Search Results (11,258)

With the capacity of generators continuing to increase, higher demands are placed on the heat dissipation of epoxy resin (EP), the main insulation material used in stator bars and windings. To overcome its low thermal conductivity, a multiscale hybrid filler strategy was adopted to investigate the effects of spherical Al₂O₃ (10 and 1 μm), platelet BN (1 μm), and SiO₂ (50 nm) on the thermal and insulating properties of EP composites. Unlike conventional studies focusing on individual fillers, this work highlights the synergistic design of fillers with different sizes and morphologies. The filler ratios were optimized by finite element simulation, and the composites were prepared by melt blending. The results show that, at a total filler loading of 38.5 wt%, the EP composite filled with spherical Al₂O₃ particles of 10 and 1 μm, platelet BN of 1 μm, and nano-SiO₂ of 50 nm achieves a thermal conductivity of 0.5497 W/(m·K), corresponding to an increase of 158.2% compared with pure EP (0.2129 W/(m·K)). This enhancement is attributed to the synergistic effect of multiscale and multishape fillers, where large Al₂O₃ particles form the main thermally conductive framework, small Al₂O₃ particles fill the gaps, platelet BN acts as a bridging filler, and nano-SiO₂ improves the interfacial region. In addition, the composite exhibits low relative permittivity and dissipation factor tanδ in the frequency range of 10⁻²–10⁶ Hz, and its breakdown strength reaches 65.99 kV/mm. These results demonstrate that simulation-guided multiscale hybrid filler design is an effective strategy for improving the thermal conductivity of EP while maintaining acceptable insulating performance. Full article

Polyester resin biocomposites containing biochar have attracted attention for improving mechanical strength and thermal stability while promoting sustainability. The pyrolysis temperature of biochar and its proportion in the polymer matrix are key factors affecting biocomposite performance. This study examined how biochar pyrolysis temperatures (400, 600, 800 °C) and incorporation levels (10, 20, 30 wt.%) influence the physical, chemical, mechanical, flammability, and morphological properties of polyester-based biocomposites. The samples were analyzed for density, water absorption, FTIR, XRD, flexural and tensile strength, ignition time, structural degradation, volumetric loss, and SEM microstructure. Biocomposites with 30 wt.% biochar produced at 800 °C showed the best mechanical properties, with a flexural strength of 95.3 MPa and an elastic modulus of 4417.4 MPa, representing increases of 14.5% and 45.7%, respectively, over the control. FTIR and XRD results revealed decreased aliphatic groups and increased aromaticity at higher pyrolysis temperatures, improving interactions between the matrix and biochar. These biocomposites also demonstrated enhanced thermal stability, with an ignition time of approximately 963 s, delayed structural degradation, and reduced volumetric loss (~19.3%). Overall, pyrolysis temperature and biochar content significantly influence the structural, mechanical, and thermal properties of polyester biocomposites, showing that biochar serves as a sustainable, performance-enhancing component in thermoset polymer matrices. Full article

The use of resin-based composite imitating gum tissue enhances the aesthetics of fillings located below the physiological gum line. The shear bond strength (SBS) between the gum-imitating composite and the traditional composite with different surface preparation methods was examined. The aim of the study was to evaluate which base material—G-aenial Universal Injectable (GC, Japan, flow) or G-aenial A’CHORD (GC, Japan, paste)—performs better, as well as to determine the most effective preparation method among sandpaper (control), 36% orthophosphoric acid (H₃PO₄), sandblasting, and 9.5% hydrofluoric acid (HF). The tested gum-imitating material was Amaris Gingiva (VOCO, Germany). The connection between the composites was evaluated using a Z005 (Zwick-Roell) universal device. Surface tests were carried out using an SJ-410 (Mitutoyo) profilometer. Evaluation of the prepared surface structures was performed using scanning electron microscopy (HITACHI S-4700). Etching with HF significantly improved the shear bond strength between composites. Sandblasting also enhanced the adhesion results, but the H₃PO₄ group achieved comparable results to the control group. However, since HF is not recommended for intraoral use, sandblasting (30 μm aluminum oxide particles applied with three passes at constant speed under a pressure of 2 bar from 1.5 cm) appears to be the most suitable clinical alternative. Full article

Artificial composite stones have recently attracted attention as multifunctional materials for construction and defense-related applications. In this study, a novel composite stone was developed using waste limestone as the primary mineral filler, combined with an unsaturated polyester resin matrix and reinforced with glass powder and chopped glass fibers. The influence of binder content and reinforcement type on physico-mechanical and microstructural behavior was investigated. Experimental characterization included water absorption, compressive strength, abrasion resistance, acid resistance, and optical microscopy. The results demonstrated that fine fillers improved matrix densification and reduced porosity, while short glass fiber reinforcement enhanced load-bearing capacity. Abrasion resistance and durability were found to depend on binder content and particle packing characteristics. Overall, the developed composite material exhibits promising mechanical performance, low water absorption, and improved durability, suggesting its potential as a candidate material for applications requiring environmental resistance, including potential use in defense-related camouflage applications. Full article

Resin 3D-printed molds are being increasingly favored for PDMS microfluidics across many disciplines. However, resin diversity, as well as secret manufacturer formulations, leads to a lack of standardization when using 3D printing for microscale applications. The impact of physical resin properties, both in its monomeric concoction and polymerized lattices at 100 µm or lower scales, needs quantification. We tested the performance of locally available resin formulations, isolating the impact of resin pigments and how it impacted the resin’s properties and performance. Lower resin viscosity improved feature fidelity (edge filleting < 25 µm) and improved resolution limit for recessed features, while cured polymer mechanical strength impacted the limit for positive mold features. We combined our findings to fabricate quality negative and positive mold structures in the mold and determined the best protocols associated with limitations during the fabrication of such structures. The methodologies in this study are expected to be widely applicable across various resin types and simplify the adoption of 3D printing protocols for specific feature fabrication in microscale molds for PDMS devices. Full article

With the requirement for reducing carbon footprint in engineering construction, porous vegetation concrete is increasingly receiving attention for use in completed slope restoration. Cemented soil is introduced after the completion of porous vegetation concrete stabilization and functions mainly as a revegetation substrate. An important consideration for cemented soil in this application is its ability to maintain strength and water stability and possess moisture retention capacity, without causing much increase in alkali release or diffusion. This present study investigated a newly developed twofold stabilization system involving both cement binders and organic waterborne epoxy resin to meet the requirements of synthetically enhancing slope stabilization and restoration. Changes in the unconfined compressive strength and water stability were analyzed, whilst mineralogical composition and microstructure characteristics were investigated. The results indicated that moderate incorporation of triethylenediamine (TETA)-cured epoxy resin (1–2% by soil mass) moderately reduced strength and increased water stability with controlled alkali release in cemented soil. Mineralogical and microstructural analysis revealed that TETA-cured epoxy resin retarded cement hydration and refined particle bonding, exhibiting less consolidated pore structure characteristics. The twofold stabilization was exceptional in enhancing structural stability exposed to repeated humidity variation, albeit it yielded increased strength reduction rate from <7% to 9–16% under UV irradiation. Potentials of calcium sulfoaluminate cement and Portland slag cement were also investigated. A pilot-scale vegetation trial with representative plant species gave general agreement with effects observed in the laboratory in alkali reduction and moisture retention. The results provided an ecological approach for better restoring completed slopes that were stabilized using porous vegetation concrete. Full article

In ultra-high-voltage GIS and GIL systems, epoxy resin insulators are still the mainstream choice. However, as a thermosetting material, epoxy resin is difficult to recycle after disposal, which limits its environmental benefits. Thermoplastic insulators, due to their recyclability, are potential alternatives. This study focuses on 30% glass fiber-reinforced PET and PA6 materials. Their injection molding behavior, hydraulic pressure performance, and insulation performance were systematically analyzed using Moldflow, ANSYS, and COMSOL, respectively. For injection molding, Moldflow simulations were conducted for filling, packing, and cooling stages. Melt temperature was varied from 260 to –310 °C (PET) and 250–300 °C (PA6), while mold temperature was varied from 80 to –130 °C (PET) and 70–120 °C (PA6). An optimization objective function, Y = Δp/20 + Δx/0.5 + Δs/1.8, was developed to determine optimal processing parameters. Based on this function, the optimal parameters identified are: PET at 290 °C melt temperature and 120 °C mold temperature; PA6 at 250 °C melt temperature and 70 °C mold temperature. For hydraulic testing, Moldflow–ANSYS coupled simulations were performed under 2.4 MPa pressure with the compliance criteria of bulk stress < 90 MPa and insert-contact stress < 20 MPa. PA6 passed within a processing window of melt temperature < 270 °C and mold temperature < 120 °C. PET failed under all tested conditions, with insert-contact stress ranging from 24.25 to 27.55 MPa, consistently exceeding the 20 MPa threshold. In terms of insulation performance, this paper utilizes COMSOL to study the electric field distribution of thermoplastic insulators in SF₆ GIS/GIL and provides optimization suggestions for insulator geometry design. This study systematically compares the injection molding processes and hydraulic pressure performance of PET and PA6 thermoplastic insulators. These results provide important process insights and design guidance for evaluating thermoplastic materials as potential alternatives to epoxy resin in GIS/GIL applications. Full article

The limited availability of high-quality timber and the increasing demand for wood-based panels have encouraged the exploration of alternative and sustainable lignocellulosic resources. Rattan waste is abundant in Indonesia; however, its low mechanical strength and limited durability restrict its direct application in composite materials. This study investigated the effect of furfuryl alcohol (FA) modification and different adhesive systems on the performance of rattan-based particleboard. Rattan particles were immersed in FA for 24 h and used to produce particleboards (300 × 300 × 10 mm) bonded with phenol formaldehyde (PF), melamine formaldehyde (MF), and urea formaldehyde (UF) adhesives at a resin content of 12%. The boards were manufactured under controlled hot pressing conditions and conditioned for 14 days prior to testing. Furfurylation significantly improved dimensional stability by reducing moisture content, water absorption, thickness swelling, and leaching, with anti-swelling efficiency values ranging from 43.25% to 71.06%. Some selected mechanical properties, including internal bonding strength, hardness, and screw holding power, were also enhanced. However, the modification showed limited influence on the modulus of elasticity and, in some cases, reduced the modulus of rupture. Among the adhesive systems, MF-bonded boards exhibited the most balanced mechanical performance. Furfurylation also produced darker and more uniform board surfaces. These findings indicate that furfurylated rattan particleboards are suitable for non-structural and decorative applications. Full article

The global expansion of wind energy increases the need for sustainable recycling strategies for glass fiber-reinforced plastic (GFRP) from end-of-life wind turbine blades (WTB). Mechanical recycling is currently the most economically and ecologically viable technology. This study compares post-industrial (PI) waste from laminate cutoffs and post-consumer (PC) GFRP waste from end-of-life WTBs to investigate the influence of waste origin, pretreatment of shredded GFRP, different particle sizes and various matrix formulations on the tensile modulus and tensile strength of pressed bulk molding compounds produced with virgin epoxy resin. Thermogravimetric analysis showed a fiber content of up to 70 wt.%, but the resin residues on the embedded glass fibers dimmish a sufficient bonding of the new matrix system. Finer GFRP fractions consistently yielded higher tensile modulus and strength, with PI and pretreated PC materials performing best. The findings of this study demonstrate that controlled particle size distribution, impurity removal and optimized resin viscosity are key factors to achieve reliable mechanical performance and enable high-value recycling routes for glass fiber composite waste. Full article

The miniaturization of medical ultrasound imaging transducers is currently limited by the thick backing layers required to dissipate backward acoustic energy. To address this, a novel hybrid composite backing material was developed by interpenetrating a three-dimensional open-cell nickel foam skeleton with a traditional tungsten-powder/epoxy-resin matrix. Two groups of composite samples with varying pores per inch (PPI) were fabricated, and their acoustic properties were systematically characterized. Experimental results indicated that the 100 PPI composite achieved macroscopic acoustic attenuation coefficients of 62.6 dB/cm at 5 MHz and 84.2 dB/cm at 7.5 MHz. These values are roughly three times higher than conventional backing materials, while maintaining a suitable acoustic impedance of 10.81 MRayl. A 5 MHz transducer utilizing a 5.0 mm layer of this proposed backing achieved a −60 dB two-way pulse-echo insertion loss, effectively eliminating backside interference with performance comparable to a 16.5 mm conventional backing. This structural strategy successfully reduces the required backing axial dimension by over 60% without compromising transducer bandwidth, offering a viable material solution for miniaturized ultrasonic transducers. Full article

The valorization of agricultural and food industry residues represents an important component of the circular bioeconomy, enabling the conversion of waste streams into value-added materials while mitigating environmental pollution. Spent coffee grounds (SCGs), a solid by-product generated during the extraction of coffee beans with hot water or steam, constitute an abundant lignocellulosic biomass residue. Due to their physicochemical properties, SCGs can be used as low-cost adsorbent materials for the treatment of metal-contaminated wastewater, offering a sustainable alternative to traditional synthetic resins. This review summarizes recent research on the application of SCGs for the removal of metal ions from aqueous systems. The adsorption performance of raw and modified SCGs, including materials obtained via carbonization and chemical functionalization, is comparatively evaluated. Furthermore, key operational parameters governing the adsorption process and the corresponding metal removal efficiencies are discussed. Full article

This study comparatively evaluated the influence of processing routes on the optical stability of three dental resin composites: a light-cured direct composite—G-ænial A’CHORD (LCC), a CAD-CAM milled composite—BreCAM.HIPC (MC), and a 3D-printed composite—Saremco Print Crowntec (PC). Specimens were analyzed before (T0) and after hydrothermal aging for 5000 (T1), 10,000 (T2), and 30,000 cycles (T3). Optical stability was assessed through the change in color (ΔE₀₀) and translucency parameter (TP) after aging and immersion in beverages. Surface topography was evaluated using atomic force microscopy (AFM), while Raman spectroscopy was employed to detect aging-induced molecular changes. After aging and staining, all composites exceeded the acceptability threshold for color change. ΔE₀₀ values of 6.8 ± 1.1 (PC), 4.6 ± 0.9 (MC), and 2.1 ± 0.9 (LCC), obtained after initial aging, further increased following prolonged immersion in coffee. After 1 day of immersion in Coca-Cola, MC exhibited the highest ΔE₀₀ values, which slightly exceeded the clinically acceptable threshold. Prolonged immersion (7 days) significantly increased staining for all materials. TP values significantly differed among materials, with the highest values detected for LCC (20.6 ± 3.6) and PC (19.1 ± 1.5) and the lowest values detected for MC (4.9 ± 0.8). Overall, the results demonstrated that ΔE₀₀ was strongly influenced by the processing route and surface topography, whereas changes in translucency parameter (TP) were predominantly governed by the intrinsic properties of the resin composites. Full article

To investigate the mitigation of high-pressure CO₂-induced degradation of wellbore cement sheath in Carbon Capture, Utilization, and Storage–Enhanced Oil Recovery applications (CCUS-EOR), conventional Class G oil well cement and modified cement systems incorporating graphene, waterborne epoxy resin, and a composite of waterborne epoxy resin with graphene were formulated. This study presents the original comparative investigation on the long-term carbonation resistance of graphene-modified, waterborne-epoxy-modified, and their composite-modified oil well cements under 130 °C and 7 MPa CO₂ partial pressure, filling the research gap of unclear synergistic effects of the two modifiers in high-temperature CCUS environments. The specimens were subjected to simulated downhole conditions, and key properties, including compressive strength and permeability, were evaluated. The underlying mechanisms were elucidated through material characterization techniques such as X-ray diffraction, X-ray computed tomography, and scanning electron microscopy. Results indicated that the waterborne epoxy resin–modified cement system exhibited superior long-term carbonation resistance, achieving a 90 d compressive strength retention rate of 84%. The graphene-modified cement showed a 90 d compressive strength retention rate of 65%, while the waterborne epoxy–graphene composite system only retained 39.7% of its compressive strength at 90 d due to negative synergistic effects. The enhanced durability of the waterborne-epoxy-modified cement is attributed to the formation of a continuous polymeric film, which acts as a protective barrier against CO₂ penetration. This study provides valuable insights for the design of CO₂-resistant cement systems in CCUS-EOR environments. Full article

This paper examines how forest by-products (potash, tar, resin and charcoal—PoTaRCh), with a special focus on charcoal production, are presented in contemporary heritage tourism and how different communication frameworks influence the audience’s perceptions and intentions in the context of low-carbon development. The research is based on a combined methodological approach. Qualitative analysis of 70 communication units from the field of heritage tourism identified three dominant communication frames: traditional heritage, ecological-educational frame and future-oriented low-carbon innovation. These findings served as the basis for the experimental part of the research, conducted through an online A/B test on a sample of 212 adult respondents interested in travel, cultural tourism and heritage-based experiences. The results of the experiment indicate that the low-carbon communication framework leads to statistically significantly higher levels of perceived relevance of PoTaRCh, visit intention and positive attitude towards sustainability compared to the traditional framework, with perceived relevance partially mediating these effects. The findings suggest that, although traditional communication patterns still dominate heritage tourism, the future-oriented low-carbon framework shows greater communication potential for attracting a sustainability- and future-oriented audience. By combining the analysis of communication content from several European countries and the experimental testing of communication frameworks, the research provides an empirical contribution to the understanding of the transition from the concept of heritage-as-preservation to heritage-as-transition in contemporary discourses of sustainable tourism. Full article

Engineered wood products manufactured with the durability and density of a Pinus radiata D. Don species usually do not achieve the mechanical properties of a structural material for construction; hence, the reinforcement of this kind of product is recommended, but the use of commonly used hazardous adhesives is a problem. Therefore, the primary objective of this research was to investigate the enhancement of various properties of glulam beams made from radiata pine through the application of a high-performance reinforcing composite, based on carbon fiber, polyvinyl alcohol, and other nanomaterials, at a laboratory scale. For this purpose, thermal and mechanical tests were performed in different composite formulations to choose the best ones and to manufacture the glulam beams, in which bending properties were measured. Based on the results, the samples reinforced with graphene stood out, and the samples mixed with epoxy resin presented statistically the same values of flexural stiffness and strength as the control samples elaborated with commercial wood adhesives. It is also important to highlight the performance of the samples M7 (PVA (7.5%) + NL (0.01%) + GP (0.01%) + NSiO₂ (0.01%)) and M8 (PVA (7.5%) + NL (0.01%) + GP (0.01%) + NTiO₂ (0.01%)), which are not mixed with epoxy resin and showed statistically the same flexural performance as epoxy resin, in terms of maximum load and displacement. As a conclusion, it could be said that this new high-performance composite could be a comparable alternative to hazardous commercial adhesives, by obtaining lower values, but close to those of the control sample, which are the most used when reinforcing wood products with engineering fibers. Full article