Предпороговые эффекты при воздействии ультрафиолетовых лазерных импульсов на медь и ее сплавы

The prethreshold processes on the surface of copper and its alloys are investigated. In the absence of obvious traces of melting, while preserving the metal in a condensed state, under a nanosecond ultraviolet laser radiation energy density of 0.1–1.0 J/cm2, manifestations of high-temperature plastic deformation were observed. These are sliding and cracking along grain boundaries, within which crystallographic slipping was observed. A microprotrusion was formed on the surface of the irradiated zone, which was outwardly similar the distribution of laser radiation in the spot. The height of the microprotrusion reached 1 µm, and sometimes even more. An increase in the number of impacting impulses led to the accumulation of damage. The data obtained are in many ways similar to the acoustoplastic, electroplastic, and magnetoplastic effects. By analogy, we consider it possible to call the discovered effect optoplastic.

On the relationship between fundamental science and contemporary applied research in the field of high-rate laser Nanowhiskerography

In practice, in various areas of life, there is often a need to use materials that have mutually exclusive requirements. Therefore, the study of the issues related to manufacturing materials in certain states for certain technical applications, and methods of controlling structurally sensitive properties to obtain specified effects, is quite relevant today. A new effect was discovered, namely, the rapid growth of amorphous and composite materials in the form of “coherent” nanowhiskers using laser-induced plasma at temperatures exceeding 4,000oC and high pressures up to 100 thousand atmospheres at a rate reaching 80-100 m/s. This method of growing whiskers is based on fundamental studies of pulsed laser radiation and predictions of Nobel Prize laureates – Ch.H. Townes, A.M. Prokhorov (splitting of a laser beam of above-threshold power) and G.A. Askaryan (effects of self-focusing of light in the condensed state of matter, and sublimation evaporation). The authors show possible practical applications of this method, such as protection of securities, banknotes, and plastic cards, as well as production of a new type of silicon batteries, automotive catalysts, and solar silicon batteries.

Self-assembly of hydrophobic-amphiphilic diblock copolymers in solution

Thermoresponsive polymers are usually characterized by a locally amphiphilic chain structure and their self-assembly in solution is controlled, in particular, by the surface activity of the monomer units or side chains. We theoretically study the condensed state of a single diblock copolymer molecule consisting of a hydrophobic block and amphiphilic block with hydrophobic groups in the backbone and pendant polar groups. The equilibrium parameters of the polymer globules of different shapes are determined using the mean-field approach to determine the most favorable structure. Morphological diagrams of condensed macromolecules are presented depending on the chain length, amphiphilic block fraction, interaction parameters, and pendant volume and length. The diagrams are compared with those of a copolymer molecule with the same fraction of amphiphilic monomer units which are regularly distributed along the chain. The diblock copolymer molecule is found to form a single spherical or flattened particle, with the core from the hydrophobic block, or a granular micelle consisting of spherical or nearly spherical particles, in agreement with the experimental data in the literature. The optimal chain parameters for self-assembly into a stable single core-shell particle are predicted.

The Future of Scandium Recovery from Wastes

With growing demand for renewable and clean energy technologies, the need in rare earth metals is increasing. Scandium, which is often considered a rare earth element (REE), is a critical metal mainly used in solid oxide fuel cells (SOFCs) and high strength aluminum alloys used in aerospace and 3D printing applications. Furthermore, scandium supply is limited due to its scarcity and the high cost of its production in Asia and Russia while Europe has no production of scandium. Therefore, scandium extraction from alternative resources such as secondary resources located in Europe is of great concern. Within this context, this work provides a condensed state-of-art review of the issue of scandium recovery from industrial wastes. Priority was given to addressing the technological and economic challenges associated with the recovery of scandium from the said residues, with particular emphasis on the bauxite residue from alumina production, which represents nearly 5 million tons on dry basis per year in Europe.

Microprocesses at the brass surface after impact of scanning beam of pulse-frequency ultraviolet nanosecond laser

A mode of laser heat treatment of the brass surface prior to conducting of diffusion bonding is proposed. We used the frequency-pulse radiation of a nanosecond ultraviolet laser at a pulse energy density W = 0.15 - 0.52 J/cm2. The metal sample was moved relative to a stationary laser beam along a raster trajectory (“snake”) so that adjacent spots were overlapped with an overlap ratio of ⩾ 99 %. The impact of radiation on brass was carried out in a subthreshold mode excluding crater formation. The process took place while the metal remained in a condensed state. A regular rough structure with a height of individual uplifts of the order of 1 micron was formed on the surface of the brass. article is devoted to creation of aerosolized detergent compositions, needful for use during operation of high-precision metal mirrors, as a rule, in field conditions. The created detergent compositions with inhibitory properties allow, simultaneously with carrying out the process of physicochemical cleaning of optical surface from technological impurities, to ensure its protection from the influence of adverse climatic factors during storage, transportation, installation and exploitation of the element with the possibility of its alignment. The high climatic resilience of the protective films investigated in this article, which are formed during the cleaning of the optical surface, is shown. In this case, the optical characteristics of the processed elements after climatic tests do not get worse.

The Magneto-Dimensional Transformation Properties of the Ultradispersed Metallic Media as a Mechanism for Managing the Macrodynamic Features of Crystallizing Thermoplastic Nanocomposites

The work considers the main elements of the magneto-dimensional transformation properties in the ultradispersed metallic media (UDM) as a nanomodifier in the process of the formation of nanocompositional polymeric materials (NCPM) based on polyolefins () from a melt. It has been shown that UDM nanoparticles in a melt under the influence and interaction with a thermoplastic matrix are capable of transforming their magnetic properties (to the level of superparamagnetic), structural-dimensional parameters, and chemical potential. With this mutual influence, the nanomodifier has an active effect on the thermoplastic melt at all stages of the formation of the structure-property relationship: structureless ensembles of macromolecules → formation of clusters (domains), lamellas, crystallites → formation of a network of intermolecular entanglements → crystallization of the thermoplastic matrix → transition to a condensed state. An important component of the formation of a fine-crystalline anisotropic NCPM structure is the intramatrix orientation of the structural elements of the thermoplastic in the melt under the influence of the magneto-dimensional transformable manifestations of the nanomodifier. A consequence of the formation of a fine-crystalline anisotropic structure of the NCPM is an increased level of a complex of physicochemical properties (such as deformation-strength, rheological, etc.). An assumption is made about the possibility of the formation of coherent wave packets from clusters (domains) and lamellas of crystallites of matrix thermoplastic with a minimum three-dimensional geometry under the action of superparamagnetic forces of nanoparticles of the nanomodifier.

Evaluating polymer interplay after hot water pretreatment to investigate maize stem internode recalcitrance

Background Biomass recalcitrance is governed by various molecular and structural factors but the interplay between these multiscale factors remains unclear. In this study, hot water pretreatment (HWP) was applied to maize stem internodes to highlight the impact of the ultrastructure of the polymers and their interactions on the accessibility and recalcitrance of the lignocellulosic biomass. The impact of HWP was analysed at different scales, from the polymer ultrastructure or water mobility to the cell wall organisation by combining complementary compositional, spectral and NMR analyses. Results HWP increased the kinetics and yield of saccharification. Chemical characterisation showed that HWP altered cell wall composition with a loss of hemicelluloses (up to 45% in the 40-min HWP) and of ferulic acid cross-linking associated with lignin enrichment. The lignin structure was also altered (up to 35% reduction in β–O–4 bonds), associated with slight depolymerisation/repolymerisation depending on the length of treatment. The increase in $${T}_{1\rho }^{H}$$ T 1 ρ H , $${T}_{HH}$$ T HH and specific surface area (SSA) showed that the cellulose environment was looser after pretreatment. These changes were linked to the increased accessibility of more constrained water to the cellulose in the 5–15 nm pore size range. Conclusion The loss of hemicelluloses and changes in polymer structural features caused by HWP led to reorganisation of the lignocellulose matrix. These modifications increased the SSA and redistributed the water thereby increasing the accessibility of cellulases and enhancing hydrolysis. Interestingly, lignin content did not have a negative impact on enzymatic hydrolysis but a higher lignin condensed state appeared to promote saccharification. The environment and organisation of lignin is thus more important than its concentration in explaining cellulose accessibility. Elucidating the interactions between polymers is the key to understanding LB recalcitrance and to identifying the best severity conditions to optimise HWP in sustainable biorefineries.