THE CARBOTHERMAL REDUCTION PROCESS OF 2: 1 TYPE CLAY MINERALS

Abstract

The 2: 1 type clay minerals of pyrophyllite and talc were converted into nitrides by carbothermal reduction. The mixtures of the minerals and carbon black were heated at 1200-1600°C in an N₂ flow. Pyrophyllite was converted into β-sialon and α Si₃ N₄. As oxides, mullite, α-quartz, and cristobalite were detected. On the other hand, α and β-Si₃ N₄ were obtained from talc. MgSiN₂ and Si₂ N₂ O were also formed as intermediates. Forsterite and enstatite were detected as oxides. The variation in the compositions of the products suggests that both the minerals were converted into the nitrides via the decomposition to the oxides and their subsequent reduction.