• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.601-601
• /
• 2013

Superhydrophobic W18O49 nanowire (NW) arrays were synthesizedusing a thermal evaporation and surface chemistry modification methods by self-assembled monolayer (SAM). As-prepared non-wetting W18O49 NWs surface shows water contact angle of $163.2^{\circ}$ and has reliable stability in underwater conditions. Hence the superhydrophobic W18O49 NWs surface exhibits silvery surface by total reflection of water layer and air interlayer. The stability analysus of underwater superhydrophobicity of W18O49 NWs arrays was conducted by changing hydrostatic pressure and surface energy of W18O49 NWs arrays. The stability of superhydrophobicity in underwater conditions decreased exponentially as hydrostatic pressure applied to the substrates increased3. In addition, as surface energy decreased, the underwater stability of superhydrophobic surface increased sharply. Specifically, sueprhydrophobic stability increased exponentially as surface energy of W18O49 NWs arrays was decreased. Based on these results, the models for explaining tendencies of superhydrophobic stability underwater resulting from hydrostatic pressure and surface energy were designed. The combination of fugacity and Laplace pressure explained this exponential decay of stability according to hydrostatic pressure and surface energy. This study on fabrication and modeling of underwater stability of superhydrophobic W18O49 NW arrays will help in designing highly stable superhydrophobic surfaces and broadening fields of superhydrophobic applications even submerged underwater.

• Journal of Powder Materials
• /
• v.11 no.3
• /
• pp.253-258
• /
• 2004

We report a carbothermal reduction process for massive synthesis of monolithic W$_{18}$O$_{49}$ phase from tungsten oxide in the presence of carbon source. Carbon black powder was used as a carbon source and added to WO$_3$ by 40 weight percent. Bundles of W$_{18}$O$_{49}$ rods were formed over the temperature range of 80$0^{\circ}C$$^{\circ}C$ to 90$0^{\circ}C$. Pure W$_{18}$O$_{49}$ bundles could be separated from the mixture of W$_{18}$O$_{49}$ and residual carbon black powder. Field emission character of W$_{18}$O$_{49}$ phase was determined using the extracted W$_{18}$O$_{49}$ rods. Flat lamp fabricated from the W$_{18}$O$_{49}$ rods showed the turn-on field of 9.3 V/${\mu}m$.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2004.04b
• /
• pp.42.1-42.1
• /
• 2004

• Bulletin of the Korean Chemical Society
• /
• v.30 no.1
• /
• pp.227-229
• /
• 2009

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2009.11a
• /
• pp.33.1-33.1
• /
• 2009

To date, nanostructured tungsten oxides with a variety of stoichiometries, such as WO3, WO2.9, W18O49, and WO2, have been prepared, because they are promising candidates for applications such as gas sensors, photocatalysts, electrochromic devices, and field emission devices. Among them, W18O49 and WO2 have been widely studied due to their outstanding chemical sensing, catalytic, and electron emissive properties. Here we report, for the first time, a one-pot solution-phase route to synthesizing a novel composite hierarchical hollow structure without adding catalysts, surfactants, or templates. The products, consisting of a WO2 hollow core sphere surrounded by a W18O49 nanorod shell (yielding a sea urchin-like structure), were generated as discrete structures via Ostwald ripening. To our knowledge, this type of composite hierarchical core/shell structure has not been reported previously. The morphological evolution and the detailed growth mechanism were carefully studied. We also demonstrate that the size of the hollow urchins is readily tunable by controlling the reactant concentrations.Interestingly, although bulk tungsten oxides are weakly paramagnetic or diamagnetic, the as-prepared products show unusual ferromagnetic behavior atroom temperature. The urchin structures also show a very high Brunauer-Emmet-Teller (BET) surface area, suggesting that they may potentially be applied to chemical sensor or effective catalyst technologies.

• Korean Journal of Metals and Materials
• /
• v.49 no.3
• /
• pp.270-274
• /
• 2011

Plasma electrolytic oxidation (PEO) treatment was performed on squeeze cast AZ31 alloy and $Al_{18}B_4O_{33}w/AZ31$ composite. Scanning electron microscope (SEM) was employed to characterize the surface morphology and cross-section microstructure of the coating. The phase structures of the PEO coating were analyzed by X-ray diffraction (XRD). The corrosion resistance of the PEO coating was evaluated by electrochemical method. The results showed that the $Al_{18}B_4O_{33}$ whisker on the surface of the composite was decomposed and $MgAl_2O_4$ was formed in the PEO coating layer of $Al_{18}B_4O_{33}w/AZ31$ composite during PEO treatment. As a result, the electrochemical corrosion potential of the PEO coated $Al_{18}B_4O_{33}w/AZ31$ composite was increased compared with that of AZ31 alloy.

• Korean Journal of Materials Research
• /
• v.32 no.2
• /
• pp.57-65
• /
• 2022

Herein a rich, Se-nanoparticle modified Mo-W₁₈O₄₉ nanocomposite as efficient hydrogen evolution reaction catalyst is reported via hydrothermal synthesized process. In this work, Na₂SeSO₃ solution and selenium powder are used as Se precursor material. The structure and composition of the nanocomposites are characterized by X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), EDX spectrum analysis and the corresponding element mapping. The improved electrochemical properties are studied by current density, and EIS analysis. The as-prepared Se modified Mo-W₁₈O₄₉ synthesized via Na₂SeSO₃ is investigated by FE-SEM analysis and found to exhibit spherical particles combined with nanosheets. This special morphology effectively improves the charge separation and transfer efficiency, resulting in enhanced photoelectric behavior compared with that of pure Mo-W₁₈O₄₉. The nanomaterial obtained via Na₂SeSO₃ solution demonstrates a high HER activity and low overpotential of -0.34 V, allowing it to deliver a current density of 10 mA cm^-2.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2008.02a
• /
• pp.89-89
• /
• 2008

• 한국전자현미경학회:학술대회논문집
• /
• 2004.11a
• /
• pp.72-76
• /
• 2004

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.33 no.3
• /
• pp.287-291
• /
• 1988

These studies were carried out to find out the polishing properties and cooking quality of the cut-polished barley. Naked barley, Youngsanbori which was produced in Chonnam province, Korea in 1981, was applied for this experiment. Polished barley was produced by the conventional method and cut-barley was manufactured by the method established by Wheat and Barley Research Institute. The yield of cut-polished barley was 68.2% and that of conventionally polished barley was 70.1 %. The ratio of length to width was 2.88 in cut-polished barley and that of conventionally polished barley was 1.36. And weight of 1,000 kernel was 9.5g in cut-polished barley and 18.5g in conventionally polished barley. Energy consumption was found to be 91.1kW/1,000kg in conventionally polished barley and 105kW/1,000kg in cut-polished barley. Whiteness, water uptake ratio and expanded volume of cooked barley were 45.5, 225.7 and 283% in conventionally polished barley and 49.5, 312.7 and 318% in cut-polished barley, respectively.