U.S. patent application number 12/162402 was filed with the patent office on 2009-02-19 for cathode for electrolytic production of titanium and other metal powders.
Invention is credited to Aaron J. Becker.
Application Number | 20090045070 12/162402 |
Document ID | / |
Family ID | 38345718 |
Filed Date | 2009-02-19 |
United States Patent
Application |
20090045070 |
Kind Code |
A1 |
Becker; Aaron J. |
February 19, 2009 |
CATHODE FOR ELECTROLYTIC PRODUCTION OF TITANIUM AND OTHER METAL
POWDERS
Abstract
Disclosed herein are electrolytic cells comprising cathodes
having a non-uniform current distribution and methods of use
thereof.
Inventors: |
Becker; Aaron J.; (Palm
Beach Gardens, FL) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY;LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1122B, 4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
38345718 |
Appl. No.: |
12/162402 |
Filed: |
February 6, 2007 |
PCT Filed: |
February 6, 2007 |
PCT NO: |
PCT/US07/03066 |
371 Date: |
July 28, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60765560 |
Feb 6, 2006 |
|
|
|
Current U.S.
Class: |
205/220 ;
205/261 |
Current CPC
Class: |
C25C 3/26 20130101; C25C
5/04 20130101; C25C 3/28 20130101; C22B 34/129 20130101 |
Class at
Publication: |
205/220 ;
205/261 |
International
Class: |
C25D 5/48 20060101
C25D005/48; C25D 3/66 20060101 C25D003/66 |
Claims
1. A method of controlling the morphology of a titanium-containing
product in an electrolytic cell comprising the steps of: (a)
providing an electrolytic cell comprising a molten electrolyte, a
cathode having a non-uniform current distribution in contact with
the molten electrolyte, and an anode in contact with the molten
electrolyte; (b) providing a titanium-containing compound to the
molten electrolyte; and (c) applying either a fixed voltage or a
fixed current across the anode and the cathode thereby depositing a
metal comprising titanium on the cathode.
2. The method of claim 1, comprising during or after step (c) the
further step of removing the titanium from the cathode when the
metal attains a morphology suitable for powder metallurgical
applications.
3. The method of claim 2, wherein the removing step is accomplished
by fluid flow, vibration, or blown gas.
4. The method of claim 2, wherein the metal is a low aspect ratio
powder with a particle size of less than 45 microns.
5. The method of claim 2, wherein the metal is asymmetric powder
particle with a particle size in a range of from 45 to 150
micron.
6. The method of claim 5, wherein the asymmetric powder particle
has an aspect ratio of greater than 1.5.
7. The method of claim 1, wherein the cathode is wire mesh,
bristles, rods, or combinations thereof.
8. The method of claim 1, wherein the metal is titanium.
9. The method of claim 1, wherein step (b) is accomplished by
adding the titanium-containing compound to the molten
electrolyte.
10. The method of claim 1, wherein the titanium-containing compound
is titanium monoxide or titanium dioxide.
11. The method of claim 1, wherein the anode is a consumable anode
and the titanium-containing compound is a component of the
consumable anode which is provided to the molten electrolyte
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/765,560, filed Feb. 6, 2006 which is
incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
[0002] Disclosed herein are electrolytic cells comprising cathodes
having a non-uniform current distribution and methods of use
thereof for the production of titanium and other multi-valence and
high (2 or more) valence metals, in particular refractory metals
such as, for example, chromium, hafnium, molybdenum, niobium,
tantalum, tungsten, vanadium, and zirconium.
BACKGROUND OF THE INVENTION
[0003] The simplest electrolytic cell for use in electrowinning
metals consists of at least two electrodes and a molten
electrolyte. The electrode at which the electron producing
oxidation reaction occurs is the anode. The electrode at which an
electron consuming reduction reaction occurs is the cathode. The
direction of the electron flow in the circuit is always from anode
to cathode.
[0004] Metal particles are removed from solid cathodes by force of
gravity or forced fluid flow across the face of the cathode. If the
metal particles grow too large or strongly stick to the surface of
the cathode, the particles are difficult to dislodge and collect.
Other levers that people have found to control particle size and
morphology include: 1. feedstock concentration, 2. temperature, 3.
electrolyte composition including special additives, and 4. current
density.
[0005] Thus, there remains a need to control metal particle size
via cathode design. It an objective herein to design electrolytic
cells to produce powders fulfilling these needs through cathode
design and fluid flow which control the cross-sectional area and
height of particles growing from the surface of the cathode.
SUMMARY OF THE INVENTION
[0006] One aspect is for electrolytic cell comprising a cathode
having a non-uniform current distribution.
[0007] A further aspect is for a method of controlling the
morphology of a metal product in an electrolytic cell comprising
the steps of (a) providing an electrolytic cell comprising a molten
electrolyte, a cathode having a non-uniform current distribution in
contact with the molten electrolyte, and an anode in contact with
the molten electrolyte; (b) providing a metal compound to the
electrolyte; and (c) applying either a fixed voltage or a fixed
current across the anode and the cathode thereby depositing metal
on the cathode.
[0008] Other objects and advantages will become apparent to those
skilled in the art upon reference to the detailed description that
hereinafter follows.
DETAILED DESCRIPTION OF THE INVENTION
[0009] Applicants specifically incorporate the entire content of
all cited references in this disclosure. Further, when an amount,
concentration, or other value or parameter is given as either a
range, preferred range, or a list of upper preferable values and
lower preferable values, this is to be understood as specifically
disclosing all ranges formed from any pair of any upper range limit
or preferred value and any lower range limit or preferred value,
regardless of whether ranges are separately disclosed. Where a
range of numerical values is recited herein, unless otherwise
stated, the range is intended to include the endpoints thereof, and
all integers and fractions within the range. It is not intended
that the scope of the invention be limited to the specific values
recited when defining a range.
[0010] The disclosure herein, while relating in particular to the
production of titanium from a titanium oxide, is also applicable to
the production of titanium from other titanium compounds as well as
for the production of other metal compounds such as, for example,
chromium, hafnium, molybdenum, niobium, tantalum, tungsten,
vanadium, or zirconium from, for example, the respective oxides,
halides, nitrides, or sulfides.
[0011] Cathode design is used to aid in controlling the
cross-sectional area of electrodepositing metal particles by
controlling the lines of constant potential parallel to the face of
the cathode surface. Isopotential lines will be parallel to the
contour of the surface of the electrode and current distribution
will be orthogonal or perpendicular to these lines and with metal
deposition rates proportional to current density, the areas of
highest current density will have the largest metal deposition
rates. Furthermore, current density is highest where the distance
between cathode and anode is shortest so as particles grow from the
cathode, current densities at the tip of the growing particles are
highest.
[0012] One embodiment for producing this non-uniform current
distribution relates to a cathode comprising a wire mesh screen. If
a screen is used to control particle cross-sectional area,
particles can only grow where there is metal mesh, so, for example
if the mesh is 100 microns across, the cross-sectional area of the
particles formed will have an average cross-section of 100 microns.
Similarly various other cathode sizes, shapes, and designs can be
used to achieve the same non-uniform current distribution effect.
For example, additional useful cathode designs include, but are not
limited to, bristles, cones, rods, combinations thereof, and
combinations with mesh screens.
[0013] The height to which particles can grow from the cathode
surface can be controlled by adjusting the electrolyte flowrate so
the fluid would shear particles as they form to the desired height.
Alternatively, mechanical means can be used to dislodge the
particles as they grow toward the anode, for example, vibration.
Gas blowers can also be used to dislodge the particles.
[0014] There are preferred particle size ranges, particle aspect
ratio ranges and particle morphologies preferred for each powder
metallurgical processing method used to make various forms of metal
parts. For example, in metal injection molding using small parts,
symmetric spherical powders with particles less than 45 microns are
preferred. In press and sintering, 45 to 150 micron asymmetric
powder particles with aspect ratios of >1.5 are preferred. Those
who desire to make thin sheet from powder prefer asymmetric
particles with large aspect ratios and can tolerate wide size
distributions above 45 microns.
[0015] Anodes useful in standard electrolytic cells can be utilized
in an electrolytic cell containing a cathode having a non-uniform
current distribution. For example, carbon anodes, inert
dimensionally stable anodes, or a gas diffusion anodes fed with a
combustible gas are all useful in electrolytic cells containing a
cathode having a non-uniform current distribution. Other useful
anodes include consumable anodes containing a compound of the
metal, such as titanium, to be deposited at the cathode. Consumable
anodes are known in the art and an example of a suitable consumable
anode is described in U.S. Pat. No. 2,722,509 which is incorporated
herein by reference. One anode or multiple anodes can be employed.
In one embodiment, the anode can be a molten metal anode as
disclosed in U.S. Patent Publication No. 2005/0121333, incorporated
herein by reference.
[0016] Typically, the metal compound to be electrowon is a metal
oxide, for example titanium oxide or titanium dioxide. It is also
possible, however, to electrowin a metal from other metal compounds
that are not oxides. These compounds include, for example, halides
such as, e.g., TiCl.sub.3, nitrides such as, e.g., titanium
nitride, and carbides such as, e.g., titanium carbide. The metal
compound may be in the form of a rod, sheet or other artifact. If
the metal compound is in the form of swarf or particulate matter,
it may be held in a mesh basket. In another embodiment, the metal
compound can also be solubilized in the electrolyte, optionally
with the assistance of standard solubilizers.
[0017] By using more than one metal compound, it is possible to
produce an alloy. The metal compounds for alloy production may be
incorporated into the molten electrolyte simultaneously, added
stepwise, or in any other manner as is necessary to produce the
desired alloy. For example, an alloy of Ti--Al--V can be produced
by mixing aluminum oxide, vanadium oxide, and TiO.sub.2 in the
electrolyte thereby to produce an alloy of Ti--Al--V in the molten
zinc cathode. The E.sub.0 and current density should be adjusted to
deposit precise composition alloy particles.
[0018] The electrolyte consists of salts which are preferably more
stable than the equivalent salts of the metal which is being
deposited. Using salts with a low melting point, it is possible to
use mixtures if a fused salt melting at a lower temperature is
required, e.g. by utilizing a eutectic or near-eutectic mixture. It
is also advantageous to have, as an electrolyte, a salt with as
wide a difference between the melting and boiling points, since
this gives a wide operating temperature without excessive
vaporization. Exemplary electrolytes include, but are not limited
to, metal fluorides, metal chlorides, and mixtures thereof.
[0019] In one embodiment, the level of metal compound provided to
the molten electrolyte is continuously adjusted in order to insure
continuous operating electrolysis.
[0020] All of the compositions and methods disclosed and claimed
herein can be made and executed without undue experimentation in
light of the present disclosure. While the compositions and methods
of this invention have been described in terms of preferred
embodiments, it will be apparent to those of skill in the art that
variations may be applied to the compositions and methods and in
the steps or in the sequence of steps of the method described
herein without departing from the concept, spirit, and scope of the
invention. More specifically, it will be apparent that certain
agents which are chemically related may be substituted for the
agents described herein while the same or similar results would be
achieved. All such similar substitutes and modifications apparent
to those skilled in the art are deemed to be within the spirit,
scope, and concept of the invention as defined by the appended
claims.
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