• Journal of the Korean Ceramic Society
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• v.34 no.3
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• pp.303-313
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• 1997

To enhance the strength and formability of MCFC matrixes, alumina/${\gamma}$-LiAlO2 fiber-reinforced ${\gamma}$-LiAlO2 ma-trixes have been investigated. The MCFC matrixes with the thickness of 500~600 ${\mu}{\textrm}{m}$ were prepared by tape-casting of the slurry containing 10~30wt% fibers, followed by heat-treating up to $650^{\circ}C$. The porosity of fi-ber-reinforced matrixes decreased with the content of fibers, while the appropriate porosity(50~60%) for MCFC matrixes could be attained by adding larger ${\gamma}$-LiAlO2 particles with the diameter of about 50${\mu}{\textrm}{m}$ up to 50 wt%. The optimum length and content of the alumina fiber, both in the alignment of fibers and the enhancement of the strength, were found to be below 250${\mu}{\textrm}{m}$ and 20 wt%, respectively. On the other hand, the strength(156 gf/$\textrm{mm}^2$) of the ${\gamma}$-LiAlO2 matrix reinforced with ${\gamma}$-LiAlO2 fibers prepared in this study was improved by 20~40% in comparison with the alumina-fiber-reinforced matrix. It was also found that the alu-mina-fiber-reinforced matrix was completely corroded in molten carbonates but the ${\gamma}$-LiAlO2 was not.

• Clean Technology
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• v.18 no.1
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• pp.63-68
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• 2012

In this study, aluminum hydroxide ($Al(OH)_3$) was synthesized by Bayer process and sodium contained in $Al(OH)_3$ was removed with the acid solution such as HCl and acetic acid for the synthesis of high purity alumina. The bauxite produced in Queensland of Australia was used for the production of alumina by Bayer, and was crushed to a particle size of below 10 um by attrition mill. The crushed bauxite was treated in sodium hydroxide solution of 5 N for the elution of aluminum component. The elution of aluminum from bauxite was carried out at $140^{\circ}C$ and 3.4 atm in autoclave. The sample solution was separated to the red mud and liquid solution by filter paper. The elution of aluminum from bauxite was confirmed with changing a structure and aluminum content in both bauxite and red mud analyzed by XRD and EDX. Aluminum contained in the separated solution was crystallized to $Al(OH)_3$ with the addition of aluminum hydroxide used as the seed material. $Al(OH)_3$ powder obtained during the crystallization process was purified by several times washing with distillated water. It was also confirmed that the sodium remained in $Al(OH)_3$ powder is removed with acid solution. The purity of $Al(OH)_3$ powder produced in this study was 99.3% and the content of sodium was reduced to approximately 0.009% after the acid treatment.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.646-650
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• 2009

Hydrocarbon gases generated from the gasification of waste could be converted into $CO_2$ and $H_2$ using reforming catalysts and then $CO_2$ was selectively adsorbed and removed to obtain pure hydrogen. To optimize adsorption efficiency for $CO_2$ removal, $Na_2CO_3$ was supported on nanoporous alumina and the efficiency was compared with commercial alumina(Degussa). Nanoporous adsorbents formed more uniform pores and larger surface area compared to adsorbents using commercial alumina. The increase of $Na_2CO_3$ loading improved adsorption of $CO_2$. Finally, the highest adsorption capacity per unit mass of $Na_2CO_3$ could be achieved when the loading of $Na_2CO_3$ reached up to 20wt%. When the content of $Na_2CO_3$ increased above 20 wt%, it aggregated on the surface, and the pore volume was decreased. Used adsorbents could be recycled by the thermal treatment.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.44.2-44.2
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• 2009

Polycrystalline materials suchas yttria and alumina have been applied as a plasma resisting material for the plasma processing chamber. However, polycrystal line material may easily generate particles and the particles are sources of contamination during the plasma enhanced process. Amorphous material can be suitable to prevent particle generation due to absence of grain-boundaries. We manufactured nitrogen-containing $SiO_2-Al_2O_3-Y_2O_3$ based glasses with various contents of silicon and fixed nitrogen content. The thermal properties, mechanical properties and plasma etching rate were evaluated and compared for the different composition samples. The plasma etching behavior was estimated using XPS with depth profiling. From the result, the plasma etching rate highly depends on the silicon content and it may results from very low volatile temperature of SiF4 generated during plasma etching. The silicon concentration at the plasma etched surface was very low besides the concentration of yttrium and aluminum was relatively high than that of silicon due to high volatile temperature of fluorine compounds which consisted with aluminum and yttrium. Therefore, we conclude that the samples having low silicon content should be considered to obtain low plasma etching rate for the plasma resisting material.

• Journal of the Korean Society of Combustion
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• v.14 no.3
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• pp.16-23
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• 2009

It is strongly desired for coal-fired power plants to utilize not only low-rank coals with high moisture contents, but also lowering cost with diversifying fuel sources. In this study, combustion characteristics of low rank coal with high moisture, and standard pulverized coals are experimentally investigated using TGA (Thermogravimetric Analysis) and DTF (drop tube furnace). The coals tested are three kinds of coal with moisture content ranging from 8.32 to 26.82%. The results show that under the air combustion condition, the burn-out time at TGA rises as moisture content increases, and standard pulverized coal with 8.32% moisture content showed the lowest activation energy of 55.73 kJ/mol. In case of the high amount of moisture, the combustion efficiency decreases due to evaporation heat loss, and unburned carbon in ash produced at combustion process in DTF increased. Aslo, initial deformation temperature of slag attached in alumina tube of DTF decreased with lowering the crytallinity of anorthite and augite. To improve the combustion reactivity and efficiency, it is effective to upgrade through drying the high moisture coal to moisture level (less than 10%) of standard pulverized coal.

• Transactions on Electrical and Electronic Materials
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• v.7 no.6
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• pp.283-292
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• 2006

So that high-strength and electrical properties apply by excellent high voltage insulator electricity material, ATH content and platinum-based flame retardant that influence in flame retardant and tracking characteristic among composite of silicone rubber studied mechanical strength and influence getting to electrical properties. Composition of ${\alpha}$, ${\omega}-vinyl$ poly (dimethyl-methylphenyl) siloxane(VPMPS) of a polymer quantity made doing mole of D4, $D3^{Me,Ph}$ and VMS by 1000:15:0.2 mole ratio and uses basic catalyst tetramethylammonium silanolate(TMAS) and do opening equilibrium polymerization to be used to main polymer for high voltage insulation insulator. Control ATH content and content of platinum-based flame retardant and made high voltage insulation silicone rubber. Measured mechanical strength of making silicone rubber using UTM, and tracking characteristic according to standard of IEC 60587, flame retardant test studied effect that flame retardant characteristic gets in tracking characteristic, measuring according to UL94V method of test.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.2
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• pp.63-70
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• 1992

$AI_2O_3/Ca-TZP$ composites was prepared by using the starting powder of alumina and Ca-TZP synthesized by hydrothermal reaction and investigated to its characteristics. The ratio of tetragonal zirconia to monoclinic within $AI_2O_3$ matrix was decreased with an addition of Ca-TZP content, but the absolute amount of tetragonal phase in composites was increased with an addition of Ca-TZP content. The value of fracture toughness in $AI_2O_3/Ca-TZP$composites was proportional to the amounts of transformed tetragonal phase which formed by crack propagation in fracture, and therefore, it was gradually increased with an addition of Ca- TZP content.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.37-44
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• 2017

Red mud is an inorganic by-product produced from the mineral processing of alumina from Bauxite ores. The development of alkali-activated slag-red mud cement can be a representative study aimed at recycling the strong alkali of the red mud as a construction material. This study is to investigate the optimum water content, compressive strength, water absorption and efflorescence of alkali-activated slag-red mud soil pavement according to binder type. The results showed that the optimum water content, moisture absorption coefficient and efflorescence area of alkali-activated slag-red mud soil pavement increased but the compressive strength of that decreased as the redmud content increased.

• Journal of Conservation Science
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• v.29 no.3
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• pp.279-286
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• 2013

It is characterized and classified as the type of red brown glass beads to compare the chemical composition and manufacturing technique on the 141 samples in 12 sites of the Three Kingdom Period analyzed until now. It can be divided into three types according to the chemical composition of stabilizers(CaO & $Al_2O_3$) and soda raw materials(MgO & $K_2O$) on the red brown glass beads except one sample. Type I of high alumina glass is identified as the most common types that is 78.6 % of the distribution ratio at analytical samples and is excavated the most from ruin sites. In contrast, type II, 13.6 % of distribution ratio at analytical samples, is about 5 % CaO and $Al_2O_3$, MgO and $K_2O$ at around 1.5 % is similar to the composition of plant ash glass. Type III is that the content of CaO is higher than $Al_2O_3$ and the content of MgO and $K_2O$ is below 1.5 %. It is the same as the composition of natron glass and its share is the lowest as 7.9 %. Of these, type III is divided into two types according to the content of MgO and $K_2O$. It is identified that manufacturing technique of type I and II is drawing and type III is casting method with microscopic investigations. Type II and III is estimated that raw materials is different because is confirmed in the majority of ruins in spite of the fact that distribution ratio is very low. So, red brown glass beads distributed in Korea Peninsula are divided into three types of glass culture.

• Resources Recycling
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• v.33 no.3
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• pp.48-56
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• 2024

In this study, physical property evaluation and physical separation of the target product were performed to investigate the possibility of using sewage sludge gasification solid residue (GSRs) as a circulating resource. Firstly, the GSRs used in this study was supplied by Sudokwon Landfill Management Corporation, and generally the GSRs was in the form of porous pellets with a particle size of several millimetres. In addition, the partially black areas were confirmed to be unburned and ungasified carbon, and the average carbon content was 5%. In addition, the content of silica, alumina and phosphorus oxide was more than 70% of the total content. It was confirmed that the metallic components of the wet grinding product were separated into individual elements. As a physical separation of metallic and non-metallic components was required, it was finally found that flotation screening was suitable. Accordingly, cationic and anionic surfactants were selected to separate metallic components in which a relatively large amount of non-metallic components were concentrated, and the separation characteristics were confirmed. As a result, it is expected that the concentration of non-metallic components such as silica, alumina and phosphorus will be easier than the separation of metallic components. Therefore, since it is possible to physically treat the gasified sludge residue, it is judged to have potential as a circular resource according to the proposed recycling method for the separated product.