Glass transition temperatures and crystallization kinetics of a synthetic, anhydrous, amorphous calcium-magnesium carbonate

Kai Uwe Hess, Jürgen E.K. Schawe, Martin Wilding, Bettina Purgstaller, Katja E. Goetschl, Sebastian Sturm, Knut Müller-Caspary, Elena V. Sturm, Wolfgang Schmahl, Erika Griesshaber, Thilo Bissbort, Daniel Weidendorfer, Martin Dietzel, Donald B. Dingwell

Publikation: Beitrag in einer FachzeitschriftArtikelBegutachtung

Abstract

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)'.

Originalspracheenglisch
Aufsatznummer20220356
Seitenumfang1
FachzeitschriftPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Jahrgang381
Ausgabenummer2258
DOIs
PublikationsstatusVeröffentlicht - 16 Okt. 2023

ASJC Scopus subject areas

  • Allgemeine Mathematik
  • Allgemeiner Maschinenbau
  • Allgemeine Physik und Astronomie

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