Research On Thermal Conductivity And Microwave Absorption Properties Of Polymer-based Composites

With the continuous advancement of electronic information technology,the new generation of electronic devices is developing rapidly towards higher frequency and integration.As a result,the electromagnetic pollution and heat dissipation problems need to be solved urgently.Electromagnetic interference and overheat can be effectively removed by mounting multifunctional polymer-based thermally conductive and microwave-absorbing materials（TCMAM）on electronic devices.However,according to the current reports,there are few studies focusing on the improvement methods of thermal conductivity and microwave absorption performance,meanwhile the research of the mechanism analysis is still insufficient.In accordance with the current research status,methods of changing the filler morphology and adding aluminum honeycomb framework were used to fabricate multifunctional composites with high thermal conductivity and good microwave absorption performance.Specifically,the work is as follows:（1）.The spherical carbonyl iron powders（CIP）and aluminum oxide powders（Al₂O₃）were used as functional fillers to fabricate TCMAM,the effect of filler content on their thermal conductivity and microwave absorption properties was analyzed.The samples all have broadband and strong absorption characteristics.As the filler content of CIP and Al₂O₃decreases and increases,respectively,the position of the reflection loss peak shifts towards higher frequency,meanwhile,the thermal conductivity of the composites increases initially and then decreases,when the filler content of CIP and Al₂O₃ are both 45 wt%,the thermal conductivity reaches the highest（1.66 W/m K）.（2）.The flaky carbonyl iron powders（FCI）and spherical Al₂O₃ were used as functional fillers to fabricate TCMAM,the effect of filler content on their thermal conductivity and microwave absorption properties was analyzed.As the filler content of FCI and Al₂O₃decreases and increases,respectively,the position of the reflection loss peak shifts towards higher frequency,the thermal conductivity increases initially and then decreases.When the filler content of FCI and Al₂O₃ are 22.5 wt%and 67.5 wt%,respectively,the minimum reflection loss（-17.85 d B）and the widest absorption bandwidth（<-10 d B）（3.54 GHz）are achieved.When the filler content of FCI and Al₂O₃ are both 45 wt%,the highest thermal conductivity is achived（3.67W/m K）.（3）.The FCI and tetra-needle like Zn O whiskers（T-Zn O_w）were used as functional fillers to fabricate TCMAM,the effect of filler content on their thermal conductivity and microwave absorption properties was analyzed.The samples have the strongest absorption property.As the filler content of FCI and decreases and T-Zn O_w increases,respectively,the position of reflection loss peak shifts towards higher frequency,the thermal conductivity shows a continuous upward trend at the same time.When the filler content of FCI and T-Zn O_w are30wt%and 50wt%,respectively,the minimum reflection loss（-28.03 d B）and the widest absorption bandwidth（<-10d B）（4.96 GHz）are achieved,meanwhile,the highest thermal conductivity is achieved（2.54 W/m K）.（4）.The aluminum honeycomb cores were inserted into the CIP/polydimethylsiloxane（PDMS）composite to fabricate honeycomb composites.The simulation softwares were used to analyze the influence of aluminum honeycomb core unit side length（l）on the thermal conductivity and microwave absorption properties of the samples.The thermal conductivity of the samples increases as l decreases,and the highest thermal conductivity is achieved when l is 2mm（1.93W/m K）,meanwhile,the reflection loss peak position of the honeycomb composites moves towards higher frequency.The measured results are basically in agreement with the simulated results.