We report the impact of gamma irradiation on the performance of a gold Schottky-contacted ZnO nanorod-based hydrogen sensor. RF-sputtered vertically aligned highly c-axis-oriented ZnO NRs were grown on Si(100) substrate. X-ray diffraction shows no significant change in crystal structure at low gamma doses from 1 to 5 kGy. As gamma irradiation doses increase to 10 kGy, the single crystalline ZnO structure converts to polycrystalline. The photoluminescence spectra also shows suppression of the near-band emission peak and the huge wide-band spectrum indicates the generation of structural defects at high gamma doses. At 1 kGy, the hydrogen sensor response was enhanced from 67% to 77% for 1% hydrogen in pure argon at a 150 °C operating temperature. However, at 10 kGy, the relative response decreases to 33.5%. High gamma irradiation causes displacement damage and defects in ZnO NRs, and as a result, degrades the sensor's performance as a result. Low gamma irradiation doses activate the ZnO NR surface through ionization, which enhances the sensor performance. The relative response of the hydrogen sensor was enhanced by ∼14.9% with respect to pristine ZnO using 1 kGy gamma ray treatment.
Radiation shielding composites of ethylene‐propylene diene monomer (EPDM), reinforced with tungsten (W) and barium sulphate (BaSO4) in different filler weight (wt%) were synthesized. The effects of W and BaSO4 on gamma and neutron attenuation properties of the composites were studied by experimental methods using 137Cs, 60Co and 252Cf radioactive sources. EPDM composites with W and BaSO4 fillers were also investigated for filler dispersion using scanning electron microscopy and X‐ray radiograph. The experimental results revealed that the incorporation of W and BaSO4 significantly improved the radiation attenuation properties of the EPDM composites. It was observed that the attenuation properties of the composite material increases with higher concentration of the filler. The half‐value layer (HVL), tenth value layer thickness and relaxation length of the composites were found to decrease with increasing concentration of the filler. The results also showed that the attenuation behaviour of 50 wt% BaSO4 filled polymer composite is comparable to that of the composite with 25 wt% W. The developed composite with 75 wt% W filler exhibited the maximum radiation attenuation with lowest HVL thicknesses.
The chemical states of epitaxial PbZrxTi1-xO3 films were investigated by an X-ray photoelectron spectroscopy as a function of the gamma-ray doses. An anomalous behaviour was observed in Pb4f states, and a core level of Pb4f shifts towards a higher binding energy at 50 kGy and towards a lower binding energy at 200 kGy. The behaviour can be explained by a radiation induced reduction of PbO to metallic Pb. The metal-insulator-metal electrodes were fabricated by lithography, and the current-voltage characteristics were measured. A negative differential resistance (NDR) was observed in the leakage currents at room temperature. A higher current and disappearance of NDR characteristics were found in the 200 kGy irradiated samples, which further confirms the presence of metallic Pb.
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