• 대한금속재료학회지
• /
• 제49권8호
• /
• pp.596-600
• /
• 2011

Thermal degradation behavior of a $WO_3-TiO_2$ monolithic catalyst was investigated in terms of structural, morphological, and physico-chemical analyses. The catalyst with 4 wt.% $WO_3$ contents were prepared by a wet-impregnation method, and a durability test of the catalysts were performed in a temperature range between $400^{\circ}C$ and $800^{\circ}C$ for 3 h. An increase of thermal stress decreased the specific surface area, which was caused by grain growth and agglomeration of the catalyst particles. The phase transition from anatase to rutile occurred at around $800^{\circ}C$ and a decrease in the Brønsted acid sites was confirmed by structural analysis and physico-chemical analysis. A change in Brønsted acidity can affect to the catalytic efficiency; therefore, the thermal degradation behavior of the $WO_3-TiO_2$ catalyst could be explained by the transition to a stable rutile phase of $TiO_2$ and the decrease of specific surface area in the SCR catalyst.

• 공업화학
• /
• 제4권4호
• /
• pp.798-806
• /
• 1993

본 연구는 유동층 반응기에서 회중석의 염소화 생성물인 텅스텐염화물로부터 고순도 tungsten oxide를 합성하기 위해 수행하였다. 텅스텐염화물은 용해시작 불과 1분 이내에 거의 완전히 $H_2O_2$ 용액에서 용해되었으며 적정용해조건은, $H_2O_2$의 농도 0.5%, 용해온도 $15^{\circ}C$, 텅스텐 염화물 0.5g에 대한 $H_2O_2$용액의 양은 30ml이었다. 이 조건하에서 얻어진 용해 생성물로부터 제조되어진 텅스텐 산화물은 순도 99.53%의 $WO_3$였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
• /
• pp.767-769
• /
• 1998

Using the R/V converting circuit, hydrogen detecting characteristics of the $WO_3$ films were investigated. The R/V converting circuit is configured with the equivalently constant current driving method connecting an unknown resistor to be measured in the feedback loop of the or-amr rather than using a separated constant current circuit. The response time of the reference voltage for the R/V converting circuit was simulated by the circuit simulator "SABER", and it was found that the response time in the high resistance range become longer and the error amounts to 10%. From the simulation results. replacing the capacitor in the feedback loop of the second stage or-amp with a 0.001uF capacitor, when measuring in the high resistance range, the response characteristics are remarkably improved. The response time was shortened from about 10 seconds to below 1 second. Using this circuit, the effect of $WO_3$ films deposited by sputtering method on hydrogen was measured.

• 대한화학회지
• /
• 제19권6호
• /
• pp.414-419
• /
• 1975

六鹽化 텅스텐(WCl6)을 여러가지 有機溶媒 속에서 리간드로서 옥신과 아닐린 및 피리딘을 각각 반응시켜서 不溶性인 텅스텐 錯化合物을 合成하였다. Dichloromethane과 DMF와 같이 서로 성질이 다른 溶媒속에서의 옥신 錯物을 合成해 보면 溶媒에 따라서 다른 錯物이 生成되었다. 아닐린의 錯物은 dichloromethane溶媒에서 合成되고 피리딘의 錯物은 아세톤溶液에서 合成되었다. 元素分析과 赤外線 스펙트럼 및 熱分析結果 錯化合物들은 組成이$[WCl_2(Hox)_2]와\;[WO_2(Ox)_2],[WCl_3A_3]\;및\;[WO_2ClPy]$임을 알아냈다.

• 한국전기전자재료학회논문지
• /
• 제18권1호
• /
• pp.12-16
• /
• 2005

Chemical mechanical polishing (CMP) process is one of the most useful methods for improving the surface roughness of films. The effects of CMP on the surface morphology of WO$_3$ films prepared by RF sputtering system were investigated in this paper. A removal rate of films increased, and the uniformity performance of surface decreased with the addition of an oxidizer to the tungsten slurry. Non-uniformity performance of surface was superior as its value was below 5 % when oxidizers of 5.0 vol% and 2.5 vol%, respectively, were added to the tungsten slurry. The optimized oxidizer concentration, reflected both the improved roughness values and hillock-free surface with the good uniformity performance, was 5.0 vol% as an atomic force microscopy(AFM) analysis of thin film topographies. Our CMP results will be a useful reference for advanced technology of thin films for gas sensor applications in the near future.

• 대한화학회지
• /
• 제16권6호
• /
• pp.361-368
• /
• 1972

5%트리옥틸아민과 5%옥틸알콜이 든 헥산유기용매 1l는 62g의 $WO_3$를 추출할 수 있었는데 반하여 아민만을 사용했을 경우는 37g의 $WO_3$밖에 추출할 수 없었다. 유기용매 추출과정에서 이러한 알콜의 아민-텅스텐 화합물의 용해도의 상승작용 및 아민과 텅스텐산간의 상호작용을 핵자기 공명분광학을 이용하여 연구하였다. 텅스텐은 고분자형의 텅스텐산 이온상태로 유기층으로 추출되어 다중텅스텐산 트리옥틸 암모니움염을 형성함을 알 수 있었으며 이 염은 텅스텐산이온과 알콜간에 수소결합을 형성함으로써 탄화수소 용매에서 더욱 안정화됨을 알 수 있었다.

• 한국진공학회지
• /
• 제8권2호
• /
• pp.141-147
• /
• 1999

The electrochromic characteristics of tungsten oxide films are largely affected by deposition conditions, such as substrate temperature and gas flow rate and also post-annealing. We have considered gas flow rate and temperature as important factors having an effect on an electrical, optical phenomenon and structural variation of $WO_3$ . The tungsten oxide films were deposited onto ITO(20$\Omega\box$, 1000$\AA$) using rf magnetron sputtering method. In particular, the films deposited at room temperature were annealed at various temperatures in air. All specimens had crystal structure except one being deposited at room temperature with nearly amorphous-like structure. The specimen deposited at $100^{\circ}C$ had a structure in which the increase in deposition temperature. The specimen deposited at $100^{\circ}C$ had a structure in which the cations$(Li^+)$ are easily movable because of void boundaries induced by regularly arrayed large grains. The specimen deposited at $300^{\circ}C$ had a dense structure with small grains but it exhibited the large mobility and charge density in $WO_3$ because of distinct grain boundaries.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2009년도 제38회 동계학술대회 초록집
• /
• pp.321-321
• /
• 2010

The PEDOT:PSS layer is usually used as hole transporting layer for the polymer bulk heterojunction solar cells. However, the interface between ITO and PEDOT:PSS is not stable and the chemical reaction between ITO and PEDOT can result in degraded device performance. We used the tungsten oxides as a hole transport layer by spin-coating. The $WO_3$ nanoparticles were well dispersed in ammonium hydroxide and deionized water and formed thin layer on the ITO anode. We found that $WO_3$ surface is more hydrophobic than the bare ITO or PEDOT:PSS-coated surfaces. The hydrophobic surfaces promote an ordered growth of P3HT films. A higher degree of P3HT ordering is expected to improve the hole mobility and the lifetime of the device using the tungsten oxide showed better stability compared to the device using the PEDOT:PSS.

• 한국환경과학회:학술대회논문집
• /
• 한국환경과학회 2005년도 봄 학술발표회지 제14권(제1호)
• /
• pp.340-343
• /
• 2005

광촉매 효율을 높이기 위해 WO$_{3}$를 첨가하여 제주에 산재해 있는 스코리아를 지지체로 하여 TiO$_{2}$ 및 WO$_{3}$/TiO$_{2}$ 광촉매를 이용하여 humic acid를 분해시킬 경우 반응영향인자에 따른 분해효율을 구한 결과 다음과 같은 결론을 얻었다. Humic acid의 분해시 Ca$^{2+}$를 첨가하였을 때가 첨가하지 않았을 때 보다 효율이 증대한 것은 이온강도가 증가하여 반발력을 감소하여 분해효율이 증대된 것이다. HCO$_{3}\;^-$를 첨가시 분해효율이 감소하는 것은 HCO$_{3}\;^-$이온이 OH radical scavenger로 작용했기 때문이다.

• BMB Reports
• /
• 제39권4호
• /
• pp.383-393
• /
• 2006

Little is known concerning the mechanisms responsible for the transplacental transfer of thiamine. So, the aim of this work was to characterize the placental uptake of thiamine from the maternal circulation, by determining the characteristics of $^3H$-thiamine uptake by a human trophoblast cell line (BeWo). Uptake of $^3H$-thiamine (50-100 nM) by BeWo cells was: 1) temperature-dependent and energy-independent; 2) pH-dependent (uptake increased as the extracellular medium pH decreased); 3) $Na^+$-dependent and $Cl^-$-independent; 4) not inhibited by the thiamine structural analogs amprolium, oxythiamine and thiamine pyrophosphate; 5) inhibited by the unrelated organic cations guanidine, N-methylnicotinamide, tetraethylammonium, clonidine and cimetidine; 6) inhibited by the organic cation serotonin, and by two selective inhibitors of the serotonin plasmalemmal transporter (hSERT), fluoxetine and desipramine. We conclude that $^3H$-thiamine uptake by BeWo cells seems to occur through a process distinct from thiamine transporter-1 (hThTr-1) and thiamine transporter-2 (hThTr-2). Rather, it seems to involve hSERT. Moreover, chronic (48 h) exposure of cells to caffeine ($1\;{\mu}M$) stimulated and chronic exposure to xanthohumol and iso-xanthohumol (1 and $0.1\;{\mu}M$, respectively) inhibited $^3H$-thiamine uptake, these effects being not mediated through modulation of the expression levels of either hThTr-1 or hSERT mRNA.