The addition of so-called “reactive” elements such as yttrium to alloys is known to enhance the protective nature of Cr2O3 or Al2O3 scales. However, the mechanism by which this enhancement is achieved remains unclear. An A.E.M. study has been performed of scales grown at 1000°C for 25 hr. in pure O2 on Co-45%Cr implanted at 70 keV with 2x1016 atoms/cm2 of yttrium. In the unoxidized alloys it was calculated that the maximum concentration of Y was 13.9 wt% at a depth of about 17 nm. SIMS results showed that in the scale the yttrium remained near the outer surface.
The article considers the valve converter with a natural current characteristic, which is called the current of parametric, for which the primary is not the source of the electric force but a parametric source of current, to the output of which connected to the counter-parallel thyristor sets assembled on the bridge scheme. The control of thyristors in the current converter is carried out taking into account the characteristic features of the parametric source, to avoid overvoltage on its reactive elements, analyzed algorithmic and modulating functions of the system borne temporary diagrams.
Reconfigurable optical-microwave filter banks using thermo-optically tuned Bragg Mach-Zehnder devices