Papers by Author: Rodolfo F. K. Gunnewiek

Abstract: In the present contribution, atomised Sn-3.0Ag-0.7Cu powder alloy with a size of less than 250 μm was first compacted and then microwave and conventionally sintered at 175 °C for 15 and 120 minutes, respectively. Despite the very different processing times applied, the degree of porosity was very similar, i.e., around 7%. The as-atomized microstructure of the conventionally sintered samples was barely altered with β-Sn dendritic matrix comprising Cu₆Sn₅ and Ag₃Sn intermetallic particles. The microwave sintered Sn-3.0Ag-0.7Cu sample exhibited a combination of fine and very coarse intermetallic particles, with the presence of well-developed needle-like Ag₃Sn, and its dendritic pattern disappeared completely. The Vickers hardness of both samples was measured and found to be consistent with their microstructures.

Abstract: Grain growth is inevitable in the sintering of pure nanopowder zinc oxide. Sintering depend on diffusion kinetics, thus this growth could be controlled by ultra-fast sintering techniques, as microwave sintering. The purpose of this work was to investigate the nanostructural evolution of zinc oxide nanopowder compacts (average grain size of 80 nm) subjected to ultra-rapid microwave sintering at a constant holding temperature of 900°C, applying different heating rates and temperature holding times. Fine dense microstructures were obtained, with controlled grain growth (grain size from 200 to 450nm at high heating rate) when compared to those obtained by conventional sintering (grain size around 1.13µm), which leads to excessively large average final grain sizes.