Effects of TiO₂ Nanoparticle Addition on Microstructure and Selected Properties of Ag-xTiO₂ Composites

The paper presents the results of a study of the microstructure and selected properties of silver-based composites reinforced with TiO₂ nanoparticles, produced by the powder metallurgy method. Pure silver powders were mixed with TiO₂ reinforcement (5 and 10 wt%) and 5 mm steel balls (100Cr6) for 270 min in a Turbula T2F mixer to produce a homogeneous mixture. The composites were made in a rigid die with a single-action compaction press under a pressure of 400 MPa and 500 MPa and then sintered under nitrogen atmosphere at 900 °C. Additionally, to improve the density and mechanical properties of the obtained sinters, double pressing and double sintering operations were conducted. As a result, compacts with a density of 90-94% were obtained. The microstructure of the sintered compacts consists of uniform grains, and the TiO₂ reinforcement phase particles are located on the grain boundaries. There were no discontinuities at the Ag-TiO₂ contact boundary, which was confirmed by SEM and TEM analysis. The use of a higher pressure had a positive effect on the hardness and flexural strength of the tested materials. It was found that the composites with 5 wt% TiO₂ pressed under 500 MPa are characterized by the highest level of mechanical properties. The hardness of these composites is 57 HB, while the flexural strength is 163 MPa.