In situ and ex situ studies on thermal decomposition process of hydromagnesite Mg5(CO3)4(OH)2·4H2O

• Published in: Journal of thermal analysis and calorimetry 2021-05, Vol.144 (3), p.599-609
• Main Authors: Yamamoto, Gen-ichiro, Kyono, Atsushi, Sano, Yoshinari, Matsushita, Yoshitaka, Yoneda, Yasuhiro
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Basic magnesium carbonate; Chemistry; Chemistry and Materials Science; Crystal growth; Crystal structure; Decomposition; Dehydration; High temperature; Inorganic Chemistry; Lattice parameters; Measurement Science and Instrumentation; Nucleation; Periclase; Physical Chemistry; Polymer Sciences; Thermal decomposition; Thermal expansion
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-020-09618-7

We investigated crystal structure and the local structure changes during the thermal decomposition of hydromagnesite by using in situ high-temperature XRD and ex situ high-temperature X-ray total scattering measurements. Hydromagnesite displayed anisotropic thermal expansion up to 220 °C. The a and c lattice parameters exhibited an increase trend with temperature, whereas the b lattice parameter and β angle did not show a regular trend with temperature. The relative expansion between 25 and 220 °C followed the c / c 0  >  a / a 0   ≫   b / b 0 . At 260 °C, the a , b , and c lattice parameters significantly decreased. Above 280 °C, hydromagnesite underwent a structural collapse with dehydration and dehydroxylation reactions, but was never accompanied by nucleation and growth of crystal phases up to 425 °C. During the thermal decomposition from hydromagnesite to periclase, the Mg atoms maintained the octahedral coordination environments in the structure.