Search Results (282)

Halogenated flame retardants have been amongst the most widely used and effective solutions for enhancing fire resistance. However, their use is currently strictly regulated due to serious health and environmental concerns. In this context, phosphorus-based and mineral flame retardants have emerged as promising alternatives. Despite this, their combined use is neither straightforward nor guaranteed to be effective. This study scrutinizes the interactions between these two classes of flame retardants (FR) through a systematic analysis aimed at elucidating the antagonistic pathways that arise from their coexistence. Specifically, this study focuses on two inorganic fillers, mineral huntite and chemically precipitated magnesium hydroxide, both of which produce basic oxides upon thermal decomposition. These fillers were incorporated into a poly(butylene terephthalate) (PBT) matrix to be utilized as advanced-mattress FR coating fabric and were subjected to a series of flammability tests. The pyrolysis products of the prepared polymeric composite compounds were isolated and thoroughly characterized using a combination of analytical techniques. Thermogravimetric analysis (TGA) and differential thermogravimetric analysis (dTGA) were employed to monitor decomposition behavior, while the char residues collected at different pyrolysis stages were examined spectroscopically, using FTIR-ATR and Raman spectroscopy, to identify their structure and the chemical reactions that led to their formation. X-ray diffraction (XRD) experiments were also conducted to complement the spectroscopic findings in the chemical composition of the resulting char residues and to pinpoint the different species that constitute them. The morphological changes of the char’s structure were monitored by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). Finally, the Limited Oxygen Index (LOI) and UL94 (vertical sample mode) methods were used to assess the relative flammability of the samples, revealing a significant drop in flame retardancy when both types of flame retardants are present. This reduction is attributed to the neutralization of acidic phosphorus species by the basic oxides generated during the decomposition of the basic inorganic fillers, as confirmed by the characterization techniques employed. These findings underscore the challenge of combining organophosphorus with popular flame-retardant classes such as mineral or basic metal flame retardants, offering insight into a key difficulty in formulating next-generation halogen-free flame-retardant composite coatings. Full article

The development of lightweight composites with superior mechanical properties and electromagnetic interference (EMI) shielding performance is essential for various structural and functional applications. This study investigates the effect of hybrid nanocarbon (graphene nanosheet (GNS) and carbon nanotube (CNT)) reinforcements on the properties of magnesium (Mg) matrix composites. Specifically, the GNS-CNT hybrid, which forms a three-dimensional interconnected network structure, was analyzed and compared to composites reinforced with only GNSs or CNTs. The objective was to determine the benefits of hybrid reinforcements on the mechanical strength and EMI shielding capability of the composites. The results indicated that the GNS-CNT/Mg composite, at a nanocarbon content of 0.5 wt.% and a GNS-CNT ratio of 1:2, achieved optimal performance, with a 55% increase in tensile strength and an EMI shielding effectiveness of 70 dB. The observed enhancements can be attributed to several key mechanisms: effective load transfer, which promotes tensile twinning, along with improved impedance matching and multiple internal reflections within the GNS-CNT network, which enhance absorption loss. These significant improvements position the composite as a promising candidate for advanced applications requiring high strength, toughness, and efficient electromagnetic shielding, providing valuable insights into the design of high-performance lightweight materials. Full article

Biodegradable magnesium-based composites show potential application in orthopedic implants, with excellent biocompatibility, low density, and biodegradable characteristics inside the human body. In this study, the stir casting procedure was employed to produce magnesium–zinc MMCs (metal matrix composites) reinforced with MgO nanoparticles, and they were characterized intensively. The analyzed compositions were Mg/4Zn, Mg/4Zn/0.4MgO, and Mg/4Zn/0.6MgO. Their mechanical properties, corrosion resistance, and microstructure were then investigated employing tensile, impact, hardness, wear, and corrosion tests, supplemented with SEM analysis. The results indicate that the Mg-4Zn-0.6MgO composite exhibited the highest performance among the tested formulations, with a tensile strength of 150 MPa, a hardness of 65 HRE (Rockwell Hardness, E-scale), and enhanced corrosion resistance. These improvements are attributed to the uniform dispersion of MgO nanoparticles and the formation of a protective Mg(OH)₂ layer, which together contribute to mechanical reinforcement and controlled degradation behavior. The combination of superior mechanical properties and customizable biodegradability verifies the engineered Mg/4Zn/0.6MgO composite as a promising candidate for a biodegradable orthopedic fixation plate without secondary surgery. Full article

Lightweight metals are increasingly used in biomedical engineering, and can be found in orthopaedics (screws, implants), stomatology, cardiology (stents) and as scaffolds. Magnesium alloys have a low density (1.74 g/cm³), which is very close to that of bone (1.75 g/cm³), as well as high biocompatibility, and are biodegradable. Unfortunately, their disadvantage is their low resistance to corrosion in the human body, which further causes deterioration of mechanical and physical properties. Improvement of these properties can be achieved by making the composite on a magnesium matrix—depending on the reinforcement added, the required properties can be obtained. This paper presents the results of a study on the extrusion of a magnesium matrix composite with titanium (Ti) reinforcement. The study included three-point bending tests, from which it is clear that the introduction of Ti reinforcement improves the bending strength of the specimens. In addition, the samples were immersed in SBF (simulated body fluid) for 1, 2, 4, 8, 12 and 24 h to determine the degradation of the Mg–Ti composite. Full article

This study investigates the use of Ultra-High Molecular Weight Polyethylene (UHMWPE) fibers and fabric to enhance the flexural performance of Ultra-High-Performance Concrete (UHPC). A total of 45 specimens were tested to examine the effects of fiber type, fabric material, adhesive, and various combined strengthening techniques. The main findings are that incorporating UHMWPE fiber into the ultra-high-strength mortar (HSM) matrix provides superior performance compared to steel fiber, particularly in enhancing crack resistance and energy absorption. UHMWPE fiber-reinforced UHPC achieved a flexural toughness of 307 KJ/m³, over three times higher than that of steel fiber-reinforced UHPC (98 KJ/m³). The use of UHMWPE fabrics was more effective in improving the ductility and toughness of the composites than the use of glass fabrics. The bonding effect of using epoxy resin with UHMWPE fabric is better than using magnesium phosphate cement (MPC). Increasing the number of fabric layers improved the flexural properties of externally bonded fabric but had no impact on internal reinforcement techniques. The best strengthening method in this study was a combination of incorporating UHMWPE fiber internally and externally bonded fabric on a concrete surface, yielding the highest toughness of 580 KJ/m³. Full article

Polylactic acid (PLA) is a bioresorbable and biocompatible material and is a promising alternative to the current materials used for permanent implants as it has osteosynthesis properties. However, this material has some drawbacks due to its low mechanical and thermal resistance after 3D printing. Extensive research has been conducted to improve the properties of this material, for example, with the addition of other compounds, such as magnesium (Mg) or Hydroxyapatite (HA). These reinforced materials have been shown to reduce the internal stress of the matrix of PLA, improving the thermal, optical and structural properties of the material, even though the performance achieved is lower than needed to be implanted. In addition, although it is known that the addition of Mg or HA affects the mechanical performance of the material, mechanical properties have not been studied in the literature. Thus, the aim of this study is to research the effect of thermal post-processing based on annealing of composites made of PLA with Mg and PLA with HA, manufactured by fused filament fabrication, with the goal of finding an improvement in the mechanical properties of these materials. As a result, different designs of annealing processes have been studied with different reinforced materials and their mechanical properties have been compared, studying axial traction and compression, radial compression as well as flexibility, among others. The comparative results achieved show the relevance of the design of the annealing process for the improvement of the mechanical properties of these materials. Full article

Due to the specific application of aluminum–magnesium–lithium (Al-Mg-Li) alloys in the transportation industry, it is necessary to consider the influence of microstructure development on material degradation under severe environmental conditions. This degradation was simulated according to the standard test method ASTM G34-01 (2018) on a newly designed and synthesized Al-2.1Mg-1.92Li alloy in the as-cast condition. The degradation susceptibility of the alloy was estimated by measuring the changes in the sample mass and microhardness, and the pH and chemical composition of the environment with respect to the exposure time. The influence of the microstructure constituents on the degradation of the alloy was determined using metallographic analysis of the exposed surface and cross-section of the samples after testing. During the degradation, dealloying of the α_Al matrix through Li, Mg and Al component dissolution resulted in a decrease in the mass of the samples, an increase in the pH of the environment and changes in its chemical composition. This observation was also confirmed by the results of the metallographic analysis. The degradation involved the formation of cavities around the Al₈Mg₅ (β) and Al₂LiMg (T) intermetallic phases through an anodic dissolution mechanism. The increase in microhardness values after exposure indicated an increase in the stress around the degradation front due to the wedge effect of the degradation products. The results of the investigation support the potential application of the synthesized Al-2.1Mg-1.92Li alloy under the severe environmental conditions defined by the ASTM G34-01 (2018) standard. Full article

Hydrogen can be easily captured by the rare-earth (RE) elements in hydrogen-rich environments, which significantly affect the phase compositions and mechanical performance of Mg-RE based alloys. However, the morphology of RE hydrides and their orientation relationships (ORs) with the Mg matrix have not been well explained. Here, a stable face-centered cubic (FCC) ${\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2$ hydride was introduced and uniformly distributed in a Mg-15Gd-2.5Y-1Al alloy after hydrogenation treatment at 500 °C and 2 MPa for 40 h. The plate-like ${\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2$ hydride with six variants was identified to exhibit an OR with the magnesium (Mg) matrix, which is ${\left[0001\right]}_{\mathrm{M}\mathrm{g}}$//${\left[001\right]}_{{\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2}$, ${\left(10\overline{1}0\right)}_{\mathrm{M}\mathrm{g}}{10.5}^{\circ }$ from ${\left(002\right)}_{{\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2}$, ${\left(1\overline{2}10\right)}_{\mathrm{M}\mathrm{g}}{10.5}^{\circ }$ from ${\left(020\right)}_{{\left(\mathrm{G}\mathrm{d},\mathrm{Y}\right)\mathrm{H}}_2}$. Further crystallographic matching calculations based on the edge-to-edge matching model suggest that such an OR is energetically favorable and provides the actual interface between the RE hydrides and the Mg matrix during precipitation. Our findings offer new insights into the microstructural regulation of Mg alloys in hydrogenation environments. Full article

This study evaluates the influence of multiwall carbon nanotubes (MWCNTs), reduced graphene oxide (rGO), and magnesium oxide (MgO) on the thermal conductivity of alkali-activated engineered composites (AAECs). Thirty-two ambient-cured AAECs consisting of two types of powdered-form reagents/activators (type 1—calcium hydroxide: sodium meta silicate = 1:2.5; type 2—calcium hydroxide: sodium sulfate 2.5:1), two dosages of MgO (0 and 0.5%) of MgO, three percentages (0, 0.3%, and 0.6%) of MWCNTs/rGO, and binary (45% ground granulated blast furnace slag ‘GGBFS’ and 55% Class C fly ash ‘FA-C’) and ternary combinations (40% GGBFS, 25% FA-C and 35% class F fly ash ‘FA-F’) of industrial-waste-based source materials, silica sand, and polyvinyl alcohol (PVA) fiber were developed using the ‘one-part dry mix’ technique. Problems associated with the dispersion and agglomeration of nanomaterials during production were avoided through the use of defined ultra-sonication with a high-shear mixing protocol. The impact of the combination of source materials, activators, and MgO/MWCNT/rGO dosages and their combinations on the thermal properties of AAECs is evaluated and discussed based on temperature–time history and thermal conductivity/diffusivity properties along with micro-structural characteristics. It was found that the change in temperature of the AAECs decreased during testing with the addition of MWCNTs/rGO/MgO. The thermal conductivity and diffusivity of AAECs increased with the increase in MWCNT/rGO/MgO contents due to the formation of additional crystalline reaction products, improved matrix connectivity, and high conductivity of nanomaterials. MWCNT AAECs showed the highest thermal conductivity of 0.91–1.26 W/mK with 49% enhancement compared to control AAECs followed by rGO AAECs. The study confirmed the viability of producing MgO/MWCNT/rGO-incorporated AAECs with enhanced thermal properties. Full article

In order to meet the demand for structural/functional integrated materials in the field of electromagnetic shielding, a graphene nanosheets (GNSs) reinforced magnesium matrix composite was fabricated using an electrophoretic deposition and subsequent accumulative roll bonding process (ARB). The microstructure, mechanical properties, and electromagnetic interference (EMI) shielding effectiveness (SE) of the GNSs/Mg composites were characterized systematically. The results showed that synergistic strengthening of the mechanical properties and EMI shielding performance of the composites was realized. The strengthening mechanisms for the mechanical and EMI shielding performance of the GNSs/Mg composites were analyzed thoroughly. After five passes of ARB, the ultimate tensile strength and elongation were 271.79 MPa and 12.9%, respectively. For the laminated structure, the strengthening is related to the thickness of the graphene layer, the dispersion, and the interfacial bonding with the metal matrix. In electromagnetic shielding aspects, after ARB-5, the SE is 93.36–105.15 dB. The introduction of well-organized multivariate multi-scale macro–micro interfaces increased the electromagnetic wave propagation paths and multiple reflection loss absorption in the internal propagation paths. Moreover, the addition of carbon nanomaterials led to an increase in the number of interfaces, which was conducive to the expansion of the internal reflection paths; carbon nanomaterials at the interfaces also improved the electromagnetic wave absorption. Full article

Traditional magnesium structural materials are used widely due to their light weight; however, their corrosion resistance is poor. In order to address this problem and improve the strength simultaneously, SiCp-, SiCnp-, and SiCnw-reinforced Mg-2Zn-0.1Y (wt. %, MZY alloy) matrix composites (SiC/MZY composites) with the same contents (0.3 wt. %) were prepared and extruded at low temperature in this paper. The effects of SiC morphology on the microstructure, mechanical properties and corrosion resistance of MZY alloy were studied. The results show that the grain size can be refined by adding SiC reinforcement. Compared with the unreinforced MZY alloy, the strengths of the SiC/MZY composites were all improved, with a yield strength of more than 440 MPa and an ultimate tensile strength of more than 450 MPa. However, only the corrosion rate of the composites reinforced by submicron SiCp was improved significantly. The hydrogen evolution corrosion rate (P_H) was reduced by 81% relative to the MZY alloy. This can be attributed to the decreased galvanic corrosion pairs, as well as the decreased potential difference between the second phase and the matrix in the SiCp/MZY composite. Additionally, a compact product film on the surface of the SiCp/MZY composite can also protect the matrix. The materials prepared in this study showed excellent strength and high corrosion resistance at relatively low cost, providing valuable insights and design ideas for the development and application of those materials in marine and offshore engineering applications. Full article

Thirty-two ambient cured alkali-activated engineered composites (AAECs) were developed by incorporating MgO, multi-walled carbon nanotubes (MWCNTs), reduced graphene oxide (rGO), and polyvinyl alcohol (PVA) fiber with a one-part dry mix technique using powder-based activators/reagents. The effects of material variables, namely binary or ternary combination source materials (fly ash C or F and ground granulated blast furnace slag ‘GGBFS’), two types of reagents with varying chemical ratios and dosages of additives (from 0 to 5% MgO and from 0 to 6% MWCNT/rGO), on the physical (slump flow, flow time, flow velocity, and density), hardness (compressive strength from 0 to 180 days and 28-day ultrasonic pulse velocity ‘UPV’), and micro-structural (SEM/EDS, XRD and FTIR) properties were evaluated. All these variables, individually or combined, influenced the properties and microstructural aspects of AAECs. Problems associated with the dispersion and agglomeration of nanomaterials, which could disrupt the microstructure and weaken its mechanical/physical properties, were avoided through the use of defined ultra-sonication with a high-shear mixing protocol. All AAECs achieved a 28-day compressive strength ranging from 26.0 MPa to 48.5 MPa and a slump flow > 800 mm, satisfying the criteria for flowable structural concrete. The addition of 5% MgO and up to 0.3% MWCNT/rGO increased the compressive strength/UPV of AAECs with MgO-MWCNT or rGO combination provided an improved strength at a higher dosage of 0.6%. A linear correlation between compressive strength and UPV was derived. As per SEM/EDS and XRD analyses, besides common C-A-S-H/N-C-A-S-H or C-A-S-H/C-S-H gels, the addition of MgO led to the formation of magnesium-aluminum hydrotalcite (Ht) and M-S-H (demonstrating self-healing potential), while the incorporation of rGO produced zeolites which densified the matrix and increased the compressive strength/UPV of the AAECs. Fourier transform infrared spectrometer (FTIR) analysis also suggested the formation of an aluminosilicate network in the AAECs, indicating a more stable structure. The increased UPV of MWCNT/rGO-incorporated AAECs indicated their better conductivity and ability of self-sensing. The developed AAECs, incorporating carbon-nano materials and MgO additive, have satisfactory properties with self-healing/-sensing potentials. Full article

The Maillard reaction (MR) between sugars and amino acids, peptides, or proteins is understood to occur gradually during the production and aging of sparkling wines, where it contributes to caramel, roasted, and toasted aromas. Divalent metal ions can accelerate the MR, although this has not been previously reported in wine or wine-like conditions. In this work, the effect of calcium (Ca) and magnesium (Mg) ions on the concentration of 10 Maillard reaction-associated products (MRPs) was measured in modified sparkling base wine during accelerated aging at 50 °C for four weeks. Chardonnay base wine was modified by the addition of fructose (0.02 M) and a single amino acid (lysine, glycine, cysteine; 0.01 M) in combination with Ca²⁺ or Mg²⁺ at zero, low (10 mg/L), or high (50 mg/L) dose levels. MRPs were quantified by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC/MS), sugar concentration was measured by enzymatic assay, and amino acids and free metal ions were monitored by capillary electrophoresis. Fructose levels did not substantially decrease during aging despite increases in all MRPs, suggesting that trace sugars or α-dicarbonyl species present in the wine matrix likely play a greater role in MRP formation than fructose. Aging duration and amino acid content had a greater effect than metal addition on the composition of the MRPs. Treatments containing cysteine and 50 mg/L Ca²⁺ had elevated concentrations of benzaldehyde and furfural ethyl ether following 4 weeks of accelerated aging. This work identified key MRPs that increase during base wine accelerated aging and informs future research on the relationship between wine composition and aging markers. Full article

Background: Bone regeneration remains a challenging issue in tissue engineering. The use of hydrogels as scaffolds for bone tissue repair has gained attention due to their biocompatibility and ability to mimic the extracellular matrix. This study aims to develop a functionalized GelMA/CMCS composite hydrogel incorporating magnesium phosphate cement (MPC) for enhanced bone regeneration. Methods: These composites were developed by incorporating potassium magnesium phosphate hexahydrate (KMgPO₄·6H₂O, MPC) powders into methacrylated gelatin/carboxymethyl chitosan (GelMA-C) hydrogels. The material’s mechanical properties, antibacterial performance, and cytocompatibility were evaluated. In vitro experiments involved cell viability and osteogenic differentiation assays using rBMSCs as well as angiogenic potential assays using HUVECs. The hydrogel was also assessed for its potential in promoting bone repair in a rat (Sprague-Dawley) model of bone defect. Results: The developed GelMA-CM composite demonstrated improved mechanical properties, biocompatibility, and osteogenic potential compared to individual GelMA or CMCS hydrogels. Incorporation of MPC facilitated the sustained release of ions which promoted osteogenic differentiation of pre-osteoblasts. In vivo results indicated accelerated bone healing in the rat bone defect model. Conclusions: The functionalized GelMA-CM composite could be a viable candidate for clinical applications in bone regeneration therapies. Full article

The reinforcing effect of β-Mg₁₄YNd₂ precipitates and SiC whiskers has been evaluated in a WE54-15%(vol.%)SiC_w composite using synchrotron radiation diffraction during compression tests from room temperature to 300 °C. The addition of SiC whiskers slightly increases the yield stress compared to an unreinforced WE54 alloy. However, whiskers are not effective in increasing the temperature at which the mechanical strength of the unreinforced WE54 alloy begins to decay. The plastic deformation process is controlled by the magnesium matrix over the entire compression temperature range. On one hand, β-Mg₁₄YNd₂ precipitates assume an additional transferred load from the magnesium matrix just after the yield point in both the WE54 alloy and WE54-15%SiC_w composite. The magnitude of transferred load becomes smaller as the temperature increases due to the relaxation process around precipitates. On the other hand, the reinforcing effect of SiC whiskers is greater than that of β-Mg₁₄YNd₂ precipitates, although its effect also tends to disappear at temperatures equal to or higher than 200 °C. Full article