Method and apparatus for altering material

• US 5,473,165 A
• Filed: 11/16/1993
• Issued: 12/05/1995
• Est. Priority Date: 11/16/1993
• Status: Expired

• Current Assignee: Sandia Corporation (Martin Marietta Corporation)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Greenly, John B., Stinnett, Regan W.
• Primary Examiner(s): Berman, Jack I.
• Assistant Examiner(s): Beyer, James
• Application Number:
  US08/153,248
• Time in Patent Office: 749 Days
• Field of Search: 250/492.21, 250/492.2, 250/492.1, 250/492.3, 427/523, 437/2, 437/174
• US Class Current: 250/492.21
• CPC Class Codes: B29C 2035/0872 using ion-radiation, e.g. alpha-rays
• CPC Class Codes: B29C 59/16 by wave energy or particle radiation , e.g. infrared heating B29C59/007 takes precedence
• CPC Class Codes: C08J 7/123 Treatment by wave energy or particle radiation C08J7/18 takes precedence
• CPC Class Codes: C23C 14/48 Ion implantation
• CPC Class Codes: C23C 8/36 using ionised gases, e.g. ionitriding
• CPC Class Codes: H01J 2237/08 Ion sources
• CPC Class Codes: H01J 2237/31701 Ion implantation
• CPC Class Codes: H01J 27/14 Other arc discharge ion sources using an applied magnetic field

Abstract

Methods and apparatus for thermally altering the near surface characteristics of a material are described. In particular, a repetitively pulsed ion beam system comprising a high energy pulsed power source and an ion beam generator are described which are capable of producing single species high voltage ion beams (0.25-2.5 MeV) at 1-1000 kW average power and over extended operating cycles (10⁸). Irradiating materials with such high energy, repetitively pulsed ion beams can yield surface treatments including localized high temperature anneals to melting, both followed by rapid thermal quenching to ambient temperatures to achieve both novel and heretofore commercially unachievable physical characteristics in a near surface layer of material.

Claims

1. A method of surface treating a material, comprising the step of irradiating a surface of the material with a repetitively pulsed ion beam, wherein each spatially contiguous pulse of the pulsed ion beam has a duration of ≦

500 ns at an accelerating gap between a cathode and an anode assembly, a total beam energy delivered to the material of >

1 Joule/pulse, an impedance of <

about 100 Ω

, an ion kinetic energy of>

50 keV, and a repetition rate >

1 Hz.

2. The method of claim 1, further including controlling the depth of surface treatment of the material by controlling the ion species comprising the ion beam.

3. The method of claim 1, further including controlling the depth of surface treatment of the material by controlling the kinetic energy level of the ion beam.

4. The method of claim 1 further including controlling the depth of surface treatment by controlling the duration of the ion beam pulse between ≧

30 ns and ≦

200 ns.

5. The method of claim 1, further including the step of surface treating at least 100 cm² with each pulse of the ion beam.

6. The method of claim 1, further including the step of surface treating 100 to 1000 cm² with each pulse of the ion beam.

7. The method of claim 1, further including the step of thermally quenching the irradiated surface of material.

8. The method of claim 7, wherein the rate of quenching the irradiated material is at least 10⁸ K/sec.

9. The method of claim 2, wherein the ion species are selected from the group consisting of argon, nitrogen, carbon, and protons.

10. The method of claim 1, wherein the ion species are produced from molecules selected from the group consisting of gases, vaporizable liquids, and vaporizable solids.

11. The method of claim 1 wherein the characteristic is the removal of surface contamination.

12. A method for altering the characteristics of a near surface layer of material, comprising:

(a) generating a repetitively pulsed ion beam, wherein the ion beam has an ion kinetic energy level >

0.1 MeV, a pulse duration of ≦

500 ns at an accelerating gap between a cathode and an anode assembly, a total beam energy delivered to the material of >

1 Joule/spatially contiguous pulse, an impedance of <

about 100 Ω

, and a pulse repetition rate >

1 Hz; and

(b) irradiating the surface of the material with the ion beam and thereby altering the near surface layer of the material defined by a predetermined depth from the irradiated surface.

13. The method of claim 12, further comprising varying the depth of the near surface layer thermally altered by controlling the kinetic energy of the ion species composing the ion beam.

14. The method of claim 12, further including varying the depth of the near surface layer thermally altered by varying the ion species composing the ion beam.

15. The method of claim 12, wherein the step of altering a near surface layer of material produces melting.

16. The method of claim 12, further including the step of thermally quenching the near surface layer of material.

17. The method of claim 16, wherein the rate of thermally quenching is at least 10⁸ K/sec.

18. The method of claim 16, wherein the step of thermally quenching further includes retaining non-equilibrium microstructrues within the near surface layer selected from the group consisting of:

amorphous, disordered crystalline and nano crystalline phases.

19. The method of claim 12, further including the step of controlling the predetermined depth of altering of material to include an interface between a layer of a first material and a layer of a second material for bonding the first material to the second material, wherein the layers of the first and second materials are included within the near surface layer.

20. The method of claim 12 wherein the step of altering a near surface layer of material produces etching of polymers.

21. The method of claim 12 wherein the step of altering a near surface layer of material produces cross-linking of polymers.

22. The method of claim 12 wherein the step of altering a near surface layer of material produces polishing of the material.

23. The method of claim 12 wherein the step of altering a near surface layer of material produces cleaning of the material.

24. The method of claim 12 wherein the step of altering a near surface layer of material produces glazing of the material.

25. The method of claim 12 wherein the material is a metal and the characteristic is hardness.

26. The method of claim 25 wherein the metal is steel.

27. The method of claim 12 wherein the characteristic is surface smoothness.

28. The method of claim 27 wherein the material is a ceramic.

29. The method of claim 27 wherein the material is a metal composition.

30. An ion beam generator for altering near surface layers of materials, comprising:

a) means for repetitively generating pulsed power signals at a rate >

1 Hz, wherein the pulsed power signal has a duration of 30-500 ns, and

b) means for generating an ion beam in a magnetically confined plasma with the pulsed power signal, whereby pulsed ion beams are produced at rates >

1 Hz and 30-500 ns in duration at an accelerating gap between a cathode and an anode assembly with a total beam energy delivered to the material of >

1 Joule/spatially contiguous pulse and an impedance of <

about 100 Ω

.

31. The ion beam generator of claim 30, wherein the means for generating an ion beam includes:

an anode assembly comprising inner and outer anode rings defining an anode annulus there between,

a cathode assembly comprising inner and outer cathode rings defining a cathode annulus there between wherein the inner and outer cathode rings also contain slow magnetic coils which, when energized, act to magnetically insulate the accelerating gap between the anode electrode rings and the cathode electrode rings,

means to pre-ionize a gas introduced into the means for generating an ion beam, and

means for completely ionizing the gas into the plasma and for moving the plasma comprising fast driving magnetic coil means which move the plasma towards and through the anode annulus into an accelerating gap between the anode assembly and the cathode assembly, wherein both the means to pre-ionize and the fast driving coil means are located to the side of the anode assembly opposite to the cathode assembly,

wherein the inner and outer anode rings are configured so as to separate the magnetic field lines from the fast driving magnetic coil means from the magnetic field lines from the slow magnetic coils such that the magnetic field approaches zero across the cathode annulus at the time of beam acceleration and wherein the slow magnetic coils are located to the opposite side of the anode annulus relative to the fast driving magnetic coil means.

32. A process for uniformly altering a characteristic of a surface of a material to a depth of less than 50 microns by irradiating the surface with a repetitively pulsed ion beam, wherein each spatially contiguous pulse of the pulsed ion beam has a duration of ≦

500 ns, a total beam energy delivered to the material of >

1 Joule/pulse, an impedance of <

100 Ω

, and a repetition rate >

1 Hz, such that continuous areas in excess of 50 cm² are created with the altered characteristic by each pulse.

33. A process for uniformly altering a characteristic of a surface of a material to a depth of less than 50 microns by irradiating the surface with a repetitively pulsed ion beam, wherein each spatially contiguous pulse of the pulsed ion beam has a duration of ≦

500 ns, a total beam energy delivered to the material of >

1 Joule/pulse, an impedance of <

100 Ω

, and a repetition rate >

1 Hz, such that continuous areas in excess of 5 cm² are created with the altered characteristic by each pulse.