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In the field of spacecraft engineering, in particular for geostationary and geosynchronous applications, a significant need exists for a thermal control film to be electrically conductive, to effectively manage the dissipation of accumulated charges. In this study, transparent-electrically conductive reduced graphene oxide is strategically applied to heated rigid (quartz glass) and flexible (Fluorinated Ethylene propylene) optical solar reflector substrates. This innovation harnesses the unique properties of graphene to seamlessly integrate electrical conductivity into space-appropriate substrates with minimum deviation in their optical transparency and thermal properties. The tape peel-off test, conducted in accordance with space materials standards (ASTM D903) using 3 M Scotch tape, reveals the better adhesion of the developed coating. A noteworthy aspect of the present work involves visualizing charge dissipation using Field Emission Scanning Electron Microscope (FESEM) electron bombardment through obtained images and decreased surface potential measured by Kelvin Probe Force microscopy (KPFM). Furthermore, a basic OSR model is fabricated by depositing a reflective back with Aluminium and graphene thin film protecting from the top to investigate the alteration in reflection by varying incident angles. This research contributes to the advancement of spacecraft materials and coatings aimed at improving spacecraft durability and functionality. • A large-scale spray-based coating is developed on heated OSR substrates to address electrostatic charging. • Minimal deviation in thermo-optical properties and decreased sheet resistance of the substrates. • The tape peel-off method (ASTM D903) demonstrates improved adhesion for practical applications. • Charge dissipation is visualized through FESEM images and surface potential mapped by KPFM. [ABSTRACT FROM AUTHOR]

Solar selective colored chromium oxide coatings were prepared on the SS304 substrate through the electrochemical deposition route to provide more options and flexibility in aesthetically design solar absorbers with acceptable energy performance. The variation of colors in the coatings was achieved by varying the coating thickness as a function of deposition time. Color changes in the coatings were also evident in the samples that were annealed under vacuum. Electron microscopic images show that nanometer sized pores are present on the coating surfaces. The pore-density, pore-size distribution and surface roughness exhibit significant changes with variations in deposition time and annealing temperature. Initially, the selectivity factor of 6.08 was recorded in the as prepared sample coated for 30 min, which improved to 7.36 on annealing the samples under vacuum at 700 °C, however, it drops to 4.22 when annealed at 900 °C. A similar trend was also observed for samples that are coated for 60 min. The results indicate that the pore-density, pore-size distribution and surface roughness play a dominant role in governing the solar selectivity of the coatings. Nanoindentation tests were performed on the coated samples and the results show that mechanical properties of the solar absorber coatings degrades with the increase in coating thickness but improve significantly with increase in annealing temperature. [ABSTRACT FROM AUTHOR]

Acquiring good adhesion of ITO thin films on polymer substrate is a major concern, especially for space related applications. Delamination of ITO coating on these polymers can seriously damage the spacecraft. This paper presents the development of highly transparent and conducting ITO thin films on as-received and surface treated fluorinated ethylene propylene (FEP) and Kapton ® substrates by reactive direct current magnetron sputtering. Stability of the ITO coating on FEP and Kapton ® substrates was studied in simulated space environments. Environmental tests such as: relative humidity, thermal cycling and thermo vacuum were performed. Thermo-optical properties and sheet resistance of ITO coated FEP and Kapton ® substrates were studied before and after environmental tests. Optimized ITO coating with thickness of ~ 15 nm on FEP and Kapton ® substrates showed sheet resistance in the range of 2–4 kΩ/sq. with high average transmittance and high IR emittance. Adhesion of ITO coating on FEP substrate was improved by Ar plasma etching. X-ray photoelectron spectroscopy and field emission scanning electron microscopic studies of etched FEP substrate showed defluorination and high roughness of the etched surface which helped for better adhesion of ITO coating. We demonstrated that ITO coated plasma etched FEP substrate showed no change in the sheet resistance and thermo-optical properties. Moreover, ITO coated etched FEP substrate showed good environmental stability than ITO coated untreated FEP substrates. [ABSTRACT FROM AUTHOR]

Transparent and conducting ITO/Ag/ITO (IAI) multilayer coatings were deposited on glass and flexible fluorinated ethylene propylene (FEP) substrates by reactive sputtering using metallic In:Sn (90%:10%) and Ag targets at room temperature. Middle Ag layer thickness was optimized to obtain maximum figure of merit ( ϕ ) and the optimum Ag layer thickness was found to be ~13 nm. The optimized IAI multilayer on glass substrate showed transmittance of ~88.6% and sheet resistance of ~7.1 Ω/sq. The transmittance increased to ~91.4% for the IAI multilayer deposited on one side etched glass. The optimized IAI multilayer coating was also deposited on flexible FEP substrates. The electrical, optical, structural and morphological properties of IAI deposited on glass and FEP substrates were compared. IAI deposited on FEP substrate showed transmittance of ~90.2% at λ = 550 nm, sheet resistance of ~6.9 Ω/sq. and figure of merit of ~52 × 10 −3 Ω −1 . Bending test of IAI deposited FEP proved the high flexibility of IAI multilayer for the flexible transparent electrode applications. Solar selectivity study of IAI on FEP substrate showed it can effectively reflect the higher wavelength region of solar spectrum and can be used as a flexible solar spectrum segregator. Optical haze measurements of IAI coated glass and FEP show that high haze value can be achieved by increasing the roughness on non-coated side of the FEP substrate. [ABSTRACT FROM AUTHOR]

ITO thin films were deposited on flexible fluorinated ethylene propylene (FEP) substrates by pulsed direct current reactive magnetron sputtering system using an In:Sn (90%–10% wt.) alloy target. The influence of the deposition parameters (argon and oxygen flow rates, and substrate temperature) and effect of coating thickness on the optical, electrical, structural and microstructural properties of ITO thin films deposited on FEP was investigated. The thickness of the ITO coatings was varied from 5 to 180 nm. The optimized ITO coating (10 nm thick) exhibited high IR emittance (79%) on FEP substrate with high average solar transmittance (94.0%) and moderate sheet resistance (3 kΩ/sq.). We also investigated in detail the angular dependence of reflectance as well as haze factor of thin ITO coatings. Our results suggest that 10 nm thick ITO coating exhibits an average haze factor of 8.6%. The high value of IR emittance, moderate sheet resistance and high solar transmittance along with low haze factor indicate the suitability of ITO thin films on FEP substrates as flexible optical solar reflector for space applications. [ABSTRACT FROM AUTHOR]