Iceland spar calcite: Humidity and time effects on surface properties and their reversibility

Natalia A. Wojas*, Agne Swerin, Viveca Wallqvist, Mikael Järn, Joachim Schoelkopf, Patrick A.C. Gane, Per M. Claesson

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Understanding the complex and dynamic nature of calcite surfaces under ambient conditions is important for optimizing industrial applications. It is essential to identify processes, their reversibility, and the relevant properties of CaCO3 solid-liquid and solid-gas interfaces under different environmental conditions, such as at increased relative humidity (RH). This work elucidates changes in surface properties on freshly cleaved calcite (topography, wettability and surface forces) as a function of time (≤28 h) at controlled humidity (≤3–95 %RH) and temperature (25.5 °C), evaluated with atomic force microscopy (AFM) and contact angle techniques. In the presence of humidity, the wettability decreased, liquid water capillary forces dominated over van der Waals forces, and surface domains, such as hillocks, height about 7.0 Å, and trenches, depth about −3.5 Å, appeared and grew primarily in lateral dimensions. Hillocks demonstrated lower adhesion and higher deformation in AFM experiments. We propose that the growing surface domains were formed by ion dissolution and diffusion followed by formation of hydrated salt of CaCO3. Upon drying, the height of the hillocks decreased by about 50% suggesting their alteration into dehydrated or less hydrated CaCO3. However, the process was not entirely reversible and crystallization of new domains continued at a reduced rate.

Original languageEnglish
Pages (from-to)42-55
Number of pages14
JournalJournal of Colloid and Interface Science
Volume541
DOIs
Publication statusPublished - 1 Apr 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • Calcium carbonate minerals
  • Capillary forces
  • Humidity effects
  • Iceland spar calcite
  • Nanomechanical properties
  • Recrystallization
  • Reversibility of aging effects
  • Surface topography
  • Surface wettability
  • Van der Waals forces

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