Study On Biomimetic Constructions And Performances Of Magnetic Wood-based Composites

The study of high-performance biomimetic smart materials is an eternal topic thoughout human development.As a natural polymer,natural wood not only has their unique characteristics in physics,chemistry and biology,but also is an anisotropic material.However,the hydroxy-rich surface and porous structure of the wood make it prone to decay,flammability and other adverse effects.This study combine the magnetic nanomaterials（MnFe₂O₄）with the natural wood by biomimetic mineralization process,constructing a series of high value-added MnFe₂O₄/wood composites with the multi-functions,such as microwave absorption,super paramagnetic,flame retardant,super hydrophobic,acid/alkali resistance and wear resistance.It provides a new research idea for the development of high value and multi-functional wood.The concrete research contents are as follows:（1）MnFe₂O₄ nanocrystals were fabricated on wood substrate using a solvothermal method through a bottom-up pathway,and forming MnFe₂O₄/wood composite.The sudy on the dynamic evolution and growth process of the MnFe₂O₄ nanocrystals indicated that the the sizes of the MnFe₂O₄on the wood surface is adjusted（50³60 nm）.After structural adjustment,the composites showed good microwave absorption performance.When the diameter of nanoparticles on the wood surface is 140 nm,the reflection loss reached the minimum value of-12 dB at 15.52 GHz.（2）Nanooctahedra MnFe₂O₄ film was coated on wood surface via a low temperature hydrothermal process.The as-prepared MnFe₂O₄/wood composite exhibited excellent performance of superparamagnetism,fire resistance and electromagnetic wave absorption.The saturation magnetization of the MW was 28.24 emu·g^-1,and expressed excellent superparamagnetism property.The composite exhibits excellent thermal stability in the face of open fire.Additinally,a minimum reflection loss of the MW was-9.3 dB at 16.48 GHz.（3）One-pot hydrothermal method was used to combine FAS-17 and MnFe₂O₄ nanosheets on the surface of wood.The prepared durable MnFe₂O₄/wood composites have super-paramagnetic,super-hydrophobic and electromagnetic absorption performances.The hydrogen bond assembly appeared in the formation process of the lamellar MnFe₂O₄ layer,causing the tight adhesion of the lamellar MnFe₂O₄ onto the wood surface.The fluoroalkylsilane macromolecules on the MnFe₂O₄layer surface via the polycondensation process provided a low surface energy to achieve superhydrophobicity.After a one-step hydrothermal reaction,the value of the saturation magnetization of the composite reached 28.08 emu·g^-1 and presented excellent superparamagnetism properties.The value of the minimum reflection loss of the FMW reached-8.29 dB at 16.39 GHz,and the absorption bandwidth improved.The value of the water contact angles of composite reached156°,and the composite maintained its superhydrophobic properties even after sand abrasion and exposure to corrosive liquids.（4）The pyrolysis behavior and kinetics of the MnFe₂O₄ nanoparticles/wood composite was analysised by Flynn–Wall–Ozawa method and Friedman method,and proving a good thermal stability of the composite in theory.The analysis of the change of different proportion of MnFe₂O₄ in these composites for the thermostability by contrasting activation energy indicated that the thermostability of composites improved as the proportion of the MnFe₂O₄ nanoparticles increased.Synthesized MnFe₂O₄/C composite under the guidance of pyrolysis behaviors and kinetic study in N₂ atmosphere exhibits good adsorption capacity（84.18 mg/g）for removing methylene blue dye in aqueous solution and easy separation characteristic.