• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.1026-1029
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• 2002

Outlet of gas has been a big problem in deforming rubber or plastic in pressing mold. Air vent has been used to solve the problem, but it has weak points such as the increased cost, the increased number of process, and vent marks on the surface of a produce. In this study, the sintering method is used for making porous metal mold. Porous metal mold has many open pores, which are very small. When Porous metal mold is used for pressing mold, all process would be made short, produce cost would be down, and it would not leave vent marks on the surface of a produce. Porosity varies from sintering and pressing conditions, which are the pressure of compacting powder, the length of sintering time, sintering temperature and sintering atmosphere etc. This study will find optimized sintering temperature condition for the Porous metal mold.

• Journal of the Semiconductor & Display Technology
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• v.19 no.2
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• pp.22-25
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• 2020

Deep red EuSi₂O₂N₂ phosphors were synthesized under various sintering gas pressures (1 atm, 2 atm, and 3 atm). They were in good agreement with the standard EuSi₂O₂N₂ ICSD card # 41-6046 (a monoclinic crystal system with space group of P2₁/a). Their photoluminescence intensities were significantly increased with increasing the gas pressures. They showed a broad band emission peaking at 680 nm due to 4f⁶5d¹ - 4f⁷ of Eu²⁺ ion, which can be efficiently excited in the visible range up to 550 nm. The best one at 3 atm was applied for red LED based on blue chip, which showed the strong deep red emission.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.83-89
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• 2000

$Si_3N_4$ powder with 2wt% $Al_2O_3$ and 6wt% $Y_2O_3$ additives was sintered by gas pressure sintering (GPS) technique. The variations in the unlubricated wear behavior depending on sintering time were compared. Tribological properties depending on sintering time are associated with fracture toughness as well as flexural strength of materials. When increasing the sintering time, the larger elongated grains were formed as a result of exaggerated grain growth. As the fracture toughness and flexural strength decreased, the wear volume increased. On the basis of these experimental results, the unlubricated wear properties of silicon nitride were found to be governed mostly by both the fracture toughness and the flexural strength of the material.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.21-25
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• 2000

Gas pressure sintered silicon nitride based composites with 5 wt% $\beta$-Si3N4 whiskers were prepared, and the variations depending on sintering additives and sintering temperature were studied. Sintering additives were 6 wt% Y2O3-1 wt% MgO(6Y1M), 6 wt%Y2O3-1 wt% Al2O3(6Y1A), 6 wt% Y2O3-1 wt% SiO2(6Y1S), and whiskers were unidirectionally oriented by a modified tape casting technique. Samples were fully densified by gas pressure sintering at 2148 K and 2273 K. As the sintering temperature increased, the size of large elongated grains was increased. Three point flexural strength of 6Y1M and 6Y1M samples was higher than that of 6Y1S sample, and the strength decreased as the sintering temperature increased. The indentation crack length became shorter for the sample sintered at higher temperature, and the difference between the cracks length parallel to and normal to the direction of whisker alignment was decreased. In case of cracks 45$^{\circ}$off the whisker alignment direction, the crack length anisotropy disappeared.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.1
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• pp.25-32
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• 2020

Generally, high-temperature, high-pressure, high-priced sintering equipment is used for diamond sintering, and conductivity is a problem for improving the surface modification of the sintered body. In this study, to improve the efficiency of diamond sintering, we identified a new process and material that can be sintered at low temperature, and attempted to develop a composite thin film that can be discharged by doping boron gas to improve the surface modification of the sintered body. Sintered bodies were sintered by mixing Si and two diamonds in different particle sizes based on CIP molding and HIP molding. In CVD deposition, CVD was performed using WC-Co cemented carbide using CH₄ and H₂ gas, and the specimen was made conductive using boron gas. According to the experimental results of the sintered body, as the Si content is increased, the Vickers hardness decreases drastically, and the values of tensile strength, Young's modulus and fracture toughness greatly increase. Conductive CVD deposited diamond was boron deposited and discharged. As the amount of boron added increased, the strength of diamond peaks decreased and crystallinity improved. In addition, considering the release processability, tool life and adhesion of the deposition surface according to the amount of boron added, the appropriate amount of boron can be confirmed. Therefore, by solving the method of low temperature sintering and conductivity problem, the possibility of solving the existing sintering and deposition problem is presented.

• The Korean Journal of Ceramics
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• v.6 no.4
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• pp.364-369
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• 2000

Silicon nitride with adding La$_2$O$_3$ was sintered by gas pressure sintering (GPS) technique at $1950^{\circ}C$, in $N_2$ gas at 3 MPa, for 2h. Mechanical properties such as hardness, flexural strength, and fracture toughness were determined as a function of the GPS holding time and the contents of La$_2$O$_3$ in silicon nitride. Also machinability of silicon nitride ball with various GPS holding time and amount of La$_2$O$_3$ was evaluated by magnetic fluid grinding (MFG) method. In this study it was found that machinability was influenced significantly with La$_2$O$_3$ contents. However, the different GPS holding time did not affect the machinability very much.

• Journal of the Korean Society of Safety
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• v.21 no.1 s.73
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• pp.48-52
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• 2006

This study is a research of safety valve development for LP gas cylinder which use sintering metal. Re-searcher wishes to apply technology of sintering metal for safety valve development and do gas flow control. The basis of this study is most suitable fluid examination that to reduce gas accident. This research concluded following results. 1. When press pin length is 42mm to 45mm powder quantity is 0.25g, in case of press pin length 36mm to 42mm powder quantity is 0.2g, displayed fluid optimization. 2. When press pin length is 39mm and powder quantity is 0.25g, press pressure displayed fluid optimization at all interests from $1.2\;tons/cm^{2}\;to\;2\;tons/cm^{2}$. 3. When apparent density is about $5.0g/cm^{3}\;to\;4.5g/cm^{3}$, fluid optimization becomes.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.384-389
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• 2011

Gas pressure sintering (GPS) of reaction bonded silicon nitride (RBSN) was performed using $Lu_2O_3-SiO_2$ additive and the properties were compared with those of specimens prepared using high purity $Si_3N_4$ powder. The relative density of RBSN and compacted $Si_3N_4$ powder were 68.9 and 47.1%, and total linear shrinkage after sintering at $1900^{\circ}C$ were 14.8 and 42.9%, respectively. High nitrogen partial pressure (5MPa) was required during sintering at $1900^{\circ}C$ in order to prevent the decomposition of the nitride and to promote the formation of SiC. The relative density and 4-point bending strength of RBSN and $Si_3N_4$ powder compact were 97.7%, 954MPa and 98.2%, 792MPa, respectively, after sintering at $1900^{\circ}C$. The sintered RBSN also showed high fracture toughness of 9.2MPam$^{1/2}$.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.266-270
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• 2004

SiC materials have been extensively studied for high temperature components in advanced energy system and advanced gas turbine because it has excellent high temperature strength, low coefficient of thermal expansion, good resistance to oxidation and good thermal and chemical stability etc. However, the brittle characteristics of SiC such as low fracture toughness and low strain-to fracture still impose a severe limitation on practical applications of SiC materials. For these reasons, SiC/SiC composites can be considered as a promising for various structural materials, because of their good fracture toughness compared with monolithic SiC ceramics. But, high temperature and pressure lead to the degradation of the reinforcing jiber during the hot pressing. Therefore, reduction of sintering temperature and pressure is key requirements for the fabrication of SiC/SiC composites by hot pressing method. In the present work, monolithic Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method in Ar atmosphere at $1800^{\circ}C$ under 20MPa using $Al_2O_3,\;Y_2O_3\;and\;SiO_2$ as sintering additives in order to low sintering temperature and sintering pressure. The starting powder was high purity $\beta-SiC$ nano-powder with all average particle size of 30mm. The characterization of LPS-SiC was investigated by means of SEM and three point bending test. Base on the composition of sintering additives-, microstructure- and mechanical property correlation, tire compositions of sintering additives are discussed.

• Journal of Powder Materials
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• v.22 no.4
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• pp.283-288
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• 2015

Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-TiC composite powders which are fabricated by high-energy ball-milling. A powder mixture of Fe and TiC is prepared in a planetary ball mill at a rotation speed of 500 rpm for 1h. Pressureless sintering is performed at 1100, 1200 and $1300^{\circ}C$ for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of $1050^{\circ}C$, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of $50^{\circ}C$, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts show incomplete densification with a relative denstiy of 86.1% after sintering at $1300^{\circ}C$ for 3h. Spark-plasma sintering at $1050^{\circ}C$ for 10 min exhibits nearly complete densification of 98.6% relative density under the sintering pressure of 50 MPa.