In this study, the low-cost processing residue of Radiata pine (Pinus radiata D. Don) was used as the lone carbon source for synthesis of CQDs (Carbon quantum dots) with a QY (The quantum yield of the CQDs) of 1.60%. The CQDs were obtained by the hydrothermal method, and +a PVA-based biofilm was prepared by the fluidized drying method. The effects of CQDs and CNF (cellulose nanofibers) content on the morphology, optical, mechanical, water-resistance, and wettability properties of the PVA/CQDs and PVA/CNF/CQDs films are discussed. The results revealed that, when the excitation wavelength was increased from 340 to 390 nm, the emission peak became slightly red-shifted, which was induced by the condensation between CQDs and PVA. The PVA composite films showed an increase in fluorescence intensity with the addition of the CNF and CQDs to polymers. The chemical structure of prepared films was determined by the FTIR spectroscopy, and no new chemical bonds were formed. In addition, the UV transmittance was inversely proportional to the change of CQDs content, which indicated that CQDs improved the UV barrier properties of the films. Furthermore, embedding CQDs Nano-materials and CNF into the PVA matrix improved the mechanical behavior of the Nano-composite. Tensile modulus and strength at break increased significantly with increasing the concentration of CQDs Nano-materials inside the Nano-composite, which was due to the increased in the density of crosslinking behavior. With the increase of CQDs content (>1 mL), the water absorption and surface contact angle of the prepared films decreased gradually, and the water-resistance and surface wettability of the films were improved. Therefore, PVA/CNF/CQDs bio-nanocomposite films could be used to prepare anti-counterfeiting, high-transparency, and ultraviolet-resistant composites, which have potential applications in ecological packaging materials.

With the rapid growth in the use of wireless electronic devices, society urgently needs electromagnetic wave (EMW) absorbing material with light weight, thin thickness, wide effective absorbing band width, and strong absorption capacity. Herein, the multi-layer magnetic composite boards are fabricated by hot-pressing magnetic fiber boards and normal veneer layer-by-layer. The magnetic fibers obtained using in-situ chemical co-precipitation are used to fabricate magnetic fiber board by hot-pressing. The magnetic wave absorbing capacities of the magnetic fiber boards obtained with 72 h impregnation time exhibit strongest adsorption capacities of −51.01 dB with a thickness of 3.00 mm. It is proved that this outstanding EMW absorption property is due to the strongest dielectric loss, the optimal magnetic loss, and the dipole relaxation polarization. Meanwhile, the EMW absorbing capacities of the corresponding multi-layer composite magnetic board increases from −14.14 dB (3-layer) to −60.16 dB (7-layer). This is due to the generated multi-interfaces between magnetic fiber board and natural wood veneer in the EMW propagation direction, which significantly benefit multireflection and attenuation of the incident waves. The results obtained in this work indicate that natural wood fibers are of great potential in the fabrication of magnetic multi-layer boards treated as EMW absorbers via a low cost, green, and scalable method.

Blue luminescent carbon quantum dots (CQDs) were prepared from cyanobacteria by a hydrothermal method. The PL quantum yields of the obtained CQDs was 5.30%. Cyanobacteria-based carbon quantum dots/polyvinyl alcohol/nanocellulose composite films were prepared, which could emit bright blue under UV light. FTIR characterization showed that the composite films had hydroxyl groups on the surface and no new groups were formed after combining the three materials. The photoluminescence (PL) spectra revealed that the emission of the prepared CQDs was excitation dependent. Studies on the water resistance performance and light barrier properties of the composite films showed that they possessed higher water resistance properties and better UV/infrared light barrier properties. Therefore, we report the cyanobacteria-based carbon quantum dots/polyvinyl alcohol/nanocellulose composite films have the potential to be applied in flexible packaging materials, anti-fake materials, UV/infrared light barrier materials and so on.

High temperature heat treatment is one of the main technologies with the highest market conversion rate and broad future prospects in the functional technology of wood. Chemical reagents are not added in the production process. The treatment improves the dimensional stability, biological durability, wood color, and acoustic properties without reducing the environmental performance of the product. However, there are some problems in heat treatment, such as the reduction of mechanical properties and surface wettability of wood, high production energy consumption, and large exhaust emissions. Therefore, understanding the influence and mechanism of high temperature heat treatment technology on wood properties is of guiding significance to further improve the quality of heat-treated wood, improve production process, and develop new equipment. This article reviews the effects of heat treatment on the properties of wood and the mechanism of heat treatment. Then, some applications of heat treatment of wood are introduced. Finally, the development direction and prospect of high temperature heat treatment technology in the future are forecasted.

Thermal modification (TM) is commonly used for improving the performance of wood under varying environmental conditions. The effect of TM on the hygroscopic properties of wood has been studied extensively; however, the sorption mechanism and the states of water of thermally modified wood (TMW) at varying relative humidity (RH) is limited. In this work, Douglas fir was modified at 180 °C, 200 °C and 220 °C for a duration of 2 h and the Hailwood–Horrobin model and NMR relaxometry were used after specimens were conditioned at eight different RHs. The results showed that TM inhibited monolayer and polylayer moisture sorption with increasing modification temperatures in all RHs. The lower slope of the sorption isotherms in TMW decreased compared with the control, indicating that the TM increased the hygroscopical stability of wood. The T₂ distribution indicated that no free water was observed in the hygroscopic moisture range. The mobility of water molecules in the cell walls was decreased by TM intensity and increased by increasing RH.