ADVANCEMENT OF SOLAR SELECTIVE DLC COATING USING CAPVD FOR SOLAR THERMAL APPLICATIONS

Abstract

Metal nitride multilayer films display a unique combination of exceptional properties with respect to optical absorption, thermal emission, corrosion resistance, adhesion between coating and surface and high temperature withstand. Most considerable aspects of nitride coatings were economical, environmentally friendly and easy to develop. Similar to nitride thin films, to achieve a considerable absorption (α) -0.92 and low emission (Є) -0.08 along with chemical and radiation stable solar selective coatings, Diamond Like Carbon (DLC) thin films exhibit the desirable properties for Concentrated Solar thermal Power(CSP)applications. The main advantages of DLC films were high hardness, chemical and radiation stability and good control over the optical properties. To achieve above-mentioned properties, optimization of each layer of the DLC coating has needed. The main aim of this research is optimization of Cr-base layer using Cr-Target current 175A to get 125 nm thicknesses, optimise the AlSiN absorber layer by controlling the AlSi- target current 175A to maintain 35nm thickness. The sequence of the DLC coating layers was selected based on their relative thickness, which was optimize to get good solar selectivity (α/Є). Individual layers of the DLC solar coatings have unique properties to get overall required high absorbance and low emission along with chemical and radiation stability. These solar selective multi-layers (Cr/DLC/AlSiN) have deposited by using available Cathodic targets (Cr , AlSi & Ti) in Cathodic Arc Physical Vapor Deposition (CAPVD) and optimized parameters were mainly depend on the target currents to control over the thickness of the each layer, base pressure 1*10⁻⁵ mbar and deposition temperature 400°C. The DLC multilayer solar selective coatings were characterized using Ultraviolet Visible Near infrared (UV- Vis- NIR) spectrophotometer, Scanning Electronic Microscopy (SEM), Transmission Electron Microscopy (TEM) and Raman spectroscopy etc. Scratch test and corrosion tests have conducted for these absorber coatings testing.

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Identifiers

DOI

10.18186/thermal.734719

Journal

Journal of Thermal Engineering

Year

2020