Gabriela Popescu

Study concerning the recovery of zinc and manganese from spent batteries by hydrometallurgical processes

Used batteries contain numerous metals in high concentrations and if not disposed of with proper care, they can negatively affect our environment. These metals represent 83% of all spent batteries and therefore it is important to recover metals such as Zn and Mn, and reuse them for the production of new batteries. The recovery of Zn and Mn from used batteries, in particular from Zn-C and alkaline ones has been researched using hydrometallurgical methods. After comminution and classification of elemental components, the electrode paste resulting from these processes was treated by chemical leaching. Prior to the leaching process the electrode paste has been subjected to two washing steps, in order to remove the potassium, which is an inconvenient element in this type of processes. To simultaneously extract Zn and Mn from this paste, the leaching method in alkaline medium (NaOH solution) and acid medium (sulphuric acid solution) was used. Also, to determine the efficiency of extraction of Zn and Mn from used batteries, the following variables were studied: reagents concentration, S/L ratio, temperature, time. The best results for extraction yield of Zn and Mn were obtained under acid leaching conditions (2M H2SO4, 1h, 80°C).

New Quaternary Type of Al-Sr-Ti-B Master Alloy for Grain Refining and Modifying of Al-Si

The paper’s aim is to present the processing of a new master alloy similar to STROBLOY. This alloy represents a combination of two master alloys, already known in aluminum industry (AlTiB and AlSr). The benefits of this new alloy are the cut of Ti, B and Sr consumption, as well as a grain refining/modification ecological technology for Al-Si and Al-Mg-Si alloys. So, this alloy was obtained from binary AlB8, AlSr10 and AlTi10 master alloys melted in an electric resistance furnace and argon atmosphere. Samples were cast in an iron mould. As STROBLOY, this new quaternary alloy contains fast dissolving SrAl4 particles important in modification stage, and nucleating particles such as TiB2 and (Al, Ti)B2 essential for grain refining of aluminum alloys.

The Combined Effect of Modifier and Grain Refiner AlTiBSr Master Alloy on Microstructure and Porosity of Aluminum Alloys

The aim of the paper is to present the influence of a new multifunctional material, a master alloy named Al-Sr-Ti-B, in aluminum foundry alloys. The Al-Sr-Ti-B master alloy represents a new combination of two master alloys, already known in aluminum industry, AlTiB and AlSr, used in treatment of aluminum alloys for grain refining and modification. As Strobloy, our master alloy contain fast dissolving SrAl4 particles and also nucleating particles as TiB2 and (Al,Ti)B2 which are important first in modification and second in grain refining of aluminum alloys. The paper presents optic and electron microscopy studies realized on AlSi7Mg alloy treated with this new multifunctional material

Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

Influence of the Heat Treatment Processes on the Properties of High Entropy Alloys Based on Al-Cr-Fe-Mn-Ni System

In the present paper, high entropy alloys based on an aluminum-chromium-iron-manganese-nickel (Al-Cr-Fe-Mn-Ni) system were prepared by induction melting and annealed in an inert atmosphere. The resulting samples were analyzed by optical microscopy, scanning electron microscopy, and X-ray diffraction to determine the structural characteristics before and after the heat treatment process. Significant phase transformations and changes in the phase distribution were noticed after the heat treatment process. The results were discussed against the thermodynamic criteria calculations for most promising compositions. Hardness tests were provided for the selected samples to indicate the changes in the mechanical properties between various compositions and between as-cast and annealed samples. Results indicated that the heat treatment process determined a significant hardness increase in one of the studied high entropy alloys.

Study on Wear Resistance FeNiCrMnAl High Entropy Alloy - Mechanical Properties

Traditional alloys is based on a single element called matrix and to improve some mechanical properties (strength, ductility, strength) are added and other metallic elements in the system. High entropy alloys have become a field of increasingly explored in the world of materials. Excellent mechanical properties obtained of the high entropy alloys recommend them to be from year to year as investigated. In the last decade more than 500 high entropy alloys journal and conference papers have been published [1]. High entropy alloys are alloys who have in their composition 5 to 13 metal elements and the concentration of each component is between 5% and 35%. These elements in the composition of high entropy alloys are divided into elements of minority and majority elements. They are called minority elements because their molar fraction is less than 5%. High entropy alloys have mixing entropy higher than traditional alloys, ΔScons≥1.61R (R = 8.314 J / (mol • K)) [1]. High entropy alloy have been obtained in the laboratory of Science and Materials Engineering faculty from Iasi using a medium frequency induction furnace with 8000 Hz. Because they have excellent mechanical properties high entropy alloys can be used in various fields with high wear and corrosion degree or electronic, magnetic applications [1]. In this work we selected pure metallic elements like: Fe, Ni, Cr, Mn and Al. The quantity of alloy developed varied between 0.5 and 1.5 kg. Metal load necessary for the preparation of metal alloys were formed technical grade, industrial accessible prices and satisfying. Friction and wear rezistance were studies by using a reciprocating sliding test machine , in a pin on disk configuration, using aluminum as counter face.In this paper it investigated the wear resistance of high entropy alloys obtained, microstructure and their mechanical properties.

CoCrFeNiMo High Entropy Alloy Produced by Solid State Processing

Mechanical alloying (MA) is a high-energy ball milling process results in the obtaining of simple and stable microstructures having increased homogeneity compared to other non-equilibrium synthesis methods. The aim of this paper was to develop a high entropy alloy with an improved hardness value suitable for coating turbine blades working in geothermal steam. CoCrFeNiMo high entropy alloy was processed in solid state, using mechanical alloying. After 40h milling time in a planetary ball mill the alloyed sample was consolidated using spark plasma sintering process. The samples obtained were investigated with the aid of optical and electron microscope, X ray diffraction and the hardness value was determined. The results obtained revealed that the powder was completely alloyed after 40 hour milling and the mixture between BCC and FCC phases resulted in 34% improved hardness value in comparison with a stainless steel usually used for turbine blades working in geothermal environment.

New High Entropy Alloy for Biomedical Applications

High Entropy Alloys (HEAs) represent a new concept of metallic materials, that contain 5 or more elements, in proportions from 5 at.% to 35 at.%, and form simple solid solutions (BCC and/or FCC) instead of complicated intermetallic phases. The high degree of randomness atomic HEA, gives them excellent properties: electrical, mechanical, electrochemical, ductility, anti-corrosion properties, stable structure etc, with applications in peak thus representing a growing research. These specific features provides HEA with excellent hardness, strength and wear strength, malleability, oxidation and corrosion resistance, with potential applications in diverse industrial areas [1÷4]. Considering these properties we decide to improve biomedical alloys with this new class of HEAs.

Pressure Influence on the AlCrFeNiMn/Graphite High Entropy Composite Microhardness

During the last years, mechanical alloying technique for high entropy alloys (HEAs) has been more often approached due to the good homogenous chemical distribution and near net shape technology provided by the respectively process. A new composite material having the matrix as HEA reinforced with graphite particles was designed. The graphite particles addition in the high entropy matrix (AlCrFeNiMn) improves the particles weldability during mechanical alloying and assures a good creep behavior for the final product. The aim of this paper is to investigate the pressure influence on the microhardness as dependence of sintering parameters which can be reflected also on the microstructure. The high entropy composite was completely alloyed after 40 hours of milling. The obtained composite was pressed using different pressures values in order to investigate the pressure influence on the microhardness and microstructure. The samples were investigated using optical microscopy, scanning electron microscopy, X-rays diffraction and microhardness tests. The microhardness values for all the samples were between 300 – 700 HV.

Some Analysis of Major Impact of Geothermal Fluid Components in Power Plant Equipment

This paper presents the results from a some analysis and major impact of geothermal fluid composition on the equipment in use in geothermal power plant. The structural analysis of material deposition improve the direct influenced of chemical composition of stem and waters included CaO, MgO, Al2O3 and SiO2 incorporated in the molten phase and the deposits in the scales formed due to equipment. The steam turbine corrosion damage, particularly of blades, discs and pomps, has long been recognized as a leading causes of reduced availability in the geothermal power plant. The corrosion process depends on temperature, pressure, chemisty and vaporous carryover by diversity of impurity. The experimental analysis procedure involves characterization of the fluid geothermal composition. Detailed information about surfaces morphological modification of the power plant components are obtained by electron microprobe analysis EDX and SEM investigation. References selection are obtaining by X-ray diffractometer patterns of the specimen.