Pore interconnectivities of mesoporous silica prepared with precursor sols aged for various times were investigated by N 2 adsorption-desorption measurement and cyclic voltammetry. With increasing aging time of the precursor sol to 4 days, an abnormal decrease in both total open volumes and specific surface areas was found. However, with further increasing the aging time to 15 days, the total open volumes and specific surface areas dramatically increased, indicative of the formation of highly interconnected pores and a remarkable increase in the silica porosity. This was further confirmed by cyclic voltammetry measurements using aqueous potassium iodide solutions on the corresponding silica films, which showed a significant rise in redox current and total charge Q across the films prepared after a longer time aging of precursor sols. This rise can be attributed to the diffusion of I − across the silica films with enhanced pore interconnectivity, despite of the decline in total porosity for some silica samples.

Undoped and Sb doped tin oxide thin films were fabricated by the dip-coating technique through a propylene oxide assisted sol-gel method. Atomic force microscope measurements reveal that the grain size increased after being calcined at higher temperature; while increasing the dopant content leads to a reduction in grain size and a corresponding increase in the concentration of grain boundaries. Positron annihilation spectroscopy analysis shows the defects are reduced with increasing Sb content to 5 %; however, further increasing the doping level to 10 % introduces more defects to the films. At all doping levels, the defects in Sb doped tin oxide films decreases significantly upon elevating the calcination temperature.

The photodegradation progress of epoxy cured with polyamide and the effect of the curing agent content under UV-A irradiation have been investigated using positron annihilation spectroscopy with an energy tunable positron beam. After 88 h of irradiation, a post-cure process and the generation of carbonyl groups reduce the value of the S parameter, compared with the virgin samples. As the irradiation time increases from 208 h to 399 h, the S parameter decreases, which may be due to the growth of carbonyl groups and the generation of free radicals. After 543 h of irradiation, a dead layer with very low S value appears near the sample surface probably induced by a dramatic decrease in the Ps formation probability. The positron results also reveal that epoxy cured with an appropriate amount of polyamide has a smaller dead layer suggesting that the amount of curing agent is a key factor affecting the photodegradation of epoxy resin.