Characterisation of oxidised aluminium powder: Validation of a new anodic oxidation bench

Nicolas Gascoin (1) , Philippe Gillard (2) , Guillaume Baudry (3)

1 Univ. Orléans, PRISME, CE
2 PRISME - Laboratoire Pluridisciplinaire de Recherche en Ingénierie des Systèmes, Mécanique et Energétique
3 LEES - Laboratoire Énergétique Explosions Structures [1998-2007]

Aluminium powder is of major interest in many applications but it presents a risk due to its high explosibility, particularly when dispersed in air. The safety is directly linked to the particles oxidation because the Minimum Ignition Energy (MIE), which is required to initiate an Al dust explosion, increases with the oxide layer thickness. This study provides a controlled method to furnish reproducible homogeneous set of powder for such safety studies. Thanks to a new experimental bench, the influence on the oxidation rate of seven treatment parameters is investigated (current density, time of treatment, acid concentration, mass of powder, particles size, stirring, neutralisation by ammonia solution). The oxide content is plotted versus the current density, the time and the acid concentration to provide reference curves for further elaboration of oxidised powder. The particles size of sieved powder is measured before and after treatment by different methods (optical and Scanning Electron Microscopes, laser measurement). A high refinement of the powder in terms of size distribution is achieved thanks to the employed sieving. The present bench and the elaborated procedure are of great interest to provide well-calibrated oxidised powder directly available for safety studies. The time must be adjusted, depending on the wanted oxide content - from 2 to 18 wt.% - and the other treatment parameters must be kept constant: acid concentration (5 wt.%), current density (1 A dm-2), treated powder (20 g). In these conditions, the ratio of the oxide layer thickness on the particles diameter is found to be constant for a given oxide content whatever the particles size.

Mots clés: Scanning Electron Microscope; Treatment parameters; Acids; Design of experiments; Explosions; Ignition; MOS capacitors; Powders; Anodic oxidation; aluminum; ammonia; oxide; experimental study; explosion; hazard assessment; measurement method; oxidation; acidity; article; concentration (parameters); controlled study; density; experimental design; laser microscopy; molecular weight; oxidation kinetics; powder; reaction time; reproducibility; scanning electron microscopy; thickness; validation study; Calibration; Electrodes; Equipment Design; Lasers; Microscopy; Electron; Scanning; Oxides; Oxygen; Particle Size; Thermogravimetry; Time Factors; Acid concentrations; Aluminium micrometric powder; Aluminium powder; Ammonia solution; Before and after; Characterisation; Dust explosion; Experimental bench; Explosibility; Hazard mitigation; Laser measurements; Minimum ignition energy; Neutralisation; Oxidation rates; Oxide contents; Oxide layer thickness; Particles sizes; Reference curves; Safety studies

Domaines: Matériaux; Génie des procédés

Nicolas Gascoin, Philippe Gillard, Guillaume Baudry. Characterisation of oxidised aluminium powder: Validation of a new anodic oxidation bench. Journal of Hazardous Materials, 2009, 171 (1-3), pp.348-357. ⟨10.1016/j.jhazmat.2009.06.010⟩. ⟨hal-00641607⟩