• Journal of Korea Foundry Society
• /
• v.21 no.4
• /
• pp.246-252
• /
• 2001

Variation in the microstructure of Mg-5%Al semi-solid slurry during isothermal heating was investigated in relation to initial microstructure, holding time, and holding temperature. Specimens with three different initial microstructures were isothermally heated. Dendritic structure in as-cast ingot was decomposed into solid globules in the semi-solid slurry during isothermal holding, while in the recrystallized specimens prepared by extrusion or rolling the size of solid particles was continuously increased during the heating. Effects of mold temperature and liquid fraction of slurry on the mold filling ability were also studied. Very thin section (0.4 mm) could be successfully filled up to 50 mm by 60% liquid slurry when the mold was heated to $600^{\circ}C$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1264-1265
• /
• 2006

Study about the feasibility and effect of high-energy ball milling on a specific Mg alloy under protection medium of alcohol was presented via comparing with conventional vacuum milling. More fine particles with wider powder size distribution but more irregular shape were shown of the powder milled under alcohol. No obvious oxide was revealed from the two kinds of Mg alloy powders with limited milling time. And since slip induced in a preferential direction, the (002) texture was formed in the Mg alloy powders at the initial stage of alcohol milling. More O and Fe contaminants were introduced into the powders milled under alcohol according to the EDS analysis.

• Journal of Korea Foundry Society
• /
• v.22 no.2
• /
• pp.82-88
• /
• 2002

Al-5.5Zn-2.5Mg-l.5Cu semi-solid slurry was prepared by cooling the liquid metal with a low superheat to a solid and liquid co-existing temperature. Relatively round solid particles could be obtained in the slurry through the simple process. The prepared slurry was deformed into the metallic mold by a press and the mechanical properties of obtained specimens were investigated. Mold filling ability of the alloy slurry was also investigated and compared with that of A356 alloy. Al-Zn-Mg-Cu alloy showed lower mold filling ability than A356 alloy probably because small amount of eutectic phase is present and the heat of fusion generated during solidification is smaller than that of A356 alloy.

• Membrane Journal
• /
• v.19 no.2
• /
• pp.113-121
• /
• 2009

Porous affinity chitosan and chitin membranes with good mechanical strength and high protein binding capacity were prepared by using silica particles as porogen. The maximum binding capacity of affinity chitosan membrane for BSA protein is 21.8mg/mL, and that of affinity chitin membrane for lysozyme enzyme is 26.1mg/mL. Chromatographic separations of BSA and lysozyme proteins using the porous affinity chitosan and chitin membranes were performed with change of the flow rate, loading amount and concentration of protein loading solutions. Protein eluted amount and binding yield were calculated from the filtration chromatograms consisted of loading/washing/elution sequences. Protein binding amount and yield were increased with decreasing of flow rate, increasing of loading amount and concentration of protein loading solutions. Those results suggest that the porous chitosan and chitin membranes prepared by using silica particles as porogen are suitable in affinity filtration chromatography for large scale separation of proteins.

• Journal of Environmental Health Sciences
• /
• v.17 no.1
• /
• pp.67-73
• /
• 1991

In this study are investigated to the optimal coagulation conditions and magnetite which was used as coagulation-aids. To accomplish this study, analysis of water quality, removing tubidity and SS from wastewater were measured with jar-tester. The results were obtained that waste water requires 10g magnetite, 100mg aluminum sulfate, and pH valuse was 6~9.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1032-1032
• /
• 2006

• Nuclear Engineering and Technology
• /
• v.52 no.9
• /
• pp.2078-2084
• /
• 2020

Magnesium oxide (MgO) and Zinc oxide (ZnO) nanoparticles (NPs) have been successfully synthesized by solid-solid reaction method. The structural properties of ZnO and MgO NPs were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results indicated a formation of pure MgO and ZnO NPs. The mean diameter values of the agglomerated particles were around to be 70 and 50 nm for MgO and ZnO NPs, respectively using SEM analysis. Further, a wide-range of nuclear radiation shielding investigation for gamma-ray and fast neutrons have been studied for Magnesium oxide (MgO) and Zinc oxide (ZnO) samples. FLUKA and Microshield codes have been employed for the determination of mass attenuation coefficients (μ_m) and transmission factors (TF) of Magnesium oxide (MgO) and Zinc oxide (ZnO) samples. The calculated values for mass attenuation coefficients (μ_m) were utilized to determine other vital shielding properties against gamma-ray radiation. Moreover, the results showed that Zinc oxide (ZnO) nanoparticles with the lowest diameter value as 50 nm had a satisfactory capacity in nuclear radiation shielding.

• Journal of the Korean Society for Heat Treatment
• /
• v.33 no.5
• /
• pp.219-225
• /
• 2020

The objective of this study was to investigate the tensile properties and thermal conductivities of Mg9.3%Al alloy in as-cast state and heat-treated state consisting of fully discontinuous precipitates (DPs), respectively. The fully DPs microstructure was obtained by solution treatment at 405℃ for 24 h, followed by furnace cooling to RT. The as-cast alloy showed a partially divorced eutectic β(Mg₁₇Al₁₂) phase particles formed along the α-(Mg) cell boundaries. The DPs had various apparent (α+β) interlamellar spacings, which is related to different transformation temperatures during the furnace cooling. The DPs microstructure exhibited better tensile strength than the as-cast one, resulting from the higher value of elongation in response to its more homogeneous microstructure. It is noticeable that the DPs microstructure had 12.4% higher thermal conductivity in average than the as-cast one between RT and 200℃. The XRD analyses revealed that the lower Al concentration in the α-(Mg) matrix may well be responsible for the better thermal conductivity of the DPs microstructure.

• Korean Journal of Materials Research
• /
• v.16 no.6
• /
• pp.373-376
• /
• 2006

[ $Ba(Mg_{1/3}Ta_{2/3})O_3$ ] nanoparticles were synthesized in water solution under mild temperature and pressure conditions by precipitation from $Ba(NO_3),\;Mg(NO_3)_2{\cdot}6H_2O\;and\;TaCl_5$ with aqueous potassium hydroxide. The average size and distribution of the synthesized $Ba(Mg_{1/3}Ta_{2/3})O_3$ nanoparticles were below 100 nm and broad, respectively. The phase of synthesized particles was crystalline reacted at $170^{\circ}C$ for 4 h. The characterization of $Ba(Mg_{1/3}Ta_{2/3})O_3$ nanoparticles were studied using XRD, SEM, and TEM.

• Korean Journal of Metals and Materials
• /
• v.50 no.6
• /
• pp.463-468
• /
• 2012

A 71.5 wt%Mg-23.5 wt%Ni-5 wt%$Fe_2O_3$ (Mg-23.5Ni-$5Fe_2O_3$) sample was prepared by a quite simple process, reactive mechanical grinding, and its hydriding and dehydriding properties were then investigated. The reactive mechanical grinding of Mg with Ni and $Fe_2O_3$ is considered to facilitate nucleation and shorten the diffusion distances of the hydrogen atoms. After the hydriding-dehydriding cycling, the Mg-23.5Ni-$5Fe_2O_3$ sample contained $Mg_2Ni$ phase. Expansion and contraction of the hydride-forming materials (Mg and $Mg_2Ni$) with the hydriding and dehydriding reactions are also considered to increase the hydriding and dehydriding rates of the mixture by forming defects and cracks leading to the fragmentation of the particles. The temperature dependence of the hydriding rate of the sample is discussed.