A new high-temperature continuous furnace offers extremely low oxygen partial pressures without the need for vacuum pumps or a hydrogen atmosphere.
Vacuum furnaces currently are widely used to process materials where conditions of low oxygen partial pressure and high temperature are required. In these furnaces, a vacuum pump system is used to remove the atmosphere (air) and to achieve oxygen partial pressures in the closed chamber in the range of 10-4 to 10-6 atmospheres. Metal oxides decompose under conditions of high temperature and low oxygen partial pressure to isolate oxygen, thus forming solid or liquid metal. Oxygen partial pressure is constant and fixed when metal and oxide exist together at a specific temperature, as shown in a diagram of standard free energy of metal oxide formation (Fig.1). Metal-oxide dissociation also occurs in an inert atmosphere having a very low oxygen partial pressure. Thus, commonly used refractory insulating materials, such as silica and alumina brick, also will dissociate when exposed to such an atmosphere. This precludes the use of refractory oxide materials as insulating materials in a furnace designed to achieve low oxygen partial pressures at high temperatures.