POWDERS BASED ON NIOBIUM-TIN COMPOUNDS FOR MANUFACTURING SUPERCONDUCTING COMPONENTS

Abstract

A powder for producing a superconducting component. The powder includes Nb.sub.xSn.sub.y, where 1≤x≤6 and 1≤y≤5. The powder does not have any separate NbO phases and/or SnO phases.

Claims

1-16. (canceled)

17: A powder for producing a superconducting component, the powder comprising: Nb.sub.xSn.sub.y, where 1≤x≤6 and 1≤y≤5, wherein, the powder does not comprise any separate NbO phases and/or SnO phases.

18: The powder as recited in claim 17, wherein the powder further comprises an oxygen content of less than 1.5% by weight, based on a total weight of the powder.

19: The powder as recited in claim 17, wherein the powder comprises a proportion of Nb.sub.3Sn or Nb.sub.6Sn.sub.5 or NbSn.sub.2, respectively, of >92%, based on all crystallographic phases detected as determined via a Rietveld analysis of an X-ray powder diffraction pattern of the powder.

20: The powder as recited in claim 17, wherein the powder further comprises a particle size D99 of less than 15 as determined via a laser light scattering.

21: The powder as recited in claim 17, wherein the powder further comprises a specific surface area as determined by a BET method of from 0.5 to 5 m.sup.2/g.

22: The powder as recited in claim 17, wherein the powder further comprises: powder particles, wherein, 95% of all of the powder particles have a Feret diameter of from 0.7 to 1 after atomization, the Feret diameter being a smallest diameter of a particle of the powder particles divided by a greatest diameter of the particle of the powder particles.

23: A process for producing the powder as recited in claim 17, the process comprising: reacting a niobium metal powder with a tin metal powder; and reducing in a presence of a reducing agent.

24: The process as recited in claim 23, wherein, the reacting of the niobium metal powder with the tin metal powder is performed in a first step so as to provide a product, and the product is reduced in the presence of the reducing agent in a second step.

25: The process as recited in claim 24, wherein at least one of, the niobium metal powder comprises less than 3% by weight of oxygen, and the tin metal powder comprises less than 1.5% by weight of oxygen, in each case based on a total weight of the powder.

26: The process as recited in claim 23, wherein the reducing agent is a gaseous reducing agent.

27: The process as recited in claim 23, wherein the reducing agent is selected from the group consisting of magnesium, calcium, CaH.sub.2, MgH.sub.2, and mixtures thereof.

28: The process as recited in claim 23, wherein the process further comprises: washing the product.

29: The process as recited in claim 28, wherein the washing of the product is performed with a mineral acid.

30: The process as recited in claim 29, wherein the mineral acid is selected from the group consisting of sulfuric acid, hydrochloric acid and nitric acid.

31: A method of using the powder as recited in claim 17 for producing a superconducting component, the method comprising: providing the powder as recited in claim 17; and using the powder to produce the superconducting component.

32: The method as recited in claim 31, wherein the superconducting component is a superconducting wire.

33: The use as recited in claim 31, wherein the superconducting component is produced by powder-metallurgical processes or by additive manufacturing processes.

34: A method of using the powder as recited in claim 17 in an additive manufacturing process, the method comprising: providing the powder as recited in claim 17; and using the powder in the additive manufacturing process, wherein, the additive manufacturing process is selected from a laser beam melting, an electron beam melting, and a laser cladding.

Description

EXAMPLES

[0039] Niobium metal powder was reacted with tin metal powder in the presence of magnesium as reducing agent under various conditions and the products obtained were washed with sulfuric acid and analyzed. Powders for which the reaction of the starting compounds was carried out conventionally without reducing agent and subsequent washing were employed as comparative experiments. The tin metal powder used had a particle size of less than 150 μm and an oxygen content of 6800 ppm in all experiments.

[0040] The results are summarized in table 1, with the information on the oxygen contents being determined by means of carrier gas hot extraction (Leco TCH600) and the specific surface area being determined by the BET method (ASTM D3663, Tristar 3000, Micromeritics). The particle size was in each case determined by means of laser light scattering (MasterSizer S, dispersion in water and Daxad11, 5 min ultrasonic treatment). The trace analysis of the metallic impurities such as Mg was carried out by means of ICP-OES using the following analytical instruments PQ 9000 (Analytik Jena) or Ultima 2 (Horiba). X-ray diffraction was carried out on pulverulent samples using an instrument from Malvern-PANalytical (X'Pert-MPD with semiconductor detector, X-ray tubes Cu LFF with 40 KV/40 mA, Ni filter).

TABLE-US-00001 TABLE 1 Phase composition O content Particle Particle X-ray from Rietveld [% by BET Mg size D90 size D99 Experiment Production diffraction analysis weight] [m.sub.2/g] [ppm] [μm] [μm] Comparative Nb + 2 Sn Nb, Nb: 51% 1.29 0.3 <300 77 98 Example 1 790° C./2 h NbSn.sub.2, NbSn.sub.2: 24% Nb.sub.3Sn, Nb.sub.3Sn: 19% NbO NbO: 6% Ex. 1 Nb + 2 Sn + NbSn.sub.2, NbSn.sub.2: 96% 0.51 0.46 <300 54 79 Mg Nb NbO: 4% 790° C./18 h Ex. 2 Nb + 2 Sn + NbSn.sub.2 NbSn.sub.2: 98% 0.75 1.9 <300 267 320 Mg Nb.sub.6Sn.sub.5 Nb.sub.6Sn.sub.5: 2% 790° C./2 h Comparative 3 Nb + Sn Nb.sub.3Sn, Nb.sub.3Sn: 92% 1.42 0.25 <300 65 85 Example 2 1050° C./6 h NbO, NbO: 3% Nb, Nb: 4% NbSn.sub.2 NbSn.sub.2 1% Ex. 3 3 Nb + Sn + Nb.sub.3Sn Nb.sub.3Sn: 100% 0.23 0.55 <300 76 88 Mg 1050° C./6 h Ex. 4 3 Nb + Sn + Nb.sub.3Sn Nb.sub.3Sn: 100% 0.54 1.2 <300 239 287 Mg 1050° C./6 h

[0041] The niobium metal powder used for producing the powders of examples 2 and 4 was obtained by a method analogous to the production process described in WO 00/67936 by reaction of NbO.sub.2 with magnesium vapor. The niobium metal powder obtained had an oxygen content of 8500 ppm, a hydrogen content of 230 ppm, a fluoride content of 2 ppm and an agglomerate size D50 of 205 μm and D90 of 290 μm. The average size of the primary particles was 0.6 μm and the pore size distribution of the agglomerates was bimodal with maxima at 0.5 and 3 μm. Such niobium metal powders display a high porosity which, contrary to expectations, does not lead to a higher oxygen content and formation of an NbO and SnO phase in the NbSn powder. Accordingly, niobium metal powders having a high porosity can also be used in the process of the invention.

[0042] In the case of the powders of example 1 and 3 and of the two comparative experiments, niobium metal powders according to the prior art without internal porosity of the particles were used, with these having an oxygen content of 2900 ppm, a hydrogen content of 10 ppm and a particle size having a D90 of 95 μm. Examples 1 and 3 show that a low oxygen content and the avoidance of the NbO and SnO phases can also be achieved using these starting materials.

[0043] The powder of example 2 was subsequently milled in an oxygen-free atmosphere, leading to a D90 of 3.1 μm and a D99 of 4.9 μm. It was surprisingly observed that milling of the powder did not lead, contrary to expectations, to an increase in the oxygen content, which was 0.78% by weight in the milled powder, nor to formation of an NbO and SnO phase.

[0044] It has also surprisingly been found that reaction of metals in the presence of magnesium does not lead to residues of the reducing agent remaining in the product. Rather, it was found that the content of Mg in the powder according to the invention is in the normal range.

[0045] FIGS. 2 to 4 show X-ray diffraction patterns of the powders according to the invention, with FIG. 2 showing the NbSn.sub.2 obtained in example 2, FIG. 3 showing the Nb.sub.3Sn obtained in example 4 and FIG. 4 showing the Nb.sub.3Sn obtained in example 3. It can clearly be seen from all the images that the powders according to the invention do not have any separate NbO phases. FIG. 1 shows the X-ray diffraction pattern of a powder as per the prior art, as is described by way of example by M. Lopez et al., (“Synthesis of nano intermetallic Nb.sub.3Sn by mechanical alloying and annealing at low temperature”, Journal of Alloys and Compounds 612 (2014), 215-220), in which the occurrence of separate NbO and SnO phases can clearly be seen.