Preparation and Properties of a Flexible Al2O3/Al/Al2O3 Composite4

A flexible Al2O3/Al/Al2O3 sandwich composite was prepared by microarc oxidation (MAO) on an aluminum foil with 50 mu m thickness. The obtained ceramic layers with a thickness of 20-22 mu m on the surface of the aluminum foil are mainly Al2O3. The composite, with exterior layers of Al2O3, can be bent more than 90 degrees without observable fracture or delamination. The morphology of the MAO coatings, which has been characterized by scanning electronic microscopy (SEM), is porous and contains microcracks. The energy-dispersive spectrum (EDS) and the X-ray diffraction (XRD) results indicate that the MAO coatings mainly contain gamma-Al2O3. Based on experimental observations, the flexibility mechanism was explained by the presence of the microcracks which improve the toughness and decrease the stiffness of the MAO coatings. The well-adhered layers of the sandwich structure can also prevent the fracture of the MAO coating. The thermal diffusivity of the composite is between that of aluminum and Al2O3 and the specific electrical resistance is 45.4% of that of Al2O3 under 50 V. This composite has the potential to be applied as tailorable low-voltage insulation material.