Self-Propagating High Temperature Synthesis in Two-Layer (Ni + Al)/(PbO2 + B + Al2O3 + Glass) Powder Mixtures

Abstract

The widespread use of flat electric heaters in equipment and household appliances requires the search for simpler and cheaper technologies for their production. This paper proposes a method for producing an electrically conductive coating (NiAl) and an electrically insulating layer (glass ceramics) in one stage: self-propagating high-temperature synthesis in a thermally coupled (Ni + Al)/(PbO₂ + B + Al₂O₃ + glass) powder mixture. The combustion wave front propagation process is investigated, and the effect of layer thickness along with the ratio of the PbO₂ + B + Al₂O₃ + glass powder mixture components on the wave front propagation velocity and the wave front temperature is described. It is revealed that the wave front of the exothermic process expands when a PbO₂ + B mixture is added to the bottom layer. The addition of this mixture makes it possible to reduce the NiAl layer thickness and ensure the formation of a uniform dielectric coating. The phase composition and microstructure of the coating are studied. Optimal ratios are determined for layer thicknesses and the composition of the powder mixture of the layers. The fundamental possibility of forming an electrically conductive and dielectric coating by the method of self-propagating high-temperature synthesis in one stage is shown.