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以炭纤维网布为基体,通过电镀工艺在炭纤维网布上形成Ni催化剂膜,采用化学气相沉积方法原位合成炭纤维网布/螺旋纳米碳纤维复合材料,采用扫描电镜(SEM)、Raman光谱和X射线衍射仪(XRD)对生长的螺旋纳米碳纤维的形态和结构进行表征。考察主要反应因素—温度对螺旋纳米碳纤维生长的影响,并就生长过程进行了讨论;对其制备出的炭纤维网布/螺旋纳米碳纤维复合材料在8.2~12.4GHz频段的电磁性能进行分析,考察其吸波性能。结果表明制备出的炭纤维网布/螺旋纳米碳纤维复合材料比单一的螺旋纳米碳纤维具有更高的电磁损耗角正切,电损耗正切值由0.7提高到3.8,表明复合材料具有较好的吸波性能。 相似文献
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对六种不同纳米碳纤维掺量的72个纳米碳纤维/混凝土试件进行了慢冻融循环试验,通过测量纳米碳纤维/混凝土经不同冻融循环次数作用后的抗剥落能力、质量损失率、相对动弹性模量和抗压强度损失率,研究了纳米碳纤维掺量对纳米碳纤维/混凝土抗冻性能的影响。另外进行了纳米碳纤维/混凝土的FE-SEM试验和压汞试验,分析了纳米碳纤维对纳米碳纤维/混凝土抗冻性能的微观改性机制。结果表明:纳米碳纤维通过改善混凝土的微观形貌,细化其孔隙结构,提高其整体性和密实度,显著改善了混凝土的抗冻性能;纳米碳纤维掺量为3vol%时,纳米碳纤维/混凝土的抗冻性能最佳。同普通混凝土相比,300次冻融循环后,纳米碳纤维/混凝土的相对动弹性模量提高了33.2%,抗剥落能力显著增强;相同冻融次数下,随着纳米碳纤维掺量的增加,纳米碳纤维/混凝土相对动弹性模量和抗压强度损失率均先增大后减小,质量损失率先减小后增大。但纳米碳纤维掺量最大为5vol%时,纳米碳纤维/混凝土的抗冻性能仍优于普通混凝土;冻融循环次数越多,纳米碳纤维对混凝土抗冻性能的改善作用越显著。 相似文献
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纳米碳纤维凭借着高的抗拉强度和弹性模量,被广泛应用于水泥混凝土的增韧剂。通过在混凝土材料中掺入不同含量(0,0.3%,0.6%和0.9%(质量分数))的纳米碳纤维,研究了纳米碳纤维掺杂量对混凝土力学性能和抗冻性能的影响。结果表明,纳米碳纤维的掺杂未生成新的产物,但加速了水化反应的进行,增加了改性混凝土的结构致密性,减小了孔隙和缺陷的数量。当纳米碳纤维的掺杂量为0.6%(质量分数)时,改性混凝土的形貌结构最佳。随着纳米碳纤维掺杂量的增加,改性混凝土的抗压强度、抗折强度和磨损量降低比率先增大后减小,单位面积的磨损量和80次冻融循环时刻的质量损失率先减小后增大。当纳米碳纤维的掺杂量为0.6%(质量分数)时,改性混凝土28 d的抗压强度和抗折强度达到最大值,分别为47.83和5.92 MPa,单位面积的磨损量最小为1.12%,磨损量降低比率最大为55.56%,80次冻融循环时刻的质量损失率最小为1.23%。综合各分析可知,纳米碳纤维的最佳掺杂量为0.6%(质量分数)。 相似文献
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以纳米多孔Ni-P涂层为催化剂模板,制备形貌良好、宏量生长的螺旋碳纤维。采用扫描电子显微镜对螺旋碳纤维进行微观形貌观察,采用X射线能量色散谱仪对纳米多孔Ni-P涂层表面进行元素分析,采用X射线衍射仪表征其物相组成。研究了反应温度、升温速率、反应气氛对螺旋碳纤维形貌及纳米多孔Ni-P涂层物相组成的影响。实验结果表明,非晶态的纳米多孔Ni-P涂层在升温过程中会形成结晶Ni相和结晶Ni3P相。随着温度的提高,用纳米多孔Ni-P涂层催化生长的螺旋碳纤维直径出现由大变小的趋势,在600℃时制备的碳纤维其螺旋形貌最佳。螺旋碳纤维的纤维直径、螺旋直径与纳米多孔Ni-P涂层中Ni(200)晶面的择优取向强度相关,这是决定螺旋碳纤维形貌的关键,Ni(200)晶面的择优取向强度越高,生长的螺旋碳纤维的纤维直径和螺旋直径越小。 相似文献
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碳纤维结构的STM观察研究 总被引:3,自引:0,他引:3
碳纤维是一种重要的工程材料,它的表面结构和内部结构是其机械性质的重要影响因素。由于传统观察手段的局限性,关于碳纤维的结构知识,特别是原子 级和纳米级的知识是很缺乏的。扫描隧道显微镜Scanning Tunneling Microscope,简称STM和能成为观察碳纤维表面和横断面的一个非常有力的工具,它能提供极高分辨率的图象(在大气中可达到原子级)。在实验中,首次用STM观察了聚丙烯腈基的碳纤维, 相似文献
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通过化学气相沉积法高重复性制备了纳米螺旋碳纤维和直线性碳纤维,并研究了金属铜纳米粒子催化剂的尺寸大小对碳纤维形貌的影响,认为粒径较大的铜纳米粒子容易催化聚合生成直线形碳纤维;反之,粒径较小的铜纳米粒子倾向于合成纳米螺旋碳纤维.利用场发射扫描电镜(FESEM)、透射电镜(TEM)和X射线粉末衍射(XRD)等测试方法对产物进行了表征. 相似文献
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This paper studies the mechanism of the formation of carbon nanostructures on carbon nanofibers with Pd nanoparticles by using different carbon sources. The carbon nanofibers with Pd nanoparticles were produced by carbonizing electrospun polyacrylonitrile (PAN) nanofibers including Pd(Ac)(2). Such PAN-based carbon nanofibers were then used as substrates to grow hierarchical carbon nanostructures. Toluene, pyridine and chlorobenzine were employed as carbon sources for the carbon nanostructures. With the Pd nanoparticles embedded in the carbonized PAN nanofibers acting as catalysts, molecules of toluene, pyridine or chlorobenzine were decomposed into carbon species which were dissolved into the Pd nanoparticles and consequently grew into straight carbon nanotubes, Y-shaped carbon nanotubes or carbon nano-ribbons on the carbon nanofiber substrates. X-ray diffraction analysis and transmission electron microscopy (TEM) were utilized to capture the mechanism of formation of Pd nanoparticles, regular carbon nanotubes, Y-shaped carbon nanotubes and carbon nano-ribbons. It was observed that the Y-shaped carbon nanotubes and carbon nano-ribbons were formed on carbonized PAN nanofibers containing Pd-nanoparticle catalyst, and the carbon sources played a crucial role in the formation of different hierarchical carbon nanostructures. 相似文献
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A. A. Didik V. I. Kodolov A. Yu. Volkov E. G. Volkova K. H. Hallmeier 《Inorganic Materials》2003,39(6):583-587
Multiwalled carbon nanotubes filled with Cu metal, Cu2O, and CuCl are produced by poly(vinyl alcohol) carbonization in the presence of CuCl or CuCl2. The structure and composition of the reaction products are analyzed by x-ray photoelectron spectroscopy, transmission electron microscopy, and selected-area electron diffraction. The carbonization products are found to contain, along with carbon nanotubes, carbon-encapsulated spherical metallic nanoparticles and carbon fibers. A simplified mechanism of nanotube growth is proposed which differs from the well-known high-temperature mechanism. 相似文献
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We report the formation of vertical carbon nanotubes utilizing diatomite as a substrate. This new material combines the advantages of carbon nanotubes and diatomite in one material. The SEM investigations showed that the average diameter of the carbon nanotubes was 60 nm and the growth was through the tip growth mechanism. Raman spectroscopy was also used for the carbon nanotubes characterization and showed two intensive peaks around 1350 cm−1 and 1580 cm−1 and several peaks at low frequency range from 100 cm−1 to 500 cm−1 which are assigned to the radial breathing mode (RBM) and used as a characteristic of single wall carbon nanotubes. The photoluminescence measurements at the room temperature showed two very narrow intensive overlapping peaks near the ultraviolet range at energy of about 3 eV. And there are two peaks with lower intensity in the infrared region at 830 nm and at 940 nm (or 1.49 eV, 1.3 eV respectively). 相似文献
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负衬底偏压对碳纳米管生长的影响 总被引:1,自引:1,他引:0
利用负衬底偏压增强热灯丝化学气相沉系统制备了碳纳米管,用扫描电子显微镜研究了碳纳米管的生长,结果表明碳纳米管的生长随着负衬底偏压的增大先增强,然后减弱,并且出现了部分准直的碳纳米管,分析和讨论了负衬底偏压对碳纳米管生长的影响。 相似文献
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《Materials Letters》2007,61(23-24):4631-4634
Hybrid carbon nanotube-semiconductor systems offer unique properties by combining the advantages of one-dimensional conductors with the broad opportunities of semiconductor technology. Thus, it is desirable to incorporate the nanotube growth in III–V semiconductor systems. We present the directed growth of carbon nanotubes from prepatterned CrNi catalyst structures on GaAs. 相似文献
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乙醇催化燃烧法可以方便的制备出碳纳米管和碳纳米纤维。介绍采用该方法制备出一种独特的竹节形的碳纳米管,利用乙醇作为碳源和燃料,提供材料生长所需的能量;利用Cu薄片作为基底;利用FeCl3或Fe(NO3)3作为催化剂先体。通过扫描电子显微镜(SEM),透射电子显微镜(TEM),对黑色絮状的沉积产物进行表征。实验结果表明,产物中的碳纳米管具有较好的竹节形结构。实验也表明制备的竹节形碳纳米管的形貌和微结构与其独特的制备条件有关,如:火焰的抖动,催化剂先体溶液的浓度,制备时间等。并对竹节形碳纳米管的形貌和生长机制进行了详细的讨论。 相似文献
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Carbon nanostructures were synthesized by decomposition of different carbon sources over an alumina supported palladium catalyst via Chemical Vapor Deposition (CVD). Several experimental conditions were varied to verify their influence in the synthesis products: temperature ramping rate, pre-annealing conditions, hydrogen pre-treatment, synthesis temperature and time, together with the use of different carbon sources. Depending on the experimental conditions carbon nanotubes and nanofibers with different shapes and structural characteristics were obtained. Straight, coiled and branched morphologies are the most common. Among our findings, the addition of hydrogen plays a significant role in the structure of the carbonaceous products. For example, the decomposition of acetylene on palladium catalysts at 800 degrees C in the absence of hydrogen produces only carbon micro- spheres as synthesis products. The incorporation of increasing amounts of hydrogen modifies the outcome, from thick fibers to carbon nanotubes. To verify the level of graphitization of the synthesis products we have used high resolution transmission electron microscopy (HRTEM) in addition to Raman spectroscopy. Our results, based on these complementary techniques, indicate the decomposition of acetylene on a palladium based catalyst, produces the best degree of graphitization in carbon nanotubes for a temperature of 800 degrees C and 100 cc/min of hydrogen flow. Similar hydrogen flows on the same catalyst, produced highly graphitized nanofibers by the decomposition of methane at 850 degrees C. 相似文献
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根据碳化硅晶须生长的特定驱动力要求,通过实验和建立气相传输模型研究了碳多孔体中碳化硅晶须原位生长的条件。模型和实验研究均表明,温度和多孔体表面气相组成对多孔体内的晶须原位生长起决定作用;体内附加反应的设置可以改变晶须生长所要求的温度和表面气相条件。 相似文献