Wood Cell Research Articles

Quasistatic and Dynamic Nanoindentation Measurements of Pinus radiata D. Don S2 and CCML Cell Wall Layers

Quasistatic nanoindentation is a proven tool that provides information on the micromechanical behavior of wood cell walls. However, quasistatic tests cannot probe the time-dependent mechanical behavior shown by wood. Nanoindentation dynamic mechanical analysis (nanoDMA) can measure the viscoelastic properties of wood cell walls. This research aimed to study the quasistatic and viscoelastic properties of individual radiata pine wood (Pinus radiata D. Don) cell wall layers. To minimize variability and retrieve both properties at the same locations, a load function composed of a multiload-quasistatic function followed by dynamic reference frequency segments was developed. Nanoindentations were then performed on the S2 layer and compound corner middle lamella (CCML) of unembedded latewood cells. Because the S2 layer is anisotropic, both transverse and longitudinal–tangential wood planes were studied. In the transverse plane, the average results of the quasistatic elastic moduli Es for the S2 layer and CCML were 15.7 GPa and 4.6 GPa, respectively. In the longitudinal–tangential plane, the Es was 3.9 GPa. In the transverse section, the hardness H of the S2 layer and CCML were 331 MPa and 277 MPa, respectively, and in the longitudinal–tangential section H was 244 MPa. To acquire the viscoelastic properties, measurements were made over more than three decades of frequency. An increase of the storage modulus E′, and a reduction of the loss modulus E″ and loss factor tanδ as frequency increased were found in both wood orientations. The quasi-static and dynamic indentations equivalent at 0.1 Hz showed similar values for Es and E′. This study contributes to our knowledge of wood cell wall micromechanical properties.

Hierarchical wood cells impose well-textured carbon nanotubes with cobalt single atoms: Bioinspired construction and application in zinc–air battery

The construction of oxygen reduction reaction (ORR) electrocatalysts with well-textured structure and desirable activity remains great challenge for the complicated procedures and poor interface. Herein, inspired by sea anemones, the highly ordered Co–based carbon nanotubes electrocatalysts were elaborately assembled on wood fibers via stoichiometry. The porous cell-wall and abundant oxygen groups in lignocellulosic scaffold impose such preferable structure, in which the Co–based carbon nanotubes with Co single atoms and Co nanoparticles were tuned to possess higher catalytic activity and capture more oxygen species. As expected, the as-prepared electrocatalyst displays outstanding ORR performance with a half-wave potential of 0.9 V. The assembled Zn–air battery using this cathode catalyst shows a high-power density of 196 mW cm−2, superior to the commercial Pt/C catalysts. This work could inspire developing other biomimetic architectures for high-performance energy storage and conversion systems.

Evaluation of the colour parameters on hygroscopicity and dimensional stability of thermally modified Populus tomentosa Carr.

The water vapour sorption and viscoelastic characteristic of thermally modified poplar wood (Populus tomentosa Carr.) based upon colour changes were studied to provide insights into the changes in hygroscopicity and dimensional stability properties by using dynamic vapour sorption (DVS) and dynamical mechanical analysis (DMA). The thermal treatments at 180, 200, and 220 ℃ for 2, 4, 6, 8, and/or 10 h under air atmosphere were applied to cause the component degradation and crosslinking reactions within the cell wall. As the thermal treatment temperature and time increased, the lightness (L*) value of wood showed a gradual decrease. After the removal of hydroxyl groups, the hydrophobicity and dimensional stability had been significantly improved, especially at low L* value. A gauss function (R2 up to 0.99) relationship was observed between water adsorption property and L* value. Based on the analysis of the multiple sorption parameters against L* value, thermal treatment degraded the hemicellulose and reduced the moisture sorption of wood cell wall and the diffusion of water through the cell wall matrix. As the L* value declined, the trend that slow moving of side chains, increasing glass transition point temperature of hemicellulose, and more additional covalent bonds resulted in increased E″ and decreased E′ values was becoming evident. From these perspectives, it could be deduced that reduced water diffusion and high polymer stiffness confined expansion of the cell wall to endow thermally modified wood with improved hydrophilicity and dimensional stability.

Wood structure-inspired injectable lignin-based nanogels as blood-vessel-embolic sustained drug-releasing stent for interventional therapies on liver cancer

An embolic reagent with easy injection, well-controlled target embolization, and sustained release of chemotherapy drugs is urgently needed for successful trans-arterial chemo-embolization (TACE) treatment. However, the development of a highly effective embolic reagent is still challenged. Here, inspired and guided by the structural supporting properties and defense mechanisms of wood cell walls, an ideal lignin-based embolic nanogel (DOX-pN-KL) was explored. Based on the mechanical support of branched lignin and the π-π stacking force between the lignin aromatic ring with anti-tumor drug doxorubicin (DOX), DOX-pN-KL showed the highest mechanical strength among the reported thermosensitive embolization nanogel and performed high drug-loading and favorable sustained-release. Moreover, further TACE treatment and tumor microenvironment evaluation of VX2 tumor-bearing rabbits showed that this nanogel can completely block all levels of vessels in long term and continuously release DOX, thus having effective inhibition on tumor growth and metastasis. DOX-pN-KL is expected to be a promising alternative reagent for interventional therapy.

COLOR IMPROVEMENT OF PRETREATED GMELINA WOOD BY IMPREGNATION OF NATURAL DYES

The purpose of this research was to improve the appearance of pretreated gmelina wood (Gmelina arborea) by coloring with a natural dye. The dyes used in this research were obtained from sappan (Caesalpinia sappan) and tegeran (Cudrania javanensis) wood waste with a size of 20-40 mesh. The anatomical characteristic that determined the permeability of the gmelina wood was investigated referring to International Anatomist Wood Association (IAWA), while the characteristic of the dye was analyzed using X-ray diffraction (XRD). The wood was colored by immersing in dye mixture (ratio dye and water of 1:5 wt/wt) at room temperature during 72h. The results showed that the lumen diameter of vessel, fiber, and pit of gmelina observed were 159 μm, 23 μm, and 6 μm, respectively. The XRD analysis showed that thestructure of sappan was more amorphous than tegeran, whichled to penetrate deeper into the wood. Thepretreated wood provided more dyes penetration compared to the untreated wood due to the removal extractives from the wood. The pretreatment on gmelina wood would facilitate the natural dye to be impregnated intothe wood cell resulting in more attractive color of the wood.

Ectopic callose deposition into woody biomass modulates the nano-architecture of macrofibrils

Plant biomass plays an increasingly important role in the circular bioeconomy, replacing non-renewable fossil resources. Genetic engineering of this lignocellulosic biomass could benefit biorefinery transformation chains by lowering economic and technological barriers to industrial processing. However, previous efforts have mostly targeted the major constituents of woody biomass: cellulose, hemicellulose and lignin. Here we report the engineering of wood structure through the introduction of callose, a polysaccharide novel to most secondary cell walls. Our multiscale analysis of genetically engineered poplar trees shows that callose deposition modulates cell wall porosity, water and lignin contents and increases the lignin–cellulose distance, ultimately resulting in substantially decreased biomass recalcitrance. We provide a model of the wood cell wall nano-architecture engineered to accommodate the hydrated callose inclusions. Ectopic polymer introduction into biomass manifests in new physico-chemical properties and offers new avenues when considering lignocellulose engineering.

Physical and Magnetic Properties of Sengon (Falcataria moluccana Miq.) Impregnated with Synthesized Magnetite Nanoparticles

Sengon is one of the fast-growing wood that dominates Indonesian plantation forests and has been used as industrial raw material, fuel, and construction material. To enhance the physical characteristics of sengon wood, it needs technology of wood quality improvement, such as impregnation method by using Fe3O4 nanoparticles. Beside to enhance the quality of sengon wood, this technology can also expand the utilization of fast-growing wood. The presented research aims to examine the effects on physical and magnetic properties of sengon wood after being treated by magnetite nanoparticles impregnation. Magnetite nanoparticles were prepared by coprecipitation method with a precursor solution of iron ions mixture and weak base (NH4OH). The treatments of the magnetic wood consisted of 3 different concentrations that is untreated, 1% and 5% magnetite nanoparticles impregnation solution with demineralized water as a dispersant. Dimensional stability parameters, such as weight percentage growth, bulking impact, and effectiveness against swelling are increasing along the increase of concentration. Characterization tests such as SEM–EDX analysis showed the existence of Fe deposition in the wood cell membranes and pores of the wood. XRD analysis showed the appearance of magnetic peaks in the diffractogram in accordance with the decreased of crystallinity while the concentration increased and FTIR analysis showed Fe-O functional groups. Sengon wood magnetic was identified based on the VSM study, as a superparamagnetic components with mild magnetic characteristics.

The effect of hemicellulose pre-extraction on the wood viscoelasticity and its implications on the fiber separation mechanism in Chemi-mechanical pulping

Chemi-mechanical pulping (CMP) is a typical high-yield pulping technology to produce various papers and paperboards due to its high yield and high fiber properties. However, it is challenging to further improve its energy efficiency without the scarification of fiber quality. To attack this challenge, herein we study the effects of different hemicellulose pre-extraction on the viscoelasticity of wood cell wall, the energy efficiency, and product properties in chemi-mechanical pulping (CMP) process. Hardwood was first pretreated by NaOH to hydrolyze the benzyl ester bonds that link lignin with hemicellulose, aiming to partially remove hemicellulose and weaken the inter-fiber connections. Then, the hemicellulose-extracted wood underwent refining. The chemical distributions of wood, fiber morphologies, fiber surface fibrillation, energy consumption, and paper properties were extensively studied. The results showed that a 40.8% removal of hemicellulose corresponded to a 90.3% reduction in wood storage modulus (E’) and a 68.3% decrease in specific refining energy consumption. Moreover, the weaker connections between microfibrils in the secondary layer, caused by hemicellulose extraction, promoted fiber surface fibrillation during pulp refining. The study elucidates the nonnegligible role of hemicellulose as the linking “bridge” between lignin and cellulose. It also provides a new mechanism in addition to the current classic pulping mechanism including lignin chemical/thermal softening and cellulose swelling in both CMP and chemi-thermomechanical pulp (CTMP). This study offers a feasible and efficient approach to extract hemicellulose from hardwood to reduce the refining energy without scarification of fiber quality, therefore, it holds promise for advanced and greener biorefineries.

Contribution of tung oil to the resistance of heat-induced wood shrinkage during thermal modification

Thermal modification is commonly employed in the wood industry as an effective commercial strategy. However, heat-induced shrinkage accompanied by treatment processes may lead to a decreased wood recovery and devaluation of the products. In this study, tung oil was used to relieve heat-induced shrinkage during the thermal modification process, and the anti-shrinkage mechanism was investigated. The results indicated that the primary cause of heat-induced shrinkage in wood was the thermal degradation of cell wall components. There was a significant correlation (Spearman correlation coefficient = 0.974, p < 0.01) between the weight percent change (WPC) and heat-induced shrinkage (HS) in the air-thermally modified samples (TMA wood). Tung oil thermally modified samples (TMO wood) presented a lower shrinkage compared to TMA wood. The thermal modification process also influenced the relative content of wood components, leading to a shift of the cell wall mesopores in TMA wood towards larger sizes as the temperature increased. On the contrary, tung oil could increase the thermal degradation temperature, improve thermal stability and decelerate thermal degradation of wood, thus preventing the enlargement of cell wall mesopores. The impregnation of tung oil into the internal structures of wood, such as vessels, fibers, and ray cells, provided additional support to the cell lumen. In addition, confocal laser scanning microscopy (CLSM) presented that tung oil was uniformly distributed in the wood cell walls and occupied portions of mesopores, reducing the total pore volume of nitrogen absorption. Therefore, tung oil is a green and renewable modifier that effectively resisted heat-induced shrinkage during thermal modification. The anti-shrinkage approach exhibits considerable potential for improving wood recovery, conserving forestry resources, and promoting the development of a sustainable wood industry.

Effects of succinic acid impregnation on physical properties of sapwood and heartwood from plantation-grown short-rotation teak

The aim of this study was to improve the properties of 15-year-old short rotation teak wood using a succinic acid (SA) treatment without excessively increasing the weight gain. The samples were classified as sapwood (SW) and heartwood (HW). Samples were immersed in 10% concentration SA solutions (w/w), followed by vacuuming at -50 kPa for 30 minutes, and applying 7 M Pa of pressure for 2 hours. They were then analysed for specific gravity (SGs), dimensional stability, including tangential/radial ratio (T/R Ratio) and water absorption (WA), weight percent gain (WPG), chemical uptake (CU) and void volume filled (WF). Our results showed that SGs increased in treated SW and HW by 2.33% and 1.23%, respectively, as compared to the untreated wood (0.60 and 0.66). The increase in SGs was the result of SA penetration into wood cell walls. The WPG and CU values increased slightly to 5.54% and 0.87 g cm−3 for SW and 3.46% and 0.62 g cm−3 for HW, respectively. The greater increase of SGs in treated SW is due to a greater ease of treatability in SW than HW. The T/R ratio of treated HW decreased by 29.34% from the initial T/R ratio, whereas SW remained unchanged. The WA of treated SW and HW decreased by 42.67% and 55.46%, respectively compared to untreated wood. Treated wood performed better on dimensional stability, especially in terms of T/R ratio and WA values for HW. Our results show that the impregnation of short rotation teak wood with SA provides a significant increase on dimensional stability with a negligible increase in weight gain.

Mesostructural changes in cellulose within wood cell wall upon hydrothermal treatment at 200 °C

Hydrothermal treatment between 150 °C and 230 °C is widely used in wood processing, from the steam treatment of timber for better dimensional stability and durability to the pretreatment for enzymatic saccharification and chemical pulping. Understanding the ultrastructural changes of wood cell walls through hydrothermal treatments is crucial for controlling and optimizing these hydrothermal treatment-based processes. Here, we studied the ultrastructure of wood cell walls of 24 hardwood species using simultaneous small- and wide-angle X-ray scattering measurements before and after the hydrothermal treatment at 200 °C. Most hardwoods show similar equatorial scattering features, representing the structure in the cross-section of the cell walls. In a water-saturated native state, there is a prominent correlation peak between 0.1 and 0.2 Å−1 and a second peak between 0.2 and 0.4 Å−1. The hydrothermal treatment above 160 ˚C drastically altered the structure at this nanometric scale: the two native correlation peaks disappeared, coincident with a buildup of a correlation peak in the 0.03–0.04 Å−1 range. The hydrothermal treatment likely removed the cell wall matrix component between the microfibrils through autohydrolysis and phase separation, leading to the collapse of microfibrils with each other in the normal wood. In cellulose-rich cell walls, such as the G-layer in tension wood, cellulose microfibrils are already collated in the native state.

Eco-friendly geopolymer-wood building materials: Interactions between geopolymer and wood cell wall

Interactions between geopolymer and wood cell wall was investigated to better understand the bonding mechanism of geopolymer-wood composites as sustainable building materials. Elemental distributions, topological chemistry, and micro-mechanical properties between geopolymer and spruce wood cell wall were mainly investigated by the scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), UV microspectrophotometry (UMSP), nanoindentation, and nanoscratch. It was discovered that lignin may migrate from the wood cell wall to the surface of the geopolymer and thereafter partially contribute to the production of the geopolymer without appreciably damaging the wood cell wall. Geopolymer mineralized and hardened the surfaces of wood cell walls (S3 and S2 layers) evidenced by the increasing H/E and H3/E2 from spruce cell walls to geopolymer. The average width of the interaction region was around 7.65 μm according to different friction coefficients.

Influence of wood modification with polyethylene glycol and various carboxylic acids on the dimensional stability of beech wood (Fagus sylvatica)

ABSTRACT The goal of this study was the fixation of water-soluble polyethylene glycol (PEG) into the wooden cell wall. The dimensional stability of beech wood (Fagus sylvatica) modified with PEG400 and various carboxylic acids (1,2,3,4-butanetetracarboxylic acid (BTCA), citric acid (CA), malic acid, pyromellitic acid, tartaric acid, L-glutamic acid hydrochloride, ethylene diamine tetraacetic acid disodium salt dihydrate, trans-aconitic acid, maleic acid and itaconic acid) was examined. Investigations of anti-swelling efficiency (ASE), weight-percent gain (WPG) and bulking effect were made. Both the highest dimensional stabilization (values of ASE at the end of examination between 37 and 40%) and the best fixation of the chemicals in the wood (total loss of WPG between 37 and 38%) were achieved with combinations of BTCA/PEG and CA/PEG. The variants impregnated without PEG had lower bulking values. Successful modification of wood seems to be possible with BTCA, CA and malic acid in combination with PEG400.

Swelling behavior of thermally modified timber from a cellular and chemical perspective

Abstract Thermally modified timber (TMT) reduces hygroscopicity, increases dimensional stability, and decay resistance. Although there is a substantial amount of research on heat-treated wood, investigations on the sensitivity of cell wall swelling behavior to water variation are limited. Therefore, this study focused on the swelling behavior of TMT from cellular and chemical perspectives. The effects of heat treatment on the hygroscopicity and swelling behavior of the wood cell walls were studied using dynamic vapor sorption and confocal laser scanning microscopy. Changes in the chemical composition and cellulose crystallinity were studied using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction. The results revealed that the hygroscopic swelling of latewood significantly decreased with increasing treatment temperature, reducing the anisotropy of the wood cell swelling. The hygroscopicity of wood was reduced by heat treatment, and a clear decrease in hysteresis was observed at elevated treatment temperatures. The FTIR spectra indicated that both hemicellulose and lignin were degraded. The crystallinity and lateral size of the cellulose increased after heat treatment. Similar changes in the chemical composition and crystallinity of cellulose were observed in the latewood and earlywood.

In situ polymerization-hydrolysis-condensation of γ-methacryloxypropyltrimethoxysilane in cell wall for improved physical properties of wood

Silane coupling agent with its special molecular structure is often used to connect organic and inorganic materials. Due to the hydrophobic nature, silane coupling agents are often applied in wood surface modification instead of cell wall. In this study, poplar wood was modified with γ-methacryloxypropyltrimethoxysilane (MPS) to improve the dimensional stability and mechanical properties of the wood through in situ polymerization and hydrolysis-condensation reactions. The SEM/EDS imaging showed that at low monomer dosage, PMPS was uniformly distributed in the wood cell walls, while parts of PMPS formed a film at the cell lumen surface when modified with high concentrations of MPS. FTIR results indicated that PMPS was grafted onto the wood fibers. The XRD of the modified wood showed that the MPS modification did not affect the crystallinity of the wood. The even-distributed polymers PMPS, together with the original hemicellulose and lignin, act as a binder between microfibrils and was proved to impede the swelling of wood more efficiently than ordinary polymer bulking. Compared with untreated wood, 5% MPS modified wood achieved an ASE value of 48.67 ± 4.65% with the WPG only 5.05 ± 0.48%. The impact strength of 30% MPS wood increased by 45.66% compared with the unmodified wood. The ability to improve both dimensional stability and high mechanical properties with PMPS provided a promising modification solution for the functional improvement of wood.

A novel strategy accomplished by cell wall annular thickening with polymer for improving the mechanical performances of plantation wood

Inspired by the multi-level physiological structure of wood cell wall, a bionic method accomplished by annular thickening of cell wall by polymer was proposed to improve the mechanical performances of plantation wood. The thickening mechanism and the contribution of annular thickening of cell wall to the mechanical performances of plantation wood was analyzed. Results indicated that wood cell wall could be annularly thickened by the modification system prepared with water-soluble vinyl monomers and organic solvent. The flexural, compressive and impact strengths of plantation wood were synchronously improved after the treatment. The modulus of rupture of the prepared wood with 22.4% weight percentage gain reached up to 95.7 MPa which was higher than the TB 17 requirement based on the Chinese National Standard (GB 50206). The thickening degree which could be controlled by adjusting modifier concentration was closely related to the mechanical performance of treated wood.

Modified Lignin Nanoparticles as Potential Conservation Materials for Waterlogged Archaeological Wood

Lignin is the most abundant component in archaeological waterlogged wood, making it a potential consolidant with high compatibility for historical wood conservation. However, its consolidation effect is limited by its low penetration into the wood. In this study, modified lignin nanoparticles (LNPs) were proposed for the first time as conservation materials for waterlogged archaeological wood. Two modified LNPs were prepared with low molecular weight, small size, and high solubility in ethylene glycol (EG) for consolidating waterlogged wood samples. These nanoparticles, hydrophilic aminated LNPs (ALNPs) and hydrophobic esterified LNPs (MALNPs), greatly improved the consolidation effect of waterlogged wood samples compared to LNPs. This was demonstrated by measuring their physical properties, dimensional stability, and mechanical properties. The surface color change was almost within the acceptable range for the human eye. We also discussed two different reinforcement mechanisms of ALNPs and MALNPs. ALNPs can form hydrogen bonds with hemicellulose/cellulose in the wood to strengthen the fragile wood cell wall, while MALNPs can fill the wood cell lumen to support the cell wall and prevent deformation during drying. Our work provides an approach of using biomaterials as consolidants for archaeological waterlogged wood and expands the use of lignin in this field.

A Versatile 2D Cellulose Platform Strategy from Natural Wood Scaffold.

A wood cell wall with cellulose as the key scaffold is a natural hierarchical lamellar structure. This wood-derived cellulose scaffold has recently attracted enormous attention and interest, but almost all efforts have been devoted to its whole tissue functionalization. Here, we report the short ultrasonic processing of a wood cellulose scaffold to directly generate 2D cellulose materials. The obtained 2D cellulose nanosheets consist of many highly oriented fibrils densely arranged and can be further converted to ultrathin 2D carbon nanosheets. The nanoparticles, nickel-iron layer double hydroxide nanoflowers, manganese dioxide nanorods, and zinc oxide nanostars, are successfully loaded in the 2D nanosheet, providing a versatile 2D platform strategy for excellent 2D hybrid nanomaterials.

Fabrication and Process Optimization of Chinese Fir-Derived SiC Ceramic with High-Performance Friction Properties.

In this study, a novel friction material with biomass-ceramic (SiC) dual matrixes was fabricated using Chinese fir pyrocarbon via the liquid-phase silicon infiltration and in situ growth method. SiC can be grown in situ on the surface of a carbonized wood cell wall by mixing and calcination of wood and Si powder. The samples were characterized using XRD, SEM, and SEM-EDS analysis. Meanwhile, their friction coefficients and wear rates were tested to study their frictional properties. To explore the influence of crucial factors on friction performance, response surface analysis was also conducted to optimize the preparation process. The results showed that longitudinally crossed and disordered SiC nanowhiskers were grown on the carbonized wood cell wall, which could enhance the strength of SiC. The designed biomass-ceramic material had satisfying friction coefficients and low wear rates. The response surface analysis results indicate that the optimal process could be determined (carbon to silicon ratio of 3:7, reaction temperature of 1600 °C, and 5% adhesive dosage). Biomass-ceramic materials utilizing Chinese fir pyrocarbon could display great promise to potentially replace the current iron-copper-based alloy materials used in brake systems.

Mechanistic Study of the Synergistic Interaction of Furfuryl Alcohol and Caprolactam in the Modification of Pinus massoniana Earlywood and Latewood

Furfurylated wood has many advantages, such as decay resistance, dimensional stability, hardness, etc. However, furfurylation increases the brittleness and decreases the flexural resistance of wood, which greatly limits its application. Therefore, caprolactam (CPL) is incorporated with furfuryl alcohol (FA) to improve the performance of furfurylated wood. In this study, an FA and CPL combinational modifier was used to treat masson pine (Pinus massoniana Lamb.) earlywood and latewood. The synergistic interaction of both components with the wood cell walls was systematically evaluated via microstructural, chemical, and thermal analysis using scanning electron microscopy (SEM), infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectrometry (XPS), and differential scanning calorimetry (DSC). The SEM images showed that polymerized modifiers were distributed in tracheids, ray cells, and pits, with a higher degree of distribution in latewood tissues. The FA-CPL co-treatment led to the highest degree of distribution in cell cavities as well as of cell wall swelling. The results of the weight percentage gain (WPG) of modified wood agreed with the SEM findings that the FA-CPL co-treatment could more effectively increase the WPG than individual modification. The results of FTIR and XPS revealed that FA and CPL might chemically bind with each other as well as react with lignin and hemicellulose in the cell walls during the curing process. In addition, the interactions between modifiers and cell walls were slightly different for earlywood and latewood. DSC analysis indicated that the wood hygroscopicity decreased and the thermal stability improved after modification.