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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. [ABSTRACT FROM AUTHOR]

The synthesis of an intermetallic compound from a powder mixture of Ni + Al + Al2O3 with an inner metal plate oriented in the direction of combustion wave propagation has been studied by experiments and theoretical calculations as applied to the problem of self-propagating high-temperature synthesis of functionally graded materials. Copper, titanium, and steel plates are considered. The propagation of the exothermic reaction front is analyzed for various thermophysical characteristics of the inner metal layer. In samples with a copper plate, the combustion front near the contact boundary is extended in the direction of the combustion wave. An increase in the average burning rate of the sample with the heat recovery effect is observed when using copper plates 1–3 mm thick. During combustion of samples with titanium and steel plates, there is a deceleration of combustion wave propagation along the contact boundary. [ABSTRACT FROM AUTHOR]

This study is devoted to the technology of producing cermet coatings using self-propagating high-temperature synthesis (SHS). The importance of the study is related to the universal usage of flat electric heaters and protective coatings intended for various purposes. A technique is proposed to obtain electrically conductive coatings by the SHS in powdered Ni + Al and Ti + Al + C mixtures. Specific features of the evolution of the autowave SHS in these mixtures are investigated. The mixture is deposited on a ceramic base as a layer of a suspension in isopropyl alcohol (0.2–2.0) × 10–3 m in thickness using a stencil. The effect of the thickness of the powdered mixture layer on the velocity of front propagation and maximum temperature is studied. These parameters are shown to naturally increase with an increase in thickness. The coating based on the Ni + Al mixture is found to consist of NiAl and Ni3Al intermetallic compounds, while that based on Ti + Al + C is found to consist of TiC and MAX phases of Ti2AlC and Ti3AlC2. The coating based on intermetallic compounds consists of rounded particles that are fused together and contains NiAl and Ni3Al phases. The coatings obtained from the Ti + Al + C mixture contain needle-shaped crystals of MAX phases and interspersed rounded particles of titanium carbide. The content of the NiAl and Ti2ALC target phases increases with the increasing layer thickness. Coatings based on NiAl, Ni3Al, and Ti2AlC, Ti3AlC2 heat-resistant phases (0.2–1.2) × 10–3 m in thickness with a specific electrical resistance of 0.1–0.6 μOhm m are obtained. [ABSTRACT FROM AUTHOR]

SHS-produced TiC–Al2O3 powders were used as a filler of organosilicon polymers and ethoxyline resin to prepare electroconducting polymeric compounds. The electrical conductivity of thus prepared polymeric compounds was found to depend on the amount of added ceramic powder, temperature, and type of polymer binder. A threshold effect observed for the temperature dependence of compound resistance can be used in designing temperature sensors and temperature/current-limiting devices. Our polymeric compounds can also be recommended as a material for film heaters with a working temperature of below 300°С. [ABSTRACT FROM AUTHOR]