• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.1
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• pp.50-59
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• 2015

It is hard to restore and manage anterior teeth esthetically and functionally; because of peri-implantitis, not only hard and soft tissue problem such as alveolar bone resorption and interdental papilla loss but also esthetic problem caused by metal abutment exposure can occur. This case presents patients using customized abutment made of Co-Cr alloy that can be made by conventional casting and compensate the shortcomings of prefabricated titanium abutments, and cement-retained prosthesis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.6 s.165
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• pp.1011-1017
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• 1999

Electrolytic in-process dressing grinding technique which enables application of metal bond wheels with fine superabrasives in mirror surface grinding operations has developed. It is possible to make efficient precision machining of hard and brittle material such as ceramic and hard metal by the employment of this technique. However, in order to ensure the success of performances such as efficient machining, surface finish, and surface quality, it is important to sustain the insulating layer that has sharply exposed abrasives in wheel surface. Using AE(Acoustic Emission) sensor, this paper will show whether the insulating layer sustains stably or not in real grinding time. And by comparing AErms value and surface roughness their thresholds for stable electrolytic in-process dressing grinding will be determined.

• Journal of Powder Materials
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• v.13 no.5 s.58
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• pp.351-359
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• 2006

Ni based($Ni_{57}Zr_{20}Ti_{18}Si_2Sn_3$) bulk metallic glass(BMG) powders were produced by a gas atomization process, and ductile Cu powders were mixed using a spray drying process. The Ni-based amorphous powder and Cu mixed Ni composite powders were compacted by a spark plasma sintering (SPS) processes into cylindrical shape. The relative density varied with the used SPS mold materials such as graphite, hardened steel and WC-Co hard metal. The relative density increased from 87% to 98% when the sintering temperature increased up to $460^{\circ}C$ in the WC-Co hard metal mold.

• Journal of Powder Materials
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• v.18 no.3
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• pp.277-282
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• 2011

[ $LiCoO_2$ ] a cathode material for lithium rechargeable batteries, was prepared using recycled $Co_3O_4$. First, the cobalt hydroxide powders were separated from waste WC-Co hard metal with acid-base chemical treatment, and then the impurities were eliminated by centrifuge method. Subsequently, $Co_3O_4$ powders were prepared by thermal treatment of resulting $Co(OH)_2$. By adding a certain amount of $Li_2CO_3$ and $LiOH{\cdot}H_2O$, the $LiCoO_2$ was obtained by sintering for 10 h in air at $800^{\circ}C$. The synthesized $LiCoO_2$ particles were characterized by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) analysis.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.6
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• pp.594-598
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• 2015

The effects of Ni on the mechanical properties of WC-Xwt.%Ni-1.5wt.%Si-1.1wt.%$B_4C$ composite (X = 21.6, 23.6, 25.6 and 27.6 wt.%) were investigated in order to replace Co with Ni as the binder metal for hard materials based on WC-Co system. Using X-ray diffraction, optical microscopy, field-emission scanning electron microscopy results, the microstructure, pore distribution and grain size of the composites sintered at $1,150^{\circ}C$ were examined with different fraction (X = 21.6, 23.6, 25.6 and 27.6 wt.%) of binder metal Ni. The average WC grain size of the $WC-Ni-Si-B_4C$ composites was about $1{\mu}m$. The Rockwell hardness : A (HRA) and transverse rupture strength were about 88HRA and $110kgf/mm^2$, respectively. The obtained sample was bonded with SM45C at a temperature of $1,050^{\circ}C$. The thickness and mechanical properties of the bonded area were investigated with different dwell time at a bonding temperature of $1,050^{\circ}C$.

• Journal of Soil and Groundwater Environment
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• v.6 no.3
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• pp.21-29
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• 2001

Organobentonite modified with hexadecyltrimethylammonium (HDTMA) was used to quantify adsorption of heavy metals. Adsorption of cadmium and lead increased with increasing pH and soil/solution ratio. Based on these experiments, an optimal soil/solution ratio and an optimal pH was selected. Adsorption experiments with cadmium and lead were conducted to quantify adsorption selectivity on bentonite and organobentonite. Adsorption of heavy metals on organobentonite was slightly reduced relative to bentonite. Because of competition between cadmium and lead, adsorption of each metal was reduced due to the presence of the other. Adsorption selectivity of cadmium was higher than lead. This study used the principle of hard soft-acid-base (HSAB) to interpret adsorption.

• Tribology and Lubricants
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• v.37 no.2
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• pp.54-61
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• 2021

The effect of the sand blasting before TiAlN coating in the manufacture of WC hard metal alloy tips have been studied. For four different tips, according to the status of processing of the sand blasting and the coating, residual stress measurement by X-ray diffraction and several tests for mechanical properties have been conducted. The results suggest that there was no difference in static mechanical properties, such as hardness, surface roughness and elastic modulus, between two coatings. Furthermore, compressive residual stress was generated equally on their surfaces. Additionally, the compressive residual stress in substrate WC was found to increase greatly when subjected to sand blasting treatment. However, the compressive residual stress decrease after coating regardless of sand blasting treatment. Nevertheless, it is confirmed that the compressive residual stress generated in the coating after sand blasting is less than that in the non-sandblasting coating. This was attributed to the plastic deformation occurring in the WC substrate during coating after sand blasting. In contrast to the scratch test results, sand blasting was assumed to have a negative effect on the adhesion between the coating and substrate. This is because there is a high possibility of microcracks due to plastic deformation in the WC substrate under the coating after sand blasting.

• Journal of Dental Rehabilitation and Applied Science
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• v.30 no.1
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• pp.81-92
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• 2014

It is so hard to obtain optimal anterior esthetics in the implant prosthesis. This is not only because of hard and soft tissue problem such as alveolar bone resorption and interdental papilla loss but also because of prosthetic limitation related to marginal exposure of metal abutment and metal ceramics and low transillumination. In this case, guided soft tissue healing is obtained using a long term provisional restoration with soft and hard tissue augmentation or immediate implantation. Then, this healed tissue is transferred to final master model using a customized impression coping and the implant is restored with a customized zirconia abutment and a all ceramics. This case presents satisfying result esthetically and functionally.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.3
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• pp.196-201
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• 2000

It is very important not only to detect PD signal but also to locate PD source in power cable line including its accessories. In this paper, the PID localization technique using interruption of metal sheath of cable or accessory is described. By interruption of metal sheath, the polarity of PD pulse to be measured on each part can be compared. With this technique, the exact location of PD in the accessory which has some defects can be found. Although the 'Soft' interruption method, that is, cable sheath is divided by semi-conductive layer with the resistance of higher than 1 k$\Omega$, was used instead of 'Hard' interruption method, it is also possible to detect exact location of PD. This technique is considered to be very effective for detecting PD localization in the type test of cable and accessories.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.272-272
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• 2009

Screen-printing metal contact is typically applied to the solar cells for mass production. And metal paste is used widely for rear contact formation of silicon solar cells. However, Screen-printing solar cell metal paste contact has low aspect ratio, low accuracy, high resistivity, hard control of unclean process. In this paper is to develop resistivity of rear contact for silicon solar cells applications. 4-point prove result, This resistivity of rear contact by Al evaporation was measured about $3.56{\times}10^6{\Omega}{\cdot}cm$ less than screen printed solar cell about $52.6{\times}10^6{\Omega}{\cdot}cm$.