The 2017 Plasma Roadmap: Low temperature plasma science and technology

Journal of Physics D: Applied Physics published the first Plasma Roadmap in 2012 consisting of the individual perspectives of 16 leading experts in the various sub-fields of low temperature plasma science and technology. The 2017 Plasma Roadmap is the first update of a planned series of periodic updates of the Plasma Roadmap. The continuously growing interdisciplinary nature of the low temperature plasma field and its equally broad range of applications are making it increasingly difficult to identify major challenges that encompass all of the many sub-fields and applications. This intellectual diversity is ultimately a strength of the field. The current state of the art for the 19 sub-fields addressed in this roadmap demonstrates the enviable track record of the low temperature plasma field in the development of plasmas as an enabling technology for a vast range of technologies that underpin our modern society. At the same time, the many important scientific and technological challenges shared in this roadmap show that the path forward is not only scientifically rich but has the potential to make wide and far reaching contributions to many societal challenges.I Adamovich et al 2017 J. Phys. D: Appl. Phys. 50 32300

An overview of using small punch testing for mechanical characterization of MCrAlY bond coats

Considerable work has been carried out on overlay bond coats in the past several decades because of its excellent oxidation resistance and good adhesion between the top coat and superalloy substrate in the thermal barrier coating systems. Previous studies mainly focus on oxidation and diffusion behavior of these coatings. However, the mechanical behavior and the dominant fracture and deformation mechanisms of the overlay bond coats at different temperatures are still under investigation. Direct comparison between individual studies has not yet been achieved due to the fragmentary data on deposition processes, microstructure and, more apparently, the difficulty in accurately measuring the mechanical properties of thin coatings. One of the miniaturized specimen testing methods, small punch testing, appears to have the potential to provide such mechanical property measurements for thin coatings. The purpose of this paper is to give an overview of using small punch testing to evaluate material properties and to summarize the available mechanical properties that include the ductile-to-brittle transition and creep of MCrAlY bond coat alloys, in an attempt to understand the mechanical behavior of MCrAlY coatings over a broad temperature range

Time-dependent gas dynamics and gas-particle heat and mass transfer during plasma spray deposition

This paper describes a time-dependent and 3-D computer model of the atmosphere pressure plasma spray process. The model uses a two-step procedure. The first deals with the formation of the primary plasma jet inside the plasma torch and solves simultaneously the time-dependent NavierStokes\ud equations, conservation equation of electric current and electromagnetism equations assuming that the electromagnetism phenomena are quasi-steady. The second involves the discharge of the plasma jet in air and the heating and acceleration of the powder particles. It is\ud based on the momentum and thermal energy equations for a three components (plasma forming gas, powder carrier gas and air) gas mixture, continuity equations for each component of the mixture and state relation. The particle model uses a stochastic and time-dependent injection description with a distribution of particle size, injection velocity and injection direction in three dimensions. Once the particles exit the injector; their acceleration, heating and vaporization are calculated with a Lagrangian scheme. Their trajectory and velocity are determined from a balance of the gravity, Archimedean, pressure gradient and drag forces. Particles are subjected to turbulent dispersion with the assumption that the turbulent eddies have random lifetimes. The temperature evolution of\ud particles along their trajectory is calculated from a heat flux balance in the boundary layer surrounding the particles. Such a model provides physical insight on phenomena that cannot be easily measured directly as the flow fields inside the plasma torch and the time-variation of the flow characteristics and particle behaviour