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WO2005025786A1 - Porous materials and process for manufacturing - Google Patents

Porous materials and process for manufacturing Download PDF

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Publication number
WO2005025786A1
WO2005025786A1 PCT/GB2004/003951 GB2004003951W WO2005025786A1 WO 2005025786 A1 WO2005025786 A1 WO 2005025786A1 GB 2004003951 W GB2004003951 W GB 2004003951W WO 2005025786 A1 WO2005025786 A1 WO 2005025786A1
Authority
WO
WIPO (PCT)
Prior art keywords
porous
particulate material
microwave energy
belt
particulate
Prior art date
Application number
PCT/GB2004/003951
Other languages
French (fr)
Inventor
George Paul Yiasemides
Original Assignee
Ceram Technology Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ceram Technology Limited filed Critical Ceram Technology Limited
Publication of WO2005025786A1 publication Critical patent/WO2005025786A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B22F3/11—Making porous workpieces or articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • This invention concerns a method of making a porous material and also a material made by such a method; and a method of making porous articles and an article made by such a method.
  • porous materials A number of methods have been used for making porous materials. These methods have included sintering a powder compact, but this is a relatively slow process. Laser perforation of thin sheets of material has been used but this tends to be an expensive process. Thirdly material may be deposited onto a polymeric foam, which foam is subsequently burnt away. Such porous materials can be used to form articles such as self lubricating bearings, catalyst substrates, or porous media for applications such as filters, silencers, etc.
  • a method of making porous material comprising applying microwave energy to a compact of particulate material, which particulate material reflects microwave radiation, such that once initial bonding of the particulate material has taken place, further bonding will not occur, with the initial bonding leaving the material porous.
  • the particulate material may be metallic.
  • the metallic material may be a pure metal or an alloy or a mixture of elemental powders and pre-alloyed powders.
  • the pore size and degree of porosity of the porous material may be determined by choosing a particulate material with an appropriate particle size and/or particle size distribution with an appropriate particle size, particle size distribution and/or particle morphology.
  • the method may be carried out in batch form or by a continuous process with the particulate material being delivered onto a belt or other carrier, with the particulate material subsequently passing through a microwave application stage.
  • the particulate compact may be in the form of sheet or a three dimensional structure.
  • Means may be provided for ensuring a required thickness of material on the belt, and an edge may be spaced above the belt to restrict the thickness of material to the spacing between the edge and the belt.
  • the spacing between the edge and the belt may be adjustable
  • the invention also provides a material formed by a method according to any of the preceding six paragraphs.
  • the invention further provides a method of making a porous article, the method comprising shaping a particulate material which reflects microwave radiation, and applying microwave energy to the particulate material until the particles thereof have bonded together yet leave the material porous.
  • a binder may be mixed with the porous material to facilitate shaping into 3D structures.
  • the binder may be removed from the material prior to, and/or during, application of the microwave energy.
  • the binder may be removed by the application of heat and/or microwave energy.
  • the binder may include stearic acid and/or a polymeric material.
  • the particulate material may be shaped by extrusion or compaction.
  • the invention still further provides a porous article made by a method according to any of the preceding four paragraphs.
  • the porous article may subsequently be infused with another material to act as a carrier therefor.
  • the porous article may be bonded onto a substrate during application of microwave energy, or as a subsequent operation.
  • the porous article may form part of a self-lubricating bearing, may be a substrate carrier, or a filter.
  • a porous steel sheet is formed as follows. Gas atomised steel powder with a particle size of between 45 and 100 microns is spread onto a conveyor belt. The belt passes beneath an edge spaced 1 mm thereabove to provide a required 1 mm thickness of powder on the belt. The powder then passes through a microwave zone where microwave energy is applied thereto which causes the particles of steel to bond together. The speed by which the compact is passed through the microwave zone is adjusted depending on the particle size and susceptibility of the material to the microwave energy. Typically the compact resides within the zone for between 1 and 60 seconds. Where the edges of the particles are in contact heating occurs causing the bonding, but with the resultant network thus formed microwave energy is reflected away.
  • the strip thus formed which is 75mm wide, is lightly rolled to remove any distortions, trimmed and calendered onto a reel.
  • the steel produced has a 40% porosity uniformly distributed throughout the strip.
  • the particle size and distribution of material can be chosen to achieve a required porosity size and level.
  • the speed of the conveyor can be adjusted to control residence time within the microwave zone.
  • This method can be used to produce strip varying in thickness from a few microns to several millimetres, and the width is only limited by the width of the microwave zone, and could be up to several metres.
  • the metallic powder used could be either elemental or in alloy form and the process variables, transverse speed, surface condition, particle size, morphology and distribution can be varied to compensate for differences in alloy behaviour within the microwave zone.
  • a tubular porous structure was formed as follows. Stainless steel powder was blended with a proprietory binder and extruded into a tube with a 25mm internal diameter and a 2mm wall thickness. The binder was then removed in a flowing atmosphere of argon using radiation heating. The tube was then subjected to microwave energy to provide bonding between the particles as described above.
  • the binder may comprise stearic acid or a polymeric material.
  • the binder may be removed at least partially by the microwave energy.
  • a material which reflects microwave energy means that the formation process is self limiting. Once initial bonding between the powder particles has taken place, substantially no further bonding will take place. Accordingly a porous material is formed without the requirement for complex microwaving arrangements and/or modification of the material.
  • Methods according to the invention can be used to produce material in sheet form for example as described in example 1 , or a wide range of articles. Such articles could be subsequently infused with materials to form part of self-lubricating bearings, or to act as a catalyst substrate. Alternatively, materials may be bonded onto a solid substrate by the microwave energy, or in a subsequent operation. Alternative uses of such material could be as a filter.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Powder Metallurgy (AREA)

Abstract

A method of making a porous material. The method comprising applying microwave energy to a compact of a particulate material which reflects microwave radiation in a bulk state, such that once initial bonding of the particulate material has taken place, further bonding will not occur. The incomplete initial bonding leaves pores within the material.

Description

POROUS MATERIALS AND PROCESS FOR MANUFACTURING
This invention concerns a method of making a porous material and also a material made by such a method; and a method of making porous articles and an article made by such a method.
A number of methods have been used for making porous materials. These methods have included sintering a powder compact, but this is a relatively slow process. Laser perforation of thin sheets of material has been used but this tends to be an expensive process. Thirdly material may be deposited onto a polymeric foam, which foam is subsequently burnt away. Such porous materials can be used to form articles such as self lubricating bearings, catalyst substrates, or porous media for applications such as filters, silencers, etc.
According to the present invention there is provided a method of making porous material, the method comprising applying microwave energy to a compact of particulate material, which particulate material reflects microwave radiation, such that once initial bonding of the particulate material has taken place, further bonding will not occur, with the initial bonding leaving the material porous.
The particulate material may be metallic. The metallic material may be a pure metal or an alloy or a mixture of elemental powders and pre-alloyed powders.
The pore size and degree of porosity of the porous material may be determined by choosing a particulate material with an appropriate particle size and/or particle size distribution with an appropriate particle size, particle size distribution and/or particle morphology.
The method may be carried out in batch form or by a continuous process with the particulate material being delivered onto a belt or other carrier, with the particulate material subsequently passing through a microwave application stage. The particulate compact may be in the form of sheet or a three dimensional structure.
Means may be provided for ensuring a required thickness of material on the belt, and an edge may be spaced above the belt to restrict the thickness of material to the spacing between the edge and the belt.
The spacing between the edge and the belt may be adjustable
The invention also provides a material formed by a method according to any of the preceding six paragraphs.
The invention further provides a method of making a porous article, the method comprising shaping a particulate material which reflects microwave radiation, and applying microwave energy to the particulate material until the particles thereof have bonded together yet leave the material porous.
A binder may be mixed with the porous material to facilitate shaping into 3D structures. The binder may be removed from the material prior to, and/or during, application of the microwave energy. The binder may be removed by the application of heat and/or microwave energy.
The binder may include stearic acid and/or a polymeric material.
The particulate material may be shaped by extrusion or compaction.
The invention still further provides a porous article made by a method according to any of the preceding four paragraphs.
The porous article may subsequently be infused with another material to act as a carrier therefor.
The porous article may be bonded onto a substrate during application of microwave energy, or as a subsequent operation. The porous article may form part of a self-lubricating bearing, may be a substrate carrier, or a filter.
Embodiments of the present invention will now be described by way of example only.
Example 1
A porous steel sheet is formed as follows. Gas atomised steel powder with a particle size of between 45 and 100 microns is spread onto a conveyor belt. The belt passes beneath an edge spaced 1 mm thereabove to provide a required 1 mm thickness of powder on the belt. The powder then passes through a microwave zone where microwave energy is applied thereto which causes the particles of steel to bond together. The speed by which the compact is passed through the microwave zone is adjusted depending on the particle size and susceptibility of the material to the microwave energy. Typically the compact resides within the zone for between 1 and 60 seconds. Where the edges of the particles are in contact heating occurs causing the bonding, but with the resultant network thus formed microwave energy is reflected away.
The strip thus formed which is 75mm wide, is lightly rolled to remove any distortions, trimmed and calendered onto a reel. The steel produced has a 40% porosity uniformly distributed throughout the strip.
With such a method the particle size and distribution of material can be chosen to achieve a required porosity size and level. The speed of the conveyor can be adjusted to control residence time within the microwave zone. This method can be used to produce strip varying in thickness from a few microns to several millimetres, and the width is only limited by the width of the microwave zone, and could be up to several metres. The metallic powder used could be either elemental or in alloy form and the process variables, transverse speed, surface condition, particle size, morphology and distribution can be varied to compensate for differences in alloy behaviour within the microwave zone.
Example 2
A tubular porous structure was formed as follows. Stainless steel powder was blended with a proprietory binder and extruded into a tube with a 25mm internal diameter and a 2mm wall thickness. The binder was then removed in a flowing atmosphere of argon using radiation heating. The tube was then subjected to microwave energy to provide bonding between the particles as described above.
The binder may comprise stearic acid or a polymeric material. The binder may be removed at least partially by the microwave energy.
It is to be realised that with such a method a wide variety of different shapes and structures can be formed from different materials, and using different shaping methods. This process could also operate in a continuous arrangement.
Using a material which reflects microwave energy means that the formation process is self limiting. Once initial bonding between the powder particles has taken place, substantially no further bonding will take place. Accordingly a porous material is formed without the requirement for complex microwaving arrangements and/or modification of the material.
Various other modifications may be made without departing from the scope of the invention. A wide range of different materials may be used, with the one requirement that they reflect microwave energy. In practice the materials will generally be metallic but other materials such as ceramic materials could be included. Different binders could be used and these could be removed in a different step, and applying different heat sources such as an initial application of microwave energy, or radiation heating.
Methods according to the invention can be used to produce material in sheet form for example as described in example 1 , or a wide range of articles. Such articles could be subsequently infused with materials to form part of self-lubricating bearings, or to act as a catalyst substrate. Alternatively, materials may be bonded onto a solid substrate by the microwave energy, or in a subsequent operation. Alternative uses of such material could be as a filter.
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.

Claims

1. A method of making porous material, the method comprising applying microwave energy to a compact of particulate material, which particulate material reflects microwave radiation, such that once initial bonding of the particulate material has taken place, further bonding will not occur, the initial bonding leaving the material porous.
2. A method as claimed in claim 1 , wherein the particulate material is metallic.
3. A method as claimed in claims 1 or 2, wherein the pore size and degree of porosity of the porous material is determined by choosing a particulate material with an appropriate particle size and/or particle size distribution, and/or particle morphology.
4. A method as claimed in any of the preceding claims, wherein the method is carried out by a continuous process with the particulate material delivered onto a belt or other carrier, with the particulate material subsequently passing through a microwave application stage.
5. A method as claimed in claim 4, further comprising means for ensuring a required thickness of material on the belt.
6. A method as claimed in claim 5, wherein the means for ensuring a required thickness of material on the belt is an edge spaced above the belt to restrict the thickness of material to the spacing between the edge and the beit.
7. A method as claimed in claim 6, wherein the spacing between the edge and the belt is adjustable.
8. A method as claimed in any of the preceding claims, wherein the particulate compact is in the form of a sheet or a three dimensional structure.
9. A material formed by a method according to any of the preceding claims.
10. A method of making a porous article, the method comprising shaping a particulate material which reflects microwave radiation, and applying microwave energy to the particulate material until the particles thereof have bonded together yet leave the material porous.
11. A method as claimed in claim 10, wherein a binder is mixed with the porous material to facilitate shaping into 3D structures.
12. A method as claimed in claim 11 , wherein the binder is removed from the material prior to, and/or during, application of the microwave energy.
13. A method as claimed in claim 11 or 12, wherein the binder is removed by the application of heat and/or microwave energy.
14. A method as claimed in any of claims 11 to 13, wherein the binder includes stearic acid and/or a polymeric material.
15. A method as claimed in any of claims 10 to 14, wherein the particulate material is shaped by extrusion or compaction.
16. A porous article made by a method as claimed in any of claims 10 to 15.
17. A porous article as claimed in claim 16, wherein the porous material is subsequently infused with another material to act as a carrier therefor.
18. A porous article as claimed in claims 16 or 17, wherein the porous article is bonded onto a substrate during application of microwave energy, or as a subsequent operation.
19. A porous article as claimed in any of claims 16 to 18, wherein the porous article forms part of a self-lubricating bearing, is a substrate carrier, or a filter.
20. A method of making a porous material substantially as hereinbefore described.
21. A method of making a porous article substantially as hereinbefore described.
22. A porous material substantially as hereinbefore described.
23. A porous article substantially as hereinbefore described.
24. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as the preceding claims.
PCT/GB2004/003951 2003-09-17 2004-09-16 Porous materials and process for manufacturing WO2005025786A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0321728.8A GB0321728D0 (en) 2003-09-17 2003-09-17 Porous materials
GB0321728.8 2003-09-17

Publications (1)

Publication Number Publication Date
WO2005025786A1 true WO2005025786A1 (en) 2005-03-24

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3421858A1 (en) * 1983-06-15 1985-01-03 Nippon Dia Clevite Co., Ltd., Narashino, Chiba Process for manufacturing a porous body from stainless steel
DE3516649A1 (en) * 1983-11-11 1986-11-13 Nippon Dia Clevite Co., Ltd., Narashino, Chiba Self-lubricating bearing
US4942278A (en) * 1988-12-05 1990-07-17 The United States Of America As Represented By The United States Department Of Energy Microwaving of normally opaque and semi-opaque substances
DE4120687C1 (en) * 1991-06-22 1993-01-21 Schunk Sintermetalltechnik Gmbh, 6301 Heuchelheim, De Porous, sintered parts prepn., used e.g. as filters, catalyst carriers - comprises mixing metal or ceramic powder with organic binder or plasticiser contg. polymer of vinyl] aromatic cpd.
DE19726961C1 (en) * 1997-06-25 1998-11-26 Forschungszentrum Juelich Gmbh Production of porous or highly porous metal, ceramic or composite moulding with cohesive structure
US20010048887A1 (en) * 1997-11-25 2001-12-06 Rustum Roy Process for sintering powder metal components

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3421858A1 (en) * 1983-06-15 1985-01-03 Nippon Dia Clevite Co., Ltd., Narashino, Chiba Process for manufacturing a porous body from stainless steel
DE3516649A1 (en) * 1983-11-11 1986-11-13 Nippon Dia Clevite Co., Ltd., Narashino, Chiba Self-lubricating bearing
US4942278A (en) * 1988-12-05 1990-07-17 The United States Of America As Represented By The United States Department Of Energy Microwaving of normally opaque and semi-opaque substances
DE4120687C1 (en) * 1991-06-22 1993-01-21 Schunk Sintermetalltechnik Gmbh, 6301 Heuchelheim, De Porous, sintered parts prepn., used e.g. as filters, catalyst carriers - comprises mixing metal or ceramic powder with organic binder or plasticiser contg. polymer of vinyl] aromatic cpd.
DE19726961C1 (en) * 1997-06-25 1998-11-26 Forschungszentrum Juelich Gmbh Production of porous or highly porous metal, ceramic or composite moulding with cohesive structure
US20010048887A1 (en) * 1997-11-25 2001-12-06 Rustum Roy Process for sintering powder metal components

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
AGRAWAL D ET AL: "METAL PARTS FROM MICROWAVES", MATERIALS WORLD, THE INSTITUTE OF MATERIALS, LONDON, GB, vol. 7, no. 11, November 1999 (1999-11-01), pages 672 - 673, XP000912681, ISSN: 0967-8638 *

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Publication number Publication date
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