High-temperature oxidation of ZrB sub(2)-SiC and ZrB sub(2)-SiC-ZrSi sub(2) ceramics up to 1700 degree C in air

The high-temperature oxidation of ZrB sub(2)-SiC and ZrB sub(2)-SiC-ZrSi sub(2) ceramics up to 1700 degree C in air has shown their high corrosion resistance. A five-stage nonisothermal oxidation mechanism is established for the samples when heated at a rate of 20 degree C/min: 1) oxygen adsorption-desorption; 2) formation of ZrO sub(2) and B sub(2)O sub(3) oxides; 3) formation of alpha -SiO sub(2) cristobalite and ZrSiO sub(4) zircon; 4) formation of amorphous SiO sub(2); and 5) formation of upper protective borosilicate film with ZrSiO sub(4) inclusions at less than 40 wt.% SiC. It is shown that small ZrSi sub(2) admixtures (