Search Results (511)

Cellulose nanofibril (CNF), as a renewable biomass material, has the characteristics of low density, high strength, and high hydrophilicity. It can also overcome shortcomings of traditional inorganic nano materials, such as difficult dispersion, high cost, and high health risks. In this work, CNF was modified with a cationic surfactant to further enhance the compatibility with hydrating cement. The effects on cement paste were assessed via compressive and flexural strength, heat of hydration, and restrained ring cracking. The reinforcing mechanisms were analyzed by microhardness test, XRD, and BSE-SEM/EDS. Results showed that cation-modified CNF improved mechanical performance, with an optimal dosage of 0.15 wt.% (by binder). Restrained ring test showed that cation-modified CNF–cement composite delayed crack initiation. An isothermal calorimetry test revealed that cation-modified CNF can increase hydration rate in early age. Microstructural analysis confirmed promotion of denser hydration products. A comprehensive consideration of experimental results indicates internal curing and “short-circuit diffusion” are likely the enhancing mechanism. Full article

To address the fluctuation and instability of renewable power generation and the steady-state demands of chemical processes, a single-channel, non-isothermal computational fluid dynamics 3D model was developed. This model explicitly incorporates the coupling effects of electrochemical reactions, two-phase flow, and heat transfer. Subsequently, the influence of key operating parameters on proton exchange membrane water electrolyzer (PEMWE) system performance was investigated. The model accurately predicts the current–voltage polarization curve and has been validated against experimental data. Furthermore, the CFD model was employed to investigate the coupled effects of several key parameters—including operating temperature, cathode pressure, membrane thickness, porosity of the porous transport layer, and water inlet rate—on the overall electrolysis performance. Based on the numerical simulation results, the evolution of the ohmic polarization curve under temperature gradient, the block effect of bubble transport under high pressure, and the influence mechanism of the microstructure of the multi-space transport layer on gas–liquid, two-phase flow distribution are mainly discussed. Operational strategy analysis indicates that the high-efficiency mode (4.3–4.5 kWh/Nm³) is suitable for renewable energy consumption scenarios, while the economy mode (4.7 kWh/Nm³) reduces compression energy consumption by 23% through pressure–temperature synergistic optimization, achieving energy consumption alignment with green ammonia synthesis processes. This provides theoretical support for the optimization design and dynamic regulation of proton exchange membrane water electrolyzers. Full article

GH2132, an Ni–Cr–Fe-based superalloy for aero-engine components, exhibits hot workability that is highly sensitive to processing parameters. The hot deformation behavior of GH2132 alloy was investigated via isothermal compression (Gleeble-3500-GTC) over 850–1100 °C and 0.001–10 s⁻¹, combined with optical microscopy and EBSD characterization. A strain-compensated Arrhenius-type hyperbolic-sine model was established, achieving high predictive accuracy (R² = 0.9916; AARE = 3.86%) with an average activation energy Q = 446.2 kJ·mol⁻¹. Flow stress decreases with increasing temperature and increases with strain rate, while microstructural softening transitions from dynamic recovery to complete dynamic recrystallization at higher temperatures and lower strain rates. Three-dimensional power-dissipation and hot-processing maps (Dynamic Materials Model) delineate safe domains and instability regions, identifying an optimal window of 1000–1100 °C at 0.001–0.01 s⁻¹ and instability at 850–900 °C with 0.01–0.1 s⁻¹. These results provide guidance for selecting parameters for hot deformation behavior during thermomechanical processing of GH2132. Full article

Based on hot-compression simulations combined with SEM and TEM analyses, the high-temperature deformation behavior and mechanisms of a new nickel-based powder superalloy FGH101 were investigated over 1020–1110 °C and strain rates of 0.001–0.05 s⁻¹. From the experimental data, the variations in the strain-rate sensitivity index m, the apparent activation energy for hot deformation Q, and the grain-size exponent p were determined as functions of strain rate and temperature. Hot deformation processing maps and mechanism maps incorporating dislocation density were established. The processing maps clearly revealed the evolution of formable regions at different temperatures and strains, while the mechanism maps successfully predicted the dislocation evolution and its operative hot deformation mechanisms by introducing the grain size evolution corrected by Burgers-vector compensation and the rheological flow stress behavior compensated by the modulus. The results indicated an optimal processing window of 1060–1100 °C at 0.001–0.003 s⁻¹. Within the tested regime, as the strain rate decreased, the operative mechanism for grain-boundary sliding transitioned from pipe-diffusion control to lattice-diffusion control. These findings provide a solid theoretical basis for the design and optimization of the isothermal forging process of the new FGH101 alloy. Full article

Metal–Organic Frameworks (MOFs) have diverse applications due to their tunable porosity, large surface area, and diverse chemical functionalities. Among them, one of the most researched MOFs is MIL-101(Cr), which, in addition, is very stable in water. We have used a commercially available substance with approximately 300 nm large crystals for the preparation of a sensing nano-thin layer for the emerging water contaminant PFOS, due to its high selectivity towards this compound. Here, we have synthesized 20 nm sized crystals of MIL-101(Cr), which are among the smallest reported, and compared them to the same material with 300 nm sized crystals. The material was characterized by TEM and XPS. It was possible to prepare insoluble monolayers at the air–water interface (Langmuir films), which were characterized with film compression isotherms, Brewster angle microscopy, and surface potential measurements. The Langmuir–Blodgett (LB) method was used to deposit monolayers on Si wafers and 434 MHz Surface Acoustic Wave resonator simultaneously. The LB layers were very stable over time. The smaller-sized MIL-101 (Cr) crystals exhibit denser, more homogeneous water coverage and packing upon compression, with no observable 10–100 µm aggregates. LB monolayers from the 20 nm particles have approximately six times lower surface roughness. The LB monolayer is far from being smooth, but this will allow excellent access to the MOF pores by the tested analyte in a chemical sensing application. The lack of research on depositing presynthesized MOFs using probably the best method for nanoarchitectonics—the LB method—is addressed. The 20 nm sized MOF crystals are the smallest deposited by this method so far. Full article

Phosphogypsum-based cemented paste backfill (PCPB) represents an effective solution for managing substantial accumulations of PG. However, its practical application is limited by excessive fluoride content and insufficient strength. To systematically investigate the influence of initial fluoride content on the hydration behavior, microstructures, and strength development of PCPB specimens, synthetic phosphogypsum was prepared using CaSO₄·2H₂O and NaF to eliminate impurity interference in this study. A series of specimens was designed with varying initial fluoride content (5–70 mg/L), sand-to-cement ratios (1:6, 1:8, 1:10), and concentrations (63 wt%, 65 wt%). Setting time, unconfined compressive strength, isothermal calorimetry, X-ray diffraction, and scanning electron microscopy were employed to elucidate the effects and underlying mechanisms of fluoride on PCPB performance. The results indicate that higher initial fluoride content markedly delayed setting and reduced early strength. Calorimetric analysis confirmed that fluoride postponed the exothermic peak and extended the induction period, primarily due to the formation of the CaF₂ layer on clinker particle surfaces, which hindered nucleation and hydration. The microscopic results further revealed that high fluoride content suppressed the formation of ettringite and C-S-H gels, resulting in more porous and loosely bonded microstructures. Leaching tests indicated that fluoride immobilization in PCPB specimens occurred mainly through CaF₂ precipitation, physical encapsulation, and ion exchange. These findings provide theoretical support for the fluoride thresholds in PG below which the adverse effects on cement hydration and strength development can be minimized, contributing to the sustainable goals of waste reduction, harmless disposal, and resource recovery in the phosphate industry. Full article

Serrin’s works provided a new perspective on classical thermodynamics through his statements of the first law and the accumulation function, and of the second law and the accumulation theorem, as well as the subsequent result by Huilgol that the work accomplished in a thermal cycle implies an inequality where the important temperatures of the thermal cycle and an integral similar to that of Clausius appears. Based on these pioneering works, explicit forms of the accumulation function have been derived for the Otto, Diesel, Stirling and Ericsson cycles. In this paper, a more straightforward derivation than that made by Huilgol is presented to obtain the inequality for the work accomplished in a cycle, following the theoretical framework of Serrin and Huilgol, and explicitly introducing that the temperature ranges in which the system exchanges heat are finite. This paper clearly shows the natural physical fact that heat exchange processes in a system have two defined extreme temperatures, corresponding to the beginning and end of the process, which can be equal in the isothermal limiting case. The derivation of the accumulation function for the ideal air-standard Brayton cycle is provided for the first time, extending Serrin’s thermodynamic framework, where the temperature constraints of the adiabatic compression and expansion processes under which it operates are analyzed. Finally, a practical example is included to illustrate the behavior of the accumulation function of the ideal air-standard Brayton cycle. Full article

Iron-rich metallurgical slag is an underutilized precursor in alkali-activated materials (AAMs), despite its abundance and potential in sustainable construction and waste immobilization. This study evaluates a binary AAM system (Aachen GP), comprising 50 wt.% blast furnace slag (BFS) and 50 wt.% iron-rich slag (Fe₂O₃ ≈ 24.6 wt.%), against a BFS-only reference (Ref GP). Characterization included isothermal calorimetry, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM–EDX), Brunauer–Emmett–Teller (BET) surface area, water permeability, porosity, and compressive strength. Aachen GP showed delayed setting (32.9 h), reduced cumulative heat (∼70 J/g), and lower bound water (4.6% at 28 days), indicating limited gel formation. Compared to Ref GP, it had higher porosity (38.4%), water permeability ($1.42\times {10}^{-10}$ m/s), and BET surface area (12.4 m²/g), but lower 28-day strength (14.4 MPa vs. 43 MPa). Structural analysis revealed unreacted crystalline phases and limited amorphous gel. While Aachen GP meets regulatory strength thresholds (≥8 MPa) for low- to intermediate-level wasteforms in Belgium and Germany, its elevated porosity may impact long-term containment. Further studies on radionuclide leaching and durability under thermal and radiation stress are recommended. Full article

Belgium and the EU-27 face a shortage of suitable supplementary cementitious materials (SCMs) capable of supporting high levels of Portland cement substitution. To reduce CO₂ emissions from the cement industry, blended cements incorporating low-grade calcined clay, limestone, and lava (a natural pozzolan) are investigated. Calcined clay is combined with limestone to produce a limestone–calcined clay cement (LC3). The reactivity of these new blends is assessed using isothermal calorimetry and compared to a reference blend with ground-granulated blast-furnace slag (GGBFS). Results show that mixtures with calcined clay develop slightly lower 28-day strength than those with GGBFS, while blends with lava exhibit strength gains only at later ages due to delayed pozzolanic activity. Overall, concrete made with low-grade calcined clay and lava achieves comparable compressive strength to the reference (CEM III/A), but with higher capillary porosity, leading to increased water absorption, drying shrinkage, and reduced freeze–thaw resistance. Despite these durability limitations, the sustainability assessment reveals that the LC3 mix with low-grade clay and lava has a lower global warming potential per unit strength at 28 days than CEM III/A and is competitive with CEM III/B. Full article

This study presents a quantum electrodynamics (QED) framework that explains the anomalous behavior of liquid water. The theory posits that water consists of two coexisting phases: a coherent phase, in which molecules form phase-locked coherence domains (CDs), and an incoherent phase that behaves like a dense van der Waals fluid. By solving polynomial-type equations, we derive key thermodynamic properties, including the minima in the isobaric heat capacity per particle (IHCP) and the isothermal compressibility, as well as the divergent behavior observed near 228 K. The theory also accounts for water’s high static dielectric constant. These results emerge from first-principles QED, integrating quantum coherence with macroscopic thermodynamics. The framework offers a unified explanation for water’s anomalies and has implications for biological systems, materials science, and fundamental physics. Future work will extend the theory to include phase transitions, solute interactions, and the freezing process. Full article

An isothermal hot compression test of GH3230 was carried out under deformation conditions with deformation temperatures ranging from 1020 to 1110 °C and strain rates ranging from 1 to 0.001 s⁻¹. On this basis, the corresponding constitutive equation of the alloy was established. $\dot{\epsilon }=exp\left(36.123\right){\left[sinh\left(0.00587\sigma \right)\right]}^{4.7946}exp\left[-451.507/\left(RT\right)\right]$. At the same time, a power dissipation diagram and thermal processing diagram were created. The peak value η can reach 0.36, and the optimum hot working parameter window of the GH3230 superalloy is 1020~1110 °C/0.1~0.001 s⁻¹. The microstructure evolution of the alloy under different conditions was studied by EBSD. With an increase in deformation temperature and a decrease in strain rate, the grain size significantly improved; the average grain size of the GH3230 alloy increased from 16.86 to 35.06 μm, and the degree of recrystallization of the alloy also improved. The maximum recrystallization volume fraction is 75.2%. At low temperature and high strain rate, the recrystallization mechanism of the microstructure is mainly CDRX, and DDRX is the auxiliary mechanism. At high temperature and low strain rate, the main corresponding recrystallization mechanism gradually transforms into DDRX. Full article

In this study, we investigated the hot deformation behavior and microstructural evolution of a novel high-magnesium-content (high-Mg) aluminum alloy, bridging the disciplines of material processing and physical metallurgy. Uniaxial hot compression tests were performed over the temperature range of 280~400 °C and strain rates of 0.001~10 s⁻¹ to investigate its hot deformation behavior. The flow stress curves were systematically analyzed, and a constitutive model was developed to describe the thermo-mechanical response of the alloy. Microstructural evolution was characterized using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The results indicate that dynamic recovery serves as the dominant softening mechanism at lower deformation temperatures (≤320 °C). As the temperature increased to 400 °C, a significant rise in dynamic recrystallization was observed. Moreover, at 400 °C, higher strain rates led to the formation of abundant, network-like, mushroom-shaped dynamically recrystallized grains. Full article

In the present work, a new analytical model of polytropic flow in constant-diameter pipelines is developed to accurately describe the flow of compressible gases, including natural gas and hydrogen, explicitly accounting for heat exchange between the fluid and the environment. In contrast to conventional models that assume isothermal or adiabatic conditions, the proposed model simultaneously accounts for variations in pressure, temperature, density, and entropy, i.e., it is based on a realistic polytropic gas flow formulation. A system of differential equations is established, incorporating the momentum, continuity, energy, and state equations of the gas. An implicit closed-form solution for the specific volume along the pipeline axis is then derived. The model is universal and allows the derivation of special cases such as adiabatic, isothermal, and isentropic flows. Numerical simulations demonstrate the influence of heat flow on the variation in specific volume, highlighting the critical role of heat exchange under real conditions for the optimization and design of energy systems. It is shown that achieving isentropic flow would require the continuous removal of frictional heat, which is not practically feasible. The proposed model therefore provides a clear, reproducible, and easily visualized framework for analyzing gas flows in pipelines, offering valuable support for engineering design and education. In addition, a unified sensitivity analysis of the analytical solutions has been developed, enabling systematic evaluation of parameter influence across the subsonic, near-critical, and heated flow regimes. Full article

Ascorbic acid (AA) and its derivatives (EAA), due to their antioxidant properties, may offer potential support in acne therapy. The aim of this study was to evaluate the effect of compound P6—(KK)₂-KWWW-NH₂—in the presence of AA or EAA on the stability and organization of phosphatidylinositol (PI) monolayers. The conducted experiments showed that the monolayers were in the expanded liquid state (37.45–48.35 mN/m) or in the transitional phase between the expanded liquid and condensed states (51.06–56.82 mN/m). Compression and decompression isotherms indicated the highest flexibility for the PI + P6 system, with the compression reversibility coefficient (R_v) ranging from 87.34% to 97.77%, increasing with temperature in successive loops. The surface pressure vs. time dependence after compound injection into the subphase revealed a decrease in monolayer surface pressure followed by stabilization after approximately 300 s for the PI + P6 + AA and PI + P6 + EAA systems. In contrast, for the PI + P6 system at 35 °C, an increase in surface pressure was observed. Full article

Alkali-activated materials (AAMs) offer a promising low-carbon alternative to Portland cement, but their development has been dominated by fly ash and slag, whose availability is increasingly limited. This research explores waste brick powder (WBP) and metakaolin residue (RN), two abundant yet underutilized by-products, as blended precursors for sustainable binder design. The novelty lies in demonstrating how complementary chemistry between crystalline-rich WBP and amorphous RN can overcome the drawbacks of single-precursor systems while valorizing construction and industrial residues. Pastes were prepared with varying WBP/RN ratios, activated with alkaline solutions, and characterized by Vicat setting tests, isothermal calorimetry, XRD with Rietveld refinement, MIP, SEM, and mechanical testing. Carbon footprint analysis was performed to evaluate environmental performance. Results show that WBP reacts very rapidly, causing flash setting and limited long-term strength, whereas the incorporation of 30–50% RN extends setting times, sustains dissolution, and increases amorphous gel formation. These changes refine the formed reaction products, leading to compressive strengths up to 39 MPa and flexural strengths of 8 MPa at 90 days. The carbon footprint of all blends remained 392–408 kg CO₂e/m³, thus providing about a 60% improvement compared to conventional Portland cement paste. The study establishes clear design rules for waste-derived blended precursors and highlights their potential as circular, low-carbon binders. Full article