False-colour scanning electron micrograph (SEM) of the ceramic material silicon nitride,which is one of the so- called "engineering ceramics" used in applications such as novel types of car engines. The unusual appearance of this SEM is due to the use of back- scattered electrons,instead of the usual secondary electrons,to produce the image. These electrons are primary electrons reflected off the specimen,& they can be used to identify a material's constituents. In this micrograph,the white needles are yttrium- silicon oxides,the black needles are the mineral cristobalite,& the dark grey areas are non- crystalline,glassy phases. Magnification: x75 at 35mm size. Gold tint. Original is BW A800/006. Ref: MICROCOSMOS,fig. 8.15,p. 157 |