• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.44-49
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• 1999

In order to improve the oxidation resistance of $Ti_3Al$, Ti-25at.%Al composites containing dispersed particles of 15wt.%SiC were prepared by a tubular mixing-spark plasma sintering method. The sintered composites had $Ti_3Al$, SiC, $Ti_5Si_3$ and TiC. The presence of $Ti_5Si_3$ and TiC indicates that some of SiC particles reacted with Ti to from more stable phases. From oxidation tests at 800, 900 and $1000^{\circ}C$ under 1 atm of pure oxygen, it was found that the oxidation rate of Ti3Al was effectively reduced by the addition of SiC. The scale was primarily composed of an outer $TiO_2$ layer having some $Al_2O_3 $islands, an intermediate relatively thick $Al_2O_3 $ layer, and an inner $TiO_2+Al_2O_3+SiO_2$ mixed layer. Beneath the scale, Kirkendall voids were seen.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.418-424
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• 1996

(Ti.W)C complex carbide was synthesized by self-propagating high temperature synthesis (SHS) chemical furnace. Attempt to find the optimal condition for synthesis of (Ti.W)C the effects of molar ratio of Ti:W:C on the synthesized powders and mechanical properties were investigated, Optimum molar ratio of these synthe-sized powder was Ti:W:C=0.7:0.2:1.0 The bulk density M,O.R Hardness Fracture toughness of (Ti.W)C complex carbide sintered at 200$0^{\circ}C$ for 60 min by hot-pressing under the pressure of 20 MPa were 7.6g/cm3, 475 MPa, 17,.7 GPa respectively.

• Journal of the Korean Chemical Society
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• v.9 no.2
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• pp.71-74
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• 1965

Reduction of Ti(Ⅳ)-oxalate complex on dropping mercury electrode has been studied as a function of oxalate concentration and of pH varied with HCl. Assuming there are equilibrium $TiO(C_2O_4)_2= \;+\;2H^+\;=\;Ti^{+4}\;+\;2C_2O_4\;=\;+\;H_2O,\;K_4$ in addition to $TiO(C_2O_4)_2\;^=\;=\;TiO^{++}\;+\;2C_2O_4=\;K_2\;Ti(C_2O_4)_2\;^-\;=\;Ti^{+3}\;+\;2C_2O_4=\;K_3$ in the system cathodic wave has been well explained for that pH is higher than 0.5. The equilibrium constants $K_2,\;K_3$ and $K_4$ have been to be $2{\times}10^{-12},\;5{\times}10^{-13}$ and $10^{-11}$, respectively. The reduction of Ti(Ⅳ)-oxalate system is $Ti^{+4}\;+\;e\;{\to}\;Ti^{+3}$ in the concentration of hydrochloric acid, higher than 3M.

• Journal of the Korean institute of surface engineering
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• v.42 no.2
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• pp.73-78
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• 2009

Quinary Ti-Al-Si-C-N films were successfully synthesized on SUS 304 substrates and Si wafers by a hybrid coating system combining an arc ion plating technique and a DC reactive magnetron sputtering technique. In this work, the effect of Si content on the microstructure and mechanical properties of Ti-Al-C-N films were systematically investigated. It was revealed that the microstructure of Ti-Al-Si-C-N coatings changed from a columnar to a nano-composite by the Si addition. Due to the nanocomposite microstructure of Ti-Al-Si-C-N coatings, the microhardness of The Ti-Al-Si-C-N coatings significantly increased up to 56 GPa. In addition the average friction coefficients of Ti-Al-Si-C-N coatings were remarkably decreased with Si addition. Therefore, Ti-Al-Si-C-N coatings can be applicable as next-generation hard-coating materials due to their improved hybrid mechanical properties.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.436-442
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• 1992

When $N_2$was used as shielding gas during the formation of Ti surface-alloyed layer by irradiation of $CO_2$laser beam on steel, TiN and F$e_2$Ti were formed regardness of carbon-content in steel. When Ti content was increased in low carbon-content steel, formation of martensitic structure was suppressed due to increase of critical cooling rate for martensitic transformation. In case of high-carbon steel, even though Ti content was about 1.5% in alloyed layer, hardness was increased by formation of martensitic structure instead of ferrite. In addition to that structure, hardness was incrreased further by precipitation of TiC in Ti alloyed-layer of high carbon-steel.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.196-200
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• 1998

Effect of diffusion induced recrystallization(DIR) on mechanical properties of hot-pressed TiC was in-vestigated. The TiC specimen was electroplated with Cr and then heat-treated at 1550. Through the DIR process a new set of (Ti, Cr) C mixed carbide grains with uniform and small size was formed at the surface. As a consequence the scattering in fracture strength decreased and the toughness increased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.5
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• pp.510-515
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• 1999

Synthesize of anatase type $TiO_2$ from $TiCl_4$ solution was studied. KOH was used on dehydration reaction of $TiCl_4$ solution. Products of dehydration reaction was calcined at 300, 500, 700, 900, $1000^{\circ}C$ during 1hour. Calcined products was studied by XRD, DTA, and FT-IR for effect of calcined temperature. The results are as follow. \circled1 Product pf dehydration reaction at$ 90^{\circ}C$ was semicrystalline anatase type $TiO_2$ because it has a peak vary broad and low at the position of anatase crysral XRD pattern. \circled2 Pure titanium oxide semi-crystalline products were produced at acid pH condition which convert to anatase crystal at $300^{\circ}C$ and to rutile crystal at $700^{\circ}C$. \circled3 The chemical composition of semicrystalline products which was produce at alkali pH conditions, were potasium titante. Potasium-titanate semi-crystalline products crystallized at 630~$640^{\circ}C$ \circled4 The transition temperature of potassium dopped titanium oxide semi-crystalline products was increased with the contents of potasium. \circled5 The optimum synthesise condition of anatase $TiO_2$ products from $TiCl_4$ and KOH are pH 3~5 and $300^{\circ}C$ calcination.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.68-68
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• 2000

펄스레이저 증착법(이하 PLD)을 이용하여 마이크로파 유전체 소자 및 절연 산화막으로의 응용을 위한 MgTiO3 박막을 다양한 기판상에서 증착하였다. 사파이어 기판에 (a,c-plane Al2O3) 성장된 MgTiO3 박막은 에피텍셜 성장(epitaxial growth)이 되었으며, SiO2/Si 및 Pt/Ti/Si 기판위세 성장된 MgTiO3 박막의 경우 003방향으로 배향(oriented) 되었다. MgTiO3 박막은 450~75$0^{\circ}C$까지 기판온도를 변화시키면서 증착시켰으며, 증착시 산소분압은 50~200 mTorr로 변화시켰다. PLD 증착시 타켓에 조사된 레이저 에너지 밀도는 약 2J/cm2였으며, MgTiO3 박막 증착후 200Torr O2 분위기에서 상온까지 1$0^{\circ}C$/min 의 속도로 냉각시켰다. 사파이어 c-plane 상에서 일머나잇(ilminite) MgTiO3 구조가 55$0^{\circ}C$ 에피텍셜 성장하는 것을 관찰할 수 있었으며, 사파이어 a-plane 상에서는 MgTiO3 구조가 $650^{\circ}C$ 이상부터 110방향으로 배향되며 성장하였다. $600^{\circ}C$ 이상에서 c-축으로 배향된 구조를 갖고 있었다. 증착된 MgTiO3 박막의 조성분석(stoichio metric analysis)을 위해 RBS 분석을 수행하여, 증착에 이용된 타켓과 동일한 조성을 갖는 MgTiO3 박막이 성장된 것을 확인할 수 있었다. 사파이어 기판상에 증착된 MgTiO3 박막은 가시영역에서 투명하였으며, 약 270nm 파장을 갖는 영역에서 급격한 흡수단을 보였다. 이때의 MgTiO3 박막은 AFM 분석을 통해 약 0.87mn rms roughness 값을 갖는 매우 평탄한 표면구조를 갖고 있는 것을 확인하였다. MIM(Pt/MgTiO3/Pt) 구조의 캐패시터를 형성시켜 MgTiO3 박막의 유전특성(dielectric properties)을 관찰하였다. PLD로 성장된 MgTiO3 박막의 유전율(relative dielectric constant)은 약 22였으며, 1MHz에서 약 1.5%의 유전손실(dielectirc loss) 값을 보였다. 또한 이때 MgTiO3 박막은 낮은 유전분산값을 보였다.

• Applied Microscopy
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• v.29 no.2
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• pp.255-263
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• 1999

We have investigated the interfacial reactions in Co/Ti multilayer thin films prepared by DC Magnetron sputtering system. We observed that the amorphous Co-Ti phase formed by SSAR (Solid State Amorphization Reaction) upon annealing at $200^{\circ}C$. Upon annealing treatments at $300^{\circ}C\;and\;400^{\circ}C$, a crystalline phase of CoTi formed at the Co/Ti interface. The sheet resistance of Co/Ti multilayer thin film increased by the formation of the amorphous phase at the Co/Ti interface, which decreased by the formation of new crystalline compound CoTi.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.317-323
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• 1999

Si3N4-TiC composites have been known as electrically conductive ceramics. $Si_3N_4-TiC$ composites with 2 wt% $Al_2O_3$ and 4 wt% $Y_2O_3$ were hot pressed in $N_2$ environment. The mechanical properties including hardness, fracture toughness, and flexural strength and tribological properties were investigated as a function of TiC content. $Si_3N_4-40$ vol% TiC composite was hot pressed at $1,750^{\circ}C$, $1,800^{\circ}C$, and $1,850^{\circ}C$ for 1, 3 and 5 hours in $N_2$ gas. Mechanical and tribolgical properties depended on microstructures, which were controlled by hte TiC content, hot press temperature, and hot press holding time. However, mechanical properties and tribological behaviors were degraded by the chemical reaction between TiC and N. The chemically reacted products such as TiCN, SiC, and $SiO_2$ were detered by the X-ray diffraction analysis.