• 한국분말재료학회지
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• 제29권2호
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• pp.99-109
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• 2022

Powder flowability is critical in additive manufacturing processes, especially for laser powder bed fusion. Many powder features, such as powder size distribution, particle shape, surface roughness, and chemical composition, simultaneously affect the flow properties of a powder; however, the individual effect of each factor on powder flowability has not been comprehensively evaluated. In this study, the impact of particle shape (sphericity) on the rheological properties of Ti-6Al-4V powder is quantified using an FT4 powder rheometer. Dynamic image analysis is conducted on plasma-atomized (PA) and gas-atomized (GA) powders to evaluate their particle sphericity. PA and GA powders exhibit negligible differences in compressibility and permeability tests, but GA powder shows more cohesive behavior, especially in a dynamic state, because lower particle sphericity facilitates interaction between particles during the powder flow. These results provide guidelines for the manufacturing of advanced metal powders with excellent powder flowability for laser powder bed fusion.

• 한국도로학회논문집
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• 제14권4호
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• pp.37-49
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• 2012

PURPOSES : This study is to investigate the fundamental properties of limestone added cement concrete for application of pavement. METHODS : As the production of Portland cement causes environmental problems, engineers have sought more environment-friendly concrete construction materials. Limestone powder can be used for concrete as a partial replacement of Portland cement. One of the great applications of limestone powder added cement concrete might be a cement concrete pavement since the concrete pavement consumes massive quantity of Portland cement. Experimental variables were different replacement level of limestone powder by 0% to 25% with 5% increment. Before hardening of fresh concrete, setting time and plastic shrinkage characteristics were investigated in addition to other basic properties. Properties of hardened concrete included compressive, tensile and flexural strength as well as drying shrinkage. RESULTS : The addition of limestone powder did not significantly affect the properties of fresh concrete. Strength deceased as the replacement ratio increased and when the replacement ratio was greater than 10% decrease rate increased. CONCLUSIONS : It was found that the partial replacement of the limestone powder to cement in pavement materials can be positively considered as its mechanical properties show comparable performance to those normal concrete.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.242-243
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• 2005

In this study, (La,Sr)$MnO_{3+\delta}$ powder used cathode material for SOFC was synthesized with precursor by GNP and the properties of powder, crystal phase, electric properties and deoxidization properties with precursor were investigated. The synthesis powder was prepared when oxidant/fuel mole and pH were 1 and 1, respectively and the synthesis powder was synthesized by GNP method using nitrate solution or oxide solution as precursor. Deoxidization peak of the nitrate solution was appeared lower temperature than the oxide solution, at $450^{\circ}C$. In this result, synthesis (La,Sr)$MnO_{3+\delta}$ powder using nitrate solution with Mn excess was suitable cathode material for SOFC due to had higher deoxidization properties. Also synthesis (La,Sr)$MnO_{3+\delta}$ powder according to precursor had difference electrical conductivity according to influence sintering density and crystal phase with precursor. Specially, the synthesis method and starting material had effect on deoxidization properties for SOFC.

• 한국분말재료학회지
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• 제27권4호
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• pp.300-304
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• 2020

In this paper, a durability study is presented to enhance the mechanical properties of an Fe-Si-Al powder-based magnetic core, through the addition of graphite. The compressive properties of Fe-Si-Al-graphite powder mixtures are explored using discrete element method (DEM), and a powder compaction experiment is performed under identical conditions to verify the reliability of the DEM analysis. Important parameters for powder compaction of Fe-Si-Al-graphite powder mixtures are identified. The compressibility of the powders is observed to increase as the amount of graphite mixture increases and as the size of the graphite powders decreases. In addition, the compaction properties of the Fe-Si-Al-graphite powder mixtures are further explored by analyzing the transmissibility of stress between the top and bottom punches as well as the distribution of the compressive force. The application of graphite powders is confirmed to result in improved stress transmission and compressive force distribution, by 24% and 51%, respectively.

• 펄프종이기술
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• 제38권2호
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• pp.22-34
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• 2006

To improve the mechanical properties of Hanji, starches such as maize, konyaku, and wheat powders were added at various concentrations in the manufacturing processes of Hanji. The effect of starches on the physical properties of Hanji was as follows. Filling rates of surface of hanji were increased with the increase of the concentration of starch. Hanji surface were completely filled at the 3.0% konyaku treatment. Konyaku powder showed higher filling rates than maize and wheat powder. The breaking length was increased with the increase of filling rates. Konyaku powder showed the highest breaking length: Tear index of hanji treated with maize and wheat powder were a little improved but that of hanji treated with konyaku powder were a little decreased compared to non-treated hanji. In conclusion, starch treatment showed the increase of the breaking length, but no effect on tear index.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.91-92
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• 2006

Metallic foams have a combination of attractive properties such as high specific mechanical properties and good energy absorption characteristics. This paper presents the properties of steel foam sandwiches produced using powder metallurgy approach. Metallic powder, solid polymeric binder and a foaming agent are dry-mixed and molded into the desired shape. The molded powder mix is then heat-treated to foam, debind and sinter the material. The resulting material has an open cell structure with high porosity. The structure and properties of sandwiches specimens produced with the process are presented and discussed.

• 열처리공학회지
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• 제9권1호
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• pp.62-68
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• 1996

In order to establish making process of water atomized iron powder for powder metallurgy, effect of heat treatment condition on change of powder properties and impurities was investigated at each tempeature of $850{\sim}950^{\circ}C$. The results are as follows. Particle morphology of iron powder changed slightly from sphercial type to irregular type and the amount of fine particle decreased more and more with increasing of heat treatment time at each temperature. The flow rate and apparent desity of iron powder also decreased due to particle coalescence in order of $850^{\circ}C$, $950^{\circ}C$, $900^{\circ}C$. Those powder Properties became to decrease particularly at $900^{\circ}C$ in alpha iron region. On the other hand, residual carbon and oxygen contents in iron powder decreased extremely with increasing of heat treatment temperature and time.

• 한국세라믹학회지
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• 제43권12호
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• pp.846-851
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• 2006

This paper discuss the adsorption and fluidity properties of recycled cement powder with different hydration hysteresis and particle size. Reactivity of hydrated fine powder was negligible low. Therefore, the adsorption and fluidity properties with super-plasticizer for hydrated recycled cement powder was very important for using additive material. Adsorption amount of super-plasticizer was increased by the finer hydrated recycled cement powder addition. And the fluidity of hydrated recycled cement powder was very poor than un-hydrated cement powder. To Improve the fluidity of hydrated recycled cement powder, PC super-plasticizer is the more effective than NS super-plasticizer.

• 한국분말재료학회지
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• 제25권5호
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• pp.415-419
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• 2018

Porous metals demonstrate not only excessively low densities, but also novel physical, thermal, mechanical, electrical, and acoustic properties. Thus, porous metals exhibit exceptional performance, which are useful for diesel particulate filters, heat exchangers, and noise absorbers. In this study, SUS316L foam with 90% porosity and $3,000{\mu}m$ pore size is successfully manufactured using the electrostatic powder coating (ESPC) process. The mean size of SUS316L powders is approximately $12.33{\mu}m$. The pore properties are evaluated using SEM and Archimedes. As the quantity of powder coating increases, pore size decreases from 2,881 to $1,356{\mu}m$. Moreover, the strut thickness and apparent density increase from 423.7 to $898.3{\mu}m$ and from 0.278 to $0.840g/cm^3$, respectively. It demonstrates that pore properties of SUS316L powder porous metal are controllable by template type and quantity of powder coating.

• 한국분말재료학회지
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• 제31권1호
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• pp.43-49
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• 2024

In this study, a core-shell powder and sintered specimens using a mechanically alloyed (MAed) Ti-Mo powder fabricated through high-energy ball-milling are prepared. Analysis of sintering, microstructure, and mechanical properties confirms the applicability of the powder as a sputtering target material. To optimize the MAed Ti-Mo powder milling process, phase and elemental analyses of the powders are performed according to milling time. The results reveal that 20 h of milling time is the most suitable for the manufacturing process. Subsequently, the MAed Ti-Mo powder and MoO₃ powder are milled using a 3-D mixer and heat-treated for hydrogen reduction to manufacture the core-shell powder. The reduced core-shell powder is transformed to sintered specimens through molding and sintering at 1300 and 1400℃. The sintering properties are analyzed through X-ray diffraction and scanning electron microscopy for phase and porosity analyses. Moreover, the microstructure of the powder is investigated through optical microscopy and electron probe microstructure analysis. The Ti-Mo core-shell sintered specimen is found to possess high density, uniform microstructure, and excellent hardness properties. These results indicate that the Ti-Mo core-shell sintered specimen has excellent sintering properties and is suitable as a sputtering target material.