Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad7473
Chao Fang, Xiaogang Zheng, Jue Liu, Han Du and George J Weng
This paper uses a Monte Carlo method to study the thermal conductivity of graphene nanoplatelet (GNP) composites. Firstly, a large number of GNPs are randomly set in a representative volume element. Then, based on a temperature satisfying the Laplace equation in a matrix, a coated surface (CS) is set up on each GNP surface, and the temperature of the CS and GNP can be obtained by the walk-on-spheres (WoS) method. Finally, the WoS method continues to be applied to calculate the heat flux density of the composite materials, further obtaining the thermal conductivity of the composites. We add the influence of interlayers in random walks. We incorporate the influence of interlayers in the WoS process, and the points that walk onto the interlayer surface have a very low probability of reaching the GNP due to the extremely low thermal conductivity of the interlayer. The calculated results are consistent with the experimental data. The model also studies the effects of the size, orientation, and aggregation of GNPs on the thermal conductivity of composite materials.
{"title":"Uncovering the thermal conductivity of graphene nanoplatelet composites with interlayers using a Monte Carlo model","authors":"Chao Fang, Xiaogang Zheng, Jue Liu, Han Du and George J Weng","doi":"10.1088/1361-6463/ad7473","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7473","url":null,"abstract":"This paper uses a Monte Carlo method to study the thermal conductivity of graphene nanoplatelet (GNP) composites. Firstly, a large number of GNPs are randomly set in a representative volume element. Then, based on a temperature satisfying the Laplace equation in a matrix, a coated surface (CS) is set up on each GNP surface, and the temperature of the CS and GNP can be obtained by the walk-on-spheres (WoS) method. Finally, the WoS method continues to be applied to calculate the heat flux density of the composite materials, further obtaining the thermal conductivity of the composites. We add the influence of interlayers in random walks. We incorporate the influence of interlayers in the WoS process, and the points that walk onto the interlayer surface have a very low probability of reaching the GNP due to the extremely low thermal conductivity of the interlayer. The calculated results are consistent with the experimental data. The model also studies the effects of the size, orientation, and aggregation of GNPs on the thermal conductivity of composite materials.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"1 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad7038
Zhao-Yang Ma, Jin-Shan He, Gan-Yun Huang and Liao-Liang Ke
The tendency of relative motion via rolling between contacting objects exists in various aspects of industry and nature because, in many practical situations, forces and moments may be simultaneously induced at the contacting interfaces. Due to the presence of adhesion, which may be prominent on small scales, research on contacts with the tendency to roll, termed herein as rolling adhesion, is very limited. In the present work, a novel double-Hertz model is developed for adhesive contact between spherical objects subjected to the combined action of normal forces and moments. The results from the new model agree well with available numerical simulations and experimental results. It has been demonstrated that the contact behavior with the effect of rolling adhesion seemingly resembles that of conventional adhesive contact, but the applied moment may impact the pull-off force and may even induce novel contact instability if large enough. The resistance moment at the interface has also been obtained analytically, which is proportional to adhesion hysteresis and contact area. Given the applicability to the full range of the Tabor parameter and nonsingular stresses involved, these results might shed light on adhesive contacts with rolling adhesion and help to characterize them better than existent models.
{"title":"On adhesive contact between spheres with rolling adhesion","authors":"Zhao-Yang Ma, Jin-Shan He, Gan-Yun Huang and Liao-Liang Ke","doi":"10.1088/1361-6463/ad7038","DOIUrl":"https://doi.org/10.1088/1361-6463/ad7038","url":null,"abstract":"The tendency of relative motion via rolling between contacting objects exists in various aspects of industry and nature because, in many practical situations, forces and moments may be simultaneously induced at the contacting interfaces. Due to the presence of adhesion, which may be prominent on small scales, research on contacts with the tendency to roll, termed herein as rolling adhesion, is very limited. In the present work, a novel double-Hertz model is developed for adhesive contact between spherical objects subjected to the combined action of normal forces and moments. The results from the new model agree well with available numerical simulations and experimental results. It has been demonstrated that the contact behavior with the effect of rolling adhesion seemingly resembles that of conventional adhesive contact, but the applied moment may impact the pull-off force and may even induce novel contact instability if large enough. The resistance moment at the interface has also been obtained analytically, which is proportional to adhesion hysteresis and contact area. Given the applicability to the full range of the Tabor parameter and nonsingular stresses involved, these results might shed light on adhesive contacts with rolling adhesion and help to characterize them better than existent models.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"11 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad773d
Zhaoying Xi, Zeng Liu, Junpeng Fang, Ang Bian, Shaohui Zhang, Jia-Han Zhang, Lei Li, Yufeng Guo and Weihua Tang
Etching plays a key role in processing and manufacturing electronic and optoelectronic devices. For ultra-wide bandgap semiconductor gallium oxide (Ga2O3), its etching investigations and evolution mechanism are still at the earlier stage, and some more research gumption should be invested. In this review, we make a summary on the etching of Ga2O3, including dry (plasma) etching, wet chemical etching, and photoelectrochemical etching, and discuss the etching results, existing problems, and feasible solutions, in order to provide guidance and advises for furtherly developing the Ga2O3 etching and Ga2O3-based electronic and optoelectronic devices.
{"title":"Etching of Ga2O3: an important process for device manufacturing","authors":"Zhaoying Xi, Zeng Liu, Junpeng Fang, Ang Bian, Shaohui Zhang, Jia-Han Zhang, Lei Li, Yufeng Guo and Weihua Tang","doi":"10.1088/1361-6463/ad773d","DOIUrl":"https://doi.org/10.1088/1361-6463/ad773d","url":null,"abstract":"Etching plays a key role in processing and manufacturing electronic and optoelectronic devices. For ultra-wide bandgap semiconductor gallium oxide (Ga2O3), its etching investigations and evolution mechanism are still at the earlier stage, and some more research gumption should be invested. In this review, we make a summary on the etching of Ga2O3, including dry (plasma) etching, wet chemical etching, and photoelectrochemical etching, and discuss the etching results, existing problems, and feasible solutions, in order to provide guidance and advises for furtherly developing the Ga2O3 etching and Ga2O3-based electronic and optoelectronic devices.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"30 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad76b7
Qi Yuan, Guoxiang Sun, Haorui Xue, Weidong Ding, Shaohao Nie and Kunhao Yu
High-power pulse generators are widely used in civil and military fields. The main switch directly determines the output characteristics of the high-power pulse generators, such as the voltage front time (tf). Pseudospark switches (PSS) show a promising future for middle voltage, high repetitive frequency pulse power applications. However, how to further improve the breakdown behavior without reducing its advantages is a challenging task. In this paper, the influence of operating parameters (anode voltage UA and gas pressure p) and structural parameter (number of cathode holes) on the breakdown behavior are investigated, the related mechanism are explained, and specific improvement schemes are proposed. It is found that the tf of the single channel PSS (SCPSS) decreased significantly with increasing p, but hardly varied with UA under moderate p. However, it is not a sound solution to increase the p excessively to reduce tf. Besides, increasing the number of cathode holes can obtain a shorter tf at low pressures (which implies superior repetition frequency performance). However, at 25 Pa, the jitter (which is defined as the standard deviation of tf in multiple tests) of the 2-channel PSS is larger than that of the SCPSS. And the jitter of the 4-channel and 8-channel PSS is also greater than 6 ns and 2 ns, respectively. Through experimental and simulation analyses, it can be explained as the stepwise penetration of the virtual anode and the non-simultaneous ignition of the channels. A scheme to increase the trigger energy (ϵ) has been adopted to improve the simultaneous ignition probability, while shortening tf and reducing jitter. After optimization, the good ignition probability of the 4-channel PSS has been improved to 82% and the jitter has been reduced to less than 1 ns at 25 Pa and 14.7 mJ.
大功率脉冲发生器广泛应用于民用和军用领域。主开关直接决定了大功率脉冲发生器的输出特性，如电压前沿时间（tf）。伪火花开关（PSS）在中压、高重复频率脉冲功率应用方面前景广阔。然而，如何在不降低其优势的情况下进一步改善击穿行为是一项具有挑战性的任务。本文研究了工作参数（阳极电压 UA 和气体压力 p）和结构参数（阴极孔数）对击穿行为的影响，解释了相关机理，并提出了具体的改进方案。研究发现，单通道 PSS（SCPSS）的 tf 随 p 的增大而显著减小，但在中等 p 条件下几乎不随 UA 的变化而变化。此外，增加阴极孔的数量可以在低压下获得更短的 tf（这意味着更优越的重复频率性能）。然而，在 25 Pa 时，双通道 PSS 的抖动（定义为多次测试中 tf 的标准偏差）大于 SCPSS。而 4 通道和 8 通道 PSS 的抖动也分别大于 6 ns 和 2 ns。通过实验和模拟分析，这可以解释为虚拟阳极的逐步穿透和通道的非同时点火。为了提高同时点火概率，同时缩短 tf 和减少抖动，我们采用了增加触发能量（ϵ）的方案。经过优化，4 通道 PSS 的良好点火概率提高到了 82%，在 25 Pa 和 14.7 mJ 条件下，抖动降低到了 1 ns 以下。
{"title":"Influence factors and improvement scheme on the breakdown behavior of pseudospark switch","authors":"Qi Yuan, Guoxiang Sun, Haorui Xue, Weidong Ding, Shaohao Nie and Kunhao Yu","doi":"10.1088/1361-6463/ad76b7","DOIUrl":"https://doi.org/10.1088/1361-6463/ad76b7","url":null,"abstract":"High-power pulse generators are widely used in civil and military fields. The main switch directly determines the output characteristics of the high-power pulse generators, such as the voltage front time (tf). Pseudospark switches (PSS) show a promising future for middle voltage, high repetitive frequency pulse power applications. However, how to further improve the breakdown behavior without reducing its advantages is a challenging task. In this paper, the influence of operating parameters (anode voltage UA and gas pressure p) and structural parameter (number of cathode holes) on the breakdown behavior are investigated, the related mechanism are explained, and specific improvement schemes are proposed. It is found that the tf of the single channel PSS (SCPSS) decreased significantly with increasing p, but hardly varied with UA under moderate p. However, it is not a sound solution to increase the p excessively to reduce tf. Besides, increasing the number of cathode holes can obtain a shorter tf at low pressures (which implies superior repetition frequency performance). However, at 25 Pa, the jitter (which is defined as the standard deviation of tf in multiple tests) of the 2-channel PSS is larger than that of the SCPSS. And the jitter of the 4-channel and 8-channel PSS is also greater than 6 ns and 2 ns, respectively. Through experimental and simulation analyses, it can be explained as the stepwise penetration of the virtual anode and the non-simultaneous ignition of the channels. A scheme to increase the trigger energy (ϵ) has been adopted to improve the simultaneous ignition probability, while shortening tf and reducing jitter. After optimization, the good ignition probability of the 4-channel PSS has been improved to 82% and the jitter has been reduced to less than 1 ns at 25 Pa and 14.7 mJ.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad76bd
Chun Liu, Ming Xu, Shengtao Chen, Li Sun, Liqing Zhang, Qianqian Li and Jiahao Wang
The lock-on effect of the gallium arsenide photoconductive semiconductor switch (GaAs PCSS) at repetition rate aggravates the current crowding and electric field distortion, which significantly increases the risk of switch damage or even failure. Therefore, it is of great significance to investigate the carrier transport and the heat generation mechanism for improving the performance and longevity of GaAs PCSS in lock-on mode. The internal physical process of an opposed-electrode GaAs PCSS at low optical energy and strong electric field is analyzed and discussed by experiment and simulation. A device-circuit hybrid simulation is employed to investigate the transient electric field, carrier concentration, and lattice temperature distribution within the GaAs PCSS in lock-on mode. The device temperature exhibits a positive correlation with the applied bias electric field, resulting in a peak temperature of 1037.25 K at an electric field of 38 kV cm−1. The temperature distribution within the GaAs PCSS indicates a greater possibility for thermal breakdown and damage near the electrodes.
{"title":"Analysis of carrier dynamics and thermal effect of the GaAs photoconductive semiconductor switch in lock-on mode","authors":"Chun Liu, Ming Xu, Shengtao Chen, Li Sun, Liqing Zhang, Qianqian Li and Jiahao Wang","doi":"10.1088/1361-6463/ad76bd","DOIUrl":"https://doi.org/10.1088/1361-6463/ad76bd","url":null,"abstract":"The lock-on effect of the gallium arsenide photoconductive semiconductor switch (GaAs PCSS) at repetition rate aggravates the current crowding and electric field distortion, which significantly increases the risk of switch damage or even failure. Therefore, it is of great significance to investigate the carrier transport and the heat generation mechanism for improving the performance and longevity of GaAs PCSS in lock-on mode. The internal physical process of an opposed-electrode GaAs PCSS at low optical energy and strong electric field is analyzed and discussed by experiment and simulation. A device-circuit hybrid simulation is employed to investigate the transient electric field, carrier concentration, and lattice temperature distribution within the GaAs PCSS in lock-on mode. The device temperature exhibits a positive correlation with the applied bias electric field, resulting in a peak temperature of 1037.25 K at an electric field of 38 kV cm−1. The temperature distribution within the GaAs PCSS indicates a greater possibility for thermal breakdown and damage near the electrodes.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"60 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad726d
J Y Yang, X J Xiang, Z J Tan, X K Zhang, S Pan, J Chen and G Z Xu
In this study, we report on the detailed atomic ordering, magnetic and electrical properties of the Heusler alloy Mn2CoAl, studied via combined experimental methods and a theoretical calculation approach. Our studies confirm the Hg2CuTi-type crystal structure of Mn2CoAl with 25% anti-site disorder between Mn (B:1/4,1/4,1/4) and Co(C:1/2,1/2,1/2) sites. Neutron powder diffraction measurements identify the antiparallel spin couplings between Mn:A↓ and Mn:B↑, Co:C↑, resulting in a ferrimagnetic structure with a net magnetic moment of ∼1.6 μB at room temperature. In terms of the electronic calculations, we find that the anti-site atoms will contribute large densities of states at the Fermi level, thus destroying the spin gapless band structure and making Mn2CoAl a normal ferrimagnetic metal. This report is intended to establish a basic understanding of the structure and physical properties of Mn2CoAl.
{"title":"Heusler alloy Mn2CoAl: structural, magnetic and electronic properties","authors":"J Y Yang, X J Xiang, Z J Tan, X K Zhang, S Pan, J Chen and G Z Xu","doi":"10.1088/1361-6463/ad726d","DOIUrl":"https://doi.org/10.1088/1361-6463/ad726d","url":null,"abstract":"In this study, we report on the detailed atomic ordering, magnetic and electrical properties of the Heusler alloy Mn2CoAl, studied via combined experimental methods and a theoretical calculation approach. Our studies confirm the Hg2CuTi-type crystal structure of Mn2CoAl with 25% anti-site disorder between Mn (B:1/4,1/4,1/4) and Co(C:1/2,1/2,1/2) sites. Neutron powder diffraction measurements identify the antiparallel spin couplings between Mn:A↓ and Mn:B↑, Co:C↑, resulting in a ferrimagnetic structure with a net magnetic moment of ∼1.6 μB at room temperature. In terms of the electronic calculations, we find that the anti-site atoms will contribute large densities of states at the Fermi level, thus destroying the spin gapless band structure and making Mn2CoAl a normal ferrimagnetic metal. This report is intended to establish a basic understanding of the structure and physical properties of Mn2CoAl.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"7 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-11DOI: 10.1088/1361-6463/ad76b9
Shengpeng Yang, Hongyang Guo, Ping Zhang, Shaomeng Wang and Yubin Gong
The plasmon excitation in two-dimensional electron gases is a significant way of achieving micro-nanoscale terahertz (THz) devices. Here, we establish a kinetic simulation model to study the THz plasmons amplification in a semiconductor double-quantum-well system with counter-streaming electron drift velocities. By comparing the simulation results with theoretical dispersion relations, we confirm two competing mechanisms of negative damping suitable for THz amplification: Cherenkov-type two-stream instability and a new non-Cherenkov mechanism called kinetic relaxation instability. The former is caused by the interlayer coupling of two slow plasmon modes and only exists when the drift velocities are much greater than the fermi velocities. The latter is a statistical effect caused by the momentum relaxation of electron-impurity scattering and predominates at lower drift velocities. We show that an approximate kinetic dispersion relation can accurately predict the wave growth rates of the two mechanisms. The results also indicate that the saturated plasmonic waves undergo strong nonlinearities such as wave distortion, frequency downshift, wave-packet formation, and spectrum broadening. The nonlinear evolution can be interpreted as the merging of bubble structures in the electron phase-space distribution. The present results not only reveal the potential mechanisms of the plasmonic instabilities in double-layer 2DEGs, but also provide a new guideline for the design of on-chip THz amplifiers.
{"title":"Negative damping of terahertz plasmons in counter-streaming double-layer two-dimensional electron gases","authors":"Shengpeng Yang, Hongyang Guo, Ping Zhang, Shaomeng Wang and Yubin Gong","doi":"10.1088/1361-6463/ad76b9","DOIUrl":"https://doi.org/10.1088/1361-6463/ad76b9","url":null,"abstract":"The plasmon excitation in two-dimensional electron gases is a significant way of achieving micro-nanoscale terahertz (THz) devices. Here, we establish a kinetic simulation model to study the THz plasmons amplification in a semiconductor double-quantum-well system with counter-streaming electron drift velocities. By comparing the simulation results with theoretical dispersion relations, we confirm two competing mechanisms of negative damping suitable for THz amplification: Cherenkov-type two-stream instability and a new non-Cherenkov mechanism called kinetic relaxation instability. The former is caused by the interlayer coupling of two slow plasmon modes and only exists when the drift velocities are much greater than the fermi velocities. The latter is a statistical effect caused by the momentum relaxation of electron-impurity scattering and predominates at lower drift velocities. We show that an approximate kinetic dispersion relation can accurately predict the wave growth rates of the two mechanisms. The results also indicate that the saturated plasmonic waves undergo strong nonlinearities such as wave distortion, frequency downshift, wave-packet formation, and spectrum broadening. The nonlinear evolution can be interpreted as the merging of bubble structures in the electron phase-space distribution. The present results not only reveal the potential mechanisms of the plasmonic instabilities in double-layer 2DEGs, but also provide a new guideline for the design of on-chip THz amplifiers.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"10 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6463/ad703a
Gazal Gupta, Raghvendra Gupta, Amit Gupta and Deepak Kumar
Based on its availability, cost and stability, rechargeable Mg batteries (RMBs) are potential candidates to fulfill the futuristic demand for high energy density storage devices. However, they are minimally explored due to sluggish Mg ion diffusion in cathode materials. Literature suggests that the Chevrel phase (CP) (Mo6S8) holds promise as a cathode (positive electrode) for RMBs due to its open structure and self-healing properties during cycling. This study reports the electrochemical performance of Mo6S8 (synthesized using cost effective precursors (Cu–Mo–MoS2)) as a cathode for RMBs for the first time. The development of Mo6S8 is a two-step process: (i) synthesis of Cu2Mo6S8 via high energy milling method using Cu, Mo and MoS2 as precursors and (ii) leaching of Cu from Cu2Mo6S8. The morphological and structural characteristics of the developed materials are recorded using x-ray diffraction and field emission scanning electron microscopy. The developed Mo6S8 is cuboid-shaped with a rhombohedral unit cell. To record the electrochemical performance of Mo6S8 as a positive electrode for rechargeable Mg batteries (RMBs), CR2016 type half-cells are fabricated. It is observed that the initial discharge capacity was 89 mA h g−1 at a current density of 25 mA g−1 (1C = 128 mA g−1). Interestingly, the capacity increases from 89 to ≈100 mA h g−1 during 50 cycles which is higher than reported in the literature. The coulombic efficiency (CE) of ≈90% is observed for 100 cycles. Additionally, the over-potential decreases with an increase in cycle number. Importantly, the authors explained the diffusion behavior of Mg ions in Mo6S8 with 0.4 M 2(PhMgCl)-AlCl3/THF (APC) electrolyte via cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic intermittent titration (GITT) technique. The diffusion coefficients have been calculated and fall in the range of 10−8−10−14 cm2 s−1. Also, the authors explain the effect of outer site activation during cycling on the diffusion kinetics of the materials using the GITT technique. This investigation of diffusion kinetics of Mg ions in Mo6S8 may pave the way for evaluating various CPs as electrode materials for future rechargeable magnesium battery systems.
可充电镁电池（RMB）具有易得性、成本低和稳定性等优点，是满足未来对高能量密度存储设备需求的潜在候选材料。然而，由于镁离子在阴极材料中扩散缓慢，对它们的研究还很少。文献表明，Chevrel 相（CP）（Mo6S8）因其开放式结构和循环过程中的自修复特性，有望成为人民币的阴极（正极）。本研究首次报道了作为人民币阴极的 Mo6S8（使用成本低廉的前驱体（Cu-Mo-MoS2）合成）的电化学性能。Mo6S8 的开发分为两步：(i) 以 Cu、Mo 和 MoS2 为前驱体，通过高能研磨法合成 Cu2Mo6S8；(ii) 从 Cu2Mo6S8 中浸出 Cu。利用 X 射线衍射和场发射扫描电子显微镜记录了所开发材料的形态和结构特征。所开发的 Mo6S8 呈立方体状，具有斜方体单胞。为了记录作为可充电镁电池（RMB）正极的 Mo6S8 的电化学性能，制作了 CR2016 型半电池。据观察，在电流密度为 25 mA g-1 （1C = 128 mA g-1）时，初始放电容量为 89 mA h g-1。有趣的是，在 50 个循环期间，容量从 89 mA h g-1 增加到 ≈100 mA h g-1，高于文献报道的水平。循环 100 次后，库仑效率（CE）≈90%。此外，过电位随着循环次数的增加而降低。重要的是，作者通过循环伏安法、电化学阻抗光谱法和电静电间歇滴定（GITT）技术解释了镁离子在 0.4 M 2(PhMgCl)-AlCl3/THF (APC) 电解质的 Mo6S8 中的扩散行为。计算得出的扩散系数在 10-8-10-14 cm2 s-1 之间。此外，作者还利用 GITT 技术解释了循环过程中外位点活化对材料扩散动力学的影响。这项关于镁离子在 Mo6S8 中扩散动力学的研究可能会为评估各种氯化石蜡作为未来可充电镁电池系统的电极材料铺平道路。
{"title":"Electrochemical studies and diffusion kinetics in the Chevrel phase (Mo6S8) for rechargeable Mg batteries","authors":"Gazal Gupta, Raghvendra Gupta, Amit Gupta and Deepak Kumar","doi":"10.1088/1361-6463/ad703a","DOIUrl":"https://doi.org/10.1088/1361-6463/ad703a","url":null,"abstract":"Based on its availability, cost and stability, rechargeable Mg batteries (RMBs) are potential candidates to fulfill the futuristic demand for high energy density storage devices. However, they are minimally explored due to sluggish Mg ion diffusion in cathode materials. Literature suggests that the Chevrel phase (CP) (Mo6S8) holds promise as a cathode (positive electrode) for RMBs due to its open structure and self-healing properties during cycling. This study reports the electrochemical performance of Mo6S8 (synthesized using cost effective precursors (Cu–Mo–MoS2)) as a cathode for RMBs for the first time. The development of Mo6S8 is a two-step process: (i) synthesis of Cu2Mo6S8 via high energy milling method using Cu, Mo and MoS2 as precursors and (ii) leaching of Cu from Cu2Mo6S8. The morphological and structural characteristics of the developed materials are recorded using x-ray diffraction and field emission scanning electron microscopy. The developed Mo6S8 is cuboid-shaped with a rhombohedral unit cell. To record the electrochemical performance of Mo6S8 as a positive electrode for rechargeable Mg batteries (RMBs), CR2016 type half-cells are fabricated. It is observed that the initial discharge capacity was 89 mA h g−1 at a current density of 25 mA g−1 (1C = 128 mA g−1). Interestingly, the capacity increases from 89 to ≈100 mA h g−1 during 50 cycles which is higher than reported in the literature. The coulombic efficiency (CE) of ≈90% is observed for 100 cycles. Additionally, the over-potential decreases with an increase in cycle number. Importantly, the authors explained the diffusion behavior of Mg ions in Mo6S8 with 0.4 M 2(PhMgCl)-AlCl3/THF (APC) electrolyte via cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic intermittent titration (GITT) technique. The diffusion coefficients have been calculated and fall in the range of 10−8−10−14 cm2 s−1. Also, the authors explain the effect of outer site activation during cycling on the diffusion kinetics of the materials using the GITT technique. This investigation of diffusion kinetics of Mg ions in Mo6S8 may pave the way for evaluating various CPs as electrode materials for future rechargeable magnesium battery systems.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"178 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6463/ad726f
Tao Shi, Ge Jin, Hong Zhang and Sheng Zou
We have constructed a transverse modulated magnetometer based on spin alignment in a paraffin-coated 85 Rb cell operated in a geophysical magnetic field of 47.1 µT. When an orthogonal driving magnetic field ( axis) is resonant on the Larmor frequency ( axis), we have proposed a new method to zero the static residual magnetic fields in the transverse plane and achieved a sensitivity of with bandwidth of 200 Hz. The repump light ( ) redistributes the populations in the ground state, rendering the state dark. This effect significantly amplifies the optical rotation signals nearly fourfold. The numerical solution of the Liouville equation is in good agreement with the experimental results. By using perturbation treatment and employing appropriate approximations, the derived analytical expressions for optical rotation are deduced to succinctly elucidate the dynamics of atomic alignment under parametric modulation. These outcomes could be extended for the advancement of an alignment magnetometer that has been designed to detect a weak magnetic signal in the geophysical range.
{"title":"A 85Rb transverse modulation magnetometer in the geophysical range based on atomic alignment states","authors":"Tao Shi, Ge Jin, Hong Zhang and Sheng Zou","doi":"10.1088/1361-6463/ad726f","DOIUrl":"https://doi.org/10.1088/1361-6463/ad726f","url":null,"abstract":"We have constructed a transverse modulated magnetometer based on spin alignment in a paraffin-coated 85 Rb cell operated in a geophysical magnetic field of 47.1 µT. When an orthogonal driving magnetic field ( axis) is resonant on the Larmor frequency ( axis), we have proposed a new method to zero the static residual magnetic fields in the transverse plane and achieved a sensitivity of with bandwidth of 200 Hz. The repump light ( ) redistributes the populations in the ground state, rendering the state dark. This effect significantly amplifies the optical rotation signals nearly fourfold. The numerical solution of the Liouville equation is in good agreement with the experimental results. By using perturbation treatment and employing appropriate approximations, the derived analytical expressions for optical rotation are deduced to succinctly elucidate the dynamics of atomic alignment under parametric modulation. These outcomes could be extended for the advancement of an alignment magnetometer that has been designed to detect a weak magnetic signal in the geophysical range.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"61 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-10DOI: 10.1088/1361-6463/ad760e
Sicheng Cao, Zhenxuan Chen, Runxuan Zhang, Chaoxian Tang, Zijun Chen, Ruixing Nie, Feng Zhao, Shenyi Huang and Zhengyong Song
Holography plays a significant role in optical research and has been utilized in numerous applications. Metasurface holograms are attracting more and more attention with the advancement of their efficient wavefront reshaping. However, the realization of multi-channel holograms and dynamic switching of them still remain challenging in the terahertz band. In this paper, anisotropic vanadium dioxide (VO2) metasurfaces are used to realize four-channel holograms at 1.5 THz. It is assembled by a set of VO2 meta-atoms with independent phase control for different channels. Depending on the polarization of incident wave and the state of VO2, four channels are independently selected. After optimization to eliminate crosstalk between top and bottom layers, two holograms are projected under x- and y-polarized incidences when VO2 is metallic. Similarly, two additional holograms are achieved as VO2 is insulating. As a novel solution to terahertz multi-channel holography, this work may be applied to compact optical system and high-volume optical encryption.
全息技术在光学研究中发挥着重要作用，并被广泛应用于各种领域。随着高效波前重塑技术的发展，元面全息图正吸引着越来越多的关注。然而，在太赫兹波段实现多通道全息图及其动态切换仍是一项挑战。本文利用各向异性的二氧化钒（VO2）元表面实现了 1.5 太赫兹的四通道全息图。它由一组可对不同通道进行独立相位控制的二氧化钒元原子组装而成。根据入射波的偏振和 VO2 的状态，可独立选择四个通道。经过优化以消除顶层和底层之间的串扰后，当 VO2 为金属时，在 x 偏振和 y 偏振入射波下投射出两幅全息图。同样，当 VO2 为绝缘层时，还能获得另外两幅全息图。作为太赫兹多通道全息技术的新型解决方案，这项研究成果可应用于紧凑型光学系统和大批量光学加密。
{"title":"Anisotropic vanadium dioxide-based metasurfaces for polarization-multiplexed holograms in the terahertz region","authors":"Sicheng Cao, Zhenxuan Chen, Runxuan Zhang, Chaoxian Tang, Zijun Chen, Ruixing Nie, Feng Zhao, Shenyi Huang and Zhengyong Song","doi":"10.1088/1361-6463/ad760e","DOIUrl":"https://doi.org/10.1088/1361-6463/ad760e","url":null,"abstract":"Holography plays a significant role in optical research and has been utilized in numerous applications. Metasurface holograms are attracting more and more attention with the advancement of their efficient wavefront reshaping. However, the realization of multi-channel holograms and dynamic switching of them still remain challenging in the terahertz band. In this paper, anisotropic vanadium dioxide (VO2) metasurfaces are used to realize four-channel holograms at 1.5 THz. It is assembled by a set of VO2 meta-atoms with independent phase control for different channels. Depending on the polarization of incident wave and the state of VO2, four channels are independently selected. After optimization to eliminate crosstalk between top and bottom layers, two holograms are projected under x- and y-polarized incidences when VO2 is metallic. Similarly, two additional holograms are achieved as VO2 is insulating. As a novel solution to terahertz multi-channel holography, this work may be applied to compact optical system and high-volume optical encryption.","PeriodicalId":16789,"journal":{"name":"Journal of Physics D: Applied Physics","volume":"73 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142223162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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