Production, Structure and Properties of Coatings Based on Al2O3 Obtained by Magnetron Method

Abstract

Al2O3 and Al2O3/ZrO2 multilayer coatings were deposited by the magnetron method by sputtering the corresponding metal targets in a mixture of oxygen and argon gases. The microstructure of the cross sections to determine the thickness and elemental composition of the obtained coatings was studied by transmission and scanning electron microscopy. The surface morphology of Al2O3 coating samples was studied by scanning probe microscopy. It is shown that the formed Al2O3 coating and the Al2O3/ZrO2 multilayer coating have a columnar structure with the columns oriented perpendicular to the surface. The columnar structure of multilayer coatings is not violated during the transition from layer to layer. The coating surface consists of globules with a diameter of about 20 nm. It was found that the Al2O3 coating has dielectric properties using the method of impedance spectrometry. Thus, it was shown that the magnetron method can be used to apply high-quality multilayer dielectric coatings, which can be used as thermal barrier coatings to protect the blades of high-temperature stages of aircraft engine turbines.

Three-stage Kinetic Model for Self-decaying of Defects in Brittle Solids

“…Therefore, in order to maintain the defect concentration at a no damage level avoiding brittle failure of the solid, there should be a particular mechanism that balances the process of thermal activation of defects with their spontaneous self-decaying by matching a difference between numbers of stationary appearing and disappearing defects at the subthreshold level. Moreover, in this case, the defects will be associated with the stochastically fluctuating thermally-excited states of a nonequilibrium quantum system weakly coupled with its equilibrium environment [5,6]. Remarkably, the kinetic equation for populations of defect states, found as a result of stochastic averaging of the microscopic Liouville-von Neumann evolution equation for the density matrix of the whole system "system + environment + weak interaction" over fast fluctuations in the states energies, being generally nonlinear and containing also states coherences, can nevertheless be reduced to a linear equation of the population balance only [4].…”

“…Moreover, the microscopic nature of these defects can be very different, from the disordered pattern of molecular bonds in the lattice (like loose atoms or dangling bonds) having mainly two alternative positions in space (the two-state defect) separated by a particular potential barrier, to the extended structural configurations of compact disordered regions encompassing hundreds of molecular units and forming the multi-state defects. Analogously, the structure and properties of Al2O3 associated with the deformation of the lattice in the vicinity of the vacancy can be described within the framework described in [5].…”