Design of Grain Composition of Conductive Cluster of Multicomponent Composite and Mechanism for Monitoring Morphology of its Microstructure
Abstract:
Modern technology requires miniaturization of the main equipment, and puts high demands on their reliability. When creating resistive materials for absorbers or heaters, technical powders are used, which have in their composition crystallites that differ in size from a fraction of micrometers to tens of microns. The purpose of this work was to investigate the relationship between the surface temperature under the influence of current flow on layered multicomponent materials. Laminated multicomponent composites with silicon nitride base and size-calibrated tantalum nitride powders were used as samples. The resistance was measured on direct current by bridge and voltmeter-ammeter method under control of the surface temperature by a contact thermocouple placed at the same thickness from the heating cluster. The electric field strength, and the current density which that promotes the heating of the material, both are also a nonlinear function of the grain composition of the conductive cluster. If the square of current density through the sample is a structure-sensitive parameter for a fine-grained structure, the square of electric field strength shows greater sensitivity in the case of predominance of the coarse microstructure. An empirical formula is proposed that relates the concentration of the coarse fraction (>30 μm) in percent with the electric current density j (in A/mm2), or the electric field strength E (in V/cm), at which the surface temperature of 800K is reached (the beginning of the visible dark red glow of incandescent bodies). It was established that the critical change in the concentration of the coarse fraction, at which the specified color temperature is observed, is 30% .
