Search Results (1,949)

This article presents an analysis of the effect of an anti-reflective layer on the measurement process using the 3D GOM (ATOS II Triple Scan; currently ZEISS) optical scanner for spherical elements manufactured using four additive methods: PolyJet Modeling (PJM), Digital Light Processing (DLP), Melted Extrusion Modeling (MEM), and Direct Metal Laser Sintering (DMLS). The research focused on analyzing the effect of the anti-reflective (AR) layer on changes in numerical data and on differences that define the shape of the measured elements. It was noted that models made of light-cured resin (EC100 (DLP) and RGD720 (PJM)) were characterized by AR layer absorption, which affected the measurement results. The use of the AR layer also increases the number of points for which a fitted sphere is created in the optical scanner software for shape analysis of the research models. The application of the AR layer also affects the average dimensional deviations (relative to the MB1 and MB2 research models), most significantly for models made using the PJM and MEM methods (approx. 0.02 mm), and least significantly for models made using the DMLS method (approx. 0.004 mm). The conducted research, presented measurement results, analyses, and conclusions, will help predict the impact of using the AR layer on the measurement process and the accuracy of the obtained results of measured geometric parameters during 3D GOM (ATOS II Triple Scan) optical measurements of models made of selected materials. Full article

In this work, flame-retardant (FR) PLA-based composites exhibiting both good flame retardancy and electromagnetic interference (EMI) shielding were fabricated through combining melt blending with fused deposition modeling (FDM) 3D printing. Intumescent flame-retardant (IFR) fillers and graphene nanoplatelets (GNPs) were incorporated to construct a synergistic system, and the resulting structure–property relationships were systematically investigated. The optimal performance was achieved with 15 wt% IFR fillers and 3 wt% GNPs. The prepared composite exhibited a residual char yield of 14.3% at 700 °C, significantly higher than that of neat PLA. Regarding flame retardancy, the limiting oxygen index (LOI) increased to 32.5%, and the vertical burning level achieved a UL-94 V-0 rating. In the cone calorimetry test, both the peak heat release rate and total heat release were markedly reduced, attributed to the formation of a dense and stable char layer. For EMI shielding, the FR composite achieved a total shielding effectiveness (SE_T) of 20.6 dB in the X-band, with an absorption proportion exceeding 80%, indicating an absorption-dominated mechanism. Meanwhile, a well-established conductive network effectively enhanced the electromagnetic loss. Overall, the synergistic effect of IFR fillers and GNPs enabled simultaneous improvements in flame retardancy and EMI shielding in FR PLA-based composites, providing a feasible strategy for designing functional 3D-printed FR PLA-based materials. Full article

Thermoplastic polyurethane (TPU) is highly versatile yet inherently flammable, restricting its use in fire-safe applications. This study incorporates sodium antimonate (SA) into TPU via melt blending (0–10 wt%). Through a comprehensive suite of analytical techniques—including thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), universal testing, and cone calorimetry—the effects of SA on the various properties of the material were investigated. Quantitative analysis reveals that 10 wt% SA delivers the best flame retardancy, reducing the peak heat release rate by ~50% (from 605 to 310 kW/m²) and total heat release by ~40% (from 32 to 19 MJ/m²), while increasing the char residue from 9.84% to 13.89%. However, to retain mechanical robustness, the SA content must be capped at ≤5 wt%. This ensures that the material retains 30% of its fracture elongation and a tensile strength of 1.7 MPa; higher loadings cause severe embrittlement due to particle agglomeration. Mechanistically, SA acts via a dual-phase mode—promoting a dense insulating char layer in the condensed phase and quenching reactive radicals in the gas phase. These findings establish a practical balance between fire safety and mechanical performance, offering a clear guideline for the rational design of flame-retardant TPU composites. Full article

The development of new principles for controlling the technical systems requires the use of reliable actuators. A sliding steel/steel contact under a high-density electric current could serve as one of their elements. The search for the factors reducing the wear of the contacts is a subject of scientific and commercial interest. One such factor is the melting that occurs within a sliding steel/steel electrical contact space. The overall goal of this study is to describe the characteristics of an M2 steel/steel sliding electrical contact during the formation of a melt-like state in the contact zone. Dry sliding of M2 steel (sample) against C45 steel (counterbody) under an alternating electric current at a density higher than 100 A/cm² is performed as a model experiment using the well-known “pin-on-ring” tribo-loading configuration. The formation of tribolayers on the sample and the counterbody is demonstrated using a scanning electron microscope and a MICRO MEASURE 3D-station non-contact device. According to the EDX analysis, the contact layers predominantly contain oxygen and iron. Two sectors with different morphological features are observed on the M2 steel sliding surface. A melt-like state is visible in one of the sectors. This state is assumed to form within a certain sublayer. A method for calculating this sublayer thickness is proposed. This thickness does not exceed 10 μm. The calculation model has revealed that the thickness of this sublayer depends mainly on the external impact power rather than on the atomic and phase composition of the tribolayer. An increase in the contact current density is consistent with an increase in the calculated thickness of this sublayer, an increase in the electrical conductivity of the contact, and a decrease in the coefficient of friction (COF). The proposed analysis of the obtained results could serve as a basis for broader generalizations. Full article

In the present study, the potential applications of Cu thin films and Ag/Cu bilayer thin films obtained by the pulsed laser deposition (PLD) technique are investigated in terms of the physicochemical effects resulting from their interaction with an aqueous solution containing Reactive Blue 21 (RB21) dye and sodium bicarbonate (NaHCO₃). The thin-film deposition process was carried out using a Q-switched Nd:YAG laser system operating at a wavelength of λ = 532 nm, with a pulse duration of τ = 10 ns, a repetition rate of ν = 10 Hz, a pulse energy of E = 180 mJ, a laser spot diameter of d = 336 μm, and an angle of incidence of α = 45°. Two types of thin films were prepared: a Cu thin film and an Ag/Cu bilayer thin film. The thermal effects induced by the interaction of the laser beam with the target materials were investigated by numerical simulations performed in COMSOL, allowing the evaluation of melt-phase formation for each material separately and providing a better understanding of the morphology and topography of the deposited thin films. The simulation results were validated through scanning electron microscopy (SEM) observations and surface roughness analyses. The two thin films were subsequently treated with an aqueous solution containing 10 g/L RB21 dye and 10 g/L NaHCO₃. Physicochemical analyses performed after treatment, including scanning electron microscopy (SEM), optical microscopy (OM), profilometry, Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and UV–Vis spectroscopy, revealed significant degradation of the RB21 dye accompanied by corrosion of the thin films, with the corrosion process being more pronounced in the case of the Cu thin film. The obtained results indicate that the method analyzed in this study may represent an alternative approach for the decomposition of recalcitrant organic dyes using thin Cu films, without relying on conventional photocatalytic processes. Equally important are the potential applications of the RB21/NaHCO₃ solution as an etching and patterning medium for thin Cu layers, while the Ag overlayer may provide a protective effect during such processes. These findings may contribute to the development of novel fabrication techniques for optoelectronic components, including solar cells, photovoltaic windows, and other industrial and laboratory applications. Full article

This study investigates the optimization of airflow distribution and pressure drops in H14 HEPA minipleat filters through the introduction of the hot-melt cell as the fundamental hydraulic unit governing local flow behavior. A coupled analytical framework integrating Falkner–Skan boundary-layer theory, Darcy–Weisbach channel friction, and Darcy porous-medium flow was developed and experimentally tested using velocity measurements obtained in a 600 m³/h test bench operating at a frontal velocity of 0.45 m/s under laminar-flow conditions. Ten primary geometric configurations and 21 hot-melt distribution scenarios (totaling 31 cases plus an optimized design case) were systematically evaluated by varying cell width (W), inlet height (H_i), and pleat length (L). Experimental and analytical results reveal significant velocity heterogeneity in the vicinity of the filter surface, which progressively decreases with distance from the filter, while localized velocity amplification is observed near the hot-melt separators. The analysis demonstrates that hydraulic diameter, pleat angle, and hot-melt spacing are the dominant parameters governing pressure drop generation and flow redistribution. Among the configurations investigated, a model-predicted optimized design (W = 46.25 mm, L = 55.00 mm, 230 pleats) yields a theoretical pressure drop reduction of up to 29.23% without significantly compromising the effective filtration area. These results provide an analytical framework for pre-prototyping optimization, although experimental verification of physical prototype validation for mechanical integrity and the preservation of initial efficiency, among other governing physical quantities, remains essential. The results demonstrate that the proposed hot-melt cell concept provides a practical engineering framework for the aerodynamic optimization of minipleat HEPA filters, enabling improved flow uniformity and reduced energy consumption in cleanroom applications. Full article

The mechanical properties of continuous-fiber-reinforced composites in FDM-3D printing are significantly influenced by process parameters. However, research in this area is constrained by printing equipment, control software, and material preparation. This study examines how the tensile and interlaminar shear properties of CCF/PA and CF/PEEK are affected by continuous-fiber nozzle temperature, platform temperature, and printing speed. Studies indicate that enhancing the nozzle temperature can notably improve mechanical properties by enhancing material flowability, ensuring consistent fiber encapsulation and reducing pore defects. Increasing the platform temperature initially boosts both tensile strength and ILSS, but, beyond a certain point, these properties decline. Inadequate platform temperature can result in uneven infiltration and diffusion among deposited CCF/PA paths, leading to void defects. Conversely, excessive platform temperature can cause semi-molten CCF/PA layers to be vulnerable to nozzle pressure and scraping, resulting in continuous-fiber debonding and interlayer tearing. Furthermore, lower printing speeds extend the melt wetting time between adjacent paths, promoting diffusion and adhesion for enhanced performance. Following an experimental investigation, the optimal parameters are identified as a nozzle temperature of 295 °C, a platform temperature of 240 °C, and a printing speed of 3 mm/s. This research provides valuable guidance for the practical production of continuous-fiber-reinforced composites using FDM-3D printing. Full article

Metallized pellets are spherical iron-bearing burden materials obtained by treating iron ore pellets through processes such as direct reduction. They contain a certain proportion of metallic iron and mainly consist of metallic iron, incompletely reduced oxides, gangue, and other nonmetallic components. They are one of the commonly used iron-bearing materials in electric smelting furnaces. The melting process of metallized pellets not only affects the melting efficiency of the charge but is also accompanied by slag–metal separation and gangue separation, which is directly related to mass transfer, heat transfer, and production efficiency during the smelting process. However, existing studies have mainly focused on the melting behavior of pellets in a single-phase molten pool, while studies on gangue separation, interfacial migration, and slag–metal separation during pellet melting at the slag–metal two-phase interface remain rare. Because this region involves complex interfacial heat transfer, fluid flow, and interfacial interactions, investigating only the overall melting process of pellets is insufficient to reveal the actual gangue separation mechanism. Therefore, a systematic investigation of the melting and separation processes of pellets at the slag–metal interface is necessary. Based on the principle of similarity, a water–oil–ice three-phase physical model was employed in this study, in which water, silicone oil, and ice balls containing dyed silicone oil samples were used to simulate molten iron, slag, and pellets, respectively. The dyed silicone oil is specially designed to simulate the gangue in the pellet. Visualization experiments were conducted to investigate the evolution of pellet melting morphology, oil droplet (gangue) release behavior, and diffusion characteristics in the oil layer under different initial oil droplet positions and static or parallel flow conditions. The results show that the initial position of the oil droplet and the parallel flow significantly affect the local melting behavior of the ice ball and the oil droplet release process. In particular, the release time of the oil droplet located above the ice ball is significantly longer than that of the oil droplet located below the ice ball. The parallel flow significantly changes the melting sequence of the ice ball and the oil droplet release path by enhancing convective heat transfer in the lower region of the ice ball. According to the initial position of the oil droplet and the flow conditions, the oil droplet release process can be classified into five typical separation types, including (1) lateral release of the upper oil droplet after the ice shells on both sides melt through, (2) release of the upper oil droplet through a hole at the bottom of the upper hemisphere, (3) direct release of the lower oil droplet through a local hole, (4) two-stage release of the lower oil droplet controlled by interfacial constraint, and (5) single-stage release of the oil droplet on the downstream flow side driven by parallel flow. The oil droplet release time in the parallel flow cases is shorter than that in the static conditions. The diffusion behavior of the oil droplet after entering the oil layer is weakly affected by the parallel flow and is mainly characterized by inertial diffusion along the initial release direction, followed by spreading toward the surrounding area. This study reveals the slag–metal separation mechanism during pellet melting at the slag–metal interface under the combined control of flow, ice shell morphology, and interfacial interactions, providing experimental evidence for optimizing the melting and separation behavior of pellet charges in electric smelting furnaces and related smelting processes. Full article

Cold-roll-bonded (CRB) Fe–Al clad sheets, which incorporate an internal steel layer within the clad structure, are candidate materials for dissimilar joining in lightweight structural applications, yet systematic comparisons of their weldability across multiple joining processes remain limited. This study evaluates the process-dependent weldability of CRB Fe–Al clad sheets using three joining processes: laser lap welding, DC resistance spot welding, and cold metal transfer-pulse (CMT-P) arc welding. Weld appearance, cross-sectional morphology, tensile shear behavior, and fracture characteristics were assessed for multiple sheet configurations and clad-layer thicknesses. Across all three processes, configurations that placed the clad sheet directly toward the heat source were prone to cracking or strength degradation when the internal steel layer melted extensively, whereas limiting steel-layer involvement produced more stable joints. Among the three processes, resistance spot welding provided the widest workable process window, while laser and CMT-P arc welding achieved peak strengths only within a narrow heat-input range. These findings indicate that the role of the internal steel layer is process-dependent and provide practical guidance for sheet configuration and parameter selection when joining CRB Fe–Al clad sheets to steel or aluminum components. Full article

In this study, Mo/β-Ga₂O₃ vertical Schottky barrier diodes (SBDs) were fabricated using a sputtering process, and the electrical characteristics were evaluated as a function of post-annealing temperature. β-Ga₂O₃ is an ultra-wide bandgap semiconductor (UWBG) with a bandgap of about 4.8 eV and a critical breakdown field of 8 MV/cm, a promising material for high-voltage power switching applications. Mo (molybdenum) has a higher work function (~4.95 eV) than the electron affinity (~4.0 eV) of β-Ga₂O₃, its melting point (2623 °C) is higher than Pt (1768 °C) and Ni (1455 °C), so it has excellent thermal stability, and it is selected as a Schottky metal. The device is a structure in which a Si-doped β-Ga₂O₃ epitaxial layer (10 μm, N_d-N_a = 2.2 × 10¹⁶ cm⁻³) is grown on an Sn-doped β-Ga₂O₃ substrate (415 μm, N_d-N_a = 4.5 × 10¹⁸ cm⁻³). The Ti/Au (10/40 nm) was used for the back ohmic junction and Mo (300 nm) was used for the front Schottky junction. Post-annealing treatment was performed at 400, 500, and 550 °C using a rapid thermal annealing process (RTA) in an Ar gas atmosphere, and in this process, the Schottky junction and ohmic junction were formed simultaneously. Electrical characteristics including current-voltage (I–V), capacitance-voltage (C–V), Schottky barrier height (SBH), ideality factor (n), turn-on voltage (V_on), on-resistance (R_on), on/off ratio, and breakdown voltage (BV) were evaluated. No obvious Schottky characteristics were observed before post-annealing treatment, which means that As-deposited Mo does not form a rectifying junction on the β-Ga₂O₃ without post-annealing treatment. After post-annealing treatment, the I–V curve of the Schottky rectification characteristics could be confirmed under all three conditions. Among the three conditions, the device annealed at 500 °C exhibits best performance, with an SBH of 0.96 eV, n of 1.01, V_on of 0.72 V, R_on of 13.8 mΩ·cm², an on/off ratio of 10⁹, a breakdown voltage of −474 V, and a PFOM of 16.3 MW/cm². As a result of temperature-dependent I–V measurement, as chuck temperature increased, the reverse leakage current increased and SBH decreased in all devices, which is consistent with the thermally activated carrier transport. These results demonstrate that the Mo/β-Ga₂O₃ SBDs are a thermally stable contact for power device applications. Full article

The Waliguan–Duohemao tectonic belt on the northeastern Tibetan Plateau hosts Qinghai’s highest-temperature hot springs (Zhacanggou 98 °C, Qunaihai 97 °C) and deep hot dry rock resources in the Gonghe Basin. However, the mechanisms governing hydrothermal circulation in this region remain poorly understood, limiting the assessment of its sustainable geothermal development potential. Through integrated fluid geochemistry, borehole temperature logging, and crustal thermal structure analyses, this study reveals the dual “water–heat” control exerted by the fault zone. The fault acts as a dominant pathway for deep meteoric water circulation, controlling mixing between deep hydrothermal fluids and shallow cold water, as evidenced by continuous hydrochemical and isotopic trends. Heat flow analysis indicates surface heat flow values up to 134.66 mW/m² in the Gonghe Basin (with a 78.6% crustal contribution), decreasing to 57.4% in the Guinan area. A deep intra-crustal partial melting layer provides additional heat in the Gonghe Basin, whereas the Guide and Tongren areas rely primarily on radiogenic heat generation. The systematic increase in crustal heat flow from southwest to northeast confirms the fault zone as an efficient conduit for deep thermal transport, highlighting the region’s substantial deep geothermal energy potential. To overcome the “heat without water” exploration bottleneck and promote sustainable resource development, we propose differentiated exploration strategies tailored to the structural heterogeneity of the belt: (1) in the western Gonghe Basin, prioritize heat source characterization and enhanced geothermal system (EGS) feasibility assessment; (2) in the central Guide area, employ high-resolution geophysical methods to detect water-conducting fault zones; and (3) in the eastern Tongren area, evaluate water source conditions and fault connectivity with recharge areas. These strategies collectively minimize exploration risks and support the long-term, sustainable utilization of geothermal resources in this high-altitude region. Full article

Lightweight fiber-reinforced phenolic-resin aerogel (NF/PRA) composites are key ablation thermal protection materials for hypersonic vehicles. However, how resin precursor solid content governs the complete processing–structure–property chain, particularly the multi-mode mechanical behavior and high-heat-flux ablation performance, remains poorly understood. In this study, high-silica fiber/phenolic-resin aerogel composites with different contents of a novolac resin precursor (15%, H15S15; 20%, H15S20; 25%, H15S25; 30%, H15S30) were fabricated via vacuum-assisted resin transfer molding combined with atmospheric-pressure drying, and were systematically characterized in terms of their microstructure, mechanical properties, thermophysical behavior, thermal insulation, and ablation resistance. A higher solid content created a denser three-dimensional nano-network in the PRA matrix, decreasing the average pore size from 75.4 to 37.4 nm and increasing the bulk density from 0.299 to 0.458 g/cm³. The abundant mesopores led to ultra-low thermal conductivities of 0.039–0.042 W/(m·K). The compressive, flexural, and shear strengths increased monotonically with the solid content, whereas the tensile strength peaked at 18.03 MPa for H15S25 and declined at higher contents owing to matrix brittleness. Notably, a higher solid content synergistically enhanced both thermal insulation and ablation resistance. After oxyacetylene flame ablation, the linear ablation rate of H15S30 was 32.7% lower than that of H15S15, and the back-face temperature was more than 58% lower. Post-ablation microstructural observations revealed a three-stage mechanism involving pyrolytic carbonization, fiber melting, and mechanical scouring, in which layer-by-layer spallation of the amorphous carbon and SiO₂-rich molten phases governs the damage. This study provides guidance for optimizing the processing–structure–property relationship of NF/PRA composites for ablation thermal protection applications. Full article

This research evaluates the compounding, processing, and performance of a sustainable biocomposite filament for additive manufacturing, utilizing poly(lactic acid) (PLA) filled with raw pine cone (Pinus sylvestris) flour at 5 and 10 wt% filler contents. Tensile properties, surface topography, and processability of extruded filaments and 3D-printed specimens were systematically investigated. Incorporating pine cone flour yielded unprinted filament tensile strengths of 21.06 MPa (5 wt%) and 18.51 MPa (10 wt%), while 3D-printed specimens retained ~85% (5 wt%) and ~79% (10 wt%) of their corresponding unprinted composite filament tensile strength. This reduction in strength is hypothesized to stem from weak interfacial adhesion and polarity mismatch between the hydrophobic PLA and hydrophilic biomass, which is suggested to promote micro-void formation. Topographical analysis revealed surface anisotropy: top surface roughness increased ($Ra$ up to 9.85 µm; $Sz$ up to 100.2 µm), likely influenced by melt viscosity, whereas lateral roughness decreased ($Ra$ down to 3.10 µm; $Sz$ down to 45.4 µm), potentially associated with suppressed die swell. Printed ductility increased (>8%), a trend attributed to potential inter-layer re-melting during deposition. To overcome limited interfacial bonding, future work should incorporate coupling agents or chemical surface modifications. Overall, among the evaluated formulations, the composite with 5 wt% filler demonstrates a favorable balance of processability, mechanical integrity, and surface quality, showing high potential for non-load-bearing prototypes, indoor decorative elements, and light-duty packaging. Full article

A systematic numerical simulation and analysis of the temperature field were conducted for the laser cladding process of CuCrZr alloy onto a 316L stainless steel substrate. First, the thermal properties of the material (density, thermal conductivity, and specific heat capacity) as a function of temperature were calculated using JMatPro software. The equilibrium phase diagram of the CuCrZr alloy was obtained using Thermo-Calc, clarifying the stability of each phase and the solid–liquid phase transition ranges. Based on these findings, three-dimensional transient heat transfer models for single-layer single-pass and single-layer multi-pass cladding were established using ANSYS finite element software and a double-ellipsoidal moving heat source model. The effects of laser power on the evolution of the temperature field, peak temperature, and thermal cycling characteristics were systematically investigated. The simulation results indicate that the temperature field exhibits typical rapid heating and rapid cooling characteristics; the peak temperature increases significantly with rising laser power, and the extent of the high-temperature region expands. A combined analysis of the phase diagram and temperature field results indicates that the peak cladding temperature exceeds the complete melting temperature of the alloy, ensuring sufficient melting. This study provides a reliable theoretical foundation and data support for optimizing laser cladding process parameters, predicting the microstructure of the cladding layer, and controlling thermal stress. Full article

The sturdy and stable unique polyhedral structure of FeOOH nanoparticles facilitates stress and load transfer, thereby forming a tighter mechanical interlock at the carbon fiber–matrix interface. In this work, the FeOOH nanocrystal layer in situ grown on flexible carbon fiber cloth was rationally designed and fabricated through hydrothermal synthesis. Then, the non-covalent cation–π bond was constructed at the interface between the iron ion-loaded FeOOH nanoparticles and indole-based poly(hexahydrotriazine) (In-PHT). Owing to the collaborative effects of physical anchoring and chemical bonding, the resultant composite exhibited an outstanding tensile strength of 322 MPa, and the friction coefficient significantly decreased by 63% compared with the composites without FeOOH nanoparticles. Moreover, the resultant worn composite showed an excellent self-healing property owing to the introduction of polyethylene wax (PEW) with a low melting point, and the healed friction coefficient remained almost unchanged. Extensive analyses verify that the phase-separated structure and Fe³⁺–π interactions across multiscale interfaces achieve the combined advantages of wear resistance and durability for recyclable carbon fiber-reinforced poly(hexahydrotriazine) composites (PHT-CFRPs). Full article