• Journal of Advanced Marine Engineering and Technology
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• v.38 no.2
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• pp.133-139
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• 2014

Titanium (Ti) metal and its alloys are desirable materials for ship hulls and other ocean structures because of their high strength, corrosion-resistance and light weight properties. And light weight and corrosion-resistant aluminum (Al) is the ideal metal for shipbuilding. The joining of Ti and Al dissimilar metals is one of the effective methode to reduce weight of the structures. Ti and Al have great differences in materials properties, and intermetallic compounds such as $Ti_3Al$, TiAl, $TiAl_3$ are easily formed at the contacting surface between Ti and Al. Thus, dissimilar welding and joining of Ti and Al are considered to be very difficult. However, it was clarified that ultra-high speed welding could suppress the formation of intermetallic compounds in the previous study. Results of tensile shear strength increases with an increase in the welding speed, and therefore extremely high welding speed (50 m/min) is good to dissimilar weldability for Ti and Al. In this study, therefore, full penetration dissimilar lap welding of Ti (upper) - Al (lower) and Al (upper) - Ti (lower) with single-mode fiber laser was tried at ultra-high welding speed, and the microstructure of the interface zones in the dissimilar Al and Ti weld beads was investigated.

• Journal of Technologic Dentistry
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• v.15 no.1
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• pp.5-25
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• 1993

Effects of hydrogenation on microstructure and mechanical properties of pure Ti and Ti-0.15Pd alloy have been studied by means of optical microscopy, differential scanning calorimeter(DSC), Xray diffraction and micro vicker's hardness test. Grain size of pure Ti and Ti-0.15Pd alloy decresed largely by hydrogenation finer than that of pure Ti and the grain size refinement was evedent in Ti-0.15Pd alloy than that in pure Ti. Ti-.015Pd alloy carried out solution treatment at 950$^{\circ}C$, the transformation of $\alpha$' martensite was occured. The amount of Hydrogen absorption in Ti-.015Pd alloy was higher than that in pure Ti. Decomposition of hydride in pure titanium and Ti-0.15Pd alloy increased largely by hydrogenation, and micro vicker's hardness of Ti-.015Pd alloy was largely than that of pure Ti by 30% after hydrogenation. The micro vicker's hardness of Ti-0.15Pd alloy after solution treatment and dehydrogenation were higher at $\beta$ phase ranger(950$^{\circ}C$) than that phase range(750$^{\circ}C$).

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.3
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• pp.117-125
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• 1996

The variation of the interfacial and the electrical properties of SiO$_{2}$TiW layers as a function of anneal temperature was extensively investigated. During the deposition of SiO$_{2}$ on TiW chemical bonds such as SiO$_{2}$, TiW, WO$_{3}$, WO$_{2}$ TiO$_{2}$ Ti$_{2}$O$_{5}$ has been created at the SiO$_{2}$/TiW interface. At the anneal temperature of 300$^{\circ}C$, WO$_{3}$ and TiO$_{2}$ bonds started to break due to the reduction phenomena of W and Ti and simultaneously the metallic W and Ti bonds started to create. Above 500$^{\circ}C$, a part of Si-O bonds was broken and consequently Ti/W silicide was formed. Form the current-voltage characteristics of Al/Sico$_{2}$(220$\AA$)/TiW antifuse structure, it was found that the breakdown voltage of antifuse device wzas decreased with increasing annealing temperature for SiO$_{2}$(220$\AA$)/TiW layer. When r, the insulating property of antifuse device of the deterioration of intermetallic SiO$_{2}$ film, caused by the influw of Ti and W.W.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.1
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• pp.7-10
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• 2002

$TiO_2$ thin films were prepared by coating and subsequent pyrolysis processes using Titanium-naphthenate as a raw material. $TiO_2$ thin films were made by spin-coating technique on the glass substrates, and heat treated at 45$0^{\circ}C$, The transmittance, refractive index, crystallinity and surface morphology of the $TiO_2$ thin films were measured by UV/Vis spec trophotometer, x-ray diffractometer and scanning electron microscope. $TiO_2$thin films on the slide glass showed the trans mittance of 70-90% and refractive index of 2.6 at 420 nm. The results of XRD and SEM showed that the $TiO_2$ thin films exhibited the anatase phase and the thread-like surface morphology.

• Journal of Environmental Science International
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• v.16 no.12
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• pp.1431-1437
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• 2007

Cobalt titanates($CoTiO_x$), such as $CoTiO_3$ and $Co_2TiO_4$, have been synthesized via a solid-state reaction and characterized using X-ray diffraction(XRD) and X-ray photoelectron spectroscopic(XPS) measurement techniques, prior to being used for continuous wet trichloroethylene(TCE) oxidation at $36^{\circ}C$, to support our earlier chemical structure model for Co species in 5 wt% $CoO_x/TiO_2$(fresh) and(spent) catalysts. Each XRD pattern for the synthesized $CoTiO_3$ and $Co_2TiO_4$ was very close to those obtained from the respective standard XRD data files. The two $CoTiO_x$ samples gave Co 2p XPS spectra consisting of very strong main peaks for Co $2p_{3/2}$ and $2p_{1/2}$ with corresponding satellite structures at higher binding energies. The Co $2p_{3/2}$ main structure appeared at 781.3 eV for the $CoTiO_3$, and it was indicated at 781.1 eV with the $Co_2TiO_4$. Not only could these binding energy values be very similar to that exhibited for the 5 wt% $CoO_x/TiO_2$(fresh), but the spin-orbit splitting(${\Delta}E$) had also no noticeable difference between the cobalt titanates and a sample of the fresh catalyst. Neither of all the $CoTiO_x$ samples were active for the wet TCE oxidation, as expected, but a sample of pure $Co_3O_4$ had a good activity for this reaction. The earlier proposed model for the surface $CoO_x$ species existing with the fresh and spent catalysts is very consistent with the XPS characterization and activity measurements for the cobalt titanates.

• Journal of the Korean Society for Heat Treatment
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• v.21 no.1
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• pp.20-25
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• 2008

Structural studies have been performed on precipitation hardening and microstructural variations found in Ti-Al-Cr ternary $L1_0$- and $L1_2$-phase alloys using transmission electron microscopy. Both the $L1_0$ and $L1_2$ phase alloys harden by aging at 973 K after solution annealing at higher temperatures. The amount of age hardening of the $L1_2$ phase alloy is larger than that of the $L1_0$ phase alloy. The phase separation between $L1_0$ and $L1_2$ phase have not been observed by aging at 973 K. But $Al_2Ti$ was formed in each matrix alloy during aging. The crystal structure of the $Al_2Ti$ phase is a $Ga_2Zr$ type in the $L1_0$ and a $Ga_2Hf$ type in the $L1_2$ phase, respectively. At the beginning of aging the fine coherent cuboidal $Al_2Ti$-phase are formed in the $L1_0$ phase. By further aging, two variants of $Al_2Ti$ precipitates grow along the two {110} habit planes. On the other hand, in the $L1_2$ phase, the $Al_2Ti$ phase forms on the {100} planes of the $L1_2$ matrix lattice. After prolonged aging the precipitates are rearranged along a preferential direction of the matrix lattice and form a domain consisting of only one variant. It is suggested that the precipitation of $Al_2Ti$ in each matrix alloy occurs to form a morphology which efficiently relaxes the elastic strain between precipitate and matrix lattices.

• Journal of the Korean Magnetics Society
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• v.1 no.1
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• pp.25-29
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• 1991

It has been found that the as-quenched ribbons of $Sm_{x}Fe_{100-x-y}Ti_{y}(3.8{\leq}x{\leq}11.5,\;3.8{\leq}y{\leq}19.2)$ are composed of metastable $TbCu_{7}-type$ structure, ${\alpha}-(Fe,\;Ti),\;Fe_{2}Ti$ and an unknown phase accompanying strong diffraction line at $d=2.14{\AA}$. The metastable $TbCu_{7}-type$ phase, which was formed by rapid quenching, did not transform fully to the stable phases after annealing at $850^{\circ}C$ for 45 minutes except the one existed in $SmFe_{11}Ti$ melt-spun ribbon. The $SmFe_{11}Ti$ melt-spun ribbon, annealed at $850^{\circ}C$ for 45 minutes in vacuum, was found to be composed of $ThMn_{12}$. $\alpha$-(Fe, Ti) and $Fe_{2}Ti$ phases. The formation of $\alpha$-(Fe, Ti) and $Fe_{2}Ti$ phases in this melt-spun ribbon was due to the evaporation of Sm atoms during the high temperature annealing. The atomic ratios for the surface and the inside of $SmFe_{11}Ti$ melt-spun ribbon annealed in vacuum were $SmFe_{25.8}Ti_{2.6}$ and $SmFe_{11.7}Ti_{1.0}$ respectively. It is thought to be that much of $\alpha$-(Fe, Ti) and $Fe_{2}Ti$ phases exist on the surface of ribbon.

• Journal of Powder Materials
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• v.6 no.4
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• pp.277-285
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• 1999

Mechanical properties of nanocrystalline Al-5at.%Ti alloy were investigated through high temperature compression test. Al-5at.%Ti nanocrystalline metal powders, which had finer and more equiaxed shape than those produced at room temperature, were produced by mechanical alloying at low temperature. The powders were successfully consolidated to 99fo of theoretical density by vacuum hot pressing. XRD and TEM analysis revealed that $Al_3Ti$ intermetallic compounds formed inside powders and pure Al region with coarse grains formed between powders, especially at triple junction. Mechanical properties in terms of hardness and strength were improved by grain size refinement, but ductility decreased presumably due to the formation of the weak interfaces between Al pool and powders.

• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.1051-1054
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• 2004

The structural transformation behavior of $Na_2Ti_3O_7$ by hydrolysis was investigated in mild and strong acidic aqueous medium. Compared with $K_2Ti_4O_9,\;Na_2Ti_3O_7$ exhibits quite different structural and morphological transformation behavior despite their similar layered structural characteristics. $TiO_2(B)$ obtained by heat treatment of $H_2Ti_3O_7\;at\;350^{\circ}C$ transforms to rutile $H_2Ti_3O_7\;at\;900^{\circ}C$. This temperature is much lower than $1200{\circ}C$, the temperature for anatase to rutile transition when $K_2Ti_4O_9$ is used as a starting titanate. A rectangular rod shape and size of $TiO_2(B)$ particles obtained from $Na_2Ti_3O_7$ is also different from a fibrous structure of $TiO_2(B)$ prepared using $K_2Ti_4O_9$. Rutile crystals of 100 nm diameter with a corn-like morphology and large surface area are directly obtained when the hydrolysis of $Na_2Ti_3O_7$ is carried out at $100^{\circ}C$ in a strong acid solution. The structure of starting titanates and the hydrolysis conditions are an important factor to decide the particle size and morphology of $TiO_2(B)\;and\;TiO_2$.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.795-797
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• 1998

A $BaTiO_3$, ferroelectric material, was mixed $SrTiO_3$, $(x)BaTiO_3-(1-x)SrTiO_3$($0.7{\leq}x{\leq}1$) ceramic capacitor with stable electrical properties in high voltage was fabricated. And microstructure, electrical property were investigated with $SrTiO_3$ mol ratio. The shrinkage, open porosity, sintering density were predominated at $9BaTiO_3-0.1SrTiO_3$. Increasing $SrTiO_3$ mol ratio, curie temperature was shifted at low temperature and maximum permittivity was increased. Also, $0.9BaTiO_3-0.1SrTiO_3$ was showed stable dielectric properties at $25{\sim}80[^{\circ}C]$. V-I properties of specimen were observed in the temperature range of $21{\sim}143[^{\circ}C]$, were divided into three regions. The region I below 10[kV/cm] was shown Ohmic conduction, the region II from 10 to 30[kV/cm] was explained by the Poole-Frenkel emission theory and the region III above 30[kV/cm] was analysed by the tunneling effect.