纳米碳材料的辐射改性及其应用进展

碳材料是自然界中与人类关系最为密切的重要材料之一,伴随着纳米科技的发展,具有纳米结构的功能碳材料的研究逐渐深入,已经出现了石墨烯、碳纳米管等性能优异的纳米碳材料。纳米碳材料具有机械强度高、导热导电能力强等诸多优点以及环境友好特性,能够满足绿色化学和可持续性发展的要求,因而其在复合材料中的应用成为相关领域的研究热点。纳米碳材料的引入可以显著提高复合材料的性能,并且还可以赋予材料新的性能,其在功能复合材料方面有良好的应用前景。然而,由于纳米碳材料自身的结构特点,其在溶剂和聚合物基体中的分散性、相容性和稳定性较差,这一直阻碍着其性能在复合材料中的发挥,甚至可能导致材料的整体性能降低。因此,提高纳米碳材料的分散能力和使用性能一直是研究的难点和热点。通过化学的方法提高纳米碳材料的分散能力,操作过程复杂,生产成本增加,且化学品试剂大多具有很强的毒性。近年来,纳米碳材料的辐射改性受到各界广泛的重视,利用辐射技术制备和官能化修饰纳米碳材料,可以显著提高纳米碳材料的分散能力和与基体的相容性。辐射刻蚀和还原技术用于纳米碳材料的制备时,可对其结构进行设计,例如辐射制备短切碳纳米管,降低了碳纳米管的长度,可有效提高分散能力。利用高能射线还可将氧化石墨烯进行还原,提供简单高效制备石墨烯的新方法和新思路。辐射接枝可用于纳米碳材料的表面修饰,例如在碳纳米管或石墨烯表面接枝聚合含碳碳双键的酯和芳香类聚合物,提高了纳米碳材料在溶剂和聚合物基体中的分散性能,有助于制备各种高性能功能材料。本文综述了近年来辐射技术在碳纳米管、氧化石墨烯及碳纳米纤维等材料改性及其应用方面的研究进展,总结了这三种纳米碳材料的优异性能及其复合材料在生物医药、能源、智能材料等领域的最新研究进展,分析了辐射改性纳米碳材料的优势,并对今后辐射技术和纳米碳材料相结合的研究方向进行了展望。随着对纳米碳材料辐射改性的研究和产业化的不断深入,分散性能优异的纳米碳材料有望实现大规模低成本的连续批量生产,未来在功能化和高性能化复合材料等领域的应用也将会更加广阔。     

纳米孔"炭"和纳米孔"碳"——对碳质多孔材料的几点思考

对碳质纳米孔隙材料提出一种新的分类方法——基于孔壁结构分类。根据这种方法，碳质多孔材料分为：纳米孔“碳”（石墨烯纳米孔材料）和纳米孔“炭”（类石墨微晶纳米孔材料）。具有相近比表面积的两种碳质材料由于具有不同的孔壁结构而可能具有完全不同的物理化学性质（比如：电化学性质）。文中简要介绍了两种新型的纳米孔“碳”——单壁微孔“碳”和碳纳米管-DNA杂化物以及区分纳米孔“碳”和纳米孔“炭”的重要判据：拉曼光谱。     

新型碳材料作为DMFC催化剂载体的研究进展

综述了新型碳材料作为直接甲醇燃料电池(DMFC)催化剂载体的研究进展,包括纳米碳材料(如碳纳米管、碳纳米纤维、碳纳米盘、富勒烯碳纳米簇等)和介孔碳材料.新型碳材料负载催化剂的活性都高于传统炭黑负载催化剂,将在DMFC中得到广泛应用.     

纳米碳材料在聚合物阻燃中的应用研究进展

综述了近年来纳米碳材料在聚合物阻燃应用方面所取得的研究进展,重点讨论了碳纳米管、富勒烯、石墨烯和纳米炭黑等纳米碳材料在单独用作阻燃剂、改性后用作阻燃剂以及与其他物质协同阻燃聚合物方面取得的研究成果,并指出聚合物/纳米碳材料阻燃体系的研究应侧重于阻燃机理,并将纳米碳材料与其他阻燃剂协同使用,以便发挥各自的优势。     

平直碳纳米纤维与螺旋碳纳米纤维的共同生长

研究了采用乙醇催化燃烧法制备的碳纳米纤维的形貌和结构，并且讨论了平直碳纳米纤维与螺旋碳纳米纤维分别对应的生长机制。分析结果表明在特定的实验条件下，可以制备出平直碳纳米纤维与螺旋碳纳米纤维的共生材料。螺旋碳纳米纤维的生长机制是基于催化剂颗粒的各向异性。本实验方法具有制备工艺简单，碳源无毒性，制备过程无环境污染等特点，因而有望实现大量生产。     

新型碳纳米纸国内外研究进展

碳纳米纸是一种综合性能良好、应用前景广阔的碳基功能材料。简要介绍了碳纳米纸的研究背景和定义,对碳纳米纸的分类、制备方法和应用进行了全面综述,分析了不同纳米碳材料制备碳纳米纸的优缺点,并对碳纳米纸的发展前景进行了展望。为新型碳纳米纸的进一步研究提供了一定的理论基础和发展方向。     

催化裂解甲烷制备-维纳米网状碳材料

通过沉淀法和相转移法的结合制备纳米催化剂.采用该催化剂催化裂解甲烷反应制备出了一维纳米网状碳材料,此类碳材料的比表面积为286m2/g.预计该材料具有良好的储氢、吸附性能.     

碳纳米纤维的制备及其复合材料在军工领域的应用

碳纳米纤维作为一种新型的碳材料，具有优异的物理、力学性能和化学稳定性。详细介绍了碳纳米纤维的主要制备方法，包括基体法、喷淋法、气相流动催化法及静电纺丝法等，并比较了各种制备方法的优缺点，阐述了碳纳米纤维复合材料在军工领域的应用，展望了碳纳米纤维及其复合材料的制备工艺及应用领域。     

纳米碳材料摩擦学应用的最新进展和未来展望

近年来随着富勒烯(C_(60))、纳米金刚石(Nano diamond)、碳纳米管(Carbon nanotube,CNT)、石墨烯(Graphene)等的相继发现和相关制备技术的成熟,纳米碳材料作为润滑材料的研究已经取得了很大的进步。首先介绍了纳米碳材料的分类及其制备方法。其次以C_(60)、纳米金刚石、碳纳米管以及石墨烯为研究对象,系统介绍了它们作为润滑油添加剂、固体润滑薄膜和润滑填料的研究进展,阐述了C_(60)等纳米碳材料的减摩抗磨机制。最后,指出了C_(60)等纳米碳材料作为润滑材料仍需解决的关键问题,并展望了它们在未来摩擦学应用方面的发展趋势。     

催化裂解甲烷制备一维纳米网状碳材料

通过沉淀法和相转移法的结合制备的纳米催化剂。采用该催化剂催化裂解甲烷反应制备出了一维纳米网状碳材料，此类碳材料的比表面积为286m^2/g。预计该材料具有良好的储氢、吸附性能。     

Electromagnetic interference shielding of carbon nanotube-fluoropolymer elastomer composites with layered structure

Abstract

This paper presents carbon nanotubes-containing polymer composites with layered gradient structure having electromagnetic interference (EMI) shielding properties. Polymer composite films were obtained on metal surface by aerosol deposition of a dispersion of carbon nanotubes in the solution of a copolymer of vinylidene fluoride with hexafluoropropylene (SCF-26) in acetone. Single-wall TUBALL (OCSiAl) carbon nanotubes were used. Three-layer coatings were formed with a concentration of nanotubes decreasing in each subsequent deposited layer. The reflection coefficient of electromagnetic radiation in the range of 20–35?GHz was measured. Gradient samples had significantly better characteristics compared to samples with uniform concentration of carbon nanotubes: the reflection coefficient reached ?6dB at 35?GHz. The outer layer of gradient structure with 0.1?wt % CNT provides a better matching of the wave resistance with free space and a smooth entrance of an electromagnetic wave into the sample. The subsequent layers with an increasing concentration of single-walled carbon nanotubes (0.3 and 0.5%) absorb electromagnetic radiation. Polymer elastomer composite EMI shielding coatings with concentration gradient can be applied by aerosol deposition to the surfaces of any composition and shape. Our results could serve as a design tool in carbon nanotubes - based EMI shielding flexible polymer coatings.     

Damage behavior of atomic oxygen on CVD SiC coating-modified carbon/carbon composite in low earth orbit environment

In this work, samples of carbon/carbon (C/C) and chemical vapor deposited (CVD) SiC-coated C/C samples were investigated to understand the AO damage mechanism in low Earth orbit (LEO) environment. The ground-based simulated atomic oxygen (AO) generator was employed. Results indicate that the CVD SiC coating exhibited improved radiation resistance properties against AO radiation as evidenced by a 16% better strength retention ratio, 60% less mass ablation, and increased strength stability. The magnitude of these influences affected the surface morphology, as observed by scanning electron microscopy (SEM) and surface resistance meter test results. The variations in the surface constituents were confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results. The main products left on surface after AO exposure are SiO₂ and SiC_xO_y film. Additionally, Si atoms are found to be the preferential reacting element in the SiC coating, and this process is accompanied by graphite precipitation, grain growth, and crack necking. Also, the damage mechanism of the AO-exposed SiC coating was revealed and is discussed.     

Influence of CVI treatment of carbon fibers on the electromagnetic interference of CFRC composites

Short carbon fibers were treated at temperatures around 1100 °C in a furnace through chemical vapor infiltration technology. The fiber surface was observed by scanning electron microscopy. The reflectivity of electromagnetic radiation by the composites that were reinforced by surface-treated carbon fibers and by as-received ones was measured in the frequency range of 8.0–18.0 GHz. The reflectivity for different carbon fiber contents of 0.2%, 0.4%, 0.6% and 1.0 wt% was investigated. Results showed that the reflectivity of the composites that were reinforced by untreated carbon fibers tended to increase with the increasing fiber contents. The minimum reflectivity was −19.3 dB, far less than −10 dB, when the fiber content was 0.4% and there were wave-absorbing properties. However, after surface treatment, the minimum reflectivity was −8.1 dB for the same fiber content of 0.4%, indicating significant wave-reflecting properties. The achieved reflectivity values after surface treatment were generally greater than those without treatment.     

碳包覆纳米金属材料的合成及应用进展

本文主要介绍了目前碳包覆纳米金属材料的主要合成途径及其形成机理，主要合成途径有：电弧放电法、化学气相沉积法、高温热解法、低温热解法、聚能法、爆炸法、机械球磨法等。根据合成工艺，总结阐述了碳包金属材料在电磁性存储、微电子技术、生物医学、催化材料、光电辐射技术等不同领域的应用。     

Correlations between switching of conductivity and optical radiation observed in thin graphite-like films

The satisfactory explanation of anomalous electromagnetics in thin graphite-like carbon films till now is absent. The most comprehensible explanation may be the high-temperature superconductivity (HTSC). The pulse widths of spasmodic switching of electrical conductivity measured in this work in the graphite-like nanostructured carbon films, produced by methods of the carbon arc (CA) and chemical vapor deposition (CVD), are 1 and 2 ns correspondingly. Such fast switching completely excludes the thermal mechanism of the process. According to HTSC logic, in the time vicinity close to jump of electroresistance, it is necessary to expect the generation of optical radiation in the infrared (IR) range. This work presents the first results on registration of IR radiation caused by the sharp change of conductivity in thin graphite-like carbon films.     

碳黑颜料对紫外线油墨固化速度影响的研究

由于颜料对紫外光的吸收作用,影响了光引发剂的光引发效率,因此它对ＵＶＩ同墨的固化速度有着很大的影响。本文采用不同的碳赤颜料在不同用量的情况下与不同的光引发剂配制丝印ＵＶＩ同墨,通过对油墨的印刷密度和固化速度的测试,研究了不同种类的碳赤颜料对ＵＶ油墨固化速度的影响。     

管状多孔炭膜的研究

介绍了管状多孔炭膜的制备方法及应用,探讨了不同材料制备支撑体炭膜和炭－炭复合膜的效果及影响炭膜孔结构性能的主要因素。研究表明,煤和酚醛树脂均是良好的制膜材料,制得的支撑体炭膜不仅具有较高的孔隙率和气体通量,而且孔隙结构均一,机械强度高。膜材料的种类,粒度及炭化工艺条件等因素对炭膜的孔结构性能影响较显著。以酚醛树脂等高分子聚合物及煤热解产物为涂膜液制得的炭－炭复合膜其孔径明显的变小,孔径分布变窄。炭     

Physical activation and characterization of multi-walled carbon nanotubes catalytically synthesized from methane

A series of treatment processes were employed to purify and then physically activate the multi-walled carbon nanotubes obtained using catalytic decomposition of methane. In order to characterize and compare the activation effect, the carbon fibers were also treated by the same activation processes. The results showed that the normal physical activation by CO₂ or steam has not too much effect on the surface area of purified multi-walled carbon nanotubes, in particular, the carbon nanotubes were burned when using the poignant activation conditions. However, the surface area of carbon fibers availably etched in the same activation processes is much increased. In addition, the mechanisms of physical activation on multi-walled carbon nanotubes and carbon fibers have been investigated.     

Study on the Electromagnetic Interference of CFRC Composites by Reflectivity

The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites （CFRC） on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the CFRC samples was observed with a scanning electron microscope （SEM）. The electromagnetic interference （EMI） was evaluated indirectly by reflectivity in the Naval Research Laboratory （NRL） testing system. The reflectivity of the electromagnetic radiation by the composites was measured in the frequency range of 8.0- 18.2 GHz for different carbon fiber contents of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% （in wt pct）, respectively. The results showed that the reflectivity decreased with the growing fiber content till the percentage of 0.6%. The minimum reflectivity was -23 dB, far less than -10 dB, and the composites were strong wave absorbers. After this percentage, the curve increased abruptly as the fiber content proceeded. The electromagnetic waves were gradually reflected. When the fiber content reached 1.0% finally, the maximum reflectivity -7.5 dB appeared and there was stronger reflection. The shielding mechanism includes mainly reflection, absorption, and multiple reflections.     

He Ion Bombardment of C70 Fullerene: An FT-IR and Raman Study

C₇₀ fullerene films deposited on a silicon substrate have been bombarded with He⁺ ions at 30 keV at room temperature in vacuum. The structural changes undergone by C₇₀ have been followed by both FT-IR and Raman spectroscopy. The results have been compared to the behavior of C₆₀ fullerene and discussed in an astrochemical context. The main conclusion is that C₇₀, contrary to C₆₀, does not form oligomers at low radiation dose but it is directly and gradually degraded to amorphous carbon (carbon black).