Influence of process parameters on synthesis of(Ca,Mg)α′-Sialon-AlN-BN powders from boron-rich slag by carbothermal reduction-nitridation

With boron-rich slag,silica fume,bauxite chalmette and carbon black as starting materials,(Ca,Mg)α′-Sialon-AlN-BN powders were synthesized by carbothermal reduction-nitridation(CRN).Phase composition and microstructure of reaction products were determined by X-ray diffraction(XRD),scanning electron microscope(SEM) and energy dispersive X-ray(EDX).The influence of synthesis temperature and holding time on synthesis was studied and synthesis mechanism was discussed in detail.The results show that synthesis temperature affects the formation of(Ca,Mg)α′-Sialon-AlN-BN significantly.Content of-Sialon in the products increases with the increase of synthesis temperature and reaches the maximum at 1480℃,which is assumed to be the best synthesis temperature.Holding time affect the phase composition significantly either.If the holding time is less than 4h,the composition of the product contain much more intermediate product,while expanding holding time can make the reaction more sufficiently.Content of α′-Sialon in the samples reaches the maximum at 8h,which is the suitable holding time for the reaction.Volatilization of SiO results in great mass loss of the samples and increases with synthesis temperature increasing and holding time expending.