TY - JOUR
T1 - Glass transition temperatures and crystallization kinetics of a synthetic, anhydrous, amorphous calcium-magnesium carbonate
AU - Hess, Kai Uwe
AU - Schawe, Jürgen E.K.
AU - Wilding, Martin
AU - Purgstaller, Bettina
AU - Goetschl, Katja E.
AU - Sturm, Sebastian
AU - Müller-Caspary, Knut
AU - Sturm, Elena V.
AU - Schmahl, Wolfgang
AU - Griesshaber, Erika
AU - Bissbort, Thilo
AU - Weidendorfer, Daniel
AU - Dietzel, Martin
AU - Dingwell, Donald B.
PY - 2023/10/16
Y1 - 2023/10/16
N2 - We report the first calorimetric observations of glass transition temperatures and crystallization rates of anhydrous, amorphous calcium-magnesium carbonate using fast scanning differential scanning calorimetry. Hydrous amorphous Ca0.95Mg0.05CO3 · 0.5H2O (ACMC) solid was precipitated from a MgCl2-NaHCO3 buffered solution, separated from the supernatant, and freeze-dried. An aliquot of the freeze-dried samples was additionally dried at 250°C for up to 6 h in a furnace and in a high-purity N2 atmosphere to produce anhydrous ACMC. The glass transition temperature of the anhydrous Ca0.95Mg0.05CO3 was determined by applying different heating rates (1000-6000 K s-1) and correcting for thermal lag to be 376°C and the relaxational heat capacity was determined to be Cp = 0.16 J/(g K). Additionally, the heating rate dependence of the temperature that is associated with the corrected crystallization peaks is used to determine the activation energy of crystallization to be 275 kJ mol-1. A high-resolution transmission electron microscopy study on the hydrous and anhydrous samples provided further constraints on their compositional and structural states. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'.
AB - We report the first calorimetric observations of glass transition temperatures and crystallization rates of anhydrous, amorphous calcium-magnesium carbonate using fast scanning differential scanning calorimetry. Hydrous amorphous Ca0.95Mg0.05CO3 · 0.5H2O (ACMC) solid was precipitated from a MgCl2-NaHCO3 buffered solution, separated from the supernatant, and freeze-dried. An aliquot of the freeze-dried samples was additionally dried at 250°C for up to 6 h in a furnace and in a high-purity N2 atmosphere to produce anhydrous ACMC. The glass transition temperature of the anhydrous Ca0.95Mg0.05CO3 was determined by applying different heating rates (1000-6000 K s-1) and correcting for thermal lag to be 376°C and the relaxational heat capacity was determined to be Cp = 0.16 J/(g K). Additionally, the heating rate dependence of the temperature that is associated with the corrected crystallization peaks is used to determine the activation energy of crystallization to be 275 kJ mol-1. A high-resolution transmission electron microscopy study on the hydrous and anhydrous samples provided further constraints on their compositional and structural states. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'.
KW - amorphous calcium-magnesium carbonate
KW - crystallization dynamics
KW - fast scanning differential scanning calorimetry
KW - glass transition temperature
KW - lyophilization
KW - scanning transmission electron microscopy
UR - http://www.scopus.com/inward/record.url?scp=85168850484&partnerID=8YFLogxK
U2 - 10.1098/rsta.2022.0356
DO - 10.1098/rsta.2022.0356
M3 - Article
C2 - 37634535
AN - SCOPUS:85168850484
SN - 1364-503X
VL - 381
JO - Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
JF - Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
IS - 2258
M1 - 20220356
ER -