Superparamagnetic behaviour of metallic Co nanoparticles according to variable temperature magnetic resonance
Investigating the size distributions of Co nanoparticle ensembles is an important problem, which has no straightforward solution. In this work, we use the combination of 59Co internal field nuclear magnetic resonance (59Co IF NMR) and ferromagnetic resonance (FMR) spectroscopies on a metallic Co nanoparticle sample with a narrow Co nanoparticle size distribution due to encapsulation within the inner channels of carbon nanotubes. High-resolution transmission electron microscopy (TEM) images showed that the nanoparticles can be represented as prolate spheroids, with the majority of particles having an aspect ratio between 1 and 2. This observation has increased the accuracy of superparamagnetic blocking size calculations from Néel relaxation model by introducing the actual volume of the ellipsoids taken from the image processing. 59Co IF NMR and FMR experiments conducted under different temperatures allowed us to observe the thermal blocking of superparamagnetic particles in full accordance with the TEM particle volume distribution. This proved that these magnetic resonance techniques can be used jointly for characterization of Co nanoparticles in the bulk of the sample.
Superparamagnetic behaviour of metallic Co nanoparticles according to variable temperature magnetic resonance, Physical Chemistry Chemical Physics, 2021.
LafargeHolcim and Svante : Preparing for the future carbon economy
LafaregHolcim in the US (LafargeHolcim) and CO2 capture technology firm Svante are developing a full-scale CO2 capture and storage solution at the Holcim Portland plant in Florence, Colorado, US. Global Cement found out more about the project from LafargeHolcim’s Derick Dreyer and Svante’s Claude Letourneau, plus how the parties are preparing for the future carbon economy…
Metal Organic Frameworks (MOF) are a class of chemical compounds characterised by metal centres that are linked by multiple carbon-based molecules known as ligands. Many MOFs have voids large enough to host solvent molecules or small gas molecules. By tuning the length of the ligands, the voids can be made more likely to favour a target molecule, e.g. CO2 rather than other molecules, even if the undesired molecules are more abundant than the target ones.
Preparing for the future carbon economy, Global Cement Magazine, p.20-24, December 2020.
Structure directing role of immobilized polyoxometalates in the synthesis of porphyrinic Zr based Metal Organic Frameworks.
We evidence the structure-directing role of the PW12O403− polyoxometalate in porphyrinic MOF synthesis whereby it promotes the formation of the kinetic topology. Its immobilization into the MOF is successfully achieved at a high temperature yielding the kinetic MOF-525/PCN-224 phases, while prohibiting the formation of the thermodynamic MOF-545 product. A combined experimental/theoretical approach uses differential PDF and DFT calculations along with solid-state NMR to show the structural integrity of the POM and its location next to the Zr-based nodes.
Structure directing role of immobilized polyoxometalates in the synthesis of porphyrinic Zr based Metal Organic Frameworks, Chem. Commun 2020.
Operando decoding of chemical and thermal events in commercial Na(Li)-ion cells via optical sensors
Monitoring the dynamic chemical and thermal state of a cell during operation is crucial to making meaningful advancements in battery technology as safety and reliability cannot be compromised. Here we demonstrate the feasibility of incorporating optical fibre Bragg grating sensors into commercial 18650 cells. By adjusting fibre morphologies, wavelength changes associated with both temperature and pressure are decoupled with high accuracy, which allows tracking of chemical events such as solid electrolyte interphase formation and structural evolution. We also demonstrate how multiple sensors are used to determine the heat generated by the cell without resorting to microcalorimetry. Unlike with conventional isothermal calorimetry, the cell’s heat capacity contribution is readily assessed, allowing for full parametrization of the thermal model. Collectively, these findings offer a scalable solution for screening electrolyte additives, rapidly identifying the best formation processes of commercial cells and designing battery thermal management systems with enhanced safety.
Operando decoding of chemical and thermal events in commercial Na(Li)-ion cells via optical sensors, Nature Energy volume 5, pages 674–683 (2020)
Evolution of the microstructure of unconsolidated geopolymers by thermoporometry
This paper studies the evolution of the pore size distribution of a fresh unconsolidated geopolymer paste between one day and a week, using thermoporometry. This was made possible by following a careful protocol for sample preparation and for analysis by differential scanning calorimetry. In contrast with nitrogen gas adsorption, this method quantifies directly the amount of water in pores. It also does not require heat and vacuum drying, thus maintaining the fragile pore structure of the unconsolidated paste. Moreover, it was found that, in a typical metakaolin‐based sodium geopolymer with a 10 to 20 hours workability period, the porosity gradually refines during the first week while the mesoporous volume is cut in half. This is probably due to the fact that the geopolymer network was still actively condensing from the activation solution. Part of the pore water never froze and, from mass balance, this residual water was attributed to the water bound in the hydration shell of the sodium counter ions. Only a minor occurrence of covalently bound protons as silanol groups was observed. The results presented here usefully complement data obtained by conventional techniques at later ages on consolidated geopolymers. It supports the growing body of literature on the structural evolution of geopolymers with time.
Evolution of the microstructure of unconsolidated geopolymers by thermoporometry, Journal of the American Ceramic Society, 2020.
A Robust Titanium Isophthalate Metal-Organic Framework for Visible-Light Photocatalytic CO2 Methanation
Isophthalic acid (IPA) has been considered to build metal-organic frameworks (MOFs), owing to its facile availability, unique connection angle-mode, and a wide range of functional groups attached. Constructing titanium-IPA frameworks that possess photoresponse properties is an alluring characteristic with respect to the challenge of synthesizing new titanium-based MOFs (Ti-MOFs). Here, we report the first Ti-IPA MOF (MIP-208) that efficiently combines the use of preformed Ti8 oxoclusters and in situ acetylation of the 5-NH2-IPA linker. The mixed solid-solution linkers strategy was successfully applied, resulting in a series of multivariate MIP-208 structures with tunable chemical environments and sizable porosity. MIP-208 shows the best result among the pureMOF catalysts for the photocatalytic methanation of carbon dioxide. To improve the photocatalytic performance, ruthenium oxide nanoparticles were photo-deposited on MIP-208, forming a highly active and selective composite catalyst, MIP-208@RuOx, which features a notable visible-light.
A Robust Titanium Isophthalate Metal-Organic Framework for Visible-Light Photocatalytic CO2 Methanation, Chem Cell Press, 2020.