For decades,the rapid development of wireless communication has provided people a smarter way of living.However,a significant increase in electromagnetic pollution is an unavoidable consequence.Evading radar detection...For decades,the rapid development of wireless communication has provided people a smarter way of living.However,a significant increase in electromagnetic pollution is an unavoidable consequence.Evading radar detection in modern warfare has also become an important prerequisite for survival on the battlefield.This review provides a comprehensive overview of the current status and types of electromagnetic absorption metamaterials,especially their design and preparation methods.Moreover,this review focuses on the strategies used to optimize the absorber absorption performance.Finally,this review presents a viewpoint on future research on electromagnetic absorption metamaterials,the main challenges that need to be addressed and the possible solutions.展开更多
Thermal cloaks offer the potential to conceal internal objects from detection or to prevent thermal shock by controlling external heat flow. However, most conventional natural materials lack the desired flexibility an...Thermal cloaks offer the potential to conceal internal objects from detection or to prevent thermal shock by controlling external heat flow. However, most conventional natural materials lack the desired flexibility and versatility required for on-demand thermal manipulation. We propose a solution in the form of homogeneous multilayer thermodynamic cloaks. Through an ingenious design, these cloaks achieve exceptional and extreme parameters, enabling the distribution of multiple materials in space. We first investigate the effects of important design parameters on the thermal shielding effectiveness of conventional thermal cloaks. Subsequently, we introduce an autonomous tuning function for the thermodynamic cloak, accomplished by leveraging two phase transition materials as thermal conductive layers. Remarkably, this tuning function does not require any energy input. Finite element analysis results demonstrate a significant reduction in the temperature gradient inside the thermal cloak compared to the surrounding background. This reduction indicates the cloak’s remarkable ability to manipulate the spatial thermal field. Furthermore, the utilization of materials undergoing phase transition leads to an increase in thermal conductivity, enabling the cloak to achieve the opposite variation of the temperature field between the object region and the background. This means that, while the temperature gradient within the cloak decreases, the temperature gradient in the background increases. This work addresses a compelling and crucial challenge in the realm of thermal metamaterials, i.e., autonomous tuning of the thermal field without energy input. Such an achievement is currently unattainable with existing natural materials. This study establishes the groundwork for the application of thermal metamaterials in thermodynamic cloaks, with potential extensions into thermal energy harvesting, thermal camouflage, and thermoelectric conversion devices.By harnessing phonons, our findings provide an unprecedented and practical approach to flexibly implementing thermal cloaks and manipulating heat flow.展开更多
基金the National Natural Science Foundation of China(Grant No.11774278)the Fundamental Research Funds for Central Universities(No.2012jdgz04)。
文摘For decades,the rapid development of wireless communication has provided people a smarter way of living.However,a significant increase in electromagnetic pollution is an unavoidable consequence.Evading radar detection in modern warfare has also become an important prerequisite for survival on the battlefield.This review provides a comprehensive overview of the current status and types of electromagnetic absorption metamaterials,especially their design and preparation methods.Moreover,this review focuses on the strategies used to optimize the absorber absorption performance.Finally,this review presents a viewpoint on future research on electromagnetic absorption metamaterials,the main challenges that need to be addressed and the possible solutions.
基金supported by the National Natural Science Foundation of China (Grant No. 11774278)the Fundamental Research Funds for Central Universities (Grant No. 2012jdgz04)。
文摘Thermal cloaks offer the potential to conceal internal objects from detection or to prevent thermal shock by controlling external heat flow. However, most conventional natural materials lack the desired flexibility and versatility required for on-demand thermal manipulation. We propose a solution in the form of homogeneous multilayer thermodynamic cloaks. Through an ingenious design, these cloaks achieve exceptional and extreme parameters, enabling the distribution of multiple materials in space. We first investigate the effects of important design parameters on the thermal shielding effectiveness of conventional thermal cloaks. Subsequently, we introduce an autonomous tuning function for the thermodynamic cloak, accomplished by leveraging two phase transition materials as thermal conductive layers. Remarkably, this tuning function does not require any energy input. Finite element analysis results demonstrate a significant reduction in the temperature gradient inside the thermal cloak compared to the surrounding background. This reduction indicates the cloak’s remarkable ability to manipulate the spatial thermal field. Furthermore, the utilization of materials undergoing phase transition leads to an increase in thermal conductivity, enabling the cloak to achieve the opposite variation of the temperature field between the object region and the background. This means that, while the temperature gradient within the cloak decreases, the temperature gradient in the background increases. This work addresses a compelling and crucial challenge in the realm of thermal metamaterials, i.e., autonomous tuning of the thermal field without energy input. Such an achievement is currently unattainable with existing natural materials. This study establishes the groundwork for the application of thermal metamaterials in thermodynamic cloaks, with potential extensions into thermal energy harvesting, thermal camouflage, and thermoelectric conversion devices.By harnessing phonons, our findings provide an unprecedented and practical approach to flexibly implementing thermal cloaks and manipulating heat flow.
