METHOD TO PRODUCE STRUCTURAL ALUMINA CERAMICS Russian patent published in 2012 - IPC C04B35/111 C04B35/626 C01F7/42 

FIELD: construction.

SUBSTANCE: to manufacture structural alumina ceramics, the initial alloy of aluminium with silicon (10-14 wt %) is treated with an aqueous solution of caustic soda with concentration of 5-27% with heat recovery from the reaction volume by a coolant with the temperature of 15-25°C. Then the aluminium hydroxide residue is released from the mother solution with inclusions of sodium methyl silicate, its washing is carried out to the value of the medium pH of 8-9. The residue is dried, thermally treated on air at the temperature of 1280-1350°C for 1-3 hours, the produced cake is ground, and the charge is prepared. Items are pressed under the pressure of 150-200 MPa and are baked on air at the temperature of 1450-1500°C for 1-2 hours. The phase composition of ceramics is represented by α-Al₂O₃ (73-77 vol.%) and NaAlSiO₄ (23-27 vol.%). It is characterised with availability of closed porosity (24%), its density - 2.9-3.0 g/cm³. The strength at impact bending is 3.5·10³-4.5·10³ J/m, the relative loss of bending strength after a heat cycle (in the mode of 1200°C - air) - 10-20%.

EFFECT: increased heat resistance of ceramics and its impact strength, reduced temperature of its baking.

7 cl, 3 ex, 1 tbl