• 한국세라믹학회지
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• 제30권4호
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• pp.309-315
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• 1993

Gas pressure sintering is a promising process in various densification methods of high strength Si3N4 ceramics. Environmental influences on gas pressure sintering of Si3N4 was investigated with the variationof packing powder, specimen container and N2 gas pressure. The specimens had higher density, larger weight loss and inhomogeneous color in graphite specimen container than in SN26 crucible. The variations of sintering densities in various packing powders (Si3N4, SN26, AlN, BN) were very small but SiC powder was synthesised in graphite crucible with Si3N4 packing powder, aluminium oxynitride compounds were synthesised in SN26 crucible with AlN packing power. Also N2 gas pressure over 20kg/$\textrm{cm}^2$ reduced the densification of Si3N4 in one step-gas pressure sintering. As the result of two step-gas pressure sintering at 700kg/$\textrm{cm}^2$ for 15min., relative density of 99.9% and 3-point bending strength of 1090MPa and dense microstructure of 3~4${\mu}{\textrm}{m}$ grain size were obtained.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.280-281
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• 2006

Powder grades pre-alloyed with 1.5-3 wt% chromium can be successfully sintered at the conventional temperature $1120^{\circ}C$ although well-monitored sintering atmospheres are required to avoid oxidation. Mechanical properties of the Cr-alloyed PM grades are enhanced by a higher sintering temperature in the range $1120-1250^{\circ}C$, due to positive effects from pore rounding, increased density and more effective oxide reduction. Astaloy CrM (Fe-3 wt% Cr-0.5 wt% Mo) with 0.6 wt% graphite added obtains an ultimate tensile strength of 1470 MPa and an impact strength of 31 J at density $7.1\;g/cm^3$, after sintering at $1250^{\circ}C$ followed by cooling at $2.5^{\circ}C/s$ and tempering.

• 한국재료학회지
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• 제30권6호
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• pp.321-325
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• 2020

The present study demonstrates the effect of magnetic pulse compaction and spark plasma sintering on the microstructure and mechanical property of a sintered W body. The relative density of green specimens prepared by magnetic pulse compaction increases with increase in applied pressure, but when the applied pressure is 3.4 GPa or more, some cracks in the specimen are observed. The pressureless-sintered W shows neck growth between W particles, but there are still many pores. The sintered body fabricated by spark plasma sintering exhibits a relative density of above 90 %, and the specimen sintered at 1,600 ℃ after magnetic pulse compaction shows the highest density, with a relative density of 93.6 %. Compared to the specimen for which the W powder is directly sintered, the specimen sintered after magnetic pulse compaction shows a smaller crystal grain size, which is explained by the reduced W particle size and microstructure homogenization during the magnetic pulse compaction process. Sintering at 1,600 ℃ led to the largest Vickers hardness value, but the value is slightly lower than that of the conventional W sintered body, which is attributed mainly to the increased grain size and low sintering density.

• 한국분말재료학회지
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• 제20권1호
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• pp.1-6
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• 2013

The key concept of nanopowder agglomerate sintering (NAS) is to enhance material transport by controlling the powder interface volume of nanopowder agglomerates. Using this concept, we developed a new approach to full density processing for the fabrication of pure iron nanomaterial using Fe nanopowder agglomerates from oxide powders. Full density processing of pure iron nanopowders was introduced in which the powder interface volume is manipulated in order to control the densification process and its corresponding microstructures. The full density sintering behavior of Fe nanopowders optimally size-controlled by wet-milling treatment was discussed in terms of densification process and microstructures.

• 한국세라믹학회지
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• 제37권6호
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• pp.545-551
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• 2000

Sintering behaviors of the glass-alumina composites for low firing temperature were investigated as a function of the particle size of glass frit. The system of glass frit was Pb-B-Si-Al-O. The median particle sizes of the glass frits were 2.72$\mu\textrm{m}$, 2.67$\mu\textrm{m}$ and 1.33$\mu\textrm{m}$, which were prepared with changing ball-milling times as 24 h, 48 h and 96 h. The glass-alumina composites showed maximum density at certain temperature, and further heating led to dedensification behaviors, so called over-firing. The sintering temperature, which showed maximum density, raised from 425$^{\circ}C$ to 475$^{\circ}C$ with increase of particle size of glass frit from 1.33$\mu\textrm{m}$ to 2.72$\mu\textrm{m}$. Especially, the over firing behaviors, which were occurred at high sintering temperatures, were greatly increased with decrease of particle size of glass frit.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.611-612
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• 2006

In a manufacturing technique of the sintered filter, pressureless sintering method has good permeability, it is not need the binder and lubricant used on compacting process, so it has little contamination and it is easy to control the pore size and shape but the mechanical strength is low relatively and it is difficult that parts of complicate form are manufactured. In the case of manufacturing the filter by press and sintering method, in order to be satisfactory characteristic of un-pressed filter, in this study sintered metal filter fabricated by using 30-40mesh stainless steel 316L powder and additive agents. Porosity and structure of pores, permeability and mechanical strength of the sintered filter were investigated with the variation sintering conditions. Porosity was nearly constant about $60{\sim}70%$, density, permeability and mechanical strength were changed markedly with quantity of additive materials and sintering conditions.

• 한국분말재료학회지
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• 제23권1호
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• pp.1-7
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• 2016

Cu-Mn compacts are fabricated by the pulsed current activated sintering method (PCAS) for sputtering target application. For fabricating the compacts, optimized sintering conditions such as the temperature, pulse ratio, pressure, and heating rate are controlled during the sintering process. The final sintering temperature and heating rate required to fabricate the target materials having high density are $700^{\circ}C$ and $80^{\circ}C/min$, respectively. The heating directly progresses up to $700^{\circ}C$ with a 3 min holding time. The sputtering target materials having high relative density of 100% are fabricated by employing a uniaxial pressure of 60 MPa and a sintering temperature of $700^{\circ}C$ without any significant change in the grain size. Also, the shrinkage displacement of the Cu-Mn target materials considerably increases with an increase in the pressure at sintering temperatures up to $700^{\circ}C$.

• 한국재료학회지
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• 제19권12호
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• pp.680-685
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• 2009

Using a polyurethane foam replica method, porous hydroxyapatite scaffolds (PHS) were fabricated using conventional and microwave sintering techniques. The microstructure and material properties of the PHS, such as pore size, grain size, relative density and compressive strength, were investigated at different sintering temperatures and holding times to determine the optimal sintering conditions. There were interconnected pores whose sizes ranged between about 300 ${\mu}m$ and 700 ${\mu}m$. At a conventional sintering temperature of 1100$^{\circ}C$, the scaffold had a porous microstructure, which became denser and saw the occurrence of grain growth when the temperature was increased up to 1300$^{\circ}C$. In the case of microwave sintering, even at low sintering temperature and short holding time the microstructure was much denser and had smaller grains. As the holding time of the microwave sintering was increased, higher densification was observed and also the relative density and compressive strength increased. The compressive strength values of PHS were 2.3MPa and 1.8MPa when conventional and microwave sintering was applied at 1300$^{\circ}C$, respectively.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제25회 춘계학술대회
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• pp.53-61
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• 1997

The effect of sintering condition on tribological behavior in the Cu-base sintered friction materials was studied through pin-on-disk type wear tester. Especially, the experiment was focused on making a comparative study between presstwed sintering and pressureless sintering. Pressureless sintering process showes more stable friction coefficient and lower wear rate than pressure sintering process. This result is related to pore size and density of pore in the sintered materials.

• 한국세라믹학회지
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• 제31권3호
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• pp.321-329
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• 1994

Functionally gradient materials(FGM), which have the continuous or stepwise variation in a composition and microstructure, are being noticed as the material that solves problems caused by heterogeneous interface of coating or joining. And these materials also expect new functions occured by gradient composition itself. Therefore, to examine possibility of thermal barrier materials, TZP/Mo·FGM and TZP/Ni·FGM were fabricated by sintering method. As to the sintered specimens, sintering shrinkage, relative density and Vicker's hardness in each composition were examined. The phenomena due to the difference of sintering shrinkage velocity during sintering process and the thermal stress induced through differences of thermal expansion coefficient in FGM were discussed. And the structure changes at interface and microsturcture of FGM were investigated. As a results, the difference of shrinkage between ceramic and metal was about 14% in TZP/Mo and 7% in TZP/Ni. The relative density and hardness were considerably influenced by metal content changes. Owing to unbalance of sintering shrinkage velocity between ceramic and metal, various sintering defects were occured. To control these sintering defects and thermal stress, gradient composition of FGM should be narrow. The microstructure changes of FGM depended on the ceramic or metal volume percents and were analogous to the theoretical design.