• Restorative Dentistry and Endodontics
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• v.12 no.1
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• pp.39-49
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• 1986

The purpose of this study was to observe characteristic properties through the polarization curves and SEM images from 4 different types of amalgam obtained by using the potentiostats (Princeton EG & G) & SEM (Jeol/35), and to investigate the degree of corrosion on the oxidation peak of the each phase of amalgam. After each amalgam alloy and Hg was triturated as the direction of the manufacturer by means of the mechanical amalgamator (Shofu Co.), the triturated mass was inserted into the cylindrical metal mold which was 12mm in diameter and 10.0mm in height and was condensed by using routine manner. The specimen was removed from the mold and stored at room temperature for about 24 hours. The standard surface preparation was routinely carried out. Anodic polarization measurement was employed to confirm the corrosion behaviour of the amalgams in a 0.9% saline solution (P.H: 6.8-7.0) at $37^{\circ}C$. The initial rest potential (corrosion potential) was determined after 30 minutes of immersion of specimen in electrolyte, and the potential scan was begun at the point of 100mV cathodic from the corrosion potential. The scan rate was 0.17mV/sec. in the study to observe the degree of corrosion of each phase. SEI and EPMA images on the determined oxidation peaks of each amalgam were observed. The results were as follows: 1. In the four anodic polarization curves, low copper amalgams have three oxidation peaks and high copper amalgams have two oxidation peaks, -270mV, +26mV and +179mV(SEC) in the low copper lathe cut, and -300mV, +39mV and +163mV(SEC) in the low copper spherical. -4mV and +154mV(SEC) in the Dispersalloy, and +17mV and +180mV(SEC) in the Tytin as high copper amalgams. 2. ${\gamma}_2$ phase in the low copper amalgam and ${\eta}$ phase in the high copper amalgam were the most corrodible phases and Ag-Cu eutectic in high copper amalgam was the most slowly corroded phase. 3. Low copper amalgam was more susceptible in corrosion than high copper amalgam.

• YAKHAK HOEJI
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• v.27 no.2
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• pp.181-184
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• 1983

DMSO-oxalyl chloride at low temperature in methylene chloride reacted with isolated secondary hydroxyl groups in some monosaccharides to give alkoxysulfonium salts, convertible to carbonyls in high yields upon addition of triethylamine. And 1, 2:5, 6-di-O-isopropylidene-.alpha.- D-allofuranose which is the key intermediate in the synthesis of 3-O-acetyl-5-O-benzoyl- 2-deoxy-2- fluoro-D-arabinofuranosyl bromide, was also obtained by oxidizing 1, 2:5, 6-di-O-isopropylidene-.alpha.- D-glucofuranose with the oxidizing reagent, followed by reduction with sodium borohydride.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.93-99
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• 1996

The formation properties and oxidation mechanism of electrochemically oxidized porous silicon(OPS) films have been studied. To examine the humidity-sensitive properties of OPS films, surface-type and bulk-type humidity sensors were fabricated. The oxidized thickness of porous silicon layer(PSL) increases with the charge supplied during electrochemical humidity sensor shows high sensitivity at high relative humidity in low temperature. The sensitivity and linearity can be improved by optimizing a porosity of PSL. (author). refs., figs.

• Resources Recycling
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• v.10 no.5
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• pp.22-28
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• 2001

Recovery of silver in the spent solution generated from MEO(Mediated Electrochemical Oxidation) process, which is a process to decompose radioactive organic mixed wastes at low temperature, was performed using chemical method. Silver nitrate in 5M nitric acid solution could be completely recovered as AgCl by using 1% excess of the stoichiometric HCl equivalents. Then, AgCl was transformed to Ag metal by reduction reaction with hydrogen peroxide under alkaline media. The optimum pH for the reduction to silver metal was found to be in the range of 12.8∼13.0.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.128-128
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• 2013

Fabrication of heterogeneous catalysts using Atomic Layer Deposition (ALD) has recently been attracting attention of surface chemists and physicists. In this talk, I will present recent results about structures and chemical activities of various catalysts prepared by ALD, particularly focusing on Ni-based catalysts. Ni has been considered as potential catalysts for $CO_2$ reforming of methane (CRM); however, Ni often undergoes rapid decrease in catalytic activity with time, and therefore, application of Ni as catalysts for CRM has been regarded as difficult so far. Deactivation of Ni catalysts during CRM reaction is from either coke formation on Ni surface or sintering of Ni particles during reaction. Two different strategies have been used for enhancing stability of Ni-based catalysts; $TiO_2$ nanoparticles were deposited on micrometer-size Ni particles by ALD, which turned out to reduce coke formation on Ni surfaces. Ni nanoparticles deposited by ALD on mesoporous silica showed high activity and long-term stability from CRM without coke deposition and sintering during CRM reaction. Ni-based catalysts have been also used for oxidation of toluene, which is one of the most notorious gases responsible for sick-building syndrome. It was shown that onset-temperature of Ni catalysts for toluene oxidation is as low as $120^{\circ}C$. At $250\circ}C$, total oxidation of toluene to $CO_2$ with a 100% conversion was found.

• Journal of Ginseng Research
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• v.14 no.3
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• pp.379-384
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• 1990

In order to study the lipid peroxidation caused by light and the protective action it in biological memberane, reverse-phase evaporation liposome (REV) was employed as a model memberance and the effect of several antioxidants and ginseng water extracts were tested. In the presence of photosensitizer, liposome was oxidized easily and the oxidation index dut to the peroxidation was increased. The oxidation index of liposome was increased according to the increase in temperature. When dl-${\alpha}$-tocopherol, ${\beta}$-carotene or L-ascorbic acid was added into the reaction mixture, the photooxidation of liposome was inhibited. Ginseng water extract and crude saponin inhibited the rate of oxidation index of liposome in low concentration but increase in high concentration. On the other hand, when lipid hydroperoxide of liposome was tested by ferrothiocyanate method, ginseng water extract and crude saponin acted as antioxidants.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.4
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• pp.320-329
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• 2019

This study was performed by the numerical approach to investigate chemical behaviors of homogeneous syngas ($CO/H_2$) with nitric monoxide (NO) in pressurized oxy-fuel conditions. Hydrogen had a dominant effect to the ignition delay time of syngas due to the fast chemistry of its oxidation. Combustion was promoted by NO at the low temperature region. It was by the additional heat release through NO oxidation and production and consumption of major radicals related to the ignition. Two stage ignition behavior was shown in the pressurized condition by the accumulation of $H_2O_2$ produced from $HO_2$ radical. Additional NO oxidation was induced by the pressurized oxy-fuel condition to produce $NO_2$.

• Clean Technology
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• v.18 no.1
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• pp.95-101
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• 2012

The Co and Ni catalysts supported on $Al_2O_3$ for partial oxidation of methane producing hydrogen were synthesized using impregnation to incipient wetness. And the promotion effects of metals such as Mg, Ce, La and Sr in partial oxidation of methane over these $Co/Al_2O_3$ and $Ni/Al_2O_3$ were investigated. Reaction activity of these catalysts for the partial oxidation of methane was investigated in the temperature range of 450~$650^{\circ}C$ at 1 atm and $CH_2/O_2$ = 2.0. The catalysts were characterized by BET, XRD and SEM/EDX. The results indicated that the catalytic performance of these catalysts was improved with the addition of 0.2 wt% metal promoter. The Mg promoted $Co/Al_2O_3$ catalyst showed the highest $CH_4$ conversion and hydrogen selectivity at higher temperature than $500^{\circ}C$. The Ce and Sr promoted Ni catalysts superior to Co-based catalysts in the low temperature range. The addition of metal promoter to $Co/Al_2O_3$ and $Ni/Al_2O_3$ catalysts increased the surface area.

• Water for future
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• v.13 no.3
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• pp.71-76
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• 1980

The oxidation ditch is an efficient, low cost form of treatment of domestic and many industrial waste. It has gained rapid acceptance because of its simplicity, low cost operation, ease of operation, simple mintenance and flexibiltiy. The objective of this investigation was to measure the removal of organics in an existing dithc that does not have return sludge and which is not preceded by primary sedimentation. To accomplish this objective, samples of the wastewater influent and effluent were collected from the wastewater treatment plant of Mansfield, Texas during practical training. These samples were collected over an extended period of time to obtain samples at various treatment temperatures. Two analytical tests, COD and suspended solids, were used to monitor the operation of the plant. The results show that high removal efficiencies were obtained at high temperatures, with the efficiency decreasing as the temperature decreased to approximatedly 16$^{\circ}C$, at which point the efficienty tmeperature relationship appeared to stabilize.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.578-582
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• 2010

$ZrB_2$ has a melting point of $3245^{\circ}C$ and a relatively low density of $6.1\;g/cm^3$, which makes this a candidate for application to ultrahigh temperature environments over $2000^{\circ}C$. Beside these properties, $ZrB_2$ is known to have excellent resistance to thermal shock and oxidation compared with other non-oxide engineering ceramics. In order to enhance such oxidation resistance, SiC was frequently added to $ZrB_2$-based systems. Due to nonsinterability of $ZrB_2$-based ceramics, research on the sintering aids such as $B_4C$ or $MoSi_2$ becomes popular recently. In this study, densification and high-temperature properties of $ZrB_2$-SiC ceramics especially with $B_4C$ are investigated. $ZrB_2$-20 vol% SiC system was selected as a basic composition and $B_4C$ or C was added to this system in some extents. Mixed powders were sintered using hot pressing (HP). With sintered bodies, densification behavior and high-temperature (up to $1400^{\circ}C$) properties such as flexural strength, hardness, and so on were examined.