A porous silicon material including silicon nanoparticles and clusters of silicon nanoparticles, where the pores are cooperatively defined by the nanoparticles within the clusters.

The present invention relates to a process for the synthesis of a composite material comprising steps of: (a) reacting gaseous magnesium (Mg) and silica (SiO.sub.2) in an inert atmosphere; (b) washing the product obtained in step (a) in an acidic medium; and (c) reacting further gaseous magnesium (Mg) with the silica (SiO.sub.2) and silicon (Si) product obtained in step (b).

The process of the invention allows Mg.sub.2Si/MgO nanocomposites to be prepared without too many separate steps, and wherein the MgO phase is homogeneously dispersed within the Mg.sub.2Si matrix. The nanocomposites obtained may for example find practical application as thermoelectric materials in thermoelectric generators.

Provided are processes to form microporous silicon useful as an active material in an electrode of an electrochemical cell the processes including subjecting a mixture of silicon oxide and a metal reducing agent, optionally aluminum, to mechanical milling to form mechanically activated silicon oxide/aluminum, thermally treating the silicon oxide/aluminum to reduce the silicon oxide and form Si/Al.sub.2O.sub.3, and removing at least a portion of the alumina from the Si to form a microporous silicon. The resulting electrochemically active microporous silicon is also provided with residual alumina present at 15% by weight or less that demonstrates excellent cycle life and safety.

Provided are processes to form microporous silicon useful as an active material in an electrode of an electrochemical cell the processes including subjecting a mixture of silicon oxide and a metal reducing agent, optionally aluminum, to mechanical milling to form mechanically activated silicon oxide/aluminum, thermally treating the silicon oxide/aluminum to reduce the silicon oxide and form Si/Al.sub.2O.sub.3, and removing at least a portion of the alumina from the Si to form a microporous silicon. The resulting electrochemically active microporous silicon is also provided with residual alumina present at 15% by weight or less that demonstrates excellent cycle life and safety.

The present application provides a method, a equipment and a system for producing a silicon-containing products by using a silicon sludge which is produced by a diamond wire cutting silicon material. The method of the present application mainly utilizes a high oxide layer on the surface of a silicon waste particle produced during diamond wire cutting. The characteristics are such that the surface oxide disproportionates with adjacent internal elemental silicon to form silicon monoxide to be removed in a vapor to achieve a physical chemical reaction with a metal, a halogen gas, a hydrogen halide gas or hydrogen to form a high value-added silicon-containing products. The process realizes the large-scale, high-efficiency, energy-saving, continuous and low-cost complete recycling of diamond-wire cutting silicon waste.

The present application provides a method, a equipment and a system for producing a silicon-containing products by using a silicon sludge which is produced by a diamond wire cutting silicon material. The method of the present application mainly utilizes a high oxide layer on the surface of a silicon waste particle produced during diamond wire cutting. The characteristics are such that the surface oxide disproportionates with adjacent internal elemental silicon to form silicon monoxide to be removed in a vapor to achieve a physical chemical reaction with a metal, a halogen gas, a hydrogen halide gas or hydrogen to form a high value-added silicon-containing products. The process realizes the large-scale, high-efficiency, energy-saving, continuous and low-cost complete recycling of diamond-wire cutting silicon waste.

A silicon-containing structure including: a silicon composite including a porous silicon secondary particle and a first carbon flake on a surface of the porous silicon secondary particle; a carbonaceous coating layer on the porous silicon composite, the carbonaceous coating layer comprising a first amorphous carbon; and the silicon composite comprises a second amorphous carbon and has a density that is equal to or less than a density of the carbonaceous coating layer, wherein the porous silicon secondary particle includes an aggregate of silicon composite primary particles, each including silicon, a silicon suboxide on a surface of the silicon, and a second carbon flake on a surface of the silicon suboxide.

A silicon-containing structure including: a silicon composite including a porous silicon secondary particle and a first carbon flake on a surface of the porous silicon secondary particle; a carbonaceous coating layer on the porous silicon composite, the carbonaceous coating layer comprising a first amorphous carbon; and the silicon composite comprises a second amorphous carbon and has a density that is equal to or less than a density of the carbonaceous coating layer, wherein the porous silicon secondary particle includes an aggregate of silicon composite primary particles, each including silicon, a silicon suboxide on a surface of the silicon, and a second carbon flake on a surface of the silicon suboxide.

A method for producing nano-silicon, involves (a) conducting a reduction treatment on an aluminosilicate, in which a content of Al.sub.2O.sub.3 is 3 to 40% by mass. A ratio between the number of atoms of aluminum contained in the aluminosilicate and the number of atoms of magnesium used as a reducing agent in the reduction treatment is within a range of 1:3.5 to 1:65. The method then involves (b) conducting acid treatment on a reduced aluminosilicate obtained from (a).

A particle with a yolk-shell structure including a shell including carbon; and a care including silicon (Si) provided inside the shell, wherein at least a part of the shell is spaced apart from the core, and the particle with the yolk-shell structure has a micropore volume of 0.15 cm.sup.3/g or less, and a method for preparing the same.