• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.1045-1053
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• 1993

Alumina hydrates were prepared by the neutralization of AlCl3.6H2O solution with NH3 gas diluted with N2 gas. The values of pH in reaction solution influenced the formation of alumina hydrates minerals. Amorphous alumina hydrates, for example, were formed at ${\gamma}$-Al2O3longrightarrow$\delta$-Al2O3longrightarrow$\theta$-Al2O3longrightarrow$\alpha$-Al2O3. (2) Bayeritelongrightarrowamorphouslongrightarrow${\gamma}$-Al2O3longrightarrow$\delta$-Al2O3longrightarrowη-Al2O3longrightarrow$\theta$-Al2O3longrightarrow$\alpha$-Al2O3. On the other hand, the shape of alumina hydrates whichw ere prepared by the reacton of Al2(SO4)3.16H2O solution and NH3 gas was spherical, the progress of its phase transformation with increasing temperature was amorphouslongrightarrow${\gamma}$-Al2O3longrightarrow$\alpha$Al2O3 in sequence.

• Corrosion Science and Technology
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• v.17 no.3
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• pp.138-145
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• 2018

The aim of this work is the attainment of the $TiO_2-nanotube$ photocatalytic-growth condition using anodization, whereby the $NH_4F-H_2O$ weight ratio is appropriately controlled. We fabricated the $TiO_2$ nanotubes using a two-step anodization (first step is 1 hr; second step is 30 hr) under the ambient pressure and the room temperature at 60 V in ethylene-glycol solutions to investigate the effects of the $NH_4F$(0.1,0.3,0.5wt%) and $H_2O$(1-3wt%) on the $TiO_2-nanotube$ geometry and the photocatalytic efficiency. Further, the decomposition efficiency of the methylene blue on the $TiO_2$ nanotubes by the UN radiation depended on the geometrical change of the nanotube geometry, indicating the proportionality of the decomposition efficiency to the surface area that was affected by the $NH_4F$ and $H_2O$ concentrations. As the $NH_4F$ weight was increased, the surface area initially decreased but slightly increased later, and the length consistently increased. As the $H_2O$ weight was increased, the surface area and length initially increased, but later decreased with the 3 wt% $H_2O$.

• Journal of Food Hygiene and Safety
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• v.12 no.3
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• pp.200-204
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• 1997

Effects of benzoate (0~0.6 g/$\ell$ ) and sorbate (0~2.0 g/$\ell$) on the growth of Escherichia coli O157:H7 in tryptic soy broth at various pH levels (4~8) and temperatures (4$^{\circ}C$, 37$^{\circ}C$) were investigated. Benzoate and sorbate were inhibited the growth of E. coli O157:H7 up to 12 hours cultivation at 4$^{\circ}C$, and 2.0 g/$\ell$ sorbate was only inhibited during 48 hours cultivation at 37$^{\circ}C$. Among the pH levels tested, pH 4 showed significant inhibitory effect against the E. coli O157:H7 on 4$^{\circ}C$ and at 37$^{\circ}C$, respectively. When used in combination 0.2 g/$\ell$ benzoate and sorbate were completely inhibited the growth of E. coli O157:H7 on pH 4 and at 37$^{\circ}C$. While on pH 5 at 4$^{\circ}C$, all of the concentration tested did not exert any inhibitory effect. The combined effects were retarded more than single treatment of E. coli O157:H7.

• Journal of the Korean Chemical Society
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• v.16 no.2
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• pp.80-83
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• 1972

The activity change of lysozyme resulted from its exposure to $Ti-H_2O_2$system in aqueous liquid at room temperature and to ${\gamma}$-irradiation in ice at $195^{\circ}K$ has been measured at room temperature with a Cary-14 spectrophotometer. The enzymatic activity of lysozyme which had been added to a previously flow-mixed solution of $TiCl_3$ and $H_2O_2$ (System I) was compared with the activity of a lysozyme-$H_2O_2$ solution after flow-mixing with $TiCl_3$ (System II), considering the differences between these two activity changes as the extent of the enzymatic inactivation by the involvement of OH radical reaction. The fraction of lysozyme inactivated by OH radical in the system containing 0.0025 M $TiCl_3-0.1M$ $H_2O_2$ (ph 3.5) was 13%, When the $TiCl_3$ concentration is double (pH 3.0), the fraction of enzyme inactivated increases to 36%. The activity of the system containing 0.025 M $TiCl_3-0.1$ M $H_2O_2$ (pH 1.5) was essentially zero. The results seem to support the previos view that the production of OH radical should be proportional to $TiCl_3$ concentration when $H_2O_2$ is present in excess. Increase in the extent of inactivation found in system I with increasing $TiCl_3$ concentration may be due to a pH effect. $H_2O_2$ seems to be less effective than $TiCl_3$ in the inactivation. 1% lysozyme solution, when ${\gamma}$-irradiated with a total dose of 3M rads, loses about 20% of its activity. Lowering of temperature also was found to yield a reduction in enzymatic activity.

• Journal of IKEEE
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• v.22 no.1
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• pp.180-184
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• 2018

Gallium oxide ($Ga_2O_3$) and silicon carbide (SiC) are the material with the wide band gap ($Ga_2O_3-4.8{\sim}4.9eV$, SiC-3.3 eV). These electronic properties allow high blocking voltage. In this work, we investigated the characteristic of $Ga_2O_3$ and 4H-SiC vertical depletion-mode metal-oxide-semiconductor field-effect transistors. We demonstrated that the blocking voltage and on-resistance of vertical DMOSFET is dependent with structure. The structure of $Ga_2O_3$ and 4H-SiC vertical DMOSFET was designed by using a 2-dimensional device simulation (ATLAS, Silvaco Inc.). As a result, 4H-SiC and $Ga_2O_3$ vertical DMOSFET have similar blocking voltage ($Ga_2O_3-1380V$, SiC-1420 V) and then when gate voltage is low, $Ga_2O_3-DMOSFET$ has lower on-resistance than 4H-SiC-DMOSFET, however, when gate voltage is high, 4H-SiC-DMOSFET has lower on-resistance than $Ga_2O_3-DMOSFET$. Therefore, we concluded that the material of power device should be considered by the gate voltage.

• Journal of Environmental Science International
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• v.23 no.7
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• pp.1359-1366
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• 2014

Seven tetracycline classes of antibiotics were treated using ultraviolet (UV) and $UV/H_2O_2$ oxidation. Two different UV lamps were used for the UV and $UV/H_2O_2$ oxidation. The performance of the UV oxidation was different depending on the lamp type. The medium pressure lamp showed better performance than the low pressure lamp. Combining the low pressure lamp with hydrogen peroxide ($H_2O_2$) improved the removal performance substantially. The by-products formation of tetracycline by UV and $UV/H_2O_2$ were investigated. The protonated form ($[1+H]^+$) of tetracycline was m/z 445, reacted to yield almost exclusively two oxidation by-products by UV and $UV/H_2O_2$ oxidation. Their protonated forms of by-products were m/z 461 and m/z 477. The structures of tetracycline's by-products in UV and $UV/H_2O_2$ system were similar.

• Journal of the Korean Chemical Society
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• v.14 no.2
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• pp.141-145
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• 1970

The reduction of Mo-thiocyanate (V) complex on dropping mercury electrode has been studied at ionic strength 0.6 with pH less than 2.3. D-C polarogram obtained from acidic solutions are reversible, diffusion controlled current. The electrode reaction of Mo-thiocyanate(V) may be represented as follows. $MoO(SCN)_3\;+\;2H^+\;+\;2e\;{\to}\;Mo(SCN)_2{^+}\;+\;H_2O\;+\;SCN^-$From this reaction, the half wave potential assumed to be $E_{1/2}\;=\;E_0'\;-\;0.059\;pH\;-\;0.03\;log{\;frac{[Mo(SCN)_2{^+}][SCN^-]}{[MoO(SCN)_3]}}$Considering the dissociation of this complex, however, it was estimated that the electrode reaction may be written by. $MoO^{+3}\;+\;3SCN^-\;+\;2H^+\;+\;2e\;{\to}\;Mo(SCN)_2{^+}\;+\;SCN^-\;+\;H_2O$.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.231.2-231.2
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• 2014

훌륭한 전기적 특성을 갖는 ZnO 기반의 산화물 반도체 박막트랜지스터(TFT)는 AMOLEDs에 적용될 수 있다. 하지만 이러한 장점에도 불구하고 산화물 반도체 TFT소자에 전압이 인가되었을 때 문턱 전압이 이동하게 되는 안정성 문제를 갖는다. 따라서 이를 해결하기 위한 연구가 널리 진행 되고 있다. 본 연구소에서는 고압 분위기 열처리를 통해 안정성의 원인으로 작용할 수 있는 산소공공(Oxygen vacancy)을 감소시키는 연구를 진행하였다. 산화물 반도체 TFT소자의 안정성을 향상시키는 대표적인 분위기 열처리로는 산소 고압 열처리(HPA)가 있으며, 또한 H2O 기체를 사용한 열처리를 통해 TFT소자의 안정성을 높일 수 있다는 연구 결과가 보고된 바 있다. 본 연구에서는 IGZO TFT소자에 H2O보다 더 큰 반응성을 갖는 산화제인 H2O2 기체를 사용한 HPA를 통해 positive bias stress(PBS) 및 negative bias illumination stress(NBIS) 조건에서 안정성이 향상됨을 확인하였고 이를 H2O 기체를 사용한 경우와 비교하였다. 그 결과 H2O2 기체를 산화제로 사용할 때 기존 H2O 기체에 비해 효과적인 PBS 및 NBIS 신뢰성 개선을 확인하였다.

• Bulletin of the Korean Chemical Society
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• v.23 no.1
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• pp.35-40
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• 2002

Photoreaction of guest organic anions in layered organic-inorganic hybrid materials was investigated. The layered hybrids were synthesized by an anion-exchange reaction of $[LiAl_2(OH)_6]Cl{\cdot}yH_2O$ layered double hydroxide with aqueous (Z,Z)- and (E,E)-muconates under inert atmospheric condition, to give new organicinorganic hybrids of $[LiAl_2(OH)_6]_2[(Z,Z)-C_6H_4O_4]{\cdot}zH_2O$ and $[LiAl_2(OH)_6]_2[(E,E)-C_6H_4O_4]{\cdot}H_2O$, respectively. The basal spacings calculated by XRPD of intercalates indicate that muconate anions have almost vertical arrangements against the host $[LiAl_2(OH)_6]^+$ lattices in the interlayer of organic-inorganic hybrid materials. When UV light was irradiated on the suspension of $[LiAl_2(OH)_6]_2[(Z,Z)-C_6H_4O_4]{\cdot}zH_2O$, the (Z,Z)-muconate anions of the gallery space of hybrids were polymerized in the aqueous media while it was isomerized into more stable (E,E)-muconate in the methanollic suspension in the presence of catalytic amount of molecular iodine. All the products were characterized using elemental analysis, TGA, XRPD, FT-IR, $^1H$ NMR and $^{13}C$ CP-MAS NMR.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.1
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• pp.61-68
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• 2000

Gas-phase hydrogen peroxide(H2O2) concentrations were measured to investigate it's distribution in the ambient air in downtown Seoul(Kwanghwamum and Mullae-dong). These measurements were made during four season, from April 30, 1998 to January 29, 1999, using Cold Trap and HPLC. Measurements were also made of other photochemical oxidants and trace gases(O3, NO2, CO and SO2) and meteorological parameters(relative humidity, temperature, solar radiation and wind speed). The mean of all observations was 0.10 ppbv and the range measured was below the level of detection(>0.01 ppbv) to 0.47ppbv. The higher seasonal mean concentrations showed during the summer(0.21 ppbv) and concentrations of H2O2 showed a diurnal variation with maximum concentrations in the afternoon(12:30∼14:00). The results from the corrrelation analysis showed that the concentration of gaseous H2O2 is strongly dependent on the other air pollutants(NO2, CO and O3) and meteorological parameters(relative humidity, temperature and solar radiation.)