Papers by Keyword: Chemical Vapor Condensation

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Authors: Chul Jin Choi, Jin Chun Kim, Ji Hun Yu, Byoung Kee Kim
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.
Authors: Jong Keun Ha, Kwon Koo Cho
Abstract: Iron(Fe)-molybdenum(Mo) alloyed nanopaticles and nanowires were produced by the chemical vapor condensation(CVC) process using the pyrolysis of iron pentacarbonyl(Fe(CO)5) and molybdenum hexacarbonyl(Mo(CO)6). The influence of CVC parameter on the formation of nanoparticle, nanowire and size control was studied. The size of Fe-Mo alloyed nanoparticles can be controlled by quantity of gas flow. Also, Fe-Mo alloyed nanowires were produced by control of the work chamber pressure. Obtained nanoparticles and nanowires were investigated by field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction.
Authors: Tae Suk Jang, J.H. Yu, D.W. Lee, B.K. Kim
Abstract: FePt binary alloy nanopowder has been synthesized by a chemical vapor condensation process using a mixture of iron acetylacetonate and platinum acetylacetonate. Particle size of the synthesized powder was less than 10 nm and the powder had very narrow size distribution with relatively high dispersivity. FePt nanopowder possessing L10 ordered phase was synthesized at the condition of well controlled precursor mixing ratio and reaction temperature with some disordered cubic phase.
Authors: D.W. Lee, Tae Suk Jang, Dae Hoon Lee, Byoung Kee Kim
Abstract: Iron and its nitride (e-Fe3N) nanoparticles were fabricated by the CVC using Fe(CO)5 precursor without the aid of LN2 chiller. The iron particles synthesized at 400 oC were a mixture of amorphous and crystalline a-Fe. Fully crystallized iron particles were then obtained above 600 oC. Iron-nitride particles that were easily formed at 500 oC at 1 atm., however, were not fully developed in vacuum unless the reaction temperature reached 850 oC. Nevertheless, the work chamber needed to be maintained in vacuum to obtain finer iron-nitride particles. The synthesized particles possessing the core-shell type structure were all nearly spherical and enclosed with Fe3O4 or Fe3O4-related amorphous layer. The iron nanoparticles (~20 nm) synthesized at 600 oC at 760 torr exhibited iHc ~ 1.0 kOe and Ms ~ 170 emu/g, whereas the iron-nitride particles (~20 nm) synthesized at 850 oC at 0.01 torr exhibited iHc ~ 0.45 kOe and Ms ~ 115 emu/g.
Authors: Jong Keun Ha, Kwon Koo Cho, Ki Won Kim, Tae Hyun Nam, Hyo Jun Ahn, Gyu Bong Cho
Abstract: Various physical, chemical and mechanical methods, such as inert gas condensation, chemical vapor condensation, sol-gel, pulsed wire evaporation, evaporation technique, and mechanical alloying have been used to synthesize nanoparticles. Among them, chemical vapor condensation(CVC) represents the benefit for its applicability to almost materials because a wide range of precursors are available for large-scale production with a non-agglomerated state. In this work, iron nanoparticles and nanowires have synthesized by chemical vapor condensation(CVC) process, using iron pentacarbonyl(Fe(CO)5) as precursor. The effects of processing parameters on the morphology, microstructure and size of iron nanoparticles and nanowires were studied. Iron nanoparticles and nanowires having various diameters were obtained by controlling the inflow of metallic organic precursor. Both nanoparticles and nanowires were crystallized. Characterization of obtained nanoparticles and nanowires were investigated by using a field emission scanning electron microscopy, transmission microscopy and X-ray diffraction.
Authors: Chul Jin Choi, X.L. Dong, Byoung Kee Kim, Jung Ho Ahn
Authors: Jin Chun Kim, Jae Wook Lee, Byung Yeon Park, Chul Jin Choi
Abstract: Fe/SiO2 nanocomposite powders were synthesized by the chemical vapor condensation(CVC) process. Phase and microstructures of the as-prepared powders were investigated with CVC experimental parameters by XRD, TEM and VSM. The analysis of XRD patterns revealed that the Fe/SiO2 powders could be produced above 700. With increasing reaction temperature, the XRD peaks became clearer. The size of powders was about 50nm at 1100oC. The Fe/SiO2 powders showed an intricate long-stand structure attributed to their magnetic characteristics. TEM results revealed that the Fe powders were covered by SiO2 layer fully or partially depending on the experimental condition. The saturation magnetization and the coercive force of the as-sytheised powders were investigated with the decomposition temperature.
Authors: C.W. Lee, S.G. Kim, Jai Sung Lee
Abstract: The influence of reaction temperature on phase evolution of iron oxide hollow nanoparticles during chemical vapor condensation (CVC) process using iron acetylacetonate was investigated. X-ray diffraction (XRD) analyses revealed that three iron oxide phases (α-Fe2O3, γ-Fe2O3, and Fe3O4) and a mixture of β-Fe2O3 and small amount of γ-Fe2O3 were synthesized at 700oC and 900oC, respectively. TEM observation disclosed that the iron oxide particles are almost composed of hollow structured nanoparticles of 10~20 nm in size and 3~5 nm in shell thickness. This result implies that reaction temperature determining various reaction parameters plays an important role for the phase- and structural evolutions of iron oxide hollow nanoparticles. Especially, the present investigation attempted to explain temperature dependence of the phase evolution of β-Fe2O3 hollow nanoparticles in association with the decomposition of iron acetylacetonate.
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