Abstract
The present invention relates to a method of electrodepositing a metal on an electrically conductive particulate substrate. There is provided a method of electrodepositing a metal on an electrically conductive particulate substrate comprising the steps of: (i) providing a cathode; (ii) providing an anode formed from the metal to be electrodeposited; (iii) providing the substrate, cathode and anode within an electrodeposition bath comprising an electrolyte; and (iv) providing a voltage between said anode and cathode causing metal ions to flow from the anode to the cathode, wherein a separator is provided between the anode and the cathode.
Claims
1. A method of electrodepositing a metal on an electrically conductive particulate substrate comprising the steps of: providing a cathode; providing an anode formed from the metal to be electrodeposited; locating the substrate, cathode and anode within an electrodeposition bath comprising an electrolyte; and applying a voltage between said anode and cathode, thereby causing metal ions to flow from the anode to the cathode.
2. The method according to claim 1, wherein a separator is provided between the anode and the cathode.
3. The method according to claim 2, wherein said separator is a semipermeable membrane.
4. The method according to claim 2, wherein said separator is an organic liquid which is immiscible with the aqueous electrolyte, said separator and aqueous electrolyte thereby forming a biphasic system comprising two immiscible liquids.
5. The method according to claim 1, wherein the substrate has an average longest dimension of less than 10 mm.
6. The method according to claim 5, wherein the substrate is a nano-scaled carbon particulate.
7. The method according to claim 1, further comprising applying agitation using at least one agitation device, thereby preventing particle agglomeration.
8. The method according to claim 1, wherein the electrodeposited metal is a ferromagnetic metal.
9. The method according to claim 8, further comprising using a magnetic field to capture magnetic metal coated particulate substrate from the electrodeposition bath.
10. The method according to claim 1, wherein the particulate substrate comprises non-electrically conductive particles coated with electrically conductive coatings.
11. The method according to claim 1, wherein the method is implemented as a batch process.
12. The method according to claim 9, wherein the captured substrate is an electrically conductive particulate comprising an electrodeposited metal thereon.
13. A conductive particulate substrate material comprising at least one layer of an electrodeposited metal thereon, manufactured by the method of claim 1.
14. A conductive particulate substrate material with an average largest dimension of less than 10 mm comprising at least one layer of an electrodeposited metal thereon.
15. The method according to claim 1, wherein the method is implemented as a continuous process.
Description
[0052] Exemplary embodiments are illustrated in referenced figures of the drawings and are part of the specification. It is intended that the embodiments and figures disclosed herein are to be considered illustrative of the present invention and do not limit the scope thereof.
[0053] FIG. 1 illustrates a schematic of a batch electrodeposition process according to one exemplary embodiment.
[0054] FIG. 2 illustrates a schematic of the semipermeable membrane electrode according to one exemplary embodiment.
[0055] FIG. 3 illustrates a schematic of a batch biphasic system according to one exemplary embodiment.
[0056] FIG. 4 illustrates a schematic of a continuous electrodeposition process according to one exemplary embodiment.
[0057] FIG. 5 illustrates a schematic of a continuous biphasic system according to one exemplary embodiment.
[0058] FIG. 6 illustrates an SEM image of iron deposited on silver plated glass micro fibres.
[0059] FIG. 7 illustrates an SEM image of iron deposited on carbon fibre.
[0060] Turning to FIG. 1, there is provided a batch electrodeposition system 7. The anode 3 which is formed from the metal to be electrodeposited, and cathode 6 are both connected to a power source 4. The electrical circuit is completed by immersing both anode 3 and cathode 6 in an electrolyte 1 housed within an electrodeposition bath 2. The electrolyte 1 allows the free movement of metal ions M.sup.+ generated from the anode 3, which migrate to the cathode 6. A separator 9 in the form of a semipermeable membrane 5 substantially envelopes the cathode 6 and the electrically conductive particulate substrate 8. The semipermeable membrane 5 is porous to the electrolyte 1 and metal ions M+, but with a pore size sufficiently small enough to confine the particulate substrate 8 proximate to the cathode 6. The semipermeable membrane 5 reduces dispersion of the particulate substrate 8 into the larger volume of electrolyte 1. Activating the power source 4 sets up a voltage between the anode 3 and cathode 6. The application of an external electric field not only aligns the particulate substrate 8 but also enhances the attractive forces between neighbouring particulate substrate 8 particulates. Above the percolation threshold, there is formed a particulate network exhibiting long-range connectivity. Containment of the substrate 8 proximate to the cathode 6 aligns the particulates relative to the cathode 6 and thus the said long-range particulate network serves as an extension to the cathode 6. This directs the migration of metal ions M.sup.+ from the anode 3 to the negatively charged particulate substrate 8 thus coating the particulate substrate 8 and resulting in the desired metal coated substrate 10. To ensure the particulate substrate 8 remains dispersed, an agitation device 11 may be introduced into the batch electrodeposition system 7. The agitation device used may be an ultrasound probe 12.
[0061] FIG. 2 provides an expanded view of the cathode 26 as shown in FIG. 1. The semipermeable membrane 21 substantially envelopes the cathode 26 and the electrically conductive particulate substrate 22. The semipermeable membrane 21 is porous to the electrolyte 25 with a pore size sufficiently small enough to confine the particulate substrate 22 proximate to the cathode 26, reducing dispersion of the particulate substrate 22 into a larger volume of electrolyte 25. Electrical connection to the power source is by an insulated wire 27. The exposed section 24 of cathode 26 imparts a negative charge on the particulate substrate 22 thus serving as a cathode. This directs the migration of metal ions M.sup.+ from the anode to the negatively charged particulate substrate 22 thus coating the particulate substrate 22 and resulting in the desired metal coated substrate 23.
[0062] FIG. 3 shows a batch biphasic system 39. The biphasic system 39 comprises an organic liquid phase 33 and an aqueous liquid phase 32 thus creating a liquid interface 37 which acts as a separator 40, thereby retaining the substrate 38 and reducing its dispersion into a large volume of electrolyte 44. The organic liquid phase 33 comprises the substrate 38 and an organic solvent, and the aqueous liquid phase 32 comprises the electrolyte 44. The cathode 34 is located in the organic liquid phase 33 and does not transcend the liquid interface 37. The cathode 34 and anode 36 are connected to the power source 35. The anode 36 is formed from the metal to be electrodeposited. is The electrical circuit is completed by immersing the cathode 34 in the organic liquid phase 33 and the anode 36 in aqueous liquid phase 32, both of which are housed within the electrodeposition bath 31. Activating the power source 35 sets up a voltage between the anode 36 and cathode 34. The application of an external electric field not only aligns the particulate substrate 38 but also enhances the attractive forces between neighbouring particulate substrates 38. Above the percolation threshold, there is formed a particulate network exhibiting long-range connectivity. Containment of the substrate 38 proximate to the cathode 34 aligns the particulates relative to the cathode 34 and thus the said long-range particulate network serves as an extension to the cathode 34. This directs the migration of metal ions M.sup.+ from the anode 36 to the negatively charged particulate substrate 38. This allows coating of the particulate substrate 38 to occur substantially at the liquid interface 37 resulting in the desired metal coated substrate 41. To ensure a dynamic interface 37 and that the substrate 38 remains dispersed, an agitation device 42 may be introduced into the biphasic system 39. The agitation device used may be a magnetic stirrer 43.
[0063] A magnet 46 may also be periodically introduced to collect the magnetic metal coated substrate 41 in the organic liquid phase 33. The magnet 46 is placed away from the liquid interface 37 and removal of any magnetic metal coated substrate 41 ensures further coating occurs and prevents agglomeration by bridging between particles.
[0064] FIG. 4 shows a continuous electrodeposition system 51 housed within an electrodeposition bath 62. The anode 61, formed from the metal to be electrodeposited, is located in the electrolyte 64. The electrolyte 64 allows the free movement of metal ions M.sup.+ from the anode 61 to cathode 63. The cathode 63 and anode 61 are connected to the power source 54. The semipermeable membrane 58 acts as a separator 59 reducing dispersion of the particulate substrate 56 into the larger volume of electrolyte 64, below the semipermeable membrane 58. The semipermeable membrane 58 is porous to the electrolyte 64 with a pore size sufficiently small enough to confine the particulate substrate 56 proximate to the cathode 63. Activating the power source 54 sets up a voltage between the anode 61 and cathode 63. The application of an external electric field not only aligns the particulate substrate 56 but also enhances the attractive forces between neighbouring particulate substrates 56. Above the percolation threshold, there is formed a particulate network exhibiting long-range connectivity. Containment of the particulate substrate 56 proximate to the cathode 63 aligns the particulate substrate 56 relative to the cathode 63 and thus the said long-range particulate network serves as an extension to the cathode 63. This directs the migration of metal ions M.sup.+ from the anode 61 to the negatively charged particulate substrate 56 thus coating the substrate 56 and resulting in the desired metal coated substrate 57. To ensure the substrate 56 remains dispersed an agitation device 55 may be introduced into the continuous electrodeposition system 51. The agitation device used may be the introduction of a purging gas such as gaseous N.sub.2 60. The particulate substrate 56 is pumped by a pump system 65 from the reservoir of dispersion 53 into the continuous electrodeposition system 51. Periodically or continuously the volume above the membrane 58 of electrolyte 64, particulate substrate 56, electrolytic ions and metal coated substrate 57 is pumped out of the electrodeposition bath 62 and passed via a magnetic collector 52. Any magnetic metal coated substrate 57 is extracted by the magnetic collector 52 and any uncoated particulate substrate 56 is re-introduced through the reservoir of dispersion 53 and pumped back into the electrodeposition bath 62. A thicker coating of magnetic material may be achieved by re-dispersing any collected magnetic metal coated substrate 57 into the electrodeposition bath 62 and repeating the aforementioned process.
[0065] FIG. 5 shows a biphasic continuous electrodeposition system 71 housed within an electrodeposition bath 82. The biphasic system 71 comprises an organic liquid phase 86 and an aqueous liquid phase 84 thus creating a liquid interface 78 which acts as a separator 79, thereby confining the particulate substrate 76 to the organic liquid phase 86 and reducing its dispersion into the larger volume of electrolyte 84. The organic liquid phase 86 comprises the particulate substrate 76 and organic solvents. The aqueous liquid phase 87 comprises the electrolyte 84. The cathode 83 is located only in the organic liquid phase 86 and does not transcend the liquid interface 78. The cathode 83 and anode 81 are connected to the power source 74. The anode 81 is formed from the metal to be electrodeposited and is located only in the aqueous liquid phase 87. Activating the power source 74 sets up a voltage between the anode 81 and cathode 83. The application of an external electric field not only aligns the particulate substrate 76 but also enhances the attractive forces between neighbouring particulate substrates 76. Above the percolation threshold, there is formed a particulate network exhibiting long-range connectivity. Containment of the particulate substrate 76 proximate to the cathode 83 aligns the particulates relative to the cathode 83 and thus the said long-range particulate network serves as an extension to the cathode 83. This directs the migration of metal ions M.sup.+ from the anode 81 to the negatively charged particulate substrate 76. This allows coating of the particulate substrate 76 to occur substantially at the liquid interface 87 resulting in the desired metal coated substrate 77. To ensure the particulate substrate 76 remains dispersed an agitation device 75 may be introduced into the continuous electrodeposition system 71. The agitation device used may be the introduction of a non-ionic surfactant 80 into the organic liquid phase 86. The particulate substrate 76 is pumped by a pump system 85 from the reservoir of dispersion 73 into the continuous electrodeposition system 71. As the substrate is pumped past a large volume of electrolyte 84 a mixture of particulate substrate 76, organic solvent, non-ionic surfactant 80 and metal coated substrate 77 is pumped out of the electrodeposition bath 82 and into a magnetic collector 72. Any magnetic metal coated substrate is extracted by the magnetic collector 72 and any uncoated substrate 76 is re-introduced through the reservoir of dispersion 73 and pumped back into the electrodeposition bath 82.
