Photosensitive lithium zinc aluminosilicate glasses that can be selectively irradiated and cerammed to provide patterned regions of glass and lithium-based glass ceramic, and composite glass articles made from such glasses and glass ceramics are provided. Compressive and tensile stress at the interface of the lithium-based glass-ceramic and lithium zinc aluminosilicate glass may be used to frustrate crack propagation in such a composite glass/glass ceramic article. Methods of making composite glass articles comprising such lithium-based glass ceramics and lithium zinc aluminosilicate glasses are also provided.

One aspect relates to a process for the preparation of a quartz glass body. The process includes providing a silicon dioxide granulate from a pyrogenically produced silicon dioxide powder, making a glass melt out of silicon dioxide granulate, and making a quartz glass body out of at least part of the glass melt. The size of the quartz glass body is reduced to obtain a quartz glass grain. The quartz glass body is processed to make a preform and an opaque quartz glass body is made from the preform. One aspect further relates to an opaque quartz glass body which is obtainable by this process. One aspect further relates to a reactor and an arrangement, which are each obtainable by further processing of the opaque quartz glass body.

Disclosed herein are opaque glass-ceramics comprising at least one nepheline crystal phase and comprising from about 30 mol % to about 65 mol % SiO.sub.2, from about 15 mol % to about 40 mol % Al.sub.2O.sub.3, from about 10 mol % to about 20 mol % (Na.sub.2O+K.sub.2O), and from about 1 mol % to about 10 mol % (ZnO+MgO). Also disclosed herein are opaque-glass ceramics comprising at least one nepheline crystal phase and at least one spinel-structure phase doped with at least one colorant chosen from transition metals and rare earth elements. Further disclosed herein are methods for making these opaque glass-ceramics.

The invention relates to the use of lithium silicate glass ceramics and glasses with caesium oxide content, which are suitable in particular for veneering oxide ceramic restorations and metal restorations.

A method for manufacturing a large sized opaque quartz glass ingot having excellent heat ray shielding and light blocking properties without using a foaming agent. The obtained opaque quartz glass has small diameter spherical bubbles and a preferable mechanical strength. Silica powder is dispersed in water to form a slurry having a silica powder concentration of 45 to 75 wt % and the average particle size of the silica powder is adjusted to 8 μm or less and the standard deviation of the particle size is adjusted to 6 μm or more by wet pulverization. The slurry is sprayed for forming granules of the silica powder. An opaque quartz glass ingot with a small bubble diameter and high mechanical strength is obtained by melting the granulated silica powder.

A glass-ceramic article comprises: a center-volume composition comprising (on an oxide basis): 55-75 mol % SiO.sub.2; 0.2-10 mol % Al.sub.2O.sub.3; 0-5 mol % B.sub.2O.sub.3; 15-30 mol % Li.sub.2O; 0-2 mol % Na.sub.2O; 0-2 mol % K.sub.2O; 0-5 mol % MgO; 0-2 mol % ZnO; 0.2-3.0 mol % P.sub.2O.sub.5; 0.1-10 mol % ZrO.sub.2; 0-4 mol % TiO.sub.2; and 0-1.0 mol % SnO.sub.2. Lithium disilicate and either β-spodumene or β-quartz are the two predominant crystalline phases (by weight) of the glass-ceramic article. The glass-ceramic article further comprises tetragonal ZrO.sub.2 as a crystalline phase. The composition of the glass-ceramic article from a primary surface into a thickness of the glass-ceramic article can comprise over 10 mol % Na.sub.2O (on an oxide basis), with the mole percentage of Na.sub.2O decreasing from the primary surface towards the center-volume. The glass-ceramic article exhibits a ring-on-ring load-to-failure of at least 120 kgf, when the thickness of the glass-ceramic article is 0.3 mm to 2.0 mm.

The subject of the invention is a material comprising a glass sheet coated on at least one portion of one of the faces thereof with a stack of thin layers comprising at least one layer based on a nitride, said stack being coated on at least one portion of its surface with an enamel layer comprising bismuth, said stack further comprising, in contact with the enamel layer, a layer, referred to as a contact layer, which is based on an oxide.

An opaque gahnite-spinel glass ceramic is provided. The glass ceramic includes a first crystal phase including (Mg.sub.xZn.sub.1-x)Al.sub.2O.sub.4 where x is less than 1 and a second crystal phase includes at least one of tetragonal ZrO.sub.2, MgTa.sub.2O.sub.6, mullite, and cordierite. The glass ceramic has a Young's modulus greater than or equal to 90 GPa, and has a hardness greater than or equal to 7.5 GPa. The glass ceramic may be ion exchanged. Methods for producing the glass ceramic are also provided.

A glass sheet having a high near-IR transmission and very low visible transmission. The glass sheet is a silicate-type and has a composition that includes, in a content expressed as weight percentages, by total weight of glass: total iron (expressed as Fe.sub.2O.sub.3) 0.02-1%, Chromium (expressed as Cr.sub.2O.sub.3) 0.05-0.8%, Cobalt (expressed as Co) 0.03-0.175%. The glass sheet shows, intrinsically, a very low visible transmission together with a high IR transmission at wavelengths of interest (i.e. 850, 900 and 950 nm) and low amounts of Cr.sup.6+ species. The glass sheet is therefore valuable within the context of autonomous cars and in particular, those with fully integrating LiDAR systems.

Disclosed is a pre-sintered ceramic block for a dental restoration, which has a low pre-sintering temperature, contains a silica main crystal phase, but does not contain or contains a small amount of lithium metasilicate crystal phase. The pre-sintered ceramic block has a low hardness, with a Vickers hardness of 0.5-3 GPa, which is significantly lower than that of a ceramic block containing a lithium metasilicate crystal phase, and same is suitable for dry machining and also wet machining when being machined into a dental restoration. (FIG. 2)