Thermal management by manipulating electromagnetic parameters

Electromagnetic absorbing materials may convert electromagnetic energy into heat energy and dissipate it.However,in a high-power electromagnetic radiation environment,the temperature of the absorbing material rises significantly and even burns.It becomes critical to ensure electromagnetic absorption performance while minimizing temperature rise.Here,we systematically study the coupling mechanism between the electromagnetic field and the temperature field when the absorbing material is irradiated by electromagnetic waves.We find out the influence of the constitutive parameters of the absorbing materials(including uniform and non-uniform)on the temperature distribution.Finally,through a smart design,we achieve better absorption and lower temperature simultaneously.The accuracy of the model is affirmed as simulation results aligned with theoretical analysis.This work provides a new avenue to control the temperature distribution of absorbing materials.

Multifunctional Composite Material with Efficient Microwave Absorption and Ultra-High Thermal Conductivity

The increasing demands for electronic devices to achieve high miniaturization,functional integration,and wide bandwidth will exacerbate the heat generation and electromagnetic interference,which hinders the further development of electronic devices.Therefore,both the issues of microwave absorption and heat dissipation of materials need to be addressed simultaneously.Herein,a multifunctional composite material is proposed by periodic arrangement of copper pillars in a matrix,based on the wave-absorbing material.As a result,the equivalent thermal conductivity of the composite structure is nearly 35 times higher than the wave-absorbing matrix,with the area filling proportion of the thermal conductivity material being 3.14%.Meanwhile,the reflectivity of the composite structure merely changes from-15.05 d B to-13.70 d B.It is proved that the designed composite structure possesses both high thermal conduction and strong microwave absorption.The measured results accord well with the simulation results,which demonstrates that the thermal conductivity of the composite structure can reach more than 10 W·m^(-1)·K^(-1)without significant deterioration of the absorption performance.

Ultra-Broadband Infrared Metamaterial Absorber for Passive Radiative Cooling

Infrared metamaterial absorber(MMA) based on metal-insulator-metal(MIM) configuration with flexible design,perfect and selective absorption,has attracted much attention recently for passive radiative cooling applications.To cool objects passively,broadband infrared absorption(i.e.8-14 μm) is desirable to emit thermal energy through atmosphere window.We present a novel MMA composed of multilayer MIM resonators periodically arranged on a PbTe/MgF_(2) bilayer substrate.Verified by the rigorous coup led-wave analysis method,the proposed MMA shows a relative bandwidth of about 45%(from 8.3 to 13.1 μm with the absorption intensity over 0.8).The broadband absorption performs stably over a wide incident angle range(below 50°) and predicts 12 K cooling below ambient temperature at nighttime.Compared with the previous passive radiative coolers,our design gets rid of the continuous metal substrate and provides an almost ideal transparency window(close to 100%)for millimeter waves over 1 mm.The structure is expected to have potential applications in thermal control of integrated devices,where millimeter wave signal compatibility is also required.