• The Journal of Korean Academy of Prosthodontics
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• v.39 no.4
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• pp.417-432
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• 2001

The pcf metal primers on the bond strength and durability of 4-META/MMA-TBB resins adhered to an Au-Ag-Pd alloy. For this study, the specimens were divided into 8 groups as follows: Thermocyle 0 : (1) control group : sandblast, (2) Group I : sandblast + Cesead Opaque Primer; (3) Group II : sandblast + Metal Primer; (4) Group III : sandblast + V-Primer; Thermocyle 10,000 (5) control sandblast: (6) Group I : sandblast + Cesead Opaque Primer: (7) Group II : sandblast + Metal Primer; (8) Group III sandblast + V-Primer. The shear bond strength was determined using an Instron were observed with the use of scanning electron microscope. Finally, the strengths of bonded joints were evaluated with regard to their adherence energy using a wedge test. The results obtained were as follows ; (1) The shear bond strength of 4-META/MMA-TBB resin to the Au-Ag-Pd alloy was significantly improved in all the groups treated with the primers (p<0.05). (2) Regardless of the adhesive primers used, a significant difference was observed in the bond strength of the thermocycle 0 groups and 10,000 groups (p<0.05). (3) Both before and after thermocycling, the strongest bond strength between the resin an the alloy was obtained after treatment with a metal primer containing MEPS (p<0.05). (4) In the wedge test, the adherence energies of the control group and Group III decreased more rapidly than those of Group I and II during the 2nd day of storage in water.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.581-593
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• 1990

A semi-solid alloy in which solid and liquid phase are co-existing is obtained by strirring of Al7075 molten metal. A semi-solid alloy is dependent on the corresponding temperature within the solid-liquid range, and the process parameters should be controlled accurately to obtain the homogeneous semi-solid alloy. The possibility o homogeneous fiber-reinforce aluminum alloy by addition of $Al_{2}$O$_{3}$ short fibers with vigorous agitation was investigated. The billet of composite materials was fabricated by squeeze casting, and homogeneous dipersion state of fibers in billet of fabricated metal matrix composites was observed. A slurry of semi-solid short fiber metal matrix composites is used in the direct rolling process, and this process showed the fabrication possibility of metal matrix composite sheets. The fabricated sheet was tested regarding vickers hardness, elongation and micro-structure. It has become clear that mashy state processing and working are very useful to obtain parts of composites material closed to near net shape.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.3
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• pp.181-196
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• 1991

The Purpose of this study was to evaluate the marginal fit of ceramo-metal crown according to the different ceramo-metal alloy types and the curvature of labio-cervical margin. Degudent $G^{(R)}$ as precious and $Verabond^{(R)}$ as non-precious ceramo-metal alloy were used. The abutment was preparaed with two different curvature types : a normal curvature type and a pronounced curvature type. 20 crowns were farbricated using four different combinations and their marginal fits were measured at 3 consecutive stages (before degassing, after degassing, after glazing) using microscope under 200 magnification. The results were as follows: 1 . Marginal fitness before degassing. The groups of precious ceramo-metal exhibited better marginal fit than the groups of non-precious ceramo-metal with significant difference(P<0.05) . In the same ceramo-metal groups, the normal curvature group exhibited better marginal fit than the pronounced curvature group but without significant difference(P>0.05). 2. Marginal fitness after degassing. By degassing, the group of pronounced curvature and non-precious ceramo-metal was deformed the most, and the degree of margin fitness of each group was the same as before degassing. 3. Marginal fitness after glazing The group of normal curvature and precious ceramo-metal exhibited better marginal fit than the group of pronounced curvature and non-precious ceramo-metal with significant difference(P>0.05), and the degree of margin fitness of each group was the same as before degassing.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.374-377
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• 2008

High temperature deformation behavior and texture evolution during ECAP(equal channel angular pressing) of Zn-0.3Al alloy were investigated in this study. ECAP was conducted at temperatures from $40^{\circ}C$ to $160^{\circ}C$ on the plate type specimen of 5mm thickness and 20mm width. The specimens obtained by ECAP showed typical texture with basal poles tilted away from the ND toward ED. A series of compression tests was carried out at temperatures from RT to $200^{\circ}C$ under the strain rate from 0.03 to 10/s. With the strain rate increased, serration behavior was observed to be prominent.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.13-19
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• 2007

To find out the optimum design of hydrogen storage and supply tank using Metal Hydride (briefly MH) and to make clear the performance characteristics under various conditions are our research purpose. In order to use the low-temperature exhaust heat, $LaNi_{4.7}Al_{0.3}$ which operates under the low pressure of 1 MPa is chosen, and we measure the basic properties, namely density, specific heat, PCT(Pressure-Concentration-Temperature) characteristics, and effective thermal conductivity. Then, a numerical calculation model of hydrogen storage using MH alloy is suggested and this thermal diffusion equation of model is solved by the backward difference method. This calculation results are compared with the experimental results of the systems which installed 1kg MH alloy and, it is found out that our calculation model can well predict the experimental results. By the experimental using MH alloy, it is recognized that the hydrogen flow rate can control by the step adjustment of brine temperature.

• The Journal of the Korean dental association
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• v.23 no.7 s.194
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• pp.577-583
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• 1985

The purpose of this investigation was to evaluate scanning electron micrographs of repeatedly cast base metal alloy. For this study two Ni-Cr-Be alloys were used; Rexillium III and Verabond. They were repeatedly cast without addition o new alloy melting with an electric resistant furnace (Castron 8, Yoshida dental equipment Mfg.Co.). They were etched with 10% H₂SO₄ Sol. at 300mA/㎠ for 3 minutes with the use of metal etching unit Oxyetch (OXY dental product Inc.), and ultrasonic cleaning in 18% HC1 Sol. was done. Etched surfaces were examined under a SEM at x 200 and x 750. The surfaces are shown in legends.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.770-781
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• 2008

In nuclear power plants, ferritic low alloy steel components were connected with austenitic stainless steel piping system through alloy 82/182 butt weld. There have been incidents recently where cracking has been observed in the dissimilar metal weld. Alloy 82/182 is susceptible to primary water stress corrosion cracking. Weld-induced residual stress is main factor for crack growth. Therefore exact estimation of residual stress is important for reliable operating. This paper presents residual stress computation performed by 6" safety & relief nozzle. Based on 2 dimensional and 3 dimensional finite element analyses, effect of welding variables on residual stress variation is estimated for sensitivity analysis.

• Journal of Welding and Joining
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• v.18 no.4
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• pp.96-103
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• 2000

This study investigated the effects of bonding temperature and bonding atmosphere on high temperature mechanical properties of transient liquid phase(TLP) bonded joints of heat resistant alloy using MBF-50 insert metal. Specimens were bonded at 1,423~1,468K for 600s. Microconstituents of {TEX}$Cr_{7}(C,B)_{3}${/TEX}were formed in the bonded region when the bonding temperature was low. The amount of microcostituents in the bonded layer decreased with increasing the bonding temperature, and the microconstituents in the bonded layer disappeared at the bonding temperature above 1,468K. The tensile strength of the joints at elevated temperatures increased with the increase the bonding temperature and was the same level as one of the base metal in the bonding temperature over 1,453K. Microstructure and alloying element distributions of the bonded region bonded in Ar and $N_2$atmosphere were similar to those of the bonded in vacuum. The creep rupture strength and rupture lives of joints were almost identical to those of base metal.

• Journal of Powder Materials
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• v.8 no.3
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• pp.157-162
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• 2001

An optimum route to fabricate the ferrous alloy dispersed $Al_2O_3$ nanocomposites such as $Al_2O_3$/Fe-Ni and $Al_2O_3$/Fe-Co with sound microstructure and desired properties was investigated. The composites were fabricated by the sintering of powder mixtures of $Al_2O_3$ and nano-sized ferrous alloy, in which the alloy was prepared by solution-chemistry routes using metal nitrates powders and a subsequent hydorgen reduction process. Microstructural observation of reduced powder mixture revealed that the Fe-Ni or Fe-Co alloy particles of about 20 nm in size homogeneously surrounded $Al_2O_3$, forming nanocomposite powder. The sintered $Al_2O_3$/Fe-Ni composite showed the formation of Fe$Al_2O_4$ phase, while the reaction phases were not observed in $Al_2O_3$/Fe-Co composite. Hot-pressed $Al_2O_3$/Fe-Ni composite showed improved mechanical properties and magnetic response. The properties are discussed in terms of microstructural characteristics such as the distribution and size of alloy particles.

• Journal of Technologic Dentistry
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• v.33 no.1
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• pp.7-14
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• 2011

Purpose: As the demand and importance of aesthetic aspects in dental treatment become higher, much attention is paid to materials used for dental prostheses. Thus, the marginal fidelity of most-commonly used alloy, IPS - Empress and ZrO2 ceramic is compared. Methods: The alloy core made by casting, IPS - Empress core made by pressing and ZrO2 ceramic core made by CAD/CAM are used to make 10 samples respectively. For each core, three points were measures and the optical microscope (Axio Imager.Alm,Zeiss co., Oberkochen, Germany) was used to observe the cores with a magnification of 100. Results: As for alloy, IPS - Empress and ZrO2 ceramic, the average and deviation of their marginal distance are $29.91\;{\pm}11.93{\mu}m$ for alloy, $33.45\;{\pm}8.61{\mu}m$ for IPS - Empress, and $31.55\;{\pm}9.85{\mu}m$ for ZrO2. The one-way ANOVA test was conducted to compare them. However, there was no statistically significant difference among them. Conclusion: The study on marginal fidelity of alloy, IPS - Empress, and ZrO2 ceramic shows they have no marginal fidelity problem clinically. Therefore, if a system is selected based on the patient's condition or treatment method, there will be no problem.