Surface fractal analysis of the pore structure in natural and heat-treated spruce wood cell walls using nitrogen adsorption/desorption test

Abstract

Abstract Surface fractal dimension evaluates the internal surface complexity of pores in a wide range of materials. Unfortunately, the scale-dependent property of surface fractal in the pore structure of natural and heat-treated wood remains unclear. In this study, derived from the Frenkel-Halsey-Hill (FHH) fractal model and the Neimark fractal model, a comprehensive surface fractal analysis of the pore structure of natural and heat-treated wood was carried out based on nitrogen adsorption/desorption data. The results showed that two regions were identified as surface fractal, i.e., the pores with diameters less than 10 nm (Region 1) and the pores with diameters larger than 10 nm (Region 2). The scale-dependent property of two fractal regions was not affected by the different heat treatment atmospheres. The FHH and Neimark surface fractal dimensions of the pores in Region 1 were 2.079–2.155 and 2.780–2.940, respectively, and showed an obvious difference. The FHH and Neimark surface fractal dimensions of the pores in Region 2 were 2.481–2.536 and 2.413–2.551, respectively, and showed a slight difference. In addition, the FHH surface fractal dimensions of the pores in Region 2 had a positive relationship with the rate of early-stage moisture absorption. These findings are expected to evaluate the relationship between the transport properties and the pore structure in wood cell walls through the surface fractal dimension.