Flat Absorber Phosphorous Black Nickel Coatings for Space Applications |
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Authors: | VMaria Shalini PArockiasamy RUma Rani AKSharma |
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Affiliation: | V.Maria Shalini,P.Arockiasamy,R.Uma Rani and A.K.Sharma Thermal Systems Group,ISRO Satellite Centre,Vimanapura Post,Bangalore-560 017,India |
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Abstract: | A new process of flat absorber black nickel alloy coating was developed on stainless steel by electrodeposition from a bath containing nickel,zinc and ammonium sulphates;thiocyanate and sodium hypophosphite for space applications.Coating process was optimized by investigating the effects of plating parameters,viz concentration of bath constituents,current density,temperature,pH and plating time on the optical properties of the black deposits.Energy dispersive X-ray spectroscopy showed the inclusion of about 6% phosphorous in the coating.The scanning electron microscopy studies revealed the amorphous nature of the coating.The corrosion resistance of the coatings was evaluated by the electrochemical impedance spectroscopy (EIS) and linear polarization (LP) techniques.The results revealed that,phosphorous addition confers better corrosion resistance in comparison to conventional black nickel coatings.The black nickel coating obtained from hypophosphite bath provides high solar absorptance (α s) and infrared emittance (ε IR) of the order of 0.93.Environmental stability to space applications was established by the humidity and thermal cycling tests. |
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Keywords: | Phosphorous black nickel alloy Electrochemical impedance spectroscopy Linear polarization Solar absorptance Infrared emittance |
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