REINFORCEMENT MECHANISMS IN ALUMINA TOUGHENED ZIRCONIA NANOCOMPOSITES WITH DIFFERENT STABILIZING AGENTS

摘要

A colloidal processing route has been applied to obtain ATZ nanocomposites in order to develop strong and tough materials for structural applications. An initial composition of 35 vol% of Al_2O_3 as the disperse phase and two different stabilizing agents for ZrO_2 as the matrix, Y_2O_3 (3 mol %) and CeO_2 (10 and 12 mol %), is proposed. The Y_2O_3-stabilized nanocomposite has obtained a fracture toughness of 4.5 MPa√m and a strength of 685 MPa, clearly insufficient for high-demanding structural applications. The CeO_2-stabilized nanocomposite, specifically the 10 % mol Ce-TZP/Al_2O_3, has reported a fracture toughness that exceeds all the values obtained up to date in monolithic ceramics and in ATZ composites. The critical fracture toughness (K_(IC)), measured under the presence of a long natural crack (13 MPa·√m), and the stress intensity threshold factor (K_(IO) ≈ 7.5 MPa·√m) ensures a safety work under the occurrence of flaws in a structural component submitted to important static loads. The major contributing factor to this behaviour is the transformation toughening that operates in the vicinity of the defect. The strength value is not indicated for high load bearing applications (627 MPa) but there are wide possibilities of improvement through changes in the processing conditions that tend to strengthen this nanocomposite.