Journal Articles

Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884

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Author: search.filters.author.Dey, A.Subject: search.filters.subject.Field emission microscopes

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    RF transparent vanadium oxide based single and bi-layer thin films as passive thermal control element for satellite antenna application
    (Elsevier Ltd, 2018) Prajwal, K.; Carmel Mary Esther, A.; Dey, A.
    Germanium coated black polyimide (GBP) is often used as passive thermal control element for sunshield membrane of satellite antenna. However, GBP degrades fast while there is no protective coating applied. The present work is aimed towards the development of protective films which could hinder the degradation of GBP. At the same time, the basic characteristic of GBP membrane that is RF transparency should not be trade off. Here, RF transparent and protective vanadium oxide (VO) and vanadium oxide/silicon dioxide (VO/SO) thin films are developed by RF magnetron sputtering technique on GBP at a constant 400 W. Field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) techniques are utilized to investigate microstructural and oxide characteristics, respectively. Thermo-optical properties such as, solar absorptance (?s) and IR emittance (?ir) are also evaluated. Introduction of SiO2 layer over vanadium oxide layer leads to decrease in ?s to about 12%. RF losses e.g. insertion loss and return loss are measured in Ka band (27–39 GHz) and they found to be RF transparent characteristic. Thermal stability of the oxide films are also studied by differential scanning calorimetry (DSC) technique. © 2018 Elsevier Ltd and Techna Group S.r.l.
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    Development of Multifunctional Thin Film Based X-Ray Intensity Filters for Space-Based Payloads
    (Springer New York LLC barbara.b.bertram@gsk.com, 2019) Prajwal, K.; Dey, A.; Sudhakar, M.; Nandi, A.; Esther, A.C.M.; Sridhara, N.; Yougandar, B.; Kumar, P.; Arya, S.; Rajendra, A.
    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. © 2019, ASM International.
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    Development of reflective co-sputtered nanostructured metallic films
    (Taylor and Francis Ltd., 2021) Prajwal, K.; Priyanka, G.L.; Hasan, M.A.; Carmel Mary Esther, A.; Sridhara, N.; Rajendra, A.; Arya, S.B.; Dey, A.
    DC magnetron co-sputtering technique is utilised to develop reflective Ag- and Al-based metal films co-sputtered with Ni deposited on quartz glass substrates. The sputtered films are characterised by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques to investigate microstructure, topology and phase analysis, respectively. Further, average thermo-optical properties such as solar reflectance, absorptance and IR emittance and electrical property such as sheet resistance of the deposited films are evaluated. The reflectance property as a function of wavelength is also investigated. Sputtered Ag and Al films show high (>93%) reflectance, however, co-sputtered Al + Ni and Ag + Ni offer comparatively lesser value, e.g. 45% and 73%, respectively. The significant lower reflectance of Al + Ni is possibly due to the presence of higher amount of Ni in the film and the formation of intermetallic compounds. © 2020 Institute of Materials, Minerals and Mining Published by Taylor & Francis on behalf of the Institute.