Importance of TEM sample thickness for measuring strain fields.

Transmission electron microscopy (TEM) has emerged as a valuable tool for assessing and mapping strain fields within materials. By directly analyzing local atomic spacing variations, TEM enables the precise measurement of local strain with high spatial resolution. However, it is standard practice to use thin specimens in TEM analysis to ensure electron transparency and minimize issues such as projection artifacts and contributions from multiple scattering.

Direct Observation of Quadrupolar Strain Fields forming a Shear Band in Metallic Glasses.

For decades, scanning/transmission electron microscopy (S/TEM) techniques have been employed to analyze shear bands in metallic glasses and understand their formation in order to improve the mechanical properties of metallic glasses. However, due to a lack of direct information in reciprocal space, conventional S/TEM cannot characterize the local strain and atomic structure of amorphous materials, which are key to describe the deformation of glasses. For this work, 4-dimensional-STEM (4D-STEM) is applied to map and directly correlate the local strain and the atomic structure at the nanometer scale in deformed metallic glasses.

Light-Controlled Lyotropic Liquid Crystallinity of Polyaspartates Exploited as Photo-Switchable Alignment Medium.

Two polyaspartates bearing -fluorinated azobenzenes (FAB) as photo-responsive groups in the side chain were synthesized: PFABLA () and co-polyaspartate PpFABLA--PBLA [, 75%(n/n) PFABLA content]. As a consequence of the /-isomerization of the side chain, PFABLA () undergoes a visible-light-induced reversible coil-helix transition in solution: Green light (525 nm) affords the coil, and violet light (400 nm) affords the helix. FAB significantly increases the thermal stability of the -isomer at 20 °C ( = 66 d for the -isomer) and effectively counters the favored back formation of the helix.