Abstract: Provided are a method for producing sodium tungstate by supplying an oxidant made of sodium nitrate or sodium nitrite to bring a tungsten containing material and the oxidant into contact with each other in an atmosphere containing oxygen to thereby continuously produce a reaction product; a method for collecting tungsten using the method; and an apparatus for producing sodium tungstate. Also provided are a method for producing a sodium tungstate aqueous solution in which a reductant is introduced into a melt containing the above-described reaction product which is then dissolved in water; and a method for collecting tungsten using the method.

Abstract: Provided are a method for producing sodium tungstate by supplying an oxidant made of sodium nitrate or sodium nitrite to bring a tungsten containing material and the oxidant into contact with each other in an atmosphere containing oxygen to thereby continuously produce a reaction product; a method for collecting tungsten using the method; and an apparatus for producing sodium tungstate. Also provided are a method for producing a sodium tungstate aqueous solution in which a reductant is introduced into a melt containing the above-described reaction product which is then dissolved in water; and a method for collecting tungsten using the method.

Abstract: Provided are a method for producing sodium tungstate by supplying an oxidant made of sodium nitrate or sodium nitrite to bring a tungsten containing material and the oxidant into contact with each other in an atmosphere containing oxygen to thereby continuously produce a reaction product; a method for collecting tungsten using the method; and an apparatus for producing sodium tungstate. Also provided are a method for producing a sodium tungstate aqueous solution in which a reductant is introduced into a melt containing the above-described reaction product which is then dissolved in water; and a method for collecting tungsten using the method.

Abstract: Provided are a method for producing sodium tungstate by supplying an oxidant made of sodium nitrate or sodium nitrite to bring a tungsten containing material and the oxidant into contact with each other in an atmosphere containing oxygen to thereby continuously produce a reaction product; a method for collecting tungsten using the method; and an apparatus for producing sodium tungstate. Also provided are a method for producing a sodium tungstate aqueous solution in which a reductant is introduced into a melt containing the above-described reaction product which is then dissolved in water; and a method for collecting tungsten using the method.

Abstract: Provided are a method for producing sodium tungstate by supplying an oxidant made of sodium nitrate or sodium nitrite to bring a tungsten containing material and the oxidant into contact with each other in an atmosphere containing oxygen to thereby continuously produce a reaction product; a method for collecting tungsten using the method; and an apparatus for producing sodium tungstate. Also provided are a method for producing a sodium tungstate aqueous solution in which a reductant is introduced into a melt containing the above-described reaction product which is then dissolved in water; and a method for collecting tungsten using the method.

Abstract: Provided are a method for producing sodium tungstate by supplying an oxidant made of sodium nitrate or sodium nitrite to bring a tungsten containing material and the oxidant into contact with each other in an atmosphere containing oxygen to thereby continuously produce a reaction product; a method for collecting tungsten using the method; and an apparatus for producing sodium tungstate. Also provided are a method for producing a sodium tungstate aqueous solution in which a reductant is introduced into a melt containing the above-described reaction product which is then dissolved in water; and a method for collecting tungsten using the method.

Abstract: A diamond electrode includes a conductive silicon substrate having a plurality of pores. The diamond electrode also includes a conductive diamond covering the conductive silicon substrate. The inner wall surfaces of the plurality of pores are at an angle of 60° to 85° with respect to a substrate of the conductive silicon substrate.

Abstract: A diamond electrode includes a conductive silicon substrate having a plurality of pores. The diamond electrode also includes a conductive diamond covering the conductive silicon substrate. The inner wall surfaces of the plurality of pores are at an angle of 60° to 85° with respect to a substrate of the conductive silicon substrate.

Abstract: A conductive polycrystalline diamond film having specific resistance of at least 1×10−4 &OHgr;cm and less than 1×103 &OHgr;cm, whose film thickness is in the range of at least 0.1 &mgr;m and not more than 500 &mgr;m, is film-formed by vapor-phase synthesis on a surface employed for pressure bonding, a surface opposite to this surface or at least two side surfaces intersecting with these surfaces on a substrate of a bonding tool tip that is applicable for bonding and packaging a semiconductor chip.

Abstract: A polycrystalline diamond is prepared by chemical vapor deposition (step 101). A surface of the polycrystalline diamond is metallized (step 102). The metallized surface of the polycrystalline diamond is grooved with a YAG laser (step 103). A wedge or the like is driven into the grooves of the polycrystalline diamond to pressurize the same, whereby the polycrystalline diamond is divided along the grooves (step 104). Alternatively, a surface of a polycrystalline diamond prepared by chemical vapor deposition is grooved with a YAG laser (step 112), and the surface of the polycrystalline diamond is metallized (step 113) after the grooving. The obtained diamond heat sink (10) includes a first layer (11a) grooved with a laser, and a mechanically divided second layer (11b). Graphite adheres to the outer peripheral surface of the first layer (11a). The outer peripheral surface of the second layer (11b) has a greater surface roughness than that of the first layer (11a).

Abstract: A semiconductor laser is provided with a heat radiating component for radiating or dissipating heat which is generated in operation. In this heat radiating component, a polycrystalline diamond layer (3) synthesized by vapor deposition is formed on an upper surface of a stem (4). A semiconductor laser element (1) is bonded, e.g. by brazing to the surface of the vapor-deposited polycrystalline diamond layer (3) through a brazing filler metal (2). The heat radiating component has a thermal expansion coefficient which is the same as that of an LSI chip to be mounted thereon to provide an excellent heat radiating property.

Abstract: A polycrystalline diamond is prepared by chemical vapor deposition (step 101). A surface of the polycrystalline diamond is metallized (step 102). The metallized surface of the polycrystalline diamond is grooved with a YAG laser (step 103). A wedge or the like is driven into the grooves of the polycrystalline diamond to pressurize the same, whereby the polycrystalline diamond is divided along the grooves (step 104). Alternatively, a surface of a polycrystalline diamond prepared by chemical vapor deposition is grooved with a YAG laser (step 112), so that the surface of the polycrystalline diamond is metallized (step 113) after the grooving.