• Journal of Korean Dental Science
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• 제10권1호
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• pp.10-21
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• 2017

Purpose: The purpose of this study was to investigate the electrochemical characteristics of nanotubular Ti-25Nb-xZr ternary alloys for dental implant materials. Materials and Methods: Ti-25Nb-xZr alloys with different Zr contents (0, 3, 7, and 15 wt.%) were manufactured using commercially pure titanium (CP-Ti), niobium (Nb), and zirconium (Zr) (99.95 wt.% purity). The alloys were prepared by arc melting in argon (Ar) atmosphere. The Ti-25Nb-xZr alloys were homogenized in Ar atmosphere at $1,000^{\circ}C$ for 12 hours followed by quenching into ice water. The microstructure of the Ti-25Nb-xZr alloys was examined by a field emission scanning electron microscope. The phases in the alloys were identified by an X-ray diffractometer. The chemical composition of the nanotube-formed surfaces was determined by energy-dispersive X-ray spectroscopy. Self-organized $TiO_2$ was prepared by electrochemical oxidation of the samples in a $1.0M\;H_3PO_4+0.8wt.%$ NaF electrolyte. The anodization potential was 30 V and time was 1 hour by DC supplier. Surface wettability was evaluated for both the metallographically polished and nanotube-formed surfaces using a contact-angle goniometer. The corrosion properties of the specimens were investigated using a 0.9 wt.% aqueous solution of NaCl at $36^{\circ}C{\pm}5^{\circ}C$ using a potentiodynamic polarization test. Result: Needle-like structure of Ti-25Nb-xZr alloys was transform to equiaxed structure as Zr content increased. Nanotube formed on Ti-25Nb-xZr alloys show two sizes of nanotube structure. The diameters of the large tubes decreased and small tubes increased as Zr content increased. The lower contact angles for nanotube formed Ti-25NbxZr alloys surfaces showed compare to non-nanotube formed surface. The corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface showed longer the passive regions compared to non-treatment surface. Conclusion: It is confirmed that corrosion resistance of alloy increased as Zr content increased, and nanotube formed surface has longer passive region compared to without treatment surface.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.33.1-33.1
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• 2009

Lead-free (1-x)$(Na_{0.5}K_{0.5})NbO_3$-xBa($Ti_{0.9}Sn_{0.1})O_3$ [NKN-BTS-100x] ceramics doped with 1 mol% $MnO_2$ have been prepared by the conventional solid state method and their structural and piezoelectric properties were investigated. The NKN-BTS-100x ceramics exhibited a dense and homogeneous microstructure when they were sintered at $1030-1150^{\circ}C$. Grain growth was observed for the specimen sintered at relatively low temperature of $1050^{\circ}C$. A tetragonal/orthorhombic morphotropic phase boundary (MPB) in the perovskite structure was also appeared for the NKN-BTS-100x ceramics (0.04$1050^{\circ}C$. The enhanced piezoelectric properties in the NKN-BTS ceramics with a MPB composition were obtained. Especially, for the NKN-BTS-6 ceramics, a high dielectric constant (${\varepsilon}^T_3/\varepsilon_0=1,400$), piezoelectric constant ($d_{33}=237$) and electromechanical coupling factor ($k_p=0.42$) were obtained.

• Korean Journal of Materials Research
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• 제21권11호
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• pp.617-622
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• 2011

The effect of oxygen on the shape memory characteristics in Ti-18Nb-6Zr-XO (X = 0-1.5 at%) biomedical alloys was investigated by tensile tests. The alloys were fabricated by an arc melting method at Ar atmosphere. The ingots were cold-rolled to 0.45 mm with a reduction up to 95% in thickness. After severe cold-rolling, the plate was solution-treated at 1173 K for 1.8 ks. The fracture stress of the solution-treated specimens increased from 450 Mpa to 880 MPa with an increasing oxygen content up to 1.5%. The fracture stress increased by 287MPa with 1 at% increase of oxygen content. The critical stress for slip increased from 430 MPa to 695 MPa with an increasing oxygen content up to 1.5 at%. The maximum recovery strain of 4.1% was obtained in the Ti-18Nb-6Zr-0.5O (at%) alloy. The martensitic transformation temperature decreased by 140 K with a 1.0 at% increase in O content, which is lower than that of Ti-22Nb-(0-2.0)O (at%) by 20 K. This may have been caused by the effect of the addition of Zr. This study confirmed that addition of oxygen to the Ti-Nb-Zr alloy increases the critical stress for slip due to solid solution hardening without being detrimental to the maximum recovery strain.

• Proceedings of the Korean Ceranic Society Conference
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• 한국세라믹학회 2000년도 춘계총회,특별강연,심포지움,연구발표회
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• pp.138.2-138.2
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• 2000

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.30-30
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• 2008

Lead-free piezoelectric ceramics 0.97$(Na_{0.5}K_{0.5})NbO_3$-0.03Ba$(Ti_{1-x}Sn_x)O_3$ [NKN-BTS-x] ceramics doped with 1 mol% $MnO_2$ have been fabricated by a sintering technique with muffling. The $MnO_2$-doped NKN-BTS-x ceramics with x$\leq$0.2 have pure orthorhombic perovskite structure at room temperature. The dense microstructure was developed with grain growth as an increase of amount of Sn. Moreover, the addition of Sn was found to have a significant influence on piezoelectric properties. In particular, the $MnO_2$-doped NKN-BTS-0.1 ceramics showed improved piezoelectric properties of piezoelectric constant ($d_{33}$=145pC/N), relatively large electromechanical coupling factor ($k_p$=43%), dielectic constant (${\varepsilon}^T_{33}/{\varepsilon}_0$=676) dielectric loss (tan$\delta$=1.3%).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.317-321
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• 2002

Piezoelectric properties of $(Pb_{1-x}Y_x)[(Ni_{1/3}Nb_{2/3})_{0.15}(Zr_{1/2}Ti_{1/2)})_{0.85}]O_{3}$ (x=0~0.05) ceramics were investigated, The stoichiometric PNN-PZT ceramics required the sintering temperature above $1100^{\circ}C$, but the addition of $Y_{2}O_{3}$ in the PNN-PZT ceramic lowered the sintering temperature down to $1000^{\circ}C$. In case of x=0.005, the electro-mechanical coupling $factor(K_p)$, the piezoelectric $constant(d_{33})$, and the maximum strain ratio of PNN-PZT ceramics sintered at $1000^{\circ}C$ were 53.1%, 395pC/N, and $2200{\times}10^{-6}$ respectively, A 30-layer piezoelectric actuator$(10{\times}10{\times}1.7mm)$ fabricated with the above material showed the maximum strain of $2.09{\mu}m$ under 100V DC bias.

• Electrical & Electronic Materials
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• 제8권2호
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• pp.190-195
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• 1995

Temperature dependences of the dielectric constant K(T), remanent polarization $P_{r}$, (T), effective birefringence overbar .DELTA.n(T), transmitted light intensity and quadratic electro optic coefficient R(T) of the two-stage sintered xBa(L $a_{1}$2/N $b_{1}$2/) $O_{3}$-(1-x)Pb(Z $r_{y}$ $Ti_{1-y}$) $O_{3}$(x=0.085, 0.09, 0.40.leq.y.leq.0.70) ceramics were investigated. Increasing the PbZr $O_{3}$ contents, the crystal structure of a specimen was changed from a tetragonal phase to a rhombohedral and cubic phase, and the phase transition was showed a diffuse phase transition(DPT) characteristics. In the compositions which located on the PE-FE phase boundary, the discrepancy was observed between the Curie temperature and temperature which a microscopic polarization and effective birefringence were disappeared.red.d.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.228-229
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• 2006

본 연구에서는 초음파 모터 등의 고출력 액츄에이터에 응용 가능한 $04Pb(Ni_{1/3}Nb_{2/3})O_3-6Pb(Zr_xTi_{1-x})O_3$ 조성시스템에 소결온도를 달리하여 압전, 유전특성 및 미세구조에 관해 고찰하였다. 본 조성을 $1200^{\circ}C$ 온도에서 2, 4, 6, 8시간 소결하여 시편을 제조하였으며 이의 결정구조 및 미세조직을 분석하였다. 소결시간 증가에 따라 전기기계결합계수와 기계적품질계수는 증가하였으며, 압전상수는 Zr(Zr+Ti)비 0.390까지 증가하였으나 그 이상 증가함에 따라 감소하였다. 압전특성은 $1200^{\circ}C$에서 4시간 소결한 Zr=0.390인 조성에서 ${\varepsilon}_r$ = 4487, $k_p$ = 0.72. $d_{33}$ = 710, $Q_m$ =109의 우수한 특성을 나타내었다.

• The Transactions of the Korean Institute of Electrical Engineers
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• 제44권8호
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• pp.1068-1074
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• 1995

Effect of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ addition on the phase changes and microwave dielectric properties of BaTi $O_{3}$-3Ti $O_{2}$ ceramics were investigated. Addition of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ to BaTi $O_{3}$-3Ti $O_{2}$ resulted in the formation of Ba $Ti_{4}$$O_{9}$, $Ba_{2}$ $Ti_{9}$ $O_{20}$, Ba(Zn$_{1}$3/Nb$_{2}$3/) $O_{3}$, and Ti $O_{2}$ phases. Ba $Ti_{4}$$O_{9}$ phase was gradually transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$. This was identified by XRD and microstructure. As the Ba $Ti_{4}$$O_{9}$ phase transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$ phase, the dielectric constant increased to 37.5. Q*f$_{o}$ value was 40000 at x=0.04, and the temperature coefficient of resonant frequency was +10ppm/.deg. C.C.. C.C.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.171-171
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• 2003

공정기술의 향상으로 DRAM(dynamic random acess memory)의 고집적화가 이루어지고 있으며, 각 개별소자 및 셀 영역의 점유면적의 감소가 요구되어지고 있다. 따라서 기존에 사용하던 NO (Si$_3$N$_4$/SiO$_2$)박막보다 유전율이 높은 고유전물질에 대한 연구가 진행되고 있다. Ta$_2$O$_{5}$, $Y_2$O$_3$, HfO$_2$, ZrO$_2$,Nb$_2$O$_{5}$, BaTiO$_3$, SrTiO$_3$ 및 (BaSr)TiO등이 고유전물질로 연구되고 있는데 그 중 공정의 안정성, 누설전류의 우수성으로 인해 Ta$_2$O$_{5}$이 많이 연구되고 있다. 본 실험에서는 TiO$_2$가 8 mol%가 첨가된 Ta$_2$O$_{5}$의 열처리 온도에 따른 전기적, 유전특성을 살펴보려고 한다살펴보려고 한다