The present application relates to boron nitride nanotube (BNNT)-nanoparticle composites, to methods of preparing such composites and their use, for example, in metal/ceramic matrix composites and/or macroscopic assemblies. For example, the methods comprise subjecting a source of hydrogen, a source of boron, a source of nitrogen and a nanoparticle precursor to a stable induction thermal plasma and cooling the reaction mixture to obtain the composite.

Some variations provide a process for fabricating a ceramic structure, the process comprising: producing a plurality of preceramic polymer parts; chemically, physically, and/or thermally joining the preceramic polymer parts together, to generate a preceramic polymer structure; thermally treating the preceramic polymer structure, to generate a ceramic structure; and recovering the ceramic structure. The process may employ additive manufacturing, subtractive manufacturing, casting, or a combination thereof. A composite overwrap may be applied to the preceramic polymer structure prior to pyrolysis, and the composite overwrap also pyrolyzes to a ceramic composite and is a part of the final ceramic structure. The ceramic structure may be silicon oxycarbide, silicon carbide, silicon nitride, silicon oxynitride, silicon carbonitride, silicon boronitride, silicon boron carbonitride, or boron nitride, for example. The ceramic structure may have at least one dimension of 1 meter or greater, and may be a fully integrated ceramic object with no seams.

Resins for 3D printing of a preceramic composition loaded with a solid polymer filler, followed by converting the preceramic composition to a 3D-printed ceramic material, are described. Some variations provide a preceramic composition containing a radiation-curable liquid resin formulation and a solid polymer filler dispersed within the liquid resin formulation. The liquid resin formulation is compatible with stereolithography, UV curing, and/or 3D printing. The solid polymer filler may be an organic polymer, an inorganic polymer, or a combination thereof. The solid polymer filler may itself be an inorganic preceramic polymer, which may have the same composition as a polymerized variant of the liquid resin formulation, or a different composition. Many compositions are disclosed as options for the liquid resin formulation and the solid polymer filler.

Polymers derived from a metallocene comprising a group IV element and at least one cyclopentadienyl group are described. Methods for preparing refractory ceramics comprising group IV carbides and/or borides using such polymer are also disclosed. In some embodiments, the method for fabricating the refractory ceramic comprises infiltrating a fiber preform with such polymer and pyrolyzing the polymeric fiber preform.

Provided is a method for charging, with ceramic, open pores formed in a matrix of a ceramic matrix composite that includes the matrix and reinforcing fibers provided in the matrix. The ceramic comes to constitute the matrix. The method includes repeating the following steps (A) and (B) in a state where the ceramic matrix composite is arranged in a liquid material serving as a matrix material. At the step (A), the ceramic matrix composite is heated such that the liquid material is brought into a film-boiling state, and the ceramic derived from the liquid material is thereby generated in the open pores. At the step (B), the ceramic matrix composite is cooled until a temperature of the ceramic matrix composite becomes lower than a boiling point of the liquid material.

A method for producing solidified fiber bundles includes applying a melt or solution to a carrier web forming a viscous coating, applying parallel filaments under tension to the carrier web, and pressing the filaments into the viscous coating, forming an impregnate. The coating is partially solidified until a plastically deformable state of the impregnate is obtained by vaporizing the solvent, thermal curing and/or cooling. The impregnate is rolled onto a winding core to form a roll while maintaining a winding tension of the filaments in the impregnate. The outer roll is fixed on the winding core by a sleeve and/or by adhesive tape. The impregnate is solidified by vaporizing the solvent, thermal curing and/or cooling. The solidified impregnate is divided up to form solidified fiber bundles. A pressure produced by the winding tension of the filaments in the impregnate is exerted on the roll.

High temperature boron-PDC (polymer derived ceramic) black materials for use as, or in, colorants, inks, pigments, dyes, additives and formulations utilizing these black materials. Boron-PDC materials having boron, silicon, oxygen and carbon, and methods of making these ceramics; formulations utilizing these black ceramics; and devices, structures and apparatus that have or utilize these formulations. Plastics, paints, inks, coatings, formulations, liquids and adhesives containing ceramic black materials, preferably polymer derived boron containing black ceramic materials, and in particular boron-SiOC derived ceramic materials.

A material useful as a proppant comprises a core chemically reacted in situ from coal dust and a polymer derived ceramic material, such that at least a portion of the coal dust is chemically converted to a ceramic, nanoparticles, graphene, nanofibers or combinations of any of these.

This disclosure enables direct 3D printing of preceramic polymers, which can be converted to fully dense ceramics. Some variations provide a preceramic resin formulation comprising a molecule with two or more CX double bonds or CX triple bonds, wherein X is selected from C, S, N, or O, and wherein the molecule further comprises at least one non-carbon atom selected from Si, B, Al, Ti, Zn, P, Ge, S, N, or O; a photoinitiator; a free-radical inhibitor; and a 3D-printing resolution agent. The disclosed preceramic resin formulations can be 3D-printed using stereolithography into objects with complex shape. The polymeric objects may be directly converted to fully dense ceramics with properties that approach the theoretical maximum strength of the base materials. Low-cost structures are obtained that are lightweight, strong, and stiff, but stable in the presence of a high-temperature oxidizing environment.

This disclosure enables direct 3D printing of preceramic polymers, which can be converted to fully dense ceramics. Some variations provide a preceramic resin formulation comprising a molecule with two or more CX double bonds or CX triple bonds, wherein X is selected from C, S, N, or O, and wherein the molecule further comprises at least one non-carbon atom selected from Si, B, Al, Ti, Zn, P, Ge, S, N, or O; a photoinitiator; a free-radical inhibitor; and a 3D-printing resolution agent. The disclosed preceramic resin formulations can be 3D-printed using stereolithography into objects with complex shape. The polymeric objects may be directly converted to fully dense ceramics with properties that approach the theoretical maximum strength of the base materials. Low-cost structures are obtained that are lightweight, strong, and stiff, but stable in the presence of a high-temperature oxidizing environment.