆定形及热性能 总被引:1,自引:0,他引:1
采用癸酸、 月桂酸和棕榈酸的三元共晶混合物作为相变材料, 以膨胀石墨为基体, 通过膨胀石墨多孔结构的毛细吸附和复合涂饰剂的包覆定形, 将多元相变材料固定在膨胀石墨的孔道结构中, 制备出结构稳定、 密封性能优异、 热稳定性好和高导热的新型三元脂肪酸/膨胀石墨复合定形相变材料. 膨胀石墨具有膨胀疏松的多孔结构和良好的吸附性能; 其熔融潜热为95.6 J/g, 结晶焓为82.8 J/g, 说明其具有很好的相变蓄热特性和热循环稳定性; 材料的导热性能可增加至0.738 W/(m·K), 与脂肪酸相比得到大幅度提高. 相似文献
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A matrix modifier composed of nickel and zirconium, and a graphite tube treated with zirconium solution were proposed for the determination of boron in cobalt-based alloys by graphite furnace-atomic absorption spectrometry. The effects of this matrix modifier and the treated graphite tube were studied, and the combination of 60 mug of nickel and 20 mug of zirconium as matrix modifier, and a graphite tube soaked with 10 g 1(-1) of zirconium solution were found to give the highest analytical sensitivity. The interference effects of major components (cobalt) and eight minor components (chromium, nickel, tungsten, iron, tantalum, molybdenum, titanium, aluminium and manganese) were studied. Boron in four cobalt-based alloys was determined by graphite furnace-atomic absorption spectrometry employing the proposed matrix modifier and the treated graphite tube, without the preseparation of matrix. The relative standard deviation was 3.3% for 0.048% of boron. A characteristic mass was 500 pg. 相似文献