[en] This study has investigated the effect of shelf aging, for up to one year in air, on the properties of gamma-irradiated ultra-high molecular weight polyethylene (UHMWPE). A variety of techniques were used to characterize the properties of treated samples. Differential scanning calorimetery (DSC) was used to characterize the morphology. The extent of cross-linking in a polymer network was detected by swelling measurements. The durometer hardness test was used to measure the relative hardness of this material, and changes in density were also measured. Results from all these measurements were combined to explain the changes in the microstructure of the aged, irradiated UHMWPE. This study shows that crystallinity is increased with radiation dose and with aging due to chain scission, which leads to a reduction in the molecular weight of the material. This allows the chains to rearrange to form crystalline regions. Positron annihilation lifetime spectroscopy confirms these conclusions. Fractional free volumes have been deduced from lifetime parameters, which correlate with the data obtained by the other techniques

[en] We report the effect of microwaves sintering on the crystal domain and electrical properties of TiO₂ nanoparticles. Commercially available TiO₂ nanoparticles of 25 nm size were coated on ITO (indium tin oxide) substrates, which were then sintered at 450 °C employing microwave and conventional sintering approaches. The structural properties of the sintered coatings were examined using atomic force microscopy (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS), whereas the charge transfer properties were investigated using electrochemical impedance spectroscopy (EIS). Structural analysis reveals that the microwave sintering of TiO₂-coated substrates results in the formation of more ordered crystal structure as compared to the conventionally sintered samples. Nyquist plots demonstrate the improved charge transfer characteristics of TiO₂ nanoparticles in microwave-sintered layers. Also, the application of the microwave-sintered TiO₂-coated ITO substrates as photoanode in dye-sensitized solar cells (DSSCs) confirms superior electrical properties compared to conventionally sintered samples.