A system and a method for producing silicon from a SiO.sub.2-containing material that includes solid SiO.sub.2. The method uses a reaction vessel including a first section and a second section in fluid communication with said first section. The method includes: heating the SiO.sub.2-containing material that includes the solid SiO.sub.2 to a SiO.sub.2-containing material that includes liquid SiO.sub.2, at a sufficient temperature to convert the solid SiO.sub.2 into the liquid SiO.sub.2; converting, in the first section, the liquid SiO.sub.2 into gaseous SiO.sub.2 that flows to the second section by reducing the pressure in the reaction vessel to a subatmospheric pressure; and reducing, in the second section, the gaseous SiO.sub.2 into liquid silicon using a reducing gas. The reducing of the pressure is performed over a continuous range of interim pressure(s) sufficient to evaporate contaminants from the SiO.sub.2-containing material, and removing by vacuum, the one or more evaporated gaseous contaminants.

A process for refining crude molten silicon. The process includes oxidatively refining the crude molten silicon in the production of technical silicon. The crude molten silicon is admixed during the refining with a particulate mediator which has a minimum amount of metallic silicon of 8% by mass and also at least one or more of the elements H, C, O, F, Cl, Ca, Fe and Al. The particulate mediator is described by a characteristic number K which has a value of 0.03 to 6 mm.sup.−1 and is calculated using the formula

[00001]$K=\frac{6.Math.\left(1-{\mathrm{.Math.}}_{m,M}\right)}{d_{50,M}}$

where d.sub.50,M is the particle size (diameter) at 50% of the mass undersize of the grading curve of the particulate mediator [mm] and the ε.sub.m,M is the mean effective porosity of the particulate mediator.

A process for refining crude molten silicon. The process includes oxidatively refining the crude molten silicon in the production of technical silicon. The crude molten silicon is admixed during the refining with a particulate mediator which has a minimum amount of metallic silicon of 8% by mass and also at least one or more of the elements H, C, O, F, Cl, Ca, Fe and Al. The particulate mediator is described by a characteristic number K which has a value of 0.03 to 6 mm.sup.−1 and is calculated using the formula

[00001]$K=\frac{6.Math.\left(1-{\mathrm{.Math.}}_{m,M}\right)}{d_{50,M}}$

where d.sub.50,M is the particle size (diameter) at 50% of the mass undersize of the grading curve of the particulate mediator [mm] and the ε.sub.m,M is the mean effective porosity of the particulate mediator.

A process for the oxidative refining of crude silicon melts during the production of technical-grade silicon. The process includes oxidative refining a crude silicon melt during the production of technical-grade silicon, where during the refining of the crude silicon melt, a finely divided mediator having a particle size parameter d.sub.50 of 1 to 200 μm is added. The finely divided mediator contains a minimum content of metallic silicon of 8% by mass and also at least one or more of the elements H, C, O, F, Cl, Ca, Fe and Al. Additionally, the finely divided mediator is added to the crude silicon melt by means of pneumatic conveying with a gas.

A process for the oxidative refining of crude silicon melts during the production of technical-grade silicon. The process includes oxidative refining a crude silicon melt during the production of technical-grade silicon, where during the refining of the crude silicon melt, a finely divided mediator having a particle size parameter d.sub.50 of 1 to 200 μm is added. The finely divided mediator contains a minimum content of metallic silicon of 8% by mass and also at least one or more of the elements H, C, O, F, Cl, Ca, Fe and Al. Additionally, the finely divided mediator is added to the crude silicon melt by means of pneumatic conveying with a gas.

A polycrystalline silicon lump packaging body is a packaging body in which the resin bag is filled with the polycrystalline silicon lumps having a surface metal concentration of 1000 pptw or less, in which a nitrate ion amount and preferably a fluorine ion amount present inside the packaging body are each 50 μg/L or less with respect to a filling void of the polycrystalline silicon lumps formed when the packaging body is left at 25° C. under 1 atm.

The invention relates to a process for the production of silicon and alumina Aluminium is contacted with a molten slag of a calcium oxide and SiO.sub.2 under conditions facilitating an aluminothermic reaction, thereby forming silicon and an aluminate slag in two phases which are separated. The aluminate slag is converted to alumina and calcium oxide, which is re-fed in the reaction. The aluminium is provided by melting of aluminium scrap or a combination of different aluminium alloys at a temperature of 700 to 1000° C. The primary aluminium melt is adjusted to a content of 8 to 14% of silicon and then cooled to below 660° C., whereby precipitates are formed, and high purity aluminium is obtained to be introduced into the reaction.

The invention relates to a process for the production of silicon and alumina Aluminium is contacted with a molten slag of a calcium oxide and SiO.sub.2 under conditions facilitating an aluminothermic reaction, thereby forming silicon and an aluminate slag in two phases which are separated. The aluminate slag is converted to alumina and calcium oxide, which is re-fed in the reaction. The aluminium is provided by melting of aluminium scrap or a combination of different aluminium alloys at a temperature of 700 to 1000° C. The primary aluminium melt is adjusted to a content of 8 to 14% of silicon and then cooled to below 660° C., whereby precipitates are formed, and high purity aluminium is obtained to be introduced into the reaction.

Systems, methods and compositions to produce fine powders are described. These include forming a hypereutectic melt including a target material, a sacrificial-matrix material, and an impurity, rapidly cooling the hypereutectic melt to form a hypereutectic alloy having a first phase and a second phase, annealing the hypereutectic alloy to alter a morphology of the target material to thereby produce target particles, and removing the sacrificial matrix to thereby produce a fine powder of the target particles. The first phase is defined by the target material and the second phase is defined by the sacrificial-matrix material. The sacrificial-matrix material forms a sacrificial matrix having the target material dispersed therethrough.

Systems, methods and compositions to produce fine powders are described. These include forming a hypereutectic melt including a target material, a sacrificial-matrix material, and an impurity, rapidly cooling the hypereutectic melt to form a hypereutectic alloy having a first phase and a second phase, annealing the hypereutectic alloy to alter a morphology of the target material to thereby produce target particles, and removing the sacrificial matrix to thereby produce a fine powder of the target particles. The first phase is defined by the target material and the second phase is defined by the sacrificial-matrix material. The sacrificial-matrix material forms a sacrificial matrix having the target material dispersed therethrough.