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.

This invention provides resin formulations which may be used for 3D printing and pyrolyzing to produce a ceramic matrix composite. The resin formulations contain a solid-phase filler, to provide high thermal stability and mechanical strength (e.g., fracture toughness) in the final ceramic material. The invention provides direct, free-form 3D printing of a preceramic polymer loaded with a solid-phase filler, followed by converting the preceramic polymer to a 3D-printed ceramic matrix composite with potentially complex 3D shapes or in the form of large parts. Other variations provide active solid-phase functional additives as solid-phase fillers, to perform or enhance at least one chemical, physical, mechanical, or electrical function within the ceramic structure as it is being formed as well as in the final structure. Solid-phase functional additives actively improve the final ceramic structure through one or more changes actively induced by the additives during pyrolysis or other thermal treatment.

A process for producing a process for producing a LnM.sub.2Cu.sub.3O.sub.x high-temperature superconductive powder, the process comprising: i) providing an aqueous solution of Ln, M and Cu and at least one mineral acid; ii) adding at least one sequestrating agent and, optionally, at least one dispersant to the solution to form a precipitate; iii) recovering the precipitate from the solution; and iv) heating the precipitate in a flow of oxygen to form the LnM.sub.2Cu.sub.3O.sub.x powder, wherein Ln is a rare earth element, preferably Y, Ce, Dy, Er, Gd, La, Nd, Pr, Sm, Sc, Yb, or a mixture of two or more thereof, and wherein M is selected from Ca, Sr, and Ba.

The invention relates to a method for preparing a composite metal oxide hollow fibre. A certain stoichiometry of composite metal oxide raw material and a polymer binding agent are added to an organic solvent, and mixed mechanically to obtain an evenly dispersed spinning solution having a suitable viscosity. After defoaming treatment, the spinning solution is extruded through a spinneret and, after undergoing a certain dry spinning process, enters an external coagulation bath; during this period, a phase inversion process occurs and composite metal oxide hollow fibre blanks are formed. The blanks are immersed in the external coagulation bath and the organic solvent is displaced; after natural drying, the blanks undergo a heat treatment process; during this period, polymer burn off, in situ reaction, and in situ sintering processes occur to obtain the composite metal oxide hollow fibre.

The use of magnesium oxide, reactive alumina and aluminium oxide as a base provides for a new erosion-resistant material upon sintering.

It is an object to provide a cubic boron nitride polycrystalline material excellent in toughness. A cubic boron nitride polycrystalline material containing fine cubic boron nitride which is granular, has a maximum grain size not greater than 100 nm, and has an average grain size not greater than 70 nm and at least one of plate-shaped cubic boron nitride in a form of a plate having an average major radius not smaller than 50 nm and not greater than 10000 nm and coarse cubic boron nitride which is granular, has a minimum grain size exceeding 100 nm, and has an average grain size not greater than 1000 nm is provided.

Foams and methods of fabricating and using the same are provided. The foams can be three-dimensional (3D), free-standing, and/or rigid and can be used as, for example, nanofiller networks. The shape and size of the foam pore interconnected network can be tailorable/tailored. The foams can be, for example, hybrid one-dimensional (1D)/two-dimensional (2D) foams of 1D and 2D materials (e.g., hybrid boron nitride nanotube (BNNT)/boron nitride nanoplatelet (BNNP) foams). A freeze-drying-based method can be used to fabricate bulk porous foam, which can be used for, e.g., nanofiller for polymer nanocomposites.

The use of magnesium oxide, reactive alumina and aluminium oxide as a base provides for a new erosion-resistant material upon sintering.

A process for producing a process for producing a LnM.sub.2Cu.sub.3O.sub.x high-temperature superconductive powder, the process comprising: i) providing an aqueous solution of Ln, M and Cu and at least one mineral acid; ii) adding at least one sequestrating agent and, optionally, at least one dispersant to the solution to form a precipitate; iii) recovering the precipitate from the solution; and iv) heating the precipitate in a flow of oxygen to form the LnM.sub.2Cu.sub.3O.sub.x powder, wherein Ln is a rare earth element, preferably Y, Ce, Dy, Er, Gd, La, Nd, Pr, Sm, Sc, Yb, or a mixture of two or more thereof, and wherein M is selected from Ca, Sr, and Ba.

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.