Wood Science and Technology最新文献

This study presents the development of a wood sponge (WS) modified with MnO₂ nanorods (MnO₂/WS) derived from balsa natural wood, an abundant and environmentally friendly raw material, for the adsorption of organic solvents, oils, and heavy metal ions from water. The MnO₂/WS composite exhibits an exceptionally low density of 0.014 g cm^− 3 and a high porosity of approximately 97%. It demonstrates consistent sorption-desorption performance over 20 cycles. Zeta potential analysis reveals that MnO₂ nanorods carry a negative charge (-22.31 mV) at pH 4.68, indicating their affinity for adsorbing positively charged heavy metal ions, which are commonly found in industrial effluents. Moreover, WS shows remarkable mechanical robustness, enduring 1000 stress-strain cycles with high shape recovery, ensuring its durability under operational conditions. The data highlight several strengths of MnO₂/WS, including cost-effective production process, high reusability, remarkable sorption capacities for carbon tetrachloride and soybean oil (29.56 and 17.65 times its mass, respectively), and efficient performance. Its capability to produce potable water from real industrial effluents positions MnO₂/WS as an ideal solution for addressing water crises.

This study investigated the effects of high-intensity microwave (HIMW) treatment on the mechanical properties of radiata pine wood. The treatment, conducted on sapwood and heartwood with 60% initial moisture content, involved varied microwave energy densities: 60, 80, and 100 kWh/m³. Tests evaluated tensile and compressive properties in three directions, alongside shear strength and bending properties. Acoustic emission (AE) and digital image correlation (DIC) techniques probed damage evolution under bending loads before and after HIMW treatment. As microwave energy density increased, compressive, tensile, and shear strength decreased, with heartwood being the most susceptible. Substantial reductions occurred in longitudinal compressive properties and tensile properties perpendicular to the grain. After HIMW treatment (80 kWh/m³ and 100 kWh/m³ for sapwood and heartwood, respectively), although there was a slight decrease in the modulus of elasticity and bending strength, there was a significant increase in bending plasticity. HIMW-treated specimens exhibited more high-frequency AE signals during elastic–plastic deformation, indicating more frequent fractures in the treated wood during three-point bending. Changes in the microscopic structure of the wood specimens caused by HIMW treatment increased the damage growth rate and stress redistribution efficiency during loading, augmenting the bending plasticity of wood.

In view of developing upcycling strategies for hardwood Kraft lignin, hydroxy-methylation of Eucalyptus Kraft lignin under alkaline conditions (pH 9 and 11) at different temperatures (50 °C and 70 °C) was studied in the present effort with the double objective of optimizing the reaction conditions and understanding the functionalization mechanism of C₅ in either terminal or internal guaiacyl units during hydroxy-methylation. Formaldehyde consumption was estimated via titration of the oximated free formaldehyde; the hydroxy-methylation degree under the reaction was estimated by calculating the ratio in Condensed hydroxyl/Guaiacyl (Condensed OH/G-OH) via a new difference UV-spectroscopy. The reliability of the difference UV-method results for the analyses of the hydroxy-methylated lignins was statistically analysed and compared with that of vacuum-dried and sonicated samples. Hydroxy-methylated samples were then fully characterised by NMR (³¹P and HSQC) and GPC. The reaction temperature of 50 °C, pH 11, and period time of one hour resulted as the optimal conditions for the hydroxy-methylation, preventing the side-reactions leading to the formation of dimethylene-glycol addition products. The ³¹P and ¹H–¹³C HSQC NMR revealed the absence of undesirable formaldehyde Cannizzaro by-products and the lack of hydroxymethyl groups in the aliphatic side chain under the studied conditions. GPC analyses, comparing two methodologies, revealed increases in molar mass of the hydroxy-methylated samples upon the formaldehyde addition. The selective hydroxy-methylation at the C5 guaiacyl site demonstrates that Eucalyptus Kraft lignin is as a promising candidate for resol production.

Three novel phenolic compounds were isolated from the heartwood of Millettia pendula along with eight known compounds. Among the known compounds, six were isolated from this species for the first time. Structural determination of the isolated compounds was accomplished using 1D and 2D nuclear magnetic resonance spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Two of the isolated compounds, 2 and 6, showed red and purple pigmentation, respectively. These compounds contained a conjugated π system composed of benzofuran and p-benzoquinone moieties. We therefore hypothesize that a hydroquinone moiety, present in precursors of 2 and 6, is autoxidized by activated oxygen in the air to form p-benzoquinone. The difference in colors between these two compounds was due to the difference in the B ring substituents. Expansion of their conjugated pi systems allows 2 and 6 to absorb and reflect light in the visible region, and results in the characteristic purple coloring of M.pendula.

Lime wood, spruce and pine are investigated with regard to its hygro-mechanical long-term behaviour. Experiments are conducted for an identification of model parameters and for model validation. Swelling and shrinkage coefficients, dry density, sorption characteristics and parameters for visco-elasticity, visco-plasticity and mechano-sorption are determined for the main material directions. Supplemented by literature values, a complete set of parameters for long-term hygro-mechanical modelling of wood species is found. Constrained swelling and shrinkage are analysed and the origin of the stress development is investigated. It is demonstrated, that creep phenomena lead to significant stress reduction by relaxation, in case of moisture changes especially due to mechano-sorption. The influence of different model parts is investigated. A numerical parameter study shows the influence of several material parameters on the stress evolution. Experimental material investigations such as those presented here are essential for the application of numerical simulation methods for the prediction of material behaviour and for the assessment of deformations, stresses and damage potential of climatically loaded timber structures.

Dynamic mechanical analysis and small-angle X-ray scattering (SAXS) measurements of hinoki wood swollen with water and/or ethanol in the temperature range of 20–78/95 °C were performed to clarify the relationship between swelling and microstructure in different swelling states. For the sample swollen in a water–ethanol mixture with an ethanol mole fraction of 0.2, a peak in tanδ, i.e., the ratio of the dynamic elastic modulus (E′) to the dynamic loss modulus (E″), was observed at around 50 °C. No clear peak was observed in the temperature range of the sample swollen with water or ethanol, but thermal softening behavior due to micro-Brownian motion of lignin was observed. The scattering behavior of the samples swollen with water and/or ethanol differed significantly from one solution to another. The SAXS intensity of samples swollen with water or mixture of water and ethanol increased with increasing temperature, while the SAXS intensity of samples swollen with ethanol changed little with increasing temperature. This suggested that the adsorption sites of ethanol were different. The position of the peak for the sample swollen with the water–ethanol mixture, observed in the Kratky plot, was shifted to the low-q side compared to the pure liquid. It was suggested that the aggregation state of the sample swollen with the mixture of water and ethanol was very different from those of the wood swollen with the pure liquid.

Cellulose nanocrystals (CNCs), derived from abundant natural cellulose, possess exceptional properties including low weight, bioavailability, and high mechanical performance. During shear loading, CNCs exhibit unique stick–slip behavior, making them excellent toughening materials for CNC neat films and nanocomposite. However, the failure behavior at the interface under specific conditions, particularly moisture and temperature, remains unclear. The study utilized molecular dynamics (MD) simulations to quantitatively investigate the hydrothermal effect on the degradation of CNC interface. The degradation mechanism induced by moisture and temperature was indicated through the reduction of adhesive energy and peak force with the consideration of hydrogen bonds. The simulation results showed that the role of water molecules in the interfacial failure depends their content. Water acted as a binder at low moisture levels, while at high moisture levels, it acted as a lubricant. Besides, temperature had a more pronounced impact on the interfacial shear performance. Our simulation results can be used as input in micromechanical models to bridge the gap between the macroscopic and microscopic behavior of films and nanocomposites.

The digital image correlation (DIC) system is a powerful tool for measuring distributions of displacement and strain on the surface of a specimen. DIC systems are employed not only for homogeneous materials such as metals but also for heterogeneous materials such as wood. Although numerous validations of DIC system accuracy for metallic materials exist, the accuracy verification for wood, especially under multiaxial stress conditions, is less common. This study investigated the accuracy of a DIC system equipped with a bilateral telecentric lens on wood (Douglas fir). The accuracy verification in uniaxial stress fields was conducted through full compression testing, while verification in multiaxial stress fields was performed through partial compression testing. Additionally, compression tests on A6063 (aluminium alloy) were conducted to examine the differences in the DIC system accuracy between homogeneous and heterogeneous materials. The accuracy of the DIC system was assessed by comparing the results with those obtained from strain gauges. The results from the full compression tests indicate that the accuracy of axial strain measured by the DIC system was comparable for the specimens of A6063 and Douglas fir in the longitudinal (L) direction but was inferior for Douglas fir in the radial (R) direction. This is because the differences in the mechanical properties of earlywood and latewood produce high strain gradients. Furthermore, the differences in Young’s modulus obtained from the DIC system and strain gauge for the specimens of A6063, Douglas fir (L), and Douglas fir (R) were − 1.23%, 2.26%, and − 12.5%, respectively. In the partial compression tests, the accuracy of strain components measured by the DIC system in the specimens of Douglas fir (R) was lower than that in A6063. In the partial compression tests, high strain gradients appear in multiple strain components, leading to a notable decrease in the accuracy of the DIC system compared to the full compression tests.

The present work has experimentally determined the specific fracture energy of the hardwood species silver birch (Betula pendula), which in recent times has caught increased attention for utilization in structural applications. The single-edge-notched beam loaded in three-point-bending was utilized for evaluating the fracture energy with the work-of-fracture method. In addition to birch, Norway spruce (Picea abies) was utilized as a reference material. The effect of two different geometries of the fracture area for each species was evaluated—one triangular and one rectangular fracture area. It should be noted that the geometry of the fracture area did influence the evaluated fracture energy, and this influence was not consistent between species. This was likely in part due to manufacturing difficulties with the triangular fracture area. In addition to the experimental testing, a numerical 2d-model including linear strain-softening behavior was used for comparative simulations. The numerical 2d-models showed reasonable agreement with the experimental results regarding the global load vs. displacement response, despite their relative simple nature. The specific fracture energy for the spruce specimens was evaluated to 221 J/(hbox {m}^2) and for the birch specimens to 656 J/(hbox {m}^2). Consequently, the present work implies a marked increase in specific fracture energy for birch, compared to spruce. This increase in specific fracture energy could potentially have a large influence on the failure behavior of birch when used in structural applications which is something that needs to be considered in future work.

Wood is a sustainable, benign, and high-performing green structural material readily available in nature that can be used to replace structural materials. However, insufficient mechanical performance (compared to metals and plastic), moisture sensitivity, and susceptibility to microorganism attack make it challenging to use wood as it is for advanced engineering applications. We here present an efficient approach to fabricating densified wood with minimal time and waste generation, demonstrating high mechanical strength, and decreased water penetration on the surface. Wood slabs were treated with deep eutectic solvents (DESs) to solubilize the lignin, followed by in-situ regeneration of dissolved lignin in the wood. Then, the slabs were densified with heat and pressure, turning the wood into a functionalized densified material. Lignin regeneration and morphological changes were observed via two-photon microscopy and Scanning Electron Microscopy (SEM), respectively. The final product is less susceptible to water absorption on the surface and has enhanced flexural strength (> 50% higher), surface hardness (100% increased), and minimal set recovery compared to natural wood. The improved mechanical performance is due to regenerated lignin which acts as a glue and fills spaces present within the interconnected cellulose network inside the wood, forming a highly dense composite during densification. Such enhancement in the properties of DES-densified wood composite makes it a favorable candidate for advanced structural and engineering applications.