• Journal of Korean Society of Environmental Engineers
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• v.27 no.9
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• pp.932-938
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• 2005

[ $TiO_2$ ] nanoparticles were prepared from the precipitation in $TiCl_4$ and the sol-gel profess in $Ti(OC_3H_7)_4$ as starting materials with various synthetic conditions. The samples were characterized by XRD, SEM, and TEM testing techniques. The photocatalytic degradation of congo red has been investigated in $TiO_2/UV$ process to evaluate photocatalytic activities for the samples. $TiO_2$ nanoparticles calcined at $400^{\circ}C$ had the best photocatalytic activity with the rate constant of the degradation of congo red as $0.0319\;min^{-1}$. The rate constant of $TiO_2$ photocatalysts was increased with the calcination temperature under $400^{\circ}C$ and decreased with the calcination temperature upper $400^{\circ}C$. In the case of $TiO_2$ photocatalysts, the photocatalytic activity wasn't greatly affected by the frequencies of usage. In the similar synthesis condition, the degradation efficiency of the $TiO_2$ particle prepared by $TiCl_4$ was increased to 8.8%, when the rate was compared with the sample prepared by $Ti(OC_3H_7)_4$. The photocatalytic activities of $TiO_2$ photocatalysts synthesized by $Ti(OC_3H_7)_4$ with various conditions were also discussed.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.512-518
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• 1997

The high temperature oxidation behaviors of titanium nitride films prepared by PACVD technique were studied in the temperature range of from 50$0^{\circ}C$ to 80$0^{\circ}C$ under air atmosphere. Ti0.88Al0.12N film, which showed the excellent microhardness from the previous work, was investigated on its oxidation resistance compared with pure TiN film. Ti-Al-N film showed superior oxidation resistance up to $700^{\circ}C$, whereas TiN film was fast oxidized into rutile TiO2 crystallites from at 50$0^{\circ}C$. It was found that an amorphous layer having AlxTiyOz formula was formed on the surface region due to outward diffusion of Al ions at the initial stage of oxidation. The amorphous oxide layer played a role as a barrier against oxygen diffusion, protected the remained nitride layer from further oxidation, and thus, resulted in the high oxidation resistive characteristics of Ti-Al-N film.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.916-924
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• 1990

The preparatin of the fine TiN powders by reduction-nitridation of TiCl3-Al-N2 system was attempted in the temperature range from 350$^{\circ}$to 100$0^{\circ}C$. The formation mechanism and kinetics of TiN were examined, and the resultant TiN powder was characterized by means of XRD, PSA and SEM-EPMA methods. TiN was formed at temperatrue higher than $600^{\circ}C$. As an intermediate phase, AlTi was obtained. The apparent activation energy for the formation of TiN was approximately 4.2kcal/mole(600$^{\circ}$~90$0^{\circ}C$). The crystallite size and lattice constnat of TiN powder obtained in the temperature range from 600$^{\circ}$to 100$0^{\circ}C$ for 2h at the Al/TiCl3 molar ratio of 1.0 were 160~255A and 4.231~4.239A, respectively. According to PSA measurement, the mean particle size ranged from 14.0 to 14.8${\mu}{\textrm}{m}$.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.1
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• pp.3-7
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• 2009

Variation in oxidation behavior with heat treatment temperature is investigated for a Ni-Ti alloy using X-ray diffraction, DSC (differential scanning calorimetry) and Auger electron spectroscopy. And the effect of oxidation on transformation behavior and superelasticity is characterized. A cold-worked 50.6Ni-Ti alloy is oxidized at 300-$700^{\circ}C$ for 1 hr in the air atmosphere. With an increase in heating temperature, the structure of $TiO_2$ changes from amorphous (300 and $400^{\circ}C$) to anatase ($500^{\circ}C$), and to rutile ($700^{\circ}C$). Activation energy of oxidation for NiTi is measured to be 51 Kcal/mol when heating temperature is $500^{\circ}C$ or above. Since Ti reacts preferably with oxygen, Ni content increases between matrix and oxide, forming $Ni_{3}Ti$ compounds. The resultant of oxidation decreases significantly $M_s$ and $A_s$ temperature in the specimen oxidized at $900^{\circ}C$ with $B_2{\rightarrow}M$ transformation path. An extra is found on cooling between two peaks in the specimen with $B_2{\rightarrow}R{\rightarrow}M$ one which is oxidized at $900^{\circ}C$ and aged at $500^{\circ}C$. Oxidation deteriorates superelasticity due to formation of Ni-rich compound.

• Journal of Powder Materials
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• v.14 no.3 s.62
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• pp.208-214
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• 2007

The microstructure and hardness of (W,Ti)C cemented carbides with a different metallic binder composition of Ni and Co fabricated by powder technology were investigated. The densifications of the prepared materials were accomplished by using vacuum sintering at $1450^{\circ}C$. Nearly full dense (W,Ti)C cemented carbides were obtained with a relative density of up to 99.7% with 30 wt.% Co and 99.9% with 30 wt.% Ni as a metallic binder. The average grain size of the (W,Ti)C-Co and the (W,Ti)C-Ni was decreased by increasing the metallic binder content. The hardness of the dense (W,Ti)C-15 wt%Co and (W,Ti)C-15 wt%Ni, was greater than that of the other related cemented carbides; in addition, the cobalt-based cemented carbides had greater hardness values than the nickel-based cemented carbides.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.13-18
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• 2014

In order to clarify the effect of Nb addition on the ductile-brittle transition property of sintered TiC, TiC-10 mol% Nb composites were researched using a three-point bending test at temperatures from room temperature to 2020 K, and the fracture surface was observed by scanning electron microscopy. It was found that the Nb addition decreases the ductile-brittle transition temperature of sintered TiC by 300 K and increases the ductility. The room temperature bending strength was maintained at up to 1800 K, but drastically dropped at higher temperatures in pure TiC. The strength increased moderately to a value of 320MPa at 1600 K in TiC-10 mol% Nb composites, which is 40% of the room temperature strength. Pores were observed in both the grains and the grain boundaries. It can be seen that, as Nb was added, the size of the grain decreased. The ductile-brittle transition temperature in TiC-10 mol% Nb composites was determined to be 1550 K. Above 1970 K, yieldpoint behavior was observed. When the grain boundary and cleavage strengths exceed the yield strength, plastic deformation is observed at about the same stress level in bending as in compression. The effect of Nb addition is discussed from the viewpoint of ability for plastic deformation.

• Journal of the Korean Ceramic Society
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• v.31 no.1
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• pp.25-30
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• 1994

W-Ti-C-N based multiphase hard materials have been prepared from WC/TiN powder mixture. By sintering at and above 190$0^{\circ}C$, the two phases of powder mixture has transformed into intermixed W, W2C and Ti(C, N) phases. For the temperature range between 180$0^{\circ}C$ and 210$0^{\circ}C$, the sintered or hot pressed samples show maximum density and hardness. The seems that metallic W grains enhance the fracture toughness of materials. The wear resistance of the material is found to increase with increasing hardness.

• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.1009-1018
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• 1995

(Ti.Si)C composite powders were synthesized by SHS method using microwave energy. Compositional and structural characterization of the powder were carried out by using scanning electron microscopy and X-ray diffraction. The average particle size of the synthesized (Ti.Si)C composite powders was smaller than that of the starting materials. From the results of the temperature profile, combustion temperature and velocity were decreased with increasing Si molar ratio. With increasing C molar ratio combustion temperature and velocity did not change. (Ti.Si)C composite was sintered at 185$0^{\circ}C$ for 60 min by using hot-pressing with 30 MPa. The best properties were obtained from the sintered specimen whose composition was 1 : 1 : 1.9 molar ratio of Ti : Si : C. The sintering density, flexural strength and vickers hardness of the sintered body were 4.71 g/㎤, 423 MPa and 21 GPa, respectively.

• Korean Journal of Materials Research
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• v.2 no.3
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• pp.207-212
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• 1992

The defect structure of calcium titanates with CaO excess or $TiO_2$ excess was studied by measuring electrical conductivities as a funcition of oxygen partial pressure at $85O^{\circ}C$ to $1050^{\circ}C$. Execess CaO may divide itself equally between A and B sites, resulting in $Ca_{Ti}$" and Vo", while excess $TiO_2$ form $V_{Ca}$" and Vo". The equilibrium electrical conductivity data indicate that the solubilities of CaO and $TiO_2$ in $CaTiO_3$ are 5000ppm and 2000ppm, respectively. Oxygen vacancies contributed to the ionic conduction which flatten the conductivity minima and did not make any defect association with oppositely charged defects.ely charged defects.

• Korean Journal of Materials Research
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• v.6 no.2
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• pp.210-220
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• 1996

The purpose of this study is to develop the processing techniques of Fiber Reinforced Metal by Liquid Phase Diffusion Bonding method with SiC fiber as a reinforcing material and CP Ti(Commercial Pure) as a matrix. The microstructure and the distribution of elements in reaction and CP Ti(Commercial Pure) as a matrix. The microstructure and the distribution of elements is reaction zone among CP Ti/Ti-15wt%Cu-20wt%Ni(TCN20)/SiC long fiber were investigated by Optical Microscope, SEM/EDX, EPMA, X-ray and AES. The results obtained in this study are as follows. 1) When Ti matrix composite materials are fabricated under the bonding condition of 1273Kx1200sec, the SiC long fiber was the most suitable reinforcing material for Ti matrix composite materials. 2) With SiC long fiber under same condition, a TiC layer(1.0-1.6$\mu\textrm{m}$) was observed on the surface of SiC long fiber. 3) Liquid Phase Diffusion Bonding has shown the feasibility of production of Ti matrix composite materials.