Microstructural Study of a Zn-Ni Alloy Prepared by Ball Milling Using Two Different Devices

Metallic zinc (Zn) has ben extensively used as protective coating of iron and steel for decades, but problems related with its high permeability has reduced its application. It was found that the corrosion resistance of zinc in form of alloys is increased by adding some transition metals. Recently, the Zn-Ni system is under research as an efficient alternative as anticorrosion coating for metals. Zn-Ni is mostly prepared by electroplating or thermal spray technologies, but there are some problems like: (i) fluctuation of Zn-Ni contents, (ii) the pollution caused by plating solutions and (iii) irregular thickness of the coating. The mechanical alloying (MA) technique can be used to fulfill the above issues because this route facilitates the synthesis of homogeneous materials from powder mixtures . Also, MA is frequently employed for the preparation of new materials based on mechanochemical reactions performed at room temperature, while avoiding the conventional ingot metallurgy [3]. This work deals with the preparation and study of a Zn-Ni alloy prepared by MA using two types of milling devices: a planetary which works manly through abrasion and impact of grinding balls and the Spex which works through the high-energy impact of balls. Zn-Ni was prepared from pure Ni and Zn powders, the equiatomic compositions were weighed and milled for 4 hours followed by sintering at 357°C during 1h

Methanol detection in commercial sanitizing gels, during the COVID-19 Pandemic

The ethanol (active) and methanol (toxic) substances content were quantified for commercial sanitizing gels. The health emergency caused by the COVID-19 epidemic has motivated to production of sanitizing gels to cover higher demand. The analytical composition of 24 commercial gels is reported (15 produced by national and transnational companies, and 9 collected gels which were in use at public areas). From the results it was found, that only one brand of 15 gels meets the quality requirements regarding 70% (wt./wt.) of ethanol content. Concerning to the collected gels, none of them contains the minimum active compound required. The non-compliance of this requirement means that these gels present its sanitizing action diminished. A striking result is that 25% of commercially packaged gels contain methanol - a toxic substance - in alarming amounts, hundreds of times more than the FDA upper limits requirement. DOI: https://doi.org/10.54167/tecnociencia.v15i1.76

Exfoliated graphite preparation based on an eco-friendly mechanochemical route

In the present study, we proposed an eco-friendly method to produce exfoliated graphite based on a dry mechanochemical process. This route represents an alternative that avoids the use and disposal problems related to highly corrosive and dangerous reagents use, manipulation and elimination. As non-toxic alternative exfoliation route, an equimolar mixture of graphite flakes and calcium carbonate was milled and leached with an aqueous solution of acetic acid (vinegar). There was a notable reduction of the graphite particle size with a significantly increased level of exfoliation, which dramatically improved the surface area of the prepared samples from 4 to 363 m2 g-1. After 16 h of processing, milled particles reached a thickness reduction of up to 5 nm and micrometric widths.The overall yield of processed graphite is around 92% based on the raw graphite. The evident benefits of the obtained exfoliated graphites in the adsorption of methylene blue (a common pollutant of textile wastewater) are presented. Exfoliated graphite represents a valid alternative as adsorption agent for dye removal reaching efficiencies above 95% after 30 min of testing with an aqueous solution of methylene blue. Contrary, the untreated graphite sample showed a null adsorption activity

Synthesis and Characterization of Zn-Ni x

Mechanical ball milling assisted by sintering in the solid state was used in this research to produce the Zn-Nix system alloy. The derivative powder compositions of Zn-Nix (x = 0, 5, 10, 15, and 20 wt.%) were obtained to study the Ni effects on the microstructural and mechanical properties. It is worth remarking that conventional methods are not appropriate for the manufacture of the Zn-Nix system alloy. The morphological structure and phases were examined by optical microscopy, X-ray diffraction, and SEM/EDS elemental mapping, whereas the mechanical behavior was accomplished by means of a diamond indentation print (Hardness Vickers). The results showed that the intermetallic γ-ZnNi phase did not form during milling time (<4 h); it appears after the sintering process, which is associated with atomic diffusion mechanism through grain boundary at the minimum interfacial energy (ΔG256°C = −13.83 kJ·mol−1). The powder Zn-Ni10 was found to have better properties. Semispherical coarser particles were seen into the metal matrix (Zn δ-hcp structure) as segregates; however, each particle contains an intermetallic compound Zn-Ni that encloses the Ni (α-fcc structure) pure phase. The Ni-α phase was then transformed into a γ-ZnNi intermetallic compound which shifts to higher values of mechanical hardness from about 60 HV to 400 HV units

Abrasive Wear Behavior of Al–4Cu–1.5Mg–WC Composites Synthesized through Powder Metallurgy

Different Al–4Cu–1.5Mg/WC composites were synthesized through powder metallurgy to establish the effect of WC particle addition on the abrasive wear behavior of an Al–4Cu–1.5Mg (wt. %) alloy. The wear tests were performed using a pin-on-disc tribometer at room temperature in dry conditions using SiC abrasive sandpaper as a counterbody and tribometer of linear configuration. The results showed that WC additions increase the hardness of the Al–4Cu–1.5Mg alloy due to the strengthening effect of particle dispersion in the aluminum matrix, which generates an improvement in the wear resistance of the composites by preventing direct contact of the sample with the counterbody, in turn delaying the plastic deformation phenomena responsible for the degradation sequence. In addition, the dominant wear mechanism was abrasive wear, and the increased friction coefficient did not bring a rapid wear rate, which was related to the enhanced deformation resistance due to the high hardness

Microstructural Study of a Zn-Ni Alloy Prepared by Ball Milling Using Two Different Devices

Metallic zinc (Zn) has ben extensively used as protective coating of iron and steel for decades, but problems related with its high permeability has reduced its application. It was found that the corrosion resistance of zinc in form of alloys is increased by adding some transition metals. Recently, the Zn-Ni system is under research as an efficient alternative as anticorrosion coating for metals. Zn-Ni is mostly prepared by electroplating or thermal spray technologies, but there are some problems like: (i) fluctuation of Zn-Ni contents, (ii) the pollution caused by plating solutions and (iii) irregular thickness of the coating. The mechanical alloying (MA) technique can be used to fulfill the above issues because this route facilitates the synthesis of homogeneous materials from powder mixtures . Also, MA is frequently employed for the preparation of new materials based on mechanochemical reactions performed at room temperature, while avoiding the conventional ingot metallurgy [3]. This work deals with the preparation and study of a Zn-Ni alloy prepared by MA using two types of milling devices: a planetary which works manly through abrasion and impact of grinding balls and the Spex which works through the high-energy impact of balls. Zn-Ni was prepared from pure Ni and Zn powders, the equiatomic compositions were weighed and milled for 4 hours followed by sintering at 357°C during 1h

AFM Analyses of 3XXX Series Al Alloy Reinforced with Different Hard Nanoparticles Produced in Liquid State

In the present work, nanocomposites-based 3XXX series Al alloy with three different types of hard nanoparticles, including TiO2, C, and CeO2, were produced employing two techniques such as mechanical milling and stir-casting method in order to evaluate the viability of integration of the reinforcement in the Al matrix. The integration and dispersion capability of the reinforcement into the Al alloy (3xxx Series) matrix was evaluated, using a phase angle difference and surface roughness analyses by atomic force microscopy operated in both the contact mode (CM-AFM) and tapping mode (TM-AFM), respectively. The distribution profile of both rugosity and the phase angle shift was used to statically quantify the integration and dispersion of the reinforcement into the extruded samples, by using the root mean square (RMS) parameter and phase shift coupled with the events number (EN) parameter. Results from Atomic Force Microscopy (AFM) analyses were corroborated by X-ray diffractometry and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness tests were conducted to identify the mechanical properties of the composites in the extruded condition and their correlation with the microstructure. A close relationship was found between the microstructure obtained from the AFM and X-ray diffractometry (XRD) analyses and mechanical properties. Among all, the C reinforcement produced the major changes in the microstructure as well as the best integration and dispersion into the Al-alloy coupled with the best mechanical properties