Structure and Properties of Alloys Obtained by Aluminothermic Reduction of Deep-Sea Nodules

Abstract

This paper brings an innovative processing route of manganese deep-sea nodules, which results in completely new grades of alloys. Deep-sea nodules were processed by aluminothermic method without the extraction of individual elements, producing complexly alloyed manganese-based “natural alloys”. Three levels of the amount of aluminum were used for the aluminothermic reduction, and hence the alloys differ strongly in the amount of aluminum, which has a significant effect on their phase composition. The alloys have very high wear resistance, comparable with tool steel. The disadvantage of low-aluminum alloy is the susceptibility to local thermal cracking during friction, which occurs especially in the case of a dry sliding wear against the static partner with low thermal conductivity.

Aluminum Alloys with the Addition of Reduced Deep-Sea Nodules

“…The milled manganese nodules from the Clarion-Clipperton zone were reduced by a stoichiometric amount of Al. Detailed information on the reduction process is given in [20]. The reduced material was melted with technically pure aluminum (min.…”

“…The above-presented methods, developed for the processing of deep-sea nodules, are rather complex and costly; hence, they make the mining and use of these raw materials even less economical. Therefore, we recently proposed an innovative approach-to reduce the nodules without the separation of individual metals, giving rise to a novel grade of materials [20]. The manganese nodules are predominantly formed by oxides of Mn and Fe in various oxidation states [1,2].…”

“…The manganese nodules are predominantly formed by oxides of Mn and Fe in various oxidation states [1,2]. The reduction of MnO2 by metallic Al is a well-known exothermic reaction, so it may also be effective in the reduction of milled manganese nodules [20]. We tested this method for the processing of crushed deep-sea nodules and obtained new manganese alloys that are characterized by very good wear-resistance [20].…”

Corrosion Properties of Mn-Based Alloys Obtained by Aluminothermic Reduction of Deep-Sea Nodules

“…as minority metallic impurities [ 1 , 3 ]. The major crystalline phases of manganese nodules are Todorokite (mixed oxides of Mn, Mg, Ca, Na, and K), Buserite (mixed hydrated oxides of Mn and Na), Birnessite (mixed hydrated oxides of Mn, Ca, and Na), and Vernadite (δ-MnO 2 ) [ 6 , 7 , 8 ]. The rest of the manganese nodules contain clay, quartzite or zeolite, and amorphous hydrated ferric oxide [ 9 , 10 ].…”

“…Therefore, we focused on manganese-based materials in this study, which can be prepared simply from the deep-sea nodules. For the processing method, we selected the direct aluminothermic reduction, which was recently proved as a feasible technology [ 8 ]. The reasons for choosing this method without any separation of the present elements are the following: The deep-sea nodules are potential sources of metals after the reserves in the soil are consumed.…”