• Korean Journal of Materials Research
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• v.29 no.3
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• pp.160-166
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• 2019

This study investigates the effect of thermo-mechanical treatment on the damping capacity of the Fe-20Mn-12Cr-3Ni-3Si alloy with deformation induced martensite transformation. Dislocation, ${\alpha}^{\prime}$ and ${\varepsilon}-martensite$ are formed, and the grain size is refined by deformation and thermo-mechanical treatment. With an increasing number cycles in the thermo-mechanical treatment, the volume fraction of ${\varepsilon}-martensite$ increases and then decreases, whereas dislocation and ${\alpha}^{\prime}-martensite$ increases, and the grain size is refined. In thermo-mechanical treated specimens with five cycles, more than 10 % of the volume fraction of ${\varepsilon}-martensite$ and less than 3 % of the volume fraction of ${\alpha}^{\prime}-martensite$ are attained. Damping capacity decreases by thermo-mechanical treatment and with an increasing number of cycles of thermo-mechanical treatment, and this result shows an opposite tendency for general metal with deformation induced martensite transformation. The damping capacity of the thermo-mechanical treated damping alloy with deformation induced martensite transformation greatly affect the formation of dislocation, grain refining and ${\alpha}^{\prime}-martensite$ and then ${\varepsilon}-martensite$ formation by thermo-mechanical treatment.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.46-52
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• 2018

Nondestructive evaluation for mechanical degradation of ultrasuper-critical (USC) heat-resistance steel, which is attractive to the next generation of power plants is studied by magnetic reversible permeability. The interrelationship between reversible permeability and high-temperature mechanical degradation has been investigated by precise measurement of permeability nondestructively. Also, the effects of microstructural variation on reversible permeability are discussed. Isothermal aging was observed to coarsen the tempered carbides ($Cr_{23}C_6$), generated the intermetallic phases ($Fe_2W$), and grow rapidly during aging. The dislocation density also decreases steeply within lath interior. The peak to peak interval (PPI) of reversible permeability profile decreased drastically during the initial 500 h aging period, and was thereafter observed to decrease only slightly. The variation in PPI is closely related to the decrease in the number of pinning sites and the degradation in tensile strength.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.741-751
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• 2021

There has been a deep interest in trying to find better-performing fuel clad motivated by the desire to decrease the likelihood of the reactor barrier failure like what happened in Fukushima in recent years. In this study, the effect of move towards accident tolerant fuel (ATF) cladding as the most attracting concept for improving reactor safety is investigated for SMART modular reactor. These reactors have less production cost, short construction time, better safety and higher power density. The SiC and FeCrAl materials are considered as the most potential candidate for ATF cladding, and the results are compared with Zircaloy cladding material from reactor physics point of view. In this paper, the calculations are performed by generating PMAX library by DRAGON lattice physics code to be used for further reactor core analysis by PARCS code. The differential and integral worth of control and safety rods, reactivity coefficient, power and temperature distributions, and boric acid concentration during the cycle are analyzed and compared from the conventional fuel cladding. The rod ejection accident (REA) is also performed to study how the power changed in response to presence of the ATF cladding in the reactor core. The key quantitative finding can be summarized as: 20 ℃ (3%) decrease in average fuel temperature, 33 pcm (3%) increase in integral rod worth and cycle length, 1.26 pcm/℃ (50%) and 1.05 pcm/℃ (16%) increase in reactivity coefficient of fuel and moderator, respectively.

• Journal of Korean Society on Water Environment
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• v.27 no.3
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• pp.300-305
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• 2011

This study aimed at analyzing the runoff quality by the layer thickness and material of soil roof to make best use of the rainwater falling on it in terms of safety and efficiency and resulted in the following assessments. It turned out that the concentrations decreased more in T-N, $NO_3$-N, $NH_4$-N, T-P and $PO_4$-P in roof rainwater except 30 cm for the RW1 soil roof after passing through it than those of first rainwater. On the other hand, the concentrations in rainwater passing through gravel roof turned out to be equal or same to those of the first rainwater. As a result of analysis of metallic stuff in runoff, there was no indication of Cd, Cr, Mn and Pb as well. The concentration of Cu, Fe and Zn in rainwater through soil roof became less than that of the first rainwater. In this research, the soil roof showed the good efficiency in lowering the concentration of such components as nitrogen, phosphorus and metals. Based on the results from this work, more practical study would be required further in the future in relation to soil roof when installing the rainwater-utilizing facilities.

• Current Applied Physics
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• v.18 no.11
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• pp.1289-1293
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• 2018

The influence of crystallization treatment on the structure, magnetic properties and magnetocaloric effect of $Gd_{71}Ni_{29}$ melt-spun ribbons has been investigated in detail. Annealing of the melt-spun samples at 610 K for 30 min, a majority phase with a $Fe_3C$-type orthorhombic structure (space group, Pnma) and a minority phase with a CrB-type orthorhombic structure (space group, Cmcm) were obtained in the amorphous matrix. The amorphous melt-spun ribbons undergo a second-order ferromagnetic to paramagnetic phase transition at 122 K. For the annealed samples, two magnetic phase transitions caused by amorphous matrix and $Gd_3Ni$ phases occur at 82 and 100 K, respectively. The maximum magnetic entropy change $(-{\Delta}S_M)^{max}$ is $9.0J/(kg{\cdot}K)$ (5T) at 122 K for the melt-spun ribbons. The values of $(-{\Delta}S_M)^{max}$ in annealed ribbons are 1.0 and $5.7J/(kg{\cdot}K)$, corresponding to the two adjacent magnetic transitions.

• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.99-106
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• 2009

The high temperature corrosion properties of heat resistant steels were investigated in oxidation atmosphere including sulfur dioxide. The heat resistant steels of T22, T92, T122, T347HFG and T304H were evaluated at 620, $670^{\circ}C$ for 400 hours. The corrosion rates showed a decreasing tendency while chrome contents of those steels increased from 2 mass.% to 19 mass.%. The in crease in temperature increasement has an more effect on the corrosion rates of low chrome steels than high chrome steels. The weight gains of T22, T92, T304H at $670^{\circ}C$ were 3.7, 1.65, 1.23 times compared with those at $620^{\circ}C$. The external scale formed on T22 was composed of hematite, magnetite and Fe-Cr spinel and internal layer including iron oxide mixed with sulfide. The scales formed on T92, T122, T304H consisted of an outer layer of hematite and inner layer of chrome oxide and hematite. The proportion of chrome oxide at inner layer was increased when the chrome contents in heat resistant steels were increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3B
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• pp.355-361
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• 2008

A water quality analysis of rainwater collected from catchment equipment ($2m{\times}1m$) was conducted to determine its suitability for domestic purposes, in this study. As the results of analysis, the pH of rainwater was $6.3{\pm}0.3$, and the turbidity of rainwater was over the 5 times than drinking water guidelines. For the usage of rainwater as the domestic and drinking water, the rainwater is need to treat. The analysis values of heavy metal as the Pb, Cd, Fe, Mn, ${Cr_6}^+$ and Cu was satisfied with drinking guidelines. Rainwater quality was improved in the rainfall duration. Overall results of analysis support the possibility of rainwater as the domestic and drinking water.

• Progress in Superconductivity and Cryogenics
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• v.25 no.2
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• pp.14-18
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• 2023

Superconducting layers deposited on the metal substrate using the pulsed laser deposition process (PLD) play a crucial role in exploring new applications of superconducting wires and enhancing the performance of superconducting devices. In order to improve the superconducting property and increase the throughput of superconducting wire fabricated by pulsed laser deposition, high temperature heating device is needed that provides high temperature stability and strong durability in high oxygen partial pressure environments while minimizing performance degradation caused by surface contamination. In this study, new heating device have been developed for PLD process that deposit and growth the superconducting material continuously on substrate using reel-to-reel transportation apparatus. New heating device is designed and fabricated using iron-chromium-aluminum wire and alumina tube as a heating element and sheath materials, respectively. Heating temperature of the heater was reached over 850 ℃ under 700 mTorr of oxygen partial pressure and is kept for 5 hours. The experimental results confirm the effectiveness of the developed heating device system in maintaining a stable and consistent temperature in PLD. These research findings make significant contributions to the exploration of new applications for superconducting materials and the enhancement of superconducting device performance.

• Corrosion Science and Technology
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• v.23 no.1
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• pp.33-40
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• 2024

The concentration and diffusion coefficient of oxide ion vacancies in the oxide scale formed on Fe-22Cr-0.5Mn ferritic stainless steel with and without molybdenum (Mo) was measured at 800℃ by the electrochemical polarization method. After pre-oxidation for 100 h in ambient air at 800 ℃, the oxide scale on one side was completely removed with sandpaper. A YSZ plate was placed on the side where the oxide scale remained. Platinum (Pt) meshes were attached on the top of the YSZ plate and the side where the oxide scale was removed. Changes in electrical current were measured after applying an electrical potential through Pt wires welded to the Pt meshes. The results were interpreted by solving the diffusion equation. The diffusion coefficient and concentration of oxide ion vacancy decreased by 30% and 70% in the specimen with Mo, respectively, compared to the specimen without Mo. The oxide ion vacancy concentration of chromia decreased due to the addition of Mo.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.115-121
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• 2008

Microstructure of glass-ceramics obtained by heat treating silicate glass containing 50 wt% electric arc furnace dust (EAF dust) and nucleation agents were observed. The crystallization temperature, $T_c$ of glassy specimen measured around $850^{\circ}C$ from different thermal analysis, so the heat treatment condition to obtain glass-ceramic specimen was selected as $950^{\circ}C/15 hr$. The nucleation agent, $TiO_2$ showed the superior effect on enhancing franklinite crystal growth which has stronger mechanical properties and more durable chemical resistance than willemite phase. Some specimens containing $TiO_2$ had the augite crystal phase and increasing $TiO_2$ amount decreased a fraction of willemite and increased a franklinite. Especially, the specimen with 5 wt% $TiO_2$ showed no willemite crystal phase and $1{\sim}2\;{\mu}m$ franklinite crystals dispersed uniformly in glassy matrix. Also, the specimens containing 5 wt% $TiO_2$ mixed with $Fe_2O_3$ showed a dendrite-shaped franklinite crystals caused by coalescence of small crystallites.