Preparation, characterization and dielectric properties of temperature stable SrTiO3/PEEK composites for microwave substrate applications

Poly(ether ether ketone) (PEEK) is a potential candidate for electronic applications due to its low permittivity, low loss, high melting point, better chemical resistance, excellent insulating properties and easy processibility. Present paper discusses the preparation and characterization of SrTiO3 filled PEEK composite for microwave substrate applications. The dielectric constant, dielectric loss and temperature variation of dielectric constant of the composites have been studied up to 1 MHz using an Impedance Analyzer. Different theoretical approaches have been employed to predict the effective permittivity of composite systems and the results are compared with that of the experimental data. The crystallinity of the bulk composite is studied by X-ray diffraction studies. Scanning electron microscopic technique has been employed to study the dispersion of the particulate filler in PEEK matrix. Vickers hardness of pure and filled PEEK composite has been measured using Microhardness Tester. The effect of particle size on the dielectric as well as mechanical properties of SrTiO3/PEEK composite system is also studied by incorporating micronsize and nanosize fillers. Present study shows that a temperature stable composite can be realized by judiciously selecting appropriate filler concentration in the PEEK matrix.

Processing and characterization of srTiO₃-TiO₂ nanoparticle-nanotube heterostructures on titanium for biomedical applications

Surface properties such as physicochemical characteristics and topographical parameters of biomaterials, essentially determining the interaction between the biological cells and the biomaterial, are important considerations in the design of implant materials. In this study, a layer of SrTiO3-TiO2 nanoparticle-nanotube heterostructures on titanium has been fabricated via anodization combined with a hydrothermal process. Titanium was anodized to create a layer of titania (TiO2) nanotubes (TNTs), which was then decorated with a layer of SrTiO3 nanoparticles via hydrothermal processing. SrTiO3-TiO2 heterostructures with high and low volume fraction of SrTiO3 nanoparticle (denoted by 6.3-Sr/TNTs and 1.4-Sr/TNTs) were achieved by using a hydrothermal processing time of 12 and 3 h, respectively. The in vitro biocompatibility of the SrTiO3-TiO2 heterostructures was assessed by using osteoblast cells (SaOS2). Our results indicated that the SrTiO3-TiO2 heterostructures with different volume fractions of SrTiO3 nanoparticles exhibited different Sr ion release in cell culture media and different surface energies. An appropriate volume fraction of SrTiO3 in the heterostructures stimulated the secretion of cell filopodia, leading to enhanced biocompatibility in terms of cell attachment, anchoring, and proliferation on the heterostructure surface.