Search Results (160)

A 2014Al matrix composite reinforced with 0.8 wt.% graphene nanoplatelets (GNPs) was prepared by pre-dispersion and ultrasonic melt casting. Subsequently, the as-cast 2014Al-GNP composite was subjected to hot extrusion under different parameters, followed by a comparative analysis of the microstructure and properties of the various alloys. Microstructure and phase composition of the prepared samples were characterized using OM, SEM, EDS, EBSD and TEM inspections. The results indicate that the addition of GNPs effectively promoted the refinement of the as-cast matrix alloy microstructure, while hot extrusion with appropriate parameters further refined the microstructure of the as-cast matrix alloy. At an extrusion ratio of 16, the Al₂Cu, Al₂CuMg, and GNPs in the microstructure displayed a band-like distribution along the extrusion direction, with reduced size and enhanced uniformity. Concurrently, the dislocation density and Kernel Average Misorientation (KAM) values of the composite increased significantly, dynamic recrystallization intensified, and the texture was further enhanced. The tensile strength reached 572.1 MPa, hardness was 369.6 HV, and elongation was 11.9%, representing improvements of 89.0%, 92.0%, and 142.9%, respectively, compared to the as-cast matrix alloy. Fracture surface analysis exhibited brittle fracture characteristics in the matrix alloy, while the extruded composite with optimal parameters displayed distinct ductile fracture features. In the extruded aluminum matrix composite, the interface between GNPs and the matrix was clean, with mutual diffusion of Al and C atoms, achieving an excellent interfacial bonding state. The significant enhancement in mechanical properties of the extruded alloy was primarily attributed to grain refinement strengthening, dislocation strengthening, and load transfer strengthening by GNPs. Full article

Carotid artery intima–media thickness (cIMT), a pre-clinical vascular change that accompanies atherosclerosis is considered as a cardiovascular risk factor. Coagulation factor XIII (FXIII) stabilizes the fibrin clot and increases its resistance to fibrinolysis. Regarding FXIII Val34Leu polymorphism, the protective effect of the Leu34 allele in the presence of elevated fibrinogen levels against myocardial infarction was demonstrated. Our aim was to investigate the effect of FXIII polymorphisms on cIMT. Patients with obesity (n = 69), type 2 diabetes mellitus (T2DM) (n = 104), and age- and sex-matched healthy controls (n = 82) were enrolled. FXIII polymorphisms (Val34Leu, His95Arg, Intron-K C>G) were determined by RT-PCR with FRET detection and melting curve analysis. cIMT was determined by B-mode ultrasound. Differences in cIMT between control (median: 0.5965, IQR: 0.5115–0.6580 mm) and T2DM (median: 0.7105, IQR: 0.5948–0.7568 mm), as well as between obese (median: 0.6105, IQR: 0.5455–0.6780 mm) and diabetic groups, were found (p < 0.0001 and p = 0.003, respectively). Genotype and allele frequencies of the studied polymorphisms did not differ between subgroups. In the study group (n = 255) after adjustment for age and sex, the presence of Intron-K G allele showed a significant and independent protective effect against cIMT progression in a separate model (p = 0.005) and after adjusting for other parameters associated with cIMT (p = 0.015). FXIII Intron-K G allele provides a protective effect against subclinical vascular disease in the studied population, and this effect is independent of the presence of obesity, as well as T2DM, Leu34 allele, and fibrinogen levels. Full article

Significant pre-consumer waste in the form of runners is generated during the injection molding of high-performance automotive components, representing both a substantial economic loss and an environmental burden. This study therefore comprehensively evaluated the mechanical recycling of pre-consumer 35% glass fiber-reinforced Polyamide 6,6 (%35GF-PA66) runners for in-process reuse in diesel injector socket production. The effects of blending recycled polymer (RP) at 2.5%, 5%, 10%, and 15% by weight and up to 10 recycling cycles with 15 wt.% RP on the thermal, mechanical, and morphological properties were investigated. Tensile strength slightly decreased (~3% at 10% RP) compared to virgin material, while elongation at break increased with higher RP content. Multiple recycling cycles had minimal impact on tensile strength, and the heat deflection temperature (HDT) remained nearly constant (~0.7 °C variation after 10 cycles, within experimental uncertainty). The melt flow index (MFI) increased significantly with successive recycling cycles, indicating molecular weight reduction due to thermomechanical degradation. DSC analysis confirmed stable melting and crystallization temperatures (variation < 1 °C), suggesting preserved crystalline structure. SEM analysis revealed increased void formation at the fiber–matrix interface and fiber attrition with successive recycling, correlating with reduced flexural properties. In-process recycling of %35GF-PA66 runners is viable, particularly at ≤15% RP and fewer cycles, offering significant cost savings (e.g., ~EUR 344,000 annually for a large producer) and environmental benefits. Full article

In this study, the influences of natural fibres (sugarcane bagasse (SB) and sawdust (SD)) on the material properties of polybutylene succinate (PBS) prepared through melt compounding were investigated. The study further evaluated the effects of incorporating halloysite nanotubes (HS) and expandable graphite (EG) on the properties of PBS/SD and PBS/SB binary and PBS/SB/SD hybrid composites. The morphological analysis indicated poor interfacial adhesion between PBS and the fibres. The obtained findings indicated enhancements in the complex viscosity of PBS in the presence of natural fibres, and further improvements in the presence of HS and EG. The stiffness of PBS hybrid composites also increased upon the addition of HS and EG. Moreover, the crystallization temperatures of PBS increased in the presence of fillers, with EG showing better nucleation efficiency. However, the mechanical properties (toughness and impact resilience) decreased due to the increased stiffness of the composites and the poor interfacial adhesion between the matrix and the fillers, indicating the need to pre-treat the fibres to enhance compatibility. Overall, the material properties of PBS/SD/SB hybrid composites were enhanced by incorporating HS and EG at low concentrations. Full article

We present an alternative process for production of binary Nb_1−βSn_β superconducting phases using pre- and post-treatment of arc-melted Nb + Sn ingots. This process combines sequential sintering, arc melting, and annealing procedures that provide dense, bulk samples of Nb_1−βSn_β with varying stoichiometry between 0.18 < β < 0.25 depending on annealing time and temperature. We show, through magnetization measurements of these Nb_1−βSn_β bulks, that annealing of arc-melted samples at 900 °C for 3 h significantly enhances J_c values compared with arc-melted Nb_1−βSn_β samples without annealing. Microstructural analyses show that optimum grain size and orientation are achieved by sintering and annealing at lower temperatures (i.e., 720 °C and 900 °C, respectively) with short annealing times (i.e., <10 h). Processing at higher temperatures and for longer times enhances grain growth and results in fewer pinning centres. The optimum process creates effective pinning centres that deliver a J_c = 6.16 × 10⁴ A/cm² at 10 K (and ~0.2 T), compared with J_c = 3.4 × 10⁴ A/cm² for Nb_1−βSn_β subjected to a longer annealing time at a higher temperature and J_c = 775 A/cm² for an arc-melted sample without post-annealing. We suggest that further work addressing post-treatment annealing times between 3 h < t_post < 60 h at temperatures between 900 °C and 1000 °C will provide the opportunity to control stoichiometric and microstructural imperfections in bulk Nb_1−βSn_β materials. Full article

The present work aims to verify whether the incremental hole-drilling technique (IHD), a widely accepted technique, is suitable for determining residual stresses in AISI 316L samples obtained by selective laser melting (SLM). The thermo-mechanical effects of cutting during the application of this technique can induce unwanted residual stresses due to the relatively low thermal conductivity of this material, leading to erroneous results. To accomplish this aim, a hybrid experimental-numerical method was implemented to analyze the ability of IHD to determine an imposed stress state. Experimentally, samples were subjected to a tensile calibration stress using a horizontal tensile test machine. To eliminate pre-existing residual stress, the samples were subjected to differential loads, instead of absolute ones. In this way, experimental strain-depth relaxation curves related to the imposed calibration stress were obtained. Based on the experimental data, IHD was numerically simulated using the finite element method. Numerical strain-depth relaxation curves, related to the same calibration stress used in the experimental study, were obtained. The comparison between the experimental and numerical strain-depth relaxation curves, as well as the stresses calculated using the so-called integral method for determining stresses via IHD, shows that IHD is a suitable technique for measuring residual stresses in additively manufactured AISI 316L samples. Full article

As a bio-based polymer, polybutylene succinate (PBS) has extensive applications in plastic products and film manufacturing. However, its low melt strength results in poor spinnability, and during the forming process, it tends to form large-sized spherulites and exhibit filament adhesion phenomena. These limitations have hindered its development in the field of fiber spinning. To enhance fiber strength, this work systematically investigated the effects of spinning temperature and spinning speed on the properties and structure of PBS pre-oriented yarns (PBS-POY). The results indicated that appropriately lowering the spinning temperature and increasing the spinning speed could improve the mechanical properties of the fibers. When the spinning temperature was 195 °C and the spinning speed reached 2500 m/min, the tensile strength of pre-oriented yarns achieved 2.09 cN/dtex. Furthermore, the evolution of properties and structures of pre-oriented yarns under maximum drawing conditions across different spinning speed systems was examined. By synchronously analyzing the correlations among mechanical properties, thermal behavior and condensed state structures, the structural performance regulation mechanism under the synergistic effect of spinning–drawing processes was revealed. The results demonstrated that fibers produced at higher spinning speeds contained more numerous and smaller spherulites. After maximum drawing, these smaller spherulites split into lamellae with higher uniformity, resulting in final fibers with smaller crystal sizes, higher crystallinity and improved orientation. As the spinning speed increased, the average crystal size of the final fibers decreased; the long period of the final fibers extended from 8.55 nm to 9.99 nm, and the mechanical strength improved to 2.72 cN/dtex. Full article

Nylon 11 is widely used in abrasion-resistant coatings due to its excellent wear resistance and processability. Here, the effects of different processing methods (pre-treatment temperatures, melting temperatures, and heating programs) and nucleating agents (silica, talcum powder, and montmorillonite) on the crystallinity behavior and wear resistance of Nylon 11 were systematically analyzed. The results show that pre-treating Nylon 11 at 80–100 °C enhances its wear resistance, and its friction coefficient drops to ~0.16. Melting temperature influences both the processing flowability and wear resistance of Nylon 11. Specifically, when the melting temperature exceeds 195 °C, wear resistance improves significantly and its friction coefficient decreases from 0.32 to 0.17. Moreover, variations in the heating program also affect the wear resistance of Nylon 11. Optimal wear resistance is achieved when Nylon 11 is held at both 165 °C and 185 °C for 10 min (friction coefficient: ~0.17). The nucleating agents (silica, talcum powder, and montmorillonite) do not change the crystalline morphology of Nylon 11, which predominantly exhibits an orthorhombic α-phase. However, as the content of nucleating agents increases (0–1 wt%), the crystallinity first rises and then declines, with its highest value being 46.48%. This work emphasizes the critical role of processing methods and nucleating agents in the wear resistance and crystallinity behavior of Nylon 11, providing valuable insights for their performance optimization. Full article

While self-healing of metals and alloys facilitated by electromagnetic pulse (EMP) energy introduced by electropulsing has been widely reported, the in-depth mechanism is still ambiguous. Here, an approximate in-situ observation was designed to explore the effect of EMP energy induced by electropulsing on the alloy interface self-healing. Electromagnetic shocking treatment (EST) utilizing EMP energy was demonstrated to promote metallic interface bridging and self-healing. At local regions, flat surfaces turn into wavy ones, especially, while local interface bridging and self-healing are commonly observed, indicating a nonlinear surface pre-melting. Based on the assumed mass–spring–damping system of the pre-melted interfaces, the mechanisms of local interface bridging and self-healing under the EST are explored. This work provides new understanding about the interface self-healing mechanism by electropulsing, as well as new insights about the effect of pulse energy (such as EMP) on metallic interface complexion. Full article

The thermal stability of bimetallic nanoparticles plays a crucial role in their performance in applications in catalysis, biotechnology, and materials science. In this study, we employ molecular dynamics simulations to investigate the melting behavior of Au-Pd nanoparticles with cuboctahedral, icosahedral, and decahedral geometries. Using a tight-binding potential, we systematically explore the effects of particle size and composition on the melting transition. Our analysis, based on caloric curves, Lindemann coefficients, and orientational order parameters, reveals distinct premelting behaviors influenced by geometry. Larger particles exhibit a coexistence of a pseudo-crystalline core and a partially melted shell, but, in decahedra and icosahedra, melting of the core occurs unevenly, with twin boundaries promoting the melting of one or two of the tetrahedral subunits before the rest of the particle. Notably, icosahedral nanoparticles display higher thermal stability, while both icosahedral and decahedral structures exhibit localized melting within twin boundaries. Additionally, we generate HAADF-STEM simulations to aid the interpretation of in situ electron microscopy experiments. Full article

Palm and palm kernel oils are preferred ingredients in industrial food processing for baked goods and chocolate-based desserts due to their unique properties, such as their distinctive melting behaviors. However, ongoing concerns about the social and environmental sustainability of palm oil production, coupled with consumer demands for palm oil-free products, have prompted the industry to seek alternatives which avoid the use of other tropical or hydrogenated fats. This project investigated replacing palm oils with chemically unhardened Swiss sunflower or rapeseed oils. Target applications were cookies and chocolate fillings. These oils were physically modified through emulsification, stabilized with finely ground oil press cake particles and crystallized waxes. Findings indicated that the emulsification of the oils increased viscosity and that the addition of wax was beneficial for long-term stability; however, the extent of this effect depended on the combination of oil and wax types. Furthermore, wax pre-crystallization and low shear during crystallization significantly improved emulsion stability. Despite these improvements, the resulting emulsions did not achieve sufficient stability and exhibited lower viscosity than palm oil. Future experiments should explore higher wax concentrations (1% or more) and develop analytical methods to better understand the wax composition and its role in oleogel formation. Full article

In this paper, the short-range ordering structures of Ga melts has been investigated using the Wulff cluster model (WCM). The structures with a Wulff shape outside and crystal symmetry inside have been derived as the equivalent system to describe the short-range-order (SRO) distribution of the Ga melts. It is observed that the simulated HTXRD patterns of the Ga WCM are in excellent agreement with the experimental data at various temperatures (523 K, 623 K, and 723 K). This agreement includes first and second peak positions, widths, and relative intensities of patterns, particularly at temperatures significantly above the melting point. A minor deviation in the second peak position has been observed at 523 K, attributed to the starting of the pre-nucleation stage. These findings demonstrate that the WCM can effectively describe the SRO structure in melt systems exhibiting a certain extent of covalency. Full article

This study reveals the significant role of the pre-melting process in growing high-quality (100) β-Ga₂O₃ single crystals from 4N powder (99.995% purity) using the edge-defined film-fed growth (EFG) method. Among various bulk melt growth methods, the EFG method boasts a fast growth rate and the capability of growing multiple crystals simultaneously, thus offering high productivity. The pre-melting process notably enhanced the structural, optical, and electrical properties of the crystals by effectively eliminating impurities such as Si and Fe. Specifically, employing a 100% CO₂ atmosphere during pre-melting proved to be highly effective, reducing impurity concentrations and carrier scattering, which resulted in a decreased carrier concentration and an increased electron mobility in the grown Ga₂O₃ single crystals. These results demonstrate that pre-melting is a crucial technique for substantially improving crystal quality, thereby promising better performance in β-Ga₂O₃-based device applications. Full article

The difference in the crystallization kinetics during growth from the melt between II–VIs (CdTe, Cd_1−xZn_xTe, ZnSe, and ZnTe) and III–Vs (GaAs and InP) is discussed. At the melt growth of II–VI crystals, the most important difference is the lack of controllability of seeding and achievement of a desired growth orientation. A pronounced tendency of self-orientation toward <111>, <110>, and sometimes <112> and <122>, but almost never toward <100> direction, has been observed regardless of whether a seed has been used or not. The main reason proves to be the tetrahedral coordination due to the high binding ratio of ionicity remaining in the II–VI melts but not occurring in III–Vs. As a result, the general effect of pre-ordering into density layers, forced by the solid surface, is in the II–VI liquids superimposed by a {111} self-orientation via tetrahedral in-plane alignment. Fitting growth kinetics seem to only be possible when this melt configuration conforms to the crystal structure, like the {111} but hardly the {100}. Otherwise, the liquid self-orientation determines the continuing crystal orientation. Additionally, an <100>-oriented seed abruptly changed into an <122> direction via a congruent twin plane. Although such considerations still need verifying atomistic simulations, they are helpful to optimize the growth methodology even for larger crystal diameters. Full article

The simulation of additive manufacturing has become a prominent research area in the past decade. Process physics simulations are employed to replicate laser powder bed fusion (L-PBF) manufacturing processes, aiming to predict potential issues through simulated data. This study focuses on calculating surface roughness by utilizing 3D surface topology extracted from simulated data, as surface roughness significantly influences part quality. Accurately predicting surface roughness using a simulation remains a persistent challenge. To address this challenge, the L-PBF technique with two different cases (pre- and post-contouring) was simulated using two-step process physics simulations. The discrete element method was utilized to simulate powder spreading, followed by the Flow-3D melting simulation. Ten layers were simulated at three different linear energy density (LED) combinations for both cases, with samples positioned at a 30-degree angle to accommodate upskin and downskin effects. Furthermore, a three-dimensional representation of the melted region for each layer was generated using the thermal gradient output from the simulated data. All generated 3D layers were stacked and merged to consolidate a 3D representation of the overall sample. The surfaces (upskin, downskin, and side skins) were extracted from this merged sample. Subsequently, these surfaces were analyzed, and surface roughness (Sa values) was calculated using MATLAB. The obtained values were then compared with experimental results. The downskin surface roughness results from the simulation were found to be within the range of the experimental results. This alignment is attributed to the fact that the physics simulation primarily focuses on melt pool depth and width. These promising findings indicate the potential for accurately predicting surface roughness through simulation. Full article