Effect of the addition of glasses as sintering aids on microstructure and properties of nanoalumina

Abstract

Alumina-Glass compositions were prepared to evaluate the effect of glass as sintering aids. The composites showed densification below 1100°C. The highest density values (~95%) were obtained for compositions based respectively on borosilicate (G2 and G3) and soda lime glasses (G4), all [A1] [A2] containing Na in the precursor powder. Samples G1 (K-based) and G5 (no K or Na in the precursor glass powder) presented irregular morphology with the presence of intergranular porosity. The composition G2, G3, and G4 presented uniform morphology corresponding to higher densification.

Novel Alumina Compounds with Niobia, Silica and Magnesia for Ballistic Armor

“…It is verified that the composition with 8.0 wt.% Nb2O5+0.8 wt.% SiO2+0.15 wt.% MgO (Fig. 1(f)) presented a visible rounding of the grains, characteristic of satisfactory sintering [1,[8][9][10]. Such aspect was not verified in the other percentages of Nb2O5.…”

“…In other works [7,8], it was verified that the isolated addition of 4.0 wt.% Nb2O5 favors the use of the material in ballistic applications, which indicates to be interesting the study of the addition of higher levels of Nb2O5 to the Al2O3, keeping the contents of SiO2 and MgO low. One of the ways of sintering ceramic materials is in the presence of liquid phase [9,10], which involves three components (solid, liquid and pores) at the sintering temperature, with more than 80.0% of the solid-state material. In this case, the additions concentrate on the grain boundaries of the Al2O3, tending to render the surfaces of the grains rounded by filling the surface defects of the grains by the second phases in the liquid phase during sintering.…”