Search Results (49)

In this work, a flexible and sustainable radar-absorbing material (RAM) based on porous carbon derived from raw Kraft black liquor was developed. The porous carbon filler was synthesized through a simple, eco-friendly one-pot polymerization route, thereby avoiding lignin extraction, purification, and chemical activation steps. Macroporosity was introduced by using poly(methyl methacrylate) microspheres as a hard template, yielding a lightweight carbon material with a foam-like morphology, low density, and high porosity. The carbon filler was incorporated into a silicone rubber matrix at different loadings (5–25 wt.%) to produce flexible composites. The structural, morphological, and textural properties of porous carbon were investigated by SEM, EDX, Raman spectroscopy, nitrogen adsorption, and mercury porosimetry. The electromagnetic properties of composites were measured in the X-band (8.2–12.4 GHz) using a vector network analyzer. The mechanical behavior was evaluated through Young’s modulus. The results show that increasing filler content enhances dielectric losses and attenuation capability. Among all composites, the sample containing 20 wt.% of porous carbon exhibited the best electromagnetic performance, achieving a reflection loss of −42.3 dB at 10.97 GHz with a thickness of 2.43 mm, corresponding to an absorption efficiency of 99.99%. This performance is attributed to a favorable combination of impedance matching and quarter-wavelength cancellation effects. The developed sustainable, lightweight, and flexible composites demonstrate potential as low-cost RAM for aerospace and electromagnetic interference mitigation applications. Full article

Noise pollution has become an increasingly discussed environmental problem in recent years. Developing a traffic infrastructure and recent sustainability goals require new solutions to mitigate noise pollution. This paper investigates the efficiency of the noise barrier made entirely of recycled materials. This solution would help achieve the United Nations sustainable development goals (SDGs). The proposed barrier target SDGs are: Good Health and Well-being (SDG 3); Industry, Innovation, and Infrastructure (SDG 9); Sustainable Cities and Communities (SDG 11); Climate Action (SDG 13). The changed barrier parameters were the parameters of the perforated panel and the air gap behind the porous material. To solve the optimisation problem, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method was used. The results showed that the proposed barrier configuration was the following: perforation shape—round, perforation diameter—5 mm, increment angle perforation—30°, thickness of the perforated panel—10 mm, porous absorbing material (composite rubber granule and hemp shive panel (RGHS))—50 mm thick, 20% of hemp shive content, air gap between absorbing material and the rigid backing—100 mm. The total thickness of the noise barrier was 180 mm. The acoustic parameters of the noise barrier structure were: α_avg. = 0.24, peaking at 0.51 (1250 Hz) and R_W = 39.7 ± 1.0 dB. These results indicate that the proposed barrier made of recycled materials could be a sustainable alternative for noise pollution mitigation and improving people’s quality of life. Full article

With the rapid development of infrared detection methods and military surveillance technologies, flexible and wearable infrared stealth materials (ISM) have attracted increasing attention. Inspired by the layered structure of penguins’ fat–feather–oil, this study prepared a three-layer MXene/waterborne polyurethane (WPU)-foam rubber-phase change microcapsule (PCM)/WPU composite material (M-F-P) via the solution blending and doctor-blading method. The outermost layer of the M-F-P composite is an MXene/WPU conductive film, which features a low infrared emissivity and Joule heating performance to adapt to suddenly cold environments. The porous foam rubber in the middle layer provides excellent thermal insulation performance, which effectively inhibits heat conduction and enhances infrared stealth efficiency. Meanwhile, as a four-directional elastic material, it exhibits deformation recovery capability in both the warp and weft directions as well as the 45° direction. The bottom layer of the PCM/WPU film has a phase change enthalpy of 154.3 J/g and possesses efficient thermal management capability. It achieves dynamic thermal regulation through the cycle of heat absorption at high temperatures and heat release at low temperatures. Full article

Shape-stabilized phase change materials (SSPCMs) have been a promising thermal energy storage (TES) solution to combine the high energy density of solid-to-liquid (SL) PCMs and the structural stability of solid–solid PCMs. Although polymeric matrices have been used for their reduced cost and ease of processability, few have evaluated the use of crosslinked natural rubber (NR). In this study, we evaluate by differential scanning calorimetry (DSC) the preparation of room-temperature tailorable SSCPMs by the design of NR matrices with different crosslink density vulcanized by dicumyl peroxide (DCP) or sulphur, with special focus on the quantification of the content of PCM. The results indicate that the amount of PCM stable in the NR matrix is low, with PCM contents between 16 and 24% and enthalpies between 16 and 20 J·g⁻¹. Likewise, it is well-known that thermophysical properties of the PCMs vary upon confinement in a small-scale porous matrix. The confinement of the PCM in the rubber network results in a measured enthalpy below the expected value, and a melting point depression of up to 23.6 °C, dependent on crosslink density. These results highlight the structural complexity of NR-PCM composites and the need for further investigation. Full article

This work proposes a novel design configuration for an elasto-poro-hydrodynamic damper (EPHD damper) that consists of an imbibed, soft, elastic, porous material enclosed by a rubber membrane. The core innovation lies in the device’s ability to collect and re-imbibe expelled fluid during decompression, ensuring potential functionality and durability across repetitive loading cycles. Damping is achieved through the synergy of three mechanisms: friction of the membrane and of the piston with solid boundaries, squeeze flow inside the porous layer, and compression of the poro-elastic structure. The EPHD damper’s behavior was evaluated both theoretically and experimentally through quasi-static, low-speed compression tests, with dynamic evaluation being reserved for future work. A numerical model successfully validated stress-deformation behavior against experimental data, with a simplified analytical model providing a good approximation. The study also identifies that the piston–membrane friction coefficient significantly influences the EPHD damper’s performance. These findings provide a valuable framework for optimizing the design and expanding its potential application to repetitive damping systems. Full article

The permeability of recycled materials such as recycled concrete aggregate (RCA) and rubber tire waste (RTW) significantly affects their suitability in geotechnical applications. RCA is typically more porous than natural aggregates, while RTW can either increase or decrease permeability depending on its content and form. This study investigates the hydraulic conductivity of fine RCA (fRCA), fRCA–RTW mixtures, and compressed shredded tire waste (RTWS) using variable-gradient tests under various consolidation pressures. Permeability is closely related to material quality, depending on intended use: low permeability suits barrier or fill layers, while high permeability benefits drainage applications. Both behaviors were achieved in this study—fRCA showed low permeability (10⁻⁶ to 10⁻⁷ m/s), while RTW addition significantly increased water flow, with filtration coefficients exceeding 1 × 10⁻³ m/s. The permeability of fRCA–RTW mixtures increased with rubber content, though greater heterogeneity was observed. The results demonstrate that recycled materials can be tailored for specific hydraulic functions, supporting their use in sustainable construction. Full article

Porous artificial reef materials made of cement used in the offshore area can repair and improve the ecological environment and enrich fishery resources. In this study, quartz sand was used as the aggregate, high-alumina cement as the cementing agent, and crushed particles of waste tires as the modifier to prepare porous cement–polymer composites. Through orthogonal tests, the effects of the aggregate particle size, the ratio of aggregate to cement, the rubber particle size, and the rubber ratio on the strength and permeability of the porous cement–polymer composites were studied. The significant degrees of different influencing factors were analyzed, and an appropriate configuration scheme for the porous cement–polymer composites was proposed. The experimental results show that the quantity of rubber particles added and the particle size of the rubber particles have a relatively large impact on the properties of the porous cement–polymer composites. Through response surface tests, the interactive effects of various factors in the porous cement–polymer composites on the compressive strength and permeability of the material were verified. The microstructure of the porous cement–polymer composites was observed by SEM. The differences in the microstructure and internal structure between the specimens with a low rubber content and large rubber particle size and those with a high rubber content and small rubber particle size were analyzed, and the influence mechanism of the differences in the microstructure and internal structure on the strength and permeability was proposed. Full article

In this study, we present a sponge-like lipophilic gel crosslinked with a branched crosslinker as an absorbent for VOC removal. The gel was synthesized by crosslinking the monomer 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) with the branched crosslinker poly(2-propyl aspartamide) grafted methacrylate (PPA-g-MA). The grafted crosslinker, PPA-g-MA, was prepared by introducing acrylate groups as crosslinking moieties to the poly(succinimide) precursor for poly(2-propyl aspartamide) (PPA), which serves as a hydrophobic backbone. Lipophilic gels were synthesized with varying TMSPMA monomer concentrations and freeze-dried to form a porous structure. To evaluate VOC absorption, the toluene removal efficiency of the sponge-like lipophilic gel was tested in a continuous gas flow system. As a result, the optimal TMSPMA monomer content for maximizing toluene removal efficiency was determined. This result suggests that while an increase in silicon content generally enhances VOC removal efficiency, the porous structure of sponge-like lipophilic gels plays a more crucial role in absorption capacity. The collapse of the porous structure, caused by excessive silicon content making the material more rubber-like, explains why there exists an optimal monomer content for effective VOC absorption. Overall, these findings provide valuable insights for developing high-performance VOC absorbents. Full article

In cold regions, the overlay effect often leads to pavement and subgrade distresses, severely compromising the functionality of roads and infrastructure. To address this issue, this study proposes a solution involving permeable pavements and roadbed structures. However, the application of permeable pavement materials in cold regions remains a significant challenge. Building on previous research, this paper introduces a novel pavement material with exceptional mechanical and temperature performance: terminal carboxylated nitrile rubber-modified epoxy asphalt. Specifically, the mechanical properties, viscosity, high-temperature rutting resistance, low-temperature cracking resistance, and modification mechanisms of five terminal carboxylated nitrile rubber-modified epoxy asphalt mixtures with varying terminal carboxylated nitrile rubber contents were investigated. Additionally, the high-temperature, low-temperature, and water stability properties of three types of porous asphalt concrete were compared. The results demonstrate that the incorporation of terminal carboxylated nitrile rubber significantly enhances the mechanical properties and low-temperature cracking resistance of the asphalt without altering the curing time. Although the high-temperature rutting resistance of the asphalt itself decreases, the high-temperature, low-temperature, and water stability properties of the porous asphalt concrete are improved. This improvement is attributed to the chemical reaction between terminal carboxylated nitrile rubber and epoxy resin, which generates a prepolymer containing new substances and forms a stable sea–island structure. This structure promotes a more homogeneous distribution of the asphalt matrix, thereby increasing the cohesive strength and toughness of the asphalt. Full article

This paper investigates the use of spent tyre rubber as a precursor for synthesising adsorbents to recover rare earth elements. Through pyrolysis and CO₂ activation, tyre rubber is converted into porous carbonaceous materials with surface properties suited for rare earth element adsorption. The study also examines the efficiency of leaching rare earth elements from NdFeB magnets using optimised acid leaching methods, providing insights into recovery processes. The adsorption capacity of the materials was assessed through batch adsorption assays targeting neodymium (Nd³⁺) and dysprosium (Dy³⁺) ions. Results highlight the superior performance of activated carbon derived from tyre rubber following CO₂ activation, with the best-performing adsorbent achieving maximum uptake capacities of 24.7 mg·g⁻¹ for Nd³⁺ and 34.4 mg·g⁻¹ for Dy³⁺. Column studies revealed efficient adsorption of Nd³⁺ and Dy³⁺ from synthetic and real magnet leachates with a maximum uptake capacity of 1.36 mg·g⁻¹ for Nd³⁺ in real leachates and breakthrough times of 25 min. Bi-component assays showed no adverse effects when both ions were present, supporting their potential for simultaneous recovery. Furthermore, the adsorbents effectively recovered rare earth elements from e-waste magnet leachates, demonstrating practical applicability. This research underscores the potential of tyre rubber-derived adsorbents to enhance sustainability in critical raw material supply chains. By repurposing waste tyre rubber, these materials offer a sustainable solution for rare earth recovery, addressing resource scarcity while aligning with circular economy principles by diverting waste from landfills and creating value-added products. Full article

As a core component of clean energy technology, proton exchange membrane fuel cells (PEMFC) play a crucial role in promoting the evolution of energy structures and realizing sustainable development, representing an environmentally friendly energy conversion strategy. This paper identifies the key core technology themes in the field of the proton exchange membrane fuel cells by constructing patent and paper datasets in the field, applying the BERTopic model for theme identification, and calculating the key core technology scores of each theme using the importance, innovativeness, and high competitiveness barriers to identify the key core technology themes in the field, so as to provide guidance and references for the relevant research and practice. The results of the study show that patent documents and academic papers show obvious differentiation in technical themes: the key core technologies identified in patent texts include ‘battery separator materials’, ‘rubber sealing materials’, and ‘porous carbon fibre materials’. The key core technologies identified in the academic paper of the thesis include ‘palladium-based electrocatalys’, ‘graphene oxide composite film’, and ‘platinum-graphene oxide catalyst’. Full article

This study assessed the mechanical performance of porous asphalt mixtures, specifically the porous friction course (PFC), incorporating 10% Reclaimed Asphalt Pavement (RAP) and rubberized asphalt. Three different methods were investigated to evaluate the stiffness of the mixtures: the resilience modulus (RM) test at a single temperature and loading frequency, the complex modulus |E*| test from compressive loading conducted at various temperatures and frequencies, and the impact resonance (IR) tests performed at three temperatures with five impacts applied to the mixture. The results demonstrated that the RAP-containing mixture exhibited a higher resilience modulus at all tested temperatures, indicating greater stiffness compared to the mixture without RAP. Additionally, the IR and |E*| tests revealed similar behavior between the two evaluated mixtures. These findings suggest that both quasi-static and vibrational tests are suitable for characterizing the stiffness of porous asphalt mixtures due to the similarity in the viscoelastic parameters of the two investigated mixtures. This study provides important insights into the practical and scientific application of recycled and modified materials in porous asphalt mixtures. Full article

To develop a cost-effective, high-viscosity asphalt for porous asphalt pavement, we utilized SBS, tackifier, and solubilizer as the main raw materials, identified the optimal composition through an orthogonal experiment of three factors and three levels, and prepared a low-cost high-viscosity asphalt. We compared its conventional and rheological properties against those of rubber asphalt, SBS modified asphalt, and matrix asphalt, employing fluorescence microscopy and Fourier transform infrared spectroscopy for microstructural analysis. The results indicate that the optimal formula composition for high-viscosity asphalt was 4–5% styrene-butadiene-styrene (SBS) + 1–2% tackifier +0–3% solubilizer +0.15% stabilizer. The components evenly dispersed and the performances were enhanced with chemical and physical modification. Compared with SBS modified asphalt, rubber asphalt, and matrix asphalt, the softening point, 5 °C ductility, and 60 °C dynamic viscosity of high-viscosity asphalt were significantly improved, while the 175 °C Brookfield viscosity was equivalent to SBS modified asphalt. In particular, the 60 °C dynamic viscosity reaches 383,180 Pa·s. Rheological tests indicate that the high- and low-temperature grade of high-viscosity asphalt reaches 88–18 °C, and that high-viscosity asphalt has the best high-temperature resistance to permanent deformation and low-temperature resistance to cracking. It can save about 30% cost compared to commercially available high-viscosity asphalt, which is conducive to the promotion and application of porous asphalt pavement. Full article

Hydrogen is a dangerous gas as it reacts very easily with oxygen and may explode; therefore, the accumulation of hydrogen in confined spaces is a safety hazard. Composites consisting of unsaturated polymers and catalysts are a common getter, where the commonly used polymer is 1,4- diphenylethynyl benzene (DEB). Silicone rubber (SR) is a good carrier for hydrogen-absorbing materials due to its excellent chemical stability and gas permeability. In this work, polysiloxane, water, and a emulsifier are ultrasonically injected into a uniform emulsion, and the hydrogen getter DEB-Pd/C (Palladium on carbon) is then added. Under the catalysis of platinum (Pt), the cross-linking agent undergoes a hydrosilylation reaction to cross-link polysiloxane in emulsion to form silicone rubber. Then, the water was removed by freeze-drying, and the loss of water constructed a porous frame structure for silicone rubber, thus obtaining porous silicone rubber. The difference in hydrogen absorption performance between porous silicone rubber and ordinary silicone rubber was compared. It was found that, with the increase in water in the emulsion, the porous frame of silicone rubber was gradually improved, and the hydrogen absorption performance was improved by 243.4% at the highest, almost reaching the theoretical saturated hydrogen absorption capacity. Porous silicone rubber was prepared by emulsion mixing, which provided a new idea for further improving the hydrogen absorption performance of silicone rubber. Full article

Sandwich structures and porous materials have been applied widely in various fields due to their excellent mechanical performance, and multifunctional composites will have a significant engineering demand in the future. Studying damped composites’ mechanical properties and failure forms has significant engineering value and significance. However, the current connecting processes for sandwich panels and porous materials must be improved. Therefore, to explore the ambiguity of the connection interface between the core material and panel in sandwich panels, as well as the mechanical properties of such structures, a sandwich panel with a metal rubber core material was prepared using vacuum brazing and cementing processes. Microscopic examinations using scanning electron microscopy and energy-dispersive spectroscopy were conducted to observe the physical bonding mechanism at the interface of the sandwich panel. The results indicate that the brazed sandwich panels exhibited a more uniform and continuous interface than the cemented sandwich panels. This work designs three-point bending compression experiments to investigate the effects of core material thickness, density, and preparation process on the bending mechanical properties of the sandwich panel. Failure modes of the sandwich panel during the experiments are analyzed. The experimental results show that the failures of the brazed sandwich panels are attributable to the bending deformation of the panel and the shear failure of the metal wire core material. The cemented sandwich panels exhibit separation failures in the area below the indenter and at both ends of the panel. The core material’s thickness and density significantly influence the bending performance of the sandwich panels. An increase in the core material’s thickness and density effectively enhances the sandwich panels’ peak load and energy absorption capacity. Full article