Correlation of radius of cathode spot of vacuum arc of metals on the size of generated droplets

The simple relation to estimate the cathode spot radius of a vacuum arc of pure metals is obtained. On its basis, is established between the cathode spot radius and the size of droplets generated by the cathode spot a correlation. This enables to find ways to reduce droplets in the plasma flow, which forms coatings by the vacuum electric arc method. The paper presents the results of experimental study of the droplet sizes depending on the vacuum arc current iд. The size and amount of the droplets on an area of 1 mm2 of the coating surface are determined using the ImageSP program. As the initial data, the microstructures of the coatings are used with an increase of: ç100, ç200, ç500, ç1000, ç1500. The droplets have been generated by a cathode spot of a vacuum arc for the alloy of the composition, at.%: 68Al–8Cr–4Nb–20Si. It is established that the number of droplets with a diameter of < 2 μm is generated most of all, and the number of droplets with a diameter > 10 μm is generated least of all. The number of generated droplets with a diameter from 2 to 10 μm slightly depends on the arc current iд. It is noted that the diameter of the alloy droplet is smaller than the diameter of the droplets generated by the cathode spot on its components due to the fact that the radius of the cathode spot on the alloy is smaller than the radius of the cathode spot on its pure components.

Increasing the wear and corrosion resistance of steel parts by methods of complex boronikeling and borovolframing

The paper presents ways to increase the wear and corrosion resistance of steel parts by chemical and thermal treatment methods. Comprehensive studies of the structure and properties of St3 steel samples were carried out after simultaneous complex saturation with boron and nickel, boron and tungsten from saturating coatings based on boron carbide. Both compounds of these elements (oxides, carbides, borides) and pure metals were used as suppliers of nickel and tungsten. Studies have shown that multicomponent saturation processes make it possible to form a multiphase structure of a surface layer with a complex of useful properties. Moreover, by chemical-thermal treatment it is possible to obtain such a combination of properties of the hardened product, which cannot be obtained by other methods.

Analysis of processing variables in Equiangular Channel Press deformations

Equiangular Channel Pressing (ECAP) is by far the most promising technique, by the severe plastic deformation (SPD) method, being able to produce large volumes of materials sufficient for practical applications. The ECAP process can be repeated until refining saturation is reached, leading to large amounts of shear strain. The reason behind the exceptional properties obtained in materials processed by ECAP was attributed to the microstructure of the material obtained in this deformation process. This work investigated the ECAP strain variables in the literature in order to analyze the effect of each of these on the microstructure of processed materials. The articles were collected from the following databases: ScienceDirect and the Scientific Electronic Library Online (SciELO) electronic library, as they include national and international literature. Based on the results found, it could be seen that several parameters must be analyzed to deform pure metals and alloys, to refine the microstructure, such as bending angle and channel angle of the strain matrix, number of passes, and pressing temperature. It was possible to verify that changes in these variables configure changes in the microstructure.

Reflections on the Spatial Performance of Atom Probe Tomography in the Analysis of Atomic Neighborhoods

Atom probe tomography (APT) is often introduced as providing “atomic-scale” mapping of the composition of materials and as such is often exploited to analyze atomic neighborhoods within a material. Yet quantifying the actual spatial performance of the technique in a general case remains challenging, as it depends on the material system being investigated as well as on the specimen's geometry. Here, by using comparisons with field-ion microscopy experiments, field-ion imaging and field evaporation simulations, we provide the basis for a critical reflection on the spatial performance of APT in the analysis of pure metals, low alloyed systems and concentrated solid solutions (i.e., akin to high-entropy alloys). The spatial resolution imposes strong limitations on the possible interpretation of measured atomic neighborhoods, and directional neighborhood analyses restricted to the depth are expected to be more robust. We hope this work gets the community to reflect on its practices, in the same way, it got us to reflect on our work.

Rationally Tailoring Catalysts for the CO Oxidation Reaction by Using DFT Calculations

Rational design of catalysts by tailoring specific surface sites with different elements could result in catalysts with high activity, selectivity and stability. In this work, we show that *CO on-top and O* on-top adsorption energies are good descriptors for catalysis of the CO oxidation reaction (COOR) on pure metals and binary alloys. The observed Brønsted-Evans-Polanyi (BEP) and scaling relations for COOR on different surfaces are incorporated into a predictive model that uses the binding strength of the four adjacent metal atoms making up the active site for COOR catalysis to estimate reaction and activation energies. The model is used to screen 161 multi-metallic catalyst candidates made by combining Ru, Pt, Pd, Cu and Au at these four sites. The screening and subsequent calculations suggest that Ru-Pt-Cu alloys are good catalysts for COOR. Our study shows that it is possible to use information from pure metals and binary alloys to predict the catalytic behavior of more complex alloys, and hereby reduce the computational cost of identifying new catalyst candidates for COOR.

Urine miRNAs as potential biomarkers for systemic reactions induced by exposure to embedded metal

Aim: Explore the potential of urine microRNAs as biomarkers that may reflect the biological responses to pure metals embedded in skeletal muscle over time. Materials & methods: We tested a panel of military-relevant metals embedded in the gastrocnemius muscles of 3-month-old, male, Sprague–Dawley rats (n = 8/group) for a duration of 1, 3, 6 and 12 months, and performed small RNA-sequencing on the urine samples. Results: Results provide potential tissue targets affected by metal exposure and a list of unique or common urine microRNA biomarkers indicative of exposure to various metals, highlighting a complex systemic response. Conclusion: We have identified a panel of miRNAs as potential urine biomarkers to reflect the complex systemic response to embedded metal exposure.