Abstract:
Solid materials capable of producing toxic and/or corrosive gases by thermal decomposition are heated in a stirred in a sealable crucible. The stirring rod is supported on a downward extending shaft using a combination of a lip seal or other mechanical seal and a ferro-fluidic seal or rotary feed through. The lip seal region is evacuated to reduce the chance that the small upward flow of corrosive gas will detrimentally react with components of the ferro-fluid. In a process for calcining sodium fluorosilicate to product silicon tetra-fluoride gas, the lip seal and ferro-fluidic seal regions are purged and/or blanked to prevent the absorption of water during an initial drying phase. Accordingly, the reaction of water with silicon tetra-fluoride to produce corrosive hydrogen fluoride gas is prevented.
Abstract:
Tetrafluorosilane is produced by a process comprising a step (1) of heating a hexafluorosilicate, a step (2-1) of reacting a tetrafluorosilane gas containing hexafluorodisiloxane produced in the step (1) with a fluorine gas, a step (2-2) of reacting a tetrafluorosilane gas containing hexafluorodisiloxane produced in the step (1) with a highvalent metal fluoxide, or a step (2-1) of reacting a tetrafluorosilane gas containing hexafluorodisiloxane produced in the step (1) with a fluorine gas and a step (2-3) of reacting a tetrafluorosilane gas produced in the step (2-1) with a highvalent metal fluoxide. Further, impurities in high-purity tetrafluorosilane are analyzed.
Abstract:
L'invention concerne un procédé de dosage d'au moins un élément dans un matériau (2) comprenant du silicium, comprenant les étapes suivantes: décomposer au moins une partie du matériau (2) avec un agent d'attaque (6) pour former une solution contenant de l'acide hexafluorosilicique (7) et les éléments à doser; chauffer cette solution jusqu'à une température telle qu'au moins une partie substantielle de l'acide hexafluorosilicique (7) soit transformée en tétrafluorure de silicium et qu'une partie substantielle du tétrafluorure de silicium s'évapore, pour obtenir une solution pour dosage dans laquelle la teneur en silicium soit sensiblement réduite tout en conservant la quantité de chaque élément à doser; et doser au moins un élément contenu dans la solution pour dosage. Application au domaine de la fabrication de substrats ou de composants pour l'optique, l'électronique ou l'optoélectrique, et notamment au contôle qualité.
Abstract:
A method for producing silicon tetrafluoride includes combining uranium oxyfluoride and silicon dioxide; heating the combination below the melting point of the uranium oxyfluoride (14) to sufficiently react the uranium oxyfluoride and the silicon dioxide to produce non-radioactive silicon tetrafluoride and an oxide of uranium (16); and removing the silicon tetrafluoride (18).
Abstract:
The present invention relates to a continuous production method for silicon tetrafluoride (SiF4) using silica (SiO2) and hydrogen fluoride (HF), and, more specifically, relates to a continuous production method for silicon tetrafluoride, wherein silica and hydrogen fluoride (HF) are reacted by filling a bed reactor with crystalline or amorphous silica in the solid state and blowing hydrogen fluoride gas directly therein, such that it is possible to continuously produce silicon tetrafluoride in a high yield, and it is possible to use diverse forms of silica as raw materials and hence it is possible to ensure relatively economic operation.
Abstract:
In one embodiment, the present disclosure relates generally to a method for thermally decomposing a complex precursor salt. In one embodiment, the method includes heating a salt in a reactor until a molten salt is formed, adding the complex precursor salt to the molten salt in the reactor and removing a volatile precursor halide formed from thermal decomposition of the complex precursor salt from the reactor.
Abstract:
The present invention relates to a method of preparing silicon tetrafluoride (STF, SiF 4 ) by using crystalline silica (SiO 2 ). More specifically, the present invention relates to a method of preparing silicon tetrafluoride by reacting finely divided crystalline silica and hydrogen fluoride (HF) in the presence of concentrated sulfuric acid in a continuous manner. According to the present invention, silicon tetrafluoride can be economically prepared with high yield from crystalline silica which exists abundantly in the natural world, and the process productivity, workability and controllability can be improved remarkably. In addition, the problem of corrosion in the recycling process by concentrating diluted sulfuric acid can be solved through controlling the ratio between reactants such that no incorporated hydrogen fluoride remains after the reaction, or on the other hand the difficulty in filtering the product by finely divided particles can be avoided through controlling the ratio between reactants such that the crystalline silica reactant is consumed completely. Furthermore, since the used sulfuric acid can be isolated and recycled, the generation of discarded sulfuric acid can be minimized.
Abstract:
The process for the production of polycrystalline silicon starting from metallurgical silicon, milled up to a predetermined granulometry, implies the reaction of metallurgical silicon with anhydrous hydrogen fluoride (HF), to obtain silicon tetrafluoride (SiF4), and to operate the synthesis of monosilane (SiH4) by a reaction of hydrogenation of the silicon tetrafluoride (SiF4) with alkaline or alkaline earth metals halide in fluid medium of organic solvent or melt salts. Then a thermal decomposition of said monosilane (SiH4) in a boiling-pseudo fluidized bed reactor is carried out, to obtain high purity granulated polycrystalline silicon.
Abstract:
The process for the production of polycrystalline silicon starting from metallurgical silicon, milled up to a predetermined granulometry, implies the reaction of metallurgical silicon with anhydrous hydrogen fluoride (HF), to obtain silicon tetrafluoride (SiF4), and to operate the synthesis of monosilane (SiH4) by a reaction of hydrogenation of the silicon tetrafluoride (SiF4) with alkaline or alkaline earth metals halide in fluid medium of organic solvent or melt salts. Then a thermal decomposition of said monosilane (SiH4) in a boiling-pseudo fluidized bed reactor is carried out, to obtain high purity granulated polycrystalline silicon.
Abstract:
The process for the production of polycrystalline silicon starting from metallurgical silicon, milled up to a predetermined granulometry, implies the reaction of metallurgical silicon with anhydrous hydrogen fluoride (HF), to obtain silicon tetrafluoride (SiF4), and to operate the synthesis of monosilane (SiH4) by a reaction of hydrogenation of the silicon tetrafluoride (SiF4) with alkaline or alkaline earth metals halide in fluid medium of organic solvent or melt salts. Then a thermal decomposition of said monosilane (SiH4) in a boiling-pseudo fluidized bed reactor is carried out, to obtain high purity granulated polycrystalline silicon.