Formation And Analysis Of Photic Or Magnetic Responsive Property On A Wood Surface

Wood as a naturally renewable biomass has excellent properties of structures and functions.After an evolution for a long time,wood cell wall has multi-level hierarchical and porous structures,and lots of hydroxyl groups,which can be recombined with other inorganic or organic compounds to prepare functional heterogeneous composites.In this study,the materials in response to light or magnetism were choosed out to fabricate photoresponsive or magnetic responsive wood using various methods for binding wood.On the basis of improving easy burning,easy decay,easy deformation,and absorbing moisture,wood is attempted to apply in smart fields such as information storage,sensors,and anti-counterfeiting,and etc.Based on the principle of bionics and the properties of materials and wood structures,this research aimed to fabricate Fe₃O₄,Ni-Cu-P,WO₃,MoO₃5 and photochromic films,and mainly analyze the formation mechanism of heterogeneous composites and optical or magnetic properties.The main research contents and results can be summarized as follows:?1?Using the chitosan?CS?-modified wood as a scaffold,magnetic Fe₃O₄ nanoparticles were constructed via an in situ codeposition method at room temperature.X-ray photoelectron spectroscopy?XPS?showed that the binding energy for nitrogen atom increased from 399.28 eV to 400.09 eV when amino group chelated with iron ions,indicating that the CS played the role of "bridge".Not only was the CS connected with wood cell wall,but also absorbed metal ions,and finally the magnetic Fe₃O₄ formed in an alkaline condition.Scanning electron microscopy?SEM?analysis revealed that the Fe₃O₄ particles evenly and uniformly deposited on the surface of wood cell wall.X-ray powder diffraction?XRD?demonstrated the trans spinel phase structures of Fe₃O₄.Vibrating sample magnetometer?VSM?showed the as-synthesized composites were magnetically soft at room temperatures and the magnetic properties can be adjusted by controlling the concentration of the precursor.When iron ions concentrations were 0.4 mol/L,1.2 mol/L and 2.0 mol/L,the saturation magnetizations Ms increased gradually and reached 4.07 memu,54.05 memu,and 57.46 memu,respectively,the remanence magnetization Mr increased from 0.57 memu,1.46 memu,to 2.77 memu,and the coercivity He reduced from 17.02 Oe,14.54 Oe,to 14.29 Oe.?2?Using a short process of electroless plating without palladium?Pd?activation,magnetic ternary Ni-Cu-P alloys on wood surfaces were created to shield the interface of electromagnetic waves.The relation of elemental compositions and corrosion ability was studied mainly.The results proved that CuSO₄ concentration,pH in plating solution,and operation temperature can remarkably affect the process of plating.With an increase of CuSO₄ concentration,the reaction rate became slow.metal deposition per unit time reduced,and surface resistivity went up.When pH or temperature was increased,the reaction rate became fast,metal deposition per unit time increased,and surface resistivity reduced.Energy dispersive spectrometer?EDS?analysis showed that,with an increase of CuSO₄ concentration,Cu content in the plating coating increased,but Ni and P content reduced,respectively;when pH was increased,Ni and Cu content increased,respectively,but P content reduced;as operation temperature was increased,Cu and P content increased,respectively,but Ni content reduced.Tafel curves showed that the total Cu and P content in the coating determined the corrosion properties of materials.Higher total Cu and P content improved the corrosion resistance.XPS results showed that the magnetic coating mainly included Ni,Cu,and P.XRD results proved the microcrystalline structures.In frequencies ranging from 9 KHz to 1.5 GHz,the composite had the excellent magnetic responsive function and the electromagnetic shielding effectiveness?ESE?was higher than 60 dB.?3?Tungsten trioxide?WO₃?crystal films with sheet-like nanostructures were grown on wood surfaces through a low-temperature hydrothermal method.Ethanol as an inducer acted as an important role in the growth of WO₃ crystals.Meanwhile the effects of reaction time and precursor concentration on morphologies and crystalline structures were studied.Raman spectroscopy?RS?,X-ray photoelectron spectroscopy,and Fourier transformation infrared?FTIR?demonstrated that WO₃ crystals were successfully recombined with wood surfaces.As reaction time increased,crystals size and crystalline degree increased.Higher a concentration of precursor helped to produce higher crystalline degree of the sample.Under the condition of ethanol of 20%,the WO₃ film grown on the wood surface was composed of 2D nanosheets that had a higher crystalline degree,with an edge length of 580?957 nm and a thickness of about 80 nm.The UV-vis analysis showed that the sample prepared with the 20%of ethanol content exhibited excellent response to light.When the sample was irradiated under UV light of 365 nm,there appeared an obvious color difference.The wetting results demonstrated that the WO₃-treated wood surfaces possessed the superhydrophilic behavior and then converted to the superhydrophobic property through the octadecyltrichlorosilane?OTS?treatment.Atomic force microscopy?AFM?analysis indicated that photoresponsive and hydrophobic performances were signally related to a change in roughness of micro-nano structures of wood surfaces.?4?By controlling reaction time,precursor concentration and pH value,hierarchical flower-like hexagonal molybdenum trioxide?MoO₃?crystals was fabricated on wood surfaces using a low-temperature hydrothermal method.XRD analysis results showed MoO₃ crystals had the hexagonal structures with crystal parameter ofa = b= 10.528A,and c = 14.787A.SEM results showed that 3D flower-like structures were formed on wood surfaces and the structures were composed of many unique bumps that were assembled using numerous hexagonal rods with a thickness of 2.0 ?m and a length of several micrometers.EDS,RS,FTIR and XPS analyzed the chemical compositions of films and proved that the atomic ration of Mo:O closes to 1:3.The UV-vis results suggested that the as-fabricated MoO₃ crystal films on wood surfaces exhibited outstanding color response to light stimulation.The calculated band gap of the MoO₃ film based on K-M model was around 2.98 eV.The mechanism of color response can be elucidated by using the model of double insertion/extraction of ions and electrons.?5?A transparent film based on a wood surface with photochromic behavior was successfully constructed using a sol-gel method.The film was made up of the photochromic material?PM?,polyvinyl alcohol?PVA?,and dextrin?DT?with an appropriate recipe.The responsive function to solar light and visible light,and hydrophobic properties were characterized.FTIR analysis showed that the film was successfully crosslinked with the wood surface.SEM observations indicated that the PM modified by the PVA and the DT deposited on the wood surface uniformly and evenly.Under the condition of solar light,the ?E*values of films remarkably increased from 3.7 to 58.2,as the PM concentration increased from 0 to 3.0%.With further increasing the PM concentration to 6.0%,AE*values changed slightly.Moreover,the reversible photochromic functions of materials can be carried out by changing the solar light and visible light.The average coloration time of the composite reached 2.0 s and the average fading time reached 5.7 s.And the coloration time and fading time in the cross section were longer than the radial or tangential sections.The wetting properties of the samples surface changed from hydrophilic function to hydrophobic function through the octadecyltrichlorosilane?OTS?treatment.