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1.
Exfoliated graphite (EG) was prepared from graphite intercalation compounds (GICs) synthesized electrochemically with different electricity consumption from 10.83 to 40.00 A h/kg. Effects of electricity consumption on the synthesis of GICs and of exfoliation temperature on different parameters of EG, i.e. exfoliation volume, volatile content, specific surface area and pore volume measured by mercury porosimetry, length and width of worm-like particles, and distance between neighboring balloons based on the zigzag model for worm-like particles of EG, were studied. These parameters were found to depend strongly on the electricity consumption and also on exfoliation temperature. Exfoliation volume, volatile content, specific surface area and pore volume on EG prepared at 1000 °C increased with increasing electricity consumption, but the distance between neighboring balloons was found to decrease. These results reveal marked development of pores in EG samples. Raising exfoliation temperature increased exfoliation volume, specific surface area and pore volume up to 800 °C. Above this temperature these parameters tended to be stable. 相似文献
2.
Qunwei Tang Xiaoming Sun Jihuai Wu Qinghua Li Jianming Lin 《Polymer Engineering and Science》2009,49(9):1871-1878
A novel poly(acrylic acid‐g‐gelatin)/graphite composite is synthesized by aqueous solution polymerization. Based on the electrical conductivity of graphite nanoplatelets and the absorbency of poly(acrylic acid‐g‐gelatin)/graphite, a novel conducting gel with a conductivity of 3.18 mS cm?1 is prepared. The effects of synthesis parameters on the electrical conductivity of the gels are investigated in detail. An appended network structure model of the poly(acrylic acid‐g‐gelatin)/graphite conducting gel is proposed. The conducting gel presents a high mechanical strength in cyclohexane, which is important for the gel applications. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers 相似文献
3.
Rong Xue Jiping Wang Yiming Chen Zhejian Zhang Zhichao Xiao Hongyan Xia 《Journal of the American Ceramic Society》2023,106(10):6317-6329
The appropriate carbon content is indispensable for the application of self-lubricating graphite/SiC composites. However, it is a big challenge to retain high carbon content in the reaction-formed graphite/SiC composites because of drastic consumption of carbon by violent reaction with liquid silicon. In this study, a hybrid powder constructed by graphite particles (G) and glassy carbon derived from phenolic resin (PFC) was used as carbon sources, or PFC@G for short, to reserve higher content of carbon in the reaction-formed composites. The weight ratio of phenolic resin to graphite particles was adjusted to obtain an appropriate PFC@G with dense microstructure and close-grained surface. Compared with the graphite/SiC composites only using raw graphite particles as carbon sources, the carbon content of the composites fabricated with compact and large PFC@G has obviously increased (up to 172%). In particular, the carbon content of the composites fabricated with the weight ratio = 0.8 reached a high value of 44.26 vol.%, which exhibited outstanding self-lubrication properties among the four kinds of the composites. The mechanism of reserving higher content of carbon in the graphite/SiC composites by constructing PFC@G is investigated, revealing that a continuous SiC layer formed on the surface of the larger size PFC@G and most closely packed graphite particles inside of PFC@G were insulate from liquid silicon by the layer. 相似文献
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以B型明胶为原料,戊二醛为交联剂,通过改进的两步去溶剂法制备了较小粒径(约100nm)的明胶纳米颗粒(Gelatin nanoparticles, GNPs);研究了分散体系浓度、去溶剂化试剂、交联剂用量的影响。结果表明:降低明胶在二次分散体系中的浓度,制得的GNPs的尺寸更小且分布均匀。残留的去溶剂化试剂丙酮必须去除,因为它会使GNPs分散性变差。在明胶质量浓度为8 g/L的分散液中,仅用质量分数为4.5%的戊二醛(与明胶质量比)即可制得稳定的GNPs,其粒径为50~150 nm,PDI (polydispersity index)约为0.14,Zeta电位绝对值< 30 mV。AFM和 TEM测试结果表明GNPs呈光滑球形,为边缘部分比核心更为疏松的非均质结构。 相似文献
6.
Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag+ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO3)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO3/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO3 and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO3. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM). 相似文献
7.
《Ceramics International》2020,46(6):7517-7522
In order to clarify the effect of graphite content on the corrosion behavior of MgO–C refractories immersed in MnO-rich slag, the MgO–C refractory samples bearing 5 wt%, 10 wt% and 15 wt% graphite were prepared, and exposed in the slag composed of 40 wt% CaO, 40 wt% SiO2 and 20 wt% MnO. The results show that metallic Mn particles and (Mg,Mn)O solid solution are formed at the slag/refractories interface. Whereas, no dense layer is formed by (Mg,Mn)O solid solution at the interface. The decrease in MnO content of slag is mainly attributed to the reaction with graphite to form liquid Mn. The graphite is found in the slag, and dissolved in the form of oxidation. The poor wetting limits the contact area of graphite and slag, reducing graphite oxidation and decarburized area. The graphite does not become the passage for slag to penetrate into the refractories due to the oxidation. On the contrary, the dissolution of MgO in slag is faster than graphite, thus is mainly responsible for the degradation of refractories. As a result, MnO and MgO contents change less in the slag contacted with the refractories bearing higher graphite content. 相似文献
8.
Alginate and gelatin blend fibers were prepared by spinning their solution through a viscose‐type spinneret into a coagulating bath containing aqueous CaCl2 and ethanol. The structure and properties of the blend fibers were studied with the aid of infrared spectra, scanning electron micrography, X‐ray diffraction, and thermogravimetric analysis. Mechanical properties and water‐retention properties were measured. The best values of the tensile strength and breaking elongation of blend fibers were obtained when gelatin content was 30 wt %. The water‐retention values of blend fibers increase as the amount of gelatin is raised. The structural analysis indicated that there was strong interaction and good miscibility between alginate and gelatin molecules resulted from intermolecular hydrogen bonds. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1625–1629, 2005 相似文献
9.
Yunho Lee Dowan Kim Jongchul Seo Haksoo Han Sher Bahadar Khan 《Polymer International》2013,62(9):1386-1394
Relatively high aspect ratio exfoliated graphite (EFG) particles with an average size of 7.4 µm and a nanometer sized thickness of 30–50 nm were successfully prepared by thermal treatment at 1050 °C and subsequent ultrasonication for application as a filler to improve the physical properties of eco‐friendly poly(propylene carbonate) (PPC). A series of poly(propylene carbonate)/exfoliated graphite (PPC/EFG) nanocomposite films with different EFG contents were prepared via a solution blending method. The physical properties were strongly dependent upon the chemical and morphological structures originating from the differences in EFG composition. The morphological structures, thermal properties, mechanical properties and barrier properties of the nanocomposite films were investigated as a function of the EFG content. While all of the PPC/EFG nanocomposite films exhibited good dispersion of EFG to some extent, Fourier transform infrared and SEM results revealed that solution blending did not lead to strong interactions between PPC and EFG. As a result, poor dispersion occurred in composite films with a high EFG content. By loading EFG particles, the oxygen permeabilities, moisture permeabilities and water uptake at equilibrium decreased as the EFG content increased. Compared with pure PPC, PPC/EFG nanocomposite films have enhanced molecular ordering. Specifically, the 2% PPC/EFG composite film shows greater molecular ordering than the other composite films, which results in the highest mechanical strength. In future work, the compatibility and dispersion of the PPC matrix polymer and EFG filler particles should be increased by modifying the EFG surface or introducing additives. © 2013 Society of Chemical Industry 相似文献
10.
Silicon-coated graphite particles were tested as anodes for lithium ion rechargeable batteries. The synthetic graphite particles
were first coated with silicon precursor containing solution by gas suspension spray method and then calcined at heat treatment
temperature at 500 °C under hydrogen atmosphere. The silicon-coated graphite showed high specific capacity and good cycle
performance due to the formation of amorphous silicon-carbon black composite layer on the surface of the graphite particles.
It has stable structure under repeated volume expansion and contraction. The silicon-coated graphite still has high irreversible
capacity due to the solid electrolyte interface (SEI) formation during the 1st cycle. However, the capacity loss could be
lessened to a certain level by controlling the composition of the solvent mixture in the electrolyte. 相似文献
11.
In studies of shock-induced phase transition of ordered pyrolytic graphite to a diamond-like phase, the lowest transition onset pressure was observed at 19.6 GPa. The phase transition in that case was considered to be martensitic. In the present study ordered pyrolytic graphite with voids between particles was loaded at pressures up to 15 GPa using a planar shock wave propagating along the basal plane of the graphitic crystal structure. As a result, both diamond-like carbon and diamond were observed in the postshock sample. The phase transition of graphite to diamond was assumed to occur by the release of distortional energy stored in the graphite particles, that is, diffusional-controlled reconstructive mechanism, on the basis of the data by high resolution electron microscopy together with electron energy loss spectroscopy. 相似文献
12.
A transmission electron microscopy study of garnet from diamond-grade gneisses of the Betic Cordillera (Spain) has revealed the presence of abundant, previously unrecognized, nanosized carbonaceous grains, coexisting with micrometer-sized graphite and diamond. The nanosized particles occur as multiwall nanotubes, and as polyhedral and quasi-spherical graphite + diamond nanoparticles, whereas larger graphite particles appear as rods and as tabular crystals. The topotactic relationships between graphite in nanoparticles and in micrometer-sized particles and the host garnet suggest that carbon nano- and microparticles precipitated from an originally homogeneous solid solution of carbon in the garnet. Based on orientation relationships and on experimental data it is suggested that the three main types of nanosized particles (nanospheres, polyhedral particles and nanotubes) were the precursor of the three main types of larger carbon phases (diamond, tabular and rod-shaped graphite particles, respectively). It is interpreted, as in the case of diamond-graphite nanocomposites, that diamond formation in the core of the nanoparticles is due to an increase of the cross-links between the layers, and then, to the collapse, at a certain point, of the whole graphite structure into diamond. This finding opens a new door for explaining the origin of some metamorphic diamonds and of coexisting graphite and diamond in ultrahigh pressure rocks. 相似文献
13.
《Ceramics International》2016,42(3):4470-4476
SiC/diamond coatings with excellent frictional properties were successfully prepared using graphite as substrate. Diamond particles with size of 25–38 μm were firstly bonded on graphite substrate through PVA glue, followed by chemical vapor deposition (CVD) of SiC with varied MTS flow on the diamond-coated graphite substrate to enhance the adhesion of diamond particles. The influence of the MTS flow on the SiC coatings was investigated. The results showed that polycrystalline SiC coating with good crystallinity has been obtained. With MTS flow increasing, the SiC grains feature increased surface roughness and greater sizes of the SiC crystallite resulting from the co-deposition of SiC and carbon with increased carbon containing species. Reciprocating sliding wear tests were conducted to investigate the coefficient of friction. With increasing applied load, while the low-flow specimens showed a remarkable increase in the friction coefficient resulting from degradation of the SiC coatings, the high-flow specimens maintained a relatively low friction coefficient during wear tests indicating strong holding force to diamond particles of the SiC coatings. The reason for low friction coefficient of the high-flow specimens was that GCr15 steel ball was wearing by the SiC/diamond coatings with good affinity to the substrate resulting in a flat–flat contact on the contact area. 相似文献
14.
Some preliminary studies to realize a carbonaceous electronic circuit were carried out using the liquid-dispersible thin-film particles of graphite oxide and their conductive reduction product. (1) The affinity of insulator substrates (diamond, silicon carbide, silicon, sapphire and three kinds of glass) for the particles was improved by heating and immersion in water. (2) The electric conductivity was measured for a wide wiring pattern formed by a large number of the reduced thin-film particles mounted on the substrate, and the value was 1600 S/m after heating at 500 °C. (3) To make the prototype of a narrow wiring or a micro device, the internal micro fabrication (position-selective removal) of a single particle was attempted using focused ion beam. Many kinds of patterns which contain narrow wiring having a width of 200 nm etc. were formed in the reduced thin-film particle having about 10 nm thickness. (4) The simple model calculation of anisotropic conductivity was executed for thin graphite which has a small number of layers and finite size. In the case of the fine graphitic carbonaceous devices and circuits, much attention must be paid to their sizes in all directions. 相似文献
15.
Production of VGCF fibres from the decomposition of a methane-hydrogen mixture over metal particles is influenced by the support on which the particles have been laid. It was found that different as-received commercial graphite supports, according to their impurity content, could promote or inhibit the VGCF growth.Good yields of vapour-grown carbon fibres with a length up to 6 cm have been fabricated by catalytic decomposition of methane over particles obtained from Fe3(CO)12. Addition to the substrate of small amounts of phosphorus from a solution of H3PO4 in ethanol, followed by impregnation with Fe3(CO)12, was found to be effective in promoting the growth of VGCFs and increasing the yield. But increasing the amount of phosphorus over P/Fe ∼0.25 had an inhibiting effect on the growth of VGCFs. So the yield of VGCFs was optimized for a given phosphorus concentration.These phenomena are interpreted by the formation of Fe-P compounds which, depending on their formulae, lower or increase the melting point of the catalyst particles. According to the VLS theory, catalytic growth up to a macroscopic scale results from the liquid state of the catalyst. 相似文献
16.
Natural graphite particles with a high crystallinity, which were sieved to obtain particles less than 63 μm, were ground with a ball mill under a dry atmosphere and various alcoholic vapors such as i-C3H8OH, n-C3H8OH, C2H5OH, and CH3OH. The size and flakiness of the ground products and the electrical conductivity of the films made from the ground products were experimentally examined. Grinding the particles under alcoholic vapors slowly reduced the particle size and was similar to grinding in dry air, but grinding in alcoholic vapors produced flakier products. The graphite films, which were composed of flakier particles and were ground in alcoholic vapor, displayed higher electrical conductivities than the feed graphite particles. The products ground in C2H5OH, i-C3H7O and n-C3H7OH vapors had 50% or less of the specific resistance of the feed particles. 相似文献
17.
Biological tissues are characterised by spatially distributed gradients, intricately linked with functions. It is widely accepted that ideal tissue engineered scaffolds should exhibit similar functional gradients to promote successful tissue regeneration. Focusing on bone, in previous work we proposed simple methods to obtain osteochondral functionally graded scaffolds (FGSs), starting from homogeneous suspensions of hydroxyapatite (HA) particles in gelatin solutions. With the main aim of developing an automated device to fabricate FGSs, this work is focused on designing a stirred tank to obtain homogeneous HA–gelatin suspensions. The HA particles transport within the gelatin solution was investigated through computational fluid dynamics (CFD) modelling. First, the steady-state flow field was solved for the continuous phase only. Then, it was used as a starting point for solving the multi-phase transient simulation. CFD results showed that the proposed tank geometry and setup allow for obtaining a homogeneous suspension of HA micro-particles within the gelatin solution. 相似文献
18.
The influence of carbon black content and carbon black distribution on performance of oxide-based cathodes, such as LiCoO2 and LiMn2O4, is investigated. The electronic conductivity of oxide material/carbon black composites is compared with electrochemical characteristics of the same composites. Uniformity of carbon black distribution in cathode composites is achieved using novel coating technology in cathode preparation. In this technology, the active particles are first pretreated in a gelatin solution. The adsorbed gelatin then controls the deposition of carbon black so that carbon black particles are uniformly distributed in the final composite. The influence of various parameters, such as pH of gelatin, amount of gelatin and concentration of carbon black on the uniformity of carbon black distribution is investigated. It is shown that the conventional technology of cathode preparation yields quite non-uniform distribution of carbon black in cathode material. At the end, we demonstrate that uniformity of carbon black distribution has a crucial impact on reversible capacity, especially at high current densities. 相似文献
19.
Hong‐Ji Duan Hai‐Quan Kang Wei‐Qin Zhang Xu Ji Zhong‐Ming Li Jian‐Hua Tang 《Polymer International》2014,63(1):72-83
Pulverized expandable graphite (pEG) and melamine ? formaldehyde (MF) resin core ? shell structure particles (pEG@MF) as specific flame retardants for rigid polyurethane foam (RPUF) were synthesized by encapsulating pEG particles with a layer of MF resin via in situ polycondensation. The initial feed weight ratio of pEG and MF prepolymer was found to be the key factor affecting the shell forming process, and the shell growth can be regarded as a combination of ‘raspberry‐like’ and conventional ‘core–shell’ formation mechanisms. With the encapsulation of a well formed MF shell, the expandability of pEG particles was significantly enhanced from 42 mL g–1 to 76 mL g–1 and thus the pEG@MF particles showed good flame‐retardant performance in RPUF. The RPUF/pEG@MF composites passed the V‐0 rate and the limiting oxygen index was remarkably increased from 21 to 28 vol% by adding only 10 wt% pEG@MF particles; both the expandability and available expandable graphite content played an important role in controlling the flame‐retardant performance of pEG@MF particles. With a loading of fine sized pEG@MF particles, desirable mechanical and thermal insulation properties of RPUF/pEG@MF composites were achieved by preserving the complete cell structure of RPUF and screening the high thermal conductivity of the pEG particles with the thermally inert MF resin shell. The exciting application of the novel pEG@MF particles indicates that the core–shell structure design of expandable graphite can serve as promising solution for fabricating halogen‐free flame‐retardant RPUF composites with high performance. © 2013 Society of Chemical Industry 相似文献
20.
In a previous work [Carbon (2002) in press], the densification of expanded graphite was modelled. This very light material consists of worm- or accordion-like particles in a loose packing. Worm-like particles are made up of thin disc-shaped graphite sheets, and the average disorientation angle of the thin discs was estimated based on the excluded volume concept. Then, using a simple picture of particle densification, the mosaicity of compressed expanded graphite was calculated and compared with the results of XRD experiments. In the present paper, the same model and assumptions are taken into account for predicting the surface area variations of two kinds of expanded graphite undergoing compaction. The constitutive graphite sheets are assumed to bend and to make flat contacts with their neighbours, thus decreasing the surface of the material. It is worth noting that the proposed modelization is free of any adjustable parameter. The calculations are shown to be in good agreement with experimental results obtained from krypton adsorption at liquid nitrogen temperature. 相似文献