Nanocomposites and nanomaterials

Structure commonalities of nanostructured diamond particles obtained during various kinds of synthesis
Oleynik G. S.1, Kotko А. V.1, Solonin Ju.M.1, Bochechka O.O.2, Kushch O.V.2, А.I. Danylenko1
1Frantsevich Institute for Problems of Materials Science of NAS of Ukraine, Kyiv, Ukraine E-mail: g.oleynik@hotmail.com
 2Bakul Institute for Superhard Materials of NAS of Ukraine, Kyiv, Ukraine
E-mail: obochechka@gmail.com

Summary of the TEM research of diamond nanoparticles substructure is presented, grouped by the obtaining method: 1. Ultradisperse diamond – synthesized from explosive materials. 2. Dynamic synthesis diamond – shock treatment of graphite. 3. Static synthesis diamond – graphite affected by high temperature and high pressure without catalyst present. 4. Natural diamond (Popigai mine).
It is established for the first time, that the characteristic substructure element common to types of diamond mentioned above is a rail, that in most cases is fragmented length-wise. The length of the fragments defines how nanostructured the particles are. Smallest fragments found in ultradisperse diamond are found to be 2–3 nm. Rails in diamond particles (except ultradisperse diamond) in many cases exists in packets, including those oriented differently. In ultradisperse diamond particles such railed substructure is only found in localized volumes.
It is found, that all mentioned diamond types consist of two phases – cubic and hexagonal (lonsdaleite) diamond. Among the examined samples the content of hexagonal phase is highest in static synthesis diamond (80 %) and lowest in ultradisperse diamond. The latter was established via microdiffraction when examining the areas of particles containing rail substructure. The data obtained regarding ultradisperse diamond synthesis shows that its synthesis occurs in two steps: formation of graphite and following martensite transformation into diamond. It is described in detail in [1].

1. Oleynik G.S., Bochechka A.A. On the mechanism of forming nanosized particles  of diamond  detonation synthesized from explosive decomposition products // Journal of Superhard materials. 2008. №3. Р. З–30.