• 한국결정성장학회지
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• 제9권2호
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• pp.185-190
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• 1999

$Al_2O_3/Fe$ 복합재료 제조는 반응소결법에 의한 2단계 공정을 통해서 제조되었으며 이 공정은 장비가 간단하고 near-net-shape이 가능한 장점이 있다.$Al_2O_3/Fe$ 복합재료를 제조하기 위해서 1차로 $650^{\circ}C$에서 5시간동안 산화/환원 처리를 행하고 $1200^{\circ}C$에서 2차로 소결처리를 행하였다. 제조된 복합재료의 상분석결과 $\alpha$-Fe 와 $\alpha$-$Al_2O_3/Fe$가 주된 상이었고 소량의 $FeAl_2O_4$가 검출되었다. 이 소량의 $FeAl_2O_4$상은 Fe가 $Al_2O_4$기공을 채우는 것을 방해함으로써 소결동안 미세구조 내에 약간의 기공을 발생시킨다.

• 한국재료학회지
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• 제26권2호
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• pp.73-78
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• 2016

$TiO_2$ nanoparticles were synthesized by a sol-gel process using titanium tetra isopropoxide as a precursor at room temperature. Ag-doped $TiO_2$ nanoparticles were prepared by photoreduction of $AgNO_3$ on $TiO_2$ under UV light irradiation and calcinated at $400^{\circ}C$. Ag-doped $TiO_2$ nanoparticles were characterized for their structural and morphological properties by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photocatalytic properties of the $TiO_2$ and Ag-doped $TiO_2$ nanoparticles were evaluated according to the degree of photocatalytic degradation of gaseous benzene under UV and visible light irradiation. To estimate the rate of photolysis under UV (${\lambda}=365nm$) and visible (${\lambda}{\geq}410nm$) light, the residual concentration of benzene was monitored by gas chromatography (GC). Both undoped/doped nanoparticles showed about 80 % of photolysis of benzene under UV light. However, under visible light irradiation Ag-doped $TiO_2$ nanoparticles exhibited a photocatalytic reaction toward the photodegradation of benzene more efficient than that of bare $TiO_2$. The enhanced photocatalytic reaction of Ag-doped $TiO_2$ nanoparticles is attributed to the decrease in the activation energy and to the existence of Ag in the $TiO_2$ host lattice, which increases the absorption capacity in the visible region by acting as an electron trapper and promotes charge separation of the photoinduced electrons ($e^-$) and holes ($h^+$). The use of Ag-doped $TiO_2$ nanoparticles preserved the option of an environmentally benign photocatalytic reaction using visible light; These particles can be applicable to environmental cleaning applications.

• 산업기술연구
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• 제21권A호
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• pp.273-278
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• 2001

In this study, we prepared nano-sized $TiO_2$ particles for various process variables by the diffusion flame reactor and we collected $TiO_2$ particles by thermophoresis. It is found that the size of $TiO_2$ particles increases, as the flame temperature or the inlet $TiCl_4$ concentration increase or the total gas flow rate decreases. We investigated the photo-degradation of phenol wish the prepared $TiO_2$ particles. We found the optimum amounts of $TiO_2$ photocatalysts for our experimental apparatus and investigated the photo-degradation efficiencies of phenol, changing the process variables such as size of $TiO_2$ photocatlysts, phase ratio of rutile/anatase, concentration of phenol, input ratio of $O_2$. Degradation efficiencies of phenol were almost 95% in 15 minutes for the standard conditions of our experiments.

• 한국세라믹학회지
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• 제30권8호
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• pp.664-670
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• 1993

Potassium tetratitanate (K2Ti4O9) and Potassium hexatitanate (K2Ti6O13) fibers have been prepared by the slow-cooling calcination process in a temperature range from 125$0^{\circ}C$ to 95$0^{\circ}C$ using the K2CO3 and TiO2 as the starting materials. Optimum fiber growth conditions have been also investigated by changing the physical parameters, such as calcination time and temperature, and cooling rate. Relatively long K2Ti4O9 fibers ( 1.2mm) have been grown with quite a high aspect ratio (c/a 500)when the starting material with a nominal composition of K2O and TiO2 with 1:4 was calcined at 115$0^{\circ}C$ for 4h, and then was slowly cooled to 95$0^{\circ}C$ with a rate of 2$0^{\circ}C$/h. In case of a K2O.6TiO2 composition, acicular shaped K2Ti6O13 fibers with 20~300${\mu}{\textrm}{m}$ long and low aspect ratio (c/a 10~15) have been formed irrespective of the coolign rate. The growth condition of fibers have been discussed based upon the phase diagram of K2O-TiOa2.

• 한국가스학회지
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• 제20권2호
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• pp.1-9
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• 2016

본 연구는 플라즈마/촉매 공정을 이용하여 n-헵테인과 일산화탄소의 동시제거에 대해 조사하였다. n-헵테인과 일산화탄소의 분해특성을 파악하기 위해 플라즈마/촉매 공정과 촉매공정의 분해효율을 비교하였고, 촉매의 종류, 온도, 전력 등을 변화시켜 실험을 진행하였다. n-헵테인의 분해효율은 반응기 내부의 온도보다는 에너지밀도에 더 영향을 많이 받는 것으로 확인되었으며, 일산화탄소는 에너지밀도와 반응기 내부 온도 모두의 영향을 받는 것으로 나타났다. 촉매의 종류를 달리하며 n-헵테인의 분해효율을 조사한 결과 $Pd/{\gamma}-Al_2O_3$ > $Ru/{\gamma}-Al_2O_3{\approx}Ag/{\gamma}-Al_2O_3$순으로 나타났다. 특히, $Pd/{\gamma}-Al_2O_3$를 사용한 경우 n-헵테인 분해 과정에서 일산화탄소가 거의 발생하지 않았으며, $CO_2$ 선택도가 100%에 가까웠다. 일산화탄소 분해효율은 $Pd/{\gamma}-Al_2O_3$ > $Ru/{\gamma}-Al_2O_3$ > $Ag/{\gamma}-Al_2O_3$ 순으로 나타났으며, $180^{\circ}C$이하의 온도에서는 플라즈마/촉매 공정의 효율이 높고, $180^{\circ}C$이상에서는 촉매 공정의 분해효율이 높았다.

• 한국지반환경공학회 논문집
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• 제7권4호
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• pp.5-13
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• 2006

본 연구는 지표수에서 휴믹산을 포함한 중금속을 제거하기 위해 $UV/TiO_2/H_2O_2$ 공정을 적용하여 각 실험인자에 대한 처리효율을 실험적으로 검토하였다. 휴믹산과 중금속을 제거하는데 있어 $UV/TiO_2/H_2O_2$ 공정은 $UV/TiO_2$ 공정보다 훨씬 더 높은 제거효율을 보여 주었다. $TiO_2$ 주입량과 UV 세기를 증가시킴에 따라 휴믹산과 중금속 제거율은 증가했다. 그러나 0.3 g/L 이상의 $TiO_2$ 주입량에서는 제거율이 감소했다. 산화제로 사용된 과산화수소의 첨가는 휴믹산과 중금속 제거에 있어 긍정적인 효과를 보여주었으며 특히 50 mg/L의 과산화수소 농도에서 가장 좋은 제거효율을 나타내었다.

• 한국환경과학회지
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• 제12권1호
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• pp.47-54
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• 2003

This paper have examined the optimum combination of SNCR and SCR by varying SNCR injection temperature and NSR ratio along with SCR space velocity. NOx reduction experiments using a SNCR/SCR combined process have been conducted in simple NO/NH$_3$/O$_2$ gas mixtures. Total gas flow rate was kept constant 4 liter/min throughout the SNCR and SCR reactors, where initial NOx concentration was 500 ppm in the presence of 5% O$_2$. Commercial catalyst, sulfated V$_2$O$\_$5/-WO$_3$/TiO$_2$, was used for SCR NOx reduction. The residence time and space velocity were around 1.67 sec, 2,400 h$\^$-1/ and 6,000 h$\^$-1/ in the SNCR and SCR reactors, respectively. SNCR NOx reduction effectively occurred in a temperature window of 900-950$^{\circ}C$. About 88% NOx reduction was achieved with an optimum temperature of 950$^{\circ}C$ and NSR=1.5. SCR NOx reduction using commercial V$_2$O$\_$5/-WO$_3$-SO$_4$/TiO$_2$ catalyst occurred in a temperature window of 200-450$^{\circ}C$ 80-98% NOxreduction was possible with SV=2400 h$\^$-1/ and a molar ratio of 1.0-2.0. A SNCR/SCR(SV=6000 h$\^$-1/) combined process has shown same NOx reduction compared with a stand-alone SCR(SV=2400 h$\^$-1/) unit process of 98% NOx reduction. The NH$_3$-based chemical could routinely achieve SNCR/SCR combined process total NOx reductions of 98% with less than 5 ppm NH$_3$ slip at NSR ranging from about 1.5 to 2.0, SNCR temperature of 900$^{\circ}C$-950$^{\circ}C$, and SCR space velocity of 6000 h$\^$-1/. Particularly, more than 98% NOx reduction was possible using the combined process under the conditions of T$\_$SNCR/=950$^{\circ}C$, T$\_$SCR/=350$^{\circ}C$, 5% O$_2$, SV=6000 h$\^$-1/ and NH$_3$/NOx=1.5. A catalyst volume was about three times reduced by SNCR/SCR combined process compared with SCR process under the same controlled conditions.

• Journal of Magnetics
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• 제16권2호
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• pp.186-191
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• 2011

[ $YBa_2C_3O_{7-x}$ ]films were fabricated on a $SrTiO_3$ (100) substrate using a trimethylaceate propionic acid (TMAP)-based MOD process by controlling the precursor solution viscosity, firing temperature, and by using various coatings. The viscosity of the precursor solution was controlled by the addition of Xylenes. The films were heat treated with different temperatures from 750 to $800^{\circ}C$. c-axis oriented films were obtained. After adding 9 ml of Xylene into the precursor solution, the $T_c$ of the YBCO film, which was coated 2 times and heat treated at $800^{\circ}C$, was 86 K and the measured $J_c$ was above 2.5 MA/$cm^2$ at 77 K in a zero-field.

• 한국결정성장학회지
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• 제9권1호
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• pp.23-28
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• 1999

Au 미립자가 분산된 $TiO_{2}$ 박막을 졸겔담금법과 열처리공정으로 실리카 유리기판위에 제조하였다. $TiO_{2}$ 박막제조는 titanium tetraisopropoxide-EtOH-HCl-$H_{2}O$-hydrogen tetrachloroaurat (III) tetrahydrate계를 이용하였다. 고농도로 Au 화합물을 함유하면서 투명한 코팅용액을 형성하는 조건을 검토하였다. Au 금속미립자의 크기를 조절하기 위하여 광환원공정을 채택하였다. UV 조사에 따른 Au 입자의 변화와 $TiO_{2}$ 매트릭스의 상전이과정을 XRD, SEM, TEM and UV-visible spectrophotometer로 관찰하였다. 분산제로서 CPCl (Cetylpyridinium chloride monohydrate)의 효과를 평가하였다.

• 한국환경보건학회지
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• 제26권3호
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• pp.69-75
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• 2000

This study was carried out to investigate the removal of nitrogen and phosphorus in municipal sewage according to the variation of volumetric ratio in the reactor. It also was performed to provide basic data necessary to the development and improvement of the process which is Anaerobic-Anoxic-Oxic(A2O). In the removal of BOD and COD, the best efficiency of the process showed in the condition of using the media, 1Q of internal recycle rate and 1:3:2 of the volumetric ratio in Anaerobic-Anoxic-Oxic process. In most cases, nitrogen and phosphorus removal efficiency of the process using the cilia media was superior to that of the process which didn't use the media. In the removal of T-N and T-P, the best efficiency of the process showed in the condition of using the media, 1Q of internal recycle rate and 1:3:2 of the volumetric ratio in Anaerobic-Anoxic-Oxic process.