Hybrid multilayer solar selective coating for high temperature solar thermal applications and a process for the preparation thereof

The present invention describes a hybrid multilayer solar selective coating having high thermal stability useful for high temperature solar thermal power generation. The hybrid multilayer solar selective coating of the present invention has been deposited using a novel combination of sputtering and sol-gel methods on metallic and non-metallic substrates, preferably on SS 304 and 321 with chrome interlayer. The hybrid multilayer solar selective coating of the present invention consists of stacks of Ti/chrome interlayer, aluminum titanium nitride (AlTiN), aluminum titanium oxynitride (AlTiON), aluminum titanium oxide (AlTiO) and organically modified silica (ormosil) layers. The chrome interlayer was deposited using an electroplating method, whereas, Ti, AlTiN, AlTiON and AlTiO layers were prepared using a four-cathode reactive unbalanced pulsed direct current magnetron sputtering technique. The ormosil layer was deposited using a sol-gel technique, which provides the enhanced absorptance and improved long term thermal stability in air and vacuum. The present invention provides a hybrid multilayer solar selective coating having absorptance >0.950, emittance