Disclosed are techniques and methods for producing silicon carbide and ceramic matrix composites from hydrocarbons. In one aspect, a method includes preforming a shape using silicon carbide fibers placed into a chamber, evacuating the chamber causing a silicon and polymer slurry to enter the chamber, and pressurizing the chamber causing the silicon and polymer slurry to permeate the silicon carbide fibers. The method includes heating the chamber to cause pyrolysis of the polymer and a hydrocarbon passed into the chamber into carbon and hydrogen gas. The carbon from the pyrolyzed polymer and hydrocarbon provide a coating of carbon on the silicon in the silicon and polymer slurry. The method includes heating the chamber to a higher temperature causing the silicon to melt and react with the carbon to form silicon carbide. The formed silicon carbide and the silicon carbide fibers form the ceramic matrix composite.

A silicon carbide ingot is provided, which includes a seed end, and a dome end opposite to the seed end. In the silicon carbide ingot, a ratio of the vanadium concentration to the nitrogen concentration at the seed end is in a range of 5:1 to 11:1, and a ratio of the vanadium concentration to the nitrogen concentration at the dome end is in a range of 2:1 to 11:1.

A method for removing boron is provided, which includes (a) mixing a carbon source material and a silicon source material in a chamber to form a solid state mixture, (b) heating the solid state mixture to a temperature of 1000° C. to 1600° C., and adjusting the pressure of the chamber to 1 torr to 100 torr. The method also includes (c) conducting a gas mixture of a first carrier gas and water vapor into the chamber to remove boron from the solid state mixture, and (d) conducting a second carrier gas into the chamber.

A method for removing boron is provided, which includes (a) mixing a carbon source material and a silicon source material in a chamber to form a solid state mixture, (b) heating the solid state mixture to a temperature of 1000° C. to 1600° C., and adjusting the pressure of the chamber to 1 torr to 100 torr. The method also includes (c) conducting a gas mixture of a first carrier gas and water vapor into the chamber to remove boron from the solid state mixture, and (d) conducting a second carrier gas into the chamber.

According to an exemplary embodiment of the present disclosure, a negative electrode active material includes metal-silicon-carbon based particles including a M.sub.aSi.sub.bC matrix, wherein M in the M.sub.aSi.sub.bC matrix is one or more selected from the group consisting of Li, Mg, Na, Ca, and Al, 0.3≤a≤1, and 1≤b≤2. Since at the time of charging and discharging a battery, formation of an irreversible phase may be minimized by the M.sub.aSi.sub.bC matrix, initial efficiency of the battery may be improved, and electrical conductivity, physical strength, and chemical stability may be improved, such that capacity and lifecycle characteristics of the battery may be improved.

According to an exemplary embodiment of the present disclosure, a negative electrode active material includes metal-silicon-carbon based particles including a M.sub.aSi.sub.bC matrix, wherein M in the M.sub.aSi.sub.bC matrix is one or more selected from the group consisting of Li, Mg, Na, Ca, and Al, 0.3≤a≤1, and 1≤b≤2. Since at the time of charging and discharging a battery, formation of an irreversible phase may be minimized by the M.sub.aSi.sub.bC matrix, initial efficiency of the battery may be improved, and electrical conductivity, physical strength, and chemical stability may be improved, such that capacity and lifecycle characteristics of the battery may be improved.

Stabilized porous silicon particles are disclosed. The particles include a porous silicon particle comprising a plurality of interconnected silicon nanoparticles and (i) a heterogeneous layer comprising a discontinuous SiC coating that is discontinuous across a portion of pore surfaces and across a portion of an outer surface of the porous silicon particle, and a continuous carbon coating that covers outer surfaces of the discontinuous SiC coating, and remaining portions of the pore surfaces and the outer surface of the porous silicon particle, or (ii) a continuous carbon coating on surfaces of the porous silicon particle, including the outer surface and pore surfaces. Methods of making the stabilized porous silicon particles also are disclosed.

Stabilized porous silicon particles are disclosed. The particles include a porous silicon particle comprising a plurality of interconnected silicon nanoparticles and (i) a heterogeneous layer comprising a discontinuous SiC coating that is discontinuous across a portion of pore surfaces and across a portion of an outer surface of the porous silicon particle, and a continuous carbon coating that covers outer surfaces of the discontinuous SiC coating, and remaining portions of the pore surfaces and the outer surface of the porous silicon particle, or (ii) a continuous carbon coating on surfaces of the porous silicon particle, including the outer surface and pore surfaces. Methods of making the stabilized porous silicon particles also are disclosed.

A production method for a composite material, which includes a porous substrate and a silicon carbide film formed on a surface of a material forming the porous substrate, includes causing a silicon source containing a silicon atom, a chlorine source containing a chlorine atom, and a carbon source containing a carbon atom to react with each other to form the silicon carbide film on the surface of the material forming the porous substrate.

A method for removing boron is provided, which includes (a) mixing a carbon source material and a silicon source material in a chamber to form a solid state mixture, (b) heating the solid state mixture to a temperature of 1000 C. to 1600 C., and adjusting the pressure of the chamber to 1 torr to 100 torr. The method also includes (c) conducting a gas mixture of a first carrier gas and water vapor into the chamber to remove boron from the solid state mixture, and (d) conducting a second carrier gas into the chamber.