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: 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: 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 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: 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: 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: A method for manufacturing a silicon single crystal is provided including producing a silicon melt in a chamber by melting a silicon raw material loaded into a silica glass crucible under a reduced pressure and high temperature, removing gas bubbles from within the silicon melt by rapidly changing at least the pressure or temperature within the chamber, and pulling up the silicon single crystal from the silicon melt after the gas bubbles are removed. When the pressure is rapidly changed, the pressure within the chamber is rapidly changed at a predetermined change ratio. In addition, when the temperature is rapidly changed, the temperature within the chamber is rapidly changed at a predetermined change ratio. In this way, Ar gas attached to an inner surface of the crucible and h is the cause of the generation of SiO gas is removed.

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.

Abstract: A silica glass crucible for pulling up a silicon single crystal including an outer layer formed from a natural silica glass layer, and an inner layer formed from a synthetic silica glass layer, wherein the synthetic silica glass layer includes a first synthetic silica glass layer formed in a region within a certain range from the center of a crucible bottom section, and a second synthetic silica glass layer formed in a region which excludes the formation region of the first synthetic silica glass layer, and wherein the first synthetic silica glass layer has a thickness of 0.5 mm or more and 1.5 mm or less and a concentration of an OH group included in the first synthetic silica glass layer being 100 ppm or less.

Abstract: A silica glass crucible for pulling up a silicon single crystal including a wall part, a corner part and a bottom part is provided with an outer layer formed from an opaque silica glass layer which includes many bubbles, and an inner layer formed from a transparent silica glass layer which substantially does not include bubbles, wherein at least one part of an inner surface of the wall part and the corner part being an uneven surface formed with multiple damaged parts having a depth of 50 ?m or more and 450 ?m or less, and wherein a region among the inner surface of the bottom part within a certain range from the center of the bottom part being a smooth surface which does is substantially not formed with damage.

Abstract: The disclosed is a method of manufacturing a silica glass crucible for pulling silicon single crystals. In the method, reduced pressure is imparted from the inner surface to the outer surface of a crucible-shaped molded product and the crucible-shaped molded product is arc-fused while rotating the same to form a silica glass crucible with a transparent layer on the inner surface side and a bubble layer on the outer surface side. The inner surface of the wall portion of the silica glass crucible is fused a second time by arc fusion to cause bubbles present in the transparent layer of the inner surface of the wall portion to be displaced toward the bottom portion of the inner surface of the wall portion. The inner surface of the bottom portion of the silica glass crucible is fuse a second time by arc fusion to cause bubbles present in the transparent layer of the inner surface of the bottom portion to be displaced toward the periphery of the inner surface of the bottom portion.

Abstract: A silica glass crucible for pulling up a silicon single crystal including a wall part and a bottom part is provided with a natural silica glass layer which forms at least one part of a an inner surface of the bottom part, and a synthetic silica glass layer which forms at least an inner surface of the wall part, wherein a concentration of Ca included in the natural silica glass layer is 0.5 ppm or less.

Abstract: Disclosed is a silica glass crucible employed in pulling silicon single crystals. The crucible comprises at least a transparent layer, semitransparent layer, and opaque layer disposed from the inner surface side to the outer surface side of the crucible. The content of bubbles in the transparent layer is less than 0.3 percent; the content of bubbles in the semitransparent layer falls within a range of from 0.3 to 0.6 percent; and the content of bubbles in the opaque layer is greater than 0.6 percent.

Abstract: A mold for the production of a silica crucible by heat-fusing silica or quartz powder attached onto an inner wall of a rotating mold, wherein a ring-shaped heat insulating barrier material having a specified inner diameter is disposed on an inner peripheral wall of an upper opening portion of the mold corresponding to an upper region of the silica crucible.

Abstract: A method of manufacturing a carbon electrode for melting an object to be melted by arc discharge, includes: a rubbing step of rubbing the surface of the carbon electrode before power is supplied with a rubbing material of the same type as the object to be melted.

Abstract: An arc discharge method of the present invention includes the steps of: heating and melting a non-conductive object by arc discharge using a plurality of carbon electrodes in an 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 to 0.9.

Abstract: A method of manufacturing a fused silica crucible by heating and melting a vitreous silica powder compact shaped into a mold using arc discharge of electrodes arranged around a rotation shaft of the mold, includes the steps of: arranging the electrodes in a ring shape, and setting a ratio W/R of a horizontal distance W between the electrode front end and the surface of the vitreous silica powder compact to a vitreous silica powder compact opening radius R, for at least a predetermined time during arc heating, to be in the range of 0.002 to 0.98.

Abstract: A precious metal foil composite comprising a precious metal foil encased, by lamination, in a transparent polymeric sheet material. The composite cards produced from this composite material are used for practical purposes by encasing the above composite together with another component having opaque decorative patterns, and finally encasing the entire assembly in a secondary hard protective covering to provide the outermost protection.

Abstract: There is disclosed a precious metal article which is formed of a solid-phase sintered product of a precious metal powder. For manufacturing the precious metal article, a moldable mixture which contains a precious metal powder and a binder removable by sintering is shaped into a prescribed molded object, and the molded object is then subjected to sintering. The moldable mixture is produced by preparing a precious metal powder, preparing a jellylike cellulose binder by blending a cellulose with water and leaving for a prescribed period of time, and blending the precious metal powder and the jellylike cellulose binder together. The most preferable moldable mixture contains 50 to 90% by weight of precious metal powder, 0.8 to 8% by weight of water-soluble cellulose binder, 0.08 to 3% by weight of a surface-active agent. 0.1 to 3% by weight of oil, balance water and unavoidable impurities.

Abstract: A precious metal foil composite comprising a precious metal foil encased, by lamination, in a transparent polymeric sheet material. The composite cards produced from this composite material are used for practical purposes by encasing the above composite together with another component having opaque decorative patterns, and finally encasing the entire assembly in a secondary hard protective covering to provide the outermost protection.