Pub Date : 2024-03-05DOI: 10.3365/kjmm.2024.62.3.163
Bum-Soon Park, Jeong-Han Lee, Jae-Cheol Park, Sung-Kil Hong, Hyun-Kuk Park
In this study, a high-melting point element, tantalum carbide (TaC) was added to improve the mechanical properties and the oxidation/corrosion resistance of Fe. The Fe-TaC composites were synthesized by high energy ball milling for the mechanical alloying of the non-equilibrium phase (Fe-Ta) and the homogeneous dispersion of TaC. Fe-TaC composite samples were fabricated using 5, 10, and 20 wt.% TaC. The ductile particles (Fe) got harden and the brittle particles (TaC) were uniformly dispersed, while facilitating short-range diffusion in the ductile matrix by the high energy ball milling method. Spark plasma sintering was performed at a sintering temperature of 850 oC and pressure of 60 MPa. As the TaC contents increased, the sintering exponential (m) increased. A higher ‘m’ value indicates a lower magnitude of shrinkage, by decreasing the lattice and grain boundary (G/B) diffusion path between the pores and particles. The hardness increased from 128.9±10.4 to 444.2±20.6 kg/mm2 as the grain size decreased from 5.13 to 3.99 μm. This enhancement is attributed to the Hall-Petch relationship and dispersion strengthening effect. The mechanical properties of the sintered bodies were studied to evaluate how the different TaC content affect their characteristics. In addition, oxidation resistance increased with increasing TaC contents. It was considered that the local oxidation resistance based on the formation of an oxide layer of TaO and Fe2O3.
{"title":"Sintering Behavior and Mechanical Properties of Dispersed-Reinforced Fe-TaC Composites Produced by High Energy Ball Milling","authors":"Bum-Soon Park, Jeong-Han Lee, Jae-Cheol Park, Sung-Kil Hong, Hyun-Kuk Park","doi":"10.3365/kjmm.2024.62.3.163","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.163","url":null,"abstract":"In this study, a high-melting point element, tantalum carbide (TaC) was added to improve the mechanical properties and the oxidation/corrosion resistance of Fe. The Fe-TaC composites were synthesized by high energy ball milling for the mechanical alloying of the non-equilibrium phase (Fe-Ta) and the homogeneous dispersion of TaC. Fe-TaC composite samples were fabricated using 5, 10, and 20 wt.% TaC. The ductile particles (Fe) got harden and the brittle particles (TaC) were uniformly dispersed, while facilitating short-range diffusion in the ductile matrix by the high energy ball milling method. Spark plasma sintering was performed at a sintering temperature of 850 oC and pressure of 60 MPa. As the TaC contents increased, the sintering exponential (m) increased. A higher ‘m’ value indicates a lower magnitude of shrinkage, by decreasing the lattice and grain boundary (G/B) diffusion path between the pores and particles. The hardness increased from 128.9±10.4 to 444.2±20.6 kg/mm2 as the grain size decreased from 5.13 to 3.99 μm. This enhancement is attributed to the Hall-Petch relationship and dispersion strengthening effect. The mechanical properties of the sintered bodies were studied to evaluate how the different TaC content affect their characteristics. In addition, oxidation resistance increased with increasing TaC contents. It was considered that the local oxidation resistance based on the formation of an oxide layer of TaO and Fe2O3.","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":"140079284","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.2024.62.3.204
Thi Nhan Hau Nguyen, Man Seung Lee
Bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) is known to selectively extract Au(III) from dilute to concentrated hydrochloric acid solutions. Therefore, Cyanex 272 can be employed in the separation of Au(III) from the hydrochloric acid leaching solutions of secondary resources containing gold metal. This work identified the extraction reaction of Au(III) by Cyanex 272 from the hydrochloric acid solutions. Au(III) extraction data was obtained by varying the concentrations of HCl (1-9 M), Au(III) (0.1-1 g/L) and Cyanex 272 (0.01-0.1 M). Among the three variables, it was found that HCl concentration had the most pronounced effect on the extraction of Au(III), which increased with HCl concentration. The extraction reaction of Au(III) by Cyanex 272 is proposed by applying slope analysis method to the extraction data. Comparison of Fourier transform infrared spectroscopy results for the fresh and loaded Cyanex 272 revealed no change in the chemical structure of Cyanex 272 after the extraction. Nuclear magnetic resonance spectroscopic data showed a change in the characteristic peaks of the phosphorus atom of Cyanex 272, indicating the formation of a coordinative bond between Au(III) and Cyanex 272. FT-IR and NMR data together with application of slope analysis clearly verified that molecular Cyanex 272 takes parts in the extraction of Au(III).
{"title":"Identification of Solvent Extraction of Au(III) by Cyanex 272 from Hydrochloric Acid Solutions","authors":"Thi Nhan Hau Nguyen, Man Seung Lee","doi":"10.3365/kjmm.2024.62.3.204","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.204","url":null,"abstract":"Bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) is known to selectively extract Au(III) from dilute to concentrated hydrochloric acid solutions. Therefore, Cyanex 272 can be employed in the separation of Au(III) from the hydrochloric acid leaching solutions of secondary resources containing gold metal. This work identified the extraction reaction of Au(III) by Cyanex 272 from the hydrochloric acid solutions. Au(III) extraction data was obtained by varying the concentrations of HCl (1-9 M), Au(III) (0.1-1 g/L) and Cyanex 272 (0.01-0.1 M). Among the three variables, it was found that HCl concentration had the most pronounced effect on the extraction of Au(III), which increased with HCl concentration. The extraction reaction of Au(III) by Cyanex 272 is proposed by applying slope analysis method to the extraction data. Comparison of Fourier transform infrared spectroscopy results for the fresh and loaded Cyanex 272 revealed no change in the chemical structure of Cyanex 272 after the extraction. Nuclear magnetic resonance spectroscopic data showed a change in the characteristic peaks of the phosphorus atom of Cyanex 272, indicating the formation of a coordinative bond between Au(III) and Cyanex 272. FT-IR and NMR data together with application of slope analysis clearly verified that molecular Cyanex 272 takes parts in the extraction of Au(III).","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":"140079430","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.2024.62.3.229
Sang-Kyu Yoo, Ji-Won Kim, Cho-Long Lee, Myung-Hoon Oh, In-chul Choi
The TiAl alloy is attracting attention as a lightweight and heat-resistant material, because of its high specific strength, excellent high-temperature formability, and fatigue strength. However, its applications are limited by its high unit price and low room temperature ductility. To overcome this issue, dissimilarly bonded materials have been extensively employed. This involves joining a brittle metal to a low-cost metal that possesses excellent plasticity, using various dissimilar bonding techniques. In this study, TiAl/HI-TEMP 820/SCM440H materials were fabricated using a vacuum brazing process under different temperature conditions. After the brazing process, the microstructure of the interfacial area revealed seven distinct layers resulting from chemical reactions between the base metals and the filler metal. These reaction layers consisted of a Ni solid solution, intermetallic compounds (Ti3Al, TiNi2Al, Ti2Ni, FeNi), and borides (CrB, TiB2, FeB). To analyze the effect of brazing temperature on the relationship between the microstructure and mechanical properties at the interface of TiAl/HI-TEMP 820/SCM440H materials, conventional uniaxial tests and nanoindentation tests were performed. The measured nanohardness exhibited a significantly large distribution for each reaction layer, with the highest hardness values observed in the intermetallic compounds and borides layers. Additionally, room temperature tensile tests confirmed that fractures initiated in the highhardness and brittle intermetallic compounds and borides layers.
TiAl 合金具有较高的比强度、出色的高温成形性和疲劳强度，因此作为一种轻质耐热材料备受关注。然而，由于其单价高、室温延展性低，其应用受到了限制。为了克服这一问题，人们广泛采用了异种粘接材料。这包括使用各种异种结合技术，将脆性金属与具有优异塑性的低成本金属结合在一起。本研究采用真空钎焊工艺，在不同温度条件下制造了 TiAl/HI-TEMP 820/SCM440H 材料。钎焊过程结束后，界面区域的微观结构显示出七个不同的反应层，这些反应层是由基体金属和填充金属之间的化学反应产生的。这些反应层包括镍固溶体、金属间化合物（Ti3Al、TiNi2Al、Ti2Ni、FeNi）和硼化物（CrB、TiB2、FeB）。为了分析钎焊温度对 TiAl/HI-TEMP 820/SCM440H 材料界面微观结构和机械性能之间关系的影响，进行了传统的单轴测试和纳米压痕测试。测得的纳米硬度在各反应层中的分布明显较大，金属间化合物层和硼化物层的硬度值最高。此外，室温拉伸试验证实，高硬度和脆性金属间化合物层和硼化物层出现断裂。
{"title":"Evaluation of Microstructure and Mechanical Properties of TiAl/HI-TEMP 820/ SCM440H Materials Manufactured through Vacuum Brazing according to Process Temperature","authors":"Sang-Kyu Yoo, Ji-Won Kim, Cho-Long Lee, Myung-Hoon Oh, In-chul Choi","doi":"10.3365/kjmm.2024.62.3.229","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.229","url":null,"abstract":"The TiAl alloy is attracting attention as a lightweight and heat-resistant material, because of its high specific strength, excellent high-temperature formability, and fatigue strength. However, its applications are limited by its high unit price and low room temperature ductility. To overcome this issue, dissimilarly bonded materials have been extensively employed. This involves joining a brittle metal to a low-cost metal that possesses excellent plasticity, using various dissimilar bonding techniques. In this study, TiAl/HI-TEMP 820/SCM440H materials were fabricated using a vacuum brazing process under different temperature conditions. After the brazing process, the microstructure of the interfacial area revealed seven distinct layers resulting from chemical reactions between the base metals and the filler metal. These reaction layers consisted of a Ni solid solution, intermetallic compounds (Ti3Al, TiNi2Al, Ti2Ni, FeNi), and borides (CrB, TiB2, FeB). To analyze the effect of brazing temperature on the relationship between the microstructure and mechanical properties at the interface of TiAl/HI-TEMP 820/SCM440H materials, conventional uniaxial tests and nanoindentation tests were performed. The measured nanohardness exhibited a significantly large distribution for each reaction layer, with the highest hardness values observed in the intermetallic compounds and borides layers. Additionally, room temperature tensile tests confirmed that fractures initiated in the highhardness and brittle intermetallic compounds and borides layers.","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":"140078882","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.2024.62.3.222
Woorak Choi, Sungchan Yun
Compound droplets can consist of two or more immiscible substances sharing an interface. Among such droplets, the low-viscosity component of Janus droplets can exhibit peculiar bouncing behavior on nonwettable surfaces. There have been recent advances in droplet control technologies, however the impact dynamics of droplets on complex surfaces, and strategies to control their behavior, have not been extensively studied. This study employs the volume of fluid method to analyze the effects of Janus droplet size and the initial interface angle on the dynamics of the two fluidic components in droplets on superhydrophobic cylinders. Janus droplets are composed of low-viscosity (W-) and high-viscosity liquid (G-component). The dynamic characteristics of Janus droplets are investigated as a function of Weber number (We), initial interface angle, the ratio of the droplet’s diameter to the cylinder’s diameter, and viscosity ratio (α). Numerical models provide a regime map of the separation ratio of Janus droplets based on We and α, and the influence of droplet size on asymmetric bouncing is discussed. This study also examines the threshold We at which separation begins after impact, varying with droplet size and α. In addition, the shape evolutions of the droplets are discussed for various initial interface angles to understand the bouncing behavior and separation efficiency. This study is expected to provide valuable strategies for controlling droplet behavior and separation in applications such as liquid purification, rheology, and solidification.
复合液滴可由两种或两种以上共用界面的不相溶物质组成。在这些液滴中，Janus 液滴的低粘度成分会在非润湿表面上表现出奇特的反弹行为。最近，液滴控制技术取得了一些进展，但对液滴在复杂表面上的冲击动力学以及控制其行为的策略还没有进行广泛的研究。本研究采用流体体积法分析了 Janus 液滴大小和初始界面角度对超疏水圆柱体上液滴中两种流体成分动力学的影响。杰纳斯液滴由低粘度液体（W-组分）和高粘度液体（G-组分）组成。研究了杰纳斯液滴的动态特性与韦伯数（We）、初始界面角、液滴直径与圆柱体直径之比以及粘度比（α）的函数关系。数值模型提供了基于 We 和 α 的 Janus 液滴分离比制度图，并讨论了液滴大小对不对称反弹的影响。此外，还讨论了不同初始界面角度下液滴的形状演变，以了解弹跳行为和分离效率。这项研究有望为液体纯化、流变学和凝固等应用中控制液滴行为和分离提供有价值的策略。
{"title":"Behavior of Compound Materials on Superhydrophobic Cylinders: Effects of Droplet’s Size and Interface Angle","authors":"Woorak Choi, Sungchan Yun","doi":"10.3365/kjmm.2024.62.3.222","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.222","url":null,"abstract":"Compound droplets can consist of two or more immiscible substances sharing an interface. Among such droplets, the low-viscosity component of Janus droplets can exhibit peculiar bouncing behavior on nonwettable surfaces. There have been recent advances in droplet control technologies, however the impact dynamics of droplets on complex surfaces, and strategies to control their behavior, have not been extensively studied. This study employs the volume of fluid method to analyze the effects of Janus droplet size and the initial interface angle on the dynamics of the two fluidic components in droplets on superhydrophobic cylinders. Janus droplets are composed of low-viscosity (W-) and high-viscosity liquid (G-component). The dynamic characteristics of Janus droplets are investigated as a function of Weber number (We), initial interface angle, the ratio of the droplet’s diameter to the cylinder’s diameter, and viscosity ratio (α). Numerical models provide a regime map of the separation ratio of Janus droplets based on We and α, and the influence of droplet size on asymmetric bouncing is discussed. This study also examines the threshold We at which separation begins after impact, varying with droplet size and α. In addition, the shape evolutions of the droplets are discussed for various initial interface angles to understand the bouncing behavior and separation efficiency. This study is expected to provide valuable strategies for controlling droplet behavior and separation in applications such as liquid purification, rheology, and solidification.","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":"140079528","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.2024.62.3.212
Yun Hyeok Song, Ji Min Lim, Sagar S. Khot, Dongmyung Jung, Yongwoo Kwon
In this study, the architecture of an interfacial switching memristor, which has a metal-insulatormetal structure of Pt/SrTiO3/Nb-SrTiO3 was investigated. The performance of a neural network that uses memristors as its synapse components was also examined with system-level simulations. A finite element solver, COMSOL Multiphysics, was used to simulate synaptic device characteristics, specifically, the conductance change, using a series of pulses for a given architecture. An open-source software, NeuroSim, was used to simulate the ability of the neural network to recognize and identify handwritten digits. Electrostatics, mass transport, and thermionic emission equations were numerically solved in a fully coupled manner to model the Schottky barrier height modulation at the Pt/SrTiO3 contact using the applied bias. The barrier height is a function of the oxygen vacancy concentration in the SrTiO3 near the contact. The gradual change of the oxygen vacancy concentration profile caused by successive pulses results in the gradual change of conductance. Utilizing the simulations, the influences of device structure modification, and more specifically, changing the size of the Schottky contact, on long-term potentiation and depression were analyzed for planar devices. The results show that a smaller Schottky contact yields a higher digit recognition rate. Based on this finding, a three-dimensional device architecture that is vertically stackable was designed.
{"title":"Simulation Study of Interfacial Switching Memristor Structure and Neural Network Performance","authors":"Yun Hyeok Song, Ji Min Lim, Sagar S. Khot, Dongmyung Jung, Yongwoo Kwon","doi":"10.3365/kjmm.2024.62.3.212","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.212","url":null,"abstract":"In this study, the architecture of an interfacial switching memristor, which has a metal-insulatormetal structure of Pt/SrTiO3/Nb-SrTiO3 was investigated. The performance of a neural network that uses memristors as its synapse components was also examined with system-level simulations. A finite element solver, COMSOL Multiphysics, was used to simulate synaptic device characteristics, specifically, the conductance change, using a series of pulses for a given architecture. An open-source software, NeuroSim, was used to simulate the ability of the neural network to recognize and identify handwritten digits. Electrostatics, mass transport, and thermionic emission equations were numerically solved in a fully coupled manner to model the Schottky barrier height modulation at the Pt/SrTiO3 contact using the applied bias. The barrier height is a function of the oxygen vacancy concentration in the SrTiO3 near the contact. The gradual change of the oxygen vacancy concentration profile caused by successive pulses results in the gradual change of conductance. Utilizing the simulations, the influences of device structure modification, and more specifically, changing the size of the Schottky contact, on long-term potentiation and depression were analyzed for planar devices. The results show that a smaller Schottky contact yields a higher digit recognition rate. Based on this finding, a three-dimensional device architecture that is vertically stackable was designed.","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":"140079223","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.2024.62.3.190
Sung-Hun Park, Jungshin Kang, Ho-Sang Sohn
To develop an eco-friendly titanium (Ti) production process, the calciothermic reduction of titanium dioxide (TiO2) was investigated. The mechanism involved in the reduction of TiO2 using calcium (Ca) was examined. The influence of a molten salt, calcium chloride (CaCl2), on the calciothermic reduction was investigated by conducting experiments at 1123 – 1223 K in an argon (Ar) atmosphere for the duration of 0.5 – 9 h. When CaCl2 was used as a molten salt, the oxygen (O) concentration in Ti decreased to 0.162 mass% owing to the removal of calcium oxide (CaO) from the surface of the Ti particles. In addition, the use of a CaCl2 – lithium chloride (LiCl) molten salt decreased the reaction temperature to 1073 K and the O concentration in the obtained Ti reached 0.333 mass%. Furthermore, after the calciothermic reduction of TiO2 at 1173 K using a perforated crucible, the residual Ca-containing salt was sufficiently separated in-situ from the crucible, and a mixture of Ti and TiH1.924 was produced via hydrogenation at 1023 K by changing the atmosphere gas from Ar to hydrogen gas (H2). The results of this study demonstrate the feasibility of the calciothermic reduction of TiO2 for the eco-friendly production of Ti and TiH2 powders.
为了开发一种生态友好型钛（Ti）生产工艺，研究人员对二氧化钛（TiO2）的钙热还原进行了调查。研究了使用钙（Ca）还原二氧化钛的机理。通过在 1123 - 1223 K 的氩（Ar）气氛中进行持续 0.5 - 9 小时的实验，研究了熔盐氯化钙（CaCl2）对钙热还原的影响。当使用 CaCl2 作为熔盐时，由于 Ti 颗粒表面的氧化钙（CaO）被去除，Ti 中的氧（O）浓度降至 0.162 质量%。此外，使用 CaCl2 - 氯化锂（LiCl）熔盐将反应温度降至 1073 K，得到的钛中的 O 浓度达到 0.333 质量%。此外，使用穿孔坩埚在 1173 K 下对 TiO2 进行钙热还原后，残留的含 Ca 盐被充分地从坩埚中就地分离出来，并通过将大气气体从 Ar 改为氢气 (H2) 在 1023 K 下进行氢化生成了 Ti 和 TiH1.924 的混合物。这项研究的结果证明了钙热还原 TiO2 以环保方式生产 Ti 和 TiH2 粉末的可行性。
{"title":"Investigation of the Calciothermic Reduction of TiO2 for the Green Production of Ti and TiH2 Powders","authors":"Sung-Hun Park, Jungshin Kang, Ho-Sang Sohn","doi":"10.3365/kjmm.2024.62.3.190","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.190","url":null,"abstract":"To develop an eco-friendly titanium (Ti) production process, the calciothermic reduction of titanium dioxide (TiO2) was investigated. The mechanism involved in the reduction of TiO2 using calcium (Ca) was examined. The influence of a molten salt, calcium chloride (CaCl2), on the calciothermic reduction was investigated by conducting experiments at 1123 – 1223 K in an argon (Ar) atmosphere for the duration of 0.5 – 9 h. When CaCl2 was used as a molten salt, the oxygen (O) concentration in Ti decreased to 0.162 mass% owing to the removal of calcium oxide (CaO) from the surface of the Ti particles. In addition, the use of a CaCl2 – lithium chloride (LiCl) molten salt decreased the reaction temperature to 1073 K and the O concentration in the obtained Ti reached 0.333 mass%. Furthermore, after the calciothermic reduction of TiO2 at 1173 K using a perforated crucible, the residual Ca-containing salt was sufficiently separated in-situ from the crucible, and a mixture of Ti and TiH1.924 was produced via hydrogenation at 1023 K by changing the atmosphere gas from Ar to hydrogen gas (H2). The results of this study demonstrate the feasibility of the calciothermic reduction of TiO2 for the eco-friendly production of Ti and TiH2 powders.","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":"140078878","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.2024.62.3.239
Yeoul Kang, Jung Woo Lee
This review provides an overview of recent advances in the materials and structural design of flexible piezoresistive sensors, which are of significant interest as smart devices in the Fourth Industrial Revolution. Recent research has focused on addressing demand for a wide pressure range and high sensitivity for use in diverse applications. In terms of sensor materials, this review begins by introducing elastomers used for matrix and substrate, which provide exceptional conformability to curved surfaces and mechanical flexibility to withstand stretching and bending. They can also incorporate sensing materials in various forms of nanostructures capable of effectively transmitting electrical signals, exploiting the nanomaterial’s electrical properties and conductivity pathways formation mechanisms under pressure, which define the sensor’s characteristics. Additionally, this review explores structural design considerations, including different types of microstructures that can deform easily even under low pressure, enhancing sensor sensitivity, as well as hierarchical structures capable of gradual changes in contact area to provide a wide range of operating pressures. Moreover, the review discusses time- and cost-efficient microfabrication techniques to facilitate practical utilization of the device. This review then summarizes the applications of high-performance sensors in fields such as health monitoring, including pulse detection and motion tracking, robotics, and human-machine interaction involving components such as touch screens and keypads.
{"title":"Research Progress in Nano Materials and Structural Designs for Flexible Piezoresistive Sensors","authors":"Yeoul Kang, Jung Woo Lee","doi":"10.3365/kjmm.2024.62.3.239","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.3.239","url":null,"abstract":"This review provides an overview of recent advances in the materials and structural design of flexible piezoresistive sensors, which are of significant interest as smart devices in the Fourth Industrial Revolution. Recent research has focused on addressing demand for a wide pressure range and high sensitivity for use in diverse applications. In terms of sensor materials, this review begins by introducing elastomers used for matrix and substrate, which provide exceptional conformability to curved surfaces and mechanical flexibility to withstand stretching and bending. They can also incorporate sensing materials in various forms of nanostructures capable of effectively transmitting electrical signals, exploiting the nanomaterial’s electrical properties and conductivity pathways formation mechanisms under pressure, which define the sensor’s characteristics. Additionally, this review explores structural design considerations, including different types of microstructures that can deform easily even under low pressure, enhancing sensor sensitivity, as well as hierarchical structures capable of gradual changes in contact area to provide a wide range of operating pressures. Moreover, the review discusses time- and cost-efficient microfabrication techniques to facilitate practical utilization of the device. This review then summarizes the applications of high-performance sensors in fields such as health monitoring, including pulse detection and motion tracking, robotics, and human-machine interaction involving components such as touch screens and keypads.","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":"140079050","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.39
Tae Hoon Park
In this paper, we investigated a transparent conductive electrode (TCE) that satisfies electrical, optical, and mechanical properties, formed by depositing ultra-thin Ag metal in the form of a random grain boundary with an indium zinc oxide (IZO) layer on a PET substrate. Commonly used ITO electrodes are brittle and difficult to apply to flexible devices. In contrast, IZO-based electrodes are mechanically flexible and can be used as flexible TCE, and have high electrical and optical properties. A 90 nm thick IZO electrode has a transmittance of 90.2% at a wavelength of 460 nm and a sheet resistance of 29.5 ohm/sq. In particular, Ag metal was deposited in the form of an atypical metal island using an RF magnetron sputtering system. At 3 nm there were few metal clusters in the form of islands, and many void channels were formed, resulting in high sheet resistance as well as a decrease in optical transmittance. However, about 5 nm thickness, the number of void channels decreased and the optical path changed, improving the electrical and optical properties. Results showed that the sheet resistance was reduced to 19.8 ohm/sq, and the transmittance was also increased to 91.1%. The mechanical properties were also found to be the same for conventional IZO and Ag/IZO TCE.
{"title":"Research on Flexible Transparent Conductive Electrodes Based on Ultra-Thin Ag in the Form of Grain Boundary with IZO Layer","authors":"Tae Hoon Park","doi":"10.3365/kjmm.2024.62.1.39","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.39","url":null,"abstract":"In this paper, we investigated a transparent conductive electrode (TCE) that satisfies electrical, optical, and mechanical properties, formed by depositing ultra-thin Ag metal in the form of a random grain boundary with an indium zinc oxide (IZO) layer on a PET substrate. Commonly used ITO electrodes are brittle and difficult to apply to flexible devices. In contrast, IZO-based electrodes are mechanically flexible and can be used as flexible TCE, and have high electrical and optical properties. A 90 nm thick IZO electrode has a transmittance of 90.2% at a wavelength of 460 nm and a sheet resistance of 29.5 ohm/sq. In particular, Ag metal was deposited in the form of an atypical metal island using an RF magnetron sputtering system. At 3 nm there were few metal clusters in the form of islands, and many void channels were formed, resulting in high sheet resistance as well as a decrease in optical transmittance. However, about 5 nm thickness, the number of void channels decreased and the optical path changed, improving the electrical and optical properties. Results showed that the sheet resistance was reduced to 19.8 ohm/sq, and the transmittance was also increased to 91.1%. The mechanical properties were also found to be the same for conventional IZO and Ag/IZO TCE.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382094","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.45
S. Joo, JiHui Son, Jeongin Jang, B. Min, Bong-Seo Kim
Mg3Sb2-based n-type materials are consisted of earth-abundant elements and possess comparable thermoelectric properties with n-type Bi2Te3 at low temperatures, which make them promising candidates for cooling and power generation applications in terms of cost and performance. Substitution of Sb atom with chalcogen elements (Te, Se S) is a conventional method for n-type doping, but doping cations such as rare-earth elements and transition metals is also widely studied for its unique advantages. In this study, La and Mn were selected for co-doping of Mg3SbBi, and the thermoelectric performances of the doped materials were investigated. Mg3La0.005MnxSbBi (0 x 0.015) polycrystalline samples were made by sintering the fine powders of the mother alloy after arc melting, in which elemental Mn and LaSb compound were included for n-type dual doping. Considering the loss of Mg at elevated temperatures by vaporization, the molar ratio of Mg, Sb, and Bi in the mixture for arc melting was set to 4 : 1 : 1 with excess Mg. Analysis shows that all the samples are n-type, and the electrical conductivity of Mg3La0.005Mn0.015SbBi increased by 62% from the Mn-free Mg3La0.005SbBi at 298 K. In addition, the lattice thermal conductivity (lat) decreased with increasing Mn content in the measured temperature range of 298-623 K. The minimum value of lat was about 0.60 W m-1K-1 in Mg3La0.005Mn0.015SbBi at 523 K, which is about 19% smaller than that of the Mn-free sample. As a result of these enhancements in thermoelectric performance, the maximum figure of merit (zTmax) of 1.12 was obtained in Mg3La0.005Mn0.01SbBi and Mg3La0.005Mn0.015SbBi at 573 K, and the zT at 298 K increased by 73% to 0.35 in Mg3La0.005Mn0.015SbBi compared to Mn-free Mg3La0.005SbBi, which is beneficial to room-temperature applications.
基于 Mg3Sb2 的 n 型材料由丰富的地球元素组成，在低温条件下具有与 n 型 Bi2Te3 相当的热电特性，这使它们在成本和性能方面成为冷却和发电应用的理想候选材料。用查尔根元素（Te、Se S）取代锑原子是 n 型掺杂的传统方法，但掺杂稀土元素和过渡金属等阳离子也因其独特的优势而被广泛研究。本研究选择 La 和 Mn 作为 Mg3SbBi 的共掺杂剂，并研究了掺杂材料的热电性能。Mg3La0.005MnxSbBi (0 x 0.015) 多晶样品由电弧熔化后的母合金细粉烧结而成，其中加入了元素锰和 LaSb 复合物以实现 n 型双掺杂。考虑到镁在高温下会因汽化而损失，电弧熔化时混合物中镁、锑和铋的摩尔比被设定为 4 : 1 : 1，并加入过量的镁。分析表明，所有样品都是 n 型，在 298 K 时，Mg3La0.005Mn0.015SbBi 的导电率比无锰的 Mg3La0.005SbBi 提高了 62%。此外，在 298-623 K 的测量温度范围内，晶格热导率（lat）随着锰含量的增加而降低。在 523 K 时，Mg3La0.005Mn0.015SbBi 的 lat 的最小值约为 0.60 W m-1K-1，比无锰样品小约 19%。由于这些热电性能的提高，Mg3La0.005Mn0.015SbBi 和 Mg3La0.005Mn0.与无锰 Mg3La0.005SbBi 相比，Mg3La0.005Mn0.015SbBi 在 573 K 时的 zTmax 增加了 73%，达到 0.35，这有利于室温应用。
{"title":"Thermoelectric Properties of N-type Mg3La0.005MnxSbBi Materials Doped with La and Mn","authors":"S. Joo, JiHui Son, Jeongin Jang, B. Min, Bong-Seo Kim","doi":"10.3365/kjmm.2024.62.1.45","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.45","url":null,"abstract":"Mg<sub>3</sub>Sb<sub>2</sub>-based n-type materials are consisted of earth-abundant elements and possess comparable thermoelectric properties with n-type Bi<sub>2</sub>Te<sub>3</sub> at low temperatures, which make them promising candidates for cooling and power generation applications in terms of cost and performance. Substitution of Sb atom with chalcogen elements (Te, Se S) is a conventional method for n-type doping, but doping cations such as rare-earth elements and transition metals is also widely studied for its unique advantages. In this study, La and Mn were selected for co-doping of Mg3SbBi, and the thermoelectric performances of the doped materials were investigated. Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>x</sub>SbBi (0 <i>x</i> 0.015) polycrystalline samples were made by sintering the fine powders of the mother alloy after arc melting, in which elemental Mn and LaSb compound were included for n-type dual doping. Considering the loss of Mg at elevated temperatures by vaporization, the molar ratio of Mg, Sb, and Bi in the mixture for arc melting was set to 4 : 1 : 1 with excess Mg. Analysis shows that all the samples are n-type, and the electrical conductivity of Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi increased by 62% from the Mn-free Mg<sub>3</sub>La<sub>0.005</sub>SbBi at 298 K. In addition, the lattice thermal conductivity (<i><sub>lat</sub></i>) decreased with increasing Mn content in the measured temperature range of 298-623 K. The minimum value of <i><sub>lat</sub></i> was about 0.60 W m<sup>-1</sup>K<sup>-1</sup> in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi at 523 K, which is about 19% smaller than that of the Mn-free sample. As a result of these enhancements in thermoelectric performance, the maximum figure of merit (<i>zT<sub>max</sub></i>) of 1.12 was obtained in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.01</sub>SbBi and Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi at 573 K, and the <i>zT</i> at 298 K increased by 73% to 0.35 in Mg<sub>3</sub>La<sub>0.005</sub>Mn<sub>0.015</sub>SbBi compared to Mn-free Mg<sub>3</sub>La<sub>0.005</sub>SbBi, which is beneficial to room-temperature applications.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384093","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 : 2024-01-05DOI: 10.3365/kjmm.2024.62.1.57
Ok Kyu Park, Seulgi Han, S. Park, Jamil Ur Rahman, Sang-il Kim, Sungmo Choi
Carbon fiber reinforced polymer (CFRP) has been extensively used in civil engineering for applications such as reinforcing and retrofitting various architectural materials. Therefore, understanding the degradation of CFRP under high temperatures is important. This study aims to investigate the thermomechanical and microstructural properties of CFRP plates at elevated temperatures up to 350 oC. The platetype CFRP composites were subjected to temperatures of 50, 100, 150, 200, 250, 300, and 350 oC, and then compared with pristine CFRP samples. X-ray diffraction analysis was conducted to examine the crystal structures of the carbon fibers and epoxy resin matrices in the CFRP. At temperatures higher than 150 oC, the FWHM increased due to the degradation and softening of the resin matrix. Delamination and debonding between the matrix and fibers were observed in samples exposed to temperatures above 200 oC. The maximum tensile strength of the CFRP plates exposed at 350 oC significantly decreased to 0.605 GPa, a reduction of approximately 40% compared to the pristine sample. On the other hand, Young's modulus remained relatively unchanged across the different temperatures. This suggests that the polymer matrix degradation plays a crucial role in the mechanical properties of CFRP, as the matrix layers contribute significantly to the distribution of forces.
{"title":"Thermomechanical Behavior and Microstructure Properties of Carbon Fiber Reinforced Polymer at Elevated Temperatures","authors":"Ok Kyu Park, Seulgi Han, S. Park, Jamil Ur Rahman, Sang-il Kim, Sungmo Choi","doi":"10.3365/kjmm.2024.62.1.57","DOIUrl":"https://doi.org/10.3365/kjmm.2024.62.1.57","url":null,"abstract":"Carbon fiber reinforced polymer (CFRP) has been extensively used in civil engineering for applications such as reinforcing and retrofitting various architectural materials. Therefore, understanding the degradation of CFRP under high temperatures is important. This study aims to investigate the thermomechanical and microstructural properties of CFRP plates at elevated temperatures up to 350 oC. The platetype CFRP composites were subjected to temperatures of 50, 100, 150, 200, 250, 300, and 350 oC, and then compared with pristine CFRP samples. X-ray diffraction analysis was conducted to examine the crystal structures of the carbon fibers and epoxy resin matrices in the CFRP. At temperatures higher than 150 oC, the FWHM increased due to the degradation and softening of the resin matrix. Delamination and debonding between the matrix and fibers were observed in samples exposed to temperatures above 200 oC. The maximum tensile strength of the CFRP plates exposed at 350 oC significantly decreased to 0.605 GPa, a reduction of approximately 40% compared to the pristine sample. On the other hand, Young's modulus remained relatively unchanged across the different temperatures. This suggests that the polymer matrix degradation plays a crucial role in the mechanical properties of CFRP, as the matrix layers contribute significantly to the distribution of forces.","PeriodicalId":17894,"journal":{"name":"Korean Journal of Metals and Materials","volume":null,"pages":null},"PeriodicalIF":1.2,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382458","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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