• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.229-229
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• 2011

• Journal of the Korean Ceramic Society
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• v.45 no.8
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• pp.477-481
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• 2008

$Eu^{2+}$ and $Dy^{3+}$ co-doped strontium aluminate, $SrAl_2O_4$ long phosphorescent phoshor was fabricated and its photoluminescence was characterized. The phosphor, $SrAl_2O_4:Eu^{2+},Dy^{3+}$ was synthesized by a coprecipitation in which metal salts of $Sr(NO_3)_2$, $Al(NO_3)_3{\cdot}9H_2O$, were dissolved in $(NH_4)_2CO_3$ solution with adding $Eu(NO_3)_3{\cdot}5H_2O$ and $Dy(NO_3)_3{\cdot}5H_2O$ as a activator and co-activator, respectively. The coprecipitated products were separated from solution, washed, and dried in a vacuum dry oven. The dried powders were then mixed with 3 wt% $B_2O_3$ as a flux and heated at $800{\sim}1400^{\circ}C$ for 3 h under the reducing ambient atmosphere of 95%Ar+$5%H_2$ gases. For the synthesized $SrAl_2O_4:Eu^{2+},Dy^{3+}$, properties of photoluminescence such as emission, excitation and decay time were examined. The emission intensity increased as the annealing temperature increased and showed a maximum peak intensity at 510 nm with a broad band from $400{\sim}650\;nm$. Monitored at 520 nm, the excitation spectrum showed a maximum peak intensity at $315{\sim}320\;nm$ wavelength with a broad band from $200{\sim}500\;nm$ wavelength. The decay time of $SrAl_2O_4:Eu^{2+},Dy^{3+}$ increased as the annealing temperature increased.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.323-329
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• 2009

Influences of ceramic filler types and dose on the sintering, phase evolution, and dielectric properties of ceramic/CaO-$Al_2O_3-SiO_2$ glass composites were investigated. All of the specimens were sintered at $900^{\circ}C$ for 2 h, which conditions are required by the lowtemperature co-firing ceramic (LTCC) technology. Ceramic fillers of $Al_2O_3,\;SiO_2$, kaolin, and wollastonite were used. The addition of $Al_2O_3$ filler yielded the crystalline phases of alumina and wollastonite, and the densification over 95% of the relative density was achieved up to 50 wt% addition of the filler. For the cases of the fillers of $SiO_2$, kaolin, and wollastonite, crystalline phases of quartz, mullite, and wollastonite formed, while the densification decreased monotonically with the filler addition. In overall, all the investigated fillers with 10 wt% addition resulted in a reasonable sintering (over 95 %) and low dielectric constants (less than 6), demonstrating the feasibility of the investigated composites for application to a LTCC substrate material with a low dielectric constant.

• Journal of Climate Change Research
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• v.7 no.3
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• pp.249-256
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• 2016

Porous $Al_2O_3$ hollow fiber membranes were successfully prepared by dry-wet spinning/sintering method. The SEM image shows that the $Al_2O_3$ hollow fiber membrane consists mostly of sponge pore structure. The contact angle and the breakthrough pressure were $126^{\circ}$ and 1.91 bar, respectively. This results indicate that the $Al_2O_3$ hollow fiber membranes were successfully modified to hydrophobic surface. The hydrophobic modified $Al_2O_3$ hollow fiber membranes were assembled into a membrane contactor system to separate $CO_2$ from a model gas mixture of the flue gas at elevated gas velocity. The $CO_2$ absorption flux was enhanced when the gas velocity increased from $1{\times}10^{-3}$ to $6{\times}10^{-3}$ m/s. Whereas the $CO_2$ absorption flux was decreased with the number of hollow fiber membrane of a module because of the concentration polarization. Furthermore, we developed an lab-scale $Al_2O_3$ hollow fiber membrane contactor modules and their system (i.e., $CO_2$ absorption using the $Al_2O_3$ membrane and monoethanolamine (MEA)) that could dispose of over $0.02Nm^3/h$ mixture gas (15% $CO_2$) with the removal efficiency higher than 95%. The results can be useful in a field of the membrane contactor for $CO_2$ separation, helping to design and extend a equipment.

• Journal of the Korean Ceramic Society
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• v.16 no.3
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• pp.142-154
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• 1979

The effects of microstructures and some additives $(CoO and Al_2O_3$) on the magnetic properties such as initial permeability, $\mu$-T curve, coercive force, and magnetic induction of MnZn ferrites have been studied. The powder was prepared by Hot Petroleum Drying Method. The basic composition of MnZn ferrites was 25.5mole % MnO, 22.0 mole% ZnO, 52.5 mole% $Fe_2O_3$. CoO in a concentration range from 0.05 to 0.5 mole% and $Al_2O_3$ from 2.5 to 7.5 mole% were added. Sintered density increased up to 97.5% of theoretical density. Permeability increased as average grain size increased, and that coercive force decreased as average grian size increased. Magnetic induction increased as sintered density increased. The variation of initial permeability with temperature in a temperature range from 0$^{\circ}$ to $60^{\circ}C$ was lowered (a flatter $\mu-T$ curve) as sintering temperature decreased. The compensation temperature To ofmagnetocrystalline anisotropy constant K1 and initial permeability varied with the species and amount of additives. When 0.05 mole% CoO was added to the basic composition, initial permeability at $15^{\circ}C$ increased from 5200 to 5900. The variation ofinitial permeability with temperature in a temperature range from 0^{\circ}to $60^{\circ}C$ was smaller (a flatter $\mu$-T curve) than that of the basic composition of Mn Zn ferrites. When 2.5 mole% $Al_2O_3$ was added, initial permeability at $15^{\circ}C$ decreased from 5200 to 3000. But the variation of initial permeability with temperature in a temperature range from 0$^{\circ}$to $60^{\circ}C$ was smaller (a flat ter $\mu-T$ curve) than when 0.05 mole% CoO was added. Experimental results showed that the conditions necessary for the occurrence of a very high permeability and a flat $\mu$-T curve were controversial even in a temperature range from $0^{\circ}$to $60^{\circ}C$.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1192-1203
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• 1996

$Al_2O_3-TiO_2$ composite oxide adsorbents which could be applied in high-temperature water were prepared by hydrolysis of aluminum and titanium alkoxide. The prepared adsorbents were calcined at $600{\sim}1400^{\circ}C$ and in order to investigate the various properties - the transition of crystals, thermal properties, and specific surface area, X-ray diffractometry, thermal analysis, FT-IR, SEM and BET method were employed. And the $Co^{2+}$ adsorption characteristics of these adsorbents in high-temperature water were investigated by batch adsorption experiment in a stirred autoclave. Since the adsorption of $Co^{2+}$ on the $Al_2O_3-TiO_2$ adsorbents was irreversible endothermic in the temperature range of $150{\sim}250^{\circ}C$, the standard enthalpy changes of 26, 43, and 80 mol% of $TiO_2$ on $Al_2O_3$ were in the range of $16.5{\sim}26.0kJ{\cdot}mol^{-1}$. The adsorbent of 26 mol% of $TiO_2$ on $Al_2O_3$ which was calcined at $600^{\circ}C$ for 2 hours showed the adsorption amount of $0.1674meq{\cdot}g^{-1}$ in the high temperature water at $250^{\circ}C$.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.285-294
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• 1994

Some supported gold catalysts were prepared by impregnation and coprecipitation methods. Effect of gold addition and active sloe formation were studied by investigating particle sizes of gold, amounts of oxygen adsorbed, adsorption properties of CO and NO, and reduction and oxidation properties, etc.. The gold particles of the catalyst by impregnation were irregular and very large as 30~100 nm, but those by coprecipitation were uniform and ultra-fine as about 4 nm. On $Au/Al_2O_3$ catalyst, the addition of gold to inactive $Al_2O_3$ caused the decomposition of $N_2O$, and CO was not irreversibly adsorbed while $O_2$ was atomically and irreversibly adsorbed. The adsorption sites of oxygen were attributed to the active sites which were restricted to the circumference of hemispherical gold particle-support interface rather than all atoms on the surface of gold particle. Also, CO was reversibly and irreversibly adsorbed on $Al_2O_3$ at low temperature, and the addition of gold weakened both reversible and irreversible adsorptions. The affinity for CO on $Au/Co_3O_4$ catalyst decreased conspicuously compared to $Co_3O_4$. The effect of gold addition did not appear in reduction step but did remarkably in reoxidation step; the added gold promoted the reoxidation of the reduced cobalt atoms.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.196-201
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• 2001

The dependence of CoFe interfacial layer thickness and plasma oxidation condition on tunneling magnetoresistance (TMR) in Ta/NiFe/FeMn/NiFe/Al$_2$O$_3$/NiFe/Ta tunnel junctions was investigated. As the CoFe layer thickness increases, TMR ratio rapidly increases to 13.7 % and decreases with further increase of the CoFe layer thickness. The increase of TMR with the CoFe thickness up to 25 was thought to be due mails to the high spin-polarization of CoFe. The maximum MR of 15.3% was obtained in the Si(100)/Ta(50 )/NiFe(60 )/FeMn(250 )/NiFe(70 )/Al$_2$O$_3$/NiFe(150 )/Ta(50 ) magnetic tunnel junction with a 16 Al oxidized for 40 sec using a Ar/O$_2$ (1:4) mixture gas.

• Journal of the Korean Electrochemical Society
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• v.10 no.3
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• pp.184-189
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• 2007

The importance of secondary battery industry is getting excited according to the development of battery industry as a high efficiency energy supplier of electronic machine of mobile information such as mobile phone, lap-top computer, PDA. It is rasing the interest about security of safety and high efficiency of cathode material for main part of secondary lithium battery. The cathode material which has been used like $LiCoO_2,\;LiMn_2O_4,\;LiNi_xCo_yMn_zO_2,\;LiNi_xCo_yM_zO_2$ (M=Al, Zr, Mg etc.,) the most typical material is $LiCoO_2$. But it is studying the development of substitute such as efficiency amelioration of $LiCoO_2$, thetiary element, olivine element because of the capacity of $LiCoO_2$, the matter of security; especially the betterment of efficiency, security research of safety has been actively processed in domestic and overseas about surface coating treatment of active cathode which is using oxide ($M_xO_3$). This study analyses side effect of battery according to increase of surface treatment, formation of precipitation for reagent condensation, non-reagent residue of oxide ($M_xO_3$) which is remains during the surface treatment of $LiCoO_2$; conducts study of new process, the consideration of the electrochemical property to improve oxide solution of mixing rate, mixture of surface treatment, dryness, calcinations conditionetc.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.74-79
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• 2004

[ $CO_3O_4/{\gamma}-Al_2O_3$ ] catalysts were reported high activity on the low temperature CO oxidation. The effects of the calcination temperature, the loaded amount of cobalt and the oxygen concentration on the characteristics of CO oxidation have been investigated for a emergency escape mask cartridge. $Co(NO_3)_2\cdot6H_2O$ was used as cobalt precursor and the catalysts were prepared by incipient wetness impregnation. TGA shows that enough calcination is accomplished at $450^{\circ}C$ and cobalt phase is $Co_3O_4$ after calcination in the temperature range of $300\ ~500^{\circ}C$. The specific surface area and pore volume of catalysts are decreased with increasing of loaded amount of cobalt. And with the increase of loaded amount of cobalt and the oxygen concentration, the catalytic activity is increased.