Surface modification results in substantial improvement in pool boiling heat transfer. Thin film-coated and porous-coated substrates, through different materials and techniques, significantly boost heat transfer through increased nucleation due to the presence of micro-cavities on the surface. The existing models and empirical correlations for boiling on these coated surfaces are constrained by specific operating conditions and parameter ranges and are hence limited by their prediction accuracy. This study focuses on developing an accurate and reliable Machine Learning (ML) model by effectively capturing the actual relationship between the influencing variables. Various ML algorithms have been evaluated on the thin film-coated and porous-coated datasets amassed from different studies. The CatBoost model demonstrated the best prediction accuracy after cross-validation and hyperparameter tuning. For the optimized CatBoost model, SHAP analysis has been carried out to identify the prominent influencing parameters and interpret the impact of parameter variation on the target variable. This model interpretation clearly justifies the decisions behind the model predictions, making it a robust model for the prediction of nucleate boiling Heat Transfer Coefficient (HTC) on coated surfaces. Finally, the existing empirical correlations have been assessed, and new correlations have been proposed to predict the HTC on these surfaces with the inclusion of influential parameters identified through SHAP interpretation. Keywords: Pool boiling, Thin film-coated, Porous-coated, Heat transfer coefficient, Machine learning, CatBoost, SHAP analysis
{"title":"Modelling of nucleate pool boiling on coated substrates using machine learning and empirical approaches","authors":"Vijay Kuberan, Sateesh Gedupudi","doi":"arxiv-2409.07811","DOIUrl":"https://doi.org/arxiv-2409.07811","url":null,"abstract":"Surface modification results in substantial improvement in pool boiling heat\u0000transfer. Thin film-coated and porous-coated substrates, through different\u0000materials and techniques, significantly boost heat transfer through increased\u0000nucleation due to the presence of micro-cavities on the surface. The existing\u0000models and empirical correlations for boiling on these coated surfaces are\u0000constrained by specific operating conditions and parameter ranges and are hence\u0000limited by their prediction accuracy. This study focuses on developing an\u0000accurate and reliable Machine Learning (ML) model by effectively capturing the\u0000actual relationship between the influencing variables. Various ML algorithms\u0000have been evaluated on the thin film-coated and porous-coated datasets amassed\u0000from different studies. The CatBoost model demonstrated the best prediction\u0000accuracy after cross-validation and hyperparameter tuning. For the optimized\u0000CatBoost model, SHAP analysis has been carried out to identify the prominent\u0000influencing parameters and interpret the impact of parameter variation on the\u0000target variable. This model interpretation clearly justifies the decisions\u0000behind the model predictions, making it a robust model for the prediction of\u0000nucleate boiling Heat Transfer Coefficient (HTC) on coated surfaces. Finally,\u0000the existing empirical correlations have been assessed, and new correlations\u0000have been proposed to predict the HTC on these surfaces with the inclusion of\u0000influential parameters identified through SHAP interpretation. Keywords: Pool boiling, Thin film-coated, Porous-coated, Heat transfer\u0000coefficient, Machine learning, CatBoost, SHAP analysis","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alberto Comoretto, Harmannus A. H. Schomaker, Johannes T. B. Overvelde
Animals achieve robust locomotion by offloading regulation from the brain to physical couplings within the body. Contrarily, locomotion in artificial systems often depends on centralized processors. Here, we introduce a rapid and autonomous locomotion strategy with synchronized gaits emerging through physical interactions between self-oscillating limbs and the environment, without control signals. Each limb is a single soft tube that only requires constant flow of air to perform cyclic stepping motions at frequencies reaching 300 hertz. By combining several of these self-oscillating limbs, their physical synchronization enables tethered and untethered locomotion speeds that are orders of magnitude faster than comparable state-of-the-art. We demonstrate that these seemingly simple devices exhibit autonomy, including obstacle avoidance and phototaxis, opening up avenues for robust and functional robots at all scales.
{"title":"Physical synchronization of soft self-oscillating limbs for fast and autonomous locomotion","authors":"Alberto Comoretto, Harmannus A. H. Schomaker, Johannes T. B. Overvelde","doi":"arxiv-2409.07011","DOIUrl":"https://doi.org/arxiv-2409.07011","url":null,"abstract":"Animals achieve robust locomotion by offloading regulation from the brain to\u0000physical couplings within the body. Contrarily, locomotion in artificial\u0000systems often depends on centralized processors. Here, we introduce a rapid and\u0000autonomous locomotion strategy with synchronized gaits emerging through\u0000physical interactions between self-oscillating limbs and the environment,\u0000without control signals. Each limb is a single soft tube that only requires\u0000constant flow of air to perform cyclic stepping motions at frequencies reaching\u0000300 hertz. By combining several of these self-oscillating limbs, their physical\u0000synchronization enables tethered and untethered locomotion speeds that are\u0000orders of magnitude faster than comparable state-of-the-art. We demonstrate\u0000that these seemingly simple devices exhibit autonomy, including obstacle\u0000avoidance and phototaxis, opening up avenues for robust and functional robots\u0000at all scales.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jay Sim, Shuai Wu, Sarah Hwang, Lu Lu, Ruike Renee Zhao
Active metamaterials are a type of metamaterial with tunable properties enabled by structural reconfigurations. Existing active metamaterials often achieve only a limited number of structural reconfigurations upon the application of an external load across the entire structure. Here, we propose a selective actuation strategy for inhomogeneous deformations of magneto-mechanical metamaterials, which allows for the integration of multiple functionalities into a single metamaterial design. Central to this actuation strategy is that a magnetic field is applied to specific unit cells instead of the entire metamaterial, and the unit cell can transform between two geometrically distinct shapes, which exhibit very different mechanical responses to elastic wave excitations. Our numerical simulations and experiments demonstrate that the tunable response of the unit cell, coupled with inhomogeneous deformation achieved through selective actuation, unlocks multifunctional capabilities of magneto-mechanical metamaterials such as tunable elastic wave transmittance, elastic waveguide, and vibration isolation. The proposed selective actuation strategy offers a simple but effective way to control the tunable properties and thus enhance the programmability of magneto-mechanical metamaterials, which also expands the application space of magneto-mechanical metamaterials in elastic wave manipulation.
{"title":"Selective Actuation Enabled Multifunctional Magneto-mechanical Metamaterial for Programming Elastic Wave Propagation","authors":"Jay Sim, Shuai Wu, Sarah Hwang, Lu Lu, Ruike Renee Zhao","doi":"arxiv-2409.07635","DOIUrl":"https://doi.org/arxiv-2409.07635","url":null,"abstract":"Active metamaterials are a type of metamaterial with tunable properties\u0000enabled by structural reconfigurations. Existing active metamaterials often\u0000achieve only a limited number of structural reconfigurations upon the\u0000application of an external load across the entire structure. Here, we propose a\u0000selective actuation strategy for inhomogeneous deformations of\u0000magneto-mechanical metamaterials, which allows for the integration of multiple\u0000functionalities into a single metamaterial design. Central to this actuation\u0000strategy is that a magnetic field is applied to specific unit cells instead of\u0000the entire metamaterial, and the unit cell can transform between two\u0000geometrically distinct shapes, which exhibit very different mechanical\u0000responses to elastic wave excitations. Our numerical simulations and\u0000experiments demonstrate that the tunable response of the unit cell, coupled\u0000with inhomogeneous deformation achieved through selective actuation, unlocks\u0000multifunctional capabilities of magneto-mechanical metamaterials such as\u0000tunable elastic wave transmittance, elastic waveguide, and vibration isolation.\u0000The proposed selective actuation strategy offers a simple but effective way to\u0000control the tunable properties and thus enhance the programmability of\u0000magneto-mechanical metamaterials, which also expands the application space of\u0000magneto-mechanical metamaterials in elastic wave manipulation.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adam McElligott, André Guerra, Alejandro D. Rey, Phillip Servio
Acoustic levitation is a container-free method for examining novel crystallization effects, though liquid-to-solid phase change has seen little investigation for levitated nanofluids. Recent developments have allowed for examining the morphological and temperature evolution of multiple levitated nanofluid droplets freezing simultaneously. The fundamental effect of adding nanoparticles to a levitated crystallization system is crystal growth rate enhancement from improved mass transfer at the growing solid front. Nucleation times are unaffected as freezing is initiated by secondary ice nucleation particles (INPs). Instead, the enhancement produces higher instantaneous nucleation pressures and more cracking in the primary ice shell. In turn, more INPs are ejected, resulting in faster protrusion formation on the droplet surface (hastened further in systems containing adjacent droplets). The crystal matrix also includes more defects, resulting in liquid escaping and forming beads at the droplet base and optical clarity loss. During crystal decomposition, thermal gradients create convective currents dampened by the same transport phenomena that enhance crystal growth. Suspension loss after a crystallization-decomposition cycle reduced opacity and light absorbance such that the droplets were 62% closer in appearance to water. However, the non-isobaric, sample-encompassing cooling process resulted in smaller particle clusters than if the droplets were frozen on a solid surface.
{"title":"Simultaneous Crystallization Effects in Multiple Levitated Plasma-Functionalized Graphene Nanoflake Nanofluid Droplets","authors":"Adam McElligott, André Guerra, Alejandro D. Rey, Phillip Servio","doi":"arxiv-2409.07555","DOIUrl":"https://doi.org/arxiv-2409.07555","url":null,"abstract":"Acoustic levitation is a container-free method for examining novel\u0000crystallization effects, though liquid-to-solid phase change has seen little\u0000investigation for levitated nanofluids. Recent developments have allowed for\u0000examining the morphological and temperature evolution of multiple levitated\u0000nanofluid droplets freezing simultaneously. The fundamental effect of adding\u0000nanoparticles to a levitated crystallization system is crystal growth rate\u0000enhancement from improved mass transfer at the growing solid front. Nucleation\u0000times are unaffected as freezing is initiated by secondary ice nucleation\u0000particles (INPs). Instead, the enhancement produces higher instantaneous\u0000nucleation pressures and more cracking in the primary ice shell. In turn, more\u0000INPs are ejected, resulting in faster protrusion formation on the droplet\u0000surface (hastened further in systems containing adjacent droplets). The crystal\u0000matrix also includes more defects, resulting in liquid escaping and forming\u0000beads at the droplet base and optical clarity loss. During crystal\u0000decomposition, thermal gradients create convective currents dampened by the\u0000same transport phenomena that enhance crystal growth. Suspension loss after a\u0000crystallization-decomposition cycle reduced opacity and light absorbance such\u0000that the droplets were 62% closer in appearance to water. However, the\u0000non-isobaric, sample-encompassing cooling process resulted in smaller particle\u0000clusters than if the droplets were frozen on a solid surface.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"127 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article proposes a source-independent method for detecting faults along Transmission Lines (TL) to reduce the protection issues arising from Inverter-Based Resources (IBRs). In the proposed method, high-frequency waves are sent from either end of a TL, and the amplitudes of the receiving waves at the other end are measured. Faults change the characteristics of TLs. Therefore, the amplitudes of the receiving waves differ when a fault occurs. Closed-form formulations are developed for describing the receiving waves before and during the faults. These formulations indicate that at least one of the receiving waves is reduced after fault inception. Therefore, faults can be detected by identifying a decrease in one of the receiving waves. To evaluate the performance of the proposed method, EMTP-RV is utilized for performing simulations. Additionally, laboratory experiments are conducted for further evaluation of the proposed method. The simulation and experimental results demonstrate that the proposed method is able to detect faults along TLs regardless of the sources supplying the grid.
{"title":"A Source-Independent Fault Detection Method for Transmission Lines","authors":"Reza Jalilzadeh Hamidi, Julio Rodriguez","doi":"arxiv-2409.07439","DOIUrl":"https://doi.org/arxiv-2409.07439","url":null,"abstract":"This article proposes a source-independent method for detecting faults along\u0000Transmission Lines (TL) to reduce the protection issues arising from\u0000Inverter-Based Resources (IBRs). In the proposed method, high-frequency waves\u0000are sent from either end of a TL, and the amplitudes of the receiving waves at\u0000the other end are measured. Faults change the characteristics of TLs.\u0000Therefore, the amplitudes of the receiving waves differ when a fault occurs.\u0000Closed-form formulations are developed for describing the receiving waves\u0000before and during the faults. These formulations indicate that at least one of\u0000the receiving waves is reduced after fault inception. Therefore, faults can be\u0000detected by identifying a decrease in one of the receiving waves. To evaluate\u0000the performance of the proposed method, EMTP-RV is utilized for performing\u0000simulations. Additionally, laboratory experiments are conducted for further\u0000evaluation of the proposed method. The simulation and experimental results\u0000demonstrate that the proposed method is able to detect faults along TLs\u0000regardless of the sources supplying the grid.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wei Zhao, Jia-He Chen, Shu-Guang Cheng, Yong Mao, Xiaojun Zhang, Zhi Tao, Hua Jiang, Zhi Hong Hang
Topological acoustics provides new opportunities for materials with unprecedented functions. In this work, we report a design of topological valley acoustic interferometers by Y-shaped valley sonic crystals. By tight-bounding calculation and experimental demonstration, we successfully tune the acoustic energy partition rate by configuring the channel. An analytical theory proposed to explain the transmission property matches well with experimental observations. An additional {pi} Berry phase is verified to accumulate circling along the shape-independent topological valley acoustic interferometer, unique in the pseudospin half systems. Based on the spectral oscillation originating from the accumulated dynamic phase and {pi} Berry phase, a simplified method to measure acoustic valley interface dispersion is explored, which overcomes the shortcomings of the traditional fast Fourier transform method and improves the measuring efficiency by simply analyzing the peaks and dips of the measured transmission spectrum. Moreover, an effective approach to tuning its transmissions, as well as the spectral line shapes proposed and realized by the local geometry design of the interferometer, exhibits strong tunability under an unchanged physical mechanism. Our work opens an avenue to design future acoustic devices with the function of sound wave manipulation based on the physical mechanism of interference and Berry phase.
拓扑声学为具有前所未有功能的材料提供了新的机遇。在这项工作中，我们报告了一种利用 Y 形山谷声波晶体设计的拓扑山谷声干涉仪。通过紧约束计算和实验证明，我们成功地通过配置通道来调节声能分配率。我们提出的解释传输特性的分析理论与实验观测结果十分吻合。额外的{pi}贝里相位被验证为沿着与形状无关的拓扑谷声学干涉仪循环累积，这在伪自旋半系统中是独一无二的。基于源于累积动态相位和{pi}贝里相位的光谱振荡，探索了一种测量声学谷界面色散的简化方法，它克服了传统快速傅里叶变换方法的缺点，并通过简单分析测量透射光谱的峰值和洼值提高了测量效率。此外，在物理机制不变的情况下，通过干涉仪的局部几何设计，提出并实现了调谐其透射率和光谱线形状的有效方法，表现出很强的可调谐性。我们的工作为未来基于干涉和贝里相的物理机制设计具有声波操纵功能的声学设备开辟了一条途径。
{"title":"Sound Wave Manipulation Based on Valley Acoustic Interferometers","authors":"Wei Zhao, Jia-He Chen, Shu-Guang Cheng, Yong Mao, Xiaojun Zhang, Zhi Tao, Hua Jiang, Zhi Hong Hang","doi":"arxiv-2409.07221","DOIUrl":"https://doi.org/arxiv-2409.07221","url":null,"abstract":"Topological acoustics provides new opportunities for materials with\u0000unprecedented functions. In this work, we report a design of topological valley\u0000acoustic interferometers by Y-shaped valley sonic crystals. By tight-bounding\u0000calculation and experimental demonstration, we successfully tune the acoustic\u0000energy partition rate by configuring the channel. An analytical theory proposed\u0000to explain the transmission property matches well with experimental\u0000observations. An additional {pi} Berry phase is verified to accumulate\u0000circling along the shape-independent topological valley acoustic\u0000interferometer, unique in the pseudospin half systems. Based on the spectral\u0000oscillation originating from the accumulated dynamic phase and {pi} Berry\u0000phase, a simplified method to measure acoustic valley interface dispersion is\u0000explored, which overcomes the shortcomings of the traditional fast Fourier\u0000transform method and improves the measuring efficiency by simply analyzing the\u0000peaks and dips of the measured transmission spectrum. Moreover, an effective\u0000approach to tuning its transmissions, as well as the spectral line shapes\u0000proposed and realized by the local geometry design of the interferometer,\u0000exhibits strong tunability under an unchanged physical mechanism. Our work\u0000opens an avenue to design future acoustic devices with the function of sound\u0000wave manipulation based on the physical mechanism of interference and Berry\u0000phase.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hannes Hempel, Martin Stolterfoht, Orestis Karalis, Thomas Unold
Photoluminescence (PL) under continuous illumination is commonly employed to assess voltage losses in solar energy conversion materials. However, the early temporal evolution of these losses remains poorly understood. Therefore, we extend the methodology to time-resolved PL, introducing the concepts of geminate PL, doping PL, and sibling PL to quantify the transient chemical potential of photogenerated electron-hole pairs and key optoelectronic properties. Analyzing the initial PL amplitudes reveals hot charge carrier separation for around 100 nm and is likely limited by the grain size of the triple cation perovskite. The following PL decay is caused by the diffusive separation of non-excitonic geminate pairs and time-resolves a fundamental yet often overlooked energy loss by increasing entropy. For triple-cation halide perovskite, we measure a "geminate correlation energy" of up to 90 meV, persisting for ~ten nanoseconds. This energy is unutilized in standard solar cells and is considered lost in the Shockley-Queisser model. Therefore, this geminate energy could substantially enhance the device's efficiency, particularly under maximum power point and low-illumination conditions.
{"title":"The Potential of Geminate Pairs in Lead Halide Perovskite revealed via Time-resolved Photoluminescence","authors":"Hannes Hempel, Martin Stolterfoht, Orestis Karalis, Thomas Unold","doi":"arxiv-2409.06382","DOIUrl":"https://doi.org/arxiv-2409.06382","url":null,"abstract":"Photoluminescence (PL) under continuous illumination is commonly employed to\u0000assess voltage losses in solar energy conversion materials. However, the early\u0000temporal evolution of these losses remains poorly understood. Therefore, we\u0000extend the methodology to time-resolved PL, introducing the concepts of\u0000geminate PL, doping PL, and sibling PL to quantify the transient chemical\u0000potential of photogenerated electron-hole pairs and key optoelectronic\u0000properties. Analyzing the initial PL amplitudes reveals hot charge carrier\u0000separation for around 100 nm and is likely limited by the grain size of the\u0000triple cation perovskite. The following PL decay is caused by the diffusive\u0000separation of non-excitonic geminate pairs and time-resolves a fundamental yet\u0000often overlooked energy loss by increasing entropy. For triple-cation halide\u0000perovskite, we measure a \"geminate correlation energy\" of up to 90 meV,\u0000persisting for ~ten nanoseconds. This energy is unutilized in standard solar\u0000cells and is considered lost in the Shockley-Queisser model. Therefore, this\u0000geminate energy could substantially enhance the device's efficiency,\u0000particularly under maximum power point and low-illumination conditions.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177773","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Negative capacitance can be used to overcome the lower limit of subthreshold swing (SS) in field effect transistors (FETs), enabling ultralow-power microelectronics, though the concept of ferroelectric negative capacitance remains contentious. In this work, we analyze the negative capacitance in ferroelectric/dielectric heterostructure rigorously using Landau-Denvonshire theory, identifying three (one) critical dielectric thicknesses for first (second) order ferroelectric phase transition upon which the stability of negative capacitance changes. A critical electric window is also identified, beyond which the ferroelectric negative capacitance cannot be maintained. Between the first and second critical thicknesses, meta-stable negative capacitance exists near zero polarization, yet it will be lost and cannot be recovered when the electric window is broken. Between the second and third critical thicknesses, stable negative capacitance always exists near zero polarization within the electric window regardless of initial polar state, resulting in hysteretic double P-E loop. Beyond the third (first) critical thickness of first (second) order phase transition, P-E loop becomes hysteresis free, though the spontaneous polarization can still be induced at sufficient large electric field. Singularities in the effective dielectric constant is also observed at the critical thickness or electric field. The analysis demonstrates that the negative capacitance of ferroelectric can be stabilized by linear dielectric within a critical electric window, and the negative capacitance can be either hysteresis free or hysteretic for first order ferroelectrics, while it is always hysteresis free for the second order ferroelectrics.
{"title":"On the negative capacitance in ferroelectric heterostructures","authors":"Yuchu Qin, Jiangyu Li","doi":"arxiv-2409.06156","DOIUrl":"https://doi.org/arxiv-2409.06156","url":null,"abstract":"Negative capacitance can be used to overcome the lower limit of subthreshold\u0000swing (SS) in field effect transistors (FETs), enabling ultralow-power\u0000microelectronics, though the concept of ferroelectric negative capacitance\u0000remains contentious. In this work, we analyze the negative capacitance in\u0000ferroelectric/dielectric heterostructure rigorously using Landau-Denvonshire\u0000theory, identifying three (one) critical dielectric thicknesses for first\u0000(second) order ferroelectric phase transition upon which the stability of\u0000negative capacitance changes. A critical electric window is also identified,\u0000beyond which the ferroelectric negative capacitance cannot be maintained.\u0000Between the first and second critical thicknesses, meta-stable negative\u0000capacitance exists near zero polarization, yet it will be lost and cannot be\u0000recovered when the electric window is broken. Between the second and third\u0000critical thicknesses, stable negative capacitance always exists near zero\u0000polarization within the electric window regardless of initial polar state,\u0000resulting in hysteretic double P-E loop. Beyond the third (first) critical\u0000thickness of first (second) order phase transition, P-E loop becomes hysteresis\u0000free, though the spontaneous polarization can still be induced at sufficient\u0000large electric field. Singularities in the effective dielectric constant is\u0000also observed at the critical thickness or electric field. The analysis\u0000demonstrates that the negative capacitance of ferroelectric can be stabilized\u0000by linear dielectric within a critical electric window, and the negative\u0000capacitance can be either hysteresis free or hysteretic for first order\u0000ferroelectrics, while it is always hysteresis free for the second order\u0000ferroelectrics.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"387 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shalaka A. Kamble, Soumen Karmakar, Somnath R. Bhopale, Sanket D. Jangale, Neha P. Gadke, Srikumar Ghorui, S. V. Bhoraskar, M. A. More, V. L. Mathe
Herein, we report a case study in which we saw the spontaneous conversion of commercial bulk graphite into LaB6 decorated carbon nanotubes (CNTs) under normal atmospheric conditions. The feedstock graphite was used as a hollow cylindrical anode filled with LaB6 powder and partially eroded in a DC electric-arc plasma reactor in pure nitrogen atmosphere. An unusual and spontaneous deformation of the plasma-treated residual anode into a fluffy powder was seen to continue for months when left to ambient atmospheric conditions. The existence of LaB6 decorated multi-walled CNTs at large quantity was confirmed in the as-generated powder by using electron microscopy, Raman spectroscopy and x-ray diffraction. The as-synthesized CNT-based large-area field emitter showed promising field-emitting properties with a low turn-on electric field of ~1.5 V per micrometer, and a current density of ~1.17 mA per square cm at an applied electric field of 3.24 V per micrometer.
在此，我们报告了一项案例研究，在该研究中，我们看到了商用块状石墨在非正常大气条件下自发转化为 LaB6 装饰碳纳米管 (CNT)。原料石墨被用作填充有 LaB6 粉末的空心圆柱形阳极，并在纯氮气氛下的直流电弧等离子体反应器中被部分腐蚀。经等离子体处理的残余阳极在环境大气条件下持续数月后，出现了不寻常的自发变形，变成了绒毛状粉末。通过使用电子显微镜、拉曼光谱和 X 射线衍射，证实在生成的粉末中存在大量 LaB6 装饰的多壁 CNT。新合成的基于碳纳米管的大面积场发射器显示出良好的场发射特性，其转一电场较低，约为每微米 1.5 V，在每微米 3.24 V 的外加电场下，电流密度约为每平方厘米 1.17 mA。
{"title":"LaB6 aided spontaneous conversion of bulk graphite into carbon nanotubes at normal atmospheric conditions","authors":"Shalaka A. Kamble, Soumen Karmakar, Somnath R. Bhopale, Sanket D. Jangale, Neha P. Gadke, Srikumar Ghorui, S. V. Bhoraskar, M. A. More, V. L. Mathe","doi":"arxiv-2409.06410","DOIUrl":"https://doi.org/arxiv-2409.06410","url":null,"abstract":"Herein, we report a case study in which we saw the spontaneous conversion of\u0000commercial bulk graphite into LaB6 decorated carbon nanotubes (CNTs) under\u0000normal atmospheric conditions. The feedstock graphite was used as a hollow\u0000cylindrical anode filled with LaB6 powder and partially eroded in a DC\u0000electric-arc plasma reactor in pure nitrogen atmosphere. An unusual and\u0000spontaneous deformation of the plasma-treated residual anode into a fluffy\u0000powder was seen to continue for months when left to ambient atmospheric\u0000conditions. The existence of LaB6 decorated multi-walled CNTs at large quantity\u0000was confirmed in the as-generated powder by using electron microscopy, Raman\u0000spectroscopy and x-ray diffraction. The as-synthesized CNT-based large-area\u0000field emitter showed promising field-emitting properties with a low turn-on\u0000electric field of ~1.5 V per micrometer, and a current density of ~1.17 mA per\u0000square cm at an applied electric field of 3.24 V per micrometer.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jiri Houska, Mariia Zhadko, Radomir Cerstvy, Deepika Thakur, Petr Zeman
The non-equilibrium atom-by-atom growth of Cu-rich Cu-Zr thin films has been investigated by a combination of magnetron sputter deposition and molecular dynamics simulations. We focus on the role of Zr in the transition from large solid solution crystals through a nanocomposite (around ~5 at.% Zr) to a metallic glass. We find, contrary to the assumption based on equilibrium phase diagram, that in this nonequilibrium case most of the grain refinement and most of the hardness enhancement (from 2.5-3 to 4-5 GPa) takes place in the compositional range (up to ~3 at.% Zr) where many or even most Zr atoms (depending on the sputtering regime) are in the supersaturated solid solution rather than at the grain boundaries. The results are important for the design and understanding of technologically important nanostructured metallic films. In parallel, from the methodology point of view, the results include an early example of modelling the atom-by-atom nanocomposite growth.
{"title":"Role of Zr in Cu-rich single-phase and nanocomposite Cu-Zr: molecular dynamics and experimental study","authors":"Jiri Houska, Mariia Zhadko, Radomir Cerstvy, Deepika Thakur, Petr Zeman","doi":"arxiv-2409.06582","DOIUrl":"https://doi.org/arxiv-2409.06582","url":null,"abstract":"The non-equilibrium atom-by-atom growth of Cu-rich Cu-Zr thin films has been\u0000investigated by a combination of magnetron sputter deposition and molecular\u0000dynamics simulations. We focus on the role of Zr in the transition from large\u0000solid solution crystals through a nanocomposite (around ~5 at.% Zr) to a\u0000metallic glass. We find, contrary to the assumption based on equilibrium phase\u0000diagram, that in this nonequilibrium case most of the grain refinement and most\u0000of the hardness enhancement (from 2.5-3 to 4-5 GPa) takes place in the\u0000compositional range (up to ~3 at.% Zr) where many or even most Zr atoms\u0000(depending on the sputtering regime) are in the supersaturated solid solution\u0000rather than at the grain boundaries. The results are important for the design\u0000and understanding of technologically important nanostructured metallic films.\u0000In parallel, from the methodology point of view, the results include an early\u0000example of modelling the atom-by-atom nanocomposite growth.","PeriodicalId":501083,"journal":{"name":"arXiv - PHYS - Applied Physics","volume":"59 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142177772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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