Abstract: A cutting method and an apparatus are provided which enable a rim area or other part of a vitreous silica crucible to be cut off so as to leave a smooth cut surface without damaging the cut edge, etc. The apparatus for cutting a vitreous silica crucible comprises a disk-shaped cutting blade (10) disposed sideways with respect to the vitreous silica crucible, a means for rotating the cutting blade (10), a cutting-blade moving means which moves the cutting blade (10) in a circumferential direction for the crucible, and a means for rotating the crucible (20). Without rotating the crucible (20), the cutting blade (10) being rotating is brought into contact with a surface of the crucible wall and pushed forward in the wall thickness direction to make a cut piercing the crucible wall. The cutting blade (10) is moved relatively to the crucible (20) in the circumferential direction for the crucible (20) while keeping the cutting blade in the state of piercing the wall.

Abstract: Leakage of silicon melt is monitored and touch of a seed crystal at the silicon melt is detected, and in addition, reinforcement of a vitreous silica crucible to be endurable during pulling for a long time and decrease of impurity concentration of a silicon single crystal can be expected. A method for manufacturing a silicon single crystal is provided.

Abstract: A silica glass crucible including an outer surface layer formed of a bubble-containing silica glass layer and an inner surface layer formed of a silica glass layer whose bubbles are invisible to the naked eye, so as to sufficiently disperse heat from the external radiation thereby preventing temperature irregularity in the silicon melt, and at the same time, exhibit excellent heat conductivity thereby giving a uniformly heated state over a wide range in the entire crucible without taking a long time for increasing the temperature to form a silicon melt, wherein an intermediate layer is interposed between the outer surface layer and the inner surface layer while in the intermediate layer, a bubble-containing silica glass layer (bubble-containing layer) including bubbles with a diameter of 100 ?m or smaller by 0.1% or more in the volumetric bubble content and a silica glass layer (transparent glass layer) including the bubbles by 0.05% or less in the volumetric bubble content are laminated.

Abstract: A vitreous silica crucible for pulling single-crystal silicon, in which the vibration of a melt surface at the initial stage of the pulling of single-crystal silicon can be suppressed, a shoulder portion of single-crystal silicon can be stably formed, and a high yield of single-crystal silicon can be achieved.

Abstract: Provided is a vitreous silica crucible which can restrain inward collapse deformation at high temperature during pulling even when the crucible has a large opening diameter. The vitreous silica crucible has an outer layer made of natural fused silica and an inner layer made of synthetic fused silica. The straight body section is outwardly-widened upwardly. Preferably, the difference in inner diameter of the lower and upper ends of the outwardly-widened section is 0.1% or more. The inner layer made of synthetic fused silica on the corner section has a layer thickness which is 20% to 80% of the wall thickness of the central portion of the corner section. Preferably, the inner layer made of synthetic fused silica on the straight body section and the bottom section is thinner than that on the corner section.

Abstract: Provided is a vitreous silica crucible for pulling silicon single crystals, which can melt a silicon raw material in a short time and improve production yield of silicon single crystals by temporal change of an opaque vitreous silica layer. The vitreous silica crucible includes an opaque vitreous silica layer(11) provided on an outer surface thereof and containing plural bubbles, and a transparent vitreous silica layer(12) provided on an inner surface and not containing bubbles substantially. The opaque vitreous silica layer(11) has a bubble diameter distribution in which the content of bubbles having a diameter of less than 40 ?m is 10% or more and less than 30%, the content of bubbles having a diameter of 40 ?m or more and less than 90 ?m is 40% or more and less than 80%, and the content of bubbles having a diameter equal to or more than 90 ?m is 10% or more and less than 30%.

Abstract: A method of manufacturing a vitreous silica crucible by a rotary mold method, which includes performing arc melting in a state in which electrodes are provided so as to be shifted from a mold central line, wherein, by this eccentric arc, the glass temperature difference during melting of a straight body portion, a curved portion and a bottom of the crucible is controlled to 300° C. or below and the thickness of a transparent layer of the straight body portion and the bottom is controlled to 70 to 120% of the thickness of a transparent layer of the curved portion.

Abstract: In order to provide a vitreous silica crucible which does not employ a crystallization accelerator but is difficult to deform during its use even under high temperature, and is easily manufactured, there is provided a vitreous silica crucible for pulling single-crystal silicon wherein the outer surface layer is formed of a bubble-containing vitreous silica layer, the inner surface layer is formed of a vitreous silica layer whose bubbles are invisible to the naked eye, a surface of the outer surface layer includes an unmelted or half-melted silica layer (abbreviated as a half-melted silica layer), and the center line average roughness (Ra) of the half-melted silica layer is 50 to 200 ?m, also preferably, and the thickness of the half-melted silica layer is 0.5 to 2.0 mm.

Abstract: In order to provide method and apparatus for manufacturing a vitreous silica crucible with little mixing of foreign matter and stable arc during arc melting, the method and apparatus for manufacturing a vitreous silica crucible have a device which blows off air from the side of arc electrodes toward a melting space of a mold, and air discharge ports which discharge the air within the heating furnace, and perform forced supply of air into the melting space during melting to make the atmospheric pressure of the melting space higher than the surroundings, and preferably, form an air pressure difference of 100 Pa or more between the melting space and the surroundings, thereby performing melting.

Abstract: A closure for silica glass crucible to be mounted on an opening portion of a silica glass crucible is provided with a peripheral edge mounting portion closely adhered to an inner peripheral end of the opening portion.

Abstract: A modification process of the synthetic quartz powder, which can make a quartz glass product hardly having bubbles at the time of fusing, is provided, along with a modification process of the synthetic quartz powder and a glass product using said modified quartz powder are provided, wherein the synthetic quartz powder is kept in helium atmosphere at least in the temperature falling process, when the amorphous synthetic quartz powder produced by the sol-gel method is carried out by heat treatment in a vacuum furnace at more than the degas temperature and less than the baking temperature, wherein the highest temperature in the helium atmosphere is preferably set to from more than 700° C. to less than 1400° C., and the helium atmosphere is kept to less than 400° C.

Abstract: A surface modified quartz glass crucible and a process for modifying the crucible includes a layer of a metal oxide on the whole or a part of the inside and/or outside of the crucible, and baking it. At least an inside surface of the crucible is coated with a said metal oxide of magnesium, calcium, strontium or barium. The coated layer of the crucible does not abrade easily and provides a high dislocation free ratio of silicon single crystals pulled by using the crucible.

Abstract: A process reinforcing a silica glass substance, such as a silica glass crucible, is provided without intermixing an impurity. The process comprises forming a silica glass powder layer on a surface of the silica glass substance, and crystallizing said silica glass powder layer under high temperature. As for a silica glass crucible, the process for reinforcing the silica glass crucible and the reinforced silica glass crucible are provided, wherein the silica glass powder layer on the whole or a part of the surface of the crucible is formed and then, crystallized under a temperature at the melting of a silicon raw material being charged into said quartz glass crucible.

Abstract: A crucible for pulling a silicon single crystal has a double structure comprising a silica crucible and a graphite crucible covering an outside of the silica crucible, wherein the silica crucible is provided at its opening end portion with an inward falling prevention means for imparting a radially outward force to a body portion of the silica crucible.

Abstract: A carbon electrode grinding apparatus for shaping a front end of an arc discharge carbon electrode is provided with front end grinding blades configured to grind a front end surface of the carbon electrode, lateral surface grinding blades configured to grind a surface from the front end surface to a base end of the carbon electrode, and rotation means configured to rotate and drive the front end grinding blades and the lateral surface grinding blades around a rotation axis line coincident with an axis line of the carbon electrode.

Abstract: There is provided a mold for use in the production of a silica crucible by heat-fusing silica or quartz powder attached onto an inner wall of a rotating mold, wherein an inner side of an upper opening portion of the mold corresponding to an upper part of the silica crucible is ground to obtain a step portion and a ring-shaped heat insulating barrier member having an inner diameter smaller than that of the mold is disposed on the step portion through a hollow disk-shaped support member having an inner diameter equal to or somewhat larger than that of the heat insulating barrier member.

Abstract: In a mold for use in the production of a silica crucible, a mold cover corresponding to a small-diameter thinned portion of an upper part of the silica crucible is detachably disposed on a mold substrate corresponding to a main body of the silica crucible, and the mold cover has a barrier function against arc heating, and an inner diameter of the mold cover is smaller than that of the mold substrate but larger than that of the silica crucible.

Abstract: In a mold for use in the production of a silica crucible, a cylindrical rim member is engagedly supported through hooks to an inner side of an upper opening portion of the mold corresponding to an upper part of a silica crucible and an outer diameter of the rim member is smaller than an inner diameter of the mold but larger than an inner diameter of the silica crucible.

Abstract: A vitreous silica crucible manufacturing apparatus includes a plurality of carbon electrodes configured to heat and melt raw material powder by arc discharge, and a value of a ratio R2/R1 of a diameter R2 of a front end of each of the carbon electrodes to a diameter R1 of a base end is set in a range of 0.6 to 0.8. Each carbon electrode has a diameter reduction portion formed at a front end position and reduced in diameter from a diameter R3 of a base end side to the diameter R2 of the front end. When a length of the diameter reduction portion is L1, the diameter of the front end is R2, the diameter of the base end is R1, an angle between the axis lines of the carbon electrodes is ?1, and X=(R1?R2)/2, a value of L1?(X/tan(?1/2)) is set in a range of 50 to 150 mm.

Abstract: Colored foreign particles contained in quartz powder material are detected in a high precision with the specified detection apparatus even when the colored foreign particles are pale colored foreign particles such as iron-based refuse, organic refuse and carbon-based refuse.