• 한국생산제조학회지
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• 제22권1호
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• pp.173-177
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• 2013

The purpose of this paper is to investigate the influences on mechanical properties of two-stroke cycle motor pistons manufactured by casting, conventional forging and powder forging, through the comparison of characteristics, merits and disadvantages of each forming technology. For each forming technology, the optimal process parameters were determined through the experiments for several conditions, and microstructure, hardness, tensile strength and elongation of pistons are compared and analyzed. In conventional forging process, material temperature was $460^{\circ}C$ and the die temperature was $210^{\circ}C$ for the Al 4032. The optimal condition was found as solution treatment under $520^{\circ}C$ for 5 hours, quenching with $23^{\circ}C$ water, and aging under $190^{\circ}C$ for 5 hours. In powder forging process, the proper composition of material was determined and optimal sintering conditions were examined. From the experiment, 1.5% of Si contents on the total weight, $580^{\circ}C$ of sintering temperature, and 25 minutes of sintering time were determined as the optimal process condition. For the optimal condition, the pistons had 76.4~78.3 [HRB] of hardness, and 500 [MPa] of tensile strength after T6 heat treatment.

• 한국세라믹학회지
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• 제50권3호
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• pp.226-230
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• 2013

We performed high pressure high temperature (HPHT) sintering for the 20 nm MgO powders at the temperatures from $600^{\circ}C$ to $1200^{\circ}C$ for only 5 min under 7 GPa pressure condition. To investigate the microstructure evolution and physical property change of the HPHT sintered MgO samples, we employed a scanning electron microscopy (SEM), density and Vickers hardness measurements. The SEM results showed that the grain size of the sintered MgO increased from 200 nm to $1.9{\mu}m$ as the sintering temperature increased. The density results showed that the sintered MgO achieved a more than 95% of the theoretical density in overall sintering temperature range. Based on Vickers hardness test, we confirmed that hardness increased as temperature increased. Our results implied that we might obtain the dense sintered MgO samples with an extremely short time and low temperature HPHT process compared to conventional electrical furnace sintering process.

• 한국분말재료학회지
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• 제21권6호
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• pp.447-453
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• 2014

Effect of oxygen content in the ultrafine tungsten powder fabricated by electrical explosion of wire method on the behvior of spark plasma sintering was investigated. The initial oxygen content of 6.5 wt% of as-fabricated tungsten powder was reduced to 2.3 and 0.7 wt% for the powders which were reduction-treated at $400^{\circ}C$ for 2 hour and at $500^{\circ}C$ for 1h in hydrogen atmosphere, respectively. The reduction-treated tungsten powders were spark-plasma sintered at $1200-1600^{\circ}C$ for 100-3600 sec. with applied pressure of 50 MPa under vacuum of 0.133 Pa. Maximun sindered density of 97% relative density was obtained under the condition of $1600^{\circ}C$ for 1h from the tungsten powder with 0.7 wt% oxygen. Sintering activation energy of $95.85kJ/mol^{-1}$ was obtained, which is remarkably smaller than the reported ones of $380{\sim}460kJ/mol^{-1}$ for pressureless sintering of micron-scale tungsten powders.

• 한국세라믹학회지
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• 제46권2호
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• pp.146-154
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• 2009

It is necessary to minimize the thickness of Ni inner electrode layer and to improve the coverage of inner electrode, for the purpose of developing the ultra high-capacity multi layered ceramic capacitor (MLCC). Thus, low temperature sintering of dielectric $BaTiO_3$ ceramic should be precedently investigated. In this work, the relationship between dielectric properties of MLCC and batch condition such as mixing and milling methods was investigated in the $BaTiO_3$(BT)-Dy-Mg-Ba system with borosilicate glass as a sintering agent. In addition, several chip properties of MLCC manufactured by low temperature sintering were compared with conventionally manufactured MLCC. It was found that low temperature sintered MLCC showed better DC-bias property and lower aging rate. It was also confirmed that the thickness of Ni inner electrode layer became thinner and the coverage of inner electrode was improved through low temperature sintering.

• 한국결정성장학회지
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• 제3권2호
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• pp.176-184
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• 1993

$Li_2O-Al_2O_3-SiO_2$계 유리조성에서, 특히 주결정상으로 $\beta$-spodumene을 석출시킬 수 있는 조성영역에서 $P_2O_5, TiO_2, ZrO_2$ 등을 첨가하여 용융한 후 소결법을 이용하여 이론밀도에 가까운 결정화 유리를 만들기 위한 최적 열처리 조건, 유리 분말의 입도 변화에 따란 영향과 그 때의 물성을 시차열분석, X-선 회절분석, 비중 측정, 열팽창 측정, 전자현미경 관찰 등을 통하여 연구하였다. $P_2O_5$를 첨가하여 소결법으로 결정화할 때 소결을 증진시키는 효과가 있었으며 9wt% 첨가한 경우가 가장 치밀한 것으로 나타났다. 최적의 열처리 조건은 $740^{\circ}C$에서 소결하여 치밀화를 시키고$ 950^{\circ}C$에서 결정화를 시켰을 때로서 상대밀도는 90% 이상이었으며 열팽창계수는 $-1{\times}10^{-7}/^{\circ}C$ 정도로서 부팽창인 것으로 나타났다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.347-351
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• 2007

The influence of compaction pressure and sintering temperature on the hydraulic cylinder block fabricated by powder metallurgy is investigated in this study. The cylinder block is powder compacted under various compaction pressures and sintered under various sintering temperatures, and its density and dimensions are measured to reveal the relation of the process condition with the product quality. Moreover, finite element analyses of the density distributions are conducted under the same conditions with the experiments and the predicted results are compared with the measured ones.

• 한국유체기계학회 논문집
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• 제17권5호
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• pp.72-77
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• 2014

Because of overload working condition of sintering cooler, the cooler fan often suffers the break or damage of rotor blade and fixing shaft. Therefore, internal flow characteristics of a steelworks sintering cooler fan by the duct shape of the cooler fan outlet, such as duct outlet opening ratio, duct height and dividing wall shape on the duct outlet flow pattern are examined in detail. The results show that relatively short duct wall height and attachment of dividing wall shape improves flow patterns considerably.

• 대한치과기공학회지
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• 제32권4호
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• pp.337-340
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• 2010

Purpose: This study was performed to compare sintering conditions for fabrication of porous Ti implant. Methods: The porous Ti implant samples were fabricated by sintering of spherical Ti powders in vacuum and atmosphere conditions. Surface morphology, composition and phase were analyzed by FE-SEM, EDX and XRD. Results: Sintered Ti implant in the vacuum consisted of particles connected in three dimensions by clear necking without excessive oxide layers. However, sintered Ti implant in atmosphere was formed excessive oxide layers with non-stoichiometric compounds. Conclusion: The porous Ti implant can be sintered in vacuum condition preferably.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.121-121
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• 2018

Copper is a promising electronic material due to low cost and high electrical conductivity. However, the oxidation problem in an ambient condition makes a crucial issue in practical applications. In here, we developed a simple and cost-effective Cu patterning method on a flexible PET film by combining a solution processable Cu nanoparticle patterning and a low temperature post-processing using acetic acid treatment, laser sintering process and acid-assisted laser sintering process. Acid-assisted laser sintering processed Cu electrode showed superior characteristics in electrical, mechanical and chemical stability over other post-processing methods. Finally, the Cu electrode was applied to the flexible electronics applications such as flexible and transparent heaters and touch screen panels.

• 한국세라믹학회지
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• 제44권7호
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• pp.354-357
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• 2007

The nitriding and post-sintering behavior of silicon powder compact containing sintering additives of 2.3 wt% and 7 wt% were investigated in this study. Regardless of the liquid phase content, elongated large grains of a typical morphology evolved in the post-sintered specimens. Phase analysis revealed a complete phase transformation into ${\beta}-Si_3N_4$ in both porous systems. Oxynitride second phases (mellilite) precipitated in the latter, while those were free in the former containing less amount of liquid phase. The post-sintering condition that yielded a favorable microstructure for a filter application was achieved when the specimens were soaked at $1800^{\circ}C$ for 2 h. It was found that the thermal conductivity of porous $Si_3N_4$ ceramics is dominated by the porosity more than this factor is influenced by the addition of $Al_2O_3$.