In Situ Thermocouples in Macro-Components Fabricated Using SALD and SALDVI Techniques. III. Fabrication and Properties of the SiC/C Thermocouple Device

Fabrication of a SiC/C thermocouple embedded in an arbitrarily-shaped SiC macro-component has been demonstrated using an integrated Selective Area Laser Deposition (SALD) with the closely related Selective Area Laser Deposition Vapor Infiltration (SALDVI) process. SALD is used to make the embedded thermocouple devices in situ and SALDVI to fabricate the macro-components. The thermocouple elements, silicon carbide and carbon lines, and the electrical insulation layer, Si₃N₄, have been deposited from tetramethylsilane (TMS), acetylene, and a gas mixture of TMS and ammonia, respectively. It is found that the fabricated in situ thermocouples respond sensitively to temperature variation. Furthermore, the electric signal of the embedded thermocouple is very stable and reproducible in response to thermal cycling. This is not the case when the thermocouple is not embedded in the SiC matrix because of the oxidation of the thermocouple elements.