Challenges Upon Reactive Plasma Spray Nitriding: Al Powders and Fabrication of AlN Coatings as a Case Study

Design and optical study of a microwave plasma torch in nitrogen used for the evaporation of aluminium wires

“…The Al wire melts in the nitrogen discharge and an AlN layer is formed on the wire surface, similar to the appearance of an AlN layer around Al particles that are fed into a discharge in the plasma spraying technique or similar to the growth of AlN crystals on an Al ingot under the influence of heat from an electric arc . The high thermal conductivity of AlN supports further heating of the Al core and evaporation via pores in the layer.…”

“… AlN powder can be produced from Al powder through a thermal inductively coupled radio frequency (RF) torch . This technology was further developed to the reactive plasma spraying method for the fabrication of AlN coatings, as recently reviewed by Shahien et al Another promising way of AlN production is the electric explosion of wires, which is based on the use of two current pulses . The first one leads to the heating of the wire causing its explosion, while the second provides a plasma in the volume of the explosion products.…”

“…In the past, the general approaches for the production of AlN have been intensively studied. These works have been stimulated by the attractive properties of AlN, for example, its high thermal conductivity, thermal and chemical stability, low thermal expansion coefficient, low dielectric constant, good mechanical strength, wide bandgap, and non‐toxicity. The main disadvantages of traditional thermal synthesis methods are the long processing times, high impurity levels of O and C in the final material, and the lack of crucible materials with long‐term stability.…”