• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.138-144
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• 2015

This paper is aimed to study the influence of aluminium dross from Thai aluminum casting factory on polypropylene matrix-polymer composite material properties. The summarized experimental results are as follows. An increase in the amount of aluminum dross polymer composite material affected to increase hardness, modulus of elasticity and abrasion resistance. However, the increase of the aluminum dross had no effects to change the yield strength and the melting temperature of the polymer composite material. The aluminum dross also affected to form the crystallinity at $117-122^{\circ}C$ and directly increased the rigid property of the composite materials. The microstructure examination revealed that the aluminum dross was located in a polymer matrix and affected to increase the dark colour of the polymer composite material.

• Corrosion Science and Technology
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• v.4 no.1
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• pp.19-22
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• 2005

Two Au-Ag-Cu-Pd dental casting alloys (Au:12% and 20%) used. The test solutions used 0.9 % NaCl solution (isotonic sodium chloride solution), 0.9 % NaCl solution containing 1 % lactic acid, and 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_2S$. The surface of two samples in three sample solutions was not natural discoloration during one year. The alloy containing 12 % gold was easily alloyed and the composition was uniform comparing with the alloy containing 20 % gold. The rest potentials have not a little effect after three months. The kinds of metals could not definitely from the oxidation and reduction waves of metal on the cyclic voltammograms. The dissolutions of gold and palladium were 12 % Au sample in the 0.9 % NaCl solution containing 1 % lactic acid and 0.1 mol $dm^{-3}$ $Na_{2}S$. The pH of solution had an affect on dissolution of copper, and sulfur ion had an affect on dissolution of silver. The copper dissolved amount from 20 % gold sample was about 26 times comparing with that of 12 % gold sample in the 0.9 % solution containing 1 % lactic acid. Corrosion products were silver chloride and copper chloride in NaCl solution, and silver sulfide and copper sulfide in NaCl solution containing $Na_{2}S$.

• Journal of Technologic Dentistry
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• v.16 no.1
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• pp.57-77
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• 1994

The purpose of this study is to investigate the extent to which dental laboratories use proper materials, procedures, devices, and equipments to fabricate crown & bridge, PFM(Porcelain Fused to Metal) crown & bridge, partial denture, complete denture, and other prosteses. 100 laboratories in Seoul were selected for this investigation. Questionnaires were constructed focusing on five topocs:crown & bridge, PFM crown & bridge, partial denture, complete denture, and other prostheses. The results from this survey were as follows : 1. Most dental laboratories used old, inexpensive, and familiar materials rather than newly developed ones. 2. Most of the dental technicians did not stick to the standard procedures of handling materials, but to their own experiences. 3. Newly developed equipments to fabricate dental prostheses were possessed by nearly 30% dental laboratories. 4. About 80% of dental laboratories were using the procedures they had learned in the school : die trimming for accurate crown margin and softening heat treatment after RPD gold casting. But less than 30% of laboratories were shown to follow the boxing procedure to produce master cast and laboratory remounting in the process of complete denture. The findings show that dental laboratory procedures to fabricate dental prostheses are incomplete and inaccurate in some instances. So, further studies are neededs to clarify the causes of some inaccurate procedures, the better and more equipments should be supplied to produce the more accurate dental posthesis, and more efforts at enancing the appropriate use of dental materials and procedures should be made.

• Journal of Korea Foundry Society
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• v.20 no.1
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• pp.21-28
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• 2000

Ni and Ni-Cr porous metals which are estimated to be easy to fabricate by squeeze casting are used as strengtheners for composite materials. As a matrix material, Al-7%wtSi-0.3 wt%Mg(AC4C) has been used. In case of Ni/AC4C and Ni-Cr/AC4C composite, $750^{\circ}C$ melt temperature and minimum 25 MPa squeezing pressure are needed to produce sound composite materials. The observation of interfacial reaction zone at various heat treatment condition showed that solutionizing temperature of above 520^{\circ}C$, the interfacial reaction zone increased proportionally with increasing heat treatment tim and reaction products formed by interfacial reaction are mainly composed of $Al_3Ni$ and $Al_3Ni_2$ phases. The tensile strength of Ni/AC4C and Ni-Cr/AC4C composite is lower than the matrix metal and this can be explained by the brittle intermetallic compounds formed at the interface of Ni and Ni-Cr reinforcements. But the properies of hardness, wear resistance and thermal expansion are better than the matrix due to the strengthening effect of Ni-Cr porous metals.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.174-181
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• 2005

In order to investigate the behavior of fatigue crack growth of SiC-particulate- reinforced Al-Si alloy composites, fatigue tests using single edge notched tension(SENT) specimens were performed. Composite materials were manufactured by using both permanent die casting and extrusion processes with different volume fractions of $10\%\;and\;20\%$. $SiC_p-reinfurced$ Al-Si composites showed the increased levels of threshold stress intensity factor range, ${\Delta}K_{th}$, for the increased volume fractions of SiC particles, which implies the increased fatigue crack growth resistance at the threshold or low ${\Delta}K$ levels, compared to the unreinforced Al-Si alloy. In the Paris region, however, the composites showed the increased rate of crack growth resulting in the unfavorable effects on the fatigue crack growth resistance. Critical stress intensity factor range at unstable crack growth leading to final fracture decreased as the volume fraction of SiC particle increased, because of the reduced fracture toughness of the composites. Extruded materials showed higher threshold and critical values than the cast materials.

• Journal of the Korean institute of surface engineering
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• v.54 no.5
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• pp.285-293
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• 2021

High-entropy TiAlCrSiN nano-composite coating was designed to improve mold life for high temperature liquid molding. Alloy design, powder fabrication and single alloying target fabrication for the high-entropy nano-composite coating were carried out. Using the single alloying target, an arc ion plating method was applied to prepare a TiAlCrSiN nano-composite coating had a 30 nm TiAlCrSiN layers are deposited layer by layer, and form about 4 ㎛-thickness of multi-layered coating. TiAlCrSiN nano-composite coating had a high hardness of about 39.9 GPa and a low coefficient of friction of less than about 0.47 in a dry environment. In addition, there was no change in the structure of the coating after the dissolution loss test in the molten metal at a temperature of about 1100 degrees.

• Tribology and Lubricants
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• v.35 no.1
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• pp.24-29
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• 2019

In this work we investigated the friction and wear characteristics of a magnesium alloy, which has been receiving much attention as a light metal in industrial applications such as automobiles and aerospace. Magnesium is one of the lightest structural material that has high specific strength, lightweight, low density and good formability. However, current issue of using magnesium alloy is that magnesium has weakness against temperature. As the temperature increases, magnesium undergoes poor creep resistance and ease of softening, and therefore, its mechanical strength decreases sharply. To solve this issue, a new type of magnesium alloy that retains high strength at high temperature has been proposed. The tribological behavior of this alloy was investigated using a tribotester with reciprocating motion and heating plate. A stainless steel ball was used as a counter surface. Results showed that extrusion process has similar wear behavior to the commonly used casting process but retains good mechanical strength and durability. The presence of an alloying element enhanced the wear properties especially in high temperature. This study is expected to be utilized as fundamental data for the replacement of high density materials currently used in mechanical industries to a much lighter and durable heat-resistant materials.

• Korean Journal of Metals and Materials
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• v.48 no.3
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• pp.248-255
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• 2010

The effect of various alloying elements and melt treatment on the microstructural control of Al-Sn metallic bearing alloy was investigated. The thickness of tin film crystallized around primary aluminum decreased with the addition of 5% Cu in Al-Sn alloy, with tin particles being reduced in size by intervening the Ostwald ripening. With the addition of Si in Al-10%Sn alloy, the tin particles were crystallized with eutectic silicon, resulting in uniform distribution of tin particles. With the addition of Cu and Si in Al-Sn alloy, both the tensile strength and yield strength increased, with the increasing rate of yield strength being less than that of tensile strength. Although the Al-10%Sn-7%Si alloy has similar tensile strength compared with Al-10%Sn-5%Cu, the former showed superior abrasion resistance, resulting from preventing the tin particles from movement to the abrasion surface.

• Transactions of Materials Processing
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• v.32 no.3
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• pp.114-121
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• 2023

During rolling, rolling mill rolls endure wear when shaping metal billets into a desired form, such as bars, plates, and shapes. Such wear affects the lifespan of the rolls and product quality. Therefore, in addition to rigidity, wear performance is a key factor influencing the performance of rolling mill rolls. Conventional methods such as casting and forging have been used to manufacture rolling mill rolls. However, powder alloying methods are increasingly being adopted to enhance wear resistance. These powder manufacturing methods include atomization, canning to shape the powder, hot isostatic pressing to combine the powder alloy with conventional metals, and various wear performance tests on rolls prepared with powder alloys. In this study, numerical simulations and experimental tests were used to develop and elucidate the wear analysis mechanism of rolling mill rolls. The wear characteristics of the rolls under various rolling conditions were analyzed. In addition, experimental tests (wear and surface analysis tests) and wear theory (Archard wear model) were used to evaluate wear. These tests were performed on two different materials in various powder states to evaluate the different aspects of wear resistance. In particular, this study identifies the factors influencing the wear behavior of rolling mill rolls and proposes an analytical approach based on the actual production of products. The developed wear analysis mechanism can serve the future development of rolls with high wear resistance using new materials. Moreover, it can be applied in the mechanical and wear performance testing of new products.

• Journal of Technologic Dentistry
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• v.45 no.2
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• pp.48-53
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• 2023

Purpose: This study aimed to provide the basic data for dental barrel finishing by observing the abrasiveness of the metal body according to the time of the barrel finishing. Methods: This study included three types of Co-Cr alloys. The specimens were manufactured by casting method using 10-mm diameter wax spheres (n=10). The cast alloys were polished for 60 minutes at intervals of 5 minutes in barrel finishing. The weight and volume of the specimens were measured, and the rate of change was calculated. The data obtained from the three groups (α=0.05) were compared and analyzed using one-way ANOVA. Results: As a result, the overall volume and weight of the group decreased after grinding compared with the control group. Conclusion: When grinding dental barrel finishing, no difference was observed in the processing rate depending on the type of alloy and the processing rate of the alloy body is within 30 minutes; hence, dental barrel finishing can be effectively used for grinding.