Abstract:
An attempt has been made to study the significance of water vapour in the conversion of a-Fe203 (hematite) to pure phase 7-Fe2O3 (maghemite or 7-hematite) which represents the information carrier for magnetic tape recording. A gas mixture of 10 v/o carbon monoxide and 90 v/o nitrogen instead of con-ventional hydrogen/nitrogen gas mixture was used as a reducing agent for a-Fe2 03 to Fe304 (magnetite). Subsequently Fe304 was oxidized by dry air to produce 7-Fe203. Air oxidation of freshly reduced active magnetite forms pure phase 7-Fe2O3 while that of altered magnetite (which was exposed to atmospheric conditions and has developed a -Fe„ 03 nuclei on its surface) results in the for-mation of a mixture of a- and 7-Fe2 03. In the presence of water forming reducing gases, 7-Fe2O3 was obtained at switching temperatures (i.e. changing over from reducing to oxidizing atmosphere) of 190-280°, whereas in the absence of water a smaller temperature range of 240-80° was found. The results suggest that the presence of water vapour is not a necessary condition in the production of 7-Fe2 O3 .
Page(s):
13-15
DOI:
DOI not available
Published:
Journal: Pakistan Journal of Scientific and Industrial Research, Volume: 22, Issue: 1--2, Year: 1979