Al(2)O3-Si3N4w COMPOSITES

The study is concerned with the modification of the properties of Al2O3, in particular aimed at improving the fracture toughness of this material, by introducing ceramic whiskers of the silicon nitride (a-Si3N4) into its matrix. The technological operations involved in the production of the Al2O3+ x% wt. Si3N4w (x = 1, 2, 3, 4, 5) composite are: mixing the starting powders, drying the mixture, granulating, uniaxial pressing at p = 20 MPa, isostatic compacting at p = 120 MPa, and hot pressing sintering in T = 1450 degrees C, p = 35 MPa for 1 h in argon. The physical properties of the Al2O3+ x% wt. Si3N4w composites thus produced, such as the density, porosity and absorptivity were determined using the hydrostatic method (Fig. 4). The phases in the Al2O3+ 5% Si(3)N(4)w were identified. Investigation of the strength properties of the composite, such as the hardness (HV1) and fracture toughness (Vickers method) was also carried out. The Al2O3+ x% wt. Si(3)N(4)w (x = 1, 2, 3, 4, 5) composites hot-pressed under a pressure of 35 MPa show high hardness of 20 GPa (for Al2O3+ 5% wt. Si3N4w) and critical value of stress intensity factor K-IC of 4,54 MPa center dot m(1/2) (for Al2O3+ 5% wt. Si3N4w). The critical value of the stress intensity factor measured in the Al2O3+ x% wt. Si3N4w (x = 1, 2, 3, 4, 5) composites can be attributed to the presence of the whiskers Si3N4 (crack deviation and bridging).