• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.51-56
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• 1995

Variation of sintered density of BaTiO3 powder calcined at 120$0^{\circ}C$ and 135$0^{\circ}C$ was investigated with respect to the grain growth behavior. It was found that BaTiO3 powder, which was calcined at 120$0^{\circ}C$, showed abnormal grain growth behavior during sintering process. At initial stage of sintering process, the densification rate of specimen was accelerated with rapid grain growth caused by the abnormal grain growth. But with the increase of sintering time, abnormally grown grain met each other and the density of specimen decreased drastically due to coalescence of pores located in triple junction. On the contrary, BaTiO3 powder calcined at 135$0^{\circ}C$ showed normal grain growth behavior and gradually densified with the increase of sintering time.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1124-1132
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• 2000

Viscoplastic response and densification behaviors of Ti-6AI-4V powder compacts under uniaxial compression are studied at room and high temperatures with various initial relative densities and strain rates. The yield function and strain-hardening law proposed by Kim and co-workers were implemented into a finite element program (ABAQUS) to compare experimental data with finite element calculations for porous Ti6A14V powder compacts. Displacement-relative density, displacement-load relations and deformed geometry of Ti-A14V powder compacts were compared with finite element results. Density distributions in Ti-6AI-4V powder compacts were also measured and compared with finite element results.

• Carbon letters
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• v.6 no.3
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• pp.173-180
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• 2005

In this study, AR (aromatic resin) pitch was employed as the matrix-precursor for carbon/carbon composite because it exhibits much higher coke yield than coal tar pitch. As a result, a fabrication process of carbon/carbon composites can be shortened. It has been known that the pitches may cause swolling problem during the carbonization process. In order to restrain the swelling occurrence, a small quantity of carbon black was added to the AR pitch. Due to addition of carbon black the swelling was decreased largely and the perform can be infiltrated with the AR pitch. The densification efficiency of the performs was compared with various matrix-precursors. The coke yield of matrixprecursors, the morphology and the degree of graphitization of carbon matrix were analyzed.

• Journal of the Korean Ceramic Society
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• v.27 no.2
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• pp.169-178
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• 1990

The sintering characteristics of ZrO2 were analyzed in terms of pore microstructure and kinetics of pore elimination. The pore structue of the ZrO2 sample prepared from colloid suspension was characterized by three distinct types of pores ; intradomain, interdomain, and intergglomerate pores. Sintering data at 1600$^{\circ}C$ showed that pores larger than a certain critical size(∼3$\mu\textrm{m}$) were difficult to remove, and this was analyzed in terms of the interagglomerate pore formed from the suspension under the condition of low kinetic stability, that is, the stability ratio smaller than its critical value. A theoretical equation for densification rate was derived and was applied to the densification rate of the ZrO2 polycrystalline body containging both the matrix(the 1st-generation) pores and the interagglomerate (the 2nd-generation) pores under the condition of slow grain growth.

• Journal of Powder Materials
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• v.4 no.1
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• pp.9-17
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• 1997

The mullite-zirconia composites were prepared by the pressureless sintering with addition of 10~20 vol% ZrO$_2$(TZ3Y) in the fused mullite and sol-gel mullite matrix. The densification rate of sol-gel mullite was higher than that of fused mullite, and the addition of ZrO$_2$(TZ3Y) was effective on the densification of fused mullite. The enhancement of densification and anisotropic growth of mullite in ZrO$_2$added specimen can be explained by the solid solution effect of $Zr^{+4}$ ion in mullite. Both mechanical strength and fracture toughness of mullite-zirconia composite were enhanced compared to those of mullite. The enhancement of mechanical properties is attributed to the hinderance of grain growth and the combined toughening effects of tetra-mono phase transformation and crack deflection due to the residual stress between mullite/ZrO$_2$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.1
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• pp.95-104
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• 2002

Densification behavior of aluminum alloy(A16061) powder was investigated under cold compaction. Experimental data were obtained under triaxial compression with various loading conditions. A special form of the Cap model was proposed from experimental data of A16061 powder under triaxial compression. The proposed yield function and several yield functions in the literature were implemented into a finite element program (ABAQUS) to compare with experimental data for densifcation behavior of A16061 powder under cold isostatic pressing and die compaction. The agreement between finite element calculations from the proposed yield function and experimental data is very good under cold isostatic pressing and die compaction.

• Journal of Powder Materials
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• v.1 no.2
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• pp.190-197
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• 1994

The densification behavior during a sintering of M2 and T15 grade high speed steel powder compacts was reported. Sintered densities over 98% theoretical were achieved by a liquid phase sintering in vacuum for both grades. The optimum sintering temperature range where full densification could be achieved without excessive carbide coarsening and incipient melting was much narrower in M2 than in T15 grade. The sintering response was mainly affected by the type of carbides present. The primary carbides in M2 were identified as $M_6C$ type whereas those in T15 were MC type which provides wider sintering range. The addition of elemental carbon up to 0.3% lowered the optimum sintering temperature for both grades, but had little effect on expanding the sintering range and sintered structure.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1245-1246
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• 2006

Ferroelectric PZT (70/30) thick films were fabricated by the screen printing method. And the PZT (30/70) precusor solution were infiltrated by the spin-coating method on the PZT thick films to obtain a densification. All PZT thick films were sintered at $1050^{\circ}C$ for 10 min. Structural properties, such as crystalline structure, microstructures and compositional ratio, of PZT thick films were investigated with the variation of the number of sol coatings using XRD, SEM and EDS, respectively. All PZT thick films exhibited a perovskite polycrystalline structure without a pyrochloer phase. The thickness of PZT thick films, 4-times screen-printed, was approximately $60{\mu}m$. And the densification of the PZT thick films increased with increasing the number of sol coatings.

• Carbon letters
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• v.8 no.1
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• pp.25-29
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• 2007

The carbon brake discs were manufactured by densification the carbon fiber preform using PG-CVI technology with Propene as a carbon precursor gas and Nitrogen as a carrier gas. The densities of carbon brake discs were tested at different densification time. The results indicate that the densification rate is more rapid before 100 hrs than after 200 hrs. The CTscanning image and the SEM technology were used to observe the inner subtle structure. CT-images show the density distribution in the carbon brake disc clearly. The carbon brake disk made by PG-CVI is not very uniform. There is a density gradient in the bulk. The high-density part in the carbon brake is really located in the friction surface, especially in the part of inner circle. This density distribution is most suitable for the stator disc.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1344-1352
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• 2005

Densification behavior of iron powder under cold stepped plastic deformation was studied. Experimental data were also obtained for iron powder under cold stepped plastic deformation. The elastoplastic constitutive equation based on yield function of Shima and Oyane was implemented into a finite element program (ABAQUS) to simulate compaction responses of i.on powder during cold stepped plastic deformation. Finite element calculations were compared with experimental data for densification, deformed geometry and density distribution. The agreement between finite element results and experimental data was good for iron powder.