n. sheikh

Polymeric absorbers used in solar thermal collectors must have appropriate thermal and mechanical properties. In this work, polyethylene/graphite (PE/NG) nanocomposite was selected as polymeric absorber and the effect of radiation on the thermal and mechanical behavior of that has been investigated. PE/NG composites containing 0.05, 0.1 and 2.25% nanographite was prepared through melt extrusion process. The SEM images of the samples proved the fair dispersion of NG in polymer matrix. Then the samples were irradiated by electron beam at doses ranging from 100 to 200 kGy. The specimens were characterized by tensile testing, Differential Scanning Calorimetry (DSC) and FT-IR spectroscopy. The results show that nanocomposite containing 2.25% graphite irradiated at 100 kGy has the best tensile strength and thermal stability. The results of DSC show that the addition of 2.25% NG to polyethylene improves the melting point and thermal properties. DSC and carbonyl index results of this composite in accelerated aging condition display no remarkable changes occur in thermal performance and structure of composite during aging. Also, with addition of NG to PE the UV/Vis absorbance of the PE/NG nanocomposite increases. Altogether, the experimental results reveal PE/NG as suitable candidates for solar thermal absorbers.

The application of gamma irradiation as a factor to graft the synthesized silver nanoparticles to the polypropylene surface and modify the de-ionized (DI) water supply system is a new experimental project. In this study, using the effect of gamma irradiation on the surface of a certain type of filter, reduces silver ions and modifies the filter surface simultaneously. Then, the effect of the modified filter on the performance of DI water supply systems, which are directly and indirectly related to quantum technologies and nuclear science, was investigated by modeling on the surface of indium phosphide (InP) semiconductor. The dose of gamma irradiation and the reduction conditions of silver nanoparticles were determined after passing the optimization stage. So, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), ultraviolet-visible absorption spectroscopy (UV-Vis), attenuated total reflection (ATR) and bacterial counting tests by plate count agar (PCA) were used. Then it was found that the desired result of filter surface modification is due to the formation of surface plasmon resonance in the colloidal solution of silver nanoparticles which is produced during gamma irradiation synthesis.

The aim of this research is to fabricate a novel temperature sensor for any calorimetry system. A new mixed solution method was introduced to prepare polystyrene/multiwall carbon nanotube nanocomposite samples with different weight percentages as 0.05, 0.1, 0.28, 1, and 2 of MWCNTs. To demonstrate the dispersion state of the inclusion into the polymer matrix, the SEM analysis was applied. Also, XRD and Raman spectroscopy analyses were carried out. The electrical percolation threshold was investigated and achieved at about 0.28 weight percent of the inclusion. Finally, the electrical resistance of the samples was measured from room temperature up to ~100ºC. Consequently, positive temperature coefficient and negative temperature coefficient effects were observed before and after Tg for the most nanocomposite samples, respectively. The best linear response of the resistance-temperature curve was achieved at 20-50ºC, which using a second-order fitting curve it can be used up t0 ~70ºC. Results show that the polystyrene/multiwall carbon nanotube nanocomposite near the percolation threshold can be used as a temperature sensor for calorimetric purposes.