Search Results (135)

This article presents the effect of laser alloying with boron on the surface layer of iron alloys: steel and grey cast iron. The general goal of this review is to specify the main differences that can be expected after this treatment of selected iron-based alloys. Boron as an alloying element is first characterized. The effects of laser alloying are described in comparison to diffusion processing. The next section describes the effect of laser alloying with boron on the microstructure, hardness, and wear resistance of the surface layer of selected iron alloys. As a result of the conducted analysis, the most significant differences in the outcomes of laser alloying with boron, which may occur during the processing of various iron alloys, are as follows: the presence of graphite in the surface layer in the case of grey cast iron treatment and a clearly visible transition zone between the alloyed zone and the hardened zone during the treatment of grey cast iron as opposed to steel; variable depths of the modified surface layer and varied grain size in the alloy zone depending on the thermophysical properties of the material being treated. Full article

Sustainable materials engineering necessitates the valorization of industrial by-products, such as coal fly ash, into functional, high-performance materials. This research addresses a core challenge in materials synthesis: establishing a deterministic technology for controlled porous structure formation to optimize the thermophysical properties of lightweight thermal insulation composites. The primary objective was to investigate the structural evolution kinetics during the high-intensity thermal processing of fly ash-based precursors to facilitate precise property regulation. We developed a novel, integrated process, underpinned by mathematical modeling of simultaneous bloating and non-equilibrium heat transfer, to evaluate key operational parameters within a vortex-layer reactor (VLR). This framework enables the a priori prediction of structural outcomes. The synthesized composite granules were subjected to comprehensive characterization, quantifying apparent density, total porosity, static compressive strength, and effective thermal conductivity. The developed models and VLR technology successfully identified critical thermal exposure windows and heat flux intensities of the heating medium required for the reproducible regulation of the composite’s porous architecture. This precise structure process control yielded materials exhibiting an optimal balance between low density (<400 kg/m³) and adequate mechanical integrity (>1.0 MPa). This work validates a scalable, energy-efficient production technology for fly ash-derived porous media. The established capability for predictive control over microstructural development provides a robust engineering solution for producing porous materials, significantly contributing to waste reduction and sustainable building practices. Full article

Urban densification intensifies urban heat islands (UHIs), leading to higher temperatures in cities which negatively affect residents’ health and comfort and increase energy consumption for air conditioning, thereby raising carbon emissions. Reducing UHIs is therefore essential. Phase change materials (PCMs) are a promising solution, as they can store and release significant amounts of thermal energy during phase transitions. Selecting paraffins with suitable properties is crucial for effective application. In this study, three paraffins (RT28HC, RT31, and RT35HC) with phase change temperatures of 28 °C, 31 °C, and 35 °C were characterized to evaluate their potential for summer UHI mitigation. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and measurements of thermophysical properties and density were performed. Results showed that RT28HC and RT35HC exhibit relatively simple and efficient phase transitions, while RT31 has a more complex mechanism with a wide phase change temperature range. During limited summer day–night temperature variations, RT31 may not fully crystallize, reducing the effective utilization of stored energy. These findings highlight the importance of selecting paraffins with appropriate phase change temperatures and thermal properties to optimize the performance of PCMs for urban heat mitigation. Full article

In the aerospace sector, integrating advanced materials with high mechanical capabilities represents the forefront of material science, especially in the field of rocketry. Bimetallic structures are increasingly used in aerospace applications due to their combination of high strength-to-weight ratio, thermal conductivity, and corrosion resistance. Among these, Inconel-copper (In718-Cu) systems are particularly promising, although large differences in thermophysical and mechanical properties between the two materials can induce residual stresses, cracks, and other interfacial defects, requiring careful process control. This study evaluates the fabrication of In718-Cu structures through Direct Energy Deposition (DED), in which In718 was deposited onto a copper substrate using an innovative deposition strategy. Interface quality and microstructure were characterized by SEM/EDS and X-ray diffraction, whereas the mechanical properties were evaluated by nanoindentation, indentation creep, and tensile testing. The results showed that crack-free samples can be achieved, with strong diffusion bonding at the interface and efficient precipitation strengthening on the copper side already in the as-built condition. A uniform distribution of precipitates and consistent penetration depth were also observed, confirming the effectiveness of the deposition strategy for producing reliable In718-Cu components. Full article

Steatotic liver diseases are increasing globally, with metabolic dysfunction-associated steatohepatitis potentially causing irreversible fibrosis progression. This study focuses on an ultrasonic diagnostic method for steatotic liver disease based on temperature dependence of sound velocity for tissue characterization. Since the temperature coefficient of sound velocity in liver is expected to decrease with increasing lipid accumulation, the temperature coefficient of sound velocity in tissue-mimicking material as a function of glycerol concentration was measured. It decreased as glycerol concentration increased, changing from positive to negative value at 37.5% glycerol concentration. Change rates in sound velocity by ultrasonic heating were then measured in vitro on liver left lobes of mice with steatotic liver induced by choline-deficient, L-amino acid-defined, and high-fat diet. There were positive values in the control group, whereas there were negative values in the steatotic liver group. In vivo measurements of mouse livers using an electrocardiogram-synchronized system showed similar results, with positive values in the control group and negative values in the steatotic liver group. Thermophysical properties can determine whether the liver is normal or steatotic. However, to estimate the lipid accumulation rate from the change rate in sound velocity, it is necessary to reduce the measurement variation. Full article

This study examines the thermal performance of phase change material (PCM)–metal foam composites under base heating, a configuration more relevant to compact thermal energy storage (TES) and electronics-cooling applications, compared to the widely studied side-heated case. Metal foams with pore densities of 10, 20, and 40 PPI, but identical porosity (volumetric value), were impregnated with two PCMs (paraffin RT55 and RT64HC) and tested under varying heat fluxes. The thermophysical properties of three PCMs (RT42, RT55, and RT64HC) were first characterized using the T-history method. A control case consisting of pure PCM revealed significant thermal lag between the heater and the PCM, whereas the inclusion of a metal foam improved temperature uniformity and accelerated melting. The results showed that PPI variation had little influence on melting completion time, while PCM type, viz., melting temperature, strongly affected duration. Heat flux was the dominant parameter: higher input power substantially reduced melting times, although diminishing returns were observed at elevated heat fluxes. An empirical correlation from the literature, originally developed for side-heated foams, was applied to the base-heated configuration and reproduced the main melting trends, though it consistently underpredicted completion times at high fluxes. Overall, embedding PCMs in metal foams enhances heat transfer, mitigates localized overheating, and enables more compact and efficient TES systems. Future work should focus on developing correlations for non-adiabatic cases, exploring advanced foam architecture, and scaling the approach for practical energy storage and cooling applications. Full article

This study evaluates the thermal performance of a prototype vacuum-tube solar cooker adapted to the climatic conditions of the Amazon region, Peru. Four grain types (Zea mays L., Triticum aestivum, Zea mays var. morochon, and Hordeum vulgare) were tested to assess temperature evolution, exposure time, and incident solar radiation. Hordeum vulgare was selected as a food model for calibration due to its well-characterized thermophysical properties and reproducible heating behavior. The results showed individual thermal efficiencies ranging from 19.3% to 35.3%, with an average of 27.3% across the three tubes. The most efficient treatment, obtained with Zea mays L., reached 180 °C under an irradiance of approximately 980 W/m². A direct relationship was observed between solar radiation intensity, exposure time, and thermal efficiency. These findings confirm that the proposed hybrid design combining a cylindrical parabolic collector with vacuum U-tubes achieves higher and more stable performance than conventional box-type cookers. The system allows complete grain cooking without fossil fuels, demonstrating its potential as a sustainable and low-cost solution for rural communities in the Andean Amazonian region, promoting clean energy adoption and reducing environmental impact. Full article

In this study, molybdenum disulfide (MoS₂)-based water nanofluids were prepared and stabilized using two surfactants with opposite charges: the cationic cetyltrimethylammonium bromide (CTAB) and the anionic sodium lauryl sulfate (SLS). Different MoS₂:surfactant ratios (1:1, 1:2, and 1:3) were examined to identify the optimal formulation ensuring stable dispersion. Stability was evaluated through dynamic light scattering (DLS), zeta potential, and UV–Vis spectroscopy analyses. The results showed that the MoS₂:SLS (1:3) nanofluid achieved the highest stability, characterized by a zeta potential of −38 mV and a mean particle size of approximately 290 nm. Thermophysical properties were then investigated for nanoparticle concentrations of 0.05, 0.1, and 0.2 wt%. The 0.1 wt% nanofluid exhibited the best performance, showing a thermal conductivity enhancement of about 49% and an increased specific heat capacity compared with pure water. This improvement is attributed to uniform nanoparticle dispersion and enhanced phonon transport. Overall, the results demonstrate that the anionic SLS surfactant at a 1:3 ratio effectively enhances the stability as well as the thermal performance of MoS₂–water nanofluids, making them promising candidates for thermal management and energy systems applications. Full article

The strategic positioning of heating and cooling segments within complex non-rectangular geometries has emerged as a critical engineering challenge across multiple industries in thermal management systems for electronic components. This analysis presents a numerical inspection of buoyancy-driven convective flow and thermal transport mechnisms of nanofluids in a parallelogrammic porous geometry. A single discrete heating–cooling segment has been placed along the slanting surfaces of the geometry. The mathematical model is formulated utilizing Darcy’s law, incorporating the Tiwari and Das approach to characterize the thermophysical properties of the nanofluid. The governing model equations corresponding to the physical process are solved numerically using finite-difference-based alternating direction implicit (ADI) and successive line over-relaxation (SLOR) techniques. Computational simulations are performed for various parametric conditions, including different nanoparticle volume fractions ($\varphi =0$–$0.05$), Rayleigh numbers ($Ra={10}^1$–${10}^3$), and parallelogram geometry ($\alpha$) and sidewall ($\gamma$) tilting angles ($-{45}^{°}\le \alpha \le +{45}^{°}$ and $-{45}^{°}\le \gamma \le +{45}^{°}$), while examining the effect of discrete thermal locations. The results reveal a significant decrement in thermal transfer rates with an increasing nanoparticle concentration, particularly at higher Rayleigh numbers. The skewness of the parallelogrammic boundaries is found to substantially influence flow patterns and thermal transport characteristics compared to conventional rectangular enclosures. Further, the discrete placement of heating and cooling sources creates unique thermal plumes that modify circulation patterns within the domain. The predictions suggest profound insights for optimizing thermal management systems by employing nanofluids in non-rectangular porous configurations, with potential applications in geothermal energy extraction, electronic cooling systems, and thermal energy storage devices. Full article

The paper presents comprehensive and complementary studies of the thermophysical properties of functional composite structures. The term functional in this case means the study of the structure while maintaining its post-production imperfections, as opposed to the study of material samples prepared solely for this purpose. The paper presents the results of experimental studies, followed by an analysis of thermophysical properties characterizing heat accumulation and anisotropic heat transfer of two types of utility composites. Composites with an epoxy matrix and two types of reinforcement, glass and carbon fibers, were studied. The research program included micro- and macrostructural analysis and comprehensive thermogravimetric, microcalorimetric and thermal diffusivity measurements. In the studies of heat transfer phenomena, the directional dependence of properties was considered. Attention was focused on maintaining high temperature resolution of measurements, and the effect of repeated temperature exposure was also determined. The results of the research are the determined quantitative and qualitative characteristics, including the temperature dependence of a set of thermophysical properties of the tested materials. Key findings include higher thermal stability and a significant thermal anisotropy ratio in the graphite-reinforced polymer composite compared to the glass-reinforced polymer composite, which exhibited a lower onset decomposition temperature. The results offer crucial data for engineering calculations, structural analyses, and defining operational limits. Analysis of the results provides insight into possible design and operational problems of real structures in relation to model data. Full article

The construction industry increasingly seeks sustainable solutions to reduce environmental impact and energy consumption. This study explores the innovative use of industrial sludge generated from the wastewater treatment of detergent manufacturing as a partial substitute for Portland cement in mortar production. The sludge, characterized by high SiO₂ (46.58%) and CaO (28.66%) content, was incorporated at substitution rates of 0% to 30%. Mortars were prepared and tested according to NF EN 196-1 standards for mechanical strength, and thermophysical properties were assessed using the Hot Disk TPS 1500 system. The results demonstrate that up to 20% sludge replacement maintains acceptable mechanical performance (compressive strength: 12.63 MPa at 28 days vs. 13.91 MPa for the control; flexural strength: 3.93 MPa vs. 4.65 MPa) while significantly enhancing thermal insulation. Thermal conductivity decreased from 1.054 W/m·K (0% sludge) to 0.797 W/m·K (20% sludge), and thermal diffusivity dropped from 0.6096 mm²/s to 0.504 mm²/s. XRD analysis revealed the formation of new phases, such as gismondine, indicating beneficial pozzolanic activity. These findings highlight the dual benefit of valorizing detergent sludge and improving building energy efficiency, offering an eco-efficient alternative to traditional mortars aligned with circular economy and low-carbon construction goals. Full article

This study investigates the use of bio-based polyurethane foams (PUFs) containing phase change material (PCM) microparticles as a sustainable alternative for the automotive sector. These foams are synthesized using polyols derived from waste cooking oil (WCO), aligning with circular economy principles. To evaluate the thermophysical properties of these materials and, more in general, their thermal behavior, the use of non-destructive thermographic techniques has been proposed. This technique enables a rapid, full-field thermal analysis without physical contact, making it especially suitable for porous and heterogeneous structures like foams. As a reference, both virgin and foams with PCM were characterized in terms of density and thermal conductivity using well-established methods. Then, Lock-in thermography has been used as the first attempt technique to investigate variations in thermal behavior due to different thermophysical material properties based on the thermal response in transmission configuration. The thermographic approach proves to be an effective tool not only for assessing thermal behavior but also for supporting quality control and process optimization of sustainable polymeric materials. Full article

The ${\gamma }^{\prime }$-Fe₄N system has a high technological relevance due to its multiple applications in the field of surface treatment against wear and corrosion of iron in steel parts, as well as in the manufacturing of high-density magnetic recording devices, and so on. In the present work, we present a wide research of the structural, elastic, magnetic, vibrational, and thermophysical properties by means of the phonon analysis. For these purposes, we have compared theoretical and experimental results. The theoretical data were obtained by employing ab initio electronic structure calculations in the framework of density functional theory (DFT), and different experimental measurements, such as X-ray diffraction, magnetization measurements, and calorimetric techniques, were used to characterize the ${\gamma }^{\prime }$-Fe₄N system. The resulting comparison showed an excellent agreement between the theoretical and experimental data reported. Full article

The use of astaxanthin (AST) is expanding from its origins as a food coloring to health-related applications. This paper evaluates the efficiency of its extraction from dried Xanthophyllomyces dendrorhous using two combined and consecutive techniques. First, cell membrane permeation is achieved with the application of pulsed electric fields (PEFs). Solid–liquid extraction is then performed with hydrophobic eutectic solvents (hESs) prepared by mixing components of essential oils (linalool, l-menthol, eugenol, geraniol, cinnamyl alcohol, or thymol) and oleic acid. The hESs were characterized by measuring of several thermophysical properties at 25 °C and 0.1 MPa. An initial screening was performed to choose the best solvent and the extraction conditions (composition, extraction time, and temperature) were evaluated using the response surface methodology. The results showed the importance of the electroporation as a preliminary step to the extraction. The more hydrophobic and less compact the hES, the more effective the solvent. Thus, the equimolar mixture of l-menthol and oleic acid achieved an efficiency of 77% for untreated biomass, 83% for that treated with PEF, and 92% for that treated with PEF and later incubated. Molecular dynamics simulations demonstrated the importance of the hydrophobic interactions between AST and the components of the best solvent. Full article

This study explores the thermophysical properties and crystallization behavior of two industrial Mold Fluxes (MF1 and MF2) used in continuous steel casting. Viscosity, density, and surface tension were measured using the Rotating Bob Viscometry (RBV) and the Maximum Bubble Pressure (MBP) method, while crystallization dynamics were assessed via the Single Hot Thermocouple Technique (SHTT). Both fluxes showed temperature-dependent viscosity with distinct break temperatures influenced by chemical composition. MF1 had higher viscosity and activation energy (127.72 kJ mol⁻¹) than MF2 (112.11 kJ mol⁻¹) due to its higher Al₂O₃ content. Density and surface tension decreased linearly from 1523 to 1623 K, with values of 2642–2618 kg m⁻³ and 299–291 mN m⁻¹ for MF1, and 2708–2656 kg m⁻³ and 348–305 mN m⁻¹ for MF2. Crystallization analysis showed that MF1 required higher cooling rates (critical cooling rates: 21 K s⁻¹ vs. 18 K s⁻¹ for MF2) for glass formation, highlighting its greater glass-former content. Full article