• 한국결정성장학회지
• /
• 제16권5호
• /
• pp.181-188
• /
• 2006

스컬용융법에 의해 성장시킨 rutile단결정을 성장 축과 수평 또는 수직으로 절단한 후 ${\phi}5.5mmx1.0mm$ 크기의 웨이퍼로 양면연마 하였다. 연마한 흑색 웨이퍼들은 $1200^{\circ}C$에서 $3{\sim}15$시간, $1300^{\circ}C$에서 $10{\sim}50$시간 annealing을 행함에 의해 옅은 황색으로 변화되었다. Annealing 후 구조적 및 광학적 특성은 비중, SEM-EBSP, XRD, FT-IR, laser Raman, PL 그리고 XPS 등으로 분석하였고, 이들 결과들은 공기중의 무게 증가, 수중의 무게 및 비중의 감소,침상의 2차상, 산소이온 확산 및 $Ti^{3+}$ 이온이 감소되는 것으로 분석되었다. 이는 스컬용융법에 의해 성장된 rutile 단결정에 $O_v,\;Ti^{3+},\;O_v-Ti^{3+}$ interstitial 그리고 $F^+-H^+$와 같은 결함의 존재를 의미한다.

• The Korean Journal of Ceramics
• /
• 제2권3호
• /
• pp.131-136
• /
• 1996

The electrical conductivity of polycrystalline TiO2 samples was measured over the temperature range 1000°-1400℃ and from 0.21 to 10-16 atm of oxygen. Based on the excellent fit observed between the theoretically derived relatin σ3=(Aσ+B)Po2-1/2+D'σ2 and the experimental conductivity data, the nonstoichimetric defect structure of TiO2 was rationalized in terms of a defect model involving quasi-free electrons and both singly and doubly ionized oxygen vacancies. The standard enthalpy of formation for the following defect reactions in TiO2. (a) OO={{{{ { 1} over {2 } }}O2(g)+VO+e'; Δ{{{{ { H}`_{o } ^{a } }}=5.15(eV) (b) OO={{{{ { 1} over {2 } }}O2(g)+VO+2e'; Δ{{{{ { H}`_{0 } ^{ a} }}=6.30(eV) (c) VO=VO+e'; Δ{{{{ { H}`_{0 } ^{a } }}=1.15(eV) were determined from the temperature dependence of A and B obtained from the above relation and from the experimental expression between the electron mobility and temperature. The electrical conductivity of TiO2 in air below approximately 950℃ appears, on the basis of this investigation, to be impurity controlled due to the presence of aluminum rather than intrinsic conduction.

• 한국재료학회지
• /
• 제31권10호
• /
• pp.552-561
• /
• 2021

For the purpose of manufacturing a high efficiency TiO₂ photocatalyst, B-doped TiO₂ photocatalysts are synthesized using a plasma electrolytic oxidation method in 0.5 M H₂SO₄ electrolyte with different concentrations of H₃BO₃ as additive. For the B doped TiO₂ layer fabricated from sulfuric electrolyte having a higher concentration of H₃BO₃ additive, the main XRD peaks of (101) and (200) anatase phase shift gradually toward the lower angle direction, indicating volume expansion of the TiO₂ anatase lattice by incorporation of boron, when compared with TiO₂ layers formed in sulfuric acid with lower concentration of additive. Moreover, XPS results indicate that the center of the binding energy peak of B1s increases from 191.45 eV to 191.98 eV, which suggests that most of boron atoms are doped interstitially in the TiO₂ layer rather than substitutionally. The B doped TiO₂ catalyst fabricated in sulfuric electrolyte with 1.0 M H₃BO₃ exhibits enhanced photocurrent response, and high efficiency and rate constant for dye degradation, which is ascribed to the synergistic effect of the new impurity energy band induced by introducing boron to the interstitial site and the improvement of charge transfer reaction.

• 대한화학회지
• /
• 제31권3호
• /
• pp.215-224
• /
• 1987

0.35. 0.75 및 1.25mol% $MgO-TiO_2$계의 전기전도도가 $600{\sim}1100^{\circ}C$ 및 $10^{-8}{\sim}10^{-1}$ atm의 산소분압하에서 측정되었다. 일정한 산소분압하에서 $log{\sigma}$ vs. 1/T은 두 온도구간에서 직선관계를 보였으며 직선의 기울기로 부터 계산된 활성화에너지는 본성 영역과 외성 영역에서 각각 1.94eV 및 0.48eV이다. $log\;{\sigma}$ vs log $Po_2$는 본성 영역에서 ${\sigma}\;{\alpha}\;$Po_2^{-1/6}$이며 외성 영역에서 ${\sigma}\;{\alpha}\;$Po_2^{-1/4}$이다. 이 계의 결함구조는 외성 영역에서 $V\"{o}$이며 본성 영역에서 $Ti^3$.로 제안되었다. 특히 외성 영역에서 polaron model이 ${\sigma}$의 T 및 p 의존성으로 부터 규명되었다.

• 공업화학
• /
• 제3권1호
• /
• pp.88-99
• /
• 1992

광 전기분해시 양극으로 사용되는 산화티타늄 반도체 전극의 안정성을 증대시키고 효율향상을 위해서 순수한 티타늄 전극을 양극 산화법, 전기로 산화법, 불꽃 산화법으로 산화 피막을 제조하였으며 In을 Ti와 $TiO_2$소지에 전기도금을 한 후 전기로 산화법으로 혼합 산화물을 제조하였다. 또한 $Al_2O_3$ 와 NiO는 진공증착 방법을 이용하여 Ti 소지위에 증착시킨 후 전기로 산화법을 이용하여 혼합 산화물을 제조하였다. 에너지변환 효율(${\eta}$)은 인가전위에 따라서 다른 값을 갖는데 0.6V로 계산하여 보면 $1200^{\circ}C$의 불꽃으로 2분간 산화시킨 전극이 0.98%로 가장 큰 값을 가졌으며 양극 산화법으로 제조한 전극의 ${\eta}$는 0.14%로 작은 값을 보여 주었다. 한편 $800^{\circ}C$ 전기로에서 10분간 산화시킨 전극의 ${\eta}$는 0.57%로 띠간 에너지는 2.9eV로 나타났다. 한편 In을 Ti 및 $TiO_2$ 소지위에 전기도금시킨 전극의 ${\eta}$는 0.8%였으며 인가전위가 증가함에 따라서 ${\eta}$는 증가하였다. 그러나 $Al_2O_3$와 NiO를 Ti소지위에 진공증착시킨 전극의 ${\eta}$는 다른 전극들에 비해서 가장 낮은 값을 나타내었다.

• 한국재료학회지
• /
• 제22권3호
• /
• pp.150-154
• /
• 2012

Ti-6Al-4V ELI (Extra Low Interstitial) alloy have been widely used as alternative to bone due to its excellent biocompatibility, although it still has many problems such as high elastic modulus and toxicity. Therefore, biomaterials with low elastic modulus and non toxic characteristics have to be developed. A novel ${\beta}$ Ti-35wt%Nb-7wt%Zr-Calcium pyrophosphate (CPP) composite that is a biocompatible alloy without elemental Al or V was fabricated by spark plasma sintering (SPS) at $1000^{\circ}C$ under 70 MPa using high energy mechanical milled (HEMM) powder. The microstructure and phases of the milled powders and the sintered specimens were studied using SEM, TEM, and XRD. Ti-35wt%Nb-7wt%Zr alloy was transformed from ${\alpha}$ phase to ${\beta}$ phase in the 4h-milled powder by sintering. The sintered specimen using the 4h-milled powder showed that all the elements were distributed very homogeneously and had higher density and hardness. ${\beta}$ Ti alloy-CPP composite, which has nanometer particles, was fabricated by SPS using HEMMed powder. During the sintering process, $CaTiO_3$, TixOy, and CaO were formed because of the reaction between Ti and CPP. The Vickers hardness of the composites increases with the increase of the milling time and the addition of CPP. The biocompatibility of the Ti-Nb-Zr alloys was improved by addition of CPP.

• 한국재료학회지
• /
• 제23권2호
• /
• pp.135-142
• /
• 2013

The Ti-6Al-4V extra low interstitial (ELI) alloy has been widely used as an orthopedic implant material because of its excellent mechanical properties and biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity of the Al and V elements. Therefore, non-toxic biomaterials with a low elastic modulus need to be developed. A high energy mechanical milling (HEMM) process is introduced to improve the effect of sintering. Rapid sintering of spark plasma sintering (SPS) under pressure was used to make an ultra fine grain of Ti-25 wt.%Nb-7 wt.%Zr-10 wt.%Mo-(10 wt.%CPP) composites with bio-attractive elements for increasing strength. These composites were fabricated by SPS at $1000^{\circ}C$ at 60 MPa using HEMM powders. During the sintering process, $CaTiO_3$, TixOy, and CaO were formed because of the reaction between Ti and CPP. The effects of CPP content on the physical and mechanical properties of the sintered Ti-Nb-Zr-Mo-CPP composites were investigated. The biocompatibility and corrosion resistance of the Ti-Nb-Zr-Mo alloys were improved by the addition of CPP.

• 대한화학회지
• /
• 제26권3호
• /
• pp.128-134
• /
• 1982

0.40, 0.80 및 1.60 mol %의 산화망간을 함유한 이산화티탄의 전기전도도를 $10^{-8}\;to\;10^{-1}$ atm의 산소분압하에서 100 ~ 400$^{\circ}$C 및 1100 ~ 1300$^{\circ}$C의 온도에서 측정하였다. 일정한 산소분압하에서 측정된 전기전도도 값을 온도의 역수에 대하여 도시한 결과 저온 및 고온 영역에서 직선관계를 나타내었으며 활성화에너지는 각각 0.18 및 3.70eV이다. 전기전도도의 산소분압 의존성은 저온영역에서 -1/6이며 고온 영역에서 -1/4이다. 저온 영역과 고온영역에서의 결함구조가 각각(Vo-2e') 및 $Ti^3$임을 밝혔으며 전기전도 메카니즘과 가능한 전도띠 모델이 제안되었다.

• 한국재료학회지
• /
• 제21권7호
• /
• pp.384-390
• /
• 2011

Ti-6Al-4V ELI (Extra Low Interstitial) alloy has been widely used as an alternative to bone due to its excellent biocompatibility. However, it still has many problems, including a high elastic modulus and toxicity. Therefore, nontoxic biomaterials with a low elastic modulus should be developed. However, the fabrication of a uniform coating is challenging. Moreover, the coating layer on Ti and Ti alloy substrates can be peeled off after implantation. To overcome these problems, it is necessary to produce bulk Ti and Ti alloy with hydroxyapatite (HA) composites. In this study, Ti, Nb, and Zr powders, which are biocompatible elements, were milled in a mixing machine (24h) and by planetary mechanical ball milling (1h, 4h, and 6h), respectively. Ti-35%Nb-7%Zr and Ti-35%Nb-7%Zr-10%HA composites were fabricated by spark plasma sintering (SPS) at $1000^{\circ}C$ under 70MPa using mixed and milled powders. The effects of HA addition and milling time on the biocompatibility and physical and mechanical properties of the Ti-35%Nb-7%Zr-(10%HA) alloys have been investigated. $Ti_2O$, CaO, $CaTiO_3$, and $Ti_xP_y$ phases were formed by chemical reaction during sintering. Vickers hardness of the sintered composites increases with increased milling time and by the addition of HA. The biocompatibilty of the HA added Ti-Nb-Zr alloys was improved, but the sintering ability was decreased.

• 한국수소및신에너지학회논문집
• /
• 제2권1호
• /
• pp.47-56
• /
• 1990

Pure titanium rods were oxidized by anodic oxidation, furnace oxidation and flame oxidation and used as a electrode in the photodecomposition of water. The maximum photoelectrochemical conversion efficiency(${\eta}$) was found for flame oxidized electrode ($1200^{\circ}C$ for 2 min in air), 0.8 %. Anodically oxidized electrodes have minimum photoelectrochemical conversion efficiencies, 0.3 %. Furnace oxidized electrode ($800^{\circ}C$ for 10min in air) has 0.5% phtoelectrochemical efficiency and shows a band-gap energy of about 2.9eV. The efficiency shows a parallelism with the presence of the metallic interstitial compound $TiO_{O+X}$(X < 0.33) at the metal-semiconductor interface, the thickness of the sub oxide layer and that of the external rutile scale.