煤沥青基线团状碳纳米材料的合成和性能

以煤沥青为碳源、二茂铁为催化剂前驱体,在氢气和氩气气氛下,采用化学气相沉积法制备出由碳纳米管自组装的线团状碳材料;利用场发射扫描电子显微镜、高分辨透射电子显微镜、X-射线衍射和拉曼光谱仪对产物进行了形貌、结构的表征和分析.结果表明:产物为高纯度的碳纳米管自组装的线团状碳材料,其直径约0.5μm,碳纳米管直径为20 nm~45 nm;另外,测试了该产物的铁磁性和微波吸收性能,结果表明,在±10 000 Oe范围内,具有较大的矫顽力值(446.13 Oe),呈明显的铁磁性;在2 GHz~18 GHz频率范围内具有一定的微波吸收性能,有望成为铁磁性材料和微波吸收材料.     

微波等离子体法合成重油残渣基定向纳米碳薄膜

以重油残渣为原料,采用微波等离子法制备了一种结构新颖的定向纳米碳薄膜材料。经场发射扫描电子显微镜、高分辨透射电子显微镜分析,结果表明：产物纯度较高,外观呈条状麦穗形,各条状物平行排列形成定向阵列,最大宽度约为65nm,长度可达900nm左右;麦穗的主干表层和穗片晶化程度较好,层与层之间清晰可见,中心部位为非晶态,可能是产物经历了由外向内的生长过程,重油残渣中的重金属Ni、Fe等对其生长起了一定的催化作用。     

以碳球为模板合成氧化铈纳米空心球

以直径约为300nm的碳球为模板,通过无机物前驱体颗粒的自组装制备出CeO2/碳球复合物,煅烧去除碳球模板后,得到CeO2纳米空心球.借助透射电子显微镜、选区电子衍射、场发射扫描电子显微镜、X射线衍射、X射线光电子能谱和热重分析仪等测试手段对复合物的形貌和结构进行了表征.结果表明:产物空心球由面心立方相CeO2颗粒构成...     

利用碳模板制备ZrO2亚微米空心球

以水热法合成的单分散碳球为模板,通过无机物前驱体颗粒自组装制备出ZrO2/碳球复合物,采用两步煅烧去除碳球模板,制备出ZrO2亚微米空心球,研究了碳球模板表面改性对空心球结构和性能的影响。借助于X射线衍射、场发射扫描电子显微镜、透射电子显微镜和比表面积分析仪对空心球的组成、形貌和结构进行了表征。结果表明:碳球模板大小均匀,粒径在450nm左右,球表面光滑、形状规则、分散性好;碱处理能有效增加碳球模板表面的官能团数目,改善碳球表面的核电状态和亲水性,进而调控核-壳结构中壳层的厚度;产物空心球由四方相ZrO2组成,随碳球表面改性时间的增加,空心球壁厚逐渐增大,比表面积从104.7m2/g逐渐减小到47.9m2/g。     

碳包覆铁纳米金属颗粒的制备

以酚醛树脂为碳源,硝酸铁为催化剂大量制备碳包覆铁纳米金属颗粒。利用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、高分辨透射电子显微镜（HRTEM）等方法,分析和表征了产物的微观形貌和结构。结果表明：产物为纳米级的准球形碳一铁核壳结构,由同心碳纳米石墨壳层包覆纳米铁组成。产物外径30～100nm,碳层间距为0．34mm,与石墨层间距非常接近。     

化学气相沉积法制备新型有序大孔碳球及其表征

以二氧化硅(SiO_2)胶体微球为模板,以苯蒸气为碳源,采用胶晶模板法和化学气相沉积法,将苯蒸气在高温下碳化并沉积在SiO_2胶晶模板表面,通过氢氟酸的溶蚀作用去除SiO_2胶晶模板,制备了新型有序大孔碳球;通过场发射扫描电子显微镜、透射电子显微镜、X-射线衍射仪和物理吸附仪等对样品结构进行了表征。结果表明,当苯蒸气沉积时间为4h时,大孔碳球结构完整、排列有序,为石墨晶型。该研究为碳材料在生物医药领域的应用研究提供了新的思路和参考。     

NiO薄膜材料的制备及其电化学电容性能

以镍箔为基底,在Ni(NO3)2溶液中,用电沉积法制备Ni(OH)2薄膜,进行热处理后转化为NiO薄膜电极材料。采用X射线衍射(XRD)和场发射扫描电子显微镜(FESEM)表征产物的结构和形貌。用循环伏安法、恒电流充放电等电化学方法系统研究所制样品的电化学性能。研究结果表明,在Ni(NO3)2溶液浓度为0.08 mol.L-1,电压为-0.9 V条件下沉积,并经过250℃热处理制备的NiO薄膜材料属于立方结构,表现出良好的电化学性能,其单电极比电容值达1220 F.g-1。     

生物质碳材料在微生物燃料电池阳极中的应用

本文以一次性筷子为原材料,通过简单的活化工艺和煅烧工艺制备了多孔碳材料(PCs)。本文采用场发射扫描电子显微镜观察到了所制备的材料的形貌,证明成功制备了多孔碳材料。将一次性筷子多孔碳材料置于微生物燃料电池阳极中,多孔碳(PC-800)产生的最大电流密度约为1. 6 m A/cm2,远远高于传统的商用碳布(CC)。本文介绍了一种利用成本、效益高、可持续发展的天然材料制备高性能MFCs阳极材料的可行策略。     

单分散磁性Fe3O4纳米颗粒溶剂热合成及性能

采用溶剂热还原方法,以FeCl3·6H2O和乙二醇为原料,在160 ℃相对低温条件下成功合成四氧化三铁纳米颗粒.利用X射线衍射仪、场发射扫描电子显微镜和振动样品磁强计等手段对产物进行分析和表征.结果表明:产物Fe3O4为反尖晶石结构,其16 h、24 h合成产物平均粒径分别为145 nm和495 nm.颗粒间没有明显团聚,大小均匀,分散性好,表现出良好的单分散性.研究了反应时间对Fe3O4粒径的影响,24 h产物的饱和磁化强度为79.3 emu/g,显示出较高的磁性能.     

碳纳米带的催化生长及其机理的研究

采用热化学气相沉积法(thermal chemical vapor deposition,TCVD)在经过高温氨气处理后的硅基铁纳米薄膜表面实现片状碳纳米带的催化生长.通过场发射扫描电子显微镜(field emission scanning electron microscopy,FESEM)的观察可知,生成的碳材料是一种准二维材料,表面具有垂直于其长度方向的纹理,厚(z方向)约几十纳米,宽(Y方向)几百纳米,类似于一种"搓板"状的结构.而其宽度沿着其长度方向则有较大的变化,时宽时窄,没有固定的规律.这种带状碳纳米纤维材料的边缘光滑,比中间略宽,类似于一种镶边结构.通过高分辨透射电子显微镜(high resolution transmission electron microscopy,HRTEM)的观察可知,碳纳米带的碳层沿着垂直于碳纳米带长度的(002)方向有统一的排列,其边缘都弯曲折叠成封闭结构.有序排列的碳层被层错和断点分割成许多微区.在对催化剂研究的基础上,本文认为片状碳纳米带的生长是通过碳原子在片层状催化剂颗粒中的扩散、析出来实现的.碳层从催化剂片层侧面中一层一层地析出,形成带状外观.     

Effects of CF4 plasma on the field emission properties of aligned multi-wall carbon nanotube films

We present a simple method to functionalize the surface and to modify the structures of aligned multi-wall carbon nanotube (CNT) arrays grown on silicon substrates using CF₄ plasma produced by reactive ion etching (RIE). Field emission (FE) measurements showed that after 2 min of plasma treatment, the emission currents were enhanced compared with as-grown CNTs; however, extended treatment over 2 min was found to degrade the FE properties of the film. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy have been employed to investigate the mechanism behind the modified FE properties of the CNT film. The FE enhancement after 2 min of etching could be attributed to favorable surface morphologies, open-ended structures and a large number of defects in the aligned CNT films. On the other hand, deposition of an amorphous layer comprising carbon and fluorine during extended CF₄ plasma treatment may hamper the field emission of CNT films.     

Synthesis and frictional properties of array film of amorphous carbon nanofibers on anodic aluminum oxide

Amorphous carbon nanofiber arrays were synthesized in porous anodic aluminum oxide templates by pyrolysis of acetylene with cobalt nanoparticles as catalyst at 640 °C. The carbon nanofibers have amorphous structures under high-resolution transmission electron microscopy and Raman spectroscopy examination. The aligned amorphous carbon nanofibers grown within the pores of the aluminum oxide membranes are uniform with lengths of about 2 μm and outer diameters of about 85 nm. The frictional properties of the array film of amorphous carbon nanofibers were investigated using an atomic force and friction force microscopy (AFM-FFM) and a ball-on-disk machine in air. The adhesion between the amorphous carbon nanofiber arrays and the anodic aluminum oxide membrane remained intact at relatively low loads. The AFM-FFM measurements indicated that the friction forces on the array film of amorphous carbon nanofibers were uniform. The array film had low friction coefficient and high wear resistance under the micro friction tests. The friction coefficient of the array film dry sliding against a corundum counterface was observed to be constant after an initial transient period and decreased with increasing the sliding velocity.     

Synthesis of vertically aligned carbon nanotubes on metal deposited quartz plates

Without plasma aid, we have successfully synthesized vertically aligned carbon nanotubes (CNTs) on iron-, cobalt- or nickel-deposited quartz plates by chemical vapor deposition with ethylenediamine as a precursor. The amine serves as both etching reagent for the formation of metal nanoparticles and carbon source for the growth of aligned carbon nanotubes. The carbon nanotubes were vertically aligned in high density on a large area of the plain silica substrates. The density and diameter of CNTs is determined by the thickness of the deposited metal film and the length of the tubes can be controlled by varying the reaction time. High-resolution transmission electron microscopy analysis reveals that the synthesized CNTs are multiwalled with a bamboo-like structure. Energy dispersive X-ray spectra demonstrate that the CNTs are formed as tip growths. Raman spectrum provides definite evidence that the prepared CNTs are multiwalled graphitic structure.     

Aligned millimeter-long carbon nanotube arrays grown on single crystal magnesia

Single crystal magnesium oxide (MgO) was found to be very beneficial to the growth of aligned carbon nanotube (CNT) arrays as long as 2.2 mm by chemical vapor deposition. Before growth, a thin film of catalyst (iron) was coated on the MgO by magnetron sputtering. Scanning electron microscopy was used to study the alignment and length, and transmission electron microscopy was used to exam the wall numbers, diameter, and graphitization. It was found that the number of walls as few as two can be controlled by the catalyst film thickness, whereas the length is a combined result of gas pressure, temperature, and time during growth. Water was found not to be a factor to the length of CNTs grown on MgO, but a significant factor when sapphire was used as the substrates.     

Selective area synthesis of aligned carbon nanofibers by laser-assisted catalytic chemical vapor deposition

Arrays of freestanding bamboo-type carbon nanofibers were grown on the surface of a porous alumina substrate by laser-assisted catalytic chemical vapor deposition. A continuous wave argon ion laser operated at a wavelength of 488 nm was used to thermally decompose pure ethylene over nickel catalysts. Two different catalyst preparation methods were used and are compared with respect to the synthesis of aligned nanofibers. First, a thin nickel film (50 nm) was evaporated on the substrate and was subsequently laser annealed into nanoparticles. This preparation produced non-aligned nanofiber films. Second, a 50 nm thick catalyst layer was electrochemically deposited within the pores of an alumina substrate. This preparation produced an array of vertically aligned nanofibers. A growth rate dependence on radial position within the irradiated area was observed. Average linear growth rates ranging from 554 nm/s to 25 μm/s are reported. The nanofibers were examined by scanning electron microscopy and Raman spectroscopy. Fiber texture and nanotexture were determined by lattice fringe analysis from high resolution transmission electron microscopy images. The alignment mechanism is also discussed.     

Nucleation and aligned growth of multi-wall carbon nanotube films during thermal CVD

The development during early growth of a multi-wall carbon nanotube film by thermal CVD with acetylene (C₂H₂) and hydrogen at 750 °C has been characterized in detail by cross-section transmission electron microscopy. The studies provide information on the nanotube growth mechanisms and the complex catalyst transformations that are essential for the onset of different growth stages. An initial random growth catalysed by supported particles is followed by aerosol growth of aligned tubes. This results in a two-layered film structure, where a film of aligned nanotubes is lifting up an initially formed nanotube network from the substrate.     

Influence of transverse magnetic field on the formation of carbon nano-materials by arc discharge in liquid

To change the structures and yields of carbon nano-products, transverse magnetic field (TMF) was introduced to arc discharge in liquid (de-ionized water, liquid nitrogen). Direct current was used to sustain the arc discharge between two graphite electrodes and cobalt powder was filled in drilled anodes as catalyst sometimes. Scanning electron microscopy and high-resolution transmission electron microscopy were used to investigate the nano-products. Some novel carbon nano-structures were obtained with the effect of TMF. For arc discharge in water, curled multi-walled carbon nanotubes and nano-structures with few layers were found in cathode depositions and floating products, respectively. For arc discharge in liquid nitrogen, twists of single-walled carbon nanotubes appeared in cathode depositions and the yields of spherical nano-particles in floating products increased.     

镀锌钢板钙改性磷化膜生长机理的研究

研究了一种新型的钙改性磷化液在镀锌钢板上的成膜机理.通过扫描电镜(SEM)研究了钙改性磷化膜微观晶粒形态;用EDX分析膜层的主要成分;用极化曲线研究了钙离子对膜层耐蚀性能的影响;通过时间-电位曲线和SEM结合的方式研究了三元磷化膜晶粒在镀锌钢板上的生长机理.     

Nanoscale coaxial cables produced from vertically aligned carbon nanotube arrays grown via chemical vapor deposition and coated with indium tin oxide via ion assisted deposition

A highly conformal homogeneous indium tin oxide (ITO) thin film coating has been produced on vertically aligned carbon nanotube arrays by ion assisted deposition. The deposition process generates, in effect, a coaxial cable structure of ITO about a carbon nanotube. The deposited ITO films are uniformly 5 nm thick and have high crystallinity and excellent optical absorption properties, indicating they would be good candidates for use in solar cells, flexible electronics and displays. The materials are analyzed by scanning and transmission electron microscopy, X-ray diffraction, and visual light spectrometry.