Search Results (229)

This paper reviews recent advances in modular permanent magnet (PM) machines and their associated thermal management strategies. It begins by examining developments in conventional PM machines and highlighting their limitations, particularly in fault tolerance and manufacturability. To overcome these challenges, modular stator configurations have been extensively investigated over the past decade. The review discusses the key advantages of modular PM machines, including improved torque density, efficiency, operational reliability, and enhanced fault-tolerant capability, supported by findings from recent studies. The paper then presents a comprehensive review of state-of-the-art thermal management techniques for PM machines, emphasizing their importance in maintaining performance, reliability, and durability under increasingly high-power densities and thermal stresses. Both passive and active cooling approaches are considered, including air cooling, liquid cooling, heat pipes, oil-spray cooling, shaft cooling, and emerging ferrofluid-based cooling technologies. Advances in thermal modelling and coupled electromagnetic–thermal optimization are also highlighted as important enablers for improving machine performance and efficiency. Furthermore, the review explores the interaction between stator modularity and thermal management, with particular attention to how modular machine architectures affect heat generation, thermal paths, cooling integration, and overall thermal performance. Finally, the paper identifies key research challenges and outlines future opportunities for the development of high-performance, thermally robust PM machines for next-generation energy and transportation applications. Full article

Grounding connectors critically influence the safety and long-term reliability of earthing systems through coupled electro-thermal, mechanical, and corrosion behaviors, yet no standardized quantitative framework exists for jointly evaluating these performance dimensions across diverse deployment scenarios. This study introduces a unified multi-criteria evaluation framework applied to six grounding connector configurations spanning four alloy families and three joining technologies. Electro-thermal response was characterized by coupled finite element simulations (0–100 A), mechanical reliability by quasi-static tensile testing (n = 10 per configuration), and corrosion durability by accelerated salt-spray exposure with image-based corroded area fraction quantification. Performance metrics were normalized and aggregated using equal-weight, Analytic Hierarchy Process, and Shannon entropy weighting schemes, with the Technique for Order of Preference by Similarity to Ideal Solution applied for multi-scenario ranking. One-way analysis of variance confirmed statistically significant effects of connector type on tensile performance (F(5, 54) = 3154.90, p < 0.001). The exothermic welded joint achieved the highest mean ultimate tensile load (61.5 ± 1.5 kN), while copper mechanical connectors exhibited the lowest steady-state temperature rise (~2 K above ambient at 100 A). Compression-crimped connectors ranked first under both equal and Analytic Hierarchy Process weighting (closeness coefficients 0.737 and 0.807, respectively), while stainless steel connectors ranked first under corrosion-critical deployment scenarios. Scenario-weighted analyses demonstrate that the optimal material–process combination shifts with environmental severity, current duty, and mechanical demand, providing a reproducible, evidence-based basis for context-dependent connector specification. Full article

Monopolar radiofrequency (MRF) is a well-established modality for non-invasive facial rejuvenation; however, its clinical utility is frequently constrained by patient discomfort and inconsistent thermal delivery. This study evaluated the efficacy, safety, and mechanistic profile of a novel MRF system incorporating continuous water cooling (RF-CWC) designed to optimize thermal distribution and enhance patient tolerance. In a prospective, single-arm clinical trial involving 22 female participants, a single RF-CWC treatment utilizing region-specific static and sliding delivery modes yielded statistically significant improvements in jawline lifting, alongside a volumetric increase in the midface and a concomitant volumetric reduction in the lower face (p < 0.001) over an 8-week follow-up period, with no adverse events reported. To elucidate the underlying cellular mechanisms, the system was further evaluated using an ultraviolet B (UVB)-induced ex vivo human skin model and an in vivo porcine model. Histological, immunohistochemical, and ELISA analyses revealed that RF-CWC effectively mitigated UVB-induced dermal degradation ex vivo by significantly up-regulating elastin, insulin-like growth factor, and hyaluronic acid, while down-regulating matrix metalloproteinase-1, interleukin-1α, and heat shock protein 72 (p < 0.05). Furthermore, the in vivo model demonstrated time-dependent increases in collagen types I and III and elastin without thermal tissue damage, with the sliding mode and higher shot counts correlating with enhanced extracellular matrix (ECM) remodeling. Comparative analyses demonstrated that RF-CWC achieved superior ECM restoration and reduced inflammatory cell infiltration relative to traditional cryogen spray-cooled RF systems. Taken together, these findings suggest that the RF-CWC system may promote robust ECM remodeling and significant facial neocollagenesis while minimizing inflammatory responses, potentially presenting an optimized, highly effective, and patient-friendly advancement in MRF technology. Full article

Thermal spray technologies are widely used in aerospace, gas turbine, and automotive industries, where nickel-based superalloys are valued for their mechanical strength and resistance to oxidation and corrosion at elevated temperatures. This study investigates the microstructure and tribological performance of Ni–5Al/Inconel 625 composite coatings deposited on AISI 1025 steel using wire arc spraying, aiming to provide a cost-effective alternative to bulk superalloys and more advanced thermal spray techniques. Microstructural characterization was performed using optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy, while surface roughness, microhardness, and dry sliding wear behavior were evaluated using ball-on-disk tests against Al₂O₃ counter-bodies. Confocal microscopy and three-dimensional triboscopic imaging were employed to analyze wear-track morphology and friction behavior. X-ray diffraction (XRD) analysis confirmed the presence of a predominantly intermetallic Ni₃Al (γ′) phase with secondary NiAl in the bond coat, indicating significant interdiffusion between the NiAl bond coat and the Inconel 625 top coat. The top coat exhibited a face-centered cubic (FCC) γ Ni-based solid solution. The coatings exhibited a typical lamellar structure with low porosity (2%–3%) and oxide content of 12%–15%, primarily chromium and niobium oxides located at splat boundaries. Abrasion, combined with interlamellar decohesion, was identified as the dominant wear mechanism. Post-deposition polishing reduced surface roughness from 11.9 µm to 2.12 µm, leading to a 2.5-fold reduction in wear volume and a significant decrease in debris pile-up. The corresponding specific wear rates were approximately 9.3 × 10⁻⁵ mm³/Nm and 3 × 10⁻⁵ mm³/Nm for the as-prepared and polished conditions, respectively, which are within the range reported in the literature for similar coatings. These findings demonstrate that wire arc-sprayed Ni–5Al/Inconel 625 coatings, particularly after polishing, offer improved wear resistance while maintaining cost-effectiveness, making them a promising alternative for tribological applications. Full article

The development of fusion technology requires materials that can withstand heat, erosion, and activation at the edge of fusion plasma. Thanks to its high melting point, superior thermal conductivity, and excellent resistance to sputtering and retention, tungsten (W) has been regarded as the leading candidate for the plasma-facing materials (PFMs) of the main chambers and divertors in controlled thermonuclear fusion reactors. Nevertheless, W-PFMs are prone to complex severe surface deterioration under extreme service conditions during operation in fusion reactors. This includes physical/chemical sputtering, which results in material loss and plasma contamination; He-induced blistering and fuzz formation, which reduce thermal conductivity by several orders of magnitude; thermal fatigue cracking caused by transient loads; and neutron irradiation embrittlement, which leads to hardening, swelling, and loss of ductility. To overcome these issues while maintaining core thermophysical properties, protective surface layers have been fabricated primarily via chemical vapor deposition (CVD), physical vapor deposition (PVD), and spray and plasma-based surface modification technologies. This review assesses the recent progress in the fabrication of protective surface layers on W for PFM application in fusion reactors from a technical perspective, thereby offering new insights that advance the feasibility of fusion reactors and accelerating the practical realization of sustainable fusion energy systems. Full article

The increasing global demand for oil and gas, together with the depletion of shallow reservoirs, has driven exploration toward deep and ultra-deep formations characterized by high-temperature and high-pressure (HTHP) conditions. In such environments, conventional drill pipes often experience thermal stress, corrosion, and mechanical degradation, which can reduce drilling efficiency and compromise operational reliability. Thermal insulated drilling pipes (TIDPs) have therefore emerged as an effective solution to minimize heat transfer between drilling fluids and the surrounding formation. This review summarizes recent advances in TIDP materials, structural design strategies, fabrication technologies, and critical performance. Relevant studies were collected from major scientific databases, including Web of Science and Google Scholar, with a focus on insulation materials, coating technologies, and thermal management approaches used in drilling systems. The analysis indicates that advanced insulation systems, including polymer-based coatings, silica aerogels, vacuum-insulated layers, and phase-change materials, can significantly enhance thermal management in drilling operations. These technologies can reduce heat loss by approximately 40–60% (i.e., 400–600 W·m⁻²) and maintain drilling-fluid temperature differentials of 10–18 °C under HTHP conditions. In addition, fabrication techniques such as plasma spraying, composite fabrication, and additive manufacturing enable the development of multifunctional insulation systems with improved thermal, mechanical, and corrosion-resistant properties. Hybrid TIDP systems integrating nanocomposites and advanced polymers show strong potential for improving drilling safety and efficiency. However, challenges related to durability, scalability, and cost remain, highlighting the need for further research on multilayer insulation architectures and sustainable materials. Full article

Functionally graded nickel-based coatings represent an advanced surface engineering approach designed to enhance the performance of components operating in high-temperature and harsh environments. Unlike conventional coatings with uniform composition, functionally graded coatings exhibit gradual variations in composition and microstructure across their thickness, enabling improved adhesion, reduced residual stresses, and enhanced multifunctional performance. This review provides a comprehensive overview of recent developments in nickel-based functionally graded coatings, focusing on substrate materials, coating compositions, and manufacturing technologies. Particular attention is given to coatings designed for high-temperature applications and harsh service conditions, including carbide-reinforced composite coatings and MCrAlY-type systems used for oxidation and corrosion protection. Various fabrication methods, including laser cladding, additive manufacturing, electrodeposition, and thermal spraying, are critically discussed in terms of their advantages and limitations. The current state of the art is analyzed with emphasis on coating performance in high-temperature and aggressive environments. Finally, key challenges and future research directions are identified, highlighting the need for improved long-term performance evaluation, advanced manufacturing approaches, and the development of multifunctional gradient coating architectures. Full article

The 2011 Fukushima accident highlighted the vulnerability of traditional Zr alloy fuel cladding under loss-of-coolant accident (LOCA) conditions, prompting the development of accident-tolerant fuel (ATF) systems. A promising near-term solution involves depositing protective coatings on existing Zr alloy cladding. Among various deposition techniques, cold spray technology has emerged as one of the leading methods due to its solid-state, low-temperature process, which minimises thermal degradation and allows for the deposition of a wide range of high-performance materials. This review provides a comprehensive examination of recent advances in cold-sprayed coatings for ATF cladding, beginning with an overview of the fundamentals of cold spray technology and its specific advantages for nuclear applications. The core of the review critically analyses three primary coating systems: Cr, FeCrAl alloys, and MAX phase composites, with a particular focus on Cr coatings, as they have been more extensively studied compared to the other two material systems. Key coating properties, including microstructure of the coating-substrate interface, mechanical properties, thermal conductivity, oxidation resistance, irradiation tolerance, and performance under normal operation and simulated LOCA conditions, are discussed in detail, with particular emphasis on the potential of cold-sprayed Cr coatings to enhance Zr alloy cladding. Cr coatings demonstrate significant improvements in oxidation resistance and irradiation stability, but also face challenges such as high-temperature interfacial reactions. To address these issues, promising solutions, such as diffusion-barrier bilayer systems, are being explored. Additionally, the review discusses FeCrAl and MAX phase composite coatings, highlighting their promising long-term performance under extreme conditions. The review concludes with recommendations for further research to optimise cold spray processes and ensure the robustness of coatings in operational reactor environments. Full article

Copper (Cu), silver (Ag), and copper–silver (Cu–Ag) powders were synthesized using ultrasonic spray pyrolysis (USP) combined with hydrogen-assisted reduction in order to examine how key processing parameters influence particle characteristics. The effects of reduction temperature, gas atmosphere, and precursor molar ratio on particle morphology, size distribution, and elemental composition were systematically investigated. Aqueous precursor solutions of copper nitrate trihydrate and silver nitrate were atomized in a USP reactor and thermally treated under hydrogen-containing or argon atmospheres at temperatures between 500 and 700 °C. The resulting powders were characterized by scanning electron microscopy (SEM), particle size analysis using ImageJ, and energy-dispersive X-ray spectroscopy (EDS). The results showed that both temperature and gas atmosphere strongly affected particle formation. Hydrogen-assisted synthesis promoted efficient reduction and high metal purity but was associated with increased particle coalescence, whereas argon atmospheres yielded finer and more uniform particles through thermally driven decomposition. In the case of Cu–Ag powders, the precursor molar ratio played a decisive role in particle stability. A 1:1 Cu:Ag ratio produced uniform particles with reduced susceptibility to surface oxidation, while Ag-rich compositions (1:3 Cu:Ag) showed increased agglomeration and partial oxidation after synthesis. Overall, this study demonstrates that careful adjustment of gas atmosphere, synthesis temperature, and precursor composition enables control over the morphology and compositional stability of Cu, Ag, and Cu–Ag powders produced by USP. These findings provide practical guidance for the scalable preparation of mono- and bimetallic metal powders for applications in electronics, catalysis, and energy-related technologies. Full article

Elastomeric ablative coatings are essential for protecting solid rocket motor (SRM) combustion chambers from extreme thermal and erosive environments, and their performance is governed by both material composition and processing strategy. This review examines the main elastomer systems used for SRM insulation, including ethylene propylene diene monomer (EPDM), nitrile butadiene rubber (NBR), hydroxyl-terminated polybutadiene (HTPB), polyurethane (PU), silicone-based compounds, and related hybrids, and discusses how their rheological behavior, cure kinetics, thermal stability, and ablation mechanisms affect manufacturability and in-service performance. A comprehensive assessment of coating technologies is presented, covering casting, molding, centrifugal forming, spraying, automated deposition, and emerging additive-manufacturing approaches for complex geometries. Emphasis is placed on processing parameters that control adhesion to metallic substrates, layer uniformity, defect formation, and thermomechanical integrity under high-heat-flux exposure. The review integrates current knowledge on how material choice, surface preparation, and application sequence collectively determine insulation efficiency under operational SRM conditions. Practical aspects such as scalability, compatibility with complex chamber architectures, and integration with quality-control tools are highlighted. By comparing the capabilities and limitations of different materials and technologies, the study identifies key development trends and outlines remaining challenges for improving the durability, structural robustness, and ablation resistance of next-generation elastomeric coatings for SRMs. Full article

Solanum betaceum (tamarillo) is Andean fruit rich in secondary metabolites with increasing relevance in food, nutraceutical, and biotechnological research. Despite growing scientific interest, the available evidence remains fragmented and methodologically heterogeneous. This systematic review consolidates and critically analyzes recent studies on the bioactive composition of S. betaceum, the effects of conventional and emerging processing technologies, and the functional activities reported for fresh fruits, by-products, and processed matrices. A comprehensive search of Lens.org, Scopus, and PubMed was conducted following PRISMA 2020 guidelines. From 1049 records identified, 65 studies published between 2020 and 2025 met the inclusion criteria and were included in the qualitative synthesis. The literature reveals substantial variability in polyphenols, anthocyanins, carotenoids, vitamin C, and other metabolites, driven by cultivar, maturity stage, edaphoclimatic conditions, and analytical approaches. Emerging technologies such as ultrasound-assisted extraction, high-pressure homogenization, and spray drying generally improved the recovery and stability of bioactive compounds, whereas intensive thermal treatments were associated with degradation of thermolabile constituents. Functional evidence supports antioxidant, antimicrobial, metabolic modulatory, and cytotoxic activities; however, interpretation is limited by inconsistent reporting practices, limited bioaccessibility assessment, and the predominance of in vitro models. Overall, S. betaceum shows considerable functional and technological potential, but further standardized methodologies, mechanistic studies, and human-relevant models are required to support translational and industrial validation. Full article

This work proposes the design, construction, and field test of a vacuum seawater desalination system (VSDS) driven by an evacuated tube solar collector (with a total absorption area of 1.86 m²) under tropical climatic condition (Thailand ambient at latitude 13°43′06.0″ N, longitude 100°32′25.4″ E). The VSDS prototype was designed and constructed to be driven by hot water, which is produced by two heat source conditions: (1) an electric heater for laboratory tests and (2) an evacuated tube solar collector for field tests under real climatic conditions. A comparative experimental study to assess the ability to produce fresh water between a conventional dripping/pipe feed column and spray falling film column is proposed in the first part of the discussion. This is to demonstrate the advantage of the spray falling film distillation column. The experimental method is implemented based on the batch system, in which the cycle time (distillation time) considered is 10–20 min so that heat loss via the concentrated seawater blow down is minimized. Later, the field test with solar irradiance under real climatic conditions is demonstrated to assess the freshwater yield and the system performance. The aim is to provide evidence of the proposed vacuum desalination system in real operation. It is found experimentally that the VSDS working with spray falling film provides better performance than the dripping/pipe feed column under the specified working conditions. The spray falling film column can increase the distillated freshwater volume from 1.33 to 2.16 L under identical cycle time and working conditions. The improvement potential is up to 62.4%. The overall thermal efficiency can be increased from 33.7 to 70.8% (improvement of 110.1%). Therefore, the VSDS working with spray falling film is selected for implementing field tests based on real solar irradiance powered by an evacuated tube solar collector. The ability to produce fresh water is assessed, and the overall performance via the average distillation rate and the thermal efficiency (or Gain Output Ratio) is discussed with the real solar irradiance. It is found from the field test with solar time (8.00–16.00) that the VSDS can produce a daily freshwater yield of up to 4.5 L with a thermal efficiency of up to 19%. The freshwater production meets the requirement for international standard drinking water criteria, indicating suitability for household/community use in tropical regions. This work demonstrates the feasibility of VSDS working under real solar irradiance as an alternative technology for sustainable fresh water. Full article

This study prepared Copper(Cu)/Aluminum(Al) composite materials using hot-rolling technology. The influence of annealing treatment on the interfacial microstructure was systematically investigated, thereby elucidating the correlation between microstructural characteristics and thermal conductivity. The results demonstrated that annealing treatment induced the formation of a continuous intermetallic compound layer at the Cu/Al interface, with its thickness increasing proportionally to elevated temperature and prolonged duration. After spraying graphene onto the aluminum surface via ultrasonic spraying technology, followed by rolling and an annealing treatment, the intermetallic compounds at the Cu/Al interface exhibited a discontinuous distribution pattern. When annealed at 300 °C, the thermal conductivity of the Cu/Al composite plate increased progressively with prolonged duration. For instance, in the absence of graphene, the value increased from 39.288 to 61.827; when graphene was applied via ultrasonic spraying with a spraying distance of 1 mm, the value increased from 49.884 to 73.203, whereas at 400 °C annealing, it exhibited a notable decline as annealing time extended. Graphene at the interface inhibits the diffusion of Cu/Al atoms, reduces the formation of intermetallic compounds, establishes efficient thermal conduction paths, and ultimately enhances the thermal conductivity of the composite material. Full article

The paper presents the results of research aimed at verifying the possibility of creating renovation layers using HVOF (High Velocity Oxygen Fuel) technology. HVOF ceramic coatings represent a promising way to increase the efficiency, reliability, and sustainability of manufacturing processes. Molds for high-pressure injection of aluminum alloys were analyzed. The degradation mechanism of the functional surfaces of the molds was determined. The paper analyzes two types of HVOF coatings—Cr₂O₃-TiO₂ and Al₂O₃-TiO₂. For both coatings, a Ni-Al interlayer was used for mechanical stability, durability, and reliable functionality in demanding operating conditions. The interlayer is used in thermal spraying as a so-called bond coat—a layer that mediates adhesion between the metal substrate and the ceramic coating. EDX maps of chemical elements from the coating surface and cross-sections were determined. The tribological properties of the coatings were evaluated by a ball-on-disk test at 20 °C and 250 °C. SEM analysis of the surface after the tribological test was performed. The resistance of the coatings was evaluated by COF and friction resistance. Full article

Additive and coating technologies, such as high-velocity oxy-fuel (HVOF) thermal spraying and direct metal laser sintering (DMLS), often require extensive post-processing to meet dimensional and surface quality requirements, which remains challenging for nickel-based superalloys such as Inconel 718. This study presents the design and topology optimisation of a cutting tool with a linear cutting edge, capable of operating in turn-milling or turning modes, offering a viable alternative to conventional grinding. A non-optimised tool served as a baseline for comparison with a topology-optimised variant improving cutting-force distribution and stiffness-to-mass ratio. Finite element analyses and experimental turn-milling trials were performed on DMLS and HVOF Inconel 718 using carbide and CBN inserts. The optimised tool achieved significantly reduced roughness values: for DMLS, Ra decreased from 0.514 ± 0.069 µm to 0.351 ± 0.047 µm, and for HVOF from 0.606 ± 0.069 µm to 0.407 ± 0.069 µm. Rz was similarly improved, decreasing from 4.234 ± 0.343 µm to 3.340 ± 0.439 µm (DMLS) and from 5.349 ± 0.552 µm to 4.521 ± 0.650 µm (HVOF). The lowest measured Ra, 0.146 ± 0.030 µm, was obtained using CBN inserts at the highest tested cutting speed. All improvements were statistically significant (p < 0.005). No measurable tool wear was observed due to the small engagement and the use of a fresh cutting edge for each pass. The resulting surface quality was comparable to grinding and clearly superior to conventional turning. These findings demonstrate that combining topology optimisation with a linear-edge tool provides a practical and efficient finishing approach for additively manufactured and thermally sprayed Inconel 718 components. Full article