Synthesis of ZrN-sialon composites from zircon and alumina by carbothermal reduction-nitridation

摘要

ZrN-sialon composites were synthesized from zircon and γ-Al_2O_3 via carbothermal reduction-nitridation. The effects of reaction temperature on the phase compositions and product morphologies were studied. The equilibrium relationship curves of the condensed phases were drawn and the temperature dependence of the phase stability was investigated. The results show that products with different phase compositions and morphologies can be obtained at different temperatures. The optimum temperature for acquiring ZrN-sialon composites was 1550 ℃ Granular ZrN and short prismatic (3-sialon (Si_3Al_3O_3N_5) were formed at 1500 ℃, accompanied by surplus Al_2O_3 and ZrO_2. The dominant products at 1550 C were ZrN and Si_3Al_3O_3N_5, whereas they were ZrN and 15R-SiAl_4O_2N_4 at 1600 ℃. β-sialon had perfect crystals with a long-column morphology, whereas 15R-SiAl_4O_2NN was plate-like.