Effects Of Atomic Oxygen Irradiation Research Articles

Atomic oxygen irradiation resistance of transparent conductive oxide thin films

One set of tungsten-doped indium oxide thin films (In2O3:W, IWO) and another set of tin-doped indium oxide thin films (In2O3:Sn, ITO) were prepared on glass substrates by radio frequency (RF) reactive magnetron sputtering method. The as-deposited IWO and ITO films have resistivity values at a level of 10−4Ω•cm. Average transmittance values of these films are above 85% in visible-light region as well as in near-infrared region. All these films were irradiated by atomic oxygen (AO) with different amount of flux in a ground-based simulation system close to the environment of low Earth orbit. Changes in characteristics including surface morphology, mechanical properties, optical and electrical properties were compared between IWO and ITO films after AO irradiation. The effects of AO irradiation on transparent conductive oxide thin films were analyzed. As a result, AO has influences on ITO and IWO thin films through the way of oxidation and erosion. Both ITO and IWO films possess suitable anti-AO properties. IWO films are more appropriate as AO protective coatings due to their compact microstructure, the coexistence of W4+ and W6+ ions in their chemical systems, and incremental WO3 protective layer under AO oxidation.

Effect of atomic oxygen irradiation on the structural and tribological characteristics of polytetrafluoroethylene and its composites

Based on the ground-based simulation facility, the effects of atomic oxygen (AO) irradiation on the structural and tribological properties of pure polytetrafluoroethylene (PTFE) and carbon fiber and MoS2-filled PTFE composites were studied by scanning electron microscopy, X-ray photoelectron spectroscopy, and a ball-on-disc tribometer. The results shown that AO irradiation had significant effects on the structural and tribological properties of pure PTFE, in which the surface morphologies, mass loss, friction coefficient, and wear rate had been changed greatly after AO irradiation. However, it was noticeable that the addition of carbon fiber and MoS2 filler to PTFE could improve the AO resist capacity and tribological properties of PTFE composites significantly. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of Atomic Oxygen Irradiation on Field Emission Cathodes in Low Earth Orbit

Effect of Atomic Oxygen Irradiation on Field Emission Cathodes in Low Earth Orbit

Effects of Atomic Oxygen Irradiation on PDMS/POSS Hybrid Films in Low Earth Orbit Environment

In order to improve the atomic oxygen (AO) erosion resistance of polyimide films in low earth orbit space environment, a type PDMS/POSS hybrid coating on polyimide substrate was prepared based on a silanol terminated polydimethylsiloxane (PDMS-OH) and Octakis(trimethylsiloxy)octaprismosilsesquioxane (Q8[Si(CH3)3]8) by copolymerizing process in DMAc solution. The atomic oxygen exposure tests were carried out using a ground-based atomic oxygen simulation facility. The mass loss, surface morphology and surface chemical compositions of PDMS/POSS hybrid films before and after exposure to incremental AO flux were investigated by using microbalance and field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The data indicated that a silica-rich layer was formed on the surface of the hybrid coating when the coating is exposed to AO flux, which could provide a protective barrier on the surface preventing further degradation of the polymer during extended exposure to AO and obviously improved the AO resistance of polyimide films.

Effects of atomic oxygen irradiation on the surface properties of phenolphthalein poly(ether sulfone)

To study the effects of low earth orbit environment on the surface properties of polymers, phenolphthalein poly(ether sulfone) (PES-C) blocks were irradiated by atomic oxygen in a ground-based simulation system. The surface properties of the pristine and irradiated blocks were studied by attenuated total-reflection FTIR (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM). It was found that atomic oxygen irradiation induced the destruction of PES-C molecular chains, including the scission and oxidation of PES-C molecular chains, as evidenced by FTIR and XPS results. The scission of PES-C molecular chains decreased the relative concentration of C in the surface, while the oxidation increased the relative concentration of O in the surface. The changes in surface chemical structure and composition also changed the surface morphology of the block, which shifted from smooth structure before irradiation to “carpet-like” structure after irradiation.

Effects of Atomic Oxygen Irradiation on Transparent Conductive Oxide Thin Films

Transparent conductive oxide (TCO) thin film is a kind of functional material which has potential applications in solar cells and atomic oxygen (AO) resisting systems in spacecrafts. Of TCO, ZnO:Al (ZAO) and In2O3:Sn (ITO) thin films have been widely used and investigated. In this study, ZAO and ITO thin films were irradiated by AO with different amounts of fluence. The as-deposited samples and irradiated ones were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Hall-effect measurement to investigate the dependence of the structure, morphology and electrical properties of ZAO or ITO on the amount of fluence of AO irradiation. It is noticed that AO has erosion effects on the surface of ZAO without evident influences upon its structure and conductive properties. Moreover, as the amount of AO fluence rises, the carrier concentration of ITO decreases causing the resistivity to increase by at most 21.7%.