• Korean Journal of Materials Research
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• v.8 no.6
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• pp.538-544
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• 1998

The spallation of a thermal barrier coating layer depends on the formation of brittle spinels. thermal expansion mismatch between ceramic and metal. the phase transformation of a ceramic layer and residual stress of coating layer. In this work. the formation mechanism of oxide scale formed by oxidation treatment at 90$0^{\circ}C$ was investigated in order to verify oxidation behavior at the interface between E-beam coated $Zr0_2$-7wt.% $Y_20_3$ and plasma sprayed CoNiCrAIY. Some elements distributed in the bond coating layer were selectively oxidized after oxidation. At the initial time of oxidation. AI-depletion zone and $\alpha$-$Al_O_3$,O, were formed at the bond coating layer by the AI-outward diffusion. After layer grew until critical thickness. spinels. $Cr_20$, and $C0_2CrO_4$ by outward diffusion of Co. Cr, Ni were formed. It was found that the formation of spinels may be related to the spallation of $Zr0_2$-7wt.% $Y_20_3$ during isothermal oxidation.

• Journal of the Korean Ceramic Society
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• v.43 no.4 s.287
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• pp.247-252
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• 2006

Joining Yittria Stabilized Zirconia (YSZ) to NiCr metal was fabricated using YSZ/NiCr Functionally Graded Materials (FGM) Interlayer by hot pressing process. Microscopic observations demonstrate that the composition and microstructure of YSZ/NiCr FGM distribute gradually in stepwise way, eliminating the macroscopic ceramic/metal interface such as that in traditional ceramic/metal joint. The thermal characteristics of this YSZ/FGM/NiCr joint were studied by thermal shock testing and therml barrier testing. Thermal shock test was conducted by gas burner rig. Acoustic Emission (AE) monitoring was performed to analyze the microfracture behavior during the thermal shock test. It could be confirmed that FGM was the excellent performance of thermal shock/barrier resistance at above $1000^{\circ}C$.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.260-266
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• 2012

Syngas and hydrogen from the $CeO_2/ZrO_2$ coated foam devices were investigated under simulated solar radiation. The $CeO_2/ZrO_2$ coated SiC, Ni and Cu foam device were prepared using drop-coating method. Syngas production step was performed at $900^{\circ}C$, and hydrogen production process was performed for ten repeated cycles to compare the CeO2 conversion in syngas production step, $H_2$ yield in hydrogen production step and cycle reproducibility. The produced syngas had the $H_2$/CO ratio of 2, which was suitable for methanol synthesis or Fischer-Tropsch synthesis process. In addition, syngas and hydrogen production process is one of the promising chemical pathway for storage and transportation of solar heat by converting solar energy to chemical energy. After ten cycles of redox reaction, the $CeO_2/ZrO_2$ was analyzed using XRD pattern and SEM image in order to characterize the physical and chemical change of metal oxide at the high temperature.

• Journal of the Korean Solar Energy Society
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• v.33 no.2
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• pp.93-100
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• 2013

Two-step thermochemical cycle using ferrite-oxide($Fe_2O_4$) device was investigated. The $H_2O$(g) was converted into $H_2$ in the first experiment which was performed using a dish type solar thermal system. However the experiment was lasted only for 2 cycles because the metal oxide device was sintered and broken down. Another problem was that the reaction was taken place mainly on a side of the metal oxide device. The m-$ZrO_2$, which was widely known as a material preventing sintering, was applied on the metal oxide device. The ferrite loading rate and the thickness of the metal oxide device were increased from 10.67wt% to 20wt% and from 10mm to 15mm, respectively. The chemical reactor having two inlets was designed in order to supply the reactants uniformly to the metal oxide device. The second-experiment was lasted for 5 cycles, which was for 6 hours. The total amount of the $H_2$ production was 861.30ml. And cerium oxide($CeO_2$) device was used for increasing $H_2$ production rate. $CeO_2$ device had low thermal resistance, however, more $H_2$ production rate than $Fe_2O_4$ device.

• Journal of Electrochemical Science and Technology
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• v.9 no.3
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• pp.176-183
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• 2018

In this study, a $Li_2ZrO_3$ coated $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ (NCA) cathode was applied to an all-solid-state cell employing a sulfide-based solid electrolyte. Sulfide-based solid electrolytes are preferable for all-solid-state cells because of their high ionic conductivity and good softness and elasticity. However, sulfides are very reactive with oxide cathodes, and this reduces the stability of the cathode/electrolyte interface of all-solid-state cells. $Li_2ZrO_3$ is expected to be a suitable coating material for the cathode because it can suppress the undesirable reactions at the cathode/sulfide electrolyte interface because of its good stability and high ionic conductivity. Cells employing $Li_2ZrO_3$ coated NCA showed superior capacity to those employing pristine NCA. Analysis by X-ray photoelectron spectroscopy and electron energy loss spectroscopy confirmed that the $Li_2ZrO_3$ coating layer suppresses the propagation of S and P into the cathode and the reaction between the cathode and the sulfide solid electrolyte. These results show that $Li_2ZrO_3$ coating is promising for reducing undesirable side reactions at the cathode/electrolyte interface of all-solid-state-cells.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.329-330
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• 2006

본연구에서는 초음파 모터 등의 고출력 액츄에이터에 응용 가능한 $0.4Pb(Ni_{1/3}Nb_{2/3})O_3$-$0.6Pb(Zr_{0.405}Ti_{0.595})O_3$ + 0.25wt% $Fe_2O_3$ 조성시스템에 $MnO_2$ (0~1 wt.%)첨가하여 압전, 유전특성 및 미세구조에 관해 고찰하였다. 본조성을 $1125{\sim}1175^{\circ}C$ 온도에서 2시간 소결하여 시편을 제조하였으며 이의 결정구조 및 미세조직을 분석하였다. $MnO_2$ 첨가량 증가에 따라 압전 상수와 전기기계결함계수는 감소하였으며, 기계적 품질계수는 0.5 wt% 첨가시까지 증가하였으나 첨가량이 그 이상 증가함에 따라 감소하였다. 압전특성은 $1125^{\circ}C$에서 소결한 $MnO_2$ 0.5wt%조성에서 ${\varepsilon}r$ = 2040, kp = 0.66, $d_{33}$ = 504, Qm=438의 우수한 특성을 나타내었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.106-111
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• 2005

Failure mechanisms were investigated for the two layer thermal barrier coatings consisting of NiCrAlY bond coat and $ZrO_2-8wt.\% Y_{2}O_3$ ceramic coating during cyclic oxidation. $Al_{2}O_3$ developed at the ceramic coating/bond coat interface first, followed by the Cr/Ni rich oxides such as $NiCr_{2}O_4 and Ni(Al,Cr)_{2}O_4$ during cyclic oxidation It was observed that the spalling of ceramic coatings took place primarily within the NiCrAlY bond coat oxidation products or at the interface between the bond coat oxidation products and zirconia based ceramic coating or the bond coat. It was also observed that the fracture within these oxidation products occurred with the formation of $Ni(Cr,Al)_{2}O_4$ spinel or Cr/Ni rich oxides. It was therefore concluded that the formation of these oxides was a life-limiting event for the thermal barrier coatings.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.340-344
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• 1998

Failure mechanisms were investigated for the two layer thermal barrier coatings consisting of NiCrAlY bond coat and $ZrO_2$-8wt.% $Y_2O_3$ ceramic coating during cyclic oxidation. $Al_2O_3$ developed at the ceramic coating/bond coat interface first, followed by the Cr/Ni rich oxides such as $NiCr_2O_4$ and $Ni(Al, Cr)_2O_4$ during cyclic oxidation. It was observed that the spalling of ceramic coatings took place primarily within the NiCrAlY bond coat oxidation products or at the interface between the bond coat oxidation products and zirconia based ceramic coating or the bond coat. It was also observed that the fracture within these oxidation products occurred with the formation of $Ni(Cr, Al)_2O_4$ spinel or Cr/Ni rich oxides. It was therefore concluded that the formation of these oxides was a life-limiting event for the thermal barrier coatings.

• Journal of Sensor Science and Technology
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• v.17 no.6
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• pp.418-424
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• 2008

The PZT based piezoelectric thick films prepared by screen printing method have been mainly used as a functional material for MEMS applications due to their compatibility of MEMS process. However the screen printed thick films generally reveal poor electrical and mechanical properties because of their porous microstructure. To improve microstructure we mixed attrition milled powder with ball milled powder of 0.01Pb$(Mg_{1/2}W_{1/2})O_3$-0.41Pb$(Ni_{1/3}Nb_{2/3})O_3$-$0.35PbTiO_3$-$0.23PbZrO_3$+0.1 wt% ${Y_2}{O_3}$+1.5 wt% ZnO composition. By mixing 25 % of attrition milled powder and 75 % of ball milled powder, the broadest particle size distribution was obtained, leading to a dense thick film with crack-free microstructure and improved dielectric properties. The X-ray diffraction analysis revealed that the film was in wellcrystallized perovskite phase. The remanent polarization was increased from $13.7{\mu}C/cm^2$ to $23.3{\mu}C/cm^2$ at the addition of 25 % attrition milled powder.

• Korean Journal of Materials Research
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• v.13 no.10
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• pp.640-644
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• 2003

NiCr thin films were fabricated by rf magnetron sputtering for applying to both the top electrode and absorption layer on Pb(Zr, Ti)O$_3$(PZT) thin films for infrared sensors. The rms roughness and resistivity of NiCr films prepared with Ni power of 80 W and Cr power of 50 W showed the most stable oxidation resistance after annealing at $600^{\circ}C$ for 5 min in oxygen ambient. The rms roughness and resistivity of NiCr films annealed at $V^{\circ}C$ in oxygen ambient were about 2$0\AA$ and $70 \mu$Ω-cm, respectively. As-deposited Ni/PZT/Pt and NiCr (Ni 80 W, Cr 50 W)/PZT/Pt structures showed well saturated hysteresis loops. However, in case of the samples annealed at $500^{\circ}C$ in oxygen ambient, only NiCr/PZT/Pt showed saturated loops having a remanent polarization of 20$\mu$C/$\textrm{cm}^2$. Ultra-thin NiCr films showed a possibility as a top electrode for infrared sensors.