• 한국결정학회지
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• 제5권2호
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• pp.85-92
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• 1994

펄스 레이저 증착법을 이용하여 강유전체 Bi4T13012 박막을 laA109(001) 위에 성장시켰다. 넓은 영역의 온도에서 증착한 박막의 상 형성과 구조적 성질을 X선 회절법을 이용하여 조사하였다. 740℃에서 증착한 박막은 박막의 c-축이 기판에 수직한 형태의 에피 성장의 경향을 보인다. 펄스 레이저 증착법을 이용하여 Bi4Ti3O12/YBa2Cu3O7-x/LaAlO3 복합구조를 in-situ 성장시켰다. Yba2Cu3O7-x의 a-, b-축이 LaAlO3와 완벽하게 평행하게 배열되어 있지 않음에도 불구하고, Bi4Ti3012 박막은 에피 성장의 경향을 보인다.

• 청정기술
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• 제27권1호
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• pp.9-16
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• 2021

Active Matrix Organic Light-Emitting Diode (AMOLED) 봉지 공정은 수분과 산소에 매우 취약하기 때문에, 수분과 산소의 함량이 최소화된 고순도의 질소를 사용하여야 한다. 본 연구의 목적은 AMOLED 봉지 공정에 사용하는 질소에서 산소를 제거하기 위한 용도로 사용되는 구리계 촉매를 최적화하는 것이다. CuO, Al2O3, 또는 ZnO의 조성으로 이루어진 2성분계 및 3성분계 촉매를 공침법을 통해서 제조하였다. 제조된 촉매들을 BET, XRD, TPR, XRF의 분석장비를 활용하여 촉매의 특성을 분석하였다. 촉매의 산소 제거 성능을 확인하기 위해 고정층 반응기에서 촉매 산소 제거 반응 실험을 수행하고 산소 분석기를 통해 산소 함량을 측정하였다. 또한 사용된 촉매의 반복 재생을 통해 촉매의 재사용 성능을 검증하였다. CuO와 Al2O3 비율이 6 : 4, 7 : 3 및 8:2로 제조된 2 성분계 촉매의 특성과 산소 제거 능력을 비교하였다. CuO와 Al2O3의 비율이 8:2인 촉매의 환원성이 가장 높았는데, 이는 CuO의 분산도가 가장 높기 때문이다. 결과적으로, 2성분계 촉매 중에서 CuO와 Al2O3의 비율이 8 : 2 인 촉매의 산소 제거 능력이 가장 우수한 것으로 나타났다. CuO : Al2O3 의 비율이 8:2인 촉매에 ZnO를 2 wt% 넣어준 촉매가 3성분계 촉매 중에는 가장 우수한 산소제거 능력을 보였으며, 이는 뛰어난 환원성에 기인한다고 할 수 있다. 또한 이 촉매는 재생 실험을 통해서도 산소 제거능력이 유지된다는 것을 확인하였다.

• 한국수소및신에너지학회논문집
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• 제33권1호
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• pp.105-112
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• 2022

Copper (Cu)-based catalysts have been widely used in a methanol steam reforming (MSR) reaction for hydrogen production for air-independent propulsion (AIP) applications and their good catalytic activities have attracted much attention. However, the agglomeration of the catalytic active site Cu causes deteriorating the catalytic performance and suppression of Cu agglomeration is a crucial issue in the AIP applications that the MSR system is typically operated at 250-300℃ for a long time. R. Sakai et al. recently showed a computational study on the anchoring effect that reduces an agglomeration of active sites by doping in a supporter. In order to present the anchoring effect on 𝛾-Al₂O₃ supported Cu-based catalysts, in this study, the adsorption energies of Cu on X-doped (X=ruthenium, phosphorus, silicon) 𝛾-Al₂O₃ were calculated and Cu adsorption energy decreased due to a change of the electronic structure originated from doping, thereby proving the anchoring effect.

• 한국응용과학기술학회지
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• 제31권2호
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• pp.313-319
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• 2014

This study was performed to obtain high conversion efficiency of $NH_3$ and minimize generation of nitrogen oxides using metal-supported catalyst with Ag : Cu ratio. Through structural analysis of the prepared catalyst with Ag : Cu ratio ((10-x)Ag-xCu ($0{\leq}x{\leq}6$)), it was confirmed that the specific surface area was decrease with increasing metal content. A prepared catalysts showed Type II adsorption isotherms regardless of the ratio Ag : Cu of metal content, and crystalline phase of $Ag_2O$, CuO and $CuAl_2O$ was observed by XRD analysis. In the low temperature($150{\sim}200^{\circ}C$), a conversion efficiency of AC_10 recorded the highest(98%), whereas AC_5 (Ag : Cu = 5 : 5) also showed good conversion efficiency(93.8%). However, in the high temperature range, the amounts of by-products(NO, $NO_2$) formed with AC_5 was lower than that of AC_10. From these results, It is concluded that AC_5 is more environmentally and economically suitable.

• 한국재료학회지
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• 제21권1호
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• pp.67-71
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• 2011

La doped CuO-ZnO-$Al_2O_3$ powders are prepared by sol-gel method with aluminum isopropoxide and primary distilled water as precursor and solvent. In this synthesized process, the obtained metal oxides caused the precursor such as copper (II) nitrate hydrate and zinc (II) nitrate hexahydrate were added. To improve the surface areas of La doped CuO-ZnO-$Al_2O_3$ powder, sorbitan (z)-mono-9-octadecenoate (Span 80) was added. The synthesized powder was calcined at various temperatures. The dopant was found to affect the surface area and particle size of the mixed oxide, in conjunction with the calcined temperature. The structural analysis and textual properties of the synthesized powder were measured with an X-ray Diffractometer (XRD), a Field-Emission Scanning Electron Microscope (FE-SEM), Bruner-Emmett-Teller surface analysis (BET), Thermogravimetry-Differential Thermal analysis (TG/DTA), $^{27}Al$ solid state Nuclear Magnetic Resonance (NMR) and transform infrared microspectroscopy (FT-IR). An increase of surface area with Span 80 was observed on La doped CuO-ZnO-$Al_2O_3$ powders from $25m^2$/g to $41m^2$/g.

• 한국재료학회지
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• 제14권10호
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• pp.696-700
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• 2004

The reduction behavior of $Al_{2}O_3/CuO$ powder mixtures, prepared from $Al_{2}O_3/CuO$ or $Al_{2}O_3/Cu-nitrate$, was investigated by using thermogravimetry and hygrometry. The powder characteristics were examined by BET, XRD and TEM. Also, the influence of powder characteristics on the microstructure and properties of hot-pressed composites was analyzed. The formation mechanism of nano-sized Cu dispersions was explained based on the powder characteristics and reduction kinetics of oxide powders. In addition, the dependence of the microstructure and mechanical properties of hot-pressed composites on powder characteristics is discussed in terms of the initial size and distribution of Cu particles. The practical implication of these results is that an optimum processing condition for the design of homogeneous microstructure and required properties can be established.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.106-106
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• 2010

CuO 나노입자는 전기화학적 전지, 가스 센서 및 태양전지와 같은 나노 전자소자에 응용할 수 있는 대단히 유용한 물질이다. CuO 나노구조를 형성하기 위한 방법은 솔-겔법, 전기 화학적 방법 및 전구체의 열적 탈착방법 등으로 연구되어 왔으나 CuO 나노입자의 열처리 효과는 상대적으로 연구가 미흡하다. 본 연구에서는 $Al_2O_3$ 기판 위에 스핀 코팅법과 열처리를 사용하여 형성한 CuO 나노입자의 물리적 성질을 살펴보았다. CuO 나노 입자를 형성하기 위해 methanol에 Cu(I) acetate (5 wt%) 을 적절히 분산한 용액을 $Al_2O_3$ 기판 위에 7000 rpm으로 스핀 코팅을 한 후 $300^{\circ}C$, $500^{\circ}C$ 및 $700^{\circ}C$로 각각 1 시간 동안 산소 분위기에서 열처리를 하였다. X-선 회절법 결과는 CuO의 (200)$K_{\alpha}$와 (400) $K_{\alpha}$ 회절에 해당하는 피크가 나타났고 주사 전자현미경 상의 결과는 CuO 나노입자가 형성되었음을 확인하였다. 나노입자의 크기는 고배율 투과 전자현미경상에 의하여 3-5 nm 인 것으로 확인하였고 300 K에서 측정한 광루미네선스 스펙트럼은 CuO의 주된 스펙트럼 피크가 푸른색 영역에서 나타남을 알 수 있었다. X-선 광전자 분광법 스펙트럼은 Cu $2p_{3/2}$와 O 1s의 전자상태를 보여주었으며 복잡한 산화상태를 갖는 CuO는 Cu-O 결합과 산소의 화학적 흡착상태를 가지는 것으로 확인되었다. 이러한 결과는 $Al_2O_3$ 기판 위에 최적화된 CuO 나노 입자의 형성 방법과 구조적, 광학적 및 전자적 특성을 이해하는데 도움을 제공해 줄 것이다.

• 한국분말재료학회지
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• 제7권4호
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• pp.212-217
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• 2000

An optimum route to fabricate the $Al_2O_3/Cu$ nanocomposites with sound microstructure and improved mechanical properties was investigated. Microstructural investigations for the composites prepared using $Al_2O_3/Cu$-nitrate showed that fine Cu particles with average size of 150 nm were homogeneously distributed within the $Al_2O_3$ matrix grains and at the grain boundaries. Fracture strength of 953 MPa and toughness of 4.8 Mpa(equation omitted)m were measured for the composite. The strengthening and toughening of the composites are explained by the refinement of the microstructure and the crack bridging/deflection, respectively.

• 한국재료학회지
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• 제14권8호
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• pp.595-599
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• 2004

We investigated the structural, electrical and magnetic properties of Mn-doped $CuAlO_2$ delafossite ceramics ($CuAl_{1-x}Mn_{x}O_2,\;0\le\;x\;\le0.05$), synthesized by solid-state reaction method in an air atmosphere at a sintering temperature of $1150^{\circ}C$. The solubility limit of Mn ions in delafossite $CuAlO_2$ was found to be as low as about 3 $mol\%$. Positive Hall coefficient and the temperature dependence of conductivity established that non-doped $CuAlO_2$ ceramic is a variable-range hopping p-type semiconductor. It was found that the Mn-doping in $CuAlO_2$ rapidly reduced the hole concentration and conductivity, indicating compensation of free holes. The analysis of the magnetization data provided an evidence that antiferromagnetic superexchange interaction is the dominant mechanism of the exchange coupling between Mn ions in $CuAl_{1-x}Mn_{x}O$ alloy, leading to an almost paramagnetic behavior in this alloy.

• 한국분말재료학회지
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• 제11권2호
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• pp.171-178
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• 2004

Effects of liquid phase and reinforcing particle morphology on the sintering of Al-6 wt％Cu-10 vol％ $Al_2O_3$ or SiC particles were studied in regards to densification, structure and transverse rupture properties. The Al-Cu liquid phase penetrated the boundaries between the aluminum matrix powders and the interfaces with reinforcing particles as well, indicating a good wettability to the powders. This enhanced the densification during sintering and the resulting strength and ductility. Since most of the copper added, however, was dissolved in the liquid phase and formed a brittle $CuAl_2$ phase upon cooling rather than alloyed with the aluminum matrix, the strengthening effect by the copper was not fully realized. Reinforcing particles of agglomerate type were found less suitable for the liquid phase sintering than solid type particles. $Al_2O_3$ and SiC particles protluced little difference on the sintering behavior but their size had a large effect. Repressing of the sintered composites increased density and bending properties but caused debonding at the matrix-particle interfaces and also fracturing of the particles.