Magnetic wood would have potential uses in electromagnetic shielding and electromagnetic wave absorption. In this paper, magnetic coatings on a wood surface were synthesized using a layer-by-layer self-assembly method. As the cationic polyelectrolyte carrier, natural macromolecular chitosan was pre-immobilized on a wood surface first, followed by the alternate adsorption of anionic polyelectrolyte sodium phytate and positively-charged Fe3O4 nanoparticles. The concentration of pH-controlled chitosan solution, sodium phytate solution, and Fe3O4 nanoparticle suspension, soaking time, and the number of alternating sedimentary layers varied. The morphology and crystal structure of the Fe3O4 modified wood samples were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The magnetic hysteresis loops showed that the modified wood had magnetic properties which were improved as the number of assembled layers increased.

Fire-retardant chitosan/sodium phytate/MgO nanoparticle (CH/SP/nano-MgO) coatings were loaded on a wood substrate via electrostatic layer-by-layer self-assembly and characterized by scanning electron microscopy and energy-dispersive spectrometry. The flammability and thermal degradation of the original wood and wood samples treated with chitosan, chitosan/sodium phytate, chitosan/sodium phytate/MgO nanoparticles were studied by limiting oxygen index (LOI), exposure combustion experiments and thermogravimetric analysis (TGA), respectively. The CH/SP/nano-MgO coating served as an intumescent fire-retardant system that created a physical protection cover and exhibited the best fire retardant performance. The LOI value was 30.2% and required approximately 16–17 s to self-extinguish when exposed to air. The TGA curves also showed that char formation protected the wood from combustion.