A hollow body includes a wall which at least partially surrounds an interior volume of the hollow body. The wall comprises a layer of glass comprising a first glass composition, comprises a base surface, and has a wall surface. The wall surface comprises at least one surface region, in which the base surface is at least partially superimposed by at least one elevated region, and at least one contact region, which extends along a contact range of a height of the hollow body. The at least one elevated region comprises a further glass composition. An exterior diameter of the hollow body has a maximum throughout the contact range. The at least one surface region is at least partially positioned in the at least one contact region.

A quartz glass body and a process for the preparation of a quartz glass body is disclosed. One process includes providing a silicon dioxide granulate from a pyrogenic silicon dioxide powder, making a glass melt out of the silicon dioxide granulate and making a quartz glass body out of at least part of the glass melt. In at least one process a silicon component different from silicon dioxide is added. A quartz glass body is obtainable by this process. A light guide, an illuminant and a formed body, are each obtainable by further processing of the quartz glass body.

A quartz glass body and a process for the preparation of a quartz glass body is disclosed. One process includes providing a silicon dioxide granulate from a pyrogenic silicon dioxide powder, making a glass melt out of the silicon dioxide granulate and making a quartz glass body out of at least part of the glass melt. In at least one process a silicon component different from silicon dioxide is added. A quartz glass body is obtainable by this process. A light guide, an illuminant and a formed body, are each obtainable by further processing of the quartz glass body.

In an exemplary embodiment, a quartz glass crucible 1 includes: a high-aluminum-content layer 14B which is made of quartz glass having a relatively high average aluminum concentration and is provided to form an outer surface 10b of the quartz glass crucible 1; and a low-aluminum-content layer 14A which is made of quartz glass having a lower average aluminum concentration than that of the high-aluminum-content layer 14B and is provided on an inner side of the high-aluminum-content layer 14B, wherein the low-aluminum-content layer 14A includes an opaque layer 11 made of quartz glass containing a large number of minute bubbles, and the high-aluminum-content layer 14B is made of transparent or translucent quartz glass having a lower bubble content than that of the opaque layer 11. The quartz glass crucible is capable of withstanding a single crystal pull-up step undertaken for a very long period of time.

In an exemplary embodiment, a quartz glass crucible 1 includes: a high-aluminum-content layer 14B which is made of quartz glass having a relatively high average aluminum concentration and is provided to form an outer surface 10b of the quartz glass crucible 1; and a low-aluminum-content layer 14A which is made of quartz glass having a lower average aluminum concentration than that of the high-aluminum-content layer 14B and is provided on an inner side of the high-aluminum-content layer 14B, wherein the low-aluminum-content layer 14A includes an opaque layer 11 made of quartz glass containing a large number of minute bubbles, and the high-aluminum-content layer 14B is made of transparent or translucent quartz glass having a lower bubble content than that of the opaque layer 11. The quartz glass crucible is capable of withstanding a single crystal pull-up step undertaken for a very long period of time.

The present invention provides a composite shaped body comprising silica nanoparticles and an organic polymer, wherein the silica nanoparticles and the organic polymer form a three-dimensional network; thereby provides: a composite shaped body which exhibits excellent formability and fabricability and which is also suited for use, for example, in producing a silica glass provided with an electrical conductivity; and a silica glass (especially, an electrically conductive silica glass) obtained by firing the composite shaped body.

The present invention provides a composite shaped body comprising silica nanoparticles and an organic polymer, wherein the silica nanoparticles and the organic polymer form a three-dimensional network; thereby provides: a composite shaped body which exhibits excellent formability and fabricability and which is also suited for use, for example, in producing a silica glass provided with an electrical conductivity; and a silica glass (especially, an electrically conductive silica glass) obtained by firing the composite shaped body.

Provided is a fumed silica for chemical-mechanical polishing with which post-polishing scratches occurring on a surface of an object to be polished can be significantly reduced, and which is important for miniaturization and multi-layering of a structure. The fumed silica according to the present invention has a BET specific surface area of 57-400 m.sup.2/g. In a liquid dispersion which is obtained by ultrasonically dispersing 6.25 mass % of this fumed silica in water at a vibration frequency of 20 kHz and an amplitude of 15-25 m for 3 minutes, the amount of residues on a sieve is 5 ppm or less as measured by wet sieving using an electroformed sieve having a mesh opening size of 5 m.

A method for forming high purity silica articles. The high purity silica articles can be particularly suitable for forming packaging such as packaging for pharmaceutical applications. The method for forming high purity silica articles can comprise, in one embodiment, (a) forming a fused quartz melt from a SiO.sub.2 raw material; (b) forming a quartz tube from the fused quartz melt; (c) treating the quartz tube with an acid composition; (d) heat treating the quartz tube subsequent to treating with the acid composition; and (e) optionally treating the quartz article with an acid composition subsequent to the heat treating operation. The method can enhance the purity of silica glass articles and products made therefrom.

A method for forming high purity silica articles. The high purity silica articles can be particularly suitable for forming packaging such as packaging for pharmaceutical applications. The method for forming high purity silica articles can comprise, in one embodiment, (a) forming a fused quartz melt from a SiO.sub.2 raw material; (b) forming a quartz tube from the fused quartz melt; (c) treating the quartz tube with an acid composition; (d) heat treating the quartz tube subsequent to treating with the acid composition; and (e) optionally treating the quartz article with an acid composition subsequent to the heat treating operation. The method can enhance the purity of silica glass articles and products made therefrom.