• 한국세라믹학회지
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• 제14권2호
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• pp.73-77
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• 1977

The surface diffusion coefficients for nickel, nickel oxide, cuppric oxide, cobalt oxide, alumina and ferric oxide have been determined at various temperatures using the sintering technique. This investigation is based on the model accounting for the sum of the contribution of volume and surface diffusion to the overall shrinkage rate during the initial stage of sintering. Simultaneous measurements of shrinkages and shrinkage rates of the materials compacts were conducted for various annealing times, the results of which were then correlated to the diffusion coefficient.

• Journal of Electrochemical Science and Technology
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• 제11권2호
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• pp.99-116
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• 2020

The article provides information on ceramic / nanostructured materials which are suitable for solid oxide fuel cells (SOFCs) working between 500 to 1000℃. However, low temperature solid oxide fuel cells LTSOFCs working at less than 600℃ are being developed now-a-days with suitable new materials and are globally explored as the "future energy conversion devices". The LTSOFCs device has emerged as a novel technology especially for stationary power generation, portable and transportation applications. Operating SOFC at low temperature (i.e. < 600℃) with higher efficiency is a bigger challenge for the scientific community since in low temperature regions, the efficiency might be less and the components might have exhibited lower catalytic activity which may result in poor cell performance. Employing new and novel nanoscale ceramic materials and composites may improve the SOFC performance at low temperature ranges is most focused now-a-days. This review article focuses on the overview of various ceramic and nanostructured materials and components applicable for SOFC devices reported by different researchers across the globe. More importance is given for the nanostructured materials and components developed for LTSOFC technology so far.

• 전기화학회지
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• 제14권4호
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• pp.196-200
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• 2011

본 연구에서는 니오븀 산화물을 비교적 저온에서 단시간 동안의 양극산화법을 통해 제조하였다. 이때, 전해질로는 NaF와 HF를 혼합하여 사용하였으며, 20~120 V의 다양한 전압 조건에 따라 생성되는 니오븀 산화물의 미세구조를 관찰하였다. 일반적으로 니오븀 금속의 양극산화 시 초기에 생성된 니오븀 산화물은 무정형 구조이나 반응이 경과함에 따라 점차 결정형 산화물로 성장하게 된다. 이러한 산화물은 XRD 분석을 통하여 결정형의 $Nb_2O_5$ 임을 확인하였고, FE-SEM 분석결과, 그 표면은 매우 밀집된 형태의 나노로드로 이루어진 마이크로콘 산화물임을 알 수 있었다. 적절한 공정변수로 제조된 니오븀 산화물은 마이크로콘 구조 전체 표면에 걸쳐 동일한 크기를 갖는 나노로드 다발을 형성하고 있으며, 이러한 나노 구조는 또한 넓은 표면적을 기대할 수 있어 염료감응 태양전지나 바이오 소재 등에 대한 다양한 분야에 응용될 수 있을 것으로 기대된다.

• 한국재료학회지
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• 제19권12호
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• pp.649-656
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• 2009

Inorganic oxide colloids dispersed in alcohol were applied to a stainless steel substrate to produce oxide coatings for the purpose of minimizing emissive thermal transfer. The microstructure, roughness, infrared emissive energy, and surface heat loss of the coated substrate were observed with a variation of the nano oxide sol and coating method. It was found that the indium tin oxide, antimony tin oxide, magnesium oxide, silica, titania sol coatings may reduce surface heat loss of the stainless steel at 300${\circ}C$. It was possible to suppress thermal oxidation of the substrate with the oxide sol coatings during an accelerated thermal durability test at 600${\circ}C$. The silica sol coating was most effective to suppress thermal oxidation at 600${\circ}C$, so that it is useful to prevent the increase of radiative surface heat loss as a heating element. Therefore, the inorganic oxide sol coatings may be applied to improve energy efficiency of the substrate as the heating element.

• 한국세라믹학회지
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• 제24권3호
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• pp.215-222
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• 1987

${\alpha}$-Ferric Hydrous Oxide and ${\alpha}$-Ferric Oxide were obtained as following processes that Ferric Nitrate solution was adjusted to pH 6-8 with Ammonium Hydroxide, refluxed the Iron precipitate for 1 hr. at 80$^{\circ}C$, washed it with water and Methanol (95%), dried it to obtain ${\alpha}$-Ferric Hydrous Oxide at 60$^{\circ}C$, and then heated in atmosphere to prepare ${\alpha}$-Ferric Oxide for 1 hr. at 450$^{\circ}C$. Mica particles cleaned with ultrasonicator (45KHz) in water were mixed with Ferric Nitrate solution and treated it to adsorb ${\alpha}$-Ferric Oxide on the surface of mica particles by using the abovementioned processes, but the heated temperature was at 500$^{\circ}C$. The maximum wavelength of reflected light on the surface of mica-${\alpha}$-Ferric Oxide (50%) was appeared at 546nm but -Ferric Oxide free mica only was at 436 nm. The maximum wavelength was shifted to longer when the weight ratios of ${\alpha}$-Ferric Oxide to mica was changed from 1% to 50%.

• 한국세라믹학회지
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• 제48권6호
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• pp.625-629
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• 2011

In this study, we show that by anodization of Nb in NaF electrolytes microcone niobium oxide layers can be formed under a range of experimental conditions. It is found that a single NaF electrolyte leads to the formation of microcones. At 1 M NaF, 40 V, 1 h, well-ordered microcones were generated on Nb discs. XRD results show that the initially formed anodic oxide is amorphous, but an amorphous to crystalline transition occurs during anodization. For the formation of favorable microcones, it is considered that proper parameters such as electrolyte concentration, voltage, anodizing time are necessary according to the kind of electrolytes.

• 세라미스트
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• 제23권2호
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• pp.132-144
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• 2020

Solid oxide fuel cell (SOFC) have attracted much attention due to clean, efficient and environmental-friendly generation of electricity for next-generation energy conversion devices. Recently, many studies have been reported on improving the performance of SOFC electrodes and electrolytes by applying atomic layer deposition (ALD) process, which has advantages of excellent film quality and conformality, and precise control of film thickness by utilizing its unique self-limiting surface reaction. ALD process with these advantages has been shown to provide functional ceramic interfaces for SOFC electrodes and electrolytes. In this article, recent examples of successful functionalization and stabilization on SOFC electrodes and electrolytes by the application of ALD process for realizing high performance SOFC cells are reported.

• The Journal of Advanced Prosthodontics
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• 제3권2호
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• pp.57-62
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• 2011

MATERIALS AND METHODS. Ceramics have a long history in fixed prosthodontics for achieving optimal esthetics and various materials have been used to improve ceramic core strength. However, there is a lack of information on how color is affected by fabrication procedure. The purpose of this study was to evaluate the effects of various dentin ceramic thicknesses and repeated firings on the color of zirconium oxide all-ceramic system (LavaTM) fabricated using CAD/CAM technology. MATERIALS AND METHODS. Thirty disc-shaped cores, 12 mm in diameter with a 1 mm thickness were fabricated from zirconium oxide based all ceramic systems ($Lava^{TM}$, 3M ESPE, St Paul, MN, USA) and divided into three groups (n = 10) according to veneering with dentin ceramic thicknesses: as 0.5, 1, or 1.5 mm. Repeated firings (3, 5, 7, or 9) were performed, and the color of the specimens was compared with the color after the initial firing. Color differences among ceramic specimens were measured using a spectrophotometer (VITA Easyshade, VITA Zahnfabrik, Bad $S{\ddot{a}}ckingen$, Germany) and data were expressed in CIELAB system coordinates. A repeated measures ANOVA and Bonferroni post hoc test were used to analyze the data (n = 10, ${\alpha}=.05$). RESULTS. $L^{\ast}a^{\ast}b^{\ast}$ values of the ceramic systems were affected by the number of firings (3, 5, 7, or 9 firings) (P<.001) and ceramic thickness (0.5, 1, or 1.5 mm) (P<.001). Significant interactions were present in $L^{\ast}a^{\ast}b^{\ast}$ values between the number of firings and ceramic thickness (P<.001). An increase in number of firings resulted in significant increase in $L^{\ast}$ values for both 0.5 mm and 1.5 mm thicknesses (P<.01, P=.013); however it decreased for 1 mm thickness (P<.01). The $a^{\ast}$ values increased for 1 mm and 1.5 mm thicknesses (P<.01), while it decreased for 0.5 mm specimens. The $b^{\ast}$ values increased significantly for all thicknesses (P<.01, P=.022). As the dentin ceramic thickness increased, significant reductions in $L^{\ast}$ values (P<.01) were recorded. There were significant increases in both $a^{\ast}$ and $b^{\ast}$ values (P<.01) as the dentin ceramic thickness increased. CONCLUSION. The number of firings and dentin ceramic thickness have a definite effect on the final color of all ceramic system tested. The mean ${\Delta}E$ value increased as the dentin ceramic thicknesses increased for zirconium-oxide based all ceramic specimens tested. However, the mean ${\Delta}E$ values were less than 3.7${\Delta}E$ units which is rated as a match in the oral environment.

• 한국세라믹학회지
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• 제54권1호
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• pp.61-65
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• 2017

Examined in this study were the effects of copper oxide (II) addition and sintering conditions on the chromatic characteristics of copper glaze. Oxidatively sintered samples exhibited the negative increase of $CIEa^*$ and the positive increase of $CIEb^*$ with the increase of CuO concentration, leading to Green and Green-Yellow coloration. On the other hand, $CIEa^*$ and $CIEb^*$ of reductively sintered samples were positively increased in direct proportion. The green color of oxidatively sintered samples was originated from the $Cu^{2+}$ ions formed by the dissolution of CuO. The reductively sintered samples resulted in dull tone red color with low chroma. Such behavior seems to be influenced by the interplay of metal Cu aggregation, metal Cu globule, and $Cu_2O$ formed in the glaze layer through the redox interaction of CuO during the sintering process.

• 한국세라믹학회지
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• 제45권11호
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• pp.694-700
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• 2008

Proton conducting oxides based on the $BaCe_{0.9}M_{0.1}O_{3-{\delta}}$ (M = La, AL) were tested for the alternative electrolyte materials of fuel cell. The power density for single cell of Air |Pt| $BaCe_{0.9}M_{0.1}O_{3-{\delta}}$ |Pt| $H_2(3%H_2O)$ system was maximum $0.04W/cm^2$ at $1000^{\circ}C$. In this system, proton transport number was proved to depend on the lattice parameters and the distortion of $CeO_6$ octahedral as a function of the ionic radii of acceptor ions. This proton conducting oxide system requires developing the new electrode materials for application.