Mixed Materials Research Articles

Numerical modelling and experimental validation of an Enhanced multi-force model of free-fall electrostatic separators

Electrostatic separation is a crucial process for separating mixed materials, especially in recycling discarded electrical and electronic equipment. This study aims to validate an enhanced numerical model for free-fall electrostatic separators by incorporating additional forces. The model simulates particle trajectories under electrostatic forces, considering electrostatic interactions and collisions. The particles’ positions, masses, and charges are recorded to create a comprehensive database for model verification. The model was validated experimentally using three-particle mixtures of PVC-PC, PS-PC, and PS-PVC; experimental validation confirms that the updated model accurately captures the complex physical processes in the electrostatic separator. Including additional forces results in more precise particle behavior, essential for optimizing separator design and improving the purity of the separated products. The results show a concordance of mass and charge 98.812% and 96.907% for PS + PVC, 99.972% and 98.715% for PC + PVC mixtures, and 92.406% for mass and 97.244% for charge in PS+PC mixtures, demonstrating the model’s accuracy and reliability.

Effects of triflute pin geometry on defect formation and material flow in FSW using CEL approach

Complicated tool pin designs in Friction Stir Welding (FSW) need to be considered in terms of material flow and defect formation. This study investigates the effects of the triflute tool's geometrical parameters on temperature, strain, void formation, and material mixing using a numerical method. The numerical model employs a coupled Eulerian-Lagrangian (CEL) formulation and successfully predicts void formation and material mixing during friction stir welding (FSW). Four tool pin designs are considered for material flow, including one cylindrical pin and three triflute pins with flute radii of 1 mm, 1.5 mm, and 2 mm. The findings indicate that the stir zone is divided into shoulder-driven and pin-driven zones, each exhibiting distinct material flow patterns. In the shoulder-driven zone, material flow toward the advancing side is dominant, while in the pin-driven zone, it flows toward the retreating side. Flutes on the FSW pin tool increase the sweeping rate, strain, and material movement in the stir zone. However, flutes with a larger radius sweep a greater amount of material and thus require more softened material to facilitate movement. Therefore, for defect-free joint formation, a higher rotational speed of the tool will be required, which may adversely affect tool lifespan and joint mechanical properties. The effectiveness of flutes with a smaller radius of 1 mm is significantly greater than that of those with a larger radius (1.5 or 2 mm) in enhancing material flow and achieving defect-free welding.

Multiphase Viscoelastic Non‐Newtonian Fluid Simulation

AbstractWe propose an SPH‐based method for simulating viscoelastic non‐Newtonian fluids within a multiphase framework. For this, we use mixture models to handle component transport and conformation tensor methods to handle the fluid's viscoelastic stresses. In addition, we consider a bonding effects network to handle the impact of microscopic chemical bonds on phase transport. Our method supports the simulation of both steady‐state viscoelastic fluids and discontinuous shear behavior. Compared to previous work on single‐phase viscous non‐Newtonian fluids, our method can capture more complex behavior, including material mixing processes that generate non‐Newtonian fluids. We adopt a uniform set of variables to describe shear thinning, shear thickening, and ordinary Newtonian fluids while automatically calculating local rheology in inhomogeneous solutions. In addition, our method can simulate large viscosity ranges under explicit integration schemes, which typically requires implicit viscosity solvers under earlier single‐phase frameworks.

Acoustic design of an innovative classroom: the Piscopia Corner in Milan

This paper reports on the measurements, design, and testing of a highly innovative classroom: the Piscopia Corner - Augmented Education Lab, built in the new MIND (Milano Innovation District) district in Milan, Italy. This educational space is designed to leverage connectivity, artificial intelligence, and sensing to enhance sustainability, inclusivity, and efficacy. As key use cases of the Piscopia Corner pivot on real-time speech transcription and translation of interactions, acoustics plays a key role. Improving classroom acoustic conditions is crucial for enhancing speech clarity, promoting student focus, and relieving teachers of vocal effort. The Italian standard UNI 11532-2:2020 states proper requirements for multimedia classrooms such as the one involved in the present case. This space aims for superior speech intelligibility, accommodating multiple speakers and addressing the needs of individuals with hearing impairments or language barriers, with a high outward intelligibility. The Piscopia Corner is a modern classroom meeting the stringent requirements of interactive audio-video activities and inclusive principles. The treated suspended ceiling integrated with sensor technology required a proper mix of materials to balance the sound absorption in frequency and improve speech intelligibility to achieve category A4 limits.

Experimental and numerical analysis of the vibrational behaviour of metallic structures filled with damping materials

This work focuses on characterizing and modeling the vibrational behavior of hollow metallic structures filled with damping material. Vibration tests are first carried on a hollow structure, then two filling materials are considered: a cast viscoelastic material and a granular material composed of epoxy and polyurethane beads. Modal parameters (natural frequencies, modal damping and mode shapes) are extracted from the Frequency Response Functions with experimental modal analysis tools. Damping ratios greater than 5~\% are measured. Given the difference in the nature of the filling materials, dissipation mechanisms are different. The effectiveness of a damping material depends on the type of structural modes (bending, torsion or wall mode) to be damped, and dissipation in filling materials cannot be modelled by a constant loss factor or viscous damping. Consequently, a finite element modeling of the structure filled with viscoelastic material is proposed. Numerical modal parameters of the structure are correlated with experimental measurements. By extension, a bead mix material law, based on a fractional Zener model, is proposed, whose parameters are obtained by inverse identification.

Deep learning-based construction and demolition plastic waste classification by resin type using RGB images

The construction and demolition sector generates a substantial portion of Australia's total waste, with plastics being a key recyclable component. The perceived financial impracticality of sorting and separating waste, coupled with the simplicity of landfilling processes often contribute to mixed material loads sent directly to landfills. Therefore, developing a commercially feasible system that can accurately separate the generated waste is imperative. This paper presents a comprehensive study on using RGB images for deep learning-based construction and demolition plastic waste classification by resin type. A large and specialised dataset of end-of-life plastic waste images is gathered. This dataset comprises four commonly used plastic types in construction projects—ABS, HDPE, PS, and PVC. Leveraging Transfer Learning with models pre-trained on ImageNet, highly accurate models tailored to this classification task are developed in this paper. Advanced Convolutional Neural Network and Vision Transformer-based models, including ResNet, ResNeXt, RegNet, and Swin Transformer, are trained and evaluated on this dataset. Another contribution of this work is Knowledge Distillation from a large, computationally intensive, and accurate model to enhance the accuracy of fast and compact models specifically designed for deployment on edge devices. This study applies Knowledge Distillation by using the output class probabilities of the large, computationally intensive Swin Transformer model to enhance the accuracy of the fast and lightweight MobileNetV3 models. The results demonstrate that RGB images offer a practical alternative to other costly and complex systems for effective plastic identification, due to their availability, low cost, ease of use, simple setups, and robustness to variations in operational conditions.

Natural sorting of sediments in the wave run-up zone works for microplastics as well

The distribution of plastic pollution in the marine environment is highly variable in time and space, making it difficult to assess pollution levels. This study shows that mixing and natural sorting of material in the wave run-up zone of a sandy beach results in a relatively stable abundance of microplastics in the size range 0.5–2 mm (S-MPs). Based on 175 samples collected over 14 months during 42 monitoring surveys at 6 stations along the shore of the Vistula Spit (Baltic Sea), the mean abundance of S-MPs was found to be 64 ± 36 items/kg DW (98.6 % fibers), with a coefficient of variation of only 56 % over more than one year. Statistical tests confirmed its independence from current wind speed, significant wave height, mean sediment grain size, sediment sorting, percentage of certain sand fractions, month, season, or location along the shore. It can therefore be used as a suitable indicator for long-term monitoring of increasing plastic pollution in the marine environment.

Closed-Loop Recycling of Wearable Electronic Textiles.

Wearable electronic textiles (e-textiles) are transforming personalized healthcare through innovative applications. However, integrating electronics into textiles for e-textile manufacturing exacerbates the rapidly growing issues of electronic waste (e-waste) and textile recycling due to the complicated recycling and disposal processes needed for mixed materials, including textile fibers, electronic materials, and components. Here, first closed-loop recycling for wearable e-textiles is reported by incorporating the thermal-pyrolysis of graphene-based e-textiles to convert them into graphene-like electrically conductive recycled powders. A scalable pad-dry coating technique is then used to reproduce graphene-based wearable e-textiles and demonstrate their potential healthcare applications as wearable electrodes for capturing electrocardiogram (ECG) signals and temperature sensors. Additionally, recycled graphene-based textile supercapacitor highlights their potential as sustainable energy storage devices, maintaining notable durability and retaining ≈94% capacitance after 1000 cycles with an areal capacitance of 4.92 mF cm⁻2. Such sustainable closed-loop recycling of e-textiles showcases the potential for their repurposing into multifunctional applications, promoting a circular approach that potentially prevents negative environmental impact and reduces landfill disposal.

Developing a hybrid-built pre-hardened alloy steel for injection moulding tools using the laser powder bed fusion process

Hybrid additive-subtractive manufacturing has been adopted as a cost-effective alternative for manufacturing plastic injection moulding tools with conformal-cooled inserts created by fusing powder and wrought material. This article reports the development of a hybrid power-wrought pre-hardened alloy steel to supplement the current material choice for fabricating injection mould inserts using this advanced manufacturing strategy. In this study, MS1 (maraging 300) steel powder was additively deposited onto pre-machined wrought Nimax steel to form a hybrid alloy material. The mechanical and microstructural properties of the fusion-bonded interface were examined. Microstructural observation revealed a 280 μm thick interfacial region consisting of a homogenous mixing of powder and substrate materials. As a result of solid solution strengthening within the region, tensile tests established robust powder-substrate bonding with tensile ruptures occurring well away from the interface. The as-built hybrid-alloy steel possessed excellent mechanical properties, with 1200 MPa in ultimate tensile strength, 12.4 % in elongation at fracture and 39 HRC (Nimax)/42 HRC (MS1) in hardness. The overall results suggested that hybrid MS1-wrought Nimax steel is a suitable pre-hardened material for manufacturing durable and high-performance injection mould inserts as part of a cost-effective hybrid additive-subtractive manufacturing strategy.

Fluid evolution and genesis of the Shipenggou gold deposit in Central Jilin Province, China: Constraints from C–H–O and in–situ sulphur isotopes of pyrite and fluid inclusions

The origin and evolution of the Shipenggou gold deposit in the Shipenggou–Jiapigou–Jinchengdong (SJJ) gold belt in Jilin Province, Northeast China, remain poorly understood. In this study, fluid inclusion and C–H–O–S isotopes from the Shipenggou deposit were investigated to clarify the fluid evolution and mineralisation process. The gold mineralisation is hosted in the biotite plagiogneiss of the Archaean Sandaogou Formation and is dominated by gold–bearing quartz veins. The orebodies are controlled by NNE– and NEE–striking brittle–ductile structures. Four stages of mineralisation have been identified: (I) milky quartz–minor pyrite, (II) quartz–pyrite–minor gold, (III) gold–quartz–polymetallic sulphide, and (IV) quartz–carbonate. Fluid inclusions were identified as four types: aqueous (VL–type), CO2–bearing (CL–type), CO2–rich (LC–type), and carbonic (PC–type). VL–, CL–, LC–, and PC–type FIs were developed within quartz from Stages I–II. Stage III quartz contains both CL– and VL–type FIs. Only VL–type FIs were observed in calcite from Stage IV. The total homogenisation temperatures (Tht) of FIs in Stages I, II, III, and IV are of 281.5–324.8, 215.5–269.1, 151.2–198.3, and 125.4–149.5 °C with salinities of 2.8–13.2, 2.8–9.6, 3.2–8.4, and 3.0–5.9 wt% NaCl eqv. Laser Raman spectroscopy analysis indicated the CL– and PC–type FIs from Stages I and II contain CO2 and minor quantities of CH4. The ore–forming fluids have developed from a medium temperature, low–medium salinity immiscible NaCl–H2O–CO2 ± CH4 system to a low temperature, low salinity homogeneous NaCl–H2O system. The HO isotopic compositions indicate that the initial ore–forming fluids were mantle–derived magmatic water. Subsequently, the ore–forming fluids were gradually joined by meteoric water. δ13C values indicate C in the fluids have originated from organic matter. Organic matter may have originated from the mantle, which mixed crust materials influenced by the subduction of the Palaeo–Pacific slab. In–situ, S isotope data of pyrite indicate that the origin of sulphur at the Shipenggou deposit is the mantle containing a crust component. Based on the above analysis results, the Shipenggou gold deposit is a mesothermal magma-hydrothermal vein–type gold deposit.

Cattaneo-Christov fluxes for nonlinear mixed convective entropy generated Reiner-Rivlin material flow

Thermal and solutal transportation processes involve in tremendous useful applications related to heat exchanger, scientific, micro-electronic device technologies and industry sectors like nuclear reactors cooling, marine engineering, nanotechnology, thin-film technology, biomedical applications and thermal conduction in soft tissue. In view of such useful applications the Cattaneo-Christov analysis for nonlinear mixed convective Reiner-Rivlin material flow in presence of constant applied magnetic field is considered. Heat source, magnetohydrodynamics and radiation are incorporated in energy equation. Cattaneo-Christov flux is employed to discuss the thermal and mass transport characteristics. Entropy calculation in radiating flow is discussed. The proposed non-linear systems are transformed into dimensionless ordinary systems through appropriate transformation. Non-linear ordinary expressions are computed for convergent series solutions through Optimal homotopy analysis technique (OHAM). Graphical interpretations for quantities under interest against pertinent variables are explored. Large magnetic parameter has opposite impact for entropy and fluid flow. An increase of temperature through thermal relaxation time parameter is noticed. Velocity has same trend for both mixed convection and Reiner-Rivlin fluid variables. Reduction in concentration is seen for solutal relaxation time parameter. Temperature enhancement is witnessed in presence of heat generation. Entropy rate enhancement for radiation is observed. Decrease in concentration is noticed for reaction. Entropy rate increases against diffusion variable is enhanced.

State of the art on solid–gas sorption based long-term thermochemical energy storage

Solid-gas sorption thermochemical heat storage technology is an innovative and promising solution for storing heat over long periods. The review focuses on the construction of composite sorption thermochemical heat storage materials and binary mixed salt materials with porous matrix as the supporting materials, which can further improve the hydration rate and cycle stability of single hydrated salt. Furthermore, the heat storage capabilities of the metal halide/ammonia working pair make it suitable for extreme environments, surpassing the limitations of water-based working pairs in terms of low-temperature adaptability. It is worth noting that common solid–gas reactors and measures to enhance heat and mass transfer are also reviewed. Meanwhile, the efficient open and closed heat storage systems and their optimization schemes are introduced, and the feasibility of the practical operation of the heat storage systems is evaluated comprehensively from the technical and economic perspectives, and the future research challenges are prospected.

Utilization of Agricultural Waste as a Total Mixed Ratio Pellet Material for Rex Rabbit Feed

This study aimed to evaluate the quality of Total Mixed Ration (TMR) pellets derived from agricultural waste and assess their potential as feed for Rex rabbits. The research employed an experimental approach, utilizing agricultural and plantation waste to produce TMR pellets. The study was conducted in two stages: pellet production and rabbit feeding trials. Three formulations of TMR pellets were developed with varying concentrations of oil palm empty fruit bunches (EFB): P1 (5% EFB), P2 (10% EFB), and P3 (15% EFB). The optimal formulation was subsequently used for the feeding trials. Rabbit feed treatments included T0 (60% commercial pellet + 40% forage), T1 (40% commercial pellet + 20% TMR pellet + 40% forage), T2 (30% commercial pellet + 30% TMR pellet + 40% forage), and T3 (60% TMR pellet + 40% forage). Results from the pellet analysis indicated no significant differences in organoleptic properties among the formulations. The durability test yielded the highest value of 98.77%, while the proximate analysis of the P1 formulation showed a dry matter content of 85.67%, ash content of 10.35%, organic matter of 89.65%, crude protein of 18.65%, crude fat of 18.72%, and crude fiber of 19.18%. In the rabbit feeding trials, there were no significant differences in rabbit performance when compared to those fed with commercial pellets. Based on these findings, it can be concluded that agricultural waste can be effectively utilized as a raw material for rabbit feed pellets, offering comparable quality to commercial alternatives. This research highlights the potential of agricultural waste in reducing environmental pollution while providing an economically viable alternative for animal feed.

Shock-driven three-fluid mixing with various chevron interface configurations

When a shock wave crosses a density interface, the Richtmyer–Meshkov instability causes perturbations to grow. Richtmyer–Meshkov instabilities arise from the deposition of vorticity from the misaligned density and pressure gradients at the shock front. In many engineering applications, microscopic surface roughness will grow into multi-mode perturbations, inducing mixing between the fluid on either side of an initial interface. Applications often have multiple interfaces, some of which are close enough to interact in the later stages of instability growth. In this study, we numerically investigate the mixing of a three-layer system with periodic zigzag (or chevron) interfaces, calculating the dependence of the width and mass of mixed material on properties such as the shock timing, chevron amplitude, multi-mode perturbation spectrum, density ratio, and shock mach number. The multi-mode case is also compared with a single-mode perturbation. The Flash hydrodynamic code is used to solve the Euler equations in three dimensions with adaptive grid refinement. Key results include a significant increase in mixed mass when changing from a single-mode to a multi-mode perturbation on one of the interfaces. The mixed width is mainly sensitive to the density ratio and chevron amplitude, whereas the mixed mass also depends on the multi-mode spectrum. Steeper initial perturbation spectra have lower mixed mass at early times but a greater mixed mass after the reflected shock transits back across the layer.

Particles reinforcement via friction stir processing (FSP): A Review

Abstract Friction stir processing (FSP) is a variant of friction stir welding (FSW) follows the same principle of operation as that of FSW; however, its purpose is very much different. FSP can be employed for the reinforcement of particulate filler in materials to form surface composites. FSP carries a tool of cylindrical shape with shoulder and pin. Being mounted with the spindle of the machine, it can rotate with high speed as well as exert vertical force and hence plunges the pin in to the materials. Heat originated due to friction softens the material beneath shoulder and as tool passed through ahead the material is processed and consolidated. During processing, materials experience severe deformation and mixing. Also, the temperature of the materials goes high significantly due to the synergetic effect of friction and plastic deformation. Due to the material mixing and thermo-mechanical nature, the process opens the door for the possible incorporation of second phase particles in the processed region. In this review, firstly processing/reinforcement approaches will be discussed which will be followed by effect of process parameters. After that, microstructure evolution and related mechanical properties will be discussed in detail. The synergism among process parameters, microstructure and mechanical properties will also be discussed.

Effect of Adding Polypropylene Plastic Waste on Compressive Strength and Flexural Strength Concrete

Indonesia is the second largest producer of plastic waste in the world after China with an annual contribution of 187.2 million tons of plastic waste. This study aims to analyze the effect of the addition of plastic seeds with polypropylene substitution on the compressive strength and flexural strength of concrete with the intention of reducing waste waste and utilizing it as a concrete mixing material and making concrete properties into green concrete. The method used is the experimental method by making several variations of concrete mixtures with plastic seeds of polypropylene type as a substitute for part of the sand. The mixing of plastic seeds is divided into several variations, namely, 3% polypropylene seeds and 6% polypropylene seeds. Analysis of the test results of the addition of polypropylene seeds compared to the concrete mixture without polypropylene seeds resulted in a compressive strength of 24.14 MPa for the addition of 3%, as well as a value of 23.25 MPa for the addition of 6% each at 28 days of concrete age. As for the flexural strength, an increase value of 0.16 MPa was obtained for the addition of 6% and the addition of 3% at the age of 28 days. This study shows that the results of the study have reached the planned quality target, namely the quality of fc'20 Mpa.

A closer look at individual collisions of dust aggregates: material mixing and exchange on microscopic scales

ABSTRACT Collisions between aggregates with different histories and compositions are expected to be commonplace in dynamically active protoplanetary discs. None the less, relatively little is known about how collisions themselves may contribute to the resulting mixing of material. Here, we use state-of-the-art granular dynamics simulations to investigate mixing between target/projectile material in a variety of individual aggregate-aggregate collisions, and use the results to discuss the efficiency of collisional mixing in protoplanetary environments. We consider sticking collisions (up to 10–20 m s–1 for our set-up) and disruptive collisions (40 m s–1) of ballistic particle–cluster aggregation (BPCA) and ballistic cluster–cluster aggregation (BCCA) clusters, and quantify mixing in the resulting fragments on both individual fragment and sub-aggregate levels. We find that the mass fraction of material that can be considered to be ‘well-mixed’ (i.e. locally made up of a mix of target and projectile material) to be limited, typically between 3 and 6 per cent for compact BPCA precursors, and increasing to 20–30 per cent for more porous BCCA clusters. The larger fragments produced in disruptive collisions are equally heterogeneous, suggesting aggregate–aggregate collisions are a relatively inefficient way of mixing material with different origins on small scales.

Determination of thermal properties of grouting materials for borehole heat exchangers (BHE)

Thermal properties of grouting materials for borehole heat exchangers (BHE) are currently analysed with varying measurement methods and analysis procedures, resulting in difficulties when comparing values of different studies. This study therefore provides the first comprehensive investigation of different analysis procedures by systematically comparing the influence of the measurement method and the sample preparation on the determination of the thermal conductivity and the volumetric heat capacity. Seven dissimilar grouting materials with varying water–solid ratios (W/S) and compositions are analysed. The thermal conductivities of the materials range between 0.9 and 1.8 W m−1 K−1 (transient plane source method, TPS). The volumetric heat capacities range between 3.01 and 3.63 MJ m−3 K−1 (differential scanning calorimetry, DSC). From the findings of this study, a standardised analysis of grouting materials is provided which suggests mixing of the grouting material at a high mixing speed and sample curing under water for 28 days at room temperature. The benefits of calculating the volumetric heat capacities of grouting materials from the specific heat capacities of dry samples measured with the DSC, the water content and the bulk density are demonstrated. Furthermore, an estimation procedure of volumetric heat capacity from the W/S and suspension density with an uncertainty of smaller ± 5% is provided. Finally, this study contributes to consistency and comparability between existing and future studies on the thermal properties of grouting materials.

Preparation and properties of GdPO4:Dy3+ phosphors and ceramics with high thermal stability

In this work, Gd1-xPO4:xDy3+ powders were synthesized by calcining the mixed raw materials at 1273 K and the optimal doping concentration was determined. Then the optimized composition powders were fabricated as ceramics after granulation, pressing and sintering. Meanwhile, the luminescent properties of the phosphors and ceramics, especially the thermal stability, were discussed. The results revealed that Gd1-xPO4:xDy3+ exhibited two strong emission peaks of blue light and yellow light under the excitation of 349 nm, ascribed to the energy level transition from 4F9/2 to 6H15/2 and 6H13/2 of the electrons of Dy3+, and the color coordinates were located in the white light region. The optimal doping concentration of Dy3+ was found as 0.1, and the electronic dipole-dipole interaction contributed to the concentration quenching. It was noted that the phosphors had good thermal stability. Specifically, the thermal stability was further improved after the ceramics was formed and the relative intensity between the blue and yellow changed the opposite, indicating different occupation sites of Dy3+.

Inheritance patterns of male asexuality in hybrid males of a water frog Pelophylax esculentus.

Gametogenesis produces gametes as a piece of genetic information transmitted to the offspring. While during sexual reproduction, progeny inherits a mix of genetic material from both parents, asexually reproducing organisms transfer a copy of maternal or paternal DNA to the progeny clonally. Parthenogenetic, gynogenetic and hybridogenetic animals have developed various mechanisms of gametogenesis, however, their inheritance is not fully understood. Here, we focused on the inheritance of asexual gametogenesis in hybrid Pelophylax esculentus (RL), emerging after crosses of P. lessonae (LL) and P. ridibundus (RR). To understand the mechanisms of gametogenesis in hybrids, we performed three-generation experiments of sexual P. ridibundus females and hybrids from all-male hybrid populations. Using fluorescent in situ hybridization, micronuclei analysis, flow cytometry and genotyping, we found that most adult hybrid males simultaneously produced two types of clonal sperm. Also, most male tadpole progeny in two successive backcrossed generations simultaneously eliminated L and R parental genomes, while some progeny produced only one type of sperm. We hypothesize that the reproductive variability of males producing two kinds of sperm is an adaptive mechanism to reproduce in mixed populations with P. ridibundus and may explain the extensive distribution of the all-male lineage across the European River Basin.