Parametric study of plasma-mediated thermoluminescence produced by Al₂O₃sub-micron powders

Abstract

Sub-micron Al2O3 powders with a surface activated by dielectric barrier discharge exhibit improved performance in wet deposition of ceramic layers. In addressing the possible mechanisms responsible for the observed improvement, a comprehensive thermoluminescence (TL) study of plasma-activated powders was performed. TL offers the unique possibility of exploring the population of intrinsic electrons/holes in the charge trapping states. This study covers a wide range of experimental conditions affecting the TL of powders: treatment time, plasma working gas composition, change of discharge configuration, step-annealing of powder, exposure to laser irradiation and aging time. Deconvoluted TL spectra were followed for the changes in their relative contributions. The TL spectra of all tested gases (air, Ar, N2 and 5% He in N2) consist of the well-known main dosimetric peak at 450 K and a peak of similar magnitude at higher temperatures, centered between 700 and 800 K depending on the working gas used. N2 plasma treatment gave rise to a new specific TL peak at 510 K, which exhibited several peculiarities. Initial thermal annealing of Al2O3 powders led to its significant amplification (unlike the other peaks); the peak was insensitive to optical bleaching, and it exhibited slow gradual growth during the long-term aging test. Besides its relevance to the ceramic processing studies, a comprehensive set of data is presented that provides a useful and unconventional view on plasma-mediated material changes.

On the air atmospheric pressure plasma treatment effect on the physiology, germination and seedlings of basil seeds

“…To better understand how the plasma treatment is influencing the germination process and faster growth we studied the effect on seeds just after treatment. From the EIS measurements we observed a variation of the single seed impedance that is likely related to a charging due to plasma seed surface interaction, in the same way charges are deposited on di electric barriers of DBDs [44][45][46][47]. The presence of charges on the seed structure could lead to intense electrical fields that could trigger the micro-and macronutrient re-distribution inside the embryo and endosperm.…”