Pub Date : 2024-05-05DOI: 10.3365/kjmm.2024.62.5.385
Se-Hyeon Choi, Go‐Eun Lee, Il-Ho Kim
Because n-type Bi2Te3-based materials exhibit lower thermoelectric performance than p-type materials and because their thermoelectric properties are sensitively changed by the composition and carrier concentration, optimizing these aspects in n-type materials is necessary to improve the thermoelectric figure of merit (ZT). In this study, the thermoelectric performance of n-type Bi2Te3-based materials was improved by reducing thermal conductivity through the formation of a Bi2Te3-Bi2Se3 solid solution, Bi2Te3-ySey and optimizing the carrier concentration through doping. As the amount of Se increased in Bi2Te3-ySey, the carrier concentration decreased, resulting in decreased electrical and thermal conductivities and increased Seebeck coefficients. As a result, Bi2Te2.85Se0.15 exhibited ZT = 0.56 at 323 K, and Bi2Te2.4Se0.6 exhibited ZT = 0.60 at 423 K. Among the Bi2Te3-ySey solid solutions, the doping effect was investigated for Bi2Te2.85Se0.15 and Bi2Te2.7Se0.3, which recorded excellent thermoelectric performance at low temperatures. When halogen element (I) was doped, the power factor improved owing to the increase in carrier concentration, and the thermal conductivity decreased. As a result, the ZT values were greatly enhanced to ZT = 0.90 at 423 K for Bi2Te2.85Se0.15:I0.005 and ZT = 1.13 at 423 K for Bi2Te2.7Se0.3:I0.0075. When the transition elements (Cu and Ag) were doped, the power factor was improved by the increase in Seebeck coefficient, and thereby Bi2Te2.85Se0.15:Ag0.01 and Bi2Te2.85Se0.15:Ag0.01 exhibited ZT = 0.76 and ZT = 0.75 at 323 K, respectively, and Bi2Te2.7Se0.3:Cu0.01 exhibited ZT = 0.73 at 423 K. Conversely, doping with other transition elements (Ni and Zn), as well as group-III (Al and In) and group-IV (Ge and Sn) elements, resulted in power factors and thermal conductivities that were similar to or slightly less than those of undoped Bi2Te2.85Se0.15, leading to minimal or no improvement in ZT. Next, n-type Bi2Te2.85Se0.15:I0.005 and Bi2Te2.7Se0.3:I0.0075, which exhibited the best thermoelectric performances, were fabricated as bulky compacts, and the uniformity of their thermoelectric properties were evaluated.
由于 n 型 Bi2Te3 基材料的热电性能低于 p 型材料，而且其热电性能对成分和载流子浓度的变化非常敏感，因此有必要优化 n 型材料的这些方面，以提高其热电性能（ZT）。在本研究中，通过形成 Bi2Te3-Bi2Se3 固溶体 Bi2Te3-ySey 降低热导率，并通过掺杂优化载流子浓度，改善了 n 型 Bi2Te3 基材料的热电性能。随着 Bi2Te3-ySey 中 Se 含量的增加，载流子浓度降低，导致导电率和热导率降低，塞贝克系数增加。因此，Bi2Te2.85Se0.15 在 323 K 时的 ZT = 0.56，Bi2Te2.4Se0.6 在 423 K 时的 ZT = 0.60。在 Bi2Te3-ySey 固溶体中，研究了 Bi2Te2.85Se0.15 和 Bi2Te2.7Se0.3 的掺杂效应，它们在低温下具有优异的热电性能。掺入卤素元素（I）后，由于载流子浓度增加，功率因数提高，而热导率降低。因此，Bi2Te2.85Se0.15:I0.005 的 ZT 值大大提高，在 423 K 时 ZT = 0.90，Bi2Te2.7Se0.3:I0.0075 在 423 K 时 ZT = 1.13。当掺杂过渡元素（Cu 和 Ag）时，功率因数因塞贝克系数的增加而提高，因此 Bi2Te2.85Se0.15:Ag0.01 和 Bi2Te2.85Se0.15:Ag0.01 在 323 K 时的 ZT 分别为 0.76 和 0.75，而 Bi2Te2.7Se0.3:Cu0.01 在 423 K 时的 ZT 为 0.73。相反，掺杂其他过渡元素（镍和锌）以及第三族元素（铝和铟）和第四族元素（锗和锡）会导致功率因数和热导率与未掺杂的 Bi2Te2.85Se0.15 相近或略低，从而使 ZT 改善甚微或没有改善。接下来，我们将热电性能最好的 n 型 Bi2Te2.85Se0.15:I0.005 和 Bi2Te2.7Se0.3:I0.0075 制成了体积较大的紧凑型产品，并对其热电特性的均匀性进行了评估。
{"title":"Uniformity of Thermoelectric Properties of N-type Bi2Te3-ySey Bulky Compacts","authors":"Se-Hyeon Choi, Go‐Eun Lee, Il-Ho Kim","doi":"10.3365/kjmm.2024.62.5.385","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.5.385","url":null,"abstract":"Because n-type Bi<sub>2</sub>Te<sub>3</sub>-based materials exhibit lower thermoelectric performance than p-type materials and because their thermoelectric properties are sensitively changed by the composition and carrier concentration, optimizing these aspects in n-type materials is necessary to improve the thermoelectric figure of merit (ZT). In this study, the thermoelectric performance of n-type Bi<sub>2</sub>Te<sub>3</sub>-based materials was improved by reducing thermal conductivity through the formation of a Bi<sub>2</sub>Te<sub>3</sub>-Bi<sub>2</sub>Se<sub>3</sub> solid solution, Bi<sub>2</sub>Te<sub>3-y</sub>Se<sub>y</sub> and optimizing the carrier concentration through doping. As the amount of Se increased in Bi<sub>2</sub>Te<sub>3-y</sub>Se<sub>y</sub>, the carrier concentration decreased, resulting in decreased electrical and thermal conductivities and increased Seebeck coefficients. As a result, Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub> exhibited ZT = 0.56 at 323 K, and Bi<sub>2</sub>Te<sub>2.4</sub>Se<sub>0.6</sub> exhibited ZT = 0.60 at 423 K. Among the Bi<sub>2</sub>Te<sub>3-y</sub>Se<sub>y</sub> solid solutions, the doping effect was investigated for Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub> and Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>, which recorded excellent thermoelectric performance at low temperatures. When halogen element (I) was doped, the power factor improved owing to the increase in carrier concentration, and the thermal conductivity decreased. As a result, the ZT values were greatly enhanced to ZT = 0.90 at 423 K for Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>:I<sub>0.005</sub> and ZT = 1.13 at 423 K for Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>:I<sub>0.0075</sub>. When the transition elements (Cu and Ag) were doped, the power factor was improved by the increase in Seebeck coefficient, and thereby Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>:Ag<sub>0.01</sub> and Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>:Ag<sub>0.01</sub> exhibited ZT = 0.76 and ZT = 0.75 at 323 K, respectively, and Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>:Cu<sub>0.01</sub> exhibited ZT = 0.73 at 423 K. Conversely, doping with other transition elements (Ni and Zn), as well as group-III (Al and In) and group-IV (Ge and Sn) elements, resulted in power factors and thermal conductivities that were similar to or slightly less than those of undoped Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>, leading to minimal or no improvement in ZT. Next, n-type Bi<sub>2</sub>Te<sub>2.85</sub>Se<sub>0.15</sub>:I<sub>0.005</sub> and Bi<sub>2</sub>Te<sub>2.7</sub>Se<sub>0.3</sub>:I<sub>0.0075</sub>, which exhibited the best thermoelectric performances, were fabricated as bulky compacts, and the uniformity of their thermoelectric properties were evaluated.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141011773","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 : 2024-05-05DOI: 10.3365/kjmm.2024.62.5.367
Mohan Chen, Myungjin Jung, Jung-Won An, Seung Yong Shin, Yunhwi Park, Sunrae Kim, Su Yong Nam, Woo-Jae Lee, Se-Hun Kwon
AlN-MgO composites with different compositions were prepared by spark plasma sintering, and the effects of their composition on their microstructure, thermal properties, and mechanical properties were systemically investigated. MgO compositions in the AlN-MgO composites were controlled from 20 to 80 wt%. The results indicated that a phase transition did not occur during the sintering process, and different solid solutions were formed within the MgO and AlN lattices. The AlN-MgO composites exhibited finer-grain microstructures than those of the sintered pure AlN and MgO samples. Transmission electron microscopy analysis showed that both oxygen-rich, low-density grain boundaries and clean boundaries with spinel phases were present in the composites. The sintered pure AlN sample exhibited the highest thermal conductivity (53.2 W/mK) and lowest coefficient of thermal expansion (4.47 × 10-6 /K) at 100 °C. And, the sintered pure MgO sample exhibited moderate thermal conductivity (39.7 W/mK) and a high coefficient of thermal expansion (13.05 × 10-6 /K). With increasing MgO contents in the AlN-MgO composites, however, the thermal conductivity of the AlN-MgO composites decreased, from 33.3 to 14.9 W/mK, while their coefficient of thermal expansion generally increased, from 6.49×10-6 to 10.73×10-6 /K with increasing MgO content. The composite with an MgO content of 60 wt% exhibited the best mechanical properties overall. Thus, the composition and microstructure of AlN-MgO composites have a determining effect on their thermal and mechanical properties.
{"title":"Microstructure, Thermal and Mechanical Properties of AlN-MgO Composites Prepared by Spark Plasma Sintering","authors":"Mohan Chen, Myungjin Jung, Jung-Won An, Seung Yong Shin, Yunhwi Park, Sunrae Kim, Su Yong Nam, Woo-Jae Lee, Se-Hun Kwon","doi":"10.3365/kjmm.2024.62.5.367","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.5.367","url":null,"abstract":"AlN-MgO composites with different compositions were prepared by spark plasma sintering, and the effects of their composition on their microstructure, thermal properties, and mechanical properties were systemically investigated. MgO compositions in the AlN-MgO composites were controlled from 20 to 80 wt%. The results indicated that a phase transition did not occur during the sintering process, and different solid solutions were formed within the MgO and AlN lattices. The AlN-MgO composites exhibited finer-grain microstructures than those of the sintered pure AlN and MgO samples. Transmission electron microscopy analysis showed that both oxygen-rich, low-density grain boundaries and clean boundaries with spinel phases were present in the composites. The sintered pure AlN sample exhibited the highest thermal conductivity (53.2 W/mK) and lowest coefficient of thermal expansion (4.47 × 10-6 /K) at 100 °C. And, the sintered pure MgO sample exhibited moderate thermal conductivity (39.7 W/mK) and a high coefficient of thermal expansion (13.05 × 10-6 /K). With increasing MgO contents in the AlN-MgO composites, however, the thermal conductivity of the AlN-MgO composites decreased, from 33.3 to 14.9 W/mK, while their coefficient of thermal expansion generally increased, from 6.49×10-6 to 10.73×10-6 /K with increasing MgO content. The composite with an MgO content of 60 wt% exhibited the best mechanical properties overall. Thus, the composition and microstructure of AlN-MgO composites have a determining effect on their thermal and mechanical properties.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141011893","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 : 2024-05-05DOI: 10.3365/kjmm.2024.62.5.351
Se-Hee Kim, Suhyun Bae, Sang-Bae Park, Hoon Seonwoo, Se-Eun Shin
Ti6Al4V is commonly used in implants because of its excellent mechanical properties, corrosion resistance, and biocompatibility. While Hydroxyapatite (HAp) is typically used for strong biological bonding between Ti6Al4V implants and bone tissue, this study takes a different approach by incorporating Equine Bone (EB), which has a chemical structure similar to human bone tissue, as a substitute for HAp. In this study, to develop implant materials with a low elastic modulus, high strength, and excellent wear resistance, Ti6Al4V used in biomedical applications was combined with natural EB. Subsequently, a Ti6Al4V-0.05EB composite was fabricated using ball milling followed by Selective Laser Melting (SLM). SLM can reproduce even the interior of a 3D structure, so various studies are being conducted to apply it as a biomaterial. However, Ti6Al4V alloys produced by SLM are known to have low ductility due to localized heat gradients, rapid solidification, and cooling rates. This reduced ductility can result in decreased formability of biomaterials, and the high elastic modulus may lead to stress shielding phenomena, potentially reducing the lifespan of the biomaterial. To minimize this, a post-heat treatment was applied to the Ti6Al4V-0.05EB composite material manufactured by SLM. Afterwards, the microstructure, mechanical properties, and wear resistance, which are important in biomaterials, were evaluated.
{"title":"Friction and Wear Behavior of Selective Laser Melted Ti6Al4V-Equine Bone Nanocomposites","authors":"Se-Hee Kim, Suhyun Bae, Sang-Bae Park, Hoon Seonwoo, Se-Eun Shin","doi":"10.3365/kjmm.2024.62.5.351","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.5.351","url":null,"abstract":"Ti6Al4V is commonly used in implants because of its excellent mechanical properties, corrosion resistance, and biocompatibility. While Hydroxyapatite (HAp) is typically used for strong biological bonding between Ti6Al4V implants and bone tissue, this study takes a different approach by incorporating Equine Bone (EB), which has a chemical structure similar to human bone tissue, as a substitute for HAp. In this study, to develop implant materials with a low elastic modulus, high strength, and excellent wear resistance, Ti6Al4V used in biomedical applications was combined with natural EB. Subsequently, a Ti6Al4V-0.05EB composite was fabricated using ball milling followed by Selective Laser Melting (SLM). SLM can reproduce even the interior of a 3D structure, so various studies are being conducted to apply it as a biomaterial. However, Ti6Al4V alloys produced by SLM are known to have low ductility due to localized heat gradients, rapid solidification, and cooling rates. This reduced ductility can result in decreased formability of biomaterials, and the high elastic modulus may lead to stress shielding phenomena, potentially reducing the lifespan of the biomaterial. To minimize this, a post-heat treatment was applied to the Ti6Al4V-0.05EB composite material manufactured by SLM. Afterwards, the microstructure, mechanical properties, and wear resistance, which are important in biomaterials, were evaluated.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141012588","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 : 2024-05-05DOI: 10.3365/kjmm.2024.62.5.377
Byoungnam Park
This study explores Mg-composition dependent cycle stability in a Zn1-xMgxO Li-ion battery, where battery cycles transition from an electronic transport-limited to an ionic transport limited regime. We investigated the impact of Mg doping in Zn1-xMgxO nanocrystals on Li-ion battery performance, focusing on Mg compositions between x=0.05 and x=0.15. Mg composition dependent structural and electrical properties were explored using field effect transistors (FETs) and various microscopic/spectroscopic methods. The electronic conductivity was found to be sensitive to changes in Mg composition. Consistently, the initial capacity decreased with an increase in Mg composition, aligning with the reduction in electronic conductivity due to Mg doping. However, with successive cycles, the capacity became independent of the electronic conductivity, an outcome attributed to the formation of a solid-electrolyte interphase (SEI) and the conversion reactions. Initially, Mg doping reduces electronic conductivity due to increased carrier trapping, leading to lower discharge capacity. However, as cycling progresses, the impact of Mg doping diminishes. The formation of the SEI layer becomes more influential, significantly affecting Li-ion transport. Over time, factors like SEI formation, conversion reaction dynamics, and structural changes within the electrode start to dominate the battery's capacity, rather than the initial electronic conductivity influenced by Mg doping. This understanding can guide the development of materials with lower resistance, facilitating faster charging and discharging rates. More importantly, this study indicates that the initial capacity is closely tied to the conductivity of the Zn1-xMgxO material.
{"title":"Mg-Composition Dependent Cycle Stability in Zn1-xMgxO Li-ion Battery: Transition from Electronic Transport-Limited to Ionic Transport Limited Cycles","authors":"Byoungnam Park","doi":"10.3365/kjmm.2024.62.5.377","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.5.377","url":null,"abstract":"This study explores Mg-composition dependent cycle stability in a Zn1-xMgxO Li-ion battery, where battery cycles transition from an electronic transport-limited to an ionic transport limited regime. We investigated the impact of Mg doping in Zn1-xMgxO nanocrystals on Li-ion battery performance, focusing on Mg compositions between x=0.05 and x=0.15. Mg composition dependent structural and electrical properties were explored using field effect transistors (FETs) and various microscopic/spectroscopic methods. The electronic conductivity was found to be sensitive to changes in Mg composition. Consistently, the initial capacity decreased with an increase in Mg composition, aligning with the reduction in electronic conductivity due to Mg doping. However, with successive cycles, the capacity became independent of the electronic conductivity, an outcome attributed to the formation of a solid-electrolyte interphase (SEI) and the conversion reactions. Initially, Mg doping reduces electronic conductivity due to increased carrier trapping, leading to lower discharge capacity. However, as cycling progresses, the impact of Mg doping diminishes. The formation of the SEI layer becomes more influential, significantly affecting Li-ion transport. Over time, factors like SEI formation, conversion reaction dynamics, and structural changes within the electrode start to dominate the battery's capacity, rather than the initial electronic conductivity influenced by Mg doping. This understanding can guide the development of materials with lower resistance, facilitating faster charging and discharging rates. More importantly, this study indicates that the initial capacity is closely tied to the conductivity of the Zn1-xMgxO material.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141012768","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 : 2024-05-05DOI: 10.3365/kjmm.2024.62.5.360
W. Choi, Jong-Hyun Lee
A Cu-based paste containing Cu formate and Cu particles was prepared for the compressionassisted sinter-bonding of Cu-finished wide-bandgap power devices onto a Cu-finished substrate at a relatively low bonding temperature of 250 oC in air. A mixture of Cu formate and Cu particles was designed to mitigate the tremendous volume shrinkage during reduction of Cu formate, which approaches approximately 90%, and could be a significant obstacle in the formation of a high-density bond-line. The mixture was spontaneously formed during the 15-min reduction of the initial Cu2O particles by a simple wet process using formic acid. In the bonding, pure Cu generated in situ from the Cu formate at a temperature exceeding 200 °C exhibited significant sinterability, and the generated hydrogen reduced oxide layers on the Cu finishes. Furthermore, the mixed particles resulted in low volume shrinkage in the bond-line during bonding, compared to the use of Cu formate particles alone. Consequently, a robust die shear strength of 22.2 MPa was achieved by sinterbonding for even 10 min at low temperature and the compression of 10 MPa, even though Cu oxide shells were formed in the bond-line because of the long sintering in air. The simple wet process provided an efficient preparation of an effective filler system before the paste formulation for the sinter-bonding.
{"title":"Thermo-Compression Sinter-Bonding in Air Using Cu Formate/Cu Particles Mixed During Reduction of Cu2O","authors":"W. Choi, Jong-Hyun Lee","doi":"10.3365/kjmm.2024.62.5.360","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.5.360","url":null,"abstract":"A Cu-based paste containing Cu formate and Cu particles was prepared for the compressionassisted sinter-bonding of Cu-finished wide-bandgap power devices onto a Cu-finished substrate at a relatively low bonding temperature of 250 oC in air. A mixture of Cu formate and Cu particles was designed to mitigate the tremendous volume shrinkage during reduction of Cu formate, which approaches approximately 90%, and could be a significant obstacle in the formation of a high-density bond-line. The mixture was spontaneously formed during the 15-min reduction of the initial Cu2O particles by a simple wet process using formic acid. In the bonding, pure Cu generated in situ from the Cu formate at a temperature exceeding 200 °C exhibited significant sinterability, and the generated hydrogen reduced oxide layers on the Cu finishes. Furthermore, the mixed particles resulted in low volume shrinkage in the bond-line during bonding, compared to the use of Cu formate particles alone. Consequently, a robust die shear strength of 22.2 MPa was achieved by sinterbonding for even 10 min at low temperature and the compression of 10 MPa, even though Cu oxide shells were formed in the bond-line because of the long sintering in air. The simple wet process provided an efficient preparation of an effective filler system before the paste formulation for the sinter-bonding.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141011545","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 : 2024-05-05DOI: 10.3365/kjmm.2024.62.5.340
Choluk Oh, O. Kwon, Younghun Bae, Hyejin Shin, Young Min Kwon, Byungjin Cho
A ceramic-based plasma etcher window (Lid) requires robust resistance to plasma, especially when exposed to harsh fluorine-based plasma conditions. In this study, a Y2O4 film was deposited using e-beam evaporation with ion beam-assisted deposition (IBAD), and the physical properties of the IBAD-based Y2O4 coating film were thoroughly examined to enhance the mechanical and chemical resistance of the ceramic part, including the Y2O4 film, against etching plasma. The hardness and surface morphology of the IBADbased Y2O4 could be precisely controlled by various deposition processing parameters, such as beam voltage, beam current, and Ar/O2 gas ratio. Following the IBAD deposition of the Y2O4 film, a plasma etching process (Ar/CF4 mixture gases with 150 W RF power for 60 minutes) was applied to evaluate the plasma resistance of the deposited Y2O4 coating film. The surface morphology characteristics of the Y2O4 films were compared using atomic force microscopy, and their grain size was studied through scanning electron microscopy image analysis. Furthermore, a nanoindenter was used to determine the hardness of the Y2O4 film. These results suggest that optimizing the IBAD coating process requires an in-depth study that fully considers the correlation between deposition processing parameters and physical properties. This optimization can be instrumental for enhancing the durability of the ceramic part.
{"title":"Optimization of Ion Beam-Assisted Deposition Process for Y2O3 Film to Enhance Plasma Resistance","authors":"Choluk Oh, O. Kwon, Younghun Bae, Hyejin Shin, Young Min Kwon, Byungjin Cho","doi":"10.3365/kjmm.2024.62.5.340","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.5.340","url":null,"abstract":"A ceramic-based plasma etcher window (Lid) requires robust resistance to plasma, especially when exposed to harsh fluorine-based plasma conditions. In this study, a Y<sub>2</sub>O<sub>4</sub> film was deposited using e-beam evaporation with ion beam-assisted deposition (IBAD), and the physical properties of the IBAD-based Y<sub>2</sub>O<sub>4</sub> coating film were thoroughly examined to enhance the mechanical and chemical resistance of the ceramic part, including the Y<sub>2</sub>O<sub>4</sub> film, against etching plasma. The hardness and surface morphology of the IBADbased Y<sub>2</sub>O<sub>4</sub> could be precisely controlled by various deposition processing parameters, such as beam voltage, beam current, and Ar/O2 gas ratio. Following the IBAD deposition of the Y<sub>2</sub>O<sub>4</sub> film, a plasma etching process (Ar/CF<sub>4</sub> mixture gases with 150 W RF power for 60 minutes) was applied to evaluate the plasma resistance of the deposited Y<sub>2</sub>O<sub>4</sub> coating film. The surface morphology characteristics of the Y<sub>2</sub>O<sub>4</sub> films were compared using atomic force microscopy, and their grain size was studied through scanning electron microscopy image analysis. Furthermore, a nanoindenter was used to determine the hardness of the Y<sub>2</sub>O<sub>4</sub> film. These results suggest that optimizing the IBAD coating process requires an in-depth study that fully considers the correlation between deposition processing parameters and physical properties. This optimization can be instrumental for enhancing the durability of the ceramic part.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141012656","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 : 2024-05-05DOI: 10.3365/kjmm.2024.62.5.325
Sang Hyup Yoo, Ki-Chae Chung, Hee-Beom Moon, Kyung Hoon Lee, Kyung-Tae Park
The tensile fracture behavior of an Al-bearing TWIP steel was investigated by conducting a series of tensile tests on smooth and notched specimens with different notch geometries, focusing on the effects of evolution of the stress triaxiality and the effective strain during deformation. The flow curve and digital image correlation (DIC) analysis evidenced suppression of dynamic strain aging due to Al addition, and therefore, the effects of local inhomogeneous deformation associated with Portevin-Le Chatelier (PLC) band on fracture could be excluded. The smooth specimen fractured with negligible necking despite the absence of PLC bands. As a result, the effective strain was uniform through the gage section and the stress triaxiality (η) of ~0.33 was nearly unchanged over the entire cross-section up to the maximum load. This led to the fracture surface of the smooth specimen being entirely covered with fine equiaxed dimples. For notched specimens, the fracture strain was drastically reduced with decreasing notch radius, indicating the high notch susceptibility of the steel. The effective strain of the notched specimens was the highest at the edge of the notch root, regardless of the notch radius, so cracks first developed at the surface of the notch root. Although the η at the center of the notched specimens (0.40~0.48 depending on the notch radius) was higher than that of the smooth one, the center of the fracture surface of all notched specimens exhibited dimple features that were very similar to the smooth one, even in size. In contrast, in spite of the same η of ~0.33, fractography at the edge of the notched specimens revealed a fracture mode transition from dimple fracture to void sheet fracture to quasi-cleavage fracture as the notch radius decreased. The present results were rationalized in terms of the local evolution of stress triaxiality and effective strain during deformation, which were analyzed using the finite elemental method and DIC technique. It can be said that the fracture mode of TWIP steel, showing limited necking, was more influenced by the distribution and/or gradient of stress traiaxiality and effective strain rather than their local absolute values - that is, the severer their gradient is, the easier the quasi-cleavage fracture occurs.
{"title":"Notched Tensile Fracture of a Fe-15Mn-0.6C-2Al Twinning Induced Plasticity Steel at Room Temperature","authors":"Sang Hyup Yoo, Ki-Chae Chung, Hee-Beom Moon, Kyung Hoon Lee, Kyung-Tae Park","doi":"10.3365/kjmm.2024.62.5.325","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.5.325","url":null,"abstract":"The tensile fracture behavior of an Al-bearing TWIP steel was investigated by conducting a series of tensile tests on smooth and notched specimens with different notch geometries, focusing on the effects of evolution of the stress triaxiality and the effective strain during deformation. The flow curve and digital image correlation (DIC) analysis evidenced suppression of dynamic strain aging due to Al addition, and therefore, the effects of local inhomogeneous deformation associated with Portevin-Le Chatelier (PLC) band on fracture could be excluded. The smooth specimen fractured with negligible necking despite the absence of PLC bands. As a result, the effective strain was uniform through the gage section and the stress triaxiality (η) of ~0.33 was nearly unchanged over the entire cross-section up to the maximum load. This led to the fracture surface of the smooth specimen being entirely covered with fine equiaxed dimples. For notched specimens, the fracture strain was drastically reduced with decreasing notch radius, indicating the high notch susceptibility of the steel. The effective strain of the notched specimens was the highest at the edge of the notch root, regardless of the notch radius, so cracks first developed at the surface of the notch root. Although the η at the center of the notched specimens (0.40~0.48 depending on the notch radius) was higher than that of the smooth one, the center of the fracture surface of all notched specimens exhibited dimple features that were very similar to the smooth one, even in size. In contrast, in spite of the same η of ~0.33, fractography at the edge of the notched specimens revealed a fracture mode transition from dimple fracture to void sheet fracture to quasi-cleavage fracture as the notch radius decreased. The present results were rationalized in terms of the local evolution of stress triaxiality and effective strain during deformation, which were analyzed using the finite elemental method and DIC technique. It can be said that the fracture mode of TWIP steel, showing limited necking, was more influenced by the distribution and/or gradient of stress traiaxiality and effective strain rather than their local absolute values - that is, the severer their gradient is, the easier the quasi-cleavage fracture occurs.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141011302","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 : 2024-05-05DOI: 10.3365/kjmm.2024.62.5.402
Jin-Hyeok Jang, T. Kang, K. Euh, Young-Hee Cho, Kee-Ahn Lee
In this study, we designed and manufactured a new Fe-bearing Al-10Si-Mg casting alloy (F alloy) and investigated its microstructure, mechanical properties, and thermal conductivity. Two types of Fe-bearing Al-10Si-Mg alloys were used: the Conventional-F alloy, injected at 720 ℃ and cooled by water quenching, and the Superheated-F alloy, heated to 820 ℃ and maintained at that temperature for 1 hour. Subsequently, it underwent a degassing process at 720 ℃ before being cooled by water quenching. Both the Conventional-F alloy and the Superheated-F alloy exhibited dendritic microstructures and Fe-intermetallic compounds. The Secondary Dendrite Arm Spacing (SDAS) of the Conventional-F alloy measured 32.4 μm, whereas the Superheated-F alloy measured 28.6 μm. Additionally, the average eutectic Si sizes were 10.3 μm for the Conventional-F alloy and 7.7 μm for the Superheated-F alloy. Fe-rich IMCs were observed in the eutectic region, with their size decreasing due to the superheating treatment. Tensile tests at room temperature were conducted at a strain rate of 10-3/s. The Conventional-F alloy exhibited a yield strength (YS) of 93.4 MPa, ultimate tensile strength (UTS) of 183 MPa, and an elongation (El.) of 6.4%. Conversely, the Superheated-F alloy displayed a YS of 115.4 MPa, UTS of 218.2 MPa, and an El. of 5.1%. The mechanical properties notably improved with the superheating treatment. Regarding thermal conductivity, the Conventional-F alloy exhibited 114.9 W/m·K, while the Superheated-F alloy displayed 153.7 W/m·K. This represents a roughly 14% increase compared to the thermal conductivity of the commercial Al-10Si-Mg material (Silafont36: 135.1 W/m·K). The effects of the Superheating Treatment on microstructural characteristics, deformation behavior, and thermal conductivity of the Fe-bearing Al-10Si-Mg casting alloys were discussed.
{"title":"Effects of Superheating Treatment on the Microstructure, Tensile and Thermal Conductivity Properties of Fe-Bearing Al-10Si-Mg Casting Alloy","authors":"Jin-Hyeok Jang, T. Kang, K. Euh, Young-Hee Cho, Kee-Ahn Lee","doi":"10.3365/kjmm.2024.62.5.402","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.5.402","url":null,"abstract":"In this study, we designed and manufactured a new Fe-bearing Al-10Si-Mg casting alloy (F alloy) and investigated its microstructure, mechanical properties, and thermal conductivity. Two types of Fe-bearing Al-10Si-Mg alloys were used: the Conventional-F alloy, injected at 720 ℃ and cooled by water quenching, and the Superheated-F alloy, heated to 820 ℃ and maintained at that temperature for 1 hour. Subsequently, it underwent a degassing process at 720 ℃ before being cooled by water quenching. Both the Conventional-F alloy and the Superheated-F alloy exhibited dendritic microstructures and Fe-intermetallic compounds. The Secondary Dendrite Arm Spacing (SDAS) of the Conventional-F alloy measured 32.4 μm, whereas the Superheated-F alloy measured 28.6 μm. Additionally, the average eutectic Si sizes were 10.3 μm for the Conventional-F alloy and 7.7 μm for the Superheated-F alloy. Fe-rich IMCs were observed in the eutectic region, with their size decreasing due to the superheating treatment. Tensile tests at room temperature were conducted at a strain rate of 10-3/s. The Conventional-F alloy exhibited a yield strength (YS) of 93.4 MPa, ultimate tensile strength (UTS) of 183 MPa, and an elongation (El.) of 6.4%. Conversely, the Superheated-F alloy displayed a YS of 115.4 MPa, UTS of 218.2 MPa, and an El. of 5.1%. The mechanical properties notably improved with the superheating treatment. Regarding thermal conductivity, the Conventional-F alloy exhibited 114.9 W/m·K, while the Superheated-F alloy displayed 153.7 W/m·K. This represents a roughly 14% increase compared to the thermal conductivity of the commercial Al-10Si-Mg material (Silafont36: 135.1 W/m·K). The effects of the Superheating Treatment on microstructural characteristics, deformation behavior, and thermal conductivity of the Fe-bearing Al-10Si-Mg casting alloys were discussed.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141012345","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 : 2024-03-05DOI: 10.3365/kjmm.2024.62.3.180
Bonil Ku, Junseong Kim, Yujin Son, K. Min, S. Baeck
Capacitors not only store and release electricity but selectively conduct alternating current. Among the various types of capacitors, multi-layer ceramic capacitors (MLCCs) have been widely used in automotive, smartphone, and wearable devices because of their compact size and high capacitance capabilities. In this study, we have developed an electrolyte for tin electroplating on multi-layer ceramic capacitors (MLCCs) to address the barium leaching issue at the termination points of the MLCCs. This issue has been effectively mitigated by introducing NaHSO4 into the conventional tin plating electrolyte as a corrosion inhibitor. This addition facilitates a rapid reaction between the dissolved barium ions and NaHSO4, resulting in the formation of a thin passivation layer on the surface of the MLCC. The BaSO4 passivation layer effectively prohibits excessive leaching of barium ions from the glass in MLCCs, thereby maintaining chip insulation resistance and preventing crack formation. However, the chemical reaction of NaHSO4 and the formation of the passivation layer can lead to the generation of tin hydroxide precipitates due to pH fluctuations. To address this issue, we increase the amount of complexing agent from 100 g/L to 130 g/L. This adjustment enhanced the ability of tin ions to form stronger complexes, thereby enabling stable electrodeposition on the termination of MLCC. Consequently, the final electrolyte for Sn electroplating (denoted as LW-3) simultaneously achieves corrosion resistance and practical working efficiency, resulting in a uniform 5.4 μmthick tin plating layer with outstanding solderability, and high temperature/humidity stability.
{"title":"Development of Electrolyte with Enhanced Corrosion Resistance for Sn Electroplating on Multi-Layer Ceramic Capacitors","authors":"Bonil Ku, Junseong Kim, Yujin Son, K. Min, S. Baeck","doi":"10.3365/kjmm.2024.62.3.180","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.180","url":null,"abstract":"Capacitors not only store and release electricity but selectively conduct alternating current. Among the various types of capacitors, multi-layer ceramic capacitors (MLCCs) have been widely used in automotive, smartphone, and wearable devices because of their compact size and high capacitance capabilities. In this study, we have developed an electrolyte for tin electroplating on multi-layer ceramic capacitors (MLCCs) to address the barium leaching issue at the termination points of the MLCCs. This issue has been effectively mitigated by introducing NaHSO4 into the conventional tin plating electrolyte as a corrosion inhibitor. This addition facilitates a rapid reaction between the dissolved barium ions and NaHSO4, resulting in the formation of a thin passivation layer on the surface of the MLCC. The BaSO4 passivation layer effectively prohibits excessive leaching of barium ions from the glass in MLCCs, thereby maintaining chip insulation resistance and preventing crack formation. However, the chemical reaction of NaHSO4 and the formation of the passivation layer can lead to the generation of tin hydroxide precipitates due to pH fluctuations. To address this issue, we increase the amount of complexing agent from 100 g/L to 130 g/L. This adjustment enhanced the ability of tin ions to form stronger complexes, thereby enabling stable electrodeposition on the termination of MLCC. Consequently, the final electrolyte for Sn electroplating (denoted as LW-3) simultaneously achieves corrosion resistance and practical working efficiency, resulting in a uniform 5.4 μmthick tin plating layer with outstanding solderability, and high temperature/humidity stability.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140078717","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 : 2024-03-05DOI: 10.3365/kjmm.2024.62.3.171
Yi Seul Choi, J. M. Oh, Chan Hee Park, Wook Jin Lee, Yong ho Park, Jong Woo Won
This study demonstrates that the addition of the rare earth element Erbium (Er) significantly enhances the machinability and tensile properties of titanium (Ti). Pure Ti alloys and Er-added Ti alloys with 0.5-1.1 wt.% Er content were prepared, and their microstructure, machinability, and tensile properties were compared. Two different types of Er secondary phase particles were identified in the microstructure: pure Er and Er-oxide. The amounts of these particles increased with higher Er content. The machinability of the Eradded Ti alloys was significantly improved due to the ability of Er secondary particles to cut machining chips or absorb heat from localized deformation within the Ti matrix. In addition, Er-added Ti alloys exhibited higher strength than pure Ti. The strength enhancement was attributed to grain refinement induced by the Er element. Er secondary phase particles reduced the β grain size during solidification, and they also served as preferential sites for α nucleation during the β → α phase transformation, resulting in a refined microstructure. In addition, the Er secondary phase contributed to the strength enhancement through the well-known precipitation strengthening mechanism. Although ductility decreased with higher Er content due to the increased amount of Er secondary phase particles, 0.5 wt.% Er-added Ti showed no such degradation; its ductility was comparable to that of pure Ti. Er-oxidation was expected to reduce oxygen content within the Ti matrix, enhancing intrinsic Ti ductility; this effect offset the adverse impact on ductility caused by the Er secondary phase particles. Above 0.5 wt.% Er, the adverse effects caused by the Er secondary phase particles overwhelmed the beneficial effect caused by the reduction in oxygen content. The present findings will contribute significantly to the development of highly machinable Ti alloys with superior tensile properties.
本研究表明，添加稀土元素铒（Er）可显著提高钛（Ti）的机械加工性能和拉伸性能。研究人员制备了纯钛合金和铒含量为 0.5-1.1 wt.% 的添加铒的钛合金，并比较了它们的微观结构、机械加工性能和拉伸性能。在微观结构中发现了两种不同类型的铒次生相颗粒：纯铒和铒氧化物。这些颗粒的数量随着 Er 含量的增加而增加。由于铒次生颗粒能够切割加工屑或吸收钛基体内局部变形产生的热量，铒添加钛合金的可加工性显著提高。此外，添加了铒的钛合金比纯钛具有更高的强度。强度的提高归因于 Er 元素引起的晶粒细化。在凝固过程中，Er 次生相颗粒减小了 β 晶粒大小，在 β → α 相变过程中，它们还是 α 成核的优先位置，从而形成了细化的微观结构。此外，铒次生相通过众所周知的沉淀强化机制促进了强度的提高。虽然由于 Er 次生相颗粒数量的增加，延展性随着 Er 含量的增加而降低，但 0.5 wt.% 的添加 Er 的 Ti 没有出现这种退化；其延展性与纯 Ti 相当。预计铒氧化会降低钛基体中的氧含量，从而提高钛的固有延展性；这种效果抵消了铒次生相颗粒对延展性的不利影响。当 Er 含量超过 0.5 wt.% 时，Er 次相颗粒造成的不利影响就会压倒氧含量降低带来的有利影响。本研究结果将极大地促进具有优异拉伸性能的高切削性钛合金的发展。
{"title":"Development of Highly Machinable Ti Alloy with Exceptional Tensile Properties by Er Alloying Element Addition","authors":"Yi Seul Choi, J. M. Oh, Chan Hee Park, Wook Jin Lee, Yong ho Park, Jong Woo Won","doi":"10.3365/kjmm.2024.62.3.171","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.171","url":null,"abstract":"This study demonstrates that the addition of the rare earth element Erbium (Er) significantly enhances the machinability and tensile properties of titanium (Ti). Pure Ti alloys and Er-added Ti alloys with 0.5-1.1 wt.% Er content were prepared, and their microstructure, machinability, and tensile properties were compared. Two different types of Er secondary phase particles were identified in the microstructure: pure Er and Er-oxide. The amounts of these particles increased with higher Er content. The machinability of the Eradded Ti alloys was significantly improved due to the ability of Er secondary particles to cut machining chips or absorb heat from localized deformation within the Ti matrix. In addition, Er-added Ti alloys exhibited higher strength than pure Ti. The strength enhancement was attributed to grain refinement induced by the Er element. Er secondary phase particles reduced the β grain size during solidification, and they also served as preferential sites for α nucleation during the β → α phase transformation, resulting in a refined microstructure. In addition, the Er secondary phase contributed to the strength enhancement through the well-known precipitation strengthening mechanism. Although ductility decreased with higher Er content due to the increased amount of Er secondary phase particles, 0.5 wt.% Er-added Ti showed no such degradation; its ductility was comparable to that of pure Ti. Er-oxidation was expected to reduce oxygen content within the Ti matrix, enhancing intrinsic Ti ductility; this effect offset the adverse impact on ductility caused by the Er secondary phase particles. Above 0.5 wt.% Er, the adverse effects caused by the Er secondary phase particles overwhelmed the beneficial effect caused by the reduction in oxygen content. The present findings will contribute significantly to the development of highly machinable Ti alloys with superior tensile properties.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140079701","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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