• 한국결정성장학회지
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• 제19권3호
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• pp.130-134
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• 2009

새로운 $CaZrO_3$, 축광성 형광체를 고온의 약한 환원 분위기에서 전통적인 고상반응법으로 합성하였다 광발광 분석 결과 $Tb^{3+}$ 이온을 첨가한 $CaZrO_3$ 축광성 형광체는 $^5D_3$, $^5D_4$ 에너지 준위에서 $^7F_1{\sim}^7F_6$ 준위로의 전이에 의해 황녹색의 발광을 나타내며, 고온의 질소분위기에서 합성한 경우의 축광성 형광체에 대한 스펙트럼의 주 피크는 $^5D_4{\rightarrow}^7F_5$ 전이에 의한 542 nm의 발광 피크가 생성되었다. $CaZrO_3:Tb^{3+}$ 축광성 형광체의 잔광 발광 스펙트럼은 좁은 영역의 546 nm의 피크가 강하게 생성되었다 잔광 휘도는 254 nm 자외선을 조사하고 전원을 끈 후에 측정하였으며, 녹황색의 축광성 형광체가 사람이 어두운 곳에서 인지 가능한 $0.32\;mcd/m^2$까지 8시간 지속됨을 관찰하였다.

• 한국세라믹학회지
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• 제30권12호
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• pp.1059-1065
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• 1993

The sliding wear behavior of the plasma sprayed zirconia containing 8wt% yttria was investigated over a range of room temperature to 800℃. Both of the friction coefficient and the wear loss increased reaching its maximum at about to 499℃. and then decreased again with increasing temperature up to 800℃. The worn surface at elevated temperature were observed and analyzed by scanning electron microscopy and X-ray diffractometer to study the mechanisms of high temperature wear behavior. Surface morphology of the worn samples changes with temperature. Monoclinic (m)/tetragonal (t) x-ray peak intensity ratio of wear debris and worn surface decreased with increasing temperature. Non-transformable tetragonal (t') to metastable tetragonal (t) phase transformation of worn surface increased with increasing temperature. The results indicate that dehumidification and above phase changes are contributing to the high temperature wear behavior of the plasma sprayed ZrO2-Y2O3 coatings.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1160-1164
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• 2013

The solid super acid catalyst $SO{_4}^{2-}$/$ZrO_2$ was prepared by impregnation method using $ZrO_2$ as the catalyst support. Catalyst forming was taken into consideration in order to separate catalyst from the mixture of cellulose acetate propionate (CAP). $Al_2O_3$ and sesbania gum powder were selected as binding agent and auxiliary agent respectively. The catalytic properties were evaluated through esterification of cellulose with acetic anhydride, propionic anhydride and characterized by XRD, FTIR and $NH_3$-TPD. In this paper, the effects of concentration of $H_2SO_4$ impregnated, calcination temperature, esterification temperature and esterification time on the yield, acyl content and viscosity of CAP were investigated. The results showed that $SO{_4}^{2-}/ZrO_2$ successfully catalyzed CAP synthesis over catalysts impregnated in 0.75 mol/L $H_2SO_4$ and calcined at $500^{\circ}C$. The yield, acetyl content and propionyl content of CAP reached the maximum value of 105.3%, 29.9% and 25.8% reacted at $50^{\circ}C$ for 8 h.

• 한국재료학회지
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• 제13권8호
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• pp.497-502
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• 2003

Crystallographic characteristics and interfacial structures of $Al_2$$O_3$and $ZrO_2$dielectric films prepared by atomic layer chemical vapor deposition (ALCVD) were investigated at atomic scale by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS)/electron energy-loss spectroscopy (EELS) coupled with a field-emission transmission electron microscope. The results obtained from cross-sectional and plan-view specimens showed that the $Al_2$$O_3$film was crystallized by annealing at a high temperature and its crystal system might be evaluated as either cubic or tetragonal phase. Whereas the $ZrO_2$film crystallized during deposition at a low temperature of ∼$300^{\circ}C$ was composed of both tetragonal and monoclinic phase. The interfacial thickness in both films was increased with the increased annealing temperature. Further, the interfacial structures of X$ZrO_2$$O_3$and $ZrO_2$films were discussed through analyses of EDS elemental maps and EELS spectra obtained from the annealed films, respectively.

• KSTLE International Journal
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• 제6권2호
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• pp.45-50
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• 2005

Plasma ceramic spray that is applied on a machine part under severe work conditions has been investigated for tribological behavior. The application of ceramic coatings by plasma spray has become essential in tribosystems to produce wear resistance and long life in severe conditions. The purpose of this study was to investigate the wear characteristics of $8\%Y_{2}O_3-ZrO_2$ coating, in view of the effect of post-spay heat treatment. The plasma-sprayed $8\%Y_{2}O_3-ZrO_2$ coating was studied to know the relationship between phase transformations and wear behavior related to post-spray heat treatment. Wear test was carried out with ball on disk type on normal loads of 50N,70N and 90N under room temperature. The phase transformation of phase and the value of residual stress were measured by X-ray diffraction method(XRD). Tribological characteristics and wear mechanisms of coatings were observed by SEM. The tribological wear performance was discussed in the focusing of residual stress. Consequently, post-spray heat treatment plays an important role in decreasing residual stress. Residual stress in the coating system has a significant influence on the wear mechanism of coating.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 추계총회,초청강연,특별강연,연구발표회
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• pp.141.1-141
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• 2000

• 한국재료학회:학술대회논문집
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• 한국재료학회 1996년도 재료학회 춘계학술발표회
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• pp.158-158
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• 1996

• E2M - 전기 전자와 첨단 소재
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• 제10권10호
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• pp.1041-1047
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• 1997

In this paper the dielectric properties of (0.8-x)Pb(Mb$_{1}$3//Nb/2/3)O$_3$/BaTiO$_3$-CaZrO$_3$(x=0.1, 0.15, 0.2, 0.25) ceramics were investigated. Specimens were prepared by the conventional mixed oxide method and sintering temperature and time were 1000~115$0^{\circ}C$ 2hr, respectively. The structural and dielectric properties with variation of sintering temperature and composition were investigated. All the specimens sintered at 115$0^{\circ}C$ for 2hr showed the highest value of 1043. With increasing the contents of CZ and frequency dielectric constant was decreased and which was decreased with increasing temperature from 3$0^{\circ}C$ to 15$0^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1127-1134
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• 2002

Fine ceramic particles of zirconia toughened alumina (ZTA), titania toughened alumina (TTA), and zirconia-titania toughened alumina (ZTTA) have been synthesized by ultrasonic spray pyrolysis (USP) at various temperatures from starting salt solutio ns of various compositions aiming for the development of catalytic material. These particles were characterized for properties such as shape, size and size distribution, diffraction pattern, and chemical and phase composition of elements by scanning electron microscopy (SEM), particle size analyzer (PSA), x-ray diffraction (XRD), and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Chemical compositions and sizes of ceramic composites have been controled by the stoichiometry of salt solutions and the flow rate of spraying solutions. The optimum experimental conditions for the various composite particle syntheses have been proposed.

• 한국전기전자재료학회논문지
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• 제18권9호
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• pp.810-814
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• 2005

[ $Pb(Zr_{0.2}Ti_{0.8})O_3/SrRuO_3$ ] heteroepitaxial thin films were deposited at various temperatures on single crystal $SrTiO_3$ substrates by pulsed laser deposition and characterized for the microstructural and ferroelectric properties. The $SrTiO_3$ substartes etched by buffered oxide etch $(pH{\thickapprox}5.8)$ solution for 20s followed by the thermal annealing at $1000^{\circ}C$ for 1h showed the terrace ledges with a 0.4nm height. The $SrRuO_3$ bottom electrodes with a thickness of 52nm grown on $SrTiO_3$ single crystal also exhibit a terrace ledge similar to that of $SrTiO_3$. The PZT thin films were grown with an epitaxial relationship and showed typical P-E hysteresis loops shown at the epitaxial films. The 56nm thick-PZT films deposited at $650^{\circ}C$ exhibit a remanent polarization $(p_r)$ of $80{\mu}C/cm^2$ and a coercive field $(E_c)$ of 160kV/cm.