BaTiO3/polyvinylidene fluoride (BT/PVDF) is the extensive reported composite material for application in modern electric devices. However, there still exists some obstacles prohibiting the further improvement of dielectric performance, such as poor interfacial compatibility and low dielectric constant. Therefore, in depth study of the size dependent polarization and surface modification of BT particle is of technological importance in developing high performance BT/PVDF composites. Here, a facile molten-salt synthetic method has been applied to prepare different grain sized BT particles through tailoring the calcination temperature. The size dependent spontaneous polarizationof BT particle was thoroughly investigated by theoretical calculation based on powder X-ray diffraction Rietveld refinement data. The results revealed that 600 nm sized BT particles possess the strong polarization, ascribing to the ferroelectric size effect. Furthermore, the surface of optimal BT particles has been modified by water-soluble polyvinylprrolidone (PVP) agent, and the coated particles exhibited fine core-shell structure and homogeneous dispersion in the PVDF matrix. The dielectric constant of the resulted composites increased significantly, especially, the prepared composite with 40 vol % BT loading exhibited the largest dielectric constant (65, 25 °C, 1 kHz) compared with the literature values of BT/PVDF at the same concentration of filler. Moreover, the energy storage density of the composites with tailored structure was largely enhanced at the low electric field, showing promising application as dielectric material in energy storage device. Our work suggested that introduction of strong polarized ferroelectric particles with optimal size and construction of core-shell structured coated fillers by PVP in the PVDF matrix are efficacious in improving dielectric performance of composites. The demonstrated approach can also be applied to the design and preparation of other polymers-based nanocomposites filled with ferroelectric particles to achieve desirable dielectric properties.

Super‐plasticity of single‐crystal beta‐SiC [111] nanowires for > 200 % elongation was observed by in situ axial‐tensile experiments in a scanning electron microscope. The SiC nanowires were characterized by a bamboo‐like structure appearing as the 3C structured segments intergrowth along the nanowire. The axial localized plasticity and super‐plasticity are suggested to result only from the 3C segments, through dislocation generation, propagation and amorphization in contrast to the highly defected structural segments that conduct elastic‐deformation only, owing to the lack of slip systems. These results provide key information for understanding the mechanical behavior of SiC nanowires.

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New hyperbranched poly(trimellitic anhydride-triethylene glycol) ester epoxy (HTTE) is synthesized and used to toughen diglycidyl ether of bisphenol A (DGEBA) 4,4(-diaminodiphenylmethane (DDM) resin system. The effects of content and generation number of HTTE on the performance of the cured systems are studied in detail. The impact strength is improved 2--7 times for HTTE/ DGEBA blends compared with that of the unmodified system. Scanning electron microscopy (SEM) of fracture surface shows cavitations at center and fibrous yielding phenomenon at edge which indicated that the particle cavitations, shear yield deformation, and in situ toughness mechanism are the main toughening mechanisms. The dynamic mechanical thermal analyzer (DMA) analyses suggest that phase separation occurred as interpenetrating polymer networks (IPNs) for the HTTE/DGEBA amine systems. The IPN maintains transparency and shows higher modulus than the neat epoxy. The glass transition temperature (T g ) decreases to some extent compared with the neat epoxy. The T g increases with increase in the generation number from first to third of HTTE and the concentrations of hard segment. The HTTE leads to a small decrease in thermal stability with the increasing content from TGA analysis. The thermal stability increases with increase in the generation number from first to third. Moreover, HTTE promotes char formation in the HTTE/DGEBA blends. The increase in thermal properties from first to third generation number is attributed to the increase in the molar mass and intramolecular hydrogen bridges, the increasing interaction of the HTTE/ DGEBA IPNs, and the increasing crosslinking density due to the availability of a greater number of end hydroxyl and end epoxide functions.