Patent GB-1021548-A (GB)
Title: Method of obtaining an intermetallic compound of niobium and tin in fabricated form
Inventor: BARBER ANTHONY CLIFFORD
IPC: H01L39/24
Filed: 1962-12-21
Abstract: A method of producing a fabricated article comprising a continuous layer of Nb3Sn over at least part of the surface includes the steps of: (a) assembling a composite structure having (i) a support layer of Nb, (ii) an intermediate layer of Sn, or a mixture of Sn and Nb, in reactive form adjacent to the support layer, and (iii) a cover layer of Nb in reactive form; (b) subjecting the composite structure to a first heat-treatment in a non-oxidizing atmosphere to obtain a continuous coating of Sn-rich phase by reaction between the intermediate and cover layers, and cooling to obtain a ductile Sn-Nb solid solution; (c) cold-working the composite structure and fabricating it into an article such as a thin sheet, foil or wire wound into shapes suitable for electrical apparatus; (d) subjecting the fabricated article to a second heat-treatment in a non-oxidizing atmosphere between 650  DEG C. and 1150  DEG C. so as to cause the Nb and Sn in the support, intermediate and cover layers to react by diffusion to give a continuous layer of Nb3Sn.  Mechanical strength in the final product may be provided by unreacted Nb in the support layer or by a support backing of a compatible metal such as Cu.  The reactive intermediate layer (ii) of Sn and the reactive cover layer (iii) of Nb may be deposited electrophoretically. Thus powdered tin may be deposited from a stirred liquid mixture containing 2% by weight zein, 0.03 g. Al(NO3)3 per 100 mils and equal volumes of nitromethane and isopropyl alcohol using a platinized titanium anode. Similar conditions may be used for depositing Nb except for an Al(NO3)3 concentratio of 0.01 g./100 mils.ALSO:A method of producing a fabricated article comprising a continuous layer of Nb3Sn over at least part of the surface includes the steps of:  (a) assembling a composite structure having (i) a support layer of Nb; (ii) an intermediate layer of Sn, or a mixture of Sn and Nb, in reactive form adjacent to the support layer; and (iii) a cover layer of Nb in reactive form;  (b) subjecting the composite structure to a first heat-treatment in a non-oxidizing atmosphere to obtain a continuous coating of Sn-rich phase by reaction between the intermediate and cover layers, and cooling to obtain a ductile Sn-Nb solid solution; (c) cold-working the composite structure and fabricating it into an article such as a thin sheet, foil or wire wound into shapes suitable for electrical apparatus;  (d) subjecting the fabricated article to a second heat-treatment in a non-oxidizing atmosphere between 650 DEG C. and 1150 DEG  C. so as to cause the Nb and Sn in the support, intermediate and cover layers to react by diffusion to give a continuous layer of Nb3Sn.  Mechanical strength in the final product may be provided by unreacted Nb in the support layer or by a support backing of a compatible metal such as Cu.  The reactive intermediate layer (ii) of Sn and the reactive cover layer (iii) of Nb may be deposited electrophoretically. Thus powdered tin may be deposited from a stirred liquid mixture containing 2% by weight zein, 0.03 g. Al(NO3)3 per 100 mils and equal volumes of nitromethane and isopropyl alcohol using a platinized titanium anode.  Similar conditions may be used for depositing Nb except for an Al(NO3)3 concentration of 0.01 g/100 mils.