Wang Song, Cottrill Anton L, Kunai Yuichiro, Toland Aubrey R, Liu Pingwei, Wang Wen-Jun, Strano Michael S
Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA, USA.
Phys Chem Chem Phys. 2017 May 24;19(20):13172-13181. doi: 10.1039/c7cp02445b.
Thermal diodes, or devices that transport thermal energy asymmetrically, analogous to electrical diodes, hold promise for thermal energy harvesting and conservation, as well as for phononics or information processing. The junction of a phase change material and phase invariant material can form a thermal diode; however, there are limited constituent materials available for a given target temperature, particularly near ambient. In this work, we demonstrate that a micro and nanoporous polystyrene foam can house a paraffin-based phase change material, fused to PMMA, to produce mechanically robust, solid-state thermal diodes capable of ambient operation with Young's moduli larger than 11.5 MPa and 55.2 MPa above and below the melting transition point, respectively. Moreover, the composites show significant changes in thermal conductivity above and below the melting point of the constituent paraffin and rectification that is well-described by our previous theory and the Maxwell-Eucken model. Maximum thermal rectifications range from 1.18 to 1.34. We show that such devices perform reliably enough to operate in thermal diode bridges, dynamic thermal circuits capable of transforming oscillating temperature inputs into single polarity temperature differences - analogous to an electrical diode bridge with widespread implications for transient thermal energy harvesting and conservation. Overall, our approach yields mechanically robust, solid-state thermal diodes capable of engineering design from a mathematical model of phase change and thermal transport, with implications for energy harvesting.
热二极管，即类似于电二极管那样不对称传输热能的器件，在热能收集与节约以及声子学或信息处理方面具有应用前景。相变材料与相不变材料的结可以形成一个热二极管；然而，对于给定的目标温度，尤其是接近环境温度时，可用的组成材料有限。在这项工作中，我们证明了一种微孔和纳米孔聚苯乙烯泡沫可以容纳一种与聚甲基丙烯酸甲酯（PMMA）融合的石蜡基相变材料，以生产出机械性能强劲的固态热二极管，其能够在环境温度下工作，在熔点以上和以下的杨氏模量分别大于11.5兆帕和55.2兆帕。此外，复合材料在组成石蜡的熔点以上和以下时热导率有显著变化，并且其整流特性可以由我们之前的理论和麦克斯韦 - 欧肯模型很好地描述。最大热整流比范围为1.18至1.34。我们表明，此类器件的性能足够可靠，能够在热二极管桥中运行，热二极管桥是一种动态热电路，能够将振荡温度输入转换为单极性温度差——类似于具有广泛影响的电二极管桥，可用于瞬态热能收集与节约。总体而言，我们的方法能够从相变和热传输的数学模型出发，生产出机械性能强劲的固态热二极管，这对能量收集具有重要意义。
