Advanced Materials Research Vols. 750-752

Abstract: Alumina nanofibers were fabricated by single-spinneret electrospinning of aluminium nitrate (Al (NO₃)₃)/polyacrylonitrile (PAN) precursor solution, followed by sintering treatment. The Al (NO₃)₃/PAN composite fibers and sintered fibers were characterized by SEM, TG, FTIR and XRD. It is found that the obtained alumina nanofibers show porous external surfaces and hollow sections. Upon calcining the composite fibers at 1000 or 1300 oC, the nanofibers are consisted of α-phased crystalline grains. Sintering temperature plays an important role in controlling the morphology and crystal structure of the nanofibers. A mechanism based on Kirkendall Effect was proposed to explain the formation process of the hollow structure.

Abstract: Rutile structure SnO₂ nanomaterials was successfully synthesized by cationic surfactant CTAB assisted method from inorganic precursor and alkali source (SnCl₄·5H₂O and NaOH) solution under microwave radiation. The final products were characterized by XRD, SEM and TEM. The results show that pure and high crystalline of SnO₂ nanomaterials was obtained after calcining at 500 °C. The gas-sensing characteristics of SnO₂ nanomaterials to formaldehyde, acetone, isopropyl alcohol, xylene, toluene, alcohol, gasoline, ammonia were investigated. The sensor based on SnO₂ nanomaterials exhibits good response properties to isopropyl alcohol.

Abstract: A non-aqueous synthetic route has been developed for the preparation of uniform Cu nanowires with length up to tens of micrometers. Unlike commonly used one-pot synthesis approach that usually involve a fast reduction of metal precursors in the presence of reducing agents, a continuous-injection approach has been to utilized to control the speed of reaction and the concentration of Cu nuclei. In this approach, copper (II) chloride dihydrate and nickel (II) acetylacetone which are dissolved in oleylamine solutions have been injected into octadecene by a syringe-pump. The as-prepared samples have been characterized by transmission electron microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results show that the products are pure Cu nanowires which have preferred <110> growth directions. The formation mechanism and major influencing factors on the synthesis of Cu nanowires have been discussed.

Abstract: Nickel molybdate is one of the significant and frequently-used basis materials for catalyst. The micro/nanohydrated nickel molybdate with different shapes has been successfully prepared via hydrothermal route using chelator as shape-control agent under the pH values from 4.5 to 6.4. The x-ray powder diffractometry, transmission electron microscope and scanning electron microscope were employed for the characterization and analysis of the phase, morphology and size of the resulting products. The chelator plays a key role for the shape and crystalline degree of the hydrated nickel molybdate. With the pH values of the initial suspension set below 4.5 or above 6.4, no any solid products could be obtained despite using the same hydrothermal preparation conditions. The formation mechanism of the related products with multiple shapes has been proposed.

Abstract: Well-aligned ZnO nanorod arrays on Chaleted Sol-Gel-Derived ZnO thin films was achieved at a temperature of 90°C by a surfactant-assisted soft chemical approach. The nanorod arrays were characterized by XRD, SEM, XPS, and UV-Vis absorbance spectra. The ZnO nanorod arrays are wurtzite crystal stuctures preferentially orienting in the direction of the c-axis and ZnO nanorods are grown verticallyon the substrate. The XPS analysis shows the Zn:O ratio of ZnO nanorod arrays near is 1:1. The UV-Vis absorbance spectra indicate that ZnO nanorod arrays have absorption of visible-light as well as ultraviolet-light. Therefore, the ZnO nanorods may be good candidates for visible-light photocatalysis materials from the viewpoint of practical applications.

Abstract: Four kinds of TiO₂/CNT (or carbon fiber) composites were successfully prepared by the sol-gel method using Ti(OBu)₄ as precursor of TiO₂, and untreated CNT, carboxylic CNT, hydroxylated CNT and carbon fiber were used as carriers, respectively. After heat treatment at 400 and 800°C, TiO₂/CNT nanocomposites and purified TiO₂ were obtained. Their structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that different carbon nanotubes and nanofiber have notable influences on the morphology and structure of TiO₂ nanocrystals.

Abstract: In this study, carbon nanofibers were synthesized on iron and copper catalysts by Chemical Vapor Deposition (CVD). Investigation was made with respect to variation on thickness and surface of fibers based on concentration of iron and copper. In order to prepare metal catalysts of respective synthesis, iron nitrate and copper nitrate were calculated in proportion to weight ratio and then dissolved into distilled water. Obtained catalyst precipitates were filtered and then dried for more than 24 hours at 110°C. Carbon nanofibers were composed by using ethylene gas of carbon source through CVD after pulverization of fully dried catalyst precipitates. Analysis through SEM was made in order to investigate structural characteristics of composed carbon nanofibers, and qualitative and quantitative analyses were conducted on elements through EDS. In addition, crystalline analysis was made on carbon nanofibers through XRD and Raman, and specific surface area measurement was carried on carbon nanofibers composed through BET.

Abstract: Polyvinyl alcohol (PVA) water solution was electrospun by both needle electrospinning and needleless electrospinning. The electrodes for needless electrospinning were rotary spiral disk and spiral coil made from stainless steel. We found that needleless electrospinning can obtain nanofibers in large-scale, while fiber diameter and diameter distribution were larger when compared to the conventional needle electrospinning. The average diameters of disk electrospun and coil electrospun nanofibers were 441±99nm and 415±103nm respectively. As for needle electrospun nanofibers, the diameters were 393±29nm and 349±25nm when the applied voltage were 10kV and 15kV respectively.

Abstract: This research was conducted to synthesize carbon nanofibers on C-fiber textiles by thermal CVD using Fe catalyst. The substrate which was a carbon textile consisting of non woven carbon fibers and attached graphite particles, was oxidized by nitric acid before the deposition process. Hydroxyl groups were created on the C-fiber textile due to the oxidization step. Fe (III) hydroxide was subsequently deposited on the oxidized surface of the C-fiber textile. To deposit ferric particles two different methods were tested: i) deposition-precipitation, ii) dip-coating. For the experiments using both type of catalyst deposition the weight ratio of Fe to C-fiber textile was also varied. Ferric particles were reduced to iron after deposition by using H₂/N₂ gas and CNFs were grown by flowing ethylene gas. Properties of carbon nanofibers created like this were analyzed through Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), N₂-sorption (BET), X-Ray Diffraction (XRD), and X-ray Photoelectron Spectoscopy (XPS). In the case of deposition-precipitation method the result shows that the diameter of carbon nanofibers grew up to 40~60nm and 30~55nm at which the weight ratios of Fe catalyst to C-fiber textiles are 1:30 and 1:70 respectively. If Fe particles were deposited by dip-coating method, the diameter of carbon nanofibers grew up to 40~60nm and 25~30nm for the ratios of Fe catalyst to C-fiber textiles 1:10 and 1:30.

Abstract: Polyaniline (PANI) nanofibers were fabricated through chemical oxidative polymerization at various organic solvent/water interfaces. The products were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). It is found that the morphologies, microstructures and properties of PANI nanofibers depend not only on the nature of organic solvents but also the adding way of aniline monomers and oxidant.