52 research outputs found
Evaluation of the compositional changes during flooding of reactive fluids using scanning electron microscopy, nano-secondary ion mass spectrometry, x-ray diffraction, and whole-rock geochemistry
No full textOutcrop chalk of late Campanian age (Gulpen Formation) from Liège (Belgium) was flooded with MgCl2 in a triaxial cell for 516 days under reservoir conditions to understand how the nonequilibrium nature of the fluids altered the chalks. The study is motivated by enhanced oil recovery (EOR) processes because dissolution and precipitation change the way in which oils are trapped in chalk reservoirs. Relative to initial composition, the first centimeter of the flooded chalk sample shows an increase in MgO by approximately 100, from a weight percent of 0.33% to 33.03% and a corresponding depletion of CaO by more than 70% from 52.22 to 14.43 wt.%. Except for Sr, other major or trace elements do not show a significant change in concentration. Magnesite was identified as the major newly grown mineral phase. At the same time, porosity was reduced by approximately 20%. The amount of Cl- in the effluent brine remained unchanged, whereas Mg2+ was depleted and Ca2+ enriched. The loss of Ca2+ and gain in Mg2+ are attributed to precipitation of new minerals and leaching the tested core by approximately 20%, respectively. Dramatic mineralogical and geochemical changes are observed with scanning electron microscopyenergy-dispersive x-ray spectroscopy, nano secondary ion mass spectrometry, x-ray diffraction, and whole-rock geochemistry techniques. The understanding of how fluids interact with rocks is important to, for example, EOR, because textural changes in the pore space affect how water will imbibe and expel oil from the rock. The mechanisms of dissolution and mineralization of fine-grained chalk can be described and quantified and, when understood, offer numerous possibilities in the engineering of carbonate reservoirs.Fil: Zimmermann, Udo. University of Stavanger; NoruegaFil: Madland, Merete Vadla. University of Stavanger; NoruegaFil: Nermoen, Anders. University of Stavanger; NoruegaFil: Hildebrand Habel, Tania. University of Stavanger; NoruegaFil: Bertolino, Silvana Raquel Alina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hiorth, Aksel. University of Stavanger; NoruegaFil: Korsnes, Reidar I.. University of Stavanger; NoruegaFil: Audinot, Jean-Nicolas. Luxembourg Institute of Science and Technology; LuxemburgoFil: Grysan, Patrick. Luxembourg Institute of Science and Technology; Luxemburg
Deliberate and accidental gas-phase alkali doping of chalcogenide semiconductors: Cu(In,Ga)Se2
No full textAlkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of gas-phase alkali transport in the kesterite sulfide (Cu2ZnSnS4) system (re)open the way to a novel gas-phase doping strategy. However, the current understanding of gas-phase alkali transport is very limited. This work (i) shows that CIGSe device efficiency can be improved from 2% to 8% by gas-phase sodium incorporation alone, (ii) identifies the most likely routes for gas-phase alkali transport based on mass spectrometric studies, (iii) provides thermochemical computations to rationalize the observations and (iv) critically discusses the subject literature with the aim to better understand the chemical basis of the phenomenon. These results suggest that accidental alkali metal doping occurs all the time, that a controlled vapor pressure of alkali metal could be applied during growth to dope the semiconductor, and that it may have to be accounted for during the currently used solid state doping routes. It is concluded that alkali gas-phase transport occurs through a plurality of routes and cannot be attributed to one single source
Insights into switchable thermoresponsive copolymer layers by atmospheric pressure plasma‐initiated chemical vapour deposition
No full textSelf-healing metallo-supramolecular amphiphilic polymer conetworks
No full textThe current challenge in self-healing materials resides in the design of materials which exhibit improved mechanical properties and self-healing ability. The design of phase-separated nanostructures combining hard and soft phases represents an attractive approach to overcome this limitation. Amphiphilic polymer conetworks are nanostructured materials with robust mechanical properties, which can be tailored by tuning the polymer composition and chemical functionality. This article highlights the design of phase-separated nanostructured polymers from metallo-supramolecular amphiphilic polymer conetworks, and their application for self-healing surfaces. The synthesis of poly(N-(pyridin-4-yl)acrylamide)-l-polydimethylsiloxane polymer conetworks from the poly(pentafluorophenyl acrylate)-l-polydimethylsiloxane activated ester is presented. Loading of ZnCl2 salt into the phase-separated polymer conetwork strengthens the network by cross-linking the poly(N-(pyridin-4-yl)acrylamide) phases, while offering reversible interactions needed for self-healing ability
A film-texture driven piezoelectricity of AlN thin films grown at low temperatures by plasma-enhanced atomic layer deposition
No full textAdvanced mechanical properties of amphiphilic polymer conetworks through hierarchical reinforcement with peptides and cellulose nanocrystals
No full textAmphiphilic polymer conetworks (APCNs) have been explored for various applications, including soft contact lenses, biomaterials, and membranes. They combine important properties of hydrogels and elastomers, including elasticity, transparency, and the capability to swell in water. Moreover, they also swell in organic solvents. However, their mechanical properties could be improved. We developed a two-level, bio-inspired, hierarchical reinforcement of APCNs using cellulose nanocrystals (CNCs) to reinforce peptide-reinforced APCNs formed from hydrophobic poly-β-benzyl-l-aspartate-block-polydimethylsiloxane-block-poly-β-benzyl-l-aspartate (PBLA-b-PDMS-b-PBLA) triblock copolymer crosslinkers and hydrophilic poly(2-hydroxyethyl acrylate) (PHEA) chain segments. Bio-inspired peptide–polymer hybrids combine the structural hierarchy often found in natural materials with synthetic macromolecules, such as block copolymers with soft and hard segments, to enhance their mechanical properties. On the other hand, CNCs provide an additional means to dissipate mechanical energy in polymeric materials, thereby enhancing reinforcement. The key to homogeneously incorporating CNCs into the APCNs is the combination of hydrophobic CNCs (HCNCs) with peptide-blocks in the APCNs, exploiting the hydrogen bonding capability of the peptides to disperse the HCNCs. The effect of HCNCs on the ability of APCNs to swell in water and organic solvents, as well as on their thermal and mechanical properties, was characterized. Additionally, the nanostructure of the materials was analyzed via small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The swellability of the HCNC-containing APCNs was independent of the HCNC concentration, and all samples were highly transparent. The ideal HCNC concentration, in terms of maximal stress, strain, toughness, and reinforcement, was found to be between 6 and 15 wt%. An increase in Young's modulus of up to 500% and toughness of up to 200% was achieved. The hierarchical reinforcement also greatly strengthened the APCNs when swollen in water or n-hexane. Thus, HCNCs and peptide segments can be used to reinforce APCNs and to tailor their properties
Scratch-healing surface-attached coatings from metallo-supramolecular polymer conetworks
No full textpeer reviewe
Periodic nanoparticle cluster arrays with sub-10nm gaps for highly sensitive biomolecular sensing
No full textInternational audienc
Surface analysis of new Microcarriers Tailored for Cell Therapy
No full textSeveral clinical studies have reported the benefit of the administration of Mesenchymal stromal cells (MSC) in various cell therapies. However, these studies have also highlighted that their routine application need urgently new cell substrates to multiply MSC in vitro in GMP conditions. Indeed, MSC are scarce in the human body. It is therefore necessary to amplify MSC in vitro to achieve clinically relevant cell doses. Microcarriers are attractive substrate. However, in practice, MSC cultivation on the microcarriers currently available on the market has been demonstrated unsuccessful.
The main aim of our research relies upon the optimization of the surface properties of microcarriers promoting MSC culture in vitro. To achieve this purpose, the outer surface of microcarriers is functionalized by grafting a thin layer composed of a “smart polymer”, mostly poly N-isopropylacrylamide (pNIPAM), whose composition has been tailored to promote the adhesion and spreading of MSC with the ability to control their fast and efficient detachment following a small change in temperature.
Due to particular shape of microcarriers, specific microscopy technique must be adapted to analyse the efficiency of grafting reaction. At this stage, we have demonstrated some reliable characterization methods based on Time-of-Flight and Nanoscale Secondary Ion Mass Spectrometry (ToF and NanoSIMS), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Fluorescent Microscopy for two type of microcarriers: Dextran and Polystyrene based carriersoptimisation de surface des microporteurs destinés à l'ingénierie tissulair
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