Plasma column and nano-powder generation from solid titanium by localized microwaves in air

This paper studies the effect of a plasma column ejected from solid titanium by localized microwaves in an ambient air atmosphere. Nanoparticles of titanium dioxide (titania) are found to be directly synthesized in this plasma column maintained by the microwave energy in the cavity. The process is i...

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Bibliographic Details
Published in:Journal of applied physics 2015-07, Vol.118 (2)
Main Authors: Popescu, Simona, Jerby, Eli, Meir, Yehuda, Barkay, Zahava, Ashkenazi, Dana, Mitchell, J. Brian A., Le Garrec, Jean-Luc, Narayanan, Theyencheri
Format: Article
Language:English
Subjects:
AIR
Anatase
Applied physics
Brookite
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Columns (structural)
Dusty plasmas
Ejection
Electron energy
Engineering Sciences
Melts
MICROWAVE RADIATION
Microwaves
NANOPARTICLES
Physics
PLASMA
POWDERS
RUTILE
SCANNING ELECTRON MICROSCOPY
SMALL ANGLE SCATTERING
Small angle X ray scattering
SOLIDS
SPECTROSCOPY
SUBSTRATES
TITANIUM
Titanium dioxide
TITANIUM OXIDES
VAPORS
X-RAY DIFFRACTION
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Summary:This paper studies the effect of a plasma column ejected from solid titanium by localized microwaves in an ambient air atmosphere. Nanoparticles of titanium dioxide (titania) are found to be directly synthesized in this plasma column maintained by the microwave energy in the cavity. The process is initiated by a hotspot induced by localized microwaves, which melts the titanium substrate locally. The molten hotspot emits ionized titanium vapors continuously into the stable plasma column, which may last for more than a minute duration. The characterization of the dusty plasma obtained is performed in-situ by small-angle X-ray scattering (SAXS), optical spectroscopy, and microwave reflection analyses. The deposited titania nanoparticles are structurally and morphologically analyzed by ex-situ optical and scanning-electron microscope observations, and also by X-ray diffraction. Using the Boltzmann plot method combined with the SAXS results, the electron temperature and density in the dusty plasma are estimated as ∼0.4 eV and ∼1019 m−3, respectively. The analysis of the plasma product reveals nanoparticles of titania in crystalline phases of anatase, brookite, and rutile. These are spatially arranged in various spherical, cubic, lamellar, and network forms. Several applications are considered for this process of titania nano-powder production.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4926491