Study On The Composition And Structure Control Of PZT Based Composite Aerogels

As a kind of functional aerogel materials,lead zirconate titanate(Pb(Zr_xTi_1-x)O₃,PZT)aerogel can convert mechanical signals into electrical signals.Because of its lower density,PZT aerogel can better match the acoustic impedance of water and has a high HFOM.The sensitivity and resolution of the transducer can be improved by using it as the piezoelectric material.However,the expensive raw materials,complicated process and long preparation period of the traditional process seriously restrict the research and application of PZT aerogels.Therefore,the following researches such as the simple and rapid preparation method of PZT aerogel,pore size controlled,aerogel component,preparation method of PZT aerogel organic-inorganic composite multilayer film and the mechanical,piezoelectric and dielectric properties of multilayer films have been carried out in this paper.Through research,the following main conclusions have been obtained.Firstly,the improvement of aging process of PZT aerogel has been researched.The cheap raw materials and simple process were used to prepare PZT wet gel,and the distillation was used to remove water to shorten the solvent replacement time.The effects of aging fluid on the composition and pore size distribution of PZT aerogel were studied,and the relationship between the pore size distribution and the light transmittance of PZT wet gel was also studied.The PZT wet gels with strong light transmission will have smaller pore size and more concentrated distribution after they supercritical dried in CO₂and turn into PZT aerogels.And different aging solutions did not change the basic pore structure,phase structure and organic groups of the prepared PZT aerogels.Secondly,the innovation of the preparation process of PZT aerogel has been studied.The gel-aging integration method has been used to prepare and age PZT wet gels,which skips the long aging process in the preparation of PZT aerogels.These processes shorten the preparation period from nearly 20 days to a minimum of 5 days.The effects of gel-aging temperature,time,sequence,and lead content on specific surface aera,pore size distribution,pore volume and component of PZT aerogels were investigated.the prepared PZT aerogel has a 3D porous structure,there specific surface aera can exceed 360 m²/g.The pores are irregularly connected pores composed of gaps between the aerogel nanoskeleton.The increasing of gel-aging temperature and lead content can increase pore size,and the increasing of the gel aging time can reduce the pores with smaller pore sizes.The pore size of PZT aerogels is mostly distributed around 250 nm.Thirdly,the annealing process of PZT aerogel has been studied.The prepared PZT aerogel exhibits an amorphous structure at room temperature and contains many kinds of organic compounds,and the mass of which accounts for about 19%.After annealing at550?,the PZT aerogels can transform into a tetragonal perovskite structure and all organic matter is decomposed.As the annealing temperature increases,the PZT aerogel skeleton collapses,the skeleton particles become larger,and the specific surface area decreases rapidly,and it still maintains a 3D porous structure.Finally,the coating process of PZT aerogel has been studied.The annealed PZT aerogel is prepared as a powder,which was then compounded with organic polymer materials to make PZT aerogel/organic polymer alternating multilayer coatings.The annealed PZT aerogel still has a tetragonal perovskite structure in the films.The multilayer films are closely combined with each other and the loose flexible layer and the dense rigid layer are alternately superposed overall.The organic phase and the inorganic phase are cross-linked to each other,but basically no chemical reaction occurs.With the increase number of layers,the d₃₃ of prepared multilayer film has a small increase,which can reach 12 pC/N,the dielectric constant increases with the increasing number of layers and decreases with the increase of frequency.With the increase of layers,the leakage current decreases,and the residual polarization and coercive electric field increase.This paper has the following features or novelties.Firstly,PZT wet gels were prepared using cheaper raw materials and a simpler preparation process,and the process of distillation to remove water reduce the time of solvent replacement.Secondly,this paper creatively uses the gel-aging integration method to prepare and age PZT wet gels,These processes shorten the preparation period from nearly 20 days to a minimum of 5 days.Finally,the sandwich-structured soft-hard alternating organic-inorganic multilayer composite coatings were designed and prepared.The relationship between the thickness and the structure,mechanical properties,dielectric properties and piezoelectric properties of the coatings were also studied.