In this paper, the nano-β-SiC/Al2O3 composite absorbing coatings produced by plasma spraying technology were reported. Where, β-SiC phase dissipates in the boundary of Al2O3 grains. Then, the relationship between microstructure and dielectric properties was built. Some results are shown as follows: with increasing of flatten ratio of particle and pores, the microwave reflectivity coefficient of composite absorbing coatings decreases and ranges to low frequency. And, there exists a threshold value, about 30wt% of nano β-SiC, the microwave reflectivity coefficient of composite absorbing coatings can reach to -8 dB. The infrared properties of β-SiC/ Al2O3composite absorbing coatings with experiment is about 0.6~0.8, respectively.
Al2O3 coatings were fabricated by multi-functional micro-plasma spray through axial
powder feed. The flight particle velocity and temperature were measured by SprayWatch-2i. With the
rising of Ar flow, the velocity of Al2O3 particles increases, but the temperature of particles decreases
gradually. Al2O3 coatings were analyzed by SEM and XRD. The microstructure of coatings is density,
low porosity and uniform morphology. X-ray diffraction results show that α-Al2O3 is the main phase
in the original Al2O3 powders, but Al2O3 coatings consist of γ-Al2O3 and a small amount of α-Al2O3.
The microhardness and bonding strength of Al2O3 coatings were also measured, which is
HV0.11183~1387 and 28.6MPa, respectively.
Nonastructured Al2O3-13wt%TiO2 (AT13) coatings were deposited by multi-function
micro-plasma spray and Metco 9M plasma spray, respectively. Constituent phases and the
microstructure of the powder particles and coatings prepared were examined with the aid of scanning
electronic microscope (SEM) and X-ray diffraction (XRD). Mechanical properties including hardness
and bonding strength were also evaluated by microhardness tester and electron tensile tester.
Multi-function micro plasma sprayed nanostructured AT13 Coating is fully-melted, dense and
uniform. However, AT13 Coating deposited by Metco 9M plasma spray is partial-melted. The
microhardness of multi-functional micro plasma sprayed AT13 Coating is HV975.7~1441.7, much
higher than that of Metco 9M plasma sprayed AT13 Coating (HV655.3~946.6). The bonding strength
results present the same, increased from 19.8 MPa to 42.7 MPa.
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