Preparation Of Porous BaTiO₃ Loading Metal And Application Research In Composites

In this thesis, porous barium titanate ?BaTiO₃? powders were firstly prepared, Ni nanoparticles were loaded on surfaces of porous BaTiO₃ particles, then BaTiO₃/PVDF composites were synthesized by solution casting method after the produced BaTiO₃ are surface treated by modifying agents, and then the effect of treated porous BaTiO₃ and single-phase Ni particles on electrical properties of composites was systematically researched. The advanced measuring instruments were used to characterize the morphology, phase and dielectric properties of porous BaTiO₃ powders and BaTiO₃/PVDF composites, and the optimum composition of improving energy density of BaTiO₃/PVDF composites was obtained and the mechanism to improve the dielectric properties of the composites was explored.A layer of porous BaTiO₃ were coated on surfaces of 100 nm of solid BaTiO₃ with P123 as template by sol-gel method. The effect of P123 concentration and pH of reaction solution on morphology of porous BaTiO₃ particles were studied. When P123 concentration was 11?14 wt%, pH of reaction solution was 3-3.5, porous BaTiO₃ with 120 nm particle size and 5-30 nm pore size were prepared. Ni nanoparticles with particle size less than 10 nm were loaded on porous BaTiO₃ particles by multiple impregnation reduction method, and the effect of volume ratio of Ni and porous BaTiO₃ particles on breakdown strength of Ni@BaTiO₃/PVDF composites was researched. It was found that the breakdown strength of the composites was firstly increased and then decreased with increasing Ni loading contents when fixed contents of BaTiO₃ was 3 vol%. When the volume ratio of Ni and BaTiO₃ was 8%, the maximum breakdown strength of Ni@BaTiO₃/PVDF composites reached 273 kV/mm, which resulted from the coulomb block effect of coulomb islands of Ni particles.Ni@BaTiO₃ particles were surface modified with modifying agents of NDZ-311-H₂O₂ and PVP-k30 by solution blending method, respectively. The dielectric permittivity and breakdown strength of NDZ-H₂O₂-Ni@BaTiO₃/PVDF ?I? and PVP-Ni@BaTiO₃/PVDF ??? composites were measured. The results showed that the dielectric permittivity of the two composites increased with increasing Ni@BaTiO₃ contents, and the breakdown strength showed a tread of first increase and then decrease with the increase of Ni@BaTiO₃ particle contents; when Ni@BaTiO₃ contents was 10 vol%, the dielectric permittivity of two composites separately reached 22.1 and 21 with low dielectric loss, and the breakdown strength reached maximum of 335 kV/mm and 321 kV/mm with 3 vol% Ni@BaTiO₃ contents, respectively. For the composites I, the calculated value of energy density reached maximum of 6.49 J/cm3 with 4 vol% Ni@BaTiO₃, indicating that NDZ-311-H₂O₂ was a better modifying agent due to the stronger bonding effect with PVDF, and the enhancement of energy density resulted from the increase of interfacial polarization effect induced by Ni nanoparticles and compatibility between inorganic and organic phase.On the basis of the composites I with high energy density, the effect of introduced single-phase Ni particles on electrical properties of Ni/?NDZ-H₂O₂-Ni@BaTiO₃?/PVDF composites was studied. It was found that dielectric permittivity of Ni/?NDZ-H₂O₂-Ni@BaTiO₃?/PVDF composites increased with increasing single-phase Ni particle contents, and breakdown strength of which firstly increased and then decreased with increasing amounts of single-phase Ni particles, meanwhile, the dielectric loss of the two composites was low. when the addition amounts of single-phase Ni was 0.1 vol%, the maximum calculated value of energy density for Ni/?NDZ-H₂O₂-Ni@BaTiO₃?/PVDF composites reached 11.41 J/cm3 at a maximum breakdown strength of 426 kV/mm, which was 75.8% and 27.2% higher than composites I, owing to the single-phase Ni were polarized and attracting charges surrounding Ni@BaTiO₃ and PVDF under an applied electric field, which uniformly distributed the charges of the composites, and the addition of Ni particles promoted a phase of PVDF transforming to P and y phase at the same time.