• Bulletin of the Korean Chemical Society
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• v.30 no.3
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• pp.630-635
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• 2009

For use as a photocatalyst, bismuth tungsten oxide, $Bi_2WO_6$, was successfully synthesized by hydrothermal treatment at pH = 11 and heating at 200 ${^{\circ}C}$ for 24h, and samples were subsequently thermal treated at 400, 600, and 800 ${^{\circ}C}$ to increase crystallinity. TEM results revealed that the initial untreated particles were sheet‐shaped, grain size was below 80 nm, and it increased with treated temperatures. These $Bi_2WO_6$ samples absorbed at around 400 nm in the visible light range and the intensity of absorption was particularly strongest in samples thermal treated at 600 ${^{\circ}C}$. Their photoluminescence abilities, related to the recombination between the excited electrons and holes, were overall small for other general photocatalysts such as TiO2, and the smallest in the case of thermal treatment at 600 ${^{\circ}C}$, as reversible result of UV‐visible absorbance. Methyl orange of 5.0 ppm aqueous solution was almost completely removed after 2 h when treated over the $Bi_2WO_6$ thermal treated at 600 ${^{\circ}C}$.

• Journal of Korean Library and Information Science Society
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• v.49 no.3
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• pp.219-240
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• 2018

The study analyzed the characteristics of two library and information science journals indexed by Web of Science (WoS) and Scopus in 2015 along with two of their non-indexed sister journals. The study also analyzed the characteristics of a SCIE- and Scopus-indexed oceanographic journal published domestically along with its sister journal indexed by Scopus only. In addition, the study collected and analyzed the articles published during 2014 and 2015 in these 6 journals as well as the citations they received in 2016. By comparing the characteristics and publication data of indexed journals and their sister journals, the study aimed to identify the properties of WoS-indexed journals that may be helpful in enhancing international journal publication. The findings from the analysis of data can be summarized as follows: WoS-indexed journals publish more frequently, focus mainly on articles, are authored by researchers from many countries, and have higher quality papers that receive more citations than their non-WoS-indexed sister journals. The study also found higher rates of co-authored papers in WoS indexed journals, which were amplified in LIS journals. This is an important factor to consider for Korean LIS journals that are dominated by singe-author articles when they prepare to be indexed in WoS.

• Korean Journal of Materials Research
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• v.24 no.5
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• pp.249-254
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• 2014

Due to their unique properties, tungsten borides are good candidates for the industrial applications where certain features such as high hardness, chemical inertness, resistance to high temperatures, thermal shock and corrosion. In this study, conditions were investigated for producing tungsten boride powder from tungsten oxide($WO_3$) by self-propagating high-temperature synthesis (SHS) followed by HCl leaching techniques. In the first stage of the study, the exothermicity of the $WO_3$-Mg reaction was investigated by computer simulation. Based on the simulation experimental study was conducted and the SHS products consisting of borides and other compounds were obtained starting with different initial molar ratios of $WO_3$, Mg and $B_2O_3$. It was found that $WO_3$, Mg and $B_2O_3$ reaction system produced high combustion temperature and radical reaction so that diffusion between W and B was not properly occurred. Addition of NaCl and replacement of $B_2O_3$ with B successfully solved the diffusion problem. From the optimum condition tungsten boride($W_2B$ and WB) powders which has 0.1~0.9 um particle size were synthesized.

• Resources Recycling
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• v.31 no.4
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• pp.19-25
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• 2022

In this study, tungsten carbide (WC) powder was prepared using a novel recycling process for hard metal sludge that does not use ammonium paratungstate. Instead of ammonia, acid was used to remove the sodium and crystallized tungstate, resulting in the formation of tungstic acid (H₂WO₄). The WC powder was successfully synthesized by the carbothermal reduction of tungstic acid through H₂O decomposition, reduction of WO₃ to W, and formation of WC. The carbon content and holding time at the carbothermal reduction temperature were optimized to remove free carbon from the WC powder. As a result, most of the free carbon in the WC powder prepared from sludge was removed, and the content of free carbon in the synthesized WC powder was lower than that in commercial WC powder. Moreover, the crystallite size of WC prepared from H₂WO₄ was much smaller than that of commercial micron-sized WC powder produced from APT. The small crystallite size of WC induces grain growth during the sintering of the WC-Co composite; thus, a WC-Co composite with large WC grains was fabricated using the WC powder prepared from H₂WO₄. The large WC grains affected the mechanical properties of the WC-Co composite. Further, due to the large grain size, the WC-Co composite fabricated from H₂WO₄ exhibited a higher toughness than that of the WC-Co composite prepared from commercial WC powder.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.110-117
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• 2011

This study investigated possibilities for a new reducing shrinkage method of soybean oil(SO) and waste oil(WO) to compare with shrinkage reducing agent(RS) and expansion additive(EA). There was no big difference to flow, air contents, and compressive strength of plain to use SO and WO. For the reducing shrinkage performance, SO and WO was more effective than RS and EA, because their fatty acid reacted with calcium hydroxide of concrete to turn soap. For the pore distribution by porosimter, $0.01{\sim}0.1{\mu}m$ pores of SO and WO were 0 ml/g, and $10{\sim}100{\mu}m$ also remarkably lower than any others. In these results, it inferred that they filled up capillary pore and mitigated autogenous shrinkage by their saponification of their fatty acid and calcium hydroxide.

• Journal of IKEEE
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• v.23 no.4
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• pp.1128-1133
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• 2019

This paper proposed colored front panel glass for Building Integrated Photovoltaic (BIPV) systems using multi-layered thin films composed of transition metal oxide (TMO) layers. Molybdenum oxide (MoO₃) and tungsten oxide (WO₃) provided complementary and suitable materials in making effective interference of reflected light from interfaces with significant difference in refractive indices. A simple, fast, and cheap fabrication method was achieved by depositing the multi-layer films in a single thermal evaporator. Magenta colored glass with optical transmittance of more than 90% was achieved with MoO₃ (60nm)/WO₃(100nm) multi-layered film. This technology could play in a critical role in commercial BIPV system applications.

• Journal of Hydrogen and New Energy
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• v.22 no.4
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• pp.443-450
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• 2011

The three-reactor chemical-looping process (TRCL) for the production of hydrogen from natural gas is attractive for both $CO_2$ capture and hydrogen production. In this study, redox property of $Fe_2O_3$ and $WO_3$ supported with $ZrO_2$ and $MgAl_2O_4$ were studied with temperature programmed oxidation/reduction (TPO/R) experiment. All metal oxides were prepared by ball mill method. Metal oxides supported with $ZrO_2$ showed the good redox property in TPO and TPR tests. Reduction behavior was matched well the theoretical reduction mechanism. Metal oxides supported with $MgAl_2O_4$ formed a solid solution ($MgFe_{0.6}Al_{1.4}O_4$, $MgWO_4$). $Fe_2O_3$ showed more narrow reaction range and lower reaction temperature than $WO_3$.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.197-197
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• 2011

In this study, in contrast with cases in which Scanning Tunneling Microscopy (STM) tip-induced reactions were instigated by the tunneling electrons, the local electric field, or the mechanical force between a tip and a surface, we found that the tungsten oxide (WO3) covered tungsten (W) tip of a STM acted as a chemical catalyst for the S-H dissociative adsorption of phenylthiol and 1-octanethiol onto a Ge(100) surface. By varying the distance between the tip and the surface, the degree of the tip-catalyzed adsorption could be controlled. We have found that the thiol head-group is the critical functional group for this catalysis and the catalytic material is the WO3 layer of the tip. After removing the WO3 layer by field emission treatment, the catalytic activity of the tip has been lost. 3-mercapto isobutyric acid is a chiral bi-functional molecule which has two functional groups, carboxylic acid group and thiol group, at each end. 3-Mercapto Isobutyric Acid adsorbs at Ge(100) surface only through carboxylic acid group at room temperature and this adsorption was enhanced by the tunneling electrons between a STM tip and the surface. Using this enhancement, it is possible to make thiol group-terminated surface where we desire. On the other hand, surprisingly, the WO3 covered W tip of STM was found to act as a chemical catalyst to catalyze the adsorption of 3-mercapto isobutyric acid through thiol group at Ge(100) surface. Using this catalysis, it is possible to make carboxylic acid group-terminated surface where we want. This functional group-selective adsorption of bi-functional molecule using the catalysis may be used in positive lithographic methods to produce semiconductor substrate which is terminated by desired functional groups.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.335-338
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• 1998

The effect of glass flit addition on microwave dielectric properties of BaTiO$_3$-3TiO$_2$ ceramic was studied. Addition of glass frit to this system obtained sintered sample below sintering temperature 105$0^{\circ}C$. At BaTiO$_3$-3TiO$_2$+ g1ass frit 3wt% + BaWO$_4$6 wt%m, this ceramic showed excellent microwave properties of dielectric constant 34, Q$\times$f 8,100, temperature coefficient of resonant frequency 4 ppm/$^{\circ}C$ .

• The Korean Journal of Ceramics
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• v.2 no.3
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• pp.157-161
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• 1996

Cry structures of $Na_xWO_3$ (0.5$\leq$x$\leq$1.0) were investigated. Transmission electron microscopy (TEM) studies indicate that there is an ordering of sodium ions when x=0.75. The direction of ordering is [110] and the wavelength of ordering is twice of the interplanar distance of (110) plane. It has been confirmed that a superlattice containing eight $Na_{0.75}WO_3$ is the unit cell of ordered structure. In this unit cell, Na sites at (000) and ($\frac{2}{1}\frac{2}{1}\frac{2}{1}$) are vacant. The ordered phase was preserved after the annealing at $600^{\circ}C$ in the air. In reduced $Na_xWO_3$ with x=0.5 and 1.0, extra phases were found with the partially ordered perovskite phase. After annealing at $600^{\circ}C$, theses phases transformed to the phases found in calcined specimens.