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用CVD法合成微米螺旋碳纤维(carbon microcoils,CMCs),用硝酸和KOH等对其进行纯化和活化处理,用扫描电镜(SEM)、光学显微镜观察其形貌,用X-射线能谱仪分析反应后催化剂成分,并采用恒流充放电、循环伏安、交流阻抗等电化学方法分析CMCs超级电容器性能。结果表明,在50 mA·g-1电流密度条件下,初始CMCs产物的比电容为12.7 F·g-1,纯化处理后的比电容为41.4 F·g-1,活化处理后则达到111.1 F·g-1,为处理前的8.75倍。表明纯化特别是活化处理使其电容性能显著提高。 相似文献
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Angela Dawson Martin Rides Alexandre Cuenat Laurie Winkless 《International Journal of Thermophysics》2013,34(5):865-882
To realize the benefits and optimize the performance of micro- and nano-structured materials and thin films, designers need to understand and thus be able to characterize their thermal, thermophysical, and thermomechanical properties on appropriate length scales. This paper describes the determination of glass-transition temperatures of polymers on the micro-scale, obtained from contact force–distance curves for poly(methyl methacrylate) and poly(vinyl acetate) measured using an atomic force microscope (AFM). Measurements were made using a standard AFM tip where thin films were heated using a temperature controlled hot stage and by using a scanning thermal microscopy (SThM) probe. The latter was used either with the hot stage or with the SThM probe providing a localized heating source via Joule heating. Differences in the glass-transition temperature measured using the hot stage and Joule heating were apparent and considered to be due to heat transfer effects between the probe, specimen, and surroundings. Gradients of force–distance curves, pull-off and snap-in forces, and adhesion energy were obtained. The results suggest that the onset of changes in the material’s mechanical properties at the glass transition was found to be dependent on the mechanical property measured, with pull-off force values changing at lower temperatures than the snap-in force and adhesion energy. 相似文献
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Timoshchuk K. I. Khalisov M. M. Penniyaynen V. A. Krylov B. V. Ankudinov A. V. 《Technical Physics Letters》2019,45(9):947-950
Technical Physics Letters - Atomic force microscopy (AFM) measurements have revealed hardening of intact fibroblasts after treatment with colchicine. The reliability of AFM measurements was... 相似文献
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本文用侧向力显微镜(Lateral Force Microscope,LFM)研究不同厚度类金刚石(Diamond-Like Carbon,DLC)膜的摩擦性能.对厚度为153.4 nm,64.9 nm,12.07nm DLC膜摩擦力和法向力的关系进行研究,实验表明施加较低载荷,摩擦力和法向力成线性关系,符合Amontons's定律;而膜厚为4.48nm、2.78 nm样品由于粗糙度、峰态和偏态的差异导致摩擦力和载荷关系不明显,研究指出针尖和薄膜的表面接触可以简化为Tomlinson模型,借助原子晶格振动的无损摩擦机理解释了这一现象. 相似文献
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Davletkildeev N. A. Sokolov D. V. Mosur E. Yu. Lopandina A. A. Bolotov V. V. 《Technical Physics Letters》2019,45(10):981-983
Technical Physics Letters - A technique for determination of the dielectric constant of individual hemoglobin molecules is presented. It is based on modeling the profiles of their images obtained... 相似文献
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We propose to estimate the mechanical characteristics of diamond-containing composites for stone-cutting wheels made of a metallic binder with a ferromagnetic component by the coercive force. For M6-14 and M6-14-1 binders, the hardness (yield stress) depends linearly on the coercive force in the range 85–100 HRB. The value of the coercive force of a diamond-containing composite rather well reproduces its structural state, which essentially depends on the composition of the binder, the original material, the manufacturing technique, and the sintering temperature of the composite. The obtained regularities enable one to determine the optimum interval of values of the coercive force for the required level of the mechanical characteristics depending on the composition of the binder. 相似文献
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Malgorzata Kopycinska‐Müller Andre Striegler Bernd Köhler Klaus‐Jürgen Wolter 《Advanced Engineering Materials》2011,13(4):312-318
The atomic force acoustic microscopy (AFAM) technique has been used to determine elastic properties of films with thicknesses decreasing from several hundreds of nanometers to several nanometers. It has been shown that metal films as thin as 50 nm can be characterized directly without the need to consider the influence of the substrate. For films with thicknesses ranging from about 30 to 50 nm, measurement parameters can be chosen such as to allow characterization of the elastic properties of either the film or the film–substrate interface. This attribute has been combined with the ability of the method to obtain qualitative stiffness images to show variations in the film–substrate adhesion. The AFAM technique has been also used to determine the indentation modulus of thin films of silicon oxide with thicknesses ranging from 7 to 28 nm. In this case, elastic properties of the substrate had to be considered. The examples of the applications of the AFAM method reported here for characterization of elastic properties of very thin films have shown that this technique has the lateral and depth resolution required to characterize the very thin films used nowadays in microelectronics industry. 相似文献
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G. E. Iacobescu M. Balasoiu I. Bica 《Journal of Superconductivity and Novel Magnetism》2013,26(4):785-792
Magnetorheological elastomers generally consist of a natural or synthetic rubber matrix interspersed with micron-sized ferromagnetic particles. The magneto-elastic properties of such a composite are not merely a sum of the elasticity of the polymer and the stiffness and magnetic properties of the filler, but also the result of a complex synergy of several effects, relevant at different length scales and detectable by different techniques. In our present work we investigate the microstructures, the surface magnetic properties, and the elastic properties of new isotropic and anisotropic magnetorheological elastomers prepared using silicone rubber and soft magnetic carbonyl iron microspheres. Similar samples were previously investigated by means of small-angle neutron scattering, which proved to be a useful method in the investigation of their microscopic properties. We combined the data from the atomic force microscopy measurements with those from small-angle neutron scattering to better understand the complicated behaviour of the studied materials. The measurements were performed by atomic force microscopy in the following modes: standard imaging non-contact atomic force microscopy, magnetic force microscopy, and nanoindentation. A comparative study of samples with different particle concentrations and strength of magnetic field applied during the polymerization process is developed. 相似文献
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螺旋碳纤维自被发现以来,因其独特的三维螺旋结构引起了研究人员的关注.探究螺旋碳纤维的制备方法及其影响因素,对研究螺旋碳纤维的生长机理有着重要的作用.螺旋碳纤维是具有规则螺旋线圈或扭转结构的碳纤维,目前制备的螺旋碳纤维主要有单螺旋碳纤维和双螺旋碳纤维.碳纤维具有密度小、拉伸强度高、拉伸模量高、热导率好、导电以及电磁屏蔽波特性等特点,并且其力学性能、热性能及电性能都具有显著的各向异性.螺旋碳纤维不但具有与碳纤维类似的优异性能,并且所具有三维螺旋结构还赋予其良好的弹性、独特的电磁学以及生物催化等特性,在电子器件、手征催化、智能材料、隐身吸波材料、高性能和多功能复合材料等领域有着潜在的应用前景.然而,如何得到螺旋形貌规整的碳纤维、螺旋碳纤维的手性拆分和分散问题以及螺旋碳纤维的规模性可控制备一直是研究的难点和关键.近年来,研究者们一直对螺旋碳纤维的生长机理及生长动力进行探究,通过构建合理的生长模型表明促进剂以及催化剂的晶型和尺寸等对碳纤维的双螺旋结构有着关键影响.目前已能通过调控不同的制备条件制得形貌规整、结构均一的螺旋碳纤维,对其在各个领域的应用进行了一定的探索并取得了很大的成功.研究者们通过将螺旋碳纤维作为填料分散在复合材料中,利用螺旋碳纤维优异的性能,提高复合材料的综合性能或赋予复合材料的多功能性,以期实现复合材料在各个领域的应用.本文归纳了螺旋碳纤维的制备与生长机理的研究进展,分别对螺旋碳纤维的制备条件以及研究者们对生长机理模型的探究进行了介绍,总结了通过调控制备方法、碳源种类、反应温度、催化剂种类、促进剂以及碳源与氢气进气量比值等条件下所得到的螺旋碳纤维的差异,从而对螺旋碳纤维的生长机理进行推测和讨论.本文分析了现阶段螺旋碳纤维所面临的问题并对螺旋碳纤维未来的发展进行了展望,以期为螺旋碳纤维的进一步可控制备和产业化发展提供参考. 相似文献
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半金属铋薄膜导电特性和粗糙度的研究 总被引:2,自引:0,他引:2
本论文利用真空镀膜方法在云母片上生长半金属Bi薄膜,测量了薄膜生长厚度与电阻之间的关系,并用原子力显微镜(AFM)研究了云母表面半金属薄膜电阻变化与薄膜粗糙度间的关系.生长初始阶段,薄膜先形成孤立的三维小岛(典型高度1 nm,直径10 nm,间距10 nm),随后互相聚结形成网状结构,薄膜不导通(R≥20 MΩ),粗糙度随膜厚增加而减小.当等效厚度d=1.74 nm时,薄膜导通(R≤13 MΩ),薄膜的形貌变为有小孔洞的连续状结构,粗糙度在此厚度附近达到最小值然后又增大.随着薄膜继续生长,连续状结构的厚度增加,薄膜电阻随之迅速减小,当d≥2.4 nm时薄膜电阻趋近于稳定值2kΩ. 相似文献
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螺旋碳纤维自被发现以来,因其独特的三维螺旋结构引起了研究人员的关注。探究螺旋碳纤维的制备方法及其影响因素,对研究螺旋碳纤维的生长机理有着重要的作用。螺旋碳纤维是具有规则螺旋线圈或扭转结构的碳纤维,目前制备的螺旋碳纤维主要有单螺旋碳纤维和双螺旋碳纤维。碳纤维具有密度小、拉伸强度高、拉伸模量高、热导率好、导电以及电磁屏蔽波特性等特点,并且其力学性能、热性能及电性能都具有显著的各向异性。螺旋碳纤维不但具有与碳纤维类似的优异性能,并且所具有三维螺旋结构还赋予其良好的弹性、独特的电磁学以及生物催化等特性,在电子器件、手征催化、智能材料、隐身吸波材料、高性能和多功能复合材料等领域有着潜在的应用前景。然而,如何得到螺旋形貌规整的碳纤维、螺旋碳纤维的手性拆分和分散问题以及螺旋碳纤维的规模性可控制备一直是研究的难点和关键。近年来,研究者们一直对螺旋碳纤维的生长机理及生长动力进行探究,通过构建合理的生长模型表明促进剂以及催化剂的晶型和尺寸等对碳纤维的双螺旋结构有着关键影响。目前已能通过调控不同的制备条件制得形貌规整、结构均一的螺旋碳纤维,对其在各个领域的应用进行了一定的探索并取得了很大的成功。研究者们通过将螺旋碳纤维作为填料分散在复合材料中,利用螺旋碳纤维优异的性能,提高复合材料的综合性能或赋予复合材料的多功能性,以期实现复合材料在各个领域的应用。本文归纳了螺旋碳纤维的制备与生长机理的研究进展,分别对螺旋碳纤维的制备条件以及研究者们对生长机理模型的探究进行了介绍,总结了通过调控制备方法、碳源种类、反应温度、催化剂种类、促进剂以及碳源与氢气进气量比值等条件下所得到的螺旋碳纤维的差异,从而对螺旋碳纤维的生长机理进行推测和讨论。本文分析了现阶段螺旋碳纤维所面临的问题并对螺旋碳纤维未来的发展进行了展望,以期为螺旋碳纤维的进一步可控制备和产业化发展提供参考。 相似文献
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We use molecular mechanics calculations to study size effects on mechanical properties of carbon nanotubes. Both single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs) are considered. The size-dependent Young's modulus decreases with the increasing tube diameter for a reactive empirical bond order (REBO) potential function. However, we observe a contrary trend if we use other potential functions such as the modified Morse potential function and the universal force field (UFF). Such confliction is only obtained for small tubes within cutoff diameters (3 nm for REBO and 1.5 nm for others). In light of these predictions, Young's moduli of large nanotubes concur with experimental results for all the potential functions. No matter which potential function is used, the Poisson's ratio decreases with the increasing tube diameter. We also study the chirality effects on mechanical properties of SWNTs. We find that the Young's moduli are insensitive to the chirality of nanotubes. The chirality effect on the Poisson's ratio is significant for the UFF but not the REBO or modified Morse potential functions. 相似文献
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碳纳米管聚合物复合材料的力学性质 总被引:1,自引:0,他引:1
用二甲基甲酰胺表面活性剂来超声分散多壁碳纳米管,制备成碳纳米管增强的环氧树脂基聚合物。常温下力学性能测试表明,随着碳纳米管含量的增加,其弹性模量先增后降。在50℃时,对于碳纳米管含量≤1%(质量分数)的复合材料,经历了可逆的粘弹性阶段后进入塑性变形,且温度对复合材料的弹性模量和拉伸强度影响较大;而对于碳纳米管含量>1%的复合材料,其力学性能反而发生退化。 相似文献
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借助偏光显微镜、扫描电镜,透射电镜以及力学性能测试研究了微观结构对双基体炭/炭复合材料力学性能的影响.结果表明:基体炭在偏光显微镜下呈现光学各向异性,材料内部形成多层次的界面结构,热解炭呈现"皱褶状"片层结构,中间相沥青炭呈现片层条带状结构,基体炭片层的走向基本上平行于纤维轴向.材料受载破坏时裂纹通过改变扩展路径而延缓其扩展速度,在纤维-基体界面处以及基体炭片层之间引起滑移,在断口形貌上体现出锯齿状的断裂形式,材料具有韧性断裂的特征,抗弯强度最高可达223MPa. 相似文献
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Owing to their unique mechanical properties, carbon nanotubes are considered to be ideal candidates for polymer reinforcement. However, a large amount of work must be done in order to realize their full potential. Effective processing of nanotubes and polymers to fabricate new ultra‐strong composite materials is still a great challenge. This Review explores the progress that has already been made in the area of mechanical reinforcement of polymers using carbon nanotubes. First, the mechanical properties of carbon nanotubes and the system requirements to maximize reinforcement are discussed. Then, main methods described in the literature to produce and process polymer–nanotube composites are considered and analyzed. After that, mechanical properties of various nanotube–polymer composites prepared by different techniques are critically analyzed and compared. Finally, remaining problems, the achievements so far, and the research that needs to be done in the future are discussed. 相似文献