Title:

Bundle draw based processing of nanofibers and method of making

Document Type and Number:

United States Patent Application 20030135971

Kind Code:

Abstract:

A process is disclosed for making ultra fine fibers comprising forming a continuous cladding about a plurality of coated metallic wires. The cladding is drawn for reducing the outer diameter and for diffusion bonding the coating within the cladding. A plurality of the drawn claddings are assembled and a second cladding is formed the remainders. The second cladding is drawn for further reducing the outer diameter. The sacrificial coating and the claddings are removed to obtain a plurality of ultra fine fibers. In some embodiments, the ultra fine fibers are converted through a doping process.

Representative Image:

Bundle draw based processing of nanofibers and method of making

Inventors:

Liberman, Michael (Deland, FL, US)
Murray, Michael C. (Eustis, FL, US)
June, Matthew R. (Daytona Beach, FL, US)
Quick, Nathaniel R. (Lake Mary, FL, US)
Salinaro, Richard (Hastings on Hudson, NY, US)

Plaque It!

What is claimed is:

1. An ultra fine fiber comprising a drawn metallic fiber having a diameter less than about 100 nanometers.

2. The fiber of claim 1, wherein the diameter of the fiber is between about 30 and 90 nanometers.

3. The fiber of claim 1, wherein the metallic fiber comprises stainless steel.

4. The fiber of claim 1, wherein the metallic fiber comprises gold.

5. The fiber of claim 1, wherein the metallic fiber comprises a metal selected from the group consisting of iron, nickel, platinum, silver, and any alloy thereof.

6. The fiber of claim 1, wherein the fiber comprises a combination of a first metal with a second component to form a material.

7. The fiber of claim 6, wherein the second component is selected from the group consisting of boron, carbon, nitrogen, oxygen, aluminum, silicon, phosphorus, sulfur, nickel, copper, zinc, gallium, germanium, palladium, silver, cadmium, indium, tin, platinum, gold, titanium, rhodium, zirconium, vanadium, titanium tetra-chloride, titanium ethoxide, aluminum sec-but-oxide, and tetra-carbonyl nickel.

8. The fiber of claim 6, wherein the material is selected from the group consisting of an alloy, a ceramic, a catalyst, an intermetallic and a glass.

9. The fiber of claim 6, wherein the material has at least one electrical function selected from the group consisting of a conductor, a semiconductor, an insulator, a capacitor, an electrode, and a photoconductor.

10. The fiber of claim 1, further comprising an outer layer adjacent an outer circumference of the fiber.

11. The fiber of claim 10, wherein the outer layer is selected from the group consisting of boron, carbon, nitrogen, oxygen, aluminum, silicon, phosphorus, sulfur, nickel, copper, zinc, gallium, germanium, platinum, silver, indium, titanium tetra-chloride, titanium ethoxide, aluminum sec-but-oxide, and tetra-carbonyl nickel.

12. The fiber of claim 1, the fiber having a longitudinal axis, the fiber further having at least a first region and a second region along its longitudinal axis, the first region having a first characteristic, and the second region having a second characteristic.

13. The fiber of claim 12, wherein the first or second characteristic is an electrical function selected from the group consisting of a conductor, a semiconductor, an insulator, a capacitor, a resistor and an electrode.

14. The fiber of claim 12, wherein the first or second characteristic is a material comprising a combination of a first metal with a second component.

15. The fiber of claim 14, wherein the first metal comprises a metal selected from the group consisting of stainless steel, gold, iron, nickel, platinum, silver, titanium, zirconium, niobium, and vanadium.

16. The fiber of claim 14, wherein the second component comprises an element selected from the group consisting of boron, carbon, nitrogen, oxygen, aluminum, silicon, phosphorus, sulfur, nickel, copper, zinc, gallium, germanium, palladium, silver, cadmium, indium, tin, platinum, indium, gold, titanium, rhodium, zirconium and vanadium.

17. The fiber of claim 14, wherein the material is selected from the group consisting of an alloy, a ceramic, a catalyst, and an intermetallic.

18. A device comprising an ultra fine fiber, the fiber comprising a drawn metallic fiber having a diameter less than 100 nanometers.

19. The device of claim 18, selected from the group consisting of a filter, a sensor, a capacitor, a resistor, a semiconductor, a fuel cell, a nanogear, a nanomechanical device, a nanochemical device, a nanoelectrical device, a nanoelectromechanical system, a nanospring, and a catalyst.

20. A filter comprising an ultra fine fiber, the fiber comprising a drawn metallic fiber having a diameter less than about 100 nanometers.

21. The filter of claim 20, wherein the fiber comprises a ductile material that is resistant to chemical corrosion.

22. The filter of claim 20, wherein the fiber comprises a material having a catalytic property.

23. The filter of claim 20, wherein the fiber comprises a material having resistance to a temperatures between about 100° C. to about 1250° C.

24. The filter of claim 20, having a thickness of between about 25 μm and about 1250 μm.

25. The filter of claim 20, having pores capable of excluding particles of a minimum size, wherein the minimum size is between about 1000 Daltons and about 1 μm.

26. The filter of claim 20, having a bulk porosity of at least about 30%.

27. A process for making ultra fine fibers comprising: providing a plurality of metallic wires; coating the wires with a sacrificial coating material to obtain a plurality of coated wires; subjecting the plurality of coated wires to at least two cycles of a drawing process, the drawing process comprising: forming a bundle of metallic wires, or claddings containing metallic wires; encasing the bundle within an outer cladding; and drawing the outer cladding to reduce the outer diameter thereof and to reduce the cross-section of the metallic wires; releasing the fibers by removing the sacrificial coating material and claddings; and obtaining a plurality of ultra fine metallic fibers, the fibers having a diameter of less than about 100 nanometers.

28. The process of claim 27, in which at least one cycle of the drawing process further comprises an annealing step.

29. The process of claim 28, wherein the annealing step comprises exposing the metallic wires to a temperature between 0.5 and 0.8 of a melting point of the wires.

30. The process of claim 27, comprising at least three cycles of the drawing process.

31. The process of claim 27, further comprising exposing at least a portion of a fiber to a second component under conditions permitting doping of the second component into the fiber.

32. The process of claim 31, wherein the conditions permitting doping comprise contacting the fiber with a doping atmosphere comprising a gas, the gas comprising an element selected from the group consisting of nitrogen, hydrogen, carbon, boron, phosphorus, silicon, aluminum, sulfur, oxygen titanium tetra-chloride, titanium ethoxide, aluminum sec-but-oxide, and tetra-carbonyl nickel.

33. The process of claim 32, wherein the conditions permitting doping further comprise heating the fibers in the doping atmosphere.

34. The process of claim 33, wherein the heating is at a temperature sufficient to break an intramolecular bond of the gas, and wherein the temperature is lower than a melting point of the fiber.

35. The process of claim 31 wherein the conditions permitting doping comprise heating the fiber at a level between about 0.5 and 0.9 of a melting point of the fibers.

36. The process of claim 35, wherein the heating is at a level between about 0.6 and 0.8 of a melting point of the fibers.

37. The process of claim 36, wherein the heating is at a level between about 0.65 and 0.69 of a melting point of the fibers.

38. The process of claim 27, wherein the coating step comprises electroplating the coating material onto the metallic wires.

39. The process of claim 27, further comprising treating an interior of the cladding with a release material to inhibit chemical interaction between the cladding and the plurality of coated metallic wires within the cladding.

40. The process of claim 39, wherein the release material is in a quantity sufficient to inhibit chemical interaction between the cladding and the plurality of coated metallic wires within the cladding, and wherein the quantity is insufficient to inhibit a diffusion bond between the coated metallic wires and the sacrificial coating material.

41. The process of claim 27, wherein the encasing step of at least one cycle comprises forming a longitudinally extending sheet of cladding material into a continuous tube about the plurality of metallic wires.

42. The process of claim 27, wherein the sacrificial coating comprises from about 5% to about 15% by volume of a combined volume of the metallic wires and the sacrificial coating material.

43. The process of claim 27, wherein the releasing step comprises chemically removing the sacrificial coating material.

44. The process of claim 27, wherein the releasing step comprises immersing the drawn metallic wires into an acid for dissolving the sacrificial coating material.

45. The process of claim 27, wherein at least one cycle comprises a reduction ratio of the cross section of the wires between about 8% and about 20%.

46. The process of claim 45, wherein the reduction ratio is about 10%.

47. The process of claim 27, wherein the metallic wires have a diameter of from about 12 μm to about 50 μm prior to the drawing process.

48. Use of an ultra fine fiber in a device, wherein the ultra fine fiber comprises a drawn metallic fiber having a diameter less than about 100 nanometers for use in a device.

49. The use of an ultra fine fiber according to claim 48, wherein the device is an electronic sensor.

50. The use of an ultra fine fiber according to claim 49, wherein the electronic sensor is a sensor selected from the group consisting of a piezo-resistive sensor, a chemo-resistive sensor, a nano-computer switch, a thermo-resistive sensor, a nano-transmitter, a nano-receiver, a thermocouple, and a nano-antenna.

51. The use of an ultra fine fiber according to claim 48, wherein the device is a biomedical sensor.

52. The use of an ultra fine fiber according to claim 51, wherein the biomedical sensor is a glucose sensor.

53. The use of an ultra fine fiber according to claim 48, wherein the device is an opto-electronic converter.

54. The use of an ultra fine fiber according to claim 53 wherein the opto-electronic converter is a photovoltaic cell.

55. The use of an ultra fine fiber according to claim 48, wherein the device is a filtration device.

56. The use of an ultra fine fiber according to claim 55, wherein the filtration device is selected from the group consisting of a nano-catalytically enhanced filtration device, an aerosol filter device, and a nano-filtration membrane.

57. The use of an ultra fine fiber according to claim 48, wherein the device is an energy device.

58. The use of an ultra fine fiber according to claim 57, wherein the energy device is selected from the group consisting of a nano-fuel cell array; a nano-storage capacitor; an infrared energy sensor, an ultraviolet energy sensor, a microwave energy sensor, an RF energy sensor, a thermocouple, and a nano-heater.

59. The use of an ultra fine fiber according to claim 48, wherein the device is a chemical device.

60. The use of an ultra fine fiber according to claim 59, wherein the chemical device is selected from the group consisting of a nano-engineered catalyst structure, a nano-chemical sensor, and a nano-chemical analyzer.

61. The use of an ultra fine fiber according to claim 48, wherein the device is a mechanical device.

62. The use of an ultra fine fiber according to claim 61, wherein the mechanical device is selected from the group consisting of a nano-electro-mechanical system, a nano-spring, a nano-lever, a nano-diaphragm, a nano cable and a nanogear.

63. The use of an ultra fine fiber according to claim 48, wherein the device is an electronic device.

64. The use of an ultra fine fiber according to claim 63, wherein the electronic device is selected from the group consisting of a transistor, a diode, an LED, a nanotorus, a cathode emitter, a rectifier, a resistor, an inductor, a nanocomputer, and a nanomemory circuit.

65. The use of an ultra fine fiber according to claim 48, wherein the device is a quantum well device.

66. The use of an ultra fine fiber according to claim 48, wherein the device is a quantum cascade device.

67. The use of an ultra fine fiber according to claim 48, wherein the device is a ceramic superconductor.

68. The use of an ultra fine fiber according to claim 48, wherein the device is a nanowire laser.

69. The use of an ultra fine fiber according to claim 48, wherein the diameter of the fiber is between about 30 and 90 nanometers.

70. The use of an ultra fine fiber according to claim 48, wherein the metallic fiber comprises stainless steel.

71. The use of an ultra fine fiber according to claim 48, wherein the metallic fiber comprises gold.

72. The use of an ultra fine fiber according to claim 48, wherein the metallic fiber comprises a metal selected from the group consisting of iron, nickel, platinum, silver, titanium, zirconium, niobium, vanadium, chromium, manganese, cobalt, molybdenum, and copper.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patent application Ser. No. 09/654,980 entitled “PROCESS OF MAKING FINE AND ULTRA FINE METALLIC FIBERS” filed on Sep. 5, 2000, which is a continuation-in-part of U.S. patent application Ser. No. 09/190,723 entitled “PROCESS OF MAKING FINE AND ULTRA FINE METALLIC FIBERS” filed on Nov. 12, 1998, now U.S. Pat. No. 6,112,395, which application claims priority under 35 U.S.C. § 119(e) to Provisional Application Serial No. 60/065,363, filed Nov. 12, 1997, entitled “PROCESS OF MAKING FINE AND ULTRA FINE METALLIC FIBERS.” The disclosures of the above-described references are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to metallic fibers and more particularly to an improved method of making fine and ultra fine fibers through a new cladding and drawing process. The invention also relates to modifications to and uses of the fibers thus produced.

[0004] 2. Description of the Related Art

[0005] In recent years, the need for high quality, small diameter metallic fibers has grown as new applications for such fibers are developed by the art. High quality, small diameter metallic fibers have been used in diverse applications such as filtration media as well as being dispersed within a polymeric material to provide electrostatic shielding for electronic equipment and the like. The need for high quality, small diameter metallic fibers has led to various new ways and processes for making these high quality metallic fibers for the various uses in the art.

[0006] Typically, high quality metallic fibers may be characterized as small diameter metallic fibers having a diameter of less than 50 micrometers with a substantially uniform diameter along the longitudinal length thereof Typically, the fibers are produced in a fiber tow and severed to have a longitudinal length at least 1,000 times the diameter of the metallic fiber.

[0007] A disadvantage of some cladding and drawing processes is the diffusion of impurities of the carbon steel into metallic fiber during the drawing process, which is exacerbated for processing nanofibers and precious metals where chemical purity is required for product applications. A substantial amount of heat and pressure are produced during the drawing process, potentially causing a fusion of undesirable materials from the carbon steel upon the surface of the metallic fibers. These undesirable materials such as carbon, hydrocarbon materials such as oils and the like can remain on the surface of the metallic fibers through the leaching process and reside thereon in the end product. In certain applications, these undesired impurities are detrimental to the application and the use of the metallic fibers. For example, these undesirable impurities may be detrimental when the metallic fibers are used in a filtration process or the like.

SUMMARY OF THE INVENTION

[0008] Methods of making ultra fine fibers, drawn metallic ultra fine fibers, devices including the ultra fine fibers, and uses for the ultra fine fibers are disclosed.

[0009] An ultra fine fiber can include a drawn metallic fiber having a diameter less than about 100 nanometers. The ultra fine fiber can have a diameter of between about 30 and 90 nanometers. The fiber can be a metallic fiber including stainless steel or gold. Alternatively, the metallic fiber can include iron, nickel, platinum, silver, or any alloy thereof.

[0010] The fiber can further include a combination of a first metal with a second component to form a material. The second component can include, for example, boron, carbon, nitrogen, oxygen, aluminum, silicon, phosphorus, sulfur, nickel, copper, zinc, gallium, germanium, palladium, silver, cadmium, indium, tin, platinum, gold, titanium, rhodium, zirconium, vanadium, titanium tetra-chloride, titanium ethoxide, aluminum sec-but-oxide, tetra-carbonyl nickel, and the like. Additionally, the material can include, for example, an alloy, a ceramic, a catalyst, an intermetallic, a glass, and the like. The material can have at least one electrical function. The material can function as a conductor, a semiconductor, an insulator, a capacitor, an electrode, or a photoconductor.

[0011] The fiber can also have an outer layer adjacent an outer circumference of the fiber. The outer layer of the fiber can contain boron, carbon, nitrogen, oxygen, aluminum, silicon, phosphorus, sulfur, nickel, copper, zinc, gallium, germanium, platinum, silver, indium, titanium tetra-chloride, titanium ethoxide, aluminum sec-but-oxide, tetra-carbonyl nickel, and the like.

[0012] The fiber has a longitudinal axis and can include at least a first region and a second region along its longitudinal axis. The first region can have a first characteristic and the second region can have a second characteristic. The first or second characteristic can be an electrical function, including, for example, a conductor, a semiconductor, an insulator, a capacitor, a resistor, an electrode, and the like. The first or second characteristic of the fiber can be a material having a combination of a first metal with a second component. The first metal can include a metal, for example, stainless steel, gold, iron, nickel, platinum, silver, titanium, zirconium, niobium, vanadium, and the like. Additionally, the second component can include an element, for example, boron, carbon, nitrogen, oxygen, aluminum, silicon, phosphorus, sulfur, nickel, copper, zinc, gallium, germanium, palladium, silver, cadmium, indium, tin, platinum, indium, gold, titanium, rhodium, zirconium, vanadium, and the like. Alternatively the material can be, for example, an alloy, a ceramic, a catalyst, or an intermetallic.

[0013] Another embodiment of the invention includes a device including a drawn metallic fiber having a diameter less than 100 nanometers. The device can be, for example, a filter, a sensor, a capacitor, a resistor, a semiconductor, a fuel cell, a nanogear, a nanomechanical device, a nanochemical device, a nanoelectrical device, a nanoelectromechanical system, a nanospring, or a catalyst.

[0014] Another embodiment of the invention is a filter including an ultra fine fiber, where the fiber includes a drawn metallic fiber having a diameter less than about 100 nanometers. The filter can include a fiber having a ductile material that is resistant to chemical corrosion. Alternatively, the filter can include a fiber having a material having a catalytic property or a fiber having a material having resistance to a temperatures between about 100° C. to about 1250° C.

[0015] The filter can have a thickness of between about 25 μm and about 1250 μm and can have pores capable of excluding particles of a minimum size, wherein the minimum size is between about 1000 Daltons and about 1 μm. Further, the filter can have a bulk porosity of at least about 30%.

[0016] Another embodiment of the invention is a process for making ultra fine fibers. The process includes providing a plurality of metallic wires, coating the wires with a sacrificial coating material to obtain a plurality of coated wires, subjecting the plurality of coated wires to at least two cycles of a drawing process, releasing the fibers by removing the sacrificial coating material and claddings, and obtaining a plurality of ultra fine metallic fibers, the fibers having a diameter of less than about 100 nanometers. The drawing process includes forming a bundle of metallic wires, or claddings containing metallic wires, encasing the bundle within an outer cladding and drawing the outer cladding to reduce the outer diameter thereof and to reduce the cross-section of the metallic wires.

[0017] At least one cycle of the drawing process can include an annealing step, and the annealing step can include exposing the metallic wires to a temperature between 0.5 and 0.8 of a melting point of the wires.

[0018] The process can include three or more cycles of the drawing process and can further include exposing at least a portion of a fiber to a second component under conditions permitting doping of the second component into the fiber. The conditions permitting doping can include contacting the fiber with a doping atmosphere including a gas. The gas can include an element, for example, nitrogen, hydrogen, carbon, boron, phosphorus, silicon, aluminum, sulfur, oxygen titanium tetra-chloride, titanium ethoxide, aluminum sec-but-oxide, tetra-carbonyl nickel, or the like. The conditions permitting doping can further include heating the fibers in the doping atmosphere, preferably at a temperature sufficient to break an intramolecular bond of the gas, and the temperature can be lower than a melting point of the fiber.

[0019] The conditions permitting doping can include heating the fiber at a level between about 0.5 and 0.9 of a melting point of the fibers. The heating can be at a level between about 0.6 and 0.8, and most preferably between about 0.65 and 0.69 of a melting point of the fibers.

[0020] The process of making ultra fine fibers can include a coating step that includes electroplating the coating material onto the metallic wires. The process of making ultra fine fibers can also include treating an interior of the cladding with a release material to inhibit chemical interaction between the cladding and the plurality of coated metallic wires within the cladding. The release material can be in a quantity sufficient to inhibit chemical interaction between the cladding and the plurality of coated metallic wires within the cladding, and the quantity can be insufficient to inhibit a diffusion bond between the coated metallic wires and the sacrificial coating material.

[0021] The process of making ultra fine fibers can include in the encasing step of at least one cycle forming a longitudinally extending sheet of cladding material into a continuous tube about the plurality of metallic wires.

[0022] In the process of making ultra fine fibers, the sacrificial coating can include from about 5% to about 15% by volume of a combined volume of the metallic wires and the sacrificial coating material. In the process of making ultra fine fibers the releasing step can include chemically removing the sacrificial coating material, or immersing the drawn metallic wires into an acid for dissolving the sacrificial coating material.

[0023] In the process of making ultra fine fibers at least one cycle can include a reduction ratio of the cross section of the wires between about 8% and about 20%, preferably about 10%. In the process of making ultra fine fibers, the metallic wires can have a diameter of from about 12 μm to about 50 μm prior to the drawing process. An embodiment of the invention includes use of an ultra fine fiber in a device, where the ultra fine fiber includes a drawn metallic fiber having a diameter less than about 100 nanometers for use in a device. The device can be an electronic sensor, and the electronic sensor can, for example, be a piezo-resistive sensor, a chemo-resistive sensor, a nano-computer switch, a thermo-resistive sensor, a nano-transmitter, a nano-receiver, a thermocouple, or a nano-antenna. The device can be a biomedical sensor, such as, for example, a glucose sensor. Alternatively, the device can be an opto-electronic converter, such as, for example, a photovoltaic cell. The device can be a filtration device, such as, for example, a nano-catalytically enhanced filtration device, an aerosol filter device, a nano-filtration membrane, or the like. The device can be an energy device, such as, for example, a nano-fuel cell array, a nano-storage capacitor, an infrared energy sensor, an ultraviolet energy sensor, a microwave energy sensor, an RF energy sensor, a thermocouple, a nano-heater, or the like. The device can be a chemical device, such as, for example, a nano-engineered catalyst structure, a nano-chemical sensor, a nano-chemical analyzer, and the like. Alternatively the device can be a mechanical device or an electronic device. The mechanical device can be a nano-electro-mechanical system, a nano-spring, a nano-lever, a nano-diaphragm, a nano cable or a nanogear. The electronic device can be a transistor, a diode, an LED, a nanotorus, a cathode emitter, a rectifier, a resistor, an inductor, a nanocomputer, or a nanomemory circuit. The device can also be a quantum well device, a quantum cascade device, a ceramic superconductor, or a nanowire laser.

[0024] The various uses of an ultra fine fiber in a device can employ a fiber having a diameter between about 30 and 90 nanometers; such an ultra fine fiber can contain, for example, stainless steel, gold, iron, nickel, platinum, silver, titanium, zirconium, niobium, vanadium, chromium, manganese, cobalt, molybdenum, copper, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a block diagram illustrating a first improved process of forming fine metallic fibers through a new cladding and drawing process of the invention.

[0026] FIG. 2 is an isometric view of a metallic wire referred to in FIG. 1 .

[0027] FIG. 2A is an enlarged end view of FIG. 2 .

[0028] FIG. 3 is an isometric view of the wire of FIG. 2 with a coating material thereon.

[0029] FIG. 3A is an enlarged end view of FIG. 3 .

[0030] FIG. 4 is an isometric view of an initial step of a first optional process of encasing an assembly of a plurality of wires of FIG. 3 within a casing.

[0031] FIG. 4A is an end view of FIG. 4 .

[0032] FIG. 5 is an isometric view of the completed step of the first optional process of encasing the assembly of the plurality of wires of FIG. 3 within the casing.

[0033] FIG. 5A is an end view of FIG. 5 .

[0034] FIG. 6 is an isometric view of an initial step of a second optional process of encasing an assembly of a plurality of wires of FIG. 3 within a casing.

[0035] FIG. 6A is an end view of FIG. 6 .

[0036] FIG. 7 is an isometric view of the completed step of the second optional process of encasing the assembly of the plurality of wires of FIG. 3 within the casing.

[0037] FIG. 7A is an end view of FIG. 7 .

[0038] FIG. 8 is an isometric view of an initial process of forming a tube about the casing of FIG. 5 with a cladding material.

[0039] FIG. 8A is an end view of FIG. 8 .

[0040] FIG. 9 is an isometric view of the completed process of forming the tube about the casing of FIG. 5 with the cladding material.

[0041] FIG. 9A is an end view of FIG. 9 .

[0042] FIG. 10 is an isometric view of the cladding of FIG. 9 after a first drawing process.

[0043] FIG. 10A is an enlarged end view of FIG. 10 .

[0044] FIG. 11 is an isometric view illustrating the mechanical removal of the tube after the first drawing process of FIG. 10 .

[0045] FIG. 11A is an enlarged end view of FIG. 11 .

[0046] FIG. 12 is an isometric view of the casing of FIG. 11 after the second drawing process.

[0047] FIG. 12A is an enlarged end view of FIG. 12 .

[0048] FIG. 13 is an isometric view of the plurality of the fine metallic fibers of FIG. 12 after removal of the coating material.

[0049] FIG. 13A is an enlarged end view of FIG. 13 .

[0050] FIG. 14 is a diagram illustrating a first portion of an apparatus for performing the first improved process of forming fine metallic fibers shown in FIG. 1 .

[0051] FIG. 15 is a diagram illustrating a second portion of the apparatus of FIG. 14 .

[0052] FIG. 16 is a diagram illustrating a third portion of the apparatus of FIG. 14 .

[0053] FIG. 17 is a block diagram illustrating a second improved process of forming ultra fine metallic fibers through a new cladding and drawing process of the invention.

[0054] FIG. 18 is an isometric view of an initial step of a first optional process of encasing an assembly of a plurality of the remainders of FIG. 12 within a second casing.

[0055] FIG. 18A is an end view of FIG. 18 .

[0056] FIG. 19 is an isometric view of the completed step of the first optional process of encasing the assembly of the plurality remainders of FIG. 12 within the second casing.

[0057] FIG. 19A is an end view of FIG. 19 .

[0058] FIG. 20 is an isometric view of an initial step of a second optional process of encasing an assembly of the plurality of remainders of FIG. 12 within a second casing.

[0059] FIG. 20A is an end view of FIG. 20 .

[0060] FIG. 21 is an isometric view of the completed step of the second optional process of encasing the assembly of the plurality of remainders of FIG. 12 within the second casing.

[0061] FIG. 21A is an end view of FIG. 21 .

[0062] FIG. 22 is an isometric view of an initial process of forming a second tube about the second casing of FIG. 19 with a second cladding material.

[0063] FIG. 22A is an end view of FIG. 22 .

[0064] FIG. 23 is an isometric view of the completed process of forming the second tube about the second casing of FIG. 19 with the second cladding material.

[0065] FIG. 23A is an end view of FIG. 23 .

[0066] FIG. 24 is an isometric view of the second cladding of FIG. 23 after a third drawing process.

[0067] FIG. 24A is an enlarged end view of FIG. 24 .

[0068] FIG. 25 is an isometric view illustrating the mechanical removal of the second tube after the third drawing process of FIG. 10 .

[0069] FIG. 25A is an enlarged end view of FIG. 25 .

[0070] FIG. 26 is an isometric view of the second casing of FIG. 25 after a fourth drawing process.

[0071] FIG. 26A is an enlarged end view of FIG. 26 .

[0072] FIG. 27 is an isometric view of the plurality of the ultra fine metallic fibers of FIG. 26 after removal of the coating material.

[0073] FIG. 27A is an enlarged end view of FIG. 27 .

[0074] FIG. 28 is a diagram illustrating a first portion of a second apparatus for performing the second improved process of forming ultra fine metallic fibers shown in FIG. 17 .

[0075] FIG. 29 is a diagram illustrating a second portion of the apparatus of FIG. 28 .

[0076] FIG. 30 is a diagram illustrating a third portion of the apparatus of FIG. 28 .

[0077] FIG. 31 is a diagram illustrating a fourth portion of the apparatus of FIG. 28 .

[0078] FIG. 32 is a diagram illustrating a fifth portion of the apparatus of FIG. 28 .

[0079] FIG. 33 is a diagram illustrating a sixth portion of the apparatus of FIG. 28 .

[0080] FIG. 34 is an isometric view of a first example of an assembly of a multiplicity of mixed first and second coated metallic wires.

[0081] FIG. 35 is an isometric view of a second example of an assembly of a multiplicity of mixed first and second coated metallic wires.

[0082] FIG. 36 is an isometric view of a third example of an array of a multiplicity of assemblies of the first and second coated metallic wires.

[0083] FIG. 37 is an isometric view of a fourth example of an array of a multiplicity of assemblies of the first and second coated metallic wires.

[0084] FIG. 38 is an enlarged view of a portion of FIGS. 16, 30 and 33 illustrating a variable cutting assembly for scoring or cutting the cladding material.

[0085] FIG. 39 is an enlarged view of a portion of FIG. 38 illustrating a cutting blade in a first position. and

[0086] FIG. 40 is an enlarged view of a portion of FIG. 38 illustrating the cutting blade in a second position.

[0087] FIG. 41 is a block diagram illustrating a first improved process of forming fine metallic fibers through a new cladding and drawing process of the invention.

[0088] FIG. 42 is an isometric view of a metallic wire referred to in FIG. 41 .

[0089] FIG. 42A is an enlarged end view of FIG. 42 .

[0090] FIG. 43 is an isometric view of the wire of FIG. 42 with a coating material thereon.

[0091] FIG. 43A is an enlarged end view of FIG. 43 .

[0092] FIG. 44 is an isometric view illustrating an assembly of a multiplicity of the metallic wire of FIG. 43 being wrapped with a wrapping material.

[0093] FIG. 44A is an enlarged end view of FIG. 44 .

[0094] FIG. 45 is an isometric view illustrating a plurality of the wrapped assemblies of FIG. 44 .

[0095] FIG. 45A is an end view of FIG. 45 .

[0096] FIG. 46 is an isometric view illustrating the plurality of the wrapped assemblies of FIG. 45 being simultaneously inserted into a preformed tube for providing a cladding.

[0097] FIG. 46A is an end view of FIG. 46 .

[0098] FIG. 47 is a sectional view along line 47 - 47 of FIG. 46 .

[0099] FIG. 47A is a magnified view of a portion of FIG. 46A .

[0100] FIG. 48 is an isometric view similar to FIG. 46 illustrating the complete insertion of the plurality of wrapped assemblies within the preformed tube for providing the cladding.

[0101] FIG. 48A is a magnified view of a portion of FIG. 48 .

[0102] FIG. 49 is an isometric view similar to FIG. 48 illustrating an initial tightening of the cladding about the plurality of the wrapped assemblies therein.

[0103] FIG. 49A is a magnified view of a portion of FIG. 49 .

[0104] FIG. 50 is an isometric view of the cladding of FIG. 49 after a drawing process.

[0105] FIG. 50A is an enlarged end view of FIG. 50 .

[0106] FIG. 51 is an isometric view of the plurality of the fine metallic fibers after removal of the coating material in FIG. 50 .

[0107] FIG. 51A is an enlarged end view of FIG. 51 .

[0108] FIG. 52 is a diagram illustrating an apparatus for wrapping a multiplicity of the metallic wires with a wrapping material.

[0109] FIG. 53 is a diagram illustrating the simultaneous insertion of the plurality of the wrapped assemblies of FIGS. 45 and 46 within the preformed tube.

[0110] FIG. 54 is a block diagram illustrating a forth improved process of forming fine metallic fibers through a new cladding and drawing process of the present invention.

[0111] FIG. 55 is a block diagram illustrating a fifth improved process of forming ultra fine metallic fibers through a new cladding and drawing process of the present invention.

[0112] FIG. 56 is a block diagram illustrating a general process for creating an alloy.

[0113] FIG. 57 is an isometric view of a metal wire.

[0114] FIG. 57A is an enlarged cross sectional view of FIG. 57 .

[0115] FIG. 58 is an isometric view of the metal wire referred to in FIG. 57 encased in a tube to thereby form a metal member;

[0116] FIG. 58A is an enlarged cross-sectional view of FIG. 58 .

[0117] FIG. 59 is an isometric view of a plurality of metal members jacketed or inserted within a composite tube.

[0118] FIG. 59A is a cross sectional view of FIG. 59 .

[0119] FIG. 60 is an isometric view of the plurality of the metal members inserted within the preformed tube after the process step of drawing the metal composite.

[0120] FIG. 60A is an enlarged end view of FIG. 60 .

[0121] FIG. 61 is an isometric view illustrating the mechanical removal of the preformed composite tube.

[0122] FIG. 61A is an enlarged end view of FIG. 61 .

[0123] FIG. 62 is an isometric view illustrating the remainder upon complete removal of the tube.

[0124] FIG. 62A is an enlarged cross sectional view of the alloy product of the heated remainder of FIG. 62 .

[0125] FIG. 63 is a block diagram of a process for making fine metallic alloy fibers of the invention.

[0126] FIG. 64 is an isometric view of a metallic alloy wire referred to in FIG. 63 .

[0127] FIG. 64A is an end view of FIG. 64 .

[0128] FIG. 65 is an isometric view illustrating a preformed first cladding material referred to in FIG. 63 .

[0129] FIG. 65A is an end view of FIG. 65 .

[0130] FIG. 66 is an isometric view illustrating the first cladding material of FIG. 65 encompassing the metallic alloy wire of FIG. 64 .

[0131] FIG. 66A is an end view of FIG. 66 .

[0132] FIG. 67 is an isometric view similar to FIG. 66 illustrating the first cladding material being sealed to the metallic alloy wire.

[0133] FIG. 67A is an end view of FIG. 67 .

[0134] FIG. 68 is an isometric view similar to FIG. 67 illustrating the tightening of the first cladding material to the metallic alloy wire in the presence of an inert atmosphere.

[0135] FIG. 68A is an end view of FIG. 68 .

[0136] FIG. 69 is an isometric view similar to FIG. 68 illustrating the first cladding material tightened to the metallic alloy wire.

[0137] FIG. 69A is an end view of FIG. 69 .

[0138] FIG. 70 is an isometric view of the first cladding of FIG. 69 after a first drawing process.

[0139] FIG. 70A is an enlarged end view of FIG. 70 .

[0140] FIG. 71 is an isometric view illustrating an assembly of a multiplicity of the drawn first claddings within a second cladding.

[0141] FIG. 71A is an end view of FIG. 71 .

[0142] FIG. 72 is an isometric view of the second cladding of FIG. 71 after a second drawing process.

[0143] FIG. 72A is an enlarged end view of FIG. 72 .

[0144] FIG. 73 is an isometric view similar to FIG. 72 illustrating the removal of the first and second claddings to provide a multiplicity of fine metallic alloy fibers.

[0145] FIG. 73A is an enlarged end view of FIG. 73 .

[0146] FIG. 74 is a block diagram illustrating an improved process of forming ultra fine fibers through a cladding and drawing process according to the invention.

[0147] FIG. 75 is an isometric view of a metallic wire used in the method of FIG. 74 .

[0148] FIG. 75A is an enlarged end view of FIG. 75 .

[0149] FIG. 76 is an isometric view of the wire of FIG. 75 with a coating material thereon.

[0150] FIG. 76A is an enlarged end view of FIG. 76 .

[0151] FIG. 77 is an isometric view of an assembly of a plurality of wires of FIG. 76 within a wrapping material.

[0152] FIG. 77A is an end view of FIG. 77 .

[0153] FIG. 78 is an isometric view of the completed assembly of the plurality of wires of FIG. 76 within the wrapping material.

[0154] FIG. 78A is an end view of FIG. 78 .

[0155] FIG. 79 is an isometric view of a cladding being formed around the assembly of FIG. 78 .

[0156] FIG. 79A is an end view of FIG. 79 .

[0157] FIG. 80 is an isometric view of the completed cladding FIG. 79 .

[0158] FIG. 80A is an end view of FIG. 80 .

[0159] FIG. 81 is an isometric view of the cladding of FIG. 80 after a first drawing process.

[0160] FIG. 81A is an enlarged end view of FIG. 81 .

[0161] FIG. 82 is an isometric view illustrating the mechanical removal of the cladding after the first drawing process of FIG. 8 leaving coated ultra fine fibers.

[0162] FIG. 82A is an enlarged end view of FIG. 82 .

[0163] FIG. 83 is an isometric view of the plurality of the coated metallic fibers of FIG. 82 .

[0164] FIG. 83A is an enlarged end view of FIG. 83 .

[0165] FIG. 84 is an isometric view of the plurality of the fine metallic fibers of FIG. 82 after removal of the coating material.

[0166] FIG. 84A is an enlarged end view of FIG. 84 .

[0167] FIG. 85 is a block diagram illustrating a process of converting fibers into a ceramic.

[0168] FIG. 86 is a micrograph of an end view magnified 16× of a 310 stainless steel bundle of assemblies.

[0169] FIG. 87 is a micrograph of an end view magnified 1,000× of the 310 stainless steel bundle of FIG. 86 showing one of the assemblies.

[0170] FIG. 88 is a micrograph of an end view magnified 25,000× of the 310 stainless steel bundle of FIG. 86 showing ends of some of the fibers.

[0171] FIG. 89 is a micrograph of a plurality of 316 stainless steel fibers magnified 500×.

[0172] FIG. 90 is a micrograph of a plurality of 316 stainless steel fibers magnified 15,000×.

[0173] FIG. 91 is a micrograph of a plurality of 316 stainless steel fibers magnified 50,000×.

[0174] FIG. 92 is a micrograph of a plurality of stainless steel fibers magnified 5,000×.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0175] A detailed description of an embodiment of the invention is provided below. While the invention is described in conjunction with that preferred embodiment, it should be understood that the invention is not limited to any one embodiment. On the contrary, the scope of the invention is limited only by the appended claims, and the invention encompasses numerous embodiments, alternatives, modifications and equivalents. For the purpose of example, numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. The invention may be practiced according to the claims without some or all of these specific details.

[0176] The metallic fibers as set forth herein are typically manufactured by cladding a metallic wire with a cladding material to provide a first cladding. The first cladding is drawn and annealed for reducing the diameter of the first cladding. A plurality of the first claddings are clad to provide a second cladding. The second cladding is subjected to a multiple drawing and annealing process for reducing the diameter of the second cladding and the corresponding diameter of the first claddings contained therein. Depending upon the desired end diameter of the first cladding, the plurality of second claddings may be clad to provide a third cladding. Multiple drawings of the third cladding reduce the diameter of the first and second claddings to provide metallic fibers within the first claddings of the desired diameter. After the desired diameter of the metallic fibers within the first cladding is achieved, the cladding materials are removed by either an electrolysis or a chemical process thereby providing metallic fibers of the desired final diameter.

[0177] In some embodiments, the fibers are made of a stainless steel and are produced by a drawing process. In other embodiments, the fibers are homogeneous metal structures including nickel, gold, platinum, silver, palladium, silicon, titanium and germanium. Two or more concentrically aligned materials that after drawing are inter-diffused by a thermal process can also be used as described in U.S. Pat. No. 6,248,192, the specification of which is hereby incorporated by reference in its entirety. The drawing process comprises cladding a stainless steel wire with a cold roll steel clad material to produce a first cladding. The first cladding is subjected to a series of drawing and annealing processes for reducing the diameter thereof. Thereafter, a plurality of the first claddings are encased within a second cladding material such as cold roll steel for producing a second cladding. The second cladding is subjected to a series of drawing and annealing processes for further reducing the diameter of the second cladding. After the second drawing process, the original wires of the first cladding are reduced to a diameter of 10 to 50 microns that is suitable for some applications. For applications requiring finer metallic fibers, a plurality of second claddings are clad with a third cladding material to provide a third cladding. Third cladding is subjected to a series of drawing and annealing for further reducing the diameter of the original metallic wires.

[0178] The cladding material is removed by subjecting the finally drawn cladding to an acid leaching process whereby the acid dissolves the cladding material leaving the metallic fibers. The metallic fibers may be severed to produce metallic sliver or cut metallic fibers or may be used as metallic fiber tow.

[0179] Throughout the several Figures of the drawings, similar reference characters refer to similar parts. FIG. 1 is a block diagram illustrating an improved process 10 for making fine metallic fibers. The improved process 10 of FIG. 1 comprises the process step 11 of providing multiple coated metallic wires 20 with each of the metallic wires 20 having a coating material 30 .

[0180] FIG. 2 is an isometric view of the metallic wire 20 referred to in FIG. 1 with FIG. 2A being an enlarged end view of FIG. 2 . In this example, the metallic wire 20 is a stainless steel wire having a diameter 20 D but it should be understood that various types of metallic wires 20 may be used in the improved process 10 .

[0181] FIG. 3 is an isometric view of the metallic wire 20 of FIG. 2 with the coating material 30 thereon. FIG. 3A is an enlarged end view of FIG. 3 . In this example, the coating material 30 is a copper material but it should be understood that various types of coating materials 30 may be used in the improved process 10 .

[0182] The process of applying the coating material 30 to the metallic wire 20 may be accomplished in various ways. One preferred process of applying the coating material 30 to the metallic wire 20 is an electroplating process. The coating material 30 defines a coating diameter 30 D. Preferably, the coating material 30 represents approximately five percent (5%) by weight of the combined weight of the metallic wire 20 and the coating material 30 .

[0183] A plurality of the metallic wires 20 with the coating material 30 are formed into an assembly of metallic wires 20 . Preferably, 150 to 1200 metallic wires 20 with the coating material 30 are formed into the assembly 34 .

[0184] FIG. 1 illustrates an optional process step 12 of encasing the assembly 34 of metallic wires 20 with a casing material 40 . Preferably, the casing material 40 is the same material as the coating material 30 .

[0185] FIG. 4 illustrates an initial step in a first example of the optional process step 12 of encasing the assembly 34 of metallic wires 20 with the casing material 40 . FIG. 4A is an end view of FIG. 4 . The step of encasing the assembly 34 within the casing material 40 includes bending a first and a second edge 41 and 42 of a longitudinally extending casing material 40 to form the casing 44 .

[0186] FIG. 5 illustrates the completed process of encasing the assembly 34 of the plurality of the wires 20 within the casing material 40 . FIG. 5A is an end view of FIG. 5 . The casing material 40 is bent about the assembly 34 of the plurality of the wires 20 with the first edge 41 of the casing material 40 overlapping the second edge 42 of the casing material 42 . The assembly 34 of the plurality of the wires 20 are encased within the casing material 40 for providing the casing 44 having a diameter 44 D.

[0187] FIG. 6 illustrates an initial step in a second example of the optional process step 12 of encasing the assembly 34 of metallic wires 20 with the casing material 40 . FIG. 6A is an end view of FIG. 6 . The step of encasing the assembly 34 within the casing material 40 includes bending a first and a second edge 41 and 42 of a longitudinally extending casing material 40 to form the casing 44 .

[0188] FIG. 7 illustrates the completed process of encasing the assembly 34 of the plurality of the wires 20 within the casing material 40 . FIG. 7A is an end view of FIG. 7 . The casing material 40 is bent about the assembly 34 of the plurality of the wires 20 with the first edge 41 of the casing material 40 abutting the second edge 42 of the casing material 42 . Preferably, the first edge 41 of the casing material 40 is welded to the second edge 42 of the casing material 40 by a weld 46 . The assembly 34 of the plurality of the wires 20 are encased within the casing material 40 for providing the casing 44 having a diameter 44 D.

[0189] FIG. 1 illustrates the process step 13 of preparing a cladding material 50 . Preferably, the cladding material 50 is a longitudinally extending cladding material 50 having a first and a second edge 51 and 52 . A surface of the cladding material 50 may be treated with a release material 54 to inhibit chemical interaction between the cladding material 50 and the plurality of metallic wires 20 or the casing material 40 . The release material 54 may be any suitable material to inhibit chemical interaction between the cladding material 50 and the plurality of metallic wires 20 or the coating material 30 or the casing material 40 .

[0190] Preferably, the cladding material 50 is made of a carbon steel material. The release material 54 may be titanium dioxide TiO ₂ , sodium silicate, aluminum oxide, talc or any other suitable material to inhibit chemical interaction between the cladding material 50 and the coating material 30 or the casing material 40 . The release material 54 may be suspended within a liquid for enabling the release material 54 to be painted onto the cladding material 50 . In the alternative, the release material 54 may be applied by flame spraying or a plasma gun or any other suitable means.

[0191] FIG. 1 illustrates the process step 14 of forming a continuous tube 55 of the cladding material 50 about the plurality of metallic wires 20 or the casing material 40 . In this example, the cladding material 50 is a carbon steel material with the plurality of metallic wires 20 being made of a stainless steel material. The coating material 30 and the casing material 40 are preferably a copper material.

[0192] FIG. 8 is an isometric view illustrating an initial process of forming the continuous tube 55 of the cladding material 50 about the plurality of metallic wires 20 and the casing material 40 . FIG. 8A is an end view of FIG. 8 . The step 14 of forming the tube 55 from the cladding material 50 includes bending the first and second edges 51 and 52 of the longitudinally extending sheet of the cladding material 50 to form a cladding 60 for enclosing the casing material 40 . The cladding 60 defines an outer diameter 60 D.

[0193] FIG. 9 is an isometric view of the completed process of forming the continuous tube 55 of the cladding material 50 . FIG. 9A is an end view of FIG. 9 . The longitudinally extending sheet of the cladding material 50 is bent with the first edge 51 of the cladding material 50 abutting the second edge 52 of the cladding material 50 . The first edge 51 of the cladding material 50 is welded to the second edge 52 of the cladding material 50 by a weld 56 .

[0194] When the optional casing material 40 is used in the process, the casing material 40 acts as a heat sink to facilitate the welding of the first edge 51 to the second edge 52 of the cladding material 50 . Furthermore, the casing material 40 acts as a heat sink to protect the assembly 34 of the plurality of coated wires 20 within the casing material 40 from the heat of the welding process.

[0195] FIG. 1 illustrates the process step 15 of drawing the cladding 60 . The process step 15 of drawing the cladding 60 provides four effects. Firstly, the process step 15 reduces an outer diameter 60 D of the cladding 60 . Secondly, the process step 15 reduces the corresponding outer diameter 20 D of each of the plurality of metallic wires 20 and the corresponding outer diameter 30 D of each of the coating materials 30 . Thirdly, the process step 15 causes the coating materials 30 on each of metallic wires 20 to diffusion weld with the coating materials 30 on adjacent metallic wires 20 . Fourthly, the process step 15 causes the casing material 40 to diffusion weld with the coating material 30 on the plurality of metallic wires 20 .

[0196] FIG. 10 is an isometric view of the cladding 60 of FIG. 9 after the first drawing process. FIG. 10A is an enlarged end view of FIG. 10 . The drawing of the cladding 60 causes the coating material 30 on each of the plurality of metallic wires 20 to diffusion weld with the coating materials 30 on adjacent plurality of metallic wires 20 and to diffusion weld with the casing material 40 . The diffusion welding of the coating material 30 and the casing material 40 forms a unitary material 70 . After the diffusion welding of the coating material 30 and the casing material 40 , the coating material 30 and the casing material 40 are formed into a substantially unitary material 70 extending throughout the interior of the cladding 60 . The plurality of metallic wires 20 are contained within the unitary material 70 extending throughout the interior of the cladding 60 . Preferably, the coating material 30 and the casing material 40 is a copper material and is diffusion welded within the cladding 60 to form a substantially unitary copper material 70 with the plurality of metallic wires 20 contained therein.

[0197] The release material 54 is deposited on the cladding material 50 of the formed tube 55 in a quantity sufficient to inhibit the chemical interaction or bonding between the tube 55 and a plurality of metallic wires 20 and the coating materials 30 and the casing material 40 within the tube 55 . However, the release material 54 is deposited on the tube 55 in a quantity insufficient to inhibit the diffusion welding of the coating materials 30 on adjacent metallic wires 20 and the casing material 40 .

[0198] FIG. 1 illustrates the process step 16 of removing the tube 55 . In the preferred form of the process, the step 16 of removing the tube 55 comprises mechanically removing the tube 55 .

[0199] FIG. 11 is an isometric view illustrating the mechanical removal of the tube 55 with FIG. 11A being an enlarged end view of FIG. 11 . In one example of this process step 16 , the tube 55 is scored or cut at 71 and 72 by mechanical scorers or cutters (not shown). The scores or cuts at 71 and 72 form tube portions 73 and 74 that are mechanically pulled apart to peel the tube 55 off of a remainder 80 . The remainder 80 comprises the substantially unitary coating material 70 with the plurality of metallic wires 20 contained therein. The remainder 80 defines an outer diameter 80 D.

[0200] FIG. 1 illustrates the process step 17 of drawing the remainder 80 for reducing the outer diameter 80 D thereof and for reducing the corresponding outer diameter 20 D of the plurality of metallic wires 20 contained therein.

[0201] FIG. 12 is an isometric view of the plurality of wires 20 of FIG. 11 reduced into a plurality of fine metallic fibers 90 by the process step 17 of drawing the remainder 80 . FIG. 12A is an enlarged end view of FIG. 12 . The substantially unitary material 70 provides mechanical strength for the plurality of metallic wires 20 contained therein for enabling the remainder 80 to be drawn without the cladding 60 . The substantially unitary coating material 30 and casing material 40 enables the remainder 80 to be drawn for reducing the outer diameter 80 D thereof and for providing the plurality of fine metallic fibers 90 .

[0202] FIG. 13 is an isometric view of the plurality of the fine metallic fibers 90 of FIG. 12 after the process step 18 of removing the unitary material 70 . FIG. 13A is an enlarged end view of FIG. 13 . Preferably, the unitary material 70 is removed by an acid leaching process for dissolving the unitary copper material 70 to provide a plurality of stainless steel fibers 90 .

[0203] One example of the process step 18 includes an acid leaching process. The remainder 80 comprising the substantially unitary copper material 30 with the plurality of stainless steel wires 20 is immersed into a solution of 8% to 15% H ₂ SO ₄ and 0.1% to 1.0% H ₂ O ₂ for dissolving the unitary copper material 70 without dissolving the stainless steel fibers 90 . The 0.1% to 1.0% H ₂ O ₂ functions as an oxidizing agent to inhibit leaching of stainless steel fibers 90 by the H ₂ SO ₄ . Preferably, the 0.5% to 3.0% H ₂ O ₂ is stabilized from decaying in the presence of copper such as PC circuit board grade H ₂ O ₂ . It should be appreciated that other oxidizing agents may be used with the present process such as sodium stanate or sodium benzoate or the like.

[0204] The above acid leaching process 16 is governed by the reaction illustrated in equation

Cu+H ₂ O ₂ +H ₂ SO ₄ →CuSO ₄ +2H ₂ O

[0205] The initial concentration of the H ₂ SO ₄ is 11.0% at a concentration of 20.0 grams per liter of Cu+2 as CuSO ₄ at a temperature of 80 degrees F. to 120 degrees F. The concentration is maintained between 8.0% to 11.0% H ₂ SO ₄ and 20.0 to 70.0 grams per liter of Cu ⁺² as CuSO ₄ .

[0206] The dissolving of the unitary copper material 70 in the presence of the H ₂ O ₂ dissolves the unitary copper material 70 without dissolving the stainless steel fibers 90 . After the unitary copper material 70 is dissolved, the stainless steel fibers 90 are passed to a rinsing process.

[0207] The removal process 18 includes rinsing the stainless steel fibers 90 in a rinse solution comprising H ₂ O having a pH of 2.0 to 3.0 with the pH being adjusted with H ₂ SO ₄ . Maintaining the pH of the rinsing solution between a pH of 2.0 to 3.0 inhibits the formation of Fe[OH] ₂ . After rinsing the stainless steel fibers 90 , the stainless steel fibers 90 may be used as cut stainless steel fibers 90 or as stainless steel fiber tow.

[0208] FIGS. 14 - 16 are diagrams illustrating a first through third portions of an apparatus 100 for performing the first improved process 10 of forming fine metallic fibers 90 shown in FIG. 1 . The process steps 11 - 18 are displayed adjacent the respective region of the apparatus 100 accomplishing the respective process step.

[0209] FIG. 14 illustrates a plurality of spools 111 - 114 containing the plurality of metallic wires 20 with the coating material 30 . Although FIG. 14 only shows four spools, it should be understood that between 150 to 1200 spools are typically provided in the apparatus 100 . The plurality of metallic wires 20 with the coating material 30 are collected by a collar 116 to form the assembly 34 of the plurality of metallic wires 20 .

[0210] A spool 120 contains the casing material 40 for encasing the assembly 34 of metallic wires 20 . The casing material 40 is drawn from the spool 120 by a series of rollers 122 . The series of rollers 122 bend the casing material 40 about the assembly 34 of the plurality of the wires 20 with the first edge 41 of the casing material 40 overlapping the second edge 42 of the casing material 42 . In the alternative, the series of rollers 122 bend the casing material 40 about the assembly 34 of the plurality of the wires 20 with the first edge 41 of the casing material 40 abutting the second edge 42 of the casing material 42 . A welder 124 welds the abutting first and second edges 41 and 42 of the casing material 40 .

[0211] A spool 130 contains the cladding material 50 for cladding the assembly 34 of metallic wires 20 and the casing material 40 . The cladding material 50 is a longitudinally extending cladding material 50 having a first and a second edge 51 and 52 . The surface of the cladding material 50 is cleaned by suitable means such as a sandblaster 132 . Although the cleaning process has been shown as a sandblaster 132 , it should be understood that the surface of the cladding material 50 may be cleaned by other suitable means as should be understood by those skilled in the art.

[0212] The surface of the cladding material 50 is treated with a release material 54 to inhibit chemical interaction between the cladding material 50 and the plurality of metallic wires 20 or the casing material 40 . In this example, the release material 54 is applied by flame spraying 134 aluminum to the surface of the cladding material 50 . The aluminum forms alumina or aluminum oxide that is bonded to the surface of the cladding material 50 . In the alternative, the release material 54 may be applied by a plasma gun, painting or any other suitable means. A dryer 136 dries the coated release material 54 on the surface of the cladding material 50 .

[0213] A series of rollers 142 bends the cladding material 50 to form the continuous tube 55 about the plurality of metallic wires 20 or the casing material 40 . In this example, the cladding material 50 is a carbon steel material with the plurality of metallic wires 20 being made of a stainless steel material. The coating material 30 and the casing material 40 are preferably a copper material. The series of rollers 142 bends the first and second edges 51 and 52 of the longitudinally extending sheet of the cladding material 50 to form a cladding 60 for enclosing the casing material 40 . The first edge 51 of the cladding material 50 abuts the second edge 52 of the cladding material 50 . A welder 144 welds the first edge 51 of the cladding material 50 to the second edge 52 of the cladding material 50 to form the tube 55 . The completed cladding 60 is rolled on a spool 146 .

[0214] FIG. 15 illustrates the second portion of the apparatus 100 shown in FIG. 1 . The cladding 60 unrolled from the spool 146 . The cladding 60 is pulled through an annealing oven 152 for annealing the cladding 60 .

[0215] The cladding 60 is drawn through a series of dies 154 - 156 for reducing an outer diameter 60 D of the cladding 60 . In addition, the drawing of the cladding 60 causes the coating materials 30 and the optional casing material 40 to diffusion weld with the coating materials 30 on adjacent metallic wires 20 to form the unitary material 70 .

[0216] The release material 54 deposited on the cladding material 50 inhibits the chemical interaction or bonding between the tube 55 and a plurality of metallic wires 20 and the coating materials 30 and the casing material 40 within the tube 55 .

[0217] FIG. 16 illustrates the third portion of the apparatus 100 shown in FIG. 1 . The tube 55 is passed through a series of upper and lower rollers 162 and 164 for positioning the tube 55 between a series of upper and lower cutting blades 166 and 168 . The upper and lower cutting blades 166 and 168 make the scores or cuts 71 and 72 shown in FIG. 11 and 11 A in the cladding 60 . The tube portions 73 and 74 are mechanically pulled apart to peel the tube 55 off of a remainder 80 . The remainder 80 comprises the substantially unitary coating material 70 with the plurality of metallic wires 20 contained therein.

[0218] The remainder 80 is drawn through a series of dies 174 - 176 for reducing an outer diameter 80 D of the remainder 80 and for reducing the corresponding outer diameter 20 D of the plurality of metallic wires 20 contained therein. The remainder 80 is drawn for reducing the outer diameter 80 D of the remainder 80 and for transforming the plurality of metallic wires 20 into a plurality of fine metallic fibers 90 .

[0219] The plurality of the fine metallic fibers 90 are directed into a reservoir 182 containing a chemical agent 184 by rollers 186 and 188 . The chemical agent 184 removes the unitary material 70 . Preferably, the chemical agent 184 is an acid for dissolving the unitary material 70 to provide a plurality of metallic fibers 90 .

[0220] FIG. 17 is a block diagram illustrating a second improved process 10 A for making ultra fine metallic fibers that is a variation of the process 10 illustrated in FIG. 1 . The initial process steps 11 A- 17 A of the second improved process 10 A of FIG. 17 are identical to the initial process steps 11 - 17 the first improved process 10 of FIG. 1 .

[0221] The improved process 10 A of FIG. 17 comprises the process step 11 A of providing multiple coated metallic wires 20 A in a manner similar to FIGS. 2 and 2 A with each of the metallic wires 20 A having a coating material 30 A as shown in FIGS. 3 and 3 A. The plurality of the metallic wires 20 A with the coating material 30 A are formed into an assembly 34 A of metallic wires 20 A.

[0222] FIG. 17 illustrates an optional process step 12 A of encasing the assembly 34 A of metallic wires 20 A with a casing material 40 . FIGS. 4, 4A , 5 and 5 A illustrate similar steps in a first example of the optional process step 12 A of encasing the assembly 34 A of metallic wire