| AVS 59th Annual International Symposium and Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS+EM-MoM |
| Session: | Atmospheric Plasma Processing and Micro Plasmas |
| Presenter: | A. Kumar, Case Western Reserve University |
| Authors: | A. Kumar, Case Western Reserve University P.A. Lin, Case Western Reserve University A. Xue, Case Western Reserve University R.M. Sankaran, Case Western Reserve University |
| Correspondent: | Click to Email |
Since their discovery, nanodiamonds have been an active area of research due to their unique size, chemical stability, high thermal conductivity, and biocompatibility.1 Nanodiamonds have been detected in outer space (meteorites, interstellar dust) and synthetically produced by high pressure/high temperature (HPHT) and detonation processes. In addition to their potential technological use, the formation of nanodiamond is of great scientific interest. While bulk graphite is more stable than bulk diamond at lower pressures and temperatures (e.g. ambient conditions), recent modeling has suggested that nanometer-sized particles of diamond-phase carbon could be thermodynamically favored at these same conditions as a result of surface energy considerations.2
Previously, microplasmas have been shown to be capable of nucleating high-purity nanometer-sized metal nanoparticles from vapor precursors.3 Here, we present a study of nanodiamond synthesis at atmospheric pressure using a similar microplasma process. Ethanol vapor was used as a carbon precursor for the nucleation of carbon clusters. Aerosol measurements confirm that carbon clusters less than 6 nm in mean diameter are nucleated in the microplasma. In situ optical emission spectroscopy (OES) indicates the presence of C2 dimers and atomic H species which have been linked to diamond nucleation. The collected product is characterized by several techniques including micro Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). Results confirm the presence of nanodiamond with uniform sizes of ca. 3 nm in diameter and crystal structures corresponding to known phases of diamond. The synthesis of nanodiamond at low pressure may allow new technologies to be realized, and help explain their formation in extraterrestrial material.
1. V. N. Mochalin et al.,“The properties and applications of nanodiamonds”, Nat. Nanotech. 7, 11 (2012).
2. P. Badziag et al., “ Nanometre-sized diamonds are more stable than graphite”, Nature 343, 244 (1990).
3. A. Kumar et al., “New insights into plasma-assisted dissociation of organometallic vapors for gas-phase synthesis of metal nanoparticles”, Plasma Proc. Polym., in review.