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Title:
HIGH SURFACE AREA METAL PRODUCTION
Document Type and Number:
WIPO Patent Application WO/2009/101394
Kind Code:
A2
Abstract:
A sponge magnesium material which is formed by melting together magnesium and sodium in an inert argon atmosphere to form an immiscible liquid. The liquid is agitated to prevent coagulation by high speed stirring, and is then rapidly cooled. Most of the sodium is then removed by chemical leaching in ethanol, with the alkoxide residue being reused.

Inventors:
JARVIS DAVID JOHN (NL)
ATKINS NICHOLAS ELSWORTH (GB)
Application Number:
PCT/GB2009/000372
Publication Date:
August 20, 2009
Filing Date:
February 10, 2009
Export Citation:
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Assignee:
CERAM RES LTD (GB)
JARVIS DAVID JOHN (NL)
ATKINS NICHOLAS ELSWORTH (GB)
Domestic Patent References:
WO1981002005A11981-07-23
Foreign References:
GB1341928A1973-12-25
Other References:
DATABASE WPI Week 199139 Thomson Scientific, London, GB; AN 1991-286703 XP002564413 & SU 1 622 080 A1 (URALS KIROV POLY) 23 January 1991 (1991-01-23)
Attorney, Agent or Firm:
SALES, Robert et al. (48 Friar Gate, Derby DE1 1GY, GB)
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Claims:
Claims

1. A method of producing a high surface area metal, the method including melting together in an inert atmosphere a first metal and a second alkali metal, which metals are immiscible together when molten, agitating the mixture, rapidly cooling the mixture to cause solidification thereof, and subsequently removing at least part of the second metal from the mixture.

2. A method according to claim 1 , characterised in that the first metal is any of magnesium, aluminium, calcium, or zinc, or alloys of these metals.

3. A method according to claims 1 or 2, characterised in that the first metal is in a polycrystalline, intermetallic or an amorphous state.

4. A method according to any of the preceding claims, characterised in that the second alkali metal is sodium, potassium, or an alloy of sodium and potassium.

5. A method according to any of the preceding claims, characterised in that the second alkali metal constitutes 20 to 80 volume % of the solidified mixture.

6. A method according to claim 5, characterised in that the second alkali metal constitutes 30 to 70 volume % of the solidified mixture.

7. A method according to any of the preceding claims, characterised in that the inert atmosphere is argon.

8. A method according to any of the preceding claims, characterised in that the agitation is provided by high speed mechanical stirring or ultrasound dispersion.

9. A method according to any of the preceding claims, characterised in that the rapid cooling is provided by any of gas atomization, casting, spray deposition or melt spinning.

10. A method according to any of the preceding claims, characterised in that after rapid cooling the material is extruded prior to removal of the second metal.

11. A method according to any of the preceding claims, characterised in that the second metal is removed by leaching with alcohol.

12. A method according to claim 11 , characterised in that the alcohol is any of methanol, ethanol, propanol, butanol, butyl cellosolve, ethyl carbitol, dimethyl formamide, or could be a mixture of ethanol, water and acetic acid.

13. A method according to claims 11 or 12, characterised in that the alkoxide byproduct produced by leaching with alcohol is reused.

14. A method according to any of the preceding claims, characterised in that the second metal is removed by leaching with ketone.

15. A method according to claim 14, characterised in that the ketone is any of acetone, biacetyl, methylethylketone, diethylketone, isopropylmethylketone, dipropylketone, diisopropylketone and dibutylketone.

16. A method according to any of the preceding claims, characterised in that the second metal is removed by evaporation.

17. A method according to claim 16, characterised in that the evaporation takes place in a non-reactive atmosphere, which may be provided by argon.

18. A method according to claims 16 or 17, characterised in that the evaporation takes place at below atmospheric pressure and above atmospheric temperature.

19. A method according to any of the preceding claims, characterised in that a third material is added to avoid coagulation of the first and second molten metals.

20. A method according to claim 19, characterises in that the third material is of nano or micro sized particles.

21. A method according to claims 19 or 20, characterised in that the third material is magnesium oxide or silicon carbide.

22. A method according to any of the preceding claims, characterised in that the mixture is passivated so as to form a thin oxide coating thereon, following solidification and removal of the second metal.

23. A method according to claim 22, characterised in that the passivation is achieved by passing a controlled air flow over the solidified material.

24. A method according to claim 23, characterised in that the passivation takes in a passivation chamber where initially air has been substantially evacuated from the chamber, and air is gradually brought in to the chamber to oxidise the surface of the material.

25. A method according to any of the preceding claims, characterised in that the material formed is in the form of a powder, ribbon or bulk solid.

26. A method according to claim 25, characterised in that when a bulk solid is required, the molten immiscible mixture is cast in a mould.

27. A high surface area metal material made by a method according to any of the preceding claims.

28. A material according to claim 27, characterised in that the material formed is usable as a scaffold material for tissue or bone growth within or outside of the body.

29. A material according to claims 27 or 28, characterised in that the material formed is usable as part of a drug delivery system, with the drug impregnating the material.

30. A material according to claim 27, characterised in that the material formed is usable as hydrogen storage material.

31. A material according to claim 30, characterised in that the hydrogen provided on the material in the form of a hydride.

32. A material according to claim 27, characterised in that the material formed is usable as a filter.

33. A filter formed from material according to claim 32.

34. A material according to claim 27, characterised in that the material formed is usable for sound proofing.

35. A sound proofing material in the form of a bulk material made up of material according to claim 34.

36. A material according to claim 27, characterised in that the material is usable to provide a flotation material.

37. A flotation material using a material according to claim 36.

38. A material according to claim 36, characterised in that the material is coated with a waterproof coating.

39. A material according to claim 27, characterised in that the material is usable as a phase change material.

40. A phase change material with material according to claim 39, characterised in that the material carries a phase change material such as a wax.

41. A material according to claim 27, characterised in that the material is usable to provide a tube for a heat exchanger.

42. A material according to claim 27, characterised in that the material is usable as a Grignard reagent.

43. A Grignard reagent made from a material according to claim 42.

44. A material according to claim 27, characterised in that the material is usable as a reducing agent in extraction of heavy metals.

45. A material according to claim 27, characterised in that the material is usable as a catalyst.

46. A material according to claim 45, characterised in that the material is doped with other material.

Description:

High Surface Area Metal Production

This invention concerns a method of producing a high surface area metal, and a material made by such a method.

The industrial use of high surface area open porous metallic materials is important, for example, in biomedical orthopaedics, filters, heat exchange devices, energy absorbers and catalysts. In this respect, the control of surface area, pore size, porosity level and connectivity are crucial for practical applications.

A number of methods have been proposed for producing such materials. A number of limitations are however often encountered with such methods. For instance such methods may be relatively expensive and may not be usable for casting complex geometries and/or for producing large bulk articles.

According to the present invention there is provided a method of producing a high surface area metal, the method including melting together in an inert atmosphere a first metal and a second alkali metal, which metals are immiscible together when molten, agitating the mixture, rapidly cooling the mixture to cause solidification thereof, and subsequently removing at least part of the second metal from the mixture.

The first metal may be any of magnesium, aluminium, calcium, or zinc, or alloys of these metals. The first metal may be in a polycrystalline, intermetallic or an amorphous state.

The second alkali metal may be sodium or potassium, or an alloy of sodium and potassium.

The second alkali metal may constitute 20 to 80 volume % of the solidified mixture, and may constitute 30 to 70 volume % of the solidified mixture.

The inert atmosphere may be argon.

The agitation may be provided by high speed mechanical stirring or ultrasound dispersion.

The rapid cooling may be provided by any of gas atomization, casting, spray deposition or melt spinning.

After rapid cooling the material may be extruded prior to removal of the second metal.

The second metal may be removed by leaching with alcohol. The alcohol may be any of methanol, ethanol, propanol, butanol, butyl cellosolve, ethyl carbitol, dimethyl formamide, or could be a mixture of ethanol, water and acetic acid. The alkoxide byproduct produced by leaching with alcohol is preferably reused.

Alternatively or in addition, the second metal may be removed by leaching with a ketone. The ketone may be any of acetone, biacetyl, methylethylketone, diethylketone, isopropylmethylketone, dipropylketone, diisopropylketone and dibutylketone.

Alternatively or in addition, the second metal may be removed by evaporation. The evaporation may take place in a non-reactive atmosphere, which may be provided by argon, and below atmospheric pressure and above atmospheric temperature.

A third material may be added to avoid coagulation of the first and second molten metals. The third material may be of nano or micro sized particles. The third material may be magnesium oxide or silicon carbide.

The mixture may be passivated so as to form a thin oxide coating thereon, following solidification and removal of the second metal. The passivation may be achieved by passing a controlled air flow over the solidified material. The passivation may take place in a passivation chamber where initially air has been substantially evacuated from the chamber, and air is gradually brought in to the chamber to oxidise the surface of the material.

The material formed may be in the form of a powder, ribbon or bulk solid. When a bulk solid is required, the molten immiscible mixture may be cast in a mould.

The invention also provides a material made by a method according to any of the preceding fourteen paragraphs.

The material formed may be usable as a scaffold material for tissue or bone growth within or outside of the body.

The material formed may be used as part of a drug delivery system, with the drug impregnating the material.

The material formed may be used as hydrogen storage material, and the hydrogen may be provided on the material in the form of a hydride.

The material formed may be used as a filter, and the invention also provides a filter formed from material according to the invention.

The material formed may be used for sound proofing.

The invention also provides a sound proofing material in the form of a bulk material made up of material according to the invention.

The material may be usable to provide a flotation material.

The invention also provides a flotation material using material according to the invention, and such material may be coated with a waterproof coating.

The material may be used as a phase change material.

The invention also provides a phase change material with material according to the invention carrying a phase change material such as a wax.

The material may be used to provide 1 a tube for a heat exchanger.

The material may be used as a Grignard reagent.

The invention also provides a Grignard reagent made from a material according to the invention.

The material may be used as a reducing agent in extraction of heavy metals.

The material may be used as a catalyst, and may be doped with other material.

An embodiment of the present invention will now be described by way of example only, and with reference to the single figure of the accompanying drawing which is a schematic cut away diagram of an example of a material according to the invention.

A sponge magnesium material is formed as follows. 107g of magnesium and 191g of the alkali metal sodium, are melted together to form an immiscible liquid under an inert gas atmosphere which may be provided by argon. This liquid is agitated to prevent coagulation by high speed stirring at 520 rpm. The mixture is poured into a wedge shaped chill mould. The material is removed from the mould and most of the sodium is removed by chemical leaching in ethanol. The alkoxide residue formed is reused.

The material thus formed is passivated in a passivation chamber, which has been evacuated of air. A controlled air flow is gradually introduced into the passivation chamber so as to form a thin oxide coating on the material.

The high surface area porous metal article produced has a continuous network of metal ligaments 10 with interconnected voids 12, as shown in the drawing.

There is thus described a method of forming sponge magnesium material which provides a number of advantageous features. This method is relatively low cost, and has a very simple and inexpensive chemical leaching step.

The method can be used to produce any of: (i) a bulk article with complex geometry produced by casting; (ii) a sheet produced by spray deposition; (iii) a ribbon produced by melt-spinning; or a loose powder produced by gas atomisation.

The method can be used with a . wide variety of metal and alloy compositions, in either solid solution, intermetallic, crystalline or amorphous form. The materials produced have a wide range of potential applications as outlined above.

It is to be realised that a wide range of modifications may be made without departing from the scope of the invention. For example the method may be used with a different metal such as aluminium, calcium, zinc, or an alloy of any of these metals or magnesium. A different alkali metal such as potassium, or a sodium and potassium alloy, could be used. A non reactive atmosphere could be provided other than by argon.

Different rapid cooling methods could be used such as atomisation, spray deposition or melt spinning. A different material or method could be used to remove the alkali metal. For example the alkali metal could be removed by evaporation, and this could take place in a substantially non reactive atmosphere at below atmospheric pressure, and raised temperatures.

The agitation of the molten liquid could be provided other than by high speed stirring, and could be provided for instance by ultrasound emulsification. After the rapid cooling, the material may be extruded prior to removal of the second metal. This combination will produce aligned pores.

A third material may be added to avoid coagulation of the first and second molten metals. The third material may be of nano or micro sized particles, and may be magnesium oxide or silicon carbide.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed * to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.




 
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