Photoluminescence-Based Techniques for the Detection of Micro- and Nanoplastics

The growing numbers related to plastic pollution are impressive, with ca. 70 % of produced plastic (>350 tonnes/year) being indiscriminately wasted in the environment. The most dangerous forms of plastic pollution for biota and human health are micro- and nano-plastics (MNPs), which are ubiquitous and more bioavailable. Their elimination is extremely difficult, but the first challenge is their detection since existing protocols are unsatisfactory for microplastics and mostly absent for nanoplastics. After a discussion of the state of the art for MNPs detection, we specifically revise the techniques based on photoluminescence that represent very promising solutions for this problem. In this context, Nile Red staining is the most used strategy and we show here its pros and limitations, but we also discuss other more recent approaches, such as the use of fluorogenic probes based on perylene-bisimide and on fluorogenic hyaluronan nanogels, with the added values of biocompatibility and water solubility

Tangential continuity of elastic/plastic curvature and strain at interfaces

The continuity vs discontinuity of the elastic/plastic curvature & curvature rate, and strain & strain rate tensors is examined at non-moving surfaces of discontinuity, in the context of a field theory of crystal defects (dislocations and disclinations). Tangential continuity of these tensors derives from the conservation of the Burgers and Frank vectors over patches bridging the interface, in the limit where such patches contract onto the interface. However, normal discontinuity of these tensors remains allowed, and Kirchhoff-like compatibility conditions on their normal discontinuities across the concurring interfaces are derived at multiple junctions. In a simple plane case and in the absence of surface-disclinations, the compatibility of the normal discontinuities in the elastic curvatures assumes the form of a Young's law between the grain-to-grain disorientations and the sines of the dihedral angles. Complete continuity of the plastic strain rate tensor at triple junctions also derives from the compatibility of the normal discontinuities in the plastic strain rates in such conditions

A Theory of Disclination and Dislocation Fields for Grain Boundary Plasticity

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A statistical analysis of the influence of microstructure and twin-twin junctions on twin nucleation and twin growth in Zr

International audienceThe purpose of the present work is (1) to study the statistical relevance of twin-twin junctions and (2) to study statistically the influence of twin-twin junctions and microstructure on nucleation and growth of twins in h.c.p. materials. A new automated twin recognition technique has been developed and is used to extract statistics from EBSD scans of high purity clock-rolled zirconium specimens loaded along the through-thickness and one of the in-plane directions. The technique allows for recognition of tensile and compressive twin systems within each individual grain. The ten possible twin-twin junction types that may occur in Zr between first generation twins are introduced as well as their associated frequencies in cases of through-thickness and in-plane compression. The present study shows that twin-twin junctions between twins belonging to the most active twinning modes are statistically relevant. It is also shown that twin-twin junctions hinder twin growth. In agreement with previous studies, it is found that irrespective of the loading direction and twin mode, both grain size and crystallographic orientation largely influence the propensity of grains for twin activation. However, the study suggests large differences in nucleation and growth mechanisms for each twinning mode