Effect on Microstructure and Nanoindentation of a AlCoFeMoNi High Entropy Alloy

In this work, elemental powders supplied by Alfa Aesar with purity higher than 99.5% in weight Al, Co, Fe, Mo and Ni were initially weighed and mixed. The MA was performed in a high-energy ball mill (SPEX-8000M) for 10 h periods, under an argon atmosphere. Methanol was used as a process control agent to avid metal agglomeration. The milled powders were melting by electric arc furnacean argon atmosphere to prevent oxidation. The ingots were remelted at least 5 times to improve chemical homogeneit

Effective Complex Properties for Three-Phase Elastic Fiber-Reinforced Composites with Different Unit Cells

The development of micromechanical models to predict the effective properties of multi-phase composites is important for the design and optimization of new materials, as well as to improve our understanding about the structure–properties relationship. In this work, the two-scale asymptotic homogenization method (AHM) is implemented to calculate the out-of-plane effective complex-value properties of periodic three-phase elastic fiber-reinforced composites (FRCs) with parallelogram unit cells. Matrix and inclusions materials have complex-valued properties. Closed analytical expressions for the local problems and the out-of-plane shear effective coefficients are given. The solution of the homogenized local problems is found using potential theory. Numerical results are reported and comparisons with data reported in the literature are shown. Good agreements are obtained. In addition, the effects of fiber volume fractions and spatial fiber distribution on the complex effective elastic properties are analyzed. An analysis of the shear effective properties enhancement is also studied for three-phase FRCs

Elliptic functions and lattice sums for effective properties of heterogeneous materials

Effective properties of fiber-reinforced composites can be estimated by applying the asymptotic homogenization method. Analytical solutions are possible for infinite long circular fibers based on the elliptic quasi-periodic Weierstrass Zeta function. This process leads to numerical convergences issues related to lattice sums calculations. The lattice sums original series converge slowly, which make the calculation difficult. This problem needs to be addressed because effective properties are highly sensitive to these values. Therefore, a systematic review and analysis for the lattice sums are a necessity. In the present work, the Eisenstein–Rayleigh lattices sums are reviewed and numerically implemented for fiber-reinforced composites with parallelogram unit periodic cell whose fibers are centered, or not, at the coordinate origin. Numerical values are reported and compared with available data in the literature obtaining good agreements. In this work, new Eisenstein–Rayleigh lattice sums are obtained that are easy to implement and a set of tables with numerical values are given

The effectiveness of published continuum constitutive laws to predict stress-assisted densification of powder compacts

Commonly used constitutive laws for crystalline and viscous materials have been compared to predict the densification behavior under hot-pressing and sinter-forging. Experimental results, from literature for one loading condition, have been used to extract the constitutive laws for amorphous and crystalline materials and, these in-turn, have been used to predict behavior under a different set of loading conditions. Ideally, the constitutive parameters obtained from one set of loading conditions and thermal history should apply to a different set of conditions. However, there is a lack of systematic experimental studies in which this can be checked. In this paper, we use constitutive parameters obtained from one set of conditions to predict the densification response under a different set of loading conditions. For both sintering of amorphous and crystalline materials, we use two different constitutive parameters and compare the predictions of these for the case where experimental results are not available. In addition, the effect of temperature on densification behavior for stress-assisted sintering has been investigated. It is shown that the two commonly used constitutive models for viscous sintering (Scherer and Skorohod–Olevsky) predict similar behavior for amorphous materials. However, for crystalline materials, the predictions of the Riedel–Svoboda and the Kuhn–Sofronis–McMeeking (KSM) models are different. Finally, it is shown that the dependence of the normalized densification on temperature, under constant heating rate conditions, with parameters obtained from isothermal experiments, is a good test for the models

Photocatalytical degradation of methyl orange (MO) using ZnO nanoparticles from alkaline wasted batteries. The effect of the MO, catalyst, and organic loads

The photocatalytic degradation of methyl orange (MO) using ZnO nanoparticles is reported. NPs in the range of 40-60 nm were obtained from wasted alkaline batteries anodes. The effect of the MO concentration and the catalyst load were analyzed finding that NPs exhibited similar photocatalytic activities than those reported for ZnO-NPs obtained from pure sources when similar conditions are used. The effect of the organic loads (COD from 60 to 900 ppm) in the catalyst efficiency was studied detecting that COD:60 ppm does not affect the ZnO photocatalytical properties. However, high COD loads (600-900 ppm) make the degradation efficiency almost null