Wood Science and Technology最新文献

Xuan paper is a classic Chinese handmade paper with long history and has been listed as a national intangible cultural heritage since 2009, which is mainly composed of wingceltis (Pteroceltis tatarinowii) phloem fibers and straw fibers. Due to the unique properties of wingceltis phloem fibers, Xuan paper is spotless, flexible, stable, and durable, and is widely used by calligraphers, painters, or museums for restoration. Uncovering the variation of phloem fiber properties throughout the traditional pulping process is essential for a comprehensive understanding of the special performance of Xuan paper. In this study, chemical, structural, and mechanical characterization was conducted on the raw bark (phloem fiber), treated phloem fiber, and pulp fiber at different steps of the traditional pulping process for making Xuan paper. The compositional and morphological analysis revealed the effective removal of the matrix polymers, while the phloem fiber almost retained the original fiber structure during the traditional process. Wide-angle X-ray scattering results indicated that the relative crystallinity of cellulose increased and crystals expanded after the lime cooking and exposure to sun and rain. Compared to the raw phloem fibers, the ultimate stress and tensile stiffness of pulp fibers decreased by 24.35% and 9.79%, respectively. However, the fracture strain and fracture toughness of pulp fibers showed a drastic promotion, which might be attributed to the energy dissipation caused by the cell wall structure, the breaking and reforming of hydrogen bonds, and the slipping and rearrangement of cellulose microfibrils.

Wood is a multiscale heterogeneous natural composite material with properties depending on its growing conditions and its genetic heritage. This variability is challenging for industries that work to perform homogeneous and reliable products. In industry, different non-destructive testing methods are in use to classify, grade, and select wood products to optimize their usage. Among them, the use of lasers to detect fiber orientation with different wavelengths. This orientation significantly influences the mechanical behavior of wood, including stress limits and stiffness. According to our knowledge, the use of laser diffusion still is limited to grain angle measurement. Our objective in this paper is to realize transmission light scattering maps for wood samples from several wood species (poplar, oak, Douglas fir, beech), and then identify the most suitable wavelength to study light diffusion in wood, depending on the property that will be measured. A supercontinuum laser is used over a wavelength range from 500 to 800 nm, allowing precise adjustment of the wavelengths. It was found that near-infrared light better scatters in the studied wood species than lower wavelength. However, the wavelength that gives the best contrast between earlywood and latewood depends on the sample studied and is not necessarily in the near infrared rays.

The present work investigated new sustainable opportunities for wood protection against xylophagous organisms (cellulolytic fungi and termites) based on the use of natural bioactive compounds present in Milicia excelsa wood and Nerium oleander bark. To achieve this, solid–liquid extractions by ethanol were carried out, obtaining extraction yields of 5.47 ± 0.78% for the extract of M. excelsa and 21.88 ± 0.53% for N. oleander. Gas chromatography coupled with mass spectrometry analyses were carried out to evaluate the chemical composition of both extracts, showing interesting compounds with biological activity such as pyrogallol, 4-acetylresorcinol, karanjin and scopoletin. Likewise, an evaluation of the cellulolytic capacity of different wood-isolated fungi (Aspergillus flavus, Penicillium chrysogenum, Trichoderma longibrachiatum, Mucor circinelloides and Mucor fragilis) was carried out through two screenings, based on their growth rate in carboxymethyl cellulose agar media, and their cellulose-degrading ability via filter paper rupture, being T. longibrachiatum the fungus with the highest growth rate in both substrates. Finally, a protective treatment for pine wood (Pinus sp.) was designed by using the ethanolic extracts separately and combined, respectively, against T. longibrachiatum and Reticulitermes grassei, comparing in both cases the biotic damage with a control. The results demonstrated that the impregnation significantly reduced T. longibrachiatum biomass consumption by over 70% for all treatments. Additionally, the M. excelsa impregnation notably decreased termite activity, with a 81% reduction in the long-term assays.

In this study we separated the chemical components of cork from Quercus variabilis by various solvent extraction and alcoholysis methods. We identified the content and chemical composition of suberin and dichloromethane extract with gas chromatography-mass spectrometry (GC-MS) and analyzed the antifungal effects of different cork extracts against wood-decaying fungi. The results showed that the main structural component of cork, suberin, averaging 36.34% of the total dry weight, exhibited a pronounced inhibitory effect on wood-decaying fungi, compared to the dichloromethane extract. By the end of the entire culture period, the colony diameter of white rot fungi was 5 mm in the 40 mg/mL suberin treatment group, 19 mm for brown rot fungi, both significantly smaller than the control group (90 mm). Hydroxy fatty acids, free fatty acids, and α,ω-diacids may be the key components contributing to the antifungal activity of suberin. The inhibitory mechanism of suberin components on wood-decaying fungi may involve suppressing the respiratory metabolism of the fungi and increasing the permeability of their cell membranes, thereby limiting their normal life activities.

As one of the most common tree species, birch wood (Betula pendula Roth) is widely used as a material of furniture and decoration indoors for its many excellent characteristics. Whereas there are some studies on the volatile composition of the essential oil from the leaves of Betula pendula Roth, only limited information is available on the odor-active constituents of birch wood. To close this gap, the odorants of birch wood were investigated by means of instrumental and sensory analyses, including techniques such as gas chromatography-flame ionization detection/olfactometry, high-resolution gas chromatography-mass spectrometry, and heart-cut two-dimensional high-resolution gas chromatography-mass spectrometry/olfactometry. Overall, a total of 20 odorants was (tentatively) identified on the basis of their respective odor qualities and retention indices and mass spectra by comparison with reference compounds. It was shown that birch wood odor is dominated by a series of terpenes, terpenoids and phenyl compounds originating from the degradation of lignin and aldehydes, ketones and acids originating from fatty acid degradation. By a sensory evaluation of the birch wood, the predominant odor attributes were determined to be earthy, pencil-like, corky/mouldy, grassy, fatty, fruity, green tea-like, herb-like, vanilla-like, and vinegar-like.

The mechanical properties of structural timber largely depend on the occurrence of knots and on fibre deviation in their vicinities. In recent strength grading machines, lasers and cameras are used to detect surface characteristics such as the size and position of knots and local fibre orientation. Since laser dot scanning only gives reliable information about the fibre orientation in the plane of board surfaces, simple assumptions are usually made to define the inner fibre orientation to model timber boards. Those models would be improved by better insight into real fibre deviation around knots. In the present work, a laboratory method is developed to evaluate growth layers geometries and fibre orientation, solely based on the fact that the fibers are parallel to the tree rings and without any further assumptions. The method simply relies on color scans and laser dot scans of Douglas fir (Pseudotsuga menziesii) timber specimen sections revealed by successive planing. The proposed method provides data on fibre orientation in 3D with an accuracy that is relevant for the calibration of detailed models.

The objective of this study was to produce hydrophobic porous wood ceramics as adsorbents for CO₂ through the resin treatment of pine. The prepared samples underwent analysis using various methods to determine their structure and properties. An orthogonal experimental approach was employed to obtain adsorbents with optimal preparation process. The highest adsorption capacity was determined to be 1.36 mmol/g at a temperature of 30 ℃ and a CO₂ concentration of 15 vol%. The effect of temperature on the microstructure of wood ceramics was studied by characterization. Increasing temperatures adversely affected the adsorption capacity. Nevertheless, the hydrophobic nature of wood ceramics resulted in little impact of humidity on CO₂ absorption. The CO₂ adsorption kinetics of wood ceramics were analyzed using kinetic studies, which demonstrated that the kinetics can be accurately fitted by both the pseudo-first-order and Avrami models. The findings of the adsorption isotherm analysis showed that the Langmuir model fit was optimal. Following 30 cycles of adsorption-desorption in the presence of simulated gas, the CO₂ sorption capacity of the wood ceramics was maintained at over 90%. In terms of CO₂/N₂ selectivity, the wood ceramics showed a clear preference for CO₂, especially at 30 °C, where the CO₂/N₂ selectivity ratio reached 24.50.

Lignin fluorescence in plant cell walls significantly interferes with Raman spectroscopic signals, resulting in compromised analytical accuracy and resolution. To address this issue, a strategy was implemented to both reduce the absolute lignin content in samples and prepare thinner plant tissue sections. This approach involved embedding plant samples in LR White resin, complemented by an ultrathin sectioning technique. Additionally, algorithms were developed to eliminate the impact of resin spectra on the imaging process. These advancements collectively enhanced the performance of Raman spectroscopy by effectively diminishing the disruptive effects of lignin fluorescence. Further analysis with confocal laser scanning microscopy (CLSM) elucidated the presence of aggregation-induced luminescence (AIE) in plant tissues, revealing a direct correlation with lignin concentration. These findings not only offer a new perspective for the application of Raman spectroscopy in plant science, but also pave the way for advancements in tip-enhanced Raman spectroscopy (TERS) detection.

The development of multifunctional electromagnetic interference (EMI) shielding materials with low cost, stable performance and mass production is still facing great challenges. High-density traditional metals limit the application of EMI shielding materials. The unique structure of wood is considered an effective way to solve the above-mentioned problems. In this study, waste wood was used as raw material to prepare low-energy metallized particleboard. The particleboard was functionally finished to show excellent hydrophobic properties and been used stably in a humid environment. Dynamic thermal mechanical properties and mechanical properties analyses of particleboard were carried out. The bend strength (MOR), elastic modulus (MOE) and tensile strength were 30.50 MPa, 5384 MPa and 7.85 MPa, respectively. Metallized particleboard exhibited excellent electromagnetic shielding effectiveness (EMI SE) (average value 81.62 dB) in the entire X-band. The preparation of wood-based shielding metallized particleboard provides a feasible strategy for replacing traditional metal materials.

This study proposed a linear model between internal bond strength and compressive elastic modulus based on Griffith’s fracture theory. The local compressive elastic modulus was determined by non-destructively detecting the inherent frequency of material vibration using a method based on rod longitudinal vibration theory. In the experiment, the inherent vibration frequencies of 10 types of medium-density fiberboard (MDF) were measured through excitation and vibration of piezoelectric ceramics based on longitudinal wave vibration theory. Then, the compressive elastic modulus of each board was calculated. The calculated compressive elastic modulus of MDF and the measured internal bond strength values were fitted into a linear regression model. A high linear correlation between them (r² = 0.972) was found, having a mean square error of (2.6times {10}^{-5}). In addition, the average error between the model prediction value and the measured value was 0.014 MPa, having an average relative error of 1.49%. The maximum error was 0.044 MPa with a maximum relative error of 5.06%, indicating that the developed model was highly consistent with reality and had very small deviations. The results indicated that this proposed method can be used to accurately estimate the internal bond strength by non-destructively detecting the compressive elastic modulus of MDF.