High quality, catalyst-free boron nitride nanotubes (BNNTs) that are long, flexible, have few wall molecules and few defects in the crystalline structure, can be efficiently produced by a process driven primarily by Direct Induction. Secondary Direct Induction coils, Direct Current heaters, lasers, and electric arcs can provide additional heating to tailor the processes and enhance the quality of the BNNTs while reducing impurities. Heating the initial boron feed stock to temperatures causing it to act as an electrical conductor can be achieved by including refractory metals in the initial boron feed stock, and providing additional heat via lasers or electric arcs. Direct Induction processes may be energy efficient and sustainable for indefinite period of time. Careful heat and gas flow profile management may be used to enhance production of high quality BNNT at significant production rates.

The present invention relates to a process for the preparation of a ceramic nanowire preform, in particular to a process for the preparation of the ceramic nanowire preform by combining a template technique and a preceramic polymer conversion technique. The process of the present invention uses carbonaceous material as a template, and prepares an isotropic ceramic nanowire preform by controlling the ratio of a precursor to a solvent, the amount of a catalyst and the ratio of a prepared precursor solution to the carbonaceous template, wherein the preform is isotropic and has lower bulk density and higher volume fraction.

High quality, catalyst-free boron nitride nanotubes (BNNTs) that are long, flexible, have few wall molecules and few defects in the crystalline structure, can be efficiently produced by a process driven primarily by Direct Induction. Secondary Direct Induction coils, Direct Current heaters, lasers, and electric arcs can provide additional heating to tailor the processes and enhance the quality of the BNNTs while reducing impurities. Heating the initial boron feed stock to temperatures causing it to act as an electrical conductor can be achieved by including refractory metals in the initial boron feed stock, and providing additional heat via lasers or electric arcs. Direct Induction processes may be energy efficient and sustainable for indefinite period of time. Careful heat and gas flow profile management may be used to enhance production of high quality BNNT at significant production rates.

A method of preparing hexagonal boron nitride (h-BN) fibers includes mixing polyvinylpyrrolidone (PVP) and boron oxide (B.sub.2O.sub.3) to form a polymer precursor or mixing PVP and ammonia borane (BH.sub.3NH.sub.3) to form the polymer precursor. The method includes forcespinning the polymer precursor to form fibers of the polymer precursor, curing the fibers to form polymer fibers, and pyrolyzing the polymer fibers to form the h-BN fibers.

A multi-composition fiber is provided including a primary fiber material and an elemental additive material deposited on grain boundaries between adjacent crystalline domains of the primary fiber material. A method of making a multi-composition fiber is also provided, which includes providing a precursor laden environment, and promoting fiber growth using laser heating. The precursor laden environment includes a primary precursor material and an elemental precursor material.

A fiber comprises a bulk material comprising: one or more of carbon, silicon, boron, silicon carbide, and boron nitride; and a metal or metal alloy whose affinity for oxygen is greater than that of the bulk material. At least a first portion of the metal or metal alloy is present at the entrance to grain boundaries at the surface of the fiber and within the fiber to a depth of at least 1 micron from the fiber surface.

A method of improving a fiber comprises heating a fiber in an inert atmosphere to 900-1300 C for sufficient time to allow at least some of a metal or metal alloy, placed on the fiber, to diffuse and/or flow into and along grain boundaries to a depth of at least 1 micron. The metal or metal alloy has a greater affinity for oxygen than that of the fiber bulk material.

A method and apparatus for producing boron nitride nanotubes and continuous boron nitride nanotube yarn or tapes is provided. The apparatus includes rotating reaction tubes that allow for continuous chemical vapor deposition of boron nitride nanotubes. The rotation of the reaction tubes allows the boron nitride nanotubes to be spun into yarns or made into tapes, without post process or external rotation or spinning of the gathered nanotubes. Boron nitride nanotube yarns or tapes of great length can be produced as a result, thereby providing industry with a readily useable format for this type of material. Dopants such as carbon can be added to engineer the band gap of the nanotubes. Catalysts may be formed outside or inside the reactor.

A method and apparatus for producing boron nitride nanotubes and continuous boron nitride nanotube yarn or tapes is provided. The apparatus includes rotating reaction tubes that allow for continuous chemical vapor deposition of boron nitride nanotubes. The rotation of the reaction tubes allows the boron nitride nanotubes to be spun into yarns or made into tapes, without post process or external rotation or spinning of the gathered nanotubes. Boron nitride nanotube yarns or tapes of great length can be produced as a result, thereby providing industry with a readily useable format for this type of material. Dopants such as carbon can be added to engineer the band gap of the nanotubes. Catalysts may be formed outside or inside the reactor.

Hexagonal Boron Nitride (hBN) is a synthetic material that may be used in several applications due to its chemical inertness, thermal stability, and other beneficial properties. hBN composite materials and method for making such composites are described here. In particular composite materials including both functionalized hBN and cement or cementitious materials and methods for making the same are discussed. Such materials may be useful for construction, well cementing (both primary and remedial cementing), nuclear industry, 3D printing of advanced multifunctional composites, and refractory materials.

Methods and apparatus for producing chemical nanostructures having multiple elements, such as boron and nitride, e.g. boron nitride nanotubes, are disclosed. The method comprises creating a plasma jet, or plume, such as by an arc discharge. The plasma plume is elongated and has a temperature gradient along its length. It extends along its length into a port connector area having ports for introduction of feed materials. The feed materials include the multiple elements, which are introduced separately as fluids or powders at multiple ports along the length of the plasma plume, said ports entering the plasma plume at different temperatures. The method further comprises modifying a temperature at a distal portion of or immediately downstream of said plasma plume; and collecting said chemical nanostructures after said modifying.