Phase evolution of matrix of C/SiCN composite during creep testing at 1300 oC

Tensile creep behavior of carbon fiber-reinforced SiCN matrix composite (C/SiCN) was investigated at 1300°C under vacuum and 45MPa for 30h. As-received and 1700°C-heat treated samples were prepared. Phase evolution and microstructure of C/SiCN was examined by virtue of X-ray diffraction, scanning electron microscope and high resolution transmission electron microscopy. It was found that crystallization happened in the as-received C/SiCN after 1300°C creep tested for 1h, though many researches indicate that the crystallization of amorphous SiCN occur above 1400°C heat treated. The matrix of as-received C/SiCN partly transformed from amorphous to β-SiC firstly and then α-SiC in the temperature range from 0h to 15h. The intensity of diffraction peaks had no significant changefrom 15h to 30h.The results revealed the applied stress promotes the occurrence of crystallization in as received C/SiCN. But the 1700°C-heat treated specimen showed little change of XRD patterns after creep testing.