Ultraviolet Nanosecond Laser Treatment to Reduce the Friction Coefficient of Silicon Carbide Ceramics

The determination of the possibility for the reduction of the friction coefficient of ceramic parts from silicon carbide by pulse-periodic treatment with an ultraviolet nanosecond laser was carried out in the framework of this research. The gas-dynamic seal of the compressor rotor of the gas-turbine engine after hot isostatic pressing and mechanical treatment was exposed to surface microstructuring in a pulse-periodic mode. For experimental investigations, a laser with a maximum energy of the pulse of 50 J, a wavelength of 355 nm, and a pulse duration below 10 ns was used. It was determined that the surface quality was improved, and the surface roughness was reduced as a consequence of the realized laser polishing modes in the beam exposure area. The average value of the friction coefficient of the ceramic material surface decreased by 15% as result of pulse-periodic laser processing.

Resonant ultrasound spectroscopy of silicon carbide ceramics SiC‒AlN

The paper discusses the possibility of using resonant ultrasonic spectroscopy (RUS) as a source of information for the physics and technology of obtaining silicon carbide ceramics by the example of samples of the composition SiC ‒ 25 % AlN, obtained by the method of spark plasma sintering. The possibility of obtaining a complete set of elastic moduli (EM) of samples with an error of less than 1 % is shown. At the same time, the requirements for surface quality are significantly reduced. The revealed functional relationship between EM and porosity makes it possible to create a non-destructive method of porosity control and calculate the elastic moduli at zero porosity (i. e., the elastic modulus of the ceramic matrix EM0). Comparison of EM0 samples obtained at different parameters of the technological process allows determining their optima values..

High-Performance SiC–Based Solar Receivers for CSP: Component Manufacturing and Joining

Concentrated solar power (CSP) is an important option as a competitive, secure, and sustainable energy system. At the moment, cost-effective solutions are required for a wider-scale deployment of the CSP technology: in particular, the industrial exploitation of CSP has been so far hindered by limitations in the materials used for the central receiver—a key component in the system. In this context, the H2020 NEXTOWER project is focused on next-generation CSP technologies, particularly on advanced materials for high temperatures (e.g., >900 °C) and extreme applications environments (e.g., corrosive). The research activity described in this paper is focused on two industrial solutions for new SiC ceramic receivers for high thermal gradient continued operations: porous SiC and silicon-infiltrated silicon carbide ceramics (SiSiC). The new receivers should be mechanically tough and highly thermally conductive. This paper presents the activity related to the manufacturing of these components, their joining, and characterization.