• 한국주조공학회지
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• 제18권5호
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• pp.488-493
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• 1998

Commercially pure titanium(cp-Ti) and Ti-15wt%Zr-4wt%Nb-4wt%Ta alloy were melted in vacuum induction furnace. According to the chemical analysis, the content of carbon was above ASTM standard in the cast ingots because of using graphite crucible. The TEM micostructures of cp-Ti and Ti alloy shows that chemically stable TiC precipitates distribute in ${\alpha}-Ti$ matrix. In order to examine the properties of cp-Ti and Ti-Zr-Nb-Ta alloy for dental applications, mechanical properties and corrosion resistance were investigated. The anodic polarization properties of Ti-Zr-Nb-Zr alloy were almost same as that of cp-Ti in 1% lactic acid. However, as the results of the anodic polarization test in 5% HCl, it was known that Ti-Zr-Nb-Zr alloy showed a rapid decrease in current density at higher potential in comparison with cp-Ti. The yield stress and tensile strengh in Ti-Zr-Nb-Ta were ${\sigma}_{0.2}=623\;MPa$, ${\sigma}_{T.S.}=708\;MPa$ and these results showed 30% increase in yield stress in comparison with cp-Ti.

• 한국재료학회지
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• 제1권4호
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• pp.229-235
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• 1991

$Ta_2O_5$ 박막은 실리콘산화막, 실리콘질화막 박막에 비해 유전율은 높으나 누설전류밀도가 높고, 절연파괴강도가 낮아 DRAM의 커패시터용 재료로서 실용화가 되지 못하고 있다. 본 연구에서는 LPCVD법으로 형성시킨 $300{\AA}$ 두께의 $Ta_2O_5$ 유전체박막에 대해 후속열처리 또는 전극재료를 변화시켜 열악한 전기적 특성의 원인을 규명하고자 하였다. 그 결과 다결정 실리콘 전극의 경우 성막상태의 $Ta_2O_5$ 박막은 전극에 의한 환원반응에 의해 전기적 특성이 열화됨을 알 수 있었고, 이를 TiN 전극의 사용으로 억제시킬 수 있었다. 다결정 실리콘 전극의 경우 성막상태의 $Ta_2O_5$ 유전체는 누설정류밀도가 $10^{-1}A/cm^2$, 절연파괴강도가 1.5MV/cm 정도였으며, $800^{\circ}C$에서 $O_2$열처리를 하면 전기적 특성은 개선되나, 유전율이 낮아진다 TiN 전극을 채용할 경우 누설전류밀도 $10^{-6}~10^{-7}A/cm^2$, 절연파괴강도 7~12MV/cm 로 ONO(Oxide-Nitride-Oxide) 박막과 비슷한 $Ta_2O_5$ 고유전막을 얻을 수 있었다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2013년도 춘계학술대회 논문집
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• pp.79-80
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• 2013

The purpose of this study was to investigate $2^{nd} $nanotube formed surface observation of the Ti-25Ta-xZr alloys using ATO(anodic titanium oxide) technique. Ti-25Ta-xZr alloy was anodized in 1M $H_3PO_4$ electrolytes containing 0.8 Wt. % NaF at room temperature. After formation of nanotube was achieved out, nanotube was eliminated, and then anodization was carried out repeatedly. The microstructures, phase transformation, and morphology of nanotubular Ti-25Ta-xZr alloys and process of nanotube growth by using ATO method was examined by optical microscopy (OM), X-ray diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The ${\alpha}$ phase and ${\beta}$ phases were affected to form the second nanotube morphology of Ti-25Ta-xZr alloys.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.161-161
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• 2013

Two-dimensional electron gas (2DEG) has been investigated at the heterointerface between two insulating dielectric perovskite oxides, $LaAlO_3$ (LAO)/$SrTiO_3$ (STO). Properties of the 2DEG have attracted an enormous interest in condensed matter physics due to multifunctional properties such as the coexistence of ferromagnetism and superconductivity, as well as the high electron mobility. Here, we have grown $Ta_2O_5$ thin films using pulsed laser deposition on $SrTiO_3$ substrate to investigate the electric properties of the $Ta_2O_5$/STO heterointerface. Our research reveal that the non-polar $Ta_2O_5$/$TiO_2$ heterointerface favors the formation of 2DEG similar to that at the LAO/STO heterointerface. The metallic behavior was found in this heterointerface with the current about $10{\sim}100{\mu}A$ at 5 V by using conventional I-V measurements, when the $Ta_20_5$ film thickness reaches over critical thickness, $d_c{\simeq}2uc$. The finding that electrons was localized at $Ta_2O_5$/STO heterointerface have attracted to be strong and new candidate for nanoscale oxide device applications.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.187-187
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• 2010

In this study, we investigated the effect of electrodes on resistance switching of TaOx film. Pt, Ni, TiN, Ti and Al metal electrodes having the different oxidation degree were deposited on TaOx/Pt stack. Unipolar resistance switching behavior in Pt or Ni/TaOx/Pt MIM stacks was investigated, but bipolar resistance switching behavior in TiN, Ti or Al /TaOx/Pt MIM stacks was shown. We investigated that the voltage dependence of capacitance was decreased with higher oxidation degree of metal electrodes. Through the C-V results, we expected that linearity ($\alpha$) and quadratic ($\beta$) coefficient was reduced with an increase of interface layer between top electrode and Tantalum oxide. Transmission Electron Microscope (TEM) images depicted the thickness of interface layer formed with different oxidation degree of top electrode. Unipolar resistance switching behavior shown in lower oxidation degree of top electrode was expected to be generated by the formation of the conducting path in TaOx film. But redox reaction in interface between top electrode and Tantalum oxide may play an important role on bipolar resistance switching behavior exhibited in higher oxidation degree of top electrode. We expected that the resistance switching characteristics were determined by oxidation degree of metal electrodes.

• 한국재료학회지
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• 제17권1호
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• pp.6-10
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• 2007

In the present study, we investigated the formation of self-organized nanostructure oxide layers on CP Ti and Ti-10Ta-10Nb alloy in an electrolyte of 1M phosphoric acid and 1.5 wt% Hydrofluoric acid. The morphology of oxide film on substrate was observed using scanning electron microscopy and transmission electron microscopy The surface roughness of titanium oxide film was analyzed by atomic force microscopy and the crystalline of specimen was investigated using X-ray diffractometer. The results of this study showed that well-aligned titanium oxide nanotubes are formed with diameter of approx. 100nm and length of approx. 500nm with CP Ti. However, it is clear that TiTaNb alloy highly irregular structure with various diameters. Transmission electron microscope investigations show that the specimens were confirmed as amorphous. Such titanium oxide nanotubes are expected a well-adhered bioacitive surface layer on titanium substrate for orthopedics and dental implants.

• 열처리공학회지
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• 제18권2호
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• pp.91-98
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• 2005

Both commercially pure titanium and Ti-6Al-4V alloy have been widely used as biomaterials because of their excellent biocompatibility, corrosion resistance and mechanical properties. However, in recent years, vanadium has been found to cause cytotoxic effects and adverse tissue reactions, while aluminium has been associated with potential neurological disorders. A newly designed ${\alpha}+{\beta}$ type Ti alloy, Ti-10Ta-10Nb alloy showed superior properties to CP Ti and Ti-6Al-4V alloy in the point of biomaterial, and elucidated the future uses as a biomaterial. Microstructural changes of Ti-10Ta-10Nb alloy after hot-rolling, warm-rolling, solution and aging treatment were investigated. According to TEM results, the microstructures after solution treatment were composed of mostly ${\alpha}$ phase with a trace of ${\beta}$ phase due to adding ${\beta}$-phase stabilizer tantalum and niobium. The microstructures after warm-rolling is coarse and elongated ${\alpha}$ phase and hot rolling resulted in very fine ${\alpha}$ widmanst$\ddot{a}$tten. The highest value of hardness was obtained by aging treatment at $400^{\circ}C$ for 20hr in which microstructure consisted of very fine ${\alpha}$ phase in ${\beta}$ matrix.

• 한국세라믹학회지
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• 제25권3호
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• pp.293-299
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• 1988

The effects of flux KCl and dopants, La2O3 and Ta2O5, on the PTCR characteristics in molten salt synthesized BaTiO3 have been studied. The resistivity of BaTiO3 at room temperature decreases with increasing amount of dopant La2O3 up to 0.2 atom%, and then increases with La2O3 content. In case of dopant Ta2O5, it increases with increasing amount ofthe dopant. These results could be explained by observation of the microstructure and defect equation. From the results of complex impedance-frequency characteristics, the grain resistances are almost same but the resistances at the grain boundary are quite different.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.185-185
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• 2014

In this study, we investigated surface characteristics of hydroxyapatite coated surface on nano/micro pore structured Ti-35Ta-xNb alloys. This paper was focus on morphology and corrosion resistance of Anodic oxidation. To prepare the samples, Ti-35Ta-xNb (x= 0, 10 wt. %) alloys were manufactured by arc melting and heat-treated for 12 h at $1050^{\circ}C$ in Ar atmosphere at $0^{\circ}C$ water quenching. Micro-pore structured surface was performed using anodization with a DC power supply at 280 V for 3 min, nanotube formed on Ti-35Ta-xNb alloys was performed using DC power supply at 30 V in 60 min at room temperature. Surface morphology and structure were examined by field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.187-187
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• 2014

In this study, we investigated mechanical properties and surface characteristics of Ti-25Ta-xHf alloys. The samples were manufactured for composition of Ti-25Ta-xHf(x=0 to 15 wt. %) alloys. Each alloy was melted twenty times in an arc-melting vacuum furnace. The microstructural phases and phase transformation of Ti-25Ta-xHf alloys were identified with the aid of an XRF, XRD and DSC. And mechanical properties were investigated using Vickers hardness, nanoindentation, and tensile test.