• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.44-49
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• 2000

Silicon nitride powders, were synthesized by the vapor phase reaction using SiH4-NH3 gaseous mixture. The reaction temperature, ratio of NH3 to SiH4 gas and the overall gas quantity were varied. The synthesized powders were characterized using X-ray, TEM, FT-IR and EA. The synthesized silicon nitride powders were in amorphous state, and the average particle size was about 100nm. TEM analysis revealed that the particle size decreased with increasing reaction temperature and gas flow quantity. As-received amorphous powders were annealed in nitrogen atmosphere at 140$0^{\circ}C$ for 2h, then the powders were completely crystallized at 0.2 ratio of NH3 to SiH4.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.690-698
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• 1995

The Poly-S $i_{1-x}$G $e_{x}$ thin films were deposited on oxidized Si wafer by RTCVD(rapid thermal chemical vapor deposition) using Si $H_4$and Ge $H_4$, at 450 ~5$50^{\circ}C$. The variation of Ge mole fraction and the deposition rate of S $i_{1-x}$G $e_{x}$ thin film were studied as a function of the deposition temperature and the Ge $H_4$/Si $H_4$input ratio, and the crystal phase and the surface roughness were studied by XRD and AFM(atomic force microscopy), respectively. The experimental results showed that the activation energy for the deposition of poly-S $i_{1-x}$G $e_{x}$ was about 32~37Kca /mol and the deposition rate of S $i_{1-x}$G $e_{x}$ thin films was increased with increasing the deposition temperature and the input ratio. From the analysis of composition, it was known that the Ge mole fraction within the poly-S $i_{1-x}$G $e_{x}$ thin film was decreased with decreasing the input ratio and increasing the deposition temperature. As-deposited S $i_{1-x}$G $e_{x}$ thin films were polycrystalline over the entire experimental range. But those were amorphous at the deposition temperature of 450, 475$^{\circ}C$ and the input ratio of 0.05. By adding the Ge $H_4$, poly-S $i_{1-x}$G $e_{x}$ thin film were deposited at relatively lower deposition temperatures($\leq$ 5$50^{\circ}C$) than those of conventional poly-Si(>$600^{\circ}C$). From surface roughness measurement of poly-S $i_{1-x}$G $e_{x}$ it was found that the surface roughness( $R_{i}$ ) increased with increasing the deposition temperature and input ratio.and input ratio.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.863-877
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• 1996

A drying model to predict the drying process in continuous dryer was developed and proved by drying experiments. The experiment showed that the difference of moisture contents between the predicted and the observed was within 0.5%(wb). There was no cracked rice found even in high drying rate with the inlet moisture content over 23%(wb), and tempering treatment in the same temperature reduced the ratio of cracked rice. There was a little difference in the ratio of cracked rice between 40$^{\circ}C$ and 45$^{\circ}C$ drying temperatures with the final drying moisture content (14.5% wb), and the cracked rice increased at 55$^{\circ}C$. As a results, it was better to make fast drying on the rice over 23%(wb) inlet content it was recommended to keep drying at 45$^{\circ}C$.

• Transactions of Materials Processing
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• v.23 no.2
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• pp.82-87
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• 2014

The plastic strain ratio is one of the factors that affect the deep drawability of Al alloy sheet. The deep drawability of Al alloy sheet is limited because of its low plastic strain ratio. Therefore an increase in the plastic strain ratio to improve the deep drawability of Al alloy sheet is needed. The current study investigated the increase of the plastic strain ratio and the change in texture of AA5083 Al alloy sheet after a 2 step asymmetric rolling with heat treatments. The average plastic strain ratio of initial AA5083 Al alloy sheets was 0.83. After the first asymmetric rolling step of 88% deformation and subsequent heat treatment at $320^{\circ}C$ for 10 minutes the value was still 0.83. After the second asymmetric rolling of 14% reduction and subsequent heat treatment at $330^{\circ}C$ for 10 minutes the plastic strain ratio rose to 1.01. The average plastic strain ratio after the 2 step asymmetric rolling and heat treatment is 1.2 times higher than that of initial AA5083 Al alloy sheet. This result is related to the development of ND/<111> texture component after the second asymmetric rolling and heat treatment.

• Journal of the Korean Chemical Society
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• v.18 no.4
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• pp.267-271
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• 1974

The tetradentate schiff base, N,N'-bis(salicylaldehyde)-ethylene diimine has been reacted with a series of Mo(IV), Mo(V), Mo(IV), and Mo(III) oxidation states to form new Complexes; $[MoO_2(C_{16}H_{14}O_2N_2)], (MoO(C_{16}H_{14}O_2N_2)]_2O, (Mo(SCN)(C_{16}H_{14}O_2N_2)]_2O, and (Mo(H_2O)(C_{16}H_{14}O_2N_2)]_2O.$ These complexes have hexa coordinated configurations and the mole ratio of these ions to the ligand was 1:1. These complexes have been identified by visible spectra, infrared specra, T.G.A., D.T.A., and elemental analysis.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1818-1820
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• 1999

This paper presents direct ${\mu}c$-Si:H thin film growth on the glass substrates using RPCVD system (remote plasma chemical vapor deposition) in low temperature. Hydrogenated micro-crystalline silicon deposited by RPCVD system in low temperature is very useful material for photovoltaic devices, sensor applications, and TFTs (thin film transistors). Varying the deposition conditions such as substrate temperature, gas flow rate, reactive gas ratio $(SiH_4/H_2)$, total chamber pressure, and rf power, we deposited ${\mu}c$-Si:H thin films on the glass substrates (Corning glass 1737). And then we measured the structural and electrical properties of the films.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.303-308
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• 1999

As a semiconductor material for electronic devices operated under extreme environmental conditions, silicon carbides(SiCs) have been intensively studied because of their excellent electrical, thermal and other physical properties. The growth characteristics of single-crystalline 4H-SiC homoepitaxial layers grown by a thermal chemical vapor deposition (CVD) were investigated. Especially, the successful growth condition of 4H-SiC homoepitaxial layers using a SiC-uncoated atmospheric pressure chamber and carried out using off-oriented substrates prepared by a modified Lely method. In order to investigate the crystallinity of grown epilayers, Nomarski optical microscopy, Raman spectroscopy, photoluninescence(PL), scanning electron microscopy(SEM) and other techniques were utilized. The best quality of 4H-SiC homoepitaxial layers was observed in conditions of growth temperature $1500^{\circ}C$ and C/Si flow ratio 2.0 of $C_{3}H_{8}\;0.2\;sccm\;&\;SiH_{4}\;0.3\;sccm$. The growth rate of epilayers was about $1.0\mu\textrm{m}/h$ in the above growth condition.

• Journal of the Korean Wood Science and Technology
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• v.28 no.2
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• pp.49-56
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• 2000

This study was designed to investigate the adsorption of heavy metal ions by untreated bark according to the treatment conditions of aqueous solution. The effect of temperature and pH of aqueous solution, particle size of bark, addition of light metal ions on the adsorption was examined, and the competition in adsorption among heavy metal ions was also evaluated. te The adsorption ratio of $Cu^{2+}$ and $Zn^{2+}$ increased with increasing themperature of solution from $-5^{\circ}C$ to $10^{\circ}C$ however, it was relatively constant at temperatures between $10^{\circ}C$ and $55^{\circ}C$. The adsorption ratio of $Cr^{6+}$ increased continuously with increasing the temperature of solution. The maximum adsorption ratio of $Cu^{2+}$, $Zn^{2+}$, and $Pb^{2+}$ was noted at pHs ranged 6 to 7; however, the adsorption ratio declined sharply on either sides of the optimum. The adsorption ratio of $Cr^{6+}$ decreased continuously with increasing the pH of solution. The adsorption ratio increased as decreasing the particle size of bark, and there was little differences in adsorption tendency between pine and oak bark. By the addition of $Ca^{2+}$ or $Mg^{2+}$(10~25 ppm), the adsorption ratio of $Cu^{2+}$ and $Zn^{2+}$ increased. An increase of the adsorption ratio was higher in oak bark than in pine bark. However, the adsorption ratio of $Pb^{2+}$ and $Cr^{6+}$ was not affected by the addition of light metal ions. As the mixed solution of 2 or 3 kinds of heavy metal ions($Cu^{2+}$, $Zn^{2+}$, $Pb^{2+}$) was treated with the untreated bark, the adsorption of $Zn^{2+}$ decreased considerably because of the competitive adsorption among heavy metal ions. Also the adsorption of $Cu^{2+}$ was more and less reduced. However the adsorption of $Pb^{2+}$ was not affected by the presence of other heavy metal ions.

• Korean Chemical Engineering Research
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• v.43 no.5
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• pp.560-565
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• 2005

Catalytic performances of zeolite catalysts such as H-mordenite(HM), H-Beta$(H{\beta})$, H-USY(HUSY) for the transmethylation between 1-methylnaphthalene(1-MN) and 2-methylnaphthalene(2-MN) were investigated in a fixed-bed flow reactor. $H{\beta}$ showed higher and more stable conversion than others to exhibit a high and stable 2-MN/1-MN ratio of 2.3 and 2,6-DMN/2,7-DMN ratio of 1.3 at the $1^{st}$ hour of time on stream under the reaction conditions as follows: reaction temperature of $350^{\circ}C$, reaction pressure of 1.5 MPa, WHSV of $2.7g_{feed}/g_{cat}{\cdot}h$ and the molar ratio of 1-MN and 2-MN of 1:1. The catalytic behavior has been discussed in relation with the catalyst pore structure and acidity.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.437-440
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• 2007

Gasification converts coal and other feedstocks into a very clean and usable gas, called syngas, that can be used to produce a wide variety products such as electricity, chemicals, transports fuels, hydrogen production, etc. This paper was studied the gasification performance effects with the variation of the gasification operating parameters such as the feeding amounts of oxygen, steam and coal. When $O_2/coal$ ratio was below 0.8, $H_2$ mole % was increased as increasing $O_2/coal$ ratio. CO mole % was increased when $O_2/coal$ ratio was below 1.2 as increasing the $O_2/coal$ ratio. As increasing steam/coal ratio, $H_2$ mole %was increased and CO mole % was decreased. The $O_2/coal$ and steam/coal ratio was $0.8{\sim}0.9$ and $0.0{\sim}0.4$, respectively, to keep the proper gasification condition that the gasifier temperature was $1300^{\circ}C{\sim}1450^{\circ}C$ and the cold gas efficiency was over 76%.