Study On The Relation Between Nano-particle Dispersion And Dielectric Properties Of Al₂O₃/Silicone Rubber Composite

In order to study the effects of nano-Al₂O₃loading and dispersion on thedielectric properties of nano-Al₂O₃silicone rubber, three methods have been usedto prepared the samples,①silicone rubber composites with nano-Al₂O₃loadingof1wt.%,2wt.%,3wt.%,4wt.%were made by “mechanical mixing method”;②silicone rubber composites with nano-Al₂O₃loading of1wt.%,2wt.%,3wt.%,4wt.%were made by “bubble method”;③coupling agent was added intosilicone rubber, which and nano-Al₂O₃mass ratio was1/13,1/11,1/9,1/7respectively, the composites were made by “bubble method” in the same way. Allthe samples were observed by transmission electron microscope （TEM）. Theresults indicated that nano-Al₂O₃agglomerated largely in the composites madeby “mechanical mixing method”, on the contrary, nano-Al₂O₃dispersed well inthe composites made by “bubble method”, and then nano-Al₂O₃reunion aftercoupling agent added. After tested the above samples, it was found that with theincrease of nano-Al₂O₃content, space charge accumulations in the compositesmade by “mechanical mixing method” increased, trap depths increased, carriermobility decreased, permittivity increased, dissipation was more than that of puresilicone rubber, but decreased with nano-Al₂O₃content improvement, the turningpoint of Ohm current and space charge limited current, i.e. the aging thresholddecreased, breakdown strength of the composites increased first and thendecreased, the3wt.%nano-Al₂O₃content one has the best breakdown strength;compared with the samples made by “mechanical mixing method”, space chargeaccumulations in the composites made by “bubble method” decreased, trapdepths decreased, carrier mobility increased, permittivity decreased, with theincrease of nano-Al₂O₃content, dissipation decreased below103Hz, butincreased above103Hz, the aging threshold increased, breakdown strength of thecomposites increased first and then decreased, the3wt.%nano-Al₂O₃content onehas the best breakdown strength, and breakdown strength of the composites arehigher than that of the ones made by “bubble method”; After the coupling agentadded in, space charge accumulations was inhibited significantly as the loadingof coupling agent increase, trap depth further decreased, carrier mobilityincreased, as well as permittivity and dissipation, both aging threshold and breakdown strength decreased. The results showed that good dispersion of nano-Al₂O₃would lead to trap depth in the nano-Al₂O₃silicone rubber decrease,carrier mobility increase, permittivity decrease, aging threshold as well asbreakdown strength increase.