Chemical bonding states and solar selective characteristics of unbalanced magnetron sputtered Ti_xM_1−x−yN_yfilms

Abstract

steel substrates via closed field unbalanced magnetron sputtering technology. These were investigated using XRD, SEM, XPS, UV-Vis, FTIR and nanoindentation techniques. Analysis of the optical properties showed the solar absorptance, in the visible range, of the Ti x M 1ÀxÀy N y films improved significantly from 51% to 81% with AlSi-doping and an increase of solar absorptance of up to 66% was recorded from films doped with Al. Moreover, the Al doping can reduce the thermal emittance in the infrared range from 6.06% to 5.11%, whereas doping with AlSi reduces the emittance to ca. 3.58%. The highest solar selectivity of 22.63 was achieved with TiAlSiN films. Mechanical studies showed enhanced hardness by $32%; enhanced yield strength by $16% and enhanced plastic deformation by $110% of Al and AlSi doped TiN matrix. IntroductionA spectrally selective surface is, generally, used to improve the photothermal conversion performance and, as such, it possesses two characteristics: high absorptance, a in the visible region of solar spectrum (0.3 to 2.5 mm) and low emittance, 3, (i.e., high reection) in the infra-red (IR) region ($2.5 mm) at operating temperatures. An excellent selective surface maximises the absorption of incoming photons in the visible region and minimises photon emission through thermal radiation in the IR energy region. Such a surface can be designed by an absorber-reector assembly. In such an approach, the reector is coated with a highly absorbing layer over the visible solar spectrum, while the infrared region is made transparent. Various types of metal nitrides based selective solar surfaces such as TiN, ZrN, HfN, TiAlN, TiAlON, NbAlN, NbAlON, MoAlN, and WAlN have been investigated by numerous groups.1-11 Over the past few years, transition metal nitride based thin lms have attracted signicant research interest as selective solar surfaces in solar thermal conversion devices. Generally, the energy conversion performance of a selective solar surface depends on the lm materials, lm design and fabrication technique used. A multi-layer lm stack with mixture of metal nitride, metal oxide and metal oxynitride lms e.g., TiAlN/AlON, and TiAl/ TiAlN/TiAlON/TiAlO has been explored for the potential commercial development of selective solar surfaces.3,12 TiAlN/ TiAlON/Si 3 N 4 selective absorbers have been produced on various substrates such as copper, nickel, stainless steel, glass and nimonic alloys.13 However, these materials are yet to be commercialized for solar energy conversion applications. View Article OnlineView Journal | View Issue solar selective surface applications, transition metal oxides based thin lms also received signicant research interests. 15-19Various synthesis methods such as evaporation, electrodeposition, chemical conversion, chemical vapour deposition and magnetron sputtering have been employed in manufacturing selective solar surfaces. Owing to its advantages in large area deposition, dry, clean and environment friendly, magnetron sputtering technique is widely used for syn...

Structural, morphological, and optical characterizations of Mo, CrN and Mo:CrN sputtered coatings for potential solar selective applications

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Structural and optical characteristics of pre- and post-annealed sol-gel derived CoCu-oxide coatings

“…the solar absorptance (ߙ) to the emittance (ε ) [32,33] (i.e., ε α = s ) of the coatings was also estimated from the UV-Vis and FTIR data of the coatings.…”

Chemical Bonding Analysis in Ti1-x-yAlxTayN Solid Solutions

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