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Flexoelectricity describes the strain-gradient-induced electric polarization existing in dielectric materials. The coefficient that exists between the strain-gradient and the induced electric polarization defines the flexoelectric coefficient tensor. It is necessary to analyze different experimental methods to evaluate the procedure of measuring the transverse flexoelectric coefficient tensor component. In this work, the transverse flexoelectric coefficient tensor component of poly(vinylidene fluoride) (PVDF) is studied using three different experimental methods and the effects of the mentioned methods are evaluated. The results presented in this work are helpful for the design of experiments of different dielectric materials, including ceramics and polymers on flexoelectricity.

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In this paper, Fe 3 O 4 based magnetic fluids with different particle concentrations were prepared by the coprecipitation technique. The size of the Fe 3 O 4 nanoparticles is about 13 nm and their shape is spherical. The tribological performances of the fluids with different concentration Fe 3 O 4 nanoparticles were evaluated in a MMW-1A four-ball machine. The results show that the tribological performance of magnetic fluids with proper Fe 3 O 4 nanoparticles can be improved significantly. The maximum nonseized load (P B ) has been increased by 38.4% compared with carrier liquid. The wear scar diameter has been reduced from 0.68 mm to 0.53 mm and the relative percentage in friction coefficient has decreased to 31.3%. The optimal concentration of the Fe 3 O 4 nanoparticles in the carrier liquid is about 4 wt.%.