A Kinetic Study on the Preparation of Al-Mn Alloys by Aluminothermic Reduction of Mn[sub.3]O[sub.4] and MnO Powders

• Published in: Metals (Basel ) Vol. 13; no. 9
• Main Authors: Salas Avilés, Juan Alberto, Flores Valdés, Alfredo, Torres Torres, Jesús, Ochoa Palacios, Rocío Maricela, Flores Saldívar, Alfredo Alan
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.09.2023
• Subjects: Alloys; Aluminum castings; Batteries; Founding; Mexico; Powders; Recycling (Waste, etc.); Specialty metals industry; Transportation equipment industry; Mexico
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met13091556

The study of aluminothermic reduction in manganese compounds is a complex challenge in preparing Al-Mn alloys. The primary objective of this study was to ascertain the activation energy values for the aluminothermic reduction of MnO and Mn[sub.3]O[sub.4] oxides derived from alkaline batteries. The study melted aluminum found in beverage cans and utilized the technique of powder addition with mechanical agitation. The kinetics of the reaction were studied under the effects of temperature (750, 800, and 850 °C), degree of agitation (200, 250, and 300 rpm), and the initial concentration of magnesium in molten aluminum (1, 2, 3, and 4% by weight). Kinetic measurements for Mn[sub.3]O[sub.4] particles suggest a reaction mechanism that occurs in stages, where manganese undergoes oxidation states [Mn[sup.+3]] to [Mn[sup.+2]] until it reaches the oxidation state Mn[sup.0], which allows it to dissolve in the molten aluminum, forming alloys with up to 1.5 wt.% of Mn. Therefore, the kinetic of the aluminothermic reduction of MnO is described by the geometric contraction model, while the mechanism of Mn[sub.3]O[sub.4] reduction occurs in two stages: geometric contraction, followed by an additional stage involving the diffusion of chemical species to the boundary layer. In addition, this stage can be considered a competition between the formation of MnO and the chemical reaction itself.