• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.05a
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• pp.38-46
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• 1999

Dispersion strengthened Cu alloys have been manufactured by spray forming and also by reactive spray forming, followed by hot extrusion of the spray deposited billets. The size of dispersed particles in the reactive spray formed alloy was much finer than that in the spray formed alloy. That was because the dominant chemical reaction between Ti and B had occurred in Cu-Ti-B alloy melt in spray forming while it had occurred after deposition of droplets in reactive spray forming. The yield strength of the reactive spray formed alloy was greater than that of the spray formed alloy. To understand the mechanism responsible for this observed strengthening, the yield strength of two Cu alloys were analyzed using the dislocation pile-up model and Orowan mechanism, which were fairly consistent with the experimental results. Increase in yield strength of reactive spray formed alloy relative to spray formed alloy was largely attributed to nano-scale TiB dispersoids.

• Proceedings of the Korean Fiber Society Conference
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• 1999.04a
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• pp.57-62
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• 1999

• Polymer Science and Technology
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• v.9 no.3
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• pp.193-199
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• 1998

• Proceedings of the Korean Society of Rheology Conference
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• 2006.06a
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• pp.157-160
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• 2006

• Clean Technology
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• v.12 no.4
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• pp.198-204
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• 2006

The modification of biodegradable polycaprolactone was accomplished by reactive extrusion with various contents of free radical initiator. Reaction conditions were in the temperature range of $130^{\circ}C$ to $180^{\circ}C$ with initiator contents of 0.1, 0.3, 0.5 and 1.0 wt%. To characterize the modified polycaprolactone (PCL), molecular weight was measured by gel permeation chromatography(GPC) and thermal, mechanical and rheological properties as well as biodegradability were measured. The modified PCL (MPCL) with 1% of initiator showed ca. 20% increase in crystallinity and ca. 50% increase in tensile modulus. Also, a large increase in rheological properties such as complex viscosity, storage and loss modulus was observed. The biodegradability of most MPCL was higher than that of virgin PCL.

• Journal of Powder Materials
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• v.4 no.4
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• pp.243-251
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• 1997

Engine valve-shaped TiAl-Mn intermetallics containing 43.5 to 47.5at%Al (Mn/Al=0.036) are successively fabricated by reactive sintering the elemental powder mixtures near-net shaped by extrusion and die forging. A duplex structure consisted of lamellar grains and equiaxed $\gamma$ grains is developed for all compositions, and the areal fraction of the lamellar grains(or equiaxed $\gamma$ grains) decreases (or increases) with increasing Al content. As Al content increased, the elongation increases with accompanying decrease in yield strength and ultimate tensile strength at both room temperature and 80$0^{\circ}C$. This indicates that the suitable composition is Ti-45at%Al-1.6at%Mn in considering the balance of ambient and elevated tensile properties. The reactive-sintered Ti-45Al-1.6Mn alloy shows superior oxidation resistance not only to the plasma arc melted one but also to the heat resistance steel STR35(representative exhaust valve head material for automotive engine). The reactive-sintered Ti-45Al-1.6Mn alloy coated with an oxidizing scale exhibits a better wear resistance than induction hardened martensitic steel STR11(representative exhaust valve tip material for automotive engine).

• Polymer(Korea)
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• v.33 no.4
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• pp.358-363
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• 2009

Maleic anhydride-grafted polypropylene has been widely used to improve the interfacial interaction between the components in PP/polar polymer blends and PP/filler composites and to maximize the physical properties and thermal properties. In this paper. the maleic anhydride (MAH)-grafted polypropylene (co-PP) was fabricated through reactive extrusion process with di-cumyl peroxide (DCP) as an initiator. The grafting degree of MAH depending on the contents of DCP and MAH was investigated by FT-IR spectra and chemical titration. The grafting degree increased with increasing MAH concentration and also showed maximum value at 0.06 wt% of DCP concentration. Melt flow index (MFI) of the grafted copolymer was increased with increasing the contents of MAH. The DSC and TGA analysis data indicate the melting temperature and thermal degradation of PP depending on the grafting degree of MAH.

• Journal of the Mineralogical Society of Korea
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• v.31 no.4
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• pp.227-234
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• 2018

In this work, we have prepared the reactive media with the pyrophyllite based using ceramic extrusion process. The characteristics of pyrophyllite were analyzed using XRD, XRF, DSC-TGA and Zeta-potential analysis. The study of pyrophyllite based ceramic reactive media were conducted under various roasting temperature (500 to $1,300^{\circ}C$) conditions. With increasing the roasting temperature, strength was increased but BET surface area was decreased. Thermally treated pyrophyllite were analyzed by means of weight loss and structural changes as detected by using XRD, DSC-TGA and SEM analysis. Pyrophyllite primarily transforms to pyrophyllite dehydroxylate after roasting at $1,000^{\circ}C$. Pyrophyllite dehydroxylate transforms to mullite and cristobalite at $1,300^{\circ}C$. This study demonstrates that pyrophyllite could be used as a reactive media for ceramic support layers from Permeable Reactive Barriers.

• Food Science and Biotechnology
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• v.14 no.4
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• pp.479-486
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• 2005

Arabinoxylan, a complex polysaccharide in cereal cell walls, has recently received research attention as a biological response modifier. The immunomodulating effect of arabinoxylans from rice bran (AXrb) was studied using a combined process of extrusion and commercial hemicellulase treatment in order to elucidate the augmentation mechanism of cell-mediated immunity in vitro. The cytotoxicity of mouse spleen lymphocytes against YAC-1 tumor cells was significantly enhanced by treatment with AXrb at $10-100\;{\mu}g/mL$. In an attempt to investigate the mechanism by which AXrb enhance NK cytotoxicity, we examined the effect of AXrb on cytokine production by spleen lymphocytes. Culture supernatants of the cells incubated with AXrb were collected and analyzed for IL-2 and IFN-${\gamma}$ synthesis by ELISA. IL-2 and IFN-${\gamma}$ production were increased significantly. These results suggest that AXrb may induce Th1 immune responses. Macrophages play an important role in host defenses against tumors by killing them and producing secretory products, which protect against bacterial, viral infection and malignant cell growth. AXrb were examined for their ability to induce secretory and cellular responses in murine peritoneal macrophages. When macrophages were treated with various concentrations ($10-100\;{\mu}g/mL$) of AXrb, AXrb induced tumoricidal activity, as well as increasing phagocytosis and the production of NO, $H_2O_2$, TNF-${\alpha}$, IL-$1{\beta}$, and IL-6. These results indicate that reactive oxygen species, reactive nitrogen species, and inflammatory cytokines are likely to be the major mediators of tumoricidal activity in AXrb-treated macrophages. Therefore, AXrb may be useful in cancer immunotherapy and it is anticipated that AXrb obtained using extrusion and subsequent enzyme treatment can be used as an ingredient in nutraceuticals and cereal-based functional food.

• Polymer(Korea)
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• v.31 no.3
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• pp.269-272
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• 2007

In this study, we investigated the effects of electron beam irradiation on the rheological properties of PLA for enhancing processability. The electron beam was irradiated onto the pure PLA, chemically modified PLA by reactive extrusion, and PLA containing functional monomer. The complex viscosity and log G'vs. log G" plot among dynamic rheological properties were chosen for comparison. The complex viscosity of irradiated pure and chemically modified PLA decreased significantly due to de-gradation of PLA molecules with increasing the E-beam dosages. Complex viscosity of irradiated PLA with functional monomer showed maximum value at moderate dosage, while at high dosage the complex viscosity was decreased by a prolonged irradiation.