The influence of a dc electric field on chemical interactions in “peroxide-metal” systems during combustion processes

Abstract

The influence of a dc-contactless electric field on the combustion of BaO 2 -Fe and MnO 2 -Fe systems was investigated. The degree of phase transformation during combustion was directly influenced by the external electric field. The mechanism of combustion in these systems, containing metal fuel and solid inner-reaction oxidizer, under conditions of an external electric field, are described. It was concluded that the field-promoted transport of active oxygen anions formed in the liquid phase of the heat-up zone of these combustion systems.Alkaline and alkaline-earth metal peroxides have been successfully used in the combustion synthesis of complex oxide materials. [1][2][3][4] Metal peroxides are used for two purposes; firstly, for the maintenance of the combustion reaction due to oxygen release as a result of their decomposition, and secondly, to introduce the required chemical element into the crystal structure. At present, in the conventional synthesis of complex oxides, such reagents as oxides, carbonates or nitrites of barium and iron are used. Substitution of these components in the combustion reaction, for example BaO 2 for BaCO 3 , allows an improvement in the ''know-how'' of powder production. It takes place due to the introduction of an additional inner-reaction source of oxygen. Also it enables the avoidance of nitrogen-and carbon-containing impurities in the synthesized products.The combustion synthesis of barium hexaferrite under conditions of a dc electric field has been previously reported. 5 In this system, one of the green mixture components was barium peroxide. An external electric field (EEF) in a combustion process is the application of an external voltage across the system without inducing any direct heating effect. It has been shown [5][6][7] that the application of an EEF, E, during the combustion synthesis of ferrites leads to changes in the combustion process characteristics and product microstructure. This allows modification of the final product properties. It was also found that depending on the EEF intensity, crystalline materials with phase ratios corresponding to the primary desired ferritization product could be obtained. At ''low'' field values (starting from ZF), the main phase was BaFe 12 O 19 up to E = 110 kV m À1 , whilst at larger fields, the Fe 2 O 3 component was more prominent. 5 However, in these systems,