• Journal of Korean Society for Atmospheric Environment
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• v.18 no.5
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• pp.411-417
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• 2002

The purpose of this study is to evaluate the emission reduction characteristics depending on the formation of the catalyst which influences the development of the diesel oxidation catalyst (DOC) suitable for small-sized diesel engines. We also attempted to suggest the feasibility of it as an after-treatment device. The reduction efficiency of DOC for CO and HC was proportional to the contents of precious metals, and the particulate matter (PM) has been reduced as much as 53∼59%. The reduction rate of soluble organic fraction (SOF) by DOC attachment revealed 100%. The composition of sulfate in PM increased from 3%, 7∼11% by installation of DOC. It is described that increase of sulfate contributed to the production of PM. This result also showed that the SOF and sulfate have trade-off relationship.

• The Journal of Korean Academy of Prosthodontics
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• v.23 no.1
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• pp.145-154
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• 1985

To study the effect of the vent and dense surface of the phophate-bonded investment on the castability of a non-precious alloy used in PFM restoration, one-ended polypropylene straw patterns of 0.15mm thick, 5mm radius. 10mm-high were cast with Vera Bond. The following results were obtained. 1. Thin patterns could be cast completely with a non-precious alloy. 2. No difference in the castability was found among the patterns with vent, chill vent and with out vent. 3. Dense surface of the phosphate-bonded investment had no effect on the cast ability of a nonprecious alloy.

• Bulletin of the Korean Chemical Society
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• v.16 no.4
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• pp.321-325
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• 1995

Adsorption mechanisms of diisobutyl dithiophosphinate (DIBDTPI) and diisobutyl monothiophosphinate (DIBMTPI) on gold and gold-silver alloys (80:20 and 50:50) have been studied. The adsorption mechanisms on gold-silver alloys can be explained by the EC mechanism involving an electron transfer step and a chemical reaction step. Thus, the adsorption should be controlled by the E of the electrochemical oxidation of the electrode involved and the pK of the metal collector complex. Both di- and mono- thiophosphinate adsorb on 50:50 Au-Ag alloy at lower potential than on 80:20 Au-Ag alloy surface. There are no significant differences between the reactivities of DIBDTPI and DIBMTPI with precious metals except that the dithio- compound can be oxidized to dimer on gold at high potentials, while the monothio- homologue cannot. In this regard, DIBDTPI may be a better surface active reagent for pure gold than DIBMTPI.

• Applied Chemistry
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• v.15 no.2
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• pp.137-140
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• 2011

Excellent active and stable platinum catalyst fuel cells currently being used as a catalyst. However, because of the high price of platinum catalyst, such as non-precious catalyst has been studied by a variety of fuel cell catalysts. In this study, Co/ PANi//CNT composite catalyst after synthesis through various heating process was to increase the activity of the catalyst. At 700℃ showed the best catalytic activity, using a composite catalyst was to be used as cathode electrodes in fuel cell.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.1
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• pp.9-22
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• 1994

Porcelain and resin are widely used in esthetic dentistry. In the field of esthetic dentistry, the color and color stability of prosthetic materials are very important in esthetics. In this study, porcelain and resin with the same color were used to veneer on the 3 different metal alloys. Color was evaluated by the CIE $L^*a^*b^*$ system. The purpose of this study was evaluated the cole, difference and cole, stability of the specimens, according to the veneered materials and types of metal alloys. Specimens were divided into 6 groups as follows ; Group 1; Porcelain on the precious metal alloy Group 2; Porcelain on the semiprecious metal alloy Group 3; Porcelain on the nonprecious metal alloy Group 4; Resin on the precious metal alloy Group 5; Resin on the semiprecious metal alloy Group 6; Resin on the nonprecious metal alloy The results obtained were as follows; 1. In porcelain specimens, $L^*$ values showed no significant difference and $a^*$ value of group 2 was lower than that of groups 1, 3 and $b^*$ value of group 2 was higher than that of groups 1, 3. The ${\Delta}E^*ab$ values between group 1-2, group 2-3 were higher than 1.5. 2. In resin specimens. $L^*$ value of group 6 was lower than that of groups 4, 5, $a^*$ value of group 4 was higher than that of group 6, $b^*$ value of group 4 was higher than that of groups 5, 6. The ${\Delta}E^*ab$ values between group 4-5, group 5-6 were higher than 1.5, and between group 4-6 was higher than 3.0. 3. Comparing with veneered materials, $L^*$ flues of porcelain were higher than that of resin. 3. Comparing with veneered materials, $L^*$ values of porcelain were higher than that of resin. In semiprecious metal alloy, $a^*$ values of porcelain were lower than that of resin. In semiprecious and nonprecious metal alloy, $b^*$ values of porcelain were higher than that of resin. The ${\Delta}E^*ab values were higher than 6.0. 4. The color stability of resin specimen was relatively inferior to porcelain specimen.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.12
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• pp.2244-2248
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• 2008

High intensity metal halide discharge lamp performance, specifically the generated luminous flux and light color content, depends critically on the arc tube design. Factors influencing the design and consequent lamp efficacy include : lamp size, geometry, arc tube composition, fill chemistry, electrode design and excitation modes. Shaping of Polycrystalline Alumina(PCA) can be realized by conventional ceramic processes. Several processes are applied nowadays. Well-known in the ceramic high pressure field for decades are the pressing and the extrusion method. Newly developed slurry and precious forming technologies give the one-body seamless tubes, which improve thickness uniformity and lighting performance. Now, we reported some optical properties with different arc tube structures of ceramic metal halide lamps.

• Resources Recycling
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• v.11 no.6
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• pp.3-11
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• 2002

Recently, waste printed circuit board (PCB) has significantly increased in its amount due to the rapid development of electronic industries. Since several kinds of noxious materials and also valuable metals are contained in it, the waste PCB is in an urgent need of recycling for the dual purposes for the prevention of environmental pollution and recovery of valuable resources. Also, the catalyst which equipped in the exhaust pipes of automobiles to reduce emission of air pollutants contains precious met-als so that their recovery from the waste auto-catalysts is required. In this study, the recovery of valuable metals from waste PCB and auto-catalyst by arc furnace melting process has been investigated, which is known to be very stable and suitable f3r less production of pollutants due to its high operating temperature. The effect of the kind of flux on the recovery of precious metals was examined by using quicklime, converter slag, and copper slag as the flux. In addition, the influence of direct and alternating current and the applying direction of direct current has been investigated. It was observed that using converter or copper slag as a flux was more desirable for a higher efficiency in the precious metal recovery compared with quicklime. For the effect of current, application of direct current taking the bottom as a negative pole generally showed a better efficiency for the extraction of valuable metals from waste PCB, which was also observed for the case of waste auto-catalyst. The average recovery of precious metals from both wastes by arc furnace melting process was very high, which was up to in the range of 95～97%.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.2
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• pp.155-166
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• 1992

In dentistry, precious metal alloys are, mainly due to economic factors, increasingly displaced by alternatives containing Ni-Cr-Co. There are some reports where hypersensitive reactions to Ni-Cr-Co alloys are presented and discussed. The reactions reported vary from mucosa contact stomatitis to generalized dermatitis without any oral mucosal reaction. The purpose of this study was to investigate the incidence of nickel, chrome, cobalt and copper, and to know whether subjects with positive skin reaction to nickel would also demonstrate adverse intraoral reaction to a non-precious metal nickel. The patch tests were performed in 81 subjects(male 39, female 42) and nickel sulfate 5% aq., potassium bichromate 0.5% at., cobalt chloride 2% aq., & copper sulfate 1% aq., were used for test allergens. And then the intraoral tests were performed in 16 subjects, 8 subjects with positive allergic skin reaction to nickel and 8 subjects with negative allergic skin reaction. A pure metallic nickel plate was attached to the buccal side of the upper second premolar. The results are as follows : 1. The frequency of nickel sensitivity was 9.9% (2 men, 6 women), cobalt was 4.9% (1 man, 3 women), and chrome was 2.5% (2 men) respectively and there was no positive reaction to copper 2. The positive reactions were 8 of 23 (34.8%) with a history of jewelry allergic reactions and 3 of 58 (5.1%) without a history of jewelry allergic reactions. 3. Three of 8 subjects with positive skin reaction. gave reactions to the metal plates.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.475-488
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• 1996

The opaque porcelain layer of porcelain-fused-to-metal(PFM) restoration is critical for the success of PFM restoration because it is the first layer placed over the treated alloy. But, the methods of opaquing technique have not been confirmed. Usually, the one layer method and two layer method have been used for the application of opaque porcelain. In the past, alloys with porcelain veneers which have been used successfully have contained various precious metals. Recent increase in the cost of precious metals stimulates considerable interest in nonprecious alloys. Although nickel-chromium alloys and nickel-chromium-beryllium alloys have been widely used, the use of cobalt-chromium alloys would be gradually increased with elimination of any potential risk of nickel-related allergic responses and/or beryllium-related toxic responses. This investigation examined one- and two-layer opaque porcelain applications to determine the effect on the bond strength of titanium added cobalt-chromium metal ceramic alloy. Bond strength of Ceramco II porcelain to titanium added cobalt-chromium alloy(2Dentitan) and gold-platinum-palladium alloy(Degudent H) were evaluated by direct shear bond strength test with Instron universal testing machine. The results were as follows; 1. When the mean shear bond strength of each experimental group were compared in $0.25cm^2$ unit area, the titanium added cobalt-chromium alloy/two layer method exhibited the greatest strength(79.7kg), followed by titanium added cobalt-chromium alloy/one layer method(76.2kg), gold-platinum-palladium alloy/two layer method(71.4kg), gold-platinum-palladium alloy/one layer method(64.2kg). 2. No significant differences in bond strength were recorded between the two opaquing techniques for gold-platinum-palladium alloy and titanium added cobalt-chromium alloy. 3. No significant differences in bond strength were recorded between the gold-platinum-palladium alloy and the titanium added cobalt-chromium alloy.

• Journal of Adhesion and Interface
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• v.24 no.3
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• pp.105-111
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• 2023

Recently, there has been a growing interest in low biofouling coatings for various industrial applications including precious metal and jewelry applications. Contaminations including cells and bacteria of the metallic substrates (i.e., accessories, earring, and piercings) may irritate the contacted tissue surfaces or induce an abnormal reaction. In this study, catechol-conjugated polyethylene glycol (PEG-C) was synthesized as low bio-fouling coating materials inspired by mussel-adhesion. PEG-C-coated copper-zinc alloy surfaces showed excellent cell viability and significant inhibitions of protein and cell adhesions to metal surfaces. Thus, PEG-C coating methods and PEG-C-coated metallic substrates can be usefully exploited for versatile industrial applications, particularly for precious metal and jewelry industries.