How does magnesium acetate tetrahydrate form anhydrous glass?

The thermal dehydration of magnesium acetate tetrahydrate is known as a process which produces noncrystal line anhydrate. The thermal dehydration of magnesium acetate tetrahydrate begins at the surface of the reaction particles; the mechanism involves the melting and/or dissolution of the ionic material in the water produced, thereby forming a fluid phase. Research has shown that the formation of this intermediate fluid phase is a characteristic phenomenon leading to the formation of anhydrous glass. Upon further heating, the newly prepared anhydrous glass exhibits a glass transition at approximately 470 K, with an activation energy Ea ≈ 550–560 kJ mol–1, followed by crystallisation via diffusion-controlled three-dimensional growth of crystal nuclei. The activation energy for this crystallisation process is approximately 280 kJ mol–1, with an enthalpy change of ΔH = –13.3 kJ mol–1, ultimately resulting in the formation of small, rounded crystalline anhydrous particles.

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