• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.855-861
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• 2006

Sinterability and microwave dielectric properties of $xZWO_{4}-(1-x)TiO_{2}$ ceramic systems with zinc-borosilicate glass and $TiO_{2}$ contents for LTCC(Low Temperature Co-fired Ceramics) were investigated. The addition of $3{\sim}10\;wt%$ ZBS glass ensured the sinterability below $900^{\circ}C$. In general, increasing ZBS glass content seemed to enhance the sinterability, but the quality factor($Qxf_{0}$) significantly decreased due to the formation of an excessive liquid and second phases. As for the addition of $TiO_{2}$, the dielectric constant(${\varepsilon}_{r}$) and temperature coefficient of resonant frequency(${\tau}_{f}$) showed to increase, while the quality factor($Qxf_{0}$) did not show an apparent change. The composition of $0.7xZnWO_{4}-0.3TiO_{2}$ ceramics sintered at $900^{\circ}C$ with 5 wt% ZBS glass demonstrated 21.6 in dielectric constant(${\varepsilon}_{r}$), 14,800 in quality factor($Qxf_{0}$), and $+5\;ppm/^{\circ}C$ in temperature coefficient of resonant frequency(${\tau}_{f}$).

• Journal of the Korean Ceramic Society
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• v.23 no.4
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• pp.69-77
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• 1986

Single crystals of zinc tungstates were grown by the Czochralski method. To obtain the seed crystals various methods were employed including 4 points platinum wirse which dipped the melt and the capillary action from the melt led the 3 differently oriented seeds such as [100], [010] and [001] directions. Optimum growing conditions were observed as neck diameter 2mm rotation speed 50-60 rpm maximum diameter 15mm and pulling rate 0-10 mm/hr. Dendrites covered on the olidified surface in a platinum crucible were turned out to be [001] direction because obviously this crystal has the strong [001] preferential growth habit. The (100) and (010) planes of single crystals showed the slip planes and the (010) plane showed the perfect cleavage surface.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.135.2-135
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• 2000

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.705-711
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• 2000

A thin film oxide semiconductor micro gas sensor array which shows only 60 mW of power consumption at an operating temperature of $300^{\circ}C$ has been fabricated using microfabrication and micromachining techniques. Excellent thermal insulation of the membrane is achieved by the use of a double-layer structure of $0.1\mum\; thick\; Si_3N_4 \;and\; 1 \mum$ thick phosphosilicate glass (PSG) prepared by low-pressure chemical-vapor deposition (LPCVD) and atmospheric-pressure chemical-vapor deposition (APCVD), respectively. The sensor array consists of such thin film oxide semiconductor sensing materials as 1 wt.% Pd-doped $SnO_2,\; 6 wt.% A1_2O_3-doped\; ZnO,\; WO_3$/ and ZnO. Baseline resistances of the four sensing materials were found to be stable after the aging for three days at $300^{\circ}C$. The thin film oxide semiconductor micro gas sensor array exhibited resistance changes usable for subsequent data processing upon exposure to various gases and the sensitivity strongly depended on the sensing layer materials.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.247-256
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• 2024

The glass series modified by tungsten oxide was created using the compounds (75-x) B₂O₃- 10SrCO₃- 8TeO₂- 7ZnO - xWO₃, where x = 0, 1, 5, 10, 22, 27, 34, and 40% mole percentage. A UV-visible spectrophotometer and thermogravimetric-differential thermal analysis (TG-DTA) methods were employed to characterize the specimen's optical and phase transition attributes, respectively. The mass-attenuation coefficient (AC) of all created glasses from BSTZW0 to BSTZ7 was estimated using Geant4 code from 0.05 to 3 MeV and compared to the XCOM software results, with a relative difference of less than 2% between the two results. The increase of WO₃ percentage lead to an increase in the Linear-AC at each studied energy, and this is mainly due to the fact that the higher the percentage of WO₃ in the glass increases its density which causes an increase in the Linear-AC, so an energy of 0.06 MeV, as an example, the values of the Linear-AC was 4.009, 4.509, 5.442, 6812, 8.564, 9.856, 10.999 and 11.628 cm^-1 form BSTZW0 too BSTZW7, respectively. The Half-VL (value layer), Mean-FP (free path), Tenth-VL, and Radiation attenuation performance (RAP) were also calculated for the current BSTZW-glass samples and revealed that BSTZW7 had the best gamma ray attenuation performance at all discussed energies when compared to other studied glass samples.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.2
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• pp.315-322
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• 2002

A thin film oxide semiconductor micro gas sensor array which shows only 60㎽ of power consumption at an operating temperature of 30$0^{\circ}C$ has been fabricated using microfabrication and rnicrornachining techniques. Excellent thermal insulation of the membrane is achieved by the use of a double la! or structure of 0.1${\mu}{\textrm}{m}$ thick Si$_3$N$_4$ and 1${\mu}{\textrm}{m}$ thick phosphosilicate glass(PSG) prepared by low pressure chemical vapor deposition(LPCVD) and atmospheric－pressure chemical-vapor deposition(APCVD), respectively. The sensor way consists of such thin film oxide semiconductor sensing materials as 1wt.％ Pd-doped SnO$_2$, 6wt.% AI$_2$O$_3$-doped ZnO, WO$_3$ and ZnO. The thin film oxide semiconductor micro gas sensor array exhibited resistance changes usable for subsequent data processing upon exposure to various gases and the sensitivity strongly depended on the sensing layer materials. Heater Part of the sensor structure has been modified in order to improve the process yield of the sensor, and as a result of modified heater structure improved process yield has been achieved.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.327-336
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• 1994

The synergistic effects in mechanical mixture catalysts of Mo-V-O and metal oxide were investigated for the selective oxidation of acrolein. The metal oxides used are $SnO_2$, ${\alpha}-Sb_2O_4$, $WO_3$, ${\alpha}-Al_2O_3$, CuO, $MnO_2$, $Cu_2O$, MgO, CoO, and ZnO. Mechanical mixtures of Mo-V-O plus $SnO_2$ or ${\alpha}-Sb_2O_4$ had resulted in higher conversion of acrolein and higher yield of acrylic acid than Mo-V-O. The origin of the synergy is attributed to the cooperation of Mo-V-O and $SnO_2$ or ${\alpha}-Sb_2O_4$, in which $SnO_2$ or ${\alpha}-Sb_2O_4$ forms dissociated oxygens at their oxygen vacancies and transports them to Mo-V-O. $Cu_2O$, MgO, CuO, and $MnO_2$, increased conversion of acrolein but decreased yield of acrylic acid. CoO and ZnO inhibited the catalytic performance of Mo-V-O. The different role of these metal oxides is explained in terms of their oxidation-reduction properties.

• Economic and Environmental Geology
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• v.31 no.5
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• pp.375-388
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• 1998

The purpose of this study is to investigate the ore genesis and occurrence of the Wondong polymetallic mineral deposits. The Pb-Zn, Fe and W-Mo mineralizations are found in skarn zones which formed mainly in or along the fault shear zones with the $N25-40^{\circ}W$ and $N10-50^{\circ}E$ directions, whereas the Cu-Mo mineralization is appeared hydrothermal replacement zone. The skarn minerals consist mainly of garnet and epidote, which were the last alteration phases between pneumatolytic and hydrothermal stages. The mineral paragenesis toward the late stage are as follows: arsenopyrite, scheelite, magnetite, pyrite, pyrrhotite, sphalerite, galena, chalcopyrite and molybdenite. Average ore grades are 0.33 g/t Au, 46.29 g/t Ag, 0.06% Cu, 4.4% Pb, 2.61% Zn and 29.39% Fe in tunnels, and 0.31 % Cu, 0.52% Pb, 6.29% Zn, 29.29% Fe, 0.03% Mo and 0.12% $WO_3$ in drill cores. Fluid inclusion data shows that Type I (liquid-rich), Type II (vapor-rich) and Type III (halite-bearing) inclusions are coexisted and their homogenization temperatures are quite similar. This indicates that boiling conditions have been reached during the mineralization. It is also likely that the ore solutions were evolved through the mixing between magmatic and meteoric waters. Rhyolite and quartz porphyry far the mineralization probably are not responsible of the Wondong polymetallic mineral deposits.

• Analytical Science and Technology
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• v.10 no.6
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• pp.439-444
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• 1997

Twelve kinds (1set) standard materials of chemical ingredients of lead zirconate titanate[$Pb(ZrTi)O_3$] have been developed in order to determine fast and accurate measurement of X-ray fluorescence spectrometry. Especially, we used diluted(ahout sixteen times) filling compound($Li_2B_4O_7/LiBO_2=4/1$) to consider removal effect of matrix, storage convenience, and homogenous characteristics. As a result from the four different laboratories, we obtained extremly good agreement about the standard curve on twelve standard materials which containing eleven elements, PbO, $ZrO_2$, $TiO_2$, SrO, $WO_3$, $La_2O_3$, $Cr_2O_3$, MgO, $Nb_2O_5$, and $MnO_2$. The correlation factor of standard curve was over 0.998. However, ZnO has relatively low correlation factor, 0.977, because the concentration was 10ppm lower than other original materials. This analysis reveals that ZnO has shown the poor linearity as well as low fluorescence intensity. In present work, XRF standard materials are useful for determining a rapid and accurate results for major and minor elements concentration among PZT.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.11a
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• pp.266-266
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• 2015

전 세계적으로 무한한 청정에너지 개발에 대한 연구가 주목받고 있다. 그 중, 수소에너지는 화석연료의 고갈과 환경문제를 동시에 해결할 수 있는 자원이며 수소 생산 방법 중에서도 태양에너지를 이용한 수소 생산 기술은 가장 이상적인 수소 생산 시스템이라 할 수 있다. 대표적인 광전극 소재로는 $WO_3$, ZnO, $Fe_2O_3$, $BiVO_4$ 등과 같은 무기 소재가 주로 사용되고 있으며, 최근에는 Si, CIGS 등과 같은 태양전지와 상기 광전극을 집적하는 탄뎀형 소재/소자가 개발되고 있다. 광전반응이 우수한 전도성 고분자는 광전기화학 전지의 소재로 개발되고 있다. 그러나 유기물의 수중 불안전성 문제 때문에 직접적으로 물에 침전시키는 것이 아니라 외부의 인가 전원용으로 그 사용이 제한적이다. 본 연구에서는 유기계 소재의 direct energy conversion을 위한 효율 및 수중 안정성 향상을 위하여 Ni계 촉매 및 그래핀옥사이드가 융합된 유기기반 광전기화학전지를 개발하였다.