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Patent 2330352 Summary

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(12) Patent Application: (11) CA 2330352
(54) English Title: REFRACTORY HARD METALS IN POWDER FORM FOR USE IN THE MANUFACTURE OF ELECTRODES
(54) French Title: METAUX DURS REFRACTAIRES EN POUDRE ENTRANT DANS LA FABRICATION D'ELECTRODES
Status: Dead
Bibliographic Data
(52) Canadian Patent Classification (CPC):
  • 261/24
(51) International Patent Classification (IPC):
  • C04B 35/58 (2006.01)
  • C01B 32/921 (2017.01)
  • B22F 1/00 (2006.01)
  • C01B 35/04 (2006.01)
  • C04B 35/56 (2006.01)
  • C04B 35/622 (2006.01)
  • C25C 3/12 (2006.01)
(72) Inventors :
  • BOILY, SABIN (Canada)
  • BLOUIN, MARCO (Canada)
(73) Owners :
  • GROUPE MINUTIA INC. (Canada)
(71) Applicants :
  • GROUPE MINUTIA INC. (Canada)
(74) Agent: NORTON ROSE FULBRIGHT CANADA LLP/S.E.N.C.R.L., S.R.L.
(74) Associate agent:
(45) Issued:
(22) Filed Date: 2001-01-05
(41) Open to Public Inspection: 2002-07-05
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data: None

Abstracts

English Abstract




The invention relates to a refractory hard metal in powder form
comprising particles having an average particle size of 0.1 to 30 µm and
each
formed of an agglomerate of refractory hard metals of the formula:
A x B y X z (I)
wherein A is a transition metal, B is a metal selected from the group
consisting of
zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,
manganese, tungsten and cobalt, X is boron or carbon, x ranges from 0.1 to 3,
y
ranges from 0 to 3 and z from 1 to 6. The refractory hard metal in powder form
according to the invention is suitable for use in the manufacture of
electrodes by
thermal deposition or powder metallurgy.

-15-


Claims

Note: Claims are shown in the official language in which they were submitted.




The embodiments of the invention in which an exclusive property or privilege
is
claimed are defined as follows:

1. A refractory hard metal in powder form comprising particles
having an average particle size of 0.1 to 30 µm and each formed of an
agglomerate of refractory hard metals of the formula:
A x B y X z (I)
wherein A is a transition metal, B is a metal selected from the group
consisting
of zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,
manganese, tungsten and cobalt, X is boron or carbon, x ranges from 0.1 to 3,
y
ranges from 0 to 3 and z from 1 to 6.

2. A refractory hard metal in powder form according to claim 1,
wherein A is a transition metal selected from the group consisting of
titanium,
chromium, zirconium and vanadium.

3. A refractory hard metal in powder form according to claim 2,
wherein A is titanium, X is boron and y is 0.

4. A refractory hard metal in powder form according to claim 3,
wherein x is 1 and z is 1.8.

5. A refractory hard metal in powder form according to claim 3,
wherein x is 1 and z is 2.

6. A refractory hard metal in powder form according to claim 3,
wherein x is 1 and z is 2.2.

7. A refractory hard metal in powder form according to claim 2,
wherein A is titanium, X is carbon and y is 0.

-9-




8. A refractory hard metal in powder form according to claim 8,
wherein x is 1 and z is 1.

9. A refractory hard metal in powder form according to claim 2,
wherein A is titanium, B is zirconium or hafnium, X is boron and y is other
than 0.

10. A refractory hard metal in powder form according to claim 9,
wherein B is zirconium, x is 0.5, y is 0.5 and z is 2.

11. A refractory hard metal in powder form according to claim 9,
wherein B is zirconium, x is 0.9, y is 0.1 and z is 2.

12. A refractory hard metal in powder form according to claim 2,
wherein B is hafnium, x is 0.5, y is 0.5 and z is 2.

13. A refractory hard metal in powder form according to claim 2,
wherein A is zirconium, B is vanadium, X is boron and y is other than 0.

14. A refractory hard metal in powder form according to claim 13,
wherein x is 0.8, y is 0.2 and z is 2.

15. A refractory hard metal in powder form according to claim 1,
wherein said average particle size ranges from 1 to 5 µm.

16. A process for producing a refractory hard metal in powder form
as defined in claim 1, comprising the steps of:

-10-



a) providing a first reagent selected from the group consisting of
transition metals and transition metal-containing compounds;

b) providing a second reagent selected from the group consisting of
boron, boron-containing compounds, carbon and carbon-containing
compounds;

c) providing an optional third reagent selected from the group
consisting of zirconium, zirconium-containing compounds, hafnium, hafnium-
containing compounds, vanadium, vanadium-containing compounds, niobium,
niobium-containing compounds, chromium, chromium-containing compounds,
molybdenum, molybdenum-containing compounds, manganese, manganese-
containing compounds, tungsten, tungsten-containing compounds, cobalt and
cobalt-containing compounds; and

d) subjecting said first, second and third reagents to high-energy
ball milling to cause solid state reaction therebetween and formation of
particles having an average particle size of 0.1 to 30 µm, each particle
being
formed of an agglomerate of grains with each grain comprising a nanocrystal
of a refractory hard metal of the formula (I) as defined in claim 1.

17. A process according to claim 16, wherein said first reagent
comprises a transition metal selected from the group consisting of titanium,
chromium, zirconium and vanadium.

18. A process according to claim 17, wherein said transition metal is
titanium.

19. A process according to claim 16, wherein said first reagent
comprises a titanium-containing compound selected from the group TiH2,
TiA13, TiB and TiC12.



-11-



20. A process according to claim 16, wherein said second reagent
comprises boron.

21. A process according to claim 16, wherein said second reagent
comprises a boron-containing compound selected from the group consisting of
A1B2, A1B12, BH3, BN, VB2, H2BO3 and Na2BO7.

22. A process according to claim 16, wherein said second reagent
comprises carbon.

23. A process according to claim 16, wherein said second reagent
comprises tetraboron carbide.

24. A process according to claim 16, wherein said third reagent is a
compound selected from the group consisting of HfB2, VB2, NbB2, TaB2, CrB2,
MoB2, MnB2, Mo2B5, W2B5, CoB, ZrC, TaC, WC and HfC.

25. A process according to claim 16, wherein step (d) is carried out
in a vibratory ball mill operated at a frequency of 8 to 25 Hz.

26. A process according to claim 25, wherein said vibratory ball mill
is operated at a frequency of about 17 Hz.

27. A process according to claim 16, wherein step (d) is carried out
in a rotary ball mill operated at a speed of 150 to 1500 r.p.m.

28. A process according to claim 27, wherein said rotary ball mill is
operated at a speed of about 1000 r.p.m.



-12-



29. A process according to claim 16, wherein step (d) is carried out
under an inert gas atmosphere.

30. A process according to claim 29, wherein said inert gas
atmosphere comprises argon or helium.

31. A process according to claim 16, wherein step (d) is carried out
under a reactive gas atmosphere.

32. A process according to claim 31, wherein said reactive gas
atmosphere comprises hydrogen, ammonia or a hydrocarbon.

33. A process according to claim 16, wherein step (d) is carried out
for a period of time of about 5 hours.

34. A process according to claim 16, wherein a sintering aid is added
during step (d).

35. A processd of preparing a grain refining agent as defined in claim
or 8, comprising subjecting TiB2 or TiC to high-energy ball milling to cause
formation of particles having an average particle size of 0.1 to 30 µm,
each
particle being formed of an agglomerate of grains with each grain comprising a
nanocrystal of TiB2 or TiC.

36. A process according to claim 35, wherein said high-energy ball
milling is carried out in a vibratory ball mill operated at a frequency of 8
to 25
Hz.



-13-



37. A process according to claim 36, wherein said vibratory ball mill
is operated at a frequency of about 17 Hz.

38. A process according to claim 35, wherein said high-energy ball
milling is carried out in a rotary ball mill operated at a speed of 150 to
1500
r.p.m.

39. A process according to claim 38, wherein said rotary ball mill is
operated at a speed of about 1000 r.p.m.

40. A process according to claim 35, wherein said high-energy ball
milling is carried out under an inert gas atmosphere.

41. A process according to claim 35, wherein said inert gas
atmosphere comprises argon or helium.

42. A process according to claim 35, wherein said high-energy ball
milling is carried out under a reactive gas atmosphere.

43. A process according to claim 42, wherein said reactive gas
atmosphere comprises hydrogen, ammonia or a hydrocarbon.

44. A process according to claim 35, wherein said high-energy ball
milling is carried out for a period of time of about 20 hours.

45. A process according to claim 35, wherein a sintering aid is added
during said high-enery bal milling.



-14-

Description

Note: Descriptions are shown in the official language in which they were submitted.


CA 02330352 2001-O1-OS
REFRACTORY HARD METALS IN POWDER FORM FOR
USE IN THE MANUFACTURE OF ELECTRODES
The present invention pertains to improvements in the field of
electrodes for metal electrolysis. More particularly, the invention relates to
a
refractory hard metals in powder form for use in the manufacture of such
electrodes.
Aluminum is produced conventionally in a Hall-Heroult
reduction cells by the electrolysis of alumina dissolved in molten cryolite
(Na3A1F6) at temperatures of up to about 950 °C. A Hall-Heroult cell
typically
has a steel shell provided with an insulating lining of refractory material,
which
in turn has a lining made of prebaked carbon blocks contacting the molten
constituents of the electrolyte. The carbon lining acts as the cathode
substrate
and the molten aluminum pool acts as the cathode. The anode is a consumable
carbon electrode, usually prebaked carbon made by coke calcination.
During electrolysis, in Hall-Heroult cells, the carbon anode is
consumed leading to the evolution of greenhouse gases such as CO and C02.
The anode has to be periodically changed and the erosion of the material
modifies the anode-cathode distance, which increases the voltage due to the
electrolyte resistance. On the cathode side, the carbon blocks are subjected
to
erosion and electrolyte penetration. A sodium intercalation in the graphitic
structure occurs, which cause swelling and deformation of the cathode carbon
blocks. The increase of voltage between the electrodes adversely affects the
energy efficiency of the process.
Extensive research has been carried out with refractory hard
metals such as TiBz, as electrode materials. TiB2 and other refractory hard
-1-

CA 02330352 2001-O1-OS
metals are practically insoluble in aluminum, have a low electrical resistance
and are wetted by aluminum. However, the shaping of TiB2 and similar
refractory hard metals is difficult because these materials have high melting
temperatures and are highly covalent.
It is therefore an object of the present invention to overcome the
above drawbacks, and to provide a refractory hard metal in powder form
suitable for the manufacture of electrode by thermal deposition or powder
metallurgy.
According to one aspect of the invention, there is provided a
refractory hard metal in powder form comprising particles having an average
particle size of 0.1 to 30 dm and each formed of an agglomerate of grains with
each grain comprising a nanocrystal of a refractory hard metal of the formula:
AXByXZ ~I)
wherein A is a transition metal, B is a metal selected from the group
consisting
of zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum,
manganese, tungsten and cobalt, X is boron or carbon, x ranges from 0.1 to 3,
y
ranges from 0 to 3 and z from 1 to 6.
The term "nanocrystal" as used herein refers to a crystal having a
size of 100 nanometers or less.
The expression "thermal deposition" as used herein refers to a
technique in which powder particles are injected in a torch and sprayed on a
substrate. The particles acquire a high velocity and are partially or totally
melted during the flight path. The coating is budded by the solidification of
the
droplets on the substrate surface. Examples of such techniques include plasma
spray, arc spray and high velocity oxy-fuel.
-2-

CA 02330352 2001-O1-OS
The expression "powder metallurgy" as used herein refers to a
technique in which the bulk powders are transformed into preforms of a desired
shape by compaction or shaping followed by a sintering step. Compaction refers
to techniques where pressure is applied to the powder, as, for example, cold
uniaxial pressing, cold isostatic pressing or hot isostatic pressing. Shaping
refers
to techniques executed without the application of external pressure such as
powder filling or slurry casting.
Typical examples of refractory hard metals of the formula (I)
include TiBl.s, TiB2, TiC, Tio.sZro.sBz~ Tio.9Zro.~Bz~ Tio.sHfo.sBz and
Zro.sVo.2B2~
TiB2 is preferred.
The present invention also provides, in another aspect thereof, a
process for producing a refractory hard metal in powder form as defined above.
The process of the invention comprises the steps of:
a) providing a first reagent selected from the group consisting of
transition metals and transition metal-containing compounds;
b) providing a second reagent selected from the group consisting of
boron, boron-containing compounds, carbon and carbon-containing
compounds;
c) providing an optional third reagent selected from the group
consisting of zirconium, zirconium-containing compounds, hafnium, hafnium-
containing compounds, vanadium, vanadium-containing compounds, niobium,
niobium-containing compounds, chromium, chromium-containing compounds,
molybdenum, molybdenum-containing compounds, manganese, manganese-
containing compounds, tungsten, tungsten-containing compounds, cobalt and
cobalt-containing compounds; and
-3-

CA 02330352 2001-O1-OS
d) subjecting the first, second and third reagents to high-energy ball
milling to cause solid state reaction therebetween and formation of particles
having an average particle size of 0.1 to 30 Vim, each particle being formed
of
an agglomerate of grains with each grain comprising a nanocrystal of a
refractory hard metal of formula (I) defined above.
The expression "high-energy ball milling" as used herein refers to
a ball milling process capable of forming the aforesaid particles comprising
nanocrystalline grains of the refractory hard metal of formula (I), within a
period of time of about 40 hours.
Examples of suitable transition metals which may be used as the
aforesaid first reagent include titanium, chromium, zirconium and vanadium.
Titanium is preferred. It is also possible to use a titanium-containing
compound
such as TiH2, TiAl3, TiB and TiCl2.
Examples of suitable boron-containing compounds which may be
used as the aforesaid second reagent include A1B2, A1B,2, BH3, BN, VB, H2B03
and Na2B40~. It is also possible to use tetraboron carbide (B4C) as either a
boron-containing compound or a carbon-containing compound.
Examples of suitable compounds which may be used as the
aforesaid third reagent include HfB2, VBZ, NbB2, TaB2, CrB2, MoB2, MnB2,
Mo2B5, W2B5, CoB, ZrC, TaC, WC and HfC.
According to a preferred embodiment, step (d) is carried out in a
vibratory ball mill operated at a frequency of 8 to 25 Hz, preferably about 17
Hz. It is also possible to conduct step (d) in a rotary ball mill operated at
a speed
of 150 to 1500 r.p.m., preferably about 1000 r.p.m.
-4-

CA 02330352 2001-O1-OS
According to another preferred embodiment, step (d) is carried
out under an inert gas atmosphere such as a gas atmosphere comprising argon or
helium, or under a reactive gas atmosphere such as a gas atmosphere
comprising hydrogen, ammonia or a hydrocarbon, in order to saturate dangling
bonds and thereby prevent oxidation of the refractory hard metal. An
atmosphere of argon, helium or hydrogen is preferred. It is also possible to
coat
the particles with a protective film or to admix a sacrificial element such as
Mg
or Ca with the reagents. In addition, a sintering aid such as Y203 can be
added
during step (d).
In the particular case of TiB2 or TiC wherein titanium and boron
or carbon are present in stoichiometric quantities, these two compounds can be
used as starting material. Thus, they can be directly subjected to high-energy
ball milling to cause formation of particles having an average particle size
of
0.1 to 30 Vim, each particle being formed of an agglomerate of grains with
each
grain comprising a nanocrystal of TiB2 or TiC.
The high-energy ball milling described above enables one to
obtain refractory hard metals in powder form having either non-stoichiometric
or stoichiometric compositions.
The refractory hard metals in powder form according to the
invention are suitable for use in the manufacture of electrodes by thermal
deposition or powder metallurgy. Due to the properties of refractory hard
metals, the emission of toxic and greenhouse effect gases during metal
electrolysis is lowered and the lifetime of the electrodes is increased, thus
lowering maintenance costs. A lower and constant inter-electrode distance is
also possible, thereby decreasing the electrolyte ohmic drop.
-5-

CA 02330352 2001-O1-OS
The following non-limiting examples illustrate the invention,
reference being made to the accompanying drawing in which the sole figure
shows the X-ray diffraction of the refractory hard metal in powder form
obtained in Example 1.
EXAMPLE 1.
A TiB2 powder was produced by ball milling 3.45g of titanium
and I.SSg of boron in a hardened steel crucible with a ball-to-powder mass
ratio
of 4.5:1 using a SPEX 8000 (trademark) vibratory ball mill operated at a
frequency of about 17 Hz. The operation was performed under a controlled
argon atmosphere to prevent oxidization. The crucible was closed and sealed
with a rubber O-ring. After 5 hours of high-energy ball milling, a TiB2
structure
was formed, as shown on the X-ray diffraction pattern in the accompanying
drawing. The structure of TiB2 is hexagonal with the space group P6/mmm
( 191 ). The particle size varied between 1 and 5 pm and the crystallite size,
measured by X-ray diffraction, was about 30 nm.
EXAMPLE 2.
A TiB2 powder was produced according to the same procedure as
described in Example 1 and under the same operating conditions, with the
exception that the ball milling was carried out for 20 hours instead of 5
hours.
The resulting powder was similar to that obtained in Example 1. The
crystallite
size, however, was lower (about 16 nm).
-6-

CA 02330352 2001-O1-OS
EXAMPLE 3.
A TiC powder was produced according to the same procedure as
described in Example 1 and under the same operating conditions, with the
exception that titanium and graphite were milled.
EXAMPLE 4.
A TiB2 powder was produced by ball milling titanium diboride
under the same operating conditions as in Example 1, with the exception that
the ball milling was carried out for 20 hours instead of 5 hours. The starting
structure was maintained, but the crystallite size decreased to 15 nm.
EXAMPLE 5.
A TiB 1.g powder was according to the same procedure as
described in Example 1 and under the same operating conditions, with the
exception that 3.6 g of titanium and 1.4 g of boron were milled.
EXAMPLE 6.
A TiB2.2 powder was according to the same procedure as
described in Example 1 and under the same operating conditions, with the
exception that 3.4 g of titanium and 1.7 g of boron were milled.
EXAMPLE 7.
A TiBo.SZro.5B2 powder was according to the same procedure as
described in Example 1 and under the same operating conditions, with the
_7_

CA 02330352 2001-O1-OS
exception that 1.9 g of titanium, 3.1 g of zirconium diboride and 0.8 g of
boron
were milled.
EXAMPLE 8.
A TiBo.9Zro,lBz powder was according to the same procedure as
described in Example 1 and under the same operating conditions, with the
exception that 2.9 g of titanium, 0.6 g of zirconium and 1.5 g of boron were
milled.
EXAMPLE 9.
A TiBo.SHfo,5B2 powder was according to the same procedure as
described in Example 1 and under the same operating conditions, with the
exception that 0.9 g of titanium, 3.3 g of hafnium and 0.8 g of boron were
milled.
EXAMPLE 10.
A Zro,gVo.2B2 powder was according to the same procedure as
described in Example 1 and under the same operating conditions, with the
exception that 3.5 g of zirconium, 0.5 g of vanadium and 1.0 g of boron were
milled.
_g_

Representative Drawing

Sorry, the representative drawing for patent document number 2330352 was not found.

Administrative Status

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Administrative Status

Title Date
Forecasted Issue Date Unavailable
(22) Filed 2001-01-05
(41) Open to Public Inspection 2002-07-05
Dead Application 2006-01-05

Abandonment History

Abandonment Date Reason Reinstatement Date
2005-01-05 FAILURE TO PAY APPLICATION MAINTENANCE FEE

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Application Fee $150.00 2001-01-05
Registration of a document - section 124 $100.00 2001-03-19
Maintenance Fee - Application - New Act 2 2003-01-06 $100.00 2002-11-13
Maintenance Fee - Application - New Act 3 2004-01-05 $100.00 2003-11-14
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
GROUPE MINUTIA INC.
Past Owners on Record
BLOUIN, MARCO
BOILY, SABIN
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Abstract 2001-01-05 1 19
Description 2001-01-05 8 297
Claims 2001-01-05 6 183
Drawings 2001-01-05 1 10
Cover Page 2002-07-05 1 29
Correspondence 2001-02-08 1 25
Assignment 2001-01-05 4 127
Prosecution-Amendment 2001-03-20 18 582
Assignment 2001-03-19 4 138