Search Results (199)

Waterlogged archaeological wood represents a unique cultural heritage but is highly susceptible to physical and chemical degradation, which complicates conservation and restoration. This study aimed to prepare artificial archaeological Cunninghamia lanceolata wood using NaOH vacuum impregnation and systematically evaluate the effects of NaOH concentration and treatment cycles as two treatment variables on wood degradation. Untreated heartwood specimens were treated with 5%, 10%, 20%, and 30% NaOH solutions for 2, 4, and 6 cycles. The NaOH treatment first induced chemical and structural deterioration, including selective degradation of hemicelluloses, changes in cellulose crystallinity, and progressive damage to the wood cell-wall structure. XRD analysis revealed a significant reduction in cellulose crystallinity from 35.96% to 10.11%, while FTIR confirmed the degradation of hemicelluloses and the relative enrichment of lignin-related structures. SEM observations further showed severe cell-wall erosion, lumen deformation, and local collapse, indicating that alkali treatment effectively reproduced typical microstructural features of degraded waterlogged wood. These chemical and microstructural changes subsequently led to marked changes in physical and mechanical properties. Mass loss increased with NaOH concentration and cycle number, while basic density decreased and maximum water content increased, indicating enhanced deterioration and water-holding capacity. Treated specimens also exhibited increased swelling and shrinkage rates and a substantial reduction in longitudinal compressive strength, with the most pronounced deterioration occurring under higher NaOH concentrations and repeated cycles. The study demonstrates that NaOH treatment can reproducibly simulate the physical, chemical, and microstructural characteristics of waterlogged archaeological wood, providing a reliable experimental model for studying wood degradation mechanisms and supporting conservation strategies. Full article

Ceramic nanofiber-based materials have wide applicability in high-temperature management and protection. The transformation of conventional two-dimensional ceramic nanofibrous membranes into three-dimensional nanofiber-based bulks can effectively improve their thermal insulation performance and expand their range of applications. Herein, lamellar-structured Al₂O₃-SiO₂ nanofibrous aerogels (LASO NFAs) with varying inorganic binder contents were prepared via a sequence of processes involving face-to-face stacking, impregnation, and calcination, using flexible Al₂O₃-SiO₂ nanofibrous membranes (ASO NFMs) as building units and aluminum dihydrogen phosphate as an inorganic binder. Varying the inorganic binder content in the aerogel matrix enables effective control over the compressive properties and interlayer spacing of the resulting aerogels. Specifically, the optimized LASO-20 NFAs demonstrated relatively good compression resilience, with a plastic deformation of 22.1% after undergoing 500 compressive cycles at a compressive strain of 50%. Moreover, profiting from the high-temperature resistance of ASO NFMs and substantial air content present within nanofiber interlayers, the LASO-20 NFAs with a thickness of 20 mm could effectively insulate against surface temperatures of 1000 °C down to 224 °C. Moreover, LASO-20 NFAs exhibited a room-temperature thermal conductivity of approximately 0.043 W·m⁻¹·K⁻¹, illustrating a favorable high-temperature thermal insulation characteristic. Furthermore, the LASO-20 NFAs presented promising service performance in extreme environments, providing a novel perspective in the development of new types of ceramic aerogels. Full article

Recycled aggregates (RAs) from construction and demolition waste (CDW) provide substantial circular-economy benefits, yet their elevated porosity, adhered mortar, and heterogeneity typically impair the mechanical performance and durability of recycled aggregate concrete (RAC). This PRISMA 2020-compliant systematic review synthesises 2180 records (2015–2026) to evaluate advanced strategies for enhancing RA quality prior to structural use. This paper critically compares removal-based treatments (mechanical, thermal, acid cleaning) with strengthening and densification approaches, including accelerated carbonation, pozzolanic and nano-silica coatings, polymer impregnation, microbial-induced calcium carbonate precipitation (MICP), and modified mixing methods such as triple-stage mixing (TSMA). Evidence shows that while all RA types (including recycled fine aggregate (RFA), recycled coarse aggregate (RCA), and their combination (RFCA)) can slightly reduce compressive strength and 30% replacement serves as a critical threshold, beyond this, strength loss accelerates, particularly in RCA and RFCA mixes. However, accelerated carbonation and TSMA consistently refine the interfacial transition zone, reduce water absorption by 17–30%, and recover 85–94% of natural aggregate concrete strength. Bio-deposition reduces water absorption by 13–21%, while acid/silica fume treatments improve late-age strength but carry environmental trade-offs. This review formulates a practice-oriented implementation framework for structural-grade RAC. Sustainability analyses indicate that carbonated RA can achieve net-positive CO₂ abatement when under low-carbon energy supply. A mechanistic schematic is presented to synthesise treatment-to-pore-structure/durability pathways across the four principal treatment routes, and a quantitative synthesis plot compares water absorption reductions across all treatment types using 13 data points drawn from included studies. A structured treatment comparison evaluates the energy intensity, industrial scalability, CO₂ footprint, and technology readiness level for each strategy. The remaining challenges include a lack of hybrid treatment studies, limited real-scale durability data, and insufficient mechanistic models linking treatment to pore structure evolution. This review recommends harmonised durability-based criteria and updates to standards (e.g., BS 8500, EN 12620) to support the scalable deployment of treated RA. Full article

To meet the stringent industrial service requirements of magnesia–chrome refractory bricks, this study adopts a technical approach that synergistically combines precise component ratio optimization with a vacuum-pressure MgSO₄ salt impregnation process to investigate the performance optimization of magnesia–chrome bricks. Samples were prepared by controlled formulation mixing, pressing at 250 MPa, drying at 110 °C, and firing at 1750 °C. Phase composition, microstructure, and physical–mechanical properties were characterized by XRD, SEM, and standard refractory test methods. The optimal additions of chromite powder and Cr₂O₃ micro-powder were determined to be 3 wt.% and 2 wt.%, respectively, which reacted with periclase to form a secondary composite spinel, creating a dense spinel bridge network that connected adjacent grains. Furthermore, when the proportion of sintered magnesia powder (MgO > 97 wt.%) was increased to 11 wt.%, the material achieved efficient densification facilitated by enhancing sintering performance. Based on this optimized formulation, and due to the high elemental compatibility between MgSO₄ and the magnesia–chrome brick matrix as well as the excellent permeability of the solution, the MgSO₄ vacuum-pressure salt impregnation process was subsequently applied. The salt solution filled the open pores and microcracks of the material, forming a crystalline salt micro-pillar reinforcing phase. Consequently, the apparent porosity of the material decreased to 10.98%, the bulk density increased to 3.23 g/cm³, and the cold compressive strength and cold modulus of rupture reached as high as 113.52 MPa and 24.91 MPa, respectively. This study innovatively establishes a new pathway for enhancing the mechanical properties of magnesia–chrome refractory bricks through the synergistic design of component ratio optimization and salt impregnation process. The prepared magnesia–chrome refractory bricks exhibit both excellent mechanical properties and volume stability. Full article

Wood is a sustainable material, but hygroscopicity can affect dimensional stability and mechanical durability. Recent research has increasingly focused on combining citric acid with various polyols as eco-friendly crosslinking systems to improve wood properties. Herein, a solvent-free and catalyst-free method was used to synthesize bio-based polyesters from citric acid and mannitol. In situ curing was carried out after vacuum-pressure impregnation of fast-growing poplar wood (Populus deltoides Marshall). Morphological characterization showed that the polyester filled the cell lumen and penetrated the cell wall structure. It was confirmed by Fourier Transform Infrared (FTIR) and cross-polarization/magic angle spinning (CP/MAS) ¹³C nuclear magnetic resonance (NMR) analysis that the polyester formed covalent ester bonds with wood hydroxyl groups, which indicated successful chemical grafting. The dimensional stability and mechanical properties of the modified wood were greatly improved. The parallel compressive strength of the grain reached 41.5 MPa, which was 41.7% higher than that of the untreated wood. This research adopted a citric acid–mannitol polyester, providing a sustainable, economical, and scalable approach for the development of high-performance, degradable wood composites for construction/furniture applications. Full article

In this study, the structure and mechanical properties of composites fabricated by polyetherimide film and powder lamination of carbon fabrics, as well as their impregnation with a polyetherimide/N-methylpyrrolidone solution at different contents, were compared. At compression sintering pressure of 10 MPa, the most uniform structure with the minimum number of discontinuities was formed by film lamination at the maximum carbon fabric content of 70 wt.%. For powder lamination, some discontinuities were found in the composites, which may be caused by the low melt flow index of the polyetherimide powder. The composites fabricated by impregnation with the dissolved PEI possessed low mechanical properties, so the compression sintering pressure was reduced to 6 MPa. After that, an improved composite was characterized by both uniform structure and high mechanical properties (even above those at film lamination), confirming the effectiveness of this fabrication method. Full article

The incorporation of phase change materials in concrete is a practical strategy that holds great promise for enhancing the energy efficiency of buildings and reducing CO₂ emissions. However, the direct contact between phase change materials and cement interferes with the cement hydration reaction, leading to a significant reduction in the mechanical strength of cementitious composites. To encapsulate polyethylene glycol and prevent leakage, this study developed a shape-stabilized phase change aggregate via the cold-bonding method and the vacuum impregnation method. The nanoscale pore structure of the aggregate was regulated by adjusting the biochar content to enhance the phase-change material loading capacity. The phase change aggregate was characterized by indicators including crushing strength and water absorption. Meanwhile, its microstructure, the correlations between nano-sized hydration products, chemical compatibility, and phase change properties were analyzed. The fabricated phase change aggregate has a crushing strength of over 5 MPa, latent heat of 42.84 J/g, and phase change temperature of 29.17 °C while also exhibiting good mechanical properties and thermal energy storage performance. The compressive strength of phase change concrete can meet the strength requirements for structural building material. Moreover, phase change aggregate contributed to reduced CO₂ emissions during service, with favorable economic and low-carbon benefits over its service life, demonstrating good performance in both economic efficiency and CO₂ emission reduction. Full article

Flexible textile membranes were prepared by impregnating woven cotton fabrics with silicone oil (SO)-based suspensions containing carbonyl iron (CI) microparticles and iron oxide microfibers ($\mu$Fe). The microfibers were obtained by a microwave-assisted microplasma process and then co-dispersed with CI in SO. In the final membranes, the CI content was kept constant at ${\mathrm{\Phi }}_{\mathrm{CI}}=10$ vol.%, whereas the microfiber fraction was 0, 10 and 20 vol.%. The resulting membranes were used as dielectric layers in planar capacitors and examined at 1 kHz under a static magnetic field of up to 150 mT and compressive pressure up to 10 kPa. In every composition, the capacitance rose with increasing magnetic flux density, but both the zero-field capacitance and the field-induced capacitance change became smaller as the microfiber content increased. A monotonic, nearly linear increase in capacitance was also observed under compression over the tested pressure range. Within a simplified parallel-plate and magnetic-stress analysis, the capacitance data were further used to estimate the apparent relative permittivity, together with capacitance-derived indicators of deformation and stiffness. These estimates suggest field-induced stiffening of the membranes and a higher apparent low-field stiffness at higher microfiber loading. The obtained hybrid CI/$\mu$Fe-based textile membranes can serve as composition-tunable dielectric layers whose electrical response is influenced by both magnetic field and compressive loading, making them relevant for flexible capacitor-based elements. Full article

Benefiting from their outstanding porosity, considerable specific surface area, and natural flexibility, cellulose nanofibers (CNFs)/MOF materials have emerged as competitive candidates for advanced flexible energy storage devices. However, conventional CNFs/MOFs aerogels or films often suffer from poor recoverability under compression, bending, and folding, accompanied by severe plastic deformation that compromises the cycling and structural stability of devices. To address this issue, we report a rationally designed flexible PU/CNFs/ZIF-8/PANI composite foam with an interconnected micro-mesoporous structure. Using polyurethane foam as a soft substrate and CNFs/ZIF-8 as building blocks, the composite was fabricated through a combined strategy of impregnation, in situ ZIF-8 growth, hot-pressing, and in situ aniline polymerization with simultaneous etching of the ZIF-8. The incorporation of carboxylated CNFs enhances the hydrophilicity of the PU skeleton. This, in combination with the hot-pressed framework, establishes an interconnected 3D network, thereby effectively preventing the agglomeration of active materials. Meanwhile, the hierarchical pores derived from the sacrificial ZIF-8 template provide abundant electroactive sites, accelerate ion transport, and facilitate high PANI loading. By virtue of this synergistic architectural effect, the resultant electrode achieves a high specific capacitance of 449 F/g at 0.2 A/g, with 97% capacitance retention after 2000 cycles at 5 A/g. Furthermore, the composite foam demonstrates excellent mechanical flexibility, with a tensile strength of 0.87 MPa and an elongation at break of 230%. This work offers a feasible approach for developing high-performance flexible supercapacitors and provides novel perspectives for the rational design of portable energy storage devices. Full article

A lightweight composite that simultaneously exhibits high strength and excellent thermal insulation is of great interest for thermal protection applications. In this study, dimensionally stable needled quartz fiber felt-reinforced phenolic aerogel composites were prepared using vacuum impregnation, sol–gel, and ambient pressure drying. The composites exhibit a multiscale porous structure formed by interconnected nanometer polymer skeletons and micronscale fibers. By regulating the thermoplastic phenolic resin concentration in the precursor solution, the pore structure of the material was refined; the average particle diameter reduced from 99.76 nm to 38.91 nm, and the average pore diameter decreased from 216.79 nm to 49.53 nm. At a phenolic resin concentration of 25%, the composite exhibits outstanding thermal insulation and mechanical properties: a low thermal conductivity of 0.0646 W·m⁻¹·K⁻¹ at room temperature, with a mere 19.5 °C temperature rise on the sample backside after 1800 s heating at 200 °C, and compressive strengths of 7.70 MPa in the XY-direction and 3.87 MPa in the Z-direction (at 10% strain). X-ray micro-CT characterized the internal structural evolution during loading, revealing a failure mechanism dominated by fiber buckling. Theoretical models and experimental data were used to analyze and quantify the contribution rates of gas and solid heat conduction in NQF/PR aerogel composites, with solid conduction accounting for over 80%. Combined with microstructural evolution, the mechanism for the high thermal insulation efficiency of NQF/PR aerogel composites was elucidated. This study prepared NQF/PR aerogel composites with promising application potential. By systematically evaluating their compressive behavior and quantifying the respective contributions of gas and solid conduction, this work provides a methodological framework to guide the rational design of similar aerogel composites. Full article

This study experimentally evaluates the mechanical and microstructural performance of single- and double-layer intraply hybrid composite (IRC) laminates produced using the hand lay-up method, focusing on Glass–Aramid (GA), Aramid–Carbon (AC), and Carbon–Glass (CG) configurations. Tensile, flexural, compressive, and density tests were conducted in accordance with relevant ASTM standards to assess the influence of hybrid type and layer number under field-representative manufacturing conditions. Microstructural investigations were performed using optical microscopy and scanning electron microscopy (SEM) to identify fabrication-induced imperfections and their relationship to mechanical behavior. The results demonstrate that increasing the laminate configuration from single to double layer significantly enhances mechanical performance across all hybrid types. Double-layer AC laminates exhibited the highest tensile strength (330.4 MPa) and Young’s modulus (11.93 GPa), corresponding to improvements of approximately 85% and 59%, respectively, compared to single-layer counterparts. In flexural loading, the highest strength was observed in double-layer CG laminates (97.14 MPa), while compressive strength was maximized in double-layer AC laminates (34.01 MPa), indicating improved stability and resistance to compression-driven failure. Statistical analysis confirmed that layer number is the dominant parameter governing mechanical response, exceeding the influence of hybrid configuration alone. Microstructural observations revealed fiber misorientation, incomplete resin impregnation, and localized voids inherent to manual fabrication. However, these imperfections were consistently distributed across all specimens and did not obscure comparative mechanical trends. Coefficients of variation generally remained below 10%, indicating acceptable repeatability despite non-ideal manufacturing conditions. Full article

This research investigated the impact of using lecithin and casein on lignocellulosic fiberboards on their characteristics and properties, including fire resistance. The six experimental variants created included: (1) unmodified reference fiberboards, (2) fiberboards coated with casein only, (3) fiberboards that were vacuum-impregnated with rapeseed or (4) soy lecithin, and (5, 6) fiberboards that were both vacuum-impregnated with lecithin and coated with casein. Evaluation of the board’s mass uptake, density profile, modulus of elasticity, compressive strength and fire behavior (single face exposure to mass loss, maximum posterior temperature, and area burned) demonstrated that vacuum-impregnation with lecithin was the primary driving force behind mass uptake (producing minor densification of the surface), while the casein coating produced only very minor changes to mechanical properties and modestly modified the fire performance. Lecithin alone produced an increase in both mass loss and area burned while producing a decrease in maximum posterior temperature (about 20%–25%). Lecithin-impregnated boards that were also casein-coated displayed a synergistic effect; these boards provided intermediate mechanical properties with the highest levels of fire performance (approximately 20%–30% lower than the reference fiberboards) in terms of both mass loss and area burned while also having approximately 20%–30% lower maximum posterior temperature compared to the reference. Full article

Serpula lacrymans is considered the most aggressive and harmful brown-rot fungus for wooden buildings worldwide, and it has led to substantial economic losses due to the deterioration of wood and wooden-base structures. This study aims to connect the loss of parallel compressive strength and mass loss caused by the fungus Serpula lacrymans in different lignocellulosic materials commonly used in building envelopes in Chile. Samples suspected to contain the fungus Serpula lacrymans were gathered from four Chilean localities. From these samples, the fungus under investigation was isolated and identified in the laboratory. It was used to inoculate wood samples of radiata pine, impregnated radiata pine with chromated copper and arsenate (CCA) salts, raulí (Nothofagus alpina), oriented strand board (OSB), and plywood to evaluate compressive strength at 0, 30, 60, and 90 days. As expected, the best mass loss results were obtained in impregnated pine and plywood, with values of 0.8% and 2.5%, respectively. However, significant parallel compression strength losses of 42% and 28%, respectively, were observed. This study provides valuable information for the structural diagnosis of wood elements attacked by the fungus Serpula lacrymans. Full article

Porous Ti-6Al-4V foams are excellent materials due to their low density, high specific strength, and excellent biocompatibility. This study investigates the fabrication of open-cell Ti-6Al-4V foams using the replica impregnation method with polyurethane templates of varying pore sizes (20, 25, and 30 ppi) and sintering temperatures (1170 °C, 1200 °C, 1250 °C, and 1280 °C). The effects of these parameters on microstructural evolution, phase composition, and mechanical properties were examined. Microstructural analysis showed that optimum densification occurred at 1250 °C. However, at 1280 °C, excessive grain growth and pore coarsening were observed. XRD, SEM, and EDS analyses confirmed that α-Ti was the matrix phase, while titanium carbide formed in situ as a result of the carbon residues released from the decomposed polyurethane template. With the development of the TiC phase and enhanced interparticle bonding due to sintering, the compressive strength progressively increased up to 1250 °C. At 1280 °C, strength decreased due to excessive TiC growth, causing brittleness and pore coarsening, reducing structural integrity. Maximum compressive strength of 40.2 MPa and elastic modulus of 858.9 MPa were achieved at 1250 °C with balanced TiC dispersion and pore structure. Max density of 1.234 g/cm³ was obtained at 1250 °C. Gibson-Ashby analysis and the fracture surfaces confirmed the brittle behavior of the foams, which is attributed to the presence of TiC particles and microcracks in the structure. The study concludes that 1250 °C provides an ideal balance between densification and structural integrity, offering valuable insights for biomedical and structural applications. Full article

This study evaluates the effect of chemical treatments on the short-beam shear strength, vibrational, and acoustic performance of banana-fibre-reinforced carbon–Kevlar hybrid composites. Banana fibres were treated with 5% NaOH and 0.5% KMnO₄ to improve fibre surface characteristics and interfacial bonding within a sandwich laminate of carbon–Kevlar intraply skins and banana fibre core fabricated by hand lay-up and compression moulding. Short-beam shear strength (SBSS) increased from 14.27 MPa in untreated composites to 17.65 MPa and 19.52 MPa with KMnO₄ and NaOH treatments, respectively, due to enhanced fibrematrix adhesion and removal of surface impurities. Vibrational analysis showed untreated composites had low stiffness (7780.23 N/m) and damping ratio (0.00716), whereas NaOH treatment increased stiffness (9480.51 N/m) and natural frequency (28.68 Hz), improving rigidity and moderate damping. KMnO₄ treatment yielded the highest damping ratio (0.0557) with reduced stiffness, favouring vibration energy dissipation. Acoustic tests revealed KMnO₄-treated composites have superior sound transmission loss across low to middle frequencies, peaking at 15.6 dB at 63 Hz, indicating effective acoustic insulation linked to better mechanical damping. Scanning electron microscopy confirmed enhanced fibre impregnation and fewer defects after treatments. These findings highlight the significant role of chemical surface modification in optimising structural integrity, vibration control, and acoustic insulation in sustainable banana fibre/carbon–Kevlar hybrids. The improved multifunctional properties suggest promising applications in aerospace, automotive, and structural fields requiring lightweight, durable, and sound-mitigating materials. Full article