Note: Descriptions are shown in the official language in which they were submitted.
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PRODUCTION OF ULTRA FINE
TRANSITION METAL POWDERS
FIELD OF THE INVENTION
This invention relates to a process for the production of ultra fine
transition metal
powders, particularly, vanadium, niobium and tantalum powders by the pyrolysis
of transition
metal complexes in a high boiling point inert solvent, such as a hydrocarbon
or higher alkyl
alcohol.
PUBLICATIONS
1. "Highly Reduced Organometallic Complexes of Vanadium, Niobium, Tantalum and
Chromium", a thesis submitted to the Faculty of the Graduate School of the
University of
Minnesota - by Marie Kathleen Pomije, (September 1995).
2. Inorg. Chem. (1998), 37 6518-6527, - Barybim et al
3. Inorganica Chemica Acta. ( 1998), 269, 58-62 - Barybin
4. Chem. Euro. J. (1995), 1, No. 8 - Ellis et al
5. Inorg. Chem. (1983), 22, 1865-1870 - Calderazzo et al
SUMMARY OF THE INVENTION
The present invention provides for the production of ultra fine transition
metal
complexes by the pyrolysis of the metal complex. Preferably, the heating of
the metal
complex is effected in a suitable inert solvent such as, for example, a
hydrocarbon, alkyl
alcohol, ether, diglyme, ester at an effective temperature for a sufficient
period of time.
Examples of suitable metal complexes comprise carbonyl and trifluorophosphine
groups wherein the metal has a valence of 0 or -1, such as [Et4N][Ta(PF3)6],
[Et4N][Nb(PF3)6] and [Et4N][V(PF3)6].
Accordingly, in one aspect, the invention provides a method of preparing ultra
fine
metal powder comprising pyrolizing a complex metal compound of said metal,
wherein said
CA 02500077 2005-03-09
metal is in a valence state selected from 0 and 1, in an inert solvent at an
effective
temperature to produce said ultra fine powder, and removing said powder from
said inert
solvent.
Preferably, said hydrocarbon is of the formula C~HZ"+z wherein n is selected
from 12
to 20.
Preferably, said alkanol is of the formula C"HZ"+~ OH wherein n is selected
from 10 to
20.
We have found that the metal powder has a mean particle size of less than 10
microns,
preferably 1 to 5 microns and more preferably, less than I micron.
The process of the invention is applicable to suitable metal complexes of the
first,
second and third transition metal series of the Periodic Table of the
Elements. Most preferred
are the Group VB elements, namely, vanadium, niobium and tantalum.
In a further aspect, the invention provides ultra fine metal powders produced
by the
processes as hereinabove defined.
In a further aspect, the invention provides for the use of the ultra fine
metal powders
according to the invention, particularly the use wherein the metal is tantalum
in cell phones.
The metal complexes of use in the practise of the invention may be made by the
reduction of salts of the metals in solution in the presence of ligand
reagents, such as carbon
monoxide, trifluorophosphine and naphthalene.
A two-step reductive trifluorophosphination to produce [Et4N][Ta(PF3)6],
[Et4N][Nb(PF3)6] [Et4N] [V(PF3)6] has been described (1,2).
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In order that the invention may be better understood, preferred embodiments
will now
be described.
EXAMPLES
EXAMPLE 1
Cobalt carbonyl, Co2(CO)8, (lOg) was dissolved in warm toluene (20 mL) and the
solution was slowly added to paraffin oil at 250 °C. The red solution
immediately darkened
and become black. Carbon monoxide gas and toluene vapours were evolved and
removed.
2
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After the cobalt carbonyl had decomposed, the paraffin oil was cooled,
filtered and the
residue washed with hexane and dried to provide sub-micron cobalt powder (3.4
g, 99 %).
EXAMPLE 2
Manganese carbonyl, Mn(CO)6, (5 g) was dissolved in warm acetone ( 10 mL) and
added to n-hexadecanol and heated to 250 °C. Carbon monoxide gas and
acetone vapours
were evolved. The solution became black and after the manganese carbonyl had
decomposed
the n-hexadecane was cooled, filtered and the residue was washed with hexane
and dried to
provide sub-micron manganese powder (1.2 g, 99 %).
EXAMPLE 3
HTa(PF3)6 (5 g) was dispersed in paraffin oil and heated to 360 °C.
Immediate
decomposition of the Ta complex was observed with evolution of hydrogen and
PF3. After
the complex was decomposed, the paraffin oil was cooled, filtered and the
residue washed
with n-hexane and dried. Sub-micron tantalum powder (1.25 g, 99 %) was
obtained.
EXAMPLE 4
[Et4N] [Ta(PF3)6], (100g), was dissolved in acetone (50mL), added to boiling n-
decanol (100mL) and stirred for 20 minutes. The black solution was filtered,
and the
collected powder was washed with acetone and air dried to given sub-micron
tantalum
powder (22g).
Although this disclosure has described and illustrated certain preferred
embodiments
of the invention, it is to be understood that the invention is not restricted
to those particular
embodiments. Rather, the invention includes all embodiments which are
functional or
mechanical equivalence of the specific embodiments and features that have been
described
and illustrated.
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