• Journal of the Korean Society for Heat Treatment
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• 제6권3호
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• pp.152-158
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• 1993

Effects of oxide film which is grown by heat treatment on the hydrogen embrittlement (HE) of 17-4 PH stainless steel were investigated. Specimems were tensile tested after cathodic hydrogen charging and the be haviors of HE were evaluated from the elongation change. It was found that specimems solution treated at $1040^{\circ}C$ for 1/2hour showed best retardation ability to HE for both aging conditions i.e. $480^{\circ}C{\times}1hr$ and $620^{\circ}C{\times}4hrs$. X-ray and Auger study revealed that the major composition of oxide films are $Cr_2O_3$ and $CuCr_2O_4$.

• The Journal of the Convergence on Culture Technology
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• 제9권3호
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• pp.593-599
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• 2023

Nickel oxide (NiO) nanoparticles were successfully synthesized by a simple liquid phase process for producing ceramics powder using a precursor impregnated with a nickel(II) nitrate hexahydrate aqueous solution in an industrial pulp. The microfibrile structure of the precursor impregnated with nickel nitrate hexahydrate aqueous solution was confirmed by scanning electron microscope (SEM), and the crystal structure and particle size of nickel oxide (NiO) particles produced as the heat treatment temperature of the precursor were analyzed by X-ray diffraction (XRD) and SEM. As a result, it was confirmed through XRD and SEM analysis that the temperature at which the organic material of the precursor is completely thermally decomposed was 495-500℃, and the size and crystallinity of the nickel oxide particles produced increased as the heat treatment temperature increased. The size of the nickel oxide particles obtained by heat treatment at 500-800℃ for 1 hour was 50-200 nm. It was confirmed by XRD and SEM analysis that a NiO crystal phase was formed at a heat treatment temperature of 380℃, only a single NiO phase existed until 800℃.

• The Journal of the Convergence on Culture Technology
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• 제9권6호
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• pp.855-859
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• 2023

Copper oxide (CuO) nanoparticles were successfully synthesized using a precursor in which industrial starch was impregnated with an aqueous solution of copper (II) nitrate trihydrate. The microstructure of the precursor impregnated with an aqueous solution of copper nitrate trihydrate was confirmed with a scanning electron microscope (SEM), and the particle size and the crystal structure of the copper oxide particles produced as the temperature of the heat treatment of the precursor increased was analyzed by X-ray diffraction (XRD) and the scanning electron microscope (SEM). As a result of the analysis, it was confirmed that the temperature at which the organic matter of the precursor is completely thermally decomposed is 450-490℃, and that the size and crystallinity of the copper oxide particles increased as the heat treatment temperature increased. The size of the copper oxide particles obtained through heat treatment at 500-800℃ during 1 hour was 100nm~2㎛. It was confirmed that the copper oxide crystalline phase is formed at a heat treatment temperature of 400℃, and only the copper oxide single phase existed up to 800℃. And it was also confirmed that the size of particles produced increased as the calcination temperature increased.

• The Journal of Korean Academy of Prosthodontics
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• 제47권1호
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• pp.39-45
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• 2009

Statement of problem: Recently precalcification treatment has been studied to shorten the period of the implant. Purpose: This study was performed to evaluate the effect of precalcification treatment of $TiO_2$ Nanotube formed on Ti-6Al-4V Alloy. Material and methods: Specimens of $20{\times}10{\times}2\;mm$ in dimensions were polished sequentially from #220 to #1000 SiC paper, ultrasonically washed with acetone and distilled water for 5 min, and dried in an oven at $50^{\circ}C$ for 24 hours. The nanotubular layer was processed by electrochemical anodic oxidation in electrolytes containing 0.5 M $Na_2SO_4$ and 1.0 wt% NaF. Anodization was carried out using a regulated DC power supply (Kwangduck FA, Korea) at a potential of 20 V and current density of $30\;㎃/cm_2$ for 2 hours. Specimens were heat-treated at $600^{\circ}C$ for 2 hours to crystallize the amorphous $TiO_2$ nanotubes, and precalcified by soaking in $Na_2HPO_4$ solution for 24 hours and then in saturated $Ca(OH)_2$ solution for 5 hours. To evaluate the bioactivity of the precalcified $TiO_2$ nanotube layer, hydroxyapatite formation was investigated in a Hanks' balanced salts solution with pH 7.4 at $36.5^{\circ}C$ for 2 weeks. Results: Vertically oriented amorphous $TiO_2$ nanotubes of diameters 48.0 - 65.0 ㎚ were fabricated by anodizing treatment at 20 V for 2 hours in an 0.5 M $Na_2SO_4$ and 1.0 NaF solution. $TiO_2$ nanotubes were composed with strong anatase peak with presence of rutile peak after heat treatment at $600^{\circ}C$. The surface reactivity of $TiO_2$ nanotubes in SBF solution was enhanced by precalcification treatment in 0.5 M $Na_2HPO_4$ solution for 24 hours and then in saturated $Ca(OH)_2$ solution for 5 hours. The immersion in Hank's solution for 2 weeks showed that the intensity of $TiO_2$ rutile peak increased but the surface reactivity decreased by heat treatment at $600^{\circ}C$. Conclusion: This study shows that the precalcified treatment of $TiO_2$ Nanotube formed on Ti-6Al-4V Alloy enhances the surface reactivity.

• Journal of the Korean Society for Heat Treatment
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• 제37권3호
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• pp.121-127
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• 2024

We investigate the effect of T6 heat treatment on the microstructure and mechanical properties of AA365 (Al-10.3Si-0.37Mg-0.6Mn-0.11Fe, wt.%) alloy fabricated by vacuum-assisted high pressure die casting by means of thermodynamic calculation, X-ray diffraction, scanning and transmission electron microscopy, and tensile tests. The as-cast alloy consists of primary Al (with dendrite arm spacing of 10~15 ㎛), needle-like eutectic Si, and blocky α-AlFeMnSi phases. The solution treatment at 490 ℃ induces the spheroidization of eutectic Si and increase in the fraction of eutectic Si and α-AlFeMnSi phases. While as-cast alloy does not contain nano-sized precipitates, the T6-treated alloy contains fine β' and β' precipitates less than 20 nm that formed during aging at 190℃. T6 heat treatment improves the yield strength from 165 to 186 MPa due to the strengthening effect of β' and β' precipitates. However, the β' and β' precipitates reduce the strain hardening rate and accelerate the necking phenomenon, degrading the tensile strength (from 290 to 244 MPa) and fracture elongation (from 6.6 to 5.0%). Fractography reveals that the coarse α-AlFeMnSi and eutectic Si phases act as crack sites in both the as-cast and T6 treated alloys.

• Proceedings of the Korean Nuclear Society Conference
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• 한국원자력학회 1999년도 춘계학술발표회요약집
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• pp.237-237
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• 1999

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 1998년도 추계학술발표강연 및 논문개요집
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• pp.69-69
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• 1998

• Journal of the Korean Society for Heat Treatment
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• 제29권4호
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• pp.168-175
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• 2016

Influence of trace amount of Ca addition on the corrosion resistance was comparatively investigated in solutionized Mg-4%Zn and Mg-4%Zn-0.1%Ca alloys. In as-cast state, the alloys were characterized by primary ${\alpha}-(Mg)$ dendrite with MgZn intermetallic compound particles. After solution-treatment, both alloys consisted of single ${\alpha}-(Mg)$ phase by dissolution of the compound particles into the matrix. It was found from the immersion and electrochemical corrosion tests that the Mg-4%Zn alloy had better corrosion resistance than the Mg-4%Zn-0.1%Ca alloy. Morphological and compositional analyses on the surface corrosion products indicate that the incorporation of Ca oxide with low PBR value into the surface corrosion products would be responsible for the decreased corrosion resistance of the Ca-containing alloy.

• Journal of the Korean Society of Industry Convergence
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• 제4권3호
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• pp.237-242
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• 2001

Ti-6Al-4V alloy can be obtained the stability of organization and product treasure, the evaluation of the cutting ability and the mechanical characteristics after the heat treatment of annealing, solution and aging. The difficulty in machining titanium alloy is how treat the heat generated during the process. Because the heat conductivity of titanium alloy is regardfully low, the heat generated during grinding is accumulated in workpiece. and it causes the increasing of grinding wheel grits' wear and makes the ground surface rough. So, these characteristics in grinding of titanium alloy will change the mechanical properties of the titanium alloy. From this study. the mechanical characteristics of annealed one and solution and aging one treated Ti-6Al-4V alloy after grinding was concerned with checking out the bending strength and hardness. For the result, both of bending strength and hardness were increased at the burned area on the surface. Roughness value was remarkably high at the table speed of 10m/min.

• Nuclear Engineering and Technology
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• 제40권6호
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• pp.505-510
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• 2008

The correlation between the tensile strength and corrosion behavior of Zr-1.0wt%Nb alloy heat treated at $480^{\circ}C$ for up to 32 hours was evaluated. The tensile strength at $400^{\circ}C$ was continuously reduced with an increasing heat treatment time, mainly due to a grain growth and a decreased area fraction of the precipitates. However, the corrosion resistance in an aqueous ammonia solution at $360^{\circ}C$ was enhanced, mainly due to the formation of $\beta$-Nb precipitates. It is thus concluded that a longer heat treatment time provides a better corrosion resistance while degrading the tensile strength.