This paper describes how effective medium theory and fractal analysis are used to investigate nonlinear microstructure-property relationships in HVOF-sprayed composite coatings produced from nano Fe-(β-SiC/SiO 2 ) agglomerate powders in order to optimize microwave absorption performance. The powder used in the study was prepared by spray granulation and deposited on Fe substrates. The microstructure of the powder and coatings was examined by SEM, the phase structure was determined by XRD analysis, and electrical permittivity and permeability were measured. To simplify calculations, electromagnetic absorption phases in the coating were assumed to be periodically distributed cubes. The results of the study indicate that multi-fractal diffraction in the coating microstructure facilitates the absorption of microwaves and is optimized when the mass fraction of nano βSiC in the composite is 28 wt%.

The fracture behavior of polymer coatings fabricated by low temperature high velocity air fuel (LTHVAF) spray was investigated. It was shown that the coatings were dense and had a mean bonding strength of 13.5 MPa. During the tensile stress process, the fracture occurred in the interior of the coatings, which indicates that the cohesive strength within coatings is less than the bonding strength between the coatings and substrate. A significant amount of crazing and honeycombed holes existed in the fracture surface. Under a tensile stress, cracks initiated at porous defects in the coatings. Dispersed particles interrupted the crack expansion, and caused a change in direction of crack propagation.