A novel nano-nonwoven fabric with three-dimensionally dispersed nanofibers: entrapment of carbon nanofibers within nonwovens using the wet-lay process

This study demonstrates, for the first time, the manufacturing of novel nano-nonwovens that are comprised of three-dimensionally distributed carbon nanofibers within the matrices of traditional wet-laid nonwovens. The preparation of these nano-nonwovens involves dispersing and flocking carbon nanofibers, and optimizing colloidal chemistry during wet-lay formation. The distribution of nanofibers within the nano-nonwoven was verified using polydispersed aerosol filtration testing, air permeability, low surface tension liquid capillary porometry, SEM and cyclic voltammetry. All these characterization techniques indicated that nanofiber flocks did not behave as large solid clumps, but retained the 'nanoporous' structure expected from nanofibers. These nano-nonwovens showed significant enhancements in aerosol filtration performance. The reduction-oxidation reactions of the functional groups on nanofibers and the linear variation of electric double-layer capacitance with nanofiber loading were measured using cyclic voltammetry. More than 65 m2 (700 ft2) of the composite were made during the demonstration of process scalability using a Fourdrinier-type continuous pilot papermaking machine. The scalability of the process with the control over pore size distribution makes these composites very promising for filtration and other nonwoven applications.     

Surface coating of carbon nanofibers/nanotubes by electrodeposition for multifunctionalization

Carbon nanomaterials in the form of paper sheets have been used as platforms to achieve multifunctionality. Combined with electrochemical deposition, room temperature synthesis of magnetic Ni coatings on individual carbon nanofibers (CNF) and/or carbon nanotubes (CNT) has been realized through solution penetration and ion diffusion. In addition to significant electrical conductivity improvement, the magnetic responses of the Ni coated carbon nanopaper sheets can be tuned within large ranges in terms of saturation magnetic field, remnant magnetization and coercivity. After being re-suspended in liquids, the magnetized CNFs/CNTs can be aligned with small external magnetic fields.     

用脉冲电沉积法制备两类纳米介孔氧化镍电致变色薄膜的研究

采用脉冲电沉积技术在ITO导电玻璃上制备了NiO电致变色薄膜,并用X射线衍射仪、扫描电镜和能谱仪分析薄膜的结构、形貌和成份,用紫外-可见光分光光度计测试薄膜的光学性能,用循环伏安法测试薄膜的电化学性能,对比研究了Co掺杂对NiO薄膜电致变色性能的影响。结果表明Co掺杂优化了NiO薄膜表面形貌,形成了均匀分布的纳米介孔微结构,从而提高了薄膜电化学活性,同时提高了薄膜的光调制幅度。     

Growth of carbon nanostructures on carbonized electrospun nanofibers with palladium nanoparticles

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.     

Biocompatible conductive architecture of carbon nanofiber-doped chitosan prepared with controllable electrodeposition for cytosensing

A novel architecture was designed by combining the biocompatibility of chitosan (CS) and excellent conductivity of carbon nanofiber (CNF). The controllable electrodeposition of soluble CNF-doped CS colloidal solution formed a robust CNF-CS nanocomposite film with good biocompatibility for the immobilization and cytosensing of K562 cells on an electrode. The formed architecture was characterized using scanning electron microscopic, infrared spectrum, contact angle, and thermogravimetric analyses. The adhesion of K562 cells on the nanocomposite film-modified electrode could be followed with electrochemical impedance spectroscopy and cyclic voltammetry. The presence of CNF facilitated the electrochemical behavior of K562 cells. The impedance of electronic transduction was related to the amount of the adhered cells, producing a highly sensitive impedance sensor for K562 cells ranging from 5 x 10(3) to 5.0 x 10(7) cells mL-1 with a limit of detection of 1 x 10(3) cells mL-1. This work suggested a strategy to prepare a biocompatible and conductive interface for immobilization and electrochemical detection of cells and opened a way for the application of CNF in cytosensing.     

多方向生长碳纳米纤维的催化燃烧制备

介绍一种简单的合成具有多方向生长结构的碳纳米纤维的工艺。该工艺采用甲醇作为碳源，在铜基底上，以硝酸镍作为催化剂先体，经甲醇催化燃烧分解直接合成该结构材料，而无需任何模板。通过扫描电子显微镜的表征，不同分支结构的碳纳米纤维被合成。透射电子显微镜的结果表明，该样品具有较好的微结构。     

液相电沉积类金刚石薄膜的组成及结构分析

利用液相电沉积的方法，从乙腈中在硅片上沉积非晶碳薄膜，首次发现了电流密度随反应时间呈波动变化的规律。红外光谱和拉曼光谱分析表明所得薄膜是一种典型的含氢类金刚石薄膜(a-C：H薄膜)，并用高斯分解的方法对非晶碳薄膜的拉曼光谱和X射线光电子能谱进行定量分析，从而确定这种a-C：H薄膜中sp^3的相对含量为30％～35％。     

Preparation of Ni nanoparticle-TiO2 nanotube composite by pulse electrodeposition

A Ni/TiO₂ nanocomposite was successfully prepared by a pulse electrodeposition (PED) technique. Highly-ordered TiO₂ nanotube arrays fabricated by anodization were employed as a substrate and loaded with Ni nanoparticles by PED. The influence of pulse electrodeposition parameters was investigated on the morphology of nickel electrodeposits. The nanocomposite was characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicated that Ni nanoparticles with average size ranging from 19 to 84 nm were obtained by changing electrodeposition parameters. At constant current off-time (t_off) and pulse time of both negative and positive currents, the particle size decreased asymptotically with increasing amplitude of both negative and positive current. A progressive decrease of the particle size was observed with increasing current off-time at constant amplitude and pulse time of both negative and positive current. Increase in the deposition time at constant current off-time, amplitude and pulse time of both negative and positive current resulted in particle growth.     

Multi-scale reinforcement of CFRPs using carbon nanofibers

In this paper, stacked-cup carbon nanofibers (CNF) were dispersed in the matrix phase of carbon-fiber-reinforced composites based on a high-performance epoxy system with and without modification by an elastomeric triblock copolymer (TCP) for increased toughness. The addition of the TCP provided an enhancement in toughness at the cost of a slight degradation in modulus and strength. The CNFs, on the other hand, provided significantly enhanced strength and stiffness in matrix-dominated configurations, including tension of quasi-isotropic composites and short beam shear strength of both quasi-isotropic and unidirectional composites. Scanning electron microscopy revealed enhanced adhesion between the matrix and carbon fibers with the addition of either TCP or CNFs. However, CNF agglomeration in the studied systems partially offset the energy dissipation processes brought about by the nanofibers, thereby limiting interlaminar fracture toughness enhancements by CNF addition. These results show good promise for CNFs as low-cost reinforcement for composites while offering insight into the codependent morphologies of multi-scale phases and their influence over bulk properties.     

Growth of carbon nanofibers catalyzed by silica-coated copper nanoparticles

Silica-coated copper nanoparticles were synthesized by coating copper nanoparticles with a silica shell through microemulsion. The copper nanoparticles are 30–40 nm in diameter and the silica coating is 10 nm in thickness. After coating, copper nanoparticles were encapsulated in a silica matrix. These particles were used as a catalyst for the growth of carbon nanofibers in a tubular furnace. It is found that carbon nanofibers are mirror-symmetric growth and 100 nm in diameter. During growth, the copper nanoparticles moved out of the silica. As the experiment progressed, the interplanar spacing of copper (2 2 0) increased from 0.1288 nm to 0.1306 nm indicating that (2 2 0) plane exhibited high catalytic activity. The out-of-sync growth of different faces provides new evidence for the research of growth mode in carbon nanofibers.     

Conducting nanocomposites based on polyamide 6,6 and carbon nanofibers prepared by cryogenic grinding

Nanocomposites based on polyamide 6,6 and carbon nanofiber have been obtained following a new procedure. It consists of the physical mixing of the polymer matrix, in the form of powder, and the corresponding amount of additive. Then, samples were prepared by compression molding and their structural characteristics, as well as their thermal and electrical properties were determined. The materials present good electrical conductivity at lower percolation thresholds than those corresponding to systems prepared by melt mixing. The study was carried out with two different grain sizes, and the findings are discussed in terms of the different size ratios of polymer to carbon nanofiber.     

Polyacrylonitrile nanofibers prepared using coaxial electrospinning with LiCl solution as sheath fluid

A modified coaxial electrospinning process including an electrolyte solution as sheath fluid was used for preparing high quality polymer nanofibers. A series of polyacrylonitrile (PAN) nanofibers were fabricated utilizing a coaxial electrospinning containing LiCl in N, N-dimethylacetamide (DMAc) as the sheath fluid. FESEM results demonstrated that the sheath LiCl solutions have a significant influence on the quality of PAN nanofibers. Nanofibers with smaller diameters, smoother surfaces and uniform structures were successfully prepared. The diameters of nanofibers were controlled by adjusting the conductivity of the sheath fluid over a suitable range and this was determined by varying LiCl concentrations. The influence of the effect of LiCl on the formation of PAN fibers is discussed and it is concluded that coaxial electrospinning with electrolyte solutions is a convenient and facile process for achieving high quality polymer nanofibers.     

Growth of carbon nanofibers on nanoscale catalyst strips fabricated with a focused ion beam

We studied the growth mode of vertically aligned carbon nanofibers (CNFs) on Ni catalyst strips fabricated using a focused ion beam (FIB). We found that the CNF growth on Ni catalysts was strongly affected by the geometry of the microfabricated Ni catalyst strips. Selective growth of vertically aligned CNFs requires ion milling from the outside edge of the sample so that the milled materials are effectively evacuated. The CNF diameter and density on the strip depends on its width. Possible mechanisms to control CNF growth using microfabricated catalysts are analyzed with a liquid model using surface free energies.     

PVP nanofibers prepared using co-axial electrospinning with salt solution as sheath fluid

A modified co-axial electrospinning process using salt solutions as sheath fluids for preparing polymer nanofibers was investigated. A series of polyvinylpyrrolidone (PVP) fibers were prepared with NaCl aqueous solutions at varying concentrations as sheath fluids. The sheath fluid had a significant influence on the formation of the compound Taylor cone. Scanning electron microscopy results demonstrated that the diameters of PVP nanofibers could be manipulated through the concentration of NaCl solutions within an appropriate range. With 2 mg ml^− 1 NaCl solution as sheath fluid, the smallest PVP nanofibers, with a diameter of 120 ± 40 nm, were obtained. Co-axial electrospinning with salt solutions as sheath fluids is a facile method for achieving finer, homogeneous polymer nanofibers.     

Titanium carbide/carbon composite nanofibers prepared by a plasma process

The incorporation of metal or metal carbide nanoparticles into carbon nanofibers modifies their properties and enlarges their field of application. The purpose of this work is to report a new non-catalytic and easy method to prepare organized metal carbide-carbon composite nanofibers on nanopatterned silicon substrates prepared by laser interference lithography coupled with deep reactive ion etching. Titanium carbide-carbon composite nanofibers were grown on the top of the silicon lines parallel to the substrate by a hybrid plasma process combining physical vapor deposition and plasma enhanced chemical vapor deposition. The prepared nanofibers were analyzed by scanning electron microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. We demonstrate that the shape, microstructure and the chemical composition of the as-grown nanofibers can be tuned by changing the plasma conditions.     

Single-walled carbon nanotube-reinforced copper composite coatings prepared by electrodeposition under ultrasonic field

Single-walled carbon nanotube-reinforced Cu composite coatings prepared by electrochemical deposition under ultrasonic field exhibit smaller crystallite size and higher lattice micro-strain compared with a pure Cu coating. The as-deposited coatings retain a good electrical conductivity comparable to pure copper and simultaneously show a significant enhancement in mechanical properties. This indicates that the present electrochemical deposition technique can be used for preparing the carbon nanotube-reinforced metals with enhanced mechanical and functional properties.     

Catalytic synthesis of carbon nanofibers and nanotubes by the pyrolysis of acetylene with iron nanoparticles prepared using a hydrogen-arc plasma method

Carbon nanofibers (CNFs) and carbon nanotubes (CNTs) were synthesized at different temperatures by the catalytic pyrolysis of acetylene with iron nanoparticles prepared using a hydrogen-arc plasma method. The obtained carbon nanomaterials were characterized by transmission electron microscopy and field-emission scanning electron microscopy. An iron nanoparticle was always located at the tip of CNFs or CNTs, whose diameter was approximately identical with the diameter of the iron nanoparticle. The structures of the products were closely related to the reaction temperature, and could be changed from fibers to tubes by simply increasing the temperature. CNFs were obtained at the reaction temperature of 550-650 °C. When the reaction temperature was increased to 710-800 °C, CNTs were obtained.