Search

We report the development, thorough characterizations and space worthiness studies of multifunctional aluminized film as x-ray intensity filter for space-based payloads, suitably designed to place in Sun–Earth Lagrangian (L1) point. The L1 point is the ideal location for uninterrupted observation of Sun to study the solar flares in hard x-rays. For our specific purpose, we make use of two different types of x-ray detectors (e.g., CdTe and CZT) which are generally used for hard x-ray studies in the energy band of 5 to 200 keV. Further, these aforesaid two detectors require specified thermal control characteristic for optimal performance. Aluminization of Kapton films is proposed which would satisfy the thermo-optical and x-ray transmission requirements of the proposed payload. The developed aluminized films are thoroughly studied by field emission scanning electron microscopy and atomic force microscopy techniques for micro-structural characteristic, x-ray diffraction for phase purity, nanoindentation for mechanical integrity at micro-structural length scale and spectrophotometer for thermo-optical properties. X-ray transmission test is carried out with two radioactive sources, namely 55Fe and 241Am, with various aluminized Kapton layer combinations. Finally, space worthiness of the aluminized Kapton films is examined by accelerated environments, e.g. humidity, thermal cycling and thermo-vacuum tests. [ABSTRACT FROM AUTHOR]

Vanadium oxide films, deposited on aluminium (Al), titanium (Ti) and tantalum (Ta) metal substrates by pulsed RF magnetron sputtering at a working pressure of 1.5 x10−2 mbar at room temperature are found to display mixed crystalline vanadium oxide phases viz., VO2, V2O3, V2O5. The films have been characterized by field-emission scanning electron microscopy, X-ray diffraction, differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy, and their thermo-optical and electrical properties have been investigated. Studies of the deposited films by DSC have revealed a reversible-phase transition found in the temperature range of 45–49 °C. [ABSTRACT FROM AUTHOR]

Sunshield membranes made of germanium‐coated black polyimide (GBP) or Kapton are often used on the reflector/transmitter antenna of satellites for thermal control applications. However, the germanium top layer is prone to degrade during ground storage and implementation. Hence, vacuum/inert gas‐sealed packaging is required for storing the membranes, followed by a staggered fabrication schedule as the shelf‐life of the GBP is identified as only ~6 months. In the present study, microstructural, thermo‐optical, and electrical properties along with X‐ray photoelectron spectroscopy (XPS) studies for evaluating oxidation states of the as‐received and degraded GBP films have been investigated thoroughly. The radio frequency (RF) loss behavior of both the films has also been studied for S band (2.5–3.5 GHz), Ku band (10.5–14.5 GHz), and Ka band (30–35 GHz). Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Protective alumina thin films of different thicknesses (35-95 nm) were grown by pulsed RF magnetron sputtering technique at room temperature on germanium (Ge) coated black polyimide or Kapton substrate which is often employed as sunshield membrane on communications satellite antennas. The thin alumina top layer provides shielding of Ge coating from degradation during storage. The alumina thin film was characterized by X-ray diffraction, field emission scanning electron microscopy and X-ray photoelectron spectroscopy (XPS) techniques to investigate microstructural and electronic characteristics. Thermo-optical properties such as IR emittance, solar absorptance, reflectance and transmittance and electrical property e.g. sheet resistance of the deposited alumina films were measured. The RF losses e.g. insertion loss and return loss were measured in both Ku band (10.5-14.5 GHz) and Ka band (27-40 GHz). Finally, to prove anti-degradation behavior of alumina thin film, water droplet spreading experiments were carried out and evaluated its chemical degradation by XPS. [ABSTRACT FROM AUTHOR]

The E-beam evaporation technique is utilised at room temperature to deposit 90, 120 and 150 nm thin alumina films on 75 μm thin titanium foils. As-grown films are annealed at 500, 700 and 800 °C in air. The phase analysis, morphology and electronic structure of the as-grown and annealed thin films are respectively investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) techniques. The XRD results show that the as-grown thin films are amorphous. The annealed thin films show crystalline peaks corresponding to a mixture of different phases of alumina. The FESEM studies reveal tripod-like nanostructure and dense nanorods in the alumina thin films annealed at 700 and 800 °C, respectively. These results are explained on the basis of experimental evidences provided by the corresponding XPS studies. [ABSTRACT FROM AUTHOR]

Crystalline vanadium oxide-titanium oxide (VO-TO) composite thin films of 197 nm are developed on quartz and silicon substrates by RF magnetron sputtering technique. A thorough structural investigation of deposited thin films is carried out by field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. Differential scanning calorimetry (DSC) and temperature-based sheet resistance measurement techniques reveals the Smart (i.e., reversible) phase transition behaviour of VO-TO films at about 45 °C. Further selective depth analysis by XPS on the VO-TO films shows the variation of the Ti doping amount along the thickness. The top region of VO-TO thin film possess lower Ti species, while beyond 50 nm thickness from the surface possess comparatively rich Ti species. This graded Ti species along the depth also results in the variation of nanomechanical properties along the depth as confirmed by nanoindentation. The simulation through the finite element approach is also carried out to depict the experimental results of nanoindentation. The nanohardness and modulus of the presently developed VO-TO composite film were measured as 6.7 GPa and 158.7 GPa, respectively at 50 nm depth. Beyond 50 nm, nanohardness and modulus were 5.6 GPa and 116.6 GPa, respectively. Further, finite element simulation predicted yield stress value of 3.52 GPa at 50 nm depth whereas higher yield stress of 4.68 GPa was predicted beyond 50 nm. [ABSTRACT FROM AUTHOR]

Abstract: Alumina thin films were deposited on titanium (Ti) and fused quartz by both direct and reactive pulsed rf magnetron sputtering techniques. X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy were utilized to study the phases and surface morphology of the films. The as-deposited alumina thin films were amorphous. However, after annealing at 500°C in vacuum, the crystalline peaks corresponding to the Theta (θ), Delta (δ) and Chi (χ) alumina phases were obtained. The optical transmittance and reflectance as well as IR emittance data were also evaluated for the thin films. The transmittance, e.g., (~90%) of the bare quartz substrate was not changed even when the alumina thin films were deposited for an hour. However, further increase in deposition time (e.g., 7h) of the alumina thin films showed only a marginal decrease (e.g., ~5%) in average transmittance of the bare quartz substrate. The direct and indirect optical band gaps and extinction coefficient of the alumina films were estimated from the transmittance spectra. The IR emittance of the Ti substrate (e.g., ~16%) was almost constant after depositing alumina thin films for an hour. Further increase in deposition time showed only a marginal increase (e.g., ~9%) in IR emittance value. Therefore, it is proposed that the alumina films developed in the present work can act as a protective cover for the Ti substrate while retaining the thermo-optical properties of the same. The nanohardness and Young׳s modulus of the alumina thin films were evaluated by the novel nanoindentation technique. The nanohardness was measured as ~6GPa. Further, Young׳s modulus was evaluated as ~116GPa. The magnitudes of the nanomechanical properties of the thin films were a little smaller than those reported in the literature. This was linked to the lack of crystalline phases in the as-deposited alumina thin films. [Copyright &y& Elsevier]

Smooth, uniform and crystalline vanadium oxide thin films were deposited on quartz by spin coating technique with four different rpm i.e., 1000, 2000, 3000 and 4000 and subsequently post annealed at 350, 450 and 550 °C in vacuum. Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were utilized for microstructural characterizations and phase analysis, respectively, for vanadium oxide powder and deposited film. Nanorods were observed to be grown after vacuum annealing. X-ray photoelectron spectroscopy (XPS) technique was utilized to study the elemental oxidation state of deposited vanadium oxide films. Thermo-optical and electrical properties such as solar transmittance (τ s ), reflectance (ρ s ), absorptance (α s ), infrared (IR) emittance (ε ir ) and sheet resistance (R s ) of different thin films were evaluated. Based on the optical characteristics the optimized condition of the film processing was identified to be spin coated at 3000 rpm. Subsequently, the nanoindentation technique was utilized to measure hardness and Young's modulus of the optimized film. The measured nanomechanical properties were found to be superior to those reported for sputtered vanadium oxide films. Finally, temperature dependent phase transition characteristics of optimized vanadium oxide films were studied by differential scanning calorimetry (DSC) technique. Reversible and repeatable phase transition was found to occur in the range of 44–48 °C which was significantly lower than the phase transition temperature (i.e., 68 °C) of bulk VO 2 . [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]

We report nanoindentation response of indium tin oxide (ITO) film deposited by reactive direct current (DC) magnetron sputtering. The phase pure ITO film showed dense and needle-like nanostructure. Detailed mechanical characterization of ITO film was carried out by the nanoindentation technique. The average nanohardness and elastic modulus were evaluated as about 17.5 GPa and 189 GPa, respectively. Comparatively higher nanohardness and modulus values were found in the present work, which is possibly linked with the dense nanostructure of the ITO film. Further, fracture toughness was measured as ~0.56 MPa m 0.5 . The corresponding projected area of indentation, elastic energy and plastic energy were also reported. [ABSTRACT FROM AUTHOR]