Study On Preparation And Sensing/Microwave Absorption Properties Of Graphene Composites

Graphene composites with excellent chemical stability,mechanical and electrical transport properties have been widely applied in human production and life,especially in the fields of high-performance electronic devices,new medical instruments,aviation and military.The dielectric parameters based on graphene-based composites are studied,including low-frequency dielectric,high-frequency dielectric and electrical conductivity.The thesis explores the application of the materials in gas sensing and microwave absorption,and the rules and mechanisms of properties regulation are discussed.We study the ethanol gas sensing of graphene oxide and melamine sponge composites prepared by self-assembly method.The sensor exhibits a highly sensitive ethanol detection based on dielectric loss which contains direct current conductivity and relaxation information.The sensitivity for dielectric loss is 14.5 times of the electrical conductivity,which is higher than other graphene oxide-based sensors at the same ethanol concentration.The composite material with three-dimensional interconnected porous structure also has good compression-recovery stability and suggests its potential application in fabricating "electronic nose" of human-like robot closer to reality.In addition to volatile organic gases,humidity is also a parameter that cannot be ignored in daily life.A freestanding film fabricated by supramolecular polymerization of graphene oxide and aniline has an ultrafast response/recovery time of 50 ms for humidity sensing.The high-speed adsorption and desorption of water vapor on the surface of the film benefit from the unique moderate hydrophobic surface.The film also has high humidity durability preventing vapor poisoning which is beneficial to the accuracy and long-term measurement.The film can be used to fabricate precision medical equipment monitoring human breath.In addition,the high-frequency dielectric parameters of graphene oxide and aniline supramolecular materials are also studied.The carrier mobility of the material can be changed by controlling the reduction time,and the absorbing performance can be effectively adjusted.The 14.2 GHz absorption bandwidth is achieved at the thickness of 6.4 mm through the structural design.The material This putty-like material has good tunable absorbing property and easy to be coated,as well as can be customized arbitrarily.Therefore,it has broad application prospect in coating stealth material.