• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.967-968
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• 2006

This research reports for the successful consolidation of $Al_2O_3$ powder with retained ultra-fine structure using MPC and sintering. Measurements in the consolidated $Al_2O_3$ bulk indicated that hardness, fracture toughenss, and breakdown voltage have been much improved relative to the conventional polycrystalline materials. Finally, optimization of the compaction parameters and sintering conditions will lead to the consolidation of $Al_2O_3$ nanopowder with higher density and even further enhanced mechanical properties.

• Journal of Hydrogen and New Energy
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• v.33 no.4
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• pp.343-352
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• 2022

Co/Al₂O₃ nanopowder was used as a catalyst to investigate the effect of catalyst support, reduction temperature, sodium borohydride (NaBH₄) concentration, sodium hydroxide (NaOH) concentration, and reaction temperature on the characteristics of NaBH₄ hydrolysis. The Co/Al₂O₃ nanopowder showed a high catalytic activity among various catalysts. Catalyst reduction at 250℃ exhibited a relatively good activity. The activity decreased with an increase in the NaBH₄ concentration. Conversely, the activity increased and then decreased with an increase in the NaOH concentration. Additionally, the activity increased with an increase in the reaction temperature. The value of apparent activation energy was 40.81 kJ/mol, which was lower than the other Co-based catalysts. Thus, Co/Al₂O₃ nanopowder catalyst can be widely used for NaBH₄ hydrolysis owing to its superior catalytic activity.

• Journal of Powder Materials
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• v.15 no.1
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• pp.37-45
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• 2008

This article presents the challenges toward the successful consolidation of $Al_2O_3$ nanopowder using magnetic pulsed compaction (MPC). In this research the ultrafine-structured $Al_2O_3$ bulks have been fabricated by the combined application of magnetic pulsed compaction (MPC) and subsequent sintering, and their properties were investigated. The obtained density of $Al_2O_3$ bulk prepared by the combined processes was increased with increasing MPC pressure from 0.5 to 1.25 GPa. Relatively higher hardness and fracture toughness in the MPCed specimen at 1.25 GPa were attributed to the retention of the nanostructure in the consolidated bulk without cracks. The higher fracture toughness could be attributed to the crack deflection by homogeneous distribution and the retention of nanostructure, regardless of the presence of porosities. In addition, the as consolidated $Al_2O_3$ bulk using magnetic pulsed compaction showed enhanced breakdown voltage.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2005.11a
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• pp.102-102
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• 2005

• Journal of the Korean Society for Heat Treatment
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• v.22 no.3
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• pp.149-154
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• 2009

Dense $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ composite was consolidated from mechanically synthesized powders by pulsed current activated sintering method within 1 min. $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ powder was synthesized from 3CuO and 2FeAI using the high energy ball milling. Dense $5Cu_{0.6}Fe_{0.4}-Al_2O_3$ with relative density of up to 95% was produced under simultaneous application of a 80 MPa pressure and the pulsed current. Mechanical properties and grain size of the composite were investigated.

• Korean Journal of Metals and Materials
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• v.50 no.6
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• pp.449-454
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• 2012

Nanopowder of FeAl and $Al_2O_3$ was synthesized from FeO and Al powders by high energy ball milling. Using the pulsed current activated sintering method, the nanocystalline $Al_2O_3$ reinforced FeAl composite was consolidated within two minutes from mechanically synthesized powders. The advantage of this process is that it allows very quick densification to near theoretical density and prohibits grain growth in nanostuctured materials. The grain size, sintering behavior and hardness of sintered $FeAl-Al_2O_3$ composite were investigated.

• Korean Journal of Metals and Materials
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• v.47 no.6
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• pp.344-348
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• 2009

Dense $4.25Co_{0.53}Fe_{0.47}-Al_{2}O_{3}$ composite was simultaneously synthesized and consolidated by pulsed current activated combustion method within 2 min from mechanically activated powders. Consolidation was accomplished under the combined effects of a pulsed current and mechanical pressure. Dense $4.25Co_{0.53}Fe_{0.47}-Al_{2}O_{3}$ with relative density of up to 96% was produced under simultaneous application of 80 MPa pressure and the pulsed current. Fracture toughness and hardness of the composite are $6MPa{\cdot}m^{1/2}$ and $570kg/mm^{2}$ respectively.

• Korean Journal of Metals and Materials
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• v.47 no.11
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• pp.754-758
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• 2009

Dense $5Cu_{0.6}Fe_{0.4}-Al_{2}O_{3}$ composite was consolidated from mechanically synthesized powders by high frequency induction heating method within 2 min. Consolidation was accomplished under the combined effects of a induced current and mechanical pressure. Dense $5Cu_{0.6}Fe_{0.4}-Al_{2}O_{3}$ with relative density of up to 95% was produced under simultaneous application of a 80 MPa pressure and the pulsed current. Fracture toughness and hardness of the composite are $7.6MPa{\cdot}m^{1/2}$ and $844kg/mm^{2}$ respectively.

• Journal of Powder Materials
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• v.16 no.2
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• pp.91-97
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• 2009

Nanopowders of $Co_3O_4$ and FeAl were fabricated by high energy ball milling. Dense 4.25 $Co_{0.53}Fe_{0.47}-Al_2O_3$ composite was simultaneously synthesized and consolidated by high frequency induction heated combustion method within 2 min from mechanically activated powders. Consolidation was accomplished under the combined effects of a induced current and mechanical pressure of 80 MPa.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.131-135
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• 2011

In this study, we fabricated the HDPE and ${\alpha}-Al_2O_3$ composites with PE-g-MA as a function of the ${\alpha}-Al_2O_3$ nanopowder weight ratios. The electron beam irradiations on HDPE/${\alpha}-Al_2O_3$ composites were carried out over a range of absorbed doses from 20 to 200 kGy to make three-dimensional network structures. The mechanical properties were characterized using UTM for confirming the changes of the flexural strength and tensile strength. It was observed that the mechanical properties of HDPE were enhanced by the addition of ${\alpha}-Al_2O_3$. However, the strength of the 5 wt% ${\alpha}-Al_2O_3$ added composites decreased due to the nano-powder aggregation. The mechanical properties of composites were increased as increasing the electron beam irradiation up to 150 kGy. We believed that the electron beam irradiated HDPE/${\alpha}-Al_2O_3$ composites can be a good candidate for a variety of industrial applications.