• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1150-1153
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• 2003

Carbon nanofilaments were formed on silicon substrate using microwave plasma-enhanced chemical vapor deposition method. The structures of carbon nanofilaments were identified as carbon nanotubes or carbon nanofibers. The formation of bamboo-like carbon nanotubes was initiated by the application of the bias voltage during the plasma reaction. The growth kinetics of bamboo-like carbon nanotubes increased with increasing the bias voltage. The growth direction of bamboo-like carbon nanotubes was vertical to the substrate.

• Journal of the Korean Society of Safety
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• v.25 no.1
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• pp.17-21
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• 2010

The chemistry and ignition delay of hydrogen/air/HFP premixed mixtures was investigated numerically with unsteady perfectly stirred reactor(PSR). The detailed chemistry of 93 species and 817 reaction mechanism was introduced for hydrogen/air/HFP mixtures. The results shows the temporal concentration variations of major or reactants such as hydrogen and oxygen during autoignition were similar to the spatial distribution of premixed flame while water vapor produced at the ignition temperature was decomposed later, which can be clarified with the relate species production rates that the the re-growth (or shoulder) of OH concentration is a result of F radicals attacking $H_20$ forming OH and HF. For the stoichiometric $H_2$/air mixture inhibited by 20% HFP, HFP thermal decomposition reaction prevails over the radical attack such as H at initial stage. Even though relatively large HFP addition contributes to delay the ignition, chemical effect on the ignition delay is not effective because of late thermal decomposition of HFP. The most small ignition delay was observed at a slightly fuel lean condition ($\phi$ = 0.9), and temperature dependency of ignition delay was clearly shown near 900 K.

• Journal of the Korean Ceramic Society
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• v.29 no.7
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• pp.525-532
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• 1992

TiO2 fine powder was synthesized in the gas phase by chemical vapor deposition using hydrolysis of TiCl4. Content of rutile phase in the powder was investigated. Powder characteristics such as size, crystallinity and morphology were also studied by means of TEM, SEM and XRD. Rutile phase in TiO2 powder started to be formed from 100$0^{\circ}C$ and the content increased with the reaction temperature and TiCl4 concentration. As the temperature increased from 80$0^{\circ}C$ to 140$0^{\circ}C$, the primary particle size increased while secondary particle size decreased. Spherical secondary particle with fine primary crystals agglomerated was produced at low temperature of 80$0^{\circ}C$ whereas the grown primary particle being final particle size was produced at higher temperature of 140$0^{\circ}C$. Other effects of TiCl4 and H2O partial pressures on particle size were also reported in this study.

• Analytical Science and Technology
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• v.30 no.3
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• pp.138-145
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• 2017

Microwave-assisted organic synthesis has gained a remarkable interest over the past years because of its advantages - (i) rapid energy transfer and superheating, (ii) higher yield and rapid reaction, (iii) cleaner reactions. Ionic liquids are well known for their unique properties such as negligible vapor pressure and high thermal stability. With these properties, ionic liquids have gained increasing attention as green, multi-use reaction media. Recently, ionic liquids have been applied as reaction media for biocatalysis. Lipase-catalyzed reactions in ionic liquids provide high activity and yield compared to conventional organic solvents or solvent free system. Since polar molecules are generally good absorbent to microwave radiation, ionic liquids were investigated as reaction media to improve activity and productivity. In this study, therefore, the effect of microwave irradiation in ionic liquids was investigated on lipase catalyzed reactions such as benzyl acetate synthesis and caffeic acid phenethyl ester synthesis. Comparing to conventional heating, microwave heating showed almost the same final conversion but increased initial reaction rate (3.03 mM/min) compared to 2.11 mM/min in conventional heating at $50^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.121-121
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• 2011

Graphene formed by chemical vapor deposition was exposed to the various plasmas of Ar, O2, N2, and H2 to examine its effects on the bonding properties of graphene to metal. Upon the Ar plasma exposure of patterned graphene, the subsequently deposited metal electrodes remained intact, enabling successful fabrication of field effect transistor (FET) arrays. The effects of enhancing adhesion between graphene and metals were more evident from O2 plasmas than Ar, N2, and H2 plasmas, suggesting that chemical reaction of O radicals induces hydrophilic property of graphene more effectively than chemical reaction of H and N radicals and physical bombardment of Ar ions. From the electrical measurements (drain current vs. gate voltage) of field effect transistors before and after Ar plasma exposure, it was confirmed that the plasma treatment is very effective in controlling bonding properties of graphene to metals accurately without requiring buffer layers.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3312-3316
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• 2013

Single crystals of hexagonal graphenes were successfully grown on Cu foils using the atmospheric pressure chemical vapor deposition (CVD) method. We investigated the effects of reaction parameters, such as the growth temperature and annealing time, on the size, coverage, and density of graphene domains grown over Cu foil. The mean size of the graphene domains increased significantly with increases in both the growth temperature and annealing time, and similar phenomena were observed in graphene domains grown by low pressure CVD over Cu foil. From the comparison of micro Raman spectroscopy in the graphene films grown with different annealing times, we found that the nucleation and growth of the domains were strongly dependent on the annealing time and growth temperature. Therefore, we confirmed that when reaction time was same, the number of layers and the degree of defects in the synthesized graphene films both decreased as the annealing time increased.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1035-1038
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• 2013

Rolling circle amplification (RCA) of DNA on an aligned-carbon nanotube (a-CNT) surface was electrically interfaced by the a-CNT based filed effect transistor (FET). Since the electric conductance of the a-CNT will be dependent upon its local electric environment, the electric conductance of the FET is expected to give a very distinctive signature of the surface reaction along with this isothermal DNA amplification of the RCA. The a-CNT was initially grown on the quartz wafer with the patterned catalyst by chemical vapor deposition and transferred onto a flexible substrate after the formation of electrodes. After immobilization of a primer DNA, the rolling circle amplification was induced on chip with the a-CNT based FET device. The electric conductance showed a quite rapid increase at the early stage of the surface reaction and then the rate of increase was attenuated to reach a saturated stage of conductance change. It took about an hour to get the conductance saturation from the start of the conductance change. Atomic force microscopy was used as a complementary tool to support the successful amplification of DNA on the device surface. We hope that our results contribute to the efforts in the realization of a reliable nanodevice-based measurement of biologically or clinically important molecules.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1839-1842
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• 1999

We have synthesized carbon nanotubes by thermal chemical vapor deposition of $C_2H_2$ on transition metal-coated silicon substrates. Carbon nanotubes are uniformly synthesized on a large area of the plain Si substrates, different from Previously reported porous Si substrates. It is observed that surface modification of transition metals deposited on substrates by either etching with dipping in a HF solution and/or $NH_3$ pretreatment is a crucial step for the nanotube growth prior to the reaction of $C_2H_2$ gas. We will demonstrate that the diameters of carbon naotubes can be controlled by applying the different transition metals.

• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.249-256
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• 1997

The effect of process parameter of plasma assisted chemical vapor deposition (PACVD) on the variation of the ratio between cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN) in the film was in-vestigated. The plasma was generated by electric power with the frequency between 100 and 500 KHz. BCl3 and NH3 were used as a boron and nitrogen source respectively and Ar and hydrogen were added as a car-rier gas. Films were composed of h-BN and c-BN and its ratio varied with the magnitude of process parameters, voltage of the electric power, substrate bias voltage, reaction pressure, gas composition, sub-strate temperature. TEM observation showed that h-BN phase was amorphous while crystalline c-BN par-ticle was imbedded in h-BN matrix in the case of c-BN and h-BN mixed film.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.637-641
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• 2004

We investigated the effects of SiH$_4$ gas on the surface of Hf-silicate films during the deposition of polycrystalline (poly) Si films and the thermal stability of sputtered Hf-silicate films in poly Si/Hf-silicate structure by using High Resolution Transmission Electron Microscopy (HR-TEM) and X-ray Photoelectron Spectroscopy (XPS). Hf-silicate films were deposited by using DC-mag-netron sputtering with Hf target and Si target and poly Si films were deposited at 600$^{\circ}C$ by using Low Pressure Chemical Vapor Deposition (LPCVD) with SiH$_4$ gas. After poly Si film deposition at 600$^{\circ}C$, Hf silicide layer was observed between poly Si and Hf-silicate films due to the reaction between active SiH$_4$ gas and Hf-silicate films. After annealing at 900$^{\circ}C$, Hf silicide, formed during the deposition of poly Si, changed to Hf-silicate and the phase separation of the silicate was not observed. In addition, the Hf-silicate films remain amorphous phase.