Preparation and experimental characterization of glass–alumina functionally graded materials

This work aims at investigating the effects of the processing conditions on the final microstructure of glass–alumina functionally graded materials (FGMs). The ingredient materials, i.e. a polycrystalline sintered alumina and a CaO–ZrO2–SiO2 glass, were accurately characterized, since their mechanical and thermal properties may deeply influence the fabricating process and the overall FGM behaviour. The functionally graded materials were obtained by means of percolation of the molten glass into the alumina substrate. Two types of samples were considered—the “Bulk” FGMs, produced starting from a glass bulk, and the “Powder” FGMs, produced starting from a glass powder; in both cases four different heating cycles were attempted. The functionally graded materials were analysed using a SEM-EDS and a X-ray diffractometer. Great attention was devoted to the resulting microstructure; moreover the depth of penetration was measured and related to the fabricating parameters, such as time and temperature.