• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.559-566
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• 1995

Alumina powder was coated with stearic acid and then mixed with isotactic polypropylene, atactic polypropylene as binders at 15$0^{\circ}C$ for 2 hours. The mixture was then injection molded at various mold temperatures using injection molding machine to investigate the effect of the molding temperature and debinding parameters on the formation of the defects. The molded specimens were debinded in both air and nitrogen atmospheres. Wicking and solvent methods were also used to enhance debinding efficiency. The specimens were prefired at 120$0^{\circ}C$ and then sintered at 150$0^{\circ}C$ for 3 hours. Various defects were formed at mold temoperature of 3$0^{\circ}C$, 6$0^{\circ}C$ and 10$0^{\circ}C$ and any noticeable defect was not formed at 85$^{\circ}C$. The density of green body increased with mold temperature. Debinding in air atmosphere was more effective than in nitrogen atmosphere. Results also proved that wicking and solvent treatments helped minimize the number of defects.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.60-63
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• 2009

Manufacturing technologies of micro spur gear and micro mold by micro PIM were studied with stainless steel feedstock. For molding of gears, micro mold with gear cavity of 1.2 mm in diameter was produced by wire EDM. The proper injection pressure was selected to 70bar by observation and measuring of shapes and shrinkage of gears before/after sintering. For fabrication of micro mold, a tiny polymer gear was produced by injection into the mold. Then, 316L feedstock was again injected/compressed on the polymer gear and debinded together with polymer gear followed by sintering. As a result, another metal mold with gear cavity reduced to about 20% was fabricated and through repetition of this process chain, micro gear mold with cavity about below 800 um was finally obtained. In reduction of size by injection/compression molding, height of gear tooth was shrunk more and the effort for decrease of roughness of micro cavity were carried out ultrasonic polishing and as a result, the roughness in cavity decreased from 3-4 um to about 200 nm.

• Journal of Powder Materials
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• v.9 no.4
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• pp.218-226
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• 2002

The purpose of the present study is to investigate the influence of thermal debinding and sintering conditions on the sintering behavior and mechanical properties of PIMed 316L stainless steel. The water atomized powders were mixed with multi-component wax-base binder system, injection molded into flat tensile specimens. Binder was removed by solvent immersion method followed by thermal debinding, which was carried out in air and hydrogen atmospheres. Sintering was done in hydrogen for 1 hour at temperatures ranging from 1000℃ to 1350℃ The weight loss, residual carbon and oxygen contents were monitored at each stage of debinding and sintering processes. Tensile properties of the sintered specimen varied depending on the densification and the characteristics of the grain boundaries, which includes the pore morphology and residual oxides at the boundaries. The sinter density, tensile strength (UTS), and elongation to fracture of the optimized specimen were 95%, 540 MPa, and 53%, respectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.04a
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• pp.23-23
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• 2006

• Journal of the Korean Ceramic Society
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• v.30 no.2
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• pp.131-138
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• 1993

The effects of silane coupling agents on the injection molding process were investigated using silicone nitride mixtrues with a binder system containing polypropylene as a major binder (55vol% solid loading). The formation of bonding between silicon nitride powder and coupling agents was confirmed through the analyses of powder surface. The use of coupling agents improved mixing characteristics judged by the torque change during mixing process. the coupling agents also reduced molten viscosity of the mixture considerably, which is a main factor to determine the flow of the mixture. However, the bonding between coupling agents and polymers had a negative effect on the debinding process by retarding the thermal decomposition.

• Journal of Korea Technology Innovation Society
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• v.5 no.3
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• pp.382-395
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• 2002

Metal Injection Molding(MIM) is a technology without any mechanical processing, which is a promising area backed up by nano powder technology developed in late 1990's. The market was about 24 billion U$ in 1999. Many applications are made in process development, uses, powder making, hindering and sintering, of which order is in terms of the number of patents. This technologies are mainly developed by US firms, and applied by Japanese firms. Europe and Korea are still catch-up stage. More efforts should be made in this field because new opportunities are opening, thanks to nano technology.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.507-508
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• 2010

• Journal of Powder Materials
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• v.13 no.1 s.54
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• pp.57-61
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• 2006

The present work illustrates the use of water-soluble cupric salts as ingredients of binder for injection molding of $W-10 wt\%$ Cu. Parts produced are dense, homogeneous and have good surface finish, compared to those produced using conventional binder system. This new binder system provides also process-simplification benefit. $CuCl_2\;and\;Cu(NO_3)_2$ with the purity of $98\%$ was selected for this study. Rapid sintering process involving thermal decomposing was successful in densification for 1h. Final density that is about $93\%$ of theoretical value could be obtained, and are distinguishable from conventionally processed W-Cu composites.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1994.04c
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• pp.25-25
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• 1994

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.219-220
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• 2006

To understand the effect of powder characteristics on the thermal debinding behavior, PIM parts produced with powders with different particle sizes and particle shapes were examined to determine their weight losses during thermal debinding. The results show that the average diameter of the pore channel in the compact increased when the temperature increased and when coarse powders were used. However, the weight loss rates did not increase proportionally with the pore size. This suggests that the different powders that are frequently used in PIM parts do not affect the thermal debinding rate significantly. This is because the pore size is much larger than the mean free path of the decomposed gas molecules. Thus, the diffusion rates of the gases are not rate-controlling in thermal debinding. The controlling mechanism of the thermal debinding rate is the decomposition of the backbone binder in the PIM parts.