Search Results (718)

Global urbanization has led to massive generation of high-water-content waste slurry, creating serious environmental challenges. Conventional treatment methods are costly and unsustainable, while cement-based foamed lightweight soils typically exhibit low strength and limited CO₂ sequestration. To address this issue, this study proposes a novel stabilization pathway by integrating a MgO–mineral powder–carbide slag composite binder with CO₂ foaming–carbonation. The approach enables simultaneous slurry lightweighting, strength enhancement, and CO₂ fixation. A series of laboratory tests were conducted to evaluate flowability, density, compressive strength, and deformation characteristics of the carbonated lightweight stabilized slurry. Microstructural analyses, including SEM and XRD, were used to reveal the formation of carbonate phases and pore structures. The results showed that MgO content strongly promoted carbonation, leading to denser microstructures and higher strength, while mineral powder and carbide slag optimized workability and pore stability. Orthogonal testing indicated that a mix with 25% mineral powder, 12.5% MgO, and 7.5% carbide slag achieved the best performance, with unconfined compressive strength up to 0.48 MPa after carbonation. Compared with conventional cement- or GGBS-based foamed lightweight soils, the proposed system exhibits superior strength development, improved pore stability, and enhanced CO₂ sequestration potential. These findings demonstrate the feasibility of recycling high-water-content waste slurry into value-added construction materials while contributing to carbon reduction targets. This study not only provides a sustainable solution for waste slurry management but also offers new insights into the integration of CO₂ mineralization into geotechnical engineering practice. Full article

Cordyceps militaris (C. militaris) is a medicinal fungus renowned for its diverse therapeutic properties, largely attributed to bioactive compounds such as cordycepin, polysaccharides, adenosine, D-mannitol, carotenoids, and ergosterol. However, the production and composition of these metabolites are highly influenced by cultivation conditions, highlighting the need for systematic optimization strategies. This review synthesizes current findings on how nutritional factors—including carbon and nitrogen sources, their ratios, and trace elements—and environmental parameters such as oxygen availability, pH, temperature, and light regulate C. militaris metabolite biosynthesis. The impacts of solid-state fermentation (using grains, insects, and agro-industrial residues) and liquid state fermentation (submerged and surface cultures) are compared, with attention to their roles in mycelial growth, fruiting body formation, and secondary metabolite production. Special emphasis is placed on mixed grain–insect substrates and light regulation, which have emerged as promising methods to enhance cordycepin accumulation. Beyond summarizing advances, this review also identifies key knowledge gaps that must be addressed: (i) the incomplete understanding of metabolite regulatory networks, (ii) the absence of standardized cultivation protocols, and (iii) unresolved challenges in scale-up, including oxygen transfer, foam control, and downstream processing. We propose that future research should integrate multi-omics approaches with bioprocess engineering to overcome these limitations. Collectively, this review highlights both current progress and remaining challenges, providing a roadmap for advancing the sustainable, scalable, and application-driven production of bioactive compounds from C. militaris. Full article

Microcellular thermoplastic polyurethane (TPU) foams with dynamic covalent bonds demonstrating exceptional self-healing capabilities, coupled with precisely controlled micron-scale cellular architectures, present a promising solution for developing advanced materials that simultaneously achieve damage recovery and low density. In this study, a series of self-healable materials (named as PU-S) with high light transmittance possessing two dynamic covalent bonds (oxime bond and disulfide bond) in different ratios were fabricated by the one-pot method, and then the prepared PU-S were foamed utilizing the green and efficient supercritical carbon dioxide (scCO₂) foaming technology. The PU-S foams possess multiple dynamic covalent bonds as well as porous structures, and the effect of the dynamic covalent bonds endows the materials with excellent self-healing properties and recyclability. Owing to the tailored design of dynamic covalent bonding synergies and micron-sized porous structures, PU-S₅ exhibits hydrophobicity (97.5° water contact angle), low temperature flexibility (T_g = −30.1 °C), high light transmission (70.6%), and light weight (density of 0.12 g/cm³) together with high expansion ratio (~10 folds) after scCO₂ foaming. Furthermore, PU-S₅ achieves damage recovery under mild thermal conditions (60 °C). Accordingly, self-healing PU-S based on multiple dynamic covalent bonds will realize a wide range of potential applications in biomedical, new energy automotive, and wearable devices. Full article

Polyurethane foams containing heterocyclic rings are characterized by high thermal resistance, but unfortunately, they are flammable. This work examined the effect of halogen-free flame retardants such as melamine and expanded graphite: EG 096 and EG 290 on the properties of foams with a 1,3-pyrimidine ring. Oligoetherol obtained from 6-aminouracil, ethylene carbonate, and propylene oxide was foamed with polymeric diphenylmethane 4,4′-diisocyanate with the addition of flame retardants. The oxygen index was determined, and flammability tests were conducted on the resulting foams. Their apparent density, water absorption, thermal resistance, thermal conductivity coefficient, and compressive strength were also examined. Both melamine and expanded graphite significantly reduce the flammability of foams. The resulting foams are classified as V-0 flammability class, and their oxygen index is in the range of 24.9–29.5 vol.%. Expanded graphite is a better flame retardant and does not cause deterioration of other foam properties. Full article

Foamed concrete has been widely applied in construction engineering; however, the performance requirements vary across different structural components. Its production typically involves a substantial consumption of cement, which imposes both environmental and economic burdens. Therefore, this study examined foamed concrete with dry apparent densities of 500–1000 kg/m³, in which cement was partially replaced (0–30%) by recycled powder from construction and demolition waste. Macroscopic performance was evaluated through drying shrinkage, compressive strength, softening coefficient, carbonation coefficient, and thermal conductivity, while microstructural analysis was conducted to clarify the underlying mechanisms. The results indicate that the internal composition of the recycled powder primarily consists of SiO₂, CaCO₃, and C-S-H gel. When recycled powder is used to replace cement, the microstructure of the resulting paste gradually deteriorates compared to that of the control group without recycled powder, and a significant amount of inert SiO₂ is introduced. As the replacement ratio of recycled powder increases, the compressive strength of foamed concrete across various density grades exhibits a gradual decline. Notably, when the replacement ratio reaches 30%, the reduction in mechanical performance becomes more substantial. However, the incorporation of recycled powder can effectively mitigate the drying shrinkage of foamed concrete. Moreover, the incorporation of recycled powder exerts minimal influence on the thermal conductivity and porosity of foamed concrete, demonstrating its favorable compatibility and potential for application in foamed concrete systems. Full article

The influence of both mixing pressure and substrate temperature on the structure and properties of spray polyurethane foams produced with a high content (80%) of tall oil-based polyol was investigated. The use of a renewable feedstock such as tall oil polyol aligns with the principles of sustainable development by reducing the carbon footprint and minimizing the environmental impact of the production process. The research focused on identifying the relationships between process parameters and the resulting materials’ thermal insulation properties, physico-mechanical performance, thermal behavior, cellular structure, and chemical composition. The results demonstrated that increasing the mixing pressure (from 12.5 to 17.5 MPa) and substrate temperature (from 40 to 55 °C) led to a reduction in average pore diameter, an increase in closed-cell content up to 94.5% and improved structural homogeneity. The thermal conductivity coefficient (λ) ranged from 18.55 to 22.30 mW·m⁻¹·K⁻¹ while apparent density varied between 44.0 and 45.5 kg·m⁻³. Higher mixing pressure positively affected compressive strength, whereas elevated substrate temperature reduced this parameter. Brittleness, water uptake, and dimensional stability remained at favorable levels and showed no significant correlation with processing conditions. These findings confirm the high quality of the materials and highlight their potential as sustainable, environmentally friendly insulation foams. Full article

This study examines the toxicological effects of carbon nanotubes (CNTs) of different diameters—single-walled CNTs (SWCNT, 2 nm) and multi-walled CNTs (MWCNT, 74 nm)—on two macrophage cell lines, rat alveolar NR8383 cells and human differentiated THP-1. Using standardized exposure conditions and employing an integrated omics approach (transcriptomic and proteomic analyses), both CNT types were found to induce cellular stress responses and inflammation, especially in NR8383 cells, with notable involvement of the Sirtuin signaling pathway. After 24 h, MWCNTs uniquely disrupted lipid metabolism in NR8383 cells, resulting in foam cell formation and syncytia. While SWCNTs were less disruptive to metabolic pathways, they significantly altered gene regulation, particularly RNA splicing mechanisms. The dispersion medium—fetal bovine serum (FBS) versus human surfactant—also modulated the observed toxicological responses, highlighting the critical role of the protein corona in influencing CNT-cell interactions. These findings demonstrate that CNT diameter significantly affects cytotoxicity and cellular response pathways in a cell-type-specific manner. Full article

The environmental impact of traditional construction materials has led to increasing interest in developing more sustainable alternatives. This study addresses the development of low-carbon autoclaved aerated concrete (AAC) through the complete replacement of ordinary Portland cement (OPC) with ground granulated blast furnace slag (BFS), activated with lime and, in some formulations, supplemented with calcium carbide slag (CCS). Five different AAC mixtures were prepared and evaluated in terms of workability, foaming behavior, compressive strength, phase composition, density, thermal conductivity, and life cycle assessment (LCA). The BFS-based mixtures activated with lime exhibited good workability and foaming stability. After pre-curing, the addition of CCS significantly improved the formation of tobermorite during autoclaving. As a result, the BFS–CCS formulations achieved compressive strengths comparable to the reference OPC-based mix while maintaining low densities (420–441 kg/m³) and thermal conductivities in the range of 0.111–0.119 W/(m·K). These results confirm the technical feasibility of producing structural-grade AAC with a lower environmental footprint. Full article

The intensifying freshwater crisis underscores the critical need for all-weather, low-energy atmospheric water harvesting technologies. Inspired by the scale-like protrusions and interconnected channels of Tillandsia leaves that enable efficient water capture and release, a polyvinyl alcohol-based foam featuring a three-dimensional porous structure is fabricated using the supercritical carbon dioxide foaming technology. Compared to the traditional freeze-drying method, this approach significantly reduces preparation energy consumption and shortens the production cycle. Lithium chloride integration endows the foam with exceptional moisture absorption capacity, reaching 300% of its weight. Leveraging graphene’s outstanding photothermal conversion properties, the foam achieves a photothermal dehydration rate of 80.7% within 80 min under 1 Sun irradiation, demonstrating a rapid water release capacity. Furthermore, the polyvinyl alcohol-based foam exhibits no performance degradation after 60 cycles, indicating remarkable stability. This technology provides a scalable, low-cost, and all-climate-applicable solution for water-scarce regions. Full article

Lightweight Aggregate Reinforced Concrete (LWARC) is increasingly used in structural systems to reduce dead load, especially in flat slabs. This study focuses on LWARC-incorporating polystyrene foam as a partial aggregate replacement, achieving a dry unit weight reduction from 23.0 kN/m³ to 19.0 kN/m³. While beneficial for lowering dead loads, this substitution exacerbates punching shear vulnerability, necessitating innovative strengthening solutions. Fiber-Reinforced Polymers (FRPs), recognized for their high strength-to-weight ratio, corrosion resistance, and adaptability, are employed to address these limitations. This paper evaluates the punching shear strengthening of LWARC flat slabs using externally bonded carbon fiber-reinforced polymer (CFRP) sheets, embedded through-section (ETS) steel bars, and ETS glass fiber-reinforced polymer (GFRP) bars. Ten specimens were tested under concentric loading, including an unstrengthened control slab. Experimental results were compared with predictions from ECP 203-2023, ACI 318-19, and BS 8110 to assess code applicability. Strengthened specimens demonstrated significant improvements in punching capacity and ductility. The ETS steel bar technique increased punching strength by 41% compared to the control, while inclined reinforcement configurations outperformed vertical layouts by 24% due to optimized shear transfer. Full article

This study investigates the feasibility of incorporating chemically recycled polyol (glycolysate), derived from semi-rigid polyurethane waste from the building industry, into rigid PUF formulations intended for thermal insulation applications. Glycolysis was performed using a diethylene glycol–glycerol mixture (4:1) at 185 °C in the presence of a dibutyltin dilaurate (DBTDL) catalyst. The resulting glycolysate was characterized by a hydroxyl number of 590 mg KOH/g. Foams containing 5–50% recycled polyol were prepared and described in terms of foaming kinetics, cellular structure, thermal conductivity, apparent density, mechanical performance, dimensional stability, flammability, and volatile organic compound (VOC) emissions. The incorporation of glycolysate accelerated the foaming process, with the gel time reduced from 44 s to 16 s in the sample containing 40% recycled polyol, enabling a reduction in catalyst content. The substitution of up to 40% virgin polyol with recycled polyol maintained a high closed-cell content (up to 87.7%), low thermal conductivity (λ₁₀ = 26.3 mW/(m·K)), and dimensional stability below 1%. Additionally, compressive strength improvements of up to 30% were observed compared to the reference foam (294 kPa versus 208 kPa for the reference sample). Flammability testing confirmed compliance with the B2 classification (DIN 4102), while preliminary qualitative VOC screening indicated no formation of additional harmful volatile compounds in glycolysate-containing samples compared to the reference. The results demonstrate that glycolysate can be effectively utilized in high-performance insulation materials, contributing to improved resource efficiency and a reduced carbon footprint. Full article

Printed circuit heat exchangers (PCHE) are ideal for use in very demanding operating conditions. In addition, they are characterized by very high efficiency, which can still be increased. This paper presents new concepts for improving PCHE heat exchangers. The aim of the described work was to evaluate the potential for improving the performance of printed circuit heat exchangers by incorporating open-cell metal foam as the heat exchanger packing material. The evaluation was conducted based on the results of numerical simulation of supercritical carbon dioxide cooling flowing through printed circuit heat exchanger channels filled with 40 PPI copper foam with 90% porosity. A unit periodic region of the heat exchanger comprising two adjacent straight channels for cold and hot fluid was analyzed. The channels had a semicircular cross-section and a length of 200 mm. Studies were conducted for three different channel diameters—2, 3, and 4 mm. The range of mass flux variations for cold fluid (water) and hot fluid (sCO₂) were 300–1500 kg/(m²·s) and 200–800 kg/(m²·s), respectively. It was found that in channels filled with metal foam, carbon dioxide cooling is characterized by a higher heat transfer coefficient than in channels without metal foam. In channels of the same diameter, heat flux was 33–63% higher in favor of the channel with metal foam. Thermal effectiveness of the heat exchanger with metal foam can be up to 20% higher than in the case of a heat exchanger without foam. Despite very high pressure drop through channels filled with metal foam, thermal–hydraulic performance can also be higher—even 4.7 in the case of a 2 mm channel. However, both these parameters depend on flow conditions and channel diameter, and under certain conditions may be lower than in a heat exchanger without metal foam. The results of the presented work indicate a new direction for the development of PCHE heat exchangers and confirm that the use of metal foams in the construction of PCHE heat exchangers can contribute to increasing the efficiency and effectiveness of the processes in which they are used. Full article

Lightweight aggregate concrete is known for its potential to decrease overall building load and cost. Aero Aggregates’ Aerolite is a foamed glass aggregate (FGA) available in seven different sizes which has the potential to replace normal weight aggregates to create lightweight concrete. This research analyzes the feasibility of using FGAs in optimized concrete mix designs and employing those designs in a full-scale building. Nine different mix designs were created using optimization methods, including the Tarantula Curve and 0.45 power chart, to determine the ideal aggregate proportions. All mixes were cast in 0.1 m diameter, 0.2 m tall cylinders and tested after 7 and 28 days to determine unit weight (density), compressive strength, and modulus of elasticity. After testing, the optimal design was identified as 65% coarse and 15% fine aggregates to be replaced with FGAs because it gave the best unit weight and compressive strength for structural lightweight concrete. The optimal concrete mix design was used to create an example building model in RAM Structural Systems to prove that FGA concrete can reduce cost, materials required, and carbon emissions on a larger scale. Full article

In the polyurethane industry, catalytically generated carbodiimides can modify the properties of isocyanate and, thus, the resulting foams. In this work, a kinetic reaction study was carried out to investigate the formation of a simple, bifunctional carbodiimide from a widely used polyurethane raw material: 4,4′-methylenediphenyl diisocyanate (MDI). The experimental section outlines a catalytic process, using a 3-methyl-1-phenyl-2-phospholene-1-oxide (MPPO) catalyst in ortho-dichlorobenzene (ODCB) solvent, to model industrial circumstances. The reaction produces carbon dioxide, which was observed using gas volumetry at between 50 and 80 °C to obtain kinetic data. A detailed regression analysis with linear and novel nonlinear fits showed that the initial stage of the reaction is second-order, and the temperature dependence of the rate constant is $k(T)=(3.4\pm 3.8)\mathrm{‧}{10}^6\cdot e^{{\displaystyle \frac{-7192\pm 389}{T}}}$. However, the other isocyanate group of MDI reacts with new isocyanate groups and the reaction deviates from the second-order due to oligomer (polycarbodiimide) formation and other side reactions. A linearized Arrhenius equation was used to determine the activation energy of the reaction, which was E_a = 60.4 ± 3.0 kJ mol⁻¹ at the applied temperature range, differing by only 4.6 kJ mol⁻¹ from a monoisocyanate-based carbodiimide. In addition to experimental results, computationally derived thermochemical data (from simplified DFT and IRC calculations) were applied in transition state theory (TST) for a comprehensive prediction of rate constants and Arrhenius parameters. As a result, it was found that the activation energy of the carbodiimide bond formation reaction from theoretical and experimental results was independent of the number and position of isocyanate groups, which is consistent with the principle of equal reactivity of functional groups. Full article

Cyclic solvent injection (CSI) with CO₂ is a promising non-thermal enhanced oil recovery (EOR) method for heavy oil reservoirs that also supports CO₂ sequestration. However, its effectiveness is limited by short foamy oil flow durations and low CO₂ utilization. This study explores how waterflooding and nanoparticle-assisted flooding can enhance CO₂-CSI performance through experimental and numerical approaches. Three sandpack experiments were conducted: (1) a baseline CO₂-CSI process, (2) a waterflood-assisted CSI process, and (3) a hybrid sequence integrating CSI, waterflooding, and nanoparticle flooding. The results show that waterflooding prior to CSI increased oil recovery from 30.9% to 38.9% under high-pressure conditions and from 26.9% to 28.8% under low pressure, while also extending production duration. When normalized to the oil saturation at the start of CSI, the Effective Recovery Index (ERI) increased significantly, confirming improved per-unit recovery efficiency, while nanoparticle flooding further contributed an additional 5.9% recovery by stabilizing CO₂ foam. The CO₂-CSI process achieved a maximum CO₂ sequestration rate of up to 5.8% per cycle, which exhibited a positive correlation with oil production. Numerical simulation achieved satisfactory history matching and captured key trends such as changes in relative permeability and gas saturation. Overall, the integrated CSI strategy achieved a total oil recovery factor of approximately 70% and improved CO₂ sequestration efficiency. This work demonstrates that combining waterflooding and nanoparticle injection with CO₂-CSI can enhance both oil recovery and CO₂ sequestration, offering a framework for optimizing low-carbon EOR processes. Full article