Ceramic of ZrB2 and its composite of the ceramics with SiC are used for ultrahigh temperature protection coatings in re-entry space vehicles because of high melting temperature of ZrB2 (3245°C). Chemical composition and microstructure of the ceramics are critical to thennal shock properties of the ceramics. Especially oxidation of boron and formation of boron oxide will degrade property of thermal resistance. Conventional TEM with Energy dispersive X-ray spectroscopy (EDS) is unable to study light elements like boron. However, parallel-recorded electron energy-loss spectroscopy (EELS) and energy-filtering GIF system associated with field-emission gun (FEG) TEM are able to carry out chemical imaging and chemical information of light elements. Bonding structure and oxidation states of an element (such as B) can be obtained by using EELS.
Figure A is a zero-loss bright-field TEM image showing an interface between ZrB2 and SiC. Figure B is a Plasmon-loss filtered TEM image of the same area. A plasmon peak at about 20 eV was used for this image.