• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.282-283
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• 2006

Densification behavior of nano-agglomerate powder during pressureless sintering of Fe-Ni nanopowder was investigated in terms of diffusion kinetics and microstructural development. To understand the role of agglomerate boundary for sintering process, densification kinetics of Fe-Ni nano-agglomerate powder with different agglomerate size was investigated. It was found that activation energy for densification was lower in the small-sized agglomerate powder. The increase in the volume fraction of inter-agglomerate boundary acting as high diffusion path might be responsible for the enhanced diffusion process.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.5
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• pp.527-536
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• 2010

Although the bubble-floc agglomerate floated and formed the float layer on the surface of the water in the DAF process, after inducing in the thickening tank a part of the bubble-floc agglomerate come up again to the surface and the other is settled at the bottom of the tank. The bubble-floc agglomerate divided into two group as the scum on the surface and the sludge of the bottom gives rise to operational troubles for the thickening process. In order to find out the cause of break-up and the effective thickening method for sludge from the DAF process, the composition of the bubble-floc agglomerate was investigated and a series of flotation experiments carried out. There was no difference of composition between the scum on the surface and the sludge of the bottom in the thickening tank. The coagulation was not effective to improve the trouble that the bubble-floc agglomerate divided into the scum and the sludge. It was estimated that for the bubble-floc agglomerate of thickening tank the trouble was caused by not the change or the difference of chemical composition but whether the bubble-floc agglomerate hold bubbles. Furthermore, for the effective thickening of sludge from the DAF process, it is required an additional flotation applied the AS ratio depending upon the solid concentration of sludge as the operation parameter.

• Elastomers and Composites
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• v.54 no.2
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• pp.156-160
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• 2019

The changes in the dispersion of carbon black in liquid polyisoprene under shear flow with time have been investigated by time-resolved ultra small-angle X-ray scattering (USAXS) method. The analyses of USAXS profile immediately after the start of shear flow clarified that the aggregates of carbon black with a mean radius of gyration of 14 nm and surface fractal dimension of 2.5 form the fractal network structure with mass-fractal dimension of 2.9. After the application of the shear flow, the scattering intensity increases with time at the observed whole entire q region, and then the a shoulder appears at $q=0.005nm^{-1}$, indicating that the agglomerate is broken and becomes smaller by shear flow. The analysis by the Unified Guinier/Power-law approach yielded several characteristic parameters, such as the sizes of aggregate and agglomerate, mass-fractal dimension of agglomerate, and surface fractal dimension of the primary particle. While the mean radius of gyration of the agglomerate decreases with time, the mean radius of gyration of the aggregate, mass fractal dimension, and surface fractal dimension don't change with time, indicating that the aggregates peel off the surface of the agglomerate.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.101-108
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• 1996

In this study, WC-l7wt% Co composite powder for thermal spray was fabricated by spray drying method. The agglomerated composite powder had spheroidal morphology and the particle size distribution was 20~60${\mu}{\textrm}{m}$. WC and Co were distributed homogeneously. However, the strength of the spray-dried agglomerate was low due to the pores within the agglomerate. Therefore, the spray-dried agglomerate was broken down during HVOF thermal spray and the microstructure was inhomogeneous with many pores within the coating layer. And the decomposition of WC to W and $W_{6}$ $C_{2.54}$ was accelerated. The strength and flowability of the agglomerate were greatly improved by sintering heat treatment(110$0^{\circ}C$, 1 hour, hi atmosphere), and then the coating layer showed dense and homogeneous microstructure with well-developed splats. The hardness of the coating layer was H $v_{300}$ = 1072.2.2.

• Journal of Powder Materials
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• v.20 no.1
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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.

• Food Science of Animal Resources
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• v.18 no.1
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• pp.50-56
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• 1998

Scanning electron microscopic appearance of infant milk formula indicated that mostly agglomerate with few or more diverse number of particles and also apple like as well as typical feature of drying in raw milk. Small particle of infant milk formula become agglomerate progressively. Some sample represent crystalline rectangular among the globular agglomerates which seem to be a different composites or those of solubility. Some sample showed the irregular porosity at central sec-scanning electron microscopic study between Korea and European products.

• Journal of Environmental Science International
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• v.5 no.5
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• pp.593-603
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• 1996

A dual-porosity filmed agglomerate model for the porous cathode of the molten carbonate fuel has been investigated to predict the cell performance. A phenomenological treatment of molecular, kinetic and electrode parameters has been given. The major physical and chemical phenomena being modeled include mass transfer, ohmic losses and reaction kinetics at the electrode- electrolyte interface. The model predicts steady-state cell performance, given the above conditions that characterize the state of the electrode. Quasi-linearization and finite difference techniques are used to solve the coupled nonlinear differential equations. Also, the effective surface area of electrode pore was obtained by mercury porosimeter. The results of the investigation are presented in the form of plots of overpotential vs. current density with varied the electrode material, gas composition and mechanism. The predicted polarization curves are compared with the empirical data from 1 c$m^2$ cell. A fair correspondence is observed.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.4 no.1
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• pp.61-67
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• 2011

Influence of hexamethyldisilazane(HMDS) in post processing technique by using n-butanol azeotropic distillation on the luminescence properties of YAG:Ce nanophosphor were studied. The organic solvent(n-butanol) azeotropic distillation which prevent powders from conglobation since lager molecules decrease the surface tension and more complete replace the residual water in the precipitate. HMDS that had larger molecules than that of n-butanol was added in azeotropic distillation. The phosphor synthesized from n-butanol azeotropic distillation exhibited lower agglomerate and better photoluminescence properties than that from HMDS added heterogeneous azeotropic distillation.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.158-163
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• 1996

Attritor mill로 분쇄처리된 $UO_2$-30mo1%CeO2$_2$(masterblend) 분말을 turbular mixer와 attritor mill 에서 $UO_2$와 혼합, $UO_2$-5mol%CeO$_2$ 분말을 만들고, 이를 통해 분말처리 및 소결분위기가 각 성형체의 소결거동에 미치는 영향을 연구하였다. $UO_2$-30mo1%CeO$_2$ 분말을 attritor mill로 1 시간동안 분쇄하면 평균 분말크기는 3.7 $\mu\textrm{m}$ 이었다. Turbular mixer에서 만들어진 $UO_2$-5mol%CeO$_2$ 분말이 H$_2$ 및 Ar-4%H$_2$ 분위기에서 소결되면, 분말처리 방법에 따라서 소결밀도는 각각 10.07-10.11, 9.81-9.85 g/㎤이었다. 이러한 방법으로는 masterblend 분쇄처리 과정에 만들어진 agglomerate 는 소결이 거의 이루어지지 않아서 소결체내에 그대로 잔존되었다. Agglomerate는 그 내부에 균열이 생성되어 있었고, 또한 $UO_2$ 지지내의 확산도 방해하여 기지내부에도 큰 기공들이 많이 분포하였다. 희석혼합을 turbular mixer 대신 attritor mill에서 하게되면, 밀도는 H$_2$ 및 Ar-4%H$_2$ 분위기에서 각각 10.54, 10.39 g/㎤ 이었으며, 결정립크기는 5, 9.5 $\mu\textrm{m}$ 이었다. 이 경우에는 소결체내에 agglomerate가 거의 잔존하지 않았다.

• Journal of Powder Materials
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• v.15 no.4
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• pp.271-278
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• 2008

Sintering behavior of iron nanopowder agglomerate compact prepared by slurry compaction method was investigated. The Fe nanopowder agglomerates were prepared by hydrogen reduction of spray dried agglomerates of ball-milled $Fe_2O_3$ nanopowder at various reduction temperatures of $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$, respectively. It was found that the Fe nanopowder agglomerates produced at higher reduction temperature have a higher green density compact which consists of more densified nanopowder agglomerates with coarsed nanopowders. The sintering behavior of the Fe nanopowder agglomerates strongly depended on the powder packing density in the compact and microstructure of the agglomerated nanopowder. It was discussed in terms of two sintering factors affecting the entire densification process of the compact.