A method for producing a glass article having high hydrolytic resistance is provided. A glass tube consisting of borosilicate glass and having an Al.sub.2O.sub.3 content of less than 1 weight-%, a ZrO.sub.2 content of 2-12 weight-%, and a glass transition temperature T.sub.g is reshaped into a glass article and is subsequently subjected to a thermal post-treatment. To reduce the alkali release of the glass article, the glass article is subjected to a treatment temperature of T.sub.B≥T.sub.g+5° K over a treatment time of t.sub.B≥5 min and is subsequently cooled during the thermal post-treatment.

Glass articles and methods for modifying a composition of a surface portion of the glass article are disclosed. The method includes heating the surface portion of the glass article with a laser beam to a temperature within a range of about 1100?C to about 2200?C such that the heating evaporates one or more metalloids and/or one or more alkali metals present at the surface portion, and modifies the composition of the surface portion such that the surface portion has a lower alkali metals concentration and/or a lower metalloids concentration as compared to a portion of the glass article that is not heated by the laser beam.

A glass glass-ceramic composite comprises a substrate comprising an alkali-containing glass bulk, the bulk comprising Al.sub.2O.sub.3 and SiO.sub.2 and alkali, and a glass-ceramic surface layer, the surface layer comprising an alkali-depleted glass ceramic comprising Al.sub.2O.sub.3 and SiO.sub.2 with at least 5% crystalline phase by volume, wherein the alkali-depleted glass ceramic surface layer comprises a mol % Al.sub.2O.sub.3 of at least 51%. A method of preparing the composite is also disclosed.

The present invention is an annealed quartz glass cloth that has an SiO.sub.2 content of 99.5 mass % or more, a dielectric loss tangent of less than 0.0010 at 10 GHz, and a tensile strength of 1.0 N/25 mm or more per cloth weight (g/m.sup.2). This provides an annealed quartz glass cloth that has a low dielectric loss tangent and that is also excellent in tensile strength; and a method for manufacturing an annealed quartz glass cloth by which strength recovers after a high-temperature heat treatment.

Frangible glass articles having a fracture behavior that resists ejection of glass particles upon fracture. In some embodiments, the frangible glass articles can have a first surface region with a first elastic compressive stress energy per unit area of glass (W.sub.el.sup.comp1), a second surface region with a second elastic compressive stress energy per unit area of glass (W.sub.el.sup.comp2), and a central region with an elastic tensile stress energy per unit area of glass (W.sub.T), where (W.sub.el.sup.comp1+W.sub.el.sup.comp2)−W.sub.T≤25 J/m.sup.2. In some embodiments, the frangible glass articles can have a total load ratio (W.sub.i/G.sub.D) less than 6.5 and a total elastic compressive stress energy per unit area of glass (W.sub.C) less than 60% of a total load (W.sub.i), where: W.sub.C=W.sub.el.sup.comp1+W.sub.el.sup.comp2, W.sub.i=W.sub.C+W.sub.T, G.sub.D=4G.sub.1C, and

[00001]$G_{1C}=\frac{K_{1C}^2\left(1-v^2\right)}{E}.$

In some embodiments, the frangible glass articles can have a differential load ratio (W.sub.d/G.sub.IC) less than

[00002]$72e^{\left(-12\frac{d1}{t}\right)}.$

A process and a plant produce hollow microspheres made of glass. According to the process an aqueous suspension is prepared from starting materials containing glass powder and water glass, feedstock particles having a diameter between 5 μm and 300 μm, in particular between 5 μm and 100 μm, being produced from the suspension. The feedstock particles are mixed with a pulverulent release agent made of aluminum hydroxide in an intensive mixer. The mixture of feedstock particles and release agent is subsequently introduced into a firing chamber of a furnace. The feedstock particles expand in the firing chamber, at a firing temperature which exceeds the softening temperature of the glass powder, to form the hollow microspheres.

A protective glass plate with the property of impact stress resistance, and the composition for making the protective glass plate comprising the following components by mass percent: SiO.sub.2: 59-63.5%, Al.sub.2O.sub.3: 11.5-16.5%, Na.sub.2O: 11.5-15.5%, K.sub.2O: 0.8-6%, MgO: 4-8.5%, B.sub.2O.sub.3: 0-1.0%, and ZrO.sub.2: 0%; when 0.3 mm<T<2.0 mm, and 0.5h≤t≤8h, CS satisfies the following relationship: 9.597Ln(t)+710≤CS≤−5.299t.sup.2+50.28t+765; when 2.0 mm≤T≤4.0 mm, and 4h≤t≤150h, CS satisfies the following relationship: 0.003t.sup.2−2.167t+858≤CS≤−61.4Ln(t)+1060; wherein T is the thickness of the glass plate and has the unit of mm; t is the chemical strengthening time and has the unit of h; and CS is the surface compressive stress generated by chemical strengthening and has the unit of MPa. The protective glass plate has an excellent property of impact resistance, and the maximum glass fragment size of the broken glass may be controlled within the range of 10-30 mm in length and 1-3 mm in width, thus it is applicable for large-scale industrial production.

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 method of manufacturing a polarizing glass sheet includes subjecting, while heating, a glass preform sheet containing metal halide particles to down-drawing, to thereby provide a glass member having stretched metal halide particles dispersed in an aligned manner in a glass matrix, and subjecting the glass member to reduction treatment to reduce the stretched metal halide particles, to thereby provide a polarizing glass sheet. A shape of the glass preform sheet during the down-drawing satisfies a relationship of the following expression:
L.sub.1/W.sub.1≥1.0
where L.sub.1 represents a length between a portion in which a width of the glass preform sheet has changed to 0.8 times an original width and a portion in which the width of the glass preform sheet has changed to 0.2 times the original width W.sub.0, and W.sub.1 represents a length equivalent to 0.5 times the original width W.sub.0 of the glass preform sheet.

The present invention discloses a glazing characterized through a high hemispherical light transmission together with an enhanced tuneable light diffusion, what we hereby call a highly transmitting glazing with optimized Hortiscatter. The glazing of the invention is particularly well suitable for a greenhouse. The invention is a global approach which allows to propose different glazing which can be utilized depending on the type of crop and the geographical zone, providing optimized Hortiscatter on demand