Calcination of oxide

The quality of magnesium oxychloride cements is highly dependent on the reactivity of the magnesium oxide used in their preparation. Typically, such oxides are prepared by calcination of the basic carbonate (Eubank, 1951 Harper, 1967), but their reactivity varies according to the conditions under which such calcination is carried out. As the reactivity alters so does the amount of oxide that can be incorporated into a cement relative to the amount of aqueous MgClj (Harper, 1967). 

Calcination temperature, °C Age, days Compressive strength, MPa MgO/MgClj, mol  

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The process of calcination of oxides, hydrogen reduction of oxides to lower oxides, hydrofluorination and hydrochlorination of oxides, etc., can often be carried out by conventional chemical engineering methods. However, the high standards of purity usually required for rare metal extraction at least necessitate novel materials of construction. In addition, a considerable development and pioneering effort has been devoted to the improvement of these techniques, particularly applied to the intermediates in the production of uranium metal, uranium trioxide, dioxide and tetrafluoride. It is possible, therefore, that the resulting processes can be more widely employed in the rare metal extraction field in the future. 

Ferrite-type catalysts may constitute an alternative for perovskites for total oxidation of hydrocarbons as it was demonstrated by ferrites prepared following two routes, that is, the hydrothermal one and the calcination of oxide mixtures with the following compositions Ni >,Fe3 04 (. = 0.5) and Mn Fe3 c04 ( = 0.65) [28]. These studies demonstrated that the structure of the catalysts is very important in providing catalytic active structures. Pure XRD ferrite structures exhibit a poor activity, while mixed-phase ferrite oxide showed a good activity. 

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