U.S. patent application number 15/669984 was filed with the patent office on 2018-02-15 for methods for producing metal powders and metal masterbatches.
This patent application is currently assigned to Nanoscale Powders, LLC. The applicant listed for this patent is Nanoscale Powders, LLC. Invention is credited to Donald Finnerty, David Henderson, John Koenitzer, Andrew Matheson, Richard Van Lieshout.
Application Number | 20180043437 15/669984 |
Document ID | / |
Family ID | 61160726 |
Filed Date | 2018-02-15 |
United States Patent
Application |
20180043437 |
Kind Code |
A1 |
Finnerty; Donald ; et
al. |
February 15, 2018 |
Methods For Producing Metal Powders And Metal Masterbatches
Abstract
A method for producing a metal powder that combines molten
reducing metal and metal halide in a space that is substantially
free of oxygen and water, wherein the molten reducing metal is
sodium and/or potassium, or aluminum (or magnesium or titanium) and
is present in a stoichiometric excess to the metal halide which is
a solid or liquid, thereby producing metal particles and salt,
removing unreacted reducing metal, optionally removing the salt,
and recovering the metal powder, is described. A method for
producing a metal masterbatch wherein the molten reducing metal is
aluminum, magnesium, and/or titanium and after combining molten
aluminum (or magnesium or titanium) and metal halide in the
reaction space, substantially removing the produced metal salt to
obtain the metal masterbatch which comprises at least a portion of
the molten aluminum (or magnesium or titanium) and at least one
metal also is described.
Inventors: |
Finnerty; Donald; (New
Freedom, PA) ; Henderson; David; (Concord, NH)
; Koenitzer; John; (Carlisle, MA) ; Matheson;
Andrew; (Belmont, MA) ; Van Lieshout; Richard;
(New Freedom, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nanoscale Powders, LLC |
Boston |
MA |
US |
|
|
Assignee: |
Nanoscale Powders, LLC
Boston
MA
|
Family ID: |
61160726 |
Appl. No.: |
15/669984 |
Filed: |
August 7, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62374212 |
Aug 12, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 9/28 20130101; C22C
1/0491 20130101; C22C 14/00 20130101; B22F 2304/10 20130101; B22F
2301/205 20130101; C22B 34/14 20130101; B22F 9/24 20130101; C22B
5/04 20130101; B22F 9/20 20130101; C22B 34/1277 20130101 |
International
Class: |
B22F 9/24 20060101
B22F009/24; C22B 34/12 20060101 C22B034/12; C22C 14/00 20060101
C22C014/00; C22B 34/14 20060101 C22B034/14 |
Claims
1. A method for producing a metal powder, the method comprising: a)
combining at least one metal halide and at least one molten
reducing metal in a space that is substantially free of oxygen and
water, wherein said molten reducing metal is present in a
stoichiometric excess to the metal halide, to obtain a reaction
product that comprises at least one metal salt and metal, and
wherein the molten reducing metal comprises i) at least 90 wt %
sodium or potassium or a mixture of potassium and sodium or ii) at
least 90 wt % aluminum, magnesium, or titanium based on total
weight of said molten reducing metal, and the at least one metal
halide is a solid or liquid, with the proviso that the molten
reducing metal is different from the metal of the at least one
metal halide; b) substantially removing unreacted said molten
reducing metal in said reaction product; c) recovering at least
said metal, wherein the metal of the metal salt is the molten
reducing metal, and the `metal` recovered from the reaction product
is from the metal of the metal halide.
2. The method of claim 1, wherein in step c), the at least one
metal salt is recovered with said metal.
3. The method of claim 2, wherein said method further comprises d)
separating said metal from said metal salt.
4. The method of claim 1, wherein two or more metal halides are
used and wherein said metal recovered comprises a metal alloy or
intermetallic compound from each metal of the two or more metal
halides.
5. The method of claim 1, wherein said at least one metal halide is
at least one metal chloride.
6. A method for producing a metal masterbatch, the method
comprising: a) combining at least one metal halide and at least one
molten reducing metal in a space that is substantially free of
oxygen and water, wherein said molten reducing metal is present in
a stoichiometric excess to the metal halide, to obtain a reaction
product that comprises at least one metal salt and metal, and
wherein the molten reducing metal comprises at least 90 wt %
aluminum, magnesium, or titanium based on total weight of said
molten reducing metal, and the at least one metal halide is a solid
or liquid, with the proviso that the molten reducing metal is
different from the metal of the at least one metal halide; b)
substantially removing said at least one metal salt to obtain said
metal masterbatch comprising at least a portion of said molten
reducing metal and the metal, wherein the metal of the metal salt
is the molten reducing metal, and the `metal` recovered from the
reaction product is from the metal of the metal halide, wherein the
removing of at least one metal salt occurs during or after
formation of said reaction product.
7. The method of claim 1, wherein said at least one metal halide
comprises Ti halide, V halide, Cr halide, Mn halide, Fe halide, Co
halide, Ni halide, Cu halide, Zn halide, Ga halide, Ge halide, As
halide, Se halide, Zr halide, Nb halide, Mo halide, Ru halide, Rh
halide, Pd halide, Ag halide, Cd halide, In halide, Sn halide, Sb
halide, C halide, Si halide, Te halide, Hf halide, Ta halide, W
halide, Hg halide, Tl halide, Pb halide, or Bi halide or any
combination thereof.
8. The method of claim 6, wherein said at least one metal halide is
at least one metal chloride.
9. The method of claim 6, wherein two or more metal halides are
used and wherein said metal recovered comprises a metal alloy,
intermetallic compound, or ceramic from each metal of the two or
more metal halides.
10. The method of claim 1, wherein said at least one metal halide
is at least one metal chloride.
11. The method of claim 6, wherein said metal masterbatch comprises
aluminum, hafnium, and zirconium.
12. The method of claim 6, further comprising adding a carbide,
nitride, or boride forming component to said metal halide or to
said molten reducing metal or both, and wherein said metal of the
reaction product comprises a metal carbide, a metal nitride, or a
metal boride or any combination thereof.
13. The method of claim 12, wherein said carbide forming component
comprises carbon containing gas, carbon tetrachloride or solid
carbon.
14. The method of claim 12, wherein said boride forming component
comprises boron trichloride or a boron hydride.
15. The method of claim 6, wherein said substantially removing said
at least one metal salt comprises vaporization of said at least one
metal salt and removal thereof from said metal masterbatch.
16. The method of claim 1, wherein said at least one metal halide
is combined as a solid with said molten reducing metal.
17. The method of claim 16, wherein said at least one metal halide
is combined as a solid with a portion of said molten reducing metal
to form a mixture, and said portion of said molten reducing metal
is at a temperature that avoids reaction with said metal
halide.
18. The method of claim 17, said method further comprising
combining said mixture with part or all of the remaining portion of
said molten reducing metal that is at a temperature that permits
reaction with said metal halide.
19. The method of claim 1, wherein said combined at least one metal
halide and at least one molten reducing metal passes through a
reaction zone that comprises at least one closed pipe that causes
turbulence in combined at least one metal halide and at least one
molten reducing metal and that optionally empties into a tank or
filter.
20. The method of claim 1, wherein said molten reducing metal
comprises said at least 90 wt % sodium or potassium or a mixture of
potassium and sodium, and wherein combined at least one metal
halide and at least one molten reducing metal passes through a
reaction zone that empties into a settling tank that includes at
least one outlet that is located at a height in the settling tank
that permits said molten reducing metal from step b) to at least
partly be removed by said outlet but not said molten salt or said
metal, and wherein said combined at least one metal halide, at
least one molten reducing metal, and at least one metal salt
together are at a temperature that results in phase separation of
the molten reducing metal from said metal salt and said metal.
21. The method of claim 18, wherein said combining said mixture
with part or all of the remaining portion of said molten reducing
metal that is at a temperature that permits reaction with said
metal halide comprises utilizing an eductor.
22. The method of claim 1, prior to at least step b), wherein said
molten reducing metal comprises at least 90 wt % sodium or
potassium or a mixture of potassium and sodium, and wherein at
least one metal halide, at least one molten reducing metal and at
least one metal salt together are at a temperature that causes
phase separation of the molten reducing metal from said metal salt
and said metal.
23. The method of claim 1, wherein said substantially removing said
at least one metal salt comprises permitting the vaporization of at
least a portion of said at least one metal salt and removal thereof
from said metal masterbatch.
24. The method of claim 1, wherein the at least one metal halide
comprises at least a first metal halide and a second metal halide,
with the first metal halide reactive with the metal salt and the
second metal halide non-reactive with the metal salt, wherein the
metal of the second metal halide is the same or different from the
molten reducing metal.
25. The method of claim 6, wherein the at least one metal halide
comprises at least a first metal halide and a second metal halide,
with the first metal halide reactive with the metal salt and the
second metal halide non-reactive with the metal salt, wherein the
metal of the second metal halide is the same or different from the
molten reducing metal.
26. The method of claim 24, wherein the second metal halide is NaCl
and the molten reducing metal is said at least 90 wt % sodium, and
the first metal halide is AlCl.sub.3.
27. The method of claim 25, wherein the second metal halide is NaCl
and the molten reducing metal is said at least 90 wt % sodium, and
the first metal halide is AlCl.sub.3.
28. The method of claim 6, wherein said at least one metal halide
comprises Ti halide, V halide, Cr halide, Mn halide, Fe halide, Co
halide, Ni halide, Cu halide, Zn halide, Ga halide, Ge halide, As
halide, Se halide, Zr halide, Nb halide, Mo halide, Ru halide, Rh
halide, Pd halide, Ag halide, Cd halide, In halide, C halide, Si
halide, Sn halide, Sb halide, Te halide, Hf halide, Ta halide, W
halide, Hg halide, Tl halide, Pb halide, or Bi halide or any
combination thereof.
29. The method of claim 24, wherein said first metal halide and
said second metal halide form a eutectic mixture.
30. The method of claim 1, wherein said at least one metal halide
is two or more metal halides, and one metal halide is a solid or
liquid and the other metal halide is a vapor, solid, or liquid.
31. The method of claim 6, wherein said at one least metal halide
is two or more metal halides, and one metal halide is a solid or
liquid and the other metal halide is a vapor, solid, or liquid.
32. The method of claim 1, wherein said metal salt at least
partially coats or encapsulates said metal.
33. The method of claim 1, wherein said molten reducing metal is
aluminum alloy.
34. The method of claim 1, wherein said molten reducing metal is
magnesium alloy.
35. The method of claim 1, wherein said molten reducing metal is
titanium alloy.
36. The method of claim 6, wherein said molten reducing metal is
aluminum alloy.
37. The method of claim 6, wherein said molten reducing metal is
magnesium alloy.
38. The method of claim 6, wherein said molten reducing metal is
titanium alloy.
Description
[0001] This application claims the benefit under 35 U.S.C.
.sctn.119(e) of prior U.S. Provisional Patent Application No.
62/374,212, filed Aug. 12, 2016, which is incorporated in its
entirety by reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to methods for producing metal
powders, salt-coated metal powders, and metal masterbatches.
[0003] Metal powders can be used for advanced metallurgical
processes, such as near net shape powder pressing, and additive
manufacturing, including laser metal deposition (LMD), direct metal
laser sintering (DMLS), selective laser sintering (SLS), and
selective laser melting (SLM). The end products find applications
in a wide variety of industries, including aerospace, medical, and
electronics. Other applications include the production of wire bar
stock for rolling into medical alloys (e.g., superconducting wires
for MRI machines), sputtering targets in electronics manufacturing
for thin film metal deposition in displays, use in semiconductors
and data storage devices, superalloy production, intermetallic
powders for the manufacture of jet engine components, and
photovoltaic cells. Metal powders can also be pressed into dense
objects using conventional pressing techniques. Salt-coated metal
powders can be used for particle strengthening of metals.
[0004] Preferably, metal powders are highly pure and have
consistent flow properties. However, processes for achieving metal
powders having such characteristics require further development.
Accordingly, there is a need in the art for methods of making pure
metal powders that have adequate flow properties such that the
powders can be used for advanced manufacturing applications.
SUMMARY OF THE INVENTION
[0005] A feature of the present invention is to provide a process
for producing high purity, low oxygen content metal powders with
good flow properties.
[0006] A further feature of the present invention is to provide a
method for producing a metal masterbatch that comprises unreacted
aluminum reducing metal and at least one other metal formed from a
reaction of the aluminum metal and a metal halide.
[0007] A further feature of the present invention is to provide a
method for producing a metal masterbatch that comprises unreacted
magnesium reducing metal and at least one other metal formed from a
reaction of the magnesium metal and a metal halide.
[0008] A further feature of the present invention is to provide a
method for producing a metal masterbatch that comprises unreacted
titanium reducing metal and at least one other metal formed from a
reaction of the titanium metal and a metal halide.
[0009] Additional features and advantages of the present invention
will be set forth in part in the description that follows, and in
part will be apparent from the description, or may be learned by
practice of the present invention. The objectives and other
advantages of the present invention will be realized and attained
by means of the elements and combinations particularly pointed out
in the description and appended claims.
[0010] To achieve these and other advantages, and in accordance
with the purposes of the present invention, as embodied and broadly
described herein, the present invention relates to a method for
producing a metal powder. The method includes: a) combining at
least one metal halide and at least one molten reducing metal in a
space that is substantially free of oxygen and water to obtain a
reaction product that includes at least one metal salt and metal;
b) substantially removing the molten reducing metal in the reaction
product; c) recovering at least the metal, and optionally the at
least one metal salt. The molten reducing metal is present in a
stoichiometric excess to the metal halide. The molten reducing
metal can be primarily 1) sodium and/or potassium or 2) aluminum,
or magnesium, or titanium. The at least one metal halide is a solid
or liquid, with the proviso that the molten reducing metal is
different from the metal of the at least one metal halide. In the
reaction product, the metal of the metal salt is the molten
reducing metal, and the `metal` recovered from the reaction product
is from the metal of the metal halide.
[0011] The present invention further relates to a method for
producing a metal masterbatch. The method includes: a) combining at
least one metal halide and at least one molten reducing metal in a
space that is substantially free of oxygen and water to obtain a
reaction product that comprises at least one metal salt and metal;
b) substantially removing the at least one metal salt to obtain the
metal masterbatch comprising at least a portion of the molten
reducing metal, and at least one other metal. Step b) can occur as
the reaction product forms and/or after the reaction product forms.
The molten reducing metal is present in a stoichiometric excess to
the metal halide. The molten reducing metal can be or primarily be
aluminum or an alloy thereof, magnesium or an alloy thereof, or
titanium or an alloy thereof. The at least one metal halide is a
solid or liquid, with the proviso that the molten reducing metal is
different from the metal of the at least one metal halide. The
metal of the metal salt is the molten reducing metal, and the
`other metal` recovered from the reaction product is from the metal
of the metal halide.
[0012] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory only and are intended to provide a further
explanation of the present invention, as claimed.
[0013] The accompanying drawings, which are incorporated in and
constitute a part of this application, illustrate some of the
features of the present invention and together with the
description, serve to explain the principles of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a process flow chart describing a method according
to an example of the present application.
[0015] FIG. 2 is a process flow diagram describing a method
according to an example of the present application.
[0016] FIG. 3 is a process flow diagram describing a method
according to an example of the present application.
[0017] FIG. 4 is a process flow diagram describing a method
according to an example of the present application.
[0018] FIG. 5 is a process flow diagram describing a method
according to an example of the present application.
[0019] FIG. 6 is a schematic illustration of a suitable bake out
vessel for a process according to an example of the present
application.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention relates to methods of producing metal
powders and/or metal masterbatches that incorporate metal halide
reduction reactions. These processes can yield high purity and/or
low oxygen content products. These methods can be practiced in
continuous, semi-continuous, or batch arrangements. As an option,
methods can be practiced as a continuous process with recycling of
excess reactant. The term "metal powders" can refer to metallic
primary particles, aggregates, agglomerates, other discrete metal
particles, or any combination thereof. The term "masterbatch" can
refer to a physical mixture comprised predominantly of two or more
different kinds of metals (e.g. in elemental form), wherein the
mixed metals retain their own respective chemical properties and
have not chemically reacted with each other. The masterbatch
optionally can be or include a metal alloy, an intermetallic
compound, metal carbide, metal nitride, metal boride, metal
silicide, metal aluminide, or any combination thereof, or other
metal compounds (e.g., one or more ceramics) in the alternative or
in addition to the indicated physical mixture of different
elemental metals.
[0021] Metal powders can be formed in a method of the present
invention by reducing a solid or liquid metal halide with a molten
reducing metal in a sealed reaction vessel that is substantially
free of oxygen and water (e.g., below 100 ppm oxygen and below 100
ppm water), wherein the molten reducing metal is present in a
stoichiometric excess to the metal halide. Metal powders and a
metal salt can be produced, which are separated from the unreacted
molten reducing metal. As an option, the metal powder can be
separated from the metal salt (e.g., from 95 wt % to 100 wt % of
the total metal powder present can be separated from the metal
salt).
[0022] In the present invention, the molten reducing metal means
that the reducing metal is present as a liquid and not a vapor or a
solid. For purposes of the present invention, as an option, minor
amounts, such as below 5 wt %, below 2.5 wt %, below 1 wt %, below
0.5 wt %, below 0.25 wt %, below 0.1 wt %, below 0.05 wt %, below
0.01 wt % or below 0.001 wt % or zero wt % (based on the total
weight of the reducing metal present) can be optionally present in
a state other than a liquid or molten state.
[0023] In the present invention, the molten reducing metal can
comprise, consists essentially of, or consists of, or include
either 1) potassium metal or sodium metal or a combination of
potassium metal and sodium metal (e.g., an alloy of sodium and
potassium), or 2) aluminum metal or alloy thereof, or magnesium
metal or alloy thereof, or titanium metal or alloy thereof. For
option 1), the molten reducing metal can comprise at least 90 wt %
sodium metal, at least 90 wt % potassium metal, or at least 90 wt %
of a combination or mixture or alloy of potassium metal and sodium
metal. This percent of at least 90 wt % in each instance can be at
least 95 wt %, at least 99 wt %, at least 99.5 wt %, at least 99.9
wt %, or 100 wt % such as from 90 wt % to 100 wt %, or from 95 wt %
to 100 wt % (all based on the total weight of the molten reducing
metal). When the amount of molten reducing metal for potassium
and/or sodium is less than 100 wt % but at least 90 wt %, the
remaining amount can be, or include for instance other metals in a
molten state, such as calcium and/or magnesium and/or one or more
other metals, and/or can be one or more oxides. For option 2), the
molten reducing metal can comprise at least 90 wt % aluminum metal,
or magnesium metal or titanium metal, such as at least 95 wt %, at
least 99 wt %, at least 99.5 wt %, at least 99.9 wt %, or 100 wt %
such as from 90 wt % to 100 wt %, or from 95 wt % to 100 wt % (all
based on the total weight of the molten reducing metal). For
purposes of the present invention, the `aluminum metal` can be or
include one or more aluminum alloys. These aluminum alloys
typically have about 90 wt % or more of aluminum in the alloy based
on the total weight of the alloy. For purposes of the present
invention, the `magnesium metal` can be or include one or more
magnesium alloys. These magnesium alloys typically have about 90 wt
% or more of magnesium in the alloy based on the total weight of
the alloy. For purposes of the present invention, the `titanium
metal` can be or include one or more titanium alloys. These
titanium alloys typically have about 90 wt % or more of titanium in
the alloy based on the total weight of the alloy. For purposes of
the present invention, for either option or any embodiment of the
present invention, these percentages for potassium, sodium,
aluminum, magnesium, and titanium are based total weight of the
components or materials only in the molten state and not in any
other state. Also, for purposes of the present invention, unless
stated otherwise, reference to "potassium" or "sodium" or
"aluminum" or "magnesium" or "titanium" means the above weight
percents or purities as provided here. An alloy is a mixture of
metals or a mixture of a metal and another element. Alloys are
defined by a metallic bonding character. An alloy may be a solid
solution of metal elements (a single phase) or a mixture of
metallic phases (two or more solutions). In the case of aluminum
alloy, the predominate element is aluminum. In the case of
magnesium alloy, the predominate element is magnesium. In the case
of titanium alloy, the predominate element is titanium. Preferred
percentages are provided above.
[0024] In the methods of the present invention, the at least one
metal halide can be, include, consists, of or comprises Ti halide,
V halide, Cr halide, Mn halide, Fe halide, Co halide, Ni halide, Cu
halide, Zn halide, Ga halide, Ge halide, As halide, Se halide, Zr
halide, Nb halide, Mo halide, Ru halide, Rh halide, Pd halide, Ag
halide, Cd halide, In halide, Sn halide, Sb halide, C halide, Si
halide, Te halide, Hf halide, Ta halide, W halide, Hg halide, Tl
halide, Pb halide, or Bi halide or any combination thereof. The
halide can be chloride, bromide or iodide. Any of the halides in
this list can be or exclusively be a chloride (in other words, one
or more metal chlorides).
[0025] As stated, in the present invention, for the various methods
and reactions described herein, the metal of the formed metal salt
is (from) the molten reducing metal (e.g., Na, K, or Al, Mg, Ti),
and the `metal` recovered from the reaction product is from the
metal of the metal halide (e.g, Ti, V, Ta, Nb, Sn, Si, Zr, Al, Cr,
Mn, Fe, Co, Ni, Cu, Zn, C, Si, Ga, Ge, As, Se, Mo, Ru, Rh, Pd, Ag,
Cd, In, Sb, Te, Hf, W, Hg, Ti, Pb, Bi, and the like), or a ceramic
thereof, or a nitride thereof, or a boride thereof, or a carbide
thereof. Two or more halides can be used. When two or more metal
halides are used, one metal halide is reactive and the second metal
halide can be reactive or non-reactive with the molten reducing
metal. When two or more metal halides are used (e.g, two metal
halides, three metal halides or more), each of the metals of the
metal halide, if reactive, can result in obtaining a metal alloy of
these metals or an intermetallic compound of these metals. If a
non-reactive metal halide is present, the metal of the metal halide
will not be part of the resulting metal. A non-reactive metal
halide, if present, for instance, can be used as an additive,
forming a complex halide salt, to lower the melting point of the
reactive metal halide, or to reduce the vapor pressure of the
reactive metal halide, or to form liquid mixtures or solutions with
other metal halides. For instance, NaCl (non-reactive metal halide)
can be used with a reactive metal halide (AlCl.sub.3). The mol % of
the non-reactive metal halide to reactive halide can be from 1:99
to 99:1, and preferably is 20:80 to 80:20, or 40:60 to 60:40, or
from 50 mol % to 65 mol % of the non-reactive metal halide to 60
mol % to 35 mol % of the reactive metal halide. A phase diagram of
the two metal halides can provide preferred mol % ratios to achieve
the desired lower melting point. When two or more halides are used,
they can be added as a mixture or separately or at different times.
When a non-reactive metal halide is used with a reactive metal
halide, the two should be added as a mixture and can be added as a
liquid or solid. When two or more metal halides are used, at least
one is a solid or liquid, but the other metal halide can be a
vapor, liquid, or solid.
[0026] As an option, in the present invention, the metal salt
formed in any of the processes of the present invention can form a
partial or complete coating around the metal that is formed in the
reaction product. As described herein, the metal that is formed can
be present as a metal powder and be present as primary particles,
agglomerates, aggregates, briquettes and the like. The metal salt
coating can be any thickness around the metal formed (e.g, around
the metal powder), for instance, from about 1 nm to about 100 nm or
more, such as from about 100 nm to about 5 .mu.m or from about 500
nm to about 10 .mu.m or thicknesses above or below any of these
ranges. The salt coating can be removed by any salt removing
technique such as an aqueous washing or sublimation and the
like.
[0027] The term "substantially free of oxygen and water" as used
herein means that any content of oxygen or water present during the
combining of the reducing metal and metal halide is insufficient to
prevent the metal powder product from having the purity described
herein. For instance, the purity (e.g., by wt %) of the finished
metal powder can be 95% metal or greater, or 99% metal or greater
such as from about 99.5% metal or greater and more preferably
99.95% metal or greater and even more preferably 99.99% metal or
greater, or 99.995% metal or greater or 99.999% metal or greater,
wherein the metal refers to the metal of the metal halide reactant
and not the reducing metal or other source of metal. The metal
powders produced by the methods described herein can be highly
pure. In particular, the metal powders can have a minimal amount of
oxygen bonded to the metal. Reducing the quantity of oxygen bonded
to the metal powder has been technically challenging in the art,
and thus improvements in metal powder purity represent a
substantial technical improvement. The reaction vessel that is
substantially free of oxygen and water can be filled or purged with
an inert gas, preferably argon, prior to or while maintaining the
molten reducing metal in the sealed reaction vessel.
[0028] In methods of the present invention, at least one metal
halide can be reacted with a stoichiometric excess of a reducing
metal. The term "stoichiometric excess" means the molar amount of
the molten reducing metal present in the reaction zone is in excess
based upon the amount of metal halide present and available to
react therewith. The molten reducing metal can be in at least a 5:1
stoichiometric excess to the metal halide, though in some cases it
can be less than a 5:1 stoichiometric excess. In other cases, it
can be more than a 5:1 stoichiometric excess, such as at least a
10:1 stoichiometric excess, or other values.
[0029] When a solid metal halide is used in the method of the
present invention, the reducing metal is heated to a temperature
above its melting point and below its boiling point to provide a
molten material which can be split into a stream that is passed
through a cooler to provide a cooled stream that has a temperature
that is still above the melting point of the reducing metal and
below a reaction temperature of the reducing metal with respect to
metal halide, and another stream that is passed through a heater to
provide a (further) heated stream of the reducing metal. The split
can be from 10:90 to 90:10 by volume (cooled stream:heated stream),
or from 20:80 to 80:20, or from 40:60 to 60:40 and the like. The
cooled stream of reducing metal is combined with solid metal
halide, such as metal halide in powder form, to disperse the metal
halide therein to form a mixture (e.g., a slurry). As an option,
the heated stream of reducing metal can be heated to a temperature
such that when its mass is combined with the mass of the mixture of
solid metal halide and cooled reducing metal, the resulting
combination has a temperature at or above a reaction temperature of
the reducing metal with respect to metal halide. As an option,
additional heating can be provided before the combination reaches
the reaction zone or, at the reaction zone, or both locations, to
provide a reaction temperature. The heated stream of reducing metal
and the mixture of cooled reducing metal and solid metal halide can
be combined, such as in an eductor, and passed through a reaction
zone with the molten reducing metal present in stoichiometric
excess to the metal halide to produce a metal reaction product. As
indicated, additional heating of the reducing metal and metal
halide materials can be provided before and/or in the reaction zone
to raise the temperature of the mixture to a reaction temperature,
or maintain the materials at a reaction temperature, or both. The
space where the metal halide and molten reducing metal are
contacting at a reaction temperature, such as the reaction zone,
and/or may be in the eductor, preferably are maintained to be
substantially free of oxygen and water. The metal reaction product
and remaining molten reducing metal can be collected from the
reaction zone in a settling and bake out vessel. The remaining
(unreacted) molten reducing metal in the reaction product can be
substantially removed, such as by pouring or siphoning or other
separation method. Metal salt and the metal reaction products that
remain in the vessel can be recovered, and the metal reaction
product can be separated from the metal salt.
[0030] When a liquid metal halide is used in the method, the
reducing metal can be passed through a heater to provide a heated
liquid stream, such as described hereinabove, that can provide a
reaction temperature with respect to metal halide when the heated
reducing metal and metal halide are combined, and without the
reducing metal being split into different streams for separate
cooling and heating. Liquid metal halide is introduced into the
heated stream of reducing metal, such as by injection, and the
resulting mixture of heated reducing metal and liquid metal halide
are passed through a reaction zone with the molten reducing metal
present in stoichiometric excess to the metal halide to produce a
metal reaction product. The space, such as the reaction zone, or
which may be the flow passageway connecting the location of liquid
metal halide introduction and the reaction zone, where the metal
halide and molten reducing metal are contacting at a reaction
temperature, can be maintained to be substantially free of oxygen
and water as previously described. The metal reaction product and
remaining molten reducing metal can be collected from the reaction
zone in a settling and bake out vessel, and the remaining molten
reducing metal in the reaction product can be substantially
removed, and the metal salt and the metal reaction products that
remain can be recovered, and the metal reaction product can be
separated from the metal salt, as previously described.
[0031] In general, when the molten reducing metal is sodium and/or
potassium, once the reaction product is formed and is present with
the excess or unreacted molten reducing metal, at least a portion
of the excess or unreacted molten reducing metal (e.g., from 10 wt
% to 100 wt %, or from 25 wt % to 99.5 wt %, or from 50 wt % to 99
wt %, or from 75 wt % to 99 wt %, or from 85 wt % to 99 wt %, or
from 95 wt % to 99.5 wt % by weight of the excess or unreacted
molten reducing metal) can be separated from the reaction product
(e.g., the metal formed and the metal salt) by causing a phase
separation between the excess or unreacted molten reducing metal
and the metal and metal salt. Generally in such a process, and if
the temperature of the molten reducing metal and metal and metal
salt are high enough, the excess or unreacted molten metal will
phase separate (liquid phase separation) and generally is on top
with the other phase of metal and metal salt at the bottom. This
permits easy separation of the two phases by various techniques,
such as decanting, siphoning, and the like. This generally occurs
when the overall mixture is at a temperature above the melting
point of the metal salt present. For instance, when the metal salt
is NaCl, a temperature above 801.degree. C. is used to achieve
phase separation. Then as stated, the remaining amount of molten
reducing metal can be removed by the various techniques described
herein.
[0032] In general, when the molten reducing metal is aluminum (or
alloy thereof), magnesium (or alloy thereof) or titanium (or alloy
thereof) phase separation is not used and generally it is preferred
to keep the excess or unused aluminum (or magnesium or titanium)
present and to instead remove the metal salt of the reaction
product by heating the reaction product and excess or unused
aluminum (or magnesium or titanium) to a temperature that causes
vaporization of the metal salt. This vaporization and removal can
occur as the reaction product forms and/or after formation of the
reaction product. Any amount of the metal salt can be removed this
way, such as from about 10 wt % to 100 wt %, or from 25 wt % to
99.5 wt %, or from 50 wt % to 99 wt %, or from 75 wt % to 99 wt %,
or from 85 wt % to 99 wt %, or from 95 wt % to 99.5 wt % by weight
of the metal salt present.
[0033] The metal powders produced by the methods described herein
can have a small particle size, and/or narrow particle size
distribution, and/or improved flow characteristics, or any
combinations of these, which can be determined using a Hall flow
meter according to standardized testing procedures, such as ASTM
B213. The methods described herein can produce primary particles
having a size ranging from about 5 to about 250 nanometers, or from
about 25 to about 200 nanometers, or from about 50 to about 175
micrometers, or from about 75 to about 150 micrometers, or other
sizes. The primary particles can form aggregates having an
aggregate size of from about 1 to about 250 microns in diameter,
from about 25 to about 200 nanometers, or from about 50 to about
175 micrometers, or from about 75 to about 150 micrometers, or
other sizes. Particle size can be determined by scanning electron
microscopy (SEM) imaging. The particle sizes indicated in this
respect can refer to average size, D50 size, or D90 size. Electron
microscopy works by bombarding a sample with a stream of electrons
and monitoring either the resulting scattering (SEM) effects. These
electrons are detected and converted into magnified images of
particles in the sample dispersion. Image analysis software uses
this information to generate particle size data for individual
particles, number based size distributions for the entire
dispersion and various shape and morphological parameters. SEM can
produce accurate 3D images of particles.
[0034] Three variables can exhibit a high degree of influence on
powder particle size: the temperature at which the reaction occurs,
the relative concentration of the metal halide to the concentration
of the reducing metal, and the melting point of the produced metal
or alloy powder. Typically, the metal powder particle size is
proportional to these variables according to Formula (1), where T
is the temperature in Kelvin:
Metal Powder Particle Size .alpha. [ [ Concentration of Metal
Halide ] [ Concentration of Reducing Metal ] ] T 1 3 ( 1 )
##EQU00001##
[0035] In view of the Formula (1), reaction conditions that favor
the production of smaller particles include a lower temperature and
a low concentration of metal halide relative to the concentration
of the reducing metal. Without wishing to be bound by theory, the
process of particle and aggregate formation parallels standard
particle flame synthesis processes. Thus, when a primary particle
or cluster encounters another cluster, they stick together to form
an aggregate that tends to have an open structure, provided the
conditions (temperature and particle density) permit continued
aggregation. Thus, smaller aggregates are produced when the
concentration of the metal halide is lower because the metal powder
particles that form are more dispersed in the reducing metal, and
therefore the metal powder particles are less likely to physically
interact and form aggregates. Finally, the particles are large and
cool enough that the aggregates freeze. Additionally, at higher
temperatures the particles are stickier so they coalesce for
longer. Therefore, the primary particles are larger and have a
smaller surface area. At higher concentrations, the particles can
collide and coalesce more rapidly before they cool, again leading
to larger primary particles and lower surface area.
[0036] A method for producing a metal masterbatch is provided that
uses a metal halide reduction reaction as part of the process. With
aluminum or an alloy thereof used as a reducing metal (in the
weight percent amounts indicated earlier) for combining with a
solid or liquid metal halide(s) as described herein, the reaction
product metal and a salt can be produced in the reaction zone and
collected with excess reducing metal in a separate vessel or tank,
wherein the salt, and not the excess reducing metal, is separated
out, so as to obtain a metal masterbatch comprising at least a
portion of the reducing metal and reaction product metal. The
reaction product metal can be, depending on the number of different
starting metal halides used and types, a metal, a metal alloy, an
intermetallic (intermetallic compound), or a ceramic (boride or
carbide). For instance, if AlCl.sub.3 and carbon tetrachloride are
used as the two starting metal halides, the resulting metal can be
an aluminum carbide. If the metal halides used are TiCl.sub.4 and
SiCl.sub.4, the resulting metal can be a Ti--Si alloy or
intermetallic, and so on. Aluminum trichloride, for instance,
sublimates at about 180.degree. C. at one atmosphere pressure, so
it can be selectively volatized and removed from excess aluminum
and the metal formed from the metal halide reduction reaction which
have a higher boiling points. Other aluminum halides with
comparable sublimation or vaporization temperatures with respect to
aluminum and reaction product metal can be selectively removed in a
similar manner.
[0037] Another advantage of the methods described herein is that
they can reduce the amount of corrosion that occurs. For example,
previous gas phase reactions typically offer a lower reaction
throughput, and they can also yield substantial corrosion because
of the increase in the reaction rate for chloride corrosion
processes at elevated temperatures. The methods of the present
invention can avoid or have reduced risk of these drawbacks and
disadvantages.
[0038] As described herein, reacting a metal halide with a molten
reducing metal using split flow of heated and cooled streams of
molten reducing metal for solid metal halide processing, or
injection of liquid metal halide, can yield particles that are
highly pure and provide improved flow properties. Preferably, the
reactions occur under conditions that remain constant or bounded by
a limited range of temperatures and stoichiometry. The methods
described herein typically involve steps that are shown in FIG.
1.
[0039] The overall process, indicated as 100 in FIG. 1, has several
alternatives, including with respect to whether a solid or liquid
metal halide is used, whether a metal powder product or a
masterbatch product is desired, and other alternatives and options
indicated herein. First, molten reducing metal (as described
herein), such as 1) sodium, potassium or both, or 2) aluminum or
magnesium or titanium, is provided 101. These metals are used for
illustration, and other reducing metals may be used. Sodium has a
melting point of about 98.degree. C., and aluminum has a melting
temperature of about 660.degree. C. Alternative A in the process
shown in FIG. 1 is for solid metal halide processing, and
alternative B is for liquid metal halide processing. In alternative
A, the molten reducing metal is split into two streams (102),
wherein a portion of the reducing metal is cooled below a reaction
temperature of the metal halide (103A) and the remaining portion is
heated to a reaction temperature with metal halide (103B). The
cooled stream of reducing metal is fed to an area (e.g., funnel)
where solid metal halide is added, such as gravity fed as a dry
flowable powder, to the flow of reducing metal through the funnel
(104). The metal halide powder combines with the cooled reducing
metal, and can form a slurry. The slurry from step 104 and the
heated reducing metal are combined in a mixing/dispersing device
(105), such as in an eductor. The resulting mixture or dispersion
is fed to a reaction zone (106), such as a pipe, mixing tank with
an agitator forming a vortex, or other reaction zone arrangement.
The metal halide can be reduced by the reducing metal to produce
metal particles. In alternative B, the molten reducing metal is
heated (122) with no split stream for cooling. Liquid metal halide
is injected or otherwise introduced into the heated molten reducing
metal (123), and the resulting combination is fed to the reaction
zone (106). After the reaction in the reaction zone for either
alternative A or B, the remaining, unreacted reducing metal can be
removed from the metal particles in a settling/bake out tank (107).
The removed excess reducing metal can be recycled by filtering and
cooling it for reuse (108). In this option, the salt byproduct then
can be removed, and the metal powder particles are recovered (not
shown). As shown in FIG. 1, another method of the present invention
is the formation of a masterbatch, such as using aluminum reducing
metal (or magnesium or titanium), wherein the reaction products and
excess (unreacted) reducing aluminum metal (or magnesium metal or
titanium metal) from the reaction zone (106) are fed to a
volatization/masterbatch formation tank where aluminum salt
reaction (or magnesium salt reaction or titanium salt reaction)
by-product of the reduction reaction is removed, such as by
heat-volatization (124) alone or in combination with other salt
removal techniques, to leave unreacted aluminum (or magnesium or
titanium) and reaction product metal in the tank as a masterbatch
material. For the case of making a masterbatch in "magnesium" or
"titanium," the resulting magnesium or titanium salt is removed as
either a slag from the surface of the reducing metal or is
heat-volatilized.
[0040] Examples of process and equipment arrangements that can be
used to perform these process flow options are shown in FIGS. 2, 3,
4, and 5.
[0041] In FIG. 2, a method for making a metal powder of the present
invention, indicated as 200, is shown which includes use of a solid
metal halide 207 and a storage tank 201 of molten reducing metal
(e.g., 1) Na and/or K, or 2) Al, Mg, or Ti). The reducing metal is
introduced in stoichiometric excess with respect to the metal
halide in this method, such as in a range described herein. The
sodium and/or potassium reducing metal or aluminum reducing metal
(or magnesium reducing metal or titanium reducing metal) is pumped
through a continuous loop 214 using pump 202, such as an
electromagnetic pump (EM pump). An electromagnetic pump is a pump
that moves ionizable liquid metal using electromagnetism. An
electromagnetic pump can have no moving mechanical parts which can
be corroded by heated reducing metal. A cold trap 203 installed on
the loop 214 is used to remove contaminants prior to starting up
production. Once the contaminants are removed, the cold trap can be
valved off until needed again. The electromagnetic pump 202 pumps
the molten sodium and/or potassium or molten aluminum (or molten
magnesium or molten titanium) to a flow split 204. As an option,
more than a predominant (>50%) amount, or from 51% to 95%, or
from 60% to 90%, or from 65% to 85%, or other amounts of the mass
flow of the molten reducing metal arriving at split 204 is directed
into the stream feeding the heater 208, and a minority amount
(<50%), or from 49% to 5%, or from 40% to 10%, or from 35% to
15%, or other amounts is directed to the cooler 205. As an option,
the flow to the cooler 205 can be from about 1 to about 7
gallons/min (GPM), or from about 2 to about 6 GPM, or about 3 GPM,
or other values, and the flow to the heater 208 can be from about
11 to about 19 GPM, or from about 13 to about 18 GPM, or about 17
GPM, or other values. The split flows can be controlled using
valves and Coriolis flow meters (not shown).
[0042] The cold sodium and/or potassium stream can be directed to
flow around a funnel 206. Metal halide powder, as a solid form of
metal halide, can be added to this funnel. The sodium and/or
potassium, or the aluminum (or magnesium or titanium) flows around
the funnel 206 and can collect the metal halide powder and the
resulting mixture or slurry can be drawn through an eductor 209.
The eductor 209 can use the hot sodium and/or potassium, or the hot
aluminum (or magnesium or titanium) flow as the motive fluid
sucking the metal halide slurry into it. The additional heat
provided by the hot sodium and/or potassium stream (or the aluminum
or magnesium or titanium stream) can initiate the reduction
reaction. The reaction can occur in a reaction zone 210. The
reaction zone 210 can be a closed pipe, a draft-tube reactor, a
stirred tank reactor, or other reactor. As an option, the reaction
can occur down a length of spiraling pipe (as the reaction zone
210) to a vessel 211. The reaction zone can be designed to provide
turbulence to increase mixing of the reducing metal and metal
halide during the reaction, such as by using spiraled piping or a
stirred reactor, or other designs. This vessel 210 can collect the
product by utilizing the high density of reaction product metal and
allowing it to settle to the bottom. The excess sodium and/or
potassium or the excess aluminum or magnesium or titanium 215 can
flow out of the vessel 211 through an outlet, such as pour spout or
decanter or siphon, and then through a filter 212 and a cooler 213
before making it back to the storage tank 201 for reuse.
[0043] After the metal production, the settling tank 211 can be
used as a bake out vessel. The vessel 211 can be heated to high
temperatures until it is void of all excess sodium and/or
potassium, or the excess aluminum (or magnesium or titanium),
leaving behind a metal/salt mixture. This mixture can be used for
post processing.
[0044] In the metal halide powder feed system, the feeding of the
metal halide powder preferably should occur in an inert atmosphere
due to its reactivity in air. As such, the powder transfer to the
feed system and all working parts of the feeder itself preferably
are maintained in an inert atmosphere, such as an argon atmosphere.
If an inert atmosphere is not kept, there can be a risk of heavy
chloride corrosion as well as contamination of the product. As an
option, a glove box set up around the feeding system can be used.
Once the metal halide powder is fed, it preferably is incorporated
into the sodium and/or potassium or into the aluminum and/or
magnesium and/or titanium in a manner that promotes complete
reaction to metal. It has been observed in experiments that metal
halide powders, such as HfCl.sub.4 powder, is not wetted by liquid
sodium, and does not easily disperse, and can form a crust of metal
that surrounds and shields unreacted powder from the sodium and/or
potassium. The funnel/eductor design is used to disperse the powder
into cold sodium and/or potassium or into cold aluminum (or cold
magnesium or cold titanium) before sucking it down into the hot
sodium and/or potassium, or the hot aluminum (or hot magnesium or
hot titanium) and initiating the reaction. This method can provide
enough agitation to get the metal halide, such as HfCl.sub.4, mixed
and promote reaction with sodium and/or potassium, or the aluminum
(or magnesium or titanium) once mixed into the hot sodium and/or
potassium or the hot aluminum (or hot magnesium or hot titanium).
Eductors work based on set flows and pressures on the inlets and
the outlet. If the suction is too great for the slurry feed, argon
gas can be sucked into the system and can cause problems. As such,
a control system can be used to control each flow rate as well as
the level in the funnel above the eductor. Further, heat tracing
preferably is used throughout the system where reducing metal is
stored and passes to monitor the temperatures and for control
thereof. If a cold spot in the system should develop, it may cause
the sodium or other reducing metal used to freeze and possibly plug
up the system.
[0045] The settling/bake-out vessel can be a dual purpose piece of
equipment that can collect and purify the product. If not
transferred or recycled to tank 201 during the reaction and process
as indicated, in post production, the vessel can be full of excess
molten reducing metal that needs to be removed. This excess molten
reducing metal can be removed by raising the temperature to
extremely high levels and evaporating the molten reducing metal
out. This high temperature may limit the applicable materials of
construction and designs. Following this molten reducing metal
removal, the vessel itself can be removed from the system for
product recovery.
[0046] In FIG. 3, a method of making a masterbatch of the present
invention, indicated as 300, is shown. In this method, a solid
metal halide 307 is used and a tank 301 of aluminum (or magnesium
or titanium) is used as a source of reducing metal. Features and
steps 302, 314, 303, 304, 305, 306, 307, 308, 309, and 310 can be
similar to or the same as features and steps 202, 214, 203, 204,
205, 206, 207, 208, 209, and 210, respectively, as described with
respect to method 200 in FIG. 2, and reference is made thereto. The
reducing metal is introduced in stoichiometric excess with respect
to the metal halide in this method, such as in a range described
herein. The method 300 of FIG. 3 differs from the method 200 shown
in FIG. 2 with regards to the materials that are removed and
retained in the collection tank that receives materials from the
reaction zone. In the method 300 of FIG. 3, the
volatization/masterbatch tank 311 is used to collect reaction
product metal and a salt produced in the reaction zone 310, and
also excess aluminum reducing metal (or excess magnesium metal or
excess titanium metal). The salt, and not the excess aluminum (or
magnesium or titanium) reducing metal, is separated out to obtain a
metal masterbatch comprising at least a portion of the aluminum (or
magnesium or titanium) reducing metal and reaction product metal.
The aluminum (or magnesium or titanium) and reaction product metal
can be intermixed as a uniform or substantially uniform physical
mixture thereof, which forms or can be formed into a unitary solid
mass of material.
[0047] In FIG. 4, a method of making a metal powder of the present
invention, indicated as 400, is shown. In this method, a liquid
metal halide 405 is used instead of a solid metal halide as used in
the methods of FIGS. 2 and 3. A tank 401 of sodium and/or
potassium, or a tank 401 of aluminum (or magnesium or titanium) is
used as a source of reducing metal. The reducing metal is
introduced in stoichiometric excess with respect to the metal
halide in this method, such as in a range described herein.
Features and steps 402, 414, 403, 404, 406, 407, 408, 409, and 415
can be similar to or the same as features and steps 202, 214, 203,
208, 210, 211, 212, 213, and 215, respectively, as described with
respect to method 200 in FIG. 2, and reference is made thereto. The
liquid metal halide 405 can be introduced into the heated molten
reducing metal using an injection or pumping device, such as using
pressurized inert gas to force metal flow.
[0048] In FIG. 5, a method of making a masterbatch of the present
invention, indicated as 500, is shown. In this method, a liquid
metal halide 505 is used instead of a solid metal halide as used in
the methods of FIGS. 2 and 3, and a masterbatch is formed in a
volatization/masterbatch tank 507 used similarly to the tank 311 as
used in the method 300 shown in FIG. 3. In method 500, tank 501 of
aluminum (or magnesium or titanium) is used as a source of reducing
metal. Features and steps 502, 514, 503, 504, 506, 507, and 508 can
be similar to or the same as features and steps 302, 314, 303, 308,
310, 311, and 312, respectively, as described with respect to
method 300 in FIG. 3, and reference is made thereto. The liquid
metal halide 505 can be introduced into the heated molten aluminum
(or magnesium or titanium) reducing metal using an injection or
pumping device similar to or the same as that described for use in
the method 400 of FIG. 4. As in the examples of the methods shown
in FIGS. 2-4, the reducing metal is introduced in stoichiometric
excess with respect to the metal halide in this method as well,
such as in a range described herein.
[0049] Additional information on the metal halide reaction and
product processing which are related to methods described herein
are provided in the following sections.
Metal Halide Reduction
[0050] In the metal halide reduction step, when using the indicated
liquid or solid forms thereof, the metal halide is reduced to a
metal and a metal salt (e.g., from the reducing metal reacting with
the halide from the metal halide) is produced as a byproduct.
[0051] As indicated, the metal halides can be reacted with a
stoichiometric excess of the reducing metal in methods of the
present invention. Metal halides that can be reacted include, for
example, one or more halides of tantalum, nickel, aluminum,
zirconium, vanadium, tin, titanium, silicon, niobium, or hafnium,
or any combination thereof. Other examples are mentioned earlier.
The metal halide can be a metal chloride. The metal halide can be a
metal bromide or metal iodide. The reducing metal is different from
the metal of the metal halide, when one metal halide is used. The
reducing metal (in molten state) can be or include a Group I
metal(s) or aluminum. Examples of reductions include: TaCl.sub.5
reduced by sodium; TaCl.sub.5 reduced by a mixture of sodium and
potassium; HfCl.sub.4 reduced by sodium, HfCl.sub.4 reduced by a
mixture of sodium and potassium; HfCl.sub.4 reduced by aluminum; a
mixture of TaCl.sub.5 and NiCl.sub.2 reduced by a mixture of sodium
and potassium; AlCl.sub.3 reduced by sodium; ZrCl.sub.4 reduced by
sodium; ZrCl.sub.4 reduced by aluminum; VCl.sub.4 reduced by
sodium; SnCl.sub.4 reduced by sodium; TiCl.sub.4 reduced by sodium;
and SiCl.sub.4 reduced by sodium. Subhalides (e.g., halides of
lower oxidation states of the metal elements that contain less
halide (e.g., TiCl.sub.2 or TiCl.sub.3) than its common halide
(e.g., TiCl.sub.4)), including subchlorides, can also be reduced in
the same manner, for example, titanium, zirconium, or tin
subchlorides. Examples of reduction reactions can proceed according
to Equations (2A), (2B), (2C), (2D), (2E), (2F), or (2G):
TaCl.sub.5(s or l)+5Na(l)-->Ta(s)+5NaCl(s) (2A),
HfCl.sub.4(s or l)+4Na(l)-->Hf(s)+4NaCl(s) (2B),
3TiCl.sub.4(l)+13Al(l)-->3TiAl.sub.3(s)+4AlCl.sub.3(g) (2C),
SiCl.sub.4(l)+CCl.sub.4(l)+8Al(l)-->SiC(s)+8AlCl.sub.3(g)
(2D),
SiCl.sub.4(l)+CCl.sub.4(l)+4Mg(l)-->SiC(s)+4MgCl.sub.2(l)
(2E)
ZrCl.sub.4(s or l)+CCl.sub.4(l)+2Ti(l)-->ZrC(s)+2TiCl.sub.4(g)
(2F)
NaAlCl.sub.4(l)+TiCl.sub.4(l)+7Na(l).fwdarw.TiAl(s)+8NaCl(s)
(2G)
[0052] In order to generate flowable reducing metal for use in the
reaction, the reducing metal is heated to a temperature above its
melting point and below its boiling point before it is combined
with metal halide and passed into a sealed reaction vessel that is
substantially free of oxygen and water. Higher temperatures can
lead to the generation of reducing metal vapors that must be
controlled. Sodium, for instance, has a melting point temperature
of about 98.degree. C. and a boiling point temperature of about
883.degree. C. (at about 1 atmosphere pressure). Aluminum has a
melting point temperature of about 660.degree. C. and a boiling
point temperature of about 2470.degree. C. (at about 1 atmosphere
pressure). It can be advantageous to stay at least 50.degree. C.,
or at least 100.degree. C., or at least 200.degree. C., or at least
300.degree. C. above the melting point. The heated reducing metal
can be initially heated sufficiently to provide a pumpable molten
material, and the mixture resulting from its combination with metal
halide can have a temperature sufficient to support the metal
halide reduction reaction by the initial heating, additional
heating before combination with metal halide, or additional heating
after combination with metal halide, or any combination thereof.
Before combining with the metal halide, the molten reducing metal,
depending on the metal, can be heated and maintained at a
temperature of from about 150.degree. C. to about 850.degree. C.,
or from about 150.degree. C. to about 350.degree. C., or from about
200.degree. C. to about 250.degree. C. For example, when the
reducing metal is sodium, more typical reaction temperatures are
from 150.degree. C. to 350.degree. C., though temperatures up to
about 850.degree. C. or other temperatures are possible. In some
instances, where the molten reducing metal is sodium, the sodium is
heated and maintained at a temperature of from about 600.degree. C.
to about 700.degree. C. until combined with the metal halide.
[0053] As indicated, the reaction zone can be a closed pipe (e.g.,
a spiraled pipe), a draft-tube reactor, a stirred tank reactor, or
other reactor. The reaction zone preferably creates turbulence
which encourages mixing of the reducing agent and metal halide in
the reaction zone. As an option, a stirred reactor that can be
used, such as described in U.S. patent application Ser. No.
15/051,267, which is incorporated in its entirety by reference
herein.
[0054] The reaction zone can be a sealed, reaction chamber, which
can be an airtight glovebox. An airtight glovebox can be
constructed largely of glass plates attached to a metal frame. A
glovebox permits an operator to manipulate objects within the
glovebox while maintaining an inert reaction environment. The
reaction chamber can be a bench-top glovebox, or it can be a larger
glovebox suitable for pilot scale operations, in which case it may
have work stations where several operators can access the interior
of the glovebox. The reaction chamber can also be large enough to
house industrial- or commercial-scale reaction vessels. For
commercial scale production, an airtight vessel having automated
loading and unloading can be used.
[0055] For any of the methods of the present invention, including
those shown in FIGS. 1-6, optionally, other reactants can also be
included during the metal halide reaction which do not interfere
with that reaction. For instance, a carbide forming, or nitride
forming, or boride forming component (i.e., ceramic forming
components) can be added to the metal halide or to the molten
reducing metal or both, wherein at least one other metal compound
that comprises a metal carbide, a metal nitride, or a metal boride
or any combination thereof can be formed. The carbide forming
component can comprise carbon containing gas, carbon tetrachloride,
or solid carbon. The boride forming component can comprise boron
trichloride or one or more boron hydrides. The nitride forming
component can be titanium nitride (TiN). The amount of metal
carbide, metal nitride, and/or metal boride, or any combination
thereof, in the reaction products in lieu of the metal formed, can
be from about 10 wt % to about 100 wt % of the total weight
reaction product (e.g, from about 40 wt % to 100 wt %, or from 60
wt % from 100 wt % or from 90 wt % to 100 wt %, or from 98 wt % to
100 wt %). From 40 wt % to 100 wt %, or from 60 wt % from 100 wt %
or from 90 wt % to 100 wt %, or from 98 wt % to 100 wt % of the
metal formed can be converted to the metal carbide, metal nitride,
or metal boride in the reaction. The other reactants, such as the
carbide or boride or nitride forming component can be added at any
stage of the process, such as at or before the reaction zone, or
can be present with the reducing metal or with the metal halide
introduction point, or be separately introduced using an additional
inlet to the flow of the reducing metal or metal halide, or
both.
Recycling of Excess Reducing Metal
[0056] In another step of the methods such as shown in FIGS. 2 and
4, the excess unreacted molten reducing metal can be separated so
that it can preferably be reused in another reduction reaction. The
excess reducing metal can be as much as 50% by weight, or more in
some cases, of the starting amount of molten reducing metal. As
illustrated in FIG. 6, the excess molten sodium and/or potassium,
or the excess molten aluminum (or magnesium or titanium) reducing
metal 660, along with the metal powder and the sodium salt and/or
potassium salt, or the aluminum salt (or magnesium salt or titanium
salt) formed during the metal halide reduction reaction step, can
be decanted into a bake out vessel 610. The bake out vessel 610 can
have a lip 615 that can facilitate the placement of a lid 620 on
top of the bake out vessel 610. The bake out vessel 610 can have
one or more ports 630 that can be used to remove excess reducing
metal material from the bake out vessel 610. The port 630 can be
adjustable so that they can extend to differing depths within the
bake out vessel 610. The port 630 can be formed of a non-conducting
ceramic in order to reduce long-range electron mediated
reduction.
[0057] To recover the molten reducing metal, the bake out vessel
can be heated to just above the melting point of the metal salt
formed as a reaction byproduct. For example, when the metal halide
is hafnium chloride and the reducing metal is sodium, the salt
produced is sodium chloride, which has a melting point of
approximately 801.degree. C. In this example, the bake out vessel
610 can be heated to just above 801.degree. C., which is just above
the melting point of sodium chloride. At this temperature, the
sodium chloride salt begins to melt and separate from the excess
(unreacted) sodium reducing metal, thereby creating a salt bath 640
and a molten reducing metal phase 660. A small amount of the sodium
dissolves in the molten sodium chloride salt (approximately 2 molar
% at 801.degree. C.). The salt bath phase 640 includes sodium salt
641 and the metal powder 645 created by reducing the metal halide.
A first outlet or port 630 can use used to pour off (decant) or
siphon out the bulk of the excess sodium molten reducing metal 660
by gravity (drain) or by applying a negative relative pressure
(siphon) in a capture tank. This molten sodium reducing metal 660
that has been poured off or siphoned off can be captured in a
capture tank and reused, such as shown in FIGS. 2 and 4.
[0058] The bake out temperature can be adjusted by adding other
salts and creating an eutectic system. For example, a 52:48 (by wt)
mix of calcium chloride and sodium chloride melts at approximately
500.degree. C. Thus, the bake out can occur in a lower temperature
range (e.g., where stainless steel can be used instead of more
expensive metals). By operating at a lower temperature, the surface
area of the resulting metal powder can also be increased since a
higher temperature leads to increased sintering.
[0059] Care should be exercised to determine the boundary between
the molten reducing metal and the salt so that only the molten
reducing metal is removed. It may not be possible to drain or
siphon off all of the excess molten reducing metal 660. For
example, there may be a layer of reducing metal 660 that is a few
millimeters thick that remains after draining or siphoning. As an
option, the amount of excess reducing metal (e.g., 1) Na and/or K,
or 2) Al and/or Mg and/or Ti) after draining or siphoning can be
5,000 ppm or less in the metal and salt products, such as less than
3,000 ppm, or less than 2,000 ppm, or less than 1,000 ppm, or less
than 500 ppm, or less than 250 ppm, or from 0 ppm to 5,000 ppm, or
from 10 ppm to 2,000 ppm, or from 100 ppm to 1,500 ppm.
[0060] Alternatively, or in addition, residual reducing metal can
be reacted with an alcohol, such as methanol.
[0061] Once the reducing metal layer has been removed or
substantially removed to the ppm levels indicated above, as an
option, the remaining reducing metal can be reacted with an
anhydrous chloride, such as anhydrous hydrogen chloride (HCl) or
chlorine gas (Cl.sub.2). However, the hydrochloric acid can attack
the metal particles that have been formed. In order to protect the
metal particles, a salt can be added to the bake out vessel 610
either prior to or after pouring the molten reducing metal, salt,
and metal powder into the bake out vessel 610. Typically, the salt
added is the same salt formed during the reduction of the metal
halide by the reducing metal. The salt produced in the
neutralization reaction typically fills the voids in the metal, and
chlorides can therefore attack the metal. By providing a layer of
molten salt, direct contact between the halides and the metal can
be reduced. Thus, the chloride tends to neutralize the free sodium,
which has valence electrons having a long mean free path in the
molten salt.
[0062] The resulting product can be a metal powder at least
partially or fully encapsulated in salt. The salt can have a
glass-like appearance because it was melted and cooled.
Salt Removal
[0063] In a further step, the salt can be removed. Metal powder
having a higher surface area is generally less dense and contains
more salt in narrower voids.
[0064] In a first method of removing the excess salt from the metal
particles, the metal particles encapsulated in salt are washed with
water. Preferably, the metal particles encapsulated in salt are
transferred to a new vessel prior to the water wash in order to
prevent oxidation of the bake out vessel. Frequently, the metal
particles are washed in serial batches in a metal beaker or other
metal container so that the concentration of salt is less than 1
ppm. An example reaction for removing excess salt is Equation (3),
after which the liquids and dissolved solids are removed:
Ta(s)+5NaCl(s)+2H.sub.2O(l)->Ta(s)+5NaCl(aq)+2H.sub.2O(l)
(3)
[0065] In a second method of removing the excess salt from the
metal particles, the salt can be evaporated. One method of
evaporating the salt is by sweeping an inert gas, such as argon,
through the chamber at a temperature close to or above the melting
point of the salt, such that the salt has an adequate vapor
pressure to permit it to be removed in a reasonable time. The salt
vaporizes, leaving behind the metal particles. The procedure can be
conducted within a rotary furnace, which can limit the formation of
a sponge from the metal particles. The inert gas can be
recycled.
[0066] In a third method of removing the excess salt from the metal
particles, ultrafiltration can be used to remove excess salts. One
such system is provided by Koch Membranes.
Metal Powder Recovery
[0067] In another further step, the metal particles are recovered
and can be subsequently dried if desired. The particles can be
dried in a vacuum oven. After drying the metal particles can be
collected and recovered as a free flowing powder.
[0068] When the metal powder is exposed to air, it can be highly
flammable, and its dust can be explosive. Thus, it must be handled
with care, and preferably in an inert atmosphere, until the powder
has been consolidated into a desired final form or else until the
powder surface has been passivated by controlled exposure to
oxygen.
Masterbatch Recovery
[0069] In masterbatch production, where aluminum is used as the
reducing metal and aluminum trichloride (AlCl.sub.3), also referred
to as aluminum chloride, is the salt formed in the reaction with
metal halide, the aluminum trichloride can be selectively separated
and removed to leave the reaction product metal and excess aluminum
as a masterbatch. The sublimation pressure of the aluminum
trichloride reaches one atmosphere at about 179.degree. C. to
183.degree. C. at approximately 1 atmosphere pressure, and the
melting-point of aluminum trichloride at 2.5 atmospheres pressure
is about 190.degree. C. to 194.degree. C. In view of these
properties of aluminum trichloride, the contents of the holding
tank can be heated under approximately one atmosphere pressure to
at least about 179.degree. C. to 183.degree. C. and below the
boiling temperature of aluminum (about 2470.degree. C.) and the
reaction product metal (e.g., Hf melt. pt.=about 2233.degree. C.,
boil. pt.=about 4600.degree. C.) to selectively volatize the
aluminum trichloride and separate it from the other contents in the
holding tank. Similar processes and reactions can be used when the
reducing metal is magnesium or titanium and the a magnesium
chloride or titanium chloride, for instance is the salt formed.
[0070] The present invention will be further clarified by the
following examples, which are intended to be exemplary of the
present invention.
EXAMPLES
Example 1 (Theoretical Example)
[0071] Using a process flow as illustrated in FIG. 2, a storage
tank containing 200 gallons of molten sodium is pumped through a
continuous loop using an electromagnetic pump. There is a cold trap
installed on the loop that is used to remove contaminants prior to
starting up production. Once the contaminants are removed the cold
trap is valved off until needed again. The electromagnetic pump
pumps the molten sodium to a flow split. The flow to the cooler can
be roughly 3 GPM and the flow to the heater can be roughly 17 GPM.
The flows can be controlled using valves and Coriolis flow
meters.
[0072] The cold sodium stream flows around a funnel. The HfCl.sub.4
powder is added to this funnel. The sodium flows around the funnel
and collects the powder and it is drawn through an eductor. The
eductor uses the hot sodium flow as the motive fluid sucking the
HfCl.sub.4 slurry into it. The additional heat provided by the hot
sodium stream initiates the reduction reaction. Feeding of the
HfCl.sub.4 powder occurs in an inert atmosphere due to its
reactivity in air. As such the powder transfer to the feed system
and all working parts of the feeder itself is maintained in an
inert atmosphere. A small glove box is set up around the feeding
system. The reaction occurs down a length of spiraling pipe
(reaction zone) to a vessel. This vessel collects the product by
utilizing the high density of Hf metal and allowing it to settle to
the bottom. The excess sodium flows out of the top of the vessel
through a filter and a cooler before making it back to the storage
tank.
[0073] After the metal production, the settling tank is used as a
bake out vessel. The vessel is heated to high temperatures until it
is void of all excess sodium, leaving behind a metal/salt mixture.
This mixture is taken for post processing by NSP.
[0074] Additional examples are provided in the following
section.
Example 2: Halide Powder Feed Test
Instrumentation Setup
[0075] A powder trickier was used for all halide powder trials to
feed the reactant powders to a beaker containing alkali metal(s).
This powder feeder consists of an adjustable hopper, discharge
tube, stand, and 2-speed control pad. All reactant powders flowed
readily through the tube given the vibration frequency at hand,
except the TaCl.sub.5 and NiCl.sub.2 50/50 powder blend. This
powder blend packed tightly inside both the tube and the hopper
base. As a result, remaining powder was fed to the reaction beaker
using a "hand-add" approach with a spatula for the TaCl.sub.5 and
NiCl.sub.2 50/50 blend.
[0076] All tests utilized an IKA 70 Watt mixer with the capability
of producing speeds from 60 to 2000 rpm. A stainless steel, 1.20
inch diameter, turbine impeller blade was utilized for the first
two tests performed, TaCl.sub.5 in excess sodium. All subsequent
tests were performed using a stainless steel, 1.65 inch diameter,
Cowles blade impeller to improve the incorporation of the reactant
powder in the alkali metal. Even though the mixer maximum capacity
was specified as 2000 rpm maximum, the mixer was utilized at speeds
as high as 2135 rpm in the powder feed tests.
[0077] A stainless steel 2000 mL beaker was implemented as the
reaction vessel for all tests. A lid was constructed for trial 3
with 3 ports for the mixer impeller, powder feed tube, and alkali
metal temperature thermocouple (TE-0111A). The lid eliminated a
large amount of dusting within the glovebox while allowing for the
reactant powder to be fed down into the alkali metal via a vertical
feed tube. The 4th and 5th trials used a similar lid with a reduced
diameter port to further minimize dusting to the glovebox.
[0078] A test setup used for this example is shown and described
with reference to FIG. 3 as described in U.S. patent application
Ser. No. 15/051,267, which is incorporated in its entirety by
reference herein. The stainless steel beaker, V-0100, contained the
alkali reducing metal. The reaction beaker was maintained at
200-250.degree. C. using a heater band (controlled via TC-0111) and
a hot plate (controlled via TC-0110). The variation in alkali metal
temperature was based upon the reactivity of the halide powder
during each trial via physical observation. Halide powders were
pre-weighed using scale WI-0120 and fed from the powder feeder,
F-0125, to V-0100 in 5-10 gram increments.
[0079] Argon was fed from an argon supply Dewar to the glovebox at
a flow rate of 110 standard cubic feet per hour (scfh). Argon
pressure was regulated down to 20-30 psig. The glovebox oxygen and
moisture content was recorded prior to the start of each trial.
Before any halide powders were exposed to the glovebox internals,
the blower was de-energized and the purifier was isolated in an
effort to preserve the integrity of the purifier. With the purifier
isolated from the system, oxygen content was not accurately
displayed on the glovebox control panel because the oxygen sensor
was also sensitive to chlorides, and therefore provided an
inaccurate reading due to the presence of chloride vapors in the
glovebox.
[0080] A vacuum filtration system was incorporated for the trials
using NaK. This system consists of a filtration separation vessel,
V-0134, that contains a 10 micron screen inserted within a
stainless steel cup to retain the solids. A catch vessel (flask),
V-0135, was used to prevent any filtered NaK carry-over and to
protect the vacuum pump, PU-0130. This vacuum filtration set-up was
also used to perform the methanol wash steps within product
recovery when NaK was utilized.
Test Procedure and Results
[0081] A first experiment was conducted to assess the minimum
reaction temperature and mixing parameters. In this first
experiment, an inert atmosphere having as little oxygen and
moisture as possible was established in the glovebox. The hot plate
and heater bands were energized and set to 200.degree. C. Once the
alkali metal was up to temperature, a pinch test was performed by
adding a small amount of reactant powder to the alkali metal. The
pinch test must be performed with the lid removed from the vessel
to observe for signs of reaction (such as a change in color or the
generation of smoke). If no sign of reaction was observed at
200.degree. C., then the temperature was increased in increments of
50.degree. C. and the pinch test was repeated until a reaction was
observed. All reactions were performed at 250.degree. C. or
less.
[0082] The halide powders were manually weighed in 5-10 gram
increments before being added to the hopper. Powder was fed from
the hopper to the vessel, with pauses in feeding when smoking was
observed. When the reaction step was completed, the mixer, heater
band, and hot plate were de-energized to allow for the system to
cool before the start of product recovery.
[0083] A total of five experiments was performed; two utilized
TaCl.sub.5 and molten sodium, whereas the remaining three reacted
TaCl.sub.5, HfCl.sub.4, and a 50/50 (wt %) mix of TaCl.sub.5 and
NiCl.sub.2, each with NaK alloy. A consolidation of the test
results displaying the amount of fed halide powder, the amount of
alkali metal used, and the final amount of collected product after
vacuum drying can be viewed for each test in Table 1 below.
TABLE-US-00001 TABLE 1 Reactant Charges and Fractional Yield
Summary Charged Recovered Fractional Yield Fed Halide Alkali
Product (actual/theoretical Test Powder (g) Metal (g) (g) product)
1. TaCl.sub.5 in 0.50 90.00 0.05 19.8% Excess Na 2. TaCl.sub.5 in
19.15 957.00 0.50 5.2% Excess Na 3. TaCl.sub.5 in 41.16 748.00
13.60 65.4% Excess NaK 4. HfCl.sub.4 in 23.78 718.70 9.80 74.0%
Excess NaK 5. TaCl.sub.5/NiCl.sub.2 19.26 728.40 5.20 56.4% in
Excess NaK
[0084] At the start of Test 5, NiCl.sub.2 showed no sign of
reaction at 200.degree. C. when performing a pinch test; however, a
reaction was visible at 250.degree. C. Therefore, Test 5 was
performed at 250.degree. C.
[0085] The 50/50 wt % NiCl.sub.2/TaCl.sub.5 (Test 5) powder mix
tightly packed within the hopper feed tube, as well as the base of
the hopper, multiple times. As a result, approximately half of the
feed was added to the NaK-containing vessel manually using a
spatula.
[0086] For the first two trials utilizing sodium, filtration took
place in the reaction beaker, with the second test using a
removable screen (<500 mesh) placed within the vessel. Material
was scraped from the reaction vessel (and screen for the second
test) before adding methanol to react residual sodium held up
within the product. The reaction products were centrifuged for
0.5-2.0 hours at 3000 rpm and decanted, and a second methanol wash
was repeated, followed by a de-ionized water wash to passivate the
tantalum product. A second de-ionized water wash was performed
using nitric acid to achieve a solution with a pH of 2. After
decanting, the sample was then vacuum dried overnight at 95.degree.
C.
[0087] For the trials performed with NaK, the vacuum filtration
system in the glovebox was utilized to remove the excess NaK from
the reacted product. Two methanol washes were performed to react
any NaK held up with the product, and vacuum filtration was used to
remove excess solvent within the product cake. As with the first
two tests, methanol washing was followed by a de-ionized water wash
in the glovebox to passivate the product followed by centrifugation
at 3000 rpm for 30 minutes and decanting. A total of five or six
water washes were performed before the product was vacuum dried
overnight at 85-95.degree. C. Each test performed with NaK utilized
varying deionized (DI) water solutions based on the product
isoelectric points. Table 2 describes the pH of the solutions used
for water washing as well as the number of washes performed.
Solution pH was adjusted using nitric acid or sodium hydroxide.
TABLE-US-00002 TABLE 2 Water Wash Criteria for Products Generated
Using NaK DI Water Wash No. of Performed Test Solution pH Washes 3.
TaCl.sub.5 in Excess 2-3 6 NaK 4. HfCl.sub.4 in Excess 7 6 NaK 5.
TaCl.sub.5/NiCl.sub.2 in Half at 2.50-3.0; Half at 10-11 5 Excess
NaK
[0088] Other observations include the following:
[0089] Significant dusting was observed in the glovebox for Tests 1
and 2, which were performed with an open lid. The rotation of the
mixer shaft can create argon currents that disperse some of the
powder feed. Dusting was observed again for Test 3, but dusting
significantly decreased so that very little was observed for Tests
4 and 5, which utilized a lid.
[0090] When draining excess sodium from the product in Test 2, it
was difficult to determine if the sodium drained through the inner
mesh strainer assembly or if a hole was present in the mesh.
Furthermore, some dark material (most likely tantalum) was removed
with the excess sodium, and caught in the <500 mesh
strainer.
[0091] Sufficient mixing was established with the mixer running at
1625-1675 rpms in Test 3; however, once powder addition began, the
mixing speed was increased to 1750 rpms to maintain a good vortex
and surface movement.
[0092] The hafnium tetrachloride powder used in Test 4 was denser
and chunkier than the tantalum pentachloride previously used.
Larger HfCl.sub.4 chunks appeared to sink in the NaK with no
visible signs of reaction, whereas the loose, fine powder generated
smoke and changed in color from white to black upon contact with
NaK. The HfCl.sub.4 powder was filtered to remove these larger
chunks prior to feeding the hopper and starting the reaction.
[0093] At the start of Test 5, NiCl.sub.2 showed no sign of
reaction at 200.degree. C. when performing a pinch test; however, a
reaction was visible at 250.degree. C. Therefore, Test 5 was
performed at 250.degree. C.
[0094] The 50/50 wt % NiCl.sub.2/TaCl.sub.5 powder mix tightly
packed within the hopper feed tube, as well as the base of the
hopper, multiple times. As a result, approximately half of the feed
was added to the NaK-containing vessel manually using a
spatula.
[0095] The amount of fed halide powder used in the last, fifth
trial is a best estimate due to losing approximately 0.86 g when
the feed tube on the lid assembly plugged during the feeding
process.
Salt Concentration Test
[0096] A salt concentration test was performed to assess the
quantity of metal halides that can be added while maintaining a
vortex. A total of 797.17 grams of sodium were used, and a total of
477.69 g NaCl were added over the course of the trial. The first
five salt charges were added in increments of 10 g, and all
subsequent charges were fed in 25 g increments.
[0097] After feeding 154.88 g of NaCl, a white-grey film skimmed
over the surface of the sodium and surface motion was halted. When
increasing the mixer speed from 1611 to 1750 RPMs, surface motion
resumed in pockets. At a mixing speed of 1950 rpms, swirling became
visible, but a vortex was still not observed. At 2008 rpms, an
off-centered vortex developed to the left of the mixer shaft.
[0098] Once NaCl addition reached 399.74 g, surface movement again
ceased, but regenerated after four minutes of no movement. After
adding 424.74 g of NaCl, movement again ceased, but was
re-initiated by probing the surface with a flat blade. The salt
feed was stopped at 477.69 g, afterchanges in fluid density and
viscosity were observed and surface mixing no longer occurred.
[0099] All tests demonstrated that the halide powder-alkali metal
reactions can be performed at 200.degree. C. except for NiCl.sub.2,
which should be reacted with alkali metals at 250.degree. C.
[0100] A dispersion of sodium and sodium chloride can have
approximately 33 to 37 wt % salt before changes in fluid density
and viscosity were observed and surface mixing no longer
occurred.
Example 3: Halide Powder and Liquid Initiation Test
Instrumentation Setup
[0101] A second set of experiments was conducted to verify the
reactivity of various powder and liquid halides with sodium metal.
All tests were performed in a glovebox, inerted with argon to
eliminate oxygen and moisture from the atmosphere.
[0102] Powder halide transfer: Aluminum Trichloride and Zirconium
(IV) Chloride powders were transferred into weighing dishes using a
microspatula. The powders were then poured into the reaction cups
from the weighing dishes.
[0103] Liquid halide transfer: Vanadium (IV) Chloride, Tin (IV)
Chloride, Titanium (IV) Chloride, and Silicon Tetrachloride were
transferred into the reaction cups using 1 mL syringes. For each
liquid halide, a volume of 0.1 mL was transferred into a syringe.
The syringes were then placed in the glovebox. The syringes were
then used to inject drops of each liquid halide into a reaction cup
containing molten sodium metal.
[0104] Reaction vessel: Stainless steel 2.5 oz. cups were
implemented as the reaction vessels for all tests. When not in use,
stainless steel foil was placed on top of each reaction cup.
[0105] A test setup used for this example is shown and described
with reference to FIG. 4 as described in U.S. patent application
Ser. No. 15/051,267, which is incorporated in its entirety by
reference herein. Each stainless steel cup, V-0100 through V-0600
contained sodium metal. The reaction cups were maintained at
240-260.degree. C. using a hot plate (manually controlled via
TC-0110). Halide powders were pre-weighed using scale WI-0120 and
poured into V-0100 and V-0200. The scale used to weigh the powder
halides only displays increments of 0.1 grams; therefore, the
amount of halide powders added to each reaction cup was known to be
less than 0.1 grams. Halide liquids were injected into the
reactions cups using 1 mL syringes. Because of the limited
dexterity in the glovebox and hazards associated with handling
syringe needles, the liquid halides were transferred from storage
bottles into syringes under the fume hood. The syringes were then
placed in the glovebox. For each halide liquid, 0.1 mL or less was
injected into the reaction cups V-0300 through V-0600. The setup
for the liquid halides was the same with the exception that four
reaction cups were used instead of two.
[0106] Argon was fed from an argon supply Dewar to the glovebox at
a flow rate of 65-70 scfh. Argon pressure was regulated down to
20-30 psig.
[0107] The glovebox oxygen and moisture content was recorded prior
to the start of each trial. Before any halide powders were exposed
to the glovebox internals, the blower was de-energized and the
purifier was isolated in an effort to preserve the integrity of the
purifier. With the purifier isolated from the system, oxygen
content was not accurately displayed on the glovebox control
panel.
Test Procedure and Results
[0108] Each test began with equipment set-up in the glovebox, and
establishing an inert atmosphere. The hot plate was energized and
set to 250.degree. C. In order to reach and maintain a sodium
temperature of 250.degree. C., the hot plate was set between
350.degree. C. and 400.degree. C. Once the sodium metal was up to
temperature, the halides were added to the reactions cups one at a
time. The tests were performed with the lid (foil) removed from the
cup to observe signs of reaction (such as a change in color or the
generation of smoke). If no sign of reaction was observed at
250.degree. C., then the temperature was increased in increments of
50.degree. C. and the test was repeated until a reaction was
observed. All reactions were performed at 250.degree. C. in order
to establish a safe minimum temperature.
[0109] Two experiments with halide powders were performed utilizing
powdered AlCl.sub.3 and ZrCl.sub.4 reacted with molten sodium.
Table 3 lists the consolidated test results displaying the amount
of halide powder added, the amount of sodium metal used, the
reaction temperature, and any observations during the reaction.
TABLE-US-00003 TABLE 3 Halide Powder Reaction Results Charged
Halide Sodium Powder Metal Reaction Test Added (g) (g) Temp (C.)
Observations 6. AlCl.sub.3 in <0.1 9.7 245 Color change to dark
gray Excess Na 7. ZrCl.sub.4 in <0.1 9.9 250 Color change to
dark gray Excess Na
[0110] Other observations from the test include the following:
ZrCl.sub.4 did not react as immediately as AlCl.sub.3.
[0111] Four experiments were performed utilizing liquid VCl.sub.4,
SnCl.sub.4, TiCl.sub.4, and SiCl.sub.4 reacted with molten sodium.
Table 4 lists the consolidated test results displaying the amount
of halide liquid added, the amount of sodium metal used, the
reaction temperature, and any observations during the reaction.
TABLE-US-00004 TABLE 4 Halide Reaction Results Halide Charged
Liquid Sodium Added Metal Reaction Test (mL) (g) Temp (C.)
Observations 8. VCl.sub.4 in 0.1 10.0 245 Color change to black
Excess Na Temperature increase of 3.degree. C. 9. SnCl.sub.4 in
0.03 9.9 256 Color change to dark gray Excess Na Blue flame Some
SnCl.sub.4 evaporation 10. TiCl.sub.4 in 0.02 10.0 251 Color change
to black Excess Na Some TiCl.sub.4 evaporation 11. SiCl.sub.4 in
0.08 10.1 251 SiCl.sub.4 mostly evaporated on Excess Na sodium
surface Color change to dark gray
[0112] Other observations from the tests include the following:
[0113] After transfer into the syringes, fuming out of the end of
the needle was noticed with VCl.sub.4, SnCl.sub.4, and TiCl.sub.4.
In the case of SnCl.sub.4 and TiCl.sub.4, fuming stopped once the
needles were inserted into rubber stoppers. In the case of
VCl.sub.4, fuming continued for 2 minutes after the needle was
inserted into the rubber stopper.
[0114] There was some pressure build up with the VCl.sub.4 syringe.
Some VCl.sub.4 was released from the syringe when the stopper was
removed from the end of the needle while in the glovebox.
[0115] TiCl.sub.4 changed from clear to yellow while in the
syringe.
[0116] There appeared to be more oxide on the sodium surface for
the SiCl.sub.4 reaction which could have resulted in the majority
of the SiCl.sub.4 laying on the surface and slowly evaporating
instead of reacting. SiCl.sub.4 is also more volatile than the
other liquid halides tested.
[0117] AlCl.sub.3, ZrCl.sub.4, VCl.sub.4, SnCl.sub.4, TiCl.sub.4,
and SiCl.sub.4 all react with sodium at approximately 250.degree.
C. There is potentially some evaporation when the liquid halides
are introduced to sodium at 250.degree. C.
Example 4: Metal Powder Characterization
[0118] Particle flow can be measured according to a standardized
protocol, such as by using a Hall flow meter according ASTM
International Standard B213.
[0119] Molecular content of the metal powders produced by the
methods described herein can be determined using LECO testers. For
example, nitrogen and oxygen content can be tested with LECO Model
TC436DR. Carbon and sulfur content can be tested with LECO Model
CS444LS. Nitrogen, oxygen, and hydrogen content can be tested with
LECO Model TCH600.
[0120] Purity can be assess by glow discharge mass spectrometry or
inductively coupled plasma mass spectrometry.
Example 5: Titanium Powder
[0121] 140 g of sodium metal was melted and brought to 250.degree.
C. in an Inconel reactor vessel. The sodium was then stirred using
a Cowles blade mixer rotating at 2200-2300 rpm. Liquid titanium
chloride (from Sigma Aldrich) was fed over approximately 1 hour
into the stirred sodium, until 60 g of titanium chloride had been
added, at which point the reaction was halted by releasing the gas
pressure on the halide feed. At the end of the reaction, the vortex
in the sodium had substantially disappeared.
[0122] Once the reaction was completed, the reactor vessel was
sealed, transferred to a furnace, and heated to 825.degree. C. for
four hours to reduce the surface area of the titanium metal
produced in the reaction.
[0123] After the high temperature treatment, the unreacted sodium
was removed from the reaction products and the titanium powder,
coated in salt, was washed in water to remove the coating of sodium
chloride encapsulating the metal. Washing continued until washwater
conductivity fell below 2 microsiemens.
[0124] The recovered titanium powder was dried overnight in a
vacuum oven at 100.degree. C. The titanium powder thus produced was
analysed by inductively coupled plasma mass spectrometry (ICP-MS)
and LECO instruments, and was found to contain below 150 ppm iron,
below 300 ppm total transition metals, and below 3000 ppm oxygen.
The results demonstrate that the titanium powder falls within the
purity limits as described in UNS No. R50550.
[0125] Visual assessment of SEM images showed particle agglomerates
predominantly in the 50 micron range, with primary structure mainly
at 3-5 microns.
Example 6: Hafnium Metal
[0126] 113 g of sodium metal was melted and brought to 250.degree.
C. in an Inconel reactor vessel. The sodium was then stirred using
a Cowles blade mixer rotating at 2000-2500 rpm. Powdered hafnium
chloride (from Areva) was pulse-fed over approximately 1 hour into
the stirred sodium, until 82 g of hafnium chloride had been added,
at which point the reaction was halted. At the end of the reaction,
the vortex in the sodium had substantially disappeared and the
reactor temperature had increased to 301.degree. C.
[0127] Once the reaction was completed, the reactor vessel was
sealed, transferred to a furnace, and heated to 825.degree. C. for
four hours to reduce the surface area of the hafnium metal produced
in the reaction. During this process step, unreacted sodium was
removed from the hafnium metal to leave a hafnium-sodium chloride
composite.
[0128] The hafnium and sodium chloride mixture was then transferred
to a vacuum furnace and heated under vacuum to 2300.degree. C.,
held at that temperature for one hour, and then cooled. This
removed the sodium chloride and produced a button of solid
hafnium.
[0129] The hafnium button was analysed via glow discharge mass
spectrometry (GDMS) and found to have 26 ppm oxygen content, 1690
ppm zirconium, and less than 150 ppm total transition metals. The
results demonstrate the production of a low oxygen hafnium metal
produced directly from hafnium powder consolidation.
Example 7: Titanium-Aluminum
[0130] 120 g of a 55% aluminum, 45% titanium powder (measured by
metal content) was first prepared, by adding aluminum chloride
powder (from Strem Chemical) to an aluminum-titanium chloride
Ziegler Natta catalyst powder (also from Strem Chemical).
[0131] Next, 140 g of sodium metal was placed in an Inconel reactor
and heated to 250.degree. C. Over approximately 2 hours, 94 g of
the titanium-aluminum chloride powder mix was pulse fed into the
sodium, which was continuously stirred by a Cowles blade mixer at
between 1600 and 2500 rpm. Powder addition continued until the
mixer could no longer maintain a vortex in the sodium. At the end
of the reaction the sodium temperature had increased to 292.degree.
C.
[0132] The Inconel reactor was then sealed, transferred to a
furnace, and heated to 900.degree. C. for 1 hour. After this step,
the unreacted sodium was removed and the metal powder washed to
remove its salt coating. Washing continued until the wash water
conductivity fell below 2 microsiemens. Finally, the powder was
dried in a vacuum over for 24 hours. The titanium-aluminum metal
thus produced was found by ICPMS analysis to contain below 100 ppm
iron and below 150 ppm total transition metals.
Example 8: Titanium-Aluminum-Vanadium
[0133] First, 120 g of a titanium-aluminum-vanadium chloride
mixture was prepared, by mixing liquid titanium chloride (from
Sigma Aldrich), aluminum chloride powder (from Strem Chemical) and
liquid vanadium chloride (from Acros Organics). The mixture was
stirred constantly to dissolve the aluminum trichloride into the
titanium chloride and vanadium chloride liquid.
[0134] Next, 140 g of sodium metal was heated to 250.degree. C. in
an Inconel vessel and stirred by a Cowles blade mixer at speeds
ranging from 1000 rpm initially, to 2500 rpm as the reaction
progressed. The liquid chloride mixture was pumped into the reactor
until 74 g had been added, over approximately 90 minutes. The
reaction stopped when the vortex in the sodium could no longer be
maintained.
[0135] The reactor vessel was then sealed and transferred to a
furnace, brought to 825.degree. C. and held at that temperature for
approximately one hour before being allowed to cool.
[0136] The recovered product was then washed to remove the sodium
chloride coating the metal powder, and the powder was dried in a
vacuum oven at 100 C for 24 hours. The results demonstrate that the
titanium powder falls within the purity limits as described in UNS
No. R56400.
Example 9: .gamma.-Titanium-Aluminide (Ti 48Al2Nb 2Cr)
[0137] First, 200 g of a titanium-aluminum-niobium-chromium
chloride mixture was prepared, by mixing liquid titanium chloride
(from Sigma Aldrich), sodium aluminum chloride powder
(NaAlCl.sub.4) (from Sigma-Aldrich), niobium chloride (from Sigma
Aldrich), and sodium chromium chloride powder (Na.sub.3CrCl.sub.5)
(produced from NaCl and CrCl.sub.2 both from Sigma Aldrich). The
mixture was heated to 180.degree. C. under 10 bar of pressure with
constant stirring to maintain a well mixed liquid chloride
feed.
[0138] Next, 5 kg of sodium metal was heated to 250.degree. C. in
an Inconel vessel and stirred by a Cowles blade mixer at speeds
ranging from 1000 rpm initially, to 2500 rpm as the reaction
progressed. The chloride mixture was pumped into the reactor until
200 g had been added, over approximately 90 minutes. The reaction
stopped when the vortex in the sodium could no longer be
maintained.
[0139] The reactor vessel was then sealed and transferred to a
furnace, brought to 825.degree. C. and held at that temperature for
approximately one hour before being allowed to cool.
[0140] The recovered product was then washed to remove the sodium
chloride coating the metal powder, and the powder was dried in a
vacuum oven at 100 C for 24 hours.
[0141] Analysis of the metal powder using ICPMS showed the product
contained under 50 ppm iron and under 150 ppm total transition
metals different from those used to make the alloy. From EDX
analysis, the .gamma.-titanium-aluminide composition fell within
the specification of Al: 32.4-33.6 wt % Cr: 2.4-2.8 wt % Nb:
4.5-5.1 wt %.
[0142] The present invention includes the following
aspects/embodiments/features in any order and/or in any
combination: [0143] 1. A method for producing a metal powder, the
method comprising: [0144] a) combining at least one metal halide
and at least one molten reducing metal in a space that is
substantially free of oxygen and water, wherein said molten
reducing metal is present in a stoichiometric excess to the metal
halide, to obtain a reaction product that comprises at least one
metal salt and metal, and wherein the molten reducing metal
comprises i) at least 90 wt % sodium or potassium or a mixture of
potassium and sodium or ii) at least 90 wt % aluminum, magnesium,
or titanium based on total weight of said molten reducing metal,
and the at least one metal halide is a solid or liquid, with the
proviso that the molten reducing metal is different from the metal
of the at least one metal halide; [0145] b) substantially removing
unreacted said molten reducing metal in said reaction product;
[0146] c) recovering at least said metal, wherein the metal of the
metal salt is the molten reducing metal, and the `metal` recovered
from the reaction product is from the metal of the metal halide.
[0147] 2. The method of any preceding or following
embodiment/feature/aspect, wherein in step c), the at least one
metal salt is recovered with said metal. [0148] 3. The method of
any preceding or following embodiment/feature/aspect, wherein said
method further comprises d) separating said metal from said metal
salt. [0149] 4. The method of any preceding or following
embodiment/feature/aspect, wherein two or more metal halides are
used and wherein said metal recovered comprises a metal alloy or
intermetallic compound from each metal of the two or more metal
halides. [0150] 5. The method of any preceding or following
embodiment/feature/aspect, wherein said at least one metal halide
is at least one metal chloride. [0151] 6. A method for producing a
metal masterbatch, the method comprising: [0152] a) combining at
least one metal halide and at least one molten reducing metal in a
space that is substantially free of oxygen and water, wherein said
molten reducing metal is present in a stoichiometric excess to the
metal halide, to obtain a reaction product that comprises at least
one metal salt and metal, and wherein the molten reducing metal
comprises at least 90 wt % aluminum, magnesium, or titanium based
on total weight of said molten reducing metal, and the at least one
metal halide is a solid or liquid, with the proviso that the molten
reducing metal is different from the metal of the at least one
metal halide; [0153] b) substantially removing said at least one
metal salt to obtain said metal masterbatch comprising at least a
portion of said molten reducing metal, and the metal, wherein the
metal of the metal salt is the molten reducing metal and the
`metal` recovered from the reaction product is from the metal of
the metal halide, wherein the removing of at least one metal salt
occurs during or after formation of said reaction product. [0154]
7. The method of any preceding or following
embodiment/feature/aspect, wherein said at least one metal halide
comprises Ti halide, V halide, Cr halide, Mn halide, Fe halide, Co
halide, Ni halide, Cu halide, Zn halide, Ga halide, Ge halide, As
halide, Se halide, Zr halide, Nb halide, Mo halide, Ru halide, Rh
halide, Pd halide, Ag halide, Cd halide, In halide, Sn halide, Sb
halide, C halide, Si halide, Te halide, Hf halide, Ta halide, W
halide, Hg halide, Tl halide, Pb halide, or Bi halide or any
combination thereof [0155] 8. The method of any preceding or
following embodiment/feature/aspect, wherein said at least one
metal halide is at least one metal chloride. [0156] 9. The method
of any preceding or following embodiment/feature/aspect, wherein
two or more metal halides are used and wherein said metal recovered
comprises a metal alloy, intermetallic compound, or ceramic from
each metal of the two or more metal halides. [0157] 10. The method
of any preceding or following embodiment/feature/aspect, wherein
said at least one metal halide is at least one metal chloride.
[0158] 11. The method of any preceding or following
embodiment/feature/aspect, wherein said metal masterbatch comprises
aluminum, hafnium, and zirconium. [0159] 12. The method of any
preceding or following embodiment/feature/aspect, further
comprising adding a carbide, nitride, or boride forming component
to said metal halide or to said molten reducing metal or both, and
wherein said metal of the reaction product comprises a metal
carbide, a metal nitride, or a metal boride or any combination
thereof. [0160] 13. The method of any preceding or following
embodiment/feature/aspect, wherein said carbide forming component
comprises carbon containing gas, carbon tetrachloride or solid
carbon. [0161] 14. The method of any preceding or following
embodiment/feature/aspect, wherein said boride forming component
comprises boron trichloride or a boron hydride. [0162] 15. The
method of any preceding or following embodiment/feature/aspect,
wherein said substantially removing said at least one metal salt
comprises vaporization of said at least one metal salt and removal
thereof from said metal masterbatch. [0163] 16. The method of any
preceding or following embodiment/feature/aspect, wherein said at
least one metal halide is combined as a solid with said molten
reducing metal. [0164] 17. The method of any preceding or following
embodiment/feature/aspect, wherein said at least one metal halide
is combined as a solid with a portion of said molten reducing metal
to form a mixture, and said portion of said molten reducing metal
is at a temperature that avoids reaction with said metal halide.
[0165] 18. The method of any preceding or following
embodiment/feature/aspect, said method further comprising combining
said mixture with part or all of the remaining portion of said
molten reducing metal that is at a temperature that permits
reaction with said metal halide. [0166] 19. The method of any
preceding or following embodiment/feature/aspect, wherein said
combined at least one metal halide and at least one molten reducing
metal passes through a reaction zone that comprises at least one
closed pipe that causes turbulence in combined at least one metal
halide and at least one molten reducing metal and that optionally
empties into a tank or filter. [0167] 20. The method of any
preceding or following embodiment/feature/aspect, wherein said
molten reducing metal comprises said at least 90 wt % sodium or
potassium or a mixture of potassium and sodium, and wherein
combined at least one metal halide and at least one molten reducing
metal passes through a reaction zone that empties into a settling
tank that includes at least one outlet that is located at a height
in the settling tank that permits said molten reducing metal from
step b) to at least partly be removed by said outlet but not said
molten salt or said metal, and wherein said combined at least one
metal halide, at least one molten reducing metal, and at least one
metal salt together are at a temperature that results in phase
separation of the molten reducing metal from said metal salt and
said metal. [0168] 21. The method of any preceding or following
embodiment/feature/aspect, wherein said combining said mixture with
part or all of the remaining portion of said molten reducing metal
that is at a temperature that permits reaction with said metal
halide comprises utilizing an eductor. [0169] 22. The method of any
preceding or following embodiment/feature/aspect, prior to at least
step b), wherein said molten reducing metal comprises at least 90
wt % sodium or potassium or a mixture of potassium and sodium, and
wherein at least one metal halide, at least one molten reducing
metal and at least one metal salt together are at a temperature
that causes phase separation of the molten reducing metal from said
metal salt and said metal. [0170] 23. The method of any preceding
or following embodiment/feature/aspect, wherein said substantially
removing said at least one metal salt comprises permitting the
vaporization of at least a portion of said at least one metal salt
and removal thereof from said metal masterbatch. [0171] 24. The
method of any preceding or following embodiment/feature/aspect,
wherein the at least one metal halide comprises at least a first
metal halide and a second metal halide, with the first metal halide
reactive with the metal salt and the second metal halide
non-reactive with the metal salt, wherein the metal of the second
metal halide is the same or different from the molten reducing
metal. [0172] 25. The method of any preceding or following
embodiment/feature/aspect, wherein the second metal halide is NaCl
and the molten reducing metal is said at least 90 wt % sodium, and
the first metal halide is AlCl.sub.3. [0173] 26. The method of any
preceding or following embodiment/feature/aspect, wherein said at
least one metal halide comprises a halide of Ti, V, Cr, Mn, Fe, Co,
Ni, Cu, Zn, Ga, Ge, As, Se, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn,
Sb, Te, Hf, Ta, W, Hg, Tl, Pb, or Bi or any combination thereof.
[0174] 27. The method of any preceding or following
embodiment/feature/aspect, wherein said first metal halide and said
second metal halide form a eutectic mixture. [0175] 28. The method
of any preceding or following embodiment/feature/aspect, wherein
said at least one metal halide is two or more metal halides, and
one metal halide is a solid or liquid and the other metal halide is
a vapor, solid, or liquid. [0176] 29. The method of any preceding
or following embodiment/feature/aspect, wherein said at one least
metal halide is three or more metal halides, and one metal halide
is a solid or liquid and the other metal halides are a vapor,
solid, or liquid. [0177] 30. The method of any preceding or
following embodiment/feature/aspect, wherein said metal salt at
least partially coats or encapsulates said metal. [0178] 31. The
method of any preceding or following embodiment/feature/aspect,
wherein said molten reducing metal is aluminum alloy. [0179] 32.
The method of any preceding or following embodiment/feature/aspect,
wherein said molten reducing metal is magnesium alloy. [0180] 33.
The method of any preceding or following embodiment/feature/aspect,
wherein said molten reducing metal is titanium alloy.
[0181] The present invention can include any combination of these
various features or embodiments above and/or below as set forth in
sentences and/or paragraphs. Any combination of disclosed features
herein is considered part of the present invention and no
limitation is intended with respect to combinable features.
[0182] Applicant specifically incorporates the entire contents 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.
[0183] Other embodiments of the present invention will be apparent
to those skilled in the art from consideration of the present
specification and practice of the present invention disclosed
herein. It is intended that the present specification and examples
be considered as exemplary only with a true scope and spirit of the
invention being indicated by the following claims and equivalents
thereof
* * * * *