Shuxi Zhao

Colour control and selectivity in TiAlN solar-thermal absorbers

Optical constants for simulations were obtained by R- and T-measurements on TiAlN thin films deposited on Corning 7059 glass. The model parameterized free carrier effects and an inter-band excitation. The calculations demonstrated that the colour effects are due to interference and inter-band absorption around 500 nm in a single layer coating. The peak shifts with the thickness of the thin film which gives a simple way to obtain different colours. Solar absorptance of 86 % can be reached already for a single TiAlN-film on an Al substrate.

Theoretical Study of a Spectrally Selective Ni-NiO Absorber

Solar-absorbers of Ni-NiO is evaluated with a method where the effective refractive index has been analyzed to determine the steepness in the transition from low reflectance in the solar wavelength range to high in infrared.

Gradient Coatings by Moving Substrate for Large Scale Production

Thin film for solar-thermal application was prepared by dc-magnetron reactive sputtering. The gradient composition is produced by moving the substrate through inhomogeneous reaction sputtering zone which has been used for large scale production.

The Optimized Optical Requirement for Spectrally Selective Absorbers

It is investigated how the intrinsic optical properties of the metal and dielectric constituents in composite spectrally selective solar absorber coatings influence its solar absorptance and thermal emittance. Theoretical modeling using Bruggeman effective medium theory has been used to analyze the basic features in the effective optical constants of the composite layer that are required in order to obtain high solar absorptance in combination with low thermal emittance. It is found that the requirement is correlated to certain dispersion of extinction coefficient and refractive index. The metallic content of used composite should be large enough to give a reasonable extinction coefficient, but not beyond the metal-nonmetal transition point. The ideal dispersion for refractive index should decrease with increasing wavelength in the transition wavelength region. So does the extinction coefficient.

A model of DC reactive magnetron sputtering for graded solar thermal absorbers

In this work we present process modelling of reactive in-line sputtering. Although modelling of reactive sputtering is often used, most models are based on assumptions which make them insufficient for use in this case. The presented model takes into account a realistic deposition rate profile and distribution of reactive gas pressure. The model has been applied to reactive sputter deposition of graded solar thermal absorbers. It has been shown that the presented model represents a simple alternative to complex Monte Carlo simulations while still representing all important features of the process.