• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.994-999
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• 1997

The sintering properties of hydroxyapatite isolated from tuna bone and hydroxyapatite-containing wollastonite sintered by solid-state reaction was investigated. As the sinterability of hydroxyapatite dependent upon the particle size by dry milling, it showed a sintering. But the hydroxyapatite-containing wollastonite was appeared good sinterability. On X-ray measurements, the major phases of hydroxyapatite-containing wollastonite by solid state reaction at $1250^{\circ}C$ were identified as hydroxyapatite and pseudowollastonite(${\alpha}-CaSiO_3$). And the phases appeared as whitlockite [$Ca_3(PO_4)_2$] by decomposition of hydroxyapatite at higher temperature above $1250^{\circ}C$. The shapes of microstructure on SEM images changed from porous to dense bulk by elevating temperature. The mean bending strength of hydroxyapatite-containing wollastonite sintered by solid-state reaction at $1300^{\circ}C$ was about 18 MPa, it was close to the cancellous bone's maximum strength, 20 MPa.

• Carbon letters
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• v.12 no.2
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• pp.95-101
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• 2011

To investigate new applications for illite as an additive for carbon-based composites, the composites were prepared with and without illite at different heat-treatment temperatures. The effects of the heat-treatment temperature on the chemical structure, microstructure, and thermal oxidation properties of the resulting composites were studied. As the heat-treatment temperature was increased, silicon carbide SiC formation via carbothermal reduction increased until all the added illite was consumed in the case of the samples heat-treated at $2,300^{\circ}C$. This is attributed to the intimate contact between the $SiO_2$ in the illite and the phenol carbon precursor or the carbon fibers of the preform. Among composites prepared at all temperatures, those with illite addition exhibited fewer pores, voids, and interfacial cracks, resulting in larger bulk densities and lower porosities. A delay of oxidation was not observed in the illite-containing composites prepared at $2,300^{\circ}C$, suggesting that the illite itself absorbed energy for exfoliation or other physical changes. Therefore, if the illite-containing C/C composites can reach a density generally comparable to that of other C/C composites, illite may find application as a filler for C/C composites. However, in this study, the illite-containing C/C composites exhibited low density, even when prepared at a high heat-treatment temperature of $2300^{\circ}C$, although the thermal oxidation of the resulting composites was improved.

• Journal of Technologic Dentistry
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• v.27 no.1
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• pp.65-71
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• 2005

Experimental Ti-13%Zr and Ti-13%Zr-5%Cu alloys were made in an argon-arc melting furnace. The grade 2 CP Ti was used to control. The alloys were cast into phosphate bonded $SiO_2$ investment molds using an argon-arc casting machine, and The hardness and microstructures of the castings were investigated in order to reveal their possible use for new dental casting materials and to collect useful data for alloy design. The hardness of the Ti-13%Zr-5%Cu alloy(379Hv) became higher than that of Ti-13%Zr(317Hv) alloy, and the hardness of this alloys became higher than that of CP Ti(247Hv). Increasing in the hardness of the Ti-13%Zr-5%Cu alloy was considered to be solid solution hardening as the Ti-Zr system shows a completely solid solution for both high temperature $\beta$phase and low temperature $\alpha$ phase and also the inclusion of the eutectoid structure($\alpha Ti+Ti_{2}Cu$). No martensitic structures are observed in the specimen made of CP Ti, but Ti-13%Zr and Ti-13%Zr-5%Cu alloys show a kind of martensitic structure. Ti-13%Zr-5%Cu shows the finest microstructure. From these results, it was concluded that new alloys for dental casting materials should be designed as Ti-Zr-Cu based alloys.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.825-830
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• 2014

$[(Co_{1-x}Cu_x)_{0.2}(Ni_{0.3}Mn_{0.7})_{0.8}]_3O_4$ ($0{\leq}x{\leq}1$) thin films prepared by metal organic decomposition process were fabricated on SiN/Si substrate for infrared sensor application. Their structural and electrical properties were investigated with variation of Cu dopant. The $[(Co_{1-x}Cu_x)_{0.2}(Ni_{0.3}Mn_{0.7})_{0.8}]_3O_4$ (CCNMO) film annealed at $500^{\circ}C$ exhibited a dense microstructure and a homogeneous crystal structure with a cubic spinel phase. Their crystallinity was further enhanced with increasing doped Cu amount. The 120 nm-thick CCNMO (x=0.6) thin film had a low resistivity of $53{\Omega}{\cdot}cm$ at room temperature while the Co-free film (x=1) showed a significantly decreased resistivity of $5.9{\Omega}{\cdot}cm$. Furthermore, the negative temperature coefficient of resistance (NTCR) characteristics were lower than $-2%/^{\circ}C$ for all the specimens with $x{\geq}0.6$. These results imply that the CCNMO ($x{\geq}0.6$) thin films are a good candidate material for infrared sensor application.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.104-112
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• 2012

This study involves investigating the correlation between variation of internal structure and heating temperature of alkali-activated fire protection materials using fly ash. Dehydration and micro crack thermal expansion occur in cement hydrates of cementitious materials heated by fire. Internal structure difference due to both the dehydration of cement hydrates and pore solution causes and influences changes in the properties of materials. Also, this study is concerned with change in microstructure and dehydration of the alkali-activated fire protection materials at high temperatures. The testing methods of alkali-activated fire protection materials in high temperature properties are make use of TG-DSC and mercury intrusion porosimetry measurements. The study results show that the alkali-activated fire resistant finishing material composed of potassium hydroxide, sodium silicate and fly ash has the high temperature thermal stability. These thermal stability is caused by the ceramic binding capacity induced by alkali activation reaction.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.175-182
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• 2022

Rare-earth elements were doped with Mg to enhance the temperature stability of dielectric properties of BaTiO₃ for its application to MLCC (Multi-Layer Ceramic Capacitor). The additives strongly affect both grain growth and densification behaviors during sintering, and hence dielectric properties. The additive effects therefore should be examined in each system with different additives. This study investigated the crystal structure, grain growth and densification behaviors and related variations in dielectric constant with respect to sintering temperature. Dielectric constant appears to be varied with grain size in a temperature range between 1200 and 1300℃, suggesting the importance of grain size control. The temperature dependence of grain size variation was well explained by an established theory correlating the grain growth behavior with grain boundary structure. This accordance provides a basis for sintering technique to control grain growth thus to improve dielectric constant in rare-earth doped BaTiO₃.

• Journal of the Korean Ceramic Society
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• v.44 no.10
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• pp.580-584
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• 2007

The ZrC layer instead of SiC layer is a critical and essential layer in TRISO coated fuel particles since it is a protective layer against diffusion of fission products and provides mechanical strength for the fuel particle. In this study, we carried out computational simulation before actual experiment. With these simulation results, Zirconium carbide (ZrC) films were chemically vapor deposited on $ZrO_2$ substrate using zirconium tetrachloride $(ZrCl_4),\;CH_4$ as a source and $H_2$ dilution gas, respectively. The change of input gas ratio was correlated with growth rate and morphology of deposited ZrC films. The growth rate of ZrC films increased as the input gas ratio decreased. The microstructure of ZrC films was changed with input gas ratio; small granular type grain structure was exhibited at the low input gas ratio. Angular type structure of increased grain size was observed at the high input gas ratio.

• Journal of the Korean Vacuum Society
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• v.5 no.4
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• pp.327-332
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• 1996

In this study, the effects of $WSi_x$, thickness and fluorine concentration in tungsten polycide gate structure on gate oxide were investigated. As $WSi_x$, thickness increases, gate oxide thickness increases with fluorine incorporation in gate oxide, and time-to-breakdown($T_{BD,50%}$) of oxide decreases. The stress change with $WSi_x$ thickness was also examined. But it is understood that the dominant factor to degrade gate oxide properties is not the stress but the fluorine, incorporated during $WSi_x$ deposition, diffused into $WSiO_2$ after heat treatment. In order to understand the effect of fluorine diffusion into oxidem fluorine ion implanted gates were compared. The thickness variation and $T_{BD,50%}$ of gate oxide is saturated over 600 $\AA$ thickness of $WSi_x$. The TEM and SIMS studies show the microstructure less than 600 $\AA$ thickness is dense and flat in surface. However, over 600$\AA$, the microstructure of $WSi_x$ is divided into two parts: upper porous phase with rugged surface and lower dense phase with smmoth interface. And this upper phase is transformed into oxygen rich crystalline phase after annealing, and the fluorine is captured in this layer. Therefore, the fluorine diffusion into the gate oxide is saturated.

• Korean Journal of Materials Research
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• v.17 no.6
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• pp.293-297
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• 2007

Microstructure and tensile strength of the vacuum brazed stainless steel(STS303) and Cu were investigated. For brazing, the BNi-2, 3, 4, 6 and 7 (A.W.S standard) were used as filler metals. The Oxides such as $Cr_2O_3$ and $SiO_2$ were observed at brazed layers between STS303 and Cu matrix. Also, the intermetallic compounds of Cr-B and Ni-P were observed at brazed layers. Brazed STS303-Cu specimens with BNi-2, 3, 4 filler metals showed almost elastic deformation followed by plastic yielding and strain hardening up to a peak stress. On the other hand, it is likely that the fracture of the brazed specimens with BNi-6 and 7 was occurred in elastic range without plastic yielding up to a peak stress. Among these filler metals, the BNi-2 brazed at $1050^{\circ}C$ showed excellent wettability and the highest tensile strength (101.6MPa).

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.216-216
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• 1999

The usage of a stationary plasma thruster (SPT) ion source, invented previously for space application in Russia, in experiments with surface modifications and film deposition systems is reported here. Plasma in the SPT is formed and accelerated in electric discharge taking place in the crossed axial electric and radial magnetic fields. Brief description of the construction of specific model of SPT used in the experiments is presented. With gas flow rate 39ml/min, ion current distributions at several distances from the source are obtained. These was equal to 1~3 mA/$\textrm{cm}^2$ within an ion beam ejection angle of $\pm$20$^{\circ}$with discharge voltage 160V for Ar as a working gas. Such an extremely high ion current density allows us to obtain the Ti metal films with deposition rate of $\AA$/sec by sputtering of Ti target. It is shown a possibility of using of reactive gases in SPT (O2 and N2) along with high purity inert gases used for cathode to prevent the latter contamination. It is shown the SPT can be operated at the discharge and accelerating boltages up to 600V. The results of presented experiments show high promises of the SPT in sputtering and surface modification systems for deposition of oxide thin films on Si or polymer substrates for semiconductor devices, optical coatings and metal corrosion barrier layers. Also, we have been tried to establish in application of the modeling expertise gained in electric and ionic propulsion to permit numerical simulation of additional processing systems. In this mechanism, it will be compared with conventional DC sputtering for film microstructure, chemical composition and crystallographic considerations.