Sintering Furnaces

High Temperature Vacuum Furnace

After the Second World War, there were rapid advances in the commercialization of advanced technologies. Before that, widespread use of high temperature furnaces approaching and exceeding 2000° C was limited to a few applications such as graphitization and abrasive manufacture. To a large extent, early high temperature furnaces were made with available alumina silicate refractories. These were initially bricks and refractory mortar, and more recently fibrous refractory board of similar compositions. Variations of these oxide ceramics had been used since ancient times and are the foundation of ceramic technology.

With a few notable exceptions (such as the toxic beryllium oxide and the radioactive thorium oxide), commonly available oxide ceramics have melting points below 2000° C, making them unsuitable for structural applications at these temperatures. Modern extreme high temperature furnaces are contructed of either graphite, tungsten, or molybdenum. Fifty years ago tantalum was more widely used in high temperature furnaces, due to its high ductility and ease of forming. Today it is seldom used, other than for tantalum-processing applications, because of its high cost and reaction with nitrogen and hydrogen atmospheres.