Photoluminescence in the blue and green regions is observed for the first time in nanocrystals of Nd2Zr2O7 synthesized by gel combustion method. This emission is attributed to the presence of oxygen vacancies.

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Carbon based nanofillers have shown phenomenal improvements in thermo-mechanical properties of poly vinyl alcohol (PVA) based nanocomposites depending on their interaction with PVA molecules and dispersion in the polymer matrix. In the present study, PVA based nanocomposites with amino-functionalized multi-wall carbon nanotubes (fMWCNTs, 0.2, 0.4, 0.8 and 1.0 wt%) were prepared by a simple casting method from aqueous solution. The relative increase in Young's modulus with 0.4% fMWCNTs was observed to be comparable with that for PVA-nanodiamond composite films which have been shown to have higher strength compared to nanotube and graphene oxide based nanocomposites. In order to investigate the nanolevel molecular packing (sub-nano level free volumes and nano level lamellar structure) and its role in thermal and mechanical properties, positron annihilation spectroscopy and small angle scattering have been used. The crystallinity and morphology of the samples were characterized using X-ray diffraction and scanning electron microscopy. The studies showed that interfacial interaction between PVA molecules and functionalities on the surface of fMWCNTs results in the formation of an ordered structure of PVA molecules which enhances load transfer between the PVA matrix and fMWCNTs leading to improved mechanical properties. The thermal properties of the composites were observed to be unaffected at the studied filler concentration.

The interphase structure of poly(vinyl alcohol) (PVA)−SiC nanofiber polymer nanocomposites has been investigated using positron annihilation lifetime spectroscopy (PALS) and small-angle X-ray scattering (SAXS). The interphase region in polymer nanocomposites extends from nanofillers' surface to bulk polymer matrix. PVA−SiC nanocomposite films with varying concentration of SiC nanofiber (0.1, 0.2, 0.5, and 1.0 wt %) were prepared using solvent casting method. PALS studies indicated the rearrangement of hydrogen bonded structure of PVA and the creation of an interphase layer with larger size nanoholes. SAXS measurements also confirmed the modification of semicrystalline structure of PVA through lamellae structure parameters. The crystallinity of the nanocomposite films have been determined using X-ray diffraction. The observed changes in the polymer nanocomposite structure are resultant of weak interaction between hydrophilic PVA and hydrophobic SiC nanofiber. The mechanical properties of the nanocomposites measured, using tensile testing method, have been explained in view of the changes in structure at interphase.

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