Search Results (4,512)

The fabrication of NiTiZr alloys by solid-state routes remains challenging due to limited atomic diffusion and the high reactivity of Ti and Zr. Mechanical alloying offers a potential pathway for synthesising such systems; however, complete alloy formation is not always achieved under practical milling conditions. Researchers have infrequently explored the mechanical alloying of NiTiZr, and this study systematically investigates the effect of milling time on microstructural evolution rather than claiming complete alloy synthesis. A high-energy planetary ball mill was used to mechanically process elemental powders of Ni, Ti, and Zr for 5–28 h. The examination revealed that longer milling times resulted in progressive crystallite refinement and increased lattice strain, while particle morphology evolved from irregular to more globular shapes due to repeated fracture and cold welding. After 28 h of milling, limited reacted regions containing Ni, Ti, and Zr were observed (~4.6% area fraction), while most of the powder remained heterogeneous and polyphasic, with no evidence of complete Ni₅₀Ti₃₀Zr₂₀ alloy formation. X-ray diffraction showed significant peak broadening without systematic 2θ peak shifts, indicating severe plastic deformation and crystallite refinement rather than definitive solid-solution formation of the allot. Differential scanning calorimetry revealed exothermic thermal events between 300 °C and 470 °C, which are attributed to defect recovery and thermally activated structural rearrangements rather than confirmed martensitic or crystallisation transformations. These results demonstrate that high-energy ball milling alone is effective for particle size reduction and defect generation but insufficient for producing a fully homogeneous Ni₅₀Ti₃₀Zr₂₀ alloy within 28 h. Additional activation energy, such as post-milling heat treatment or extended processing, is required to promote complete alloying in this system. Full article

The modification of road bitumen using micro-sized carbonaceous materials offers a promising route to enhance pavement performance; however, the influence of microdispersed coke derived from coal and petroleum sources has not been sufficiently clarified. In this study, coal and petroleum coke from Pavlodar Petrochemical Plant LLC (Pavlodar, Kazakhstan) were mechanochemically activated and used as the modifiers for BND 100/130 bitumen, produced by Asphaltbeton 1 LLC (Almaty, Kazakhstan). X-ray diffraction and scanning electron microscopy were used to determine the structure and morphology of the resulting coke powders. Standard tests and the Superpave Multiple Stress Creep and Recovery (MSCR) methodology were used to determine the physico-mechanical and rheological properties of the modified binders. Microdispersed granular coke powders produced after mechanochemical activation had a minimum average particle diameter of 8.28 µm (petroleum coke) and 16.64 µm (coal coke), and were mainly an amorphous carbon phase with traces of graphite. Addition of 1 wt.% microdispersed coke resulted in better performance of binder and an enhancement in grades of BND 100/130 to BND 70/100, in line with ST RK 1373-2013. MSCR testing showed that Jnr_3.2 is between 2.0–3.0 kPa⁻¹, which is in the S category of AASHTO M 332-20. This study showed how micro-sized coal and petroleum coke can be effectively used as a high-carbon modifier in bitumen, which reflects the possibility of their practical use in asphalt pavements that are subjected to normal traffic conditions. Full article

This research aims to investigate the modifications of the structural, dielectric, and sensing properties of CaFeO_3−δ ceramics produced by solid-state reaction induced by varying sintering temperatures in the range of 1000–1200 °C. A single crystallographic orthorhombic (Pcmn) structure was revealed by X-ray diffraction with Rietveld analysis, both for the powders and sintered ceramics, irrespective of the sintering temperature. The increase in the sintering temperature induces better densification and a larger grain size. Dielectric measurements reveal a pronounced enhancement of the relative permittivity, reaching 2 × 10⁵ at 1 kHz and 330 °C for the sample sintered at 1200 °C/4 h. This composition also displays the highest electrical conductivity, 0.4 S/m at 1 MHz. Cole–Cole analysis indicates a clear deviation from ideal Debye behavior, while the relaxational features of the dielectric permittivity suggest a strong correlation between the dielectric response and Fe-related conduction mechanisms. Gas sensing tests show that the ferrite ceramics exhibit consistent ethanol response trends. The ceramic sintered at 1200 °C/4 h achieved the highest sensitivity, of 56.28%, which can be attributed to its higher density, larger ceramic grains, and reduced low-frequency conductivity. The CaFeO_3−δ ceramic sintered at 1200 °C/4 h shows a combination of high permittivity, enhanced conductivity, and strong ethanol sensitivity, making it a promising material for dielectric components, capacitive devices, and gas sensing applications. Full article

A Cu-containing FeCrMnNiAl multi-principal element alloy was processed by laser-based and electron beam-based powder bed fusion (PBF-LB/M and PBF-EB/M) to investigate processing–microstructure–property relationships. In focus were alloy variants with a relatively high Cu content. Two PBF-LB/M scan strategies, employing a Gaussian beam with and without a re-scan with a laser featuring a flat-top profile, were compared to PBF-EB/M processing, followed by heat-treatments between 300 °C and 1000 °C. The phase constitution, elemental partitioning and grain boundary characteristics were analyzed by X-ray diffraction, electron backscatter diffraction and energy-dispersive X-ray spectroscopy. Mechanical behavior was assessed by hardness and tensile testing. Both manufacturing routes promoted the evolution of stable multi-phase microstructures composed of face-centered-cubic (FCC)- and body-centered-cubic (BCC)-type phases across all heat-treatment conditions. PBF-LB/M processing resulted in finer, dendritic microstructures and suppressed formation of a Cu-rich FCC phase due to higher cooling rates, whereas PBF-EB/M promoted the evolution of Cu-rich FCC segregates and equiaxed grain morphologies. Heat-treatment above 700 °C led to recrystallization, accompanied by an increase of the FCC phase fraction, grain coarsening, and recovery. At lower heat-treatment temperatures, the changes in microstructure are different. Here, it is assumed that small, non-clustered Cu-rich precipitates formed at the grain and sub-grain boundaries, although this assumption is only based on the assessment of the mechanical properties. The size of these precipitates is below the resolution limit of the techniques applied for analysis in the present work. Additional structures seen within the Cu-rich areas of PBF-EB/M-manufactured samples treated at lower temperatures also seem to have an influence on the hardness and yield strength. All of the conditions investigated exhibited pronounced brittleness, limiting reliable tensile property evaluation and indicating the need for further optimization of processing strategies and microstructural control for high-Cu-fraction-containing multi-principal element alloys. Full article

Laser processing has been widely investigated as an effective approach for improving surface properties and consolidating advanced materials, particularly complex alloys such as titanium aluminides (TiAl). In this study, laser surface remelting was applied to binary (Ti-45Al) and ternary (Ti-45Al-2Co and Ti-45Al-2Ni) alloys produced by powder metallurgy via blended elemental (BE) and pre-alloyed (PA) powder routes. Laser powers of 50 and 100 W were employed, resulting in a high-energy-density surface remelting regime applied to both green compacts and sintered samples with relatively high initial porosity, under an argon-controlled atmosphere. Microstructural and phase analyses were performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD), while mechanical behavior was assessed by instrumented microindentation. Laser processing promoted the formation of a dense and homogeneous surface layer, approximately 150 μm thick, accompanied by significant microstructural refinement and enhanced hardness and elastic modulus. While rapid solidification led to crack formation in laser-treated sintered samples, the green compacts exhibited defect-free modified layers. Overall, the results demonstrate that laser surface remelting is an effective strategy for enhancing the surface integrity and mechanical performance of TiAl alloys processed by powder metallurgy. Full article

Protein crystals are intrinsically hydrated systems, and their structural integrity is strongly influenced by environmental humidity. Understanding the effects of relative humidity (RH) variation on crystal stability is therefore essential for both fundamental research and applied studies. In this work, the structural response of tetragonal hen egg-white lysozyme (HEWL) to controlled RH variation was investigated using in situ X-ray powder diffraction (XRPD). Polycrystalline HEWL samples were subjected to systematic gradual dehydration and rehydration cycles, as well as to non-gradual RH variation protocols. Pawley analysis of the XRPD data enabled monitoring of the evolution of unit cell parameters and unit cell volume as a function of RH. Under all experimental conditions, the tetragonal polymorph (space group P4₃2₁2; a = 79.105 (4) Å, c = 38.231 (2) Å) was preserved. RH variation induced smooth, continuous and anisotropic lattice changes, characterized by a decrease in the a (=b)-axis and a concomitant increase in the c-axis upon dehydration, while rehydration resulted in the opposite behavior. The overall magnitude of lattice variation remained limited (within ±2%), indicating a high degree of structural stability. Partial degradation of crystallinity was observed only after prolonged exposure to low RH levels. These findings demonstrate the remarkable structural resilience of tetragonal HEWL and highlight the effectiveness of in situ XRPD as a powerful tool for probing hydration-driven lattice responses in protein crystals under realistic environmental conditions. Full article

The properties of a Ca₉La(VO₄)₇ single crystal were studied using dielectric spectroscopy and second-harmonic generation. The crystal structure of Ca₉La(VO₄)₇ grown using the Czochralski technique was refined using single-crystal data. The distribution of Ca²⁺ and La³⁺ cations over structural positions was determined. The crystal structure refinement results were compared with those obtained previously from powder X-ray diffraction data. It was shown that the refinement carried out using two different data sets leads to approximately the same results for the distances in the polyhedra, but their distortion is significantly less in the case of using single-crystal data for calculation. Dielectric properties and conductivity measurements were performed on polished single-crystal wafers cut parallel and perpendicular to the c axis. Second-harmonic generation and dielectric temperature measurements revealed the presence of a reversible ferroelectric first-order phase transition at about 1224 K from the ferroelectric β-phase (space group R3c) to the paraelectric β′-phase. The ferroelectric–paraelectric phase transition is accompanied by a complex structural rearrangement, including a 60° rotation of the V1O₄ tetrahedron, as well as slight displacements of the Ca²⁺ and La³⁺ cations. It has been shown that the conductivity differs only slightly along the polar axis and perpendicular to it. Above the phase transition temperature, the activation energy of the conductivity is the same for all directions, E_a~1.2 eV. The influence of composition on the phase transition temperature and the formation of ferroelectric and nonlinear optical properties is discussed. Full article

This work aims to develop a controlled ball milling strategy for preparing FeCoCrNiCu high-entropy alloy (HEA) powders with improved compositional homogeneity while maintaining limited oxygen uptake. Specifically, a novel two-step combined ball milling strategy integrating gradient ball-size configurations with a sequential milling procedure is proposed and systematically evaluated. Compared with conventional single-step milling, the mixed-ball and two-step configurations enhance mechanical alloying (MA) efficiency and promote the formation of more stable FCC and BCC dual-phase structures, as confirmed by X-ray diffraction (XRD) analysis. Compositional standard deviation derived from energy-dispersive X-ray spectroscopy (EDS) measurements indicates improved macroscopic uniformity, while oxygen/nitrogen/hydrogen (ONH) analysis verifies that oxygen incorporation remains limited within the tested processing window. Systematic comparison of jar filling degrees and sampling interruptions further reveals the coupled influence of collision energy distribution and exposure frequency on oxidation behavior. The results demonstrate that controlled energy distribution and minimized atmospheric disturbance are critical for balancing alloying efficiency and oxygen control in FeCoCrNiCu powders. Full article

Interest in non-centrosymmetric crystalline materials exhibiting second harmonic generation (SHG) has increased due to their potential applications in optical sensing and biosensing. Saccharide-based metal complexes are particularly attractive systems, as chiral sugars can promote non-centrosymmetric crystal packing. In this work, a new lanthanum–β-d-fructose compound, [La(C₆H₁₂O₆)(H₂O)₅]Cl₃ (LaFRUCl), was synthesized using a simple and low-cost method and characterized by single-crystal X-ray diffraction. The compound crystallizes in the orthorhombic space group P2₁2₁2₁ and consists of infinite (La³⁺–fructose)_n chains extending along the [001] direction, forming a one-dimensional Metal–Organic Framework. The nonlinear optical response was evaluated using the Kurtz–Perry powder technique with a Nd:YAG laser (1064 nm) and compared to a sucrose reference. The measured SHG efficiency is comparable to that of previously reported alkaline earth metal–sugar analogs. While the compound’s SHG emission is significant, evaluation of its structural stability under aqueous or physiological conditions is be required before considering biological applications. Full article

This work focuses on obtaining a titanium nitride coating on the surfaces of titanium and its alloy powders using a novel method, self-shearing reactive milling, under a nitrogen pressure of 50 bar. The Ti, Ti6Al4V, and Ti-5553 spherical powders were milled for up to 10 h at ambient temperature without grinding balls. As a result of the experiments, a thin, brittle TiN coating formed on the powders’ surfaces. The cross-sections of the milled powders reveal that the TiN layer thickness is in the nanometer range (about 500 nm). By analyzing the sequence of X-ray diffraction patterns, it is evident that only for the Ti6Al4V powder milled for 10 h, two peaks are observed that can be attributed to a TiN phase. On the other hand, Raman spectroscopy revealed characteristic TiN spectra even for samples collected at the initial stage of self-shearing reactive milling. An important aspect of the experiment was the preservation of the spherical shape of the milled powders, which makes them a potential feedstock for additive manufacturing of functionally graded biomaterials. Full article

Zero-valent iron (Fe(0)) nanoparticles have a wide range of applications, including catalysis, energy storage, and even reported roles in human neurochemistry. This study demonstrated that [Fe₃(CO)₁₂] dissolves in N,N-Dimethylformamide (DMF) within a minute to resolve the dissolution problem of this complex. Dodecylamine (DDA) was used to produce DDA-coated Fe(0) at 383 K in 30 s with a microwave reactor. The powder X-ray diffraction (PXRD) of the Fe(0) profile indicated a pure-phase face-centred cubic (FCC) structure with Fm$\overline{3}$m space group. Varying the synthesis time from 30 s to 5 min did not significantly affect the unit cell parameters (3.5276 (±0.0001) and 3.5391 (±0.0001) Å). Microwave use yielded well-dispersed, pure Fe(0) nanoparticles, and the particle size, shape, elemental analysis, and surface oxidation of the Fe(0) nanoparticles were studied using scanning electron microscopy and dispersive X-ray spectroscopy (SEM/EDX). Annular Dark-Field Scanning Transmission Electron Microscopy (ADF-STEM) and Fourier-transform infrared (FT-IR) spectroscopy confirmed the surface coating of Fe(0) nanoparticles with DDA. Thermogravimetric analysis (TGA) was used to demonstrate the surface adsorption of DDA on Fe(0) nanoparticles. In addition, STEM showed that the average nanoparticle size under the stated synthesis conditions was 25.7 nm. This comparatively straightforward procedure offers advantages over existing practical approaches to the synthesis of Fe(0) nanoparticles, including safety, speed and reaction control. Full article

This study investigates the long-term resistance of an environmentally friendly composite made from a blend of local Ordinary Portland Cement (OPC) and ground granite waste powder (G). The composite was subjected to complete static immersion for up to twenty-four weeks in three types of water: potable water, groundwater, and seawater. The experimental work evaluated the effects of exposure to these three water types on various characteristics of the granite–cement composite (GCC), including compressive strength, mass gain, portlandite [CH] content, bulk density (D), total porosity (p), compactness, water absorption (A), and pH of the immersing media. Additionally, scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal analysis (TGA and DTA) were used to investigate how exposure to the three water environments altered the internal microstructure of the hydration phases of the composite over the twenty-four-week period. This systematic approach provides valuable insights into the variations that may occur in solid hydration outcomes and their sustainability in flooding scenarios. The data obtained from these analyses revealed that the granite–cement composite exhibits acceptable thermal resistance and endurance to deterioration in aquatic environments. The cement formulation contains 20% by mass of ground granite waste powder, with a water-to-cement ratio of 35%. After 24 weeks of complete static immersion, the composite achieved compressive strength values close to 24 MPa. Solidifying radioactive waste in cement–granite is a newly developed method that improves sustainability by formulating a more stable, durable, cost-effective, and less hazardous waste form. Therefore, the granite–ordinary cement composite being studied is recommended as an inert matrix for solidifying and stabilizing certain categories of radioactive waste. Full article

Antimony oxide nanoparticles (Sb₂O₃ NPs) were synthesized via a chemical vapor deposition (CVD) method and systematically characterized to evaluate their multifunctional performance. Powder X-ray diffraction (PXRD) confirmed the formation of an orthorhombic Sb₂O₃ phase with an average crystallite size of 53.50 nm, while SEM analysis revealed elongated nanostructures with diameters in the range of 20–100 nm. The stoichiometric composition of Sb₂O₃ (Sb:O ≈ 2:3) was verified by EDAX, and optical studies indicated a direct band gap of 3.10 eV. The electrochemical sensing capability of Sb₂O₃ NPs was investigated using a modified nickel mesh electrode for the detection of Metronidazole (MTZ) in 0.1 N KOH. The presence of Sb₂O₃ NPs resulted in an additional irreversible reduction peak at −0.14 V, confirming enhanced electrocatalytic activity toward MTZ, along with excellent cycling stability (94.36% retention after 10 cycles). In addition, the photocatalytic performance of Sb₂O₃ NPs was evaluated through the degradation of Acid Orange (AO) dye under UV-Vis irradiation, achieving a degradation efficiency of 73.31%. These results demonstrate that Sb₂O₃ nanoparticles are promising multifunctional materials for environmental remediation and electrochemical sensing applications, highlighting their potential for industrial implementation. Full article

This study investigates the potential of Quercus robur leaves as a bio-coagulant for the removal of heavy metal ions, including zinc (II), iron (III), copper (II), and chromium (VI), from water. The Quercus robur leaves were used in two forms: Quercus robur powder (QRP) and Quercus robur extract (QRE). The extract was prepared using distilled water to extract the active compounds responsible for coagulation, such as proteins, polysaccharides, and total phenolics. The QRP was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and zeta potential analysis to identify the active functional groups, surface morphology, crystallinity, and surface charge, all of which are key factors influencing its performance in the coagulation–flocculation process. In this work, the Response Surface Methodology (RSM)-based Central Composite Design (CCD), with two factors (bio-coagulant dosage and initial metal concentration), was used examine the effects of each factor and their interaction, while the responses were zinc (II) removal, iron (III) removal, copper (II) removal, and chromium (VI). The results revealed high removal efficiency for these metal ions, reaching up to 100% for all metal ions treated with QRP and QRE. The quality of the model predictions was evaluated using analysis of variance (ANOVA). For all metal ions, the R² (≥97%), R² adjusted (≥95%), and p-values (<0.05), indicating an excellent model accuracy. These results show that bio-coagulants (QRP and QRE) based a Quercus robur leaves are a promising, effective, and reliable option for removing heavy metal ions from water, and that the models developed can be used to optimize the coagulation-flocculation process. Full article

Wear of crushing and grinding equipment components causes frequent maintenance and downtime; therefore, effective repair hardfacing routes are required to extend service life. This study investigates plasma transferred arc (PTA) surfacing of 35L cast steel using a high-chromium Fe–Cr–C powder (PG-S27) and clarifies how the welding current (40–120 A) governs layer geometry, microstructure, phase constitution, hardness, and dry-sliding tribological behavior. All deposits exhibited a dendritic–eutectic structure; increasing current led to dendrite coarsening, wider interdendritic regions, and deeper penetration/dilution. X-ray diffraction indicated an α-Fe matrix with chromium carbide phases (Cr₇C₃/Cr₂₃C₆), while the carbide-related signal decreased with higher current, consistent with enhanced dilution. The coatings showed a strong hardening effect compared with the substrate (~190 HV), reaching ~625–650 HV at 40–80 A and decreasing to ~556–589 HV at 100–120 A. In dry ball-on-flat sliding, the steady-state friction coefficient was nearly unchanged (μ ≈ 0.50–0.55) across all regimes; however, wear resistance depended strongly on current: the lowest wear was achieved at low-to-moderate currents (40–80 A), whereas higher currents (100–120 A) resulted in substantially increased material loss, approaching the substrate level. These results identify 40–80 A as the most favorable current window for obtaining wear-resistant PTA layers from PG-S27 on 35L steel. Full article