Ionic conductivity and relaxation studies in PVDF-HFP:PMMA-based gel polymer blend electrolyte with LiClO4 salt

Poly(vinylidene fluoride-hexafluropropylene) (PVDF-HFP) and poly(methyl methacrylate) (PMMA)-based gel polymer electrolytes (GPEs) comprising propylene carbonate and diethyl carbonate mixed plasticizer with variation of lithium perchlorate (LiClO4) salt concentrations have been prepared using a solvent casting technique. Structural characterization has been carried out using XRD wherein diffraction pattern reveals the amorphous nature of sample up to 7.5[Formula: see text]wt.% salt and complexation of polymers and salt have been studied by FTIR analysis. Surface morphology of the samples has been studied using scanning electron microscope. Electrochemical impedance spectroscopy in the temperature range 303–363[Formula: see text]K has been carried out for electrical conductivity. The maximum room temperature conductivity of 2.83[Formula: see text][Formula: see text]S cm[Formula: see text] has been observed for the GPE incorporating 7.5[Formula: see text]wt.% LiClO4. The temperature dependence of ionic conductivity obeys the Arrhenius relation. The increase in ionic conductivity with change in temperatures and salt content is observed. Transport number measurement is carried out by Wagner’s DC polarization method. Loss tangent (tan [Formula: see text]) and imaginary part of modulus ([Formula: see text]) corresponding to dielectric relaxation and conductivity relaxation respectively show faster relaxation process with increasing salt content up to optimum value of 7.5[Formula: see text]wt.% LiClO4. The modulus ([Formula: see text]) shows that the conductivity relaxation is of non-Debye type (broader than Debye peak).

Microstructural Investigation on Tungsten for Applications in Future Nuclear Fusion Reactors

Tungsten is a promising armour material for plasma facing components of nuclear fusion reactors. Two materials with different density and purity have been examined by optical microscopy, X-ray diffraction (XRD), instrumented indentation tests (FIMEC) and mechanical spectroscopy. For both the materials yield stress and elastic modulus strictly depend on the residual porosity. Moreover, the material with higher porosity (≈ 9%) is not stable and remarkable modulus variations are observed during heating. The IF spectrum exhibits a relaxationQ-1peak superimposed to an exponentially increasing background. The peak is a single Debye peak with activation energyH= 74.86 kJ mol-1and pre-exponential factor τ0= 1.76 x 10-9s that has been ascribed to dislocation interaction with intrinsic point defects (autointerstitial and substitutional).

Anelasticity and grain boundary sliding

We describe a theoretical and numerical analysis of an existing model of anelasticity owing to grain boundary sliding. Two linearly elastic layers having finite thickness and identical material constants are separated by a given fixed spatially periodic interface across which the normal component of velocity is continuous, whereas the tangential component has a discontinuity determined by the shear stress σ * ns and the boundary sliding viscosity η *. We derive asymptotic forms giving the complex rigidity for the extremes of low-frequency forcing and of high-frequency forcing. Using those forms, we create master variables allowing results for different interface shapes, and arbitrary forcing frequency, to be collapsed (very nearly) into a single curve. We then analyse numerically, with finite interface slope, three proposed factors that may weaken and broaden the theoretical prediction of a single Debye peak in the loss spectrum. They are, namely, stress concentrations at interface corners, spatial variation in grain size and spatial variation in boundary sliding viscosity η *. Our results show that all these factors can, indeed, contribute to a moderate weakening of the loss peak. By contrast, the loss peak markedly broadens only when the boundary sliding viscosity η * differs by an order of magnitude across adjacent interface. The shape of the loss spectrum (self-similar to a single Debye peak) is insensitive to the other two factors.