solar selective absorber based cermets of type double nitride material and its manufacturing method

摘要

A thin-film spectrally selective coating for receiver tube of vacuumed type for use in thermodynamic solar installations and operating both at medium temperature (up to 400° C.) and at high temperature (up to 550° C.), coating where the optically absorbing layer is a multilayer of cermet material of type: WyN—AlNx or MoyN—AlNx, material prepared with reactive co-sputtering technique from an Al target and a W or Mo target, process conducted under a transition regimen, under PFM (Plasma Emission Monitoring) or CVM (Cathode Voltage Monitoring) monitoring for the sole Al target, with inletting near the Al target of a N2 amount adequate for obtainment of a high-transparency, high growth rate sub-stoichiometric ceramic AlN and with inletting near the W or Mo target of a N2 amount adequate for obtainment of the sole W2N or Mo2N phase, phase very stable at high temperature, such as to make the cermet material as close as possible to the formulation W2N—AlNx or Mo2N—AlNx (with x comprised between 0.90 and 1.00, preferably 0.95) and, therefore, cermet material employable at least up to the temperature of 550° C.