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Nano-tailoring organo-mineral materials - Controlling strength and healing with organic molecules in mineral interfaces

Periodic Reporting for period 2 - NanoHeal (Nano-tailoring organo-mineral materials -Controlling strength and healing with organic molecules in mineral interfaces)

Reporting period: 2017-01-01 to 2018-12-31

Natural or artificial, cement materials are of key importance to the society. They play a key role in every aspect of our lives, housing, buildings, transport, etc. Therefore, understanding the strength of man made and natural cement material is a problem of great relevance to the European Society, with huge implications to our environment, monuments and buildings.
NanoHeal addresses these scientific, industrial and societal challenges by focusing on the investigation of the strength of cemented aggregate materials like concrete and sedimentary rocks with the following aims:
• to develop innovative probes and models for nanoscale processes that open novel perspectives in design and control of organo-mineral materials.
• to measure and improve the strength and durability of 1) new man-made cemented materials like “green concrete”, speciality cements in construction and oil and gas recovery, and biocompatible implants and 2) natural sedimentary rocks inside reservoirs and as construction materials
• to educate young interdisciplinary researchers at the intersectoral interface between fundamental science and European industry.
The work performed to meet these objectives can be summarised as follows.
Innovative experimental probes for nanoscale processes:
• Surface forces apparatus(SFA) and atomic layer deposition (ALD) have been developed to measure calcite-calcite interactions for the first time ever.
• Atomic force microscopy (AFM) with functionalized tips in combination with X-ray photoelectron spectroscopy (XPS) hav been developed to measure mineral interactions in the presence of organic molecules and detail the contribution from each group.
• High resolution synchrotron X-ray diffraction, high resolution scanning electron microscopy (HRSEM) and scanning transmission electron microscopy with electron dispersive system (STEM-EDS) have been utilized to determine the effects of incorporation of different organic molecules and inorganic substituting molecules on calcite, magnesite and chalk.
• Low amplitude rheometer measurements have allowed characterization of elastic properties of colloidal gel networks in calcite pastes.
• Developed high speed AFM measurement of atomic step dynamics to reveal the controlling dissolution mechanism.
• Developed high force AFM measurements of atomic step dynamics to reveal the influence of stress on calcite growth.
• Developed methods for measuring the surface forces between monolayers of specifically relevant organic molecules in sodium chloride solutions.
• Developed in situ XRD to probe recrystallization during setting of pure CaCO3 cement
• Applied high resolution TEM to study amorphous-crystalline contacts during recrystallization driven fast quartz dissolution in natural magnesium-silica-hydrate (MSH) cements
Innovative models:
• Developed a comprehensive numerical package (open access) for simulating electro-hydrodynamics.
• Developed a predictive model for phase stability in CaCO3. This is an innovative model in that it provides the basis for predicting the crystallite morphology, reaction sites, ionic and electronic transport and therefore insight into the role of organic / inorganic additives and co-adsorbates.
• Developed a discrete element model for brittle fractures in elastic solids, with fast and accurate fracture criteria.
• Coupled a geochemical model to a surface charging methods to predict changes in surface energies for CaCO3 in contact with different brines
• Designed continuum models for growth and dissolution of confined crystals. This is the first new theoretical work on force of crystallization in 60 years.
• Developed molecular dynamics approaches to compute surface interactions between calcium carbonate surfaces.
• Developed a theoretical model to quantify the impact of surface roughness on the interactions and phase behavior of calcium carbonate nanoparticles
• Developed a mesoscopic simulation model (stochastic rotation dynamics) to investigate the phase behavior, assembly, structure and dynamics (viscosity, shear thinning/thickening) of nanoparticle suspensions as a function of particle shape and volume fraction.
New man-made cemented materials:
• A range of different calcium carbonate polymorph cements designed for osteoconductivity, biocompatibility and biodegradability.
• Amorphous calcium carbonate (ACC) and vaterite to form novel calcite cement.
Strength and durability of concrete and natural sedimentary rocks:
• Provided fundamental insight to the transport of reactive fluids at the grain and pore scale in porous minerals.
• Quantified flow channeling and enhanced wettability in multiphase electrolyte systems.
• Related recrystallization during setting of calcium carbonate cements to strengthening mechanism.
• Integrated flow, fracture and wetting models that will be employed to counter weakening due to corrosion of fluids in fractures.
Educate young researchers:
• All 15 ESRs were enrolled in PhD programs at renowned universities
• 12 ESRs will have obtained their PhD degrees by the end of April 2019. The remaining 3 wer
The main results achieved so far that are detailed above are all progress beyond the state of art. We will only mention some highlights of how NanoHeal changed the state of art:
• First new theoretical work on force of crystallization in 60 years!
• First description of magnesium-silica cement formed naturally at Earth’s surface
• First experimental proof of a major prediction of the classical model of elasticity of fractal gels
• First measurements of surface forces in calcite-calcite and calcite-mica systems in the surface forces apparatus.
• First computational study of solvation forces of hydrated calcium carbonate surfaces at nanometer separations.
The high quality training through the NanoHeal school and the research work performed will give the 15 ESRs exceptional skills and will form them as tomorrows research leaders in Europe. The results so far are important steps towards understanding nanoscale processes that open novel perspectives in design and control of organo-mineral materials. When a carbon tax one day is enforced, European cement industry and oil companies will use the knowledge developed by NanoHeal in designing new low carbon cements and to store CO2 in carbonate reservoirs.
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