Abstract: C-B4C-SiC composites with silicon additive obtained by the hot press sintering method are studied by means of transmission electron microscopy(TEM).When the specimens are heated to 1800℃,their structure does not change.When the specimens are heated to 2000℃,carbon begins to graphitize. Moreover,two monoclinic phases are observed.One monoclinic phase named as the M phase belongs to C-center monoclinic lattice with a=0.90nm,b=0.59nm,c=0.54nm and β=119.3°.The other monoclinic phase named as the Ml phase also belongs to C-center monoclinic lattice but with a=0.85nm,b=0.49nm,c=0.53nm and β=123.6°.

Key words: C-B_4C-SiC composite, electron microscopy