Nano engineering and thermophysics
从燧人氏钻木取火开始, 人类文明的发展就和“热能”息息相关. 现代科技史上, 瓦特改良的蒸汽机奠定了工业革命. 1822年, 傅里叶提出导热定律和传热方程的数学解法, 由此发展的傅里叶变换广泛应用在诸如音频、图像处理等众多领域. 到了 20世纪初, 普朗克关于黑体辐射的研究成为量子力学的开端. 2020年开始的新冠病毒疫情之后, 利用高温杀灭空气中的病毒也获得不少关注.
作为一个历久弥新的学科, 在科技发展日新月异的今天, 关于热的基础研究和前沿应用也在不断推进. 2005年, 《科学》杂志在创刊 125周年之际提出的 125个科学前沿问题中, 就包括地球这个巨系统的热能平衡问题:“温室效应会使地球温度上升多高? ” 2021年, 日裔美籍科学家真锅淑郎和德国科学家克劳斯·哈塞尔曼因“建立地球气候的物理模型、量化其可变性并可靠地预测全球变暖”的相关研究获得诺贝尔物理学奖. 同年, 上海交通大学携手《科学》杂志再次提出了 125个科学新问题, 特别关注了“物质传热的极限是什么? ”这个热物理的基础问题. 可以预见, 对于热物理深层机理的研究必将引发新的技术革新.
在电力紧缺的今天, 全球约 60%的能源都以废热的形式白白浪费. 从这个角度来讲, 热物理的进展对于我国最近强调的“碳达峰、碳中和”至关重要. 根据这一战略目标, 我国力争于 2030年二氧化碳排放达到峰值, 2060年实现碳中和. “双碳”目标与我国建成社会主义现代化强国的第二个百年奋斗目标相呼应. “十四五”作为“双碳”目标提出后的第一个五年规划期, 也是实现“双碳”目标的关键期和窗口期. 要实现这一伟大目标, 必须以能源科技创新为先导.
而在利用的和废弃的能源中, 占比最大的都是热能. 关于热能的研究涉及材料、电子器件、生物、能源等诸多学科, 纳米工程的引入为热物理的进展注入了新的活力. 除了废热回收, 微纳米电子器件、电池中的过热问题会直接影响其性能和使用寿命, 成为 5G、量子计算、芯片、电动汽车等国家战略技术领域目前的研究热点. 作为工程应用的基础, 我们对于热物理、尤其是纳米工程中热物理的认知还是远远不够的. 因此, 物理、工程、材料、电子等多学科的交叉研究将在上述新兴领域大有用武之地.
鉴于纳米关键热物理问题研究的挑战性与紧迫性, 《物理学报》特组织本专题, 并邀请国内外活跃在相关领域前沿的中青年专家撰稿, 从多个角度、跨学科、深入浅出地介绍最新热点研究成果并探讨基础科学和工程应用中的问题, 包括仿生辐射制冷、导热智能材料及应用、纳米相变材料与储热、量子技术需要的稀释制冷机、固体锂电池热管理、第三代半导体和芯片热管理、声子弱耦合与热输运和热调控等.
在此, 我们乐于和读者分享这些热物理的前沿进展, 也希望这些工作在不久的将来会深刻地影响人类的生活.
作为一个历久弥新的学科, 在科技发展日新月异的今天, 关于热的基础研究和前沿应用也在不断推进. 2005年, 《科学》杂志在创刊 125周年之际提出的 125个科学前沿问题中, 就包括地球这个巨系统的热能平衡问题:“温室效应会使地球温度上升多高? ” 2021年, 日裔美籍科学家真锅淑郎和德国科学家克劳斯·哈塞尔曼因“建立地球气候的物理模型、量化其可变性并可靠地预测全球变暖”的相关研究获得诺贝尔物理学奖. 同年, 上海交通大学携手《科学》杂志再次提出了 125个科学新问题, 特别关注了“物质传热的极限是什么? ”这个热物理的基础问题. 可以预见, 对于热物理深层机理的研究必将引发新的技术革新.
在电力紧缺的今天, 全球约 60%的能源都以废热的形式白白浪费. 从这个角度来讲, 热物理的进展对于我国最近强调的“碳达峰、碳中和”至关重要. 根据这一战略目标, 我国力争于 2030年二氧化碳排放达到峰值, 2060年实现碳中和. “双碳”目标与我国建成社会主义现代化强国的第二个百年奋斗目标相呼应. “十四五”作为“双碳”目标提出后的第一个五年规划期, 也是实现“双碳”目标的关键期和窗口期. 要实现这一伟大目标, 必须以能源科技创新为先导.
而在利用的和废弃的能源中, 占比最大的都是热能. 关于热能的研究涉及材料、电子器件、生物、能源等诸多学科, 纳米工程的引入为热物理的进展注入了新的活力. 除了废热回收, 微纳米电子器件、电池中的过热问题会直接影响其性能和使用寿命, 成为 5G、量子计算、芯片、电动汽车等国家战略技术领域目前的研究热点. 作为工程应用的基础, 我们对于热物理、尤其是纳米工程中热物理的认知还是远远不够的. 因此, 物理、工程、材料、电子等多学科的交叉研究将在上述新兴领域大有用武之地.
鉴于纳米关键热物理问题研究的挑战性与紧迫性, 《物理学报》特组织本专题, 并邀请国内外活跃在相关领域前沿的中青年专家撰稿, 从多个角度、跨学科、深入浅出地介绍最新热点研究成果并探讨基础科学和工程应用中的问题, 包括仿生辐射制冷、导热智能材料及应用、纳米相变材料与储热、量子技术需要的稀释制冷机、固体锂电池热管理、第三代半导体和芯片热管理、声子弱耦合与热输运和热调控等.
在此, 我们乐于和读者分享这些热物理的前沿进展, 也希望这些工作在不久的将来会深刻地影响人类的生活.
2021, 70 (23): 230202.
doi: 10.7498/aps.70.20211760
Abstract +
In the research of cryogenic physics and quantum information science, it is essential to maintain a steady low temperature of millikelvin regime continuously. Dilution refrigerator is a widely used refrigeration device to achieve extremely low temperature. It utilizes the phase separation effect of superfluid 4He and its isotope 3He mixed solution at ultra-low temperatures. The performance of heat exchanger is the key factor to determine the performance of continuous cycle refrigerating machine. At extremely low temperatures, there appears a huge interfacial thermal resistance between helium and metal (Kapitza resistance), and the problem of heat exchange can be effectively solved by using the porous sintered metal particles to increase the contact area. Therefore, it is of significance to study the heat exchange between metal particles and liquid helium at extremely low temperature and to develop the relevant high-performance sintered Ag powder heat exchanger.
2021, 70 (23): 236502.
doi: 10.7498/aps.70.20211662
Abstract +
The history of semiconductor materials is briefly reviewed in this work. By taking GaN-based high electron mobility transistor as an example, the heat generation mechanisms and thermal management strategies of wide bandgap semiconductor devices are discussed. Moreover, by taking β-Ga2O3 as an example, the thermal management challenges of emerging ultrawide bandgap semiconductors are briefly discussed. The following discussions focus on the interfacial thermal transport which widely exists in the semiconductor devices mentioned above. The recent advancements in room-temperature wafer bonding for thermal management applications are summarized. Furthermore, some open questions about the physical understanding of interfacial thermal transport are also mentioned. Finally, the theoretical models for calculating thermal boundary conductance are reviewed and the challenges and opportunities are pointed out.
2022, 71 (1): 014401.
doi: 10.7498/aps.71.20211889
Abstract +
Effective thermal control technologies are increasingly demanded in various application scenarios like spacecraft systems. Thermal conductivities of materials play a key role in thermal control systems, and one of the basic requirements for the materials is their reversibly tunable thermal properties. In this paper, we briefly review the recent research progress of the thermal smart materials in the respects of fundamental physical mechanisms, thermal switching ratio, and application value. We focus on the following typical thermal smart materials: nanoparticle suspensions, phase change materials, soft materials, layered materials tuned by electrochemistry, and materials tuned by specific external field. After surveying the fundamental mechanisms of thermal smart devices, we present their applications in spacecraft and other fields. Finally, we discuss the difficulties and challenges in studying the thermal smart materials, and also point out an outlook on their future development.
2022, 71 (1): 016501.
doi: 10.7498/aps.71.20211776
Abstract +
The present paper briefly reviews the development progress of solid-liquid phase change materials, particularly the nano-porous shape-stabilized phase change materials. We outline the designs and syntheses of the heat storage functional materials and the thermophysical mechanism of loading, crystallization, and thermal transport in nano-confined space. Besides, the remarkable methods to enhance the heat storage and release performance of heterogeneous materials are included. However, at present, the single-size porous materials cannot satisfy the requirements for high heat storage/release rate and great thermal energy density simultaneously. Based on this, the novel hierarchical porous frameworks materials are explored to overcome these obstacles. For this purpose, some scientific problems, opportunities, and challenges are summarized at the end of this paper.
2022, 71 (2): 024401.
doi: 10.7498/aps.71.20211854
Abstract +
As a new type of cooling technology, radiative cooling achieves temperature reduction through spectral regulation. Compared with the traditional active cooling technologies such as absorption-based cooling and compression-based cooling, the radiative cooling offers unique advantages, which are of great significance in environmental protection and energy utilization. First of all, the basic principle of radiative cooling and the radiative cooling within the natural biological systems are introduced in this review. The biological systems achieve their regulations of radiative cooling through controlling the materials, microstructures and behaviors in the systems, which also provide inspiration for us to explore new radiative cooling materials and devices. We also summarize the various mechanisms of radiative cooling in the biological systems and the optimization of such cooling structures. The recent research progress of bio-inspired radiative cooling is also presented. At the end, the outlook of the research directions, potential applications, and the material fabrication approaches for bio-inspired radiative cooling are discussed. The radiative cooling materials and devices with high power output and intelligent control should be an important development direction of bio-inspired radiative cooling in the future. With the integration of advanced micro/nano fabrication technology, bio-inspired radiative cooling will have a broader market and much room of applications in the future.
2022, 71 (2): 026501.
doi: 10.7498/aps.71.20211887
Abstract +
This paper briefly describes the characteristics of all-solid-state lithium-ion battery and the significance of investigation on the internal thermal transport. The related experimental and theoretical works on the thermal transport properties of cathode materials, anode materials, solid-state electrolytes, and electrode-electrolyte interfaces are introduced and summarized. In view of the unclear mechanism of the influence of lithium insertion and extraction process on the thermal conductivity of electrode materials, the challenge of solid-state amorphization to the research of thermal transport, and the limitation of models and methods in heat transport across the interface, we systematically sort out the important scientific issues of thermal transport in all-solid-state lithium-ion battery.
2022, 71 (2): 023601.
doi: 10.7498/aps.71.20211876
Abstract +
2022, 71 (8): 086302.
doi: 10.7498/aps.71.20220036
Abstract +
With the development of nanoscale thermophysics, a vast number of novel phenomena have emerged, which closely relate to phonon weak couplings. The causes of phonon weak couplings mechanism and related physical discoveries are discussed in this article, including the size effect of low-dimensional systems, multi-temperature model, and van der Waals cross interfaces. Corresponding frontier researches are also summarized. The current problems of phonon weak couplings, such as how to add phonon wave-like behaviors into the theoretical model, are also briefly discussed and prospected.
2022, 71 (8): 089201.
doi: 10.7498/aps.71.20212277
Abstract +
Icing, frosting, and fogging are all natural phenomena in cold climates, which bring a lot of inconvenience and safety problems to our daily life and industry when formed on the infrastructures. Solar-thermal anti-icing, anti-frosting or anti-fogging surfaces have attracted a lot of interest due to their effectiveness and green ecofriendly features in comparison with the conventional mechanical, thermal, and chemical methods. This short review aims at summarizing the recent progress of solar-thermal anti-fogging/anti-icing/anti-frosting surfaces. First of all, both the fundamental of solar-thermal energy conversion and the mechanism of solar-thermal anti-fogging/anti-icing/anti-frosting are introduced. After that, recent advances in solar-thermal anti-fogging surfaces, and superhydrophobic solar-thermal anti-icing/anti-frosting surfaces are summarized according to the categories of photothermal materials. The results of our collaborative research groups in this field are highlighted in this review. In the end, through comparing those reported surfaces, we point out the bottlenecks in the existing researches of this field, and suggest the potential significant research directions in the future.
2022, 71 (16): 166501.
doi: 10.7498/aps.71.20220306
Abstract +
With the rapid increase of the thermal power density of microelectronic devices and circuits, controlling its temperature has become an urgent need for the development and application of the electronic industry. By virtue of the ultrahigh thermal conductivity of graphene, developing high-performance graphene-based composite thermal interface materials has attracted much research attention and become one of hot research topics. The understanding of phonon transport mechanism in graphene-based composites at atomic scale can be helpful to enhance the heat conductive capability of composites systems. In this review, focused on graphene-based thermal interfaces materials, the heat conduction mechanism and the regulating strategy are introduced on both the internal thermal resistance and interfacial thermal resistance. Finally, the reseach progress and opportunities for future studies are also summarized.
2022, 71 (16): 168401.
doi: 10.7498/aps.71.20220757
Abstract +
Epidemic viruses seriously affect human health and the normal operation of society, so it is particularly important to effectively kill viruses. In this work, the thermal performance of a thermoelectric air disinfection system are studied. Utilizing the characteristics of semiconductor thermoelectric sheets with both cold and hot ends, the system can increase the air temperature by heating (cound be used in sterilization), and then, reduce the temperature of the air by cooling. The measurement results show that the air temperature can be increased to 80 ℃ first, and then cooled to 35 ℃. The total energy utilization rate of the system can reach up to 1.2. In addition, combined with the measurement results and numerical calculations, the parameters such as the number of thermoelectric element series, input power, air flow, and boundary insulation can be used to analyze their effects on the system performance. The system may have broad potential applications in public health, medical care, and household disinfection.
2023, 72 (3): 034401.
doi: 10.7498/aps.72.20221981
Abstract +
The acoustic mismatch model and diffuse mismatch model are widely used to calculate interfacial thermal conductance. These two models are respectively based on the assumption of extremely smooth and rough interfaces. Owing to the great difference between the actual interface structure and the two hypotheses, the predictions of these two models deviate greatly from the actual interfacial thermal conductance. The recently proposed mixed mismatch model considers the effect of interface structure on the ratio of phonon specular transmission to diffuse scattering transmission, and the prediction accuracy is improved. However, this model requires molecular dynamics simulation to obtain phonon information at the interface. In this work, the mixed mismatch model is simplified by introducing the measured roughness value, and the influence of interface structure on the contact area is taken into account to achieve a simple, fast and accurate prediction of interface thermal conductance. Based on this model, the interfacial thermal conductances of metals (aluminum, copper, gold) and semiconductors (silicon, silicon carbide, gallium arsenide, gallium nitride) are calculated and predicted. The results of Al/Si interface are in good agreement with the experimental results. This model is helpful not only in understanding the mechanism of interface heat conduction, but also in comparing with the measurement results.
