• Bulletin of the Korean Chemical Society
• /
• v.33 no.3
• /
• pp.839-842
• /
• 2012

We report for the first time the synthesis of niobium dioxide nanowires on a sapphire substrate by chemical vapor transport method. We identified single crystalline nature of as-synthesized nanowires by scanning electron microscopy and transmission electron microscopy. Niobium dioxide nanowires with their large surface-to-volume ratio and high activities can be employed for electrochemical catalysts and immunosensors. The Raman spectrum of niobium dioxide nanowires also confirmed their identity.

• Journal of Industrial Technology
• /
• v.35
• /
• pp.89-94
• /
• 2015

Graphene is a carbon-based two dimensional honeycomb lattice with monoatomic thickness and has attracted much attention due to its superior mechanical, electronic, and physical properties. Here, we present a synthesis of high quality graphene on Pt substrate using a chemical vapor deposition (CVD). We optimized synthesis condition with various parameters such as synthesis temperature, time, and cooling rate. Based on the results, we concluded that graphene synthesis is driven by mainly carbon adsorption on surface rather than precipitation of carbon which is dominant in other metal substrate. In addition, Pt substrate can be repeatedly used several times with high quality graphene.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.5
• /
• pp.681-686
• /
• 2004

Ti-ZSM-5 prepared by secondary synthesis, from the reaction of H-ZSM-5 with vapor phase $TiCl_4$, was characterized with several physicochemical techniques including FT-IR and UV/VIS-DRS. It was found that zeolite structure, surface area and pore volume did not change, and the framework aluminum could not be replaced by titanium atom during the secondary synthesis of Ti-ZSM-5. The incorporation of titanium into the framework might be due to reaction of $TiCl_4$with the silanol groups associated with defects or surface sites. The formation of extra-framework titanium could not be avoided, unless the samples were further treated by water vapor at 550 $^{\circ}C$ or higher temperature. High temperature steam treatment of Ti-ZSM-5 prepared by chemical vapor deposition with $TiCl_4$was efficient to prevent the formation of non-framework titanium species. Ti-ZSM-5 zeolites prepared in this work contained only framework titanium species and exhibited improved catalytic property close to TS-1 prepared by hydrothermal synthesis.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.6
• /
• pp.1687-1691
• /
• 2014

This study reports on the synthesis of carbon nanofibers via chemical vapor deposition using Co and Cu as catalysts. In order to investigate the suitability of their catalytic activity for the growth of nanofibers, we prepared catalysts for the synthesis of carbon nanofibers with Cobalt nitrate and Copper nitrate, and found the optimum concentration of each respective catalyst. Then we made them react with Aluminum nitrate and Ammonium Molybdate to form precipitates. The precipitates were dried at a temperature of $110^{\circ}C$ in order to be prepared into catalyst powder. The catalyst was sparsely and thinly spread on a quartz tube boat to grow carbon nanofibers via thermal chemical vapor deposition. The characteristics of the synthesized carbon nanofibers were analyzed through SEM, EDS, XRD, Raman, XPS, and TG/DTA, and the specific surface area was measured via BET. Consequently, the characteristics of the synthesized carbon nanofibers were greatly influenced by the concentration ratio of metal catalysts. In particular, uniform carbon nanofibers of 27 nm in diameter grew when the concentration ratio of Co and Cu was 6:4 at $700^{\circ}C$ of calcination temperature; carbon nanofibers synthesized under such conditions showed the best crystallizability, compared to carbon nanofibers synthesized with metal catalysts under different concentration ratios, and revealed 1.26 high amorphicity as well as $292m^2g^{-1}$ high specific surface area.

• Journal of Powder Materials
• /
• v.15 no.4
• /
• pp.314-319
• /
• 2008

Nano-sized tungsten disulfide ($WS_2$) powders were synthesized by chemical vapor condensation (CVC) process using tungsten carbonyl ($W(CO)_6$) as precursor and vaporized pure sulfur. Prior to the synthesis of tungsten disulfide nanoparticles, the pure tungsten nanoparticles were produced by same route to define the optimum synthesis parameters, which were then successfully applied to synthesize tungsten disulfide. The influence of experimental parameters on the phase and chemical composition as well as mean size of the particles for the produced pure tungsten and tungsten disulfide nanoparticles, were investigated.

• Carbon letters
• /
• v.14 no.2
• /
• pp.99-104
• /
• 2013

We investigated the effects of parametric synthesis conditions of catalysts such as sintering temperature, sorts of supports and compositions of catalysts on alignment and length-control of carbon nanotubes (CNTs) using catalyst powders. To obtain aligned CNTs, several parameters were changed such as amount of citric acid, calcination temperature of catalysts, and the sorts of supports using the combustion method as well as to prepare catalyst. CNTs with different lengths were synthesized as portions of molybdenum and iron using a chemical vapor deposition reactor. In this work, the mechanisms of alignment of CNTs and of the length-control of CNTs are discussed.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.421-421
• /
• 2012

Graphene has drawn enormous attention owing to its outstanding properties, such as high charge mobility, excellent transparence and mechanical property. Synthesis of Graphene by chemical vapor deposition (CVD) is an attractive way to produce large-scale Graphene on various substrates. However the fatal limitation of CVD process is high temperature requirement(around $1,000^{\circ}C$), at which many substrates such as Al substrate cannot endure. Therefore, we propose plasma enhanced CVD (PECVD) and decrease the temperature to $400^{\circ}C$. Fig. 1 shows the typical structure of RF-PECVD instrument. The quality of Graphene is affected by several variables. Such as plasma power, distance between substrate and electronic coil, flow rate of source gas and growth time. In this study, we investigate the influence of these factors on Graphene synthesis in vacuum condition. And the results were checked by Raman spectra and conductivity measurement.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2006.02a
• /
• pp.186-186
• /
• 2006

• Journal of the Korean Institute of Gas
• /
• v.16 no.6
• /
• pp.143-147
• /
• 2012

Photocatalytic properties of $TiO_2$ nanopowders has been received much attention due to their high potentials for environmental applications such as remediation of polluted environments. The $TiO_2$ nanopowders doped with metal or non-metal elements have been synthesized by variety methods such as flame method, chemical vapor synthesis, sol-gel, ion implantation, which affect a doping behavior in different ways resulting in different surface characteristics, leading to different photocatalytic activity. In addition to an effect of synthesis methods, the photocatalytic activity of $TiO_2$ nanopowders can be improved by subsequent heat-treatments. In this study, to obtain a highly efficient photocatalyst, we synthesized $TiO_2$ nanopowders doped with tungsten by the chemical vapor synthesis method (CVS) and determined their physical properties and photocatalytic activity, together with subsequent post-treatment in the range of $300^{\circ}C$ to $700^{\circ}C$.

• Journal of Powder Materials
• /
• v.6 no.3
• /
• pp.238-245
• /
• 1999

The preparation of $n-TiO_2$ powder by the Chemical Vapor Synthesis process (CVS) was studied using the liquid metal organic precursor (TTIP). The residence time and the collection methods were considered as main processing variables through the experiments. The CVS equipment consisted of a micropump and a flashvaporizer, a tube furnace and a tubular collection device. The synthesis was performed at $1000^{\circ}C$ with various sets of collection zone. The residence time and the total system pressure were controlled in the range of 3~20 ms and 10 mbar, respectively. Nitrogen adsorption, X-ray diffraction and electron microscopy were used to determine particle size, specific surface area and crystallographic structure. The grain size of the as-prepared $n-TiO_2$ powder was in the range of 2~8 nm for all synthesis parameters and the powder exhibited only little agglomeration. The relationship between particle characteristics and the processing variables is reviewed based on simple growth model.