• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.539-549
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• 1989

Polycrystalline TiO2 thin films were deposited on Si and Al2O3 substrates by CVD method. Ethyl titanate, Ti(OC2H5)4, was used as a source material for Ti and O, and Ar was used for carrier gas. In the surface chemical reaction controlled deposition condition, the apparent activation energy of 6.74 Kcal/mole was obtained, and the atomic adsorption on substrate surface was proved to be governed by Rideal-Elley mechanism. In the mass transfer controlled deposition condition, the deposition rate was in a good agreement with the result which was calculated by the simple boundary layer theory. It was also observed that TiO2 thin films show different surface morphology according to the different deposition mechanism, which was fixed by deposition conditions. This phenomenon could be well explained by the surface perturbation theory.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.212-216
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• 2021

We investigated the feasibility of hydrogen storage with electrochemically formed VO₂ nanotubes. The VO₂ nanotubes were fabricated through the anodization of vanadium metal in fluoride ion-containing organic electrolyte followed by an annealing process in an Ar-saturated atmosphere at 673 K for 3 h at a heating rate of 3 K /min. During anodization, the current density significantly increased up to 7.93 mA/cm² for approximately 500 s owing to heat generation, which led to a fast-electrochemical etching reaction of the outermost part of the nanotubes. By controlling the anodization temperature, highly ordered VO₂ nanotubes were grown on the metal substrate without using any binders or adhesives. Furthermore, we demonstrated the hydrogen sorption properties of the anodic VO₂ nanotubes.

• The Journal of Natural Sciences
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• v.5 no.1
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• pp.67-75
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• 1992

In the our country, especially in Yeongil and Wolsung area, abundant authigenic zeolites are found from the tuffaceous sediments and volcanic rocks of Miocene age showing wide variation in their mineralogy and abundance from horizon to horizon. The principal zeolite species identified are clinopti-lolite. mordenite. heulandite. ferrierite, and erionite. etc. Zeolite minerals are widely used in many countries in the following applications; (a) in air separation adsorption processes; (b)as desiccants; (c)in inorganic building materials; (d)in papermaking; (e)in fertilizers; (f)as soilconditioners-this application is based upon the ability of the zeolite to ion exchange with soil nutrients; (g)in the treatment of radioactive wastes; and (h)as adsorbents for toxic gases, etc. In the present paper, using natural zeolite mordenite treated with IN hydrochloric acid or IN sodium chloride solution as column packings, separation characteristics of argon, nitrogen, carbon monoxide, and methane gases have been studied by gas chromatography. By the use of mordenite treated with hydrochloric acid solution, the tailing peak of methane showed from untreated mordenite was satisfactorily reduced, although it was difficult to separate it from carbon monoxide with a column activated at $300^{\circ}C$. Using a column activated at $350^{\circ}C$, methane could be separated from carbon monoxide easily but only carbon monoxide eluted as a bad defined peak. Mordenite treated with sodium chloride solution was generally similar to chromatograms obtained by using the untreated mordenite. Both the above chemical treatments of mordenite had little effect on the separations of argon and nitrogen. The separations and the HETP values obtained from natural zeolite mordenite treated with continuously hydrochloric acid and sodium chloride solutions were almost identical with those obtained with synthetic molecular sieve 5A zeolite. On the other hand, the efficiency of column was good in the range 20~3Oml/min of the carrier helium gas rate.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.402-402
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• 2012

최근 반도체 공정 중 fluorocarbon (CxHyFz) 가스와 함께 플라즈마 밀도가 큰 유도결합형 플라즈마을 사용한 식각장비가 많이 사용되고 있다. 특히 저 유전상수 값을 가지는 박막을 밀도가 큰 플라즈마와 함께 fluorocarbon 가스를 이용하여 식각을 하게 되면 매우 복잡한 현상이 생긴다. 따라서 식각률에 대한 모델을 세우고 적용하는 일이 매우 어렵다. 본 연구에서는 CF4가스를 Ar가스와 함께 혼합하고 기판 플라즈마와 유도결합형 플라즈마를 동시에 가진 식각장비를 사용하여, 저 유전상수 값을 갖는 박막을 식각하였다. 또한, 간단한 식각모델인 Langmuir adsorption model를 이용하여 식각률(Etch rate)에 대한 합리적인 이해를 얻기 위해, 기판과 유도결합형 플라즈마의 파워에 따른 식각률을 계산하고, 식각모델에서 사용되는 매개변수인 이온플럭스(Ion Flux)와 식각수율(Etch yield)을 연구하였다. 기판의 플라즈마 파워가 20에서 100 W 증가하면서 식각률이 269에서 478 nm/min로 증가하였으며, 식각수율이 0.4에서 0.59로 증가하는 것을 관찰하였다. 반면에 기판의 플라즈마 파워 증가에 따라 이온 플럭스는 3.8에서 $4.7mA/cm^2$로 변화가 크지 않았다. 또한, 유도결합형 플라즈마의 파워가 100에서 500 W 증가하면서, 식각률이 117에서 563 nm/min로 증가하였으며, 이온플럭스가 1.5에서 $6.8mA/cm^2$으로 변화하였다. 그러나, 식각수율은 0.46에서 0.48로 거의 변화하지 않았다. 그러므로 저 유전상수 값을 가지는 박막 식각의 경우, 기판의 플라즈마는 식각수율을 증가시키며 유도결합형 플라즈마는 이온 플럭스를 증가시켜 박막 식각에 기여하는 것으로 사료된다.

• Clean Technology
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• v.28 no.3
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• pp.210-217
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• 2022

Boron(B) is a rare resource used for various purposes such as glass, semiconductor materials, gunpowder, rocket fuel, etc. However, Korea depends entirely on imports for boron. Considering the global boron reserves and its current production rate, boron will be depleted on earth in 50 years. Thus, a process including proper adsorbent materials recovering boron from seawater is demanded. This research proposed carbonized nanofibers prepared from electrospun PAN(polyacrylonitrile) mats as promising materials to adsorb boron in aqueous solution. First, the mechanism of boron adsorption on carbonized nanofibers was investigated by DFT(density functional method)-based molecular modeling and the calculated energetics demonstrated that the boron chemisorption on the nitrogen-doped graphene surface by a two-step dehydration is possible with viable activation energies. Then, the electrospun PAN mats were stabilized in air and then carbonized in an argon atmosphere before being immersed in the boric acid aqueous solution. Analytically, SEM(scanning electron microscopy) and Raman measurements were employed to confirm whether the electrospinning and carbonization of PAN mats proceeded successfully. Then, XPS(X-ray photoelectron spectroscopy) peak analysis showed whether the intended nitrogen-doped carbon nanofiber surface was formed and boron was properly adsorbed on nanofibers. Those results demonstrated that the carbonized nanofibers prepared from electrospun PAN mats could be feasible adsorbents for boron recovery in seawater.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.37-41
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• 1997

The optical property, the environmental stability and the crystallization of ZnS thin films prepared by ion-assisted deposition (IAD) were investigated and compared with those of conventional electron-beam deposited thin films. The humidity(R.H. 85%) test and the thermal(15$0^{\circ}C$) show that the IAD films have relatively higher refractive index, smaller extinction coefficient and environmentally more stable than the conventional films. It is believed to originate from the reduced adsorption of moisture which reflect the increased packing density and the improved microstructure by ion bombardment. XRD experiments also confirm that conventionally grown films have an amorphous in comparison with the crystalline structured IAD films.

• Journal of Environmental Science International
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• v.16 no.6
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• pp.683-688
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• 2007

In this study, N doped $TiO_2$ (TiO-N) thin film was prepared by DC magnetron sputtering method to show the photocatalytic activity in a visible range. Various gases (Ar, $O_2\;and\;N_2$) were used and Ti target was impressed by 1.2 kW -5.8 kW power range. The hysteresis of TiO-N thin film as a function of discharge voltage wasn't observed in 1.2 and 2.9kW of applied power. Cross sections and surfaces of thin films by FE-SEM were tiny and dense particle sizes of both films with normal cylindrical structures. XRD pattern of $TiO_2$ and TiO-N thin films was appeared by only anatase peak. Red shift in UV-Vis adsorption spectra was investigated TiO-N thin film. Photoactivity was evaluated by removal rate measurement of suncion yellow among reactive dyes. The photodegradation rate of $TiO_2$ thin film on visible radiation was shown little efficiency but TiO-N was about 18%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.397-404
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• 2006

Effects of surface defect distribution on flame instability during flame-surface interaction are experimentally investigated. To examine chemical quenching phenomenon which is caused by radical adsorption and recombination processes on the surface, thermally grown silicon oxide plates with well-defined defect density were prepared. ion implantation technique was used to control the number of defects, i.e. oxygen vacancies. In an attempt to preferentially remove oxygen atoms from silicon dioxide surface, argon ions with low energy level from 3keV to 5keV were irradiated at the incident angle of $60^{\circ}$. Compositional and structural modification of $SiO_2$ induced by low-energy $Ar^+$ ion irradiation has been characterized by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS). It has been found that as the ion energy is increased, the number of structural defect is also increased and non-stoichiometric condition of $SiO_x({\le}2)$ is enhanced.

• The Korean Journal of Pesticide Science
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• v.19 no.3
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• pp.174-184
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• 2015

In the present study, the metabolism of [$^{14}C$]butachlor was investigated in rice plant according to the OECD test guideline No. 501. [$^{14}C$]Butachlor was treated as granule to paddy water by application of 1.5 kg ingredient (a.i.)/ha at the 3~4 leave stage of rice plant. At 85 days after treatment (DAT), samples of panicle, foliage, and roots were taken for radioactivity analysis. Upon harvest at 126 DAT, rice plants were separated into brown rice, husk, straw, and root parts. Amounts of total radioactivity absorbed by rice plant ranged from 8.6 to 9.8% of applied radioactivity (AR). Total radioactive residues (TRRs) of rice plant at 126 DAT was the highest as 4.0421 mg/kg (7.3% AR) in the straw followed by 1.4595 mg/kg (2.4% AR) in the root, 0.7257 mg/kg (0.1% AR) in the husk. The lowest level recording 0.1020 mg/kg (0.1% AR) was found in brown rice. Each part was extracted with various solvents and solvent/water mixtures. Greater than 70% of TRRs was readily extractable from foliage, panicle, husk and straw. Only 34.0% of the brown rice and 43% of root based on TRRs were extractable showing that the residues were completely assimilated in the plant tissue. The level of non-extractable radioactivity was ranged from 26.2 to 66.0% of TRRs. From this study, five tentative major metabolites (M1, M2, M3, M4 and M5) were observed in rice extracts. Among the metabolites, 2,6-diethylaniline assigned as M4 was identified in rice plant by comparing to retention time of reference standard. Un-metabolized butachlor was not detected in any fractions. In soil extracts, N-(butoxymethyl)-N-(2,6-diethyl phenyl)acetamide, 2,6-diethylaniline, M2, M3 and M5 were observed. And the concentration of butachlor was low level (ca. 0.03 mg/kg).

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.1
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• pp.9-16
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• 2017

Hydrogen forms metal hydrides with some metals and alloys leading to solid-state storage under moderate temperature and pressure that gives them the safety advantage over the gas and liquid storage methods. However, it has disadvantages of slow hydrogen adsorption-desorption time and low thermal conductivity. To improve characteristics of metal hydrides, it is important that activation and thermal conductivity of metal hydrides are improved. In this study, we have been investigated hydrogen storage properties of Hydralloy C among Ti-Mn alloys. Also, the characteristics of activation and thermal conductivity of Hydralloy C were enhanced to improve kinetics of hydrogen adsorption-desorption. As physical activation method, PHEM (planetary high energy mill) was performed in Ar or $H_2$ atmosphere. Hydralloy C was also activated by $TiCl_3$ catalyst. To improve thermal conductivity, various types of ENG (expanded natural graphite) were used. The prepared samples were compacted at pressure of 500 bar. As a result, the activation properties of $H_2$ PHEM treated Hydralloy C was better than the other activation methods. Also, the amounts of hydrogen storage showed up to 1.6 wt%. When flake type ENG was added to Hydralloy C, thermal conductivity and hydrogen storage properties were improved.