Abstract
This paper studied the feasibility of a new solution-processed method to manufacture black tungsten nanostructures by laser conversion of tungsten hexacarbonyl precursor on the Inconel 625 substrate under argon atmosphere at ambient pressure. The results show that sublimation of the precursor can be prevented if the decomposition temperature (>170 °C) is achieved using the laser heating method. Three different laser powers from 60–400 W were used to investigate the role of laser parameters on the conversion. It was found that lower laser power of 60 W resulted in a mixture of unconverted precursor and converted tungsten. Higher laser powers >200 W resulted in α-W (BCC) in one step without further heat treatment. Different oxygen concentrations from 0.5 ppm to 21 vol% were used in the laser canister to investigate the effect of oxygen concentration on the conversion. It was found that the hard vacuum (>10−4 torr) or hydrogen is not necessary to obtain α-W (BCC). The solar absorptance varied from 63–97%, depending on the amount of precursor deposited on the substrate and oxygen content in the laser canister. This solution-based laser conversion of tungsten precursor is a scalable method to manufacture tungsten coatings for high-temperature applications.
Highlights
Nanostructured W coatings were manufactured by laser conversion of tungsten hexacarbonyl on Inconel 625 substrates under an argon environment at ambient pressure
The results show that a network of black W nanostructures was obtained
XRD analysis revealed the formation of α-W at higher laser powers and W/WOx peaks with an oxygen concentration of 21 vol%
Summary
The highest melting point element known, with low thermal expansion coefficient, good thermal and electrical conductivity, wear-resistance, and chemical stability, has a wide range of applications, such as ohmic contacts, interconnects, solar thermal absorbers, IR reflectors, diffusion barriers, and high-strength metal matrix composites [1,2,3,4]. One growing use of W is as a high-temperature, absorber layer to increase the solar absorptivity and decrease the thermal emissivity of solar thermal collectors or receivers for various energy applications [1,5,6,7]. Creating plasmonic nanostructured metals (nanorods, nanoparticles, nanoporous films) is of great interest as they augment the absorption of electromagnetic radiation over a tunable range of UV to near IR [8,9]. Gesheva et al [10]
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