Preparation Of BaTiO₃/PVDF Composite Piezoelectric Film And Its Sensor Properties

Sensor technology,as one of the top ten technologies which were given priorities to develop in the 21st century,has far lagged behind the communication technology and computer technology.The reason lies that some shortcomings,such as large volume,hard texture,of the traditional sensors were greatly limited the practical application of the sensor technology.Therefore,researching and developing flexible pressure sensors with high performances,but also small volume and low cost,has been becoming a new development trend in the current sensor technology research and application.A new type of flexible pressure sensor with PVDF(polyvinylidene fluoride)as the core component has attracted much attention due to its light weight,strong toughness,high mechanical strength and adaptability to curved surface work,but its piezoelectric properties are much lower than those of piezoelectric ceramics such as lead zirconate titanate.So,it is not very advantageous in practical application.BaTiO₃(barium titanate)is also a kind of ceramics with excellent piezoelectric properties.Its piezoelectric properties are lower than lead zirconate titanate,but it is lead-free,thus more environmentally friendly.Also,BaTiO₃piezoelectric ceramics have the problems existing in ceramic materials such as poor flexibility and difficulty in processing ceramic materials.So,if BaTiO₃and PVDF can be combined to obtain a kind of composite material with both softness and piezoelectric properties,it can be regarded as a way to solve the problems.Therefore,BaTiO₃was chosen as the filler and PVDF as the matrix in this paper to prepare BaTiO₃/PVDF composite piezoelectric film with good flexibility and high piezoelectric performance.Based on the BaTiO₃/PVDF composite piezoelectric film,film sensors were prepared,their performances and applications were also tested and analyzed.The main research contents are as follows:(1)The preparation process of BaTiO₃/PVDF composite piezoelectric film was optimized in this paper.The secondary heat treatment process was designed to prepare the films and the drying time of the films was shortened to 1/15 of the original one.The results of SEM,TGA,DSC and mechanical properties analysis of the composite films showed that the quality and properties of films were significantly improved.The clamping end of the device used to polarize the thin films was modified as a bullet,this made the device more stable when clamping the films,and the success rate of film polarization was increased by 30%.The preparation and polarization conditions of BaTiO₃/PVDF composite films were explored in this paper and the reasonable preparation and polarization process was obtained:BaTiO₃filling amount 15wt%,polarization field intensity 160MV/m,polarization time 40 min,and polarization temperature 90?.Finally,the highest piezoelectric constant of the composite films prepared by using above process and treatment flow was up to 38p C/N.(2)The BaTiO₃/PVDF composite piezoelectric film sensors were designed and prepared in this paper.Aiming at the problem that the film is easy to be damaged,a"sandwich"structure was designed,which is composed of composite piezoelectric film layer,PDMS layer and PI tape layer from inside to outside.Gold electrode is used as the upper and lower counter electrode of the composite films,and silver wires with excellent conductivity as the electrode lead.PDMS adhesive with good softness was used as a buffer layer which can also transfer the external force to the composite piezoelectric film.PI tape with high temperature resistance and insulation used as the packaging layer,can effectively reduce the interference of external electric field and ambient temperature to the composite piezoelectric thin film sensors.(3)The output voltage,stability,durability and sensitivity of the BaTiO₃/PVDF composite piezoelectric film sensors were tested in this paper by building an experimental platform.The experimental results showed that the BaTiO₃/PVDF composite piezoelectric film sensors have excellent performances,the output voltage was 7.55V under 5N pressure,and the reaction time was 52ms,which is significantly better than PVDF film sensors and commercial PVDF film sensors.The application analysis of BaTiO₃/PVDF composite piezoelectric film sensors were carried out.It showed that BaTiO₃/PVDF composite piezoelectric film sensors could respond sensitively to the bending and deformation of fingers at different angles and output smoothly,and could sense the vibration signals with different pronunciations well and repeatably.So,it is considered that BaTiO₃/PVDF composite piezoelectric film sensors have potential applications in the monitoring of tiny deformation and artificial intelligence speech recognition.