Abstract: Nanosized Fe based powders have been synthesized by both chemical vapor
condensation (CVC) and plasma arc discharge (PAD) processes. Fe, Fe-C and Fe-N nanopowders were successfully synthesized. The influence of experimental parameters on microstructures and phase composition of nanopowders was investigated. The prepared powders were nearly spherical
in shape and core-shell type in structure. Various kinds of Fe-C and Fe-N composite nanopowders could be synthesized by controlling the carrier gas and precursor decomposition temperature, etc.
Abstract: To investigate the catalytic mechanism for the growth of carbon nanotubes (CNTs), carbon materials was synthesized at 680°C with a gas mixture of CO-H2 after reduction at 800°C by H2 gas. The synthesized carbon materials on reduced metallic surface were comprehensively explored by scanning electron microscopy (SEM) and X-ray diffraction patterns (XRD) at various reaction times
of 2, 10, 70, and 150 min, respectively. The carbon materials synthesized by metal Pt were little affected by reaction time, and only the sintered particles were observed without formation of CNTs. From X-ray analysis, iron oxides synthesized for 2 min were completely converted to iron carbide (Fe3C) without Fe peaks. After 5 min, iron carbide (Fe3C) and carbon (C) phases were observed at the
beginning of CNTs growth. It was found that the intensity of carbon(C) peak was gradually increased with the continuous growth of CNTs as reaction time increases. The carbon materials synthesized from the metal Pt were amorphous. It was also found that a catalyst on growth of CNTs was metal carbide.
Abstract: Cu oxide nanoparticles were formed by reacting with Polyamic acid (PAA) with Cu during imidization. In this paper, we investigated the effect of holding time during curing on the Cu oxide nanoparticle formation. Cu thin films were deposited on SiO2/Si substrates by thermal evaporation. Polyamic acid was then spin-coated on the Cu thin film. The polyamic acid films were soft-baked at 135°C for 30 minutes and thermally cured at 350°C with various holding time in a nitrogen atmosphere. The size of the Cu2O nanoparticles formed in the polyimide (PI) matrix increased as the holding time increased. The size and distribution of Cu oxide particles were characterized using Transmission Electron Microscope (TEM). The degree of imidization of PI also increased proportional to the increase in holding time. The degree of PI imidization was analyzed by Infrared (IR) spectroscopy. Very uniform Cu2O particles less than 5 nm in size with particle density greater
than 2×1012/cm2 were fabricated by controlling the holding time during curing.
Abstract: The effect of H2 gas during the carbon nanotubes (CNTs) synthesis with CO-H2 gas mixture was investigated using by mass measurement, and scanning electron microscopy (SEM). The maximum weight and yield of the synthesized carbon (C) were obtained when the mixture ratio of H2:CO was 3:7 and 9:1, respectively. In case of 100% carbon monoxide (CO) without hydrogen (H2)
addition, the weight of carbon increased, but CNTs were not observed. The CNTs were formed when the contents of H2 reaches at least 10%, and their structures became more distinct with an increase of H2 addition, and then the shapes of CNTs were more thin and straight. When the contents of H2 was 80% (H2:CO = 8:2), the shapes and growth of CNTs showed an optimal condition. On the other hand,
when the contents of H2 was higher than the critical value, the shapes of CNTs became worse due to transition into inactive surface of catalyst. It was found that H2 played a major role in the shapes and structures of CNTs.
Abstract: During the crystallization study of the bulk metallic glass 46.8Ti8.2Cu7.5Ni10Be27.5 (Vit4) we have demonstrated that the primary crystals appearing during isothermal annealing in the glass region, above Tg and before Tx, were of quasicrystalline nature and beryllium free. The formula of the quasicrystalline phase so obtained and determined by electron techniques (EDX and EELS) was
Zr63Ti14.4Ni12.4Cu10.2. We have synthesized phases in the system Zr75-xTixCu25-yNiy by melt spinning and obtained either amorphous or quasicrystalline phases. For the amorphous phases, we have studied the crystallization by in-situ neutron diffraction and obtained quasicrystals as primary crystals. Neutron and X-ray diffraction, DSC studies are presented.
Abstract: Nanostructured Fe-Co based alloys are believed to be good candidates for imparting
improved magnetic behavior in terms of higher permeability, lower coercivity, reduced hysteresis loss and higher Curie temperatures. In the present work, Fe-Co alloys with Ni additions were prepared using mechanical alloying (MA). Grain size and internal strain in the MA powders was measured using X-ray diffraction. It has been shown that the grain size could be reduced down to less than 5 nm
in these alloys. Nanocrystalline materials thus obtained were also evaluated for magnetic behavior and the influence of grain size and internal strain on the magnetic properties has been discussed.
Abstract: Nano-sized Si/C/N powders are prepared from hexamethyldisilazane ((CH3)3Si)2NH) by chemical vapor deposition (CVD) at different pyrolysis temperatures from 900°C to 1200°C. The as-formed Si/C/N nano powder is amorphous, and after controlled heat-treatment, SiC crystals formed. The composition of the Si/C/N powders prepared at different conditions is analyzed and the result shows that the nitrogen content of the Si/C/N powder is related to the synthesizing temperature. Si/C/N powders heat-treated at different temperatures are mixed with paraffin wax and the microwave permittivity of the mixture is measured. The result shows that the e¢, e², and the dissipation factor tg d ( e²/ e¢) of the mixture are high at the frequency of 8.2~12.4GHz, and the
nitrogen content and the degree of crystallization have influence on the microwave permittivity. We believe that the high value of e¢, e² ,and tg d are due to the dielectric relaxation as the result of nitrogen atoms doped in silicon carbide lattice.
Abstract: Heagonal GaN nanorods have been synthesized through ammoniating ZnO/Ga2O3 films deposited by radio frequency(rf) magnetron sputtering on Si(111) substrates.X-ray diffraction(XRD), Fourier transform infrared spectrophotometer (FTIR), transimission electron microscopy(TEM), high-resolution transmission electron microscopy(HRTEM) and selected-area electron diffraction
(SAED) are used to analyze the structure,composition and morphology of the synthesized GaN nanorods. TEM result shows that GaN nanorods own bamboo-shaped morphalogy and have a single-crystal hexagonal wurtzite structure.The average length and dimeter of the nanorods are 3μm and 50 nm espectively.Ga2O3 and NH3 reactived directly and synthesized GaN nanorods without any
catalyzer and the process of space-confined reactions.
Abstract: A simple and facilitate method was reported to synthesize zinc oxide and lead oxide nanorods. Two metal oxides nanorods were directly obtained from grinding solid metallic salts and sodium hydroxide in agate mortar with the assistance of a suitable surfactant in only one step, which is different from the results of hydroxides in solution. The as-prepared products were characterized by XRD, TEM and SEM. An explanation describing possible mechanism for the rod-formation is given.
Abstract: Sub-micrometer diamond tube arrays are formed on freestanding diamond film via
focused ion beam pattern technology and chemical etching method. First, the sub-micrometer holes are fabricated on Si substrate by using FIB milling method. Then, diamond film is grown by hot filament chemical vapor deposition method on patterned Si substrate. By controlling the deposition parameters, the diamond can be grown along the wall of holes and the diamond tubes in sub-micrometer scale are formed. Finally, Si substrate is etched by chemical etching method and the
diamond tube arrays are fabricated on a freestanding diamond film. Scanning electron microscopy and Micro-Raman spectroscopy measurements are performed to characterize the structure and phase purity of diamond tubes. The electron emission properties from the diamond tube arrays are studied, the result presents that the enhanced emission property can be obtained from diamond tube