• Journal of the Korean Ceramic Society
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• v.31 no.5
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• pp.552-560
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• 1994

A composite of TiB2-Al2O3 system was successfully prepared from a mixture of TiO2, B2O3, and Al by self-propagating high temperature synthesis (SHS) with a novel characteristic, utilizing the internal oxidation heat of aluminium metal of the mixture, instead of by a conventional technique, externally heating a mixture of Ti, B and Al2O3. From a mixture with B/Ti molar ratio of =2.0, pure two phases of TiB2 and $\alpha$-Al2O3 with good crystallinity and small, uniform sizes were formed. However, when the B/Ti molar ratio of the mixture goes to a value less than 2.0, in addition to the above main minerals, a small smounts of metastable phases such as TiB and Ti3B4 were formed. It was found that about 60%, the optimum green density of compacts gave their highest reaction rate and temperature during SHS process. TiB2-Al2O3 system composite with B/Ti molar ratio of =2.0 could be pressurelessly sintered even at 190$0^{\circ}C$ under Ar gas flows without any addition of sintering aids, showing their good properties such as 91.2% in relative density, 2750 kgf/$\textrm{mm}^2$ in Vickers hardness and 2620 kgf/$\textrm{cm}^2$ in flexural strength.

• Journal of the Korean Ceramic Society
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• v.36 no.6
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• pp.632-639
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• 1999

• Journal of the Korean Ceramic Society
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• v.40 no.2
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• pp.109-112
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• 2003

The grain-boundary microcracking materials in the system $Al_2$TiO$_{5}$ -ZrTiO$_4$(ZAT) is influenced by the thermal expansion anisotropy. The range of ZAT compositions investigated had showed very low thermal expansions of 0.3~1.3$\times$10$^{-6}$ K loin compared to 8.29$\times$10$^{6}$ K of pure ZrTiO$_4$and 0.68$\times$10$^{6}$ K of polycrystalline $Al_2$TiO$_{5}$ , respectively, compared with the theoretical thermal expansion coefficient for a single crystal of $Al_2$TiO$_{5}$ , 9.70$\times$10$^{6}$ K. The low thermal expansion and microcraking temperature are apparently due to a combination of thermal contraction and expansion caused by the large thermal expansion anisotropy of the crystal a ies of the $Al_2$TiO$_{5}$ phase.

• Korean Journal of Materials Research
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• v.17 no.8
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• pp.447-451
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• 2007

We investigated the dependence of the various annealing conditions and thickness ($6\sim45nm$) of the Ti-doped $Al_2O_3$ coating on the electrochemical properties and the capacity fading of Ti-doped $Al_2O_3$ coated $LiCoO_2$ films. The Ti-doped-$Al_2O_3$-coating layer and the cathode films were deposited on $Al_2O_3$ plate substrates by RF-magnetron sputter. Microstructural and electrochemical properties of Ti-doped-$Al_2O_3$-coated $LiCoO_2$ films were investigated by transmission electron microscopy (TEM) and a dc four-point probe method, respectively. The cycling performance of Ti-doped $Al_2O_3$ coated $LiCoO_2$ film was improved at higher cut-off voltage. But it has different electrochemical properties with various annealing conditions. They were related on the microstructure, surface morphology and the interface condition. Suppression of Li-ion migration is dominant at the coating thickness >24.nm during charge/discharge processes. It is due to the electrochemically passive nature of the Ti-doped $Al_2O_3$ films. The sample be made up of Ti-doped $Al_2O_3$ coated on annealed $LiCoO_2$ film with additional annealing at $400^{\circ}C$ had good adhesion between coating layer and cathode films. This sample showed the best capacity retention of $\sim92%$ with a charge cut off of 4.5 V after 50 cycles. The Ti-doped $Al_2O_3$ film was an amorphous phase and it has a higher electrical conductivity than that of the $Al_2O_3$ film. Therefore, the Ti-doped $Al_2O_3$ coated improved the cycle performance and the capacity retention at high voltage (4.5 V) of $LiCoO_2$ films.

• Korean Journal of Materials Research
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• v.10 no.6
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• pp.398-402
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• 2000

Three kinds of $Al_3Ti-Cr$ alloys, namely, $Al_{67}Ti_{25}Cr_8,\;Al_{66}Ti_{24}Cr_{10}\;and\;Al_{59}Ti_{26}Cr_{15}$, were prepared by induction melting followed by the thermomechanical treatment. The corrosion behavior in 3.5% NaCl solution and the high-temperature oxidation behavior at 1000, 1100 and $1200^{\circ}C$ for the prepared alloys were investigated. Electrochemical results indicated increased resistance to localized corrosion with increasing Cr content. Cr additions were found to prevent passive film from undergoing brittle fracture. XPS results revealed the passive films of $Al_3Ti-Cr$ alloys were composed mainly of $Al_2O_3$ that coexisted with $TiO_2$ and $Cr_2O_3$. The overall oxidation resistance of the prepared alloys were excellent. Specifically, the oxidation resistance increased in the order of $Al_{59}Ti_{26}Cr_{15},\;Al_{66}Ti_{24}Cr_{10}\;and\;Al_{67}Ti_{25}Cr_8$. As the Al content in the base alloys increased, the $Al_2O_3$ formation was facilitated leading to the increased oxidation resistance.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.1
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• pp.57-63
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• 2012

$Al_2TiO_5$ ceramics were sintered by a solid-state reaction. LAS (${\beta}$-spodumene) and $Fe_2O_3$ were added to the $Al_2TiO_5$ composition for enhancement of sintering behavior such as mechanical strength and thermal shock resistance. The sintered body was much densified by addition of LAS and $Fe_2O_3$ because LAS formed the liquid-phase and $Fe_2O_3$ suppressed the grain growth. We have systematically investigated the sintering characteristics, microstructures, mechanical properties, and thermal shock resistance according to the change of the amount of additive. When the additive of LAS (20 wt%)-$Fe_2O_3$ was added to $Al_2TiO_5$, it confirmed that superior mechanical properties of the fracture strength of over 120 MPa and the thermal shock resistance of over $1,200^{\circ}C$ were achieved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.5-8
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• 2004

전자빔 증착법 (e-beam evaporation)를 이용하여 $TiO_2$ 박막과 $Al_2O_3/TiO_2$ 이중박막을 제조한 후, $800^{\circ}C$ 공기 중에서 열처리하여, 알루미나 층의 유무에 따른 두 박막의 전기전도 특성과 100 ppm CO 가스에 대한 반응 특성을 고찰하였다. 알루미나 층이 증착되지 않은 순수한 $TiO_2$ 박막의 전기 전도도 (in dry air)는 $100^{\circ}C-500^{\circ}C$ 온도범위에서 온도가 증가함에 따라 증가하였으며 알루미나 층이 증착된 $Al_2O_3/TiO_2$ 이중막보다 높은 전도도를 나타내고 있으나, 약 $300^{\circ}C$이상의 온도에서는 $Al_2O_3/TiO_2$ 이중막의 전기 전도도가 급격히 증가하여 $TiO_2$ 박막의 전기전도도 보다 더 높은 값을 나타내었다. 또한 온도에 따른 CO 가스 감도(sensitivity)는 $TiO_2$ 박막의 경우 $400^{\circ}C$까지는 서서히 증가하여 그 이상의 온도에서 급격히 감소하였으나, $Al_2O_3/TiO_2$ 이중막은 $250^{\circ}C$에서 감도가 급격히 증가하여 최대값을 나타내었으며, $350^{\circ}C$에서 감도가 급격히 감소하는 특성을 나타내었다.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.169-175
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• 2012

Purpose: In this study, brazing characteristics of $ZrO_2$ and Ti-6Al-4V brazed joints with increasing temperature were investigated. Materials and methods: The sample size of the $ZrO_2$ was $3mm{\times}3mm{\times}3mm$ (thickness), and Ti-6Al-4V was $10mm(diameter){\times}5mm(thickness)$. The filler metal consisted of Ag-Cu-Sn-Ti was prepared in powder form. The brazing sample was heated in a vacuum furnace under $5{\times}10^{-6}$ torr atmosphere, while the brazing temperature was changed from 700 to $800^{\circ}C$ for 30 min. Results: The experimental results shows that brazed joint of $ZrO_2$ and Ti-6Al-4V occurred at $700-800^{\circ}C$. Brazed joint consisted of Ag-rich matrix and Cu-rich phase. A Cu-Ti intermetallic compounds and a Ti-Sn-Cu-Ag alloy were produced along the Ti-6Al-4V bonded interface. Thickness of the reacted layer along the Ti-6Al-4V bonded interface was increased with brazing temperature. Defect ratios of $ZrO_2$ and Ti-6Al-4V bonded interfaces decreased with brazing temperature. Conclusion: Thickness and defect ratio of brazed joints were decreased with increasing temperature. Zirconia was not wetting with filler metal, because the reaction between $ZrO_2$ and Ti did not occur enough.

• Journal of the Korean Vacuum Society
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• v.5 no.2
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• pp.147-155
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• 1996

Optical properties of $TiO_2/M/Ag/M/TiO_2$ films have been changed with the diffusion barrier metal M. Optimum opticla properties of $TiO_2/M/Ag/M/TiO_2$ as the transparent heat mirror film, could be obtained with Ti among diffusion barrier metals of Ti, Cu, Zr and Al. $TiO_2/M/Ag/M/TiO_2$ film, which was fabricated by sputtering of 18 nm-thick $TiO_2$ and Ag, and 4nm-thick Ti, showed maximum transimittance of 89% at visible wavelength and infrared reflectance of 97% at wavelength of 3000 nm. Optical properties of this film was not degraded by Xenon-sunshine weather test for 240 hours. For specimens with barrier layers of Cu, Zr, and Al, degradation of optical properties by weather test was increased in a sequence of films with Cu, Zr, and Al barrier layers.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.107-113
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• 2009

This study investigated the decomposition activities of toluene on 10 mol% Al-W-incorporated mesoporous titano (15 mol %) silicates. The mesopore sizes observed in the transmission electron microscopy images ranged from 2.0 to 5.0 nm, and the pores were irregular on the addition of 10 mol% Al or W ions, but changed to regular hexagonal forms with the simultaneous additions of Al and W. The X-ray photon spectroscopy results showed a shift of the special peak for Ti2p in Al-incorporated mesoporous titanosilicates to a stronger binding energy compared to those of mesoporous titanosilicates and Al-incorporated mesoporous titanosilicates. Three O1s peaks in the spectra of the Al and W coexisted samples were observed at 530.5 and 531.7, 533, and 533.7eV, which were assigned to $Ti-Os\;in\;TiO_2\;and\;Ti_2O_3,\;Si-O\;in\;SiO_2\;and\;Al-O\;in\;Al_2O_3$, respectively. The toluene molecules desorbed at lower temperatures over W-incorporated mesoporous titanosilicates, and the amounts of toluene desorbed were also small; however, Al-incorporated mesoporous titanosilicates adsorbed much more toluene, particular over $Al_7.5-W_2.5-Ti_15-Si_75$. The photocatalytic decomposition of toluene was more enhanced over $Al_7.5-W_2.5-Ti_15-Si_75$ than over Al- or W-incorporated mesoporous titanosilicates only.