The physico-chemical and thermo-mechanical properties ofaluminosilicate ceramics (high melting point, low thermalexpansion coefficient, excellent thermal shock resistance, lowdensity and good corrosion resistance) make this class ofmaterials a good option for high temperature structuralapplications. Al2O3-SiO2 compounds show an excellentrefractory behaviour allowing a wide use as wear resistantthermal barrier coatings, in metallurgical and glass plants and inhigh temperature heat exchangers. Moreover the low values ofthermal expansion coefficient and of complex permittivity allowto extend the use of this ceramic for microelectronic devices,radome for antennas and electromagnetic windows formicrowaves and infrared. The present paper presents the results ofan extensive experimental activity carried out to produce thickaluminosilicate coatings by plasma spray technique. APSdeposition parameters were optimized on the basis of a surfaceresponse approach, as specified by design of experiments (DoE)methodologies. Samples were tested for phase composition, totalporosity, microstructure, microhardness, deposition efficiency,fracture toughness and modulus of rupture. Finally, coatings werecharacterized for their particularly interesting electromagneticproperties: complex permittivity was measured at microwavefrequency using a network analyzer with wave guide.
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