• Proceedings of the PSK Conference
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• 2003.10b
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• pp.234.2-234.2
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• 2003

Recently, the need for ultra-fine particles, especially nano-sized particles has increased in the fields preparing raw powders such as pharmaceutical additive and high value added products in the Nano-Technology processes. Therefore, the research in ultra-fine grinding is very important, especially, in nanometer grinding. In the previous paper, a series of wet grinding experiments using grinding aids using a stirred ball mill have been performed on grinding rate constant based on grinding kinetics. (omitted)

• Clean Technology
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• v.10 no.3
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• pp.139-148
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• 2004

The recovery of stainless steel fiber by removing cutting oil from grinding swarf, which is classified as specified wastes, was investigated. Swarf loaded with grinding oil was regenerated by supercritical carbon dioxide. And, the effects of temperature(313.15K-323.15K), pressure(10MPa-30MPa) on regeneration efficiency were studied. Regeneration effiency was increased as the pressure was increased. Also, at the same pressure, the experiments at higher temperature were more efficient for regeneration. The experiment results was predicted by applying a one-parameter mathematical model assuming linear desorption kinetics. The predicted value showed good agreement with experimental data.

• Journal of the Mineralogical Society of Korea
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• v.20 no.2 s.52
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• pp.135-145
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• 2007

The needs for the ultra fine particles have been increased in preparation field of raw powders such as fine ceramics and high functional products. In this study, a series of wet grinding experiments were carried out on inorganic powders such as calcite, pyrophyllite and talc by a stirred ball mill. The particle size distribution of ground products of each test material fur a given grinding time was found to be expressed by the grinding rate (selection function) which was obtained from the grinding kinetics analysis. The median diameter decreased from 6.49 to $0.47{\mu}m$ in calcite, and decreased from 3.91 to $1.14{\mu}m$ in pyrophyllite. However, in talc, median diameter was decreased a little bit from 10.30 to $6.67{\mu}m$. The grinding rate changing on calcite and pyriphyllite were similar at the same conditions. However, in the case of talc, it was observed that the grinding rate was not increased compared to other samples.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.36.1-36.1
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• 2007

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

• Advanced Composite Materials
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• v.18 no.2
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• pp.187-195
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• 2009

Much attention has been paid to the processing of inorganic whisker, especially calcium carbonate whisker, which can be used as reinforcement materials of polymer composite due to its low price. Unfortunately, the present synthesis technique of calcium carbonate whisker starts from calcinations of limestone, which involves high energy consumption and furthermore is a highly environment polluting reaction. In this report, needle-like aragonite was synthesized with a reversible solution reaction from limestone without calcination. Optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to characterize the morphology and crystal structure of intermediates as well as that of the product, aragonite. GCC (grinding calcium carbonate) powder was dissolved in an aqueous solution of magnesium sulfate with reflux and air flush. EDTA titration was used to evaluate reaction rate of the dissolution. A kinetics equation of the dissolution reaction was constructed, which displayed second-order kinetics with respect to the concentration of magnesium sulfate. A rate constant of $0.0015\;l^{-3}{\cdot}mol^{-1}{\cdot}h^{-1}$ was obtained. The dissolution reaction gave fiber-like magnesium hydroxide sulfate and gypsum crystal. Then needle-like aragonite with a length of $9.13\;{\pm}\;1.02\;{\mu}m$ and an aspect ratio of $5.64\;{\pm}\;1.37$ was synthesized from the dissolution product with $CO_2$ bubbling at $70^{\circ}C$.

• Resources Recycling
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• v.33 no.2
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• pp.37-45
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• 2024

Molybdenum is used in various industries because of its high heat and corrosion resistance. It was selected as a critical mineral in Korea. However, there have been recent challenges in production because of the increased depth and decreased grade of molybdenum veins. Consequently, it is necessary to enhance the effectiveness of the molybdenum beneficiation process. In this study, a basic evaluation of beneficiation characteristics was conducted to enhance the effectiveness of the domestic molybdenum ore beneficiation process. The properties of the beneficiation process were assessed using mineralogical analysis, work index, and flotation kinetics. The results revealed that the allowable particle size of the molybdenum ore for liberation was ~100 ㎛. In addition, the work index was calculated to be 14.57 kWh/t. The operating conditions in the flotation units were achieved by determining the optimal flotation time for each process based on flotation kinetics. Finally, the characteristics of molybdenum ore beneficiation provided in this study can be utilized to diagnose the grinding and flotation processes of large-scale molybdenum beneficiation plants.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.721-727
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• 2002

In order to overcome trade-off among compositions, process and properties of the glasses with high PbO-base composition for PDP Rib, we studied glass crystallization and crystallization kinetics by Differential Thermal Analysis(DTA). Glass powder was obtained through melting/cooling/grinding, with 3 wt%TiO2 addition for the crystal nucleation and growth in $62PbO-19B_2O_3-10SiO_2-9(Al_2O_3-K_2O-BaO-ZnO)$(in wt%) composition glass. This powder was heat-treated for 1 to 10 h at $445^{\circ}C$ for nucleation. DTA measurements were performed to obtain the crystallization peak with $5∼25^{\circ}C/min$ heating rates. DTA crystallization peak temperature increased with increasing the heating rate and decreased with increasing the heating time. Because the Avrami parameter (n) was approximately 1, the surface crystallization occurred. The maximum nucleation time was 2 h.