Formation Of Graphite Structure Research Articles

A comparative study of structural properties of oleic acid coated metal nanoparticles (Co, Ni, Fe) by co-precipitation method

Metal nanoparticles of cobalt, nickel and iron were synthesized by chemical co-precipitation method using Sodium Borohydride as the reducing agent. The metallic particles were coated with oleic acid to prevent the formation of oxides on the surface layers. The structural analysis of both coated and uncoated samples were carried out using XRD technique and FTIR spectroscopy. XRD patterns of the uncoated samples showed the significant presence of oxide phases of the metallic nanoparticles while in the case of coated samples, the metallic phase was observed. A significant observation from the XRD patterns of the coated samples was the presence of a broad peak centred at 20–210 which is indicative of the graphitic structures typically observed as (002) reflections of graphite. However, the broadened peak depicted the formation of layered graphitic structures of Graphene/ nano tubes/fullerene/ nano onions. The stretching vibration of C = O and symmetric stretching vibrations of the –COO–functional group in the FTIR spectrum, indicated that the layer of oleic acid was successfully coated on the surface of MNPs. The graphitic structures of all oleic acid coated metal nanoparticles were confirmed by Raman spectroscopy. The formation of graphitic structure was the result of the catalytic action of metal nanoparticles..

Ionic liquid-induced low temperature graphitization of cellulose-derived biochar for high performance sodium storage

Abstract The graphitization of biochar by high temperature carbonization above 2000 °C or metal-based catalytic approaches posed specific hindrances to the industrial production of high-quality graphitic carbon from biomass. The use of imidazolium-based ionic liquids (ILs) to induce fast graphitization of biochar at a low temperature range has not yet been reported. In this work, the carbonization of microcrystalline cellulose and 1-butyl-3-methylimidazolium acetate (BMIMAcO) at the temperature range of 750 °C–1400 °C led to enhanced graphitization of the biochar in comparison with the carbonization of microcrystalline cellulose alone. The incorporation of intact imidazolium rings into carbon skeleton played a critical role in the formation of graphitic structure with high nitrogen content. The IL-induced cellulose carbon obtained at 1000 °C (ICC-1000) with 5.67 at.% of nitrogen-doping presented interconnected graphitic nanosheets with 0.488 nm interlayer spacing and abundant mesopores and macropores on the surface. When used as anodes of sodium-ion batteries (SIBs), the ICC-1000 exhibited stable reversible capacity around 391 mAh g−1 at 100 mA g−1 for 100 cycles and 136 mAh g−1 at 500 mA g−1 for 1000 cycles, showing satisfactory sodium storage performance. Kinetic analysis of Na+ storage revealed that the ICC-1000 showed obvious capacitive characteristics and improved electric conductivity. DFT calculations suggested an interlayer spacing of 4.9 A for optimal Na+ intercalation in multilayer graphene, and the capacity of pristine multilayer graphene was greatly improved from 69.8 to 527.3 mAh g−1 after 4.8 at.% of N-doping.

Partially graphitic nanoporous activated carbon prepared from biomass for supercapacitor application

In this present work, the preparation of partially graphitic nanoporous carbon from biomass (bamboo bagasse) is carried out using potassium ferrocyanide and -KOH as activating agent with controlled temperature and gas flow rates. The physico-chemical properties of biomass-derived graphitic nano-porous carbon were characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red Spectroscopy (FTIR), Thermal Gravimetric Analysis (TGA), Raman spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and electrochemical measurements. It is interesting that the activation with the iron salts plays a significant role in the formation of graphitic structures. The graphitic nanoporous carbonaceous materials show high specific surface area of 1360 m2 g−1, low impedance, large pore volume and high specific capacitance. Thus, the iron-catalyzed graphitic carbon is excellent candidate for the supercapacitor applications. This contemporary- novel method to synthesis of nanoporous carbon represents a great potential for apparent and diversified applications in energy storage materials.

Optimum stabilization processing parameters for polyacrylonitrile-based carbon nanofibers and their difference with carbon (micro) fibers

Carbon nanofiber webs have high electrical and thermal conductivity, porosity and surface area, etc. making them favorable in many applications. In this paper, three types of polyacrylonitrile (PAN) copolymers are electrospun (average diameter of 150–500 nm) and carbon nanofibers are produced (average diameter of 110–300 nm). The effects of chemical composition and processing parameters on the formation of graphitic structure, morphology and electrical conductivity of the carbon nanofibers are studied. Unlike carbon fibers in micro scale, using PAN without acidic comonomers is suitable for production of carbon nanofibers. Common processing parameters for stabilization of PAN microfibers are not applicable to PAN nanofibers. Nanofibers stabilized using common microfibers procedure cannot tolerate high carbonization temperatures. While, thermal stabilization at higher temperature (300 °C) results in proper stabilized structure with ability to tolerate carbonization conditions. Progress of stabilization reactions higher than 98% is inappropriate for obtaining electrically conductive nanofiber webs, whereas 85–90% progress is considered adequate for development of proper structure during carbonization to obtain optimum electrical conductivity. Formation of nanofiber mats in shape of an interconnected sponge-like structure is believed to be necessary for obtaining much higher electrical conductivity (17–26 S/cm compared to 1–8 S/cm). Reducing fiber diameter from micro to nanoscale, the effect of processing parameters as well as the rate of thermochemical reactions can be different.

Magnetism of FePt Nanoclusters in Polyimide

FePt nanoclusters have been implanted onto polyimide films and subjected to thermal annealing in order to obtain a special magnetic phase (L10) dispersed within the polymer. SQUID measurements quantified the magnetic features of the as-prepared and annealed hybrid films. As-implanted FePt nanoparticles in polyimide films exhibited a blocking temperature of 70 ± 5 K. Thermal annealing in zero and 10 kOe applied magnetic field increased the magnetic anisotropy and coercivity of the samples. Wide Angle X-Ray Scattering confirmed the presence of FePt and L10phase. All samples (as deposited and annealed) exhibited electron spin resonance spectra consisting of two overlapping lines. The broad line was a ferromagnetic resonance originating from FePt nanoparticles. Its angular dependence indicated the magnetic anisotropy of FePt nanoparticles. SEM micrographs suggest a negligible coalescence of FePt nanoparticles, supporting that the enhancement of the magnetic properties is a consequence of the improvement of the L10structure. The narrow ESR line was assigned to nonmagnetic (paramagnetic) impurities within the samples consistent with graphite-like structures generated by the local degradation of the polymer during implantation and annealing. Raman spectroscopy confirmed the formation of graphitic structures in annealed KHN and in KHN-FePt.

Mechanical and tribological properties of hot-pressed electrospun MWCNTs/carbon nanofibril composite fabrics

Mechanical and tribological properties of electrospun fiber fabrics are of paramount importance to their utility as components in a large number of applications. Post-spin heat treatment assisted with static pressure has been used to enhance the properties of electrospun fabrics and to activate its high surface energy. High-resolution transmission electron microscopy (HRTEM) showed a formation of graphitic structure of 9.5-nm crystallite sizes that has been calculated from Raman breathing modes. Hot-pressed multi-walled carbon nanotubes (MWCNTs)/carbon fabric with 130 ± 32-nm fibril diameters showed an outstanding flexibility and strength. Also, adding MWCNTs enhanced the fabric tensile strength (from 40 to 60 MPa) and lowered the fabric coefficient of friction (COF) (from 1.70 to 0.15) and its abrasive mass loss (0.2 mg has been achieved). The hot-pressed electrospun MWCNTs/carbon nanofibril composite fabrics can be considered as a good candidate, by controlling fabric MWCNT weight percent, for both journal bearing (COF below 0.4) and brake pad (COF from 0.4 to 0.7) applications.

Graphitized carbon from wastepaper as electrodes for high-performance electric double-layer capacitors

Graphitized carbon electrode material was prepared from wastepaper by graphitization in molten sodium metal. X-ray diffraction and Raman spectroscopy were used to investigate the structural change of resulted carbons, both of which well proved the formation of graphite structure. Graphitized carbons have surface area that is nearly 26 times larger than initial carbonized paper and exhibit better electrochemical performances. The electrochemical performances of graphitized carbons were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge methods. The cyclic voltammetry results show a maximum specific capacitance of 194 F g−1. Therefore, wastepaper can be a promising electrode material for high-performance electric double-layer capacitors (EDLCs).

Preparation, Characterization and Microwave Absorption Properties of Nano/Micro Carbon Fiber

Carbon fiber with diameter in the range of nano to micro meter was prepared by carbonization of polyacrylonitrile (PAN) and polymethylmethacrylate (PMMA) blend fiber which was produced via wet spinning of PAN/PMMA blend solution. At the same technical condition, the high molecular of PAN favored the production of thin diameter of carbon fiber, and the high drawing ratio led to small diameter of the obtained nano/micro carbon fiber. The formation of graphite structure during carbonization was characterized by Raman and X-ray diffraction. The results improved that high temperature of carbonization developed high degree of graphitization and high conductivity of the nano/micro carbon fiber. The composites containing 2-8wt% of the obtained nano/micro carbon fiber were fabricated. The complex permittivity ε’ and ε’ for the composites in the frequency range of 8-12 GHz was measured, and the reflection loss for 180×180×3mm3 composites was also investigated. The microwave absorption property of these composites was improved greatly with increasing content of the nano/micro carbon fibers. At the addition of 8 wt% of the nano/micro carbon fiber, the reflection loss of the composite displayed -16dB at 11.3GHz, and the band with smaller than -5dB was 3GHz. Moreover, the calculated results based on the complex permittivity seem identical with the experimental values.

Formation of Graphitic Structures in Cobalt- and Nickel-Doped Carbon Aerogels

We have prepared carbon aerogels (CAs) doped with cobalt or nickel through sol-gel polymerization of formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by ion exchange with M(NO3)2 (where M = Co2+ or Ni2+), supercritical drying with liquid CO2, and carbonization at temperatures between 400 and 1050 degrees C under a N2 atmosphere. The nanostructures of these metal-doped carbon aerogels were characterized by elemental analysis, nitrogen adsorption, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Metallic nickel and cobalt nanoparticles are generated during the carbonization process at about 400 and 450 degrees C, respectively, forming nanoparticles that are approximately 4 nm in diameter. The sizes and size dispersion of the metal particles increase with increasing carbonization temperatures for both materials. The carbon frameworks of the Ni- and Co-doped aerogels carbonized below 600 degrees C mainly consist of interconnected carbon particles with a size of 15-30 nm. When the samples are pyrolyzed at 1050 degrees C, the growth of graphitic nanoribbons with different curvatures is observed in the Ni- and Co-doped carbon aerogel materials. The distance of graphite layers in the nanoribbons is approximately 0.38 nm. These metal-doped CAs retain the overall open cell structure of metal-free CAs, exhibiting high surface areas and pore diameters in the micro- and mesoporic region.

Partially Carbonized Polyimide Membranes with High Permeability for Air Separation.

Partially carbonized polyimide (CPI) membranes were prepared from a solution of 30 wt% polyamic acid in N, N-dimethylacetamide. The polymer membranes formed on an alumina support were thermally treated, involving imidization in air at 180°C and carbonization in N2 at relatively low temperature (400–500°C). The cross-sectional views of the supported CPI membranes show that the membranes consist of a top layer (thickness, 10 μm) on the support and a CPI/alumina thin layer in the support. The CPI membranes carbonized at 500°C showed high permeability for O2 of 1000–30000 barrer and permselectivity for O2/N2 of 3–6. The permeability of the CPI membranes was much higher than that of the reported polymer membranes and the carbon membranes. The pores formed under carbonization at 500°C and 400°C were effective for separating O2/N2 and CO2/CH4 mixtures, respectively. TG analysis indicated that the carbonization proceeds even at a constant temperature of 500°C. The successive generation of flexible pores before the formation of graphite structure with rigid pores seems to contribute to the higher permeability of the CPI membranes.

Formation of Graphite Structure in Carbon Crystallites

The formation of graphite structure in carbon crystallites 0.2 to 100 nm in size is examined. It is shown that the energetically favorable structure of such crystallites differs from that of graphite. The inter- atomic distances and interplanar spacing d 002 in the crystallites depend on their in-plane dimension L a . A model is proposed according to which the only mechanism of graphitization in microcrystalline carbon materials is crystallite growth.

Carbon anode materials based on copolymers of nitrogen-containing monomers with DVB

Through the measurement of electrochemical properties of carbon anodes based on copolymers of 4-VP and AN with crosslinker DVB, it is found that the introduction of crosslinker DVB can favor the enhancement of reversible capacity, and the highest can be up to 600 mAh g− 1. Measurements of Thermal gravity analysis, elemental analysis, X-ray powder diffraction, scanning electron microscopy and specific surface area indicate that the incorporation of DVB into polymer PAN can not only affect the contents of nitrogen and hydrogen, but also favor the carbonization process. In addition, it can result in improvement of the regularity of the obtained carbon structure, i.e. the formation of graphite structure, and the number of micropores is increased. By virtue of all these factors, charge capacity below and above 0.9 V enhances and charging voltages decrease with the addition amount of DVB.

Thermoelectric power of heat-treated CVD carbon fibers

We measured thermoelectric power (TEP) in the temperature range from 5 to 300 K for heat-treated carbon fibers prepared by chemical vapor deposition of cyanoacetylene on pitch-based carbon fibers. The thermoelectric power of the fiber heat-treated at 2,000°C is positive and exhibits almost monotonic temperature dependence above about 20 K. Thermoelectric power decreases with increasing heat-treatment temperature (HTT), which indicates the formation of graphite structure. TEP for fibers heat-treated over 3000°C have negative dips around 25 K that are ascribed to the phonon-drag effect. TEP for the fiber with 3300°C HTT shows an anomaly near 15 K in addition to the negative dip, suggesting the highly graphitized structure. TEP of the HNO 3-intercalated graphite fiber (HTT; 3300°C) is also measured.

Study on Formation of Graphite Structure in Chilled Zone of Camshaft Made of Cast Iron

Study on Formation of Graphite Structure in Chilled Zone of Camshaft Made of Cast Iron

Properties of graphitized pitch cokes: Influence of the precarbonization treatment of pitch on the formation of graphitic structure

X-ray analysis, an abradability test, and porosimetric measurements were used to study the effect of the original texture of pitch cokes on properties of graphitization products obtained by their thermal processing at 2100 °C. It has been established, from the interlayer spacing d 002, crystallite dimension L c , relative peak intensity I rel , and parameters of abradability, that the product F 2100 prepared from pitch coke with highly directional structure, obtained by two stage filtration of molten pitch during the pre-carbonizing treatment, was characterized by the properties most suitable for its intended purpose. Comparing them with the graphitization products of quinoline extract (QS), pitch coke from unprocessed pitch containing quinoline - insoluble (QI) substances, and of the petroleum coke, the evidence could be brought that the transition into the graphitic structure could be ‘thermally accelerated’, for the sample F 2100, by 200 to 250 K. There could be found, in all graphitized samples, a new conspicuous region of mesopores with maxima of radii of 7.5 or 22.5 nm, respectively, corresponding to slots formed during the destruction of the lamellar structure.

石炭チャーの炭酸ガスによるガス化速度に及ぼす炭種の影響

Apparent rates of CO2 gasification of chars obtained from thirteen different kinds of coals were measured at temperatures of 1073-1273 K and under pressures of 0.3-1.6 MPa by means of a high pressure TGA apparatus. Changes of the surface area and the carbon structure of the reaction residue during gasification were also measured at various char conversions from 0 to 0.90.The initial surface area of char obtained by carbonization prior to gasification was shown to depend not only on the coal nature and carbonization temperature but also on the heating rate.For all chars employed the apparent initial reaction rate increased in proportion to P0.25. During gasification the surface area of the reaction residue increased rapidly at the early stage of the reaction and then decreased after showing a maximum which was greater for lower temperatures.The instantaneous rate based on the unit surface area also changed with the conversion. For all coal chars it decreased and leveled off at a conversion less than about 0.3. In a coversion range between 0.3 and 0.8 it was almost steady and decreased again towards completion of the reaction . Though the steady rate decreased with the rank of raw coal, the activation energies were approximately the same for all chars, being 190-210 KJ/mol.The growth of (002) peak in the X-ray diffraction spectrum for some kinds of chars, which was specified as caused by graphite structure formed during reaction, corresponded well to the decrease of instantaneous rate at the final stage of the reaction. The formation of graphite structure in such a low temperature was inhibited by deashing the char before gasification.