Study On The Wood/SiO₂ Aerogel Nanocomposites

The nano science and technology are one of the new technologies which being applied on the wood science would greatly attention to wood scientists in recently years. Because of this, Wood-inorganic composites have been one of the most active research subjects in the field of wood function modification. Some update research development on nano-metered composites and wood inorganic composites are reviewed in this paper. The aerogel conception being introduced to fabricate Wood-inorganic composites. The new wood-Silica aerogels composites were fabricated by sol-gel process and supercritical drying technique. Comprehensive research was performed on the principle of technology to preparation, dissemination and interface of Silica aerogels in woody cell, the performance of composites and the composite mechanism of wood-Silica aerogels composites.Silica gels were fabricated with tetraethoxysilane (TEOS), ethanol (EtOH), water and HCI/HF acid by controlling sol-gel condition and component. Supercritical CO2 drying technique and pressure-vacuum impregnation of Silica gels were successfully confirmed. The Silica aerogels in wood cell consist of colloidal particles with diameters of about 13-126 nm. The silica aerogels were coherent, monolithic non-crystalline solid materials with low density and nanosized porous. The physics and mechanics research of the basswood-Silica-aerogels inorganic composites showed compressive strength parallel to grain of wood, bending strength and static bending as lower as untreated wood except hardness. But the kind of physics and mechanics alder wood- Silica-aerogels inorganic composites as well as untreated wood. It did improve the air water absorption which the alder and basswood Silica-aerogels inorganic composites not only have the dimensional stability but also excellent fire retardancy.Systematic research of the complex mechanism of wood silica-aerogels composites were carried out by XRD TEM SEM EDAX FTIR XPS and thermal analysis such as DMA/DSC/TG. The results show that, Silica aerogelscompacted the wood very well and retained porous structure of wood. There are three kind of coalescent mode between woods to silica aerogels. Firstly, SiO2 aerogels are coalescence with hydroxyl group of wood cellulose substances by hydrogen bonding. Secondly, XPS of C1s spectra have greatly changed than untreat wood. The C3 and C4 vanish which C3 have some increase. The results indicate that carbonyl group of hemicelluloses and lignin participates in condensation reaction of TEOS. SiO2 aerogels are coalescence with wood substances by covalent bonds. The SiO2 aerogels are coalescence with wood substances in 'molecular composite' and become part of wood. The third, SiO2 aerogels are condensed with homopolymer, which fill in wood cell.