• Journal of Korea Foundry Society
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• v.28 no.4
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• pp.166-169
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• 2008

This study deals about the development of fusible core with low melting temperature by addition of ceramic particles. A new concept of salt core was introduced to produce an integrated casting part having a complicated inner shape or requiring under-cut in high pressure die casting or squeeze casting process. The mechanical properties of fusible core were improved due to the addition of ceramic particles which helped to produce fine microstructure. The new technology for the preparation of new fusible core materials which possess high compression strength was established. Addition of ceramics particles increased the mechanical properties of fusible core materials. There was an increasing relationship between percentage of ceramic particles and mechanical strength was existed up to 60%.

• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.462-470
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• 1995

The characteristics of spray-dried granules are important for dry pressing operation since they have great influences on die-filling, compaction ratio, and resulting green microstructure. An attempt was made to control granule morphology and the packing structure of fine Si3N4 particles in granules by adjusting suspension property. Mercury porosimetry was used to characterize the pore structures of both granules and green compacts. Finally, the effects of particle packing structure in granules and green microstructure on sintering behavior were investigated.

• Transactions of Materials Processing
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• v.14 no.3 s.75
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• pp.277-281
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• 2005

LTCC(Low temperature co-fired ceramic) is being recognized as a significant packaging material of electrical devices for the advantages such as relatively low temperature being needed for process, low conductor resistance and high printing resolution. In the process of LTCC electrical devices, the punched via-hole quality is one of the most important factors on the performance of the device. However, its mechanism is very complicated and optimization of the process seems difficult. In this paper, to clarify the process, via-hole punching experiments were carried out and the punched holes were examined in terms of their burr formation. The effects of thickness of PET sheet, ceramic sheet and punch-to- die clearance on via-hole quality were also discussed. Optimum process conditions are proposed and a factor $\kappa$ is introduced to express effect of the process variables.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.179-180
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• 2006

Densification behavior of various metal and ceramic powder was investigated under cold compaction. The Cap model was proposed based on the parameters obtained from axial and radial deformation of sintered metal powder compacts under uniaxial compression and volumetric strain evolution. For ceramic powder, the parameters were obtained from deformation of green powder compacts under triaxial compression. The Cap model was implemented into a finite element program (ABAQUS) to compare with experimental data for densification behavior of various metal and ceramic powder under cold compaction.

• Journal of Powder Materials
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• v.26 no.6
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• pp.508-514
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• 2019

In the development of advanced ceramic tools, material improvements and design freedom are critical in improving tool performance. However, in the die press molding method, many factors limit tool design and make it difficult to develop innovative advanced tools. Ceramic 3D printing facilitates the production of prototype samples for advanced tool development and the creation of complex tooling products. Furthermore, it is possible to respond to mass production requirements by reflecting the needs of the tool industry, which can be characterized by small quantities of various products. However, many problems remain in ensuring the reliability of ceramic tools for industrial use. In this study, alumina inserts, a representative ceramic tool, was manufactured using the digital light process (DLP), a 3D printing method. Alumina inserts prepared by 3D printing are pressurelessly sintered under the same conditions as coupon-type specimens prepared by press molding. After sintering, a hot isostatic pressing (HIP) treatment is performed to investigate the effects of relative density and microstructure changes on hardness and fracture toughness. Alumina inserts prepared by 3D printing show lower relative densities than coupon specimens prepared by powder molding but indicate similar hardness and higher fracture toughness values.

• International journal of advanced smart convergence
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• v.4 no.1
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• pp.120-126
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• 2015

This research is a comparison of the characteristics of the displacement isolines due to powder-die-wall friction that arise during the compaction of ceramic powders in conventional die. It has been done using the CosmosWorks software package of the SolidWorks simulation software. The results of comparative simulation with FEM showed that the comparison of the displacement isolines and distribution of deformation of the ceramic powders. In the case of conventional uniaxial dry compaction for long length cylindrical green compact, considerable bending of the layers in the form of a cone can be observed. It is symmetry along centerline of cylindrical green compact. The distributions of the deformation of the green compacts (diameter 14 mm, height 20 mm) as a result of conventional compaction under ultrasonic vibration with power 1 and 2 kW are reduced to 4% and 6.5% when compared with conventional compaction without ultrasonic vibration respectively. Thus, density distribution can be minimized by increasing the power of ultrasonic vibration.

• Journal of the Korean Ceramic Society
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• v.50 no.3
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• pp.186-194
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• 2013

The relationship between composition and properties of enamel glass was investigated by introducing a mixture design. The enamel glass was manufactured by mixing various components under the following constraints: $45{\leq}SiO_2{\leq}55$, $10{\leq}B_2O_3{\leq}18$, $6{\leq}Na_2O{\leq}15$, $1{\leq}Li_2O{\leq}6$, $5{\leq}K_2O{\leq}10$, $0{\leq}TiO_2{\leq}8$, $0{\leq}ZrO_2{\leq}8$, 13.3MO (mol %). A mathematical model for the calculation of some properties of enamel glasses as a function of their composition was developed by the experimental statistical method. The results showed that the proposed model with the experimental measurement were in good agreement and the mixture experimental design was an effective method for optimizing the composition of the enamel glass with respect to its properties.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.9
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• pp.80-89
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• 1997

Die sinking electrical discharge machining(EDM) was conducted for ceramic composite of 33 weight percent TiC based on AI$_{2}$O$_{3}$ ceramic matrix according to the change of current and duty factor(DF). Material removal rate(MRR) was increased as the current and the duty factor increased, but better surface mor-pholoty was obtained in the region of lower current and duty factor. From the scanning electron microscopy(SEM) photographs and the energy dispersive X-ray spectroscopy(EDX) of the EDMed surface, EDM trace formed by one discharge spark was analyzed. Although the bending strength after EDM was highly decreased, reliability obtained by weibull analysis was increased twice. The bending strength was recovered or more by barrel polishing after EDM. From the FEM analysis of temperature for one spark, the possible melting region of AI$_{2}$O$_{3}$and TiC was obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.10 s.253
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• pp.1242-1248
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• 2006

Densification behavior of nanocrystalline titania powder was investigated under cold compaction. Experimental data were obtained under triaxial compression with various loading conditions. Lee and Kim proposed the Cap model by developing the parameters involved in the yield function of general Cap model and volumetric strain evolution under cold isostatic pressing. The parameters in the Drucker/Prager Cap model and the proposed model were obtained from experimental data under triaxial compression. Finite element results from the models were compared with experimental data for densification behavior of nanocystalline ceramic powder under cold isostatic pressing and die compaction. The proposed model agreed well with experimental data under cold compaction, but the Drucker/Prager Cap model underestimated at the low density range. Finite element results, also, show the relative density distribution of nanocystalline ceramic powder compacts is severe compared to conventional micron powder compacts with the same averaged relative density.

• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.87-92
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• 2008

Purpose: In this study, we tried to compare marginal accuracy when produce ceramic crown using all ceramic materials and existent metal-ceramic system. Material and methods: All-ceramic systems were E-max (Ivoclar/Vivadent, Lichtenstein), Lava(3M, U.S.A.) and Wol-ceram(Teamziereis, Germany). Metal-ceramic system(PFG) was composed of Au-Pt alloy (Metalor, Switzerlandand) and overlying ceramic(D-sign, Ivoclar/Vivadent, Lichtenstein). We fabricated metal master die with upper diameter of 7.95mm, bottom diameter of 9.00mm, height of 5.00mm, and taper of $6^{\circ}$. All ceramic system used 0.5mm thickness ceramic coping, while metalceramic system used 0.3 thickness metal coping. By adding dentin and enamel ceramics on each coping, a crown with a proximal thickness of 1.0 mm and occlusal thickness of 2.0mm was fabricated. Pressure of 2kg was applied for 10 seconds on each crown with static load compressor. Before and after cementation, we measured the marginal gap at 4 points of each crown using optical microscope. The data was analyzed using a Student's t test and repeated-measures of analyses of variance(ANOVA) followed by a Bonferroni test. A p value<0.05 was considered significant. Results: As experiment results, marginal accuracy of wol-ceram and Lava is no good when compared with marginal accuracy of PFG. But marginal accuracy of E.max is good when compared with PFG. This result showed not significant. The marginal accuracy of E.max is good when compared with marginal accuracy of wol-ceram and Lava. Conclusion: The marginal accuracy of E.max is very good when compared with marginal accuracy of another group.