Polymer-network hydrogel facilitated synthesis of Ca-α-SiAlON balls composed of nanoparticles

In this work, preparation of Ca-α-SiAlON balls composed of nanoparticles with the stoichiometric composition of Ca1Si9Al3O1N15 was successfully developed through a hydrogel route. A polyacrylamide gel embedding nano-silica and dispersed Al3+ and Ca2+ ions was first dried then calcined under N2 flow up to 1450 °C for 1 h. Ca-α-SiAlON was formed owing to carbothermal reduction and nitridation (CRN) process, with the polymer acting as carbon source. Due to homogeneity of mixture constituents at molecular level, the soaking time of optimal synthesis condition was reduced to 1 h. In addition, FE-SEM investigation of the resultant powder showed that ball-shaped Ca-α-SiAlON was obtained at 1450 °C after 1 h. It was found that nanoparticles were formed on the surface of the balls after CRN process. Moreover, the ball-milled nanopowder was sintered under N2 atmosphere by pressureless sintering (PLS). This nitride ceramic exhibits high Vickers hardness (13.5 GPa), proper fracture toughness (4.82 MPa m1/2) and a very low specific wear rate (2.49▒×▒10−4 mm3 N−1 m−1) at a contact stress of 5 MPa. All These findings imply that Ca-α-SiAlON ceramics are promising candidate for tribological applications.