Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014)
    Nanomaterials Tuesday Sessions
       Session NM-TuP

Paper NM-TuP16
Synthesis and Evaluation of Nanocrystalline Diamond Powder Prepared by Coaxial Arc Plasma Gun

Tuesday, December 9, 2014, 4:00 pm, Room Mauka

Session: Nanomaterials Poster Session
Presenter: Hiroshi Naragino, Kyushu University, Japan
Authors: H. Naragino, Kyushu University, Japan
A. Tominaga, Kyushu University, Japan
K. Sumitani, Kyushu Synchrotron Light Research Center, Japan
S. Hattori, Kyoto Prefectural Technology Center for Small and Medium Enterprises, Japan
T. Yoshitake, Kyushu University, Japan
Correspondent: Click to Email
Diamond possesses several superior physical properties including high hardness, wide bandgap, and chemical inertness. Furthermore, it is possible to impart functionalities by doping and surface modification. Nano-sized diamond powder shows different properties from bulk diamond. Nanodiamond has mainly been produced by detonation method so far. However, high-purity nanodiamond powder has been difficult to be fabricated by detonation. Moreover, the functionalization of nanodiamond is made after growth, because of in-situ doping being impossible. Our research group has proposed a new novel method that employs a coaxial arc plasma gun (CAPG), which enables us to fabricate nanodiamond crystallites. The specifics to this method are as follows: i) the growth is made using a simple apparatus equipped with a coaxial arc plasma gun, ii) high-purity nanodiamond can be fabricated in principle, iii) doping can be easily made by using doped targets, and iv) the grain size is expected to be changed by controlling the discharge condition of coaxial arc plasma gun. In this work, we experimentally proved the generation of nanodiamond by powder X-ray diffraction (XRD) and transmission electron microscope (TEM) and that the grain size is evidently enlarged with the electric power applied to an arc plasma gun. Moreover, the density of nanodiamond powder was measured using a sink-float method. Nanodiamond powder was fabricated using CAPG (ULVAC, APG-1000) equipped with a graphite target. The inside of the chamber fitted with CAPG was evacuated to < 10-6 Pa and hydrogen was introduced at 5 sccm. The head of the arc plasma gun was pointed at quartz plate heated at 550deg. C. The powder that quickly and automatically exfoliated from the quartz plate was gathered in the collection cell located under the quartz plate. In order to confirm the formation of diamond, the films were structurally investigated by TEM and powder XRD using synchrotron radiation at beamline 15 of the SAGA-LS. The films exhibited diamond-111 and -220 diffraction rings in the electron diffraction patterns and the existence of diamond grains was confirmed from the dark-field TEM images. The XRD patterns also exhibited diffraction peaks due to diamond. The grains size was increased from 2 to 80 nm with increasing electric power applied to an arc plasma gun. From the density measurement, the density of nanodiamond powder was estimated to be approximately 1.77 g/cm3. This value is smaller than that of diamond (3.5 g/cm3), and indicates that the nanodiamond contains the non-diamond phase such as an amorphous carbon. The details of preparation apparatus and preparation mechanism are explained in the conference.