A Novel Trend In Producing Ceramic Based Nanocomposite Material using α- Al2o3 Powder and FeCl2 Solution as Starting Materials

In recent years, it has been established that the incorporation of nano metallic particles into a ceramic matrix lead to enhanced fracture properties. Alumina-iron nanocomposite powders are prepared by a two-step process. In the first step, a-alumina-ferrous chloride powder mixture was formed by mixing a-alumina powders with ferrous chloride solution followed by drying in an oven at 60 °C for 24 h. In the second step, the ferrous chloride in the dry power mixture was selectively reduced to iron particles. A reduction temperature of 750 °C for 15 min in dry H2 was chosen based on the thermodynamic calculations The concentration of iron in ferrous chloride solution was calculated to give 20 vol.% Fe in the final composite product. Two techniques were used to produce composite bulk materials. The alumina-iron nanocomposite powders were divided to two batches. The first batch of the produced mixture was hot pressed at 1400 °C and 27 MPa for 30 min in a graphite die. To study the effect of oxygen on the Al2O3/Fe interface bonding and mechanical properties of the composite, the second batch was heat treated in air at 700 °C for 20 min to partially oxidize the iron particles before hot pressing Characterization of the composites was undertaken by conventional density measurements, X-ray diffractometry (XRD), Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA). The mechanical properties of the produced composites are also investigated. The suggested processing route (mixing, reduction and hot pressing) produces ceramic-metal nanocomposite much tougher than the virgin alumina. The fracture strength of the produced Al2O3/Fe nanocomposite is nearly twice that of the pure alumina. The presence of spinal phase, FeAlO4 as thick layer around the iron particles in the alumina matrix has a detrimental effect on interfacial bonding between iron and alumina and the fracture properties of the composite.