Polypyrrole and silver nanoparticles have been synthesized at 277 K by chemical route. Nanoparticles of polypyrrole-silver (PPy-Ag) composites were prepared by mixing polypyrrole and silver nanoparticles in different weight percentages. Dielectric properties as a function of temperature in the range from 300 K to 550 K and frequency in the range from 50 Hz to 1 MHz have been measured. Dielectric constant decreased with increase in frequency and temperature. Dielectric loss decreased with increase in frequency and increased with increase in temperature. Using dielectric data AC conductivity has been determined. Conductivity was found to be in the order of 10 −3 (Ω −1 m −1 ) and it increased with increase in temperature. Temperature variation of conductivity data has been analyzed in the light of Mott's polaron hopping model. Activation energy for conduction has been determined. Activation energy was determined to be in the order of meV and it has increased with increase in frequency and Ag nanoparticles content. This is the first time that PPy-Ag nanocomposites have been investigated for dielectric properties and AC conductivity and data analyzed thoroughly.
Laser shock peening (LSP) is a unique and efficient surface modification technique that surface engineers have commonly adopted to tailor metallic materials' surface and subsurface properties. The primary goal of this review paper is to highlight LSP as a surface modification technique for materials used in aeroengine, as this further ameliorates the commercialization of LSP in aeroengine sectors. The recent research articles focused on the application of LSP to improve the surface characteristics (i.e. surface residual stresses, hardness) and to resist the corresponding service challenges (i.e. fatigue, wear) of the aeroengine metallic material have been reviewed. In addition, a brief explanation of LSP and its controlling parameters is included. From the aeroengines perspective, challenges and future aspects for improving LSP application and commercialization are summarised based on the authors' experience and published literature.
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