Impact of nano-aluminum-oxide impregnation, densification, and vapor pre-treatment on the physical and mechanical properties of white willow wood

Fast-growing wood species are often characterized by low density, unsatisfactory mechanical properties, and poor biological durability. Therefore, various modification techniques have been tested to improve these disadvantages. The aim of this research work was to investigate the effects of densification of Salix alba (white willow) under hot pressing for 15 and 30 minutes on its physical and mechanical properties. Vapor pre-treatment for four and six hours was also applied to mitigate the negative effects of cracks and checks caused by breakage in wood cell wall under pressure. Markedly, separate sets of specimens were impregnated with aluminum oxide nano-suspension to evaluate if an increase in thermal conductivity would improve the properties of wood. The results indicated that densification significantly enhanced both the physical and mechanical properties of the wood. The four-hour vapor pre-treatment demonstrated the optimal improving results in both hot pressing durations. Though impregnation of specimens with the nano-suspension improved some properties (including spring back, hardness, and physical properties), most of the studied mechanical properties did not show any statistically significant improvement. Therefore, it was concluded that densifying willow wood for 15 minutes with a four-hour vapor pre-treatment yields optimal results. The enhancement in mechanical properties due to nano-aluminum oxide was not substantial enough to justify the associated costs, and thus, its use is not recommended for industrial applications.