• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.682-688
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• 2016

In $TiO_2$-CuO systems, low-temperature sinterability was investigated by a conventional sintering method. Sintering temperatures were set at under $950^{\circ}C$, at which the volume diffusion is inactive. The temperatures are less than the melting point of Ag ($961^{\circ}C$), which is often used as an internal conductor in low-temperature co-fired ceramic technology. To optimize the amount of CuO dopant, various dopant contents were added. The optimum level for enhanced densification was 2 wt% CuO. Excess dopants were segregated to the grain boundaries. The segregated dopants supplied a high diffusion path, by which grain boundary diffusion improved. At lower temperatures in the solid state region, grain boundary diffusion was the principal mass transport mechanism for densification. The enhanced grain boundary diffusion, therefore, improved densification. In this regard, the results of this study prove that the sintering mechanism was the same as that of activated sintering.

• Korean Journal of Materials Research
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• v.17 no.9
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• pp.463-468
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• 2007

The interdiffusion characteristics of Cu-plug/Capping Layer/NiSi contacts were investigated. Capping layers were deposited on Ni/Si to form thermally-stable NiSi and then were utilized as diffusion barriers between Cu/NiSi contacts. Four different capping layers such as Ti, Ta, TiN, and TaN with varying thickness from 20 to 100 nm were employed. When Cu/NiSi contacts without barrier layers were furnace-annealed at $400^{\circ}C$ for 40 min., Cu diffused to the NiSi layer and formed $Cu_3Si$, and thus the NiSi layer was dissociated. But for Cu/Capping Layers/NiSi, the Cu diffusion was completely suppressed for all cases. But Ni was found to diffuse into the Cu layer to form the Cu-Ni(30at.%) solid solution, regardless of material and thickness of capping layers. The source of Ni was attributed to the unreacted Ni after the silicidation heat-treatment, and the excess Ni generated by the transformation of $Ni_2Si$ to NiSi during long furnace-annealing.

• Korean Journal of Materials Research
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• v.12 no.9
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• pp.696-700
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• 2002

The Ti-aluminide intermetallic compound was formed from high purity elemental Ti and Al foils by self-propagating, high-temperature synthesis(SHS) in hot press. formation of $TiAl_3$ at the interface between Ti and Al foils was controlled by temperature, pressure, heating rate, and so on. According to the thermal analysis, it is known in this study that the heating rate is the most important factor to form the intermetallic compound by this SHS reaction. The V layer addition between Al and Ti foils increased SHS reaction temperatures. The fully dense, well-boned inter-metallic composite($TiA1/Ti_3$Al) sheets of 700 m thickness were formed by heat treatment at $1000^{\circ}C$ for 10 hours after the SHS reaction of alternatively layered 10 Ti and 9 Al foils with the V coating layer. The phases and microstructures of intermetallic composite sheets were confirmed by EPMA and XRD.

• Journal of the Korean Society for Heat Treatment
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• v.29 no.1
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• pp.1-7
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• 2016

Titanium and its alloys can be usually joined with brazing method. And the alloys should be brazed at low temperature to keep their original microstructure. In this study, the mechanical strength and microstructure of the CP-Ti joint-brazed with $Zr_{54}Ti_{22}Ni_{16}Cu_8$ filler metal having melting temperature of $774{\sim}783^{\circ}C$ were investigated. The tensile strengths of the joint-brazed at $800^{\circ}C$ with $100^{\circ}C/min$ of cooling rate showed more than 400 MPa which was as high as base metal. The $Widmanst{\ddot{a}}tten$ structure consisting of Ti and $Ti_2Ni$ phase was observed in the joint area. However, the tensile strengths of the joint-brazed at $800^{\circ}C$ with $15^{\circ}C/min$ of cooling rate were decreased and the Ti, $(Ti,Zr)_2Ni$ and $Ti_2Ni$ phases were observed at the joint area. It is believed that the $(Ti,Zr)_2Ni$ laves phases could decrease the mechanical strength of the joint and the cooling rate should be controled to get high strength of the titanium joint.

• Korean Journal of Materials Research
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• v.11 no.12
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• pp.1057-1062
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• 2001

We investigated the change of mechanical properties for TiNi shape memory alloy by heat treatment. 6061Al matrix composites with TiNi shape memory alloy as reinforcement were fabricated by vacuum casting. TiNi alloy has the maximum tensile strength at 673K treated and there is no change of tensile strength and hardness at 448K treated. The composites, prepared by vacuum casting, showed good interface bonding by vacuum casting. It was about 3$\mu\textrm{m}$ of thickness of the diffusion layer. Tensile strength of the composite was in higher than that of 6061Al alloy as increased value of about 70MPa at room temperature and about 110MPa at 363K. We thought that the increase of the tensile strength at 363K was due to reverse transformation of the TiNi shape memory alloy.

• Economic and Environmental Geology
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• v.26 no.1
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• pp.107-114
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• 1993

For the blue sapphires from Santung, China, the color change before and after has been investigated by UV-Visible spectrophotometry method. The blue sapphires from Shantung show four groups of absorption bands: the bands A (374, 386 and 450 nm) being attributed to single $Fe^{3+}$ ion, the band B (560, 579 and $704n{\breve{m}}$) to $Fe^{2+}$/$Ti^{4+}$ pairs, the band C (-800 nm) to $Fe^{2+}$/$Fe^{3+}$ pairs, and the D (528 nm) to $Ti^{3+}$ dd transitions. From those UV-VIS characteristics the origin of blue color of the sapphires is confirmed to be attributed by the factors such as $Fe^{2+}$/$Fe^{3+}$ and $Ti^{3+}$/$Ti^{4+}$. The absorption spectra of natural blue sapphires before and after heat treatment show distintive features, comparing with those of sapphires from other localities: the bands of 689 nm and of $Cr^{3+}$ are not recorded on the spectra of sapphires from Shantung. The band (492 nm), which resulted from $Ti^{3+}$, is not shown and the intensity of the band 528 nm decreases after the heat treatment. Decoloration of ink-blue sapphires are found to be successful by heat treatment with the control of annealing and atmosphere. During the diffusion process the excess components of impurities contained originally in the host crystal were expelled to the surface of crystals, enhancing the transparency of the crystals noticeably.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.6
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• pp.290-297
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• 2004

The color enhancement of natural ruby produced from Mong Hsu were carried out by the heat treatment using gas diffusion. The natural ruby in this paper has a colored patch of which the color ranges from blue to a color close to black. The most favorable heat treatment conditions were as follows; range of temperature $1400~1600^{\circ}C$, duration 12 hrs, $O_2$ atmosphere. The color tone of ruby obtained under the optimum conditions was overall clear red by partial removal of colored patch. From EPMA results, part of blue or black colored patch within ruby were found to occur by charge transfer between $Fe^{2+}{\;}and{\;}Ti^{4+}$ . These results are consistent with the XRF that contents of $Fe(Fe^{2+}{\;}or{\;}Fe^{3+}$) and $Ti^{4+}$ ion to cause a blue or black colored patch after heat treatment became slightly less than with non-treated ruby. The silk formed on the surface of ruby heat treated for 12 hrs at $1700^{\circ}C$ were found to be generated by re-crystallization of rutile $TiO_2$ by XPS analysis.

• Journal of the Korean Society for Heat Treatment
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• v.6 no.1
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• pp.17-25
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• 1993

The Cu - $Nb_3Sn$ composites wire as a superconducting material was prepared by in situ method as follow: Cu - 15wt.% Nb alloys which were melted in a high -frequency induction furnace and casted in bar were cold-worked up to the final diameter of 0.24 mm, electroplated with Sn, pre-treated in two steps and then diffused at $550{\sim}650^{\circ}C$ for 24 ~ 96 hrs. The overall $J_c$ and $T_c$ of the specimens were measured by the four point-probe method at 10 K in the magnetic field of 0 Tesla. The overall $J_c$ of the composites wire which diffused at $550^{\circ}C$ after pre-treating in two steps were generally higher than those of the wire at either $600^{\circ}C$ or $650^{\circ}C$. For the specimens diffused at $550^{\circ}C$, the overall $J_c$ were increased until 72 hrs. of diffusion time and then decreased. However, in case of diffusion at $600^{\circ}C$ and $650^{\circ}C$, the overall $J_c$ were gradually decreased from the beginning. The maximum overall $J_c$ obtained in this experiment was $1.3{\times}10^4\;A/cm^2$, which was measured for the specimen diffused at $550^{\circ}C$ for 72 hrs. When the specimens were diffused at $550^{\circ}C$ for 72 hrs, after pre-treating, the measured critical temperature, $T_c$ was 16.19 K. Similar $T_c$ value were obtained in other specimens regardless of diffusion time and temperature.

• The Korean Journal of Ceramics
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• v.7 no.2
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• pp.70-73
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• 2001

Phase transformation of TiSi$_2$ confined in sub-micron area of which the size is around or smaller than the grain size of C49 TiSi$_2$ phase is studied. It has been known that the C49 to C54 phase change is massive transformation that occurs abruptly starting from C54 nuclei located at triple point grain boundaries of C49 phase. When the C49 phase is confined in sub-micron area, however, the massive phase transformation is observed to be hindered due to the lack of the triple point grain boundaries of C49 phase. Heat treatment at higher temperatures starts to decompose the C49 phase, and the resulting decomposed Ti atoms diffuse to, and react with, the underneath Si material to form C54 phase that exhibits spherical interface with silicon. The newly formed C54 grains can also trigger the massive phase transformation to convert the remaining undecomposed C49 grains to C54 grains by serving as nuclei like conventional C54 nuclei located at triple point grain boundaries.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.8
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• pp.49-55
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• 1992

We Have investigated the properties of the titanium nitrite films widely used in VLSI devices as diffusion barrier in Al-based metallization. TiN films were formed by reactive sputtering from Ti target in Ar-N$_2$ mixtures, varying deposition parameters such as N$_2$ partial pressure, substrate temperature, power, and total pressure. All the samples received the heat treatment at 45$0^{\circ}C$ for 30 min. The resulting films are characterized by mechanical stylus($\alpha$-step), x-ray diffraction(XRD), scanning electron microscopy(SEM), and four point probe method. The Tin film properties strongly depend on the deposition condition. The stoichiometry and Ti deposition rate are critically affected by nitrogen partial pressure, and the resistivity, in particular, is dependent on both the substrate temperature and sputtering power.