水热法在碳纤维表面生长ZnO纳米线及性能研究

采用水热法在碳纤维表面生长ZnO纳米线,通过扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和SmileView软件对ZnO纳米线进行分析。XPS结果确认碳纤维表面纳米线为ZnO纳米线,SEM图片说明T700碳纤维表面ZnO纳米线取向度高于T300碳纤维表面ZnO纳米线,关于生长时间的分析表明最优值为4h。此外,通过附着生长在碳纤维表面制备了改性的ZnO纳米线,XPS测试结果表明ZnO纳米线表面涂层为CoO。     

纳米碳纤维的低温制备——催化剂粒子尺寸的影响

以采用电阻加热法制备的纳米铜粒子为催化剂,在低温下催化乙炔制备了纳米碳纤维。所制备的纳米碳纤维具有螺旋型和直线型两种形貌。采用透射电子显微镜(TEM)和扫描电子显微镜(SEM)对纳米碳纤维进行了表征。纳米铜催化剂粒子在催化纤维的生长过程中,经历了一个重要的形状变化过程。催化剂粒子尺寸对所制备的纳米碳纤维的形貌有很大的影响。通常有两根螺旋纳米碳纤维以对称模式在单个粒径小于50nm的催化剂粒子上生长,它们的旋向相反,但是具有相同的螺旋直径、螺旋长度、螺旋缠绕程度和纤维直径。较大尺寸的催化剂粒子易生长直线型纳米碳纤维。     

CuO/ZnO复合纳米树阵列的制备及光学特性

通过热氧化法在铜基板上制备CuO纳米线,采用凝胶法制备ZnO/CuO复合纳米树阵列。通过扫描电镜(SEM)、X射线衍射(XRD)、光致发射光谱对样品结构、形貌、光学特性进行表征。结果表明,CuO/ZnO纳米树形貌规整完美,在CuO纳米线上二次生长的ZnO纳米棒具有各向晶体生长性质,CuO/ZnO复合纳米树在可见光区域出现了优越的发光性能;以甲基橙为模拟污染物,通过光催化测试表明,CuO/ZnO复合纳米树还具有卓越的光催化性能。     

图案化金属铜纳米线阵列的制备与表征

采用紫外线光刻技术与电化学沉积相结合的方法,成功制备了不同图案的铜纳米线阵列:一种是圆形图案;另一种是QDU图案.首先利用紫外线光刻技术在多孔阳极氧化铝模板(AAO)生成预设图案,以此作为"二次模板";再利用电化学方法将铜纳米线沉积到"二次模板"的开孔中.扫描电镜(SEM)测试结果表明,大面积、高规整的铜纳米线图案阵列各自独立地立在基底上, 同时,用电子能谱(EDS)分析了铜纳米线的化学成分.透射电镜(TEM)也探测到了铜纳米线的微结构.     

硅基底上铜纳米粒子催化生长碳纤维的研究

采用微波加热法,在单晶硅基底上生长了铜纳米粒子,并以铜纳米粒子为催化剂,乙炔为碳源,氢气为保护气,在管式炉中制备了碳纤维.利用高视频显微仪观察单晶硅片的预处理情况,采用扫描电子显微镜(SEM)观察硅基底上铜纳米粒子的生长情况和碳纤维的形貌特征,并利用能量色散谱仪(EDS)对铜纳米粒子进行成分及元素分布分析.研究表明,采用抛光-腐蚀的硅片预处理方法,可以更高效地得到具有取向性、长径比大的碳纤维.     

基于铜粉的室温气固反应自生长刺球状半导体Cu_2S纳米线阵列

本研究通过简单的气-固硫化反应对ITO玻璃上涂覆的铜颗粒膜进行硫化反应,得到了大面积的自生长刺球状结构的半导体Cu2S纳米阵列。采用SEM,TEM,EDS、XRD,以及UV-vis等方法对反应生长的半导体Cu2S纳米线阵列的微观结构及光吸收性能进行了系统研究。实验结果表明,合成的Cu2S为刺球状纳米线阵列,纳米刺球的直径分布在50~100μm之间;刺球上的纳米线为单斜晶系的Cu2S单晶,晶体生长方向为[-102];纳米线的平均直径为100nm,长度分布在20~50μm之间。合成的刺球状纳米线阵列具有良好的光吸收性能,反应20小时样品在可见光波长范围内(400~800nm)平均光吸收率达到了93%;反应30小时样品在可见光波长范围内(400~800nm)平均光吸收率达到了92%。同时两种刺球状纳米线阵列结构对于大的光线入射角仍然保持很高的光吸收性能,对光线入射角的变化不敏感。当入射光角度从0°增加到60°时,光吸收率仅下降3%,明显优于文献已报道的规则排列纳米线阵列的光吸收性能。本项研究合成方法简单,工艺可控,成本低,可以采用更广的基体材料。合成的纳米结构具有优良的综合光吸收性能,在光电领域有很好的应用潜力。     

SiO2纳米颗粒复合Bi2Te3纳米线阵列的制备

为结合一维纳米材料和纳米颗粒复合材料的优点,本文尝试进行了在氧化铝模板(AAO)中生长Bi2Te3-Si O2纳米颗粒复合纳米线阵列。通过在电化学溶液中添加Si O2纳米颗粒,制备包含纳米颗粒的Bi-Te纳米线阵列。应用XRD、SEM、TEM等方法对合成的样品进行了分析观察。研究发现Si O2纳米颗粒的加入对纳米线的形貌和结构都有明显的影响。在模板法沉积Bi2Te3纳米线阵列时,添加Si O2纳米颗粒将明显改变纳米线生长方式,Bi2Te3纳米线不再是等径的纳米棒,而是枝晶生长过程,最后形成Z字型的不断反复弯折纳米线,该枝晶状纳米线的直径远小于模板的孔径。这一新颖的现象为制备直径更小,并具备精细界面结构的纳米线热电材料提供了一种新的可能途径。     

SOI基上制备CuO纳米线

在SOI基上制备光电纳米器件具有良好的光电集成应用前景,通过铜膜生长法在SOI基上制备了形貌为类针状的Cu(OH)2前驱体纳米线,并采用热处理法600℃条件下成功制备了CuO纳米线。通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射测试(XRD)对样品结构、形貌进行了表征。SEM、TEM测试结果表明,Cu(OH)2前驱体纳米线结构一致,尺寸均匀,表面光滑。在Cu(OH)2前驱体纳米线上二次生长的CuO纳米线具有类蒲草状细长光滑的结构,CuO纳米线直径约为80~100nm,长度约为10μm,CuO纳米线结晶性良好。     

纳米线阵列的电化学优化光吸收增强研究

通过在自生长的半导体Cu2S纳米线阵列表面进一步应用电化学表面沉积处理,在纳米线表面形成尺寸更小的Cu2S纳米颗粒结构,实现了在不减小纳米线直径或增加纳米线长度的情况下,有效提高了纳米线阵列光吸收性能。利用I-V循环扫描曲线研究了以Cu2S纳米线阵列为工作电极的Cu2S沉积电位,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见-近红外分光光度计,对纳米阵列的相结构、微观表面形貌、晶体结构及光吸收能力进行了表征和分析。研究表明:沉积于单斜晶系Cu2S纳米线阵列上的纳米颗粒为斜方晶系Cu2S,沉积后纳米线表面结构改变,粗糙度明显增加,起到了减少纳米线的光反射、优化原纳米线阵列光吸收综合能力的作用。     

交流电化学沉积铜纳米线阵列及其机理探讨

利用二次阳极氧化的方法制备孔高度有序的阳极氧化铝(AAO)为模板,采用交流电化学沉积方法,在AAO模板孔道内制备Cu纳米线。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线衍射仪(XRD)对Cu纳米线的形貌、晶体结构进行研究。结果表明:模板的孔径均匀,孔道平直。Cu纳米线均匀分布在AAO模板纳米孔隙中,直径均一,并沿Cu(Ⅲ)晶面择优生长;AAO模板孔道生长铜纳米线不光滑,成凹凸状,并对此沉积机理进行探讨。     

不同碳硅比对合成高比表面积碳化硅的影响

以淀粉和工业水玻璃为原料,经过碳热还原反应制备出碳化硅纳米线.采用XRD、SEM、氮吸附-脱附和荧光光谱仪(PL)对所制备的样品进行表征,同时考察了碳硅比(物质的量比,下同)对碳化硅形貌、比表面积和荧光性能的影响.结果表明,当碳硅比为4.5时,合成的碳化硅为直的纳米线,比表面积为45m2/g,发光强度也达到最大.     

Production and characterization of single-crystal FeCo nanowires inside carbon nanotubes

We describe the synthesis of novel monocrystalline FeCo nanowires encapsulated inside multiwalled carbon nanotubes (MWNTs). These FeCo nanowires exhibit homogeneous Fe and Co concentrations and do not contain an external oxide layer due to the presence of insulating nanotube layers. The method involves the aerosol thermolysis of toluene-ferrocene-cobaltocene solutions in inert atmospheres. The materials have been carefully characterized using state-of-the-art high-resolution transmission electron microscopy (HRTEM), electron-energy-loss spectroscopy (EELS), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), electron diffraction, HREELS-STM elemental mapping, X-ray powder diffraction, and SQUID magnetometry. We noted that the formation of FeCo alloys occurs at relatively low pyrolytic temperatures (e.g., 650-750 degrees C). These single-crystal nanowires, which have not been reported hitherto, always exhibit the FeCo (110) plane parallel to the carbon nanotube axis. The FeCo nanomaterials have shown large coercive fields at room temperature (e.g., 900 Oe). We envisage that these aligned ferromagnetic nanowires could be used in the fabrication of high-density magnetic storage devices and magnetic composites.     

Synthesis of SiC nanowires with in-situ deposition of carbon coating

SiC nanowires are effective reinforcement materials in ceramic matrix composites. A compliant coating such as carbon on nanowires is necessary in order to moderate the nanowire/matrix interfacial bounding for taking the most advantages of SiC nanowires. SiC nanowires with an in-situ deposition of carbon shell coating were fabricated by a novel chemical vapor growth process. Highresolution transmission electron microscopy examinations showed that the nanowires consisted of a single crystal beta-SiC core with an amorphous carbon shell 2-5 nm in thickness. The nanowires were straight with a length generally over 10 microm and a diameter 15-150 nm. The growth direction of the core SiC nanowires is (111). A simple three-step growth model for SiC nanowires was proposed based on a vapor-solid growth mechanism. Because the carbon-coated nanowires were grown directly on continuous Tyranno-SA SiC fibers, in-situ application of the present technique on the fabrication of SiC nanowire-reinforced SiC/SiC composites is expected.     

Preparation and characterization of SiC nanowires and nanoparticles from filter paper by sol–gel and carbothermal reduction processing

The carbothermal reduction of SiO₂ gel containing filter paper (as carbon precursors) in argon was used to prepare SiC nanowires and nanoparticles. The resulting SiC ceramic, as well as the conversion mechanism of carbon/silica composites to SiC nanowires and nanoparticles, have been investigated by scanning electron microscopy (SEM), Transmission electron microscopy (TEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TG) techniques. XRD and IR studies show that the materials, obtained from reaction at 1550 °C for 1 h in static argon atmosphere, are β-SiC. SEM and TEM reveal that SiC nanowires is single crystal wires with diameters ranging from 50–200 nm and their lengths over several tens of microns. According to thermodynamic analysis, SiC nanowires and SiC nanoparticles in the resulting SiC ceramic are formed by gas-gas reaction of SiO (g) and CO (g).     

Controlled growth of CuO nanowires on woven carbon fibers and effects on the mechanical properties of woven carbon fiber/polyester composites

The effect of CuO nanowires on the improvement of the mechanical properties of woven carbon fiber (WCF)-based polyester resin composite was studied. The composite was manufactured by the vacuum-assisted resin transfer molding (VARTM) process. CuO nanowires were grown on woven carbon fiber sheets in subsequent steps of seeding followed by growth. Scanning electron microscopy (SEM) showed the growth of CuO nanowires on the surface of the carbon fibers; this growth increased with the number of seeding cycles and the length of the growth time. The concentration of the growth solution did not have a significant effect. The maximum amount of growth occurred for 8 seeding cycles with a 60 mM growth solution and a growth time of 8 h. An analysis of the percent weight change, along with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, supported the above findings. The crystalline peak height of the CuO nanowires increased with the nanowire growth. The new absorption peaks arising in the FTIR spectra also indicated growth of CuO nanowires on the WCF. The mechanical properties in terms of tensile strength, modulus, and impact resistance improved significantly after the growth of nanowires on the carbon fibers: the modulus and strength improved by up to 33.1% and 42.8%, while the impact energy absorption increased by 136.8% relative to bare WCF.     

基于碳纳米管模板的氮化镓纳米线束合成

通过金属有机物化学气相沉积方法在碳纳米管模板上生长氮化镓纳米线束.对所生长的纳米结构进行了扫描电镜和X射线能谱分析,结果显示氮化镓纳米晶体可以与碳纳米管形成纳米线束状复合物.纳米线束状复合物直径为100～200 nm,长度为1.5～2.5μm,纳米线的两端呈现尖角状.由于氨气很容易吸附在碳纳米管表面,可知所获得的纳米结构的初始生长机制为碳纳米管的表面氮化.该研究也证明金属有机物化学气相沉积将是用于制造化合物纳米结构材料的一项有效的技术.     

Layer-by-layer assembly of TiO2 nanowire/carbon nanotube films and characterization of their photocatalytic activity

We report on the layer-by-layer (LbL) formation of TiO(2)-MWNT-TiO(2) coatings on quartz with either trititanate derived TiO(2) nanowires or Degussa P25 as the photocatalytically active material. The optimized deposition sequence is discussed in detail and the morphology of the prepared coatings is analyzed by SEM and XRD. The heterogeneous photocatalytic performance of the coatings was tested in the methyl orange oxidation reaction. The apparent first order rate constant fell in the 0.01-0.20 h(-1) range over a 2.5 × 2.5 cm(2) film depending on the type and the thickness of the titanate coating. Building a multiwall carbon nanotube layer into the middle of the layer improved the photocatalytic activity for each material for all of the studied thicknesses. P25 based films performed 2-5 times better than TiO(2) nanowire films; however, the pores in the P25 based films were largely blocked because the isotropic P25 nanoparticles form closely packed layers by themselves and even more so with the comparably sized multiwall carbon nanotubes. Therefore, films derived from titanate nanowires appear to be more suitable for use as multifunctional, photocatalytically active filtration media.     

CuO纳米线在碳纤维上的制备与表征

通过热氧化镀铜碳纤维,在碳纤维上制备了CuO纳米线。利用热重分析研究了镀铜碳纤维的热氧化过程。通过扫描电子显微镜、X射线衍射以及透射电子显微镜研究了退火温度、时间以及碳纤维对CuO纳米线生长的影响。结果表明,所制备的CuO纳米线为单斜型单晶结构,在碳纤维上制备CuO纳米线的最佳条件为400℃退火2h。并讨论了CuO纳米线在碳纤维上的生长机理。     

Electric field-assisted deposition of nanowires on carbon nanotubes for nanoelectronics and sensor applications

Manipulation and control of matter at the nanoscale and atomic scale levels are crucial for the success of nanoscale sensors and actuators. The ability to control and synthesize multilayer structures using carbon nanotubes that will enable the building of electronic devices within a nanotube is still in its infancy. In this paper, we present results on selective electric field-assisted deposition of metals on carbon nanotubes realizing metallic nanowire structures. Silver and platinum nanowires have been fabricated using this approach for their applications in chemical sensing as catalytic materials to sniff toxic agents and in the area of biomedical nanotechnology for construction of artificial muscles. Electric field-assisted deposition allows the deposition of metals with a high degree of selectivity on carbon nanotubes by manipulating the charges on the surface of the nanotubes and forming electrostatic double-layer supercapacitors. Deposition of metals primarily occurred due to electrochemical reduction, electrophoresis, and electro-osmosis inside the walls of the nanotube. SEM and TEM investigations revealed silver and platinum nanowires between 10 nm and 100 nm in diameter. The present technique is versatile and enables the fabrication of a host of different types of metallic and semiconducting nanowires using carbon nanotube templates for nanoelectronics and a myriad of sensor applications.     

Synthesis,characterization and growth mechanism of ZnO nanowires on NiCl<Subscript>2</Subscript>-coated Si substrates

Well-crystallized ZnO nanowires have been successfully synthesized on NiCl₂-coated Si substrates via a carbon thermal reduction deposition process. The pre-deposited Ni nanoparticles by dipping the substrates into NiCl₂ solution can promote the formation of ZnO nuclei. The as-synthesized nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectrum. The results demonstrate that the as-fabricated nanowires with about 60 nm in diameter and several tens of micrometers in length are preferentially arranged along [0001] direction with (0002) as the dominate surface. Room temperature PL spectrum illustrates that the ZnO nanowires exist a UV emission peak and a green emission peak, and the peak centers locate at 387 and 510 nm. Finally, the growth mechanism of the nanowires is briefly discussed.