An ultralow oxygen partial pressure-controlling system and its applicationto oxidation studies

An ultralow oxygen partial pressure-controlling system, based on solid-stat e electrochemical principles, has been developed This system consists of an oxygen sensor and an oxygen pump and is controlled by a PC computer. The o xygen sensor is used to measure the oxygen partial pressure in an enclosed system, while the oxygen pump is used to transport oxygen from the ambient air into the enclosed system or from the enclosed system to the ambient air . The operating conditions of this system have been studied The results sho wed that it can be used to establish a stable oxygen partial pressure in th e range of 10(-18)similar to 5 x 10(5) Pa (1 x 10(-23)similar to 5 atm) in the enclosed system. This system has been used to investigate the selective oxidation of the Cr and the oxide formation on the surface of a Ni-Cr allo y under three different low oxygen partial pressures. The oxide morphology was studied using atomic force microscopy (AFM). The results agreed well wi th those in the literature and also confirm the reliability of this system.