PROCEDE DE FABRICATION D'UN MATERIAU COMPOSITE CERAMIQUE A BASE DE NITRURE DE SILICIUM ET DE BETA-EUCRYPTITE.

摘要

The process of fabricating a sintered ceramic composite material made of silicon nitride and beta -eucryptite materials, comprises creating (101) a first mixture of silicon nitride powder in crystalline form and a powder of a first lithium aluminosilicate in crystalline form, performing (105) a first heat treatment on silicon nitride composite and the first lithium aluminosilicate obtained from the first mixture to sinter silicon nitride and to obtain a ceramic composite made of silicon nitride and beta -eucryptites, and performing a second heat treatment to crystallize the beta -eucryptites. The process of fabricating a sintered ceramic composite material made of silicon nitride and beta -eucryptite materials, comprises creating (101) a first mixture of silicon nitride powder in crystalline form and a powder of a first lithium aluminosilicate in crystalline form, performing (105) a first heat treatment on silicon nitride composite and the first lithium aluminosilicate obtained from the first mixture to sinter silicon nitride and to obtain a ceramic composite made of silicon nitride and beta -eucryptites, and performing a second heat treatment to crystallize the beta -eucryptites. The lithium aluminosilicate composition is represented as (Li 2O) x(Al 2O 3) y(SiO 2) z, where entire molar fractions (x, y, z) is different from (1, 1, 2). The first heat treatment is carried out at a first temperature greater than melting temperature of beta -eucryptite under the operating conditions. The second heat treatment is carried out by maintaining the ceramic composite and beta -eucryptite at a temperature of 500-800[deg] C, and comprises performing nucleation at a specified temperature and growth at a temperature greater than the nucleation temperature. The silicon nitride powder is washed to remove the silica polluting the powder before mixing it with the lithium aluminosilicate. The first lithium aluminosilicate powder is fabricated by producing a mixture of lithium carbonate, alumina and silica powder, and calcining a powder obtained from the mixture to obtain the first lithium aluminosilicate. The calcination step comprises raising the temperature to reach a maximum and then decreasing the temperature. The crystals of silicon nitride powder are nanometric or micrometric, and the crystals of the first lithium aluminosilicate powder are nanometric or micrometric.