Search Results (7,406)

Volatile organic compounds (VOCs) emitted from hardwood papers are associated with cellulose fibers, paper fillers, and the manufacturing process used. Volatiles emitted from samples of office (printing and writing) papers from various brands and countries were analyzed by gas chromatography–mass spectrometry (GC-MS) and an electronic nose (e-nose) based on piezoelectric quartz crystals. Dodecanoic acid 1-methylethyl ester (isopropyl dodecanoate) and nonanal have shown to be the dominant compounds in most of the samples analyzed, regardless of the pulpwood used in paper manufacturing: Eucalyptus globulus, acacia, and birch. 3-Hydroxybutanone was detected only in Spanish papers, suggesting it as a potential marker. Additionally, the content in acetic acid enables the identification of recycled paper. Full article

Background: Staphylococcus aureus bacteremia (SAB) is a common and life-threatening bloodstream infection often caused by methicillin-resistant SA (MRSA) isolates. Up to 35% of SAB patients fail to clear infection with gold-standard anti-MRSA antibiotics, even if the isolate meets susceptibility breakpoints in conventional assays in vitro. Such outcomes are termed persistent and may involve small colony variant (SCV) adaptation of SA in vivo. Methods: In this study, we assessed virulence phenotypes and mechanisms in persistent (PB) vs. resolving (RB) MRSA isolates from SAB. Results: Overall, PB isolates caused less hemolysis or biofilm formation than RB isolates, but proteolysis was equivalent. Attenuation of these virulence phenotypes increased longitudinally during the course of SAB. Although PB vs. RB isolates had similar human endothelial cell invasion rates, PB isolates more frequently formed SCVs intracellularly and inversely correlated with pH. Study PB and RB isolates exhibited distinct susceptibilities to prototypic human host defense peptides (HDPs), which were influenced by antibiotics and pH. Furthermore, mechanistic signatures of HDPs differed between PB and RB isolates. Conclusions: Together, these results reveal that MRSA isolates from PB vs. RB outcomes of SAB have differential virulence profiles that suggest coordinated immune subversion in PB. Understanding MRSA adaptations that promote persistence in SAB may enable innovative agents and strategies to address these challenging infections. Full article

The increasing density of wireless and wearable electronic devices necessitates the development of lightweight, flexible, and absorption-dominated electromagnetic interference (EMI) shielding materials. In this study, electrospun poly(vinylidene fluoride) (PVDF) composite mats reinforced with carbon nanotubes (CNTs) and graphene nanosheets at low filler loadings (1–3 wt.%) were fabricated and systematically investigated for X-band (8.0–12.5 GHz) EMI shielding performance. Raman, FTIR, and thermal analyses confirm enhanced electroactive β-phase formation and improved thermal stability upon nanofiller incorporation. The formation of interconnected conductive networks within the electrospun fibrous architecture leads to a significant increase in electrical conductivity from 10⁻⁷ S·cm⁻¹ for pure PVDF to 10⁻² S·cm⁻¹ and 10⁻¹ S·cm⁻¹ for CNT/PVDF and Graphene/PVDF composites, respectively, at 3 wt.% loading. Consequently, the total EMI shielding effectiveness (SE_T) increases from 2.5 dB for pure PVDF to 40 dB for CNT/PVDF and 42 dB for graphene/PVDF composites at 3 wt.%. The shielding effectiveness arising from absorption (SE_A) dominates the overall EMI shielding performance, contributing more than 85% of the total shielding effectiveness (SE_T), which clearly indicates an absorption-controlled shielding mechanism. The combination of high absorption-dominated EMI shielding, low filler content, and mechanical flexibility highlights these electrospun CNT/PVDF and graphene/PVDF composites as promising candidates for next-generation flexible, wearable, and biomedical EMI shielding applications. Full article

Continuous monitoring of pathological motor features is vital for post-stroke rehabilitation but remains challenged by power reliance and low sensitivity of wearable sensors. Here, we develop a high-sensitivity, self-powered breathable nanogenerator (BN-TENG) utilizing fish-scale-derived biological hydroxyapatite/carbon (Bio-HAp/C) fillers within electrospun polyvinylidene fluoride (PVDF) nanofibers. The Bio-HAp/C enhances electron-trapping capability, while a high-resilience ethylene-vinyl acetate (EVA) spacer optimizes contact-separation dynamics. The BN-TENG achieves a superior sensitivity of 16.28 V·N⁻¹ and remarkable stability over 10,000 cycles. By implementing a multi-node sensing strategy, the sensor successfully captures complex hemiplegic patterns, including compensatory shoulder hiking, distal muscle spasticity, and postural asymmetry. By resolving subtle micro-vibrations missed by traditional electronics, this work provides a sustainable, autonomous interface for characterizing pathological motor features and assessing rehabilitation progress in hemiplegic patients. Full article

Silica-based bioceramics are promising bone substitutes with tunable degradation and mechanical properties. We aimed to assess bone response in critical-size calvarial defects in rats, empty or filled with 3D-printed sphene ceramic (CaTiSiO₅) scaffolds produced using direct ink writing from preceramic polymers and reactive fillers. Scaffold characterization was performed using scanning electron microscopy, X-ray diffraction, porosity analysis, and compressive strength testing. Bilateral cylindrical 5 mm calvarial defects were created in 20 rats: one was randomly filled with sphene scaffold, while the contralateral remained empty. Ten animals were killed at 4 weeks, the rest at 8 weeks. Specimens were collected for micro-X-ray computed tomography (micro-CT) analysis, followed by undecalcified histology. The scaffolds exhibited porous structure with complete sphene phase purity and compressive strength of 17.91 MPa (SD 4.6). In vivo, no adverse event was noted during healing. Overall bone regeneration—as measured by BV/TV—was comparable between groups: Bone volume/total volume (BV/TV) increased over time in the empty and sphene groups, reaching ~40%, with no significant differences between groups or time points. BV/TV was significantly higher in the external regions of the defects compared to the internal areas in both groups at the two time points. The sphene group showed a significantly greater volume of new bone extending beyond the original cortical boundary at both 4 and 8 weeks (p = 0.013). In the sphene group histology revealed partial bone ingrowth within the scaffold, while bone in the control group was limited to defect edges. After 8 weeks, new bone adjacent to the cortical surface was thicker in the sphene group (p < 0.05). These initial findings are consistent with prior preclinical studies, supporting the biocompatibility and osteoconductive nature of sphene ceramic scaffolds. Full article

Blast furnace cement-dolomite mortars prepared from commercial cement (CEM-III/B) containing ~75% of slag and natural dolomite were aged under accelerated conditions at 60 °C in 1 M NaOH for 0–24 months. The hydration products and microstructure features of the mortars were studied using XRD, TGA and SEM-EDS methods, with blast furnace cement paste for comparison. The results showed that the presence of dolomite enhanced slag hydration, as the carbonates released during dedolomitisation promoted Ca and Si dissolution from the slag grains. After prolonged ageing, a multi-rim structure was observed around the slag particles: the inner rim primarily consisted of a hydrotalcite-like phase mixed with C-S(A)-H gel, while the outer rims were richer in C-S(A)-H gel, with varying calcium content. Monocarbonate phase was additionally detected at the slag–paste interface in the presence of dolomite. The observed increase in mechanical strength during ageing had to do with two reasons: (i) the increase in hydration product content and (ii) the densification of microstructure due to the formation of calcium carbonate, which filled pores and microcracks and the possible carbonation of C-S (A)-H gel in the binding paste. Under the investigated alkaline ageing conditions, dolomite acts as a chemically active component rather than an inert filler, influencing both slag hydration kinetics and the composition of the resulting hydration products. Full article

Flexible electrode materials with tailored electrical and mechanical properties are essential for reliable electrocardiographic (ECG) sensing. In this work, p-toluenesulfonic-acid-doped polypyrrole (PPy–TSA) films were modified using polymeric and inorganic fillers, as well as their combinations (polyethylene glycol, graphene, carbon nanotubes, and zeolite), to tune their functional performance. The reference PPy–TSA film exhibits typical morphological and chemical characteristics of doped polypyrrole and serves as a reliable baseline for comparison. All composite films retain electrical conductivity within the range required for ECG applications while showing improved mechanical compliance (i.e., enhanced ability to conform to the skin and sustain deformation). Based on the optimized balance between electrical and mechanical properties, flexible ECG electrodes were fabricated using the TSA-doped PPy-based composite film. ECG recordings obtained with the several proposed electrodes show good agreement with those acquired using a commercial ECG electrode, demonstrating the potential of PPy-based composite films for flexible bioelectronic sensing applications. Full article

Polymer nanocomposites offer significant potential for improving the strength-to-weight ratio and dynamic behavior of drone blades. This study examines the vibration characteristics of tapered aramid (Kevlar)/epoxy composite blades reinforced with nanocarbon fillers—graphene (2D), multi-walled carbon nanotubes (MWCNTs, 1D), and fullerene (0D)—to determine the most effective filler for enhancing stiffness and operational stability. The laminated blades (300 mm length, 200 mm width, root thickness 13 mm, tip thickness 8 mm) incorporate ply drop-offs and a central honeycomb core. Modeling was performed using classical laminate plate theory integrated with the finite element method (FEM) in MATLAB (R2016a). Under clamped–free–free–free boundary conditions, the study considered rotational speeds of 750–2250 rpm, setting angles of 30–60°, various fiber orientations, and nanofiller contents of 0–10 wt.%. The results indicate that while the setting angle minimally affects natural frequency, it significantly influences damping in modes (1,2) and (2,1). Increasing nanofiller content improves stiffness, with optimal performance observed near 5 wt.%. At 1500 rpm in mode (1,1), MWCNTs provided the greatest enhancement. Overall, MWCNTs exhibited superior stiffness improvement and rotational stability compared to other fillers. Full article

Properties of composite materials with polymer matrix and inorganic filler are affected by preparation methods and starting components’ properties. For example, filler powder particle size distribution, phase composition and presence/absence of dopants can greatly affect properties of resulting composites. The present research attempts to clarify the influence of synthetic CaCO₃ powder properties on alginate/CaCO₃ composite material preparation process. Composite materials in the form of granules, networks and films were created from suspensions of synthetic powders of calcium carbonates CaCO₃ in aqueous solutions of sodium alginate. Powders of calcium carbonates CaCO₃ were synthesized from 0.5 M aqueous solutions of calcium chloride CaCl₂ and aqueous solutions of potassium K₂CO₃ (at molar ratio Ca/CO₃ = 1), sodium Na₂CO₃ (at molar ratio Ca/CO₃ = 1), and ammonium (NH₄)₂CO₃ (at molar ratios Ca/CO₃ = 1 and Ca/CO₃ = 0.5) carbonates. Phase composition of powder synthesized from CaCl₂ and K₂CO₃ was presented by calcite. Phase composition of powders synthesized from other soluble carbonates included calcite and vaterite. The powder preparation protocol excluded the stage of synthesized powder washing for by-product removal. This preparation protocol provided preservation of reaction by-product in the synthesized powder at a very low level. The presence of NH₄Cl as a reaction by-product even in small quantities can be taken as a reason for visually observed subsequences of cross-linking reaction at the stage of suspensions preparation. Aqueous solution of sodium alginate and suspensions containing powders synthesized from potassium K₂CO₃ and sodium Na₂CO₃ carbonates demonstrated similar dependence of viscosities from shear rate. The presence of (NH₄)₂CO₃ in the powder synthesized at molar ratio Ca/CO₃ = 0.5 was the reason for the lower viscosity of the suspension in comparison with suspensions loaded with powders containing KCl, NaCl and (NH₄)₂Cl as reaction by-products due to decomposition of unstable (NH₄)₂CO₃ and gas phase formation. The presence of (NH₄)₂Cl in the powder synthesized at molar ratio Ca/CO₃ = 1 in contrast was a reason for the highest viscosity suspension in comparison with those under investigation. Additionally, (NH₄)₂Cl presence in synthetic powders shows the ability to facilitate partial dissolution of CaCO₃ providing a higher concentration of Ca²⁺ cations at the stage of suspension preparation, thus aiding the cross-linking process of alginate hydrogel. Granules, meshes and films were created via interaction of suspensions of calcium carbonates CaCO₃ in aqueous solutions of sodium alginate with 0.25 M aqueous solutions of calcium chloride CaCl₂ to provide the formation of matrix of composites via Ca-crosslinking of sodium alginate followed by washing and freeze drying under deep vacuum. The created composite materials in the form of granules, meshes and films based on Ca-cross-linked alginate and powders of synthetic calcium carbonate can be recommended for skin wound and bone defect treatment and drug delivery carriers. Full article

Methacrylate-POSS (M-POSS) is a novel organic–inorganic additive shown to reinforce dental composites and reduce polymerization shrinkage. This study aimed to evaluate the influence of M-POSS addition (0.5, 2, 10, or 15 wt.%) on the mechanical properties of an experimental polymer matrix (bis-GMA/UDMA/TEGDMA/HEMA = 35/35/20/10 wt.%) and a dental resin composite (45 wt.% silanized silica as filler). Vickers hardness (HV), three-point bending strength (FS), diametral tensile strength (DTS), and shrinkage stress generated during polymerization were studied. The results show HV values between 16 and 18 compared to 15 ± 1 in the control group. Hardness in the control composite was 34 ± 4, and after modification, it showed similar or slightly lower values between 32 and 35. FS increased from 90 ± 4 MPa before modification to 100 ± 5 MPa for 2 wt.% M-POSS, and then decreased to 78 ± 5 MPa for materials containing 15 wt.% M-POSS. FS of composites were within the range of 61–77 MPa, with a similar tendency in variation to that of matrices. DTS values decreased after M-POSS addition, from 37 ± 4 MPa before modification to 31–33 MPa after modification. Flexural modulus decreases after modification, both for matrices and composites. The morphology of composites with >10 wt. % M-POSS showed visible surface irregularities. In conclusion, M-POSS affects matrix hardness, resulting in an increase in HV. The addition of M-POSS also increases FS values of the matrix, but only up to a certain concentration. However, the introduction of M-POSS does not significantly affect the HV or bending strength of the composites. Although DTS values decreased, this change was not statistically significant. Finally, contraction stress was significantly reduced for groups containing 2 wt.% and 10 wt.% M-POSS, representing an anticipated and promising improvement. Full article

Composite materials are commonly employed because of their superior mechanical and electrical properties, as well as their lower density compared to metals. In this research, ceramic waste from the Casablanca region (Morocco) was incorporated into a composite material by combining it with finely ground ceramic fragments (CB) in an unsaturated polymer (UP) resin. The study objectives include the characterization of ceramic waste, evaluation of the mechanical stiffness, influenced by CB content and specimen thickness, and the assessment of its hydric behavior and erosion resistance in aggressive chemical environments. This valorization approach includes a baseline assessment of unmodified ceramic waste and UP’s compatibility and systematic documentation of geometry-dependent stiffness in short-cylinder compression tests. Several methods were used to characterize the material, including XRD, optical microscopy, FTIR-ATR, erosion testing, hydric behavior analysis, surface area measurement, and Young’s modulus. The results showed increased tensile strength and stiffness compared to the starting materials through the evolution of Young’s modulus, demonstrating the enhanced mechanical quality of the composite. Additionally, the material properties changed with the CB content and thickness of the sample, which indicated the potential for optimization. These findings advocate for the reuse of Moroccan industrial ceramic waste as a viable mineral filler for semi-structural polymer composites, supporting the circular economy, environmental sustainability, and public health. Full article

The transition from passive containment to active, responsive management is defining the next generation of intelligent packaging. This evolution creates a critical demand for materials that can be precisely engineered to monitor, regulate, and protect. Hydrogen-bonded organic frameworks (HOFs) have emerged as a uniquely versatile platform in this regard, owing to their synthetically tunable porosity, inherent biocompatibility, and exceptional solution processability derived from reversible supramolecular assembly. This review moves beyond cataloging applications to dissect the fundamental mechanisms by which HOFs enable smart packaging functions, including the following: (i) selective gas capture and atmosphere tailoring via molecular recognition within designed pores; (ii) high-sensitivity optical and electrochemical sensing for real-time quality and safety signaling; and (iii) stimuli-responsive release of active agents (e.g., antimicrobials). We further explore the frontier of integrating HOFs as functional fillers or coatings within polymeric matrices, a key step toward practical devices. Despite challenges such as structural stability and maintaining permanent porosity due to relatively weak hydrogen bonds, this work aims to provide a design blueprint for advancing HOFs from laboratory curiosities to core components of sustainable, multifunctional packaging systems. Full article

The conducted study was focused on the development of a new type of polymer blends intended for additive manufacturing applications, in particular, the material extrusion method (MEX). The developed materials were prepared from recycled poly(ethylene terephthalate) and amorphous copolymers poly(ethylene terephthalate-glycol) (PETG), and poly(cyclohexylenedimethyl terephthalate-glycol) (PCTG). The basic blend systems were additionally modified with POE-g-GMA impact modifier (IM) during the reactive extrusion process. The main aim of the work was to assess the effectiveness of using composite additives and their influence on the mechanical and thermomechanical parameters of the tested systems. To prepare the composites, selected polymer blends were modified with 10% of talc (T) and carbon fibers (CF). The properties evaluation includes the mechanical/thermomechanical testing, thermal analysis and structural observations. The accuracy of printing was measured using optical scanning methods. The test results indicate that even the relatively small amount of the CF filler could lead to a significant increase in tensile modulus from reference 1.6 GPa to 2.9 GPa; the same improvement applies to strength values, where the CF-modified materials reached 45 MPa, compared to the reference 31 MPa. The heat deflection tests (0.455 MPa) after annealing revealed the maximum HDT of around 170 °C for both types of CF-modified materials. The Vicat test results were also favorable for annealed materials. Considering that the Vicat/HDT results after the 3D-printing process usually reach around 70 °C, the performed heat treatment strongly enhanced the heat resistance for most of the prepared blends. The performed studies revealed that for most of the prepared materials, the brittleness was a common drawback for both MEX-printed and injection-molded materials. Full article

The microstructural evolution and tensile behavior of Inconel 617 welded joints produced by gas tungsten arc welding (GTAW) with ERNiCrCoMo-1 filler were systematically investigated. Detailed microstructural characterization revealed that Cr-rich M₂₃C₆ and Ti-rich MC carbides are the dominant precipitates, while Mo-rich M₆C forms locally along grain boundaries after thermal exposure. The fusion and weld zones exhibit fine dendritic morphologies with uniformly distributed precipitates, resulting in significant strengthening through precipitation and dislocation–pinning mechanisms. Owing to the low heat input and compositional compatibility between the weld and base metals, the heat-affected zone remains extremely narrow and free of compositional transitions. The welded joint attains tensile strengths of 920 MPa at room temperature and 605.5 MPa at 750 °C, corresponding to joint efficiencies of 117% and 121%, respectively, with fracture consistently occurring in the base metal. Deformation analysis shows that plasticity at room temperature is governed by planar slip and dislocation entanglement, whereas deformation twinning predominates at elevated temperatures owing to the reduced stacking-fault energy and the pinning effect of M₂₃C₆ carbides. These results provide key insights into the deformation and strengthening mechanisms controlling the high-temperature performance of GTAW-welded Inconel 617 joints and offer guidance for their application in advanced nuclear and high-temperature energy systems. Full article

Epoxy resin (E-51) exhibits excellent adhesion and is widely used in the preparation of functional composite coatings. However, its smooth surface lacking micro/nano composite structures limits its self-cleaning capability and optical properties. Direct incorporation of organic silicone or inorganic fillers often faces severe phase separation and filler agglomeration issues, resulting in defects in coating durability and weather resistance. To address these challenges, this study developed a synergistic modification strategy integrating surface energy modulation with the architectural design of micro/nano-structures. Amino-terminated PDMS undergoes ring-opening addition reactions with epoxy groups in the epoxy resin, while functionalized barium sulfate nanoparticles modified with dual silane coupling agents are incorporated to enhance optical properties. This synergistic approach not only resolved interfacial compatibility but also endowed the PDMS@EP-BaSO₄ coating with outstanding comprehensive properties; the water contact angle increased to 123.5°, demonstrating an easy-to-clean benefit. Visible light reflectance reached 95%, and emissivity rose to 90%. Furthermore, when applied to metal surfaces, the coating exhibited excellent stability against acid–alkali–salt corrosion, extreme temperatures, and ultrasonic agitation. This work provided a novel approach for developing protective coatings that integrated high reflectance, high emissivity, and long-term anti-soiling properties. Full article