U.S. patent application number 11/125984 was filed with the patent office on 2005-09-15 for composite magnetic particles and foils.
This patent application is currently assigned to Surfect Technologies, Inc.. Invention is credited to Eichman, John W. III, Griego, Thomas P., Velasquez, Geronimo.
Application Number | 20050202269 11/125984 |
Document ID | / |
Family ID | 23224723 |
Filed Date | 2005-09-15 |
United States Patent
Application |
20050202269 |
Kind Code |
A1 |
Griego, Thomas P. ; et
al. |
September 15, 2005 |
Composite magnetic particles and foils
Abstract
A method and apparatus for microencapsulating or
electrodeposited coating of ferromagnetic and soft-magnetic
sub-micron or nano sized powderized material comprising use of a
rotary flow-through device assisted by an electromagnet within the
electrode ring to alternately position the powder at the face of
the cathode ring and electroplate the powder and reorient it prior
to another repositioning. The invention is also of a process and
apparatus for forming a strip, mesh, or film from magnetic
powderized material in an organized bipolar arrangement, which is
particularly useful for electroforming foils with the magnetic
particles positioned in a monolayer within a multilayer metallic
foil.
Inventors: |
Griego, Thomas P.;
(Corrales, NM) ; Eichman, John W. III; (Grants,
NM) ; Velasquez, Geronimo; (Albuquerque, NM) |
Correspondence
Address: |
PEACOCK MYERS, P.C.
P O BOX 26927
ALBUQUERQUE
NM
87125-6927
US
|
Assignee: |
Surfect Technologies, Inc.
Albuquerque
NM
|
Family ID: |
23224723 |
Appl. No.: |
11/125984 |
Filed: |
May 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11125984 |
May 10, 2005 |
|
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|
10228709 |
Aug 27, 2002 |
|
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6890412 |
|
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60315502 |
Aug 27, 2001 |
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Current U.S.
Class: |
428/606 ;
204/290.01 |
Current CPC
Class: |
Y10T 428/12431 20150115;
C25D 17/16 20130101; H01M 8/1004 20130101; C25C 7/002 20130101;
C25D 5/006 20130101; H01M 4/0452 20130101; C25C 5/02 20130101; H01F
1/009 20130101; B22F 2998/00 20130101; Y02E 60/50 20130101; Y02E
60/10 20130101; B82Y 25/00 20130101; B22F 2998/00 20130101; B22F
1/0018 20130101 |
Class at
Publication: |
428/606 ;
204/290.01 |
International
Class: |
B32B 015/00 |
Claims
What is claimed is:
1. A composition comprising coated substrate materials created by
the process of: providing to a rotary flow-through
electrodeposition cell electrolytic fluid and substrate material
particles; employing an electrode; and via one or more magnets or
electromagnets, drawing substrate material particles in the cell
against the electrode.
2. The composition of claim 1 wherein said coated substrate
materials comprise nanoparticles.
3. The composition of claim 1 comprising a composite foil.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/228,709, entitled "Electrodeposition Apparatus and
Method Using Magnetic Assistance and Rotary Cathode for Ferrous and
Magnetic Particles", filed on Aug. 27, 2002 and issuing as U.S.
Pat. No. 6,890,412 on May 10, 2005, which claims the benefit of the
filing of U.S. Provisional Patent Application Ser. No. 60/315,502,
entitled "Electrodeposition Apparatus and Method Using Magnetic
Assistance and Rotary Cathode for Ferrous and Magnetic Particles",
filed on Aug. 27, 2001, and the specification thereof is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention (Technical Field)
[0003] The present invention relates to apparatuses and methods for
electroplating and electrochemically modifying the surface finish
of ferrous and magnetic powders, particularly by continuous
magnetically assisted centrifugal means for encapsulation, and
electrodeposition on powders without limitation on particle size,
but specifically including submicron- or nano-sized particles.
[0004] 2. Background Art
[0005] The technologies for electrochemical enhancement of the
surfaces of the particles in bulk powders has previously been
limited to two main types: chemical copper and electrolytic nickel
auto-catalytic processes; and rotary electroplating devices which
require frequent stopping and starting of the electrolytic cell's
rotation to tumble the powder to achieve uniform dispersion of the
coating upon the particles. A limitation of the previous art using
chemical or auto-catalytic processes is the cost of the chemical
consumption due to the enormous surface areas of powders. Another
limitation of known devices using the rotary techniques is the need
to stop the cell to tumble the powder in order to disperse the
coating and prevent agglomeration of the particles. Known devices
of the latter type known in the art are typified by the disclosure
of U.S. Pat. No. 5,879,520, the teachings of which are hereby
incorporated by reference. Further background in the field of
rotary flow-through electroforming/electrodeposition devices and
methods is supplied by U.S. Pat. Nos. 5,487,824 and 5,565,079, the
disclosures of which are hereby incorporated by reference.
[0006] Previous rotary flow-through devices are capable of
centrifugal clarification of the particles in solution and fixing
them against the cathode ring for electrical contact. A
disadvantage occurs, however, when rotation of the cell must be
stopped to tumble the powder particles to foster even
electrodeposition upon the individual particles. During this "stop
phase," the particles are re-suspended in the electrolyte solution.
If the particles are of sufficient density, continuing the rotation
of the cell re-clarifies the solution and again fixes the particles
against the electrical contact ring, but the need periodically to
stop and re-start cell rotation prolongs total processing times.
But very significantly, in the case of submicron-sized, low mass
powders, the method of repeatedly stopping and resuming cell
rotation is unacceptable from a practical standpoint, because the
material particles remain in suspension (rather than in contact
with the cathode) for impermissibly, nearly indefinite, lengths of
time.
[0007] Each time the cell rotation is resumed (after stopping to
tumble the substrate powder), time is required to clarify the
solution and re-fix the particles to the face of the cathode ring;
heavier particles are thrown into renewed contact with the cathode
first, while finer particles require comparatively more time to
move outward under centrifugal force. This results in heavier
particles having preferential electrical contact with the cathode,
resulting in a wide variance in the uniformity of the thickness
distribution. In many cases, ultrafine particles will receive no
electrodeposition at all.
SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)
[0008] The invention is a continuous rotary flow-through
electrodeposition system including a vertical rotating cell. The
system has a plurality of nozzles and electrodes alignable
concentrically to the rotating cell. The cell includes a generally
annular electrode ring on the wall of the cell vessel. The rotating
cell preferably features a generally toroidal magnet, or annular
magnet array (permanent magnets or preferably electromagnetic coil)
disposed within the annular electrode (cathode) in the vessel. This
innovation promotes catalytic efficiency.
[0009] The cell is provided with a catch basin and a canopy that
catch flow-through electrolyte for return to the solution
reservoir.
[0010] The present invention can also be used with or without a
sintered membrane or laser cut slots to allow solution to
flow-through, since the cell is configured to permit overflow of
process solution from the top port thereof without discharging
therewith the powder material being treated. Further, the present
invention is operated, in phase with stop and start rotation cycle
of the cell. This provides an efficient method of positioning the
particles on the electrode surface during process. The
electromagnet is energized in sequence to the cell start of the
rotation cycle and then de-energized during the stop phase to allow
the metal powder to re-suspend and achieve dispersion of the
deposit. The stop and start rotation cycle is repeated at high
frequency with each cycle assisted by the electromagnet attracting
the fine particles to efficiently clarify the suspended powder and
prevent the discharge of metal powder from the cell. After a
chemical is applied and the electrodeposit is achieved the next
step is to recover the electrolyte solution and retain the
electroplated powder for further process steps such as rinsing.
This is done by continuously energizing the electromagnet during
the purge and fill cycles as a sequence of chemicals and rinse
water is applied during the multi-step electroplating process. FIG.
9 illustrates the sequence of on/off events for the process cycle
during both the electrodeposition process and the chemical change
sequence.
[0011] The following process sequence is typical for a single or
multilayer electrodeposition of metal from standard electroplating
solutions:
[0012] 1. Load powder into cell.
[0013] 2. Rinse with electromagnet ring energized.
[0014] 3. Use high speed rotation to purge rinse water with
electromagnetic ring energized.
[0015] 4. Insert anode into cell and inject electrolyte solution
with electromagnetic ring energized.
[0016] 5. Operate cell with start/stop cycle described above and
sequenced switching of the electromagnetic ring until the required
amp minutes are accumulated.
[0017] 6. Use high speed purge rotation with electromagnetic ring
energized to remove the electrolyte and retain the electroplated
powder.
[0018] 7. Spray or flow deionized water into cell with
electromagnetic ring energized to rinse the remaining electrolyte
solution while retaining the powder in the cell. Repeat as
necessary.
[0019] 8. Use high speed purge rotation with electromagnetic ring
energized to remove the electrolyte and retain the electroplated
powder.
[0020] 9. Repeat the electroplating steps to add another deposit or
other process steps such as etch or passivation.
[0021] 10. Circulate with electromagnetic ring energized and inject
hot air or Nitrogen to dry the powder in the cell.
[0022] A primary object of the processes of the invention is to
provide effective electrolytic microencapsulation of
submicron-sized or "nano scale" ferromagnetic or soft magnetic
particles.
[0023] A primary object of the apparatus of the present invention
is to permit the multi-step electroplating process without physical
transfer of the plating fixture or cumbersome manual filtered
exchange of solutions.
[0024] A primary advantage of the invention is that it can process
submicron-sized materials with high efficiency, with or without a
sintered membrane or slotted dome.
[0025] Other objects, advantages and novel features, and further
scope of applicability of the present invention will be set forth
in part in the detailed description to follow, taken in conjunction
with the accompanying drawings, and in part will become apparent to
those skilled in the art upon examination of the following, or may
be learned by practice of the invention. The objects and advantages
of the invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The accompanying drawings, which are incorporated into and
form a part of the specification, illustrate several embodiments of
the present invention and, together with the description, serve to
explain the principles of the invention. The drawings are only for
the purpose of illustrating a preferred embodiment of the invention
and are not to be construed as limiting the invention. In the
drawings:
[0027] FIG. 1 is a top plan view of a preferred embodiment of the
apparatus of the invention;
[0028] FIG. 2 is a schematic side sectional view of an overall
system according to the invention, showing the anode in the "down
position" within the cell;
[0029] FIG. 3 is a schematic side sectional view of an overall
system according to the invention, showing the anode and feed
nozzle assemblies in the raised position, withdrawn from the
electrolytic cell bowl assembly;
[0030] FIG. 4 is an enlarged side sectional view of certain
components of the apparatus of the present invention as seen in
FIG. 3;
[0031] FIG. 5 is an enlarged side sectional view of the annular
electrode component of the invention with a torroidal electromagnet
coil disposed therein;
[0032] FIG. 6 is an isolated, perspective, blown-apart view of the
main elements of the annular electrode and imbedded electromagnetic
field coil according to the present invention
[0033] FIG. 7 is an enlarged side sectional view of the cathode and
electromagnetic field coil elements of the invention shown in FIG.
5;
[0034] FIG. 8 is a side view of the bowl vessel, annular cathode,
and embedded electromagnetic filed coil elements of the invention,
showing on the left side of the figure how the substrate material
is drawn to the cathode by the force of the electromagnetic coil
when the coil is on, and showing on the right side of the figure
how the substrate material is in suspension when the coil is turned
off; and
[0035] FIG. 9 is a time-way diagram illustrating a sequence of
on/off events for the process cycle during both the
electrodeposition process and the chemical change sequence
according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS (BEST MODES FOR CARRYING
OUT THE INVENTION)
[0036] The present invention offers major improvements to
apparatuses and methods in electrolytic cell technologies for
microencapsulating or coating powdered materials. The apparatus of
the invention incorporates some of the desirable aspects of devices
and processes known in the art, such as multiple return drains and
multiple selectable feed nozzles, while yet overcoming various
disadvantages manifested in previous efforts.
[0037] The present invention capitalizes upon the fundamental
concept of harnessing centrifugal force to compact bulk materials,
particularly submicron- or nano-sized powders, in solution or
suspension (preferably aqueous) against an electrolytic cathode
contact. Throughout this disclosure, "substrate material" or
"substrate powder" refers to the bulk materials to be treated, and
specifically includes but is not limited to super-fine ferrous and
magnetic powders having mean particle diameters in the nanometer or
submicron range.
[0038] The central component of the apparatus is the cell, which
features an upper dome mounted upon a bowl. The substrate material
is loaded through a top opening in the cell, and the plating cell
is rotated at sufficiently high rpm to centrifugally throw the
substrate material against the cathode contact at the outer
perimeter of the cell and is assisted by the electromagnetic ring
to improve efficiency for handling sub-micron ferromagnetic
materials such as iron, nickel cobalt and other alloys with soft
magnetic properties. Electroplating solution is then introduced at
the top opening, and flows through the cell, eventually exiting
through a filter disposed between the dome and the top edge of the
bowl, or alternatively by overflowing at the top opening of the
cell. A key advantage of the present invention is that the cell
containing the electroplating solution and the substrate material
incorporates an annular magnet, preferably an electromagnet, the
magnetic force of which draws the particles toward the cathode,
thus increasing the efficiency of the device by, among other
things, reducing significantly the duration of the "stop" stage of
the stop-start method. The invention therefore improves
dramatically on the known stop-start and sequential switching
methodologies to circulate the particle position for even coverage
and prevention of agglomeration/bridging of the substrate material.
Thus, in marked contrast with prior devices, the magnetically
assisted cathode of the present invention results in the efficient
movement and controlled agitation of the substrate material in the
cell.
[0039] The overall and general configuration of a preferred
embodiment of the constant rotary flow-through plating apparatus
according to the invention is illustrated in FIGS. 1-8. Principal
components of the invention include a rotational drive shaft 20,
upon which the cell is disposed, the shaft 20 and cell both being
disposed concentrically with and above a rotatable drain basin 24.
A motor and drive shaft are used to rotate the cell generally
according to convention. Bearings may provide for smooth rotatable
disposition of the cell. The cell rotates about its vertical axis
A, which is coaxial with the shaft 20. The cell includes a constant
flow-through bowl assembly 36 rotatable about the axis A. As
mentioned bowl bearings smooth and ease the rotation of the cell
bowl assembly 36. An annular electrode 44 as a, in typical usage
serving as a cathode, is mounted in the bowl assembly. An anode
assembly 50 is mounted upon a movable boom according to known
construction, so that the anode assembly is controllably movable
between a use position immersed in solution within the bowl
assembly 36 and a retracted position exterior thereof. The upper
circumferential rim or edge of the basin 24 is in sealed, but
removable, contact with the lower circumferential rim of a closed
overarching, e.g., generally hemispherical, canopy 38, so that the
combination of the shaft 20, basin 24 and canopy 38 substantially
surround and enclose the platen 30 and bowl assembly 36.
[0040] In this disclosure, reference is made to an "anode" assembly
and to "cathode" contact strips. It is immediately understood by
one of skill in the art that the electrochemical roles of the
electrodes in an electrolytic cell may be reversed according to the
type of electrolysis to be performed. Thus, in every cell there is
a primary electrode and an opposing electrode, and which of the
pair functions as the anode and which serves as the cathode may be
selectively determined by the operator to perform the desired
electrolytic process within the cell. Thus, while the electrode 50
movable upon an overhead boom in this disclosure is denoted as an
"anode," it may actually serve as a cathode in various alternative
embodiments or processes without departing from the scope of the
invention. Likewise, the annular "cathode" 44 may in alternative
applications function as an anode. Further, the anode 50 may be
either soluble or insoluble according to know principles in the
art, depending upon the specific electrolytic process to be
performed.
[0041] The placement of the anode 50 upon an adjustable boom
permits the anode or anode assembly to be controllably disposed
into the cell for immersion into the electrolyte, and then
controllably withdrawn to a position exterior of the cell. Thus,
the anode 50 is positionable outside the bowl assembly 36 so as not
to be within the cell during, for example, post- or
non-electrolytic processing steps, such as rinsing. Further, a
multi-anode assembly may be provided, wherein one type of anode may
be withdrawn, and another controllably disposed in its stead, to
perform a series of process steps in the cell using different anode
types.
[0042] A specialized dome 40 is mounted upon and above the bowl
assembly 36, with an annular filter 42 disposed between and in
sealed contact with the lower circumferential rim of the dome 40
and the rim of the bowl assembly 36. The bowl assembly 36 and dome
40, together with the anode assembly 50, collectively are the
principal elements of the electrolytic cell of the invention. The
drain port 26 of the basin 24 is locatable above the inlet of a
solution reservoir 80, which may be any one of a plurality of
solution reservoirs disposed radially about the exterior of the
drain basin 24. Solution from within the reservoir 80 may be pumped
into the bowl assembly 36, via one or more feed nozzles 83, by
means of a suitable pump 81 and re-circulation conduit 84.
[0043] The flow of working solution through the apparatus of the
invention during any given treatment cycle is described with
reference to FIGS. 1 and 2. At the outset of operation, with the
substrate material previously disposed inside the bowl assembly 36,
the re-circulation conduit 84 is connected with the discharge port
85 of a selected solution reservoir 80 containing the first
solution or liquid of interest (e.g., a pre-rinse, perhaps
de-ionized water). Solution is then pumped by the pump 81, via the
discharge port 85, from the reservoir 80 through a filter and then
the re-circulation conduit 84 to the feed nozzles 83 and into the
bowl assembly 36, until the desired solution level in the bowl
assembly is attained. An advantage, therefore, is the
re-circulation of filtered treatment solution, improving process
efficiency without demanding fluid restocking with new, unused
solution. The driving mechanisms of the apparatus are actuated to
rotate the bowl assembly 36, and the centrifugal force from the
bowl assembly's rotation casts the substrate material against an
arcuate segment of the inside wall of the bowl assembly in a manner
to be further described. The working solution likewise is urged
toward the inside wall of the bowl assembly 36 (where the intended
electrolytic processes occur), and tends to flow under centripetal
force up to the point of maximum cell diameter, i.e. the annular
juncture of the bowl assembly 36 with the dome 40. An annular
osmosis filter 42 is situated at the juncture between the rim of
the dome 40 and the rim of the bowl assembly 36. The solution then
is forced through the osmosis filter 42, and is free to flow by
gravity down the exterior bowl skirt 73 and/or the inside surface
of the canopy 38 to be collected in the bottom of the drainage
basin 24. Recovered solution may then be released through the drain
port 26 for return to the solution reservoir 80 for re-use or
reclamation, as desired.
[0044] FIGS. 1-2 show the complete scheme of the invention. The
apparatus includes the ability to carry out multiple chemical
processes and that is facilitated by having anode tools and wrench
tools that can drop in and out of the cell, so the apparatus is
essentially an open overflowing cell. This permits the chemistries
to be purged through the cell to prepare the cell to receive the
next chemistry. The drain basin can be addressed to return to a
multitude of reservoir tanks so that the user can either carry out
preplate, like an acid dip for removing an oxide layer on a the
substrate powders, or other pretreatment to clean or to reduce the
surface tension of the substrate powders to make them more
wettable. Any of the enhancements that preplate processes are known
for could be applied in this system followed by the
post-electrodeposition schemes which would include rinsing, and
neutralization or some type of an anti-tarnish agent.
[0045] Another aspect of the embodiment of FIG. 2 and in FIG. 3 is
that the computer control system carries out the sequencing and the
phasing of the switching of the electromagnetic power source, if it
is used with electromagnets, or the cathode power source which is
supplied to the cathode ring 44 (which could also be configured as
the opposing electrode for anodic processing). The invention will
handle either the cathodic orientation or a anodic orientation on
the cathode ring 44. So the ability to computer control all of the
sequences of this process step boosts the efficiency of this cell
to viable commercial application. The computer control can be a
time-way that is controlled by programmable logic control.
[0046] Combined reference is made to FIGS. 1 and 2. Shown therein
are the control elements of the invention, including an
electromagnetic power source 101 and a cathode power source 102,
both of which may be controllably operated by a control panel 103.
The control panel 103 may be either manually operated, computer
operated, or both, or various combinations of the two. It is within
the skill of an ordinary software engineer to device a computer
program that permits most of the operations of the invention, in
various different electrodeposition applications, to be largely
automated through computer control. Notable, of course, in most
applications, the electromagnet 100 is turned off during the
activation of the cathode to perform the selected electrochemical
process, and visa-versa, e.g., in most (but not necessarily all)
methods of the invention, when the electromagnet 100 is active, the
cathode 44 is deactivated. (When the apparatus is entirely at rest
and not in use, of course, all electrical systems are turned
off.)
[0047] The bowl assembly 36 is situated to be rotated by the action
of the drive shaft 20. Reference is made to FIGS. 4 and 8, which
provide further detail of the bowl assembly 36. The bowl assembly
36 includes a rigid, durable bowl 70 in the shape of a truncated
cone, having a generally disk-shaped planar floor 71 integrally
molded with a frustum-shaped wall 72. Depending downward and
radially outward from the wall 72, and preferably integrally molded
therewith, is a bowl skirt 73. The entire bowl 70, including the
floor 71 and skirt 73, preferably is molded from a suitable inert
material, preferably a plastic such as a thermoplastic, or
alternatively may be of copolymers, fiberglass or fiber
composite.
[0048] Continued reference is made to FIGS. 4 and 8, and added
reference is made to FIGS. 5-7 illustrating that the bowl 70 has in
the interior surface of the wall 72 thereof an annular cathode 44.
Referring particularly to FIG. 6, it is seen that the cathode 44
preferably is assembled from to parts, a top cathode 44' and a
bottom cathode 44", which are adapted to be brought into concentric
registration to define the complete cathode 44. As indicated by
FIG. 6, the upper cathode 44' and the lower cathode 44" when
combined into registry (see FIGS. 5 and 7) define an annular
interior space there between in which is disposed a magnet 100,
electromagnet, or magnetic array. Thus, the magnet 100 is generally
annular in the preferred embodiment, although in alternative
embodiments the magnet 100 is fashioned from specific radially
arrayed groups of magnets. In the preferred embodiment depicted in
the drawing figures, the magnet 100 is a generally toroidal coil,
which when conducting electricity functions as an electromagnet.
When activated, the electromagnet generates a significant magnetic
flux, the field of which extends a considerable distance, such that
substrate particles in the bowl 70 are affected thereby. In
alternative embodiments, the magnet 100 may be a plurality of
electromagnetic coils, or a plurality of permanent magnets,
disposed in selected radial arrays around the axis A of the bowl
70. In any embodiment, the magnetic flux from the magnet 100 is
sufficient to cause substrate material particles in suspension in
the electrolytic fluid to be drawn by magnetic force--even from
areas near axis A--toward the cathode 44. By this innovation, even
nano-sized particles, which ordinarily would remain in suspension
for unduly extended periods of time if acted upon only by
centrifugal force, can be quickly drawn to the cathode 44.
[0049] FIG. 8 is a side sectional view of the assembled
electrolytic cell of the preferred embodiment of the invention. The
bowl 70 includes the annular cathode 44 within the bowl wall 72.
The dome 40 is removably mounted concentrically upon the bowl 70 by
temporarily securing the rim flange 99 of the dome to the upper rim
77 of the bowl wall 72, as by bolts or the like, but with the
filter 42 sandwiched there-between. The cell is rotatably coupled
to the shaft 20 according to convention, so as to rotate
concentrically about axis A.
[0050] FIG. 8 depicts the apparatus with the electromagnet 100
turned off, and on the right side of the figure the substrate
material particles are floating out in the electrolytic liquid. On
the left side of the figure, the energization of the magnet 100
results in the substrate work being compacted up against the
cathode. FIG. 8 also depicts the electrolytic liquid level.
[0051] A key advantage of the present invention thus is presented.
The electrolytic cell (mainly including the bowl assembly 36)
containing the electroplating solution and the substrate material
undergoes rotation, wherein the cell rotates about its own axis A.
As the cell orbits around the central axis A of the apparatus, the
substrate material is cast by centrifugal force against the
"outermost" portion of the interior of the bowl 70. As suggested by
FIG. 8, during the "start" or rotational stage of the the
centrifugal force due to rotation of the cell impels the substrate
material within the bowl 70 to collect along the wall 72. During
cell rotation, species from the solution is electrolytically
deposited upon the substrate material; however, especially in the
case of fine powders, a substantial portion of the substrate
material remains in suspension, due to its low mass/particle ratio.
The forgoing is largely in accordance with known technologies.
However, in the invention, during the "stop" stage, when rotation
of the cell is ceased (as a step associated with the tumbling of
the substrate material to promote even and efficient
electrodeposition), the magnet 100 is controllably actuated to
accelerate migration of the substrate material particles toward the
cathode 44. An advantage of the invention therefore is that the
substrate material to be treated tends to collect at a
comparatively rapid rate, and in a manner to promote efficient
electro processing thereof.
[0052] Thus, while cell rotation is repeatedly interrupted and
re-started to tumble the substrate material, the "stop" periods are
exploited to maximum effect by actuation of the magnet 100.
[0053] The mode of applying the working electrical potential to the
substrate is explained with combined reference to FIGS. 1-8,
especially FIG. 4. Electricity at the user-selected and appropriate
voltage and amperage is supplied from the dual stage slip ring 87
to the electrical cable 90. Current flows through the cable 90 to
the electromagnet 100. Electrical potential is applied at
controlled intermittent times to the cathode 44 via the shaft
20.
[0054] As previously mentioned, when rotation of the bowl assembly
36 is stopped, the substrate material beneficially tumbles or rolls
along the inside of wall 72 due to inertial forces. Once the
tumbling ceases (or at some other pre-determined time), the cell
rotation is re-started to again throw the substrate material to the
electrode 44. So long as some portion of the collected substrate is
in electrical contact with the annular cathode 44, the substrate
undergoes electrolytic processing by the electrical current in the
cathode.
[0055] The present invention utilizes a rotary cathode cell which
has an annular cathode 44 which is fed by currents that come up
through the shaft. During the process, the rotation of the cell is
stopped and started to assist with tumbling the powders. The
operating principle is distinguishable from known devices, however,
in that there is additionally provided a magnet 100, preferably an
electromagnet, that is either in toroidal coil form or a spool-type
electromagnet, that is embedded into the cathode ring 44 itself, so
that during the non-plating phase of the process, the
electromagnetic field from the magnet is harnessed to draw the
powered substrate material to the annular cathode 44 to further
assist in more rapid clarification of the suspended particles to
the cathode where the electrolytic process is carried out. The
apparatus permits treatment of small particles which would include
the submicron and nano scale ferrous powders, or nickel powder, or
cobalt powders, or any other powder that exhibits a para-magnetic
or magnetic capability for being drawn to the cathode.
[0056] Advantages offered are time, efficiency and that efficiency
would be in terms of the electrical connectivity, but mostly in the
ability to retain smaller particles. Applicants determined that in
handling submicron structures, the density of that material will
hold the particles in suspension beyond the efficiency range of any
of the previous attempts in the art. A time-way diagram of the
operation of the invention would show the phase of the cell
rotating, which allows the particles to tumble, then the phase
where the electromagnet is energized to draw the substrate powder
to the cathode; the magnet 100 is then de-energized and then at
that point, the substrate powders are affixed on the cathode 44
under centrifugal force and that allows the magnet to be switched
off, and then sequentially the current is supplied to the cathode
to carry out the electrolytic process.
[0057] By means of the control panel sequential switching of the
energizing/de-energizing of the coil is accomplished.
De-energization of the magnet 100 is normally done during the
electrodeposition phase, because the linking of the particles under
a magnetic field would be tight, which would promote undesirable
bridging of the particles together or of undesirable agglomeration
of particles. Thus, the inventive process using the rotary devices
can be performed without agglomeration of the particles.
[0058] Nevertheless, the invention includes the ability to create
electroformed films using the electromagnetic force, where the user
preferentially energizes the electromagnet 100, affixes the powder
to the cathode 44, continue the electromagnets' actuation through
the plating phase, and end up with a north-south oriented field of
substrate particles that would be standing off of the cathode face,
perpendicular to the axis of rotation. Such application allows the
electroformation of a foil, with the substrate particles standing
in a preferred or an influenced orientation; that could generate an
enhanced foil product, or the foil itself could be further
processed by oxidizing or removing the substrate particles through
etching, and ending up with a porous or spongy form that has a
high-order arrangement of the particles now in an annular form. A
benefit of using the magnetic field to orient or organize the
magnetic particles in a bipole arrangement enhances the product
foil for applications such as fuel cell membrane electrode
assemblies and battery electrodes as well as flat panel display
electrodes.
[0059] The primary contemplated use of the invention would be for
the electro processing of metallic powders that exhibit a magnetic
attraction. When powders become finely divided, powders that
exhibit paramagnetic or ferramagnetic qualities, which would have
very low magnetic attractability in their smaller divided state,
the smaller division would be enough to make it mobile, and
attractive to the magnetic force. Thus, there are materials other
than ferrous powders and nickels and cobalts (those that typically
in bulk form exhibit a strong magnetic attraction) that can be
electroprocessed by the invention.
[0060] Other embodiments include use of permanent magnets. In such
case, the electronic control systems and the switching of an
electromagnet power source are not necessary. In a more passive
scheme, there is preferably an array of permanent magnets that are
encapsulated, such as a neodymium magnet, that have a magnetic
field. This array of magnets is around of the periphery of the
rotating cell. The magnets themselves are fixed in positions that
are preferably equidistant from each other. If there were four,
they would have a north-south, east-west orientation of the
magnets. As the substrate powder is being rotated and as it moves
into a stronger field of the power, it is attracted to the cathode,
and as the cathode continues to rotate, it creates more gap
distance and magnetic flux would drop, so then the powder is
released and at that point experiences a tumbling action that
contributes to electrodeposition without agglomeration.
[0061] During electrodeposition of magnetic powders such as nickel,
their position against the rotating cathode can be altered by
placing stationary magnets exterior to the cell. As the powders
pass the magnetic flux, their position against the cathode will
change slightly as they are temporarily aligned with the passing
flux. The magnets can be placed at various planes relative to the
plane of the cell floor, thereby providing additional powder
alignments. When the cell is cycled, the magnetic fields can be
removed in order for the powders to change position against the
cathode.
[0062] In yet another alternative embodiment, the cell is provided
with a magnetic floor. Such a system preferably has an entire floor
that is magnetic. This embodiment has a high exposure of the
mechanical cathode area. The cathode efficiency on the work itself
would be very low because the process deposits preferentially to
the equipment. In this configuration, a shallow rotating tray with
a cathodic cell floor is employed. Magnetic fields can also be
placed below the cell floor in order to temporarily alter the
position of magnetic powders, thereby increasing exposure to the
anode placed on the solution surface. The solution flow is laminar,
with the inlet preferably placed at the center of the rotating
floor. The solution and the powders are circulated as they both
spill over the outside edge of the rotating cell. The powders will
have many opportunities to achieve contact with the cell floor
cathode. While the powders are in the sump, they can be
de-agglomerated by being subjected to turbulent solution flow prior
to being pumped back to the electrodeposition cell.
[0063] In order to have the highest efficiency, the electromagnet
100 preferably includes a soft iron core. The soft iron core is the
softest magnet material that is practically available and that will
allow that when the current is switched on and off for the
electromagnet, there will be minimal residual magnetivity in the
core. The cathode 44 preferably is made from of stainless steel.
There will be some magnetization of the cathode, but the inertia of
the solution overcomes the magnetic attraction between the
substrate particles which will become magnetized, and any residual
magnetivity that could be retained in the stainless steel cathode.
Using the range of kinetics that are available, and in speed
parameters, and the starting and stopping acceleration curves, the
apparatus overcomes any residual magnetic effects.
Particle-to-particle linking will be the case. However, according
to some base experimentation, just observations of how particles
are behaving in liquid forms, and the particles seem to be breaking
up.
[0064] Another aspect of the inventive cell is that it permits the
processing of materials that are diamagnetic, in other words, those
that exhibit no attraction (their lattice form does not allow them
to polarize to either cathode). (Paramagnetics will attract
preferentially to the north or the south.) There are elements that
have diamagnetic properties such as bismuth that have a diamagnetic
attraction that is actually repelled by both poles, and one can
according to the invention perform some preferential treatments on
larger scale particles, where the current is pulsed on and the
diamagnetic repulsion of the particles aids in a process
arrangement of that nature. In that embodiment, the cell rotation
would be operated on a continuous basis, and the switching of the
electromagnet would be the mechanism for tumbling the powders and
breaking them up to prevent agglomeration and to get dispersion of
the deposit layer over the whole particle.
[0065] Although the invention has been described in detail with
particular reference to these preferred embodiments, other
embodiments can achieve the same results. Variations and
modifications of the present invention will be obvious to those
skilled in the art and it is intended to cover all such
modifications and equivalents. The entire disclosures of all
patents and publications cited above, are hereby incorporated by
reference.
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