• The Korean Journal of Ceramics
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• v.5 no.3
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• pp.230-234
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• 1999

Ti(CN)-0.3mole% $Mo_2C$ ceramics were prepared by pressureless sintering. $Mo_2C$ dissolved in Ti(CN) more easily in a nitrogen environment than in the other environment because nitrogen forced Mo to form a solid solution, (Ti, No)(C, N). A "core-rim" structure developed within the grains. The boundary between the "core" and the rim was delineated by thermal etching in the sample with more than 2 mole% $Mo_2C$. The rim thickness and the grain size decreased as the $Mo_2C$ content increased. The hardness and the flexural strength showed maxima of 18.2 GPa and 1.23 GPa, respectively when the $Mo_2C$ content was 2 mole%. The post-sintering heat treatments improved the properties.oved the properties.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.7-12
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• 1989

The effects of composition ratios and sintering conditions in Co1-xMgxO ceramics on the sintering characteristics, electrical properties and oxygen sensing characteristics were investigated. In the same sintering conditions, porosity decreased with increase of MgO contents. The relationshiop of temperature and resistance in Co1-xMgxO ceramics showed NTC(negative temperature coefficient) characteristics at the temperature range from $700^{\circ}C$ to 1,10$0^{\circ}C$. In the case of pure CoO, however, the PTC(positive temperature coefficient) characteristics were shown over about 90$0^{\circ}C$. The electrical conductivity of Co1-xMgxO ceramics decreased proportionally with decrease of oxygen partial pressure at the range from 1 to 10-4(atm). Particularly, Co0.5Mg0.5O ceramics showed the highest sensitivity to oxygen gas.

• Journal of Technologic Dentistry
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• v.26 no.1
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• pp.89-96
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• 2004

Hydroxyapatite powder were synthesized by precipitation method, varying pH, and reaction temperature. The powders were heated at 1,200$^{\circ}{\cdots}$ and 1,300$^{\circ}{\cdots}$ for fabrication of dental prosthesis. The results are as follows: Synthesized powder showed the smallest particle in size, under the conditions of pH 11 and reaction temperature 37$^{\circ}{\cdots}$. The hydroxyapatite was partially converted to $\alpha,\;\beta$-TCP at 1,200$^{\circ}{\cdots}$ and 1,300$^{\circ}{\cdots}$. Mechanical strength of sample was affected by such powder preparation conditions as pH and reaction temperature and sintering temperature. The mechanical strength of sample prepared under the same conditions was increased with increasing pH, reaction temperature and sintering temperature.

• Journal of Korea Foundry Society
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• v.10 no.2
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• pp.154-161
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• 1990

The microstructures of sintered products of $Fe_2O_3$or $Fe_3O_4$-Oxide added cast iron powder was investigated. And the effects of particle size distribution was investigated too. As the result, the structures of sintered products did not related to the species of Fe-Oxide. Th porosity of sintered products was decreased in size and spherodized with increasing sintering temperature, decreasing Fe-Oxide quantity. Fe-Oxide itself did not hinder sintering of cast iron powder particularly, therefore sintering could be occurred without termination of reduction of it. And the sintered products of finer particle size distribution had finer and more spherodized porosity, and had minimized the deviation of size and shape of porosity.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.363-368
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• 2000

Densification, grain growth, and phase transformation of nanocrystalline ceramic powder were investigated under pressureless sintering, sinter forging, and hot pressing. A constitutive model for densification of nanocrystalline ceramic powder was proposed and implemented into a finite element program (ABAQUS). A grain growth model was also proposed by including the effect of applied stress on grain growth when phase transformation occurs. Finite element results by using the proposed models well predicted densification behavior, deformation, and grain growth of nanocrystalline titania powder during pressureless sintering, sinter forging, and hot pressing.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.79-84
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• 2003

In this study we propose an unsteady I-dimensional model of an iron ore sintering bed with multiple solid phases, which confers a phase on each solid material. This model contains coke combustion, limestone decomposition, gaseous reaction, heat transfers between each phase, and geometric changes of the solid particles. Simulation results are compared with the limited experimental data set of various coke contents and air supply rates. Effect of the coke diameter is also evaluated. They predict the experimental results well and show applicabilities to the various system of the fuel bed with various solid materials.

• Journal of Powder Materials
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• v.18 no.3
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• pp.238-243
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• 2011

Al/AlN composites were synthesized by mechanical alloying using process control agents(PCAs). Three different PCAs which contain N element, were examined to see the effectiveness of ball-milling and the nitridation during sintering. Among examined PCAs, $C_8H_6N_4O_5$ was the most effective to facilitate ball-milling and to form nitrides during a subsequent sintering. By a proper control of ball-milling and sintering, we could obtained surface-hardened Al-based composites.

• Transactions of Materials Processing
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• v.18 no.3
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• pp.262-267
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• 2009

Selective laser sintering is a kind of rapid prototyping process whereby a three-dimensional part is built layer wise by laser scanning the powder. This process is highly influenced by powder and laser parameters such as laser power, scan rate, fill spacing and layer thickness. Therefore a study on fabricating Fe-Ni-Cr powder by selective laser sintering has been performed. In this study, fabrication was performed by experimental facilities consisting of a 200W fiber laser which can be focused to 0.08mm and atmospheric chamber which can control atmospheric pressure with argon. With power increase or energy density decrease, line width was decreased and line surface quality was improved with energy density increase. Surface quality of quadrangle structure was improved with fill spacing optimization.

• Applied Chemistry for Engineering
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• v.1 no.2
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• pp.147-153
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• 1990

Poly(hydroxypropyl methacrylate) membranes and matrix devices having tertiary amine moiety were prepared by sintering method, and their permeation characteristics were investigated. The water content of this membrane was increased with decreasing the pH of the medium. The permeability of this membrane was increased with decreasing the sintering pressure. Using sintered matrix device 'burst effect' was found at the early stage, and initial insulin release of glucose oxidase immobilized matrix device could be controlled by glucose concentration of the solution.

• Journal of Powder Materials
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• v.1 no.2
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• pp.208-216
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• 1994

A radically new approach to the in situ synthesis of the consituent phases of a composite structure has enabled the production of a new WC/Co materials with an ultrafine microstructure. The process for synthesizing nanophase WC/Co powders consists of spray drying from solution to form a homogeneous precursor powder, and thermochemical conversion of the precursor powder to the nanophase WC/Co powder. Near theoretical density of pure nanophase WC-10 wt%Co has been obtained in only 30 sec at 140$0^{\circ}C$. But WC particles were grown up very rapidly with longer sintering time to get full density. To overcome coarsening of WC particle during sintering, VC, TaC and VC/TaC were used as the grain growth inhibitor with different amount respectively. VC/TaC doped WC-10 wt%Co was shown superior hardness and TRS and microstructure was maintained ultrafine scale (average WC size is less than 0.1 ${\mu}{\textrm}{m}$).