Search Results (74)

This study examines the effects of kraft lignin, milled hemp stalks, and dicumyl peroxide (DCP) crosslinking on polybutylene succinate (PBS) composites, focusing on rheological, mechanical, and thermal properties as well as accelerated weathering and fungal performance. Two composite series were produced via twin-screw extrusion, (a) simple blends (B-series) and (b) DCP-crosslinked formulations (R-series), with emphasis on hybrid lignin–hemp composites (B-PLH and R-PLH). Rheological analysis showed that hemp fiber increased viscosity, while lignin reduced it, and DCP further enhanced shear-thinning behavior. Mechanical testing confirmed that R-PLH exhibited a 16% increase in flexural strength (42.6 MPa) and a 2.4-fold increase in flexural modulus (1785 MPa) over neat PBS, but tensile strength declined by 19%. Thermal analysis revealed a 14–26% reduction in mass loss rate and increased char formation (up to 16.3% in R-PLH), indicating improved thermal stability. Water absorption showed that hemp fibers increased hydrophilicity, further increased by DCP. Accelerated weathering led to significant color change and surface degradation, particularly in R-PLH. Despite lignocellulosic content, all composites exhibited ≤2% fungal degradation, indicating limited mass loss due to fungal exposure under conditions used in this study. Overall, B-PLH and R-PLH offer a balance of stiffness and thermal stability, though trade-offs in tensile strength and weathering resistance should be considered for sustainable applications. Full article

The composite material MgH₂-EEWNi-Cr (20 wt. %) with a hydrogen content of 5.2 ± 0.1 wt.% is characterized by improved hydrogen interaction properties compared to the original MgH₂. The dissociation of the material occurs in three temperature ranges (86–117, 152–162, and 281–351 °C), associated with a complex of effects consisting of changes in the specific surface area of the material, alterations in the crystal lattice during ball milling, and changes in the electronic structure in the presence of a Ni–Cr catalyst, based on first-principles calculations. The decrease in desorption activation energy (E_d = 65–96 ± 1 kJ/mol, ΔE_d = 59–90 kJ/mol) is due to the catalytic effect of N–Cr, leading to a faster decomposition of the hydride phase. Based on the results of ab initio calculations, Ni–Cr on the MgH₂ surface leads to a significant decrease in hydrogen binding energy (ΔE_b = 60%) compared to pure magnesium hydride due to the formation of Ni–H and Cr–H covalent bonds, which reduces the degree of H–Mg ionic bonding. The results obtained allow us to expand our understanding of the mechanisms of hydrogen interaction with storage materials and the possibility of using these as mobile hydrogen storage and transportation materials. Full article

The existing scientific literature indicates that flowable short fiber-reinforced composites (SFRCs) can be used for direct restoration due to their favorable mechanical properties. However, there is a lack of data on the mechanical properties of SFRCs designed specifically for indirect CAD/CAM restorations. This study aims to fabricate a novel experimental SFRC CAD/CAM block and evaluate its fracture toughness and polishability as an indirect restoration in comparison with different conventional resin-based CAD/CAM blocks with different compositions. Fourier-transform infrared spectroscopy (FTIR) was employed to analyze the chemical structure of the Experimental SFRC group, while the microstructure of specimens from each group was examined using scanning electron microscopy (SEM). Then, this study divided the specimens into three groups—Group 1 (Grandio blocks), Group 2 (Cerasmart 270), and Group 3 (Experimental SFRC)—with 30 specimens in each group. Each group was then subdivided into sub-groups for the fracture toughness test, which evaluated resistance to crack propagation, and the surface roughness test, which assessed surface topography. FTIR analysis showed that the experimental SFRC exhibited distinct spectral changes after polymerization, confirming successful chemical reactions and network formation. SEM analysis showed that the Experimental SFRC block had a polymeric matrix with randomly oriented, well-dispersed short fibers. Grandio blocs exhibited a dense nanohybrid structure with irregular fillers, while Cerasmart 270 displayed a more uniform microstructure with evenly dispersed nano-sized spherical fillers. The Experimental SFRC showed the highest fracture toughness (2.758 MPa·√m), surpassing the other groups (p < 0.05) and highlighting its superior resistance to crack propagation. Regarding surface roughness Ra, the novel Experimental SFRC group (0.182) presented a significant difference compared to other groups (p < 0.05) but within clinical acceptance, and they can be well polished for clinical use after milling. The Cerasmart 270 block showed the lowest surface roughness Ra (0.135) among the groups, which is attributed to its filler size, geometry, and composition, resulting in a smoother surface. The higher fracture toughness of the Experimental SFRC among the groups suggests superior resistance to crack propagation, attributed to the incorporation of short fibers that enhance energy absorption and reduce brittleness, thereby supporting its suitability for high-stress-bearing clinical applications. Full article

During sulfite delignification of wood, sulfo derivatives of lignin—lignosulfonates (LS)—are formed as a byproduct. Due to their amphiphilic nature, LS are used as plasticizers, dispersants, and stabilizers. The functions and performance characteristics of this surface-active polyelectrolyte are determined by its behavior in aqueous solution, at surfaces and interfaces, which, in turn, is determined by its chemical composition. This study investigated the effect of LS with various molecular weight compositions (M_w 9–50 kDa) on the behavior and aggregation stability of aqueous dispersions of elemental sulfur (S⁰) under conditions simulating hydrothermal leaching of sulfide ores. Using conductometry, potentiometry, tensiometry, and viscometry, a detailed study of the physicochemical properties of aqueous LS solutions (C_LS 0.02–1.28 g/dm³) obtained from a few sources (Krasnokamsk, Solikamsk, and Norwegian Pulp and Paper Mills) was conducted. The composition, molecular weight, and concentration of LS were found to significantly affect their specific electrical conductivity, pH, intrinsic viscosity, and surface activity. LS introduction during the formation of sulfur sols is shown to promote their stabilization through electrostatic and steric mechanisms. Optimum dispersion stability (293 K, pH 4.5–5.5) was observed at moderate LS concentrations (0.02–0.32 g/dm³), when a stable adsorption layer forms on the surface of sulfur particles. High-molecular-weight LS samples provided more effective spatial stabilization of sulfur particles. It has been established that increasing temperature (293–333 K) and changing pH (1–7) significantly affect the aggregative stability of systems; specifically, the sol stability decreases with increasing temperature, and the stabilizing effect of different LS types reverses upon changing pH. The obtained results highlight the potential of using naturally occurring polymeric dispersants to control the aggregation stability of sulfur-containing heterophase systems and can be applied to the design of stable colloidal systems in chemical engineering and hydrometallurgy. Full article

This paper presents a composite control strategy for gearless coal mill to improve the disturbance immunity under low-speed variable operating conditions. First, the gearless coal mill encounters power supply voltage fluctuations, mechanical failures, or ambient temperature changes during operation. These situations can cause the system to suffer from the problem of insufficient control accuracy of the rotational speed. Therefore, a non-singular fast terminal sliding mode control strategy is proposed to improve the speed response. Then, to address the problem of load perturbation caused by different coal quality, this paper designs the extended state observer. Feed-forward compensation of the perturbation is performed to improve the robustness. Finally, due to the parameter mismatch problem caused by heat in operations that take a long time, this paper proposes a sliding-mode-based deadbeat predictive current control. The strategy possesses the fast dynamic response of deadbeat predictive current control while retaining the strong robustness of sliding mode control. Lyapunov proved the stability of the proposed control strategy. The experimental results verified that the proposed control strategy had better control performance. Full article

Electric arc furnace (EAF) waste, a mixture of dust and slag, was investigated as a potential secondary source of zinc. The waste primarily consisted of zinc and iron oxides, with the presence of refractory zinc ferrite, which hinders the complete recovery of zinc. This is the first study that examined the effect of mechanical treatment through high-energy planetary ball milling on the phase transformation, metal speciation, and leachability of the EAF waste. The raw material was characterized by particle size distribution, morphology, phase composition, and sequential extraction, and then subjected to milling at different rotation rates (100–400 rpm). The resulting powders were analyzed using XRD, SEM–EDS, and sequential leaching, and tested for acid (H₂SO₄) and alkaline (NaOH) leachability. Milling progressively reduced particle size, increased surface roughness, and induced structural changes, including the mechanical activation effect at low milling rates (100 rpm) and the synthesis of secondary franklinite at higher milling energies (200 rpm and 400 rpm). Sequential extraction revealed changes in zinc and iron speciation from acid-soluble to residual fractions for increased milling intensities. Leaching experiments showed rapid zinc dissolution in both acidic and alkaline solutions, while iron dissolved only in acid. The highest zinc extractions (67% in H₂SO₄, 55% in NaOH) were obtained from mechanically activated material at 100 rpm, while zinc leachability decreased for higher milling rates due to the induced mechanical synthesis of refractory phase. The kinetic model of leaching of the main components of the EAF was also established. Full article

Olive Mill Solid Waste (OMSW) presents an environmental challenge due to its toxicity and difficulties in its recycling. Prior studies suggest its potential as a substrate ingredient for cultivating edible mushrooms. Here, we investigate how varying OMSW concentrations in the substrate affect the synthesis pathways of α-glucan and β-glucan polysaccharides, alongside transcriptional and metabolic changes in Pleurotus eryngii. We also assessed the mushroom’s protein and nitrogen content. Our results highlight the critical role of substrate composition, demonstrating that the OMSW concentration significantly influences mushroom growth, yield, protein content, gene expression, and metabolite profiles. These findings establish OMSW not only as a viable recycling resource but also as a modulator of health-promoting compound synthesis in P. eryngii. Full article

Wildfires are integral to many forest ecosystems, yet their ecological effects are often influenced by historical land use and management. In this study, we assess the short-term impacts of fire and management on Castanea sativa Mill. stands in the fayal-brezal zone of northern Tenerife (Canary Islands), where traditional agroforestry systems have been widely abandoned. We established 12 transects across four stands: managed-burned, managed-unburned, oldfield-burned, and oldfield-unburned. We analyzed forest structure, understory species richness and composition, and soil nutrient content one year after a large wildfire. Forest structure has primarily been determined by management history, with oldfield plots showing greater tree density, basal area, and basal sprouting. Fire has had a limited effect on tree mortality, affecting ~10% of individuals on average. Understory species richness was significantly higher in managed plots, particularly those affected by fire, suggesting a positive interaction between disturbance and management. Species composition differed significantly among treatments, with Indicator Species Analysis identifying distinct taxa associated with each condition. Fire in oldfield plots led to increased compositional similarity with managed stands, indicating fire’s potential homogenizing effect. Principal Component Analysis of soil nutrients did not reveal clear treatment-related patterns, which was probably due to microenvironmental variability and the short post-fire interval. Overall, our results highlight the dominant role of land-use legacy in structuring these forests, with fire acting as a secondary but influential driver, revealing significant changes in species composition as well as in species richness. These findings have direct relevance for conservation and restoration strategies as well as for maintenance in these stands of Castanea sativa. They should also encourage managers of these protected areas, where land abandonment and fire are increasingly shaping forest dynamics. Full article

Case studies of climate adaptation approaches are needed to inform the broader use of these strategies across longleaf pine (Pinus palustris Mill.) ecosystems in the Southern US. To address this need, we evaluated overstory structure and tree regeneration in longleaf pine-hardwood stands, and a transition approach was implemented to intentionally facilitate change to encourage adaptive responses. Stand density reduction and species selection were prescribed to reduce tree vulnerability to drought stress. Turkey oaks (Quercus laevis W.) were also planted as a part of an assisted population migration strategy. After the treatments, Hurricane Michael impacted the study stands. The percent reduction in large overstory longleaf pines due to the hurricane was 6.3 ± 6.1% (grand mean ± standard deviation, which was derived from the stand means). At least one live planted turkey oak was present in 74 ± 26% of the planted clusters of turkey oaks that could be located six years after planting them. Our findings demonstrate the ability of transition stands to accommodate a large-scale disturbance event and maintain ecosystem functionality, the desired stand structure, and species composition. The relative success of forestry assisted migration plantings of turkey oaks may alleviate some concerns about the risk of maladaptation. Full article

The production of fruit crops plays a vital role in the agricultural sector, contributing significantly to the social and economic development of rural communities. In Brazil, fruit production is diverse due to favorable edaphoclimatic conditions, with avocado (Persea americana Mill.) emerging as an important crop. Its production continues to expand in both cultivated areas and yield, making it a key export to non-producing countries. However, despite its importance, nutritional management information, crucial for achieving high yields, remains limited. Current guidelines on nutrition monitoring are outdated, general, and based on data from other countries with different edaphoclimatic conditions, making them not directly applicable to Brazilian orchards. Furthermore, outdated nutritional information becomes less reliable over time, as climate change alters soil conditions and crop nutrient concentrations and requirements, reinforcing the need for the establishment of up-to-date and specific nutritional information. This study aimed to establish nutritional standards for ‘Hass’ avocado production using the Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis (CND) methodologies, and to define sufficiency ranges (SRs) and Critical Levels (CLs) for both macronutrients (N, P, K, Ca, Mg, and S) and micronutrients (B, Cu, Fe, Mn, and Zn). The analyses were based on yield (t ha⁻¹) and leaf nutrient content data from commercial orchards, with datasets divided into younger (4–9 years) and older (10–26 years) plant groups. The DRIS effectively established nutritional standards for younger plants, explaining 11% of yield variation through nutritional balance. CND, in turn, was effective for both groups, accounting for 14% of yield variation and outperforming DRIS in associating nutritional status with productivity. SRs and CLs for ‘Hass’ avocado production were defined using both DRIS and CND. Together, these indices and diagnostic parameters offer valuable tools for enhancing nutritional monitoring and fertilization strategies in Brazil. Notably, SRs and CLs varied according to plant age. Full article

Refractory metal-based Mo-Si-B alloys have long been considered the most promising candidates for replacing nickel-based superalloys in the aerospace and energy sector due to their outstanding mechanical properties and good oxidation of the Mo-silicide phases. In general, the addition of vanadium to Mo-Si-B alloys leads to a significant density reduction, while small amounts of titanium provide additional strengthening without changing the phase evolution within the Mo_ss-Mo₃Si-Mo₅SiB₂ phase field. In this work, high-energy ball milling studies on Mo-40V-9Si-8B, substituting both molybdenum and vanadium with 2 and 5 at. % Ti in all constituents, were performed to evaluate the potential milling parameters and investigate the effects of Ti doping on the milling characteristics and phase formation of these multicomponent alloys. After different milling durations, the powders were analysed with regard to their microstructure, particle size, oxygen concentration and microhardness. After heat treatment, the silicide phases (Mo,V)₃Si and (Mo,V)₅SiB₂ precipitated homogeneously within a (Mo,V) solid solution matrix phase. Thermodynamic phase calculations using the CALPHAD method showed good agreement with the experimental phase compositions after annealing, confirming the stability of the observed microstructure. Full article

Natural rutile is a widely available titanium mineral which shows great potential as a photocatalyst for environmental remediation when processed correctly. Industries invest large sums in the transformation of the rutile mineral into pure, synthetic nano titania. Still, the present study proves that bare natural rutile with trace element content can also be applied as a photocatalyst, without harsh chemical interventions, simply by processing via nano grinding. Samples with different mean primary particle size values were obtained by wet stirred media milling, their compositional and structural properties were investigated, and their photocatalytic properties were evaluated under both visible- and UV-light illumination for the degradation of phenol and ibuprofen. By changing the grain size and the particle size distribution, and due to the doping effect of impurities present in the mineral, the band gap values of the samples and their photocatalytic activities changed as well. The nano milled rutile exhibited visible light photocatalytic activity, with a 33% degradation efficiency in the case of both phenol and ibuprofen, after 22 h of irradiation. The present study not only highlights the photocatalytic degradation of a pharmaceutical by natural rutile mineral, but its findings also suggest that ground nano rutile can function as an environmentally friendly photocatalyst, as it not only avoids the use of harmful chemicals typically employed in TiO₂ synthesis but also offers a simpler, more cost-effective alternative for producing photocatalytic materials. Full article

The aim of this paper is to analyse the influence of the following different supplementary cementitious materials (SCMs): milled quartz sand, microsilica, waste metakaolin, milled window glass, and a binary additive made of one part waste metakaolin and one part microsilica, on the properties of ultra-high-performance concrete, and choose the best additive according to the physical, mechanical, and structural properties of concrete. In all mixes except the control mix, 10% of the cement was replaced with pozzolanic additives, and the changes in the physical, mechanical, and structural properties of the concrete were analysed (density, compressive strength, water absorption, capillary water absorption, degree of structural inhomogeneity, porosity, freeze–thaw resistance prediction coefficient Kf values); X-ray diffraction analysis (XRD) and scanning electron microscopy analysis (SEM) results were then interpreted. Concrete with microsilica and the binary additive (microsilica + metakaolin) was found to have the highest compressive strength, density, closed porosity, and structural homogeneity. Compared to the control sample, these compositions have 50% lower open porosity and 24% higher closed porosity, resulting from the effect of pozzolanic additives, with which the highest density and structural homogeneity was achieved due to the different particle sizes of the additives used. Full article

In recent years, significant increases in premature failures of rock bolts that are attributed to stress corrosion cracking (SCC) have been observed in underground reinforcement systems, which pose serious safety concerns for underground operations. A multitude of studies have focused on understanding the environmental factors, such as the composition of the corrosive medium, temperature, and humidity, in promoting the SCC of rock bolts, but the SCC failure mechanism associated with microstructural changes is still unclear due to the complexity of the underground environments. To understand its failure mechanism and develop effective mitigation strategies, this study evaluated different testing conditions, employing pin-loaded and bar-loaded coupon tests using representative specimens. The tests were conducted in an acidified sulfide solution. The failure characteristics and crack paths of the failed specimens were examined. It was observed that the steel with lower carbon content exhibited a reduced susceptibility to SCC. The subcritical cracks observed in the specimens were influenced by the microstructure of the material. SCC was observed not only on the original surface of rock bolts, which featured mill scale and decarburization, but also on freshly machined surfaces. Evidence for the occurrence of hydrogen-induced SCC was identified and discussed. The proposed testing methods and the obtained results contribute to a deeper understanding of SCC in rock bolts as well as promote the development of more durable materials for underground mining applications, ultimately enhancing the safety and reliability of rock bolt systems. Full article

Polyamorphic transitions driven by high-energy mechanical milling (nanomilling) are studied in thioarsenide As₄Se_n-type glassy alloys obtained by melt quenching deviated from arsenic triselenide As₂Se₃ stoichiometry towards tetraarsenic pentaselenide (g-As₄Se₅) and tetraarsenic tetraselenide (g-As₄Se₄). This employs a multiexperimental approach based on powder X-ray diffraction (XRD) analysis complemented by thermophysical heat transfer, micro-Raman scattering (micro-RS) spectroscopy, and revised positron annihilation lifetime (PAL) analysis. Microstructure scenarios of these nanomilling-driven transformations in arsenoselenides are identified by quantum-chemical modeling using the authorized modeling code CINCA (the Cation Interlinked Network Cluster Approach). A straightforward interpretation of a medium-range structure response of a nanomilling-driven polyamorphism in the arsenoselenides is developed within the modified microcrystalline model. Within this model, the diffuse peak-halos arrangement in the XRD patterning is treated as a superposition of the Bragg-diffraction contribution from inter-planar correlations supplemented by the Ehrenfest-diffraction contribution from inter-atomic (inter-molecular) correlations related to derivatives of network As₂Se₃-type and molecular As₄Se₄-type conformations. Changes in the medium-range structure of examined glassy arsenoselenides subjected to nanomilling occur as an interplay between disrupted intermediate-range ordering and enhanced extended-range ordering. The domination of network-forming conformations in arsenoselenides deviated from As₂Se₃ stoichiometry (such as g-As₄Se₅) results in rather slight changes in their calorimetric heat-transfer and micro-RS responses. At the atomic-deficient level probed by PAL spectroscopy, these changes are accompanied by reduced positron trapping rate of agglomerated multiatomic vacancies and vacancy-type clusters in an amorphous As-Se network. Under an increase in As content beyond the g-As₄Se₅ composition approaching g-As₄Se₄, nanomilling-driven polyamorphic transitions, which can be classified as reamorphization (amorphous I-to-amorphous II) phase transitions, are essentially enhanced due to the higher molecularity of these glassy alloys enriched in thioarsenide-type As₄Se₄ cage-like molecular entities and their low-order network-forming derivatives. Full article