U.S. patent application number 15/025537 was filed with the patent office on 2016-08-18 for non-evaporable getter alloys particularly suitable for hydrogen and carbon monoxide sorption.
The applicant listed for this patent is SAES GETTERS S.P.A.. Invention is credited to Antonio BONUCCI, Alberto CODA, Andrea CONTE, Alessandro GALLITOGNOTTA.
Application Number | 20160237533 15/025537 |
Document ID | / |
Family ID | 49958554 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160237533 |
Kind Code |
A1 |
CODA; Alberto ; et
al. |
August 18, 2016 |
NON-EVAPORABLE GETTER ALLOYS PARTICULARLY SUITABLE FOR HYDROGEN AND
CARBON MONOXIDE SORPTION
Abstract
Getter devices with improved sorption rate, based on powders of
quaternary alloys particularly suitable for hydrogen and carbon
monoxide sorption, are described. Quaternary alloys having a
composition comprising zirconium, vanadium, titanium and aluminum
as main constituent elements are also described.
Inventors: |
CODA; Alberto; (GERENZANO,
IT) ; GALLITOGNOTTA; Alessandro; (ORIGGIO, IT)
; BONUCCI; Antonio; (HAMBURG, DE) ; CONTE;
Andrea; (MILANO, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAES GETTERS S.P.A. |
Lainate MI |
|
IT |
|
|
Family ID: |
49958554 |
Appl. No.: |
15/025537 |
Filed: |
November 19, 2014 |
PCT Filed: |
November 19, 2014 |
PCT NO: |
PCT/IB2014/066169 |
371 Date: |
March 28, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 53/04 20130101;
H01J 61/26 20130101; B01D 2257/108 20130101; C22C 30/00 20130101;
H01J 7/183 20130101; B01D 2253/1122 20130101; C22C 16/00 20130101;
C22C 1/0458 20130101; B01D 2257/502 20130101 |
International
Class: |
C22C 30/00 20060101
C22C030/00; B01D 53/04 20060101 B01D053/04; H01J 61/26 20060101
H01J061/26; C22C 1/04 20060101 C22C001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 20, 2013 |
IT |
MI2013A001921 |
Claims
1. A getter device containing non-evaporable getter alloy powders
having high gas sorption efficiency, particularly for hydrogen and
carbon monoxide, wherein said alloy powders comprise as
compositional elements zirconium, vanadium, titanium and aluminum
and have an atomic percentage composition of said elements which
can vary within the following ranges: zirconium from 38 to 44.8%
vanadium from 14 to 29% titanium from 13 to 15% aluminum from 11.5
to 35% said atomic percentage ranges being considered with respect
to the sum of zirconium, vanadium, titanium and aluminum in the
non-evaporable getter alloy, said non-evaporable getter alloy
optionally comprising one or more additional elements in an atomic
percentage composition lower than 8% with respect to the total of
the alloy composition, said one or more additional elements being
selected from the group consisting of iron, chromium, manganese,
cobalt or nickel in an atomic percentage composition comprised
between 0.1 and 7% with respect to the total of the alloy
composition while minor amounts of other chemical elements may be
present in the alloy composition in a percentage lower than 1% with
respect to the total of the alloy composition, being the sum of
zirconium, vanadium, titanium, aluminum and said optionally present
additional elements balanced to 100% atomic percentage
composition.
2. The getter device according to claim 1, wherein said one or more
additional elements are selected from the group consisting of iron,
chromium, manganese, cobalt or nickel in an atomic percentage
composition comprised between 0.1 and 5% with respect to the total
of the alloy composition.
3. The getter device according to claim 1, wherein said getter
alloy powders are mixed with metal powders.
4. The getter device according to claim 3, wherein said metal
powders are selected between titanium and zirconium or mixtures
thereof.
5. The getter device according to claim 1, wherein said alloy
powders have a particle size lower than 500 .mu.m.
6. The getter device according to claim 5, wherein said alloy
powders have a particle size lower than 300 .mu.m.
7. The getter device according to claim 1, wherein said alloy
powders are compressed and sintered to form a single body getter
element.
8. The getter device according to claim 7, wherein said getter
device is a getter pump, a cartridge for a getter pump or a pump
containing one or more pumping elements.
9. Use of the getter device according to claim 1, for the removal
of hydrogen and carbon monoxide.
10. A hydrogen sensitive system containing the getter device
according to claim 1.
Description
[0001] The present invention relates to new getter alloys having an
increased hydrogen and carbon monoxide sorption rate, to a method
for sorbing hydrogen with said alloys and to hydrogen-sensitive
devices which employ said alloys for the removal of hydrogen.
[0002] The alloys which are the subject-matter of this invention
are particularly useful for all the applications which require high
sorption rate of significant quantities of hydrogen and carbon
monoxide.
[0003] Among the most interesting applications for these new
sorbing alloys there are illumination lamps, vacuum pumps and gas
purification.
[0004] The use of getter materials for hydrogen removal in these
applications is already known, but the currently developed and used
solutions are not suitable for meeting the requirements which are
imposed by the continuous technological developments which set more
and more rigid limits and constraints.
[0005] In illumination lamps, with particular reference to high
pressure discharge lamps and low pressure mercury lamps, the
presence not only of hydrogen even at low levels but also of other
gaseous contaminants significantly decreases the device
performance. More information regarding the degradation phenomena
can be found in EP 1704576 relating to a different material for
hydrogen and residual carbon monoxide sorption.
[0006] In this particular applicative field not only the material
capacity to effectively sorb hydrogen at high temperatures is
particularly important, but for some lamps also a high sorption
rate and low activation temperature of the material as regards to
the sorption of other gas species, with respect to conventional NEG
alloys.
[0007] Another applicative field which can benefit from the use of
getter alloys capable of hydrogen sorption at high temperatures is
that of getter pumps. This type of pumps is described in various
patents such as U.S. Pat. No. 5,324,172 and U.S. Pat. No.
6,149,392, as well in the international patent publication WO
2010/105944, all in the name of the applicant. Being able to use
the getter material of the pump at high temperature increases the
performance thereof in terms of sorption capacity towards other
gases, but in this case a high sorption rate is a main issue same
as the capacity in order to obtain better device performances.
[0008] Another applicative field that benefits from the advantages
of a getter material capable of hydrogen and carbon monoxide
sorption with high sorption rate is the purification of the gases
used in semiconductor industries. As a matter of fact, particularly
when high flows are requested, typically higher than some l/min,
the getter material has to quickly sorb gaseous species in order to
remove gas contaminants such as N.sub.2, H.sub.2O, O.sub.2,
CH.sub.4, CO, CO.sub.2.
[0009] Two of the most efficient solutions for hydrogen removal are
disclosed in EP 0869195 and in the international patent publication
WO 2010/105945, both in the name of the applicant. The first
solution makes use of Zirconium-Cobalt-RE alloys wherein RE can be
a maximum of 10% and is selected among Yttrium, Lanthanum and other
Rare Earths, In particular, the alloy having the following weight
percentages: Zr 80.8%-Co 14.2% and RE 5%, has been particularly
appreciated. Instead, the second solution makes use of
Yttrium-based alloys in order to maximize the removable amount of
hydrogen also at temperatures above 200.degree. C. but their
properties of irreversible gas sorption are essentially limited
with respect to the needs of many applications requiring vacuum
conditions.
[0010] A particular solution, useful for quickly gettering hydrogen
and other undesired gases such as CO, N.sub.2 and O.sub.2 is
described in U.S. Pat. No. 4,360,445, but the oxygen-stabilized
zirconium-vanadium-iron intermetallic compound disclosed therein
can be successfully used only in a particular range of temperature
(i.e. -196.degree. C. to 200.degree. C.) that requires a large
amount of oxygen lowering of sorption capacity and rate per gram,
i.e. limiting its field of possible application.
[0011] As an alternative, U.S. Pat. No. 4,839,035 disclosed a
non-evaporable getter alloy suitable to remove hydrogen and carbon
monoxide focusing on Zr-rich compositions selected in the
zirconium-vanadium-aluminum system. Even if those alloys seem to be
effective in facilitating some steps in the manufacturing process,
the absorption rates when exposed to H.sub.2 and CO are not enough
to be applied in many applications, as for example in getter pumps
for high vacuum systems. The international patent publication
number WO 2013/175340, in the applicant's name, describes some
stable getter alloys containing zirconium, vanadium and titanium
(i.e. not requiring a large amount of oxygen in order to obtain an
intermetallic compound) and having an improved sorption capacity
with respect to several gaseous contaminants. However, WO
2013/175340 is silent on the way to obtain an improvement of the
sorption speed with respect to hydrogen and, simultaneously, to
other gaseous species, i.e. carbon monoxide.
[0012] Therefore improved characteristics versus hydrogen and
carbon monoxide of the alloys according to the present invention
have to be intended and evaluated in a twofold possible meaning,
namely an increased sorption rate for H.sub.2 and with low hydrogen
equilibrium pressure. For the most interesting alloys according to
the present invention, this property should be considered and
associated with an unexpected improved sorption performance with
respect to other gaseous species and with particular reference to
CO. Moreover, these alloy have shown lower activation temperatures
and lower particle losses in combination with higher embrittlement
and resistance to hydrogen cycling
[0013] It is therefore an object of the present invention to
provide getter devices based on the use of a new non-evaporable
getter material capable of overcoming the disadvantages of the
prior art. These objects are achieved by a getter device containing
powders of a quaternary non-evaporable getter alloy, said
non-evaporable getter alloy comprising as compositional elements
zirconium, vanadium, titanium and aluminum and having an atomic
percentage composition of said elements which can vary within the
following atomic percentage ranges:
[0014] a. zirconium from 38 to 44.8%
[0015] b. vanadium from 14 to 29%
[0016] c. titanium from 13 to 15%
[0017] d. aluminum from 11.5 to 35%
said atomic percentage ranges being considered with respect to the
sum of zirconium, vanadium, titanium and aluminum in the
non-evaporable getter alloy.
[0018] Inventors have surprisingly found that quaternary alloys in
the Zr--V--Ti--Al system have an improved H.sub.2 and CO sorption
rate when the titanium amount is selected in the range comprised
between 13 and 15%.
[0019] Optionally, the non-evaporable getter alloy composition can
further comprise as additional compositional elements one or more
metals in an overall atomic concentration lower than 8% with
respect to the total of the alloy composition. In particular, these
one or more metals can be selected from the group consisting of
iron, chromium, manganese, cobalt, and nickel in an overall atomic
percentage preferably comprised between 0.1 and 7%, more preferably
between 0.1 and 5%. Moreover, minor amounts of other chemical
elements can be present in the alloy composition if their overall
percentage is less than 1% with respect to the total of the alloy
composition.
[0020] These and other advantages and characteristics of the alloys
and devices according to the present invention will be clear to
those skilled in the art from the following detailed description of
some not limiting embodiments thereof with reference to the annexed
drawings wherein:
[0021] FIG. 1 shows a device containing getter bodies according to
one embodiment of the present invention;
[0022] FIGS. 1a and 1b show some sintered getter bodies according
to the present invention suitable to be used in the getter device
of FIG. 1;
[0023] FIGS. 2 to 4 show devices made with a single compressed
alloy body according to different possible embodiments; and
[0024] FIGS. 5 to 8 show other getter devices based on alloy
powders according to the present invention.
[0025] In the field of getter pumps, the requirement is sorbing
hydrogen in an effective way by operating at high temperatures, for
example at 200.degree. C., in such a way that the getter material
is capable of effectively sorbing the other gas impurities as well
N.sub.2, H.sub.2O, O.sub.2, CH.sub.4, CO, CO.sub.2 possibly present
in the chamber that is to be evacuated. In this case, all the
alloys which are the subject-matter of the present invention have
features that are advantageous in this application, whereby those
having higher affinity toward several gas impurities are
particularly appreciated.
[0026] FIG. 1 shows discoidal getter elements (121, 121', . . . )
conveniently assembled in a stack (120) to obtain an object with
increased pumping performances. The stack may be equipped with a
heating element coaxial to the supporting element (122) and mounted
on a vacuum flange or fixed in the vacuum chamber by means of
suitable holders. Some not limiting embodiments of gettering
elements suitable to be used to obtain said stacks are shown in
FIGS. 1a and 1b.
[0027] FIGS. 2 and 3 show, respectively, a cylinder 20 and a board
30 made by cutting an alloy sheet of suitable thickness or obtained
by compression of alloy powders. For their practical use the
devices must be positioned in a fixed position in the container
that is to be maintained free from hydrogen. The devices 20 and 30
could be fixed directly to an internal surface of the container,
for example by spot welding when said surface is made of metal.
Alternatively, devices 20 or 30 can be positioned in the container
by means of suitable supports, and the mounting on the support can
be carried out by welding or mechanical compression.
[0028] FIG. 4 shows another possible embodiment of a getter device
40, wherein a discrete body of an alloy according to the invention
is used, particularly for those alloys having high plasticity
features. In this case the alloy is manufactured in the form of a
strip from which a piece 41 having a desired size is cut, and the
piece 41 is bent in its portion 42 around a support 43 in the form
of a metal wire. Support 43 may be linear but it is preferably
provided with curves 44, 44', 44'' that help the positioning of
piece 41, whose shaping can be maintained by means of one or
several welding points (not shown in the figure) in the overlapping
zone 45, although a simple compression during the bending around
support 43 can be sufficient considering the plasticity of these
alloys.
[0029] Alternatively, other getter devices according to the
invention can be manufactured by using powders of the alloys. In
the case that powders are used, these preferably have a particle
size lower than 500 and even more preferably lower than 300 in some
applications being included between 0 and 125
[0030] FIG. 5 shows a broken view of a device 50, having the shape
of a tablet 51 with a support 52 inserted therein; such a device
can be made for example by compression of powders in a mold, having
prepared support 52 in the mold before pouring the powder.
Alternatively, support 52 may be welded to tablet 51.
[0031] FIG. 6 shows a device 60 formed by powders of an alloy 61
according to the invention pressed in a metal container 62; device
60 may be fixed to a support (not shown in the figure) for example
by welding container 62 thereto.
[0032] Finally, FIGS. 7 and 8 show another kind of device
comprising a support 70 manufactured starting from a metal sheet 71
with a depression 72, obtained by pressing sheet 71 in a suitable
mold. Most of the bottom part of depression 72 is then removed by
cutting, obtaining a hole 73, and support 70 is kept within the
pressing mold so that depression 72 can be filled with alloy
powders which are then pressed in situ thus obtaining device 80
(seen in the section taken along line A-A' of FIG. 7) in which the
powder package 81 has two exposed surfaces, 82 and 83, for the gas
sorption.
[0033] In all the devices according to the invention the supports,
containers and any other metal part which is not formed of an alloy
according to the invention is made of metals having a low vapor
pressure, such as tungsten, tantalum, niobium, molybdenum, nickel,
nickel iron or steel in order to prevent these parts from
evaporating due to the high working temperature to which said
devices are exposed.
[0034] The alloys useful for the getter devices according to the
invention can be produced by melting the pure elements, preferably
in powder or pieces, in order to obtain the desired atomic ratios.
The melting must be carried out in a controlled atmosphere, for
example under vacuum or inert gas (argon is preferred), in order to
avoid the oxidation of the alloy which is being prepared. Among the
most common melting technologies, but not limited to these, arc
melting, vacuum induction melting (VIM), vacuum arc remelting
(VAR), induction skull meting (ISM), electro slug remelting (ESR),
or electron beam melting (EBM) can be used. The sintering or high
pressure sintering of the powders may also be employed to form many
different shapes such as discs, bars, rings, etc. of the
non-evaporable getter alloys of the present invention, for example
to be used within getter pumps. In a possible embodiment of the
present invention, moreover, sintered products can be obtained by
using mixtures of getter alloy powders having a composition
according to claim 1 optionally mixed with metallic powders such
as, for example, titanium, zirconium or mixtures thereof, to obtain
getter elements, usually in the form of bars, discs or similar
shapes as well described for example in EP 0719609.
[0035] As an example, polycrystalline ingots can be prepared by arc
melting of appropriate mixtures of the high purity constituent
elements in an argon atmosphere. The ingot can be then grinded by
ball milling in a stainless steel jar under argon atmosphere and
subsequently sieved to a desired powder fraction, usually of less
than 500 .mu.m or more preferably less than 300 .mu.m.
[0036] In a second aspect thereof, the invention consists in the
use of a getter device as described above for hydrogen and carbon
monoxide removal. For example, said use can be directed to hydrogen
and carbon monoxide removal from a closed system or device
including or containing substances or structural elements which are
sensitive to the presence of said gases. Alternatively, said use
can be directed to hydrogen and carbon monoxide removal from gas
flows used in manufacturing processes involving substances or
structural elements which are sensitive to the presence of said
gases. Hydrogen and carbon monoxide negatively affect the
characteristics or performances of the device and said undesired
effect is avoided or limited by means of at least a getter device
containing a quaternary non-evaporable getter alloy comprising as
compositional elements zirconium, vanadium, titanium, aluminum and
having an atomic percentage composition of said elements which can
vary within the following ranges: [0037] a. zirconium from 38 to
44.8%; [0038] b. vanadium from 14 to 29% [0039] c. titanium from 13
to 15% [0040] d. aluminum from 11.5 to 35% said atomic percentage
ranges being considered with respect to the sum of zirconium,
vanadium, titanium and aluminum in the non-evaporable getter
alloy.
[0041] Optionally, the non-evaporable getter alloy composition can
further comprise as additional compositional elements one or more
metals in an overall atomic concentration lower than 8% with
respect to the total of the alloy composition. In particular, these
metals can be selected from the group consisting of iron, chromium,
manganese, cobalt, and nickel in an overall atomic percentage
preferably comprised between 0.1 and 7%, more preferably between
0.1 and 5%. Moreover, minor amounts of other chemical elements can
be present in the alloy composition if their overall percentage is
less than 1% with respect to the total of the alloy
composition.
[0042] The use according to the invention finds application by
using the getter alloy in the form of powder, of powders pressed in
pills, laminated on suitable metal sheets or positioned inside one
of the suitable containers, possible variants being well known to
the person skilled in the art.
[0043] Alternatively, the use according to the invention can find
application by using the getter alloy in the form of sintered (or
high-pressure sintered) powders, optionally mixed with metallic
powders such as, for example, titanium or zirconium or mixtures
thereof.
[0044] The considerations above regarding the positioning of the
getter material according to the present invention are general and
are suitable for the employment thereof independently of the mode
of use of the material or of the particular structure of its
container.
[0045] Non-limiting examples of hydrogen-sensitive systems which
can obtain particular benefits from the use of the above-described
getter devices are vacuum chambers, cryogenic liquids
transportation (e.g. hydrogen or nitrogen), solar receivers, vacuum
bottles, vacuum insulated flow lines (e.g. for steam injection),
electronic tubes, dewars, etc.
[0046] The invention will be further illustrated by means of the
following examples. These non-limiting examples illustrate some
embodiments which are intended to teach the skilled person how to
put the invention into practice.
EXAMPLES
[0047] Several polycrystalline ingots have been prepared by arc
melting of appropriate mixtures of the high purity metallic
constituent elements in an argon atmosphere. Each ingot has been
then grinded by ball milling in a stainless steel jar under argon
atmosphere and subsequently sieved to the desired powder fraction,
i.e. less than 300 .mu.m.
[0048] 150 mg of each alloy listed in table 1 (see below) were
pressed in annular containers in order to obtain the samples
labeled as sample A, B, C, D, E, (according to the present
invention) and reference 1.
TABLE-US-00001 TABLE 1 Zr Ti V Al Reference 1 % at 45.1 15.03 30.3
9.54 Sample A % at 44.5 14.8 28.5 12.1 Sample B % at 44.0 14.7 26.9
14.4 Sample C % at 43.5 14.5 25.3 16.6 Sample D % at 42.6 14.2 22.3
20.9 Sample E % at 41.7 13.9 19.4 25.0
[0049] They have been compared in their sorption performance versus
hydrogen and carbon monoxide.
[0050] The test for H.sub.2 and CO sorption capacity evaluation is
carried out on an ultra-high vacuum bench. The getter sample is
mounted inside a bulb and an ion gauge allows to measure the
pressure on the sample, while another ion gauge allows to measure
the pressure upstream of a conductance located between the two
gauges. The getter is activated with a radiofrequency oven at
550.degree. C..times.60 min, afterwards it is cooled and kept at
200.degree. C. A flow of H.sub.2 or CO is passed on the getter
through the known conductance, keeping a constant pressure of
3.times.10.sup.-6 torr. Measuring the pressure before and after the
conductance and integrating the pressure change in time, the
pumping speed and the sorbed quantity of the getter can be
calculated. The recorded data have been reported in table 2.
TABLE-US-00002 TABLE 2 H.sub.2 CO sorption sorption rate (l/s) rate
(l/s) Reference 1 3.9 2.7 Sample A 16.8 7.7 Sample B 18.7 9.0
Sample C 20.1 9.4 Sample D 19.7 8.0 Sample E 18.5 6.9
* * * * *