To increase the capacitance of an Al electrolytic capacitor, the anodic oxide film, Al2O3, was partly replaced by an Al2O3-ZrO2 (Al-Zr) composite film prepared by the vacuum infiltration method and anodization. The microstructure and composition of the prepared samples were investigated by scanning electron microscopy and transmission electron microscopy. The coated and anodized samples showed multi-layer structures, which consisted of an inner Al hydrate layer, a middle Al- Zr composite layer, and an outer Al2O3 layer. The thickness of the coating layer could go up to 220 nm when the etched Al foil was coated 8 times. The electrical properties of the samples, such as specific capacitance, leakage current, and withstanding voltages, were also characterized after anodization at 100 V and 600 V. The capacitances of samples with ZrO2 coating were 36.3% and 27.5% higher than those of samples without ZrO2 coating when anodized at 100 V and 600 V, respectively.

This paper investigates the effect of prolonged high temperature exposure on concentric laminated Al2O3-ZrO2 composites. An ultrafine scale microstructure with a cellular 7 layer concentric lamination with unidirectional alignment was fabricated by a multi-pass extrusion method. Each laminate in the microstructure was 2-3μm thick. An alternate lamina was composed of 75%Al2O3-(25%m-ZrO2) and t-ZrO2 ceramics. The composite was sintered at 1500˚C and subjected to 1450˚C temperature for 24 hours to 72 hours. We investigated the effect of long time high temperature exposure on the generation of residual stress and grain growth and their effect on the overall stability of the composites. The residual stress development and its subsequent effect on the microstructure with the edge cracking behavior mechanism were investigated. The residual stress in the concentric laminated microstructure causes extensive micro cracks in the t-ZrO2 layer, despite the very thin laminate thickness. The material properties like Vickers hardness and fracture toughness were measured and evaluated along with the microstructure of the composites with prolonged high temperature exposure.

산소이온전도체 13mol% CaO안정화 ZrO2에 대한 AI2O3의 첨가효과를 살펴보기 위해 출발원료분말을 (Zr0.87 Ca0.13 O1.871-x AI2O3)x,(x=0,0.01,0.02,0.03,0.05)와 같은 조성이 되도록 공침법으로 합성하고 1400˚C에서 소결시켜, AI2O3의 첨가에 따른 /grain size의 변화, AI2O3의 형태 및 존재위치, 소결밀도의 변화, 그리고 저항률의 변화를 살펴보았다. 그 결과, 결정립의 크기는 1mol% A I2O3첨가까지는 증가하였고, 2mol%첨가이상에서는 입계로 석출하기 시작한 AI2O3의 pinning효과에 기인되어 감소하였다. 또 1mol% AI2O3첨가시에 격자상수값의 급격한 감소가 보여지고, 그 이상에서는 변화가 별로 없어 13mol%CaO안정화 ZnO2의 고용도한은 최대 1mol%임을 알 수 있었다. 전기전도도 또한 1mol% AI2O3첨가시에 증가됨을 나타냈다. ZrO2에의 고용도한까지의 AI2O3첨가는 결정립성장을 촉진시키며 밀도값의 증대를 가져오고 전기전도도의 증가를 가져오는 긍정적인 효과를 나타냈다.