Zinc oxide thin films (thickness ~0.6 pm) were deposited on zinc substrates by the spray-CVD method and a new kind of sensor structure Pd/ZnO/Zn was fabricated for hydrogen detection. The sensor was exposed to air mixed with different concentrations of H2 (2000-20000 ppm) and showed high sensitivity and a short time response at room temperature. The recovery time of the sensor to the zero base level was found to be faster after exposure to. higher hydrogen concentrations. The sensitivity was bias-dependent with best performanCe at 0.05 V. Because of the key role of sensing played by the adsorption and desorption processes at the Pd surface and the Pd/ZnO interface, the contact resistance at the Pd/ZnO interface changed reversibly. The sensor showed high selectivity to hydrogen at room temperature and was insensitive to CO, CO2 and LPG even at higher concentrations.
A tensile ruptured gum specimen shows formation of crystalline regions at an angle of 45° to the flow lines, whereas a tensile ruptured filled specimen shows formation of depression. A tear fractured gum specimen shows again the formation of crystallites at an angle of 45° to the flow lines. Tear fractured filled specimens show the enhancement of crystallinity throughout the matrix, but the surface is rough. Flex fractured gum specimen show a large number of cracks on the surface while the filled vulcanizate shows formation of balls presumably due to coiling of polymer chains on the filler surface. An abraded gum surface shows dimple structure, while a filled vulcanizate indicates coarse ribbed structure. Addition of lignin, in general, reduces the crystallinity of tensile and tear fractured samples and increases the fibrosity of flex cracked and abraded samples.
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