• Korean Journal of Materials Research
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• v.30 no.12
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• pp.709-714
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• 2020

For zinc-air batteries, there are several limitations associated with zinc anodes. The self-discharge behavior of zinc-air batteries is a critical issue that is induced by corrosion reaction and hydrogen evolution reaction (HER) of zinc anodes. Aluminum and indium are effective additives for controlling the hydrogen evolution reaction as well as the corrosion reaction. To enhance the electrochemical performances of zinc-air batteries, mechanically alloyed Zn-Al and Zn-In materials with different compositions are successfully fabricated at 500rpm and 5h milling time. Investigated materials are characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), and energy dispersive spectrometer (EDS). Alloys are investigated for the application as novel anodes in zinc-air batteries. Especially, the material with 3 wt% of indium (ZI3) delivers 445.37 mAh/g and 408.52 mAh/g of specific discharge capacity with 1 h and 6 h storage, respectively. Also, it shows 91.72 % capacity retention and has the lowest value of corrosion current density among attempted materials.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1579-1587
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• 2022

The effects of hydride amount (20-850 wppm), orientation (circumferential and radial), and temperature (room temperature, 100 ℃, 200 ℃) on the axial mechanical properties of Zircaloy-4 cladding were comprehensively examined. The fraction of radial hydride fraction in the cladding was quantified using PROPHET, an in-house radial hydride fraction analysis code. Uniaxial tensile tests (UTTs) were conducted at various temperatures to obtain the axial mechanical properties. Hydride orientation has a limited effect on the axial mechanical behavior of hydrided Zircaloy-4 cladding. Ultimate tensile stress (UTS) and associated uniform elongation demonstrated limited sensitivity to hydride content under UTT. Statistical uncertainty of UTS was found small, supporting the deterministic approach for the load-failure analysis of hydrided Zircaloy-4 cladding. These properties notably decrease with increasing temperature in the tested range. The dependence of yield strength on hydrogen content differed from temperature to temperature. The ductility-related parameters, such as total elongation, strain energy density (SED), and offset strain decrease with increasing hydride contents. The abrupt loss of ductility in UTT was found at ~700 wppm. Demonstrating a strong correlation between total elongation and offset strain, SED can be used as a comprehensive measure of ductility of hydrided zirconium alloy.

• Journal of Sensor Science and Technology
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• v.32 no.1
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• pp.39-43
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• 2023

Microscale thermophysical property measurements of liquids have been developed considering the increasing interest in the thermal management of cooling systems and energy storage/transportation systems. To accurately predict the heat transfer performance, information on the thermal conductivity, heat capacity, and density is required. However, a simultaneous analysis of the thermophysical properties of small-volume liquids has rarely been considered. Recently, we proposed a new methodology to simultaneously analyze the aforementioned three intrinsic properties using heater-integrated fluidic resonators (HFRs) in an atmospheric pressure environment comprising a microchannel, resistive heater/thermometer, and mechanical resonator. Typically, the thermal conductivity and volumetric heat capacity are measured based on a temperature response resulting from heating using a resistive thermometer, and the specific heat capacity can be obtained from the volumetric heat capacity by using a resonance densitometer. In this study, we analyze methods to improve the thermophysical property measurement performance using HFRs, focusing on the effect of the ambience around the sensor. The analytical method is validated using a numerical analysis, whose results agree well with preliminary experimental results. In a vacuum environment, the thermal conductivity measurement performance is enhanced, except for the thermal conductivity range of most gases, and the sensitivity of the specific heat capacity measurement is enhanced owing to an increase in the time constant.

• Progress in Superconductivity and Cryogenics
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• v.25 no.1
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• pp.11-15
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• 2023

In recent years, the interaction force between a permanent magnet and a closed superconductor coil has been gradually investigated in depth. The principle and application potential of an energy storage/convertor composed of a magnet and a closed superconducting coil have been proved. However, the study on the force between a magnet and a non-closed superconducting coil (superconducting roll stack) has hardly been reported in previous literature. The behavior of this kind of interaction and its influence to the interaction force between a permanent and a closed superconducting coil are also still unclear. In this paper, first we investigated the interaction force between a magnet and a superconducting roll stack. Then, a series of experiments were designed and conducted to clarify the factors affected the interaction force, including the geometrical parameters of the superconducting roll stack and the magnetic field density at the roll stack. Moreover, the comparison of the interaction forces between the magnet and roll stack or a closed coil was also introduced.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.2
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• pp.175-185
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• 2023

A hybrid supercapacitor is a promising energy storage device in view of its excellent capacitive performance. Commercial three-dimensional foam nickel (Ni) can be used as an ideal framework due to an interconnected network structure. However, its application as an electrode material for supercapacitors is limited due to its low specific capacity. Herein, we report a successful growth of MnO₂ on the surface of graphene by a one-step hydrothermal method; thus, forming a three-dimensional MnO₂-graphene-Ni hybrid foam. Our results show that the mixed structure of MnO₂ with nanoflowers and nanorods grown on the graphene/Ni foam as a hybrid electrode delivers the maximum specific capacitance of 193 F·g^-1 at a current density 0.1 A·g^-1. More importantly, the hybrid electrode retains 104% of its initial capacitance after 1,000 charge-discharge cycles at 1 A·g^-1; thus, showing the potential application as a stable supercapacitor electrode.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1199-1209
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• 2023

Where concrete structures are designed to have a service life of over 100 years, their performance must be monitored, for the prediction models available are fraught with uncertainties that need to be eliminated. The present study was conducted to meet that need by monitoring a pilot structure for low and intermediate radioactive waste storage. Long-term operation of the sensors was observed to be adequate to determine the value of the parameters that characterise structural durability, such as corrosion current density. The parameters analysed were correlated to calculate their reciprocal impact: where applied in conjunction with artificial intelligence tools, temperature, for instance, was found suitable for finding activation energy and expansion coefficients and detecting outliers. The results showed the pilot structure to perform satisfactorily.

• Geomechanics and Engineering
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• v.37 no.2
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• pp.149-166
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• 2024

The acoustic emission (AE) technique is utilized to estimate the rock failure status in underground spaces. Understanding the AE characteristics under loading conditions is essential to ensure the reliability of AE monitoring. The AE characteristics depend on the material properties (p-wave velocity, density, UCS, and Young's modulus) and damage stages (stress ratio) of the target rock mass. In this study, two groups of granite specimens (based on the p-wave velocity regime) were prepared to explore the effect of material properties on AE characteristics. Uniaxial compressive loading tests with an AE measurement system were performed to investigate the effect of the rock properties using AE indices (count index, energy index, and amplitude index). The test results were analyzed according to three damage stages classified by the stress ratio of the specimens. Count index was determined to be the most suitable AE index for evaluating rock mass stability.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1553-1561
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• 2024

Nondestructive radiography using cosmic ray muons has been used for decades to monitor nuclear reactor and spent nuclear fuel storage. Because nuclear fuel assemblies are highly dense and large, typical radiation probes such as x-rays cannot penetrate these target imaging objects. Although cosmic ray muons are highly penetrative for nuclear fuels as a result of their relatively high energy, the wide application of muon tomography is limited because of naturally low cosmic ray muon flux. This work presents a new image reconstruction algorithm to maximize the utility of cosmic ray muon in tomography applications. Muon momentum information is used to improve imaging resolution, as well as muon scattering angle. In this work, a new convolution was introduced known as M-value, which is a mathematical integration of two measured quantities: scattering angle and momentum. It captures the objects' quantity and density in a way that is easy to use with image reconstruction algorithms. The results demonstrate how to reconstruct images when muon momentum measurements are included in a typical muon scattering tomography algorithm. Using M-value improves muon tomography image resolution by replacing the scattering angle value without increasing computation costs. This new algorithm is projected to be a standard nondestructive radiography technique for spent nuclear fuel and nuclear material management.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.7
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• pp.467-472
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• 2015

Thermal batteries are primary power sources for military applications requiring high reliability, robustness and long storage life. Conventional electrodes for thermal batteries are prepared by compacting powder mixtures into pellets. Separator is composed of halide mixture, such as LiCl-KCl eutectic salt, blended with MgO to immobilize the molten salt. In order to increase the power density and energy density, the resistance of electrolyte should be reduced because the resistance of electrolyte is predominant in thermal batteries. In this study, wetting behaviors and impregnation weight of molten salts as well as the micro structures of ceramic felt were investigated to be applicable to thin electrolyte. Discharge performances of single cell with the ceramic separator impregnated by molten salt were evaluated also. Zirconia felt with high porosity and large pore outperformed alumina felt in wetting characteristics and molten salt impregnation as well as discharge performances. Based on the results of this study, ceramic felt separator impregnated with molten salt have revealed as an alternative of conventional thick MgO based separator with no conspicuous sign of thermal runaway by short circuit.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.467-470
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• 2006

For a mobile application such as cellular phone, micro fuel cells should be extremely compact and thin. RHFC can be an alternative solution because RHFC gives higher power density than DMFC and does not need ahydrogen storage vessel In this paper, RHFC using methanol fuel is made as a novel planar design without a PROX. Both reformer and cell are made closely in a same plate to share the heater of reformer with the cell. The PBI membrane is used in the cell. The reason is that high temperature of reformer can cause a performance drop when perfluorosulfonic acid membrane such as Nafion is used such a high temperature operation also guarantees the higher CO tolerance to MEA catalyst. The cell is designed as an air-breathing type which the cathode of the cell is opened to the air. The commercial Cu/ZnO/Al2O3 steam reformer catalyst is packed in reformer channel. The active area of MEA is $11.9cm^2$ and the peak power density was $27.5mW/cm^2$.