• 한국재료학회지
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• 제16권4호
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• pp.218-224
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• 2006

RF sputtering process was applied to produce thin hydroxyapatite(HAp) films on Ti-6Al-4V alloy substrates. The effects of different heat treatment conditions on the hardness between HAp thin films and Ti-6Al-4V alloy substrates were studied. Before deposition, the Ti-6Al-4V alloy substrates were heat treated for 1h at $850^{\circ}C\;under\;3.0{\times}10^{-3}torr$, and after deposition, the HAp thin films were heat treated for 1h at $400^{\circ}C,\;600^{\circ}C\;and\;800^{\circ}C$ under the atmosphere, and analyzed FESEM-EDX, FTIR, XRD, nano-indentor, micro-vickers hardness, respectively. Experimental results represented that the surface defects of thin films decreased by relaxation of internal stress and control of substrate structure followed by heat treatment of substrates before the deposition, and the HAp thin films on the heat-treated substrates had higher hardness than none heattreated substrates before the deposition, and the hardness properties of HAp thin films and Ti-6Al-4V alloy substrates appeared independent behavior, and the hardness of HAp thin films decreased by formation of $VTiO_3(OH),\;{\theta}-Al_{0.32}V_2O_5,\;Al_{0.33}V_2O_5$.

• Korean Chemical Engineering Research
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• 제53권3호
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• pp.276-281
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• 2015

$TiO_2-SiO_2$ 나노복합소재는 자체가 화학적으로 안정할 뿐만 아니라 광학적, 열적 특성이 매우 우수하여 광화학센서, 촉매 등 다양한 분야에 적용되고 있다. 이러한 구조를 구현하는 방법으로 티타늄이 첨가된 폴리카보실란(PCS) 혼합용액을 전기방사한 후 이를 적절한 산화분위기에서 열처리하여 부직포상의 $TiO_2-SiO_2$ 나노복합섬유를 만들 수 있는데, 이는 기존의 졸겔공정에 의해 제조되는 섬유보다 더 쉽고 안정적인 방법이다. 공정 중 방사된 섬유를 산화분위기에서 $1200^{\circ}C$ 이상까지 열처리하게 되면 크리스토발라이트 기지조직 내에서 아나타제 나노결정상이 매우 균일하게 형성되었다. 또한, 열처리 후 섬유의 표면과 단면은 매우 치밀하고 매끈하였으며 10~20nm 크기의 아나타제 결정입자들이 내부에 균일하게 분포하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2015년도 추계학술대회 논문집
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• pp.137-137
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• 2015

The purposed of this work was to observe hydroxyapatite precipitation phenomena on micro-pore formed Ti-Nb alloy by PEO technique. The Ti-30Nb and Ti-30Ta alloys were remelted at least ten times in order to avoid inhomogeneity, and then cylindrical specimens (diameter 10 mm, thickness 4 mm) were cut by using laser from cast ingots of the Ti alloys. Heat treatment was carried out at $1050^{\circ}C$ for 2 h for homogenization in argon atmosphere. The morphologic change of the alloys were examined by X-ray diffractometer (XRD) and field emission scanning electron microscopy (FE-SEM).

• 한국세라믹학회지
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• 제50권6호
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• pp.489-494
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• 2013

Nano-sized titanium oxide powders were synthesized by a polymer matrix technique using pulp and Titanium tetraisopropoxide (TTIP) as starting materials. The synthesized powders were characterized by XRD and FE-SEM. The particle size of the powders was controlled by preparation conditions, such as heat treatment temperature and time. After investigating various drying and heat treatment conditions, 50-100 nm sized homogeneous titanium oxide particles were obtained by treating at $600^{\circ}C$ for 1 h. The crystallization and rapid growth of particles was accelerated by increasing heat treatment temperature and time. Anatase phase generated below $600^{\circ}C$ transformed to the rutile phase with increasing heat treatment temperature. Moreover, above $800^{\circ}C$, heat treatment time had a very large influence on particle growth, and changing the heating condition also had a large influence on crystal growth.

• 전기학회논문지
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• 제58권2호
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• pp.322-326
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• 2009

In this work, nanoporous $TiO_2$ powder was fabricated using Ketjen black, and applied in photovoltaic device based on the Dye-sensitized Solar Cells (DSCs). $TiO_2$ powder was fabricated using Ti-isopropoxide and 2-propanol by sol-gel combustion method. For added $0{\sim}2g$ variable of Ketjen black, characteristic of porosity, size of particle and crystallite of obtained $TiO_2$ nano powder was investigated. The photovoltaic efficiency of the prepared DSCs was measured using $TiO_2$ film which prepared on each different heat treatment temperature($100^{\circ}C{\sim}600^{\circ}C$) with paste of $TiO_2$ powder. The porosity and size in particle of $TiO_2$ powder made with Ketjen black Ig was influenced significantly effect to DSCs characteristic. Heat treatment at $500^{\circ}C$ makes the better photovoltaic efficiency which around 6.11%($J_{sc}=13.35mA/cm^2$, $V_{oc}=0.73V$, ff=0.63). The sol-gel combustion method was useful to DSCs fabrication.

• 한국수소및신에너지학회논문집
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• 제13권3호
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• pp.224-232
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• 2002

CdS-$TiO_2$ nano-composite sol was prepared by the sol-gel method in organic solvents at room temperature and further hydrothermal treatment at various temperatures to control the physical properties of the primary particles. Again, CdS-$TiO_2$ composite particulate films were made by casting CdS-$TiO_2$ sols onto $F:SnO_2$ conducting glass and then heat-treatment at $400^{\circ}C$. Physical properties of these 61ms were further controlled by the surface treatment with $TiCl_4$, aqueous solution. The photo currents and hydrogen production rates measured under the experimental conditions varied according to the $CdS/[CdS+TiO_2]$ mole ratio and the mixed-sol preparation method. For $CdS-TiO_2$ composite sols prepared in IPA, CdS particles were homogeneously surrounded by $TiO_2$ particles. Also, the surface treatment with $TiCl_4$ aqueous solution caused a considerable improvement in the photocatalytic activity, probably as a result of close contacts between the primary particles by the etching effect of $TiCl_4$. It was found that the photoelectrochemical performance of these particulate films could be effectively enhanced by this approach.

• 열처리공학회지
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• 제21권2호
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• pp.94-100
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• 2008

The implant prototypes with various porosities were fabricated by Spark Plasma Sintering of atomized spherical titanium balls. The interface was observed by optical microscope. Sintering temperature and holding time were selected at the point of big change of Z-axis ratio during sintering. These experiments show that Spark Plasma Sintering of spherical titanium balls can be efficiently used to produce implants surfaced with titanium balls with various porosities in a short time less than 120 seconds by manipulating the current condition such as z-axis, temperature and balls size.

• 한국재료학회지
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• 제12권5호
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• pp.391-397
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• 2002

Synthesis and process development of nano-size Ti powder by SFE(Sodium/halide Flame Encapsulation) method were investigated. Four concentric coflow burner was used and its flame configuration was $TiCl_4/Ar/Na/Ar$ in order from the center. Flame has been controlled by the various processing parameters such as temperature of burner and flow rates of both $TiCl_4$(g) precursor and Na(g). It was found that yellow-colored flame was shown in the flow rates of 70cc/min of $TiCl_4$(g) precursor and 2 $\ell$ /min of Na(g) which were regarded as optimum flame condition. The powders encapsuled by NaCl were produced having the average powder size of 250nm. The results of X-ray diffraction showed that powders from the optimized condition consisted of pure Ti and NaCl. TEM analysis confirmed that the several Ti powders of 20-100nm were encapsulated with NaCl. After removing sodium chloride by heat treatment, the spherical Ti powders with the size range of 80 to 150nm were obtained.

• 한국분말재료학회지
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• 제9권2호
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• pp.110-115
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• 2002

In order to obtain the nano size $10wt%Cu-TiO_2$composite powders by mechanical alloying method for useful composite catalysis, the effects of mechanical alloying time on the formationof $10wt%Cu-TiO_2$ composite powders were analyzed. The phase transformation behaviors were experimented as the heat treating temperature increased. Homogeneous 10wt% Cu-rutile type $TiO_2$composite powders were synthesized in 40 hours by mechanical alloying. After 60 hours mechanical alloying 50 nm size $TiO_2$powders were obtained. Both the phase of mechanically alloyed 10 wt% $Cu-TiO_2$ and pure $TiO_2$ powders were not transformed to anatase after annealing at the temperature range between 350 to 500 $^{\circ}C$. The intermetallic compound of $Cu_2Ti_4$O was formed after 10 hours mechanical alloying, however it could be considered that this intemetallic phase dose not prevent the transformation of rutile $TiO_2$ to the anatase phase after heat treatment at the temperature between 350 and $550^{\circ}C$.

• Corrosion Science and Technology
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• 제11권5호
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• pp.191-195
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• 2012

The aim of this study was to investigate effects of hafnium content on the corrosion behavior of Ti alloys in electrolyte containing chloride ion. For this study, Ti-Hf binary alloys contained 10 wt%, 20 wt% and 30 wt% Hf were manufactured in a vacuum arc-melting furnace and subjected to heat treatment for 12h at $1000^{\circ}C$ in an argon atmosphere. The pitting corrosion behavior of the specimens was examined through potentiodynamic and potentiostatic tests in 0.9 wt% NaCl electrolyte at $36.5{\pm}1^{\circ}C$. The corrosion morphology of Ti-xHf alloys was investigated using optical microscopy (OM) and X-ray diffractometer (XRD). From the optical microstructures and XRD results, needle-like martensite ($\alpha$') phases of the Ti-xHf alloys increased with an increase of Hf addition. Corrosion current density $(I_{corr})$ and current density $(I_{300mV})$ in passive region decreased, whereas, corrosion potential increased with Hf content. At the constant potential ($300mV_{SCE}$), current density decreased as time increased.