• Korean Journal of Materials Research
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• v.20 no.6
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• pp.338-343
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• 2010

As an alternative to the W plug used in MOSFETs, a Cu plug with a NiSi contact using Ta / TaN as a diffusion barrier is currently being considered. Conventionally, Ni was first deposited and then NiSi was formed, followed by the barrier and Cu deposition. In this study, Ti was employed as a barrier material and simultaneous formation of the NiSi contact and Cu plug / Ti barrier was attempted. Cu(100 nm) / Ti / Ni(20 nm) with varying Ti thicknesses were deposited on a Si substrate and annealed at $4000^{\circ}C$ for 30 min. For comparison, Cu/Ti/NiSi thin films were also formed by the conventional method. Optical Microscopy (OM), Scanning Probe Microscopy (SPM), X-Ray Diffractometry (XRD), and Auger Electron Microscopy (AES) analysis were performed to characterize the inter-diffusion properties. For a Ti interlayer thicker than 50 nm, the NiSi formation was incomplete, although Cu diffusion was inhibited by the Ti barrier. For a Ti thickness of 20 nm and less, an almost stoichiometric NiSi contact along with the Cu plug and Ti barrier layers was formed. The results were comparable to that formed by the conventional method and showed that this alternative process has potential as a formation process for the Cu plug/Ti barrier/NiSi contact system.

• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.881-886
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• 2009

Research into the replacement of injured systems and tissue in the human body is advancing rapidly. Recently, Ti-Ni shape memory alloys have shown excellent biofunctionality related to their shape memory effect and superelasticity. In this study, the effect of an acid or an alkali treatment on the bioactivity in 49Ti-Ni and 51.5Ti-48.5Ni alloys is investigated in an effort to utilize Ti-Ni alloy as a biomaterial. In addition, the biocompatibility in a SBF solution is assessed through in vitro testing. A porous surface was formed on the surface of both alloys after a chemical treatment. According to the in vitro test, apatite formed on the surfaces of both alloys. The forming rate of apatite in the Ti-rich alloy was faster that in the Ni-rich alloy. The formation of apatite provided proof of the bioactivity of the Ti-Ni alloy. A small quantity of Ni was eluted at the initial stage, whereas Ni was not found for 12 days in the Ti-rich alloy and for 8 days in the Ni-rich alloy. In the case of the treated 51.5Ti-Ni alloy, the shape memory property was worsened but the biocompatibility was improved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.465-469
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• 1997

In this paper, shape memory compsites are made by powder metallurgy. And then, an self-strengthening effect of the composites by shape memory effect above inverse transformation temperature A/sab f/ of TiNi alloy discussed. Moreover, TiNiCo/Al composite is made by using TiNiCo alloy as fiber. And it is discused aboutaffection of Co in the shape memory composite. The results of the intelligent properties of TiNi/Ai-radical shape memory composite, using SMA, by powder metallurgy are the tensile strength of TiNiCo wire is much higher than that of TiNi wire. and the strength of TiNiCo/Al composite is generally higher than that TiNi/Al composite.

• Journal of the Korean Ceramic Society
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• v.30 no.11
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• pp.949-954
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• 1993

Microstructural development at the ZrO2/NiTi bonding interface and reaction products were examined and identified with SEM and AEM. Ti-oxide, Ti2Ni and Ni2Ti layer were observed whose thickness depends on bonding temperature typically. The development of Ti-oxide layer is related with oxygen ion in ZrO2 and liquid phase Ti2Ni. It is considered that compositional deviation from homogeneity and residual stress caused by thermal expansion mismatch are closely related with the formation of the Ti2Ni phase.

• Journal of Powder Materials
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• v.6 no.4
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• pp.270-276
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• 1999

Ti-Ni-Cu alloy powders were fabricated by ball milling, and the properties of these powders were characterized. Mixed 50Ti-(50-x)Ni-xCu powders of 5 to 10at.%Cu composition were milled for 100 hours using SUS 1/4" balls in argon atmosphere. Ball to powder ratio was 20:1 and rotating speed was 100 rpm. Tensile strength, microstructure and phase transformation of ball milled Ti-(50-x)Ni-xCu powders were studied. After 100 hours milling, Ti, Ni and Cu elements were alloyed completely and an amorphous phase was formed. Amorphous phase was crystallized to martensite(B 19') and austenite(B2) after heat treatment for 1 hour at $850^{\circ}C$. As the Cu contents were increased, tensile strength of extruded 6061Al/TiNiCu was decreased, and B19'martensite phases In the TiNi particles were the causes of high tensile stress of extruded 6061Al/TiNiCu.NiCu.

• Journal of Powder Materials
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• v.3 no.3
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• pp.174-180
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• 1996

Microstructure and phase transformation of mechanically alloyed TiNi powders added to aluminium matrix for enhancing the damping properties were studied. Four compositions between 48.5 and 51.5 at% Ti intermetallic compounds were selected to control the fraction of martensite phase. Mechanically alloyed TiNi powders were heat-treated at vacuum of $10^{-6}$ torr for crystallization. Ball milled AI/TiNi composite powders were swaged at room temperature and rolled at 450 $^{\circ}C$. After mechanical alloying for 10 hours, Ti and Ni elements were alloyed completely and amorphous phase was formed. Amorphous phase was crystallized to martensite (Bl9') and austenite(B2) after heat treating for 1 hour at the temperature of 850 $^{\circ}C$, and TiNi$_3$, intermetallic compound was partially formed. Considerable amount of martensite phase was remained after swaging and rolling.

• Journal of Biomedical Engineering Research
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• v.14 no.3
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• pp.283-290
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• 1993

In thls study, the effects of the composltional change of cast Ni-Ti alloys on its characteristics including mechanical properties, phase transformation temperature, and ion releasing rate were investigated. brittle:behavior was shown in the stress-strain curve of the alloy containing low Ti content (Ni-44.0%Ti). By increasing the Ti content, the trend in stress-strain curves changed from that of superelasticity to that of shape memory effect(Ni-44.4%Ti, Ni-45.1%Ti, Ni-45, 5%Ti). Phase transformation temperature ($A_f, {\;}M_5$ point) increased with increasing the Ti content. lon releasing rate of four types of Mi-Ti alloys was very low compared to that of the dental commerical Ni-Cr alloy.

• Journal of Powder Materials
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• v.11 no.1
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• pp.55-59
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• 2004

TiNi bodies were produced from (Ti＋Ni) powder mixture by spark-plasma sintering procerg. The sintering behavior was investigated through the measurement of change in density, densification rate, phase analysis and microstructure. Irrespective of heating rate, sintered bodies with above 97％ relative density could be obtained. TiNi with B2 structure was confirmed as the major phase and $Ti_2Ni,\;TiNi_3$, unreacted Ti, Ni as the second phase. Increase in heating rate suppressed a formation of intermediate phase during sintering process. Increase in holding time at sintering temperature led to a compositional homogenization.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.2
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• pp.99-107
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• 2009

This study produced a design curve and fatigue limit for a variation in volume ratio and reduction ratio of TiNi/Al composites. In many cases, stress-life curve does not indicate fatigue limit, so it was presented by probabilistic-stress-life curve. Goodman diagram was used to analyze the fatigue strength of materials with a finite life determined by repeated load and the fatigue strength of endurance limit with an infinite life. The fatigue experiment was conducted using the scenk-type plane bending specimen in same shape. The result of the fatigue test, which had been conducted under consistent stress amplitude, was examined. (i) The optimal condition for TiNi/Al in accordance with hot pressing (ii) Impacts of fatigue limit caused by a variation in reduction ratio and volume ratio of TiNi/Al composites (iii) Probability distribution for fatigue limit of TiNi/Al2024 and TiNi/Al6061.

• Applied Microscopy
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• v.26 no.3
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• pp.379-388
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• 1996

Structure of premartensite in $Ti_{50}Ni_{49}Fe_1\;and\;Ti_{50}Ni_{50}$ prepared by self-propagating high temperature synthesis (SHS) method has been investigated by a detailed transmission electron microscopy. $Ti_{50}Ni_{49}Fe_1$ consists of microdomain area and needle type domain area. On the other hand, $Ti_{50}Ni_{50}$ consists of microdomain-free and microdomain area, and needle type domain area. Various types of extra superreflections, such as 1/2<100>, 1/2<110> and 1/4<210> type superreflection have been observed in the selected area electron diffractions from microdomain area. Such extra superreflections are due to transformation from B2 structure to distorted B2 structure or premartensite. The present study shows that incommensurate phase forms as an intermediate phase during martensitic transformation. Particularly, in Fe-free $Ti_{50}Ni_{50}$, two types of matrix phases have been observed, microdomain and microdomain-free area. Types of extra superreflections in $Ti_{50}Ni_{50}$ are different from those in $Ti_{50}Ni_{49}Fe_1$, i.e. 1/7<321> type superreflections have been observed, instead of 1/2<110>, 1/2<100>, 1/4<210> types in $Ti_{50}Ni_{49}Fe_1$.