• Journal of Powder Materials
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• v.21 no.3
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• pp.191-195
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• 2014

This study reports a simple way of fabricating the porous Cu with unidirectional pore channels by freeze drying camphene slurry with Cu oxide coated Cu powders. The coated powders were prepared by calcination of ball-milled powder mixture of Cu and Cu-nitrate. Improved dispersion stability of camphene slurry could be achieved using the Cu oxide coated Cu powders instead of pure Cu powders. Pores in the frozen specimen at $-25^{\circ}C$ were generated by sublimation of the camphene during drying in air, and the green bodies were sintered at $750^{\circ}C$ for 1 h in $H_2$ atmosphere. XRD analysis revealed that the coated layer of Cu oxide was completely converted to Cu phase without any reaction phases by hydrogen heat treatment. The porous Cu specimen prepared from pure Cu powders showed partly large pores with unidirectional pore channels, but most of pores were randomly distributed. In contrast, large and aligned parallel pores to the camphene growth direction were clearly observed in the sample using Cu oxide coated Cu powders. Pore formation behavior depending on the initial powders was discussed based on the degree of powder rearrangement and dispersion stability in slurry.

• Journal of the Korean Ceramic Society
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• v.49 no.3
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• pp.260-265
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• 2012

Impedance spectroscopy was used to monitor the hydration in the electrical/dielectric behaviors of chemical mechanical planarization (CMP)-blended cement mixtures. The electrical responses were analyzed using their equivalent circuit models, leading to the separation of the bulk and electrode based responses. The role of the CMP slurry was monitored as a function of the relative compositions of the CMP-blended cements, i.e. water, CMP slurry, and ordinary Portland cement. The presence of $Al_2O_3$ nanocrystals in the CMP slurries appeared to accelerate the hydration process, along with a more tortuous microstructure in the hydration, with enhanced hydration products. The frequency-dependent impedance spectroscopy was proven to be a highly efficient approach for evaluating the electrical/dielectric monitoring of the change in the pore structure evolution that occurs in CMP-blended cements.

• Journal of Korea Foundry Society
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• v.10 no.4
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• pp.309-315
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• 1990

Aluminum alloy matrix composites reinforced by SiC particles were prepared by rheocompocasting, a process which consists of the incoporation and distribution of reinforcement by stirring within a semi-solid alloy. When the volume fraction of SiCp and stirring speed were fixed, the dispersion of SiCp in Al-matrix alloy depended on stirring time and solid volume fraction in slurry. The results were as follows : 1) As a dispersed SiCp during stirring at $647^{\circ}C$ in 6063-Al alloy, SiC was better dispersed than that other temperature, where solid volume fraction was 43% in slurry. 2) When increased solid fraction in slurry, rate of dispersing SiC increased during stirring and porosities decreased in matrix alloy after casting. 3) Inspite of stirring with 800rpm, since solid particles of matrix alloy in slurry joined each other and occured joining growth, so that SiC was not dispersed into solid particle.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1159-1164
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• 2003

Two processing routes (i.e., the gel casting and polymer preform routes) using polymer beads were studied to fabricate porous ceramics with a cellular structure. The gel casting route, comprising the gel casting of a ceramic slurry mixed with polymer beads, was found to be inadequate to produce porous ceramic bodies with a interconnected pore structure, due to complete coating of the slurry on the polymer beads, which left just isolated pores in the final sintered bodies. The polymer preform route, involving the infiltration of a polymer beads preform with the ceramic slurry, successfully produced porous ceramics with a highly interconnected network of spherical pores. The pore size of 250-300 $\mu\textrm{m}$ was demonstrated and the porosity ranged from 82 to 86%. This process is advantageous to control the pore size because it is determined by the sizes of polymer beads used. Another feature is the avoidance of hollow skeleton, giving a high strength.

• Transactions on Electrical and Electronic Materials
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• v.5 no.6
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• pp.233-236
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• 2004

Copper metallization has been used in high-speed logic ULSI devices instead of the conventional aluminum alloy metallization. One of the key issues in copper CMP is the development of slurries that can provide high removal rates. In this study, the effects of slurry chemicals and pH for slurry dispersion stability on Cu CMP process characteristics have been performed. The experiments of copper slurries containing each different alumina and colloidal silica particles were evaluated for their selectivity of copper to TaN and $SiO_{2}$ films. Furthermore, the stability of copper slurries and pH are important parameters in many industries due to problems that can arise as a result of particle settling. So, it was also observed about several variables with various pH.

• 연구논문집
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• s.31
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• pp.53-63
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• 2001

Numerical investigation based on the control-volume using finite-difference method has been made by the development of computer program in order to figure out the pattern of the flow field inside screw decanter. The typical flow pattern inside screw decanter is characterized by the two strong recirculation zones separated by the main stream from slurry discharge hole to exit. These recirculation regions and flow pattern are strongly influenced by the centrifugal force and the change of the value of slurry viscosities, that is,500, 1,000 and 3,000cp respectively. The wear of screw decanter appeared experimentally in two spots; one is near the circumferential area of the slurry discharge hole and the other is on the decanter blades at a certain height from the bottom to a different degree after the continuous long-term operation. These wears are partly explained by the flow pattern and the strong turbulence intensity near the recirculation attachment region.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.11a
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• pp.71-72
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• 2004

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.574-579
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• 2007

Porous $Al_2O_3$ ceramics were prepared by the gelcasting foams method (a slurry foaming process) with acrylamide monomer. The foaming and gelation behavior was investigated with the parameters such as the type and concentration of surfactant, solid loading of slurry, and the concentrations of initiator and catalyst. Density, porosity, microstructure, and strength of the green and sintered samples were characterized. Of the four kinds of surfactants tested, Triton X-114 showed the highest foaming ability for the solid loading of 55-30 vol%. The gelation condition giving the idle time off min was found to set the foamed structure without significant bubble enlargement and liquid lamella thinning. The green samples were fairly strong and machinable and showed maximum strength of 2.4 MPa in diametral compression. The sintered samples showed densities of 10-36% theoretical (i.e. porosity 90-64%) with a highly interconnected network of spherical pores with sizes ranging from 30 to $600{\mu}m$. The pore size and connectivity increased but the cell strut thickness decreased with decreasing the solid loading. Flexural strength of 37.8-1.7 MPa was obtained for the sintered samples.

• Korean Journal of Materials Research
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• v.12 no.9
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• pp.691-695
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• 2002

A low temperature anode-supported tubular solid oxide fuel cell was developed. The anode-supported tube was fabricated using extrusion process. Then the electrolyte layer and the cathode layer were coated onto the anode tube by slurry dipping process, subsequently. The anode tube and electrolyte were co-fired at $140^{\circ}C$, and the cathode was sintered at $1200^{\circ}C$. The thickness and gas permeability of the electrolyte depended on the number of coating and the slurry concentration. Anode-supported tube was satisfied with SOFC requirements, related to electrical conductivity, pore structure, and gas diffusion limitations. At operating temperature of $800^{\circ}C$, open circuit voltage of the cell with gastight and dense electrolyte layer was 1.1 V and the cell showed a good performance of 450 mW/$\textrm{cm}^2$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2001.05a
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• pp.70-70
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• 2001