Abstract The treatment techniques utilised to improve the qualities of recycled concrete aggregate (RCA) for its efficient use in cement mortar and concrete are critically examined in this review study. The use of RCA is often constrained by residual adhering mortar, which leads to increased porosity and water absorption and to reduced density, mechanical strength, and durability. The analysis consolidates results from published research on four primary therapeutic methods: sodium silicate treatment, rapid carbonation, cement-slurry impregnation, and polymer impregnation. These methods are evaluated based on their effects on water uptake, porosity, compressive strength, interfacial transition zone properties, and longevity. The analysed data suggest that the application of sodium silicate efficiently consolidates the bonded mortar and reduces water permeability, whereas carbonation facilitates calcium carbonate formation, enhances pore architecture, and strengthens aggregate–paste adhesion. Cement-slurry infusion improves the surface quality and mechanical properties of RCA, whereas polymer infusion significantly enhances impermeability and long-term resilience, although its elevated expense may limit widespread use. In summary, sodium silicate treatment and carbonation offer an advantageous balance of efficacy, feasibility, and ecological benefits. This analysis delineates the relative benefits and drawbacks of existing therapies and underscores the necessity for standardised treatment protocols, long-term efficacy evaluations, and assessments of environmental and economic impacts to facilitate the wider systemic implementation of treated RCA.
Abstract Copper ferrite (CuFe₂O₄) nanoparticles were synthesized by a mixed alcohol–polyol-assisted sol–gel route using octane-2-ol and glycerol, followed by calcination at 500–900°C. XRD confirmed cubic spinel CuFe₂O₄ with crystallite sizes of 14.25–16.46 nm and improved crystallinity with increasing calcination temperature. TGA indicated major xerogel decomposition below 500°C, while the calcined samples showed good thermal stability above 500°C with an atmosphere-dependent weight gain at 430–500°C. FESEM revealed predominantly near-spherical particles with improved definition and coarsening at higher temperatures. Magnetic measurements showed ferrimagnetic behavior, with markedly higher saturation magnetization for samples calcined at 800–900°C. Overall, the mixed alcohol–polyol-assisted sol–gel route offers an effective approach for tailoring the structural, morphological, thermal, and magnetic properties of CuFe₂O₄ nanoparticles.
Abstract This study contrasts a near-eutectic Sn-Zn alloy (Sn-1) with a multicomponent Sn-Cu-Zn-Sb-Pb system (Sn-2) to elucidate the interplay between compositional complexity, phase formation, and electrical transport. While conventional characterization confirms expected phase evolution, the results reveal a decisive trade-off: Sn-1 achieves superior conductivity (1.105 × 10⁵ S/cm), whereas Sn-2 exhibits a marked reduction (26.7%). This degradation is not merely compositional but structurally driven, as increased chemical complexity promotes intermetallic formation that intensifies electron scattering. The findings challenge the simplistic assumption that multicomponent design inherently enhances performance, highlighting instead that excessive complexity can be detrimental to electrical efficiency.
Abstract The effect of welding speed on weld geometry, microhardness, tensile properties, and fracture behaviour of laser beam welded 3 mm thick Ti-6Al-4V butt joints was investigated. Autogenous joints were produced at 1.5–4.0 m/min using a fibre laser at a power of 3.3 kW, while the remaining process parameters were kept constant. Full penetration was obtained under all conditions. Increasing welding speed markedly narrowed the fusion zone and heat-affected zone; between 1.5 and 4.0 m/min, the fusion-zone width decreased by approximately 42% at the weld face and 66% at the root. Microhardness profiles shifted from bilateral HAZ softening at lower speeds to a distinct fusion-zone hardness peak of approximately 450 HV0.1 at 4.0 m/min, consistent with faster cooling and an increased tendency for α′ martensite formation. Ultimate tensile strength showed a statistically significant decreasing trend, from 881 to 769 MPa (joint efficiency from 73% to 64%), and the total strain at fracture decreased from 1.02% to 0.77%. Fracture occurred along the fusion line or adjacent HAZ; fractography revealed predominantly quasi-cleavage features in these regions, whereas the base material exhibited ductile dimpling. Within the investigated range, higher welding speed reduced weld width but adversely affected tensile performance through evolving local hardness gradients and geometric stress concentration.
This study investigates the fabrication, microstructural evolution, and mechanical properties of Al2O3-Cu-Cr ceramic-metal composites containing 2.5 vol.% metallic phase produced by uniaxial pressing followed by free sintering in a reducing atmosphere. The composites were sintered at temperatures ranging from 1200 degrees C to 1400 degrees C in order to evaluate the influence of thermal processing on densification behaviour, phase stability, and mechanical performance. The results demonstrated a strong dependence of physical properties on sintering temperature. Increasing the temperature from 1200 degrees C to 1400 degrees C improved the relative density from 82.85% to 97.99%, while open porosity decreased from 16.57% to 0.09%. Simultaneously, water absorption was reduced from 4.66% to 0.2%, indicating near-complete densification at 1400 degrees C. XRD analysis confirmed the presence of stable alpha-Al2O3, Cu, and Cr phases without formation of undesirable secondary reaction products. SEM/EDS observations revealed a homogeneous distribution of discrete Cu-Cr metallic regions within the alumina matrix and satisfactory ceramic-metal interfacial bonding. The composites sintered at 1400 degrees C exhibited a hardness of 13.8 +/- 1.6 GPa and fracture toughness of 4.41 +/- 0.78 MPa & centerdot;m0.5. Digital image correlation analysis during compression testing demonstrated localized strain evolution preceding brittle fracture. The results indicate that Cr addition may contribute to improved microstructural stability and densification behaviour of Al2O3-Cu composites processed by conventional powder metallurgy routes.
