Influence of surface modification of BaTiO3 nanoparticles on the dielectric properties of BaTiO3/epoxy composite films
Creators: name: Sundar, Udhay
Publisher: name: No Publisher Supplied
Year: 2017

description: Polymer-Ceramic nanocomposite dielectric films have received a lot of attention re-cently due to the flexibility and the ease of processing of polymers coupled with the functional properties of the ceramic nanoparticles. However, a common problem asso-ciated with inorganic-organic composites is the inherent incompatibility of the two materials. BaTiO3, which is the ceramic nanoparticle of interest is hydrophilic, that is it has an affinity to water due to the presence of hydroxyl groups on its surface. On the other hand the epoxy matrix and organic solvent are hydrophobic, that is they repel water. This leads to the separation of the BaTiO3 nanoparticles and the epoxy matrix creating an inhomogeneous dispersion, which is not ideal. In addition, the ceramic na-noparticles tend to agglomerate due to van der Waals attractive forces resulting in the formation of particle clusters within the epoxy matrix and leading to inhomogeneous distribution. Two methods used to overcome this attractive force are electrostatic stabi-lization, which involves developing a charge on the surface of the particle so that they begin to repel each other and steric stabilization, which reduces the surface energy of the particle by bonding with a surfactant or coupling agent.      This work seeks to understand the influence of surface modification of the Ba-TiO3 nanoparticles in composite dielectrics where the dielectric permittivity, leakage current and dissipation are studied to achieve optimal dielectric performance of these composites. The BaTiO3 nanoparticles were surface treated using (i) ethanol and (ii) silane coupling agent to aid in uniform distribution of the particles within the epoxy matrix. The BaTiO3/epoxy composite films were fabricated using a modified sol-gel method and were spin-coated onto stainless steel substrates followed by curing at 75oC for 8 hours in air. The samples were then corona poled at 30 kV/mm for 30 mins. The piezoelectric strain coefficients d33 and d31 were measured for all the samples, along with the real and imaginary permittivity, electrical resistivity and conductivity and dielec-tric breakdown strength and leakage current. Energy Dispersive X-Ray Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) micrograph images were taken to investigate the surface morphology and particle distribution, respectively.     This work identified that the ideal volume fraction of the coupling agent for the surface treatment of the BaTiO3 nanoparticles was determined to be 0.020. The vol-ume fraction of BaTiO3 that yielded the highest dielectric and piezoelectric properties was 50%. The piezoelectric strain coefficients d33 and d31 for the samples that were pre-pared using SCA 0.02 for 0.5 volume fraction of BaTiO3 was found to be 1.16 pC/N and 2.65 pC/N, respectively. The dielectric constant was recorded to be 48.03 at 20 MHz, a low conductivity value of 2.38*10-4 S/m and a high breakdown strength of 85 kV/Cm was recorded for this composite type.