Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence.

A high-pressure phase of TiO(2) with an alpha-PbO(2)-type structure has been synthesized via very energetic Nd-YAG laser pulse irradiation of oxygen-purged Ti target. The nanometer-size alpha-PbO(2)-type particles were (11;0), (010), and (001) faceted but the larger ones were spherical. The combined effects of rapid heating and cooling, the nanophase effect, and dense surfaces account for the formation of coherently strained alpha-PbO(2) particles. The refined cell volume indicated a considerable residual stress to stabilize the dense structure to ambient condition.

Dense gamma-Al(2)O(3)condensates, with residual stress up to 3 GPa and ranging from nanometer to an unexpected micrometer size, were formed by pulsed laser ablation on Al target under oxygen background gas for a very rapid heating and cooling effect. Analytical electron microscopic observations indicated such nanoparticles tended to coalesce over {111} facets to form multiple twin and tilt boundary. The micrometer-size particles changed, upon electron irradiation, into metastable orthorhombic delta form full of twin variants and faults parallel to {100}.

A high-pressure phase of TiO2 with a baddeleyite-type related structure has been synthesized via very rapid heating-cooling under energetic Nd-YAG laser pulse irradiation of the Ti target in oxygen ambient. Spherical nanoparticles transformed martensitically into baddeleyite-type and then α-PbO2-type structures with accompanied transformation twinning, shearing and shape change into ellipsoid upon electron irradiation. The relatively large particles followed the same transformation path yet with alternative lattice correspondence and additional multiple deformation twinning of the baddeleyite type.