Microstructure and mechanical properties of fine grained carbon-bonded Al2O3–C materials

Fine grained carbon-bonded Al2O3–C materials as used in ceramic filters have been manufactured by uniaxial and isostatic pressing, respectively. The variation in the microstructure over the cross section of the samples which in particular depends on the shaping technique plays an important role in the wetting of the material by liquid steel. Moreover, the amount and grain size of the binder has a decisive influence on the porosity and bulk density and therefore on the mechanical properties. For this, two different grain size distributions of Carbores® P binder were used, and in addition the fraction of binder was varied from 5–30 wt%. Tests of the cold crushing strength and of the cold modulus of rupture were performed at room temperature. The adjusted bulk density, open porosity and shrinkage of the samples were determined and the microstructure was analyzed by means of scanning electron microscopy. For control of a homogeneous distribution of carbon in the samples, the residual carbon content was measured also within individual samples at different positions.