• Korean Journal of Materials Research
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• v.8 no.9
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• pp.813-818
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• 1998

Ultrafine powders of $\textrm{In}_{2}\textrm{O}_{3}$-doped $\textrm{SnO}_{2}$ were synthesized by a coprecipitation method and the effects of pH value and the amount of In2Q addition on particle size were investigated. The influence of pH value on particle size could be negligible, whereas the amount of $\textrm{In}_{2}\textrm{O}_{3}$ has influenced on particle size and specific surface area. The gas sensitivity to hydrocarbOn($\textrm{C}_{3}\textrm{H}_{8}$, $\textrm{C}_{4}\textrm{H}_{10}$) increased with $\textrm{In}_{2}\textrm{O}_{3}$ addition and reached a maximum at 3wt.% addition. From the results of impedance analysis and I-V characteristics. it was showed that the agglomeration structure of particles and the boundaries between agglomerates were the important factors to determine the gas sensing mechanism.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.741-745
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• 2002

Yttria-stabilized zirconia(YSZ) nanopowders were prepared by sol-gel method using zirconium-n-butoxide(ZNB) and yttrium nitrate as precursors. In addition, the effect of water content added during the hydrolysis reaction of ZNB was investigated on the phase composition and pore structure of the product powders. The phase composition of YSZ nanopowders with calcination temperatures showed the same trend, irrespective of $H_2O$ amounts added during the hydrolysis reaction of ZNB. All powders dried at $100^{\circ}C$ were amorphous and transformed to cubic phase at $400^{\circ}C$, which converted to tetragonal phase at $1,000^{\circ}C$. Monoclinic phase also appeared at $1,000^{\circ}C$. The powders showed the mixture of tetragonal and monoclinic phases from $1,000^{\circ}C$ to $1,400^{\circ}C$. The pore size distributions of the dried powders prepared with small amounts of water(less than or equal to $H_2O/ZNB=20$) showed mesopores, while those prepared with large amounts of water(greater than or equal to $H_2O/ZNB=50$) exhibited micropores.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.4
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• pp.178-184
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• 2010

The $12CaO{\cdot}7Al_2O_3$(C12A7) powders were successfully synthesized using combustion method with microwave-assistant and C12A7:H were fabricated by post-annealed process in Ar/H atmosphere. X-ray diffraction patterns and TGDSC were used for investigating to the precursors of crystalline and reaction depending on temperature. C12A7:H that was treated post-annealed process were investigated TG-MS and Hall-measurement for confirming H ions doping and checking electrical resistivity of C12A7:H. H ion substituted to $O^{2-}$ ions in the C12A7 cages were confirmed at $289.5^{\circ}C$ by TG-MS and C12A7:H calcined at $1000^{\circ}C$ in Ar/H=8:2 atmosphere for 8~10 h has low electrical resistivity about $10^2{\Omega}{\cdot}cm$ at room temperature.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.143-149
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• 2015

Carbon-coated $Li_2MnSiO_4$ powders as the active materials for the cathode were synthesized by planetary ball milling and solid-state reaction, and their phase formation behavior and charge-discharge properties were investigated. Calcination temperature and atmosphere were controlled in order to obtain the ${\beta}-Li_2MnSiO_4$ phase, which was active electrochemically, and the carbon-coated $Li_2MnSiO_4$ active material powders with near single phase ${\beta}-Li_2MnSiO_4$ could be fabricated. The particles of the synthesized powders were secondary particles composed of primary ones of about 100 nm size. The carbon incorporation was essential to enable the Li ions to be inserted and extracted from $Li_2MnSiO_4$ active materials, and the initial capacity of 192 mAh/g could be obtained in the $Li_2MnSiO_4$ active materials with 4.8 wt% of carbon.

• Journal of the Korean Electrochemical Society
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• v.1 no.1
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• pp.1-7
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• 1998

For the purpose of finding new cathode materials for medium-temperature $(700\~800^{\circ}C)$ solid oxide fuel cells, $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3,\;(x=0.0\~0.5)$ are prepared, and their thermal stability and conductivity characteristics are investigated. Also, the cathodic activities are measured after the cathode layer being attached on CGO (cerium-gadolinium oxide) electrolyte disk. The X-ray analyses indicate that the materials prepared by calcining the citrate-gels at $800^{\circ}C$ have the orthorhombic perovskite structure without discernible impurities. The thermal stability of the undoped Co perovskite is so poor that it is decomposed to the individual binary oxide even at $1300^{\circ}C$. But the partially Fe-doped cobaltates exhibit a better thermal stability to retain their structural integrity up to $1400^{\circ}C$. The observation whereby both the undoped and Fe-doped cobaltates melt at ca. $1300^{\circ}C$ leads us to perform the electrode adhesion at <$1300^{\circ}C$. The cathodic activity of $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3,\;(x=0.0\~0.5)$, electrodes is superior to $La_{0.9}Sr_{0.1}MnO_3$, among the samples of $x=0.0\~0.5$, the x=0.2 cathode shows the best activity for the oxygen reduction reaction. It is likely that the Fe-doping provides a better thermal stability to the materials but in turn imparts an inferior cathodic activity, such that the optimum trade-off is made at x=0.2 between the two factors. The total electrical conductivity and ion conductivity of $Gd_{0.8}Ca_{0.2}Co_{1-x}Fe_xO_3$, are measured to be 51 S/cm and $6.0\times10^{-4}S/cm\;at\;800^{\circ}C$, respectively. The conductivity values illustrate that the materials are a mixed conductor and the reaction sites can be expanded to the overall electrode surface, thereby providing a better cathodic activity than $La_{0.9}Sr_{0.1}MnO_3$.

• Journal of Sasang Constitutional Medicine
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• v.8 no.1
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• pp.43-56
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• 1996

As considering a study of the So-um-In and So-yang-In desease, I know each of Extra-disease (表病) and Intra-disease (裏病). I takes serious view of the Extra-Intra-Um-Yang-Up-Down (表裏陰陽升降). I try to join costitutional disease to the parts of human body, which base on the theory on Sa-sang constituional Medicine. And I make some diagrams of them. They could be summerized as follows. 1.The Extra-qi (表氣) is four-viscera (四臟) and four back parts of hurman body (後四海). The Intra-qi (裏氣) is four-digestive organs (四腑) and four fore parts of human body (前四海). 2. It is important that Yang-qi (陽氣) go up at So-um-In Extra-disease (少陰人 表病) and Um-qi (陰氣) go down at So-yang-In Extra-disease (少陽人 表病). And It is important that Um-qi (陰氣) go down at So-um-In Intra-disease (少陰人 裏病) and Yang-qi of Large Intestine (大關局) go up at So-yang-In Intra-disese (少陽人 裏病). 3. Looking into the Extra-disease, ◈ Sin-Yang-Gon-Yiel (腎陽困熱) and Ha-Cho-Chuk-Hyel (下篇蓄血) of So-um-In disease are the disease that Yang-qi don't go up from the buttock. So-Yang-sang-Pung (少陽傷風) of So-yang-In disease is the disease that Um-qi don't go down from the upper back. ◈ Yui-Ga-Sil (胃家室) of So-um-In disease is the disease that Yang-qi don't go up from the lower abdomen Gyel-Hung (結胸) of So-yang-In disease is the disease that Um-qi don't go down from the thorax. ◈ Mang-Yang (亡陽) of So-um-In disease is the disease that Yang-qi don't go up from Intra-qi so it go out to the Extra-qi. Mang-Um (亡陰) of So-yang-In disease is the disease that Um-qi don't go down from the Extra-qi so it go into the Extra-qi. ◈ Dea-Jang-Pa-Han of So-um-In disease and Sim-Ha-Gyel-Hung (心下結胸) of So-yang-In desease are half of Extra-qi and Inrea-qi. 4. Looking into the Intra-disease, ◈ The Intra-disease of So-um-In is Tae-um symtom (太陰證) and So-um symtom (少陰證). The So-um symtom is more severe than Tae-um symtom because a cold wave of Large Intestine (大腸冷氣) involve a warm wave of Stomach (胃局). ◈ The Intra-disease of So-yang-In is not to go up Yang-qi of Large Intestine. Deficit of Yang-qi from Large Intestine which go up at Stomach is more sever than deficit of Yang-qi from Stomach which go up at extremes.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.5-9
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• 2008

Cordierite has a very low thermal expansion coefficient, but has problem that it has a weak mechanical strength and is apt to be attacked by acid such as sulfur for using as a diesel particulate filter support. The physical properties of $ZrTiO_4$ modified with $SiO_2,\;Al_2O_3$, MoOx, $Cr_2O_3\;and\;Nb_2O_5$ were investigated with XRD, SEM, UTM and thermal expansion, etc. in this paper. $ZrTiO_4$ powder was synthesized as a monoclinic structure with processes that starting materials of $TiO_2\;and\;ZrO_2$ were mixed with ball mill and calcined above $1240^{\circ}C$ for 3 hr. Additive modified $ZrTiO_4$ specimens for flexural strength and thermal expansion measurement were obtained by mixing $ZrTiO_4$ powder with additives, pressing and firing at $1300^{\circ}C$ for 3 hr. The porosity of additive modified $ZrTiO_4$ decreased monotonically with increasing additive content by 5 wt% regardless of additive types and saturated for further increase of additive by 10wt. The flexural strength of $Al_2O_3$ (5, 10 wt%) modified $ZrTiO_4$ shows a large increase, but that of other additives modified $ZrTiO_4$ decreased. The thermal expansion coefficient of additive modified $ZrTiO_4$ except $Nb_2O_5$ decreased continuously with the content of additive. In particular, the lowest thermal expansion coefficient of $ZrTiO_4$ was obtained for the additive of $SiO_2$.