Search Results (703)

To develop a high-performance inorganic fireproof coating suitable for steel structures, this study utilized magnesium phosphate cement (MPC) as the matrix and introduced expanded perlite (EP) as a lightweight aggregate. The effects of EP content (40–55%) and magnesium-to-phosphorus ratio (M/P = 4:1–7:1) on the dry density, compressive strength, bond strength, and fire resistance of the coating were systematically investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to reveal the phase evolution and microstructure evolution mechanisms at high temperatures. The results indicate that increasing EP content significantly reduces the dry density and thermal conductivity of the coating, enhancing thermal insulation performance. However, excessive incorporation leads to the deterioration of mechanical properties, with an optimal EP content of 45%. The M/P ratio influences the interfacial bond strength and high-temperature structural stability by regulating the proportion of the hydration product K-struvite (KMgPO₄·6H₂O) and residual MgO. Compressive strength peaked at M/P = 6:1 (0.80 MPa), while bond strength was optimal at M/P = 5:1 (0.097 MPa), corresponding to the best fire resistance (back-side temperature of 180.4 °C). At high temperatures, K-struvite dehydrates and transforms into anhydrous KMgPO₄, which, together with residual MgO and crystallized SiO₂ from EP, forms a dense ceramic skeleton, ensuring the structural integrity of the coating. Comprehensive performance evaluation determined the optimal mix ratio as M/P = 5:1 and EP content = 45%. The coating with this ratio exhibits a dry density of approximately 560 kg/m³, a 14-day compressive strength of 0.53 MPa, a bond strength of 0.097 MPa, and a back-side temperature of 180.4 °C under flame exposure, demonstrating a favorable balance of lightweight character, mechanical integrity, and thermal insulation performance suitable for steel structure fire protection applications. Full article

A method has been developed to delaminate the organic components (paint, foam) from the steel skins of composite polyisocyanurate (PIR) steel insulation panels at ambient temperature and in 20 min using selected solvents combined with ultrasonication. Using this method, polyisocyanurate foam can be selectively delaminated from polymer-based paint (PVC plastisol) and, in turn, the polymer paint can be selectively delaminated from the galvanised steel. Both the foam and paint are removed as intact layers, leaving the galvanised steel intact for the next steps of recycling, enabling the subsequent individualised recycling of each sub-component or layer. Several solvents have been tested, and the data show that H-bonding solvents (e.g., H₂O, alcohols) are less effective at delaminating these polymers. Whilst high polarity, medium H-bonding acetonitrile and DMSO remove PVC paint and some PIR foam, the most effective solvent for both PIR foam and PVC paint removal is medium polarity, medium H-bonding acetone. Full article

Flashover events can induce rapid surface condition changes on outdoor ceramic insulators, while early-stage degradation is typically assessed indirectly through long-term ageing or electrical diagnostics. This study proposes an event-based, surface-focused evaluation framework to assess short-term flashover-induced surface degradation using normalized wettability indicators. A controlled experimental comparison was conducted on uncoated, TiO₂-RTV-coated, and SiO₂-RTV-coated 150 kV ceramic insulators subjected to a single flashover pre-stress under humid tropical conditions. Static contact angles decreased from 42.6° to 18.3° for uncoated ceramic, from 112.4° to 86.7° for TiO₂-RTV, and from 115.8° to 92.6° for SiO₂-RTV after flashover exposure. The corresponding relative wettability retention values were 43.0%, 77.1%, and 80.0%, while the wettability degradation index values were 0.57, 0.23, and 0.20, respectively. Surface morphology and elemental presence were qualitatively examined via SEM–EDS. The results show that both nanocomposite coatings effectively preserve post-flashover surface hydrophobicity compared with uncoated ceramics, with the SiO₂-RTV system exhibiting the highest short-term wettability retention. By integrating static contact-angle measurements, qualitative surface morphology, and normalized wettability indicators, this study proposes an event-based evaluation framework for RTV-coated ceramic insulators. Flashover-voltage and leakage-current measurements were included only as supplementary validation to support the surface-based interpretation, without implying direct electrical performance modeling. This surface-focused, event-based approach provides an experimental basis for post-flashover condition assessment of ceramic insulators operating in humid outdoor environments. Full article

With the rapid development of electrified railways in high-altitude regions, section insulators in catenary systems frequently experience gap breakdown and surface flashover under low atmospheric pressure conditions, posing serious threats to safe train operation. This paper investigates the discharge mechanisms of section insulators in high-altitude environments and conducts research on discharge characteristics under extremely non-uniform electric fields, along with structural optimization. First, the physical mechanisms of gap discharge and surface flashover in section insulators are analyzed. A three-dimensional electric field simulation model of the section insulator is established, and numerical analysis is performed to reveal the electric field distribution characteristics. The results indicate that the electric field is predominantly concentrated at the junction between metal electrodes and insulators, as well as at the tip of the arcing horn. The local maximum field strength reaches 3.84 × 10⁵ V/m, exceeding the corona inception field strength of air, which readily induces discharge. Subsequently, power frequency and lightning impulse discharge tests are conducted in both plain region and regions at an altitude of 4300 m. The results show that under high-altitude conditions, the power frequency breakdown voltage decreases by 28%, and the 50% lightning impulse breakdown voltage decreases by 42%. The discharge voltages under standard atmospheric conditions are obtained through correction. Finally, optimization schemes involving arcing horn structural modification and surface coating application are proposed. Adjusting the arcing horn angle to 55° and adding a grading ring structure with a radius of 70 mm reduces the local maximum field strength by 26%. After applying an RTV insulating coating, the field strength at the junction decreases by 35.9%, effectively enhancing the insulation performance of section insulators in high-altitude regions. Full article

Olive pomace biochar, obtained through the pyrolysis of lignocellulosic biomass, has emerged as a sustainable and multifunctional additive for polymer composites. Its physicochemical properties, including porosity, surface area, and electrical conductivity, can be tailored by controlling feedstock type and pyrolysis conditions. Although mechanical reinforcement and thermal stability improvements are well documented, the influence of biochar on surface-related properties such as wettability and contact angle remains insufficiently explored for environmentally relevant composite systems. In this study, epoxy-based composites containing biochar synthesized at 750 °C were evaluated in terms of their water interaction behavior by monitoring the evaporation dynamics of ultra-pure water droplets (10 μL, 0.055 mS/cm conductivity) at eight time intervals between 20 and 580 s using high-resolution digital microscopy. Image enhancement and segmentation were performed prior to Discrete Cosine Transform (DCT) analysis to describe droplet geometry in the frequency domain. Time-dependent variations in the standard deviations of DCT coefficients were optimized using the Bat Algorithm, resulting in mathematical models capable of accurately representing droplet evolution and surface–fluid interactions. The primary novelty of this study lies in the development of a hybrid experimental–computational framework that integrates droplet-based wettability measurements with signal-domain analysis and metaheuristic optimization. Unlike conventional studies focusing solely on material characterization, this approach establishes quantitative relationships between surface behavior and numerical descriptors derived from DCT and the Bat Algorithm. The proposed methodology provides a data-driven tool for predicting wettability trends in biochar-reinforced composites and supports the development of moisture-resistant materials for coatings, packaging, and thermal insulation applications within the context of sustainable composite design. Full article

Thermal barrier coatings (TBCs) are an effective means of providing thermal insulation and protecting the hot-section components of gas turbine engines. Their quality and performance characteristics largely depend on the microstructural features and the bond strength between the bonding layer and the substrate. The present study aims to determine the optimal plasma spraying parameters that ensure the formation of NiCrAlY coatings with superior microstructural integrity and adhesion strength. The objective of the study is a thermally sprayed nickel–chromium–aluminum–yttrium (NiCrAlY) bond coat deposited onto an Inconel 718 nickel-based superalloy, which is widely used in aircraft gas turbine engines due to its high strength and excellent oxidation resistance at elevated temperatures. It was found that the coating produced under the optimized conditions exhibited a significantly higher adhesion strength compared with the samples obtained under other spraying regimes. The results confirm that a precise adjustment of the atmospheric plasma spraying (APS) process parameters, taking into account the equipment configuration, allows for a substantial improvement in coating quality and performance. Full article

Geopolymer coatings exhibit outstanding corrosion resistance, high-temperature performance and thermal insulation. This thus holds broad application prospects in anti-corrosion of metals, protection of building structures, and functional coatings. However, the large-scale application of geopolymers is constrained by the availability of precursor materials. In South China, construction waste soil is predominantly composed of weathered residual soil of granite (WRSG), which is rich in silicate and aluminosilicate minerals. This soil can serve as a precursor for geopolymer synthesis upon activation. In this study, geopolymers were prepared using activated WRSG as the precursor material. The mix proportion of the geopolymers was optimized through single-factor experiments. Additionally, the hydration process and products of the geopolymer were characterized. The experimental results show that both high alkali content and low water-to-soil ratio contribute to achieving high compressive strength. The geopolymer has early strength characteristics. Its one-day compressive strength can reach 48% of 28-day value. The hydration products of the geopolymer mainly consist of amorphous sodium–aluminum–silicate–hydrate gel and primary minerals such as quartz and albite. With the increasing age, the content of chemically combined water and gel clusters grows, which densifies the microstructure and elevates the degree of hydration reaction of geopolymers. Full article

A nano-TiO₂-modified silicone-based reflective thermal insulation coating is successfully synthesized. The influence of the nano-TiO₂ content on the microstructure, adhesion strength as well as near-infrared reflectivity (NIR) of the coatings before and after heat treatment is investigated. The results demonstrate that the coating is an organic/inorganic composite coating composed of muscovite, rutile-phase titanium dioxide and an organosilicon binder before heat treatment. The addition of an appropriate amount of nano-TiO₂ helps fill the pores in the coating, resulting in a dense coating and improved adhesion. Meanwhile, due to the reduced average size of the pigment, the reflectance of the coating is maintained or enhanced. When the addition amount is 5.0 wt.%, the coating achieves the highest bonding strength of Grade 1 with a reflectivity of 0.830. After heat treatment at 1000 °C for an hour, the coating transforms into an inorganic coating composed of partially melted muscovite and rutile-phase TiO₂. The nano-TiO₂ promotes the formation of a molten phase, which further increases the coating density and makes the surface smoother. Consequently, the coating’s bonding strength and reflectance are further improved, reaching Grade 0 and 0.945 respectively. Full article

Accelerating decarbonization in hot-climate buildings requires integrated retrofit strategies that address energy performance, environmental impact, thermal comfort, and economic feasibility within a unified decision framework. This study develops and validates a simulation-driven multi-criteria approach to evaluate retrofit packages across three representative ASHRAE hot sub-climates (1B, 2B, 2A). An academic building was modeled using DesignBuilder (Stroud, UK) and validated in accordance with ASHRAE Guidelines. The retrofit analysis integrates envelope enhancements (insulation and reflective coatings), glazing-integrated photovoltaics (GIPV), rooftop photovoltaics (RTPV), and a Dedicated Outdoor Air System (DOAS). The performance evaluation incorporates dynamically simulated energy consumption, operational CO₂ emissions, thermal comfort indicators (PMV and DCH), and techno-economic metrics (IRR, ROI, PBP). Weighting factors were derived from a structured stakeholder consultation to reflect context-sensitive sustainability priorities. The results indicate energy reductions of approximately 51–57% and carbon emission reductions of 40–53% across the examined zones, while discomfort hours decreased by roughly 42–46%. This demonstrates significant improvements in thermal comfort under integrated retrofit strategies, particularly with DOAS integration, highlighting the importance of ventilation-driven comfort enhancement. Economic feasibility was climate-dependent; envelope-focused solutions yielded high returns, while integrated strategies delivered balanced environmental and economic performance. The proposed framework enables systematic, climate-specific prioritization of retrofit alternatives and supports scalable, economically viable NZEB transitions in rapidly expanding hot-climate educational infrastructure. Full article

An innovative preparation route for iron-based soft magnetic materials is presented, focusing on the influence of the mechanical surface treatment of powder particles on their structural and magnetic properties. High-purity Fe (99.98% purity) and FeNiMo (supermalloy) powders were mechanically milled (ball-to-powder ratio of 6:1; 120 min), surface-treated by controlled milling, coated with an inorganic SiO₂ insulating layer, and subsequently compacted into ring-shaped specimens. Structural characterization was carried out using optical microscopy and scanning electron microscopy. Magnetic properties were evaluated by hysteresis loop measurements, initial magnetization curves, and coercivity analysis at 200 K. The results demonstrate that mechanical surface treatment improves the homogeneity and continuity of the SiO₂ insulating layer. This improvement leads to reduced coercivity from 2100 to 1980 A·m⁻¹ for Fe powders, while FeNiMo powders showed a decrease from 1990 to 1910 A·m⁻¹, along with lower energy losses. The proposed method provides a laboratory-scale approach for studying the influence of powder surface treatment on the magnetic behavior of Fe-based soft magnetic composites. Full article

This paper introduced a simple, efficient method to prepare mechanically strong lignin-based foams (lignofoams) with open-cell structures using a facile baking technique. The self-expansion of lignin occurred without any additional chemical blowing agents, foaming agents, plasticizers, or lubricants. During heating, kraft lignin softened, and the internal water, either initially adsorbed or generated in situ through the dehydration of hydroxyl groups, acted as a natural blowing agent for foaming a porous foam structure. Incorporating a small amount of polypropylene (PP) enhanced mechanical properties by coating the inner walls of open cells. The porous, softened composite was then cooled to room temperature and solidified into the self-expanded lignofoam. The resulting lignofoams exhibited tunable densities ranging from 0.21 to 0.49 g/cm³ and a maximum compressive strength of 3.6 MPa. The lignofoam also showed excellent thermal insulation properties with low thermal conductive coefficients (0.057–0.098 W/mK). These features highlight the great potential of lignofoam for a bio-based thermal insulation material for construction applications. Full article

Thermal insulation is necessary for deepwater wells to achieve safe and effective production. Based on the comparison of different thermal insulation measures and the control requirements, this paper proposes two indicators to analyze thermal insulation performance. A model is established by considering the wellbore radial thermal resistance and wellbore-formation heat transfer process in order to calculate the two indicators. The analysis shows that there exists an overlapping effective range between vacuum-insulated tubing and insulation-coated tubing, and a similar overlap is observed between insulating liquid and insulated tubing. When comparable insulation performance can be achieved, insulating liquid should be prioritized, while vacuum-insulated tubing should be considered only as the final option. Under high production or a high geothermal gradient, annular temperature change is the primary control objective, whereas under low-production or low-temperature conditions, wellhead temperature becomes the dominant control target. The combination of insulated tubing and insulating liquid exhibits pronounced synergistic effects. In the case of a well under high-temperature and high-production conditions, the composite insulation reduces annular temperature change by 64.26%, and in low-temperature, low-production wells, it increases wellhead temperature by 100.43%. In practical applications, insulating fluids should be preferred, with insulated tubing employed as a supplementary measure. Full article

The use of sustainable building materials is becoming increasingly important in order to reduce their environmental impact. This article draws attention to the lack of life cycle assessment (LCA) of building façades, which would take into account national conditions. The aim of the work is to assess the environmental impact of various building façade solutions. The analysis concerned a ventilated façade on an aluminum substructure with a fiber cement board and external thermal insulation composite system (ETICS) with expanded polystyrene (EPS). The assessed façades differed with regard to the used insulation materials. The study aims to select more ecological façades, while at the same time taking into account national conditions, which is important at the stage of designing a building. The study also aims to fill a gap in the existing literature by providing information concerning the environmental analysis of building façades based on real data. Based on a comparative analysis, it was shown that ETICSs with EPS have higher façade-damage category indicators in all impact categories except for eutrophication, human toxicity (carcinogenic and non-carcinogenic), and resource use related to minerals and metals, for which the ventilated façade shows higher values. Additionally, hot-spots for the analyzed façades were also presented. In the case of a ventilated façade, the determinant is the used insulating material, which is mineral wool. In the case of ETICS, it is the finish coat. For the first time in Poland, the LCA of a ventilated façade and ETICS was presented based on real data. The results of this study can be used as the first step of a full cradle-to-grave LCA for buildings. Full article

Intumescent fire-protective coatings based on epoxy binders are widely used to enhance the fire resistance of steel structures due to their high adhesion, mechanical strength, and durability. However, epoxy binders undergo exothermic thermo-oxidative degradation, which can adversely affect fire-protective performance. In this study, the effect of brominated epoxy resin content on the fire-retardant behavior of intumescent coatings was investigated using two systems: one initially supporting flame propagation and one inherently self-extinguishing. For the initially combustible coating, partial substitution of the epoxy diane resin with a brominated analogue at 12.5% resulted in complete self-extinguishing behavior according to UL-94, while higher substitution levels (≥50%) caused a 20–28% reduction in fire-protective efficacy as assessed by BS 476. For the initially non-combustible coating, a decrease in fire-protective performance of 15–20% was observed regardless of the substitution degree. Thermal analysis showed that coatings containing brominated resins exhibit an onset of thermal degradation approximately 80 °C lower than halogen-free analogues. FTIR and SEM analyses revealed that brominated resins alter the thermolysis mechanism, promoting the formation of oxygen-containing degradation products and a more heterogeneous, irregularly porous foamed char, thereby reducing its thermal insulation capacity. Overall, brominated epoxy resins exert a dual effect, improving self-extinguishing behavior while impairing fire-protective efficacy under prolonged thermal exposure. Brominated resin contents in the range of 10–50% represent a practical compromise, enabling self-extinguishing behavior while maintaining acceptable fire-protective performance. Full article

Observations of photoelectric conversion in Fe- and Mn-rich semiconductor mineral coatings highlight their potential role in the origin of life and the evolution of environmental conditions. However, natural silicate minerals, which make up most of the Earth’s crust, are generally considered wide-bandgap insulators and are not expected to exhibit a photoelectric effect. In this study, we experimentally confirm measurable impurity-like photoelectron activity in natural silicate minerals and explore possible regulatory mechanisms. We show that electron-active elements (e.g., structural Fe and Ti) and lattice defects in minerals such as pyroxene and mica can reduce the optical gap (E_opt) to below ~4.13 eV, producing small photocurrents ranging from 0.010 to 0.114 μA/cm² on ITO substrates (background signal excluded). The structural types of these minerals—chain, island, layer, and framework—may influence their photoelectric responses by affecting electron transport pathways. Notably, light wavelength strongly controls both the photoelectric relative activity (PRA = 3–10 for silicates) and the decay kinetics (0.002–0.021 s⁻¹) of minerals. Visible light (400–800 nm) markedly enhances photocurrent densities in low-bandgap minerals such as limonite (E_opt = 2.11 eV). In contrast, ultraviolet light (UVB, 300 nm) enhances photoelectric responses in high-bandgap minerals, including feldspar and quartz (E_opt = 4.31 and 6.08 eV, respectively). Multivariate statistical analysis further indicates that elemental composition governs spectroscopic features that influence photoelectric behavior. Among these, Fe, Al, Si, and Ti are identified as key regulatory elements. These results provide new insights into the role of natural silicates in photoelectron-driven environmental and geological processes and highlight the potential of silicate-based materials for solar energy conversion applications. Full article