• 대한금속재료학회지
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• 제47권8호
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• pp.508-515
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• 2009

Ti-6Al-4V biomaterial is widely used as a bone alternative. However, Ti-6Al-4V ELI alloy suffers from numerous problems such as a high elastic modulus and high toxicity. Therefore, non-toxic biomaterials with low elastic moduli need to be developed. Ti-HA(hydroxyapatite) composites were fabricated in the present work by pulsed current activated sintering (PCAS) at $1000^{\circ}C$ under 60 MPa using mixed Ti and HA powders. The effects of HA content on the physical and mechanical properties of the sintered Ti-HA composites have been investigated. X-ray diffraction(XRD) analysis of the Ti-HA composites, including Ti-40 wt%HA in particular, revealed new phases, $Ti_{2}O$, CaO, $CaTiO_3$, and TixPy, formed by chemical reactions between Ti and HA during sintering. The hardness of the Ti-HA composites decreased with an increase in HA content. The corrosion resistance of these composites was observed to be an excellent candidate as a commercial Ti-6Al-4 V ELI alloy. A Ti-5 wt%HA composite fabricated by PCAS is recommended as a new biomaterial, because it offers good corrosion resistance, compressive strength, wear resistance, and biocompatibility, and a low Young's modulus.

• 한국세라믹학회지
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• 제16권4호
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• pp.225-236
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• 1979

The effect of $Ti^{+4}$ addition on the sinterability, microstructure, and temperature dependence of electromechanical coupling factor of magnetostrictive Ni-Cu-Co ferrite was investigated. The density of Ni-Cu-Co ferrite slightly increased by 2.0 mole % addition of either $TiO_2$ or $Fe_2TiO_4$, but tended to decrease by more than 2.0 mole % addition of $TiO_2$ or $Fe_2TiO_4$. As the content of either $TiO_2$ or $Fe_2TiO_4$ increased, the magnetocrystalline anisotropy compensation temperature also increased. Microstructure studies showed the stable grains when Ni-Cu-Co ferrite was sintered above 1, 20$0^{\circ}C$.

• 분석과학
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• 제5권3호
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• pp.319-325
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• 1992

플라즈마 아크 용해법으로 이론밀도비 99% 이상인 Mo-1.17 Ti-0.18 Zr-0.06 C 잉고트를 제조하였다. 이때 산소함량은 초기 830ppm에서 40ppm으로 감소하였다. 열간단조 후, 50% 냉간 압연하여 두께 2mm의 판재를 만들어 시편으로 사용하였다. Mo 합금판재의 재결정거동을 조사하기 위하여 $800{\sim}2100^{\circ}C$ 구간에서 1시간 동안 등시열처리하였고, $1400^{\circ}C$, $1500^{\circ}C$, $1600^{\circ}C$에서 0~10800sec 동안 등온열처리하였다. 완전한 재결정은 Mo의 경우 $1400^{\circ}C$에서 종료되었으나 Mo 합금의 경우 $1700^{\circ}C$에서 완료되었다. 또한 Mo 합금의 50%-1시간 재결정온도는 약 $1500^{\circ}C$로서 Mo에 비하여 $300^{\circ}C$ 이상 증가된 것을 알 수 있었다. Mo 합금의 재결정에 필요한 활성화에너지는 508kJ/mol이었다.

• 한국환경과학회지
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• 제13권6호
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• pp.537-542
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• 2004

$V_{2}O_{5}/TiO_{2}$ catalysts promoted with Mn were prepared and tested for selective catalytic reduction of NOx in $NH_3.$ The effects of promoter content, degree of catalyst loading were investigated for NOx activity while changing temperatures, mole ratio, space velocity and $O_2$ concentration. Among the various $V-{2}O_{5}$ catalysts having different metal loadings, $V-{2}O_{5}$(1 wt.%) catalyst showed the highest activity(98%) under wide temperature range of $200-250^{\circ}C.$ When the $V-{2}O_{5}$ catalyst was further modified with 5 wt.% Mn as a promoter, the highest activity(90-47%) was obtained over the low temperature windows of $100-200^{\circ}C.$ From Mn-$V_{2}O_{5}/TiO_{2}$, it was found that by addition of 5 wt.% Mn on $V_{2}O_{5}/TiO_{2}$ catalyst, reduction activity of catalyst was improved, which resulted in the increase of catalytic activity and NOx reduction. According to the results, NOx removal decreased for 10%, but the reaction temperature down to $100^{\circ}C.$

• 한국분말재료학회지
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• 제11권4호
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• pp.322-327
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• 2004

Ultrafine titanium carbide particles were synthesized by the reaction of liquid-magnesium and vaporized TiCl$_{4}$+C$_{x}$Cl$_{4}$(x = 1 and 2) solution. Fine titanium carbide particles with about 50 nm were successfully produced by combining Ti and C atoms released by chloride reduction of magnesium, and vacuum was then used to remove the residual phases of MgCl$_{2}$ and excess Mg. Small amounts of impurities such as O, Fe, Mg and Cl were detected in the product, but such problem can be solved by more precise process control. The lattice parameter of the product was 0.43267 nm, near the standard value. With respect to the reaction kinetics, the activation energy for the reactions of TiCl$_{4}$+C$_{2}$Cl$_{4}$and Mg was found to 69 kJ/mole, which was about half value against the use of TiCl$_{4}$+CCl$_{4}$, and such higher reactivity of the former contributed to increase the stoichiometry until the level of TiC$_{0.96}$ and decrease the free carbon content below 0.3 wt.%.

• The Korean Journal of Ceramics
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• 제5권3호
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• pp.255-259
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• 1999

The effects of $SiO_2$ and MnO addition on the sinterability and the electrical properties of 0.4mol% Nb-doped SrTiO3 varistor were investigated. The $SiO_2$ content was fixed at 0.3mol% and the MnO content varied from 0 to 1.0mol%. With 0.3 mol% $SiO_2$ and 0.3 mol% MnO addition, optimum density was obtained by sintering at $1200^{\circ}C$ without excess liquid phase. Impedance spectroscopy was performed on the sintered specimens with 0.3 mol% $SiO_2$ and various MnO contents. It was found that the resistivities of grains was increased with increasing MnO content. The dielectric constant was measured to be above 50000 in the specimen with 0.3~1.0mol% Mn content. The non-linear coefficient increased substantially with MnO addition, and it varied from 1 to 9 depending on the MnO content.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.1579-1584
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• 2015

광촉매반응에서 티타니아에 금속물질을 담지하면 광촉매표면이 변화되며 담지된 금속물질은 반응속도를 증가시킨다. 회분식 광반응기를 이용하여 $TiO_2$ 광촉매에 대한 금속물질 담지와 담지된 촉매의 소성조건 영향을 조사하였다. 광분해 효율을 증진시키기 위해 $TiO_2$ 촉매에 여러 종류의 금속물질을 담지하였다. 모든 실험에서의 수분함량은 3wt%, 반응기 온도는 $40^{\circ}C$이었다. $TiO_2$에 팔라듐을 담지한 경우가 가장 우수하였으며, Pt와 W을 첨가한 경우도 양호하였다. Pd/$TiO_2$ 촉매에 백금 또는 텅스텐을 부가적으로 담지하여도 제거효율에서의 증가는 없었다. 적절한 소성조건을 얻기위해 소성온도와 소성시간에 대하여 다양하게 실험을 수행하였으며, 실험결과 최적의 소성조건은 소성온도 $400^{\circ}C$, 소성시간 1시간이었다.

• 한국재료학회지
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• 제23권6호
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• pp.339-343
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• 2013

Porous Ti-systems with unidirectionally aligned channels were synthesized by freeze-drying and a heat treatment process. $TiH_2$ powder and camphene were used as the source materials of Ti and sublimable vehicles, respectively. Camphene slurries with $TiH_2$ content of 10 and 15 vol% were prepared by milling at $50^{\circ}C$ with a small amount of oligomeric polyester dispersant. Freezing of the slurry was done in a Teflon cylinder attached to a copper bottom plate cooled at $-25^{\circ}C$ while unidirectionally controlling the growth direction of the camphene. Pores were generated subsequently by sublimation of the camphene during drying in air for 48 h. The green body was heat-treated at $1100^{\circ}C$ for 1 h in a nitrogen and air atmosphere. XRD analysis revealed that the samples composed of TiN and $TiO_2$ phase were dependent on the heat-treatment atmosphere. The sintered samples showed large pores of about 120 mm which were aligned parallel to the camphene growth direction. The internal wall of the large pores had relatively small pores with a dendritic structure due to the growth of camphene dendrite depending on the degree of nucleation and powder rearrangement in the slurry. These results suggest that a porous body with an appropriate microstructure can be successfully fabricated by freeze-drying and a controlled sintering process of a camphene/$TiH_2$ slurry.

• 한국세라믹학회지
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• 제26권2호
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• pp.249-257
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• 1989

Dielectric properties and the stability of the perovskite phase in the Pb(Mg1/3Nb2/3)O3 system have been investigated as a function of amount of BaTiO3 and firing temperature. In the specimens fired at 120$0^{\circ}C$, the pyrochlore phase was eliminated by the addition of 10-15m/o BaTiO3 and also the dielectric constant increased. However, the dielectric constant decreased with further addition of BaTiO3 even though no pyrochlore phase was found to be present. The reducing tendency of the pyrochlore phase decreased with lowering the firing temperature in the system of Pb(Mg1/3Nb2/3)O3 with BaTiO3. Dielectric properties in PMN ceramics were affected by the character of the BaTiO3 rather than the pyrochlore phase.

• Journal of Welding and Joining
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• 제25권1호
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• pp.57-62
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• 2007

In the coarse grained HAZ of conventional TiN steel, most TiN particles are dissolved and austenite grain growth easily occurrs during high heat input welding. To avoid this difficulty, thermal stability of TiN particles is improved by increasing nitrogen content in EH36-TM steel. Increased thermal stability of TiN particle is helpful for preventing austenite grain growth by the pinning effect. In this study, the mechanical properties and microstructures of high heat input welded Tandem EGW joint in EH36-TM steel with high nitrogen content were investigated. The austenite grain size in simulated HAZ of the steel at $1400^{\circ}C$ was much smaller than that of conventional TiN steel. Even for high heat input welding, the microstructure of coarse grained HAZ consisted of fine ferrite and pearlite and the mechanical properties of the joint were sufficient to meet all the requirements specified in classification rule.