Agglomerates of wet particles: effect of size distribution

International audienceWe analyze the strength of agglomerates of wet frictional particles subjected to axial compression by means of particle dynamics simulations. The numerical model accounts for the cohesive and viscous effects of the binding liquid up to a debonding distance [1]. We show that wet agglomerates undergo plastic deformation due to the rearrangements of primary particles during compression [2]. The compressive strength is characterized by the plastic threshold before the onset of failure by the irreversible loss of wet contacts between primary particles [3]. The agglomerate plastic threshold is proportional to the characteristic cohesive stress defined from the liquid-vapor surface tension and the mean diameter of primary particles, with a pre-factor that is a nearly linear function of the debonding distance and increases with size span. We analyze the effect of particle size distribution and show that the plastic strength is an increasing function of the size ratio when the size of the particles in the largest size class is increased.References1. F. Radjai, F. Dubois, Discrete-element modeling of granular materials (Wiley-Iste, 2011)2. T-Trung. Vo, P. Mutabaruka, J-Y. Delenne, S. Nezamabadi, F. Radjai, EPJ Web Conf. 140, 08021 (2017)3. T-Trung. Vo, P. Mutabaruka, S. Nezamabadi, J.Y. Delenne, E. Izard, R. Pellenq, F. Radjai, Mechanics Research Communications 92, (2018

Magnetism as indirect tool for carbon content assessment in nickel nanoparticles

International audienceWe report a combined experimental and theoretical study to ascertain carbon solubility in nickel nanoparticles embedded into a carbon matrix via the one-pot method. This original approach is based on the experimental characterization of the magnetic properties of Ni at room temperature and Monte Carlo simulations used to calculate the magnetization as a function of C content in Ni nanoparticles. Other commonly used experimental methods fail to accurately determine the chemical analysis of these types of nanoparticles. Thus, we could assess the C content within Ni nanoparticles and it decreases from 8 to around 4 at. % with increasing temperature during the synthesis. This behavior could be related to the catalytic transformation of dissolved C in the Ni particles into graphite layers surrounding the particles at high temperature. The proposed approach is original and easy to implement experimentally since only magnetization measurements at room temperature are needed. Moreover, it can be extended to other types of magnetic nanoparticles dissolving carbo