微米尺度导热与界面有序孔洞隔热协同的集热超构材料研究

The efficiency of thermoelectric generator in low-grade thermal energy utilization is still relatively low because of the difficulty to establish a large temperature difference. In order to solve this problem, it is vital to enhance the heat flux at the hot side of thermoelectric generator via thermal concentration technology. An interesting and novel idea is to introduce the thermal metamaterial methods that are used for sound manipulation to the concentration of heat flux. Thermal metamaterial is commonly build with alternant layered structure by using material with high and low thermal conductivity respectively. In order to enhance the thermal concentration efficiency of thermal metamaterial, the key issue is the realization of directional thermal flow in heat conduction channel. Thus, the control of the shape and size for the layers, as well as the thermal resistance for the heterogenous interface is vital. The method of decreasing the layer thickness to microscale and introducing orderly porous interface will both limit the heat transfer to the desired channel and hence imcrease the thermal concentration efficiency. In this application, the mask-assisted deposition and screen-printing technology will be adopted to prepare the micro-scale laminated structure. And the orderly porous interface will be constructed using regional hole self-assembly technology, aiming at an enhancement of the thermal concentration efficiency. Then, we will study the effect on the heat flux distribution from the layer size, configuration and interfacial resistance. The controllable fabrication method of desired thermal metamaterial also will be investigated. Finally, this work can provide an effective thermal concentration method for high-efficiency thermoelectric conversion in low-grade thermal energy utilization.

当前制约低品位热能利用中热电发电效率的瓶颈是器件两端大温差建立和保持，关键在于发展新型高效传热集热手段，实现器件热端的热流聚集。热超构材料是一种利用高导热和高隔热材料交替层叠排列形成复合结构材料，其表现出的热能富集功能为热电器件大温差的建立提供了新思路。目前热超构材料仍存在集热效率较低的问题，关键在于提高超构材料中导热通道热传导的定向性，其中多层结构的形状和尺寸控制，以及多层异质界面热阻调控是核心。而热超构材料中叠层结构厚度降低至微米尺度，协同基于有序孔洞设计的高阻界面构筑，有望提升热传导微区可控定向性，提高集热效率。因此本申请拟采用掩膜沉积印刷和区域有序孔洞形成技术，制备微米尺度导热和界面有序孔洞隔热的集热超构材料，研究结构排布、叠层尺寸与界面热阻等对热传递性能的影响关系，完善具有微米尺度和高阻界面的集热超构材料的可控制备方法，为低品位热能高效热电转化的实现提供新型集热手段。

本项目以定向的叠层超结构作为热功能基元，根据稳态热传导方程和变换热力学模拟对基本结构的热流调控和热超结构的新颖热现象进行了理论和实验上的研究和分析。首先采用数值计算的方法研究了在稳态情况下材料热导率、叠层尺寸以及界面热阻对该结构的温度分布，特别是对热流偏转角度的调控效率的影响，并进一步从宏观和微观尺度对其模拟结果进行了实验验证。结果表明：增大两种叠层材料热导率的比值以及构筑高阻界面，同时增加有效区域内的叠层密度，对提高热超构材料的热流调控效率起到关键作用；发展了一种基于超短脉冲激光微米尺度叠层超结构的高效低成本的可控制备方法，实现了小尺寸的高密度叠层超结构的制备；最后利用变换热力学理论设计了两种分别以热功能基元排列组合而成的具有新颖热功能的新型热功能器件——热斗蓬和热聚集器，通过对其结构的进一步优化设计，实现了对热的高效聚集和有效屏蔽。通过进一步对叠层结构热功能基元进行优化和设计，将会在热管理方面发挥出更大的潜在应用，如芯片冷却、太阳能电池集热和建立温差较大的热电装置等。