Study On The Functional Materials Prepared From Nanofibrillated And In Situ Processed Lignocellulosic Materials

Lignocellulose material is a kind of abundant biomass resource on the earth.With it's merits of renewability,biodegradability and biocompatibility,lignocellulose material has been widely used in the fields of energy,green electronics,biological devices,etc.The intensive study of lignocellulose material is of great significance for the sustainable development of human civilization and reduced dependence on nonrenewable resources.This paper focused on the lignocellulose material and carried out the following researches:(1)Cellulose nanocrystals(CNCs)and cellulose nanofibrils(CNFs)from different cellulose raw materials were fabricated using oxalic acid hydrolysis and subsequent mechanical fibrillation,and the effects of oxalic acid concentration and raw material sources on the properties of the resultant CNCs and CNFs were investigated.In addition,the chemical structure,crystallinity,and thermal stability of CNCs were compared.The results showed that the cellulose raw materials were esterified during the hydrolysis process,and the obtained cellulose nanomaterials were endowed with functional carboxyl groups.The thermal stability of the prepared CNCs is better than that of CNCs obtained by sulfuric acid hydrolysis.The yield of CNCs is low due to the weak acidity of oxalic acid.(2)Versatile cellulose nanocrystals with a high yield of 36.9%,excellent thermal stability and functional carboxyl groups were prepared by oxalic acid hydrolysis and disk milling pretreatment using bleached kraft eucalyptus pulp as the raw material.The prepared CNC film with high transmittance and low haze demonstrated excellent thermal stability,which can be used at 150? for 4 h without discernible change in appearance.In addition,the 3D printed patterns with porous structures can be potentially applied in tissue engineering scaffolds due to the excellent biocompatibility of CNCs.(3)The lignin component in natural wood material was removed using sodium hypochlorite solution,and the delignification efficiency for L wood(cutting wood along the growth direction of tree)and R wood(cutting wood vertical to the growth direction of tree)was compared.The R wood showed a higher delignification efficiency.Anisotropic transparent paper with high transmittance(?90%)and high haze(?90%)was developed by directly shear pressing the delignified R wood.The obtained transparent paper demonstrated anisotropic light scattering and polarization effect.A 14% enhancement in the total energy conversion efficiency and 18% improvement in the short circuit density for Ga As solar cell were achieved by utilizing the anisotropic transparent paper as the light management coating layer.(4)An anisotropic porous material was fabricated by removing the lignin component in natural wood material using sodium chlorite solution.The porous material exhibited fast and anisotropic liquid and solid particle mass transport property,with a high transport speed along the channel direction approximately five times faster than that perpendicular to the channel direction.The chitosan film with anisotropic microstructure and birefringence was prepared by virtue of the anisotropic mass transport property and unidirectional capillary forces in the porous material.(5)The similarities and differences in microstructures for hardwood and softwood were compared,and the mechanical property and thermal conductivity of some natural wood materials were characterized.The results showed that natural wood materials,including hardwood and softwood,possess excellent hydrophilicity,an interconnected pore network,low thermal conductivity,and favourable mechanical properties.The solar steam generation devices were prepared by carbonizing the top surface of natural wood materials.Different natural wood materials have different microstructures,resulting in significantly different solar steam generation performances with the more porous wood showing higher evaporation efficiencies.