Origin of Surface Irregularities on Ti–10V–2Fe–3Al Beta Titanium Alloy

We studied the origin of different characteristics and properties of a Ti–10V–2Fe–3Al beta (β) titanium alloy with surface height irregularities that occurred during machining. The height differences were observed in two different regions, labeled as “soft region” and “hard region.” The present study showed a higher Fe and a lower Al content in the hard region, which resulted in higher β-phase stability to resist primary alpha (α_p) phase precipitation caused by a failure of the solution treatment process. In contrast, the soft region contained a higher volume fraction of α_p phase and a lower volume fraction of the matrix, which consisted of a combination of β and secondary alpha (α_s) phase. A high number of α_s/β interface in the matrix with a predicted hardness of 520 HV generated an improvement of hardness in the hard region. Therefore, the hard and the soft regions had different abilities to resist wear during machining process, resulting in surface height irregularities.     

Inversion of three-stage stress-strain relation for stainless steel in tension and compression

Presented in this paper is a new stress-strain relation for stainless steel alloys that provides the stress as an explicit function of the strain. The relation is an approximate inversion of a recently proposed three-stage stress-strain relation based on a modified Ramberg-Osgood equation. The three-stage relation is a much more accurate formulation than the previous two-stage formulations and is applicable to both tensile as well as compressive stresses. The new relation is derived by making a rational function assumption on the fractional deviation of the actual stress-strain curve from an idealized linear elastic behaviour. The new expression is valid over the full range of the stress well beyond the elastic region. The validity of the inverted expression is tested over a wide range of material parameters. These tests demonstrate that, the new expression results in stress-strain curves which are both qualitatively and quantitatively in excellent agreement with the fully iterated numerical solution of the full-range stress-strain relation with a maximum error below 4%.     

Adsorption behavior of Co(II) and Ni(II) from aqueous solutions onto titanate nanotubes

Adsorption of Co²⁺ and Ni²⁺ from aqueous solutions onto titanate nanotubes (TNTs) synthesized by hydrothermal method in single and binary systems was investigated. The prepared TNTs were completely characterized showing very high surface area compared to previous studies (320 m²/g). The high surface area showed very good optimum removal conditions compared with previous studies (60 min contact time, 0.1 g TNTs dose at pH 5 and room temperature) with high adsorption capacity compared with previous studies as well as conventional adsorbent. Langmuir and Freundlich isothermal models were fitted during this study and Dubinin–Kaganer–Radushkevich isotherms showed physisorption with exclusion of ion exchange mechanism. Pseudo first and second-order kinetics were studied showing more fitting to pseudo second-order equation. Binary system and calculation of separation coefficient showed high ability for Co²⁺ adsorption by TNTs than Ni⁺² in binary system.     

Co1−xZnxFe2O4 (0 ≤ x ≤ 1) nanocrystalline solid solution prepared by the polyol method: Characterization and magnetic properties

Highly crystalline stoichiometric Co_1?xZn_xFe₂O₄ (0 ≤ x ≤ 1) nanoparticles were successfully synthesized by the polyol process. X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), transmission electron microscopy (TEM), infrared spectroscopy (IR), zero-field ⁵⁷Fe Mössbauer spectrometry and magnetic measurements using a SQUID magnetometer were employed to investigate the effect of the substitution of Zn²⁺ ions for Co²⁺ ones on the structure, and the magnetic properties of the cobalt ferrite, CoFe₂O₄. The unit cell parameter almost increases linearly with increasing Zn concentration, x, following Vegard's law. The red and blue shifts observed for the metal-oxygen ν₁ and ν₂ IR vibration bands, respectively, were consistent with the preferential entrance of Zn²⁺ ions in tetrahedral sites. Besides, detailed magnetic investigation in correlation with the cation distribution has been reported. All the particles exhibit superparamagnetic behaviour at room temperature. In addition, the magnetic characteristics (blocking temperature, saturation magnetization, coercivity, Curie temperature) clearly depend on the chemical composition and cation distribution. Both the blocking temperature and Curie temperature decrease drastically with Zn composition, x, increase. Further, the saturation magnetization follows an almost bulk-like behaviour with values notably larger than that of the bulk, mainly attributed to cation distribution deviation.     

Synthesis and characterization of radiation cross-linked PVP hydrogels and investigation of its potential as an antileishmanial drug carrier

Polymer Bulletin - The aim of this study was to elaborate a suitable hydrogel to be used as drug carrier for antileishmanial treatment. Therefore, a PVP hydrogel was synthesized using gamma...     

Relaxor behavior in (Ba1−3x/2Bix)(ZryTi1−y)O3 ceramics

New ferroelectric ceramics Bi-BZT of ABO₃ perovskite type were synthesized in the (Ba_1−3x/2Bi_x)(Zr_yTi_1−y)O₃ system by solid state reaction route. The effect of the substitution of barium by bismuth in the A cationic site on structural and dielectric properties was investigated. The dielectric constant was studied in the temperature range from 20 K to 320 K at frequencies ranging from 0.2 to 100 kHz. A clear relaxor behavior was observed for samples with x ≥ 0.075 and y = 0.1. In this case the value of the relaxation parameter γ ≈ 2 estimated from the linear fit of the modified Curie–Weiss law, indicates the relaxor nature of the Bi-BZT ceramics. The dielectric relaxation rate follows Vogel–Fulcher relation with an activation energy of 0.26 eV and 0.27 eV, an attempt frequency f₀ = 3.4 × 10¹² Hz and 5.7 × 10¹² Hz and a static freezing temperature T_VF = 98 K and 94 K respectively for x = 0.075 and x = 0.1.