• Transactions of the Korean hydrogen and new energy society
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• v.28 no.4
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• pp.419-425
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• 2017

In this study, an efficient dye-sensitive solar cells (DSSC) was developed after post-treatment of ZnO on $TiO_2$ photoelectrode. The $TiO_2$ electrode with ZnO post treatment was prepared with Titanium isoporopoxide in Zinc Nitrate Hexahydrate aqueous solution by incineration for 30 min at $450^{\circ}C$. The ZnO-post treated $TiO_2$ electrode showed strong dispersion force between particles in relation to the control $TiO_2$, referring high specific surface area and dye-adsorption rate. Proper addition of ZnO enhanced electron mobility and reduced internal resistance and electron recombination. Light conversion efficiency of DSSCs containing the ZnO-posttreated $TiO_2$ electrode increased 35.4% when compared to the DSSCs using $TiO_2$ electrode. It is similar to the DSSCs with $TiCl_4$ post treatment $TiO_2$ electrode. Increasing of light conversion efficiency was due to high specific surface area and dispersion force, and low dye-adsorption rate and electron recombination. Taken together, ZnO may be used as posttreatment of photoelectrode and replaced $TiCl_4$ that has high toxicity and causticity.

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.11a
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• pp.173-173
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• 2002

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.321-324
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• 2003

The effects of various sintering additives such as $Bi_2O_3+V_2O_5$, $BiVO_4$, $B_2O_3$, and $CuO+V_2O_5$ on the low-temperature sintering and microwave dielectric properties of $(ZnMg)TiO_3$ system were studied. Sintering was enhanced by the sintering additives and highly dense samples were obtained for $(Zn_{0.8}Mg_{0.2})TiO_3$ at the sintering temperature of $910^{\circ}C$. $(Zn_{0.8}Mg_{0.2})TiO_3$ with 6.19 mol.%$B_2O_3$ was found to show the best sintering and microwave dielectric properties.

• Korean Journal of Materials Research
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• v.19 no.3
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• pp.142-150
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• 2009

In this paper, non-treated ACF (Activated Carbon Fiber) /$TiO_2$ and Zn-treated ACF/$TiO_2$ were prepared. The prepared composites were characterized in terms of their structural crystallinity, elemental identification and photocatalytic activity. XRD patterns of the composites showed that the non-treated ACF/$TiO_2$ composite contained only typical single and clear anatase forms while the Zn-treated ACF/$TiO_2$ contained a mixed anatase and rutile phase with a unique ZnO peak. SEM results show that the titanium complex particles are uniformly distributed on and around the fiber and that the titanium complex particles are more regularly distributed on and around the ACF surfaces upon an increase of the $ZnCl_2$ concentration. These EDX spectra show the presence of peaks from the C, O and Ti elements. Moreover, peaks of the Zn element were observed in the Zn-treated ACF/$TiO_2$ composites. The prominent photocatalytic activity of the Zn-treated ACF/$TiO_2$ can be attributed to the three different effects of photo-degradation: doping, absorptivity by an electron transfer, and adsorptivity of porous ACFs between the Zn-$TiO_2$ and Zn-ACF.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.133-133
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• 2016

화학저항식(Chemiresistive) 가스센서의 저항변화를 향상시키기 위해서는 센서 소재의 비표면적을 향상시키는 방향 및 전자천이를 증가시키는 방향으로 연구가 진행되어야 하며, 그 중 센서의 비표면적을 향상시키는 예로써 중공 나노섬유가 있을 수 있다. 본 연구에서는 비표면적의 향상뿐만 아니라 중공 나노섬유의 전자천이를 증가시켜 센서의 검출 성능을 더욱 향상시키기 위한 목적으로 $TiO_2/ZnO$ 이중층 중공 나노섬유를 제안하었다. 제안된 $TiO_2/ZnO$ 이중층 중공 나노섬유는 템플레이트 합성법을 통해 제작되었으며, 그 공정은 다음과 같다; 전기방사(Electrospinning) 공정을 통해 폴리머 나노섬유를 제작한 후 $TiO_2$ 층과 ZnO 층을 ALD(Atomic Layer Deposition) 공정을 통해 차례대로 증착시킨다. 그 후 후열처리 공정을 통해 코어 폴리머를 제거함으로써 $TiO_2/ZnO$ 이중층 중공 나노섬유를 얻을 수 있다. 이 때, ZnO 층의 두께는 각각 달리하여 제작되었으며, 최종적으로 이들에 대한 가스 센싱 특성 및 메커니즘에 대한 체계적인 조사를 진행하였다. 단층 중공나노섬유는 셀 층의 두께가 Debye length와 유사할 때 셀 층 표면이 완전공핍층이 형성되고, 그 보다 크게 되면 부분적인 공핍층이 형성되게 되어 감응도가 감소하게 된다. 그러나 이중층 중공 나노섬유의 경우 셀 층의 두께가 Debye length 보다 더 크게 되더라도 TiO2와 ZnO의 헤테로접합으로 인해 ZnO에서 TiO2로 전자의 이동을 야기시키게 되어 환원성 가스에 대한 감응도가 단층 ZnO 중공 나노섬유에 비해 향상되게 된다.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1257-1261
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• 1994

Phsysical and dielectric properties of $(1-x)CaTiO_3-xLa(Zn_{1/2}Ti_{1/2})O_3$ ceramics were investigated at the temperature range of $25^{\circ}C$ to $80^{\circ}C$ at the frequency of 6 GHz. As increasing addition of the amount of $La(Zn_{1/2}Ti_{1/2})O_3$ to x = 5 mol,Q value was increased due to grain growth and increase of density. For more addition, Q value decreased due to electrical defect. Temperature coefficient of resonant frequency could be controlled by the amount of $La(Zn_{1/2}Ti_{1/2})O_3$, which could be explained by volume mixing rule.

• Journal of the Korean Ceramic Society
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• v.28 no.11
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• pp.897-907
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• 1991

This study was conducted to research the formation and the color development of CoO-ZnO-Fe2O3-TiO2-SnO2 system for the purpose of synthesizing the spinel pigments which are stable at high temperature. After preparing CoO-ZnO-Fe2O3, in which CoO causes the color, as a basic composition, $\chi$CoO.(1-$\chi$)ZnO.Fe2O3 system, $\chi$CoO.(1-$\chi$)ZnO.TiO2 system and $\chi$CoO.(1-$\chi$)ZnO.SnO2 system were prepared with $\chi$=0, 0.2, 0.5, 0.7, 1.0 mole ratio respectively. The manufacturing was carried out at 128$0^{\circ}C$ for 90 minutes. These specimens were analyzed by the reflectance measurement and the X-ray diffraction analysis and the results were summarized as follows: 1. All of the specimens formed the spinel structure and were colored with stable yellow or blue. 2. As the content of CoO and Fe2O3 in the specimens being increased, the reflectance of each specimen was measured becoming lower and the colors were changed from yellow to greyish blue and from blue to dark blue. 3. As the substituting amount of Co2+ ion for Zn2+ ion in $\chi$CoO-ZnO-TiO2-SnO2 system being increased, the colors were changed from blue to greyish blue. The colors were changed from yellow to grayish green owing to the tetrahedral Co2+ ions being increased, the octahedral Co2+ ions being decreased with increasing the amount of Sn4+ ions. 4. CoO-ZnO-Fe2O3-TiO2-SnO2 system, in which Zn2+ was substituted with Co2+ and Fe3+ was substituted with Ti4+ and Sn4+, easily formed the spinel structure without regard to the amount of substitution or the ion owing to the selectivity of the coordination number: 4 of Zn2+, 4 of Co2+, 6 of Fe3+ or 6 of Ti4+ and Sn4+.

• Clean Technology
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• v.21 no.1
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• pp.39-44
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• 2015

This study investigated the effects of six metal oxide nanoparticles (NPs: CuO, NiO, TiO₂, Fe₂O₃, Co₃O₄, ZnO) on seed germination and germination index (G.I) for five types of seeds: Brassica napus L., Malva verticillata L., Brassica olercea L., Brassica campestris L., Daucus carota L. NPs of CuO, ZnO, NiO show significant toxicity impacts on seed activities [CuO (6-27 mg/L), ZnO (16-86 mg/L), NiO (48-112 mg/L)], while no significant effects were observed at > 1000 mg/L of TiO₂, Fe₂O₃, Co₃O₄. Tested five types of seed showed different sensitivities on seed germination and root activity, especially on NPs of CuO, ZnO, NiO. Malva verticillata L. seed was highly sensitive to toxic metal oxide NPs and showed following EC₅₀s : CuO 5.5 mg/L, ZnO 16.4 mg/L, NiO 53.4 mg/L. Mostly following order of toxicity was observed, CuO > ZnO > NiO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂, where slightly different toxicity order was observed for carrot, showing CuO > NiO ≈ ZnO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.397-403
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• 2003

Microwave dielectric properties of (1-x)ZnW $O_4$-xTi $O_2$ ceramic systems were investigated with calcination temperatures and Ti $O_2$ contents. The ZnW $O_4$ ceramic could be suitably sintered at 1075$^{\circ}C$ and showed the dielectric constant of 13.6, quality factor(Q$\times$ $f_{O}$value) of 22,000 and temperature coefficient of resonant frequency($\tau$$_{f}$) of -65$\pm$2ppm/$^{\circ}C$. Increasing the amount of Ti $O_2$ in the range of 0.25 to 0.45 mol, the dielectric constant and $\tau$$_{f}$ increased due to the role of Ti $O_2$ but the quality factor decreased due to the increase of phase boundaries. The 0.7ZnW $O_4$-0.3Ti $O_2$ ceramic showed the dielectric constant of 19.8, qualify factor(Q$\times$ $f_{0}$) of 20,000 and $\tau$$_{f}$ of -3$\pm$1ppm/$^{\circ}C$.>.EX>.>.>.

• Korean Journal of Materials Research
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• v.32 no.2
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• pp.94-97
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• 2022

We fabricated 3 types of ETL, mp TiO₂, ZnO, and ZnO coated on mp TiO₂(ZMT) to compare the photoelectric conversion efficiency (PCE) and fill factor (FF) of Perovskite solar cells. The structure of the cells was FTO/ETL/Perovskite (CH₃NH₃PbI₃)/spiro-MeOTAD/Ag. SEM morphology assessment of the ETLs showed that mp TiO₂ was porous, ZnO was flat, and the ZMT porous surface was filled with a thin layer. Via XRD measurements, the crystal structures of mp TiO₂ and ZnO ETL were found to be anatase and wurtzite, respectively. The XPS patterns showing energy bonding of mp TiO₂, ZnO, and ZMT O 1s confirmed these materials to be metal oxides such as ETL. The electrical characteristics of the Perovskite solar cells were measured using a solar simulator. Perovskite solar cells with ZMT ETL showed showed PCE of 10.29 % than that of conventional mp TiO₂ ETL devices. This was considered a result of preventing Perovskite from seeping into the ETL and preventing recombination of electrons and holes.