• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.130-133
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• 2009

$Cu_2ZnSnSe_4$(CZTSe) is one of the promising materials for the solar cell due to its abundant availability in the nature. In this study, we report the fabrication of CZTSe thin film by Pulsed Laser Deposition(PLD) method using quaternary compound target on sodalime glass substrate. The quaternary CZTSe compound target was synthesized by solid state reaction method using elemental powders of Cu, Zn, Sn and Se. Powders were milled in high purity ethanol using zirconia ball with mixed size of 1 and 3 mm at the same proportions for 72 hours milling time. The structural, chemical and mechanical properties of the synthesized CZTSe powders were investigated prior to the deposition process. The CZTSe compound powder, and $500^{\circ}C$ of sintering temperature shows the best properties for PLD target. Results show that the as-deposited CZTSe thin films with the precursors by PLD have a composition near-stoichiometric.

• Journal of Biosystems Engineering
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• v.20 no.3
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• pp.262-274
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• 1995

A rice mill pilot plant was designed and developed in the basis of the simulation results on the mill plants. The performance of the developed rice mill plant was evaluated, and the simulation model on the mill system was validated with the experimental data in the mill plant. The results of this study were as followings : 1. A rice mill pilot plant with the capacity of 0.5 t/h was designed and developed. 2. The hulled ratio of the mill plant was 87.3%, and the milled rice recovery and the head rice recovery of the cleaned rice were 74% and 87% , respectively. The degree of milling of the cleaned rice was 10.6% with a high polish. The intensity of the cleaned rice appeared high compared with that of the milled rice in the analysis of whiteness test using an image processing system. 3. The bottleneck, processing time, and production amount of the developed mill system almost coincided with those of the simulation of the rice mill plant. The developed simulation model of the rice mill plant was proven to be applicable to the design of a rice mill plant through experiments.

• Journal of Powder Materials
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• v.9 no.3
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• pp.167-173
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• 2002

A new approach to produce nanostructured WC/Co composite powders by a mechanochemical process was made to improve the mechanical properties of advanced hardmetals. Homogeneous spherical W-Co salt powders were made by spray drying of aqueous solution from ammonium metatungstate($(NH_4)_6(H_2W_{12}O_{40})\cdo4H_2O$,AMT) and cobalt nitrate hexahydrate (Co(NO$_3$)$_2$.6$H_2O$). spray dried W-Co salt powders were calcined for 1 hr at $700^{\circ}C$ in atmosphere of air. The oxide powder was mixed with carbon black by ball milling and this mixture was heated with various temperatures and times in $H_2$. The $WO_3/CoWO_4$ composite oxide powders were obtained by calcinations at $700^{\circ}C$. The primary particle size of W/Co composite oxide powders by SEM was 100 nm. The reduction/carburization time decreased with increasing temperatures and carbon additions. The average size of WC particle carburized at $800^{\circ}C$ by TEM was smaller than 50 nm.

• Journal of Powder Materials
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• v.22 no.3
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• pp.208-215
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• 2015

Fe-TiC composite powders were fabricated by planetary ball mill processing. Two kinds of powder mixtures were prepared from the starting materials of (a) (Fe, TiC) powders and (b) (Fe, $TiH_2$, Carbon) powders, respectively. Milling speed (300, 500 and 700 rpm) and time (1, 2, and 3 h) were varied. For (Fe, $TiH_2$, Carbon) powders, an in situ reaction synthesis of TiC after the planetary ball mill processing was added to obtain a homogeneous distribution of ultrafine TiC particulates in Fe matrix. Powder characteristics such as particle size, size distribution, shape, and mixing homogeneity were investigated.

• Journal of Powder Materials
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• v.23 no.3
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• pp.195-201
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• 2016

Composite materials consisting of pure aluminum matrix reinforced with different amounts of graphite particles are successfully fabricated by mechanical ball milling and spark plasma sintering (SPS) processes. The shrinkage rates of the composite powders vary with the amount of graphite particles and the lowest shrinkage value is observed for the composite with the highest amount of graphite particles. The current slopes of time increase with increase in the amount of graphite particles whereas the current slopes of temperature show the opposite trend. The highest thermal conductivity is achieved for the composite with the least amount of graphite particles. Therefore, the thermal properties of the composite materials can be controlled by controlling the amount of the graphite particles during the SPS process.

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.449-454
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• 2015

The fabrication process of zirconia gel-casting was studied to obtain dense zirconia on a large scale or with complicated shapes. As an experimental parameter, two different particle sizes ($0.1{\mu}m$ and $0.7{\mu}m$) of zirconia powder were applied to the gel-casting process. The viscosity behavior of slurries incorporating 40 vol% of zirconia powder was examined as a function of the dispersant content and the solid load to determine the optimum dispersion conditions. In addition, the gelation time with an initiator, the de-binding behavior, and the main factors affecting densification were examined. The densification of the gel-casted zirconia green body depended on the mixing ratio between the monomer and the dimer and on the zirconia particle size. A green body with a small particle size of $0.1{\mu}m$ showed less densification, with a relative density of 93%. This may be due to the excess number of bubbles created through interactions between the larger particle surface and polymer additives during the ball-milling process.

• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.887-892
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• 1999

The inner crack-like pore with controlled amount of Ca impurity in the high purity alumina single crystal sapphire had been created by micro-fabrication technique which includes ion implanation photo-lithography Ar ion milling and hot press technique. The crack-like pores in two-hour hot pressed specimen were extremely stable even after heat treating at 1,80$0^{\circ}C$ for 5 hours almost no healing was observed. But the crack-like pores in one-hour hot pressed specimen at 1,30$0^{\circ}C$ were healed by heat treatment and the amount of healing was increased with the heat treatment time and temperature and the amount of Ca addition. The edges of crack-like pore parallel to <1100> direction in (001) basal plane were stable but the edges normal to this direction in (00101) plane <1120> direction were unstable to facetting This means that the surface energy of alumina along the <1100> direction in (0001) basal plane in much lower than <1120> direction.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.5 no.1
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• pp.34-43
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• 1996

In nowdays many dental CAD/CAM system were developed. Among those only Cerec and Celay were used globally as clinical application. Celay is a machinable ceramic system that is capable of milling inlays, onlays, and veneers from prefabricated industrial ceramic blocks(Vita Celay Blanks). The advatages of Celay are to simplify the manufactures and to save the processing time. For esthetics In-Ceram Alumina bridges were introduced into maxillary anterior restoration. They have a high strength, a high translucency and an excellent marginal adapation. But the laboratory processes are very difficult and complicated. So the construction of In-Ceram Alumina bridge combined with celay system was desgined. The patient is a 28 year old age male. The chief complain is missing of maxillary left central incisor. He wants to restore anterior bridge for esthetically. The Alumina bridge framework was constructed easily by celay system. Glass ilfiltration was occurred. After that, vitadura-${\alpha}$porcelain build up was occurred by conventional method. The translucency of In-Ceram Alumina 3 unit bridge revealed to be superior to that of porcelain fused to metal bridge. So we report it with clincal case and literature reviews.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.26 no.2
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• pp.68-83
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• 2017

With the increasing popularity of dental CAD / CAM, the kinds of materials that can be used and the range that can be utilized are also increasing. One of the biggest advantages of a dental CADCAM is that you can make a final prosthesis with one visit, but in case of zirconia or a complex aesthetic prosthesis, it is often difficult to make it in one day. In this case, temporary PMMA material can be used to provide a temporary crown with aesthetic and functional properties to the patient and can be used as a test crown or template for the final prosthesis. And if you are with a 5-axis milling machine in a clinic, you can make a temporary crown precisely to a large extent in a short time. In this article, various applications and clinical cases of PMMA temporary crown in the clinic will be presented.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.3
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• pp.26-33
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• 2003

The term 'High Speed Machining' has been used for many years to describe end milling with small diameter tools at high rotational speeds, typically 10,000-100,000rpm. The process was applied in the aerospace industry for the machining of light alloys, notably aluminum. In recent year, however, the mold and die industry has begun to use the technology for the production of components, including those manufactured from hardened tool steels. With increasing cutting speed used in modern machining operation, the thermal aspects of cutting become more and mole Important. It not only directly influences in rate of tool weal, but also affects machining precision recognized as thermal expansion and the roughness of the surface finish. Hence, one needs to accurately evaluate the rate of cutting heat generation and temperature distributions on the machining surface. To overcome the heat generation, we used to cutting fluid. Cutting fluid plays a roles in metal cutting process. Mechanically coupled effectiveness of cutting fluids affect to friction coefficient at tool-workpiece interface and cutting temperature and chip control, surface finish, tool wear and form accuracy. Through this study, we examined the behavior of heat generation in high-speed machining and the cooling performance of various cooling methods.