Study On Preparation And Performance Of Flexible Strontium Titanate Nanofiber Membrane

Strontium titanate（STO）,as a ceramic material with typical perovskite structure,has many special physical chemistry properties,including electromagnetic properties,pressure-sensitive properties,thermoelectric properties,photocatalytic properties and electrocatalytic properties,and become a research hotspot in physical,chemistry and materials fields.With the rapid development of electrospinning and nanotechnology,flexible ceramic materials have been gradually developed and used in electrospinning.Flexible ceramic nanofibers due to its large specific surface area,high active sites of porosity,flexibility and easy recovery,etc.,which have attracted extensive attention.At present,a variety of binary or ternary oxide ceramics have been successfully prepared into flexible electrostatic spinning nanofiber materials,which have abundant applications in the fields of flame retardant,heat insulation,filtration,separation,catalysis and sensing.This paper will explore the feasibility of preparing flexible strontium titanate nanofiber membrane by focusing on the simple and convenient electrostatic spinning process,and study its effective application in the fields of piezoresistive effect and visible light catalysis.The main research results obtained are as follows:（1）It have prepared stannum doped strontium titanate（SSTO）nanofiber membrane by doping Sn⁴⁺into STO lattice,systematically studied the calcination temperature on the influence of nanofiber microstructure and crystal structure,and then analyzed the structure-activity relationship between microstructure and mechanical properties,thirdly,explored the piezoresistive properties of SSTO nanometer fiber membrane.The obtained sample was preliminary attempted to apply to piezoresistive pressure sensor as a core component,which can be used as an intelligent wearable device to detect human body signal.It was found that the optimal calcination temperature of SSTO precursor nanofiber hybrid film is600℃.When the calcination temperature is lower than 600℃,the polymer polymer in the hybrid film as a soft template for fiber forming cannot be completely degraded,and the grain growth is not complete,and the specific properties of ceramic materials cannot be fully displayed.When the temperature is higher than 600℃,the grain size is too large,leading to the fiber bending and easy to fracture.The SSTO nanofiber membrane had a breaking strength of 0.22 MPa,the elongation at break of 1.8%,and a Young’s modulus of13.3 MPa,which can be bent and twisted.The sandwich piezoresistive pressure sensor with flexible SSTO nanofiber membrane as the core sensor has high sensitivity(2.24 k Pa^-1),fast pressure response time（12 ms）and recovery time（32 ms）in the low pressure range（<400MPa）,and a long stable service life（>1000 cycles）.It can be used for real-time monitoring of human activity signals,including limb bending,nose breathing,throat-swallowing and pulse behavior.（2）On the basis of experimental theory,the Zr⁴⁺was introduced into the STO lattice to obtain flexible zirconium doped strontium titanate（ZSTO）nanofiber membrane with enhanced mechanical properties.It was found that the incorporation amount of zirconium has an important influence on the mechanical properties of ZSTO nanofiber membrane.Therefore,it was found that with the increase of doping amount of zirconium,the fiber surface became smoother,grain size and pore volume decreased under the same conditions.It can be seen by X-ray diffraction patterns that the doping critical point of Zr⁴⁺was 30mol%,beyond this critical point,it was difficult to crystallize.When the doping amount of zirconium is 20 mol%,the maximum specific surface area reached 30.4 m² g^-1.In addition,we preliminarily explored the degradation performance of ZSTO nanofiber membrane in visible light photocatalytic,appropriated the incorporation of zirconium can encourage visible light stimulate activity to STO,but due to the wide band gap width of STO,it could improve the incorporation of the visible light catalytic properties of zirconium but still low.However,the ZSTO nanometer fiber membrane has certain mechanical strength,can be easy to use and recycle.（3）On the basis of the flexible ZSTO nanofiber membrane above,silver phosphate was modified on the surface of ZSTO nanofiber by one-step hydrothermal synthesis method.The heterogeneous structure（AZSTO）nanofiber membrane was obtained.By observing the microscopic morphology of nanofibers,it can be found that the silver phosphate grains were evenly distributed and grow on the surface of the fibers.This homogeneously distributed heterostructure can effectively promote the separation of photogenerated electrons and holes.The bandgap widths of STO,ZSTO and AZSTO were 3.41,3.27 and2.49 e V respectively,calculated by diffuse reflectance spectroscopy,successfully increasing the excitation wavelength from the ultraviolet region to the visible range.The experimental results showed that the degradation efficiency of tetracycline hydrochloride by ZSTO and AZSTO nanofiber membrane increased from 41%to 85%in 60 min,and the antibacterial efficiency of AZSTO nanofiber membrane against S.aureus and E.coli was over 99.99%under visible light irradiation,revealing its excellent photocatalytic degradation and antibacterial performance.At the same time,the main active substances in photocatalytic degradation were superoxide radical and photogenic hole.Finally,flexible AZSTO nanofiber membrane has good cyclic stability and recyclability in environmental protection.