Sampling Procedure, Characterization, and Quantitative Analyses of Industrial Aluminum White Dross

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Effect of (5%) CO2 on the Oxidation Rate During Cooling of Industrial Aluminum White Dross

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Preliminary Experimental Study of the Thermal Stability and Chemical Reactivity of the Phosphate-Based Binder used in Al2O3-Based Ceramic Foam Filters (CFFs)

Filtration of liquid aluminium is widely used in the industry for the removal of inclusions, and Ceramic Foam Filters (CFFs) are often the filtration media of choice. It is known that PH3 (phosphine) can be released from used phosphate bonded CFFs when in contact with water. Additionally, there is a need of an improved understanding of the thermal stability and the chemical reactivity of these types of filters, as there is limited information available in the public domain. In the present preliminary study, three CFFs, i.e. Substrate 1–3, with varying AlPO4 (aluminium phosphate) content were studied under controlled conditions. Samples of the substrates, as produced and in contact with 5N pure aluminium, were heat-treated in a vacuum induction furnace at 850 °C and 1300 °C, as well as thermally studied at 850 °C using a Differential Scanning Colorimeter connected to a Thermogravimetric Analyser (DSC-TG). All tests were performed under an inert atmosphere of argon (Ar). Mass changes of ~0.001 % were registered for the pure substrates, and 0.003-0.10 % when in contact with aluminium. In the latter case, diffusion of P (phosphorous) from the bulk of the substrate to the interface was established to have taken place. A colour change, from white to orange/brown, was also observed at the interface, which is a clear sign that a chemical reaction has taken place. As a result, the thermal stability of the substrates can be questioned under present conditions

Heat Treatment of Mg-Containing Aluminum Alloys 5182 and 6016 in an Oxidizing Atmosphere with 4% CO2

Oxidation of liquid aluminum (Al) during processing is a widely known problem, and magnesium (Mg), as a common alloying element, increases the oxidation rate of the alloy. It has been established that small additions of CO2 (≥ 4%) in an oxidizing atmosphere have a significant inhibiting effect on the rate of oxidation of Al alloys 5182 (AlMg4.5Mn0.4) and 6016 (AlSi1.2Mg0.4) discs based on oxide layer thickness and mass gain when heat-treated at 750 °C for 7 h. The phases present in the oxide layers for each alloy have now been identified and compared with discs heated in synthetic air and argon (Ar) under the same experimental conditions. The XRD analyses revealed the presence of MgO for all Al alloy 5182 discs, in addition to MgAl2O4 and Al2O3 when heated in synthetic air, and Mg2C3 when heated in the mixed cover gas containing 4% CO2. The low Mg-containing Al alloy 6016 revealed the presence of MgAl2O4 for all discs, in addition to MgO when heat-treated in the mixed cover gas containing 4% CO2, as well as Al2O3 when heated in Ar. For both alloys, Transmission Electron Microscopy (TEM) combined with Energy Dispersive X-ray Spectroscopy and Electron Energy Loss Spectroscopy (EDS-EELS) analyses revealed that the mixed cover gas also resulted in a nanometer-thin amorphous C layer, never previously detected, on top of the thin nanocrystalline MgO layer, retarding the evaporation of Mg and inhibiting the oxidation rate for both alloys