• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.412-417
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• 2011

Formation and characterization of hydroxyapatite-based porous ceramics derived from polymer pyroysis were investigated. Polymer based process is chosen for preparing porous hydroxyapatite-based ceramics having a high mechanical strength. The hydroxyapatite-based porous ceramic was prepared by a self-blowing process of a polymethylsiloxane with filler and pyrolyzed at above $1000^{\circ}C$. Biphasic material consisted of hydroxyapatite and CaO has been prepared by solid state reaction from calcium hydroxide($Ca(OH)_2$) and calcium hydrogen phosphate dihydrate($CaHPO_4{\cdot}2H_2O$) as a filler material. The influence of filler content on mechanical properties was evaluated. The change of crystalline phase, microstructure and mechanical properties were investigated and discussed.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.232-236
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• 2020

Three-dimensional (3D) multilayered Pt electrodes were fabricated to develop a porous electrode using a pattern-transfer printing process. The Pt thin films were deposited using a transferred sputtering pattern having a 250 nm line width on the substrate, and the uniform line patterns were efficiently transferred using our proposed method. Temperature-programmed desorption (TPD) analyses were used to evaluate the porosity of the electrodes. It was possible to distinguish between two resolved maxima at 168 and 227 ℃, which could be described in terms of desorption reactions on the Pt (111) planes. The results of the TPD analysis of the 3D and multilayered Pt electrodes prepared through transfer printing were compared to those of an electrode fabricated through screen printing using a commercial Pt-carbon paste commonly used as porous electrodes. It was confirmed that the 3D multilayered electrodes exhibited a desorption concentration approximately 100 times higher than that of the Pt-carbon composite electrode, and the desorption concentration increased by approximately 0.02 mg/mol per layer. The 3D multilayered electrode effectively functions as a porous electrode and a catalyst.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.263-270
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• 2018

Recently, porous ceramic materials with anti-static performance are urgently needed for semiconductor and OLED/LCD display manufacturing industry. In this work, we fabricated porous titanium manganese oxide ceramics having the surface resistivity of $10^8-10^{10}$ ohm and enhanced mechanical strength by partial sintering method using nanosized titanium oxide. By addition of nano-sized titanium oxide in the matrix, neck formation between grains was strengthened, which remarkably increased flexural strength up to 170 MPa (@porosity: 15 %), 110 MPa (@porosity: 31 %), compared to 80 MPa (@porosity: 26 %) for pristine titanium manganese oxide ceramics. We evaluated the performances of our ceramics as air-floating module for OLED flexible display manufacturing devices.

• Journal of the Korean Ceramic Society
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• v.31 no.2
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• pp.137-146
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• 1994

This experiments were focused on a modification of mechamical properties and structure in porous aluminum titanate ceramics by new additives which have been not researched yet. These were consisted of four kinds of additives i.e. Bi2O3, FeO, ZnO and NiO by addition amount of 1 wt% and 5 wt% respectively. The addition of Bi2O3 retarded a degree of syntehsis of aluminum titanate and accelerated in FeO, ZnO, NiO additives. Also, the most effective accelerator in synthesis of alunium titanate was FeO. A additives for the most effective of modification of microstructure, sharp distribtion of pore size and mechanical proterties was on ZnO addition and showed the lowest average pore size and narrowed pore size distribution. In order to improve of microstructure and pore size distribution in porous aluminum titanate ceramics was desired the addition amount of 1 wt% compare to 5 wt%.

• Journal of the Korean Ceramic Society
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• v.32 no.8
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• pp.893-900
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• 1995

The porous wollastonite ceramics were fabricated after firing calcium silicates, obtained using natural resources and by-products of power plants by hydrothermal synthesis, without organic fibers or asbestos for reinforcement agent. A specimen from diatomite as a SiO2 staring raw material had the highest strength owing to normal grain growth and good densification from homogeneous sperhcial C-S-H hydrates. A specimen from SiO2 sol as a SiO2 starting raw material showed tobermolite, but fly ash and mixed system did xonotlite after hydrothermal synthesis. The specimen from fly ash showed the lowest firing shirikage and strength changes in the firing range from 50$0^{\circ}C$ to 120$0^{\circ}C$. The other phases in all specimens changed to wollastonite phase after firing at 100$0^{\circ}C$. Also the average pore size was distributed from 0.2${\mu}{\textrm}{m}$ to 2${\mu}{\textrm}{m}$.

• Laser Solutions
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• v.15 no.4
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• pp.6-11
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• 2012

Laser beam can be either absorbed or scattered in porous ceramic material and its optical characteristics need to be understood. Electro-magnetic multiphysics software was used to simulate and understand the actual scattering phenomena in porous materials. 785nm femtosecond laser was irradiated on the surface of ceramic material and strong scattering occurred in drilling process. The computer results showed the scattering and absorption phenomena of Aluminum oxide were a mixture of dielectric and metallic material. The computer simulation showed the laser beam was almost extinct at the aspect rate of 5 approximately.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.5
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• pp.649-655
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• 1999

Biofiltration of polluted gas streams contained $H_2S$ was studied. The experiments were performed in a laboratory-scale reactor with a porous ceramic media inoculated with sulfur oxidizing bacterium, TAS which was isolated from activiated sludge. The concentration of $H_2S$ in the inlet gas varied from 109 to 3,841 ppm, at the various space velocities(SV) of 50 $h^{-1}$ to 250 $h^{-1}$. Various tests have been conducted to evaluate the effects of such parameters as pH, concentration of sulfate ion and retention time on the pressure drop and maximum elimination capacity. The removal efficiency of $H_2S$ decreased as the $H_2S$ concentration or gas velocity increased in the inlet gas. Pressure drop was insignificant in this system. The maximum elimination capacity could reach up to 16.35g-S/kg-dry packing material/day.

• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.837-841
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• 2003

Duplex microstructure of zirconia and alumina has been achieved via an organic-inorganic solution technique. Zirconium 2,4-pentanedionate, aluminum nitrate and polyethylene glycol were dissolved in ethyl alcohol without any precipitation. The organicinorganic precursor gels were turned to porous powders having volume expansion through explosive, exothermic reaction during drying process. The volume expansion was caused by abrupt decomposition of the organic groups in the gels during the vigorous exothermic reaction. The volume expanded, porous powders were crystallized and densified at 1500$^{\circ}C$ for 1 h. At the optimum amount of the PEG polymer, the metal cations were well dispersed in the solution and a homogeneous polymeric network was formed. The polymer content also affected on the specific surface area of the synthesized powder and the grain size of the sintered composite.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.801-806
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• 2002

The decomposition and/or conversion of carbon dioxide to carbon have been studied using oxygen-deficient ferrites for the reduction of $CO_2$ emission to the atmosphere. In this work, the homogeneous precipitation method using urea decomposition was employed to induce in situ precipitation of Ni ferrite($Ni_{0.4}Fe_{2.6}O_4$) on the porous ceramic fiber support (50 mm diameter${\times}$10 mm thickness). Effects of ferrite loading conditions on the CO2 decomposition efficiency were discussed in this paper. Removal of residual chloride ions and urea by solvent exchange from the porous media after ferrite deposition apparently helps to form spinel ferrite, but does not increase the efficiency of $CO_2$ decomposition. Porous ceramic fiber composites containing 20 wt% (1g) ferrite samples showed 100% efficiency for $CO_2$decomposition during the first three minutes, but the efficiency decreased rapidly after the elapsed time of ten minutes. The characteristic reduction time for the $CO_2$ decomposition efficiency was estimated as about 3∼7 min.

• Journal of the Korean Ceramic Society
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• v.45 no.9
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• pp.537-543
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• 2008

Effect of template size ratio on porosity and mechanical properties of porous zirconia ceramics were investigated using two different size (${\sim}8{\mu}m$ and ${\sim}50{\mu}m$ in diameter) of polymethyl methacrylate-coethylene glycol dimethacrylate (PMMA) microbeads as sacrificial templates. Porosity of the porous zirconia ceramics increased with decreasing the template size ratio ($8{\mu}m: 50{\mu}m$) whereas the compressive and flexural strengths of the porous zirconia ceramics increased with increasing the template size ratio. By controlling the template size ratio, sintering temperature and sintering time, it was possible to produce porous zirconia ceramics with porosities ranging from 57% to 69%. Typical flexural and compressive strength values of porous zirconia ceramics with ${\sim}60%$ porosity were ${\sim}37\;MPa$ and ${\sim}85\;MPa$, respectively.