Low Content Research Articles

Conversion of soybean oil under subcritical water conditions into liquid biofuels with low oxygen contents

Although the hydrotreatment of natural triglycerides is a well-established route for producing sustainable aviation fuel and renewable diesel, its high hydrogen consumption is a concern. The hydrothermolysis of natural triglycerides is considered a highly promising alternative route; however, the correlation between process parameters and fuel properties and detailed chemical structures of the produced fuel have not been established. Herein, we investigated the conversion of soybean oil to gasoline-, jet fuel- and diesel-fraction hydrocarbons with low oxygen contents. The properties of fuels produced under various reaction conditions were analyzed comprehensively using simulated distillation, total acid number (TAN), and elemental analysis. Under the optimized reaction conditions of 420 °C, 4.5 MPa, an oil-to-water ratio of 6:1, and reaction time of 10 min, 26 % gasoline-, 62 % jet fuel-, and 90 % diesel-range hydrocarbons with a low oxygen content of 5.1 %, low TAN of 0.04 mg KOH g−1, and high calorific value of 42.7 MJ kg−1 resulted. To elucidate the reaction mechanism, the liquid products produced from soybean oil were analyzed using comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry. In addition, based on the oleic acid conversion under varying hydrothermal conditions, we proposed deoxygenation, cracking, cyclization, and aromatization pathways. The findings of this study present possibilities for producing sustainable biofuels with low oxygen contents for the aviation industry.

The influence of fines content on ground collapse due to internal erosion of sand-fines mixtures around defective pipes

Ground collapse caused by defective pipelines has become a global issue with the continuous advancement of urbanization. This study reproduced the internal erosion process of sand-fines mixtures around defective pipes through a series of model tests considering a relatively wide range of fines content and three hydraulic conditions. The erosion characteristics and the evolution of the cavity were analyzed to determine the triggering mechanisms of ground collapse. The results indicate that the formation and evolution of the cavity predominantly depend on fines content under hydraulic loading, which is replaced by ground settlement at lower fines content. Moreover, the scouring of groundwater amplifies the impact of internal erosion, which means the marked ground settlement at lower fines content or the expansion of the cavity even to ground collapse at higher fines content. To prevent sudden ground collapse, it is not recommended to use sand-fines mixtures with a fines content of more than 10% as embedment materials.

Valorization of lignin-rich solid residues from different eucalyptus wood conversion processes as oil structurants via electrospinning

The growing demand for sustainable materials has been driving research towards the use of biopolymers from natural resources. This study explores the valorization of lignin-rich solid residues derived from different eucalyptus wood conversion processes, specifically autohydrolysis (AHL), steam-explosion (SEL), and kraft pulping (EKL), via electrospinning. The potential of these electrospun nanostructures as eco-friendly oil structurant is investigated for lubricant applications. Solutions of AHL, SEL, and EKL fractions in a 3:1 v/v trifluoroacetic acid (TFA)/N,N-dimethylformamide (DMF) binary solvent were prepared at concentrations of 0.015, 0.03, and 0.05 g/mL. AHL and SEL samples exhibited superior spinnability due to higher carbohydrate content and molecular weight and lower ash content. Increasing the solution concentration to 0.05 g/mL resulted in the consecution of larger average fiber diameters (up to 0.44 and 0.39 μm, for AHL and SEL, respectively) and reduced bead formation. Stable oleo-dispersions were achieved solely with electrospun homogeneous nanofiber mats, while nanostructures predominantly composed of electrosprayed particles, like those obtained with EKL produced physically unstable dispersions from which the oil readily separates. The rheological response and microstructure of oleo-dispersions were significantly affected by both the conversion process of eucalyptus wood and the spinning solution concentration. The rheological properties of the oleo-dispersions can be tailored by modifying the spinning solution concentration, with G′ values ranging from 5·102 to 5·104 Pa and consistency and flow indices roughly ranging from 90 to 990 Pa sn and from 0.06 to 0.19, respectively, depending on the nature of the lignin-rich fraction and the type of electrospun nanostructure employed. These results highlight the potential of electrospun nanostructures obtained from lignin-rich solid residues in advanced materials applications, promoting the valorization of waste streams derived from different biorefinery processes, as well as the development of novel environmentally friendly lubricants.

Investigating the interdependence of microstructure and properties in low-Cu content Al-Zn-Mg alloys via thermodynamic calculation

This paper redesigned the Al-Zn-Mg alloy composition by thermodynamic calculations and experiments, and also explained the precipitation strengthening of the 7xxx alloy. At a Zn/Mg ratio of 3.3–5.3, only the η phase is present. The η phase was experimentally verified as the main contributor to precipitation strengthening. The Al-7.6Zn-2.2Mg-0.2Cu-0.2Cr-0.4Mn-0.15Zr alloy exhibited excellent mechanical properties, with yield and tensile strengths of 510 MPa and 542 MPa under T6 treatment. The low copper content 7xxx alloy designed in this study achieves a yield strength exceeding 500 MPa solely through the compositional design of the Zn/Mg ratio.

Screen-printed electrodes decorated with low content Pt–Ni microstructures for sensitive detection of Zn(II), ascorbic acid and paracetamol in pharmaceutical products and human blood samples

In this study, we report for the first time, a method for simultaneous detection of paracetamol (PA) and its toxic impurities, 4-aminophenol (4-AP), as well as commonly co-formulated drugs, ascorbic acid and zinc (AA and Zn(II)), using screen-printed electrodes (SPEs) as a sensing platform. To improve the electrochemical performance of the SPEs, these are decorated with platinum and nickel microstructures (Pt–Ni), using a simple electrodeposition technique. The structures and morphologies of the synthesized Pt–Ni/SPE electrode were confirmed by FE–SEM, TEM, EDX, XRD and AFM measurements. Furthermore, electrochemical characterization of the as-prepared sensor was investigated using cyclic voltammetry and electrochemical impedance spectroscopy methods. Under optimum conditions, the content of 4-AP, PA, AA and Zn(II) was quantified using cyclic voltammetry, differential pulse voltammetry and square-wave voltammetry techniques. The designed sensor exploits a dual effect, leveraging the efficiency of Pt for Zn(II) detection and Pt–Ni for the detection of 4-AP, AA, and PA. On one hand the as-prepared Pt–Ni/SPE sensor exhibits a linear response towards 4-AP and PA, ranging from 0.5 to 200 μM for both, with detection limits of 0.33 µM and 0.23 µM (S/N = 3) for 4-AP and PA, respectively. On the other hand, it demonstrates a linear response towards PA, AA, and Zn(II), ranging from 0.01 to 0.8 μM for Zn(II), 10 to 1800 μM for AA, and 0.5 to 200 μM for PA, with detection limits of 0.004 µM, 9.0 µM, and 0.15 µM for Zn(II), AA, and PA, respectively. Crucially, the as-fabricated sensor, with its remarkable reproducibility, recovery, long-term stability, and anti-interference capabilities, effectively quantified 4-AP, PA, Zn(II) and AA in both pharmaceutical formulations and human plasma samples.

Chronic undernutrition impairs renal mitochondrial respiration accompanied by intense ultrastructural damage in juvenile rats

This study investigated whether chronic undernutrition alters the mitochondrial structure and function in renal proximal tubule cells, thus impairing fluid transport and homeostasis. We previously showed that chronic undernutrition downregulates the renal proximal tubules (Na++K+)ATPase, the main molecular machine responsible for fluid transport and ATP consumption. Male rats received a multifactorial deficient diet, the so-called Regional Basic Diet (RBD), mimicking those used in impoverished regions worldwide, from weaning to a juvenile age (3 months). The diet has a low content (8 %) of poor-quality proteins, low lipids, and no vitamins compared to control (CTR). We investigated citrate synthase activity, mitochondrial respiration (oxygraphy) in phosphorylating and non-phosphorylating conditions with different substrates/inhibitors, potential across the internal membrane (Δψ), and anion superoxide/H2O2 formation. The data were correlated with ultrastructural alterations evaluated using transmission electron microscopy (TEM) and focused ion beam scanning electron microscopy (FIB-SEM). Citrate synthase activity decreased (∼50 %) in RBD rats, accompanied by a similar reduction in respiration in non-phosphorylating conditions, maximum respiratory capacity, and ATP synthesis. The Δψ generation and its dissipation after carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone remained unmodified in the survival mitochondria. H2O2 production increased (∼100 %) after Complex II energization. TEM demonstrated intense matrix vacuolization and disruption of cristae junctions in a subpopulation of RBD mitochondria, which was also demonstrated in the 3D analysis of FIB-SEM tomography. In conclusion, chronic undernutrition impairs mitochondrial functions in renal proximal tubules, with profound alterations in the matrix and internal membrane ultrastructure that culminate with the compromise of ATP supply for transport processes.

Unraveling the mechanisms of biochar and steel slag in alleviating lithium stress in tomato (Solanum lycopersicum L.) plants via modulation of antioxidant defense and methylglyoxal detoxification pathways

With progress in technology, soaring demand for lithium (Li) has led to its release into the environment. This study demonstrated the mitigation of the adverse effects of Li stress on tomato (Solanum lycopersicum L.) by the application of waste materials, namely coconut shell biochar (CBC) and steel slag (SS). To explore the impact of Li treatment on tomato plants different morphological, biochemical parameters and plant defense system were analyzed. Tomato plants exposed to Li had shorter roots and shoots, lower biomass and relative water contents, and showed decreases in physiological variables, as well as increases in electrolyte leakage and lipid peroxidation. However, the application of CBC and SS as passivators, either singly or in combination, increased growth variables of tomato and relieved Li-induced oxidative stress responses. The combined CBC and SS amendments reduced Li accumulation 82 and 90% in tomato roots and shoots, respectively, thereby minimizing the negative impacts of Li. Antioxidant enzymes SOD, CAT, APX and GR reflected 4, 5, 30, and 52% and glyoxalase enzymes I and II 7 and 250% enhancement in presence of both CBC and SS in Li treated soil, with a concurrent decrease in methylglyoxal content. Lithium treatment triggered oxidative stress, increased enzymatic and non-enzymatic antioxidant levels, and induced the synthesis of thiols and phytochelatins in roots and shoots. Hence, co-amendment with CBC and SS protected tomato plants from Li-induced oxidative damage by increasing antioxidant defenses and glyoxalase system activity. Both CBC, generated from agricultural waste, and SS, an industrial waste, are environmentally benign, safe, economical, and non-hazardous materials that can be easily applied on a large scale for crop production in Li-polluted soils. The present findings highlight the novel reutilization of waste materials as renewable assets to overcome soil Li problems and emphasize the conversion of waste into wealth and its potential for practical applications.

Characteristics and environmental implications of coal fines at Hwange Colliery Company, Zimbabwe: A comprehensive analysis

The study investigates the characteristics and environmental implications of coal fines at Hwange Colliery Company in Zimbabwe, aiming to address gaps in understanding and propose sustainable management strategies. The research encompasses a comprehensive analysis, including particle size distribution, proximate properties, elemental composition of coal fines, water and soil quality analysis. Sample collection and analysis were conducted following standardized procedures, revealing significant variations among sites in terms of particle size distribution and proximate properties. The sieve analysis revealed that around 80 % of the coal fines passed through the 2 mm sieve. Sites A and B exhibited lower moisture content and higher carbon content in contrast to site C, possibly due to variances in disposal duration. With an average gross calorific value of 17.43 MJ/kg, the coal fines showcase notable potential for energy extraction. Elemental analysis uncovered traces of heavy metals like Fe, Co, Cr, Ni, and Cu, posing an environmental risk if not managed appropriately. The water quality analysis revealed generally low turbidity levels in groundwater, with readings ranging from 0.34 to 0.55 NTU. However, elevated sulfate concentrations in some samples, averaging 113.67 mg/l, coupled with traces of nickel at levels up to 0.07 mg/l, warrant continuous monitoring to ensure compliance with safety standards. Soil analysis indicated the presence of heavy metals near coal fines dump sites, with lead levels reaching up to 52.32 mg/L, nickel at 36.17 mg/L, and copper at 53.70 mg/L, impacting soil enzyme activity and agricultural productivity. The study emphasizes the importance of improved waste management practices and sustainable utilization strategies to mitigate environmental risks and enhance resource efficiency in coal mining operations.

Rheology, stability, and physicochemical properties of NaOH-tannic acid solvent for β-chitin dissolution

The applicability of chitin in food systems is limited by its poor solubility in ordinary solvents. This study explores a novel solvent system composed of sodium hydroxide and tannic acid (NaOH/TA) in combination with a repeated freeze-thaw process for dissolving chitin. The highest chitin solubility in 8% NaOH/0.3% TA and 10% NaOH/0.3% TA was 2.1% and 2.3% (w/v), respectively. The lower NaOH and excessive tannic acid content may lead to reduction of chitin solubility. We also observed a unique rheological property of the chitin/NaOH/TA system. A higher concentration of TA reduced the chitin solution's shear viscosity, storage modulus, loss modulus, and gelling temperature. Its shear viscosity decreases with increasing shear rate, showing a shear thinning behavior. When the chitin/NaOH/TA solution system was stored at 30oC, the crystalline degree of chitin decreased, and the diffraction peak shifted, suggesting the formation of different intermolecular forces. The TA contents show no significant effect on the crystallinity of chitin. With increased storage time, the molecular weight of chitin decreased, and the degree of deacetylation (DD) increased. These results underscore the potential applications of the chitin/NaOH/TA system in the food industry.

Effect of ultrasound-assisted pH-shifting treatment on the physicochemical properties of melon seed protein

Melon seeds have received considerable attention in recent years because of their high protein content, but they have not yet been fully used. The modification of melon seed protein (MSP) using ultrasound-assisted pH-shifting treatment was investigated in this study by analyzing structural characteristics and functional properties. The particle size, free sulfhydryl content, surface hydrophobicity, solubility, secondary structure, water-holding capacity, oil-holding capacity, emulsification activity index, and emulsification stability index of MSP were determined. MSP treated with ultrasound-assisted, pH-shifting had a smaller particle size, lower free sulfhydryl content, higher surface hydrophobicity, and solubility increased from 43.67 % to 89.12 %. The secondary structure of MSP was affected by ultrasonic treatment, manifesting as an α-helix increase and β-helix, β-turn, and random coil content decrease, which may be the reason why the protein structure became more compact after treatment. The water and oil holding capacities of MSP increased from 2.74 g/g and 3.14 g/g in untreated samples to 3.19 g/g and 3.97 g/g for ultrasound-treated samples, and further increased to 3.97 g/g and 5.02 g/g for ultrasound-assisted, pH-shifting treatment at pH 9.0, respectively. The emulsification activity index of MSP was 21.11 m2/g before treatment and reached a maximum of 32.34 m2/g after ultrasound-assisted, pH-shifting treatment at pH 9.0. The emulsification stability of MSP was maximized by ultrasonic treatment at pH 7.0. Ultrasound-assisted, pH-shifting treatment can effectively improve the functional properties of MSP by modifying the protein structure, which improves the potential application of melon seed protein in the food industry.

Investigating the Discoloration of Leaves of Dioscorea polystachya Using Developed Atomic Absorption Spectrometry Methods for Manganese and Molybdenum.

The Chinese yam (Dioscorea polystachya, DP) is promising for the food and pharmaceutical industries due to its nutritional value and pharmaceutical potential. Its proper cultivation is therefore of interest. An insufficient supply of minerals necessary for plant growth can be manifested by discoloration of the leaves. In our earlier study, magnesium deficiency was excluded as a cause. As a follow-up, this work focused on manganese and molybdenum. To quantify both minerals in leaf extracts of DP, analytical methods based on atomic absorption spectrometry (AAS) using the graphite furnace sub-technique were devised. The development revealed that the quantification of manganese works best without using any of the investigated modifiers. The optimized pyrolysis and atomization temperatures were 1300 °C and 1800 °C, respectively. For the analysis of molybdenum, calcium proved to be advantageous as a modifier. The optimum temperatures were 1900 °C and 2800 °C, respectively. Both methods showed satisfactory linearity for analysis. Thus, they were applied to quantify extracts from normal and discolored leaves of DP concerning the two minerals. It was found that discolored leaves had higher manganese levels and a lower molybdenum content. With these results, a potential explanation for the discoloration could be found.

High internal phase Pickering emulsion solely stabilized by low-content chitosan: Insight into relations between network microstructures and rheological properties

Nano-sized and well-dispersed chitosan particles (CSPs) are prepared by adjusting pH towards pKa of chitosan (CS) aqueous solutions. The prepared CSPs are able to stabilize high internal phase Pickering emulsions (HIPPEs) with low CSP contents, at minimum of 0.2 wt% CSP stabilizing a maximum of 85 % oil phase fraction in a near-neutral environment. It is clarified by microscopy, small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS) measurements that CSPs act as Pickering particle emulsifiers to form a network immobilizing oil droplets in HIPPEs. Using power-law analysis on SAOS results, the solid-like but frequency-dependent rheological response is attributed to the physical connection among CSPs, while the overshoot of the loss modulus in LAOS test is assigned to the featured resistance of networks to the applied large deformation. The oil phase fraction, CSP concentration, temperature and ionic strength are found to be key factors for the rheological behavior and emulsion stability. This work is expected to guide the design and processing of HIPPE stabilized solely by polysaccharides.

Adjusting the hydrophobicity of recombinant microgels to improve interfacial activity: Using a promising pickering emulsion stabilizer with a dense cubic structure

Developing recombinant microgels (RMs) with high mechanical and anti-coalescence properties provides a safe and economical method for constructing uniform and stable Pickering emulsions. Previously, we prepared RMs based on polysaccharides using freeze–thaw cycles, displaying excellent stability. Because RMs can be formed between polysaccharides, we studied whether they can be formed between polysaccharides and proteins for preparing Pickering emulsions. Therefore, we report a heat-induced gelation method to generate RMs with bovine serum albumin (BSA) and κ-carrageenan (KC). Owing to heat-induced treatment (90 °C), the high hydrophilicity of KC could be regulated by the exposed hydrophobic groups of BSA, and the system rapidly gelated after cooling (−18 °C) to obtain a dense recombinant structure. The TPA and SEM results further demonstrated that the RMs with a BSA:KC ratio of 1:2 have a typical cubic structure (0.93 μm) and excellent gel strength. RMs adsorbed at the oil–water interface to form non-covalent binding layers, which improved interfacial activity and reduced interfacial tension (95.10°) to obtain more uniform and stable Pickering emulsions. The above results indicate that synthesizing RMs provides a feasible method for constructing uniform and stable Pickering emulsions with low oil content, these are similar to high internal phase emulsions with semi-solid rigid structures.

Mineral and cross-linking in collagen fibrils: The mechanical behavior of bone tissue at the nano-scale

The mineralized collagen fibril is the main building block of hard tissues and it directly affects the macroscopic mechanics of biological tissues such as bone. The mechanical behavior of the fibril itself is determined by its structure: the content of collagen molecules, minerals, and cross-links, and the mechanical interactions and properties of these components. Advanced glycation end products (AGEs) form cross-links between tropocollagen molecules within the collagen fibril and are one important factor that is believed to have a major influence on the tissue. For instance, it has been shown that brittleness in bone correlates with increased AGEs densities. However, the underlying nano-scale mechanisms within the mineralized collagen fibril remain unknown. Here, we study the effect of mineral and AGEs cross-linking on fibril deformation and fracture behavior by performing destructive tensile tests using coarse-grained molecular dynamics simulations. Our results demonstrate that after exceeding a critical content of mineral, it induces stiffening of the collagen fibril at high strain levels. We show that mineral morphology and location affect collagen fibril mechanics: The mineral content at which this stiffening occurs depends on the mineral’s location and morphology. Further, both, increasing AGEs density and mineral content lead to stiffening and increased peak stresses. At low mineral contents, the mechanical response of the fibril is dominated by the AGEs, while at high mineral contents, the mineral itself determines fibril mechanics.

Combinatory Use of hLF(1-11), a Synthetic Peptide Derived from Human Lactoferrin, and Fluconazole/Amphotericin B against Malassezia furfur Reveals a Synergistic/Additive Antifungal Effect.

The increasing resistance of Malassezia yeasts against commonly used antifungal drugs dictates the need for novel antifungal compounds. Human lactoferrin-based peptides show a broad spectrum of antimicrobial activities. Various assays were performed to find the optimal growth conditions of the yeasts and to assess cell viability, using media with low lipid content to avoid peptide binding to medium components. In the current study, we tested the antimicrobial susceptibility of 30 strains of M. furfur that cover the known IGS1 genotypic variation. hLF(1-11) inhibited the growth of all species tested, resulting in minimum inhibitory concentrations (MIC) values ranging from 12.5 to 100 μg/mL. In the combinatory tests, the majority of fractional inhibitory concentration indexes (FIC) for the tested strains of M. furfur were up to 1.0, showing that there is a synergistic or additive effect on the efficacy of the antifungal drugs when used in combination with hLF(1-11). Results showed that hLF(1-11) could be combined with fluconazole or amphotericin for the antimicrobial treatment of resistant strains, enhancing the potency of these antifungal drugs, resulting in an improved outcome for the patient.

Large-scale production of cefazolin in a microreactor with a low impurity content and high yield

Cefazolin is crucial in the field of healthcare because of its efficacy against bacterial diseases, but trace amounts of polymer impurities produced during synthesis may cause severe allergic reactions. In this work, an efficient system based on a membrane dispersion microreactor was designed for scalable cefazolin production with a high yield and low impurity content. At a production scale of 200 kg, the yield could reach 90 %, and the polymer impurity content could reach <0.008 %. Density functional theory calculations were used to investigate the formation mechanisms of the polymer impurities. The results revealed that the activation energy of cefazolin ring-opening and substitution reactions decreased by 22.4 kJ/mol and 6.4 kJ/mol respectively under alkaline conditions, resulting in increased polymer content. Computational fluid dynamics simulation indicates that the organic base in the substrate can be rapidly dispersed in the membrane dispersion microreactor, thus avoiding excessive local base concentration. In conclusion, the development of a membrane dispersion microreactor system offers a scalable and efficient method for cefazolin production with significantly lower polymer impurity content, thereby addressing a critical challenge in antibiotic synthesis and ensuring safer and more reliable healthcare applications.

Hydrothermal carbonization of combined food waste: A critical evaluation of emergent products

Hydrothermal carbonization (HTC) increasingly appears as an eco-friendly method for managing food waste (FW). In this work, a combination of FW was subjected to HTC, and products were critically evaluated. This involved a lab-scale pressure reactor and optimization of HTC conditions: temperature (220–340 °C) and residence time (90–260 min) via central composite design type of response surface methodology (CCD-RSM). Results showed varying temperatures and residence time to impact the hydrochar (HC) and hydrothermal carbonization aqueous phase (HTC-AP) properties. Although HC produced through HTC exhibited lower ash content (<2%) despite higher fixed carbon (>55 %) with respect to the raw FW, the heating value of HC ranged from 19.2 to 32.5 MJ/kg. Temperature primarily influenced FW conversion, affecting carbonaceous properties. Saturated fatty acids (SFA) were found to be predominant in the HTC-AP under all tested operating conditions (77.3, 48.4, and 37.1 wt% for HTC at 340, 280, and 220 °C in 180 min, respectively). Total phosphorus recovery in HC and HTC-AP respectively peaked at 340 °C and 220 °C in 180 min. The study concludes that HTC holds promise for energy-dense biofuel production, nutrient recovery, and fostering a circular economy.

Lignin pyrolysis assisted by molten salt medium: Evolution behavior of volatiles and biochar structure

This study focuses on the use of a molten salt reaction medium (NaCl-KCl-LiCl) in the lignin pyrolysis process to modify the pyrolysis volatiles and biochar structure. The effect of pyrolysis reaction temperature (300°C, 400°C, 500°C, and 600°C) and lignin/molten salt mass ratios (3:1, 1:1, 1:3 and 1:5) on the evolution behavior of volatiles and biochar structure was explored. The pyrolysis products were determined using GS-MS, CO2 adsorption-desorption analyses, SEM, elemental analysis, proximate analysis, Raman, XRD, and TG/DTG analysis. Results indicated that the introduction of molten salt can enhance the lignin depolymerization, leading to the production of phenolic precursors. Moreover, the metal cation (Na+, K+ and Li+) of molten salt can in-situ induce the modification of biochar structure with high porosity. The lower sulfur content in biochar was attributed to the immobilize function of molten salt. The evolution behaviour of volatiles and biochar structure during molten salt-assisted lignin pyrolysis was proposed. This study can serve as a benchmark for the high-value recycling of industrial lignin waste.

Asymmetric electrical-magnetic composite foams with oriented cells fabricated by supercritical CO2 foaming and thermal stretching for efficient absorption dominated electromagnetic interference shielding

Asymmetric composite foams (TCFAs) based on thermoplastic polyurethane (TPU) containing carbon nanotubes (CNTs) and Fe3O4-decorated reduced graphene oxide (Fe3O4@rGO) electrical-magnetic dual networks with oriented cell structures and a silver layer were fabricated through supercritical carbon dioxide foaming, thermal stretching and a knife coating process. The oriented cells prolonged the electromagnetic (EM) wave transmission path and induced more multiple reflections, and the asymmetric silver layer enabled a special “absorption-reflection-reabsorption” mechanism, which contributed to a high electromagnetic interference (EMI) shielding effectiveness (SE) of 89.5 dB with an A value of 0.748 at a relatively low total filler content of 1.784 vol%. By regulating the oriented cell structure and the incorporation of asymmetric design, the TCFA-1 achieved 10 times improvement in EMI SET with a low EMI SER of 1.27 dB. This work offers new insights into the design and fabrication strategies for high performance absorption-dominated EMI shielding foams.

Impact of weak interlayer characteristics on the mechanical behavior and failure modes of cemented tailings backfill: A study on thickness, strength, and dip angle

The mechanical properties of cemented tailings backfill (CTB) are crucial for managing ground pressure and sustaining mine productivity. However, multiple fillings often result in weak interlayers (WI) within the backfill, compromising its stability. This study investigates the mechanical behavior and failure modes of composite cemented tailings backfill (CCTB) with different WI characteristics—thickness (ranging from 0 mm to 30 mm), strength (cement-tailings ratio from 1:4 to 1:20), and dip angle (from 0° to 9°)—after 28 days of curing through uniaxial compression tests. Regression and error analysis methods were employed to establish the relationships between WI physical characteristics and CCTB mechanical properties. Additionally, the inherent mechanisms of mechanical strength deterioration in CCTB containing WI were discussed based on experimental and simulation results of CCTB failure modes. The results found that the uniaxial compressive strength (UCS) and elastic modulus (E) of CTB decrease with lower cement content, while the peak strength strain (PSS) increases. Incorporating WIs weakens CCTB, reducing UCS and E, and increasing PSS. Regression analysis combined with error analysis revealed that WI thickness has an exponential relationship with UCS, E, and PSS. As WI thickness increases, reduction coefficients for UCS and E rise significantly, exacerbated by the WI’s diminished strength. The WI’s dip angle significantly affects CCTB’s mechanical behavior, disrupting stress distribution and load transfer, resulting in heightened stress concentrations and structural weakening. COMSOL simulations corroborated these experimental findings, providing deeper insights into stress distribution and failure mechanisms within the CCTB structure. These findings aim to provide a theoretical basis for mitigating the impact of WI characteristics on the stability and load-bearing capacity of CCTB in future mining operations.