Abstract: The invention provides a method for fabricating analyzers, the method comprising providing a radiation manipulating material on a first surface of a flexible support; contacting a second surface of the flexible support to a permeable mold, wherein the mold has a first flexible support contact surface and a second surface; and applying negative pressure to the second side of the flexible support to cause the flexible support to conform to the first flexible support contact surface of the mold. Also provided is a system for fabricating crystal analyzers, the system comprising crystal structures reversibly attached to a flexible support; a porous mold reversibly contacting the flexible support, wherein the mold defines a topography; and a negative pressure applied to the flexible support to cause the crystal structures to conform to the topography.

Abstract: Fused tuckstone defining lower and upper surfaces. The lower surface includes a support surface to rest on metallic structure of a glass furnace, a tank surface intended to face an upper edge of a tank of the furnace, and a lower transition surface connecting the support and tank surfaces. The upper surface includes a superstructure surface to receive a side wall of a superstructure of the furnace and an upper transition surface connecting the superstructure and lower surfaces. At least a part of the lower transition surface has a crystal density of more than four times the crystal density at a depth of 4 centimeters below the lower transition surface, a crystal density being evaluated by the number of crystals having a surface area of more than 12 ?m2 per mm2 of surface after polishing, the crystal density at the depth being evaluated after cutting of the tuckstone.

Abstract: A refractory object may include a zircon body that is intentionally doped with a dopant including an alkaline earth element and aluminum. The refractory object can have an improved creep deformation rate. In an embodiment, the refractory object can have a creep deformation rate of not greater than about 1.8 E-5 h?1 at a temperature of 1350° C. and a stress of 2 MPa. In another embodiment, the zircon body may include an amorphous phase including an alkaline earth metal element.

Abstract: A laminate sheet article including: a core including an electrical semi-conductor or an electrical conductor; and a continuous glass clad layer on at least four of six sides the core of the sheet article. Also disclosed is an apparatus for making a sheet laminate article as defined herein. Also disclosed is a method of making and using the article.

Abstract: An optical ceramic material heat treatment apparatus, comprising: a furnace body that is capable to contain an optical ceramic material to be heat treated in the inside thereof; a temperature drop control heater that generates heat during dropping a temperature of the optical ceramic material; a refrigerant intake unit that introduces a refrigerant into the inside of the furnace body to flow the refrigerant therein; and a control unit that controls the temperature drop rate, wherein the temperature drop control heater is arranged in the inside of the furnace body and/or in the refrigerant intake unit, the control unit controls at least one of an amount of heat generation of the temperature drop control heater, and a flow rate of the refrigerant in the inside of the furnace body to control a temperature drop rate at the optical ceramic material or in the vicinity thereof to be kept in a predetermined profile.

Abstract: A casting mold includes a carbon film with which at least a surface of the casting mold which forms a cavity is covered, and mold oil with which a surface of the carbon film is coated. In the casting mold, aluminum powder is added to the mold oil.

Abstract: An apparatus is provided that heats the glass of a primary glass product to be formed. The apparatus includes a laser that emits light at a wavelength for which the glass of the primary glass product is at most partly transparent, such that the light is absorbed at least partially in the glass. The apparatus also includes a mold having a forming mandrel having a thermally stable ceramic material, at least in the region that forms the contact surface with the glass during the forming process.

Abstract: The present invention concerns a crucible for solidifying a silicon ingot from molten silicon, characterised in that it is coated at least partially on the inner surface thereof with an outer layer provided in the form of a stack of laminations, each lamination having a thickness varying from 5 to 150 ?m, and being formed from a material obtained by thermal decomposition of polysilazane(s) and/or polysiloxane(s) and wherein inorganic particles are embedded having a size varying from 50 ?m to 200 ?m. The present invention further concerns a method for preparing such crucibles.

Abstract: Fused cast refractory product comprising in percentages by weight on the basis of the oxides and for a total of 100%, —ZrO2; balance to hj 100%, —Hf2O: <5% SiO2: 2% to 10%; —Y2O3: 0.4% to 2.0%; —CaO: 4.0% to 8.0%; —B2O3+Na2O+K2O: 0.4% to 3.0% —Al2O3: 0.3% to 2.0%; —P2O5: <0.05%; —Fe2O3+TiO2: <0.55%; —other species: <1.5%. Application in glass melting furnaces.

Abstract: For permitting temperature manipulation of a melt even at a conductivity below 10?1 ??1 cm?1 and thus permitting refining of the melt at temperatures about 1700° C., the invention provides a method and a device for temperature manipulation of a melt (16), in particular in a refiner unit. The melt (16) is heated at least by ohmic resistance heating with at least two electrodes (4) that are arranged in the melt (16). At least a part of the melt (16) is cooled. The device (1) for temperature manipulation, refining, purification and homogenisation of a melt (16) comprises at least one arrangement for accommodating melt material (36, 16), defining an inner chamber, and at least two electrodes (4) for ohmic resistance heating of the melt (16). The electrodes (4) project into the inner chamber of the arrangement, in particular of a vessel (2).

Abstract: To provide a tin oxide refractory which prevents volatilization of SnO2 in a high temperature zone from an early stage and which also has high erosion resistance to glass. A tin oxide refractory comprising SnO2, SiO2 and ZrO2 as essential components, wherein the total content of SnO2, SiO2 and ZrO2 in the tin oxide refractory is at least 70 mass %, and, based on the total content of SnO2, SiO2 and ZrO2, the content of SnO2 is from 32 to 98 mol %, the content of SiO2 is from 1 to 35 mol % and the content of ZrO2 is from 1 to 35 mol %.

Abstract: A disc roll includes a plurality of annular disc members each defining a hole and having a peripheral surface; and a rotary shaft fitted into the holes of the annular disc members by insertion, whereby the peripheral surfaces of the disc members serve as a conveying surface of the disc roll. The disc members include an inorganic fiber, mica and a clay having a content of particle components that have a particle size of 5 ?m or larger of not higher than 30% by weight based on the weight of the clay.

Abstract: The present invention relates to a molten, fluid refractory product comprising, in weight percentages on the basis of the oxides and for a total of 100% of the oxides: ZrO2+Hf2O: remainder to 100% 4.0%<SiO2<6.5% Al2O3?0.75% 0.2%<B2O3<1.5% 0.3%<Ta2O5 Nb2O5+Ta2O5<1.4% Na2O+K2O<0.2% BaO<0.2% P2O5<0.15% Fe2O3+TiO2<0.55% other oxide species: <1.5% the “A/B” ratio of Al2O3/B2O3 content by weight being no higher than 1.50. The invention can be used in glass melting furnaces.

Abstract: A press forming apparatus includes a mounting plate, a heating mechanism, and a die. The mounting plate supports a glass material on an upper surface of the mounting plate. The heating mechanism heats the glass material on the mounting plate to a temperature which allows press formation of the glass material. The die is provided to face the upper surface of the mounting plate and press forms the glass material heated by the heating mechanism between the die and the mounting plate.

Abstract: The present invention relates to a fused refractory product having the following average chemical composition, as a percentage by weight on the basis of the oxides and for a total of 100%: ZrO2: 60.0%-80.0%; SiO2: 4.0%-10.0%; Al2O3: balance to 100%; Y2O3?5.0%; Na2O+K2O+B2O3?0.3% and SiO2/(Na2O+K2O+B2O3)?5.0; other oxide species: ?2.0%; the ratio of the ZrO2/Al2O3 weight contents being between 2.0 and 6.0.

Abstract: Methods are disclosed for treating zircon-containing forming structures, e.g., zircon isopipes, with one or more treatment glass compositions in which defect-causing reactions between the zircon of the forming structure and molten glass are suppressed at the delivery temperature of the treatment glass. The treatment compositions can be used during start-up of a forming structure, between runs of the same production glass on a given forming structure, and/or when transitioning between runs of two production glasses on a given forming structure. The treatment compositions can be used with production glasses that are ion-exchangeable.

Abstract: Low-carbon monolithic refractories are provided. Methods of manufacturing glass employing low-carbon monolithic refractories are also provided. Methods and apparatuses for glass manufacture for reducing the formation of carbon dioxide blisters during glass manufacture are also provided.

Abstract: Feeder channel for molten glass including an infrastructure including a block self-cast and sintered in situ. Furthermore, a method for manufacturing a block of such an infrastructure and a supply channel for a glassmaking furnace are claimed.

Abstract: An interposer sheet can be used for making semiconductor bodies, such as of silicon, such as for solar cell use. It is free-standing, very thin, flexible, porous and able to withstand the chemical and thermal environment of molten semiconductor without degradation. It is typically of a ceramic material, such as silica, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbide, silicon carbonitride, silicon oxycarbonitride and others. It is provided between a forming surface of a mold sheet, and the molten material from which a semiconductor body will be formed. It may be secured to the forming surface or deposited upon the melt. The interposer sheet suppresses grain nucleation, and limits heat flow from the melt. It promotes separation of the semiconductor body from the forming surface. It can be fabricated before its use. Because free-standing and not adhered to the forming surface, problems of mismatch of CTE are minimized.

Abstract: A creep-resistant zircon article and a method of manufacturing the creep-resistant zircon article are described herein. In one example, the creep-resistant zircon article has the shape of a forming apparatus (e.g., isopipe) which is used in the fusion process to manufacture glass sheets.

Abstract: A forming mold made from a polyporous refractory material is provided for forming a glass piece. The forming mold includes an outer surface and a plurality of forming structures provided on the outer surface. Each of the forming structures includes a forming surface matching with a shape of the glass piece. The forming mold is structured and arranged to be pumped down from the outer surface to generated an absorption force on molten glass material provided at the at least one forming surface for sucking the molten glass material on the forming structure to form the glass piece.

Abstract: A sintered product having an average chemical composition such that, in weight percentages on the basis of the oxides: Cr2O3=80.0-99.0%; 0.5%?TiO2?9.0%; 0.2%?MgO?3.0%; and ZrO2?5.0%, provided that the ratio of TiO2/MgO is between 1.5 and 9.0 and the molar ratio TiO2/Cr2O3 is less than 0.12.

Abstract: The invention provides a fused cast refractory product having the following mean chemical composition by weight, as a percentage by weight based on the oxides: 25%<MgO<30%; 70%<Al2O3<75%; other species: <1%. The invention is applicable to a regenerator associated with a soda-lime glass fusion furnace operating under reducing conditions.

Abstract: A method for manufacturing a crucible for the crystallization of silicium comprising the steps of •preparing a slurry of solids and liquids, said solids consisting of •silicon metal powder •up to 25% (w/w) SiC powder •up to 10% (w/w) SiN •up to 0.5% (w/w) of a catalyst •up to 1% (w/w) of a binder •forming the slurry into a green body of a crucible •heating the green body in a nitrogen atmosphere, optionally comprising inert gas, to react the silicon at least partially to silicon nitride.

Abstract: The invention relates to a process for manufacturing a refractory product, comprising the following successive steps: a) mixing of raw materials so as to form a suitable feedstock so that the block obtained in step d) comprises more than 85% of ZrO2, b) melting of said feedstock until a molten material is obtained, c) optionally, casting said molten material, d) cooling of the molten material to solidification in the form of a block, e) optionally, heat treatment, process comprising a compression operation in which a compression pressure of greater than 0.2 MPa is applied to at least one portion of the outer surface of the block obtained in step d), the compression operation beginning at a temperature above the temperature at which, in said block, tetragonal zirconia is converted to monoclinic zirconia or “phase transformation temperature”, and ending at a temperature below said phase transformation temperature.

Abstract: A method and a device for the continuous production of glass and glass ceramic products from a glass melt is provided, which simplifies the changing between two kinds of glass. The device includes a melting crucible and an induction coil, which preferably extends around the melting crucible in order to heat a glass melt by means of an induction field generated by the induction coil. The wall elements, which form the side wall of the crucible, have cooling channels, through which a cooling fluid can be conducted, so that the glass melt solidifies on the side wall and forms a skull layer. The interior side of the wall elements is formed at least in part by an aluminum nitride-containing ceramic.

Abstract: The present invention relates to a molten, fluid refractory product comprising, in weight percentages on the basis of the oxides and for a total of 100% of the oxides: ZrO2+Hf2O: remainder to 100% 4.0%<SiO2<6.5% Al2O3?0.75% 0.2%<B2O3<1.5% 0.3%<Ta2O5 Nb2O5+Ta2O5<1.4% Na2O+K2O<0.2% BaO<0.2% P2O5<0.15% Fe2O3+TiO2<0.55% other oxide species: <1.5% the “A/B” ratio of Al2O3/B2O3 content by weight being no higher than 1.50. The invention can be used in glass melting furnaces.

Abstract: The invention relates to a particulate powder, said powder having a median circularity of greater than 0.87 wt % and less than 9.0 wt % of particles having a size greater than 100 ?m. The powder and at least 80 wt % of the particles have a chemical composition in wt % on the basis of the oxides and for a total of 100%: Cr2O3+Al2O3+ZrO2+MgO+Fe2O3+SiO2+TiO2?90%; Cr2O3+Al2O3+MgO?60%; Cr2O3?9%; 20%?SiO2?0.5%; and other oxides: ?10%. The invention can be used for a glass furnace.

Abstract: A device selected from among a glass furnace and a channel for dispensing the glass comprising a block and/or a coating made of a sintered material obtained by sintering a particular mixture comprising a chromium oxide content, indicated as “CrT”, of between 10% and 82%. The die fraction is such that 0.39·(CrT)+24<CrM<0.39·(CrT)+52, CrM denoting the chromium oxide content by weight of the die fraction in wt % on the basis of the oxides of the die, and the aggregate is such that xII?97%, xIII?70%, and xIV?xIII?70%, CrG denoting the chromium oxide content by weight of one grain in wt % on the basis of the oxides of said grain.

Abstract: The invention relates to a molten cast refractory product comprising, in weight percentages on the basis of the oxides and relative to a total of 100% of the oxides: ZrO2+Hf2O is the remainder making up 100%, 4.5%<SiO2<6.0%, 0.80%?Al2O3<1.10%, 0.3%<B2O3<1.5%, Ta2O5+Nb2O5<0.15%, Na2O+K2O<0.1%, K2O<0.04%, CaO+SrO+MgO+ZnO+BaO<0.4%, P2O5<0.05%, Fe2O3+TiO2<0.55%, and other oxide species<1.5%, the “A/B” ratio of the Al2O3/B2O3 contents by weight being between 0.75 and 1.6. The invention can be applied to glass melting furnaces.

Abstract: The present invention is related to a monolithic float glass forming chamber and its method of construction. The forming chamber being of the type that includes a bottom wall; side walls and a roof wall to form an elongated chamber, the elongated chamber including a forming section and a cooling section for a desired thickness and ribbon width of molten glass, wherein each type of wall comprises: a first refractory structure with a mixture of a castable and pumpable refractory material and an insulation material; and a second refractory structure with a castable and pumpable refractory material, the first and second refractory structures being formed at the same construction site.

Abstract: The present invention relates to a molten, fluid refractory product comprising, in weight percentages on the basis of the oxides and for a total of 100% of the oxides: ZrO2+Hf2O: remainder to 100% 4.5%<SiO2<6.0% Al2O3<0.80% 0.3%<B2O3<1.0% Ta2O5+Nb2O5<0.15% Na2O+K2O<0.1% K2O<0.04% CaO+SrO+MgO+ZnO+BaO<0.4% P2O6<0.05% Fe2O3+TiO2<0.55% other oxide species, optionally including Y2O3: <1.5%, where Y2O3<0.3%, the “A/B” ratio of Al2O3/B2O3 content by weight being 0.5 to 2.0. The invention can be used in glass melting furnaces.

Abstract: A powder including, in percentages by weight: (a) 94% to 99% of particles of at least one refractory material, the main constituent(s) of which are alumina and/or zirconia and/or silica; (b) 1% to 6% of a hydraulic cement; (c) 0 to 0.03% of organic fibers; (d) optionally, 0.075% to 1% of a surfactant; and (e) optionally, a setting accelerator, where the fraction of particles having a size below 40 ?m being distributed, in percentages by weight relative to the weight of the powder, in the following manner: (1) fraction<0.5 ?m: ?4%, (2) fraction<2 ?m: ?5%, fraction<10 ?m: ?16%, and fraction<40 ?m: 29-45%, where the proportion of zirconia in the fraction of particles having a size smaller than 10 ?m, called “fines”, is between 35% and 75% by weight relative to the total weight of said fraction.

Abstract: Glass melting furnace comprised by several sections which are built entirely with refractory concrete of diverse refractory materials according to operation conditions, chemical environment, temperature, and mechanical load to which its several sections are exposed, as well as to the material thickness required, to assure an structural integrity and durability similar to the ones of furnaces of conventional design as well as a lower investment cost.

Abstract: A fused refractory product having the following average chemical composition, in % by weight on the basis of oxides and for a total of 100%: ZrO2: 30-50%; SiO2: 8-16%; Al2O3: balance to 100%; Y2O3?50/ZrO2 and Y2O3?5%; Na2O+K2O+B2O3?0.2% and SiO2/(Na2O+K2O+B2O3)?5×Y2O3; CaO: ?0.5%; and other oxide species: ?1.5%.

Abstract: Refractory materials are provided which contain P2O5/R2O3 constituents, where R is Y, Sc, Er, Lu, Yb, Tm, Ho, Dy, Tb, Gd, or a combination thereof, and/or V2O5/R?2O3 constituents where R? is Y, Sc, one or more rare earth elements, or a combination thereof. In certain embodiments, the refractory materials are xenotime-type materials and/or xenotime-stabilized zircon-type materials. The refractory materials can be used in the manufacture of glass and glass-ceramics. For example, the refractory materials, especially those that contain P2O5/R2O3 constituents, can be used as forming structures (“isopipes”) in the fusion process for making flat sheets of glass such as the glass sheets used as substrates in the manufacture of flat panel displays.

Abstract: A reactive-ceramming process for making YPO4 ceramics involving the reaction between a YP-glass and a Y-source material. The invention can be used to synthesize, inter alia, phase-pure YPO4 ceramic material 5 at a relatively low temperature in a relatively short period of time and at a low cost. Invention can be used to make large piece of YPO4 blocks suitable for, e.g., an isopipe in a fusion down-draw process for making large-size glass sheets.

Abstract: A refractory object can include at least 10 wt % Al2O3. Further, the refractory object may contain less than approximately 6 wt % SiO2 or may include a dopant that includes an oxide of Ti, Mg, Ta, Nb, or any combination thereof. In an embodiment, at least approximately 1% of the Al2O3 in the refractory object can be provided as reactive Al2O3. In another embodiment, the refractory object may have a density of at least approximately 3.55 g/cc, a corrosion rate of no greater than approximately 2.69 mm/year, or any combination of the foregoing. In a particular embodiment, the refractory object can be used to form an Al—Si—Mg glass sheet. In an embodiment, the refractory object may be formed by a process using a compound of Ti, Mg, Ta, Nb, or any combination thereof.

Abstract: A method of making sheet glass using a pulling roll comprised of a high-temperature millboard material. The millboard comprises aluminosilicate refractory fiber, silicate, mica, and kaolin clay. A method of manufacturing a pulling roll is disclosed, together with a roll produced by the methods disclosed herein. The method comprises forming a pulling roll and densifying at least a portion of the pulling roll by exposing to the pulling roll to high temperatures.

Abstract: The present invention provides a method for identifying a glass defect source, whereby a glass defect source can directly be identified without using a mathematical simulation. The method for identifying a glass defect source, which comprises a step of constructing a glass melting furnace by using, as lining furnace material, a fusion cast refractory containing at least one tracer component selected from Cs2O, SrO, BaO and ZnO, a step of melting a glass material by the glass melting furnace and forming the molten glass material to produce glass products, and a step of extracting one having a glass defect from the glass products and analyzing its component composition to determine the position of a glass defect source in the glass melting furnace.

Abstract: Disclosed is a mold for glass substrate molding, which enables to produce a glass substrate having high flatness by a method for producing a glass substrate through press molding of molten glass. Also disclosed is a method for producing a glass substrate by using such a mold. Specifically disclosed is a mold comprising a lower mold having a first molding surface for pressing a molten glass supplied thereto, and an upper mold having a second molding surface for pressing the molten glass against the first molding surface. In the first molding surface, the surface roughness Ra of the peripheral portion which is in contact with the molten glass after pressing is higher than the surface roughness Ra of the central portion which is in contact with the molten glass before pressing.

Abstract: Isopipes (13) for making a glass or a glass-ceramic using a fusion process are provided. The isopipes are made from an alumina material which has a higher static fatigue than existing alumina materials intended for use as isopipes. In particular, the alumina materials have times-to-failure (static fatigues) of greater than one hour at 1200° C. at an applied stress of 10,000 psi. These high levels of static fatigue allow alumina isopipes to replace zircon isopipes in the manufacture of high performance glass sheets by the fusion process, including glass sheets which are incompatible with zircon isopipes but compatible with alumina isopipes, e.g., chip and scratch resistant glass sheets which have high alkali contents.

Abstract: This invention relates to dense, vertically cracked thermal barrier coatings made from high purity yttria or ytterbia stabilized zirconia powders. The high purity yttria or ytterbia stabilized zirconia powder consisting essentially of less than about 0.01 weight percent silicon dioxide (silica), less than about 0.002 weight percent aluminum oxide (alumina), less than about 0.005 weight percent calcium oxide, less than about 0.005 weight percent ferric oxide, less than about 0 to about 0.002 weight percent magnesium oxide, less than about 0 to about 0.005 weight percent titanium dioxide, from about 1.5 to about 2 weight percent hafnium oxide (hafnia), from about 6 to about 25 weight percent yttrium oxide (yttria), less than 0.1 weight percent other impurity oxides, and the balance zirconium oxide (zirconia) and the balance zirconium oxide (zirconia).

Abstract: Refractory materials are provided which contain P2O5/R2O3 constituents, where R is Y, Sc, Er, Lu, Yb, Tm, Ho, Dy, Tb, Gd, or a combination thereof, and/or V2O5/R?2O3 constituents where R? is Y, Sc, one or more rare earth elements, or a combination thereof. In certain embodiments, the refractory materials are xenotime-type materials and/or xenotime-stabilized zircon-type materials. The refractory materials can be used in the manufacture of glass and glass-ceramics. For example, the refractory materials, especially those that contain P2O5/R2O3 constituents, can be used as forming structures (“isopipes”) in the fusion process for making flat sheets of glass such as the glass sheets used as substrates in the manufacture of flat panel displays.

Abstract: Glass melting furnace comprised by several sections which are built entirely with refractory concrete of diverse refractory materials according to operation conditions, chemical environment, temperature, and mechanical load to which its several sections are exposed, as well as to the material thickness required, to assure an structural integrity and durability similar to the ones of furnaces of conventional design as well as a lower investment cost.

Abstract: A sintered product presenting a mean chemical composition such that, in percentages by weight based on the oxides: Cr2O3: 72.0%-98.9% 2%<Al2O3?20% 0.1%?TiO2?6.0% ZrO2<4.0% SiO2?0.9%.

Abstract: A highly zirconia-based refractory suitable for an electric melting furnace, which has a high electrical resistivity and does not exhibit a chipping off phenomenon and which is scarcely susceptible to extraction of components even when in contact with molten low alkali glass and, hence, is less susceptible to cracking during operation. The highly zirconia-based refractory that includes, as chemical components by mass %, from 85 to 95% of ZrO2 in terms of inner percentage, from 3.0 to 10% of SiO2 in terms of inner percentage, from 0.85 to 3.0% of Al2O3 in terms of inner percentage, substantially no Na2O, from 0.01 to 0.5% of K2O in terms of outer percentage, from 1.5 to 3.0% of SrO in terms of inner percentage, and from 0.1 to 2.0% of Nb2O5 and/or Ta2O5 as a value obtained by [(Nb2O5 content)+(Ta2O5 content/1.66)], in terms of inner percentage.

Abstract: Refractory materials are provided which contain P2O5/R2O3 constituents, where R is Y, Sc, Er, Lu, Yb, Tm, Ho, Dy, Tb, Gd, or a combination thereof, and/or V2O5/R?2O3 constituents where R? is Y, Sc, one or more rare earth elements, or a combination thereof. In certain embodiments, the refractory materials are xenotime-type materials and/or xenotime-stabilized zircon-type materials. The refractory materials can be used in the manufacture of glass and glass-ceramics. For example, the refractory materials, especially those that contain P2O5/R2O3 constituents, can be used as forming structures (“isopipes”) in the fusion process for making flat sheets of glass such as the glass sheets used as substrates in the manufacture of flat panel displays.

Abstract: The present invention provides a fused refractory product having the following average chemical composition, as a % by weight based on the oxides and for a total of 100%; ZrO2: 30%-46%; SiO2: 10%-16%; Al2O3: complement to 100%; Y2O3?50/ZrO2 and Y2O3?5%; Na2O+K2O: 0.5%-4%; CaO: ?0.5%; and other species: ?1.5%. Application to a glass-melting furnace.

Abstract: Isopipes (13) for making a glass or a glass-ceramic using a fusion process are provided. The isopipes are made from a silicon nitride refractory material that is: (a) produced in block form in an atmosphere having a pO2 of less than 0.1 using less than 10 weight percent of one or more sintering aids, (b) machined into an isopipe configuration, and (c) exposed to a partial pressure of oxygen equal to or greater than 0.1 for a period of time and at a temperature sufficient to form a SiO2 layer (31) which exhibits substantially only a passive oxidation mechanism. The SiO2 layer (31) serves as a protective barrier for further oxidation of the silicon nitride during use of the isopipe (13). The isopipes (13) exhibit less sag during use than isopipes composed of zircon.