Abstract
The effects of heat-treatment on permeability are the main topic of the present study. Longitudinal dowel shape pairs of specimens were prepared from three native species and their specific gas permeability values were measured. From each pair, one specimen was kept for heat-treatment and the other was impregnated with 200 ppm nano-silver suspension; the size range of nanoparticles was 20-80 nm. In six consecutive steps, each pair was heated at 50, 75, 100, 125, 150, and 185°C. Results showed that gas permeability increased when specimens were heated at 50°C as a result of the loss of bond-water and consequent shrinkage. Permeability sharply decreased when the specimens were heated at 75°C and gradually increased at each step up-to 150°C. At 185°C, permeability again decreased in. The sharp decrease in permeability at 75°C was possibly due to irreversible hydrogen bonding in the course of water movements within the vessel perforations and pore system of cell walls. The gradual increase in permeability at higher temperatures, though, might be due to higher internal stresses that are released as micro-cracks develop, thus leading to a greater capability of fluid-transfer. Nano-silver impregnation intensified this process.
Highlights
IntroductionUnderstanding wood permeability is of vital importance as it has great impact on its utilization in different industries (such as: wood preservation, wood drying, pulp and paper) (Chen et al 1998, Dermoe et al 2012)
Understanding wood permeability is of vital importance as it has great impact on its utilization in different industries (Chen et al 1998, Dermoe et al 2012)
To minimize variation between heat-treated specimens (HT) and nano-silver-impregnated heat-treated specimens (NSI-HT) specimens, dowel-shape cylinders of 12 cm in length and 18 mm in diameter were procured in longitudinal direction of trees; two 5 cm long specimens were cut from each 12 cm long specimens; the upper specimens were kept as HT specimens, and the lower specimens were impregnated with nano-silver suspension once their specific gas permeability were measured
Summary
Understanding wood permeability is of vital importance as it has great impact on its utilization in different industries (such as: wood preservation, wood drying, pulp and paper) (Chen et al 1998, Dermoe et al 2012). Gas permeability values in solid woods can be measured with 0.001 second precision Taghiyari et al 2010, Taghiyari and Sarvari 2010, Taghiyari 2011a) and can be helpful in scientific and industrial purposes. Most industries in which permeability is important, deals with impregnation of solid woods with liquid or extraction liquids from them. Finding a correlation between gas and liquid permeabilities can be helpful for industrial decision-making processes. The present study is aimed at analyzing the effects of heat treatment on gas and liquid permeabilities of some untreated as well as nanosilver-impregnated native hardwoods, as well as possible relationship between gas and liquid permeabilities
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