Shaped and fired articles of TiO.sub.2

Transparent, solid, shaped and fired, non-vitreous, homogeneous microspheres having diameters in the range of 1 to 200 microns and comprising predominantly polycrystalline titanium dioxide in its anatase form.

A solid, shaped and fired, non-vitreous, homogeneous, transparent, continuous refractory fiber comprising predominantly polycrystalline titanium dioxide in its anatase form, and one or more other metal oxides.

A solid, shaped and fired, non-vitreous, homogeneous, transparent, continuous, refractory fiber comprising predominantly polycrystalline titanium dioxide in its anatase form, and one or more other metal oxides selected from the group consisting of chromium oxide, aluminum oxide, iron oxide, cobalt oxide, and silica.

A solid, shaped and fired, non-vitreous, homogeneous, transparent, continuous, refractory fiber comprising predominantly polycrystalline titanium dioxide in its anatase form, and one or more other metal oxides present in an amount sufficient to impart a color to said fiber.

Transparent, solid, shaped and fired, non-vitreous, homogeneous microspheres comprising predominantly polycrystalline titanium dioxide in its anatase form and one or more of the oxides of silicon, chromium, aluminum, iron, and cobalt.

A method for forming continuous fibers of solid, transparent refractory comprising predominantly polycrystalline titanium dioxide in its anatase form, which method comprises extruding in air an aqueous acidic titanium oxide sol or aqueous acidic mixture of a titanium compound calcinable in air to titanium dioxide, and heating and firing the resulting amorphous fibers to remove water, acid, organic material, and carbon therefrom and form said continuous fibers.

A method for forming refractory microspheres of solid transparent refractory comprising predominantly polycrystalline titanium dioxide in its anatase form, which method comprises dispersing as droplets in an organic dehydrating liquid an aqueous acidic titanium oxide sol or aqueous acidic mixture of a titanium compound calcinable in air to titanium dioxide, recovering the resulting amorphous microspheres from said liquid, and heating and firing said recovered microspheres to convert them to said refractory microspheres.

In a retro-reflective sheeting comprising a monolayer of spherical lense elements and associated reflector adapted in combination therewith to provide retro-reflection, the improvement comprising using as said lense elements transparent, solid, shaped and fired microspheres comprising predominantly polycrystalline titanium dioxide in its anatase form.

A plastic composite comprising a plastic matrix having dispersed therein a plurality of solid, shaped and fired, non-vitreous, homogeneous, refractory fibers comprising predominantly polycrystalline titanium dioxide in its anatase form.