Wood Science and Technology最新文献

The water sorption and hysteresis behavior of four high extractive content woods —western red cedar, Chinese juniper, tubi, and messmate—were examined at 30, 45, 60, 75, 90, and 99.5 °C by comparing the water sorption isotherms before and after extraction. A significant dry weight loss during water sorption tests was observed for cedar and juniper, complicating their water sorption and hysteresis behavior. Gas adsorption analysis revealed that the cumulative pore volume of dried cell walls in all four species significantly increased after extraction, indicating a comparable extent of likely bulking of extractives within the lignin structure. Across the temperature range of 30 to 99.5 °C, cedar and juniper showed significantly higher equilibrium moisture content values after extraction throughout the entire hygroscopic range. In contrast, only minor differences were observed for tubi and messmate after extraction. This discrepancy may be attributed to variations in the hygroscopicity of extractives deposited in the cell walls. When applying the bulking effect theory, it is important to consider the hygroscopicity of bulked extractives. Tubi shows a distinctly higher magnitude of sorption hysteresis even at 99.5 °C, and no significant differences in the magnitude of hysteresis were observed for either tubi or messmate after extraction.

The mechanical properties of wood are significantly enhanced and its application scope is broadened through compression treatment. However, balancing deformation fixation with the performance of compressed wood is challenging. This study significantly enhanced the dimensional stability of compressed wood while preserving its mechanical properties by grafting N-Methylolacrylamide (NMA) onto wood cell walls and applying thermally assisted surface compression. The NMA-modified compressed wood exhibited improved hydrophobic qualities and a considerably low set recovery of only 0.29%, which is attributable to the cross-linked network formed by the condensation of NMA with wood components. Furthermore, the NMA-modified compressed wood exhibited outstanding mechanical properties, such as improved hardness, bending strength, and impact toughness. Its bending strength (263.5 MPa) was approximately 2.6 times greater than that of natural wood (100.3 MPa). NMA-modified compressed wood, which is characterized by high-dimensional stability and mechanical properties, exhibits significant potential as an engineering material.

Photonic crystals (PCs) with periodic nanostructures enable high-quality structural coloration, making them highly suitable for applications in printing and dyeing. However, PC-based structural coloration on wood surfaces remains a challenge. In this work, PCs were successfully constructed on wood (Birch, Betula spp.) surfaces via gravitational deposition, displaying bright, vibrant, and angular-dependent structural colors with stimulus-responsivity to water. Monodisperse polystyrene (PS) microspheres were used as building units. The colors were tunable through precisely modulating the diameter of the PS colloidal microspheres. The stacking configuration of the PS spheres within the interfacial transition region transitions from disordered to ordered. Drying-induced deformation of the micro-nano structures on the wood surface can lead to interfacial defects, such as disordered packing and cracks. Thanks to the water-responsive property of PCs, the coatings show promising potential for application in anti-counterfeiting labels. This work provides methodological and mechanistic insights for structural coloration on wood substrates, while offering many attractive opportunities for biomass materials.

This contribution aims to increase the understanding of the complex mechanical behavior of wood through a framework for simulating mixed-mode failure. Based on physical properties assessment, appropriate constitutive laws, and experimental validation, a generally applicable numerical strength prediction tool for wood from different species and with various natural imperfections is introduced. The 3D orthotropic elastic plastic non-local CDM model considers the local fiber orientation and is implemented as material subroutines in the commercial software Abaqus. Herein, orthotropic Hill-plasticity with exponential hardening represents the plastic behavior in compression. Separated stress-based gradient-enhanced transient non-local damage represents the brittle material behavior in tension and shear. The methodology is validated with experimental data on tensile veneer tests, shear- and compression tests. Moreover, the methodology is applied to four-point bending tests of boards with heterogeneities. The numerical results demonstrate that the proposed model is able to reproduce different crack patterns observed in the four-point bending tests. Detailed investigations of the impact on the strength of the boards can be performed with this method to optimize species-independent strength prediction and engineered wood products. Further combination with other material laws e.g. moisture is possible.

Trees that are exposed to subzero temperatures in winter are susceptible to freeze damage, which adversely affects tree physiological activities and wood end-use. Freezing stress threatens the survival of trees by inducing the accumulation of ice bodies within wood tissues. However, accurately assessing ice content in wood tissues remains a challenge. This study aimed to develop a theoretical-empirical prediction model of frozen water content (FWC) to evaluate the quantity of ice forming in wood tissues. Differential scanning calorimetry was employed to examine the changes in FWC of pine (Pinus koraiensis Siebold & Zucc.) and poplar (Populus simonii Carr.) wood tissues under a series of subzero temperature points at two cooling rates. The corresponding responses of specific extracellular resistance(r_e) and intracellular resistance(r_i) were obtained by electrical impedance spectroscopy. Experimental study showed that FWC increased as temperature decreased, with a notable transition around − 40 °C. The corresponding r_e initially increased and then decreased, peaking at − 40 °C. The change trend of r_i was consistent, but reached its peak value at − 30 °C. In the temperature ranges of 0 to − 30 °C and below − 40 °C, the specific theoretical linear models between FWC and r_i, and the logistic model of FWC at a semi-lethal temperature zone of − 30 °C to − 40 °C were respectively established for both wood species. The theoretically predicted values fitted well with experimental values, with the prediction error below 5%, verifying the validity of the theoretical model. This study provides new insights for exploring the freezing behaviors of water in wood and for assessing the mechanisms of winter damage to trees by nondestructive approaches.

This paper presents theoretical formulas for calculating the stress wave velocity in standing trees and logs based on the stress wave propagation equations for both. On this basis, a theoretical model for the conversion ratio of wave velocity between standing trees and logs is constructed. The accuracy and reliability of this theoretical model are verified through actual measurements of the wave velocity conversion ratio in several different tree species, and the following conclusions were obtained: the theoretical wave velocity conversion ratios for the tested tree species are all greater than 1.1. Radiata pine and loblolly pine have the highest theoretical conversion ratios, both at 1.19, while western hemlock has the lowest value at 1.10. The theoretical conversion ratio for larch used in this study is similar to that of radiata pine and loblolly pine, at 1.18. Except for loblolly pine, the theoretical conversion ratios for the other species are all lower than those of larch and radiata pine. This may be due to differences in species or factors such as moisture content. Therefore, when calculating the theoretical wave velocity conversion ratio for a specific species in the future, it is best to use the elastic constant values for that particular species in its green condition. The measured wave velocity conversion ratio for ponderosa pine is the highest at 1.36, while red pine has the lowest at 1.10. The difference between the measured and theoretical wave velocity conversion ratios for radiata pine is the smallest, at only − 0.8%, while the largest difference is for ponderosa pine, at 22.5%. Overall, except for western hemlock and ponderosa pine, the measured and theoretical conversion ratios for other species are relatively close, with differences within 10%. With the exception of a few species, the theoretical model for the wave velocity conversion ratio between standing trees and logs proposed in this paper is accurate and feasible.

Phenolics, which are secondary plant metabolites, have an important place in nutritional therapy due to their potent antioxidant properties. Phenolics also show anti-inflammatory, anti-mutagenic, and anti-fungal effects. Pinus brutia, a natural source of phenolics, is known for its wound-healing, immunity-enhancing, and ailment-treating properties. Encapsulation has many advantages for biologically active ingredients, such as enhancing thermal stability, masking unwanted tastes or odors, protecting bioactive compounds from environmental degradation (such as moisture, oxygen, and light), and improving bioavailability by enabling controlled or targeted release. The first stage of the study involved the extraction of phenolics from Pinus brutia bark (PBB) using four different solvents, including methanol, ethanol, ethanol–water (70:30, v/v), and methanol–water (70:30, v/v). The phenolic compound profile of the extracts was determined using HPLC–DAD. An experimental design was used to achieve maximum encapsulation efficiency in the PBB extract-β-cyclodextrin inclusion complex (PBB–β–CD). To this purpose, various parameters (β–cyclodextrin ratio, temperature, PBB extract volume, and time) were optimized using Response Surface Methodology–Central Composite Design. The significant parameters and optimum conditions that influenced the response were identified. Under optimum conditions, the experimental encapsulation efficiency was 90.45 ± 1.34%, closely matching the predicted encapsulation efficiency of 93.31%. The PBB–β–CD was characterized using SEM and FT–IR, confirming the efficiency of the encapsulation process. Based on the data obtained in this study, it is anticipated that the inclusion complex developed as a result of encapsulation of PBB extract with β-CD can be used in various fields such as nutraceutical and biomedical.

Understanding the water vapor diffusion characteristics of bamboo is crucial for optimizing the manufacturing of bamboo-based products. Its radial structure, composed of distinct anatomical regions—such as the bamboo outer layer (BOL), inner layer (BIL), pith ring (BPR), and membrane (BM)—results in variations in chemical composition and contributes to complex moisture diffusion behavior. To explore how these regions contribute to moisture transport, three types of bamboo samples were prepared: intact (BOL/BM), BM removed (BOL/BPR), and both BM and BPR removed (BOL/BIL). Water vapor diffusion was assessed using the wet cup method (humidity levels of 85% and 0%). The work measured diffusion in both the outer-to-inner (BM-BOL, BPR-BOL, BIL-BOL) and inner-to-outer (BOL-BM, BOL-BPR, BOL-BIL) directions. The results indicated that the moisture diffusion was significantly more efficient in the inner-to-outer direction compared to the outer-to-inner direction. BOL-BIL showed the lowest water vapor resistance factor (µ = 62.73 ± 1.55), attributed to the exposure of parenchyma cells and vessels following BPR removal. Conversely, BOL-BPR showed the highest resistance (µ = 108.96 ± 4.93) due to the high lignin content and thick-walled cell structure of BPR. The BM’s layered and porous architecture, formed by collapsed pith cells, facilitated efficient moisture diffusion, endowing it with optimal hygroscopic properties. However, BPR’s inhibitory effect increased resistance in BOL-BM (µ = 81.17 ± 2.43). This study elucidates the distinct roles of BPR and BM in water vapor diffusion within bamboo, enhancing the understanding of its internal moisture diffusion mechanisms and providing a foundation for the development of moisture-resistant bamboo materials.

Laser-induced technology is an efficient and eco-friendly method for graphene preparation, enabling in situ generation of graphene through laser irradiation of carbon-containing precursors. The formation process of laser-induced graphene (LIG) using moso bamboo as the precursor was systematically investigated through a combined approach of molecular dynamics simulations and experimental characterization. For simulations, an innovative simplified moso bamboo model comprising three primary components (cellulose, hemicellulose, and lignin) was constructed by the Materials Studio software. The LIG formation process was simulated at the atomic scale using LAMMPS software with the ReaxFF reactive force field to elucidate the underlying mechanism. During experiments, the multiple characterization techniques were employed to analyze the microstructure, elemental composition, structural features, crystalline phases and defect structure of the LIG. The simulation results indicated that the formation of bamboo-derived LIG follows a pyrolysis-dominated mechanism, achieving a graphene yield of 35.29%. The process generated defective carbon networks dominated by hexagonal rings (53.65%), with concomitant release of small gas molecules, including H₂ (50.20%), CO (39.87%), H₂O (5.94%), and CO₂ (3.99%). The characterization results from Raman, TEM, XPS, and XRD confirm that laser irradiation successfully converted biomass moso bamboo into a carbon-based material dominated by sp² hybridization, exhibiting a defective multilayer graphene structure. In addition, SEM and EDS observations reveal the microporous structure of LIG and changes in elemental composition before and after processing, which align with the simulation results, validating the rationality of the constructed simplified model. By revealing the synergistic pyrolysis-graphitization mechanism of moso bamboo, this study validates the applicability of the multicomponent simplified model to real biomass systems, enabling controllable preparation of biomass-derived graphene and enhanced resource utilization of moso bamboo.

This comparative study explores the influence of incorporating cellulose nanofibrils (CNFs) obtained from bleached and lignin-containing cellulose pulp as reinforcements in an epoxy matrix. The research aims to identify optimal nanocellulose loading levels for improved mechanical properties of corresponding composites. Bleached CNF (BCNF) and lignin-containing CNF (LCNF) were introduced at different weight percentages (0.5, 0.75, and 1%) using high-energy mechanical mixing and the composites were characterized through mechanical, morphological, chemical, and thermal analyses. The results indicated that BCNF exhibited superior performance compared to LCNF in improving the mechanical properties of the epoxy composites. Specifically, a 0.75% BCNF loading significantly enhanced the composite’s toughness (41% increase) and elastic modulus (79% increase) while reducing brittleness, making the material stronger and more ductile. In contrast, LCNF composites displayed lower mechanical performance and reduced ductility. The interaction between BCNF and the epoxy matrix was more pronounced, as confirmed by QCM-D and FTIR analysis, suggesting better compatibility. Thermal analysis showed that both BCNF and LCNF reduced the thermal stability of the epoxy matrix, but LCNF, with lignin, provided some protection. Lignin’s aromatic and antioxidant structure helped maintain thermal resistance, making LCNF composites at 1% loading thermally comparable to neat epoxy. However, higher BCNF loading (1%) led to decreased mechanical properties, likely due to nanocellulose aggregation. This research highlights the potential of optimizing nanocellulose content for tailored performance in bio-based composite materials.