• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.1
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• pp.48-56
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• 1998

Pr\ulcornerO\ulcorner-based ZnO varistors were fabricated in the range of $Y_2$O$_3$additive content from 0.5 to 4.0mol%, and its microstructure and electrical properties were investigated. Yttrium was distributed nearly in the grain boundaries and the cluster phase formed at nodal point but more in cluster phase. The average grain size was decreased markedly from 34.9 to 8.6${\mu}{\textrm}{m}$ with increasing $Y_2$O$_3$additive content. It is believed that the decrease of grain size is attributed to the formation of cluster phase and the weakening of driving force for liquid sintering. As a result, $Y_2$O$_3$was acted as the inhibitor of the grain growth. With increasing $Y_2$O$_3$additive content, the varistor voltage, the activation energy, and the nonlinear exponent increased whereas the leakage current decreased, especially 4.0mol% $Y_2$O$_3$-added varistor exhibited very good I-V characteristics; nonlinear exponent 87.42 and leakage current 46.77nA. On the other hand, as $Y_2$O$_3$additive content increases, the varistor showed tendency of the salient decrease for donor concentration and the increase for barrier height. Conclusively, it is estimated that ZnO:Pr varistor compositions added more than 2.0mol% $Y_2$O$_3$are to be used to fabricate useful varistors.

• Transactions on Electrical and Electronic Materials
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• v.9 no.3
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• pp.96-100
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• 2008

The microstructure, voltage-current, and capacitance-voltage relations ofP CCYA doped ZnO-based varistors were investigated for different amounts of $Al_2O_3$. As the $Al_2O_3$ amount increased, the average grain size (d) increased from d=4.3 to $d=5.5{\mu}m$ and the sintered density $({\rho})$ increased from ${\rho}=5.63$ to ${\rho}=5.67g/cm^3$. As the $Al_2O_3$ amount increased, the breakdown voltage $(V_B)$ increased from $V_B=633$ to $V_B=71$ V/mm and the non-ohmic coefficient $({\alpha})$ increased from ${\alpha}=47$ to ${\alpha}=4$. $Al_2O_3$ served as a donor due to the donor density $(N_d)$, which increases in the range of $N_d=0.77-1.85{\times}10^{18}/cm^3$ with increasing amount of $Al_2O_3$.

• Nuclear Engineering and Technology
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• v.34 no.4
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• pp.323-330
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• 2002

Various types of compounds were tested with the aspects of decomposition and formation of residue in a $CO_2$ or 7H$_2$+93$N_2$ atmosphere. The evaporation temperature range of each compound was determined from thermogravimetric curve. Decomposition of dicarbon amide, stearic acid, acrowax and zinc stearate was studied by thermogravimetry in $CO_2$ or in 7H$_2$+93$N_2$ atmosphere. All compounds were decomposed in $CO_2$ atmosphere at lower than 40$0^{\circ}C$, but the residue, ZnO remained for zinc stearate. ZnO did not decompose in $CO_2$ atmosphere up to 130$0^{\circ}C$, but reduced into Zn metal and disappeared in the temperature range of $600^{\circ}C$ to 120$0^{\circ}C$ in 7H$_2$+93$N_2$ atmosphere. The effect of residue, which trapped in closed pores of sintered pellet, on the thermal stability was studied using the resintering test at 1$700^{\circ}C$ in 7H$_2$+93$N_2$ atmosphere. In the case of oxidative sintered pellet with admixing zinc stearate, the cavity formation accompanied with a density drop after resintering is due to the pressure of the Zn gases trapped in the isolated pores.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.86.2-86.2
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• 2012

산화금속은 높은 결정성, quantum size effect, 높은 투과도, 대기중의 안정도 등과 같은 탁월한 성질들로 인하여 오늘날 실리콘의 대체물로서 많은 연구가 보고되고 있다. 이러한 금속산화물의 크기와 모양을 조절하며 대량 생산하기 위한 합성방법으로 가수분해, 금속양이온 응축법과 같은 다양한 수용액상 방법이 연구되고 있다. 하지만 2차원 단일 층에 나노물질을 정렬하고 전기적 접합을 형성하는 것이 매우 어렵다는 점 때문에 나노물질을 기판 위에 자유롭게 성장시키는 방법에 대해서는 아직 많이 보고 되어있지 않다. 본 연구에서 저온의 수용액에서 1차원의 나노막대가 2차원의 스피넬 구조 위에 heteroepotaxial 접합을 이루며 성장시키는 방법을 이용하였다. P-n접합 형성을 위하여 (0001)방향으로 배향된 n-type ZnO 나노막대를 (111)방향의 p-type Co3O4 나노플레이트 위에 성장시킨 구조를 제작하였으며 이를 바탕으로 다이오드소자를 제작하여 ideal factor, turn-on voltage, rectifying ratio등의 전기적 특성을 평가하였다.

• Food Science of Animal Resources
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• v.28 no.1
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• pp.27-31
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• 2008

This study investigated the effects of copper and zinc sources on growth performance, nutrient digestibility, carcass traits and meat characteristics in finishing pigs. Dietary treatments included 1) inorganic copper ($CuSO_4{\cdot}5H_2O$ 30ppm), 2) organic copper (Cu-methionine, 30 ppm), 3) inorganic zinc (ZnO, 80 ppm) and 4) organic zinc (Zn-methionine, 80 ppm). ZnO treatment improved the ADFI (average daily feed intake) compared to Cu-met and Zn-met treatments (p<0.05) during 5 weeks of treatment. However, during the entire experimental period, the ADG (average daily gain), ADFI and F:G ratio (feed conversion ratio) were not significantly different among the treatments (p>0.05). DM and N digestibility were not significantly different among the treatments after 5 weeks (p>0.05). At the end of the experiment, DM and N digestibility were decreased with Zn-met treatment relative to the other three treatments. The pH value of meat from $CuSO_4$ treated pigs was greater than Zn-met and ZnO treated pigs (p<0.05). Sensory evaluation was carried out for randomly selected (n = 16) paired loin samples. Meat color levels were increased (p<0.05) with Cu treatments compared to Zn treatments. $CuSO_4$ decreased the marbling of meat relative to the other treatments (p<0.05). The firmness was greater with ZnO treatment compared to Cu-met and ZnO treatments (p<0.05). These results indicate that inorganic Zn can improve growth performance, however, inorganic Cu and Zn are as effective as organic Cu and Zn at improving nutrient digestibility, carcass traits and meat quality. This form of organic additive can be friendlier to the environment than inorganic supplements.

• Journal of the Korean Ceramic Society
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• v.44 no.6 s.301
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• pp.303-307
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• 2007

Transparent In-doped zinc oxide (IZO) thin films are deposited with variation of pulsed DC power at Ar atmosphere on coming 7059 glass substrate by pulsed DC magnetron sputtering. A c-axis oriented IZO thin films were grown in perpendicular to the substrate. The optical transmittance spectra showed high transmittance of over 80% in the UV-visible region and exhibited the absorption edge of about 350 nm. Also, the IZO films exhibited the resistivity of ${\sim}10^{-3}{\Omega}\;cm$ and the mobility of ${\sim}6cm/V\;s$. Organic Light-emitting diodes (OLEDs) with IZO/N,N'-diphenyl-N, N'-bis(3-methylphenl)-1, 1'-biphenyl-4,4'-diamine (TPD)/tris (8-hydroxyquinoline) aluminum ($Alq_3$)/LiF/Al configuration were fabricated. LiF layer inserted is used as an interfacial layer to increase the electron injection. Under a current density of $100\;mA/cm^2$, the OLEDs show an excellent efficiency (9.4 V turn-on voltage) and a good brightness ($12000\;cd/m^2$) of the emission light from the devices. These results indicate that IZO films hold promise for anode electrodes in the OLEDs application.

• Journal of the Korean Chemical Society
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• v.48 no.6
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• pp.577-582
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• 2004

The azacrown compounds, 1,4-dioxa-7,10,13-triazacyclopentadecane-N,N',N''-triacetic acid, $N-ac_3[15]aneN_3O_2(II_a)$ and 1,4-dioxa-7,10,13-triazacyclopentadecane-N,N',N''-tripropioc acid, $N-pr_3[15]aneN_3O_2(II_b)$ were synthesized by modified methods. Potentiometry was used to determine the protonation constant of the $N-ac_3[15]aneN_3O_2\;and\;N-pr_3[15]aneN_3O_2$. The stability constants of complexes of the trivalent metal ions of $Ce^{3+},\;Eu^{3+},Gd^{3+},and\;Yb^{3+}$ and divalent metal ions of $Co^{2+},\;Ni^{2+},\;Cu^{2+},\;and\;Zn^{2+}$ with the ligands $N-ac_3[15]aneN_3O_2\;and\;N-pr_3[15]aneN_3O_2$ have been determined at $25{\pm}0.1^{\circ}C$ in 0.1 M $NaClO_4$ solution by potentiometric methods. The metal ion affinities of the two triazamacrocyclic ligands with three pendant acetate or propionate groups are compared to those obtained for the similar ligands, 1,7-dioxa-4,10,13-triazacyclopentadecane-N,N',N''-triacetic acid, and 1,7-dioxa-4,10,13- triazacyclopentadecane-N,N',N''-tripropioc acid. The trends in stability of complexes for different metal ions due to changes in the nitrogen position of the donor atoms of the ligand are discussed.

• Clean Technology
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• v.23 no.4
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• pp.429-434
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• 2017

To investigate the effect of magnesium oxide addition, $Cu/ZnO/MgO/Al_2O_3$ (CZMA) catalysts were prepared using co-precipitation method with fixed molar ratio of Cu/Zn/Mg/Al as 45/45/5/5 mol% for low-temperature water gas shift reaction. Synthesized catalysts were characterized by using BET, $N_2O$ chemisorption, XRD, $H_2-TPR$ and $NH_3-TPD$ analysis. The catalytic activity tests were carried out at a GHSV of $28,000h^{-1}$ and a temperature range of $200{\sim}320^{\circ}C$. At the same condition, magnesium oxide added catalyst (CZMA 400) showed that the lowest reduction temperature and stable presence of $Cu^+$, that is active species and abundant weak acid site. Also magnesium oxide added catalysts (CZMA) showed higher catalytic activity at temperature range above $240^{\circ}C$ than the catalyst without magnesium oxide (CZA). Consequently, CZMA 400 catalyst is considered to be excellent catalyst showing CO conversion of 77.59% without deactivation for about 75 hours at $240^{\circ}C$, GHSV $28,000h^{-1}$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.266-267
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• 2009

본 논문에서는 As-doped ZnO 박막의 플라즈마 식각 특성 및 메커니즘에 관하여 실험을 수행하였다. p-type과 n-type ZnO 박막의 실험은 유도 결합 플라즈마 식각 장비(inductively coupled plasma; ICP)를 이용하였고, $CH_4/Ar$ 플라즈마의 가스의 비, RF 전력, DC 바이어스 전압과 공정 압력에 대한 식각 속도의 변화를 관찰 하였다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.965-970
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• 1994

ZnO transparent conducting oxide thin films have been prepared by Pyrosol deposition method and the effects of the different experimental variables on the electrical resistivity and optical transmittance of the prepared films have been investigated in details. The best film with a resistivity of about 8 X 10S0-2TΩcm and transmittance about 80% has been obtained at the substrate temperature of 4$25^{\circ}C$ by using HS12T+CHS13TOH(1:3) solvent and NS12T carrier gas after annealing at 20$0^{\circ}C$ for 40 minutes in vacuum. Furthermore, We have also found the effect of substrate temperature on crystallographic orientation and surface morphology. Annealing of the as-deposited film in vacuum leads to a substantial reduction in resistivity without affecting the optical transmittance and crystallographic orientation.