The Preparation Of Rutile Whiskers By Molten Salt Method And Their Effect On The Dielectric Properties Of Silicone Rubber

Ceramic-polymer composites with high mechanical flexibility,low dielectric constant and low dielectric loss,high heat conductivity,low thermal expansion coefficient and other excellent performance as flexible substrates.Ceramic whiskers have excellent physical and chemical properties,compared with the ceramic particles can further improve the dielectric properties,thermal properties,mechanical properties and friction performance of composite materials,etc.The experiment respectively add the rutile whiskers,micron particles and nanoparticles,as well as their surface modified powders to silicone rubber matrix,the composite materials were prepared by room temperature curing,the effect of rutile morphology,volume fraction and the modification on microwave dielectric properties of the composites were investigated systematically.The molten salt synthesis method was applied to synthesize rutile whiskers,amorphous TiO2,ZnSO4·7H2O,Na2SO4 as raw materials,their molar ratio is 1:1:1,the conventional heating and microwave heating were adopted respectively,the influence of heating temperature,heating rate and holding time on the morphology of rutile whiskers was studied by designing a reasonable experimental scheme.Under the condition of microwave heating,the rutile whiskers with good morphology were synthesized by heating rate of 15 ?/min,calcination temperature of 700 ? and calcination time of 15 min,the diameter of which is about 0.5?m,the length diameter ratio is about 25.Compared with conventional heating,the synthesis temperature is reduced by 100?,and the holding time shortened from 4h to 15 min,this is due to the material is heated evenly and uniformly by microwave heating.The ?r and ?f improved with rutile filler loading,but the Q×f reduced,and under the same volume fraction,the ?r of rutile whiskers-silicone rubber composites is slightly larger,followed by nanoparticles,micron particles is minimal.For the Q×f,at the same amount,the Q×f value of rutile whiskers-silicone rubber composites is maximum,followed by micron particles,nanoparticles is minimal.After modification of rutile powder by KH570,the ?r and Q×f of surface-modified ceramic-silicone rubber composites are improved.When the rutile filler volume fraction is 19%,the ?r,Q×f and ?f of the surface-modified rutile whiskers-silicone rubber composites are 3.645,3655 GHz,+45.6ppm/?.The ?r of the composite materials in 1MHz and microwave frequency are compared with the Lichtenecker model,Maxwell-Garnet model and JayasundereSmith model.Under 1 MHz,the ?r of composites are basically consistent with the theoretical values of the three models,under the microwave frequency,the ?r is lower than the theoretical values,and with the increase of rutile filler volume fraction,the deviation is bigger and bigger,closest to the Maxwell-Garnet model.And the effects of water absorption on the microwave dielectric properties of the composites were also investigated.With the increase of immersion time,water absorption of the composites are more and more big.Under the same soaking time,the water absorption of rutile whiskers-silicone rubber composites is maximum,followed by nanoparticles,micron particles is minimal.Under the microwave frequency,with the increase of water absorption of composites,the ?r of composites did not change,Q×f decreased gradually.