Pub Date : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.633
Duck Bin Yun, Jin Sung Park, Sang Cheol Lee, Jong Kyo Choi, Sung Jin Kim
The objective of this study was to examine the wear-corrosion behavior of 18Mn(V, Mo) steel, which had a minor amount of Cr addition (< 3 wt%), in an artificial seawater environment, and compare it to conventional carbon steel. A variety of electrochemical experiments, including linear polarization resistance, impedance spectroscopy, and galvanostatic polarization, were conducted, along with weight loss measurements after immersion and wear-corrosion testing. These tests aimed to determine the static corrosion and wear-corrosion mechanisms of 18Mn(V, Mo) steel with respect to Cr addition. The results of this study indicated that the addition of Cr to 18Mn(V, Mo) steel refined the V4C3 particles in the microstructure, which led to an increase in surface hardness. Moreover, the 18Mn(V, Mo) steel with Cr addition exhibited the lowest corrosion and corrosion-wear losses, compared to 18Mn(V, Mo) steel without Cr and conventional carbon steel. This beneficial effect was primarily attributed to the formation of a thin Crenriched corrosion scale that adhered to the underlying steel. This corrosion scale served as a protective barrier against the penetration of corrosive species and as a lubricant for mechanical wear. The 18Mn(V, Mo) steel with Cr addition has potential application in various industrial fields, particularly in marine and offshore environments, owing to its low corrosion-induced wear loss rate in a brine environment.
{"title":"Effect of Cr addition on the Corrosion-Wear Behaviors of 18Mn(V, Mo) Steel in a Seawater Environment","authors":"Duck Bin Yun, Jin Sung Park, Sang Cheol Lee, Jong Kyo Choi, Sung Jin Kim","doi":"10.3365/kjmm.2023.61.9.633","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.633","url":null,"abstract":"The objective of this study was to examine the wear-corrosion behavior of 18Mn(V, Mo) steel, which had a minor amount of Cr addition (< 3 wt%), in an artificial seawater environment, and compare it to conventional carbon steel. A variety of electrochemical experiments, including linear polarization resistance, impedance spectroscopy, and galvanostatic polarization, were conducted, along with weight loss measurements after immersion and wear-corrosion testing. These tests aimed to determine the static corrosion and wear-corrosion mechanisms of 18Mn(V, Mo) steel with respect to Cr addition. The results of this study indicated that the addition of Cr to 18Mn(V, Mo) steel refined the V4C3 particles in the microstructure, which led to an increase in surface hardness. Moreover, the 18Mn(V, Mo) steel with Cr addition exhibited the lowest corrosion and corrosion-wear losses, compared to 18Mn(V, Mo) steel without Cr and conventional carbon steel. This beneficial effect was primarily attributed to the formation of a thin Crenriched corrosion scale that adhered to the underlying steel. This corrosion scale served as a protective barrier against the penetration of corrosive species and as a lubricant for mechanical wear. The 18Mn(V, Mo) steel with Cr addition has potential application in various industrial fields, particularly in marine and offshore environments, owing to its low corrosion-induced wear loss rate in a brine environment.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47336763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-05DOI: 10.3365/kjmm.2023.61.8.608
M. Heo, Seung-Hwan Kwon, W. Seo, Sang‐il Kim, Hyun-sik Kim
YbCd2Sb2-based Zintl phases have been identified as promising materials for thermoelectric applications due to their high Seebeck coefficient and electrical conductivity. However, their high thermal conductivity limits their overall thermoelectric performance. To address this, Mg has recently been introduced as an alloying element at Cd atomic sites to reduce the lattice thermal conductivity of YbCd2Sb2 . Zhang et al. have reported a high zT (a figure-of-merit for the thermoelectric performance) of 1.4 at 700 K in Yb(Cd0.8Mg0.2)2Sb2. They have demonstrated that the high zT is due to significantly suppressed phonon transport, in other words, low lattice thermal conductivity. They attributed the significantly low lattice thermal conductivity to severely distorted lattices that could not be described even with the Debye-Callaway model. Here, the Debye-Callaway model and Callaway-von Baeyer model have been utilized to evaluate the effect of Mg alloying on the lattice thermal conductivity of Yb(Cd1-xMgx)2Sb2 (x = 0, 0.1, 0.2) by estimating their theoretical lattice thermal conductivities. We found that appropriately fitting the parameter included in the phonon relaxation rate (of the Debye-Callaway model), which represents a fractional change of bulk modulus to that of local bond length, could describe the significantly suppressed lattice thermal conductivities of Yb(Cd1-xMgx)2Sb2 (x = 0, 0.1, 0.2).
{"title":"Lattice Thermal Conductivities of Yb(Cd1-xMgx)2Sb2 Analyzed via Debye-Callaway Model","authors":"M. Heo, Seung-Hwan Kwon, W. Seo, Sang‐il Kim, Hyun-sik Kim","doi":"10.3365/kjmm.2023.61.8.608","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.608","url":null,"abstract":"YbCd<sub>2</sub>Sb<sub>2</sub>-based Zintl phases have been identified as promising materials for thermoelectric applications due to their high Seebeck coefficient and electrical conductivity. However, their high thermal conductivity limits their overall thermoelectric performance. To address this, Mg has recently been introduced as an alloying element at Cd atomic sites to reduce the lattice thermal conductivity of YbCd<sub>2</sub>Sb<sub>2</sub> . Zhang <i>et al</i>. have reported a high <i>zT</i> (a figure-of-merit for the thermoelectric performance) of 1.4 at 700 K in Yb(Cd<sub>0.8</sub>Mg<sub>0.2</sub>)<sub>2</sub>Sb<sub>2</sub>. They have demonstrated that the high <i>zT</i> is due to significantly suppressed phonon transport, in other words, low lattice thermal conductivity. They attributed the significantly low lattice thermal conductivity to severely distorted lattices that could not be described even with the Debye-Callaway model. Here, the Debye-Callaway model and Callaway-von Baeyer model have been utilized to evaluate the effect of Mg alloying on the lattice thermal conductivity of Yb(Cd<sub>1-<i>x</i></sub>Mg<sub><i>x</i></sub>)<sub>2</sub>Sb<sub>2</sub> (<i>x</i> = 0, 0.1, 0.2) by estimating their theoretical lattice thermal conductivities. We found that appropriately fitting the parameter included in the phonon relaxation rate (of the Debye-Callaway model), which represents a fractional change of bulk modulus to that of local bond length, could describe the significantly suppressed lattice thermal conductivities of Yb(Cd<sub>1-<i>x</i></sub>Mg<sub><i>x</i></sub>)<sub>2</sub>Sb<sub>2</sub> (<i>x</i> = 0, 0.1, 0.2).","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45169079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-05DOI: 10.3365/kjmm.2023.61.8.553
Ye-Jin Lee, Jun-Seob Lee, S. Kwon, J. Shin, Y. Cho, Seok Kim, Je-hyun Lee
The localized corrosion behavior of precipitation-hardened UNS N07718 was investigated by immersion tests in 6 wt% FeCl3 + 1.0 wt% HCl and the use of electrochemical techniques in a simulating solution of a diluted-sour environment of 25 wt% NaCl + 0.5 wt% CH3COOH. The Ti carbides and Nb-Mo carbides with 1-10 µm size were distributed in the alloy. After immersion at a solution temperature higher than 45oC, localized corrosion with a depth of over 25 µm was identified, and the critical pitting temperature was determined to be 45oC. Potentiodynamic polarization showed that the surface of the UNS N07718 was immediately passivated in the experimental solution. The passivity-maintaining current density was gradually increased with increasing solution temperature, and finally, localized corrosion was initiated or propagated at 0.5 VSSE in 80oC. The localized corrosion was initiated or propagated at the interface between the Ti and Nb-Mo carbides and the alloy substrate. Scanning Kelvin probe microscopic images revealed that the contact-potential difference values were in the order of Ti carbide > Nb-Mo carbide > alloy substrate, indicating that the carbides and alloy substrate act as a cathode and an anode, respectively, forming a micro-galvanic couple. Therefore, it is concluded that localized corrosion is initiated at the interface between the carbides and substrates in UNS N07718.
{"title":"Localized Corrosion Behavior of UNS N07718 in a Solution Simulating a Diluted-sour Environment","authors":"Ye-Jin Lee, Jun-Seob Lee, S. Kwon, J. Shin, Y. Cho, Seok Kim, Je-hyun Lee","doi":"10.3365/kjmm.2023.61.8.553","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.553","url":null,"abstract":"The localized corrosion behavior of precipitation-hardened UNS N07718 was investigated by immersion tests in 6 wt% FeCl3 + 1.0 wt% HCl and the use of electrochemical techniques in a simulating solution of a diluted-sour environment of 25 wt% NaCl + 0.5 wt% CH3COOH. The Ti carbides and Nb-Mo carbides with 1-10 µm size were distributed in the alloy. After immersion at a solution temperature higher than 45oC, localized corrosion with a depth of over 25 µm was identified, and the critical pitting temperature was determined to be 45oC. Potentiodynamic polarization showed that the surface of the UNS N07718 was immediately passivated in the experimental solution. The passivity-maintaining current density was gradually increased with increasing solution temperature, and finally, localized corrosion was initiated or propagated at 0.5 VSSE in 80oC. The localized corrosion was initiated or propagated at the interface between the Ti and Nb-Mo carbides and the alloy substrate. Scanning Kelvin probe microscopic images revealed that the contact-potential difference values were in the order of Ti carbide > Nb-Mo carbide > alloy substrate, indicating that the carbides and alloy substrate act as a cathode and an anode, respectively, forming a micro-galvanic couple. Therefore, it is concluded that localized corrosion is initiated at the interface between the carbides and substrates in UNS N07718.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41848392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-05DOI: 10.3365/kjmm.2023.61.8.602
Woon-Seop Choi
Recently, transition metal dichalcogenides (TMDCs) with 2D structure have attracted interest due to their many unique optical and electrical properties. The primary preparation methods for 2D materials are chemical vapor deposition (CVD), exfoliation, and other vacuum technologies. Large-scale synthesis of WS2 via solution-process is rare due to the higher temperature needed for tungsten-based precursors. Combination of spin coating or dip coating with CVD have been studied recently to make large-area 2D TMDC with good electrical properties. Here, we report a new synthetic route for large WS2 crystal that combined solution coatings and CVD process. A solution of sodium tungstate and hydrazine hydrate with sodium thiosulphate was coated on a silicon wafer via dip and spin coating. The films were then treated with CVD at various positions and temperatures to facilitate crystallization. The double coating conditions and CVD parameters were modified to obtain WS2 crystals. Triangular shaped 44 ± 4 µm WS2 crystals could be obtained with simple annealing above 900oC without gas treatment. The synthesized WS2 was found to be bulk with a triangular shape, as confirmed by Raman and AFM analyses. A PL peak of WS2 at 643 nm was observed at an early crystallization stage.
{"title":"Transition Metal Dichalcogenide WS2 Films Prepared with a Combination of Spin/Dip Coating and CVD","authors":"Woon-Seop Choi","doi":"10.3365/kjmm.2023.61.8.602","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.602","url":null,"abstract":"Recently, transition metal dichalcogenides (TMDCs) with 2D structure have attracted interest due to their many unique optical and electrical properties. The primary preparation methods for 2D materials are chemical vapor deposition (CVD), exfoliation, and other vacuum technologies. Large-scale synthesis of WS2 via solution-process is rare due to the higher temperature needed for tungsten-based precursors. Combination of spin coating or dip coating with CVD have been studied recently to make large-area 2D TMDC with good electrical properties. Here, we report a new synthetic route for large WS2 crystal that combined solution coatings and CVD process. A solution of sodium tungstate and hydrazine hydrate with sodium thiosulphate was coated on a silicon wafer via dip and spin coating. The films were then treated with CVD at various positions and temperatures to facilitate crystallization. The double coating conditions and CVD parameters were modified to obtain WS2 crystals. Triangular shaped 44 ± 4 µm WS2 crystals could be obtained with simple annealing above 900oC without gas treatment. The synthesized WS2 was found to be bulk with a triangular shape, as confirmed by Raman and AFM analyses. A PL peak of WS2 at 643 nm was observed at an early crystallization stage.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46010327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-05DOI: 10.3365/kjmm.2023.61.8.581
Yong-Wan Kim, Young-Geun Ha
The potential applications of advanced electronic materials in large-area, printable, and flexible electronics have generated significant interest. However, creating high-performance, low-voltage thin-film transistors (TFTs) for these applications remains difficult due to a lack of advanced gate dielectric and semiconductor materials that meet both ease-of-fabrication requirements and high electrical performance. In this study, we present high-performance gate dielectric thin-films, which were fabricated using a facile solution-based technique, and then employed to realize low operating voltage organic and metal oxide semiconductor-based thin-film transistors. The high-k oxide gate dielectrics were produced via a simple dip-coating method, resulting in the formation of thin-oxide layers. These novel oxide gate dielectrics demonstrated exceptional dielectric properties, with large capacitances (up to 430 nF/ cm2), low-level leakage current densities (< 3 × 10-8A/cm2 at 4 V), featureless morphology (rms roughness < 0.36 nm), and high transparency (> 85%). Consequently, these dip-coated gate dielectrics can be incorporated into thin-film transistors, utilizing pentacene as p-type organic semiconductors. Furthermore, by employing dip-coating, indium oxide and indium-gallium-zinc oxide can be utilized as n-type inorganic semiconductors, allowing for the fabrication of low-voltage operation and high-performance inorganic TFTs. The resulting TFTs functioned at ultralow voltages (< ± 2 V) and achieved high transistor performance (hole mobility: 0.28 cm2V-1·s-1, electron mobility: ~2.0 cm2V-1·s-1 and on/off current ratio >105).
{"title":"Utilizing Dip-Coating to Fabricate Gate Dielectric and Semiconductor for Thin-Film Transistors","authors":"Yong-Wan Kim, Young-Geun Ha","doi":"10.3365/kjmm.2023.61.8.581","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.581","url":null,"abstract":"The potential applications of advanced electronic materials in large-area, printable, and flexible electronics have generated significant interest. However, creating high-performance, low-voltage thin-film transistors (TFTs) for these applications remains difficult due to a lack of advanced gate dielectric and semiconductor materials that meet both ease-of-fabrication requirements and high electrical performance. In this study, we present high-performance gate dielectric thin-films, which were fabricated using a facile solution-based technique, and then employed to realize low operating voltage organic and metal oxide semiconductor-based thin-film transistors. The high-k oxide gate dielectrics were produced via a simple dip-coating method, resulting in the formation of thin-oxide layers. These novel oxide gate dielectrics demonstrated exceptional dielectric properties, with large capacitances (up to 430 nF/ cm2), low-level leakage current densities (< 3 × 10-8A/cm2 at 4 V), featureless morphology (rms roughness < 0.36 nm), and high transparency (> 85%). Consequently, these dip-coated gate dielectrics can be incorporated into thin-film transistors, utilizing pentacene as p-type organic semiconductors. Furthermore, by employing dip-coating, indium oxide and indium-gallium-zinc oxide can be utilized as n-type inorganic semiconductors, allowing for the fabrication of low-voltage operation and high-performance inorganic TFTs. The resulting TFTs functioned at ultralow voltages (< ± 2 V) and achieved high transistor performance (hole mobility: 0.28 cm2V-1·s-1, electron mobility: ~2.0 cm2V-1·s-1 and on/off current ratio >105).","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41368324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Magnesium (Mg) has good physical properties including light weight, excellent specific strength and high stiffness, and Mg is used in many fields. But current production methods of Mg have disadvantages, such as the generation of sulfur oxide and chlorine gas. In this situation, The Korea Institute of Geoscience and Mineral Resources (KIGAM) developed a Molten Salt Electrolysis Using Liquid Metal Cathode (MSELMC) method to produce high-purity magnesium. The MSE-LMC method can obtain 99.998-99.999% highpurity magnesium by the electrolysis of MgO dissolved in (MgF2)-LiF molten salt at 1053-1083 K, and by vacuum distilling an alloy generated by reacting with a metallic liquid cathode at 1200-1300 K. This study developed a numerical analysis model using COMSOL Multiphysics electrodeposition module to optimize the design of the electrolysis process. The model temperature was 1053K and molten salt was 54MgF2-46LiF with a 0.6wt% MgO system. 10A constant current was applied at the anode. This model uses the Butler-Volmer equation and the Nernst equation for the electric reaction. The Stokes-Einstein equation and Nernst-Einstein relation were used to calculate the diffusivity and electric mobility of salts. Unlike the experiment, in this model chlorine gas was generated. However, this model satisfied Faraday’s law. Therefore we define a new parameter using electric flux and voltage to conduct a quantitative evaluation according to the electrode shape, and compared that parameter by the changing angle of the anode.
{"title":"Development of Numerical Analysis Model for New Magnesium Electrolysis Process Using COMSOL","authors":"MaeHyun Cho, Hyeong-Jun Jeoung, Jungshin Kang, Kunok Chang","doi":"10.3365/kjmm.2023.61.8.625","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.625","url":null,"abstract":"Magnesium (Mg) has good physical properties including light weight, excellent specific strength and high stiffness, and Mg is used in many fields. But current production methods of Mg have disadvantages, such as the generation of sulfur oxide and chlorine gas. In this situation, The Korea Institute of Geoscience and Mineral Resources (KIGAM) developed a Molten Salt Electrolysis Using Liquid Metal Cathode (MSELMC) method to produce high-purity magnesium. The MSE-LMC method can obtain 99.998-99.999% highpurity magnesium by the electrolysis of MgO dissolved in (MgF2)-LiF molten salt at 1053-1083 K, and by vacuum distilling an alloy generated by reacting with a metallic liquid cathode at 1200-1300 K. This study developed a numerical analysis model using COMSOL Multiphysics electrodeposition module to optimize the design of the electrolysis process. The model temperature was 1053K and molten salt was 54MgF2-46LiF with a 0.6wt% MgO system. 10A constant current was applied at the anode. This model uses the Butler-Volmer equation and the Nernst equation for the electric reaction. The Stokes-Einstein equation and Nernst-Einstein relation were used to calculate the diffusivity and electric mobility of salts. Unlike the experiment, in this model chlorine gas was generated. However, this model satisfied Faraday’s law. Therefore we define a new parameter using electric flux and voltage to conduct a quantitative evaluation according to the electrode shape, and compared that parameter by the changing angle of the anode.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49496851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-05DOI: 10.3365/kjmm.2023.61.8.573
Min Jeong Ko, Su Young Kim, Jong-Oh Jo, Jae-Rang Lee, Yong Ha Kim, Y. Won
On the road to carbon neutrality, a great deal of attention is being paid to emerging technologies such as the DRI (direct reduced iron) process. This study proposes a two-stage DRI process using reformed COG (coke oven gas), and determined optimal process parameters. The reduction and carbonization of Carajás iron ore used in the field were examined by monitoring the weight loss of the samples, and EDS and XRD measurements with respect to the reaction temperature and operating time for different reducing environments. While the reduction of iron ore is completed in 60 min at 800oC regardless of the reducing environment, the carbonization of reduced iron is attainable only at 800oC with high hydrogen content in the reducing gas. Thus, a countercurrent scheme in the proposed DRI process is justified, in which COG containing high hydrogen content is flowed into the 2nd stage operated at 800oC and subsequently directed to the 1st stage operated at 600oC. The reduction of iron ore is initiated in the 1st stage for 60 min irrespective of the reducing environment, and the completion of the reduction and the following carbonization is fulfilled in the 2nd stage for 40 min under a high reducing environment. An equilibrium analysis supported that the cracking of CH4 in COG to graphite leads to the formation of CO from CO2 and the successive formation of Fe3C from reduced Fe. The carbonization of iron ore is possible only in the presence of CO2 . It also showed that too high or low reducing environments are not desirable to accomplish the DRI process. This study is expected to be provide an effective guideline for optimizing similar DRI processes.
{"title":"Lab-scale Process Parameter Determination of a Two-stage DRI (direct reduced iron) Process Using Reformed COG (coke oven gas)","authors":"Min Jeong Ko, Su Young Kim, Jong-Oh Jo, Jae-Rang Lee, Yong Ha Kim, Y. Won","doi":"10.3365/kjmm.2023.61.8.573","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.573","url":null,"abstract":"On the road to carbon neutrality, a great deal of attention is being paid to emerging technologies such as the DRI (direct reduced iron) process. This study proposes a two-stage DRI process using reformed COG (coke oven gas), and determined optimal process parameters. The reduction and carbonization of Carajás iron ore used in the field were examined by monitoring the weight loss of the samples, and EDS and XRD measurements with respect to the reaction temperature and operating time for different reducing environments. While the reduction of iron ore is completed in 60 min at 800oC regardless of the reducing environment, the carbonization of reduced iron is attainable only at 800oC with high hydrogen content in the reducing gas. Thus, a countercurrent scheme in the proposed DRI process is justified, in which COG containing high hydrogen content is flowed into the 2nd stage operated at 800oC and subsequently directed to the 1st stage operated at 600oC. The reduction of iron ore is initiated in the 1st stage for 60 min irrespective of the reducing environment, and the completion of the reduction and the following carbonization is fulfilled in the 2nd stage for 40 min under a high reducing environment. An equilibrium analysis supported that the cracking of CH4 in COG to graphite leads to the formation of CO from CO2 and the successive formation of Fe3C from reduced Fe. The carbonization of iron ore is possible only in the presence of CO2 . It also showed that too high or low reducing environments are not desirable to accomplish the DRI process. This study is expected to be provide an effective guideline for optimizing similar DRI processes.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45865396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-05DOI: 10.3365/kjmm.2023.61.8.616
Alloyssius E.G. Gorospe, Dongwoo Kang, Dongwook Lee
Lithium-ion batteries (LIBs) have undergone countless enhancements in the past decade, mainly improvements in the basic components: electrodes, electrolyte, and separator. The separator, which acts as a physical barrier between the two electrodes, does not directly participate in the charge and energy storage.However, it is involved in the safety, form factor, and packaging density of the LIBs. While it occupies relatively less internal space than other components, the separator can be replaced with active materials such as gel polymer electrolytes (GPEs) which can serve as both the electrolyte and physical barrier between the electrodes. GPEs can potentially minimize the risks of liquid electrolytes, including flammability, electrolyte leakage, and explosion. Here we report the characteristics of polyurethane (PU)-based gel swollen in concentrated electrolyte solutions in separator-less cells. The poreless PU-based gel electrolyte conducts lithium ions, while preventing internal short-circuits. This is attributed to the presence of soft segments, which allow ion transport, and hard segments, which ensure mechanical integrity. Electrochemical measurements carried out in LFP half cells and symmetric Li cells revealed that the separator-less cells were operable between 0.2 C to 1 C rates, and that during long term cycling, the cells achieved stable Li electroplating overpotential, as the number of cycles increased.
{"title":"Electrochemical Characteristics of Elastic, Non-Polar Polyurethane-Based Polymer Gel Electrolyte for Separator-Less Lithium-Ion Batteries","authors":"Alloyssius E.G. Gorospe, Dongwoo Kang, Dongwook Lee","doi":"10.3365/kjmm.2023.61.8.616","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.616","url":null,"abstract":"Lithium-ion batteries (LIBs) have undergone countless enhancements in the past decade, mainly improvements in the basic components: electrodes, electrolyte, and separator. The separator, which acts as a physical barrier between the two electrodes, does not directly participate in the charge and energy storage.However, it is involved in the safety, form factor, and packaging density of the LIBs. While it occupies relatively less internal space than other components, the separator can be replaced with active materials such as gel polymer electrolytes (GPEs) which can serve as both the electrolyte and physical barrier between the electrodes. GPEs can potentially minimize the risks of liquid electrolytes, including flammability, electrolyte leakage, and explosion. Here we report the characteristics of polyurethane (PU)-based gel swollen in concentrated electrolyte solutions in separator-less cells. The poreless PU-based gel electrolyte conducts lithium ions, while preventing internal short-circuits. This is attributed to the presence of soft segments, which allow ion transport, and hard segments, which ensure mechanical integrity. Electrochemical measurements carried out in LFP half cells and symmetric Li cells revealed that the separator-less cells were operable between 0.2 C to 1 C rates, and that during long term cycling, the cells achieved stable Li electroplating overpotential, as the number of cycles increased.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48955838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-05DOI: 10.3365/kjmm.2023.61.8.561
Insung Choi, Won-chan Jeong, Danbi Song, J. Suh, Kwang-Hyeon Lee, Yongjai Kim, I. Jung
There has been an increased demand for surface modification technologies to enhance corrosionresistance and wear-resistance. Among the representative surface coating technologies, laser cladding has attracted great attention because of its multiple advantages including low heat input, low dilution ratio, controllable clad height, etc. Recently, laser cladding has been considered as a surface coating technology for the next-generation small modular reactor, although submerged arc welding was utilized for the 3rd generation nuclear reactor. Cobalt-free materials are required as cladding materials in the nuclear reactor because cobalt has a long half-life. In this work, nickel based cobalt-free Alloy 82 powder was utilized. The main experimental parameters for laser cladding were intensively investigated by varying laser power, scan speed, powder supply, carrier and shield gas, overlap ratio, etc. Additionally, cross-sectional area calculation and EPMA analysis were carried out to examine the dilution ratio. Mechanical properties were also evaluated using microhardness tests and wear tests at high temperatures. Finally, corrosion tests were performed to compare a laser clad surface with an uncoated carbon steel surface. Our study indicates that the laser cladding using Alloy 82 powder is feasible for corrosion protection in next-generation small modular reactors.
{"title":"Laser Cladding of Alloy 82 Powder for Corrosion Protection in Small Modular Reactors","authors":"Insung Choi, Won-chan Jeong, Danbi Song, J. Suh, Kwang-Hyeon Lee, Yongjai Kim, I. Jung","doi":"10.3365/kjmm.2023.61.8.561","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.561","url":null,"abstract":"There has been an increased demand for surface modification technologies to enhance corrosionresistance and wear-resistance. Among the representative surface coating technologies, laser cladding has attracted great attention because of its multiple advantages including low heat input, low dilution ratio, controllable clad height, etc. Recently, laser cladding has been considered as a surface coating technology for the next-generation small modular reactor, although submerged arc welding was utilized for the 3rd generation nuclear reactor. Cobalt-free materials are required as cladding materials in the nuclear reactor because cobalt has a long half-life. In this work, nickel based cobalt-free Alloy 82 powder was utilized. The main experimental parameters for laser cladding were intensively investigated by varying laser power, scan speed, powder supply, carrier and shield gas, overlap ratio, etc. Additionally, cross-sectional area calculation and EPMA analysis were carried out to examine the dilution ratio. Mechanical properties were also evaluated using microhardness tests and wear tests at high temperatures. Finally, corrosion tests were performed to compare a laser clad surface with an uncoated carbon steel surface. Our study indicates that the laser cladding using Alloy 82 powder is feasible for corrosion protection in next-generation small modular reactors.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47637925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-05DOI: 10.3365/kjmm.2023.61.8.545
Hong-Min Kim, Se-Yeong Park, Dong-Geun Lee
Beta-type titanium alloys have a low elastic modulus, excellent cold workability, and are widely used as implant materials. High strength is possible by forming a precipitation in the β-matrix via solution treatment and aging treatment. However, beta titanium alloys require a large amount of beta-stabilizing elements (Fe, Nb, Mo, Ta, etc), and these expensive beta stabilizing elements increase the manufacturing cost of these alloys. In this study, Ti-5Mo-2Fe metastable beta-titanium alloy was designed by adding Mo and Fe, which were relatively inexpensive and had excellent biocompatibility among beta-stabilizing elements, and an ingot was manufactured by vacuum arc remelting. Solution treatment was maintained at 850oC for a holding time of 1 hour, followed by furnace cooling. Aging treatments were conducted in a range of temperature 350~500oC and holding time 2 h~48 h. The microstructure behaviors and mechanical properties were analyzed according to these aging treatment conditions. Isothermal ω phases were precipitated by aging treatment, and hardness and yield strength were found to be significantly higher for conditions of 400oC, 8h. As holding time and temperature increased, these phases transformed into secondary alpha phases and the hardness and yield strength decreased due to this microstructural evolution.
{"title":"Microstructural Evolution and Mechanical Properties According to Aging Conditions of Ti-5Mo-2Fe Alloy","authors":"Hong-Min Kim, Se-Yeong Park, Dong-Geun Lee","doi":"10.3365/kjmm.2023.61.8.545","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.8.545","url":null,"abstract":"Beta-type titanium alloys have a low elastic modulus, excellent cold workability, and are widely used as implant materials. High strength is possible by forming a precipitation in the β-matrix via solution treatment and aging treatment. However, beta titanium alloys require a large amount of beta-stabilizing elements (Fe, Nb, Mo, Ta, etc), and these expensive beta stabilizing elements increase the manufacturing cost of these alloys. In this study, Ti-5Mo-2Fe metastable beta-titanium alloy was designed by adding Mo and Fe, which were relatively inexpensive and had excellent biocompatibility among beta-stabilizing elements, and an ingot was manufactured by vacuum arc remelting. Solution treatment was maintained at 850oC for a holding time of 1 hour, followed by furnace cooling. Aging treatments were conducted in a range of temperature 350~500oC and holding time 2 h~48 h. The microstructure behaviors and mechanical properties were analyzed according to these aging treatment conditions. Isothermal ω phases were precipitated by aging treatment, and hardness and yield strength were found to be significantly higher for conditions of 400oC, 8h. As holding time and temperature increased, these phases transformed into secondary alpha phases and the hardness and yield strength decreased due to this microstructural evolution.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2023-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46917659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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