• Korean Journal of Metals and Materials
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• v.48 no.12
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• pp.1097-1102
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• 2010

Silver coated copper powders were prepared by a chemical reduction method with controlling the deposition process variables such as the feeding rate of the silver ionic solution and concentration of the reductants at room temperature. The characteristics of the products were evaluated by scanning electron microscope (SEM), X-ray diffractometer (XRD), atomic absorption spectrophotometer (AA) and a 4 probe resistivity measurement system. The optimum condition of the preparation of Ag coated Cu powders was at 0.05 M of potassium sodium tartrate and 2 ml/min of the feeding rate of the silver ionic solution. Our method successfully produced dense, uniform, and well-dispersed Ag coated Cu powder of $2{\sim}2.5{\mu}m$ witha silver layer of 100~200 nm. Additionally, we found that thespecific resistivity of the 30 wt.% Ag coated Cu powder was similar to that of pure silver, so that the composite powder could be used as an alternative electromagnetic shielding material for silver.

• Journal of the Korea Institute of Building Construction
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• v.4 no.4
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• pp.87-94
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• 2004

As the bentonite is main material to prevent from collapse of drilling hole at underground excavation works, it is increased using quantity on construction industry day by day. But, the discarded bentonite that is over using at underground excavation works is caused various enviromental trouble as soil and water pollution est. Therefore, this study aims to propose a foundamental report for pozzolan reaction of discarded Bentonite powder by heat-treatment and cooling as concrete mineral admixture. To find out pozzolan reaction ability of discarded Bentonite powder by indirect cooling & cooling using of water after heat-treatment, the experiments are excuted flow test & compressive strength on age of mortar using discarded Bentonite powder. As a result of this study, discarded Bentonite powder can be utilized as concrete mineral admixture by heat-treatment and especially, pozzolan reaction ability of discarded Bentonite powder is superior to the situation of 600℃. 60min ＆amp; cooling using of water.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2005.11a
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• pp.87-88
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• 2005

Ultra-fine copper powders with particle size about 150 nm were synthesized from copper hydroxide slurry by wet method using hydrazine as reduction agent and several sur factants at below $80^{\circ}C$. The particle size distribution and dispersion of synthesized powders as function of temperature, feeding rate of reduction and especially, sur factants were character ized by XRD, BET, PSA and SEM by this process.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.420-421
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• 2006

In the present study, ultrafined Zr-V-Fe based alloy powder prepared by a plasma arc discharge process with changing process parameters. The chemical composition of synthesized powder was strongly influenced by the process parameters, especially the hydrogen volume fraction in the powder synthesis atmosphere. The synthesized powder had an average particle size of 50 nm. The synthesized Zr-V-Fe based particles had a shell-core structure composed of metal in the core and oxidse in the shell.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.23.2-29
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• 2003

As the bentonite is main material to prevent from collapse of drilling hole at underground excavation works, the quantity of bentonite is increasingly used on construction industry day by day. But, the discarded bentonite that is excessively used at underground excavation works causes various environmental trouble such as soil and water pollution etc. Therefore, this study aims to propose a foundamental report about pozzolan reaction of discarded Bentonite powder by heat-treatment and cooling as concrete mineral admixture. To find out the strength-development properties of mortar with discarded Bentonite powder by indirect cooling & cooling using of water after heat-treatment, the experiments such as flow test, and compressive strength test on curing age of mortar are excuted. As a result of this study, discarded Bentonite powder can be utilized as concrete mineral admixture by heat-treatment and especially, the strength-development properties of mortar mixing with discarded Bentonite powder is superior to the situation of $600^{\circ}C$.60min-cooling using of water.

• Journal of Powder Materials
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• v.17 no.5
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• pp.373-378
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• 2010

Nanostuctured TiAl powder was synthesized by high energy ball milling. A dense nanostuctured TiAl was consolidated using pulsed current activated sintering method within 2 minutes from mechanically synthesized powders of TiAl and horizontally milled powders of Ti+Al. The grain size and hardness of TiAl sintered from horizontally milled Ti+Al powders and high energy ball milled TiAl powder were 35 nm, 20 nm and 450 kg/$mm^2$, 630 kg/$mm^2$, respectively.

• Journal of the East Asian Society of Dietary Life
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• v.23 no.6
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• pp.713-722
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• 2013

The purpose of this study was to examine the effects of dietary green tea powder supplementation on bone metabolism in streptozotocin-induced diabetic rats. Thirty-two male Sprague-Dawley rats (body weight $210{\pm}3g$) were divided into two groups, diabetic and non-diabetic groups. Each group was randomly divided into two subgroups which were fed with the control and 1% green tea powder diets. The serum and urine concentrations of calcium and phosphorus were determined. Serum osteocalcin and ALP and urinary DPD crosslinks value were measured in order to monitor bone formation and resorption. Bone mineral density (BMD) and bone mineral content (BMC) were estimated using PIXImus in the spine and femur. Body weight gain and FER were lower in the diabetic group than in the non-diabetic group regardless of diets. The serum concentration of calcium and phosphorus were not changed among all groups. Urinary calcium and phosphorus excretion were higher in the diabetic group than in the non-diabetic group regardless of diets; however, they were not significantly different by green tea powder intake. Serum alkaline phosphatase (ALP) was increased in the diabetic group than in thenon-diabetic group. Further, there were no significant differences in serum osteocalcin and urinary deoxypyridinoline crosslinks value among all groups. The levels of spine and femur bone mineral density of the diabetic group were significantly lower than that of the non-diabetic group. Within the diabetic group, spine BMD was significantly higher in rats fed with the green tea powder diet than in rats fed the control diet. Therefore, this study suggests that green tea powder has a beneficial effect on bone health, although it is not directly applicable to humans.

• Journal of Powder Materials
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• v.14 no.1 s.60
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• pp.56-62
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• 2007

Getter property of nano-sized metallic powders was evaluated as a possible candidate for the future getter material. For the purpose, Ti powders of about 50 nm were prepared by electrical wire explosion. Commercial Ti powders of about 22 micrometer were tested as well for comparison. The room-temperature hydrogen-sorption speed of nano-sized Ti powders was $1.34\;L/sec{\cdot}cm^{2}$ which was more than 4 times higher than that of micron-sized ones. The value is comparable to or even higher than those of commercial products. Its sorption speed increases with activation temperature up to $500^{\circ}C$ above which it deteriorates due to low-temperature sintering effect of nano-sized particles.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.4
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• pp.227-239
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• 2021

A practical and effective method of X-ray powder diffraction analysis was investigated for quantitative analysis of the mineral content of natural samples. Sample mounting experiments were conducted to select the best randomly oriented powder sample mount. A comparative experiment was also made between a reference intensity ratio (RIR) method, which compares a single peak intensity with standard material, and the Rietveld method, which calculates a full X-ray diffraction pattern, to search for the effective method of mineral quantification. In addition, samples containing amorphous minerals were quantitatively analyzed by the Rietveld method and the efficiency was reviewed. As a result of the study, the optimal random orientation could be reached by the side mounting method. The Rietveld method using the full pattern of X-ray diffraction was more suitable for mineral quantitative analysis, rather than the RIR method using a specific peak. However, either method could depend on the analyst's experience in addition to analytical technique. Moreover, amorphous minerals can be quantitatively analyzed by the Rietveld method, and the analysis results make the geological analysis possible.

• Journal of the Korea Institute of Building Construction
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• v.2 no.3
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• pp.139-146
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• 2002

As the bentonite is main material to prevent from collapse of drilling hole at underground excavation works, it is increased using quantity on construction industry day by day. But, the discarded bentonite that is over using at underground excavation works is caused various environmental trouble as soil and water pollution est. This study aims to propose a foundamental report for pozzolan reaction of discarded Bentonite powder by heat-treatment and cooling as concrete mineral admixture. To find out pozzolan reaction ability of discarded Bentonite powder by indirect cooling & cooling using of water after heat-treatment, the experiments are excuted Phenolphtalein test, setting test, pH test and the analysis by X-ray diffractor. As a result of this study, discarded Bentonite powder can be utilized as concrete mineral admixture by heat-treatment and especially, pozzolan reaction ability of discarded Bentonite powder is superior to the situation of 50$0^{\circ}C$~$700^{\circ}C$, 60min.