METHODS OF ADJUSTING CARBON AND SILICA CONTENT IN RICE HULL ASH (RHA) BYPRODUCTS TO CONTROL CARBOTHERMAL REDUCTION FORMING NANOSTRUCTURED SILICON CARBIDE, SILICON NITRIDE, SILICON OXYNITRIDE NANOCOMPOSITES

In various aspects, methods of making a silicon carbide or silicon nitride from rice hull ash (RHA) byproduct are provided. A treated silica depleted rice hull ash product (SDRHA) comprising silicon oxide at ≤about 65% by weight and carbon ≥about 35% by weight may be heated in an environment free of any additional carbon sources, but in an inert atmosphere, having a temperature of ≥about 1,200° C. to ≤about 1,700° C. for a carbothermal reaction that forms a product (e.g., nanocomposite product) comprising at least one of silicon carbide (SiC), silicon nitride (SiN), and silicon oxynitride (SiNO or non-stoichiometric SiNO, where x ranges from greater than 0 to less than 4). A negative electroactive material is also provided that includes silicon oxynitride (SiNO), which may be used in a lithium ion battery.