Boron nitride nanosheets as an effective strategy against the slow crack growth and hydrothermal ageing in zirconia composites

Abstract

[EN]This paper explores the effectiveness of boron nitride nanosheets in preventing the premature failure of yttria-stabilized tetragonal zirconia ceramics, particularly in humid environments. A simple, low-cost and scalable technique -shear exfoliation in a kitchen blender- was used to prepare BNNS, and pure zirconia and composites with 1, 2.5 and 5 vol. % BNNS were spark plasma sintered. Accelerated hydrothermal ageing experiments in autoclave revealed a remarkable improvement of low temperature degradation resistance in all the composites. Fracture toughness and slow crack growth of the composites with 1 and 2.5 vol. % BNNS were evaluated by bending tests performed in notched specimens. Although the composites presented fracture toughness values similar to those of the reference zirconia, an increase of ∼18 % on crack-tip toughness was achieved. Similar R-curves evaluated in air and in oil-impregnated 2.5 vol. % BNNS composites revealed a limitation of stress-assisted corrosion by water in zirconia, thanks to the BNNS incorporation.