Selective laser sintering of alumina-molybdenum nanocomposites

Abstract

Alumina/molybdenum nanocomposites were obtained from alumina and molybdenum particles. Alumina with different molybdenum contents (0, 1, 2.5, 5, 10 and 20 wt %) was first uniaxially pressed at 100 MPa to obtain green compacts that were later sintered using a carbon dioxide (CO2) laser. Samples were characterized by X-ray diffraction and Scanning Electron Microscope to evaluate the morphological and microstructural characteristics of the composites. SEM results show that for mixtures with 1, 2.5, 5 and 10 wt % Mo, metallic Mo appears dispersed within the alumina grains (grain boundaries and triple points). Nevertheless, for the mixture with 20 wt % Mo, it also appears in the alumina matrix as Mo in triple points and grain boundaries, although MoO3 is also identified (as inclusion). The presence of these phases was confirmed by X-ray Diffraction technique. These metallic molybdenum particles distributed in the alumina matrix at triple points and grain boundaries promote the densification of the composite. Metallic molybdenum has also a pinning effect, which drastically affects the microstructural evolution during the sintering, mainly on the grain size of alumina. The best results were observed for the composite Al2O3-10 wt % Mo, with an average alumina grain size <10 μm and few pores.