• Proceedings of the Materials Research Society of Korea Conference
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• 2002.11a
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• pp.76-76
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• 2002

• Journal of Welding and Joining
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• v.13 no.3
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• pp.134-146
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• 1995

Aluminium nitride(AlN) is currently under investigation as potential candidate for replacing alumium oxide(Al$_{2}$ $O_{3}$) as a substrate material for for electronic circuit packaging. Brazing of aluminium nitride(AlN) to Cu with Ag base active alloy containing Ti has been investigated in vacuum. Binary Ag$_{98}$ $Ti_{2}$(AT) and ternary At-1wt.%Al(ATA), AT-1wt.%Ni(ATN), AT-1wt.% Mn(ATM) alloys showed good wettability to AlN and led to the development of strong bond between brate alloy and AlN ceramic. The reaction between AlN and the melted brazing alloys resulted in the formation of continuous TiN layers at the AlN side iterface. This reaction layer was found to increase by increase by increasing brazing time and temperature for all filler metals. The bond strength, measured by 4-point bend test, was increased with bonding temperature and showed maximum value and then decreased with temperature. It might be concluded that optimum thickness of the reaction layer was existed for maximum bond strength. The joint brazed at 900.deg.C for 1800sec using binary AT alloy fractured at the maximum load of 35kgf which is the highest value measured in this work. The failure of this joint was initiated at the interface between AlN and TiN layer and then proceeded alternately through the interior of the reaction layer and AlN ceramic itself.

• Journal of the Korean institute of surface engineering
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• v.49 no.3
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• pp.307-315
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• 2016

The properties of AlTiN films by a cathodic arc deposition process have been studied. Oblique angle deposition has been applied to deposit AlTiN films. AlTiN films have been deposited on stainless steel (SUS304) and cemented carbide (WC) at a substrate temperature of $500^{\circ}C$. AlTiN films were analyzed by scanning electron microscopy, glow-discharge light spectroscopy, micro-vickers hardness, and nanoindenter. When applying a current of 50 A to the cathodic arc source, it showed that the density of macroparticle of AlTiN films was 5 lower than other deposition conditions. With the increase of the bias voltage applied to the substrate up to -150 V, the density of macroparticle was decreased. The change of the $N_2$ flow rate during coating process made no influence on the film properties. For the multi-layered films, the film prepared at oblique angle of $60^{\circ}$ showed the highest hardness of 28 GPa and $H^3/E^2$ index of 0.18. AlTiN films have been shown a good oxidation resistance up to $800^{\circ}C$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.543-544
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• 2006

The effect of the additives, $Y_2O_3$ and MgO, on the sintering and properties of $Al_2O_3-TiC$ composites was investigated. It is known that MgO is used as additive for improving densification and $Y_2O_3$ is applied as sintering aid. In this study, the amounts of TiC were varied in the range of 30-47 wt%. The 0.5 wt% MgO and also varied amounts of $Y_2O_3$ from 0.3 to 1 wt% were added into the composites. The sintering of $Al_2O_3-TiC$ composites was performed in a graphite-heating element furnace at different sintering temperature, 1700 and $1900\;^{\circ}C$, for 2 hr under an argon atmosphere. The results demonstrated that the properties of the composites sintered at $1700\;^{\circ}C$ were much better than those sintered at $1900\;^{\circ}C$. The comparisons on physical properties, mechanical properties and microstructure of composites with and without additives were reported. Comparing with other samples, $Al_2O_3-30wt%TiC$ composites with 0.5wt% MgO and $1\;wt%Y_2O_3$ exhibited the highest density of approximately 98% of theoretical and flexural strength of 302 MPa.

• Journal of the Korean Ceramic Society
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• v.35 no.4
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• pp.311-318
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• 1998

The reaction bonded alumina ceramics with reinforced particles which have low shrinkage were pro-duced by blending of SiC or TiC or ZrO2 powders to the mixture of Al metal and Al2O3 powder. The powd-ers were attrition milled isostantically pressed and preheated tio 110$0^{\circ}C$ with a heating rate of $1.5^{\circ}C$/min The specimens were then sintered at the temperature range 1500 to 1$600^{\circ}C$ for 5 hours with a heating rate of 5$^{\circ}C$/min. The specimens showed 5-9% weight gain and 2-9% dimensional expansion through the complete oxidation of Al after preheating up to 11--$^{\circ}C$ the overall dimensional change of the specimens after the reaction sintering at 1500-1$600^{\circ}C$ was 6-12% The maximum densities were 92% theoretical. The fine grain-ed(average grain size :0.4 ${\mu}{\textrm}{m}$) microstructure were observed in the specimen with ZrO2 and SiC. But the microstructure of specimen with TiC was relatively coarse.(average grain size : 2.1 ${\mu}{\textrm}{m}$) The mullite phase was formed by the reaction of Al2O3 and SiO2 in a specimen with SiC. In the TiC contained specimen TiC was oxidized into TiO2 and finally reacted with Al2O3 to form Al2TiO5 during sintering.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.229-234
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• 2017

In this study, TiAl alloy was fabricated by a centrifugal casting method for turbo charge of automotive. Optimum conditions for defectless morphology using various ceramic mold were investigated. The crystal structure, microstructure, and chemical composition of the TiAl prepared by centrifugal casting were studied by X-ray diffractometer (XRD), optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS), microvickers hardness analyzer (HV). Two kinds of dendrite structures were observed with 4-fold and 6-fold symmetries. The FE-SEM, EDS and HV examinations of the as-cast TiAl showed that the thickness of the oxide layer (${\alpha}$-case) was typically less than $50{\mu}m$.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.512-520
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• 2014

PURPOSE. The purpose of this study was to assess the surface characteristics and the biocompatibility of zirconium (Zr) coating on Ti-6Al-4V alloy surface by radio frequency (RF) magnetron sputtering method. MATERIALS AND METHODS. The zirconium films were developed on Ti-6Al-4V discs using RF magnetron sputtering method. Surface profile, surface composition, surface roughness and surface energy were evaluated. Electrochemical test was performed to evaluate the corrosion behavior. Cell proliferation, alkaline phosphatase (ALP) activity and gene expression of mineralized matrix markers were measured. RESULTS. SEM and EDS analysis showed that zirconium deposition was performed successfully on Ti-6Al-4V alloy substrate. Ti-6Al-4V group and Zr-coating group showed no significant difference in surface roughness (P>.05). Surface energy was significantly higher in Zr-coating group than in Ti-6Al-4V group (P<.05). No difference in cell morphology was observed between Ti-6Al-4V group and Zr-coating group. Cell proliferation was higher in Zr-coating group than Ti-6Al-4V group at 1, 3 and 5 days (P<.05). Zr-coating group showed higher ALP activity level than Ti-6Al-4V group (P<.05). The mRNA expressions of bone sialoprotein (BSP) and osteocalcin (OCN) on Zr-coating group increased approximately 1.2-fold and 2.1-fold respectively, compared to that of Ti-6Al-4V group. CONCLUSION. These results suggest that zirconium coating on Ti-6Al-4V alloy could enhance the early osteoblast responses. This property could make non-toxic metal coatings on Ti-6Al-4V alloy suitable for orthopedic and dental implants.

• Journal of Powder Materials
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• v.5 no.2
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• pp.98-110
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• 1998

$Ti_{52}Al_{48}$ and $(Ti_{52}Al_{48})_{100-x}B_x(x=0.5, 2, 5)$ alloys have been Produced by mechanical milling in an attritor mill using prealloyed powders. Microstructure of binary $Ti_{52}Al_{48}$ powders consists of grains of hexagonal phase whose structure is very close to $Ti_2Al$. $(Ti_{52}Al_{48})_{95}B_5$ powders contains TiB2 in addition to matrix grains of hexagonal phase. The grain sizes in the as-milled powders of both alloys are nanocrystalline. The mechanically alloyed powders were consolidated by vacuum hot pressing (VHP) at 100$0^{\circ}C$ for 2 hours, resulting in a material which is fully dense. Microstructure of consolidated binary alloy consists of $\gamma$-TiAl phase with dispersions of $Ti_2AlN$ and $A1_2O_3$ phases located along the grain boundaries. Binary alloy shows a significant coarsening in grain and dispersoid sizes. On the other hand, microstructure of B containing alloy consists of $\gamma$-TiAl grains with fine dispersions of $TiB_2$ within the grains and shows the minimal coarsening during annealing. The vacuum hot pressed billets were subjected to various heat treatments, and the mechanical properties were measured by compression testing at room temperature. Mechanically alloyed materials show much better combinations of strength and fracture strain compared with the ingot-cast TiAl, indicating the effectiveness of mechanical alloying in improving the mechanical properties.

• Korean Journal of Metals and Materials
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• v.50 no.9
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• pp.677-684
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• 2012

A feasible way to fabricate in-situ Al/TiC composites was investigated. An elemental mixture of $Al-TiO_2-C$ pellet was directly added into an Al melt at $800-920^{\circ}C$ to form TiC by self-combustion reaction. The addition of CuO initiates the self-combustion reaction to form TiC in $1-2{\mu}m$ at the melt temperature above $850^{\circ}C$. Besides the CuO addition, a diluent element of excess Al plays a significant role in the TiC formation by forming a precursor phase, $Al_3Ti$. Processing parameters such as CuO content, the amount of excess Al and the melt temperature, have affected the combustion reaction and formation of TiC, and their influences on the microstructures of in-situ Al/TiC composites are examined.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.987-992
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• 1998

Titanium aluminide intermetallic compound was formed from high purity elemental Ti and A1 foils by selfpropagating, high-temperature synthesis(SHS1 in hot press. Formation of $TiAl_3$ intermetallics at the interface between Ti and Al foil was observed to be controlled by temperature, pressure and heating rate. Especially, the heating rate is the most important role to form intermetallic compound by SHS reaction. According to DTA experiment, the SHS reactions appeared at two different temperatures below and above the melting point of Al. It was also observed that both SHS reaction temperatures increased with increasing the heating rate. After the SHS reaction of alternatively layered 10 Ti and 9 A1 foils at the heating rate of $20^{\circ}C$/min, the $700\mu\textrm{m}$ thick titanium aluminide sheet was formed by heat treatment at $810^{\circ}C$ for 4hours.