Provided is a process for producing satisfactory particles held in porous silica. The process comprises (a) the step of preparing porous silica, (b) the step of bringing the porous silica into contact with a liquid which contains either a metal or a compound that has the metal as a component element and infiltrating the liquid into the pores of the porous silica, and (c) the step of subjecting, after the step (b), the impregnated porous silica to a heat treatment to thereby form fine particles comprising the metal or the metal compound in the pores of the porous silica. When porous silica is synthesized by hydrolyzing an alkoxysilane in a solvent-free system, it is possible to synthesize porous silica having a fine pore diameter. Use of this porous silica as a template facilitates formation of particles (e.g., W, Cu, Cr, Mn, Fe, Co, or Ni or an oxide of any of these metals) that show peculiar properties not observed in the bulk material.

The present invention relates to spherical, dense micrometre-sized particles comprising colourants. The invention also relates to a material comprising these particles intended for use in papermaking, paint, agri-food, cosmetics or pharmaceuticals. It also relates to the process for preparing these particles and their incorporation in a matrix.

A method for producing particles, includes the following steps: introducing into a reaction chamber at least one reaction flow including a first chemical element (typically silicon) and propagating in a flow direction; projecting a ray beam through the reaction chamber, intersecting each reaction flow in an reaction flow interaction area, in order to form, in each reaction flow, the cores of particles including the first chemical element, and introducing, in the reaction chamber, a second chemical element, interacting with each reaction flow in order to cover the cores of particles with a layer including the second chemical element. Each reaction flow is preferably free of an agent oxidizing the first chemical element.

The invention relates to a method, in which siliceous biomass is modified in the spectrum of the existing non-silicon metals and these non-silicon metals are fixed onto the siliceous skeleton of the plant by burning. The ashes produced can be used as auxiliary agents for heterogeneous catalysis in the chemical industry and as loading materials for plastics, elastomers, pigments, paints and sizing materials.

The titanium dioxide fine particle-dispersed composite particles (1) of the present invention include silica particles (10) and fine titanium dioxide particles (20). The fine titanium dioxide particles (20) are dispersed inside the silica particles (10). The fine titanium dioxide particles (20) are of the rutile type and have an average primary particle diameter of 2 nm to 8 nm. The titanium dioxide fine particle-dispersed composite particles (1) of the present invention have high transparency to visible light.

A nanoparticle has at least one dimension less than 500 nm and comprises a silica surface and a plurality of zwitterionic functional groups covalently bound to the silica surface. Such nanoparticles and dispersions contain such nanoparticle are prepared and used for a variety of purposes.

The present invention is a low dielectric silica powder, which has an average particle size of 0.1 to 30 ?m and a dielectric loss tangent of 0.0005 or less at 10 GHz. An object is to provide: a silica powder with an extremely small dielectric loss tangent; a resin composition containing the same; and a method for manufacturing a silica powder with a low dielectric loss tangent and strong adhesion at the interface to resin.

Hollow silica-based particles having cavities inside the outer shell having a low refractive index. The method of producing the silica-based particles comprises the following steps (a) and (b): (a) a step in which, when an aqueous silicate solution and/or an acidic silicic acid solution and an aqueous solution of an alkali-soluble inorganic compound are simultaneously added in an alkali aqueous solution to prepare a dispersion liquid of composite oxide particles, an electrolytic salt is added at the molar ratio of a mole number of the electrolytic salt (M.sub.E) versus that of SiO.sub.2 (M.sub.S) [(M.sub.E)/(M.sub.S)] in the range from 0.1 to 10, and (b) a step of furthermore adding an electrolytic salt, if necessary, to the dispersion liquid of composite oxide particles and then removing at least a portion of elements constituting the composite oxide other than silicon by adding an acid to prepare a dispersion liquid of silica-based particles.

Aqueous dispersion containing a hydrophilic metal oxide powder comprising a metal oxide and a surface modification of the metal oxide, wherein a) the metal oxide is selected from the group consisting of TiO.sub.2, ZrO.sub.2, SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, Fe.sub.3O.sub.4, Sb.sub.2O.sub.3, WO.sub.3, CeO.sub.2 and mixed oxides thereof and b) the surface modification b1) comprises silicon atoms and aluminum atoms and b2) the silicon atoms are at least partly bonded to a hydrocarbon radical via a C atom and b3) the Al/Si molar ratio of the surface modification is 1:2-1:20.

A composite material comprising an amorphous, porous material with nanocrystalline material in its pores has been found to be a UV absorber. The porous material is a matrix of pores that act as a scaffold for the nanocrystalline material. The particles of the nanocrystalline material are isolated, which mean that they do not connect to each other. In some embodiments, the nanocrystalline material is completely inside the pores of the porous material. In some embodiments, the nanocrystalline material may stick out of some or all of the pores of the porous material. In some embodiments, the nanocrystalline material is a cerium oxide material. In some embodiments, the nanocrystallite ranges in size from 2 to about 100 nm on its longest axis, with an aspect ratio from about 1 to about 1.5.