Testing Multiwall Carbon Nanotubes on Ion Erosion for Advanced Space Propulsion
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Testing Multiwall Carbon Nanotubes on Ion Erosion for Advanced Space Propulsion Yoke Khin Yap 1,*, Jitendra Menda 1, Lakshman Kumar Vanga 1, Vijaya Kayastha 1, Jiesheng Wang 1, Lyon B. King 2,**, Svetlana Dimovski 3,Yury Gogotsi 3 1
Department of Physics, Michigan Technological University, Houghton, MI 49931, USA. Department of Mechanical Engineering-Engineering Mechanics, Michigan Technological University, Houghton, MI 49931, USA. 3 Department of Materials Science and Engineering and A. J. Drexel Nanotechnology Institute, Drexel University, Philadelphia, PA 19104, USA. * Email: [email protected], **Email: [email protected] 2
ABSTRACT Are carbon nanotubes more resistant than diamonds against ion erosion? Here, we report an evaluation of multiwall carbon nanotubes (MWNTs) as the protective coating against plasma erosion in advanced space propulsion systems. We have compared polycrystalline diamond films with MWNTs, amorphous carbon (a-C) and boron nitride (BN) films. Two types of MWNTs were investigated including vertically aligned (VA) MWNTs, and those horizontally laid on the substrate surfaces. Only diamond films and VA-MWNTs survived erosion by 250 eV krypton ions of a flight-quality Hall-effect thruster. VA-MWNTs are found to bundle at their tips after ion erosion.
INTRODUCTION The space exploration program faces enormous challenges as it seeks to achieve dramatic improvements in safety, cost, and speed of missions to the frontiers of space. Plasma propulsion systems have been recognized as far more efficient than chemical thrusters. This recognition has led to the development of highly efficient electric propulsion (EP) thrusters that are currently the only feasible technology for many deep space missions. However, these EP devices have in common electrode sputter erosion as a life-limiting process. To facilitate long thruster life, critical surfaces in EP thrusters are fabricated from sputter-resistant materials such as molybdenum (Mo). Carbon-based materials have shown nearly an order-of-magnitude improvement in sputter erosion resistance over Mo [1]. Among the tested carbon-based materials, diamond films prepared by chemical vapor deposition (CVD diamond) provide improvement by a factor of 1.5 in volumetric sputter erosion rate over others [2]. For thruster surfaces that are subject to sputter damage, yet must be electrical insulators, boron nitride ceramic has traditionally been used to increase the lifetime [3]. Recently, Meezan, et. al. found that polycrystalline diamond plates had 25% better resistance to sputtering that the traditional boron nitride ceramic [4]. On the other hand, unique mechanical properties of carbon nanotubes (CNTs) have triggered tremendous curiosities on their applications. CNTs are predicated to have
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extremely high Young’s modulus values, similar to that of in-plane modulus of graphite (~1000GPa). This is much higher than the bulk modules of diamond (~443 GPa). Thus, it is interesting to find out the resistance of CNTs to ion erosion. In this paper, we discuss our pr
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