The relationship between the resistivity of silicon carbide tubes and temperature and its aging mechanism.

As a high-temperature heating element, the resistance characteristics of silicon carbide tubes (SiCTUs) are closely related to temperature changes. Between room temperature and 850°C, the resistance decreases with increasing temperature due to the enhanced carrier mobility within the material at high temperatures. Above 850°C, the resistance begins to rise again; this turning point is related to the carrier scattering effect caused by intensified lattice vibrations within the material. This nonlinear variation dictates that the heating rate of SiCTUs must be strictly controlled during operation to avoid drastic resistance fluctuations caused by sudden temperature changes, which could affect equipment stability.

The aging mechanism mainly stems from three factors. Prolonged high-temperature use promotes the formation of a silicon oxide protective layer on the SiCTU surface, which, while delaying further oxidation, leads to a slow increase in resistance. Chemical corrosion is another key factor; in the presence of water vapor or alkaline substances, temperatures above 900°C accelerate material corrosion, causing abnormally high resistance. Furthermore, repeated thermal cycling induces microcrack propagation, ultimately leading to irreversible changes in resistance. These aging processes significantly shorten the lifespan of the element and may cause equipment failure.

To slow down aging, attention must be paid to environmental control. Avoid operating the silicon carbide tube in direct contact with carbonaceous materials; it is recommended to use an airtight corundum inner tube to isolate corrosive gases. In power equipment applications, the operating temperature should not exceed 1400℃, as even short periods of high temperature will significantly shorten its service life. Regularly monitoring resistance changes can predict the degree of component aging in advance, allowing for timely replacement to ensure safe equipment operation. Through proper use and maintenance, the service life of silicon carbide tubes can be effectively extended.