Interfacial effect of surface modified TiO2 and SiO2 nanoparticles reinforcement in the properties of wood polymer clay nanocomposites

Induced Wood-Inorganic Composites in Standing Trees via Slow-Release Drip

It is a novel idea to fabricate wood-inorganic composites by utilizing the transpiration of bionic trees to realize the self-assembly of inorganic precursors in wood formation. We selected a 10-year-old poplar and diffused the solvent or sol containing SiO₂ precursor into the xylem via the slow-release drip method. In combination with the moisture in xylem, reactions such as hydrolysis, polycondensation and self-assembly were induced in order to form wood inorganic composites. It was found, through microscopic observation, that such inorganic substances were yellowish brown and widely existed in vessels, wood fibers and ray cells. For the new grown wood, the fiber–tissue ratio and cell wall thickness underwent an increase, while the vessel diameter and tissue ratio experienced a decline. Moreover, such change was related to the concentration of precursors. EDS analysis proved that the elemental composition of sediments in wood cells was C, O, Si, K and Ca. XPS confirmed that the newly formed wood contained silicon oxide, illustrating that the standing tree slow-release drip technology could induce wood to fabricate inorganic composites.

Polyimide/fluorinated silica composite films with low dielectric constant and low water absorption

In this study, KMnO4 was applied as an etchant to partially decompose the silica microspheres into mesoporous structures. 1H,1H,2H,2H-perfluorodecyltriethoxysilane was grafted onto the surface of the hollow silica. A fluorinated silica/polyimide hybrid material was prepared. Meanwhile, the influence of fluorinated silica on the dielectric property and moisture absorption property of the hybrid material was discussed. It is found that the fluorinated silica can lower the dielectric constant and hygroscopicity of the hybrid film. The fluorinated silica is characterized by strong hydrophobicity, good dispersibility, and good thermal stability. Even at a very low filling level of only 2 wt%, the dielectric constant of the polyimide hybrid is significantly reduced to 2.61 without sacrificing thermal stability. The water absorption rate of the polyimide hybrid film is reduced from approximately 3.1% to 2.1 wt%. Moreover, this provides a new idea for reducing the dielectric and water absorption properties of materials.

Multi-Functional Luminescent Coating for Wood Fabric Based on Silica Sol-Gel Approach

Environmentally friendly protection coatings have obtained increasing attention for their use in wooden materials, which can be destroyed easily when exposed to outdoor environments. A series of silane sol coatings coordinated with Eu³⁺ was prepared by hydrolyzing silane compounds. The obtained luminescent coating with three-dimensional net structure showed excellent optical, anti-ultraviolet aging, and thermal stability. The hybrid silane-modified compound coating was well-distributed on the wood by Si–O bonds to prevent its removal. The compound coating could stave off the decomposition of wood by converting ultraviolet light into red light and a charring action can endow the wood with thermal stability at high temperature, demonstrating the improvement of fire resistance and radiation residence following prolonged exposure to ultraviolet light, proving its excellent anti-ultraviolet aging properties.

Mechanical Properties and Strength Reliability of Impregnated Wood after High Temperature Conditions

The paper presents the results of the research into the impact of impregnation of wood on its bending strength and elastic modulus under normal conditions and after thermal treatment and investigates its structural reliability. Pinewood, non-impregnated and pressure impregnated with a solution with SiO₂ nanoparticles, was used in this research. The use of nanoparticles decreases the flammability of timber among others. Some of the tested samples were treated at 250 °C. This temperature corresponds to the boundary of the self-ignition of wood. This elevated temperature was assumed to be reached by a given speed of heating within 10 min, and then the samples were stored in these conditions for 10 and 20 min. The tests demonstrate that the bending strength of the impregnated wood was slightly improved, the impregnation did not impact the elastic modulus of the material in all such conditions, and the residual strength decreased less for the wood impregnated after being exposed to the elevated temperatures. The reliability analysis proves a positive effect of impregnation with a solution with SiO₂ on the durability of wood, both after being exposed to normal and elevated temperatures. The distribution of the failure rates indicates a more intensive degradation of non-impregnated wood. The distribution of the survival function demonstrates a more probable non-destruction of impregnated wood after elevated temperature conditions.

Magnetic-Responsive Janus Nanosheets with Catalytic Properties

In this article, we describe a method to fabricate magnetic-responsive Janus nanosheets with catalytic properties via the surface protection method. Fe₃O₄ nanoparticles and PW₁₂O₄₀^3--based ionic liquid are located on the two opposite sides of the Janus nanosheets, respectively. The Janus nanosheets are characterized by Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and ζ-potential analyses. They are used as recyclable catalysts to the esterification reaction of methanol and oleic acid for their magnetic-responsive and catalytic properties. The esterification ratio is up to 80% and there is nearly no change when Fe₃O₄ nanoparticles/PW₁₂O₄₀^3--based ionic liquid composite nanosheets were recycled four times.

Hydrothermal Synthesis of Nanooctahedra MnFe₂O₄ onto the Wood Surface with Soft Magnetism, Fire Resistance and Electromagnetic Wave Absorption

In this study, nanooctahedra MnFe₂O₄ were successfully deposited on a wood surface via a low hydrothermal treatment by hydrogen bonding interactions. As-prepared MnFe₂O₄/wood composite (MW) had superior performance of soft magnetism, fire resistance and electromagnetic wave absorption. Among them, small hysteresis loops and low coercivity (<±5 Oe) were observed in the magnetization-field curve of MW with saturation magnetization of 28.24 emu/g, indicating its excellent soft magnetism. The MW also exhibited a good fire-resistant property due to its initial burning time at 20 s; while only 6 s for the untreated wood (UW) in combustion experiments. Additionally, this composite revealed good electromagnetic wave absorption with a minimum reflection loss of −9.3 dB at 16.48 GHz. Therefore, the MW has great potential in the fields of special decoration and indoor electromagnetic wave absorbers.

Effect of Surface-Modified TiO₂ Nanoparticles on the Anti-Ultraviolet Aging Performance of Foamed Wheat Straw Fiber/Polypropylene Composites

Surface modification and characterization of titanium dioxide (TiO₂) nanoparticles and their roles in thermal, mechanical, and accelerated aging behavior of foamed wheat straw fiber/polypropylene (PP) composites are investigated. To improve the dispersion of nanoparticles and increase the possible interactions between wheat straw fiber and the PP matrix, the surface of the TiO₂ nanoparticles was modified with ethenyltrimethoxy silane (A171), a silane coupling agent. The grafting of A171 on the TiO₂ nanoparticles' surface was characterized by Fourier transform infrared spectroscopy (FTIR). The wheat straw fibers treated with A171 and modified TiO₂ nanoparticles were characterized by FTIR and thermogravimetric analysis (TGA). FTIR spectra confirmed that the organic functional groups of A171 were successfully grafted onto the TiO₂ nanoparticles and wheat straw fibers, and the modified TiO₂ nanoparticles were adsorbed onto the wheat straw fibers. Thermogravimetric analysis showed that a higher thermal stability of the wheat straw fiber was obtained with the modified TiO₂ nanoparticles. The flexural, tensile, and impact properties were improved. A higher ultraviolet (UV) stability of the samples treated with modified TiO₂ nanoparticles was exhibited by the study of the color change and loss in mechanical properties.

Effect of γ-irradiation on the hydrolytic and thermal stability of micro- and nano-TiO2 based urea–formaldehyde composites

The hydrolytic stability and thermal behavior of organic–inorganic composites prepared by two-stage polymerization of urea–formaldehyde resin (UF) with micro- and nano-TiO₂ before and after irradiation has been investigated.