Ahmed I. Ali

Influences of Ag-NPs doping chitosan/calcium silicate nanocomposites for optical and antibacterial activity.

Chitosan (CS)/calcium silicate nanocomposites pure and doped with Ag ions (1, 2mol%) were prepared via sol-gel method. The prepared CS/calcium silicate nanocomposites were investigated through X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The XRD results, indicating that after increasing the Ag ions in the CS/calcium silicate nanocomposite the crystallinity degree increased regularly in the prepared nanocomposites accompanying to the continuously rearrangement in the internal structure of nanocomposite under the effect of inorganic nanoparticles. Correspondingly, the optical properties of the prepared nanocomposites films were measured using UV/vis spectroscopy. The reflectance increased while the energy band gap decreased from 3.96eV to 2.43eV with Ag-ions concentration. More over the transition type changed from direct into indirect by adding Ag-ions, indicate that new band between valence and conduction band were formed. In addition, the optical parameters showed an increase in refractive indices and decrease in the surface and volume energies losses with increasing Ag-ions. Correspondingly, the prepared nanocomposites exhibited good antibacterial activity against gram positive (Staphylococcus aureus), gram negative (Pseudomonas aeruginosa) bacteria and fungi (Candidia albicans). The results suggested that the prepared CS/calcium silicate nanocomposites can be a promised candidate for optical sensors applications and smart packaging materials.

Ferroelectric, and piezoelectric properties of BaTi1−xAlxO3, 0 ≤ x ≤ 0.015

Single phase polycrystalline samples of BaTi1−x Al x O3, 0 ≤ x ≤ 0.015, have been prepared by a conventional powder processing method. The Rietveld refinements of X- ray powder diffraction patterns at room temperature indicate that the samples crystallize in tetragonal structure with group symmetry P4mm. Because of the oxygen vacancies, the volume of the unit cell increases with increasing x. Field emission scanning electron microscopy revealed that the particle size of pure BTO ceramics was affected by the Al content. Dielectric, ferroelectric and piezoelectric properties of pure BTO as well as Al-doped BTO were studied. It was found that the dielectric permittivity (e′) increases significantly with increasing x while the transition from ferroelectric phase to a paraelectric phase changes slightly. The Curie-Weiss law is verified over a wide temperature range. Both ferroelectric and piezoelectric properties of BTO are enhanced by the substitution of Ti4+ by Al3+ ions. Piezoelectric strains of Al-doped BTO showed a suitable behavior for application compared with that of pure BTO compound. Finally, the results obtained in this work are discussed and compared with those for similar materials.