Bamboo Structure Research Articles

Extraction of high-quality moso bamboo fibers by enzyme/alkali synergistic mechanism

As an emerging non-wood resource, moso bamboo has attracted extensive attention because of its short growth cycle and high holocellulose content. However, the internal structure of moso bamboo is more compact than that of wood, leading to higher chemical consumption during the pulping process, which greatly reduces the quality of the extracted fibers. Herein, an innovative pulping system including enzymes and alkali is proposed to achieve higher-quality extraction of moso bamboo fibers. Benefiting from the synergistic effects of high-temperature and alkali-resistant cellulase, xylanase, and laccase, supplemented with alkaline pulping, adequate retention and softening of moso bamboo fibers were ultimately achieved. The sample treated with an enzyme/alkali system resulted in a relative increase in fiber length of 7.19 % and a 31.26 % increase in beating efficiency over alkaline pulping. In addition, the tensile index and tearing index of the paper treated with the enzyme/alkali system reached 50.17 N·m·g−1 and 9.12 mN·m2·g−1, which were 22.52 % and 20.53 % higher than those of the alkaline pulping, respectively. This work provides new insights into the production of high-performance moso bamboo fibers and paper with low energy and alkali consumption.

Behavior of laminated bamboo columns under low cyclic reversed loading

Laminated bamboo, a type of eco-friendly engineered bamboo product, is increasingly gaining attention in the field of civil engineering. Although there has been considerable research on the material properties of laminated bamboo, studies focusing on the seismic performance of laminated bamboo columns are still relatively scarce. This paper discusses in detail the behavior of laminated bamboo columns and BFRP (Basalt fiber reinforced polymer) reinforced laminated bamboo columns under low cyclic reversed loading. In particular, the effects of slenderness ratio and axial compression ratio on laminated bamboo columns and BFRP reinforced laminated bamboo columns are studied. The hysteresis behavior of the column specimens is first tested through experiments. The results show that under low cyclic reverse loading, the failure of laminated bamboo columns is due to the tensile fracture and compressive bending of bamboo strips, as well as the tensile fracture of BFRP. To quantify the mechanical performance of laminated bamboo columns, parameters of interest are defined and discussed, including load-bearing capacity, stiffness, energy dissipation, and equivalent viscous damping. The load-bearing capacity and stiffness of laminated bamboo columns and BFRP reinforced laminated bamboo columns are significantly affected by the slenderness ratio and axial compression ratio. The yield loads for the column specimens with slenderness ratios of 37.0, 63.4, and 77.5 are within the ranges of 2.08–7.64 kN, 1.63–5.15 kN, and 1.82–7.51 kN, respectively. Laminated bamboo columns exhibit a satisfactory energy dissipation, with the maximum observed equivalent viscous damping exceeding 50 %. Furthermore, combining theoretical calculations and fitting analysis, bilinear skeleton curve models for both laminated bamboo columns and BFRP reinforced laminated bamboo columns are presented, showing a good agreement with experimental results. This research aims to provide some references for the design of laminated bamboo structures in future practical engineering.

Aging properties of bamboo scrimber after cyclic dry-wet exposure

In outdoor applications, bamboo scrimber structures are inevitably expose to prolonged cyclic dry-wet environments. To ensure the service life, it is necessary to understand how the bamboo scrimber behaves during dry-wet cycles. This study presents the aging properties of bamboo scrimber subjected to six cycles of dry-wet exposure. The tensile, compressive and flexural behavior of bamboo scrimber specimens were evaluated at the 1, 2, 4 and 6 cycles. The microstructures of bamboo scrimber specimens before and after the exposure were observed by scanning electron microscopy (SEM). Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) tests were conducted to identify the chemical changes in scrimber fibers and quantify the crystallinity of cellulose, respectively, which was projected to explain the reduced mechanical properties of bamboo scrimber after the exposure. The results indicated that after six aging cycles, the bamboo scrimber specimens showed mass loss (5.32 % - 6.22 %) and thickness expansion (tensile 17.97 %, compression 4.87 %, flexural 3.98 %). From SEM images, after the aging, the interfacial bond between the bamboo fibers and matrix was weakened and the cell walls of the thin-walled cells became thinner; gaps appeared between cell walls, and the inter-cellular arrangement was less compact. Regarding the tensile and flexural strengths of bamboo scrimber, after the first cycle, there was a significant decrease (29.50 %, 17.15 %); in subsequent cycles, no apparent changes were observed. It is worth mentioning that the compressive strength of the specimens after six accelerated aging cycles was slightly improved by 16.17 % due to the expansion of the specimen.

Cell-Shearing Chemistry Directed Closed-Pore Regeneration in Biomass-Derived Hard Carbons for Ultrafast Sodium Storage.

The closed-pore structure of hard carbons holds the key to high plateau capacity and rapid diffusion kinetics when applied as sodium-ion battery (SIB) anodes. However, understanding and establishing the structure-electrochemistry relationship still remains a significant challenge. This work, for the first time, introduces an innovative deep eutectic solvent (DES) cell-shearing strategy to precisely tailor the cell structure of natural bamboo and consequently the closed-pore in its derived hard carbons. The DES shearing force effectively modifies the pore architecture by simultaneously shearing and dissolving amorphous components to form closed pore cores with adjustable sizes, as well as disintegrating crystalline cellulose through generation of competing hydrogen bonds to elaborately tune the pore wall thickness and ordering. The optimized closed-pore structure featuring appropriate pore size (∼2 nm) and ultra-thin (1-3 layers) disordered pore walls, exhibits abundant active sites and delivers rapid ion diffusion kinetics and high reaction reversibility. Consequently, a high reversible capacity of 422 mAh g-1 at 30 mA g-1 along with an exceptional rate capability (318.6 mAh g-1 at 6 A g-1) are achieved, outperforming almost all previous reported hard carbons. The new concept of cell-shearing chemistry for closed-pore regeneration significantly advances the applications of biomass materials for energy storage.

Anisotropic membrane with high proton conductivity sustaining upon dehydration.

In fuel cells and electrolyzers, suboptimal proton conductivity and its dramatic drop at low humidity remain major drawbacks in proton exchange membranes (PEMs), including current benchmark Nafion. Sustained through-plane (TP) alignment of nanochannels was proposed as a remedy but proved challenging. We report an anisotropic composite PEM, mimicking the water-conductive composite structure of bamboo that meets this challenge. Micro- and nanoscale alignment of conductive pathways is achieved by in-plane thermal compression of a mat composed of co-electrospun Nafion and poly(vinylidene fluoride) (PVDF) nanofibers stabilizing the alignment. This translates to pronounced TP-enhanced proton conductivity, twice that of pure Nafion at high humidity, 13 times larger at low humidity, and 10 times larger water diffusivity. This remarkable improvement is elucidated by molecular dynamics simulations, which indicate that stronger nanochannels alignment upon dehydration compensates for reduced water content. The presented approach paves the way to overcoming the major drawbacks of ionomers and advancing the development of next-generation membranes for energy applications.

Structural and Chemical Analysis of Three Regions of Bamboo (Phyllostachys Edulis)

This study focuses on three different regions of moso bamboo (Phyllostachys edulis): an inner layer (IB), middle layer (MB), and outer layer (OB), to comprehensively characterize the structural features, chemical composition (ash, extractives and lignin contents), and the lignin monomeric composition as determined by analytical pyrolysis. The results show that bamboo presents a gradient structure. From the IB to OB, the vascular bundle density and fiber sheath ratio increase, the porosity decreases (from 45.92% to 18.14%), and the vascular bundle diameter–chord ratio increases (from 0.85 to 1.48). In terms of chemical composition, the ash, extractives, and acid-soluble lignin content gradually decrease from IB to OB. The holocellulose content follows the trend: MB (66.3%) > OB (65.9%) > IB (62.8%), while the acid-insoluble lignin content exhibits the opposite trend: IB (22.6%) > OB (17.8%) > MB (17.7%). Pyrolysis products reveal the diversity of carbohydrates and lignin derivatives, with a lignin monomeric composition rich in syringyl and guaiacyl units and lower amounts of H-units: the IB has an H:G:S relation of 18:26:55, while 15:27:58 is the ratio for the MB and 15:40:45 for the OB; S/G ratio values were, respectively, 1.22, 1.46, and 0.99. A comprehensive analysis highlights significant gradient variations in the structure and chemistry of bamboo, providing robust support for the classification and refinement methods of bamboo residues for potential applications.

Bamboo spatial structure, developing an integrated computational workflow and a tailored semi-automated fabrication apparatus

This paper studies the development of a semi-automated process for designing and fabricating node-based lattice spatial structures using bamboo as an ecological material. The study addresses the challenges of integrating bamboo—a naturally variable material—into spatial structures and was conducted through a hybrid workshop at the Digital Craft House, University of Art, Tehran, during COVID-19. Traditional CAD tools are often limited when applied to non-industrialized, organic materials like bamboo. This research introduces a tailored computational workflow and a semi-automated fabrication apparatus explicitly designed to create complex, freeform bamboo structures. Combining online and in-person sessions allowed participants to engage with both the theoretical and practical aspects of the design-to-fabrication process. This approach enabled the continuous development and refinement of custom tools and methods during COVID. The workshop showcased how synthesizing advanced computational approaches and natural materials could trigger new architectural solutions and autonomy by developing a single-layer, freeform spatial structure, promoting ecological and advanced architectural practices.

“Bamboo-like” strong and tough sodium alginate/polyacrylate hydrogel fiber with directional controlled release for wound healing promotion

Skin, as the biggest organ and outermost surface of the human body, is prone to injury due to various challenges, especially the expanding potential of accidents, which bring a huge social and economic burden. Hydrogels are emerging as the most promising candidate for wound dressings, which not only fulfill the varied requirements of dressings but also serve as drug carriers. But limited breathability, rapid drug release, and inadequate mechanical properties remains a significant challenge. Herein, we report a strong and tough sodium alginate/polyacrylate hydrogel fibers-based dressing with directional controlled drug release for wound healing promotion. Mimicking the bamboo structure, the drug solution is encapsulated within the fiber, and the rate of drug release can be modulated by controlling the wall thickness of the fiber. A cross-network structure in the hydrogel fiber through hydrogen bond and calcium ion crosslinking resulted in a 38 % increase in tensile strength. By precisely controlling the feeding process during weaving, drug-loaded fibers can be prepared at specific locations to facilitate targeted delivery to skin wound sites. Drug-loaded fabric has the breathability and biocompatibility required for dressings to promote wound healing. The findings highlight the potential of alginate/polyacrylate hydrogel fabrics for effective wound treatment.

High-performance bamboo-wood composite materials based on the natural structure and original form of bamboo: Fracture behavior and mechanical characterization

Reducing the destruction of bamboo's original structure to produce high-utilization and high-performance engineered bamboo products has long been a goal in the industry. This study developed a new natural arc-shaped laminated bamboo-wood lumber (NALBWL) based on the natural structure and original form of bamboo, using equal arc-shaped bamboo split (EASB) and poplar veneer. A multi-scale analysis of the bending performance and crack propagation dynamics of EASB and NALBWL was conducted. EASB's modulus of elasticity (MOE) and rupture (MOR) were 1.06 and 1.17 times higher than those of air-dried bamboo, respectively, exhibiting excellent mechanical properties. Additionally, its toughness in the full and elastic-plastic stages were 1.24 and 1.38 times higher than those of air-dried bamboo. NALBWL's MOE and MOR were 12.73 GPa and 174.41 MPa, fully meeting structural material requirements and even surpassing most engineered bamboo products. Moreover, NALBWL's radial bending load values were 2.29 and 2.24 times higher than that of EASB and air-dried bamboo, respectively, and it also demonstrated excellent water heat and drying resistance in impregnation and peeling performance. Real-time crack propagation analysis indicated that NALBWL's superior mechanical properties benefited from the respective advantages of bamboo and poplar veneer. This work showcased the application of "natural form-inspired design" in developing bamboo-wood composite materials, and the conclusion provided a reference for the sustainable development of engineered bamboo products and the study of biomass material fracture mechanisms.

Degradation-driven vegetation-soil-microbe interactions alter microbial carbon use efficiency in Moso bamboo forests

Microbial carbon utilization efficiency (CUE) is a crucial indicator for evaluating the efficiency of soil carbon sequestration and transformation, which is applied to quantify the proportion of soil carbon extracted by microbes for anabolism (growth) and catabolism (respiration). Previous studies have shown that the degradation of Moso bamboo forests (Phyllostachys edulis) destroyed the aboveground bamboo structure, reduced vegetation carbon storage, and weakened ecosystem carbon sequestration capacity. Interestingly, soil organic carbon stocks are gradually increasing. However, the mechanism by which degradation-induced changes in soil and vegetation characteristics affect microbial CUE and drive soil carbon sequestration remains unclear. Here we selected four stands with the same origin but different degradation years (intensive management, CK; 2 years' degradation, DM1; 6 years' degradation, DM2; and 10 years' degradation, DM3) based on the local management profiles. The principle of space-for-time substitution was used to investigate the changes in microbial CUE along a degradation time and to further identify the controlling biotic and abiotic factors. Our finding showed that microbial CUE increased by 12.27 %, 31.01 %, and 55.95 %, respectively, compared with CK; whereas microbial biomass turnover time decreased from 23.99 ± 1.11 to 17.16 ± 1.20 days. Promoting microbial growth was the main pathway to enhance microbial CUE. Massive inputs of vegetative carbon replenished soil carbon substrate content, and altered microbial communities and life history strategy, which in turn promoted microbial growth and increased microbial CUE. These findings provide theoretical support for the interactions between carbon dynamics and microbial physiology in degraded bamboo forests, and reinforce the importance of vegetation and microbial properties and soil carbon substrates in predicting microbial CUE.

A Compendium of Research, Tools, Structural Analysis, and Design for Bamboo Structures

Bamboo is known for its ability to grow at a high speed, with strong sustainability indicators and remarkable strength properties. However, despite these qualities, the practice of designing bamboo structures is still in its early stages in many regions. This paper aims to review the current approaches to structural analysis and design for bamboo structures as found in the existing literature. Through this comprehensive review, this study seeks to identify existing research gaps and areas that require further exploration. The limited design philosophy for bamboo structures can be attributed to the scarcity of studies on the characteristics and mechanics of bamboo material. These findings highlight the necessity for more comprehensive guidelines and standards to enhance the structural analysis and design of bamboo structures. This study identifies gaps in the following areas: lack of consideration for bamboo fiber distribution, lack of guidelines for load parameters specific to bamboo structures, inadequate coverage of bamboo culm connections, inadequate coverage on connection stiffness, limited scope on connection types, and species-specific limitations in standards.

Stiffness and stability of bamboo stem- A optimal design perspective

During the evolution process, a bamboo stem achieves a significant height (up to 20 m) to fulfil its phototropic requirements. While on land, the stem is mostly subjected to bending load which makes it liable to fail by uprooting. However, this failure is prohibited by smart structure of bamboo stem which includes graded arrangement of fibre bundles in the cross-section and a tapered cantilever form of the stem. This paper attempts to understand the optimal design of bamboo stem through the relationship between the stellar arrangement of stiff fibre bundles in the cross-section and the tapered form. In this work, a comparison between two types of stellar arrangement, namely uniform and graded, is presented in view of non-linear bending analysis through elastica theory and fracture-induced delamination, both numerically. It is observed from the results that a bamboo stem prefers to evolve with graded stellar arrangement which provides gradation of stiffness and toughness over the cross-section; the trend in toughness being opposite to that of stiffness. Moreover, interplay of stellar arrangement and gradation of stiffness-toughness thereof is found to be the governing mechanism for ensuring its mechanical integrity and stability in view of an optimal design perspective. The smart structure of bamboo is recommended for bio-mimicking.

An Investigation into the Variables Influencing the Structural Bamboo Architecture Using Filled Concrete and Cement Mortar

Bamboo, as a green building material, plays a vital role in construction. Bamboo has good properties and appearance, making it highly attractive for building structures and designs. Since the compressive capacity of bamboo is considerably lower than its tensile capacity, with the ratio typically ranging between 300% to 900%, this limits its application dimensions in construction. Therefore, filling the original bamboo structural members with specific materials or applying different connection methods can not only maintain the appearance of the bamboo structure but also improve its compressive capacity and overall durability, thus expanding the application range of bamboo structural members and enhancing the performance of the architectural design process. Two hollow bamboo specimens were among the eight BFC specimens tested for this paper. Key components such as transverse stiffeners, steel bars, filler materials, and bamboo nodes were examined for their influence on the specimens’ ductility, peak strain, ultimate bearing capacity, and failure mechanisms. The test results showed that the ratio of the ultimate bearing capacity of BFC specimens to hollow bamboo samples could reach up to 538%, while the peak strain differences were minimal. A non-linear finite element model was developed and its accuracy confirmed based on the test results. This work proposes a new approach to determine the final axial compressive capacity of BFC columns by creating an elastic model of transversely isotropic cylinders. As a result, the primary goal of this study is to establish a foundation for more scientific building design techniques and procedures by examining the axial compression mechanics of structural bamboo filled with cement and concrete (BFC) and how it influences building design.

Effect of hygro-mechanical treatment combined with saturated steam on bamboo cell wall: Structural, chemical, and hygroscopic properties

Bamboo has shown great potential in various fields such as construction, furniture, and decoration due to its fast growth rate, short degradation cycle, strong carbon sequestration ability, and excellent mechanical properties. The effects of hygro-mechanical treatment combined with saturated steam (SC treatment) on bamboo cell walls are less studied. This study explored the effects of SC treatment at different temperatures (140°C, 160°C, 180°C) on the cell wall structure, chemical composition, and hygroscopic properties of bamboo. The study utilized Fourier transform infrared spectroscopy (FTIR) and Confocal Raman microscopy (CRM) to analyze the chemical properties of bamboo, X-ray diffraction (XRD) to analyze the crystal structure, Small Angle X-ray Scattering (SAXS) to analyze the microstructure, Brunauer-Emmett-Teller (BET) to analyze porosity, and Dynamic Vapor Sorption (DVS) to assess humidity adsorption. The lignin and hemicellulose in the bamboo were degraded under saturated steam treatment, leading to reduced stability of the bamboo fiber structure. Compression under these conditions severely damages the orderly arrangement of the fiber structure, resulting in a decrease in the microfibril orientation. The reduction in orientation significantly affected the moisture transfer rate in bamboo and the micromechanical properties of the fiber cells. Simultaneously, the reduction of lignin and hemicellulose decreases the hygroscopic properties of bamboo. The results of this study indicate that SC treatment significantly improves the crystallinity and dimensional stability of bamboo while reducing its porosity, hygroscopicity, and micromechanical properties. Among the three experimental groups, the 160°C saturation steam-compression treatment was considered the best method for significantly improving bamboo performance while maintaining structural integrity.

Multifunctional bamboo-based fiber composites fabricated by assembling 3D network structures of bamboo and spatial distribution of silver nanoparticles

Bamboo-based composites have been commonly used in engineering applications as a renewable carbon recycling material. Despite its prevalent use, bamboo possesses inherent drawbacks, including flammability, moisture absorption, and susceptibility to microbial corrosion, significantly diminishing the service life of the composites as outdoor materials. Hence, a straightforward synthesis strategy was used to prepare multifunctional bamboo-based fiber composites (BFCs). This involved constructing a three-dimensional (3D) network interface within the bamboo via the combination of mechanical and chemical pretreatments, including alkali treatment, in-situ reduction, impregnation, lamination, and hot pressing. The obtained dense structure, together with the successful incorporation of functional AgNPs, enables the composites to exhibit outstanding mechanical properties (328 MPa cm3 g−1 of tensile specific strength). Moreover, the bamboo-based composite shows good flame retardancy (self-extinguishing within 5 s after ignition), improved thermal conductivity (0.258 W m−1 K−1), a self-cleaning ability, and commendable antibacterial activity against two common pathogenic bacterial (E. coli and S. aureus). This versatile bamboo-based fiber composite material holds promise for diverse outdoor applications, including roofs, wall panels, outdoor flooring, etc.

An exploratory study on bamboo permeability for evaluation of treatability with chemical solutions

The rapid and uniform impregnation of resins and preservative fluids is critical to improving the quality and durability of wood-based materials. Permeability coefficients obtained in laboratory experiments aid in the development of optimal conditions for uniform resin filling on an industrial scale. However, due to the shape and orientation of pores in the bulk structure of bamboo, simplified permeability equations may not be sufficient to provide realistic resin impregnation predictions. In this study, the permeability coefficients for Dendrocalamus asper bamboo were determined using air flow measurements and Forchheimer's equation in the x, y, and z directions, and they were correlated to the bamboo microstructure, providing a detailed perspective on how to further investigate this property for real-world applications, such as pressure treatments with chemical solutions. Porosity was measured using mercury intrusion porosimetry (MIP) and water immersion methods to aid in the permeability analysis. The results showed that the longitudinal direction had 1000 to 10,000 times higher permeability coefficients than the radial and tangential directions. This finding is consistent with the alignment of transport vessels as well as the limited pore network in the transversal bamboo section. The outer region of bamboo had higher radial permeability than the middle and inner layers, despite having lower porosity. It is hypothesized that the greater number of vessels, albeit smaller, provides a more direct path for air to flow. The Darcian permeability coefficients of bamboo were found to be comparable to those reported in the literature for wood. This exploratory study provided insights into a novel approach for assessing the treatability of bamboo species.

Experimental Study on the Dowel-Bearing Strength of Bambusa blumeana Bamboo Used for Sustainable Housing Construction

This study addresses the critical issue of dowel-bearing strength in Bambusa blumeana, a key sustainable construction material crucial for climate change mitigation. Given the lack of bamboo connection standards, this research focuses on determining the dowel-bearing strength of Bambusa blumeana, emphasizing factors such as dowel diameter, node placements, and the physical properties of bamboo. A predictive equation is derived, enhancing the practicality of bamboo in structural design. The results underscore a notable correlation between dowel diameter and characteristic strength, with implications for engineering practices. Node placements significantly affect dowel-bearing capacity, while bamboo’s physical attributes, including thickness, culm diameter, and moisture content, exhibit modest correlations with strength. The derived equation aims to assist in structural design, mitigating splitting and bearing failures in bamboo structures. This research establishes a foundation for optimizing the use of Bambusa blumeana in sustainable construction, advancing the understanding of its dowel-bearing strength for improved sustainability and resilience in the construction industry. Future research suggestions include exploring bamboo–mortar composites, additional node placements, and employing more comprehensive empirical equations and curve-fitting techniques. The study advocates for further investigations with more diverse and larger bamboo samples to bolster robustness. Additionally, delving into bamboo ductility may offer valuable insights.

Nanoarchitectonics of bamboo-based heterojunction photocatalyst for effective removal of organic pollutants

A high-performance photocatalyst with both efficient and reusable performance is essentially demanded for the purification of organic wastewater and the removal of indoor formaldehyde. However, recovery of photocatalyst particles from the reaction system remains a challenge. Herein, based on the abundant pore structure of natural bamboo and the outstanding photocatalytic activity of ZnO/WO3, we fabricated an efficient bamboo-based photocatalyst (ZnO/WO3@bamboo) for the efficient photocatalytic degradation of formaldehyde and organic dyes. The pretreatment of bamboo substrates with NaOH solution resulted in the formation of nucleation sites for ZnO/WO3 growth within bamboo cellulose channels. Subsequently, the as-prepared ZnO and WO3 were mixed in different mass ratios, and loaded on the pretreated bamboo substrates using the hydrothermal method. The results showed that the ZnO/WO3@bamboo had the effective function of photocatalytic degradation of formaldehyde gas and organic dyes. Moreover, the as-prepared ZnO/WO3@bamboo photocatalyst demonstrated superior recycling ability toward organic pollutants, which was described by photocatalytic degradation efficiency of formaldehyde gas more than 89% after 10 cycles, and organic dyes over 93% after 20 cycles. The coupling of ZnO and WO3 leads to electron delocalization, which caused the electron holes generated in the valence band (VB) of ZnO to delocalize to the VB of WO3, and reduced the recombination of electron-hole. Therefore, the photocatalytic degradation performance of the ZnO/WO3@bamboo was enhanced. The proposed ZnO/WO3@bamboo photocatalyst holds great promise in the field of air pollution and wastewater remediation.

A clean, simple, and efficient method for preparing vibration-reducing low-carbon bamboo building materials with high strength

Large-format bamboo panels prepared by bamboo flattening are adhesive-free and retain the natural structure of bamboo, making them ideal materials for interior architecture. However, due to poor dimensional stability and vibration-reducing properties, flattened bamboo easily deforms and vibrates when applied to building walls and floors due to ambient humidity changes or external excitation, impacting both comfort and structural safety. In this work, a clean, efficient, and simple densification process for flattened bamboo is developed to prepare low-carbon bamboo building materials with enhanced vibration reduction. The results indicated that the densification process reduced the vibration intensity of the flattened bamboo under excitation, changed its vibrational modes, avoided low-frequency resonance, and improved its vibration reduction and suppression properties. The dynamic stiffness of the densified bamboo increased to 3.23–3.63 times, while the root mean square (RMS) and transfer function value decreased by 20.84 % and 62.5 %, respectively. The MOE (16.2 GPa) and MOR (276 MPa) increased to 2.73 times and 2.22 times, respectively. The densified bamboo met the dimensional stability requirements of the GB/T 18102–2020 building material standards. Compared with damping, the increased stiffness played the primary role in improving the vibration-reducing properties of densified bamboo. The hydrothermal mechanical treatment changed the structure and composition. From a macroscopic perspective, the gradient structure of the vascular bundles and parenchyma cells was gradually plasticized and homogenized, compacting large capillary pores and channels such as those in parenchyma cells, vessels, and sieve tubes. On a microscopic level, defects such as pits, intercellular spaces, and micropores were filled, and microfibrils between the middle lamellae were tightly stacked, forming a mechanically-interlocked structure. At the molecular scale, there was an increase in the crystallinity and orientation of cellulose molecular chains, accompanied by an increase in hydrogen bond density. The densified bamboo developed in this study shows good application potential for vibration-reduction structures such as buildings and rail transit.

Processing natural bamboo into white bamboo through photocatalyzed lignin oxidation

Scalable and highly efficient bamboo whitening remains a great challenge. Herein, an effective bamboo whitening strategy is proposed based on photocatalyzed oxidation, which involves H2O2 infiltration and UV illumination. The as-prepared white bamboo well maintains the nature structure of natural bamboo and demonstrates high whiteness and superior mechanical properties. The absorbance value is significantly decreased to 3.5 and the transmittance is increased to 0.04 % in UV–visible wavelength range due to the removal of light-absorbing chromospheres of lignin, resulting in a high whiteness when the UV illumination time is 8 h. In addition, the white bamboo displays a high tensile strength of 30 MPa and a high flexural strength of 36 MPa due to the well-preserved lignin units (lignin preservation is about 89 %). XRD patterns and analysis show that photocatalyzed oxidation has no effect on the crystal parameters of cellulose. Compared with the traditional bamboo whitening technology, our photocatalyzed oxidation strategy demonstrates significant advantage including chemical and time conservation, high efficiency, environment friendliness, and mechanical robustness. This highly efficient and environmentally friendly photocatalyzed oxidation strategy for the fabrication of white bamboo may pave the way of bamboo-based energy-efficient structural materials for engineering application.