High Temperature Functionalization and Surface Modification of Nanodiamond Powders
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High Temperature Functionalization and Surface Modification of Nanodiamond Powders Vadym N. Mochalin1, Sebastian Osswald1, Cristelle Portet1, Gleb Yushin1,2, Christopher Hobson1, Mickael Havel1, and Yury Gogotsi1 1 Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA, 19104 2 Georgia Institute of Technology, Atlanta, GA, 30332-0245 ABSTRACT High temperature annealing in vacuum, air, hydrogen, chlorine, and ammonia are described as a means to change surface chemistry and phase composition of nanodiamond powders of three different grades, which have different sp2/sp3 carbon ratios. The changes in surface chemistry and phase composition of the powders are analyzed using Raman spectroscopy and Fourier Transform Infra Red (FTIR) spectroscopy. Advantages and limitation of hightemperature treatment techniques as well as potential applications of the gas-treated nanodiamond powders are discussed. INTRODUCTION Nanodiamond powder (ND) is produced in commercial quantities by detonation of carbonaceous explosives in a closed chamber. Discovered in the former Soviet Union in the 1960s [1] this material has attracted increasing attention of both the scientific and industrial communities during the past decade. The interest in ND has been growing due to the broad range of its applications, which currently include lubricants and motor oil additives, electro- and electroless plating bath additives, and polymer- and metal-matrix composites [2]. Among other applications of ND, which are envisioned to emerge in the near future, are biomedical applications in imaging and drug delivery, biocompatible and biodegradable composite materials, as well as superhard and thermally conductive composites [3]. These applications are only possible due to unique properties and a moderate cost of ND. Primary ND particles (~5nm in diameter) are composed of an inert diamond core covered with a layer of terminating surface functional groups, surrounded by fragments of graphene shells and amorphous carbon [1, 4]. Due to the mechanism of detonation synthesis, primary ND particles are very uniform in size, but they form aggregates of tens to hundreds of nanometers. Though very uniform in size, ND particles differ greatly in terms of their surface terminations, carbon phase composition and the contetnt of non-carbon impurities [4]. To a large extent, this is a result of different post-synthetic purification procedures used by different manufacturers. Therefore, in order to successfully implement ND and fully benefit from its properties, ND should be carefully characterized, and based upon the information obtained, it should be purified and its surface modified to produce functionalities that will target a particular application. High temperature treatment has been used for ND powder functionalization and surface modification in the past. According to Chen et al. [5], progressive graphitization of ND is initiated in Ar environment at 800°C, and is accompanied by a decrease in primary ND particle size. Thoug
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