## 3 Results and Analysis  
The structure of the original wood surface, such as vessel and pits in the vessel, appeared rough under the high-power mirror (Figure 2a). After spraying the wood with chitosan solution and the drying curing treatment, a thin film formed on the wood surface, suggesting that chitosan had been loaded on the wood surface (Figure 2b). After spraying the wood with sodium phytate solution and drying curing treatment on the exterior, the thickness of the film noticeably increased, and the structures, such as conduits on the wood surface, were further obscured, which made the wood surface smoother (Figure 2c). Finally, the Al(OH)\({}_{3}\) solution was sprayed, and the wood surface was loaded with a large number of particles that were tightly arranged, which completely covered the wood surface (Figure 2d). The accelerated ultraviolet aging test was conducted for 720 hours on the original wood and wood coated with chitosan/sodium phytate/Al (OH)\({}_{3}\). The color value before UV irradiation was used as the initial reference value to determine the color differences \(\Delta L^{\star}\), \(\Delta a^{\star}\), and \(\Delta b^{\star}\) and the total color difference \(\Delta E^{\star}\) after lighting for 2, 6, 12, 24, 36, 48, 60, 72, 96, 120, 144, 168, 192, 240, 360, 480, 600, and 720 hours. As the diagram indicates (Figure 3), the \(\Delta L^{\star}\) of the original wood was significantly reduced, and the \(\Delta a^{\star}\) and \(\Delta b^{\star}\) were significantly increased after 720 hours of UV exposure. The \(\Delta L^{\star}\) of CH/SP/Al (OH)\({}_{3}\) wood was opposite that of the original wood, and the \(\Delta a^{\star}\) and \(\Delta b^{\star}\) were the same as those of the original. Generally, the \(\Delta L^{\star}\), \(\Delta a^{\star}\), and \(\Delta b^{\star}\) of the CH/SP/Al (OH)\({}_{3}\) wood increased as the irradiation time of the ultraviolet lamp increased, but the degree of change was noticeably smaller than that of the original wood, which indicated that CH/SP/Al (OH)\({}_{3}\) coatings attached to the wood surface showed strong photostability and conferred a UVprotective effect on wood. It could be inferred that the structure of six hydroxyl groups around the Al atom enhanced the UV absorption in the specified range [34]. Figure 3: Changing parameters \(\Delta L^{*}\), \(\Delta a^{*}\), \(\Delta b^{*}\), and \(\Delta\)E\({}^{*}\) of the original wood and the CH/SP/Al(OH)\({}_{3}\) wood. Figure 2: SEM images of (a) original wood; (b) CH wood; (c) CH/SP wood and (d) CH/SP/Al(OH)\({}_{3}\) wood. As shown in Figure 4, the initial static contact angle of the original wood was 75\({}^{\circ}\), and the wood had hydrophilic characteristics. As time progressed, the water droplets gradually adsorbed into the wood interior, and the contact angle decreased to 32\({}^{\circ}\) after 60 s, as there were gaps on the wood surface, and tubular holes were abundant. The initial static contact angle of the CH/SP/Al (OH)\({}_{3}\) wood was 140\({}^{\circ}\), and the wood showed high hydrophobicity. As time progressed, the contact angle decreased to 120\({}^{\circ}\) slowly after 60 s, and the wood still showed high hydrophobicity. These results, combined with SEM image analysis, revealed that the micro-nano structure introduced into the wood substrate induced hydrophobicity. The trapped air pressure balances the gravity of the water droplet and produces a gas layer on the wood surface, inducing the droplet to seemingly \"sit\" on the wood surface [35]. Chitosan, sodium phytate, and Al (OH)\({}_{3}\) were used to conduct flame-retardant finishing of the wood by electrostatic LbL self-assembly. The effect of each component on the flame-retardant properties of the wood was studied using the limiting oxygen index (LOI) for assessment (Figure 5a). The LOI value of the original wood that belonged to combustible material was 24.6. After loading chitosan on the wood surface, the LOI value increased to 26.5, and the flame retardancy was improved.