• 한국표면공학회:학술대회논문집
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• 한국표면공학회 1999년도 춘계학술발표회 초록집
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• pp.5-5
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• 1999

A novel process is proposed to improve oxidation resistance of Ti-Al intermetallic compounds at elevated temperatures by both Cr addition and pre-sulfidation, where TiAl alloys withlor without Cr addition were sulfidized at 1173K for 86.4ks at a 1.3 Pa sulfur partial pressure in a $H_2-H_2S$ gas mixture. The pre-sulfidation treatment formed a thin Cr-Al alloy layer as well as 7~10 micrometer $TiAl_3$ and $TiAl_2$ layer, due to selective sulfidation of Ti. Oxidation resistance of the pre-sulfidation processed TiAl 4Cr alloy was examined under isothermal and heat cycle conditions between room temperature and 1173K in air. Changes in $TiAl_3$ into $TiAl_2$ and then TiAl phases as well as their effect on oxidation behavior were investigated and compared with the oxidation behavior of the TiAl-4Cr alloy as TiAl and pre-sulfidation processed TiAl aHoys. After oxidation for up to 2.7Ms a protective $Al_2O_3$ scale was formed, and the pre-formed $TiAl_3$ changed into $TiAl_2$ and the $Al_2Cr$ phase changed into a CrAlTi phase between the $Al_2O_3$ scale and $TiAl_2$ layer. The pre-sulfidation processed TiAl-4Cr alloy had very good oxidation resistance for longer times, up to 2.7 Ms, in contrast to those observed for the pre-sulfidation processed TiAl alloy where localized oxidation occurred after 81 Oks and both the TiAl and TiAl-4Cr alloys themselves corroded rapidly from the initial stage of oxidation

• 한국표면공학회지
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• 제39권1호
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• pp.43-48
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• 2006

The oxidation behavior and Biocompatibility of pure Ti and Ti-8Ta-3Nb alloy were studied in dry air atmosphere. The specimens showed that Ti-8Ta-3Nb alloy had higher oxidation resistance than pure Ti at $650^{\circ}C$. Cytotoxicity test also revealed that moderate oxidation treatment lower cell toxicity and Ti-8Ta-3Nb alloy showed better results compared with pure Ti. The weight gains during the oxidation increase rapidly at temperature above $600^{\circ}C$.

• 한국주조공학회지
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• 제29권5호
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• pp.187-191
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• 2009

Microstructures and shape memory characteristics of $Ti_{50}Ni_{20}Cu_{30}$ alloy strips fabricated by arc melt overflow have been investigated by means of XRD, optical microscopy and DSC. The microstructure of as-cast strips exhibited columnar grains normal to the strip surface. X-ray diffraction analysis showed that one-step martensitic transformation of B2-B19 occurred in the alloy strips. According to the DSC analysis, it was known that the martensitic transformation temperature ($M_s$) of B2 $\rightarrow$ B19 in $Ti_{50}Ni_{20}Cu_{30}$ strip is $57^{\circ}C$. During thermal cyclic deformation with the applied stress of 60 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be $3.7^{\circ}C$ and 1.6%, respectively. The as-cast strip of $Ti_{50}Ni_{20}Cu_{30}$ alloy also showed a superelasticity and its stress hysteresis was as small as 14 MPa. These mechanical properties and shape memory characteristics of the alloy strips were ascribed to B2-B19 transformation and the controlled microstructures produced by rapid solidification of the arc melt overflow process.

• 한국항행학회논문지
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• 제7권2호
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• pp.211-216
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• 2003

본 논문에서는 오래 전부터 NMOS의 게이트 전극으로 사용된 폴리실리콘을 대체할 수 있는 Ta-Ti 합금의 특성에 대해 연구하였다. 실리콘 기판 위에 열적으로 성장된 $SiO_2$ 위에 Ta과 Ti의 두 타깃을 사용하여 co-sputterring 방법으로 Ta-Ti 합금을 증착하였다. 각각의 타깃은 100W의 sputtering power로 증착하여 시편을 제작하였다. 또한 비교 분석을 위하여 Ta을 100W의 sputtering power로 증착한 시편도 제작하였다. 제작된 Ta-Ti 합금 게이트의 열적/화학적 안정성을 검토하기 위하여 $600^{\circ}C$에서 급속열처리를 수행한 결과 소자의 성능 저하는 나타나지 않았다. 또한 전기적 특성 분석 결과 Ta-Ti 합금은 NMOS에 적합한 일함수인 4.13eV를 산출해 낼 수 있었고, 면저항 역시 폴리실리콘에 비해 낮은 값을 얻을 수 있었다.

• 대한기계학회논문집A
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• 제29권10호
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• pp.1315-1320
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• 2005

TiNi alloy fiber was used to recover the original shape of materials using its shape memory effect. The shape memory alloy plays an important role within the metal matrix composite. The shape memory alloy can control the crack propagation in metal matrix composite, and improve the tensile strength of the composite. In this study, TiNi/A16061 shape memory alloy(SMA) composite was fabricated by hot press method, and pressed by a roller for its strength improvement. The four kinds of specimens were fabricated with $0\%,\;3.2\%,\;5.2\%\;and\;7\%$ and volume fraction of TiNi alloy fiber, respectively. A fatigue test has performed to evaluate the crack initiation and propagation for the TiNi/A16061 SMA composite fabricated by かis method. In order to study the shape memory effect of the TiNi alloy fiber, the test has also done under both conditions of the room temperature and high temperature. The relationship between the crack growth rate and the stress intensity factor was clarified for the composite, and the cold rolling effect was also studied.

• 열처리공학회지
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• 제7권4호
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• pp.253-261
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• 1994

Transformation behavior and superelastic behavior of Ti-Ni-Cu alloys with various Cu content has been investigated by means of electrical resistivity measurement, X-ray diffraction, tensile test and transmission electron microscopy. Two types of heat treatment are given to the specimens: i) Solutions treatment. ii) thermo-mechanical treatment. The transformation sequence in solution treated Ti-Ni-Cu Alloys substituted by Cu for Ni up to 5at.% occurs to $B2{\rightleftarrows}B19^{\prime}$ and it proceeds in two stages by addition of 10at.%Cu, i. e, $B2{\rightleftarrows}B19{\rightleftarrows}B19^{\prime}$. Also, it has been found that Ti-30Ni-20Cu alloy transformed in one stage : $B2{\rightleftarrows}B19$. The thermo-mechanically treated Ti-47Ni-3Cu alloy transformed in two stages: B2${\rightleftarrows}$rhomboheral phase${\rightleftarrows}B19^{\prime}$, while transformation sequence in Ti-45Ni-5Cu and Ti-40Ni-10Cu alloy transformed as same as solution treated specimens. The critical stress for inducing slip deformation in solution treated and thermo-mechanically treated Ti-40Ni-10Cu alloy is about 90MPa and 320Mpa respectively.

• 한국주조공학회지
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• 제24권6호
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• pp.314-322
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• 2004

The CaO crucible is expected to serve as a useful tool for melting Ti and its alloys due to its thermodynamic stability. However, tjere still remain problems that need to be resolved in the melting of Ti and its alloys to enable commerical use. The cause of the defects of Ti-6AI-4V alloy castings melted in the CaO crucible were examined and compared with induction skull melting. The key factors of the melting technique using the CaO crucible, affecting the quality of Ti-6AI-4V alloy castings, were investigated. Defects of the Ti-6AI-4V alloy castings are caused by the chemical reduction of CaO by Ti. Pressurizing with argon gas in a vacuum induction chamber is effective for reducing the defects. Preheating of the charged material in the crucible and quick pouring into a mold of lower temperature, just after melting down, are important for produsing sound Ti-6AI-4V castings.

• The Journal of Advanced Prosthodontics
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• 제1권1호
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• pp.56-61
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• 2009

STATEMENT OF PROBLEM. The success of titanium implants is due to osseointegration or the direct contact of the implant surface and bone without a fibrous connective tissue interface. PURPOSE. The purpose of this study was to evaluate the osteoblast precursor response to titanium-10 tantalum-10 niobium(Ti-Ta-Nb) alloy and its sputtered coating. MATERIAL AND METHODS. Ti-Ta-Nb coatings were sputtered onto the Ti-Ta-Nb disks. Ti6-Al-4V alloy disks were used as controls. An osteoblast precursor cell line, were used to evaluate the cell responses to the 3 groups. Cell attachment was measured using coulter counter and the cell morphology during attachment period was observed using fluorescent microscopy. Cell culture was performed at 4, 8, 12 and 16 days. RESULTS. The sputtered Ti-Ta-Nb coatings consisted of dense nanoscale grains in the range of 30 to 100 nm with alpha-Ti crystal structure. The Ti-Ta-Nb disks and its sputtered nanoscale coatings exhibited greater hydrophilicity and rougher surfaces compared to the Ti-6Al-4V disks. The sputtered nanoscale Ti-Ta-Nb coatings exhibited significantly greater cell attachment compared to Ti-6Al-4V and Ti-Ta-Nb disks. Nanoscale Ti-Ta-Nb coatings exhibited significantly greater ALP specific activity and total protein production compared to the other 2 groups CONCLUSIONS. It was concluded that nanoscale Ti-Ta-Nb coatings enhance cell adhesion. In addition, Ti-Ta-Nb alloy and its nanoscale coatings enhanced osteoblast differentiation, but did not support osteoblast precursor proliferation compared to Ti-6Al-4V. These results indicate that the new developed Ti-Ta-Nb alloy and its nanoscale Ti-Ta-Nb coatings may be useful as an implant material.

• 한국진공학회지
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• 제10권2호
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• pp.234-240
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• 2001

본 연구에서는 Mg을 첨가한 Cu-alloy에 의해 TiN의 확산방지능력을 향상시키고자 하였다. Cu(Mg) 박막은 대기노출시킨 TiN박막위에 증착되었으며 열처리시 Cu 박막내의 Mg은 TiN의 표면에 있는 산소와 반응하여 매우 얇은(~100 $\AA$) MgO를 형성하게되고 MgO에 의해 TiN의 확산방지능력은 Cu(4.5 at.%Mg)의 경우 $800^{\circ}C$까지 향상됨을 알 수 있었다. 그러나 Cu(Mg) a]toy는 TiN위에서 접착특성이 좋지 않기 때문에 TiN을 $O_2$plasma 처리하였으며 $O_2$ plasma 처리후 $300^{\circ}C$ 진공열처리를 통해 접착력이 크게 향상되는 것을 알 수 있었다. 이는 $O_2$ plasma 처리에 의해 TiN표면에 Mg과 반응할 수 있는 산소의 양이 증가하는 데 기인하며 이에 따라 Mg의 계면이동이 크게 증가되어 치밀한 MgO가 형성됨을 확인하였다. 그리고 $O_2$ plasma 처리시 RF power를 증가시키면 계면으로 이동하는 Mg의 양이 오히려 감소하였고 이것은 TiN의 표면이 $TiO_2$로 변하여 Mg과 결합할 수 있는 산소의 양이 상대적으로 감소하였기 때문인 것으로 생각된다. 또한 접착층으로서 Si을 50$\AA$ 증착하여 접착력을 크게 향상시켰으며 Si 증착에 의한 TiN의 확산방지능력은 감소되지 않는 것을 알 수 있었다.

• 한국표면공학회지
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• 제49권6호
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• pp.560-566
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• 2016

In this study, porcelain bonding strength and mechanical properties of sintered Ni-Cr-Ti alloy for dental prosthodontics have been researched experimentally. Mechanical and morphological characteristics of the alloys were examined by Vickers hardness test, tensile and bonding strength test, surface roughness test, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. In the sintered Ni-13Cr-xTi alloys, morphology of sintered alloy showed porous matrix diffused with alloying elements of Cr and Ti, and showed dendritic structure after melting process. From the XRD results, the second phases of NiCr, $Ni_3Cr$, and $Ni_3Ti$ were formed in the case of sintered and melted Ni-13Cr-xTi alloys. The tensile strength and hardness of Ni-13Cr-xTi alloys increased, as Ti content increased. Surface roughness increased, as Ti content increased. The bonding strength between metal and porcelain of Ni-13Cr-5Ti alloy was higher than those of Ni-13Cr and Ni-13Cr-10Ti alloys