J. Compos. Sci., Volume 8, Issue 12 (December 2024) – 45 articles

In the present work, carbonate minerals are added in non-polar and polar polymer matrices to develop halogen-free flame-retardant composites. The examined fillers of calcium carbonate and magnesium carbonate delivered improved rheological performance in both non-polar (PE) and polar (EVA/PE) polymer compounds compared to the natural magnesium hydroxide and huntite/hydromagnesite mineral fillers. The presence of EVA in the matrix enhanced the mechanical behavior of all compounds in tensile testing. The thermal stability of the composites was particularly improved for the polar systems with the incorporation of the carbonate minerals, as this was evidenced under thermogravimetric analysis. The dielectric behavior of the fabricated systems was examined via broadband dielectric spectroscopy. The HFFR compounds attained higher values of the real part of dielectric permittivity from the unreinforced systems in the whole frequency and temperature range of the conducted tests. This behavior is ascribed to the higher permittivity values of the fillers with respect to the polymer matrices and the occurrence of interfacial polarization. All minerals improved the flame retardancy of the compounds in terms of LOI values, while the addition of EVA yielded further improvements, especially for the magnesium carbonate and the magnesium hydroxide minerals. Full article

Contamination by heavy metals (HMs) such as Pb, Cd, Cr, and Hg poses significant risks to the environment and human health owing to their toxicity and persistence. Geopolymers (GPs) have emerged as promising materials for immobilizing HMs and reducing their mobility through physical encapsulation and chemical stabilization. This study explored the novel use of isotactic polypropylene functionalized in the molten state with maleinized hyperbranched polyol polyester (PP-g-MHBP) as an additive in coal fly ash (CFA)-based GPs to enhance HM immobilization. Various characterization techniques were employed, including compressive strength tests, XRD, ATR-FTIR, SEM-EDX, XPS analyses, and TCLP leaching tests, to assess immobilization effectiveness. These results indicate that although the addition of PP-g-MHBP does not actively contribute to the chemical interactions with HM ions, it acts as an inert filler within the GP matrix. CFA/PP-g-MHBP-based GPs demonstrated significant potential for Cd²⁺ immobilization up to 3 wt% under acidic conditions, although the retention of Pb²⁺, CrO₄²⁻, and Hg²⁺ varied according to the specific chemistry of each metal, weight percentage of the added metal, matrix structure, and regulatory standards. Notably, high immobilization percentages were achieved for CrO₄²⁻ and Hg²⁺, although the leaching concentrations exceeded US EPA limits. These findings highlight the potential of CFA/PP-g-MHBP-based GPs for environmental applications, emphasizing the importance of optimizing formulations to enhance HM immobilization under varying conditions. Full article

In this work, an effective route for achieving high-performance all-polymer materials through the proper manipulation of the material microstructure and starting from a waste material is proposed. In particular, recycled polyethylene terephthalate (rPET) fibers from discarded safety belts were used as reinforcing phase in melt-compounded high-density polyethylene (HDPE)-based systems. The formulated composites were subjected to hot- and cold-stretching for obtaining filaments at different draw ratios. The performed characterizations pointed out that the material morphology can be profitably modified through the application of the elongational flow, which was proven able to promote significant microstructural evolutions of the rPET dispersed domains, eventually leading to the obtainment of micro-fibrillated all-polymer composites. Furthermore, tensile tests demonstrated that hot-stretched and, especially, cold-stretched materials show significantly enhanced tensile modulus and strength as compared to the unfilled HDPE filaments, likely due to the formation of a highly oriented and anisotropic microstructure. Full article

Fiber coatings protect the glass surface of fiber from extrinsic environmental factors. The coating of shape memory alloy over fiber is useful in sensor fabrication where the state of deformation is affected by the phase transformation of the coated material. In addition, coated plastic fibers can be used in elevated temperature environments. To this end, the present research aims to investigate the effect of the Ni-Ti-Sn composite coating over the fiber. Homogeneous particle distribution, agglomeration, porosity and the ability to obtain uniform coating thickness have been general concerns in fiber coatings. Hence, the present study comprehensively investigated the mechanical and thermal behavior as well as morphological properties of Ni-Ti-Sn nanopowders deposited on polymer fiber optics. Five sets of polyamide-coated samples with different Ni-Ti-Sn proportions were fabricated and characterized. Morphological studies confirmed that an even coating thickness enhanced the mechanical integrity and optical performance. The optimum composition demonstrated superior tensile strength of 29.5 MPa and a 25% increase in elongation compared to the uncoated sample. The Ni-Ti-Sn alloy composition investigated in the present study is promising for industrial applications where thermal stability and mechanical performance are warranted. Full article

While ensuring thermal safety is critically required in the operation of the composite energetic material, the cutting temperature is a crucial parameter that must be investigated and controlled in its cutting process to avoid thermal explosion. In this paper, we elucidate the mechanisms of heat generation and conduction during the cutting process of a composite energetic material by establishing a microstructure-based finite element (FE) simulation model considering thermal effects. Specifically, we simulated the cutting process of the composite energetic material by FE simulations, with a focus on the variations in the cutting force, the initiation and conduction of the cutting temperature, and the correlation of the damage behavior of the composite energetic material. Subsequently, we conducted a parametric investigation of the effect of cutting speed on the damage behavior and cutting response of the composite energetic material. This paper provides valuable insights for the exploration of the cutting processes of composite energetic materials. Full article

Limestone-calcined clay (LC3) cement has emerged as a promising low-carbon alternative to ordinary Portland cement (OPC), offering significant potential to reduce carbon emissions while maintaining comparable mechanical performance. However, the absence of a prediction model for the formulation of the LC3 system presents challenges for optimisation within the evolving concrete industry. This study introduces a multi-objective optimisation (MOO) framework to design the optimal LC3 system, aiming to maximise compressive strength while minimising environmental and economic costs, simultaneously. The MOO framework integrates a regularised multivariate polynomial regression (MPR) model, achieving an R² of 0.927 and MSE of 3.445 for mechanical performance prediction. Additionally, life cycle assessment quantifies the environmental impact, and collected market prices contribute to financial considerations of the LC3 system. Utilising a dataset of 366 LC3 mortar mixtures, the optimisation challenges the conventional 2:1 calcined clay-to-limestone ratio (CC:LS). For high strength (≥65 MPa), target a CC:LS ratio of 1:1 to 1.6:1; for lower strength (<65 MPa), increase calcined clay content, resulting in a CC:LS ratio of 1.6:1 to 2:1. The proposed framework serves as a valuable starting point to enhance the efficiency of LC3 system design and help decision-making to achieve desired mechanical, economic, and environmental objectives. Full article

During the past decade, there has been a continued increase in the demand for bone defect repair and replacement resulting from long-term illnesses or traumatic incidents. To address these challenges, tissue engineering research has focused on biomedical applications. This field concentrated on the development of suitable materials to enhance biological functionality and bone integration. Toward this aim, it is necessary to develop a proper material that provides good osseointegration and mechanical behavior by combining biopolymers with ceramics, which increase their mechanical stability and mineralization process. Hydroxyapatite (HAp) is synthesized from natural resources owing to its unique properties; for example, it can mimic the composition of bones and teeth of humans and animals. Biopolymers, including chitosan and alginate, combined with HAp, offer good chemical stability and strength required for tissue engineering. Composite biomaterials containing hydroxyapatite could be a potential substitute for artificial synthetic bone grafts. Utilizing various polymers and fabrication methodologies would efficiently customize physicochemical properties and suitable mechanical properties in synergy with biodegradation, thus enhancing their potential in bone regeneration. This review summarizes the commonly used polymers in tissue engineering, emphasizing their advantages and limitations. This paper also highlights recent advances in the production and investigation of HAp-based polymer composites used in biomedical applications. Full article

The paper presents an overview of conductive polymer composites based on thermosetting materials, thermoplastics, and elastomers modified with carbon nanotubes (CNTs). To impart conductive properties to polymers, metal, carbon-dispersed materials, or their combinations are used. The inclusion of dispersed materials in polymers is associated with their microstructural features, as well as with polymerization methods. Such polymerization methods as melt mixing, solution technology, and introduction of fillers into the liquid phase of the composite with subsequent polymerization due to the use of a catalyst are known. Polymer composites that are capable of conducting electric current and changing their properties under the influence of an electric field, i.e., having one or more functional purposes, are called “smart” or intelligent. One such application is electric heating elements with the function of adaptive energy consumption or the effect of self-regulation of temperature depending on the surrounding conditions. A wide variety of polymers and dispersed materials with conductive properties determines a wide range of functional capabilities of the composite, including a positive temperature coefficient of resistance (PTCR) required to control temperature properties. The most effective filler in a polymer for obtaining a composite with desired properties is carbon nanomaterials, in particular, CNT. This is due to the fact that CNTs are a nanosized material with a high bulk density at a low weight, which allows for high electrical conductivity. Calculation of model parameters of polymer composites containing carbon nanostructures can be carried out using neural networks and machine learning, which give a fundamentally new result. The article contains sections with an assessment of various types of polymer matrices based on thermosets, thermoplastics, and elastomers. To impart electrically conductive properties, various options for fillers based on Ag, Au, Cu, Ni, Fe, and CNTs are considered. Methods for introducing dispersed fillers into polymer matrices are presented. Functional composites with a positive temperature coefficient and methods for their regulation are considered. The mechanisms of various electrophysical processes in conductive composites are considered, taking into account the resulting electrical conductivity based on the tunnel effect and hopping conductivity. An analysis of electric heaters based on various polymer matrices and dispersed fillers is carried out, taking into account their operating modes. Thus, the conducted review of modern scientific and practical research in the field of obtaining electrically conductive composites based on various types of polymer matrices with nanosized additives allows us to assess the prospects for the formation of functional composites for electrical heating, taking into account the mechanisms of electrical conductivity and new technologies based on machine learning and neural networks. Full article

This study demonstrates the improvement of core loss through the reduction of eddy current loss in soft magnetic composites (SMCs) composed of TiO₂-coated Fe powder and epoxy resin. A thin and uniform TiO₂ insulating layer was successfully deposited on the surface of Fe powder via a sol-gel process, employing titanium (IV) butoxide (TBOT) as the precursor. Scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy analyses confirmed the formation of a core/shell Fe/TiO₂ structure, with a coating thickness of several tens of nanometers. Increasing the TBOT concentration and coating duration time led to an improved quality factor (Q factor) and a shift of the maximum Q factor values to higher frequency regions. Notably, the permeability was decreased slightly from 14.2 to 13.4, but the core loss, measured at various AC frequencies under 20 mT and then separated into hysteresis loss and eddy current loss at 1 MHz, was significantly reduced from 573 to 435 kW/m³ when the Fe powder was coated with TiO₂ using a 2.5 wt.% TBOT solution for 8 h. This reduction in core loss is attributed to the effective suppression of inter-particle eddy currents by the TiO₂ insulation layer. Full article

This article provides information on the processing of chromium-containing waste from the Aktobe ferroalloy compounds plant using chemical reagents followed by high-temperature heat treatment for the synthesis of a composite chromite pigment used in the textile industry. This technology was developed for the first time for the purpose of recycling industrial waste and rational use of natural resources. The obtained pigments were analyzed by the X-ray phase of a D878-PC75-17.0 incident beam monochromator and the phase composition of the composite chromite pigment was studied. The thermogravimetric analysis of the composite chromite pigments was performed using a TGA/DSC 1HT/319 analyzer to determine the change in mass with time and temperature. According to the TGA results, the mass loss was determined to be 0.18% of the total mass. The elemental composition of the composite chromite pigment was determined using a JEOL JSM-6490 LV SEM device and the content of chromium oxide (Cr₂O₃) was determined, which reached up to 50%. The thermodynamic patterns of the processes occurring during the production of chromite pigments were studied using the integrated Chemistry software pack HSC-6. The results of testing printed and processed cotton and composite fabrics by the proposed method showed that the color fastness to washing and wet and dry friction is 4 points and the wear resistance assessment is 4860 and 6485 cycles, respectively. Composite chromite pigment based on technogenic wastes is recommended for use in various coloring compositions, including those used for printing on cotton and composite fabrics. Full article

ABS plastic is an inexpensive material with attractive physical and chemical properties. Unfortunately, it is susceptible to degradation under UV radiation, so it limits the use of this material outdoors. In this paper, we demonstrate a low-cost approach to reduce the photodegradation of ABS plastic by using additives of kraft lignin and dioxane lignin as UV absorbers. Lignin is an abundant plant polymer, which is a waste product of the pulp and paper industry. Non-regular structure of lignin hampers its use in industry. However, there is possible use of lignin as an addition to enhance the properties of resulting materials. In this study, we obtained composites of ABS and lignin with the hot extrusion method. Adding up to 15% of lignin to ABS plastic does not have a significant negative impact on tensile properties. We irradiated the resulting composites with UV and studied the UV effects on their mechanical properties and chemical structure. Oxidative degradation was characterized by FTIR and 2D NMR methods. The results showed that small lignin additions reduced the photodegradation of ABS. The previously undescribed product of the degradation of the obtained composites was detected with the use of the set of 2D NMR spectra of the composites. We proposed a scheme for the formation of this photodegradation product based on the obtained data. Full article

In recent decades, the aviation industry has increasingly adopted composite materials for various aircraft components, due to their high strength-to-weight ratio and durability. To ensure the safety and reliability of these structures, Health and Usage Monitoring Systems (HUMSs) based on fiber optics (FO), particularly Fiber Bragg Grating (FBG) sensors, have been developed. However, both composite materials and optical fibers are susceptible to environmental factors such as moisture, in addition to the well-known effects of mechanical stress and thermal loads. Moisture absorption can lead to the degradation of mechanical properties, posing a risk to the structural integrity of aircraft components. This research aims to quantify and monitor the impact of moisture on composite materials. A new formulation of the Bragg equation is introduced, incorporating mechanical strain, thermal expansion, and hygroscopic swelling to accurately measure Bragg wavelength variations. Experimental validation was performed using both uncoated and polyimide-coated optical fibers subjected to controlled hygrothermal conditions in a climate chamber. The results demonstrate that uncoated fibers are insensitive to humidity, whereas coated fibers exhibit measurable wavelength shifts due to moisture absorption. The proposed model effectively predicts these shifts, with errors consistently below 2.6%. This approach is crucial for improving the performance and reliability of HUMSs in monitoring composite structures, ensuring long-term safety in extreme environmental conditions. Full article

The current study investigates the process of preparing and analysing porous-structured ceramics made from zirconium, aluminium, and magnesium ceramic oxides. The starch consolidation casting (SCC) technique, with different types of starches (potato and tapioca), was used for this purpose. Our objective was to methodically examine the impact of different processing factors, such as the temperature at which pre-sintering and sintering occur, and the proportions of ceramic powders, on the microstructure, mechanical characteristics, and porosity of the resultant composites. Pre-sintering effectively reduced the rate of shrinkage during the final sintering stage; this resulted in more controlled and predictable shrinkage, leading to better dimensional stability and reduced risk of defects in the final product. A higher alumina content was associated with an increase in apparent porosity and a reduction in volume shrinkage and apparent densities. The mercury intrusion porosimetry (MIP) findings concluded that the prepared porous ceramics have a multi-modal pore structure. The highest calculated compressive strength was 76.89 MPa for a sample with a porous structure, which was manufactured using 20 wt.% tapioca starch and 30 wt.% alumina content. The main advantage of alumina is its ability to improve compressive strength by refining the grain structure and serving as a barrier against fracture development. Full article

The present study synthesized silver nanoparticles supported on a thermosensitive polymer with a core–shell structure, formed by a polystyrene (PS) core and a poly(N-isopropylacrylamide) (PNIPAM)/Poly(N, N-methylenebisacrylamide) (MBA) shell. The PS core was synthesized via semicontinuous heterophase polymerization at a flow of 0.073 g/min, enabling polystyrene nanoparticles with an average size (Dz) of 35.2 nm to be obtained. In the next stage, the conditions required for polymerization synthesis were established in seeded microemulsion using PS nanoparticles as seed and semicontinuously adding the thermosensitive shell monomer (PNIPAM/MBA) under monomer-flooded conditions to favor shell formation. The non-homopolymerization of PNIPAM/MBA was demonstrated by obtaining nanoparticles with a core–shell structure, with average particle sizes of 41 nm and extremely low and narrow polydispersity index (PDI) values (1.1). The thermosensitive behavior was analyzed by QLS, revealing an average shrinkage of 4.03 nm and a percentage of shrinkage of 23.7%. Finally, silver nanoparticles were synthesized on the core–shell heat-sensitive nanoparticles in a colloidal solution containing the latices, while silver nanoparticles were anchored onto the cross-linked heat-sensitive network via the formation of complexes between the Ag+ ions and the nitrogen contained in the PNIPAM/MBA network, favoring anchorage around the network and maintaining a size of 5 nm. Full article

The rapid perishability of strawberries due to factors such as fungal decay, mechanical damage, and respiration significantly limits their shelf life. In this study, a novel multi-component edible coating composed of bacterial cellulose, chitosan, and gellan gum (BChG) was developed to enhance the postharvest quality and extend the shelf life of strawberries. The coated fruits were evaluated over a 15-day storage period for key parameters such as weight loss, total soluble solids (TSS), titratable acidity (TA), enzymatic activity, color retention, antioxidant activity, and microbiological analysis. The results demonstrated that coated strawberries exhibited significantly lower weight loss, reduced cellulase activity, and higher retention of TSS and TA compared to uncoated controls. The evaluation of microbial quality indicated that coatings, particularly those with higher concentrations of chitosan, control the growth of total mesophilic aerobic bacteria (TMAB) and molds and yeasts (MY), due to the antimicrobial properties of chitosan. This contributed to extending the shelf life of the fruit by preventing spoilage and reducing the risk of toxic compound formation. Additionally, the BChG coatings also preserved the characteristic red color of the fruit and maintained higher antioxidant activity, with BChG-4 being the most effective formulation. The inclusion of chitosan in the coatings was found to play a crucial role in reducing respiration, delaying ripening, and enhancing the fruit’s resistance to oxidative damage. Overall, multi-component coatings, particularly those with higher chitosan concentrations, offer a promising method for extending the shelf life of strawberries, reducing postharvest losses, and preserving fruit quality under ambient storage conditions. Full article

By incorporating various types of permanent magnetic powders, composite magnets with cost-effectiveness and a wide range of magnetic properties can be achieved. In this study, the anisotropic composite magnets were fabricated using the hot press forming method, which involved blending neodymium iron boron (NdFeB) powder and samarium iron nitrogen (SmFeN) powder. The experiment demonstrated that the magnet density reaches its maximum point when the doping level of SmFeN reaches 20 wt.%, aligning remarkably well with the corresponding theoretical value of 19.22 wt.% achieved through a cubic stacking arrangement. In the absence of an applied magnetic field or under a sufficiently high oriented magnetic field (3 T), the remanence variation pattern in composite magnets doped with different amounts of SmFeN aligns consistently with the density pattern, yielding a maximum value of 20%. However, in the actual solidification process, the orientation field is insufficient (e.g., 1.5 T), necessitating a doping amount that exceeds the value corresponding to peak density by 28% to achieve optimal remanence. This observation suggests that the incorporation of a higher proportion of small-sized and relatively low coercivity SmFeN magnetic powder can effectively facilitate the rotational alignment of neighboring large-sized NdFeB magnetic powder under weak magnetic fields, thereby inducing a synergistic effect. Full article

Graphene is considered to be one of the most promising reinforcement phases for nanocomposites due to its unique two-dimensional planar structure with excellent mechanical properties. After the design of origami, the 2D material will obtain a negative Poisson’s ratio in the in-plane direction and become a metamaterial with unusual mechanical properties. Inspired by this, an origami pattern is adopted for graphene at an atomic scale using a molecular dynamics (MD) approach, and then origami graphene is embedded into a single-crystal copper matrix to obtain origami graphene/copper nanocomposites with auxetic behaviors. In the modeling, the periodic boundary condition is chosen to exhibit the Poisson’s ratio of the whole system. Under the isothermal–isobaric ensemble, the interactions between C-C, Cu-Cu, and C-Cu atoms are, respectively, determined by three potential functions: AIREBO, EAM, and LJ. The effect of the origami graphene/copper interfacial gap on the critical strain of incremental Poisson’s ratio, critical strain of engineering Poisson’s ratio, and moduli of the origami graphene/copper nanocomposites is studied to determine the optimum distance between the two phases. The influences of the mass fraction of carbon atom and temperature on those properties are discussed in detail after the MD model is confirmed. Full article

Piezoelectric materials can realize the mutual conversion of mechanical energy and electric energy, so they have excellent application prospects in the fields of sensors, energy collectors and biological materials. The poly(vinylidene fluoride) (PVDF)-based polymers have the best piezoelectric properties in the piezoelectric polymer, but they still have a large room for improvement compared with the piezoelectric ceramics. Improving their content of the polar β phase has become a consensus to polish up the piezoelectric performance. Most available studies construct hydrogen bonds or coulomb interactions between the surface of the dopant and molecular chains by doping, which promotes the molecular chains arrangement and thus facilitates the formation of the polar β phase. Recent studies show that the ordered arrangement of molecular chains is also important for piezoelectric properties. At present, the main way to improve the piezoelectric performance of PVDF is through doping or complex heat treatment process. Here, the poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) film was treated by directional heat treatment which used a heating table. Compared with uniform heat treatment like muffle furnace heat treatment, this simple vertical temperature gradient has many advantages for the content of the β phase and the crystallinity of P(VDF-TrFE). The results of the experiment showed that the content of the β phase of films remained at about 88%. When the film thickness was limited to 100 μm and the heat treatment temperature was limited to 200 °C, its crystallinity could reach 75% and the highest piezoelectric coefficient could reach 33.5 ± 0.7 pC/N. P(VDF-TrFE) films based on the experimental methods described above that show great potential for future applications in electronic devices and biomedical applications. Full article

The presented research on adhesives was conducted with the aim of supporting the design of composite repairs for composite aircraft structures that can withstand specific environmental conditions. Double-sided strap joint specimens of epoxy-based CFRP adherents and straps were bonded by two types of adhesives. Room-temperature curing epoxy adhesives EC-9323 and EA-9395 were used for bonding. The specimens’ shear strength and failure modes were evaluated under four different environmental conditions from −72 °C up to 70 °C unconditioned and at 70 °C after humidity conditioning. The results show that EC-9323 performed excellently at room temperature, but very poorly at elevated temperatures after hot–wet conditioning. Adhesive EA-9395 performed consistently well across all tested conditions. The failure mode analysis explained the performance trends and the effect of the environment on the fractured surface. This study will support proper repair design and verification of numerical simulations. The novelty of this article lies in its combined analysis of multiple environmental factors, providing a more realistic assessment of joint performance. Full article

To investigate the distribution characteristics of the micropore structure in high-performance self-compacting concrete (C80), high-resolution X-ray computed tomography, AVIZO software (version 2024.1), and scanning electron microscopy were employed to observe and analyze the internal pore structure of C80 self-compacting concrete specimens. The main conclusions are as follows: There is a large number of pore structures within the carbonate rock-based high-performance self-compacting concrete. At a testing precision range of 10 μm, the micropores exhibit a circular feature with good overall circularity. Observations through SEM, scanning electron microscopy, reveal that there are micro-cracks or interconnected crack structures within the high-performance concrete, with widths ranging from 0.5 to 2 μm, and the sample contains tiny voids of 3 to 10 μm. A statistical analysis of the micropores within the carbonate rock-based self-compacting concrete indicates that the pore diameter follows a three-parameter normal distribution. Due to the limitations of experimental observation and precision, the experimental statistical results show a positively skewed (high peak and left-skewed) phenomenon. This paper proposes a “correction of skewed peak” method for the analysis and discussion of the calculation of the “third parameter C” in the statistical results. The results show that the method proposed in this paper can quickly, objectively, and optimally determine the third parameter, compensating for the missing data not accounted for below 10 μm and the limitations of the finite number of experimental samples, providing a reference for examining the distribution of pores within concrete. Full article

Arsenic contamination in groundwater poses serious health risks, as exemplified by the Blackfoot disease epidemic in Taiwan, which was caused by prolonged arsenic exposure. This study investigates the use of biochar derived from the wastewater treatment sludge of the Far Eastern Memorial Hospital (New Taipei City, Taiwan) as an efficient adsorbent for arsenic removal. A novel iron-doped sludge biochar (Fe-SBC) was developed to enhance arsenic adsorption efficiency, facilitate adsorbent recovery, and reduce operational costs. The adsorption mechanism of arsenic on Fe-SBC, modified with iron hydroxide complexes, was examined through Density Functional Theory (DFT) simulations. The results demonstrate a high arsenic removal efficiency of approximately 90% using continuous adsorption systems. The DFT calculations revealed strong chemical interactions between arsenic and the biochar, evidenced by high adsorption energy (−156.8 kJ mol⁻¹) and a short bond distance (1.48 Å), correlating with the high adsorption performance observed experimentally. Additionally, arsenic byproducts desorbed from the adsorbent were repurposed into antibacterial agents and pigments. Four distinct pigment colors—green, blue, gray, and orange—were produced through different preparation methods, with the antibacterial agents showing effective antimicrobial properties. This study highlights the potential of Fe-SBC for sustainable arsenic remediation and resource recovery. Full article

Background: This study aims to compare the compressive strength and microhardness of four tooth-colored restorative materials: bulk fill glass hybrid (GH), resin-modified glass ionomer (RMGIC), conventional glass ionomer (CGIC), and resin-based composite (RBC). Methods: Stainless steel molds were used to prepare 20 specimens for each material. Half of the specimens were subjected to 10,000 thermal cycles; the materials were subjected to compressive strength and microhardness tests. Mean values were statistically compared using a one-way ANOVA Test and Bonferroni pairwise comparisons. Results: GH (147.03 ± 20.19 MPa) had lower compressive strength than RBC (264.82 ± 30.95 MPa) but showed no significant difference with CGIC (130.19 ± 30.38 MPa) and RMGIC (183.52 ± 18.45 MPa). RMGIC’s compressive strength also significantly fell short of RBC (p < 0.05), but it significantly increased after thermocycling (160.14 to 183.52 MPa). As for microhardness, no significant difference was found between the groups. Thermocycling significantly increased the microhardness of CGIC (from 24.27 to 31.8 ± 2.66). Conclusion: Resin-based materials outperformed the other materials. Glass hybrid restorative material performed as well as resin-modified glass ionomer regarding compressive strength; however, further studies are necessary before considering glass hybrids for use as a permanent restoration. Full article

Approximately 10 billion tons of fine and coarse aggregate are manufactured worldwide annually, solely to be used as concrete for constructed structures. With approximately 80% of conventional concrete comprising sand and stone, activities in their extraction and relocation harm the natural environment. Manufacturing concrete causes substantial amounts of ecological damage and energy consumption. The replacement of natural aggregate with waste glass, therefore, theoretically removes this environmental damage and energy consumption. The research presented in this paper tested the theory that waste glass concrete aggregate represents a potential solution to curtail the adverse impact of concrete on the natural environment. Testing this theory entailed the review of the existing literature and analyses of the findings from a survey of 107 organizations situated in five countries within the concrete manufacturing supply chain. The findings of this research demonstrate that environmental implications exist with the use of both natural aggregate and glass waste. Significant CO₂ reductions can be achieved by using glass as aggregate in concrete. This is found to be up to 60% and 65% for fine and coarse aggregates, respectively. In addition, using glass in its aggregate can potentially improve the strength of concrete. With a concrete grade of 20, an improved compressive strength test of up to 10 could be possible. Similarly, with concrete grades of 25 and 30, an improved tensile strength test of up to 9 could be possible. This depends on differences in the percentage of natural aggregate that has been substituted with glass. Full article

This review provides a comprehensive exploration of the current research landscape surrounding nanoclay-reinforced epoxy composites. A primary challenge in developing these nanocomposites is the hydrophilic nature of pristine clay, which hinders its dispersion within the epoxy matrix. To address this issue, organic modifiers are frequently employed to enhance clay compatibility and facilitate effective incorporation into the nanocomposite structure. The unique properties of nanoclay make it a particularly attractive reinforcement material. The performance of nanoclay/epoxy nanocomposites is largely determined by their morphology, which is influenced by various factors including processing methods, clay types, modifiers, and curing agents. A thorough understanding and control of these parameters are essential for optimizing nanocomposite performance. These advanced materials find extensive applications across multiple industries, including aerospace, defense, anti-corrosive coatings, automotive, and packaging. This review offers an in-depth analysis of the processing techniques, mechanical properties, barrier capabilities, and thermal characteristics of nanoclay-reinforced epoxy nanocomposites. Additionally, it explores their diverse industrial applications, providing a holistic view of their potential and current use. By examining the multifaceted landscape of epoxy/clay nanocomposites, this review illuminates the intricate relationships between fabrication methods, resulting properties, and potential industrial applications. It serves as a comprehensive resource for researchers and practitioners seeking to advance the development and application of these innovative materials. Full article

This study investigated the adhesion and mechanical properties of woven fabric-reinforced laminates (FRLs) made with four distinct Kevlar fabrics of varying areal densities (36 g/m², 60 g/m², 140 g/m², and 170 g/m²) under different fabric-to-adhesive weight ratios (1:0.5, 1:1, and 1:1.5) in both the warp and weft directions. A novel aspect of this research lies in our systematic study of the effect of adhesive quantity on FRLs, a topic that has received limited attention despite its critical role in laminate performance. Additionally, the application of a newly developed yarn pullout test alongside the standard T-peel test provides unique insights into the interfacial behavior of laminates. The results show that in lower areal density fabrics (36 g/m² and 60 g/m²), adhesive quantity minimally affects the pullout and T-peel forces or tear strength, indicating that structural integrity can be maintained with reduced adhesive application. In contrast, higher areal density fabrics (140 g/m² and 170 g/m²) benefit from an increased adhesive ratio, with a transition from 1:0.5 to 1:1 significantly enhancing the pullout resistance, while further increases to 1:1.5 yielded diminishing returns. Tensile strength remained consistent across all samples, highlighting that it is largely dictated by the inherent properties of the fibers and fabric structure rather than the adhesive. This study concludes that a 1:1 fiber-to-adhesive ratio offers an optimal balance of adhesion quality and mechanical performance for FRLs. By addressing the understudied impact of adhesive quantity on FRLs and introducing the yarn pullout test, this research provides novel and practical guidelines for optimizing FRLs in applications demanding high structural integrity and adaptability under challenging conditions. Full article

Linerless composite pressure vessels, or type V pressure vessels, are gaining increased interest in the transportation industry because they offer improved storage volume and dry weight, especially for low-pressure cryogenic storage. Nevertheless, the design and manufacturing of this type of pressure vessel bring several challenges due to the inherent difficulties in the manufacturing process implementation, assembly, and related analysis of structural integrity due to the severe operating conditions at cryogenic temperatures that should be taken into consideration. In this work, a novel analysis procedure using a finite element model is developed to perform an end-to-end simulation of a linerless pressure vessel, including the relevant features associated with automated fiber placement manufacturing processes regarding thickness and tape profiles, followed by an analysis of the structural response under service conditions. The results show that residual stresses from manufacturing achieve values near 50% of the composite ply transverse strength, which reduces the effective ply transverse load carrying capacity for pressure loading. Transverse damage is triggered and propagated across the vessel thickness before fiber breakage, indicating potential failure by leakage, which was confirmed by hydrostatic tests in the physical prototype at 26 bar. The cryogenic condition analysis revealed that the thermal stresses trigger transverse damage before pressure loading, reducing the estimated leak pressure by 40%. These results highlight the importance of considering the residual stresses that arise from the manufacturing process and the thermal stresses generated during cooling to cryogenic conditions, demonstrating the relevance of the presented methodology for designing linerless cryogenic composite pressure vessels. Full article

This review is devoted to experimental studies and modeling in the field of mechanical and physical properties of polymer concretes and polymer-modified concretes. The review analyzes studies carried out over the past two years. The paper examines the properties of polymer concretes based on various polymer resins and presents the advantages and disadvantages of various models developed to predict the mechanical properties of materials. Based on data in the literature, the most promising polymers for use in the field of road surface repair are polymer concretes with poly(meth)acrylic resins. It was found that the most adequate and productive models are the deep machine learning model—using several hidden layers that perform calculations based on input parameters—and the extreme gradient boosting model. In particular, the extreme gradient boosting model showed high R² values in forecasting (in the range of 0.916–0.981) when predicting damping coefficient and ultimate compressive strength. In turn, among the additives to Portland cement concrete, the most promising are natural polymers, such as mammalian gelatin and cold fish gelatin, and superabsorbent polymers. These additives allow for an improvement in compressive strength of 200% or more. The review may be of interest to engineers specializing in building construction, materials scientists involved in the development and implementation of new materials into production, as well as researchers in the interdisciplinary fields of chemistry and technology. Full article

In order to further improve the corrosion resistance of 7075-T6 aluminum alloy after shot peening, corrosion-resistant superhydrophobic coatings (EP-HDTMS@SiO₂) containing epoxy resin (EP), cetyltrimethoxysilane (HDTMS), and nano-silica (SiO₂) were prepared by a simple spraying method on the surface of shot-peened AA 7075-T6 aluminum alloy. The effects of different EP/SiO₂ mass ratios on the micro-morphology, surface wettability, and corrosion resistance of the superhydrophobic composite coatings were analyzed. Due to the combination of microstructure and the modification of low surface energy organics, the contact angle of EP-HDTMS@SiO₂ coatings reached the superhydrophobic level (152.6°). The electrochemical tests showed that the corrosion current densities (I_corr) of the EP-HDTMS@SiO₂ composite coatings were both significantly lower than those of the EP-HDTMS coatings and matrix aluminum alloys. The addition of SiO₂ nanoparticles could improve the hydrophobicity and corrosion resistance of epoxy-based composite coatings. Due to the increase in surface roughness and epoxy resin, the shot-peened AA 7075-T6 alloy coating had high adhesion after the peel test. The prepared coatings also showed excellent corrosion resistance in the neutral salt spray test. This study provides a simple method for preparing stable superhydrophobic coatings on metal surfaces, which is expected to expand the application of 7075 aluminum alloy in harsh environments. Full article

In this work, new self-adhesive materials were obtained based on cross-linked silicone self-adhesives obtained by modifying the composition with the addition of a silicon filler, olivine. Silicone pressure-sensitive resin DOWSIL 7358 was used as a basis and modified with various amounts of olivine. New materials (self-adhesive tape samples) were characterized in terms of peel adhesion, tack, cohesion at room and elevated temperatures, SAFT test (shear adhesion failure temperature), pot life (storage stability), and shrinkage (dimensional stability). During the tests, an increase in thermal resistance (>225 °C) and a drastic reduction in shrinkage values (below 0.5%) were noted for all modified samples tested. All tests were performed in compliance with international standards, e.g., FINAT FTM 1, FINAT FTM 8, FINAT FTM 9, FINAT FTM 14, and GTF 6001. This allows us to conclude that the new material has significant application potential due to the good performance results. The results of adhesion and tack were in ranges accepted in the PSA industry, cohesion was kept at an unchanged level (above 72 h), and a great increase in the thermal resistance was observed (from 147 °C for pure resin to high above 225 °C for even the smallest additions of the olivine powder. Moreover, the shrinkage of prepared adhesive films was reduced significantly. In the available literature, there are no references to the modification of adhesives using powdered silicon minerals of natural origin, which is a novelty due to their higher bulk density compared to commercial powdered silicon fillers. Full article

This work investigates the impact of friction stir processing (FSP) on the microstructure and mechanical characteristics of AA 6061 alloy and its composites, which are strengthened with boron nitride nanoparticles and vanadium carbide microparticles. Composite samples were created using different proportions of reinforcing particles, including mono and hybrid composites. The efficacy of FSP as a technological method for enhancing the grain size of AA 6061 alloy and its composites has been proven. Adding reinforcing particles led to enhanced grain refinement, especially when using VC particles, which demonstrated greater efficacy than BN particles; thus, mono composite AA6061/VC shows the highest percentage reduction (94.29%) in grain size. Hybrid composites with a higher concentration of VC particles exhibited a more symmetrical microhardness profile. The microhardness of hybrid composites with a larger concentration of VC particles (40 vol.%BN + 60 vol.%VC) shows the most significant enhancement, with an increase of 51.61%. The Young’s and shear modulus of all composite samples processed by (FSP) had greater values than the wrought AA 6061 alloy. The investigated composite samples, especially 60% BN and 40% VC, enhanced the tribological properties of AA6061 and reduced the wear rate by about 52%. The observed characteristics may be due to BN and VC particles in the hybrid compost. This is because these particles effectively prevent grain elongation and inconsistent movement. This is because reinforcing particles can be tailored to have specific properties for specific applications. Full article