Luo Xiao, Luan Yuxuan, Cai Yutian, Shen Sheng
Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA.
Sci Rep. 2021 Mar 11;11(1):5765. doi: 10.1038/s41598-021-85140-6.
In this work, we demonstrate two types of heterogeneous irradiated-pristine polyethylene nanofiber junctions, 'heavily-irradiated-pristine' (HI-P) and 'lightly-irradiated-pristine' (LI-P) junctions, as high-performance solid-state thermal diodes. The HI-P junction rectifies heat flux in a single direction, while the LI-P junction shows dual-directional rectification under different working temperatures. We accurately model the phase transition of polyethylene nanofibers with a finite temperature range rather than a step function. The finite-temperature-range model suggests that the rectification factor increases with temperature bias and there is a minimum threshold of temperature bias for notable rectification. Besides, the finite-temperature-range model shows better prediction for the heat flow data from experiments, while the step function model tends to overestimate the rectification performance around the optimal length fraction of irradiation. Although both the models show that an optimal rectification occurs when the interface temperatures in the forward and the reverse biases are equal, the optimized rectification factor is determined by the temperature bias and the temperature range of phase transition. This work elucidates the influence of both the temperature bias and the temperature range of phase transition on thermal rectification performance, which could incredibly benefit the evaluation and design of thermal diodes.
在这项工作中，我们展示了两种类型的异质辐照 - 原始聚乙烯纳米纤维结，即“重辐照 - 原始”（HI - P）结和“轻辐照 - 原始”（LI - P）结，作为高性能固态热二极管。HI - P结在单一方向上整流热流，而LI - P结在不同工作温度下表现出双向整流。我们用有限温度范围而非阶跃函数精确模拟了聚乙烯纳米纤维的相变。有限温度范围模型表明，整流因子随温度偏置增加，并且存在显著整流的最小温度偏置阈值。此外，有限温度范围模型对实验热流数据的预测更好，而阶跃函数模型在辐照的最佳长度分数附近往往高估整流性能。尽管两个模型都表明当正向和反向偏置下的界面温度相等时会出现最佳整流，但优化的整流因子由温度偏置和相变温度范围决定。这项工作阐明了温度偏置和相变温度范围对热整流性能的影响，这对热二极管的评估和设计可能极为有益。
