Search Results (105)

The increasing demand for critical raw materials such as copper and cobalt highlights the need for efficient beneficiation of low-grade ores. This study investigates a copper–cobalt sulfide ore (0.99% Cu, 0.028% Co) using froth flotation to produce high-grade concentrates. Various types of surfactants are applied in different ways, each serving an essential function such as acting as collectors, frothers, froth stabilizers, depressants, activators, pH modifiers, and more. A series of flotation tests employing different collectors (SIPX, PBX, AERO, DF 507B) and process conditions was conducted to optimize recovery and selectivity. Methyl isobutyl carbinol (MIBC) was consistently used as the foaming agent, and 700 g/L was used as the slurry density at 25 °C. Dosages of 30 and 100 g/t¹ were used in all tests. Notably, adjusting the pH to ~4 using HCl significantly improved cobalt concentrate separation. The optimized flotation conditions yielded concentrates with over 15% Cu and metal recoveries exceeding 80%. Mineralogical characterization confirmed the selective enrichment of target metals in the concentrate. The results demonstrate the potential of this beneficiation approach to contribute to the European Union’s supply of critical raw materials. Full article

Polyurethane foam is widely used as a primary filling material in car seats. While it provides good damping and energy absorption, the mechanical properties are complex but play a vital role in vibration attenuation and vehicle ride comfort. This study proposes a comprehensive experimental and analytical method to characterize the visco-hyperelastic properties of seat-grade polyurethane foam. Quasi-static and dynamic compression tests were conducted on foam blocks to obtain load–deflection curves and dynamic stiffness. A visco-hyperelastic material model was developed, where the hyperelastic response was derived via the hereditary integral and difference-stress method, and viscoelastic behavior was captured using a Prony series fitted to dynamic stiffness data. The model was validated using finite element simulations, showing good agreement with experimental results in both static and dynamic conditions. The proposed method enables accurate characterization of the visco-hyperelastic material properties of seat-grade polyurethane foam. Full article

In functionally graded polymer foam, mechanical properties and chemical composition vary in a prescribed direction according to a power law distribution. However, most manufacturing methods lack precise control over pore size, limiting their application. In this case, the graded foam structure can be formed from separate layers, with each layer assigned unique values in terms of mechanical properties or chemical composition based on the power law distribution. The hypothesis of the work is that the application of functionally graded (FG) foam materials inside the rotor blades or wings of an unmanned aerial vehicle can provide the ability to vary their stiffness properties. The aim of this work is to conduct an investigation of the static behaviour of a composite box plate with constant and variable heights that simulate the dimensions and changing profile of a helicopter rotor blade. In the numerical analysis, two models of composite box plate are considered and the material properties of graded polymeric foam core are assumed to vary continuously by the power law along the width of cross-sectional structures. It is not possible to model the continuous flow of graded properties through the foam in construction; therefore, the layers of foam are modelled using discontinuous gradients, where the gradient factor changes step by step. The numerical results are obtained using ANSYS software. The results of the numerical calculation showed that the use of graded foam affects the parameters under study. The stiffness of a structure significantly decreases with an increase in the power law index. Full article

Objectives: The objective of this study is to compare the bone-regenerating capacity between chitosan foam and chitosan membrane scaffolds. Methods: A medium-weight chitosan acidic mixture was used to prepare two scaffolds of freeze-dried chitosan foam (CF). One of the two CF scaffolds was physically crosslinked by NaHCO₃ to obtain chitosan membrane (CM). A morphological assessment of the specimens’ porosity was carried out by scanning electron microscopy (SEM). An MTT assay of the CM and CF specimens using rats’ bone marrow mesenchymal stem cells (MSCs) was carried out. Then, 38 albino rats were subjected to surgical implantation in a critical-size defect of the femur bone. The rats were divided into three groups according to the type of implanted scaffold (Control (no scaffold) n = 10, CM (chitosan membrane) n = 14, CF (chitosan foam) n = 14). Each group was equally subdivided into two subgroups according to the time of euthanasia (21 d, 35 d). The femur bones were dissected for a histological analysis (hematoxylin and eosin, and Masson trichrome). The results of the histological analysis were graded according to a scoring system. A statistical analysis of the pore size and histological grading was carried out. Results: CF had a higher mean pore size (65.42 µm) compared to CM (6.44 µm); CM showed a significantly higher proliferation of MSCs at 72 h. Both the CM and CF groups showed a significantly higher bone regeneration and lower inflammation than the control group. The CF group showed a significantly higher bone regeneration score than the CM group, especially at 35 d with more dense compact lamellar bone structure. Conclusions: The higher mean pore size of CF allowed for a higher bone regenerating capacity than the crosslinked CM. Full article

Foam and hydrogel profile control are commonly utilized water-blocking and profile modification techniques in oil fields. This study integrates a foam system with a gel system, employing an organic titanium crosslinking agent to crosslink polyvinyl alcohol, thereby forming a gel system. Concurrently, a gas-evolving agent is incorporated into the system to induce in situ foaming, thereby creating an environmentally benign foam gel system. The fundamental constituents of this system comprise 2 wt% to 5 wt% polyvinyl alcohol, 2 wt% to 4 wt% crosslinker, and 0.3 wt% to 0.9 wt% gas-generating agent. By varying the amounts of each component, the strength grade, gelation time, and foaming volume of the foam gel can be effectively adjusted. The results of the temperature resistance performance evaluation indicate that within the temperature range of 80 °C to 130 °C, the gelation performance of the foam gel is stable and good. At 90 °C, the foam gel can remain stable for 340 days with minimal strength variation. The plugging experiments indicate that the formulated foam gel system exhibits superior injectability and can effectively seal the sand-filled tube model, achieving a blocking efficiency of up to 96.36%. Full article

Traditional assessments of balance and postural control often face challenges related to accessibility, cost, subjectivity, and inter-rater reliability. With advancements in technology, smartphones equipped with inertial measurement units (IMUs) are emerging as a promising tool for assessing postural control, measuring both static and dynamic motion. This study aimed to develop and validate a novel smartphone application by comparing it with research-grade posturography instruments, including motion capture and force plate systems to establish construct- and criterion-related validity. Twenty-two participants completed the quiet stance under varying visual (eyes open—EO; eyes closed—EC) and surface (Firm vs. Foam) conditions, with data collected from the smartphone, force plate, and motion capture systems. Intraclass correlation coefficients (ICCs) and Pearson correlation coefficients assessed the reliability and validity for all outcome measures (sway area and sway velocity). The results demonstrated reliability, with strong validity between the devices. A repeated-measures ANOVA found no significant differences between the devices. Postural outcomes revealed the significant main effects of both the visual (EO vs. EC) and surface (Firm vs. Foam) conditions. In conclusion, the study demonstrated the validity, sensitivity, and accuracy of the custom-designed smartphone app, offering the potential for bridging the gap between at-home and clinical balance assessments. Full article

Kluyveromyces marxianus is a food-grade yeast known for its diverse beneficial traits, making it an attractive candidate for both food and biotechnology applications. This study explores the potential of Kluyveromyces marxianus as a promising alternative protein source for single-cell protein (SCP) production. Various Kluyveromyces strains were isolated and screened from traditional fermented dairy products, with Kluyveromyces marxianus NS127 identified as the most promising strain due to its superior growth characteristics, high SCP yield, and environmental tolerance. Notably, Kluyveromyces marxianus NS127 demonstrated significant substrate conversion capacity with a biomass yield of 0.63 g biomass/g molasses, achieving a dry biomass concentration of 66.64 g/L and a protein yield of 28.37 g/L. The protein extracted from the dry biomass exhibited excellent solubility (62.55%) and emulsification properties (13.15 m²/g) under neutral conditions, alongside high foaming stability (93.70–99.20%) across a broad pH range (3–11). These results underscore the potential of Kluyveromyces marxianus NS127 as a viable alternative protein source and provide a solid theoretical foundation for its industrial application. Full article

The porous structure, in which many pores are intentionally placed inside the material, has excellent impact energy absorption properties. Recent studies have attempted to fabricate multi-layered porous structures with different mechanical properties within a single porous structure sample, and the mechanical properties of these structures are being elucidated. However, these studies mainly attempted to vary the densities, pore structures, and alloy compositions within a single material, such as aluminum, for the entire sample. Since multi-materials are now being promoted to utilize the most suitable material type in the right place, porous structures made of different materials, such as a combination of aluminum and resin, are expected to be required in the future. In this study, we attempted to fabricate two-layered porous structure samples of different materials by printing a resin porous structure using a 3D printer on an aluminum foam fabricated by a precursor foaming process. Static compression tests were performed on the resulting two-layered porous structure samples to investigate their mechanical properties. The resin porous structure printed by the 3D printer and the aluminum foam were both designed to expose the porous structure on the surface of the specimen so that the deformation behavior can be easily observed. The density of the resin porous structure was varied by systematically varying the filling rate of the resin porous structure to be printed, and the effect on the compression properties was investigated. The fabricated two-layered porous structure was effectively bonded between the two layers by the anchor effect, which is a mechanical bonding caused by the resin penetrating into the pores. The layers exhibited robust bonding with no evidence of separation. It was possible to fabricate a two-layered porous structure that exhibited both properties of aluminum foam and those of resin porous structure. It was found that the plateau stress in the resin porous structure layer can be controlled between about 0.5 MPa and 40 MPa, and the deformation behavior and energy absorption properties of the two-layered porous structure can be controlled by varying the resin filling rate of the resin porous structure layer. That is, it was indicated that multi-layered porous structures with various densities and consisting of various types of materials allow for the optimal design of porous structures used in structural materials. Full article

In response to global energy, resource, and climate challenges, foamed concrete—a sustainable, low-carbon building material—offers advantages due to its lightweight nature and high thermal insulation. This study focused on alkali-activated foamed concrete (A07 grade, average density of 723 kg/m³) prepared from slag and fly ash under alkaline conditions. Using S95-grade slag powder and I-grade ground fine fly ash as raw materials, a sodium silicate and NaOH solution as the activator, and YS-200 composite cement foaming agent, alkali-activated foamed concrete with a density grade of A07 was prepared by physical foaming. The effects of water–binder ratio, fly ash content, and alkali equivalent on compressive strength, water absorption, drying shrinkage, and frost resistance were investigated. With a dry density of 300–1800 kg/m³ (1/10 to 1/3 of conventional concrete), it reduced building weight by 25–40%. Full article

The most commonly used methods to chemically assess grape and wine quality with high sensitivity and selectivity require lengthy analysis time and can be resource intensive. Here, we developed a rapid and non-destructive method that would help in grading and decision support. In this work, we demonstrate that integrating a three-dimensional (3D) material for volatile sampling with mass spectrometry detection can be used to sample grapes for phytosanitary, quality or smoke-taint assessments at low levels of marker compounds. An efficient zeolitic imidazolate framework-8 (ZIF-8) material was synthesised in situ on nickel foam (NF), taking advantage of its ultrahigh surface area, structural diversity, and functionality as an emerging nanostructured material for preconcentrating low-level wine and grape quality-related volatiles. When used as a sorbent in thermal desorption tubes and coupled directly to active capillary mass spectrometry, the average signal across the selected analytes increased by ~50% as compared to Tenax TA, a commercially available polymer, in a measurement that takes less than two minutes. The first integration of 3D materials into mass spectrometry opens new possibilities for developing new material architecture with enhanced selectivity of next-generation multifunctional instrumentation for volatile analysis and product quality assessment. Full article

The enhancement of the utilization rate of solid waste, along with balancing the comprehensive performance of materials, presents a significant challenge in the development of new functional building materials. This study examined the effects of high concentrations of iron tailing powder on the crystallization characteristics, pore structure, compressive strength, and water absorption of modified magnesium oxysulfate (MOS) foam cement with different dry densities. Furthermore, employing chemical foaming technology, the study characterized and analyzed the microstructure of modified MOS foam cement hydration products through scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The results indicated that the addition of an acidic modifier effectively facilitated the hydration reaction in the MgO-MgSO₄-H₂O system, enhancing the micro-crystallization characteristics of MOS foam cement. The internal pores were uniformly round, with a dense crystal structure within the pore walls. The compressive strength of the material with 40% dry density A08 grade iron tailing powder reached 6.83 MPa, and the lowest water absorption was 5.32% at a dry density of A09. Full article

In recent years, due to the diversity of fire scenes in ports and ships, the problem of fire command is complicated. In the case of power failure, the original command platform and fire extinguishing system will not be able to be used normally, or the fire extinguishing resources carried by the ship when it is on fire cannot be used. In the traditional firefighting ability research, there is no clear measure of firefighting ability, resulting in inaccurate calculation results. By corresponding to the quantity and composition of resources for the study of fire extinguishing capability, the combination of the fire dynamics simulation software PyroSim2020 and a calculation model that converts its resources into the total amount and flow of fire extinguishing agent can be provided. Based on the analytic hierarchy process (AHP), a firefighting demand grade calculation and judgment model was established, which included five factors: fire scale, combustion material characteristics, foam extinguishing agent performance, firefighting object characteristics, and external factors. It concluded that the demand assignment values of each index element were 2, 5, 6, 9, and 10, and further proposed the grade judgment criteria for the calculation results of comprehensive fire demand. Through the quantitative simulation of firefighting demand based on the fire scenario and calculation model test of the consumption prediction of cooperative firefighting equipment, it can also provide a strategic reference for related cooperative fire rescue. Full article

This study explores the strengthening mechanism of the surfactant branched block polyethylene oxide–polypropylene oxide (BB-PEO-PPO) in sodium oleate (NaOL) flotation systems. A comprehensive characterization of BB-PEO-PPO was performed using flotation experiments, contact angle measurements, surface tension analysis, zeta potential measurements, infrared spectroscopy, and foam dynamics assessments. Flotation results showed that the combination of BB-PEO-PPO and NaOL improved iron recovery by 2.71% and reduced the total iron (TFe) grade in tailings by 2.05%, demonstrating a significant enhancement in collecting efficiency. The addition of BB-PEO-PPO effectively reduced foam size and lowered the zeta potential on the surface of activated quartz. At a slurry temperature of 15 °C, BB-PEO-PPO increased the solubility of NaOL radicals, facilitating their chemical adsorption onto activated quartz and improving the hydrophobicity of quartz particles. Notably, the presence of BB-PEO-PPO extended the flotation foam discharge time (D50) by 50% without substantially increasing foam volume, thereby significantly enhancing foam stability. Full article

This work investigates the mechanical behaviour of sandwich beams with cellular cores using a multiscale approach combined with a meshless method, the Natural Neighbour Radial Point Interpolation Method (NNRPIM). The analysis is divided into two steps, aiming to analyse the efficiency of NNRPIM formulation when combined with homogenisation techniques for a multiscale computational framework of large-scale sandwich beam problems. In the first step, the cellular core material undergoes a controlled modification process in which circular holes are introduced into bulk polyurethane foam (PUF) to create materials with varying volume fractions. Subsequently, a homogenisation technique is combined with NNRPIM to determine the homogenised mechanical properties of these PUF materials with different porosities. In this step, NNRPIM solutions are compared with high-order FEM simulations. While the results demonstrate that RPIM can approximate high-order FEM solutions, it is observed that the computational cost increases significantly when aiming for comparable smoothness in the approximations. The second step applies the homogenised mechanical properties obtained in the first step to analyse large-scale sandwich beam problems with both homogeneous and functionally graded cores. The results reveal the capability of NNRPIM to closely replicate the solutions obtained from FEM analyses. Furthermore, an analysis of stress distributions along the beam thickness highlights a tendency for some NNRPIM formulations to yield slightly lower stress values near the domain boundaries. However, convergence towards agreement among different formulations is observed with mesh refinement. The findings of this study show that NNRPIM can be used as an alternative numerical method to FEM for analysing sandwich structures. Full article

The purpose of this study was to analyze the effects of phase-change components on the properties of geopolymer foams. Geopolymer foams are lightweight foamed geopolymers that are characterized by a high degree of porosity. Phase change materials, on the other hand, are compounds that, when added to a material, allow it to absorb, store, and then release large amounts of energy. Three types of PCMs, i.e., MikroCaps, GR42, and PX25, were introduced at 15% by weight. Geopolymer materials were produced based on silica fly ash, and hydrogen peroxide H₂O₂ was used to foam the geopolymer structure. The PCM geopolymer composites were cured at 60 °C. The produced materials were tested for physical, chemical, and thermal properties. The tests included oxide and mineral composition analysis of the base material, PCM particle size analysis, apparent density and porosity tests on the foams, water leachability tests, thermal tests (λ, Cv, Cp, α), and structural and textural analysis. The most relevant tests to confirm the performance of the phase-change materials were thermal tests. With the introduction of PCMs, volumetric heat capacity increased by as much as 41% and specific heat by 45%, and thermal diffusivity decreased by 23%. The results confirm the great potential of geopolymer composites as modern insulation materials for buildings and structures. Full article