• Journal of Powder Materials
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• v.21 no.5
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• pp.389-398
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• 2014

Macroporous ceramics with tailored pore size and shape could be used for well-established and emerging applications, such as molten metal filtration, biomaterial, catalysis, thermal insulation, hot gas filtration and diesel particulate filters. In these applications, unique properties of porous materials were required which could be achieved through the incorporation of macro-pores into ceramics. In this article, we reviewed the main processing techniques which can be used for the fabrication of macroporous ceramics with tailored microstructure. Partial sintering, replica templates, sacrificial fugutives, and direct foaming techniques was described here and compared in terms of microstructures and mechanical properties that could be achieved. The main focus was given to the direct foaming technique which was simple and versatile approach that allowed the fabrication of macro-porous ceramics with tailored features and properties.

• Journal of Mechanical Science and Technology
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• v.19 no.11
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• pp.2025-2031
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• 2005

Eshelby type micro mechanics model with a newly developed piezoelectric Eshelby tensor is proposed for predicting the effective electroelastic properties of the piezoelectric composite. The model is applied for piezoelectric solids containing both porosities and metal inhomogeneities. The effective electroelastic moduli of the composites such as stiffness, piezoelectric constants, and dielectric constants are predicted by the present model, which are extensively compared with the existing experimental results from the literatures. The validity of Eshelby type model for predicting the effective properties of the composite is thoroughly examined. It can be concluded from this study that a new mechanism is needed to compute correctly the dielectric constants among the effective properties of the composites.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.5 s.98
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• pp.98-103
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• 1999

The application field of porous mold is more and more expended. A mixture of alumina and cast iron is used for making porous mold using slip and vacuum casting method in this study. Slip casting is a process that slurry is poured into silicon rubber mold, dried in vacuum oven, debinded and sintered in furnace, In this procedure, slurry is composed of powder, binder, dispersion agent, and water. Vacuum casting is a technique for removing air bubbles existed in the slurry under vacuum condition. Since ceramics has a tendency of over-shrinkage after sintering, cast iron is used to compensate dimensional change. The results shows that sintering temperature has a great effect on characteristics of alumina-cast iron composite sintered parts. Finally ceramic-metal composite sintered mold can be used for aluminum alloy casting of shoe mold using this process.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.782-784
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• 2008

Ag/Ni bimetallic cluster loading on porous carbon fibers was accomplished in order to enhance the HCl removal efficiency of the carbons. The surface properties of the Ag/Ni/carbons were determined by XRD and SEM. N2/77 K adsorption isotherms were investigated using BET and Boers t-plot methods. The HCl removal efficiency was confirmed by a gas chromatography technique, and it was found that that efficiency was predominantly improved in the presence of Ag/Ni clusters compared with the efficiencies of the as-received and single-metal-plated carbons. This indicates that synergetic reactions exist between Ag/Ni and HCl gas, resulting in advanced HCl removal capacity of porous carbons.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.64-71
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• 1988

A special set of constitutive equations is formulated to predict elastic-plastic strain hardening responses of porous metals. Including the effect of the material's strain hardening in the yield function, the constitutive equations are capable of showing no dip phenomena in uniaxial strain compression and prediction work-hardening response for plastically precyled porous metal. The proposed constitutive equations are compared with experimental data for porous tungsten.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.65-72
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• 2019

Dual porous structures are observed for the first time on a metallic Cu surface underneath anodic Cu oxide by the application of an anodizing voltage to Cu in oxalic acid. The as-prepared porous Cu surface contains macropores of less than $1{\mu}m$ diameter and mesopores of about tens of nanometers diameter with circular shapes. The size and density (number of pores/area) of the macropores are dependent on the applied voltage. It is likely that the localized dissolution (corrosion) of Cu in oxalic acid under the anodizing voltages is responsible for the formation of the mesopores, and the combination of a number of the mesopores might create the macropores, especially under a relatively high anodizing voltages or a prolonged anodizing time. The variations of pore structure (especailly macropores) with applied voltage and time are reasonably explained on the basis of the proposed mechanism of pore formation.

• Analytical Science and Technology
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• v.19 no.3
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• pp.226-238
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• 2006

The electroplating of the Ag ions from aqueous solution on activated porous carbons was investigated over a wide range of plating time. The adsorption capacities of Ag metallic carbons were associated with their internal porosity and were related to physical properties such as surface area and pore size distribution. And, surface morphologies and quantitative analysis for the metal supported carbons are investigated by scanning electron microscopy (SEM) and energy disperse X-ray (EDX) measurements to explain the changes in adsorption properties. It is considered that the pH is an very important factor at the reason of water pollutant with increasing acidity in industrial field. The results of ICP-AES analysis showed that the residual concentration of Ag ions decreased with an increasing electroplating time. The metallic Ag-activated porous carbons electroplated showed microbicidal effects and strong antibacterial activity against six kinds of strains that were used. Finally, we confirmed that the presence of the electrolytic plated Ag-activated porous carbons is a determining factor in the HCl removal by chemical reaction, clarifying the surface chemical behavior.

• Journal of Periodontal and Implant Science
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• v.50 no.2
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• pp.106-120
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• 2020

Purpose: A new form of porous polyethylene, characterized by higher porosity and pore interconnectivity, was developed for use as a tissue-integrated implant. This study evaluated the effectiveness of porous polyethylene blocks used as an onlay bone graft in rabbit mandible in terms of tissue reaction, bone ingrowth, fibrovascularization, and graft-bone interfacial integrity. Methods: Twelve New Zealand white rabbits were randomized into 3 treatment groups according to the study period (4, 12, or 24 weeks). Cylindrical specimens measuring 5 mm in diameter and 4.5 mm in thickness were placed directly on the body of the mandible without bone bed decortication, fixed in place with a titanium screw, and covered with a collagen membrane. Histologic and histomorphometric analyses were done using hematoxylin and eosin-stained bone slices. Interfacial shear strength was tested to quantify graft-bone interfacial integrity. Results: The porous polyethylene graft was observed to integrate with the mandibular bone and exhibited tissue-bridge connections. At all postoperative time points, it was noted that the host tissues had grown deep into the pores of the porous polyethylene in the direction from the interface to the center of the graft. Both fibrovascular tissue and bone were found within the pores, but most bone ingrowth was observed at the graft-mandibular bone interface. Bone ingrowth depth and interfacial shear strength were in the range of 2.76-3.89 mm and 1.11-1.43 MPa, respectively. No significant differences among post-implantation time points were found for tissue ingrowth percentage and interfacial shear strength (P>0.05). Conclusions: Within the limits of the study, the present study revealed that the new porous polyethylene did not provoke any adverse systemic reactions. The material promoted fibrovascularization and displayed osteoconductive and osteogenic properties within and outside the contact interface. Stable interfacial integration between the graft and bone also took place.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.6 s.336
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• pp.23-30
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• 2005

In this paper, OPPS(oxidized porous poly-silicon) field emitters were fabricated by using various emitter-electrode metal and these electron emission characteristics were investigated for different thermal annealing effects. The addressed OPPS field emitter with Pt/Ti emitter electrode annealed at $300^{\circ}C$-1hr showed the efficiency of $2.98\%$ at $V_{ps}$=12 V and one annealed at $350^{\circ}C$-1hr showed the highest efficiency of $3.37\%$at $V_{ps}$=16V. They are resulted from the improvement of interfacial contact characteristics of thin emitter metal to an oxidized porous poly-silicon and the decrease of electrical resistance of emitter metal. The brightness of the OPPS field emitter increases linearly in $V_{ps}$ and after oxidation process for $900^{\circ}C$-50min, the brightness of the OPPS field emitter with the as-deposited Pt/Ti emitter electrode was 3600 cd/$m^2$ at the $V_{ps}$=15 V, 6260 cd/$m^2$ at the $V_{ps}$=20 V. Thermal treatment improved the adhesion between the Ti buffer layer and the oxidized porous poly-silicon and also played an important role in the uniform distribution of electric field to the emitter electrode.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.2
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• pp.244-251
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• 2009

Porous media have especially large surface area per volume, which contain complex fluid passage. If porous media can be applied to cool a CPU or an electronic device with large heat dissipation, it could result in heat transfer enhancement due to the enlargement of the heat transfer area and the flow disturbance. This study is aimed to identify the heat transfer and pressure drop characteristics of high-porosity metal foams in a horizontal channel. Experiment is performed with the various heat flux, velocity and pore density conditions. Permeabilities, which is deduced from Non-Darcy flow model, become lower with increasing pore density. Nusselt number also decreases with higher pore density. High pore density with same porosity case shows higher pressure loss due to the increase of surface area per unit volume. The fiction factor decreases rapidly with increase of Reynolds number in Darcy flow region. However, it converges to a constant value of the Ergun coefficient in Non-Darcy flow region.