• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.41-42
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• 2006

Small powder size is very useful in achieving detailed structures. STS 316 nanopowders with an average diameter of 100 nm and $5{\mu}m$ were utilized to produce feedstock. The mixing behavior of the feedstock indicated that the nanoparticle feedstock produced the highest mixing torque at various powder loading compared to the micropowder feedstock. The nanoparticles feedstocks showed that elastic properties are dominant in flow behavior and high viscosity. Conversely the micropowders feedstocks, viscous properties are dominant in flow behavior and less viscosity, nanopowders feedstock perform lower flow activation energy than feedstock with bigger particles.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.223-224
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• 2006

In this paper, rheological characteristics of Metal Injection Moulding (MIM) feedstock using locally binder of palm stearin are presented. The feedstock consisted of 316L-grade stainless steel powder with three different particle sizes and the binders comprise palm stearin and polyethylene. The viscosity of MIM feedstock at different temperatures and shear rates was measured and evaluated. Results showed that, the feedstock containing palm stearin exhibited suitable rheological properties and suitable to produce a homogeneous feedstock that is favorable for injection molding process.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.495-496
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• 2006

The kneading process and formulations of feedstock obviously affect the quality of MIM products. In the present work, the rheological behaviour of the composite MIM feedstock, metal matrix (Cu) with few additions of ceramic powders $(Al_2O_3)$, was measured by a self-designed/manufactured simple capillary rheometer. Experimental results show that the distribution between powders and binder is more uniformly when blending time increased. Though high powder loading will increase the feedstock viscosity, the fluidity reveals relatively stable through the load curves of extrusion. Besides, the temperature-dependence of viscosity of the feedstock approximately follows an Arrehnius equation. Basing on Taguchi's method, the kneading optimization conditions and the rheological model of the feedstock were established, respectively.

• Journal of Welding and Joining
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• v.25 no.4
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• pp.35-41
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• 2007

In kinetic spraying process, the critical velocity is an important criterion which determines the deposition of a feedstock particle onto the substrate. In other studies, it was experimentally and numerically proven that the critical velocity is determined by the physical and mechanical properties and the state of materials such as initial temperature, size and the extent of oxidation. Compared to un-oxidized feedstock, oxidized feedstock required a greater kinetic energy of in-flight particle to break away oxide film during impact. The oxide film formed on the surface of particle and substrate is of a relatively higher brittleness and hardness than those of general metals. Because of its physical characteristics, the oxide significantly affected the deposition behavior and critical velocity. In this study, in order to investigate the effects of oxidation on the deposition behavior and critical velocity of feedstock, oxygen contents of Al feedstock were artificially controlled, individual particle impact tests were carried out and the velocities of in-flight Al feedstock was measured for a wide range of process gas conditions. As a result, as the oxygen contents of Al feedstock increased, the critical velocity increased.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.4
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• pp.447-461
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• 2016

Recently, the Renewable Fuel Standard(RFS) has been commenced from July 31, 2015 in the New and Renewable Energy Act for expanding the supply of renewable energy and reduction of national GHG target in Korea. The biodiesel is only a means of implementation for the RFS, therefore the biodiesel supply expansion is important for fulfilling the RFS obligation policy. The major key points of the biodiesl supply are expanding domestic feedstocks due to the over 60% dependence on foreign feedstock and reducing the price of feedstock because of the over 70% occupation of feed stock price in the biodiesl production cost. Therefore, we estimated actual amount of potential feedstocks which are possible to use for biodiesl production in Korea and investigated technical and political improvements for expanding biodiesl. For estimating a potential feedstocks, first selected the potential biodiesl feedstocks by investigating the status of global biodiesl feedstocks and then analyzed the possible potential amount of each feedstock by surveying the generation situations, the distribution structures and the technical level.

• Journal of Powder Materials
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• v.22 no.1
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• pp.1-5
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• 2015

Powder injection molding is an important manufacturing technology to mass produce superalloy components with complex shape. Injection molding step is particularly important for realizing a desired shape, which requires much time and efforts finding the optimum process condition. Therefore computer aided engineering can be very useful to find proper injection molding conditions. In this study, we have conducted a finite element method based simulation for the spiral mold test of superalloy feedstock and compared the results with experimental ones. Sensitivity analysis with both of simulation and experiment reveals that the melt temperature of superalloy feedstock is the most important factor for the full filling of mold cavity. The FEM based simulation matches well the experimental results. This study contributes to the optimization of superalloy powder injection molding process.

• Journal of Powder Materials
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• v.9 no.4
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• pp.251-260
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• 2002

In the viscosity measurement of PIM feedstock, slip correction methods require a number of experiments and produce a high level of error. In this study, a rotational rheometer with a parallel-discs configuration having different surface roughness was tried to minimize the effect of the slip phenomenon. Disc surface was prepared in 3 different roughness conditions - a smooth and 2 roughened surfaces. Results with the roughened surfaces were compared with the results obtained with a slip correction method. Relationship between powder characteristics such as size and shape and a surface roughness of the disc was examined for feedstock of 4 different powders with a same binder. As results, the effect of the slip phenomenon could be sufficiently minimized on the roughened surface in most cases. However, the effect of the slip phenomenon could not be sufficiently minimized for feedstock of a round-particular-shape powder and in the case of very narrow gap size.

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.630-638
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• 2010

The present investigation has been performed on the mixing behavior and microstructural development during fabrication of Fe micro-nano powder feedstock for a micro-powder injection molding process. The mixing experiment using a screw type blender system was conducted to measure the variations of torque and temperature during mixing of Fe powder-binder feedstock with progressive powder loading for various nano-powder compositions up to 25%. It was found that the torque and the temperature required in the mixing of feedstock increased proportionally with increasing cumulative powder loading. Such an increment was larger in the feedstock containing higher content of nano-powder at the same powder loading condition. However, the maximum value was obtained at the nano-powder composition of not 25% but 10%. It was owing to the 'roller bearing effect' of agglomerate type nano-powder acting as lubricant during mixing, consequently leading to the rearrangement of micro-nano powder in the feedstock. It is concluded that the improvement of packing density by rearrangement of nano-powders into interstices of micro-powders is responsible for the maximum powder loading of about 71 vol.% in the nano-powder composition of 25%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.679-680
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• 2010

• 한국환경농학회:학술대회논문집
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• 2011.07a
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• pp.290-290
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• 2011