A polymetalloxane is described having a constituent unit represented by the following general formula (1):

##STR00001##

wherein R.sup.1, R.sup.2, R.sup.3, M a, b and m are as defined.

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 present disclosure relates to a method for preparing high-temperature superconducting yttrium barium copper oxide (YBCO) wire by 3D-printing, this method is divided into the following four steps: firstly, preparing a nano-level superconducting powder precursor; and then, preparing a printing paste with suitable viscosity and supporting characteristics; after that, using a CAD 3D modeling, exporting STL format model data and slicing by a professional software; implementing one-step preparing strands with low AC loss by twisting the print nozzle. Finally, the printed twisted wire is formed into a practical superconducting twisted cable through the processes such as plastic removal process, crystallizing process, oxygen supplementing process and assembling process in order. The present disclosure firstly provides an application for applying high temperature superconducting material to direct ink writing 3D-printing technology. By preparing micro/nano level superconducting core filaments based on 3D-printing, the diameter of the core filaments could be reduced, and thereby a material-structure integrative design could be implemented. The present disclosure simplifies the preparation of high temperature superconducting wires, improves the current-carrying capacity and the production efficiency of the high temperature super conducting wires, and reduces the production cost.

Provided herein are nanofibers and processes of preparing nanofibers. In some instances, the nanofibers are metal and/or ceramic nanofibers. In some embodiments, the nanofibers are high quality, high performance nanofibers, highly coherent nanofibers, highly continuous nanofibers, or the like. In some embodiments, the nanofibers have increased coherence, increased length, few voids and/or defects, and/or other advantageous characteristics. In some instances, the nanofibers are produced by electrospinning a fluid stock having a high loading of nanofiber precursor in the fluid stock. In some instances, the fluid stock comprises well mixed and/or uniformly distributed precursor in the fluid stock. In some instances, the fluid stock is converted into a nanofiber comprising few voids, few defects, long or tunable length, and the like.

A method of producing a metal oxide fiber is described, including a spinning step of spinning a composition containing a polymetalloxane and an organic solvent to obtain a thread-like product; and a firing step of firing the thread-like product obtained in the spinning step at a temperature of 200° C. or higher and 2,000° C. or lower to obtain a metal oxide fiber, where the polymetalloxane has a repeating structure composed of a metal atom selected from the group consisting of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Pd, Ag, In, Sn, Sb, Hf, Ta, W and Bi, and an oxygen atom and where the weight average molecular weight of the polymetalloxane is 20,000 or more and 2,000,000 or less.

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 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.

Provided herein are nanofibers and processes of preparing nanofibers. In some instances, the nanofibers are metal and/or ceramic nanofibers. In some embodiments, the nanofibers are high quality, high performance nanofibers, highly coherent nanofibers, highly continuous nanofibers, or the like. In some embodiments, the nanofibers have increased coherence, increased length, few voids and/or defects, and/or other advantageous characteristics. In some instances, the nanofibers are produced by electrospinning a fluid stock having a high loading of nanofiber precursor in the fluid stock. In some instances, the fluid stock comprises well mixed and/or uniformly distributed precursor in the fluid stock. In some instances, the fluid stock is converted into a nanofiber comprising few voids, few defects, long or tunable length, and the like.

Provided herein are nanofibers and processes of preparing nanofibers. In some instances, the nanofibers are metal and/or ceramic nanofibers. In some embodiments, the nanofibers are high quality, high performance nanofibers, highly coherent nanofibers, highly continuous nanofibers, or the like. In some embodiments, the nanofibers have increased coherence, increased length, few voids and/or defects, and/or other advantageous characteristics. In some instances, the nanofibers are produced by electrospinning a fluid stock having a high loading of nanofiber precursor in the fluid stock. In some instances, the fluid stock comprises well mixed and/or uniformly distributed precursor in the fluid stock. In some instances, the fluid stock is converted into a nanofiber comprising few voids, few defects, long or tunable length, and the like.