Effect of silver nanoparticles on the microstructure and mechanical properties of alumina ceramics

In this work, the effect of additions of silver nanoparticles on the microstructure and mechanical properties of alumina-based ceramic was studied. The processing method for the manufacturing of alumina/silver composites imply high energy mechanical milling in a planetary type mill, cold uniaxial compaction and pressureless sintering in an inert atmosphere at 1500 degrees C for 2 h. From the results after the milling step, approximately 45% of the powders have a particle size less than 1 mu m. The microstructure observed by SEM is very fine and homogenous; the presence of silver apparently inhibits the grain growth of the alumina. With respect to mechanical properties, increases of the silver content in the matrix causes decrease of Young's modulus and flexural strength of the composite obtained in 1.5 and 4.6%, respectively. On the other hand, the presence of silver greatly enhances the fracture toughness of alumina, from an increase of 4.2 MPa m(-0.5) for monolithic alumina to 10 MPa m(-0.5) for alumina with silver additions of 2 wt%, representing an improvement of 138% in toughness of alumina. Lastly, hardness for this same sample was incremented in 12%.