| Popis: |
The phase formation processes and the main properties of samples from zirconia-alumina ramming mix on a phosphate bond, thermal-treated in the temperature range 200—2100 °C, have been studied. It was found that, the most complete interaction of P2O5 with cubic ZrO2 occurs in the temperature range 1200—1400 °C. This manifests itself in a significant destabilization of the cubic ZrO2 phase (the amount of which varies from 70 to 35 %) and is accompanied by a drop in the samples strength (cold crushing strength varies from 62—72 to 35—44 N/mm2), which remains sufficient to maintain the structural strength of lining. The destabilization process of the ZrO2 cubic phase ends at a temperature of 1700 °C. An increase in the thermal treatment temperature of the samples from 1700 to 2000 °C causes the decomposition of aluminium, calcium and zirconium phosphates and leads to the re-stabilization of ZrО2. These processes contribute to compaction (apparent density increases from 4.28 to 4.30 g/cm3) and hardening of the samples structure (cold crushing strength increases from 72 to 95 N/mm2). A further increase in temperature from 2000 to 2100 °C leads to some melting of the sample surface due to the melting of corundum at a temperature of 2050—2070 °C. It has been established that, in the phase formation process in the temperature range 200—2000 °C the strength of lining made of zirconia-alumina ramming mix is sufficiently high to ensure its structural strength during service. In connection with the above, the maximum service temperature of the lining made of the developed zirconia-alumina ramming mix should not exceed 2000 °C. The results of the carried out studies were used in the development of a new type of product — zirconia-alumina ramming mix on a phosphate bond, intended for making a working lining layer at the border of combustion chambers and mixing industrial reactors for carbon black production. |
