Formation of Carbide-Derived Carbon on β-Silicon Carbide Whiskers

Carbon was synthesized on β-SiC whiskers by extraction of Si atoms from SiC. In this study, three different elevated temperature extraction methods were used to remove Si atoms from SiC: treatments in either Cl₂ or HCl and vacuum decomposition. In all chlorination experiments and vacuum treatment at 1700°C, carbon preserved the original shape of SiC whiskers. At higher temperatures (2000°C), vacuum decomposition led to a distortion in the shape of the whiskers. High-resolution transmission electron microscopy and Raman spectroscopy showed that the structure of carbide-derived carbon depends on the Si extraction method and the process parameters. Chlorination of SiC resulted in the formation of mostly amorphous nanoporous carbon. High-temperature treatment of SiC in HCl environment produced fullerene-like structures, while high-temperature vacuum decomposition resulted in the formation of graphite. Transmission electron microscopy studies of the carbon coating thickness produced in Cl₂ at various chlorination times revealed linear reaction kinetics at 700°C. Raman studies showed that the carbon structure became more ordered with increasing chlorination temperature. The results obtained demonstrate that by using the silicon extraction technique, one can precisely control the thickness and morphology of the carbon coating.     

光转换薄膜用碳量子点的合成及其发光性能

开展了光转换薄膜用碳量子点的合成及其发光性能研究,着重探讨了氮(N)源种类对碳量子点发光性能的影响。结果表明,以尿素为N源时,合成出发射峰值位于440～530 nm范围的具有不同颜色特征的碳量子点。而以二乙烯三胺为N源时,合成出发射峰值位于450～460 nm的蓝光N掺杂碳量子点;随着激发波长的增大,碳量子点的发射光谱产生红移。采用不同N源时所合成碳量子点的发光特性差异,主要源于碳量子点晶粒尺寸的不同和表面官能团的化学修饰作用,后者填补了碳量子点的表面缺陷、或使碳量子点的带隙产生了差异,进而导致了不同的发光特性。     

多壁碳纳米管改性聚乙烯超薄膜的制备与性能研究

以多壁碳纳米管(MWCNT)和聚乙烯(PE)为原料,采用溶液拉伸法制备了一种新型复合材料薄膜PE/MWCNT。研究了拉膜温度、转筒转速和对二甲苯溶液浓度等因素对PE/MWCNT成膜性能的影响,获得了最佳的成膜条件。通过扫描电镜、差示扫描量热仪、热重分析仪与微机控制万能试验机对其结构和性能进行表征。PE/MWCNT超薄膜填补了复合材料的空白。     

氯化 Ti3AlC2 陶瓷制备碳化物衍生碳的结构表征

以三元碳化物陶瓷Ti_3AlC_2为原料,在500°C~1000°C温度范围内氯化制备具有纳米孔结构的碳化物衍生碳(Ti_3AlC_2-CDC)。高温氯化制备得到的Ti_3AlC_2-CDC由无定形碳和石墨组成。氯化温度越高,石墨化程度越明显,石墨有序度越高。Ti_3AlC_2-CDC的结构与前驱体Ti_3AlC_2的层状结构保持一致。但随着温度升高,Ti_3AlC_2-CDC会逐渐裂解为单片层或多片层。采用N2吸附技术研究了700°C、800°C和1000°C下制备的Ti_3AlC_2-CDC的孔隙结构特征,通过分析试样的吸附等温线特征和孔径分布探讨了温度对CDC孔结构的影响。     

碳纤维/聚合物自润滑复合材料的机械及摩擦性能

采用以钢铁为基体高分子自润滑复合材料为衬层制作的传动件,兼有优良的减磨耐磨性能和高的承载能力。研究了组分对复合材料性能的影响,制备了机械和摩擦学性能好的碳纤维增强复合材料,其黏结强度和压缩强度分别达到16~18 MPa和85~91 MPa,冲击强度达19.67~23.45 kJ/m2;与锡青铜ZQSn6-6-3摩擦对比试验表明,复合材料在重载工况下具有更优良的摩擦性能,工作状况稳定,油摩擦因数为0.077,仅为ZQSn6-6-3的59%。试验还发现,轻载启动和在摩擦面开设润滑油槽有助于改善摩擦状况。     

Carbon-Methanol Based Adsorption Heat Pumps: Identifying Accessible Parameter Space with Carbide-Derived Carbon Model Materials

In adsorption heat pumps, the properties of the porous adsorbent and the refrigerant determine the performance. Major parameters for this working pair are the total uptake of the adsorptive, its kinetics, and the heat transfer characteristics. In the technical application despite powdered adsorbents, thin consolidated layers of the adsorbent can be attractive and obtained by a binder-based approach but likely result in competing material properties. Thus, for a process optimization, the accessible parameter space and interdependencies have to be known and were deduced in this work for model porous carbons (carbide-derived carbons derived from TiC and ZrC) and methanol as well as the addition of different amounts of boron nitride, silver, and graphite as heat-conductive agents and the use of two binders.     

碳纳米管薄膜

碳纳米管薄膜是新出现的材料,由于具有良好的力学、光学、电学等性质,广泛应用于各个领域。本文主要介绍了碳纳米管薄膜的合成方法、图形化方法、性质及其应用。     

高硬度、低应力类金刚石薄膜的制备及其摩擦学行为

采用直流磁控溅射金属Al和C石墨组合靶,在单晶硅和不锈钢基底上成功制备出含Al的非氢类金刚石a-C（Al）薄膜。采用XPS、Raman、纳米压痕仪和摩擦磨损试验机等手段分析和研究了a-C（Al）薄膜的结构、力学以及摩擦磨损性能。结构表征显示,引入到类金刚石碳膜中的金属以原子或纳米团簇的形式存在,且一定程度上促进碳网络中sp2杂化键的形成。力学性能测试表明,a-C（Al）薄膜获得较低内应力同时,仍具有高硬度特性。摩擦学性能表明,a-C（Al）薄膜干摩擦时其摩擦系数约为0.07,磨损率仅为4.6×10–16 m3 N-1 m-1左右。良好的综合力学性能以及致密、连续的石墨化碳转移膜是a-C（Al）碳膜获得较好摩擦、磨损性能的关键因素。     

Platinum-Containing Diamond-like Carbon Thin Films

This paper reports a composite thin film of platinum–diamond-like carbon (Pt-DLC). "Nonreactive" and reactive rf sputter deposition techniques were used for the preparation of these thin films under various ratios of Ar/CH₄. As-deposited thin films were characterized for microstructures using transmission electron microscopy and Raman spectroscopy, compositions using electron probe for microanalysis, surface morphology using scanning electron microscopy, and sheet resistance using four-point probe. Correlations among the growth parameter, film composition, and structure are presented. Such correlations were found to depend on the deposition technique. Improved electrical conductivity and reduced film stress were also found due to the addition of platinum to DLC.     

Surface Energy Analysis of Carbon Fibers and Films

Amorphous and graphitic carbon fibers and film surfaces are characterized by wettability measurements and surface energy analysis which isolate the (London-d) dispersion γ^d_svand (Keesom-p) polar γ^p_sv contribution to solid-vapor surface tension γ_sv =γ^d_sv + γ^p_sv Graphitized carbon fibers which are surface treated to provide strong bonding to polar matrix resins show consistent strong polar contributions to total surface tension with γ^d_sv|γ_sv ≃ γ^p_sv|γ_sv ≃ 0.50. Amorphous carbon films prepared for biological implant applications display dominant dispersion character in surface energy with γ^d_sv|γ_sv ≃ 0-74 to 0.95 and γ^p_sv|γ_sv ≃ 0.05 to 0.24.     

Low-Temperature Synthesis of Diamond-like Carbon Films on Steel Substrates by Electron-Cyclotron-Resonance Plasma-Enhanced Chemical Vapor Deposition

Using microwave electron-cyclotron-resonance plasma-enhanced chemical vapor deposition, diamond-like carbon films were directly grown at low temperatures (lessthan equal to400°C) on Fe-based alloy substrates without diamond seeding or use of a template layer. A single, broad line in the Raman spectra was observed in the region of 1328-1335 cm^-1 for films grown in gas mixtures with a ratio of CH₄:H₂ greaterthan equal to 2%. In contrast, disordered carbon and graphite phases appeared in the spectra for film grown with a concentration of 20% CH₄ in hydrogen. Diamond nucleation with an amorphous carbon layer was observed in the initial growth stage, while many diamond particles with irregular morphological features were observed on the surface of thicker films. These growth features are a consequence of the catalytic nature of the Fe-based substrate.     

Carbon Cloth Reinforced Carbon Aerogel Films Derived from Resorcinol Formaldehyde

Carbon cloth reinforced RF (Resorcinol Formaldehyde) aerogel films have been produced with extremely high RC ratio (molar ratio of resorcinol to catalyst) or with no catalyst at all. The gels were subcritically dried. Carbon aerogel films were obtained by pyrolysis of the RF aerogel films. The structure of the composite porous films was investigated using infrared spectrometer, optical and electron scanning microscope. The IR measurements indicated that the bottom surface reflectance of the films is higher than the top surface. The microscopical pictures revealed that the bottom surface of the films has a denser structure than the top surface, and the presence of carbon cloth in the sol-gel process strongly influences the structure of the films. The carbon cloth fibers act as catalytic sites. The particles are more likely to form around the fibers instead of within the sol. This leads to a somewhat reduced specific surface area as was shown via N₂ sorption and BET analysis.Using the 4-probe method the electrical conductivity of the carbon cloth reinforced carbon films was found to be higher than that of pure carbon aerogel films.     

Synthesis and Characterization of Low-Dielectric Silica Aerogel Films

Thin films of silica aerogel on a silicon wafer have been synthesized via supercritical drying of wet gel films that were obtained by spin coating the polymeric silica sol, followed by aging in an isopropanol (IPA) or tetraethoxysilane/isopropanol (TEOS/IPA) solution. The viscosity of the sol and the spin rate required to form uniform coating layers were optimized. The film thickness and microstructures could be controlled by adjusting the concentration of the sol, the spin rate, and the aging conditions. The porosities and the dielectric constants of the thin films were in the range of 76%–90% (densities of 0.59–0.22 g/cm³) and 2.0–1.5, respectively. The degree of planarization in the aerogel thin film was ∼100%, and the gap-filling capability on a 0.2 μm tungsten patterning wafer was excellent. In particular, aging the wet gel film in the TEOS/IPA solution was very effective in improving the properties of the aerogel films.     

四氟化碳的合成与开发

详细介绍了四氟化碳的性质、制备、精制、用途及经济等方面的状况,同时评述了四氟化碳的发展前景。     

四氟化碳的合成与开发(续)

(接第3期第17页 )2.2.1 吸附法意大利一家公司的专利介绍一种用特制的合金脱除全氟烷中水分和氧的方法[36]。该合金组成质量分数为Zr47%~70%,V24%~45%,Fe5%~10%,将其加工成直径<125靘的粒子,在真空或惰性气体保护下于300℃处理全氟烷,可有效去除水分和氧。杜邦公司的专利介绍一种使含空气和CO的全氟烷与MnO2和CuO混合粒子接触,在高温下使CO氧化为CO2;再用蛭石承载的碱石灰或NaOH粒子吸收CO2,最后用4A分子筛干燥提纯全氟烷的工艺[37]。催化剂粒子通常为8~24目,质量分数为MnO267%~86%、CuO14%~33%,反应温度200℃。该方法可连续进行…     

碳源入射角对超薄四面体非晶碳膜结构和性能的影响

利用45°双弯曲磁过滤阴极真空电弧技术制备超薄四面体非晶碳膜,研究碳源入射角变化对超薄四面体非晶碳膜润湿性、表面能、粗糙度、表面形貌、摩擦系数和微观结构的影响以及它们之间的构效关系.结果表明:碳源入射角从0°增加到60°,薄膜与水的接触角由77.6°小幅增加到了82.4°,与甘油的接触角由64.7°小幅增加到71.2°...     

Metalizable Polymer Thin Films in Supercritical Carbon Dioxide

We report an environmentally “green” method to improve adhesion at a polymer/metal interface by using supercritical carbon dioxide (scCO₂). Spun-cast polystyrene (PS) and poly(methyl methacrylate) (PMMA) thin films on cleaned Si wafers were used for this study. Film thicknesses of both polymer films were prepared in the range of 100 Å to 1600 Å. We exposed the films to scCO₂ in the pressure-temperature (P–T) range corresponding to the density-fluctuation ridge, where the excess swelling of both polymer films occurred, and then froze the swollen structures by quick evaporation of CO₂. A chromium (Cr) layer with film thickness of 300–400 Å was deposited onto the exposed film by using an E-beam evaporator. X-ray reflectivity (XR) measurements showed that the interfacial width between the Cr and exposed polymer layers increased by a factor of about two compared with that without exposure to scCO₂. In addition, the large interfacial broadening was found to occur irrespective of the thickness of both polymer films. After the XR measurements, the dewetting structures of the PS/Cr films induced by additional annealing were characterized by using atomic force microscopy, showing improved surface morphology in the exposed films. Contact angle measurements showed that a decrease in interfacial tension with exposure to scCO₂ accompanied the increase in interfacial width.     

Pyrolytic Deposition of Carbon Films Containing Nitrogen and/or Boron

Carbon films containing nitrogen and/or boron were prepared in a closed system by the pyrolysis of appropriate precursor materials. The decomposition products of the pyrolysis were identified and the resulting films were characterized by chemical and physical means. The electrical conductivity of the heteroatom-containing films is similar to that of pure amorphous carbon films. Boron nitride was present in the C-N-B film as revealed by XPS and IR spectroscopy. Oxygen appeared to have a role in the adherence of the films to the silica substrate.     

电活性防静电多壁碳纳米管薄膜的制备及性能研究

利用异氰酸酯将氨基碳纳米管交联在一起,制备了电活性防静电碳纳米管薄膜。通过红外光谱证实了氨基碳纳米管与异氰酸酯发生了交联。XRD谱图说明,碳纳米管薄膜中CNT的有序结构没被破坏。SEM图片表明碳纳米管在薄膜中的分散均匀性得到了提高。电导率测试得出碳纳米管薄膜的电导率平均值为1.871×10~(-6)S/m,具有良好的防静电性。另外,MWNT薄膜具有一定的储能性能,比电容值为86 F/g,高于纯MWNT。     

碳晶柔性电热膜的制备与性能研究

以碳晶为填料制备环氧树脂基电热涂料,进而制得碳晶发热聚氨酯薄膜。对碳晶进行了X射线衍射分析、扫描电镜等测试,分析了碳晶电热涂料的体积电阻率、电热膜的电热性能及碳晶电热膜传感阵列网格尺寸与最高发热温度的关系。结果表明:6k碳纤维球磨24 h得到的碳晶最优;在碳晶含量为60%时,制备的聚氨酯薄膜电热转换效率最高,可达90%。