Topology of nanometric graphite films

This work submits the results of a study in which the combinational scattering (CS) spectroscopy and electronic and optical microscopy of nanometric single-crystal graphite films obtained by precipitating in gas phase were used. It is shown the graphite material samples synthesized in this manner are fine, highly streamlined films that grow alongside of the substrate surface. The films feature a fairly smooth surface and thicknesses of 100-1 atomic layers. The study of the topologic properties of the material, such as the formation of folds along the entire surface and the occurrence of waveform ripples on some surface areas, showed that they may appear due to large differences in the carbon film and nickel substrate thermal expansion factors. The film thickness was assessed for the observed parameters of the periodic structures and the results comply with data obtained using other techniques. In some areas of the material in study, the graphene layers spontaneously split and form bubbles. The results of the CS analysis of various bubbles on studied film surfaces are evidence that, similar to the film itself, the walls of bubbles are composed of different numbers of graphite layers. It is shown that transparent bubbles in which meshlike topology is observed are formed with a single atomic layer.     

射频辉光放电等离子体辅助化学气相沉积法制备类金刚石碳膜工艺与性能表征

使用射频辉光放电等离子体辅助化学气相沉积技术（简称RFGDPECVD）在玻璃载玻片表面沉积类金刚石薄膜。用原子力显微镜（AFM）、摩擦试验仪、划痕试验机测定了其表面形貌、耐磨性及附着性。采用X射线光电子能谱（XPS）、分光光度计对两种气源（C4H10、C2H2）制备的DLC薄膜微观组成和透光率进行了检测和对比。结果表明：DLC薄膜的表面光滑、平整,表面粗糙度随沉积时间的增加单调递增;耐磨性及附着性优良;与C4H10相比使用C2H2作为碳源气体可以得到较高Sp^3含量和较低Sp^1含量的DLC膜;C2H2制备DLC薄膜的透光率低于C4H10;同一种碳源气体,反应流量比例越小,则DLC薄膜的透光性越好。     

The carbonization of granular polyaniline to produce nitrogen-containing carbon

Polyaniline (PANI) was prepared by the oxidative polymerization of aniline. The deprotonated product, a PANI base, was carbonized in an inert atmosphere at temperatures up to 800 °C for various times. The mass decreased to 40–50 wt.% at temperatures above 600 °C. The progress of molecular structure during carbonization was followed by infrared and Raman spectroscopies. The carbonization at 650 °C for 1 h is suggested for the optimum conversion of PANI to carbon. The product retained the original globular structure of PANI. The conductivity of the carbonized material was low for carbonizations below 600 °C, <10^?10 S cm^?1, and increased to 10^?4 S cm^?1 after treatment at 800 °C. The content of nitrogen, ～10 wt.%, was not affected appreciably by the carbonization.     

Preparation and characterization of nickel-coated graphite nanosheets

Nickel-coated graphite nanosheets have been fabricated by simple oxidation and reduction process. The resulting products have a homogeneous and consecutive distribution of nickel coated on the surface of graphite nanosheets. The addition of polyvinylpyrrolidone (PVP) can control the size of nickel particles. Scanning electron microscopy (SEM) images, XRD pattern of the composites all confirm the deposition of nickel. The magnetic property of the coated GNs was characterized by Magnetic Property Measurement System (MPMS).     

Large-scale synthesis of onion-like carbon nanoparticles by carbonization of phenolic resin

Onion-like carbon nanoparticles have been synthesized on a large scale by carbonization of phenolic-formaldehyde resin at 1000 °C with the aid of ferric nitrate (FN). The effects of FN loading content on the yield, morphology and structure of carbonized products were investigated using transmission electron microscopy (TEM), high-resolution TEM and X-ray diffraction. It was found that the onion-like carbon nanoparticles, which had a narrow size distribution ranging from 30 to 50 nm, were composed mainly of quasi-spherically concentric shells of well-aligned graphene layers with interlayer spacing of 0.336 nm. Based on the results of the investigation, the formation mechanism of onion-like carbon nanoparticles was also discussed.     

Improvement of single-walled carbon nanotube transparent conductive films using substrate pretreatment

This study sought to improve the characteristics of single-walled carbon nanotube (SWCNT) transparent conductive films (TCFs), such as their sheet resistance and transparency, by applying pre-treatments to their PET substrates. Oxygen–argon plasma pretreatment was found to increase the surface energies of the PET substrates from 33.9 to 74.2 mJ/m², which improves the electric conductivity of the SWCNT-TCFs and provides a lower sheet resistance at a given light transmittance. Polymer electrolyte solution pretreatment was used to vary the surface functionality and modulate the surface charges quantitatively, as confirmed by the measurement of the resulting substrate zeta potentials, which varied between ?45.8 and 18.2 mV. When the surfaces became negatively charged through pretreatment, the electric conductivities of the SWCNT-TCFs were increased. Both pre-treatments also improve the adsorption of SWCNTs onto the PET substrates and reduce the loss of coating solution during the spray deposition of SWCNTs.     

Preparation and tribological studies of nanocomposite films fabricated using spin-assisted layer-by-layer assembly

Uniform and smooth composite multilayer films composed of gold nanoparticles and polyelectrolytes ([Au/(PAH-PSS)_nPAH]_m) multilayers were fabricated on a silicon substrate using a time-and cost-efficient spin-assisted layer-by-layer (SA-LbL) self-assembly technique. The microstructure and morphology of the multilayer films were characterized by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The tribological behavior of the composite multilayer films was evaluated using a ball-on-plate tribometer. It was found that the density of the monolayer of gold nanoparticles on the silicon substrate was dependent on the deposition time, but the coverage of the Si substrate by the gold nanoparticle kept almost unchanged at a deposition duration above 30 min. The antiwear life and load-carrying capacity of the [Au/(PAH-PSS)_nPAH]_m composite film substantially increased with increasing number of the polymer bilayers and gold nanoparticles monolayer, which could be attributed to the robust organic-inorganic nanocomposite structure and PAH and PSS fragments transferred onto the counterpart surface.     

Pt催化作用下无氢碳化制备纳米WC粉及其烧结性能研究

针对无氢碳化中反应速率缓慢、颗粒长大的问题,在无氢碳化过程中添加少量Pt作为催化剂,制备纳米WC粉。采用热压烧结对WC粉进行烧结得到无粘结相硬质合金。研究了Pt添加对WC粉的形貌和烧结性能的影响,以及Pt和烧结温度对烧结样品的致密化,组织和力学性能的影响。结果表明,少量的Pt可显著降低无氢碳化温度,制备的WC粉粒径细小且均匀。随着烧结温度升高,无粘结相硬质合金的致密度增加,晶粒尺寸增大,硬度与断裂韧性增加,但烧结温度过高,出现异常长大晶粒和W₂C,导致无粘结相硬质合金的断裂韧性严重下降。最佳烧结工艺为,烧结温度1700 ℃,保温60 min,压力40 MPa,所得无粘结相硬质合金致密度达到98.8%,平均晶粒尺寸为263.6 nm,维氏硬度和断裂韧性分别为2887 kg.mm^_-2和7.1 MPa.mm^_1/2。     

Fabrication of carbon nanotube based transparent conductive thin films using layer-by-layer technology

This paper presents a simple and convenient process for the fabrication of carbon nanotube based optically transparent and electrically conductive thin films. Single-walled carbon nanotubes (SWNTs) are chemically treated to introduce negatively charged carboxylic groups on their surfaces, so that a stable SWNT aqueous dispersion can be obtained without any surfactant. The substrate surface is modified by a layer-by-layer nanoassembly technique, in which a positively charged hydrophilic polymer molecular layer is formed on the top of the substrate. This helps the SWNT dispersion to be cast onto the substrate using convenient wet coating techniques and increases the bonding force between the thin films and the substrates. Using the developed process, large sizes of conductive pure SWNT thin films that are uniform and highly transparent have been fabricated.     

Nano-grain structure of nickel films prepared by emulsion plating using dense carbon dioxide

A nanocrystalline nickel film was prepared by an electroplating method in a constantly agitated ternary system of dense carbon dioxide (CO₂) and electroplating solution using a surfactant. The averaged grain size of the plated Ni film was 11.1 nm. In contrast, a nickel film prepared from an electroplating solution by a conventional method without the use of surfactant had an average grain size of about 19.8 nm. The Vickers hardness of the film obtained by the new method was about 680 Hv, while that prepared from the electroplating solution alone was only about 550 Hv. As a consequence, it can be deduced that grain-size strengthening was observed in the electroplated film obtained using this emulsion system.     

Improvement of water/resin wettability of graphite using carbon black nano particles coating via ink media

Carbon coated graphite with high resin and water wettability characteristics could expand the refractory and carbon–carbon composites application in different fields. Improvement of water and resin wettability of graphite using carbon black coating via ink media is reported. Present method is based on preparing colloidal disperion of carbon black in ink followed by adding proper amount of graphite to the mixture which was dried and heat treated at 250 °C afterwards. The results showed that by controlling the amount of carbon black in ink and optimizing the process, a uniform coating with a thickness of 50 nm could be developed on the graphite surface.The wettability was evaluated by measuring contact angle and the microstructure of samples was characterized by optic microscope (OM) and scanning electron microscope (SEM). Also Raman spectroscopy was employed to support the results. The microstructure of coating was found to be uniform composed of carbon black nanoparticles. It was also demonstrated that the coating that could enhance the phenolic resin wettability was well. We also showed the coating could be applied on other ceramic particles such as MgO.     

A review of helical carbon materials structure,synthesis and applications

The helical structures possess unique physical and chemical properties,such as superelasticity,high specific strength,chirality,and electromagnetic cross-polarization characteristics.With the development of nanoscience and nanotechnology,helical structures with various scales have been discovered or synthesized artificially.Among them,the helical carbon materials receive much attention around the world.Herein,we present a brief review of the development of helical carbon materials in terms of structures,synthesis techniques and mechanisms,and applications.The controllable designing of catalysts,carbon sources and reaction parameters plays a key role to optimize the properties of the helical carbon materials.At the same time,the applications in microwave absorption devices,sensors,catalysts,energy conversions and storage devices,and solar cell are also presented.For the good chemical and physical properties,helical carbon materials have a good application prospect in many fields.The potential issues and future opportunities of the helical carbon materials are also proposed.     

Preparation and electrochemical performances of graphite oxide/polypyrrole composites

Graphite oxide/polypyrrole composites (GPys) were prepared by in situ polymerization and reduced by NaBH₄ to prepare reduced graphite oxide/polypyrrole composites (R-GPys). On the basis of the morphological and structural characterization of the composites by Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) tests, the electrochemical performances of the composites were investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance techniques. The experimental results showed that the specific capacitances of the composites before and after reduction (197 and 180 F/g) were highly improved compared with that of pristine graphite oxide (11 F/g) and polypyrrole (112 F/g), respectively. The capacitance retention of about 73% for R-GPys compared with 12% for PPy and 47% for GPys after 1200 cycles indicated the high cycle stability of the R-GPys and its potential as an electrode material for supercapacitor applications.     

石墨抗氧化SiC涂层的制备与性能研究

本文以SiC、Si和酚醛树脂为主要原料,通过浸涂和气相渗硅两步法在石墨表面制备了SiC抗氧化涂层。利用XRD、SEM研究了涂层的相组成与形貌。结果表明,气相渗硅后涂层的主相为α-SiC,β-SiC和Si,其中Si是气相渗硅过程中残留的。涂层与基体之间具有过渡结构,致密度良好。抗氧化和抗热震实验表明：由气相渗硅工艺制备的SiC涂层结构致密,具有良好的抗氧化性能,1200℃空气条件下氧化16 h后试样每小时增重量约为2.18 mg/cm₂。涂层具有良好的抗热震性能,经1000 ℃—室温循环热震15次后试样质量变化百分率仅为-0.17%。     

Preparation and microwave absorption properties of FeNi/graphite nanocomposites

FeNi/graphite nanocomposites were prepared by reducing FeCl3-NiCl2-GlCs in H2. The elemental composition, structure, magnetic and microwave absorption of FeNi/graphite nanocomposites were investigated using X-ray diffraction, energy dispersive spectra, hysteresis loop and electromagnetic parameter analysis. The results show that with the increase of the reduced temperature, the number and size of particles of FeNi increases, and the FeNi/graphite nanocomposites changes to soft magnetism. FeNi/graphite nanocomposites bear microwave absorption properties. With the increase of the thickness of the sample, the matching frequency tends to shift to the low frequency region, and theoretical reflection loss becomes less at the matching frequency. Microwave absorption property in the low frequency region of FeNi/graphite nanocomposites prepared at 600 ℃ （FeNi/C600） is the best. When the thickness is 2 ram, the maximum theoretical reflection loss of FeNi/C600 is -4.3 dB and the matching frequency is 3.5 GHz.     

Properties of copper/graphite/carbon nanotubes composite reinforced by carbon nanotubes

Electroless Cu plating was used for flake G powder and CNTs, Cu-G-CNTs (copper/graphite/carbon nanotubes) composites were manufactured by means of powder metallurgical method. The influences of CNTs on the mechanical properties, conductivity properties, friction, and wear performance of the composite were examined. The results indicate that adding a small amount of CNTs can improve comprehensive property of the composites, especially mechanical property. However, excessive CNT, which is easily winding reunion and grain boundary segregation, results in performances degradation.     

核壳结构镍碳纳米胶囊和碳纤维的制备

以脱油沥青（Deoiled Asphalt）为碳源、二茂铁为催化剂,采用化学气相沉积法（CVD）制备碳纤维（CFs）,其裂解后的残渣经真空热处理制得含镍碳纳米胶囊（CNCs）。用场发射扫描电镜（FESEM）、高分辨透射电镜（HRTEM）、X射线衍射仪（XRD）和拉曼光谱（Raman）对产物进行表征。结果表明：碳纤维纯度较高,属中空结构,直径主要分布在200～500 nm范围内;含镍碳纳米胶囊为准球形核壳结构,核为金属镍,壳为石墨化碳,大小在5～30 nm范围,晶化程度较高,结构较完善。     

Adsorption of oxygen-containing compounds at fluorinated graphite and fluorinated carbon fiber

The surface properties of fully fluorinated samples of natural graphite (FG) and carbon fiber (FCF) were studied by gas chromatography, IR spectroscopy, and static adsorption. It was found that for fluorocarbons, the contributions from the O atom (for ethers) and the OH group (for alcohols) are comparable with the contribution from the methylene unit to the retention parameters, which is typical only of highly homogeneous, hydrophobic, and nonpolar surfaces. Unusual properties of fluorocarbons compared to known hydrophobic adsorbents include weaker adsorption of secondary alcohols than ketones, their dehydrogenation products. An analysis of the retention parameters of isomeric propanols and butanols revealed that the FCF surface is accessible to the adsorption of these molecules, and is mainly formed by planar homogeneous fragments. In contrast, the FG structure is porous; the pore width is comparable with the molecule size, which makes the adsorption equilibrium more difficult to reach. Original Russian Text ? T.M. Roshchina, S.V. Glazkova, N.A. Zubareva, E.A. Tveritinova, A.D. Khrycheva, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 187–192.     

石墨和炭黑制备的TiCN涂层及其磨损性能

采用等离子喷涂的方法,利用石墨和炭黑两种碳源成功制备出纳米晶Ti CN涂层。对两种喂料进行差热分析,对涂层的相组成、组织结构、晶粒度及磨损性能进行了分析。结果表明,采用炭黑和石墨分别可以制备出主相为Ti C0.2N0.8和Ti C0.7N0.3的致密涂层,主相的平均晶粒度为71.68 nm(Ti C0.2N0.8)、59.44 nm(Ti C0.7N0.3);两种涂层都具有较高的硬度和优异的耐磨性,并且随涂层中C含量的增加而提高,Ti C0.7N0.3的耐磨性能相对更好。     

纳米金刚石薄膜的制备和应用

纳米金刚石薄膜的优异性能吸引了众多学者的关注,同时也成为CVD金刚石薄膜研究领域的新热点。文章对国内外的纳米金刚石膜制备的研究状况做了详细介绍,并对纳米金刚石薄膜的应用进行了讨论。