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Claesson, P. M., Wojas, N., Corkery, R., Dedinaite, A., Schoelkopf, J. & Tyrode, E. (2024). The dynamic nature of natural and fatty acid modified calcite surfaces. Physical Chemistry, Chemical Physics - PCCP, 26(4), 2780-2805
Open this publication in new window or tab >>The dynamic nature of natural and fatty acid modified calcite surfaces
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2024 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 26, no 4, p. 2780-2805Article in journal (Refereed) Published
Abstract [en]

Calcium carbonate, particularly in the form of calcite, is an abundant mineral widely used in both human-made products and biological systems. The calcite surface possesses a high surface energy, making it susceptible to the adsorption of organic contaminants. Moreover, the surface is also reactive towards a range of chemicals, including water. Consequently, studying and maintaining a clean and stable calcite surface is only possible under ultrahigh vacuum conditions and for limited amounts of time. When exposed to air or solution, the calcite surface undergoes rapid transformations, demanding a comprehensive understanding of the properties of calcite surfaces in different environments. Similarly, attention must also be directed towards the kinetics of changes, whether induced by fluctuating environments or at constant condition. All these aspects are encompassed in the expression “dynamic nature”, and are of crucial importance in the context of the diverse applications of calcite. In many instances, the calcite surface is modified by adsorption of fatty acids to impart a desired nonpolar character. Although the binding between carboxylic acid groups and calcite surfaces is strong, the fatty acid layer used for surface modification undergoes significant alterations when exposed to water vapour and liquid water droplets. Therefore, it is also crucial to understand the dynamic nature of the adsorbed layer. This review article provides a comprehensive overview of the current understanding of both the dynamics of the calcite surface as well as when modified by fatty acid surface treatments. Calcium carbonate, particularly in the form of calcite and surface modified calcite, is an abundant mineral widely used in both human-made and biological systems.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2024
National Category
Physical Chemistry
Identifiers
urn:nbn:se:ri:diva-70385 (URN)10.1039/d3cp04432g (DOI)
Note

NW, PC and ET acknowledge financial support from Omya International AG

Available from: 2024-01-22 Created: 2024-01-22 Last updated: 2024-06-11Bibliographically approved
Wojas, N., Tyrode, E., Corkery, R., Ernstsson, M., Wallqvist, V., Järn, M., . . . Claesson, P. M. (2023). Calcite Surfaces Modified with Carboxylic Acids (C2 to C18): Layer Organization, Wettability, Stability, and Molecular Structural Properties. Langmuir, 39(42), 14840-14852
Open this publication in new window or tab >>Calcite Surfaces Modified with Carboxylic Acids (C2 to C18): Layer Organization, Wettability, Stability, and Molecular Structural Properties
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2023 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 39, no 42, p. 14840-14852Article in journal (Refereed) Published
Abstract [en]

A fundamental understanding of the interactions between mineral surfaces and amphiphilic surface modification agents is needed for better control over the production and uses of mineral fillers. Here, we controlled the carboxylic acid layer formation conditions on calcite surfaces with high precision via vapor deposition. The properties of the resulting carboxylic acid layers were analyzed using surface-sensitive techniques, such as atomic force microscopy (AFM), contact angle measurements, angle resolved X-ray photoelectron spectroscopy (XPS), and vibrational sum-frequency spectroscopy. A low wettability was achieved with long hydrocarbon chain carboxylic acids such as stearic acid. The stearic acid layer formed by vapor deposition is initially patchy, but with increasing vapor exposure time, the patches grow and condense into a homogeneous layer with a thickness close to that expected for a monolayer as evaluated by AFM and XPS. The build-up process of the layer occurs more rapidly at higher temperatures due to the higher vapor pressure. The stability of the deposited fatty acid layer in the presence of a water droplet increases with the chain length and packing density in the adsorbed layer. Vibrational sum frequency spectroscopy data demonstrate that the stearic acid monolayers on calcite have their alkyl chains in an all-trans conformation and are anisotropically distributed on the plane of the surface, forming epitaxial monolayers. Vibrational spectra also show that the stearic acid molecules interact with the calcite surface through the carboxylic acid headgroup in both its protonated and deprotonated forms. The results presented provide new molecular insights into the properties of adsorbed carboxylic acid layers on calcite.

National Category
Mechanical Engineering
Identifiers
urn:nbn:se:ri:diva-67911 (URN)10.1021/acs.langmuir.3c01252 (DOI)2-s2.0-85175357225 (Scopus ID)
Note

This work was funded by Omya International AG. ET acknowledges support from the Swedish Research Council (VR).

Available from: 2023-11-27 Created: 2023-11-27 Last updated: 2024-02-28Bibliographically approved
Wojas, N., Dobryden, I., Wallqvist, V., Swerin, A., Järn, M., Schoelkopf, J., . . . Claesson, P. M. (2021). Nanoscale Wear and Mechanical Properties of Calcite: Effects of Stearic Acid Modification and Water Vapor. Langmuir, 37(32), 9826-9837
Open this publication in new window or tab >>Nanoscale Wear and Mechanical Properties of Calcite: Effects of Stearic Acid Modification and Water Vapor
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2021 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 37, no 32, p. 9826-9837Article in journal (Refereed) Published
Abstract [en]

Understanding the wear of mineral fillers is crucial for controlling industrial processes, and in the present work, we examine the wear resistance and nanomech. properties of bare calcite and stearic acid-modified calcite surfaces under dry and humid conditions at the nanoscale. Measurements under different loads allow us to probe the situation in the absence and presence of abrasive wear. The sliding motion is in general characterized by irregular stick-slip events that at higher loads lead to abrasion of the brittle calcite surface. Bare calcite is hydrophilic, and under humid conditions, a thin water layer is present on the surface. This water layer does not affect the friction force. However, it slightly decreases the wear depth and strongly influences the distribution of wear particles. In contrast, stearic acid-modified surfaces are hydrophobic. Nevertheless, humidity affects the wear characteristics by decreasing the binding strength of stearic acid at higher humidity. A complete monolayer coverage of calcite by stearic acid results in a significant reduction in wear but only a moderate reduction in friction forces at low humidity and no reduction at 75% relative humidity (RH). Thus, our data suggest that the wear reduction does not result from a lowering of the friction force but rather from an increased ductility of the surface region as offered by the stearic acid layer. An incomplete monolayer of stearic acid on the calcite surface provides no reduction in wear regardless of the RH investigated. Clearly, the wear properties of modified calcite surfaces depend crucially on the packing d. of the surface modifier and also on the air humidity.

Place, publisher, year, edition, pages
American Chemical Society, 2021
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:ri:diva-56145 (URN)10.1021/acs.langmuir.1c01390 (DOI)
Available from: 2021-09-01 Created: 2021-09-01 Last updated: 2023-06-08Bibliographically approved
Wojas, N., Swerin, A., Wallqvist, V., Järn, M., Schoelkopf, J., Gane, P. & Claesson, P. M. (2021). Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization. Langmuir, 37(48), 14135
Open this publication in new window or tab >>Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization
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2021 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 37, no 48, p. 14135-Article in journal (Refereed) Published
Abstract [en]

A profound understanding of the properties of unmodified and saturated fatty acid-modified calcite surfaces is essential for elucidating their resistance and stability in the presence of water droplets. Additional insights can be obtained by also studying the effects of carboxylic acid-saturated aqueous solutions. We elucidate surface wettability, structure, and nanomechanical properties beneath and at the edge of a deposited droplet after its evaporation. When calcite was coated by a highly packed monolayer of stearic acid, a hydrophilic region was found at the three-phase contact line. In atomic force microscopy mapping, this region is characterized by low adhesion and a topographical hillock. The surface that previously was covered by the droplet demonstrated a patchy structure of about 6 nm height, implying stearic acid reorganization into a patchy bilayer-like structure. Our data suggest that during droplet reverse dispensing and droplet evaporation, pinning of the three-phase contact line leads to the transport of dissolved fatty carboxylic acid and possibly calcium bicarbonate Ca(HCO3)2 molecules to the contact line boundary. Compared to the surface of intrinsically hydrophobic materials, such as polystyrene, the changes in contact angle and base diameter during droplet evaporation on stearic acid-modified calcite are strikingly different. This difference is due to stearic acid reorganization on the surface and transport to the water-air interface of the droplet. An effect of the evaporating droplet is also observed on unmodified calcite due to dissolution and recrystallization of the calcite surface in the presence of water. In the case where a water droplet saturated with octanoic acid is used instead of water, the stearic acid-coated calcite remains considerably more stable. Our findings are discussed in terms of the coffee-ring effect. © 2021 The Authors. 

Place, publisher, year, edition, pages
American Chemical Society, 2021
Keywords
Calcite, Contact angle, Drops, Evaporation, Magnetic bubbles, Phase interfaces, Saturated fatty acids, Calcite surface, Droplet evaporation, Effect of water, Octanoic acids, Presence of water, Property, Reorganisation, Surface-modified, Three-phase contact line, Water droplets, Stearic acid
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:ri:diva-57359 (URN)10.1021/acs.langmuir.1c02387 (DOI)2-s2.0-85120076956 (Scopus ID)
Note

Funding text 1: This work was funded by the Omya International AG. A.S. is a researcher at Pro2BE at the Karlstad University, the research environment on Processes and Products for a Circular Biobased Economy.

Available from: 2021-12-22 Created: 2021-12-22 Last updated: 2023-06-08Bibliographically approved
Wojas, N. (2021). The dynamic surface nature of calcite and its role in determining the adsorptive stability toward hydrophobizing carboxylic fatty acids. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>The dynamic surface nature of calcite and its role in determining the adsorptive stability toward hydrophobizing carboxylic fatty acids
2021 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

Calcium carbonate has attracted a lot of interest over the centuries. Nowadays, mainly as mineral pigment and filler, it has a wide use in technological applications ranging from paper, construction, polymers, and environmental solutions to consumer goods. Amongst these uses, the filler pigment is required to display either hydrophilicity (for applications in aqueous colloidal systems, including, for example, in paper and emulsion paints), or, in contrast, oleophilicity (for applications in contact with oil-based systems, such as plastics and volatile solvent-containing sealants).  To achieve oleophilicity, and resulting hydrophobicity, the filler is surface treated, typically using carboxylic fatty acids. In this thesis, effects of humidity and fatty carboxylic acids vapor on CaCO3 surface wettability and nanomechanical properties were studied, with the aim to gain knowledge on layer packing density and order, as well as resistance to water exposure and mechanical wear. A better understanding of the dynamic nature of the calcite surface presented in this work allows the industry to increase sustainable control over materials production and storage. First, a setup combining an atomic force microscope (AFM) with a humidifier was used to map nanomechanical properties of growing surface domains (hydrated form of CaCO3) formed by ion dissolution, diffusion, and redeposition, a process that is not reversible upon drying. Secondly, AFM and contact angle goniometer measurements showed that the stability of the calcite surface improves with increasing carboxylic acid chain length (C2 to C18). Meanwhile, X-ray photoelectron spectroscopy and vibrational sum frequency spectroscopy techniques demonstrated that a coherent layer with maximum packing density of carboxylate and carboxylic acid species was achieved with the use of stearic acid (C18) with high enough vapor pressure and exposure time. The AFM images successfully visualized that a complete C18 monolayer is capable of countering nano-wear of the calcite surface despite the humidity (under the range of loads investigated in this work) and the layer has self-healing properties, while calcite displayed high abrasive wear. Further, when calcite coated by a highly packed monolayer of C18 was covered with a water droplet, a large contact angle hysteresis resulted in a coffee ring effect (CRE). That is leading to formation of hillocks at the contact line consisting of dissolved fatty carboxylic acid and possibly calcium bicarbonate Ca(HCO3)2 molecules transported from the bare calcite region that also is created next to the droplet edge. Interestingly, C18 coated calcite remained considerably more stable in the case where a water droplet saturated with octanoic acid was used instead of water; thus, it was concluded that the CRE can be contained via reduction of the liquid surface tension and contact angle hysteresis.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2021. p. 100
Series
TRITA-CBH-FOU ; 2021:46
Keywords
calcite, recrystallization, surface modification, fatty acids, wear resistance, water resistance, contact angle hysteresis, AFM, XPS, VSFS, Kalcit, rekristallisation, ytmodifiering, fettsyra, nötningsbeständighet, vattenbeständighet, kontaktvinkelhysteres, Physical Chemistry, Fysikalisk kemi, Natural Sciences, Naturvetenskap, Chemical Sciences, Kemi, Tribology (Interacting Surfaces including Friction, Lubrication and Wear), Tribologi (ytteknik omfattande friktion, nötning och smörjning)
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear)
Identifiers
urn:nbn:se:ri:diva-57380 (URN)978-91-8040-066-4 (ISBN)
Public defence
2021-12-09, 13:00 (English)
Opponent
Supervisors
Note

Delarbeten1. Iceland spar calcite: Humidity and time effects on surface properties and their reversibility2. Calcite surfaces modified with carboxylic acids (C2 to C18): layer organization, wettability and stability properties3. Nanoscale Wear and Mechanical Properties of Calcite: Effects of Stearic Acid Modification and Water Vapor4. Surface modified and unmodified calcite: Effects of water and saturated aqueous octanoic acid droplets on stability and saturated fatty acid layer organization

Available from: 2021-12-22 Created: 2021-12-22 Last updated: 2023-12-28Bibliographically approved
Wojas, N., Swerin, A., Wallqvist, V., Järn, M., Schoelkopf, J., Gane, P. & Claesson, P. M. (2019). Iceland spar calcite: Humidity and time effects on surface properties and their reversibility. Journal of Colloid and Interface Science, 541, 42-55
Open this publication in new window or tab >>Iceland spar calcite: Humidity and time effects on surface properties and their reversibility
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2019 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 541, p. 42-55Article in journal (Refereed) Published
Abstract [en]

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.

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, Atomic force microscopy, Calcite, Calcium carbonate, Contact angle, Crystallization, Humidity control, Hydration, Phase interfaces, Surface properties, Wetting, Aging effects, Capillary force, Iceland spars, Nanomechanical property
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-37696 (URN)10.1016/j.jcis.2019.01.047 (DOI)2-s2.0-85060193864 (Scopus ID)
Note

 Funding details: Vetenskapsrådet, VR, 2015-05080; Funding text 1: Omya International AG provided financial funding of this research. Per M. Claesson acknowledges a grant from the Swedish Research Council (VR) [grant number 2015-05080 ].

Available from: 2019-02-01 Created: 2019-02-01 Last updated: 2023-06-08Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6181-1347

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