Mechanochemical Activation of Aluminum: 3. Kinetics of Interaction between Aluminum and Water

Abstract

Two regimes of oxidation by water are revealed for nanocrystalline aluminum prepared by the mechanical activation of its mixture with graphite and distributed in the matrix of amorphous carbon. At the temperatures 50 ° C < T < 90 ° C, nanosized aluminum particles interact with water under quasi-isothermal conditions. The main products are hydrogen and pseudoboehmite AlOOH; a low content of bayerite Al(OH) 3 is also formed. After the induction period, the kinetics of interaction can be satisfactorily described by the law of a diminishing sphere. The effective activation energy of the reaction is equal to 61 ± 10 kJ/mol and is identical for the samples of submicron aluminum prepared by different procedures. At temperatures above 90-95 ° C, the oxidation of mechanically activated aluminum by water is transformed into a thermally self-accelerated explosion process. Under these conditions, the oxidation of aluminum to α -Al 2 O 3 is accompanied by an exothermal reaction between the metal and the carbon matrix during which aluminum carbide Al 4 C 3 is formed.

Hallmarks of mechanochemistry: from nanoparticles to technology

“…Table 2 presents some literature findings on mechanical activation of several brittle substances. [168][169][170][171][172][173][174][175][176] At the initial stage of MA of brittle substances, the main process is the comminution of particles and formation of new surfaces. A typical curve for increase of specific surface area is shown in Fig.…”

“…The mechanochemically assisted synthesis of KNLNT with the composition (K 0.485 Na 0. 485 Infrared spectroscopy analysis was used to follow the vibrations of the carbonate ions in the powder mixture during mechanochemical activation. The aim was to obtain insight into possible symmetry changes of the carbonate species.…”

“…Experiments were done under heating at a low rate (10 1C min À1 ) 484 and during a shockwave initiation. 173 The preparation of nanocomposites by a mechanochemical method is a usual way for improving the properties of materials used in hydrogen storage. 186 As an example, mechanical activation of Mg-C-H 2 , 477 Ti-C 475 and Ti-BN 481 composites lead to the decrease of hydrogenation temperature.…”

“…487 Reactions of mechanically activated Al with ethanol and butanol have been studied as well. 173 The analysis of reactivity of mechanochemically activated nanocomposites is also given there.…”

Influence of concentration modifier on the structure and functional properties of aluminum oxyhydroxide modified

“…1 is the microphotography of the electro explosive aluminum nanopowder. The synthesis process of nanofibers in salt solutions was carried out under the same conditions as the synthesis in distilled water [5]. The volume of solution was 200 ml and the weight of aluminum nanopowder was 0.075.…”