Sinter-Forging of Chemically Precipitated Nanocrystalline TiO₂

Abstract

Two mechanisms appear to occur during the sinter-forging of nanocrystalline titania. The first mechanism occurs at stresses below ≈ 25 MPa where the densification kinetics are shown to be independent of the stress. However, at higher stresses, the densification kinetics are greatly enhanced by a plastic flow mechanism. The nucleation rate of rutile during the concurrent anatase-to-rutile phase transformation is shown to be enhanced by compressive stresses; however, the overall transformation rate is increased only at high stresses. At these high stresses, the enhanced densification and increased nucleation and transformation rates allow for the production of nanocrystalline grain sizes in nearly dense samples.