Abstract
With good high temperature and corrosive resistance performance, ceramic based composites can be used as promising materials to replace metal thermocouple materials. In this study, Si3N4–MoSi2 composites were prepared via hot pressing technology. X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy (SEM) were used to analyze the microstructure of the composites. The mechanical properties and electrical conductivity were tested. The results showed that the composites were composed of β-Si3N4, MoSi2, a small amount of Mo5Si3, and an amorphous glassy phase. The MoSi2 phase was evenly distributed in the matrix. The percolation network was formed with increasing MoSi2 content. The strength of the composites reached its maximum value when the MoSi2 content reached a critical point. The electrical conductivity behaved like a typical percolation phenomenon. The percolation threshold was about 30% to 45%.
Highlights
The thermocouple is the most widely used temperature testing device in many industrial areas [1,2,3]
With increasing requirements from metallurgy, chemical, and aerospace engineering, the stable properties of thermocouple materials, which can be used in high temperature and corrosive environments, is still a big challenge in materials science, especially when they are used in molten salt electrolysis as the temperature testing device
As demonstrated in this figure, the composites after hot compressing were mainly composed of the β-Si3 N4 and MoSi2 phase
Summary
The thermocouple is the most widely used temperature testing device in many industrial areas [1,2,3]. A traditional metallic thermocouple is not able to satisfy the requirements when they are exposed to the above-mentioned working environments Based on this condition, ceramic based composites, which have good high temperature and corrosive resistance performance, have been used as candidate materials to replace metallic thermocouple materials [9,10,11,12,13]. Previous studies have demonstrated that Si3 N4 –MoSi2 composites have good mechanical, anti-oxidation, and corrosive resistance performances [14,15,16,17,18] As a result, they are able to be used as candidate materials to fabricate thermocouple electrode materials. Materials 2018, 11, 986 tested and analyzed to shed light on their potential application as new high temperature and corrosive resistance thermocouple materials
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