• Journal of Powder Materials
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• v.17 no.4
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• pp.281-288
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• 2010

A carbon doped $TiO_2$ (C-$TiO_2$) photocatalyst, which shows good photocatalytic activity to Ultraviolet irradiation and visible irradiation, was successfully prepared by co-grinding of $TiO_2$ with ethanol or Activated Carbon(C), followed by heat treatment at $200^{\circ}C$ in air for 60 min. Ethanol and C were used as a representative agent of liquid and solid for carbon doping. Their influence on improving photocatalytic ability and carbon doping degree was studied with degradation of methyl orange and XPS analysis. The product prepared by co-grinding of $TiO_2$ with Ethanol had Ti-C and C-O chemical bonds and showed higher photocatalytic activity than the product prepared by co-grinding of $TiO_2$ with C, where just C-O chemical bond existed. As a result, mechanochemical route is useful to prepare a carbon doped $TiO_2$ photocatalyst activating to visible irradiation, where the solid-liquid operation is more effective than solid-solid operation to obtain a carbon doped $TiO_2$.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.123-124
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• 2007

3성분계 Ti-Si-C 코팅은 PECVD 기술에 의해 WC-Co 기판에 합성되었다. 이 연구에서 Ti-Si-C코팅에서의 비정질 silicon carbide 상의 효과는 XRD, XPS, TEM에 의해 분석되었다. TiC 결정의 입자크기는 비정질 silicon carbide의 침투 현상 때문에 Si의 함유량이 증가됨에 따라 감소된다. Ti-Si-C 코팅은 5.2%의 Si함유량에서 나노크기의 nc-TiC결정과 비정질 a-SiC로 이루어져 있고 최고 경도 33GPa와 탄성율 330GPa를 각각 보여주고 있다. 이 수치들은 순수한 TiC(-21GPa, 260Gpa)보다 눈에 띄게 높아졌다.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.777-783
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• 2003

The mechanical properties of B$_4$C/Al composites normally depend on the species and quantity of reaction products between B$_4$C and Al and then the control of reaction products is necessary to make desirable composites for lightweight advanced or armor materials. TiB$_2$ is chemically inert with aluminum and has a lower contact angle (85$^{\circ}$ at 100$0^{\circ}C$) to liquid aluminum than B$_4$C. Thus, TiB$_2$ coating on B$_4$C may lower infiltration temperature of aluminum when the B$_4$C/Al composites is fabricated by infiltration process. In this study, the effects of TiB$_2$ on the microstructure and mechanical properties of the B$_4$C/Al composites have been investigated. TiB$_2$ coated B$_4$C powder was prepared using the sol-gel technique. It was found that the B$_4$C surface is homogeneously covered with TiB$_2$ having a particles size of 20-50 nm. While the B$_4$C/Al composites prepared by infiltration after TiB$_2$ coating had 17 wt% of unreacted Al, on the other hand, the B$_4$C/Al composites without coating included 14 wt% of Al. As a result, the composites infiltrated after the coating showed higher fracture toughness and lower hardness. This strongly suggests that TiB$_2$ not only lowers the infiltration temperature, but also inhibits the reaction between B$_4$C and Al.

• Journal of the Korean Ceramic Society
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• v.38 no.5
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• pp.412-417
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• 2001

본 연구는 습식법으로 수산화 알루미늄과 티타니아를 출발물질로 하여 $Al_2$O$_3$-TiO$_2$복합분체를 제조하였으며, 2 mol의 Al(OH)$_3$분말에 대하여 TiO$_2$분말량을 1, 3, 5, 7, 9, 11 wt%로 첨가하여 $Al_2$O$_3$-TiO$_2$복합분체의 특성을 조사하였다. 제조된 $Al_2$O$_3$-TiO$_2$계 복합분체는 $700^{\circ}C$~140$0^{\circ}C$까지 하소하여 XRD 분석을 한 결과 100$0^{\circ}C$까지는 TiO$_2$(rutile)상과 η-Al$_2$O$_3$상이 공존하다가 110$0^{\circ}C$부터 130$0^{\circ}C$까지는 η-Al$_2$O$_3$에서 $\alpha$-Al$_2$O$_3$로의 상전이가 일어나서 $\alpha$-Al$_2$O$_3$상과 TiO$_2$(rutile)상이 나타났으며 하소온도 140$0^{\circ}C$, TiO$_2$첨가량이 5 wt%일 때부터 $Al_2$TiO$_{5}$가 생성되기 시작하였다. TiO$_2$첨가량에 따른 비표면적값은 첨가량이 7 wt%까지는 감소하였으나 그 이상 첨가시 증가하였다. 입도분석 결과 평균입경은 15.74~23.21$mu extrm{m}$로서 TiO$_2$첨가량이 3 wt%일 때 가장 작은 값을 가졌으며 TiO$_2$첨가량은 5 wt% 이상부터 점차 감소하였다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.7
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• pp.73-81
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• 1992

We have investigated the thermal reaction property and the oxygen behavior of TiN/Ti/Si structure after different hear treatments using x-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy measurements. During the heat treatment in N$_2$ amibient, the considerable amount of oxygen atoms incorporates into TiN/Ti/Si Structures. It is found that oxygen atoms pile up at the top surface of TiN and TiN/Ti interface, forming a compound of TiO$_2$ above $600^{\circ}C$. Inside the TiN film, the oxygen content increases as the annealing temperature increases, mostly TiO and Ti$_2$O$_3$ rather than thermodynamically stable TiO$_2$. Above the annealing temperature of 55$0^{\circ}C$, the TiSi$_2$ formation has initiated. One thing to note is that a severe blistering is observed in the sample annealed at $600^{\circ}C$, due to (1) the difference of thermal expansion coefficient between TiN and Si` (2) the compressive stress induced by the volume reduction caused by the Ti-Silicide grain while elevating temperatures.

• Journal of Powder Materials
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• v.22 no.4
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• pp.266-270
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• 2015

The synthesis of NiTi alloy powders by hydrogen reduction and dehydrogenation process of NiO and $TiH_2$ powder mixtures is investigated. Mixtures of NiO and $TiH_2$ powders are prepared by simple mixing for 1 h or ball milling for 24 h. Simple-mixed mixture shows that fine NiO particles are homogeneously coated on the surface of $TiH_2$ powders, whereas ball milled one exhibits the morphology with mixing of fine NiO and $TiH_2$ particles. Thermogravimetric analysis in hydrogen atmosphere reveals that the NiO and $TiH_2$ phase are changed to metallic Ni and Ti in the temperature range of 260 to $290^{\circ}C$ and 553 to $639^{\circ}C$, respectively. In the simple-mixed powders by heat-up to $700^{\circ}C$, agglomerates with solid particles and solidified liquid phase are observed, and the size of agglomerates is increased at $1000^{\circ}C$. From the XRD analysis, the presence of liquid phase is explained by the formation and melting of $NiTi_2$ inter-metallic compound due to an exothermic reaction between Ni and Ti. The simple-mixed powders, heated to $1000^{\circ}C$, lead to the formation of NiTi phase but additional Ni-, Ti-rich and Ti-oxide phases. In contrast, the microstructure of ball-milled powders is characterized by the neck-grown particles, forming $Ni_3Ti$, Ti-oxide and unreacted Ni phase.

• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.413-419
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• 2002

Particulate composites of $Al_2O_3$/TiC/SiC, $Al_2O_3$/TiC and $Al_2O_3$/SiC have been fabricated by hot pressing and their R-curve behaviors and mechanical properties were investigated. $Al_2O_3$ containing 30 vol% TiC particles showed higher toughness by 8% than that for monolithic alumina and its fracture strength was increased significantly by approximately 30%. On the other hand, the addition of 30 vol% SiC of $3{\mu}m$ in $Al_2O_3$ decreased the fracture strength slightly but induced a rising R-curve behavior owing to the strong crack bridging of SiC particles. In case of $Al_2O_3$/TiC/SiC, arising R-curve behavior was also observed and the fracture toughness reached 6.6 MPa${\cdot}\sqrt{m}$ at the crack length of $1000{\mu}m$, which was lower than that of $Al_2O_3$/SiC, however, while the fracture strength was higher by about 20%. The fracture toughness seemed to be decreased as smaller TiC particles roughened the SiC interface and pullout of the SiC particles for crack bridging became less active.

• Journal of Powder Materials
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• v.9 no.6
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• pp.455-462
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• 2002

The microstructures and properties of TiC dispersed nickel-base alloy were studied in this work. The alloy prepared by powder metallurgical processing was solution treated, 1st-aged at $880^{\circ}C$ for 16 hours, and then 2nd-aged at $760^{\circ}C$ for 4 hours. Microstucture of sintered specimen showed that TiC particles are uniformly dispersed in Ni base alloy. In the specimen aged at $880^{\circ}C$ for 8 hours, the fine $\gammaNi_3$(Al,Ti) precipitates with round shape are observed and the very fine $\gammaNi_3$(Al,Ti) particles with round shape are precipitated in the specimen aged at $760^{\circ}C$ for 4 hours. The presence of ${\gamma}$precipitates in TiC/Ni base alloy increased the hardness and wear resistance of the specimen. The hardness and wear resistance of the Ni-base with TiC are higher than those of conventional Ni-base superalloy X-750 because of dispersion strengthening of TiC particles. The hardness, transverse rupture strength and resistance of the specimen 2nd-aged at $760^{\circ}C$ for 4 hours are higher than those of 1st-aged specimen due to ultrafine $\gammaNi_3$(Al,Ti) precipitates.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.638-639
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• 2006

Multilayered coatings on tungsten carbide cutting tools are widely used for enhancing cutting performance. In this paper, we review the CVD TiC/TiCN multilayer as a function of the multilayer period. The TiC/TiCN multilayers in initial stage show preferred (220) orientation but shifts to (200) orientation with decreasing multilayer period. The nanohardness of TiC/TiCN multilayers were found to increase with decreasing multilayer period and shows a maximum of 23.8 GPa at a period = 33.5 nm.

• Journal of Plant Biology
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• v.39 no.3
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• pp.179-184
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• 1996

The purpose of this study is to obtain the most efficient combination of Agrobacterium tumefaciens strains and Ti plasmids for the construction of dicotyledonous plant vector system. Ti plasmid-curing A. tumefaciens A136 and KU12C3 were transformed with four kinds of Ti plasmids, pTiBo542, pTiA6, pTiKU12 and pTiAch5, respectively. The stems of 28 species of dicotyledonous plants were then inoculated with these transformants and examined for crown gall formation. The different combination of A. tumefaciens strains and Ti plasmids showed quite a difference in terms of the crown gall formation. Agrobacterium strins A136 and KU12C3 have a same plant host range in case that both strains harour the same kind of Ti plasmid, pTiBo542 or pTiAch5. However, the above-mentioned both strains have quite different host range in the event of containing the same Ti plasmid, pTiKU12 or pTiA6. In case that KU12C3 contains pTiA6 or pTiKU12, this strain has a wider plant host range than A136. The plant host range of pTiBo542 is the widest, followed by pTiA6, pTiKU12 and pTiAch5. Twelve plants among 28 tested plants are not transformed by any virulent Agrobacterium strains used in this study. In conclusion, A. tumefaciens KU12C3 and A136 harboring pTiBo542 showed the widest host range for transforming dicotyledonous plants. Also, it was acertained that the host range of Ti plasmids is affected by chromosomal level.