| Abstrakt: |
Self-propagating high-temperature synthesis with direct passage of current through the powder mixture is characterized by various forms of reaction initiation. Taking into account the general features, three types of initiation were detected: contact, breakdown, and volume. These types operate in all the examined powder mixtures, depending on the heating conditions, the preparation quality of the components, compacting pressure, and other parameters. Contact and breakdown initiation take place in the conditions with the nonuniform electrical resistivity of the powder mixture and lead to incomplete transformation of the initial components into the final product. Volume initiation is optimum from the viewpoint of increasing the quality of synthesized compounds; in this initiation, a cavity forms inside the synthesized specimen as a result of the maximum temperature in the central part of the volume filled with the powder mixture in heating by the direct passage of electric current. |
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