Characterization of Magnesia Foam Ceramics Prepared by Foam Impregnation and Its Application in Crude Magnesium Refining

Reticulated porous MgO ceramics were fabricated by suspension impregnation method, which involves replication of polyurethane foam with mixed slurry of MgO and MgF and subsequent sintering treatments. The objective of the present study is to find a suitable method to ensure uniform macropore or micropore structure of ceramics foam using low-melting additives at moderate sintering temperatures. The microstructures of Magnesia Foam Ceramics (MFC) were evaluated by scanning electron microscopy (SEM) coupled with X-ray diffraction (XRD). The loading amount and apparent porosity of MFC are related to the slurry viscosity and PPI of PU foam. More importantly, compared with different filtration methods of molten crude magnesium, we can draw a conclusion that MFC can clean MgO inclusions and refining agent effectively based on the test results of electron dispersive spectroscopy (EDS) and density of crude magnesium before and after filtration.These results are attributed to the formation of filter sieve removing particles larger than or close to the pore size and to liquid inclusions held to the filter wall by surface forces, owing to specific surface area resulted by macropores and micropores formed in MFC in the presence of polyurethane foam and sintering binder MgF powders.