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Improved microwave absorption technology

Waveguides are essentially conduits that guide various forms of high frequency electromagnetic waves. They protect sensitive components from damaging reflected radiation and can now be better coated by a new cost-efficient spray technology thanks to work by EU-funded researchers.
Improved microwave absorption technology
Conventional technology for absorbing reflected high frequency microwave radiation uses pressed and fired ferrite tiles glued on waveguide walls. However, the solution is problematic both in terms of performance (air gaps and use of adhesive materials) and expense of labour and materials.

The ‘Nanostructured thermally sprayed magnetic coatings for microwave absorption applications’ (Namaco) project was initiated to develop new nano-structured ferrite powders and the process for thermally spraying them under controlled conditions to deposit coatings with low porosities and very small grain sizes on waveguide components.

Researchers focused on high velocity oxy fuel (HVOF) spraying and advanced plasma spray (APS) technologies. They identified materials and powder types to be sprayed and developed methods to measure the magnetic loss factor. The actions enabled comparison of conventional ferrite materials with HVOF and APS sprayed samples in the frequency range of interest, namely 2–3 GigaHertz.

Following laboratory demonstration of acceptable microwave absorption, the researchers conducted scaled-up industrial thermal spraying trials. They produced powders suitable to applications identified by project partners and demonstrated successful spray deposition followed by manufacture and evaluation of full sized demonstrator components.

Cost estimates suggested a 40 % reduction compared to conventional sintered and bonded ferrite tiles with increasing cost benefits for larger production quantities.

Namaco produced novel materials and technology for spray coating of sensitive waveguide components to absorb reflected high frequency microwave radiation. In addition, the thermal spray approach extends the potential applications to curved and complex surfaces beyond the range of conventional ferrite tiles.

Investigation of other ferrite powder compositions could inspire design of other broadband devices or of absorbers suitable over a wider microwave frequency range than is currently possible. Taken together, the Namaco project outcomes have the potential to significantly enhance the European position in the field of high frequency radiation absorption technology.

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