• 한국재료학회지
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• 제21권2호
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• pp.83-88
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• 2011

Nano-technology is a super microscopic technology to deal with structures of 100 nm or smaller. This technology also involves the developing of $TiO_2$ materials or $TiO_2$ devices within that size. The aim of the present paper is to synthesize $WO_x$ doped nano-$TiO_2$ by the Sonochemistry method and to evaluate the effect of different percentages (0.5-5 wt%) of tungsten oxide load on $TiO_2$ in methylene blue (MB) elimination. The samples were characterized using such different techniques as X-ray diffraction (XRD), TEM, SEM, and UV-VIS absorption spectra. The photo-catalytic activity of tungsten oxide doped $TiO_2$ was evaluated through the elimination of methylene blue using UV-irradiation (315-400nm). The best result was found with 5 wt% $WO_x$ doped $TiO_2$. It has been confirmed that $WO_x-TiO_2$ could be excited by visible light (E<3.2 eV) and that the recombination rate of electrons/holes in $WO_x-TiO_2$ declined due to the existence of $WO_x$ doped in $TiO_2$.

• 한국전기전자재료학회논문지
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• 제28권11호
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• pp.715-720
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• 2015

The photoinduced hydrophilicity of $TiO_2/WO_3$ double layer films was fabricated by using a conventional rf-magnetron sputtering method. The photoinduced hydrophilic reaction of the $TiO_2$ surface was enhanced by the presence of $WO_3$ under the $TiO_2$ layer by irradiation of a 10 W cylindrical fluorescent light bulb. However, when the $TiO_2$ and $WO_3$ layers were separated by an insulating layer, the surface did not appeared high hydrophilic, under the same light bulb. The enhanced photoinduced hydrophilic reaction can be explained by the charge transfer between $TiO_2$ and $WO_3$ layers. It was also demonstrated that visible light passing through the $TiO_2$ layer could excite $WO_3$. Thus, visible light can be used for the hydrophilic reaction in the present $TiO_2/WO_3$ system.

• 한국분말재료학회지
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• 제20권6호
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• pp.474-478
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• 2013

The most general photocatalyst, $TiO_2$ and $WO_3$, are acknowledged to be ineffective in range of visible light. Therefore, many efforts have been directed at improving their activity such as: band-gap narrowing with non-metal element doping and making composites with high specific surface area to effectively separate electrons and holes. In this paper, the method was introduced to prepare a photo-active catalyst to visible irradiation by making a mixture with $TiO_2$ and $WO_3$. In the $TiO_2-WO_3$ composite, $WO_3$ absorbs visible light creating excited electrons and holes while some of the excited electrons move to $TiO_2$ and the holes remain in $WO_3$. This charge separation reduces electron-hole recombination resulting in an enhancement of photocatalytic activity. Added Ag plays the role of electron acceptor, retarding the recombination rate of excited electrons and holes. In making a mixture of $TiO_2-WO_3$ composite, the mixing route affects the photocatalytic activity. The planetary ball-mill method is more effective than magnetic stirring route, owing to a more effective dispersion of aggregated powders. The volume ratio of $TiO_2(4)$ and $WO_3(6)$ shows the most effective photocatalytic activity in the range of visible light in the view point of effective separation of electrons and holes.

• 한국재료학회지
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• 제24권1호
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• pp.6-12
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• 2014

In the present work, $WO_3$ and $WO_3-TiO_2$ were prepared by the chemical deposition method. Structural variations, surface state and elemental compositions were investigated for preparation of $WO_3-TiO_2$ sonocatalyst. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and transmission electron microscopy (TEM) were employed for characterization of these new photocatalysts. A rhodamine B (Rh.B) solution under ultrasonic irradiation was used to determine the catalytic activity. Excellent catalytic degradation of an Rh.B solution was observed using the $WO_3-TiO_2$ composites under ultrasonic irradiation. Sonocatalytic degradation is a novel technology of treating wastewater. During the ultrasonic treatment of aqueous solutions sonoluminescence, cavitaties and "hot spot" occurred, leading to the dissociation of water molecules. In case of a $WO_3$ coupled system, a semiconductor coupled with two components has a beneficial role in improving charge separation and enhancing $TiO_2$ response to ultrasonic radiations. In case of the addition of $WO_3$ as new matter, the excited electrons from the $WO_3$ particles are quickly transferred to $TiO_2$ particle, as the conduction band of $WO_3$ is 0.74 eV which is -0.5 eV more than that of $TiO_2$. This transfer of charge should enhance the oxidation of the adsorbed organic substrate. The result shows that the photocatalytic performance of $TiO_2$ nanoparticles was improved by loading $WO_3$.

• 청정기술
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• 제23권2호
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• pp.172-180
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• 2017

HCl에 의한 원소수은의 염화수은으로의 산화반응에 대한 열역학적 검토 결과 수십 ppm 수준의 HCl이 존재하는 경우에 SCR 반응 온도범위에서 원소수은의 염화수은으로의 전환은 100% 가능한 것으로 확인하였다. SCR공정 운전 온도범위에서 Cu, Fe, Mn의 염화물이 담지된 $V_2O_5-WO_3/TiO_2$ 촉매가 우수한 NO 제거 활성을 보였다. $NH_3-TPD$ 측정결과 $NH_3$의 흡착강도를 나타내는 탈착온도가 높은 촉매가 우수한 NO 제거활성을 나타내었다. 반응가스에 HCl을 공급할 경우 원소수은의 산화반응이 촉진되는 결과를 얻을 수 있었다. 그러나, NO와 함께 $NH_3$가 존재하는 SCR반응 조건에서는 촉매표면에 강하게 흡착되는 $NH_3$에 의해 촉매표면에 HCl의 흡착이 방해를 받기 때문에 HCl에 의한 원소수은의 염화수은으로의 산화반응 활성이 억제되는 것으로 나타났다. SCR반응 조건에서 금속염화물이 담지된 $V_2O_5-WO_3/TiO_2$ 촉매가 금속염화물이 담지되지 않은 $V_2O_5-WO_3/TiO_2$ 촉매에 비해 우수한 수은 산화활성을 보이는데 이는 촉매 표면에 존재하는 금속염화물의 염소기가 수은 산화반응에 참여하여 활성을 증가시키기 때문으로 판단된다.

• 한국환경과학회지
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• 제14권7호
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• pp.699-709
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• 2005

This study aimed at improving the $TiO_2$ photocatalytic degradation of HA. In this study, the Degradation of Humic Acid using Jeju Scoria Coated with $WO_3/TiO_2$ in the presence of UV irradiation was investigated as a function of different experimental condition : photocatalyst dosage, $Ca^{2+}\;and\;HCO_{3}_{-}$ addition and pH of the solution. Photodegradation efficiency increased with increasing photocatalyst dosage, the optimum catalyst dosage is 2.5 g/L and Photodegradation efficiency is maximized to $WO_3/TiO_2=3/7$. This indicates that $WO_3$ retains a much higher Lewis surface acidity than $TiO_2,\;and\;WO_3$ has a higher affinity for chemical species having unpaired electrons. The addtion of cation($Ca^{2+}$) in water increased the photodegradaion efficiency. But the addtion of $HCO_{3}^{-}$ ion in water decreased a photodegradation efficiency. Photodegradation efficiency increased with decreasing pH < pzc, the electrostatic repulsion between the HA and the surface of $TiO_2$ decreased.

• 센서학회지
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• 제5권2호
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• pp.21-27
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• 1996

부탄가스 감지를 위해 $WO_{3}$를 기본물질로 하고 산화물을 첨가제로 한 후막형 가스감지 소자를 스크린 프린팅법으로 제조하였고 가스에 대한 감도특성 등을 조사하였다. 첨가 산화물중 $TiO_{2}$를 첨가한 $WO_{3}$ 후막의 부탄가스에 대한 감도가 다른 첨가물을 적용한 후막의 감도보다 상대적으로 높음을 알 수 있었고, $TiO_{2}$의 첨가량이 2wt.%일 때 가장 높은 감도를 나타냄을 알 수 있었다. 열처리 온도를 $900^{\circ}C$까지 변화시켜 보았는데 $650^{\circ}C$일 때 가장 좋은 감도를 나타냈으며, 동작온도를 $400^{\circ}C$까지 변화시켰을 때 $350^{\circ}C$에서 가장 좋은 감도를 가짐을 알 수 있었다. $WO_{3}$에 $TiO_{2}$를 2wt.% 첨가하고, $650^{\circ}C$에서 열처리한 후막의 동작온도 $350^{\circ}C$에서 공기중 20000ppm의 부탄가스에 대해 80%의 감도를 나타내었다.

• Korean Chemical Engineering Research
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• 제51권3호
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• pp.313-318
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• 2013

$V_2O_5-WO_3/TiO_2$ 촉매의 질소산화물 환원반응에 있어서 $V_2O_5$ 함량이 NO 환원 및 $N_2O$ 생성에 미치는 영향을 조사하기 위하여 분말촉매를 사용한 미분반응기에서 실험 연구를 수행하였다. 고정된 비율의 $WO_3$와 $TiO_2$에 $V_2O_5$ 함량을 1에서 8 wt%까지 변화시킨 촉매에서 NO 환원반응과 암모니아 산화반응 특성이 조사되었다. $V_2O_5-WO_3/TiO_2$ 촉매에서 NO 환원 반응은 $200^{\circ}C$ 이하에서도 상당량 진행되지만, $V_2O_5$ 함량을 1 wt% 촉매의 경우 700 ppm의 NO를 99.9%이상 전환시키는 최저 반응온도가 $340^{\circ}C$에서 아주 좁은 활성 온도창으로 일어났다. 그리고 이 활성온도는 촉매의 $V_2O_5$ 함량이 증가됨에 따라 점점 저온 쪽으로 이동하여, 6 wt% 촉매의 경우 $220{\sim}340^{\circ}C$에서 높은 활성을 보였다. $V_2O_5$ 함량이 8 wt% 촉매의 경우 전 온도 구간에서 6 wt% 촉매보다 낮은 NO 환원율을 보였다. 그러나 반응온도 $340^{\circ}C$ 이상에서는 촉매의 $V_2O_5$ 함량이 증가함에 따라 NO 전환율이 감소하였다. 이는 $V_2O_5-WO_3/TiO_2$ 촉매의 NO 환원을 위한 촉매 활성점 상당 크기 이상의 $V_2O_5$ 입자와 관계되는 것으로 판단되며 촉매 입자가 클수록 $320^{\circ}C$ 이상에서 암모니아 산화에 의해 발생되는 $N_2O$ 생성을 고려하여야 한다. $V_2O_5-WO_3/TiO_2$ 촉매는 배기가스 중의 질소산화물 제거를 위하여 현재 통상적으로 $350{\sim}450^{\circ}C$의 영역에서 운전되고 있으나, 고온 영역에선 2차 오염물인 $N_2O$의 발생을 피할 수 없고 에너지 소비량이 많으므로, $250{\sim}320^{\circ}C$의 저온 영역에서 적합한 촉매로써 $V_2O_5$ 함량이 높은 $V_2O_5-WO_3/TiO_2$ 촉매의 사용이 권장되었다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 추계종합학술대회 논문집
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• pp.601-604
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• 1998

NOX detecting gas sensors using TiO2 doped tungsten oxide semiconductor were prepared and their electrical and sensing characteristics have been investigated. In normal air condition, the sensors of WO3, TiO2 doped WO3 show grain boundary heights of 0.34 eV, 0.25 eV, respectively. The grain boundary barrier energy variation was increased by doping TiO2 into large variation of resistance to NOX gases. And doping the TiO2 4 wt.%, the particle size of WO3 polycrystal films showed higher sensitivity and better sorption characteristics to NOX gas than the pure WO3 films material in air at operating temperature of $350^{\circ}C.$ The TiO2 doped WO3 semiconductor gas sensor shows nano-sized particle size and good sensitivity to sub-ppm concentration of NOX.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.342-343
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• 2005

In this study,. the microwave dielectric properties of the $0.6TiTe_3O_8-0.4CaWO_4$ ceramics with sintering temperature were investigated for LTCC application. According to the X-ray diffraction patterns, the $0.6TiTe_3O_8-0.4CaWO_4$ ceramics had columbite structure of the $TiTe_3O_8$ phase and scheelite structure of the $CaWO_4$ phase. Increasing the sintering temperature, the bulk density, the dielectric constant and the quality factor of the $0.6TiTe_3O_8-0.4CaWO_4$ ceramics were increased. In the case of the $0.6TiTe_3O_8-0.4CaWO_4$ ceramics sintered at $810^{\circ}C$, the bulk density, the dielectric constant and the quality factor were 5.72$g/cm^2$, 33.6, 22,013GHz respectively.