Magnesium hydroxide thermal decomposition

The impure hydroxide obtained above is purified by converting to a double salt, ammonium beryllium fluoride, which subsequently, on thermal decomposition, gives beryllium fluoride. The latter is heated with magnesium metal... 

The lime is produced by the thermal decomposition of calcium carbonate in shells dredged up from the ocean floor. The precipitated magnesium hydroxide is filtered off and treated with hydrochloric acid ... 

Hydroxides, hydroxy carbonates, and hydrates of aluminum, calcium, and magnesium that potentially meet these requirements are shown in Table 7.1, together with relevant thermal properties and gaseous products evolved on decomposition. However, of those in commercial use, aluminum hydroxide makes up about 90% of the market by tonnage, with magnesium hydroxide and basic magnesium carbonate products being used in niche applications. 

By reacting aluminum hydroxide with oxalic acid, basic aluminum oxalate can be produced, which is thermally stable to 330°C, losing 51% of its mass on decomposition at temperatures above 450°C. It is reported to have a flame-retarding and smoke-suppressing action similar to ATH, but because of its increased thermal stability, it can be used in polyamides and thermoplastic polyesters. However, unlike magnesium hydroxide, in these polymers it does not cause hydrolytic degradation.2... 

Hornsby, P.R., Wang, J., Rothon, R., Jackson, G., Wilkinson, G., and Cosstick, K., Thermal decomposition behaviour of polyamide fire retardant compositions containing magnesium hydroxide filler, Polym. Deg. Stab., 51, 235-249, 1996. 

The thermal decomposition of magnesium hydroxide was studied by Gordon and Kingery [18]. Their results, given in Figure 5.12, show... 

The data on thermal decomposition of activated magnesium hydroxide are well described by the first-order equation. The rate constant increases by a factor of 5-7 while the time of magnesium hydroxide activation in a vibration mill increases till 6 h. An increase of the decomposition rate is due to the fact that the nuclei formation of a new phase is simplified in the case of amorphous phase not only on the surface but also in the bulk. 

Calcining magnesium hydroxide, such as that produced in either a brine or seawater process, involves heating a filter cake that contains between 50 and 72% magnesium hydroxide solids, the balance being water. The thermal decomposition involves the following reaction ... 

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