Abstract: A silica glass crucible includes a cylindrical side wall portion, a curved bottom portion, and a corner portion that is provided between the side wall portion and the bottom portion and has a higher curvature than a curvature of the bottom portion, in which a first region provided from a crucible inner surface to a middle in a thickness direction, a second region that is provided outside the first region in the thickness direction and has a different strain distribution from the first region, and a third region that is provided outside the second region in the thickness direction and up to the crucible outer surface and has a different strain distribution from the second region, are provided, and internal residual stresses of the first region and the third region are compressive stresses, whereas an internal residual stress of the second region includes a tensile stress.

Abstract: A scale composition determination device (10) determines that Fe2O3 has been generated in the outermost layer of a scale (SC) in the case where the absolute value of a difference between temperatures of a steel material SM measured by radiation thermometers (20a, 20b) is equal to or more than a predetermined temperature, and determines that Fe2O3 has not been generated in the outermost layer of the scale (SC) in the case where the absolute value of the difference between the temperatures of the steel material SM measured by the radiation thermometers (20a, 20b) is not equal to or more than the predetermined temperature.

Abstract: Device (1) for determining at least one component parameter, particularly the density and/or a density-related parameter, of a plurality of, particularly additively manufactured, components (3), the device (1) comprising:—a supporting unit (2) configured to support a plurality of components (3) whose at least one component parameter is to be determined, the supporting unit (2) comprising a supporting unit base body (4) comprising a plurality of receiving sections (5) in a defined spatial relationship, whereby at least one receiving section (5) is configured to detachably receive a component (3) whose component parameter is to be determined; one component parameter of components (3) whose at least one component parameter is to be determined being received in respective receiving sections (5) of the supporting unit (2).

Abstract: A method of making a glass sheet includes exposing a refractory block material comprising at least one multivalent component to a reducing atmosphere for a time and at a temperature sufficient to substantially reduce the at least one multivalent component of the refractory block material. The method also includes flowing molten glass over the refractory block material that has been exposed to the reducing atmosphere while preventing substantial re-oxidation of the at least one multivalent component.

Abstract: One aspect relates to a method for the manufacture of doped quartz glass. Moreover, one aspect relates to quartz glass obtainable according to the method including providing a soot body, treating the soot body with a gas, heating an intermediate product and vitrifying an intermediate product.

Abstract: The present invention provides a method of manufacturing a vitreous silica crucible having a transparent layer by use of waste vitreous silica. According to the present invention, there is provided a method of manufacturing a vitreous silica crucible for manufacturing a monocrystalline or polycrystalline silicon ingot, including a process of vitrifying a silica powder sintered body having a crucible shape in the whole or part of the thickness direction by arc fusing the silica powder sintered body from the inner surface side, wherein the method further includes at least one means of (1) depressurizing the silica powder sintered body from the outer surface side during the arc fusing, and (2) forming a synthetic vitreous silica layer on the inner surface by spraying synthetic silica powder onto the inner surface of the silica powder sintered body during the arc fusing.

Abstract: Optical elements (130) are attached to a support film (110) at select locations, the select locations corresponding to locations of light emitting elements (140) on another substrate, e.g. the substrate of the title (150). The film is placed on the substrate containing the light emitting elements such that the optical elements are in contact with their corresponding light emitting elements. The optical elements are laminated to the light emitting elements, and the support film is removed. The optical elements may include wavelength conversion elements, lens elements, combinations of elements, and so on. Other elements, such as conductors and reflectors may also be positioned on the laminate film.

Abstract: A mold for making a fused silica crucible includes a cylindrical can having an interior bore. A graphite insert is received in the bore and has an upper surface adapted to form the lower surface of the crucible while the interior bore of the can forms the side wall of the crucible. Silica grain is deposited in the mold while it rotates. Bores formed in the can above the insert and in the insert draw air through the silica during fusion.

Abstract: A method for producing a silica container having a rotational symmetry includes forming a preliminarily molded article by feeding a powdered substrate's raw material to an inner wall of an outer frame having aspiration holes with rotating the frame, and forming a silica substrate. The preliminarily molded article is aspirated from an outer peripheral side with controlling a humidity inside the outer frame by ventilating gases present in the outer frame with charging from inside the preliminarily molded article a gas mixture comprised of an O2 gas and an inert gas and made below a prescribed dew-point temperature by dehumidification, and at the same time heated from inside the preliminarily molded article by a discharge-heat melting method with carbon electrodes, thereby making an outer peripheral part of the preliminarily molded article to a sintered body while an inner peripheral part to a fused glass body.

Abstract: There is provided a method of manufacturing a vitreous silica crucible having a suitably controlled inner surface property. The present invention provides a method of manufacturing a vitreous silica crucible by heating and fusing a silica powder layer in a rotating mold by arc discharge generated by carbon electrodes including: a preparation process for determining optimal fusing temperatures during heating and fusing the silica powder layer at plural points of different heights of the silica powder layer; a temperature measuring process for measuring actual temperatures during heating and fusing the silica powder layer at the plural points; a temperature controlling process for controlling the actual temperatures at the plural points so that the actual temperatures matches the optimal fusing temperatures at the respective points.

Abstract: A novel array of hollow silica glass microneedles is provided. The array is prepared from a silica dispersion. A novel apparatus is provided comprising a negative mold component having tapered openings therein and a positive mold component having positive elements that are received within the tapered openings of the negative mold component. An assembly is prepared of the negative mold component and the positive mold component, with an aqueous silica dispersion received within the space between the outer surface of the positive elements and the inner surface of the openings. The assembly is heated to remove air and water vapors from the silica dispersion, then the assembly is further heated to sinter the remaining silica to silica glass. The sintered silica glass when removed from the mold components is in the form of an array of microneedles.

Abstract: The present invention provides a silica container for pulling single crystal, the container having a straight body portion, a curved portion, and a bottom portion, wherein an outer side of the container is made of opaque silica glass containing bubbles, and an inner side of the container is made of transparent silica glass, and a mixed silica layer in which a phase in which a crystalline silica powder is fused and a phase in which an amorphous silica powder is fused are mixed in a granular texture is provided on at least an inner surface layer portion of the straight body portion. As a result, there is provided the silica container for pulling single crystal silicon which can suppress melt surface vibration of a silicon melt in the silica container at a high temperature.

Abstract: A porous soot sheet is formed using a roll-to-roll glass soot deposition and sintering process. The soot sheet formation involves depositing glass soot particles on a deposition surface to form a supported soot layer, removing the soot layer from the deposition surface to form a soot sheet, and heating a portion of the soot sheet to locally-sinter the glass soot particles and form a porous soot part having a sintered peripheral edge.

Abstract: A silica crucible is made in a mold cavity of the type in which ambient atmosphere can be drawn through silica grain in the cavity. In one embodiment, a silica grain layer is formed in the mold cavity and gas, which may comprise helium, nitrogen, hydrogen, or a mixture thereof, is introduced into the mold cavity. The silica grain layer is heated while substantially no ambient atmosphere is drawn through the silica grain. Thereafter, at least a portion of the silica grain layer is fused while drawing ambient atmosphere through the silica grain. The gas displaces air in the mold cavity thereby reducing nitrogen oxides and ozone.

Abstract: Methods for producing glass articles of a wide range of geometrical shapes, including shapes that are heretofore difficult or impossible to make monolithically. The glass articles are made by first building the nascent glass article from glass powder and a binder using a three-dimensional printing free-form fabrication process followed by sintering the nascent glass article at a temperature that is hundreds of degrees above the glass powder composition's glass transition temperature while supporting the nascent glass article in a bed of an inert powder having a high flowability.

Abstract: A method includes a providing a molten glass fiber core and disposing a plurality of nanoparticles that include a transition metal oxide on the molten glass fiber core at or above the softening temperature of the glass fiber core, thereby forming a nanoparticle-laden glass fiber. The plurality of nanoparticles are embedded at the surface of said glass fiber core. A method includes providing a mixture of molten glass and a plurality of nanoparticles. The plurality of nanoparticles include a transition metal. The method further includes forming nanoparticle-laden glass fibers, in which the plurality of nanoparticles are embedded throughout the glass fibers.

Abstract: A method of manufacturing a mirror substrate that includes the steps of providing a polishable substrate surface layer formed from ultra low expansion (ULE) glass, depositing successive layers of powdered ULE glass onto the polishable substrate surface layer, and selectively lasing each successive layer of powdered ULE glass to produce successive fused layers of ULE glass joined to one another to form a mirror substrate having an optimized three-dimensional topology. A mirror substrate manufactured according to the prescribed method is also disclosed.

Abstract: The present invention provides a vitreous silica crucible which can suppress the sidewall lowering of the crucible under high temperature during pulling a silicon single crystal, and a method of manufacturing such a vitreous silica crucible. The vitreous silica crucible 10 includes an opaque vitreous silica layer 11 provided on the outer surface side of the crucible and containing numerous bubbles, and a transparent vitreous silica layer 12 provided on the inner surface side. The opaque vitreous silica layer 11 includes a first opaque vitreous silica portion 11a provided on the crucible upper portion, and a second opaque vitreous silica portion 11b provided on the crucible lower portion. The specific gravity of the second opaque vitreous silica portion 11b is 1.7 to 2.1, and the specific gravity of the first opaque vitreous silica portion 11a is 1.4 to 1.8, and smaller than that of the second opaque vitreous silica portion.

Abstract: A method of forming a cladding portion of an optical fiber preform assembly includes positioning a glass core cane in a mold cavity and loading the mold cavity with silica glass soot. The silica glass soot is compressed in an axial direction as the vibratory energy is applied to the mold body to form a soot compact around the glass core cane, wherein the soot compact is the cladding portion of an optical fiber preform assembly and the glass core cane is a core portion of the optical fiber preform assembly.

Abstract: A process is disclosed for simple and rapid production of a shaped body comprising fused silica and a shaped body which leads to virtually no contamination of a melt in contact with the shaped body even at high temperatures. The disclosed process comprises the steps of: a) provision of fused silica in the form of essentially amorphous SiO2 grains of which not more than 5% have a diameter greater than 15 mm, b) addition of water to the fused silica grains to produce a slip, c) casting of the slip into a mold which comprises a hollow body having the inverse shape of the shaped body to be produced, and d) drying of the slip to give an intermediate body, which is then sintered and cooled. A shaped body producible in accordance with the aforementioned process is also disclosed, which comprises at least 99.0 mol % of SiO2.

Abstract: A method for producing a silica container having a rotational symmetry includes forming a preliminarily molded article by feeding a powdered substrate's raw material to an inner wall of an outer frame having aspiration holes with rotating the frame, and forming a silica substrate. The preliminarily molded article is aspirated from an outer peripheral side with controlling a humidity inside the outer frame by ventilating gases present in the outer frame with charging from inside the preliminarily molded article a gas mixture comprised of an O2 gas and an inert gas and made below a prescribed dew-point temperature by dehumidification, and at the same time heated from inside the preliminarily molded article by a discharge-heat melting method with carbon electrodes, thereby making an outer peripheral part of the preliminarily molded article to a sintered body while an inner peripheral part to a fused glass body.

Abstract: Provided are an apparatus and a method for manufacturing a vitreous silica crucible, which enable accurate measurement of a fume generation amount, prevention of deterioration of an inner surface property, and real-time control of a raw material melting state. Provided is an apparatus for manufacturing a vitreous silica crucible 50 by supplying silica powder into a mold 10 to form a silica powder layer 11, and heating and melting the silica powder layer 11 by arc discharge. The apparatus includes the mold 10 for defining an outer shape of a vitreous silica crucible, an arc discharge unit having a plurality of carbon electrodes 13 and a power-supply unit 40, and a fume-amount measurement unit 30 for detecting an amount of fumes 80 generated in the mold 10.

Abstract: Accurate temperature measurement during manufacturing a vitreous silica crucible is enabled. The present invention provides an apparatus for manufacturing a vitreous silica crucible including: a mold for forming a silica powder layer by supplying silica powder therein; an are discharge unit having carbon electrodes and a power supply unit and for heating and fusing the silica powder layer by arc discharge; and a temperature measurement unit for measuring temperature of a fused portion in the mold, wherein the temperature measurement unit is an radiation thermometer for measuring temperature by detecting radiation energy of a wavelength of 4.8 to 5.2 ?m.

Abstract: The present invention is directed to a single-crystal silicon pulling silica container, the silica container including a straight body portion, a curved portion, and a bottom portion, wherein the OH group concentration in the straight body portion is 30 to 300 ppm by mass, the OH group concentration in the bottom portion is 30 ppm by mass or less, and the difference in the OH group concentration between the straight body portion and the bottom portion is 30 ppm by mass or more. As a result, a low-cost single-crystal silicon pulling silica container, the silica container that can reduce cavity defects called voids and pinholes in pulled single crystal silicon, is provided.

Abstract: A glass, glass-ceramic, or ceramic bead is described, with an internal porous scaffold microstructure that is surrounded by an amorphous shield. The shield serves to protect the internal porous microstructure of the shield while increasing the overall strength of the porous microstructure and improve the flowability of the beads either by themselves or in devices such as biologically degradable putty that would be used in bone or soft tissue augmentation or regeneration. The open porosity present inside the bead will allow for enhanced degradability in-vivo as compared to solid particles or spheres and also promote the growth of tissues including but not limited to all types of bone, soft tissue, blood vessels, and nerves.

Abstract: Embodiments of the invention generally relate to a transparent material having an increased resistance to plasma erosion. The material is formed from yttrium oxide (Y203) at a starting powder composition ranging from about 5 weight percent (wt %) to about 40 weight percent; aluminum oxide (Al203) at a starting powder composition ranging from about 5 weight percent to about 30 weight percent; silicon dioxide (SiO2) at a starting powder composition ranging from about 10 weight percent to about 80 weight percent; and magnesium oxide (MgO) at a starting powder composition ranging from about 1 weight percent to about 20 weight percent. The material may be a glass or glass-ceramic.

Abstract: A method for producing a silica container having a rotational symmetry is provided. The method includes forming a preliminarily molded article by feeding a powdered substrate's raw material to an inner wall of an outer frame having aspiration holes with rotating the frame, and forming a silica substrate. The preliminarily molded article is aspirated from an outer peripheral side with controlling a humidity inside the outer frame by ventilating gases present in the outer frame with charging from inside the preliminarily molded article a gas mixture comprised of an O2 gas and an inert gas and made below a prescribed dew-point temperature by dehumidification, and at the same time heated from inside the preliminarily molded article by a discharge-heat melting method with carbon electrodes, thereby making an outer peripheral part of the preliminarily molded article to a sintered body while an inner peripheral part to a fused glass body.

Abstract: The present invention provides a method of manufacturing a vitreous silica crucible including: a silica powder supplying process of supplying a material silica powder into a mold for molding a crucible, to form a silica powder layer, and an arc fusing process of arc fusing the silica powder layer by arc discharge generated by carbon electrodes, wherein the arc fusing process includes processes of measuring a temperature of the silica powder layer, and controlling a vitreous silica fused state based on a reference temperature which is a temperature at a local maximum point which appears first in the arc fusing process.

Abstract: This disclosure involves a new spinel and glass micro-composite material and process for making such. The composite has excellent transmission in the 0.5-5.0 ?m wavelength region suitable for various visible and mid IR applications utilizing windows, domes and other geometric shapes. The composite can be made at a temperature about 40% lower than the glass melting temperature and about 50% lower than the spinel sintering temperature. The composite material has high modulus and fracture toughness which are important for impact resistance in armor and other practical applications.

Abstract: A near-net or net shape fused silica glass article, such as a radome. The article is formed by depositing silica soot onto a mandrel having a shape that corresponds to the shape of the fused silica glass article. In some embodiments, the mandrel is inductively heated to a temperature that is sufficient to consolidate or sinter the silica soot upon deposition onto the mandrel to form fused silica glass. The fused silica glass article may have an outer layer that is under compression and/or multiple layers comprising various dopants that can alter or affect physical, mechanical, electrical, and/or optical properties.

Abstract: There are provided an apparatus and a method for manufacturing a vitreous silica crucible which can prevent the deterioration of the inner surface property in the manufacturing process of a vitreous silica crucible. The apparatus includes a mold defining an outer shape of a vitreous silica crucible, and an arc discharge unit having electrodes and a power-supply unit, wherein each of the electrodes includes a tip end directed to the mold, the other end opposite to the tip end, and a bent portion provided between the tip end and the other end.

Abstract: A method for producing a silica container, the method including forming a preliminarily molded silica substrate to an intended shape by feeding a powdered substrate's raw material (silica particles) to an inner wall of a carbon-made outer frame having aspiration holes with rotating the outer frame, and forming the silica substrate wherein the preliminarily molded substrate is degassed by aspiration from its outer peripheral side with charging from an inner peripheral side of the preliminarily molded silica substrate a reducing gas containing more than 10% by volume of an H2 gas, and at the same time heated from inside the preliminarily molded silica substrate by a discharge-heat melting method with carbon electrodes, thereby making an outer peripheral part of the preliminarily molded silica substrate to a sintered body while an inner peripheral part of the preliminarily molded silica substrate to a fused glass body.

Abstract: The present invention provides a method of manufacturing a vitreous silica crucible by heating and fusing a silica powder layer in a rotating mold by arc discharge generated by carbon electrodes comprising: a preparation process for determining optimal temperatures during heating and fusing the silica powder layer for one or more selected from the group consisting of the silica powder layer, fume generated during arc fusing, and arc flame generated in the arc discharge; a temperature measuring process for measuring actual temperatures during heating and fusing for one or more selected from the group where the optimal temperatures are determined; and a temperature controlling process for controlling the actual temperatures for one or more selected from the group where the actual temperatures are measured so that the actual temperatures match the optimal temperatures.

Abstract: The disclosure relates to methods of forming a vessel and to the resulting vessel. The vessel may be formed by providing a first fumed silica soot layer comprised of primary particles of fumed silica soot, and then providing over the first fumed silica soot layer a second fumed silica soot layer comprised of agglomerated particles formed into an agglomerated form from primary particles of fumed silica soot. The primary particles of the first fumed silica soot layer may have a substantially uniform density distribution, and the agglomerated particles of the second fumed silica soot layer may have a substantially non-uniform density distribution. The methods may include consolidating the first and second soot layers together to form a consolidated body.

Abstract: An abrasive element consisting substantially of a glass material that is at least partially devitrified.

Abstract: The present invention provides a method of manufacturing a vitreous silica crucible including: a silica powder supplying process of supplying a material silica powder into a mold for molding a vitreous silica crucible, to form a silica powder layer, and an arc fusing process of arc fusing the silica powder layer by arc discharge generated by carbon electrodes, wherein the arc fusing process includes processes of measuring temperatures at measuring points provided on different heights of an inner surface of the silica powder layer while rotating the mold, and controlling the arc discharge to enable detection, at each measuring point, of a local maximum point which appears first in the arc fusing process.

Abstract: There is provided a method of manufacturing a vitreous silica crucible having non-bubbles on the inner surface without necessitating new apparatuses for grinding and polishing and without damaging the productivity. According to the present invention, there is provided a method of manufacturing a vitreous silica crucible including the processes of: gathering a vitreous silica layer containing residual bubbles existing in a near-surface region of the transparent layer of the vitreous silica crucible by controlling the number of rotations applied to the vitreous silica crucible in a state that an inner surface side of the vitreous silica crucible is fused by arc heating; and moving a portion of a non-bubble layer in the surface of the transparent layer exposed by movement of the residual bubble-containing layer to cover a region in which bubbles have gathered with the non-bubble layer.

Abstract: A high-surface quality glass sheet is formed using a roll-to-roll glass soot deposition and sintering process. The glass sheet formation involves providing glass soot particles, depositing a first fraction of the glass soot particles on a deposition surface to form a supported soot layer, electrostatically attracting and collecting a second fraction of the glass soot particles onto a surface of a charged plate, removing the soot layer from the deposition surface to form a soot sheet, and heating at least a portion of the soot sheet to sinter the glass soot particles to form a glass sheet.

Abstract: The present invention relates to a process for production of a TiO2—SiO2 glass body, comprising a step of, when an annealing point of a TiO2—SiO2 glass body after transparent vitrification is taken as T1(° C.), holding the glass body after transparent vitrification in a temperature region of from T1?90(° C.) to T1?220(° C.) for 120 hours or more.

Abstract: A method and apparatus for making an optical fiber preform. The apparatus has an outer wall and an inner wall. The outer wall surrounds the inner wall and the inner wall surrounds an inner cavity of the apparatus. A consolidated glass rod is deposited in the inner cavity after which particulate glass material, such as glass soot, is deposited in the inner cavity around the glass rod. A radially inward pressure is applied against the particulate glass material to pressurize the particulate glass material against the glass rod.

Abstract: The present invention relates to a method for producing a glass body containing: hydrolyzing a silicon compound and a compound containing a metal serving as a dopant, in a flame projected from a burner to form glass fine particles; and depositing and growing the formed glass fine particles on a base material, in which a raw material mixed gas containing a gas of the silicon compound, a gas of the compound containing a metal serving as a dopant, and either one of a combustible gas and a combustion supporting gas is fed into a central nozzle (A) positioning in the center of the burner; the other gas of the combustible gas and the combustion supporting gas is fed into a nozzle (B) different from the central nozzle (A) of the burner; a combustible gas or a combustion supporting gas is arbitrarily fed into a nozzle different from the nozzles (A) and (B); and a flow rate of the raw material mixed gas is 50% or more and not more than 90% of the largest flow rate among flow rate(s) of the combustible gas(ses) and the

Abstract: A titania and sulfur co-doped quartz glass member is provided. Due to co-doping of titania and sulfur, the quartz glass member undergoes zero expansion at a certain temperature and low thermal expansion over a wide temperature range, and is thus suited for use in a commercial EUV lithography tool. A manufacturing method and an optical member for EUV lithography are also provided.

Abstract: Described herein is a method for producing a quartz glass crucible, including the steps of: preparing a crucible base material that is made of quartz glass and has a crucible shape; producing a synthetic quartz glass material by the direct process or the soot process; processing the synthetic quartz glass material into a crucible shape without pulverizing the synthetic quartz glass material; and welding the synthetic quartz glass material processed into the crucible shape to the inner surface of the crucible base material. As a result, there are provided a quartz glass crucible that avoids generation of dislocation in a silicon single crystal, the generation of dislocation caused by the crucible itself, at the time of production of a silicon single crystal and has high heat resistance, a method for producing the quartz glass crucible, and a method for producing a silicon single crystal, the method using such a quartz glass crucible.

Abstract: A method for making a smooth ceramic including loading ceramic powder to be densified into a hot press die, placing one or more spacers with a polished surface between a hot press punch and the ceramic powder, placing the die and punch into a hot press and hot pressing the ceramic powder, and removing a smooth ceramic shape that requires no subsequent polishing or processing and has a surface roughness of 5 nm RMS or better. The smooth ceramic shape may be transparent, and it may be spinel, magnesia, yttria, lutetia, scandia, YAG, any composites thereof, or any of their rare earth doped compounds. Also disclosed is the related smooth ceramic made by this process.

Abstract: A method and an apparatus for making an optical fiber preform comprising the steps of (i) depositing a plurality of rods are deposited into an inner cavity of an apparatus; (ii) depositing particulate glass material in the inner cavity between the rods and the inner wall; and (iii) applying pressure against the particulate glass material to pressurize the particulate glass material against the plurality of rods.

Abstract: A method is provided for producing a silica container arranged with a substrate, having a rotational symmetry, comprised of mainly a silica, and containing gaseous bubbles at least in its peripheral part, and an inner layer, formed on an inner surface of the substrate and comprised of a transparent silica glass; wherein a powdered silica, having particle diameter of 10 to 1000 ?m, containing Ca, Sr, and Ba with the total concentration of 50 to 5000 ppm by weight, and releasing hydrogen molecules with the amount of 3×1016 to 3×1019 molecules/g upon heating at 1000° C. under vacuum, is prepared at least as a powdered raw material for forming the inner layer, and then the inner layer is formed from the powdered silica as the powdered raw material for forming the inner layer.

Abstract: The disclosure relates to methods of forming a vessel and to the resulting vessel. The vessel may be formed by providing a first fumed silica soot layer comprised of primary particles of fumed silica soot, and then providing over the first fumed silica soot layer a second fumed silica soot layer comprised of agglomerated particles formed into an agglomerated form from primary particles of fumed silica soot. The primary particles of the first fumed silica soot layer may have a substantially uniform density distribution, and the agglomerated particles of the second fumed silica soot layer may have a substantially non-uniform density distribution. The methods may include consolidating the first and second soot layers together to form a consolidated body.

Abstract: A vibratory finishing medium element having at least a portion comprising a devitrified material.

Abstract: The present invention provides an alkali-free glass having a high strain point, a low viscosity and low devitrification, which is easily subjected to float molding and fusion molding. The glass herein has a strain point of 725° C. or higher, an average thermal expansion coefficient at 50 to 300° C. of 30×10?7 to 40×10?7/° C., a temperature T2 at which a glass viscosity becomes 102 dPa·s of 1,710° C. or lower, a temperature T4 at which a glass viscosity becomes 104 dPa·s of 1,330° C. or lower, a glass surface devitrification temperature (Tc) of 1,330° C. or lower, and a glass internal devitrification temperature (Td) of 1,330° C. or lower.

Abstract: An arc discharge method includes the steps of heating and melting a non-conductive object by arc discharge using a plurality of carbon electrodes in a output range of 300 to 12,000 kVA; and setting a ratio of the distance between a contact position at which the carbon electrodes come in contact with each other and a front end to the diameter of the carbon electrode during the start of the arc discharge to be in the range of 0.001 and 0.9.