Powder Treatment for Increased Thickness of Iron Coatings Produced by the Powder Aerosol Deposition Method and Formation of Iron–Alumina Multilayer Structures

The powder aerosol deposition (PAD) method is a well-known process to fabricate dense layers at room temperature directly from the powder. It is particularly suitable for the deposition of ceramic materials. Compared to these, the use of metal powders (here iron), which are significantly more ductile and have a higher density than typical ceramic powders, has not yet been investigated in detail for PAD. In the first step of this work, the iron powder is characterized by scanning electron microscopy and x-ray diffraction. In order to improve the deposition behavior, the influence of heat treatment on the crystallite and the particle size of the iron powder is investigated. It is shown that the crystallite size of iron powders is reduced down to a nanocrystalline size during deposition. The magnetic properties of the iron powder as well as the layers are investigated by means of coercive field development. Although the initial coercivity raises after deposition, potential applications for flux guiding in microelectronic sensors and devices are feasible. In the second step, thin metal layers (iron) and ceramics (aluminum oxide) are deposited alternatingly to produce iron–alumina multilayer structures.