U.S. patent application number 10/564427 was filed with the patent office on 2006-08-10 for method for the production of metal powders or metal hydride powders of the elements ti,zr, hf,v,nb.ta and cr.
Invention is credited to Manfred Bick, Bernd Sermond.
Application Number | 20060174727 10/564427 |
Document ID | / |
Family ID | 33560122 |
Filed Date | 2006-08-10 |
United States Patent
Application |
20060174727 |
Kind Code |
A1 |
Bick; Manfred ; et
al. |
August 10, 2006 |
Method for the production of metal powders or metal hydride powders
of the elements ti,zr, hf,v,nb.ta and cr
Abstract
A method for the production of metal powders or metal hydride
powders of the elements Ti, Zr, Hf, V, Nb, Ta and Cr is disclosed,
whereby an oxide of the said elements is mixed with a reducing
agent and said mixture, optionally with a hydrogen atmosphere (for
the production of metal hydrides), is heated until the reduction
reaction commences, the reaction product is quenched, then washed
and dried. The oxide used has an average particle size of 0.5 to 20
?m, a BET specific surface of 0.5 to 20 m.sup.2/g and a minimum
content of 94 wt. %.
Inventors: |
Bick; Manfred; (Oberursel,
DE) ; Sermond; Bernd; (Assler, DE) |
Correspondence
Address: |
FULBRIGHT & JAWORSKI, LLP
666 FIFTH AVE
NEW YORK
NY
10103-3198
US
|
Family ID: |
33560122 |
Appl. No.: |
10/564427 |
Filed: |
June 29, 2004 |
PCT Filed: |
June 29, 2004 |
PCT NO: |
PCT/EP04/07032 |
371 Date: |
February 1, 2006 |
Current U.S.
Class: |
75/364 |
Current CPC
Class: |
C01B 6/02 20130101; C22B
34/14 20130101; Y02P 10/20 20151101; B22F 2998/10 20130101; Y02P
10/234 20151101; C22B 3/10 20130101; B22F 9/20 20130101; C22B 34/00
20130101; C22B 5/04 20130101; B22F 2998/10 20130101; B22F 9/20
20130101; B22F 9/16 20130101 |
Class at
Publication: |
075/364 |
International
Class: |
B22F 9/22 20060101
B22F009/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 15, 2003 |
DE |
103 32 033.4 |
Claims
1-21. (canceled)
22. A process for preparing a metal powder or a metal hydride
powder an oxide of at least one of Ti, Zr, Hf, V, Nb, Ta and Cr
with a reducing agent and heating mixture in an oven, optionally
under an atmosphere of hydrogen until a reduction reaction starts,
and leaching the reaction product; and washing and drying the
resultant product to yield the metal powder or metal hydride
powder, wherein the oxide has a mean particle size of 0.5 to 20
.mu.m, a BET specific surface area of 0.5 to 20 m.sup.2/g and a
minimum content of 94 wt. %.
23. A process according to claim 22, wherein the mixture is heated
to 800 to 1400.degree. C. in an oven.
24. A process according to claim 22, wherein the oxide has a mean
particle size of 1 to 6 .mu.m.
25. A process according to claim 22, wherein the oxide has a BET
specific surface area of 1 to 12 m.sup.2/g.
26. A process according to claim 25, wherein the oxide has a BET
specific surface area of 1 to 8 m.sup.2/g.
27. A process according to claim 22, wherein the oxide has a
minimum content of 96 wt. %.
28. A process according to claim 27, wherein the oxide has a
minimum content of 99 wt. %.
29. A process according to claim 22, wherein the proportion of Fe
and Al impurities in the oxide are each <0.2 wt. %, calculated
as the oxides.
30. A process according to claim 29, wherein the proportion of Fe
and Al impurities in the oxide are each <0.1 wt. %, calculated
as the oxides.
31. A process according to claim 22, wherein the proportion of Si
impurities in the oxide is <1.5 wt. %, calculated as
SiO.sub.2.
32. A process according to claim 31, wherein the proportion of Si
impurities in the oxide is <0.3 wt. %, calculated as
SiO.sub.2.
33. A process according to claim 22, wherein the proportion of Na
impurities in the oxide is <0.05 wt. %, calculated as
Na.sub.2O.
34. A process according to claim 22, wherein the proportion of P
impurities in the oxide is <0.2 wt. %, calculated as
P.sub.2O.sub.5.
35. A process according to claim 22, wherein the loss on ignition
of the oxide at 1000.degree. C. as constant weights is <1 wt.
%.
36. A process according to claim 22, wherein the tamped down bulk
density according to EN ISO 787-11 (previously DIN 53194) of the
oxide is 800 to 1600 kg/m.sup.3.
37. A process according to claim 22, wherein a proportion of up to
15 wt. % of said oxide is replaced by an additive selected from the
group consisting of MgO, CaO, Y.sub.2O.sub.3 and CeO.sub.2.
38. A process according to claim 22, comprising reacting a reducing
agent comprising an alkaline earth metal, alkali metal, or a
hydride thereof with a compound to reduce the compound.
39 A process according to claim 38, wherein the reducing agent
comprises at least one of Mg, Ca, CaH.sub.2 or Ba.
40. A process according to claim 22, wherein the reducing agent has
a minimum content of 99 wt. %.
41. A process according to claim 22, wherein the reaction is
performed under a protective gas.
42. A process according to claim 22, wherein the reaction product
is leached with hydrochloric acid.
43. A process according to claim 23, wherein the oxide used has a
mean particle size of 1 to 6 .mu.m.
Description
[0001] The invention provides a process for preparing metal powders
and metal hydride powders of the elements Ti, Zr, Hf, V, Nb, Ta and
Cr.
[0002] Metal powders of the elements Ti, Zr, Hf, V, Nb, Ta and Cr
and powdered hydrides of these metals are used, for example, in the
following areas of application: titanium for the production of
titanium components for the aircraft and automobile industries, for
the production of titanium alloys and for the production of
sintered AlNiCo magnets; titanium, zirconium and hafnium in the
pyro-industry, for the production of electric detonator systems
(e.g. in airbags) and ignition delay elements, in getter materials
in vacuum tubes, lamps, vacuum equipment and gas purification
plants; hafnium as an alloying element in niobium, tantalum,
titanium, molybdenum and tungsten alloys; vanadium as an
alternative metal electrode in metal-hydride/nickel-hydride
batteries and in TiAl.sub.6V.sub.4 alloys; niobium in the
production of equipment for the chemicals industry and as an
alloying element for ZrNb alloys (nuclear industry) and NbHfTi
alloys (highly heat-resistant materials for jet engines or
explosion chambers); tantalum in capacitors.
[0003] As a result of the sometimes very high requirements placed
on the reliability of the products mentioned above (e.g. airbag
detonators), it is desirable to produce the metal powders or metal
hydride powders reproducibly and with identical properties from
batch to batch (in particular with respect to burning time,
ignition point, mean particle size, particle size distribution and
oxidation value).
[0004] The metal powders can be produced by a reduction process. In
this case, oxides of the metals (Ti, Zr, Hf, V, Nb, Ta and Cr) are
reduced, for example with calcium or calcium hydride. The reduction
process is performed in a vessel which can be sealed, rendered
inert and evacuated. The reducing agents(s) are normally added in
excess. After reduction, the oxides of the reducing agents being
produced are removed by leaching with acid and then washing with
water. The acid content of the metal powder obtained is between 1
and 5% when using this method.
[0005] Alternatively, the metal powders can be obtained from the
relevant metal by hydrogenation and dehydrogenation (HDH method).
The relevant metal is hydrogenated and, in this then brittle form,
can be crushed mechanically to give powders of the desired
fineness. In order to avoid damage due to the uptake of oxygen and
nitrogen, ultrapure hydrogen has to be used for the hydrogenation
process. Crushing the hydrogenated metal to the desired particle
size must also be performed in a pure protective gas atmosphere
(e.g. helium or argon). Subsequent removal of the hydrogen is
achieved by decomposing the metal hydride under vacuum at elevated
temperature. Metal hydride powders are produced in the same way.
The dehydrogenation process is then simply omitted.
[0006] A disadvantage of the metal powders and hydrides produced in
this way is, inter alia, that these do not have reproducible
burning times, reproducible specific surface areas, reproducible
particle size distributions or reproducible ignition points.
[0007] The object of the invention is to overcome the disadvantages
of the prior art and to provide metal powders and metal hydride
powders of the elements Ti, Zr, Hf, V, Nb, Ta and Cr that have a
burning time of 4 s per 50 cm to 3000 s per 50 cm and an ignition
point of 160.degree. C. to 400.degree. C. and above this in
individual cases.
[0008] The burning time, expressed in s/50 cm is determined as
follows. The substance being tested is first sieved through two
sieves with mesh sizes of 250 .mu.m and 45 .mu.m in order to
eliminate problematic agglomerates. Optionally, the sample can be
carefully moved about with a brush during this procedure. The fine
material that has passed through the 45 .mu.m sieve is used to
determine the burning time. 15 g of the sample are placed loosely
in a metal channel, described below, smoothed out with a piece of
cardboard and any excess removed by wiping it off. The metal
channel is provided with two marks that are located at a spacing of
500 mm from each other. Upstream of the first mark, an additional
approximately pea-sized amount of substance is applied and is
ignited with a burner. With the aid of a time-exposure photograph,
the time required to pass through the distance between the first
and the last mark is now determined. The analytical result for
burning time is cited with the dimensions [s/50 cm].
[0009] The ignition point is determined as follows: 10 g of the
substance being tested are introduced into a pre-heated so-called
"ignition block" and the temperature at which self-ignition occurs
is measured. The ignition block, consisting of an iron cube with an
edge-length of 70 mm and with drilled holes for the material and a
thermocouple (20 mm and 8 mm diameter, each hole 35 mm deep,
distance between mid-points of hole 18 mm), is preheated to a
temperature slightly below the ignition temperature, using a
blowlamp, after inserting the thermometer or thermocouple in the
drilled hole provided for this purpose. This temperature is
determined using a trial sample. A heaped spatula (10 g) of the
metal powder or hydride being tested is now introduced into the
material hole in the pre-heated ignition block and the block is
heated with a full blowlamp flame until the powder self-ignites.
The temperature reached at that time is the ignition point.
[0010] Furthermore, it is desirable that the metal powder or metal
hydride powder has a metal or metal hydride content of at least 75
wt. %, preferably at least 88 wt. %, particularly preferably 90 wt.
%, a mean particle diameter of 1 to 15 .mu.m, a preferred particle
size distribution (measured by means of laser diffraction) of 1 to
20 .mu.m and a BET specific surface area of 0.2 to 5 m.sup.2/g.
[0011] The mean particle diameter is determined as follows using a
"Fisher sub-sieve size particle sizer" (called FSSS in the
following). A description of this method of measurement can be
found in "Instructions, Fisher Model 95 Sub-Sieve Sizer, catalog
number 14-311, part no. 14579 (rev. C), published 01-94" from
Fisher Scientific. Express reference is made here to this
description of the measurement process.
[0012] The object is achieved by a process for preparing metal
powders or metal hydride powders of the elements Ti, Zr, Hf, V, Nb,
Ta and Cr, in which an oxide of these elements is mixed with a
reducing agent and this mixture is heated in an oven, optionally
under an atmosphere of hydrogen (metal hydrides are then formed),
until the reduction reaction starts, the reaction product is
leached and then the product is washed and dried, wherein the oxide
used has a mean particle size of 0.5 to 20 .mu.m, preferably 1 to 6
.mu.m, a BET specific surface area of 0.5 to 20 m.sup.2/g,
preferably 1 to 12 m.sup.2/g, and particularly preferably 1 to 8
m.sup.2/g, and a minimum content of 94 wt. %, preferably 96 wt. %
and particularly preferably 99 wt. %.
[0013] The proportion of Fe and Al impurities in the oxide is
preferably <0.2 wt. %, particularly preferably <0.1 wt. %
each (each calculated as the oxide). The proportion of Si
impurities in the oxide is preferably <1.5 wt. %, particularly
preferably <0.3 wt. % (calculated as SiO.sub.2). The proportion
of Na impurities in the oxide is preferably <0.05 wt. %
(calculated as Na.sub.2O). The proportion of P impurities in the
oxide is preferably <0.2 wt. % (calculated as P.sub.2O.sub.5).
The loss on ignition of the oxide at 1000.degree. C. (constant
weight) is preferably <1 wt. %, particularly preferably <0.5
wt. %. The tamped down bulk density according to EN ISO 787-11
(previously DIN 53194) of the oxide is preferably 800 to 1600
kg/m.sup.3. A proportion of up to 15 wt. % of the oxide can be
replaced by additives consisting of MgO, CaO, Y.sub.2O.sub.3 or
CeO.sub.2.
[0014] It was found that, by targeted selection of the oxidic raw
materials with the properties described above and then performing
the process, products are obtained that have a burning time of 4 s
per 50 cm to 3000 s per 50 cm, an ignition energy of 1 .mu.J to 1
mJ, a mean particle size of 1 to 8 .mu.m, a BET specific surface
area of 0.2 to 5 m.sup.2/g, an ignition point of 160.degree. C. to
400.degree. C. and above that in individual cases, wherein
reproducible particle size distributions are obtained in each case.
The combination of average particle size and specific surface area
within each of the ranges cited above for the oxidic starting
compound, together with the minimum content cited, leads to the
desired product.
[0015] The reducing agents preferably used may be: alkaline earth
metals and alkali metals and the hydrides of each. Magnesium,
calcium, calcium hydride and barium or defined mixtures of these
are particularly preferred. The reducing agent preferably has a
minimum content of 99 wt. %, particularly preferably 99.5 wt.
%.
[0016] Powdered pure metals, partially hydrogenated metals or metal
hydrides are obtained, depending on the amount of hydrogen added
during the reduction process in the oven. The higher the hydrogen
content of the process product, the greater is the burning time
(i.e. the metal burns more slowly) and the higher the ignition
point, and vice versa.
[0017] Leaching the reaction product is preferably performed with
hydrochloric acid and this is particularly preferably used in a
slight excess.
[0018] The invention is explained in more detail using the examples
given below.
EXAMPLE 1
Preparation Of Zirconium Powder
[0019] 43 kg of ZrO.sub.2 (powdered zirconium oxide (natural
baddeleyite) with the following properties: ZrO.sub.2+HfO.sub.2
min. 99.0%; HfO.sub.2 1.0-2.0%; SiO.sub.2 max. 0.5%; TiO.sub.2 max.
0.3%; Fe.sub.2O.sub.3 max. 0.1%; loss on ignition max. 0.5%; mean
particle size (using FSSS) 4 -6 .mu.m; proportion of monoclinic
crystal structure min. 95%; specific surface area (BET) 0.5-1.5
m.sup.2/g) and
[0020] 31.5 kg of Ca (calcium in the form of granules with the
following properties: Ca min. 99.3%; Mg max. 0.7%)
[0021] were mixed for 20 minutes under an atmosphere of argon. Then
the mixture was introduced into a container. The container was
placed in an oven that was subsequently closed and filled with
argon up to a pressure of 100 hPa above atmospheric pressure. The
reaction oven was heated to a temperature of about 1250.degree. C.
over the course of one hour. As soon as the reaction material had
reached the temperature of the oven, the reduction reaction
started: ZrO.sub.2+2Ca.fwdarw.Zr+2CaO
[0022] 60 minutes after switching on the oven heating system, it
was then switched off. When the temperature had dropped to
<50.degree. C., the reaction material was removed from the
crucible and leached with concentrated hydrochloric acid. A
zirconium powder with the following analytical characteristics was
obtained: Zr+Hf 96.1%; Hf 2.2%; O 0.7%; Si 0.21%; H 0.16%; Mg
0.11%; Ca 0.13%; Fe 0.07%; Al 0.1%; Cl 0.002%; mean particle size
4.9 .mu.m; particle size distribution d.sub.50 9.9 .mu.m; specific
surface area 0.5 m.sup.2/g; ignition point 220.degree. C.; burning
time 80 sec/50 cm.
EXAMPLE 2
Preparation of Zirconium Powder
[0023] 36 kg of ZrO.sub.2 (powdered zirconium oxide with the
following properties: ZrO.sub.2+HfO.sub.2 min. 99.0%; HfO.sub.2
1.0-2.0%; SiO.sub.2 max. 0.2%; TiO.sub.2 max. 0.25%;
Fe.sub.2O.sub.3 max. 0.02%; loss on ignition max. 0.4%; mean
particle size (using FSSS) 3-5 .mu.m; proportion of monoclinic
crystal structure min. 96%; specific surface area (BET) 3.0-4.0
m.sup.2/g) and
[0024] 17 kg of Mg (magnesium in the form of granules with the
following properties: Mg min. 99.8%; bulk density max. 0.4-0.5
g/cm.sup.3)
[0025] were placed in a container in the oven, in the same way as
described in example 1. The oven was heated to 1050.degree. C. As
soon as the reaction material reached the temperature of the oven,
the reduction reaction started: ZrO.sub.2+2Mg.fwdarw.Zr+2MgO
[0026] The oven heating system was switched off 20 minutes after
the start of the reduction reaction. When the temperature had
dropped to <50.degree. C., the reaction material was removed
from the crucible and leached with concentrated hydrochloric acid.
A zirconium powder with the following analytical characteristics
was obtained: Zr+Hf 91.7%; O 1.6%; Si 0.14%; H 0.13%; Mg 0.59%;
Ca<0.001%; Fe 0.045%; mean particle size 2.5 .mu.m; particle
size distribution d.sub.50 4.3 .mu.m; ignition point 175.degree.
C.; burning time 24 sec/50 cm.
* * * * *