Effects of dry ice on gas permeability of nano-silver-impregnated Populus nigra and Fagus orientalis.

Effects of dry-ice treatment (frozen CO(2) at -78.5°C) on gas permeability of untreated and nano-silver-impregnated poplar and beech specimens were studied here on the basis of their biological structure and woody mass as well as their vessel element types. A 200 ppm aqueous dispersion of silver nano-particles was used for impregnation; the size range of silver nano-particles was 20-80 nm. Dry-ice treatment increased gas permeability by 87 and 45% in poplar and beech, respectively. Nano-silver impregnation also increased gas permeability by 190 and 89% in poplar and beech, respectively. Dry-ice treatment on nano-silver-impregnated specimens increased gas permeability even more (31% increase in poplar but only 0.96% in beech). It may be concluded that dry-ice treatment on solid woods may be used as a practical method to increase permeability in species that because of their biological structures are impermeable; since this method alters the biological structure slightly and consequently decreases mechanical strength of solid woods insignificantly, it may substitute methods such as incising to increase permeability.