• 대한예방의학회:학술대회논문집
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• 2000.10a
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• pp.308-309
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• 2000

• Journal of Technologic Dentistry
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• v.8 no.1
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• pp.51-55
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• 1986

The castability of base metal alloys for dental casting in influenced by burn-out temperature and recent percentage. Burn-out temperatures for casting are set at 200$^{\circ}F$ interval from 1000$^{\circ}F$ to 1800$^{\circ}F$. According to recast metal percent in new cast alloy metal alloys are tested. The results are as followings: 1. In the new alloy(100%), the castability is the most. 2. The burn-out temperature in 1600$\sim$1800$^{\circ}F$, castability of 100% new alloy was more four times than of 50% new alloy plus 50% recast alloy. The using of 50% new alloy and 50% recast alloy, therefore, was unlike in castability. 3. The burn-out temperature in 1600$^{\circ}F$, castability of 100% new alloy was more than four times in soaking 20 minutes, but there was no any difference at 18700$^{\circ}F$. 4. It is investigated that the optimal burn-out temperature is 1600$^{\circ}F$ for the C & B alloy.

• Journal of the Korean Chemical Society
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• v.56 no.4
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• pp.448-458
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• 2012

In order to develop alloy resistance in aggressive sulphat ion, the corrosion behavior of metallic glasses $Ni_{92{\cdot}3}Si_{4.5}B_{32}$, $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ (at %) at different concentrations of $H_2SO_4$ solutions was examined by electrochemical methods and Scanning Electron Microscope (SEM) and X-ray Photoelectron Microscopy (XPS) analyses. The corrosion kinetics and passivation behavior was studied. A direct proportion was observed between the corrosion rate and acid concentration in the case of $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ alloys. Critical concentration was observed in the case of $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ alloy. The influence of the alloying element is reflected in the increasing resistance of the protective film. XPS analysis confirms that the protection film on the $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ alloy was NiS which is less protective than that formed on Cr containing alloys. The corrosion rate of $Ni_{82,3}Cr_7Fe_3Si_{4.5}B_{3.2}$ and $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$. alloys containing 7% and 13% Cr are $7.90-26.1{\times}10^{-3}$ mm/y which is lower about 43-54 times of the alloy $Ni_{92{\cdot}3}Si_{4.5}B_{32}$ (free of Cr). The high resistance of $Ni_{75.5}Cr_{13}Fe_{4.2}Si_{4.5}B_{2.8}$ alloy at the very aggressive media may due to thicker passive film of $Cr_2O_3$ which hydrated to hydrated chromium oxyhydroxide.

• Journal of Korea Foundry Society
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• v.30 no.4
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• pp.151-156
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• 2010

The high-strength low-alloy (HSLA) steels have low carbon contents (0.05~0.25% C) in order to produce adequate formability and weldability, and they have manganese contents up to 1.7%. Small quantities of silicon, chromium, nickel, copper, aluminum, molybdenum are used in various combinations. The results contained in this paper can provide the valuable information on the development of $-40^{\circ}C$ low temperature HSLA. Furthermore, the present experimental data will provide important database for casting steel materials of the offshore structure.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.824-825
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• 2006

Homogeneous microstructures of the PM compacts are difficult to attain when mixed elemental powders are used. This study examined the microstructures of pressed-and-sintered and MIM products that contain Ni and Mo.Ni-rich areas, which were lean in carbon and were soft and were found easily in regular specimens. Gaps or cracks near the Ni-rich or Mo-rich areas were also frequently observed. This problem worsened when Ni and Mo particles were large and were irregular in shape. By using ball milling treatment and ferroalloy powders, the microstructure homogeneity and mechanical properties were improved. The addition of 0.5wt%Cr further improved the distribution of Ni because Cr reduced the repulsion effect between nickel and carbon. With the elimination of Ni-rich areas, more bainites and martensites were formed and mechanical properties were significantly improved.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.11a
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• pp.56-56
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• 2001

Ni-W alloy deposit is one of the best alternatives to hard chromium plating because of its good mechanical properties (high hardness, high strength, and good wear resistance). Ni-W alloy is deposited from weakly acidic or alkaline electrolytic bath with nickel sulfate, sodium tungstate or APT, and some kinds of organic hydroxy-acid complex and ammonia salts. W content of the deposit can be changed from 0 to 5Owt% and the coating with high W content is more attracted. But, meanwhile, the deposited layers are always found high internal stress, which cause them to become brittle and to bond insufficiently with the substrate. On the second hand, as the W content is incresed, the current efficiency reduced, which results in large quantities of hydrogen evolution and then produces bubbles on surface and pitting appearance In this paper, the influence of some additives on Ni-W alloy electroplating was investigated by means of compositional analysis and SEM. The initial results showed that 2-butyne-1,4-diol was the best brightener for Ni-W plating process. It could brighten and level deposit, but decreased the cathodic current efficiency. Its optimum concentration range is from O.lgjL to 0.5gjL. Besides, three kinds of additives including 2-butyne-1,4-diol were examined with Dagguchi method.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.4
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• pp.426-431
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• 2008

The high-strength low-alloy(HSLA) steels have low carbon contents($0.05{\sim}0.25%$ C) in order to produce adequate formability and weldability, and they have manganese contents up to 1.7%. Small quantities of silicon, chromium, nickel, copper, aluminum, molybdenum are used in various combinations. The results contained in this paper can provide the valuable information on the development of $-40^{\circ}C$ low temperature HSLA. Furthermore, the present experimental data will provide important database for casting steel materials of the offshore structure.

• The Journal of Korean Academy of Prosthodontics
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• v.17 no.1
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• pp.23-34
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• 1979

In this study, the adhesive strength of three commercial polycarboxylate cements to ten types of dental casting alloys, such as gold, palladium, silver, indium, copper, nickel, chromium, and human enamel and dentine were measured and compared with that of a conventional zinc phosphate cement. The $8.0mm{\times}3.0mm$ cylindrical alloy specimens were made by casting. The enamel specimens were prepared from the labial surface of human upper incisor, and the dentine specimens were prepared from the occulusal surface of the human molar respectively. Sound extracted human teeth, which had been kept in a fresh condition since, extraction, were mounted in a wax box with a cold-curing acrylic resin to expose the flattened area. The mounted teeth were then placed in a Specimen Cutter (Technicut) and were cut down under a water spray, and then the flat area on the all specimens were ground by hand with 400 and 600 grit wet silicone carbide paper. Two such specimens were then cemented together face-to-face with freshly mixed cement, and moderate finger pressure was applied to squeeze the cement to a thin and uniform film. All cemented specimens were then kept in a thermostatic humidor cabinet regulated at $23{\pm}2^{\circ}C.$ and more than 95 per cent relative humidity and tested after 24 hours and 1 week. Link chain was attached to each alloy specimen to reduce the rigidity of the jig assembly, and then all the specimens were mounted in the grips of the Instron Universal Testing Machine, and a tensile load was delivered to the adhering surface at a cross head speed of 0.20 mm/min. The loads to which the specimens were subjected were recorded on a chart moving at 0.50 mm/min. The adhesive strength was determined by measuring the load when the specimen separated from the cement block and by dividing the load by the area. The test was performed in a room at $23{\pm}2^{\circ}C.$ and $50{\pm}10$ per cent relative humidity. A minimum of five specimens were tested each material and those which deviated more than 15 per cent from the mean were discarded and new specimens prepared. From the experiments, the following results were obtained. 1) It was found that the adhesive strength of the polycarboxylate cement to all alloys tested was considerably greater than that of the zinc phosphate cement. 2) The adhesive strength of the polycarboxylate cements was superior to the non precious alloys, such as the copper, indium, nickel and chromium alloys, but it was inferior to the precious gold, silver and palladium alloys. 3) Surface treatment of the alloy was found to be an important factor in achieving adhesion. It appears that a polycarboxylate cement will adhere better to a smooth surface than to a rough one. This contrasts with zinc phosphate cements, where a rough helps mechanical interlocking. 4) The adhesion of the polycarboxylate cement with enamel was found superior to its adhesion with dentine.

• Clean Technology
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• v.25 no.1
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• pp.14-18
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• 2019

In general after the etching process, waste etching solution contains metals. (ex. Nickel (Ni), Chromium (Cr), Zinc (Zn), etc.) In this work, we proposed a recycling process for waste etching solution and refining from waste liquid contained nickel to make nickel metal nano powder. At first, the neutralization agent was experimentally selected through the hydrolysis of impurities such as iron by adjusting the pH. We selected sodium hydroxide solution as a neutralizing agent, and removed impurities such as iron by pH = 4. And then, metal ions (ex. Manganese (Mn) and Zinc (Zn), etc.) remain as impurities were refined by D2EHPA (Di-(2-ethylhexyl) phosphoric acid). The nickel powders were synthesized by liquid phase reduction method with hydrazine ($N_2H_4$) and sodium hydroxide (NaOH). The resulting nickel chloride solution and nickel metal powder has high purity ( > 99%). The purity of nickel chloride solution and nickel nano powders were measured by EDTA (ethylenediaminetetraacetic) titration method with ICP-OES (inductively coupled plasma optical emission spectrometer). FE-SEM (field emission scanning electron microscopy) was used to investigate the morphology, particle size and crystal structure of the nickel metal nano powder. The structural properties of the nickel nano powder were characterized by XRD (X-ray diffraction) and TEM (transmission electron microscopy).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.230-233
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• 2008

Stainless steels are alloy steels with iron as the primary constituent and chromium, nickel, and manganese as principal alloying elements. In addition to automotive, construction, and transportation industries, stainless steels have a variety of applications in the food, chemical, and pharmaceutical industries. Some common products made from stainless steel are sinks, wash basins, kitchen vessels, and cutlery. Among ferritic stainless steels, type 409 can be cold-formed easily and are used for deep-drawn parts such as vessels for the chemical and food industries. In this study, forming analyses and experiments to prevent the occurrence of inferiority such as wrinkles, crack, and neck for automotive muffler part are carried out to save the optimal conditions during forming by modifying the blank size and shape, blank holding force etc.