金属膜介电性能调控研究

Research on dielectric manipulation of metal films

微米级粉体吸收剂性能指标已经达到理论极限,纳米结构金属薄膜由于具有更高的磁导率有望成为一种新型的微波吸收材料,但目前受限于界面匹配性能,必须控制其介电常数使其适合界面匹配.本文主要讨论金属薄膜的介电机制以及对其介电常数调控的可能性.基于重整化有效媒质理论的计算结果表明,可以通过相应技术途径使连续金属膜变成不连续,并控制不连续金属膜单元尺寸,当单元尺寸处于微米量级范围内时,金属膜的有效介电常数可以降到微波可匹配范围内.

The microwave properties of the micron absorbent have reached the theoretical limit,for its three dimension structer and have no further promotion spaces.Meanwhile,too high planar density also limits its applications in more filed, e.g.all kinds of aircraft.The metal film has a two dimension structure with magnetic moments lying on the plane.And the nano-structure of films also benefits higher microwave permeability.The permeability of magnetic films usually is above 100 at 2GHz,which could give excellent microwave properties with very low thickness and planar density,and the film has a potential to be the excellent microwave absorption material.The metal film usually has the good conductivity,which leads to the high microwave reflection and the bad interfacial microwave match.The complex permittivity of the metal film must been controlled to be suitable for the interfacial microwave match,so that the incident microwave could be easy to penetrate into films and be transformed into heat.Patterned films possess the discontinuous structure and could be regarded as the effective medium composed of metal and air.Low permittivity of metal films could be achieved by this way.The dielectric mechanism of patterned metal films,and how to manipulate it,are discussed in the paper.The calculation work has been conducted based on re-generalized effective medium theory.The results indicate patterned films with cell size in the micron range could suppress the effect of eddy current,and reduce the permittivity of films below 1000.The permittivity of patterned films combined their high permeability would give a perfect interfacial match property for the microwave absorption application.Based on the calculation result,a new type film microwave absorption material will be realized.The further preparation process should be tried to tailor the metal film.