1 American Institute of Aeronautics and Astronautics Preliminary Sputter-erosion Characterization of Multiwalled Carbon Nanotubes 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. 2 Department of Mechanical Engineering, 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: ykyap@mtu.edu, ** Email: lbking@mtu.edu ABSTRACT This paper presents preliminary results of ion sputter erosion characterization of carbon nanotubes. Relative erosion rates were compared by exposing multiwall carbon nanotubes (MWNTs), polycrystalline diamond films, amorphous carbon, and boron nitride to the exhaust plume of a 1.5-kW Hall-effect thruster operating on krypton propellant. Two types of MWNTs were investigated: films composed of vertically aligned tubes and those horizontally laid on the substrate surface. Only diamond films and vertically aligned MWNTs survived erosion by 250-eV krypton ions. The vertically aligned tubes were found to bundle at their tips into nanocones 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 sputter erosion of electrodes and other surfaces 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]. Unique mechanical properties of carbon nanotubes (CNTs) have triggered tremendous curiosities on their applications. CNTs are predicated to have 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