Author Affiliations
Abstract
1 School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing 100084, China
2 Zhuhai Huafa Properties Co., Ltd, Zhuhai 519030, China
Phase-change material (PCM) is widely used in thermal management due to their unique thermal behavior. However, related research in thermal rectifier is mainly focused on exploring the principles at the fundamental device level, which results in a gap to real applications. Here, we propose a controllable thermal rectification design towards building applications through the direct adhesion of composite thermal rectification material (TRM) based on PCM and reduced graphene oxide (rGO) aerogel to ordinary concrete walls (CWs). The design is evaluated in detail by combining experiments and finite element analysis. It is found that, TRM can regulate the temperature difference on both sides of the TRM/CWs system by thermal rectification. The difference in two directions reaches to 13.8 K at the heat flow of 80 W/m2. In addition, the larger the change of thermal conductivity before and after phase change of TRM is, the more effective it is for regulating temperature difference in two directions. The stated technology has a wide range of applications for the thermal energy control in buildings with specific temperature requirements.
phase change composites controllable thermal rectification building applications Journal of Semiconductors
2024, 45(2): 022301
1 College of Science, Hunan Province Key Laboratory of Materials Surface & Interface Science and Technology, Central South University of Forestry and Technology, Changsha 410004, Hunan, China
2 College of Science, Jiujiang University, Jiujiang 332005, Jiangxi, China
The immunity of topological states against backscattering and structural defects provides them with a unique advantage in the exploration and design of high-precision low-loss optical devices. However, the operating bandwidth of the topological states in certain photonic structures is difficult to actively tune and flexibly reconfigure. In this study, we propose a valley topological photonic crystal (TPC) comprising two inverse honeycomb photonic crystals, consisting of hexagonal silicon and Ge2Sb2Te5 (GST) rods. When GST transitions from the amorphous phase to the crystalline phase, the edge band of the TPC appears as a significant redshift and is inversed from a"∪"to an"∩"shape with topological phase transition, which enables active tuning of the operating bandwidth and propagation direction of topological edge states. Both the topological edge and corner states in a triangular structure constructed using TPCs can be simultaneously adjusted and reconfigured via GST phase transition, along with a change in the group number of corner states. Using the adjustability of topological edge states and electromagnetic coupling between two different topological bearded interfaces, we develop a multichannel optical router with a high tuning degree of freedom, where channels can be actively reconfigured and their on/off states can be freely switched. Our study provides a strategy for the active regulation of topological states and may be beneficial for the development of reconfigurable topological optical devices.
topological edge states topological corner states phase change material active reconfiguration topological photonic crystal 激光与光电子学进展
2024, 61(5): 0536001
郑州轻工业大学 物理与电子工程学院,郑州 450001
为了实现红外吸收波长的主动调控,提出一种Ge2Sb2Te5(GST)相变材料的可调谐金属/介质/金属(MDM)型近红外光学超构表面吸收器。首先,采用时域有限差分(FDTD)法对器件的吸收性能进行仿真分析;然后,根据电场分布特点分析了吸收器等离子体震荡吸收的物理机制。仿真结果表明:当改变GST的晶化分数时,所提吸收器实现了吸收峰中心位置从1.17 μm偏移到1.8 μm,偏移宽度为630 nm,吸收器在通信波长为1.55μm时可以实现高-低吸收率的转换。
超构表面 吸收器 Ge2Sb2Te5相变材料 metasurface, absorber, Ge2Sb2Te5 phase change mate
近年来,随着弹载电子设备集成度越来越高,内部热耗不断增加,如何实现设备的高效热管理,成为制约弹载电子设备进一步发展的重大难题。该文提出了一种应用于大功率弹载微波组合的相变储热模块,通过仿真分析手段研究了储热模块主体结构对储热模块整体储热性能的影响。综合考虑可制造性、质量、储热能力等多方面因素后,确认了储热模块的结构形式和最终选用的相变介质材料。利用增材制造技术加工出储热模块样品,并搭建热测试平台完成了该样品的散热效果评估。实验表明,在60 ℃环境下,模块总热耗为211 W,工作10 min后,模块表面最高温度为104.1 ℃,满足组合使用要求。该储热设计技术有效地解决了模块短时大功率下温升过高的问题,在弹载电子设备热管理领域有着广阔的应用前景。
相变材料 储热模块 弹载 散热能力 phase change materials heat storage module missile-borne meat dissipation capacity
青海大学,新能源光伏产业研究中心,西宁 810016
为提升水合盐相变材料的性能,以Na2SO4·10H2O-Na2HPO4·12H2O共晶盐(EHS)作为基体材料,采用HF/HNO3刻蚀法制备亲水性纳米碳化硅(Nano-SiC),并以Na2SiO3·9H2O和改性Nano-SiC作为复合添加剂制备复合纳米相变流体材料(Nano-SiC EHS PCMs)。结果表明:改性后Nano-SiC在EHS PCMS中具有良好的分散稳定性,同时Na2SiO3·9H2O和Nano-SiC 协同作用下使得EHS PCMs过冷度降低到0.3 ℃,无相分层现象。Nano-SiC EHS PCMs在固液相变体系中热导率均有提升,同时添加0.2% (质量分数)Nano-SiC后EHS PCMS储能时间缩短了21.8%。添加质量分数为0.15% Nano-SiC的EHS PCMs熔融焓和结晶焓分别为267.3 J/g和231.4 J/g,经过1 000次冷热循环后焓值变化甚小,该体系具有良好的循环稳定性。
纳米碳化硅 表面改性 共晶盐 纳米相变流体 nano silicon carbide surface modified eutectic hydrated salt phase change nanofluids
1 华南师范大学生物光子学研究院,激光生命科学教育部重点实验室,广东 广州 510631
2 华南师范大学生物光子学研究院,广东省激光生命科学重点实验室,广东 广州 510631
温度响应型纳米材料作为造影剂的巨大潜力推动了近年来光声成像领域的研究和发展,然而,目前报道的温度响应型纳米探针的响应温度超过了人体可以容忍的范围,同时可逆性低,这两个问题是其实际应用的严重障碍,影响了其有效成像和长期监测的效果。鉴于此,笔者设计了一种聚(N-异丙基丙烯酰胺)(PNIPAM)包裹金纳米棒(AuNR)的温度响应型相变纳米探针AuNR@PNIPAM,其可在生理温度附近表现出增强且可切换的近红外二区光吸收,实现对肿瘤的高对比度成像。当AuNR@PNIPAM微凝胶热靶向到肿瘤组织后,金纳米棒核吸收近红外光能量触发PNIPAM壳相变。当温度高于PNIPAM的体积相变温度时,PNIPAM水凝胶经历溶胀到坍缩的体积相变,使金纳米棒周围的折射率变大,诱导微凝胶的局域表面等离子体共振峰发生红移并使其吸收峰强度增大。体内外实验均证明,利用所制备的AuNR@PNIPAM微凝胶,在外部近红外光刺激下动态调制温度场,可以获得对比度增强的光声图像。本工作可为开发温度响应型智能光声纳米探针从而增强成像对比度提供一定的参考。
生物光学 温度响应 相变 聚(N-异丙基丙烯酰胺) 对比度增强 中国激光
2023, 50(21): 2107104
国防科技大学电子科学学院,湖南 长沙 410073
当前物联网、云计算等产生的海量非结构化数据,极大提高了对数据处理算力和能效的需求。神经形态计算借鉴生物大脑的信息处理方式,以神经元与神经突触为基本单元,从互联架构与信息处理模式等方面模拟生物神经系统,能够实现实时、超低功耗信息处理,成为大数据时代计算技术发展的前沿热点。其中,光子神经形态计算技术是在光域上进行神经形态计算数据处理的技术,既能够充分发挥光子高速传输、低功耗、高并行度的优势,又能够避免光电和电光转换带来的额外时间功耗开销,具有很大的研究和应用价值。近年来,相变材料作为一种具有高折射率对比度和非易失特性的光学材料,可在光、电、热等激励作用下进行折射率的连续调节,为非易失光子神经形态计算提供了一种可行的解决方案,成为当前的研究热点。本文首先介绍了光子神经形态计算的基本原理和实现方法,在此基础上讨论了相变材料用于光子神经形态计算的原理。其次,针对不同类型的实现途径,研究了不同相变材料的特点和选型办法,综合分析了当前应用较多的两类相变材料以及各类光突触器件和阵列集成应用。最后对基于相变材料的光子神经形态计算技术的发展进行了展望。
材料 相变材料 神经形态计算 光神经网络 激光与光电子学进展
2023, 60(21): 2100007