Plasma Spray-CVD: A New Thermal Spray Process to Produce Thin Films from Liquid or Gaseous Precursors |
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Authors: | M Gindrat H-M H?hle K von Niessen Ph Guittienne D Grange and Ch Hollenstein |
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Affiliation: | (1) Sulzer Metco Switzerland AG, Rigackerstrasse 16, CH-5610 Wohlen, Switzerland;(2) Centre for Research in Plasma Physics, CRPP, EPFL, Station 13, CH-1015 Lausanne, Switzerland |
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Abstract: | New dedicated coating processes which are based on the well-known LPPS™ technology but operating at lower work pressure (100 Pa)
are being actively developed. These hybrid technologies contribute to improve the efficiencies in the turbine industry such
as aero-engines and land-based gas turbines. They also have a great potential in the domain of new energy concepts in applications
like Solid Oxide Fuel Cells, membranes, and photovoltaic with the adoption of new ways of producing coatings by thermal spray.
Such processes include Plasma Spray-Thin Film (PS-TF) which gives the possibility to coat thin and dense layers from splats
through a classical thermal spray approach but at high velocities (400-800 m/s) and enthalpy (8000-15000 kJ/kg). Plasma Spray-PVD
(PS-PVD) which allows producing thick columnar-structured Thermal Barrier Coatings (100-300 μm) from the vapor phase with
the employment of the high enthalpy gun and specific powder feedstock material. On the other hand, the Plasma Spray-CVD (PS-CVD)
process uses modified conventional thermal spray components operated below 100 Pa which allows producing CVD-like coatings
(<1-10 μm) at higher deposition rates using liquid or gaseous precursors as feedstock material. The advantages of such thermal
spray-enhanced CVD processes are the high ionization degree and high throughput for the deposition of thin layers. In this
article, we present an overview of the possibilities and limitations encountered while producing thin film coatings using
liquid and gaseous precursors with this new type of low pressure plasma spray equipment and point out the challenges faced
to obtain efficient injection and mixing of the precursors in the plasma jet. In particular, SiO
x
thin films from Hexamethyldisiloxane (HMDSO or C6H18OSi2) can be deposited on wafers at deposition rates of up to 35 nm/s at an efficiency of about 50%. The process was also used
for producing metal oxide coatings (Al2O3, ZnO, and SnO2) by evaporating different metals in combination with an oxygen gas flow. The effect of process parameters on the deposition
rate, coating build up, uniformity, and quality of the coatings are discussed. An overview of different potential applications
of this new technology will be also presented. |
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