Mechanism of oxidation/deoxidation of liquid silicon: theoretical analysisand interpretation of experimental surface tension data

A theoretical analysis of the behaviour of molten metals in the presence of oxygen is presented. A generalised Wagner approach has been adopted for mo lten metals, forming volatile oxides (Si, Sn, Al, etc.), in which the descr iption of oxygen transfer from the gas phase to the condensed phase must ac count for the double contribution of molecular oxygen and oxygen linked as oxide, which leads to define the concert of 'oxygen effective pressure'. Fr om the analysis of the system at varying operating conditions, it was possi ble to relate the gas-phase composition at the surface, which is hardly mea surable, to the composition in the feed or at the outlet. The application o f this theory to the molten silicon-oxygen system is presented and the effe ctiveness of such a theory as a supporting tool for experimental work of ca pillary phenomena and crystal growth processes is discussed and verified. ( C) 2000 Elsevier Science B.V. All rights reserved.