Pub Date : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.659
Tae-Hun Kim, Chiwon Kim, Chan-Hee Lee, Jinseop Kwack, Donghyeon Jeon, Hyun-Uk Hong
In this study, the influence of heat input and post-seam annealing (PSA) temperature on the microstructure and impact toughness of electric resistance welded (ERWed) API X70 steel pipe was investigated. The ERW seam welds of pipes were fabricated with low, moderate, and high heat inputs, and followed by the PSA process at 950 ℃. Regardless of heat input, the API X70 steel pipe exhibited good weldability, resulting in similar microstructure factors, i.e., metal flow angle (~70o), bondline width (~22 μm), and ferrite grain size (~4.4 μm). Although (Mn, Si)-rich oxide penetrators which are known to impair impact toughness were observed at the bondline, the area fraction was estimated to be as low as 0.011% in all the ERW seam welds. The impact toughness was not affected by these penetrators because of their minimal fraction, leading to ductile fracture at -20 ℃. However, different PSA temperatures (870, 950, and 1040 ℃) resulted in the different grain sizes of the seam welds. The ERW seam weld annealed at 1040 ℃ (PSA1040) exhibited the largest ferrite grain size near the bondline, whilst the smallest grain size was found in the ERW weld annealed at 870 ℃ (PSA870). In spite of having the smallest grain size, PSA870 exhibited the lowest impact toughness value, showing brittle fracture at –20 ℃. It was observed that the difference in residual stresses was not macroscopically detectable by the hole drilling method. The kernel average misorientation (KAM) maps indicated that the highest level of residual stress was observed near the bondline of PSA870, as evidenced by a high density of dislocations. This study provides instructive results, indicating that the impact toughness of ERW seam welds are significantly more affected by residual stresses than by the grain refinement effect.
{"title":"A Study on the Relationship between Microstructure and Impact Toughness with Different Heat Inputs and Post-Seam Annealing Temperatures in API X70 Electric Resistance Welded Steel Pipe","authors":"Tae-Hun Kim, Chiwon Kim, Chan-Hee Lee, Jinseop Kwack, Donghyeon Jeon, Hyun-Uk Hong","doi":"10.3365/kjmm.2023.61.9.659","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.659","url":null,"abstract":"In this study, the influence of heat input and post-seam annealing (PSA) temperature on the microstructure and impact toughness of electric resistance welded (ERWed) API X70 steel pipe was investigated. The ERW seam welds of pipes were fabricated with low, moderate, and high heat inputs, and followed by the PSA process at 950 ℃. Regardless of heat input, the API X70 steel pipe exhibited good weldability, resulting in similar microstructure factors, i.e., metal flow angle (~70o), bondline width (~22 μm), and ferrite grain size (~4.4 μm). Although (Mn, Si)-rich oxide penetrators which are known to impair impact toughness were observed at the bondline, the area fraction was estimated to be as low as 0.011% in all the ERW seam welds. The impact toughness was not affected by these penetrators because of their minimal fraction, leading to ductile fracture at -20 ℃. However, different PSA temperatures (870, 950, and 1040 ℃) resulted in the different grain sizes of the seam welds. The ERW seam weld annealed at 1040 ℃ (PSA1040) exhibited the largest ferrite grain size near the bondline, whilst the smallest grain size was found in the ERW weld annealed at 870 ℃ (PSA870). In spite of having the smallest grain size, PSA870 exhibited the lowest impact toughness value, showing brittle fracture at –20 ℃. It was observed that the difference in residual stresses was not macroscopically detectable by the hole drilling method. The kernel average misorientation (KAM) maps indicated that the highest level of residual stress was observed near the bondline of PSA870, as evidenced by a high density of dislocations. This study provides instructive results, indicating that the impact toughness of ERW seam welds are significantly more affected by residual stresses than by the grain refinement effect.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45100683","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 : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.669
Kwangsu Choi, Hyo Yun Jung
A Fe-based filler material with the composition of Fe-20Ni-5Co-2.5Mn-0.2C was used for welding 9% Ni steel, and the effect of post-weld heat treatment on the microstructure and mechanical properties of the welded joints was investigated. Post-weld heat treatment of the welded joint was performed in the temperature range of 200 to 600 ℃. After the experimental selection, the microstructure changes of the weld metal and base metal were investigated in detail at heat treatment temperatures of 350 and 600 ℃. Grain morphology, size, and the location of precipitated cementite were studied using SEM and EBSD phase maps. The mechanical properties of the weld joint were characterized by tensile properties and micro-hardness. Based on the experimental results, this study provides key insights into the applicability of post-weld heat treatment to weld joints of 9% Ni steel prepared using Fe-based filler material to improve the mechanical properties, toughness and ductility of the weld joints.
{"title":"The Effects of Post-Weld Heat Treatment on the Microstructure and Mechanical Properties of 9% Ni Steel Weld Joint with Fe-Based Filler Material","authors":"Kwangsu Choi, Hyo Yun Jung","doi":"10.3365/kjmm.2023.61.9.669","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.669","url":null,"abstract":"A Fe-based filler material with the composition of Fe-20Ni-5Co-2.5Mn-0.2C was used for welding 9% Ni steel, and the effect of post-weld heat treatment on the microstructure and mechanical properties of the welded joints was investigated. Post-weld heat treatment of the welded joint was performed in the temperature range of 200 to 600 ℃. After the experimental selection, the microstructure changes of the weld metal and base metal were investigated in detail at heat treatment temperatures of 350 and 600 ℃. Grain morphology, size, and the location of precipitated cementite were studied using SEM and EBSD phase maps. The mechanical properties of the weld joint were characterized by tensile properties and micro-hardness. Based on the experimental results, this study provides key insights into the applicability of post-weld heat treatment to weld joints of 9% Ni steel prepared using Fe-based filler material to improve the mechanical properties, toughness and ductility of the weld joints.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48026155","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 : 2023-09-05DOI: 10.3365/kjmm.2023.61.9.694
Won-Bum Park, Yong-Woo Kim, Sun-Joong Kim, Youn-Bae Kang
Wet chemical analysis techniques for four elements (M = As, Pb, Sb, and Sn) in Ag – M binary alloys were investigated with emphasis on the choice of solvent acid and the characteristic wavelength used in the ICP-AES (Inductively-Coupled Plasma Atomic Emission Spectrometer) analysis. The elements are representative tramp elements in ferrous scrap. The activity of these elements needs to be increased to remove them efficiently during the molten scrap refining process. The activity of these elements in the molten scrap (molten iron alloy) is usually measured by a chemical equilibration technique with molten Ag. Therefore, performing an accurate and reliable chemical analysis of these elements in the molten iron alloy and the molten Ag alloy is important. Preliminary tests using conventional acids (hydrochloric acid, nitric acid) resulted in unreliable results. In the present study, the proper choice of acids as solvents was investigated for each element M in the Ag-M alloys. Several synthesized Ag-M alloys of known compositions were analyzed using two ICP-AES systems independently, for cross-checking. As and Pb in Ag alloys could be successfully dissolved in the nitric acid-based solution. On the other hand, Sb and Sn in Ag alloys did not dissolve in the nitric acid-based solution completely, leaving some precipitates. It was found that the addition of hydrofluoric acid could resolve this problem. In addition to this, the effect of the mass of the Ag-M alloy and wavelength selection during ICP-AES analysis on the accuracy and the reproducibility were investigated. An optimized procedure for the wet chemical analysis of these elements in Ag-M alloys is reported.
{"title":"Development of Wet Chemical Analysis Technique for Tramp Elements (M = As, Pb, Sb, and Sn) in Silver-M Alloys","authors":"Won-Bum Park, Yong-Woo Kim, Sun-Joong Kim, Youn-Bae Kang","doi":"10.3365/kjmm.2023.61.9.694","DOIUrl":"https://doi.org/10.3365/kjmm.2023.61.9.694","url":null,"abstract":"Wet chemical analysis techniques for four elements (M = As, Pb, Sb, and Sn) in Ag – M binary alloys were investigated with emphasis on the choice of solvent acid and the characteristic wavelength used in the ICP-AES (Inductively-Coupled Plasma Atomic Emission Spectrometer) analysis. The elements are representative tramp elements in ferrous scrap. The activity of these elements needs to be increased to remove them efficiently during the molten scrap refining process. The activity of these elements in the molten scrap (molten iron alloy) is usually measured by a chemical equilibration technique with molten Ag. Therefore, performing an accurate and reliable chemical analysis of these elements in the molten iron alloy and the molten Ag alloy is important. Preliminary tests using conventional acids (hydrochloric acid, nitric acid) resulted in unreliable results. In the present study, the proper choice of acids as solvents was investigated for each element M in the Ag-M alloys. Several synthesized Ag-M alloys of known compositions were analyzed using two ICP-AES systems independently, for cross-checking. As and Pb in Ag alloys could be successfully dissolved in the nitric acid-based solution. On the other hand, Sb and Sn in Ag alloys did not dissolve in the nitric acid-based solution completely, leaving some precipitates. It was found that the addition of hydrofluoric acid could resolve this problem. In addition to this, the effect of the mass of the Ag-M alloy and wavelength selection during ICP-AES analysis on the accuracy and the reproducibility were investigated. An optimized procedure for the wet chemical analysis of these elements in Ag-M alloys is reported.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42419561","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 : 2023-09-05DOI: 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":" ","pages":""},"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.2023.61.8.553
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":" ","pages":""},"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.2023.61.8.608
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":" ","pages":""},"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.2023.61.8.602
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":" ","pages":""},"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":" ","pages":""},"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}
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":" ","pages":""},"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}
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":" ","pages":""},"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}
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