• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.798-806
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• 1993

In this study we developed the synthesis of high purity tungsten oxide from tungsten chlorides obtained by the chlorination of scheelite in a fluidized bed reactor. Within a minute of dissolution time, tungsten chlorides were almost dissolved in $H_2O_2$ solution. The proper dissolution conditions for the tungsten chlorides were as follows : $H_2O_2$ concentration 0.5%, dissolution temperature $15^{\circ}C$ and $H_2O_2$ amount to 0.5g tungsten chlorides 30ml. Under above conditions, the tungsten oxide prepared from dissolved product was identified as $WO_3$ and the purity of $WO_3$ was 99.53%.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.767-769
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• 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.

• Journal of the Korean Chemical Society
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• v.19 no.6
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• pp.414-419
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• 1975

The insoluble tungsten complexes with 8-hydroxy quinoline (oxine=Hox), aniline (A), and pyridine(Py) in several organic solvents have been synthesized. Using the different solvents with oxine, two different complexes have been synthesized in dichloromethane and dimethylformamide(DMF), respectively. Only one kind of complex has been synthesized with aniline in dichloromethane and with pyridine in acetone. The complexes may be formulated as $WCl_2(Hox)_2,\;[WO_2(Ox_2)],\;[WCl_3A_3],\;and\;[WO_2ClPy]$ by the results of elemental analysis, infrared spectral data, and thermogravimetric analysis.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.1
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• pp.12-16
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• 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.

• Journal of the Korean Chemical Society
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• v.16 no.6
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• pp.361-368
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• 1972

The organic solvent mixture of 5 % trioctylamine and 5 % n-octyl alcohol in n-hexane could be loaded with tungsten to 62 g $WO_3$/1 whereas the amine alone could be loaded only to 37 g $WO_3$/1. Molecular interaction between amine and tungstate ion during the solvent extraction process and the synergistic effect of alcohol in enhancing the solubility of the amine-tungstate complex have been studied by NMR spectroscopy. Tungsten has been shown to be extracted as a polymeric tungstate ion into the organic phase to form a trioctyl ammonium polytungstate salt, which was more stabilized in the hydrocarbon medium by interacting with alcohol via hydrogen bonding between the tungstate ion and alcohol.

• Journal of the Korean Vacuum Society
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• v.8 no.2
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• pp.141-147
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• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.321-321
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• 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.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2005.05a
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• pp.340-343
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• 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
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• v.39 no.4
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• pp.383-393
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• 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.

• Journal of Powder Materials
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• v.24 no.1
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• pp.41-45
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• 2017

The effects of the heat treatment temperature and of the atmosphere on the dehydrogenation and hydrogen reduction of ball-milled $TiH_2-WO_3$ powder mixtures are investigated for the synthesis of Ti-W powders with controlled microstructure. Homogeneously mixed powders with refined $TiH_2$ particles are successfully prepared by ball milling for 24h. X-ray diffraction (XRD) analyses show that the powder mixture heat-treated in Ar atmosphere is composed of Ti, $Ti_2O$, and W phases, regardless of the heat treatment temperature. However, XRD results for the powder mixture, heat-treated at $600^{\circ}C$ in a hydrogen atmosphere, show $TiH_2$ and TiH peaks as well as reaction phase peaks of Ti oxides and W, while the powder mixture heat-treated at $900^{\circ}C$ exhibits only XRD peaks attributed to Ti oxides and W. The formation behavior of the reaction phases that are dependent on the heat treatment temperature and on the atmosphere is explained by thermodynamic considerations for the dehydrogenation reaction of $TiH_2$, the hydrogen reduction of $WO_3$ and the partial oxidation of dehydrogenated Ti.