Untangling competition between epitaxial strain and growth stress through examination of variations in local oxidation

Understanding oxide formation during corrosion of high-performance alloys in harsh environments is of great fundamental and industrial interest and provides a potential route for reducing the significant annual cost of corrosion globally. However, corrosion mechanisms involve multiple length scales, requiring a multitude of advanced experimental procedures. Here, we use correlated high resolution electron microscopy techniques over a range of length scales, combined with crystallographic modelling to show that there is a clear competition between epitaxial strain and growth stress during oxidation. The degree to which these competing mechanisms operate is shown to depend on the orientation of the substrate grains leading to significant local variations in oxide microstructure and thus protectiveness, even across a single sample. This leads to the possibility of tailoring substrate crystallographic textures in order to promote gradual phase transformation and the development of stress driven, well-oriented protective oxides, and so to improving overall corrosion performance.

In Situ Local Oxidation of SnO Induced by Laser Irradiation: A Stability Study

In this work, semiconductor tin oxide (II) (SnO) nanoparticles and plates were synthesized at room conditions via a hydrolysis procedure. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the high crystallinity of the as-synthesized romarchite SnO nanoparticles with dimensions ranging from 5 to 16 nm. The stability of the initial SnO and the controlled oxidation to SnO2 was studied based on either thermal treatments or controlled laser irradiation using a UV and a red laser in a confocal microscope. Thermal treatments induced the oxidation from SnO to SnO2 without formation of intermediate SnOx, as confirmed by thermodiffraction measurements, while by using UV or red laser irradiation the transition from SnO to SnO2 was controlled, assisted by formation of intermediate Sn3O4, as confirmed by Raman spectroscopy. Photoluminescence and Raman spectroscopy as a function of the laser excitation source, the laser power density, and the irradiation duration were analyzed in order to gain insights in the formation of SnO2 from SnO. Finally, a tailored spatial SnO/SnO2 micropatterning was achieved by controlled laser irradiation with potential applicability in optoelectronics and sensing devices.

Destruction of microplastics in the natural environment

<p>Morphological structure and chemical composition of environmental microplastics (MPs) extracted from water and bottom sediments of Lake Onego were studied. Raman spectroscopy was used to identify MPs polymer types and scanning electron microscopy with energy dispersive microanalysis was used to study the morphology and trace elements composition of inclusions on their surface. The features of the destruction of MPs, as well as the presence of various chemical elements on their surface including heavy metals, were investigated. Four main mechanisms of MPs microdestruction have been identified: (1) Local destruction of monophasic MPs caused by local oxidation and cleavage of thin flakes and fragments with the formation of nanoscale plastics. (2) The destruction of multiphase microplastics predominantly determined by the selective destruction of one of the phases of the composite, for example, the ligament scission between the individual components of the plastic with their separation. (3) Microbiological destruction of MPs under the influence of diatoms by fixing spores of diatoms on defects of MPs with their subsequent growth, deflection, and separation of nanoscale polymer particles. (4) Mineralogical destruction of MPs associated with the sorption of chemical elements and crystallization of nanocrystals, which under appropriate conditions begin to grow and break-up the MPs accelerating the process of its destruction. The last mechanism have not yet been reported. These mechanisms initiate nanoplastics formation, which increases particles mobility in the aquatic environment and their threat to water organisms. At the same time, the fouling with diatoms (with a silica shell) and the sorption of heavy elements increase the bulk specific density of MPs and contribute to its accumulation in bottom sediments.</p><p>The study was supported by the Russian Science Foundation grant number 19-17-00035.</p>

Thermodynamic insights into Henry's constant in hyperthermal oxidation of silicon for fabricating optical waveguides

Hyperthermal oxidation of silicon is envisaged to be an alternative to silicon-on-insulator (SOI) waveguide fabrication for photonic integrated circuit (PIC) devices, and thus the local oxidation of silicon (LOCOS) technique has attracted attention.

Influence of impurity and alloying elements on high temperature oxidation resistance of E110 type zirconium alloys

The structural-phase state has been investigated and content of oxygen and hydrogen in the E110 type alloy after high-temperature oxidation simulating an accident of the LOCA type has been determined. Tubular samples with a diameter of 9.13 mm and a wall thickness of 0.7 mm from the Zr—1% Nb alloy obtained on the electrolytic zirconium basis (E110), the zirconium sponge basis (E110G), and from a modified alloy Zr—1% Nb—0.12% Fe—0.13% O (E110M) were selected for the study. The samples were subjected to a steam oxidation at a temperature of 1100 °C to 18% local oxidation depth. It was found that the E110G alloy based on a zirconium sponge absorbed oxygen and hydrogen less under LOCA conditions.