• 한국세라믹학회지
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• 제28권12호
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• pp.969-974
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• 1991

The influences of A(Cu1/3Nb2/3)O3(A=Pb, Ba and Sr) on the ferroelectric-paraelectric phase transition of BaTiO3 ceramics has been investigated. The tetragonality of crystal structure decreased with increasing A(Cu1/3Nb2/3)O3 content at room temperature. A linear correlation between Curie point and the tetragonality of lattice was not observed. In all three systems the variation of Curie point with the mole fraction showed similar tendency that the Curie point decreased at lower mole fraction but gradually increased in the region of higher mole fractions, Diffuse phase transitions were observed at higher mole fractions. The variation of Curie points could be explained by internal stress and Jahn-Teller distortion of BO6 due to Cu2+, and it was thought that the diffuse character of phase transition was caused by compositional fluctuation.

• 한국안광학회지
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• 제3권1호
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• pp.229-235
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• 1998

Co, Cu, Cr이 포함된 $80SiO_2-20TiO_2$, 코팅박막을 졸-겔법으로 제조하고 전이금속의 함량에 따른 표면반사율과 색상의 변화를 분석 연구하였다. 모든 경우에 있어서 전이금속의 함량이 증가함에 따라서 반사율이 점차 감소하였다. Co의 경우에 550~670nm 영역에서, Cu의 첨가시에는 400~500nm 범위에서, Cr의 경우에는 410~650nm 영역에서 반사율이 크게 감소하였다. 코팅박막의 표면반사광을 색차계로 색도분석을 행한 결과, Co의 경우에 5mol% 첨가시에는 약한 황녹색을 보이나 첨가량 증가에 따라서 점차 녹색조로, 그리고 20mol%에서는 청녹색으로 변화하였으며 명도는 90.29(5mol%)에서 85.42(20mol %)로 감소, 또 첨가량에 따른 색차는 20mol%에서 5.37로 증가하였다. Cu의 경우에는 첨가량이 증가할수록 원정에서 황녹색 중간영역으로 발산하였다. 명도의 변화는 상대적으로 작았으며 색차는 6.48로 Co의 경우에 비하여 더 큰 변화를 보였다. Cr의 경우에 있어서는 Co와는 반대로 첨가량이 증가함에 따라 거의 황색축에 근접한 값을 보였으며 명도는 90.33(5mol%)에서 80.43(20mol%)로 크게 감소하였다. 색차는 11.60(10%), 18.09(15%), 23.21(20%)로 Co나 Cu에 비하여 매우 큰 변화를 보였다. Lab 색도도가 xy색도도에 비하여 본 연구의 색도표현에 더 용이하였다.

• Progress in Superconductivity
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• 제10권2호
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• pp.128-132
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• 2009

Polycrystalline samples of $(Ru_{0.8}Nb_{0.2})Sr_2(Gd_{1.5-x}Nd_xCe_{0.5})Cu_2O_z$($ 0{\leq}x{\leq}1.25$) have been synthesized by a solid-state reaction route. The X-ray diffraction data revealed that the Nd solubility limit can be placed between x=0.5 and x=0.75. The superconducting transition temperature decreased with increasing Nd content, confirming that Nd entered the lattice. Room-temperature thermoelectric power measurements showed that all the samples are in the underdoped state and the partial substitution of Nd for Gd resulted in a decrease in the carrier density on the superconducting layers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.91-94
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• 2002

The conditions of zone-melting method such as a sample travel speed in a furnace, content of Nd422, control of melting temperature, and heat-treatment with/without Ar gas for $NdBa_{2}Cu_{3}O_{7-\delta}$ superconductor was optimized, As a results, a $NdBa_{2}Cu_{3}O_{7-\delta}$ sample with a surface area of $25mm^{2}$ showed a good superconducting properties when its travel speed was 6 mm/h, The improvement of superconductivity added with 10~20 wt% of Nd422 phase increasing pinning effect was also shown. The critical current density, $J_{c}$ was remarkable affected by the condition of heat-treatment temperature of $NdBa_{2}Cu_{3}O_{7-\delta}$superconductor with/without Ar ambient gas.

• 한국세라믹학회지
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• 제27권3호
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• pp.355-360
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• 1990

One of the possible ways to make a flexible wire of high-Tc superconductiong ceramics is the extrusion of a mixture slurry of superconducting powder with an appropriate polymer binder. The fabrication procedure for $YBa_2Cu_3O_{7-{\delta}}$ superconducting coils with this plastic mass is described. The major factors limiting the formation of extruded wire are the binder content, powder size, and entrapped gas in the mixture slurries. The optimum content of binder for both good flexbility and strength of wire was estimated to be 30wt%. The finer the powder size is, the more homogeneous structure the extruded wire has. The vacuum degassing before extrusion was necessary to remove the entrapped gas in as-extruded wire. The formability of wire depends greatly on the wire radius and binder content. After burning out the binder and the successive sintering, the contacts between the superconducting grains could be made. The resistivity vs. temperature behavior measured in the final wire showed the transition temperature of 90K with narrow transition width. However, the critical current densities of these wires are much lower in comparison to those of conventional bulk specimens.

• 공업화학
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• 제21권3호
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• pp.328-332
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• 2010

본 연구에서는 다이에틸렌글리콜 용매 상에서 공침법을 이용하여 기공성 아연 구형 산화물과 구리-아연 복합 산화물을 합성하였다. 합성된 물질들의 물리화학적 특성은 전자현미경, X-선 회절분석, $N_2$ 흡착, $H_2$-TPR 방법을 통하여 분석되었고, 다양한 Cu 함량(0, 6.6, 21.3 36.4, 54.6, 77.8 wt%)을 포함한 Cu-ZnO 복합 산화물을 고정층 반응 장치에서 일산화탄소 산화 반응성을 고찰하였다. 합성된 산화물 중에서 Cu 함량이 증가할수록 Cu-ZnO의 비표면적과 미세 기공 부피는 감소하였으며, Cu (36.4 wt%)-ZnO이 가장 좋은 일산화탄소 산화 반응성을 나타내었다.

• 한국전기전자재료학회논문지
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• 제22권8호
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• pp.665-670
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• 2009

Lead-free piezoelectric ($Na_{1/2}K_{1/2}$)$NbO_3$ ceramics doped with CuO and $MnO_2$ were fabricated using the conventional oxide-mixing technique. With increasing content of CuO and $MnO_2$, the dielectric constant(${\varepsilon}_{33}$) and mechanical quality factor($Q_m$) value increased, while electromechanical coupling factor($K_p$) and piezoelectric constant($d_{33}$) decreased. The piezoelectric and dielectric properties ($Na_{1/2}K_{1/2}$)$NbO_3$ ceramics doped with CuO 2.461 wt% and $MnO_2$ 0.538 wt% at sintered temperature $1050\;^{\circ}C$ were attained ${\varepsilon}_{33}$ = 403, $K_p$ = 15, $Q_m$ = 122 and $d_{33}$ = 36 pC/N. Based on response surface methodology results using design of experiment, it was concluded that ($Na_{1/2}K_{1/2}$)$NbO_3$ doped with CuO 0.477 wt% and $MnO_2$ 0.269 wt% has possibility composition of being used for piezoelectric transformer.

• 한국세라믹학회지
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• 제38권7호
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• pp.597-601
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• 2001

The effect of CuO, $B_2$ $O_3$, $V_2$ $O_{5}$ and CuO-B $i_2$ $O_3$additives on microwave dielectric properties of (P $b_{0.45}$C $a_{0.55}$) [(F $e_{0.5}$N $b_{0.5}$)$_{0.9}$S $n_{0.1}$] $O_3$(PCFNS) were investigated. The PCFNS ceramics were sintered at 11$65^{\circ}C$. To decrease the sintering temperature for using as a low-temperature co-firing ceramics (LTCC), CuO, $B_2$ $O_3$, $V_2$ $O_{5}$ and CuO-B $i_2$ $O_3$were added to the PCFNS. As the content of CuO increased, the sintered density and dielectric constant increased and the temperature coefficient of resonance frequency ($\tau$$_{f}$) shifted to the positive value. When the CuO-B $i_2$ $O_3$were added, dielectric properties were $\varepsilon$$_{r}$ of 83, Q. $f_{0}$ of 6085 GHz, and $\tau$$_{f}$ of 8ppm/$^{\circ}C$ at a sintering temperature of 100$0^{\circ}C$. The relationship between the microstructure and properties of ceramics was studied by X-ray diffraction and scanning electron microscopy.icroscopy.y.icroscopy.y.

• 공업화학
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• 제16권6호
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• pp.737-741
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• 2005

본 연구에서는 제조한 MCM-41에 Cu의 함량에 따른 NO의 전환율을 고찰하였다. MCM-41은 실리카 원으로 colloid silica를 사용하였고, template로 cetyltrimethylammonium chloride (CTMACl)를 사용하여 수열 합성하였으며, Cu/MCM-41은 Cu(II) acetylacetonate를 사용해서 Cu의 농도를 5, 10, 20 그리고 40%로 변화시켜 제조하였다. 표면 특성은 pH, FT-IR로 분석하였고, 육방배열의 1차원 기공 구조는 XRD로 고찰하였다. $N_2/77K$ 등온흡착 특성은 BET식과 t-plot을 이용하여 확인하였으며, NO 제거 효율은 가스크로마토그래프를 이용하여 측정하였다. 실험 결과, Si-OH와 Si-O-Si의 stretching vibration peak가 관찰되었으며, (100), (110), (200) 그리고 (210)의 육방배열의 1차원 구조를 확인하였다. Cu 금속이 도입된 MCM-41은 Cu 도입량이 증가할수록 비표면적과 미세기공부피는 감소한 반면에 NO 제거 효율은 증가하였다. 결과적으로 Cu/MCM-41의 Cu의 함량이 증가함에 따라 전체 촉매작용 반응과 NO 제거율이 증가하였다.

• 대한기계학회논문집A
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• 제20권1호
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• pp.44-52
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• 1996

Influence of frictional and mechanical properties was studied with the content(8-18 wt.%) and shapes(flake of irregular) of graphite that was used as lubricant components of copper-based sintered materials. The density, hardness and bending strength of friction materials with the shape of flake graphite were lower and decreased rapidly than that of irregular, as the content of graphite increases up to 18 wt.%. In friction test, wear rate was about 2.0-$2.5{\times}10^{-7}\textrm{cm}^3$/kgf.m and coefficient of friction was 0.30-0.37, independent on graphite content and shape. As the temperature of friction materials increased, wear rate decreased rapidly because oxides such as $Cu_2O$ and $SnO_2$ in the surface of friction material were formed.