Search Results (464)

Dental restorative resins available today still have limitations that may affect their durability. This study explores reinforcing a universal microhybrid dental composite resin with organomodified nanoclay at low filler loadings (0, 0.5, 1, 3, and 5 wt%). The morphology, structural features, and light transmittance of the composites were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), attenuated total reflection–Fourier transform infrared (ATR–FTIR), and UV–Vis spectroscopy. The degree of conversion and polymerization shrinkage were measured with ATR–FTIR and a linear variable displacement transducer (LVDT). Water sorption and solubility parameters and flexural properties were assessed gravimetrically and with a dynamometer, respectively. The composites mainly showed exfoliated structures and an improved degree of conversion. Polymerization shrinkage and solubility were lower than those of unmodified dental resin. The highest degree of conversion was observed in composites with 0.5–1 wt% nanoclay. The incorporation of 1 wt% nanoclay resulted in the lowest shrinkage and sorption, along with the highest flexural modulus and strength. Overall, the results suggest that low nanoclay concentrations can improve the physicochemical and mechanical properties of dental composites, highlighting their potential to develop advanced restorative materials that can address current clinical challenges. Full article

This work presents a comparative study of micro- and nano-scale fillers in liquid composite molding processes, focusing on how particle size and morphology affect resin rheology, flow behavior, and filler filtration within fiber preforms. Glass microspheres and organo-modified montmorillonite were dispersed in epoxy resin and injected through glass-mat preforms at different fiber volume fractions (ranging from 0.27 to 0.47). Our study integrates rheological characterization, in situ flow-front tracking, unsaturated permeability analysis, thermogravimetric quantification of retained particles, and microstructural observations by SEM. Despite their smaller loading, nanoclay suspensions showed a markedly higher viscosity increase than microsphere systems, yet their permeability remained nearly unchanged. In contrast, microsphere-filled resins exhibited strong filtration at the flow inlet, density-driven settling near the lower tool face, and significant permeability loss. The results demonstrate that nano-fillers, although more viscous, maintain homogeneous distribution and flow continuity, whereas micro-fillers promote cake formation and local compaction. This controlled side-by-side comparison clarifies how filler size and shape govern filtration mechanisms in liquid composite molding (LCM), providing design guidelines for processing filled resin systems without compromising part quality. Full article

Anthropogenic phosphorus (P) release from human activities continues to degrade freshwater systems, underscoring the need for effective and sustainable approaches to P removal and management. This study investigates steel slag–chitosan–nanoclay hydrogel composites as a waste-derived alternative to metal-doped biopolymer hydrogels for P removal from wastewater and stormwater. Steel slag aggregates (SSAs), a by-product of steel manufacturing, were incorporated into chitosan-based hydrogel matrices to produce composite sorbents derived from waste materials with potential for cost-effective application. Two formulations (SSA20 and SSA40) were synthesized and compared with a chitosan–nanoclay–iron (CH/NC/Fe) reference hydrogel. Phosphorus adsorption affinity was evaluated using a standardized 24 h batch protocol at environmentally relevant concentrations representative of municipal wastewater (10 mg P L⁻¹) and stormwater or agricultural runoff (1 mg P L⁻¹). The SSA40 composite exhibited the highest P adsorption affinity (Rd = 2.39 ± 0.22 L g⁻¹), outperforming both standalone SSA and the Fe-based hydrogel reference. Scanning Electron Microscopy and Energy-Dispersive X-Ray Spectroscopy (SEM–EDX) analyses revealed strong polymer–slag interactions and metal–phosphate associations, consistent with coupled adsorption and precipitation mechanisms. The SSA-based hydrogels also exhibited self-induced acidification (pH 3.3–4.2), enhancing phosphate uptake while providing intrinsic pH buffering. This study introduces a stable, waste-derived hydrogel composite and demonstrates a reproducible, environmentally relevant batch-testing approach for comparative evaluation of hydrogel phosphorus sorbents, supporting evidence-based strategies for sustainable phosphorus pollution control. Full article

Bio-based, biodegradable, and renewable polymers offer a promising alternative to traditional synthetic polymers derived from petroleum or other non-renewable resources. However, their use is limited by suboptimal properties and high costs. Incorporating sustainable reinforcements into the polymer matrix significantly improves biopolymer performance while preserving key properties, sustainability, and cost-effectiveness. Bio-based polymeric composites have emerged as a crucial category of biopolymers, playing a key role in advancing a sustainable, circular economy. This review provides an updated overview of bio-based polymer composites and nanocomposites, focusing on reinforcement strategies using natural nanofillers and engineered nanoparticles. We summarize key synthesis and processing methods, discuss structure–property relationships, and highlight recent advances in applications such as food packaging, biomedical devices, energy systems, environmental remediation, 3D printing, and supercapacitors. Polymer nanocomposites are versatile, with their performance depending on the type, size, and interactions between the fillers and the polymer matrix. Progress in metallic, ceramic, carbon-based, natural, and hybrid fillers has improved their properties. Using bio-based polymers and renewable fillers supports sustainability. Natural nanofillers derived from renewable sources and industrial byproducts offer a sustainable approach to developing high-performance, biodegradable nanocomposites. Smart nanocomposites can react to external stimuli by integrating specialized fillers that enhance their mechanical and mobility properties. Shape memory nanocomposites can be remotely activated—using heat, electricity, magnets, or light—enabling advanced applications. Finally, we address major challenges and outline future directions for scalable, circular-material solutions, drawing on perspectives from the circular economy and life cycle assessment (LCA). Full article

In this work, poly(acrylic acid)-based layers were injected to form a sandwich layer between the cationic and anionic species for a compact and effective fire-retardant coating on cotton fabric using the layer-by-layer coating technique. From the SEM analysis, as the number of tri-layers increases, the attachment intensity increases, as can be seen for poly(acrylic acid) chitosan and bentonite clay PCB-5TL (the highest tri-layers), while in the case of halloysite-based coatings, as the number of tri-layers increases, instead of attachment, the agglomeration increases due to the high surface area of halloysite nanoclay tubes. FTIR and UV confirmed the finding from the new peak entry and an increase in thickness. The highest thermal residue, ~18%, was obtained for poly(acrylic acid) chitosan and halloysite nanoclay PCH-5TL with a maximum degradation peak intensity at ~389 °C. From the flammability and after-burning SEM investigation test, it was observed that the halloysite-based coating with a higher number of layers offered higher resistance against the flame spread and ignition and, thus, produced a higher amount of char. Full article

The building-integrated photovoltaic (BIPV) system has advantages in construction and energy, but due to the use of flammable polymer packaging materials, it introduces complex fire safety-related challenges. Although polymer backboards are traditionally considered to be the main combustible components in photovoltaic modules, recent studies have shown that ethylene–vinyl acetate (EVA) packaging materials play a key role in the development of fires. This study investigated the fire behavior, optical properties and system-level fire effects of montmorillonite (MMT) nano-clay-modified EVA packaging materials. Through the 50 kW/m² conical calorimeter test, optical transmittance measurement and the accelerated aging test, pure EVA and EVA containing 3% MMT were evaluated, and the measured fire parameters were further incorporated into the simplified BIPV cavity fire model. The results show that MMT modification reduces the peak heat release rate of EVA by about 30%, delays the ignition time, and increases the formation of carbides, while maintaining the optical transmittance of more than 88%. At the system level, the reduction in heat release leads to a decrease in the cavity temperature and delays the ignition of adjacent insulation materials. These findings establish a direct link between material-level fire behavior and the fire performance of BIPV systems, indicating that nano-clay-modified EVA is a feasible strategy that can improve the fire safety of BIPV systems integrated into the facade without compromising optical or durability requirements. Full article

This study develops a unified multiscale–machine learning framework to interpret and predict thermo-mechanical wear regime transitions in MWCNT- and nanoclay-reinforced bio-based epoxy composites. A physics-informed master wear formulation integrating real contact mechanics, geometry-dependent shear transfer, interfacial adhesion energetics, and fracture-controlled matrix detachment was combined with interpretable machine learning analytics on a unified tribological dataset. In the CNT system, increasing loading from 0.1 to 0.4 wt.% enhanced interfacial adhesion energy density from 0.00813 to 0.01906 J/m², resulting in a monotonic reduction in the wear rate from 0.00918 to 0.00613 mm³/N·m (~33% reduction). In contrast, nanoclay exhibited an optimum behavior, with a minimum wear at 0.25 wt.% (0.000093 mm³/N·m; 7.9% reduction vs. neat clay baseline), followed by deterioration at a higher loading due to dispersion loss. The unified probabilistic regime classification of low-wear conditions (k < 0.007 mm³/N·m) achieved an ROC − AUC = 0.9256 and balanced accuracy = 94.3%, with thermo-mechanical severity identified as the dominant regime-switching driver. Reinforcement identity significantly modulated regime stability, confirming distinct shear transfer (Carbon Nano Tubes(CNT)) and confinement/tribofilm (clay) mechanisms within a common mathematical framework. By enabling the durability-oriented design of bio-based tribological systems and extending component service life through predictive stability mapping, this work contributes to resource-efficient materials engineering and reduced lifecycle waste, supporting Sustainable Development Goals SDG 9 (Industry, Innovation and Infrastructure), SDG 12 (Responsible Consumption and Production), and SDG 13 (Climate Action). Full article

This study presents an analytical investigation of the dynamic behavior of concrete beams reinforced with different types of nano-clay (NC) particles and resting on a Winkler–Pasternak elastic foundation. The equivalent elastic properties of the nanocomposite were determined using an Eshelby-based homogenization model. An improved quasi-three-dimensional beam theory was applied to formulate the governing equations of motion, which were subsequently then analytically solved using Navier’s method. The analysis shows that NC reinforcement systematically elevates the natural frequencies of the beam, with the magnitude of improvement varying by particle type and concentration. Increasing the NC volume fraction to 30% leads to a significant rise in the fundamental frequency, reaching about 30% for hectorite (SHca-1) compared with the unreinforced beam, whereas montmorillonite (SWy-1) produces a more moderate increase of approximately 13%. This reinforcing effect remains consistent across different span-to-depth ratios, indicating that the influence of nano-clay content on the dynamic response is largely independent of beam slenderness. Furthermore, increasing the Winkler foundation stiffness results in an almost linear rise in frequency of approximately 18–22%, whereas the Pasternak shear parameter produces a stronger effect, reaching around 25% enhancement depending on the reinforcement type. These results indicate that incorporating nano-clay platelets can be an effective strategy for enhancing the vibrational stiffness of concrete beams and improving their dynamic performance when interacting with supporting soil media. Full article

3D printing (3DP) of cement-based systems (CBSs) is a highly demanded technology in the construction field. Material requirements include specific rheological conditions for proper extrusion, followed by fast stiffening and strength gain to allow the construction process to continue, taking into account variable environmental conditions if the construction is on-site. To guarantee quality control of the process, it is essential to define field-oriented testing methodologies that allow real-time monitoring of mechanical properties’ evolution of the printed material, which will govern construction speed. This study evaluates the cone penetration test (CPT) method as a field-oriented test method to estimate the mechanical properties of 3DP CBSs over time. CPT penetration depth measurements were used to calculate shear yield stress and fresh compressive strength over time for 90 min. The experimental results were compared to two widely used laboratory tests: the fresh compressive strength test (squeeze test—SQT) and DSR test (vane test—VT). CBS pastes with and without fly ash and with three inorganic modifiers (nanoclays) and two types of organic rheology-modifying admixtures were considered. The results showed that CPT is highly conditioned by the stiffness of the paste, measured by the compressive Young Modulus (E), overestimating CBSs’ strength. The increase in E over time showed an inflection point at 130 kPa, corresponding to the evolution from plastic to pseudo-rigid behavior in the pastes. The corresponding time was used to define a linear adjustment for the average strength calculated using the CPT regarding both the fresh compressive SQT and shear yield stress VT. Full article

This study aimed to investigate the effect of time and different disinfecting agents on nanocomposite filler composed of natural clay nanoparticles (modified and non-modified) added to maxillofacial silicone elastomers and readymade pigment additives. A total of 360 disk-shaped samples were divided into nine pigment-based groups, each with four subgroups (n = 10) exposed to different disinfectants: distilled water, 1% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and effervescent tablets. Color changes (ΔE) were measured before and after disinfection using a colorimeter. The ΔE values were assessed against perceptibility (ΔE = 1.1) and acceptability (ΔE = 3) thresholds. Nanoclay additives were also characterized using FTIR, XRD and EDX. Statistical analysis, including ANOVA and post hoc HSD tests, revealed that while all samples exhibited some color change, most remained below the acceptability threshold. Colorless silicone showed minimal, non-significant change according to perceptibility threshold (ΔE = 1.1). Blue pigments displayed significant change only with effervescent tablets. Red and mixed pigments showed perceptible changes with NaOCl, CHX, and effervescent tablets. However, nanoclay-containing specimens showed no significant perceptible alterations. Overall, despite minor perceptible changes in some pigments, all disinfecting agents tested resulted in color differences below the acceptability threshold, indicating their safe use for disinfecting maxillofacial silicone materials without compromising esthetics. Nevertheless, nanoclays are more reliable agents for the pigmentation of maxillofacial silicone as they show non-significant chromatic alteration. Full article

Anthropogenic activities generate waste that negatively impacts the environment, especially water resources, due to the accumulation of heavy metal ions. Several adsorption methods have been developed, including the use of natural materials such as algae and activated clay. This study aimed to evaluate the effect of pH on batch adsorption of heavy metal ions using Nostoc sphaericum hydrocolloid (HA)/activated nanoclay (NR) composites. The NR/HMB-HA and NR/HUT-HA composites were prepared with a 2:8 mass ratio of HA and NR, using types of clay with code HMB and HUT, previously activated with 1 M NaCl and acid treatment. The adsorption capacity was evaluated using batch tests at pH 4.5 and 5.5, analyzing the removal percentage, adsorption kinetics, adsorption isotherms, and regeneration cycles for unimetal and multimetal systems. The composites present a load point close to 5.1. The FTIR analysis showed changes in the intensity of functional groups following adsorption, confirming the interaction with metallic ions. Both composites showed high affinity in multimetallic systems, especially at pH 5.5, with high selectivity for Pb²⁺ (≈99% removal), followed by As, Cd, and Zn, from an initial concentration of 10 ppm for each metal ion. Equilibrium is reached in approximately 90 min, allowing adsorption of up to 69.9% after five regeneration cycles in a multimetal system. The kinetic study showed that multimetal absorption at equilibrium is governed by chemisorption processes in the order Pb > As > Zn > Cd, with q_e values between 0.392 and 0.058 mmol/g and diffusivity from 15.506 × 10¹¹ to 1.692 × 10¹¹ m²/s. Likewise, the isotherms study indicated a favorable process with maximum adsorption (q_max) between 16.696 and 5.223 mmol/g at pH 5.5. Altogether, the developed composites show high potential for the removal of heavy metals in contaminated waters, in addition to their high reuse capacity. Full article

Developing adsorbents that combine high capacity with structural robustness remains a critical challenge for dye wastewater treatment. In this study, we propose a “pollutant-induced gelation” strategy to address this limitation, using Fe(III)-activated palygorskite nanorod aggregates as a model system for the highly efficient sequestration of Congo red (CR). Unlike conventional modification methods that rely solely on surface functionalization, this approach leverages the adsorbed dye itself as a synergistic assembly promoter. The addition of CR significantly consolidates the Fe(III)-mediated aggregation of palygorskite nanorods, leading to the formation of an integrated three-dimensional porous network with distinct gel-like rheological behavior. This dye-induced gel network not only provides abundant confined spaces for pollutant entrapment but also enhances the structural integrity of the adsorbent, facilitating separation and potential reuse. Compared to pristine palygorskite, the Fe(III)-activated material exhibited a 95.4–277% increase in adsorption capacity across a pH range of 4–10. The adsorption process followed pseudo-second-order kinetics and the Temkin isotherm model, and was thermodynamically spontaneous and exothermic. Mechanistic studies revealed a synergistic interplay: Fe(III) served as primary cross-linking nodes to construct the network framework, while CR molecules acted as inducers to reinforce the gel architecture, enabling strong physical immobilization of dye aggregates. This work provides a new paradigm for designing intelligent, gel-based adsorbents from natural nanoclays, transforming a pollutant into a structural promoter. Full article

The development of sustainable pigments from natural sources is gaining interest due to environmental concerns and the need for bio-based alternatives to synthetic dyes. This study investigates the synthesis of hybrid pigments by adsorbing anthocyanins—extracted from pomegranate agro-waste—onto halloysite (HA) nanotubes. A full factorial design was applied to evaluate the influence of pH and surfactant type (cetylpyridinium bromide and sodium dodecyl sulfate) on pigment colour and the thermal and structural stability of the hybrids. Adsorption was carried out in 400 mL dispersion baths containing 10 g of HA and 5% w/w anthocyanins. Surfactants (2% w/w) were added before the pigment, followed by 200 µL of silane. Dispersions were stirred at high speed for 1 h and then at 500 rpm for 23 h to ensure adsorption without premature desorption. Characterisation (TGA, XRD, FTIR, UV-Vis/NIR, SEM, EDX, BET) confirmed the preservation of HA structure and minimal changes in thermal behaviour. Pigment colour varied with synthesis conditions, especially pH: a higher pH increased brightness and yielded yellowish tones, while a lower pH resulted in reddish-blue hues with greater variability. The results confirm halloysite’s potential as a stable carrier for natural dyes and demonstrate that pH effectively tunes hybrid pigment colour. Full article

Quaternary Ni-Zn-Mg-Al metallic mixed oxide (MMO) catalysts were synthesized by co-precipitation from layered double hydroxide precursors. The effect of varying Zn content on physicochemical properties and catalytic performance was evaluated. Mg-Al and ternary Ni-Mg-Al and Zn-Mg-Al catalysts were synthetized for comparative purposes. XRD, N₂ sorption, MP-AES, CO₂-TPD, NH₃-TPD, SEM, and EDS characterized the materials’ physicochemical properties. The tested reaction was the transesterification between glycerol and dimethyl carbonate to obtain glycerol carbonate to improve the biodiesel industry. The catalyst containing both Ni and Zn showed the highest glycerol conversion among the evaluated materials. This was related to the increased number and strength of surface basic and acid active sites. Specifically, a high density of strong basic sites and acid ones in the quaternary catalysts was required for the reaction mechanism. The catalyst with 20 at% of Zn (MMO-Ni₁₅Zn₂₀) achieved the highest glycerol carbonate yield (89.6%) under mild reaction conditions and was solvent-free. MMO-Ni₁₅Zn₂₀ catalytic performance was associated with its high total basicity and predominance of strong basic sites and a moderate amount of acid sites. The differences observed between catalytic performances suggest that these results depend on the influence of structural, textural, acid, and basic properties. Reuse tests of the MMO-Ni₁₅Zn₂₀ catalyst showed moderate stability, with a progressive decrease in activity due to the loss of strong basic sites and the formation of agglomerated regions. Nevertheless, MMO-Ni₁₅Zn₂₀ maintained a GC selectivity of 100% in the successive cycles. Full article

The dry sliding wear behaviour of nanoclay-filled bio-based epoxy composites was systematically investigated using a Taguchi L16 experimental design by varying nanoclay content (0–0.35 wt.%), normal load, sliding speed, and sliding time against an EN24 steel counterface. Wear loss, specific wear rate (SWR), frictional response, thermal rise, and energy-based descriptors were quantified, followed by mathematical and machine-learning (ML) based modelling. The results demonstrate that nanoclay addition significantly improves tribological performance up to an optimal content of 0.25 wt.%, beyond which wear instability increases. Compared with neat epoxy, the 0.25 wt.% nanoclay composite exhibited a reduction in steady-state coefficient of friction from ~0.53 to ~0.42, along with a 25–30% decrease in specific wear rate and the lowest energy-to-wear conversion efficiency, indicating more effective utilization of frictional energy. Taguchi analysis identified normal load as the dominant factor governing wear variation (~68% contribution), followed by sliding speed (~17%), while nanoclay content contributed ~5%. An energy-based wear model showed improved correlation with experimental wear volume (R² ≈ 0.93) compared to a classical Archard-type formulation. ML prediction using a random forest model with leave-one-out cross-validation achieved an R² ≈ 0.64 for SWR. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses confirmed a transition from severe abrasive wear in neat epoxy to stable tribofilm formation at 0.25 wt.% nanoclay, followed by heterogeneous debris-mediated wear at higher filler content. The observed reduction in wear loss and frictional energy dissipation supports sustainable materials innovation aligned with SDG 9 (Industry, Innovation and Infrastructure) and SDG 12 (Responsible Consumption and Production), while improved operational efficiency is consistent with SDG 7 (Affordable and Clean Energy). Full article