Search Results (231)

A rising demand for low-gluten beer fuels research into enzymatic solutions. This study optimized Aspergillus niger prolyl endopeptidase (AN-PEP) application timing during brewing to reduce gluten while preserving physicochemical quality. Ale-type beers were produced with AN-PEP (2% v/v) added at mashing, boiling, post-boiling, or post-fermentation, plus a control. Three mashing profiles (Mash A, B, C) were also tested. Gluten was quantified by R5 ELISA (LOQ > 270 mg/L). Color, bitterness, ABV, and foam stability were assessed. Statistical analysis involved ANOVA and Tukey’s HSD (p < 0.05). Enzyme activity and thermal inactivation were also evaluated. Initial gluten levels consistently exceeded LOQ. Significant gluten reduction occurred only post-fermentation. Mashing, boiling, and post-boiling additions effectively lowered gluten to below 20 mg/L. Post-fermentation addition resulted in significantly higher residual gluten (136.5 mg/L). Different mashing profiles (A, B, C) with early enzyme addition achieved similar low-gluten levels. AN-PEP showed optimal activity at 60–65 °C, inactivating rapidly at 100 °C. Physicochemical attributes (color, extract, bitterness, ABV) were largely unaffected. However, foam stability was significantly compromised by mashing and post-fermentation additions, while preserved with boiling and post-boiling additions. AN-PEP effectively produces low-gluten beers. Enzyme addition timing is critical: while mashing, boiling, or post-boiling additions reduce gluten to regulatory levels, only the beginning of boiling or post-boiling additions maintain desirable foam stability. These findings offer practical strategies for optimizing low-gluten beer production. Full article

The sustainable utilization of solid waste is crucial for environmental protection. This work investigates the fabrication of foamed ceramics from Cr slag and municipal solid waste incineration (MSWI) fly ash, focusing on the effects of three inhibitors—NH₂SO₃H, ZnO·TiO₂, and (NH₄)₂HPO₄—on material properties and Cr leaching behavior. Experimental analysis, chemical thermodynamic calculations, and material characterization were all employed. Results show that the prepared foamed ceramics meet the JG/T 511-2017 standard for building materials, exhibiting excellent physical properties but significant Cr leaching. Among the inhibitors, (NH₄)₂HPO₄ with a molar ratio of n(P)/n(Cr) = 1 shows the best performance, achieving a bulk density of 205 kg/m³, compressive strength of 0.850 MPa, Cr leaching concentration of 188 μg/L, and a 70.0% of Cr leaching inhibition rate. The improvement is attributed to the AlPO₄ formation that enhancing the strength, and Ca₂P₂O₇ that stabilizing Cr during sintering. This work provides a feasible method for the safe resource utilization of Cr-containing waste. Full article

Despite efforts to recycle, boro-alumino-silicate pharmaceutical glass (BASG) results in a significant portion of glass cullet currently landfilled. Highly contaminated fractions of BASG cullet are largely unemployed because of the presence of metals in their composition that prevents recycling. This waste glass can be eligible to produce sustainable alkali-activated materials (AAMs) reducing at the same time consumption of raw materials and CO₂ emissions. The ‘weak’ alkaline attack (NaOH < 3 M) determines the gelation of glass suspensions. Condensation reactions occur in hydrated surface layers, leading to strong bonds (Si-O-Si, Al-O-Si, etc.) between individual glass particles. Alkali are mostly expelled from the gel due to the formation of water-soluble hydrated carbonates. Microwave treatment has been implemented on samples after precuring at 40 °C, saving time and energy and achieving better mechanical properties. To improve the stability and reduce the release of glass components into solution, the consolidated monoliths were subjected to boiling/drying cycles. The chemical stability, cytotoxicity and antibacterial behavior of the final products have been investigated with the purpose of obtaining new competitive and sustainable materials. For further stabilization and for finding new applications, the activated and boiled samples can be fired at low temperature (700 °C) to obtain, respectively, a homogeneous foam or a compact material with glass-like density and microstructure. Full article

The miniaturization and high integration of modern electronic devices have intensified thermal management challenges. Therefore, developing efficient heat sinks has become crucial to ensuring the stability and performance of high-performance CPUs. Previous studies have not considered the thermally demanding Intel i9 CPU; the current study targets this processor and explores the advantages of more complex minichannel path designs. In addition, this work investigates the enhanced heat transfer performance by integrating metal foams into microchannels. Using a computational approach, this study evaluates the thermal performance of uni-path, dual-path, and staggered-path (SP) minichannel heat sinks with water, Al₂O₃, and CuO nanofluids at varying Reynolds numbers. The impact of aluminum foam filling has also been examined. Results confirm that higher Reynolds numbers enhance fluid flow, reduce heat sink temperature, and improve temperature uniformity. Among the configurations, the SP heat sink combined with Al₂O₃ nanofluid achieves the best trade-off between cooling efficiency and energy consumption. While lower porosity foam and higher nanofluid volume fractions enhance heat transfer, they also increase flow resistance, leading to higher energy consumption. Due to its high specific heat capacity, Al₂O₃ nanofluid outperforms CuO, with optimal cooling observed at a 3–4% volume fraction. The performance evaluation criterion (PEC) captures the trade-off between heat dissipation and energy efficiency. It shows that the SP model with high-porosity aluminum foam and Al₂O₃ nanofluid turns out to be the most effective design. This combination maximizes cooling efficiency while minimizing excessive energy costs, demonstrating superior thermal management for high-performance microelectronic devices. Full article

Commercially pure aluminum (Al) was refined through the addition of the Al-5Ti-0.25C master alloy, resulting in the formation of Al₃Ti and TiC phases, which serve as refining agents. Open-cell metallic foams were successfully produced using the replication casting technique, with pore sizes ranging from 1.00 to 3.35 mm. For the infiltration process, refined aluminum was used, while unrefined aluminum served as a baseline reference. The resultant foams underwent multiple annealing cycles at 480 °C, with the most refined and homogeneous microstructure observed after 504 h. Comprehensive microstructural characterization was conducted utilizing scanning electron microscopy and optical microscopy. Additionally, uniaxial compression tests were performed to generate stress–strain profiles for the foams, facilitating an assessment of their energy absorption capacity. The findings indicated an enhancement in energy absorption capacity by a factor of 2.4 to 3, which can be attributed to the incorporation of Al-5Ti-0.25C and the subsequent annealing process. Full article

The self-foaming method offers a promising approach for producing AlCuFe metallic foams without the need for external foaming agents. Although it is well established that both alloy composition and heat treatment play a fundamental role in pore formation, the specific influence of annealing time on the resulting microstructure and physical properties remains insufficiently explored. In the present study, the effects of annealing time on the microstructure, phase evolution, and magnetic properties of self-foaming Al₅₈Cu₂₇Fe₁₅ alloys are investigated. Metallic foams were synthesized using the self-foaming method, heat-treating the samples at 850 °C for 6, 9, 15, and 24 h. X-ray diffraction (XRD), differential thermal analysis (DTA), and scanning electron microscopy (SEM) reveal that prolonged annealing increases porosity, reaching 64% and 61% after 15 and 24 h, respectively. The porosity formation mechanism was attributed to a peritectic reaction involving the liquid metastable τ phase and the solid λ and β phases. Magnetic measurements indicated complex behavior consistent with the Curie–Weiss law, influenced by phase composition and interactions between Coulomb forces, Hund’s rule exchange, and Fe 3d–Al s, p orbital hybridization. Full article

Lung computed tomography (CT) images are widely used to diagnose chronic obstructive pulmonary disease (COPD) by evaluating signs of lung tissue destruction. Accurate diagnosis requires standardizing the CT numbers in lung CT images to distinguish between normal and damaged tissue. The CT number standardization method proposed by Chen-Mayer et al., which uses the linearity of Martinez’s formula, showed promising results in phantom studies. However, our findings reveal that the CT number of water varies significantly, depending on scanning conditions and the characteristics of its container, making it an unreliable reference for lung CT number standardization. To enhance the standardization method, we modified the approach to exclude water and used only solid foams from the COPD gene2 phantom as references. To evaluate the proposed method, we collected 234 CT images of the COPD gene2 phantom from 8 different CT scanners and assessed performance by analyzing CT number standard deviations and variations. The modification resulted in improved reliability and consistency in CT number standardization. Additionally, for a detailed analysis, we segmented the dataset based on CT dose index (CTDI), X-ray tube potential, and reconstruction algorithms to examine the impact of different scanning protocols on standardization performance. Full article

To address the demands of the low-carbon era, this study proposed a solution by using eggshell powder (ESP), fly ash, and ground granulated blast furnace slag together with alkaline solution in the preparation of lightweight geopolymer foam concrete (LWGFC). The aim of this study is to investigate the influence of replacing precursor materials with 5–20% ESP on the expansion behavior, physical, mechanical characteristics, and thermal conductivity of LWGFC. Additionally, the study examines the effect of varying the silicate modulus (SiO₂/Na₂O ratios of 1.0, 1.25, and 1.5) on the properties of LWGFC. Incorporating ESP from 5% to 20% with a constant SiO₂/Na₂O ratio reduced the initial setting time, while a high SiO₂/Na₂O ratio controlled the setting time and expansion volume. The high SiO₂/Na₂O ratio decreased the porosity and enhanced the compressive strength of the LWGFC but increased the thermal conductivity. The inclusion of more than 10% ESP content negatively affected compressive strength; however, a high SiO₂/Na₂O ratio can mitigate this detrimental effect. The thermal conductivity of optimal-content ESP mixtures with a SiO₂/Na₂O ratio of 1.0 was about 0.84 W/m·K, which is 2.1% lower than mixtures with a ratio of 1.25 and 18.6% lower than those with a ratio of 1.5. High-content ESP mixtures had a density of 1707 kg/m³, 0.97 W/m·K, and a compressive strength of 18.9 MPa at a low SiO₂/Na₂O ratio. Finally, the inclusion of ESP in the LWGFC, along with the use of an appropriate silicate modulus, resulted in improved strength development while decreasing porosity. Full article

With increasing natural gas processing demands, triethylene glycol (TEG) in dehydration systems becomes contaminated by gas-carried impurities, leading to problematic foaming, degradation, and significant glycol losses that compromise operational economics, pipeline integrity, and product quality. To systematically investigate impurity effects, we conducted comprehensive single-factor TEG regeneration experiments simulating field conditions. Through precise measurements of foaming height, defoaming time, and interfacial tension, we established clear correlations between impurity types and TEG foaming characteristics. Our results demonstrate a distinct hierarchy of foaming influence: chemical additives > solid impurities > water-soluble inorganic salts > MDEA > hydrogen sulfide > hydrocarbons. Chemical additives showed the most pronounced effect on surface tension, reducing it to 31.1 mN/m at 1500 mg/L. Water-soluble inorganic salts affected foaming through combined decomposition and crystalline morphology effects, ranked as MgCl₂ > NaHCO₃ > KCl > NaCl > Na₂SO₄ > CaCl₂ (MgCl₂ achieving 33.8 mN/m at 2000 mg/L). Solid impurity impacts correlated strongly with particle morphology (CaCO₃ > Fe₂O₃ > CaSO₄ > ZnO > CuO > Al₂O₃ > FeS), stabilizing at 1.5 mg/L. Hydrocarbons showed negligible influence, while hydrogen sulfide and MDEA caused only minor surface tension reductions with limited foaming effects. Based on these findings, we propose targeted mitigation strategies for industrial implementation. Full article

In this study, the mechanical behavior of AA6082 foams with Weaire–Phelan (WP) cell structures under compressive loading was analyzed. The foams were produced using the lost-PLA replication method, a cost-effective and straightforward manufacturing technique. A total of six aluminum alloy samples were fabricated and subjected to compression tests to assess both their mechanical performance and the repeatability of the results. The produced foams demonstrated a well-defined morphology and high-quality surface finish, accurately replicating the geometries of the original PLA 3D-printed templates. The experimental density of the foams closely matched theoretical values, confirming the consistency of the replication process. The compressive stress–strain response of the Weaire–Phelan cell foams displayed an initial linear elastic region, followed by three distinct plateau regions with increasing stress levels. The final densification phase occurred when the structure could no longer accommodate further plastic deformation, leading to a sharp increase in the compression load. From the stress–strain data, the specific energy absorption of the foams was calculated. The average specific energy absorption was measured to be 4 J/cm³, with a standard deviation of 0.49 J/cm³ across the six tested samples. These results indicate reliable mechanical performance and reproducibility of the manufacturing process, making these foams suitable for applications requiring energy absorption and lightweight structural components. Full article

Bistable microstructures are promising for implementation in many mictroelectromechanical system (MEMS)-based applications due to their ability to stay in several equilibrium states, high tunability and unprecedented sensitivity to external stimuli. As opposed to the extensively investigated one-dimensional curved beam-type devices of this kind, microfabrication of non-planar two-dimensional bistable structures, such as plates or shells, represents a remarkable challenge. Recently reported by us, a new moldless stamping procedure, based on pressing a soft stamp over a thin suspended metallic film, was demonstrated to be a feasible direction for the fabrication of initially curved micro plates. However, reliable implementation of this fabrication paradigm and its further development requires better understanding of the role of the process parameters, and of the effect of both the plate and the stamp material properties on the shape of the formed shell and on the postfabrication residual stresses, and therefore on the shell behavior. The need for an appropriate choice of these parameters requires the development of a systematic modeling approach to the stamping process. Here, we report on a finite element (FE)-based methodology for modeling the processing sequences of a successfully fabricated aluminum (Al) micro shell of realistic geometry. The model accounts for the elasto-plastic behavior of the plate material, the nonlinear material behavior of the foam and the contact between them. It was found that the stamping pressure and the plate material parameters are the key parameters affecting the residual shell curvature as well as its shape. Consistently with previously presented experimental results, we show that the fabrication procedure partially relieves the prestresses emerging during preceding fabrication steps, leaving a nontrivial distribution of residual stresses in the formed shell. The presented analysis approach and results provide tools for designers and manufacturers of systems including micro structural elements of shell type. Full article

The present study was performed on real-life I4-aluminum cylinder heads produced industrially by applying the lost foam technique to Al-Si-Mg alloys (356 and 357). This work, in addition, introduces a new Al-Cu alloys coded 220 alloy. The main aim of this study is to analyze the effects of liquid metal treatment on the hardness and tensile properties of such castings. The effects of liquid metal treatment (modification with 200 ppm Sr, grain refining with 150 ppm B and degassing using pure Ar) of the castings produced by the lost foam technique on the tensile strength and hardness properties were evaluated. Hydrogen plays an important role in the formation of porosity. At the same time, the foam mold leaves an impression on the casting surface taking the shape of fine holes. In addition, segregation of hydrogen occurs in front of the solidification front. Thus, the porosity is a combination of hydrogen level and the solidification rate. Gains of 17% and 24% are observed for the hardness and yield strength for alloy 357 compared to alloy 356, caused by the difference in their magnesium (Mg) contents in the sense that, in the T6 heat-treated condition, precipitates in the form of ultra-fine Mg₂Si phase particles are formed. The enhancement in the mechanical properties of the used alloy depends mainly of the volume fraction of the precipitated Mg₂Si particles. The hardness of alloy 220 increases by 18% and the yield strength by 15% compared to that measured for alloy 356. In this case, the hardening phase Al₂Cu is responsible for this increase. Thus, this study demonstrates that liquid metal treatments significantly enhance the hardness and yield strength of Al-Si-Mg and Al-Cu alloys, with the gain attributed to refined microstructures and reduced porosity. Full article

Application of rare earths (RE) as grain refiners is well-known in the technology of aluminum alloys for the automotive industry. In the current study, Al-2.4%Cu-0.4%Mg alloy (coded 220) and Al-7.5%Si-0.35%Mg alloy (coded 356.1), were prepared by melting each alloy in a resistance furnace. Strontium (Sr) was used as a modifier, while titanium boride (TiB₂) was added as a grain refiner. Measured amounts of Ce and La were added to both alloys (max. 1 wt.%). The alloy melts were poured in a preheated metallic mold. The main part of the study was conducted on tensile testing at room temperature. The results show that although RE would cause grain refining to be about 30–40% through the constitutional undercooling mechanism, grain refining with TiB₂ would lead to approximately 90% refining (heterogenous nucleation mechanism). The addition of high purity Ce or La (99.9% purity) has no modification effect regardless of the alloy composition or the concentration of RE. Depending on the alloy ductility, the addition of 0.2 wt.%RE has a hardening effect that causes precipitation of RE in the form of dispersoids (300–700 nm). However, this increase vanishes with the decrease in alloy ductility, i.e., with T6 treatment, due to intensive precipitation of ultra-fine coherent Mg₂Si-phase particles. There is no definite distinction in the behavior of Ce or La in terms of their high affinity to interact with other transition elements in the matrix, particularly Ti, Fe, Cu, and Sr. When the melt was properly degassed using high-purity argon and filtered using a 20 ppi ceramic foam filter, prior to pouring the liquid metal into the mold sprue, no measurable number of RE oxides was observed. In conclusion, the application of RE to aluminum castings would only lead to formation of a significant volume fraction of brittle intermetallics. In Ti-free alloys, identification of Ce- or La-intermetallics is doubtful due to the fairly thin thickness of the precipitated platelets (about 1 µm) and the possibility that most of the reported Al, Si, and other elements make the reported values for RE rather ambiguous. Full article

The shift toward sustainable energy sources is essential to curb greenhouse gas emissions and satisfy energy demands. Among renewable options, carbon-based materials—such as agricultural residues and municipal solid waste—provide a dual advantage by generating energy and fuels while also reducing landfill waste. A notable innovation is transforming plastic waste into methane-rich streams via catalytic hydrogasification, a process in which carbon-based feedstocks interact with hydrogen using a selective catalyst. In this study, a structured catalyst was developed, characterized, and tested for converting plastic waste samples. The thermal degradation properties of plastic waste were first studied using thermogravimetric analysis. The catalyst was prepared using an Oxygen Bonded Silicon Carbide (OBSiC) open-cell foam as the carrier, coated with γ-Al₂O₃-based washcoat, CeO₂, and Ni layers. It was characterized in terms of specific surface area, coating adhesion, pore distribution, acidity, and the strength of its active sites. Experimental tests revealed that a hydrogen-enriched atmosphere significantly enhances CH₄ formation. Specifically, during catalytic hydrogasification, methane selectivity reached approximately 59%, compared to 6.7%, 13.7%, and 7.8% observed during pyrolysis, catalyzed pyrolysis, and non-catalyzed hydrogasification tests, respectively. This study presents a novel and effective approach for converting plastic waste using a structured catalyst, a method rarely explored in literature. Full article

The present article presents the results of physical and chemical studies of opoka. In particular, the opoka was subjected to chemical analysis, X-ray phase, differential thermal analysis, scanning microscopy, and X-ray energy dispersive elemental microanalysis. The opoka was studied with the aim of using it as an available raw material for obtaining a sodium silicate mixture and, in the future, developing an energy-saving technology for obtaining a building heat-insulating and sound-insulating foam glass material based on it, using synthesis. As a result of the studies, the chemical composition of the opoka was determined, which is 69–80% represented by silica. The elemental composition of the opoka was established, which is represented by 94.25% oxides of Si, Al, and Fe. The presence of such oxides makes it an ideal raw material component of a silicate-sodium mixture for the subsequent synthesis of foam glass material from it. Experimental exploratory studies on the synthesis of foam glass based on opoka have been carried out. The experimentally obtained sample of foam glass material consists of 93.37% Si, Al, Mg, and Na oxides, has a porous structure with a pore size of 2–5 microns, an average density of 375 kg/m³, thermal conductivity of 0.063 W/(m °C) at 25 °C, and noise absorption of 51.6 Db. Full article