Microstructure and properties of MgAlON-bonded magnesia,magnesia-alumina spinel and corundum materials

MgAlON-bonded magnesia,magnesia-alumina spinel and corundum materials were prepared by reaction sintering.The influence of different major phases on the formation temperature of single MgAlON bonding phase and that of volume expansion caused by chemical reactions and the vapouring of oxides on the sintering of the materials were studied.The results show that athough the mixed powders used to form MgAlON bonding phase have the same composition and the same amount,the temperatures at which single MgAlON bonding phase forms in MgAlON-bonded magnesia,magnesia-alumina spinel and corundum samples are different,and rise in turn.On the matter of MgAlON-bonded magnesia samples,the volume expands significantly and a big amount of MgO vapours during the sintering process,magnesia grains bond loosely with the matrix in the fired samples,and thus the samples have low bulk density and low compressive strength.For MgAlON-bonded corundum samples,the volume expands slightly and a small amount of oxides vapours during the sintering process,corundum grains bond tightly with the matrix in the fired samples,and therefore the samples have high bulk density and high compressive strength.As to MgAlON-bonded magnesia-alumina spinel samples,the volume expansion and the amount of oxides vapoured during the sintering process,the bonding between grains and the matrix in the fired samples,and the bulk density and compressive strength of the fired samples are all between those of the above two kinds of samples.