Functionally Graded MoSi2-Al2O3 Tubes For Temperature-Sensor Applications

Thermocouple sheaths made of molydisulfide-alumina composites take on the corrosive environment in a glass melting furnace.

Platinum coatings are widely used on alumina (Al2O3) sheaths for thermocouples in the U.S. glass industry to protect the thermocouple wires and alumina sheath from corrosion and dissolution of the temperature-sensing unit. The cost associated with platinum coatings can be prohibitively high considering the steps necessary at glass plants to maintain and secure an inventory of platinum. There also is a need to improve the performance of the platinum-coated Al2O3 sheaths, because the failure rate of the thermocouples can be as high as 50%. These issues are driving the glass industry to search for alternative materials that can replace platinum and still provide the durability and performance needed to survive in an extremely corrosive glass environment.