Synthesis of aluminum hydroxide thin coating and its influence on the thermomechanical and fire-resistant properties of wood

Abstract

Abstract Aluminum hydroxide [Al(OH)3] film on wood substrate has been synthesized by means of the hydrothermal (HT) method for improvement of wood’s mechanical properties and resistance to combustion. The HT temperature was set to 100°C and 120°C, and the reaction time varied from 4 h to 10 h. X-ray diffraction (XRD) and X-ray photoelectron spectrometry (XPS) results show that the thin film grown on wood surface was amorphous Al(OH)3 and the relative crystallinity of treated woods slightly improved. SEM observation revealed that the Al(OH)3 film is composed of regular micro/nano-sized spheres, whose production and size increase with the reaction time, and some AlO(OH) structures emerged at 120°C with reaction times longer than 6 h. The storage modulus of the wood treated at 100°C and 120°C for 8 h can be improved by 30%, while the viscoelastic properties are also influenced by the HT treatment and Al(OH)3 coating. The limiting oxygen index of raw wood rose from 24.7% to 27.9% after the treatment, which can be interpreted as a moderate improvement of the fire resistance.