Band 113, Heft 10

This study focused on the colloidal stability enhancement of iron oxide nanoparticles synthesized using aqueous extract of the Ceratonia siliqua L. (carob pod) by optimizing the synthesis parameters. The synthesis parameters were determined as the concentration of iron ions, the concentration of extract, pH of extract, temperature, stirring rate, and reaction time. The significance of the studied factors in controlling the particle size distribution of nanoparticles was quantitatively evaluated via analysis of variance (ANOVA). Iron oxide nanoparticles were produced with an average zeta potential of +41 ± 0.8 mV, hydrodynamic size of 78 ± 22 nm, and a polydispersity value of 0.42 ± 0.06, respectively. As a result of the stability study by measuring the zeta potential, it was determined that the colloidal stability was maintained for 3 months. Green iron oxide nanoparticles (gIONPs) showed inhibition zones of 24.27 ± 0.12 mm and 20.83 ± 0.11 mm in 250 mg/mL concentration against Gram-negative ( Escherichia coli ) and Gram-positive ( Staphylococcus aureus ) bacterial strains, respectively. S. aureus was susceptible to the gIONPs according to the standard antibiotics of Cefotaxime (≥23 mm), Tetracycline (≥19 mm), Gentamicin (≥15 mm), and Cefoxitin (≥22 mm). E. coli was susceptible to the gIONPs according to the standard antibiotics of Tetracycline (≥19 mm) and Gentamicin (≥15 mm), but showed resistance to the Cefotaxime (15–22 mm) and Cefoxitin (≤21 mm) standard antibiotics. This study suggests that the green synthesized iron oxide nanoparticles could be used as an antimicrobial agent and a promising candidate for usage in sensor, biomedical, and electronics applications for being in a highly stable structure.

Renewable fuel is gaining more attention in the current energy crisis, and biomass is one of the potential sources of producing renewable fuel. The objective of the present research is to analyze the pyrolysis and kinetic behavior of neem seed biomass. Pyrolysis and kinetic behavior of neem seed were analyzed using thermogravimetric analysis (TGA) at different heating rates, viz. 5, 10, 15, and 20 K min −1 . The kinetic study was conducted on the neem seed using various kinetic models such as Friedman, Kissinger, Flynn–Wall–Ozawa (FWO), and Kissinger–Akahira–Sunose (KAS). Thermodynamic analysis was carried out using the data extracted from the TGA curves. The results showed that the neem seed degraded in three stages, stage I: <100 °C, stage II: 100–550 °C, and stage III: >550 °C. A maximum mass loss of 73.14 % occurred at stage II owing to the loss of cellulose and hemicellulose. The activation energy determined by Friedman, KAS, and FWO models was 5.11–18.64, 10.62–57.41, and 13.77–61.51 kJ mol −1 , respectively. Thermodynamic analysis revealed that the pyrolysis of neem seed was an endothermic and spontaneous process. Moreover, the previously reported average activation energy required for the pyrolysis of various seeds and shells was compared with the present study and concluded that the variation in activation energy of neem seed adheres to the outcomes reported earlier.

LaCoO 3 , SrCoO 3 and La 0.7 Sr 0.3 CoO 3 materials were synthesized using the modified proteic method using gelatin as a chelating agent, to study the effect of metal type in the formation of the perovskite structure, as well as to test its adsorptive capacity when removing a dye from aqueous medium. The formation of the perovskite phase was predominant, and the modified proteic method was efficient in producing materials with relatively high surface areas, in comparison to other methods of synthesis. The materials showed removal efficiency of Bezaktiv red dye until 95 %. The experimental data were applied to kinetic models pseudo-first order, pseudo-second-order and variable constants. In studies for the reuse of adsorbents, it was proven that the adsorbents maintained their efficiency and the perovskite structure was maintained, signaling its stability after adsorption and recovery conditions.

The surge of interest in ferrimagnetic materials over the years has been driven by their fascinating multifunctional properties. The elastic properties of these materials are a subject of much interest and vital importance due to their wide range of technological and industrial applications. In the present work, the structural and elastic properties of tetragonal copper ferrite (CuFe 2 O 4 ) nanoparticles synthesized by a citrate assisted sol-gel auto combustion technique have been investigated. The nanocrystalline powder of copper ferrite was characterized by using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and UV–Visible spectroscopic techniques. The X-ray diffraction pattern revealed pure spinel structure of copper ferrite nanoparticles with Jahn–Teller tetragonal distortion. The band gap of copper ferrite nanoparticles was found to be 3.14 ± 0.03 eV using the diffuse reflectance spectra. The values of elastic moduli (Young’s modulus ( E ) = 186.3 ± 0.5 GPa, bulk modulus ( B ) = 124.1 ± 0.3 GPa, and rigidity modulus ( G ) = 74.4 ± 0.2 GPa) and Debye temperature ( θ D = 500.5 ± 0.5 K) suggest that the synthesized nano-structured copper ferrite is a promising candidate for high temperature and high pressure applications.

The mechanical and thermomechanical properties of superlattice Mg 3 Cd (D0 19 ) in the pressure range 0–50 GPa were investigated using the first-principles method. The lattice constants, unit cell volume, and density were investigated. The calculated lattice constants are in good agreement with experimental and other theoretical values. The elastic moduli (such as bulk modulus, shear modulus, Young’s modulus) of polycrystalline materials were derived from the single-crystal elastic constants. In addition, Poisson’s ratio, B/G , and Cauchy pressure were investigated. The calculated results show that Mg 3 Cd is a ductile material and exhibits metallic properties under various pressures. The dependence of thermodynamic properties on temperature and pressure are also discussed by using the quasi-Debye model approximation.

In this work, different Fe/Ni ratios with constant Co content were prepared to explore microstructure and properties of ultrafine WC-10 wt.%(Co–Fe–Ni)-Cr 3 C 2 cemented carbides. The increase in Fe content in binder has difficulty in controlling carbon content. Therefore, the carbon window was determined by phase diagram to prepare carbon-balanced cemented carbides. The increase in Fe/Ni ratio in the binder deteriorates the uniformity of the binder phase distribution and refines the WC and binder phase grains by affecting the solubility of WC in binder and the wettability of the binder. Grain size, microstructural irregularities and solid solution strengthening of binder phase affect the mechanical properties of cemented carbides. The relative density of cemented carbide with Fe/Ni = 30:70 in the binder is 99.8 % and the transverse fracture strength is 2449 MPa maximum, but the fracture toughness is slightly low. Because of the passivation characteristics of Ni, the alloy with Fe/Ni = 0:100 in the binder has better resistance to corrosion resistance.

CoCrNiCu X ( X = Mn, MnFe, FeAl) high-entropy alloys were prepared by mechanical alloying and spark plasma sintering. The relationship between microstructural and mechanical properties of CoCrNiCu X powders and bulks was investigated. The effects of the addition and substitution of elements on crystal structure transition, microstructural evolution, and mechanical properties were assessed. The results indicated that, with the addition of Fe, the crystal structure of the alloys was transformed from fcc phase to a mix of fcc and bcc phases. By substituting Mn with Fe and Al, the formation of bcc phase was promoted, which caused precipitation hardening that significantly improved the hardness and compression strength of the investigated high-entropy alloys.

In this study, SiC (0, 5, 10, 15, 20 wt.%) reinforced seamless aluminium pipes were fabricated using powder metallurgy followed by hot extrusion. The microstructural (optical microscopy, scanning electron microscopy) and mechanical (tensile and crush behaviour) properties of silicon carbide reinforced seamless aluminium pipes were studied. Experimental results showed that the SiC particles form some clusters in the Al matrix and were oriented in the direction of extrusion. Tensile tests indicated that the addition of SiC particles to pure Al matrix resulted in a significant increase in tensile properties of the SiC-reinforced seamless aluminium pipes. Compared to pure Al pipe, 20 % SiC reinforced aluminium pipe exhibited higher yield strength (127 vs. 83 MPa, increased by ∼53 %) and ultimate tensile strength (150 vs. 129 MPa, increased by ∼16 %). Two types of deformation mode (symmetrical ring and asymmetric diamond) were observed in the samples with L / D :1 and L / D :2 ratios under crushing load. Maximum initial collapse force (6.7 kN) was obtained in 10 % SiC reinforced aluminium pipe with L / D :1 ratio.