U.S. patent application number 15/295647 was filed with the patent office on 2017-10-12 for porous materials.
The applicant listed for this patent is NANO-NOUVELLE PTY LTD. Invention is credited to Geoffrey Alan Edwards, Stephanie Maya Moroz, Gregory David Morwood, Penelope Nicolle Rackemann, Oriana Lauren Sanicola, Timothy Allan Webb, Manuel Christoph Wieser, Tan Xing.
Application Number | 20170292189 15/295647 |
Document ID | / |
Family ID | 59999047 |
Filed Date | 2017-10-12 |
United States Patent
Application |
20170292189 |
Kind Code |
A1 |
Edwards; Geoffrey Alan ; et
al. |
October 12, 2017 |
Porous Materials
Abstract
A porous membrane material comprising a porous membrane
substrate coated with a thin, uniform coating of a metal or metal
alloy. The membrane material can have high electrical conductivity.
The membrane material can exhibit a very high ratio of electrical
conductivity to thermal conductivity. The porous membrane substrate
may be removed to form the membrane.
Inventors: |
Edwards; Geoffrey Alan; (Pt.
Arkwrite, AU) ; Moroz; Stephanie Maya; (Mooloolaba,
AU) ; Morwood; Gregory David; (Mudjimba, AU) ;
Wieser; Manuel Christoph; (Alexandra Headland, AU) ;
Webb; Timothy Allan; (Buderim, AU) ; Rackemann;
Penelope Nicolle; (Sippy Downs, AU) ; Xing; Tan;
(Sippy Downs, AU) ; Sanicola; Oriana Lauren;
(Currimundi, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NANO-NOUVELLE PTY LTD |
Marcoola |
|
AU |
|
|
Family ID: |
59999047 |
Appl. No.: |
15/295647 |
Filed: |
October 17, 2016 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13509180 |
Aug 23, 2012 |
|
|
|
PCT/AU2010/001511 |
Nov 11, 2010 |
|
|
|
15295647 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10T 428/24999 20150401;
H01M 8/1053 20130101; B01D 69/122 20130101; B01D 67/0072 20130101;
B01D 67/003 20130101; Y10T 428/249953 20150401; B01D 2325/30
20130101; C23C 18/1644 20130101; B01D 2325/26 20130101; C25D 3/12
20130101; B01D 71/024 20130101; C25D 3/22 20130101; C23C 18/38
20130101; B01D 2325/22 20130101; B01D 2325/24 20130101; C23C 18/32
20130101; B01D 71/68 20130101; H01M 8/1062 20130101; C25D 3/562
20130101; B01D 67/0079 20130101; Y02E 60/50 20130101; C25D 3/32
20130101; B01D 67/0088 20130101; B01D 69/02 20130101; B01D 71/16
20130101; B01D 69/10 20130101 |
International
Class: |
C23C 18/16 20060101
C23C018/16; C25D 3/32 20060101 C25D003/32; C23C 18/38 20060101
C23C018/38; C25D 3/56 20060101 C25D003/56; C23C 18/32 20060101
C23C018/32; C25D 3/22 20060101 C25D003/22; C25D 3/12 20060101
C25D003/12 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 11, 2009 |
AU |
2009905532 |
Mar 11, 2010 |
AU |
2010901022 |
Jun 8, 2010 |
AU |
2010902509 |
Claims
1. A porous material comprising a porous polymeric membrane
substrate having a pore size in a range from 0.1 .mu.m to 10 .mu.m
and coated with a thin and uniform coating of one or more metals or
metal alloys, the coating having a thickness that falls in the
range from .about.10 nm to .about.1 .mu.m, wherein the coating
extends all through the thickness of the porous material and
wherein the coating imparts high conductivity to the membrane such
that the porous material has an equivalent conductivity of from
0.05 S/cm to 440,000S/cm and wherein the porous material has a
volume fraction of solid of less than 80%.
2. A porous material comprising a porous polymeric membrane
substrate having a pore size in a range from 0.1 .mu.m to 10 .mu.m
and coated with a thin, uniform coating of one or more metals or
metal alloys, the coating having a thickness that falls in the
range from .about.10 nm to .about.1 .mu.m, wherein the coating
extends all through the thickness of the porous material and
wherein the coating imparts high conductivity to the membrane such
that the porous material has an equivalent conductivity of from 10
to 440,000S/cm and wherein the porous material has a volume
fraction of coating of less than 80%.
3. A porous material as claimed in claim 1 wherein an equivalent
conductivity of the porous material is at least .about.0.016% of
that obtained for thin films of similar composition and thickness
deposited on solid substrates.
4. A porous material as claimed in claim 1 wherein an equivalent
conductivity of the porous material is 0.0065% or greater than that
obtained for solid materials of similar composition, or .about.
1/50.sup.th or greater than that obtained for solid materials of
similar composition, or .about. 1/20.sup.th or greater than that
obtained for solid materials of similar composition, or .about.
1/10.sup.th or greater than that obtained for solid materials of
similar composition, or .about.1/5.sup.th or greater than that
obtained for solid materials of similar composition, or 1/2 or
greater than that obtained for solid materials of similar
composition.
5. A porous material as claimed in claim 1 wherein an equivalent
solid conductivity of the porous material ranges from about 10 S/cm
to 281000 S/cm, or from10 S/cm to 1500 S/cm, or 100 S/cm to 1500
S/cm.
6. A porous material as claimed in claim 1 wherein the one or more
metals or metal alloys is selected from the group consisting of
copper, tin, nickel, iron, aluminum, titanium, cobalt, zinc,
manganese, silver, gold, antimony, cadmium, tellurium, bismuth,
platinum, palladium, ruthenium, rhodium, chromium, magnesium,
calcium, beryllium, zirconium, molybdenum, lead, vanadium,
potassium, niobium, cadmium, iridium, osmium, rhenium, indium,
gallium, germanium, thallium, selenium and alloys thereof, and
alloys comprising SnNi, SnFe, SnBi, SnSe, SnSb, SnSbNi, SnSbCo,
CuSn, CuZn, Mg.sub.2Si, MnSn, MgSn, alloys based on the combination
of titanium and aluminum.
7. A porous material as claimed in claim 1 wherein the material is
post-treated to add additional functionality.
8. A porous material as claimed in claim 1 wherein the different
material of the coating comprises nanoparticles such that the
nanoparticles are applied to a surface of the substrate.
9. A porous material as claimed in claim 1 wherein the coating
comprises nanolayers of the different material.
10. A porous material as claimed in claim 9 wherein the coating
comprises a plurality of nanolayers.
11. A porous material as claimed in claim 1 wherein the porous
material has a ratio of compressive strength (measured in Mpa) to
volume fraction of solids (measured as volume fraction) of greater
than 5 Mpa/v.sub.f, or greater than 10 MPa/v.sub.f, or greater than
50 MPa/v.sub.f, or greater than 100 MPa/v.sub.f.
12. A porous material as claimed in claim 1 wherein a thin layer of
solid material is placed on top of the uniform coating, to provide
a contacting surface.
13. A porous material comprising a porous polymeric membrane
substrate having a pore size in a range from 0.1 .mu.m to 10 .mu.m
and coated with a thin, uniform coating of a one or more metals or
metal alloys wherein the coating extends all through the thickness
of the porous material and wherein the coating imparts high
conductivity to the membrane and wherein the porous material has a
volume fraction of solid of less than 50%, or less than 40%, or
less than 30%, or less than 25% or less than 5.5% wherein the
porous material has a ratio of compressive strength (measured in
Mpa) to volume fraction of solids (measured as volume fraction) of
greater than 5Mpa/v.sub.f, or greater than 10 MPa/v.sub.f, or
greater than 50 MPa/v.sub.f, or greater than 100 MPa/v.sub.f.
14. A porous material comprising a porous polymeric membrane
substrate having a pore size in a range from 0.1 .mu.m to 10 .mu.m
and coated with a thin, uniform coating of one or more metals or
metal alloys wherein the coating extends all through the thickness
of the porous material and wherein the coating imparts an
equivalent solid conductivity in the range of 0.05 S/cm to 440,000
S/cm to the membrane and wherein the porous material has a volume
fraction of solid of less than 50%, or less than 40%, or less than
30%, or less than 25% or less than 5.5%.
15. A porous material comprising a porous polymeric membrane
substrate having a pore size in a range from 0.1 .mu.m to 10 .mu.m
and coated with a thin, uniform coating of one or more metals or
metal alloys wherein the coating extends all through the thickness
of the porous material and wherein the coating imparts an
equivalent solid conductivity in the range of 0.05 S/cm to 1500
S/cm to the membrane and wherein the porous material has a volume
fraction of coating of less than 50%, or less than 40%, or less
than 30%, or less than 25% or less than 5.5%.
16. A porous material comprising a porous polymeric membrane
substrate having a pore size in a range from 0.1 .mu.m to 10 .mu.m
and coated with a thin uniform coating of one or more metals or
metal alloys, the coating having a thickness that falls within the
range of from .about.10 nm to .about.200 nm wherein the coating
extends all through the thickness of the porous material and
wherein the coating imparts an equivalent solid conductivity in the
range of 0.05 S/cm to 1500 S/cm to the membrane and wherein the
porous material has a volume fraction of solid of less than 50%, or
less than 40%, or less than 30%, or less than 25% or less than
5.5%.
17. A porous material comprising a porous polymeric membrane
substrate having a pore size in a range from 0.1 .mu.m to 10 .mu.m
and coated with a thin uniform coating of a different material, the
coating having a thickness that falls within the range of from
.about.10 nm to .about.200 nm wherein the coating extends all
through the thickness of the porous material and wherein the
coating imparts an equivalent solid conductivity in the range of
0.05 S/cm to 1500 S/cm to the membrane and wherein the porous
material has a volume fraction of coating of less than 50%, or less
than 40%, or less than 30%, or less than 25% or less than 5.5%.
18. A porous material as claimed in claim 1 wherein the coating has
a thickness that falls in the range of from .about.10 nm to
.about.860 nm, or from .about.10 nm to .about.300 nm, or from
.about.10 nm to .about.280 nm, or from .about.10 nm to -260 nm, or
from .about.10 nm to .about.200 nm.
19. A porous material as claimed in claim 1 wherein the coating
further comprises sulfur.
20. A porous material as claimed in claim 19 wherein the sulfur is
present as a distinct layer.
21. A porous material as claimed in claim 19 wherein the sulfur is
intimately mixed with one or more of the metals or metal
alloys.
22. A porous material as claimed in claim 1 wherein the one or more
metal alloys contain cobalt and one or more other metals.
23. A porous material as claimed in claim 1 wherein the volume
fraction of solid is less than 50%, or less than 40%, or less than
30%, or less than 25% or less than 5.5%.
24. A porous material as claimed in claim 2 wherein the volume
fraction of solid is less than 50%, or less than 40%, or less than
30%, or less than 25% or less than 5.5%.
25. A porous material as claimed in claim 6 wherein the one or more
metals or metal alloys are selected from copper, tin, nickel, iron,
aluminium, titanium, cobalt, zinc, manganese, silver, gold, and
alloys thereof.
26. A porous material comprising a porous polymeric membrane
substrate having a pore size in a range from 0.1 .mu.m to 10 .mu.m
and coated with a thin and uniform coating of one or more metal
phosphides, the coating having a thickness that falls in the range
from .about.10 nm to .about.1 .mu.m, wherein the coating extends
all through the thickness of the porous material and wherein the
coating imparts high conductivity to the membrane such that the
porous material has an equivalent conductivity of from 0.05 S/cm to
440,000 S/cm and wherein the porous material has a volume fraction
of solid of less than 80%.
27. A porous material as claimed in claim 26 wherein the one or
more metal phosphides are selected from one or more of copper
phosphide, iron phosphide, tin phosphide, and nickel phosphide.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part of U.S. application Ser. No.
13/509,180, which is the U.S. national phase of PCT/AU2010/001511
filed Nov. 11, 2010, which claims priority to AU 2009905532 filed
Nov. 11, 2009, AU 2010901022 filed Mar. 11, 2010, and AU 2010902509
filed Jun. 8, 2010, the entire respective disclosures of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to novel porous materials. In
one aspect, the invention relates to porous membrane materials
where specific functionalities are provided by a thin, uniform
coating that is applied to an existing porous membrane
material.
BACKGROUND TO THE INVENTION
[0003] Porous materials, and porous membrane materials, have wide
ranging application. Materials with controlled pore structures are
useful in, for example, filters for separation, water purification,
air treatment, catalysis, and removal of heavy metal or biological
contaminants. Materials with controllable pore sizes and
conductivity are useful for applications such as batteries,
supercapacitors, fuel cells and gas sensors. Pores in the nanometer
size range are useful for separation processes and reactions
involving biologically active molecules.
[0004] The pore structure can be critical to the performance of the
porous material and/or membrane. For example, the function of
filtration membranes is often to filter particles of a specific
size. Usually the maximum size of particle that can pass through
the membrane is specified. Thus tight control of pore structure is
necessary to enable correct specification of this particle size. It
may also be important to have a pore structure that achieves the
required maximum particle size whilst exhibiting good permeability
and that provides adequate mechanical strength.
[0005] Pore structures are critical to fluid flow through
membranes. A common desire is to maximize the permeability of a
membrane, which leads to lower pressure drops and therefore less
energy is required to move fluid through the membrane. The
permeability is a strong function of the pore structure, hence
controlled and advanced pore structures are desirable.
[0006] Conducting membranes are also desired in many applications.
In particular, combinations of conductivity and controlled pore
structure for managing fluid flow are desired in applications such
as dye-sensitized solar cells, batteries, gas sensors, fuel cells,
super-capacitors, electrolyzers, photo-electrodes and some water
treatment and air treatment applications. For example, many gas
sensors work by using a material that changes conductivity with
exposure to gas. The porous nature of the gas sensor may affect its
operation by controlling how much material is exposed to the gas,
and how quickly this exposure occurs. Dye-sensitized solar cells,
fuel cells and batteries also require conducting porous electrodes.
The porous nature of these electrodes can also be critical, as the
pore structure controls movement of fluids and/or ionic species in
solution. In some filtration and water treatment applications, it
is important to have a conducting membrane so that a voltage may be
applied to the membrane. Permeability is again critical in terms of
the pressure drop associated with flow, and associated energy
requirements.
[0007] In some applications a high ratio of electrical conductivity
to thermal conductivity is desired. In other words, materials with
high electrical conductivity and low thermal conductivity are
needed. Materials with high electrical conductivity usually exhibit
high thermal conductivity. The requirement of high ratio of
electrical to thermal conductivity therefore presents a significant
challenge. An example of such an application is thermoelectric
materials.
[0008] The field of membranes is vast and many other
functionalities are required in different applications
[0009] Current membranes can be categorized into two main groups:
polymer-based membranes and ceramic membranes. Whilst there are a
wide variety of advanced pore structures and architectures
available for polymeric membranes, these membranes are limited by
their operating temperatures and resistance to certain
environments. In addition, inorganic materials such as ceramics can
provide functionalities that cannot be provided by polymers. For
example, in many applications it would be advantageous to have
conducting membranes.
[0010] Ceramic membranes exist but are much more limited in terms
of available pore structures and architectures.
[0011] Polymeric membranes include filter membranes. These may be
made from a variety of polymers, including cellulose, cellulose
nitrate, cellulose acetate, mixed cellulose esters, nylon, PTFE
(Teflon), polyether sulfones (PES), polyamides, vinyl polymers and
polycarbonates. The membranes are available in a range of pore
types and sizes. Typically the pore sizes are specified by the
maximum particle size that can pass through the membrane. For
example, a particular membrane type may be available in specified
pore sizes from 0.1 .mu.m to 10 .mu.m. Track-etched filter
membranes (typically polycarbonates) have straight cylindrical
pores. However many membranes have much more complex and irregular
pore structures. These include the cellulose-based filter
membranes, and some nylon, PTFE and PES filter membranes.
[0012] Membranes can be made with a wide range of thicknesses, for
example a few micrometers thick up to hundreds of micrometers thick
or even greater into the millimeter range.
[0013] It is an object of the present invention to provide
materials that significantly expand the available combinations of
pore structure and functionality in membranes.
[0014] The present inventors have found that it is possible to
provide desired functionalities by applying thin, uniform coatings
to existing porous materials or membranes. In this way, it is
possible to combine the pore structures provided by polymer-based
membrane materials with functionalities provided by inorganic
materials. This functionality can be added while essentially
preserving, or at least altering in a controlled manner, the pore
characteristics of the existing materials.
[0015] Unusual combinations of controlled pore structures and
properties such as conductivity, resistance to environment and
electrical conductivity to thermal conductivity ratio may be
achieved by applying a thin coating of uniform thickness to an
existing porous membrane. Since the coating may be very thin, the
effect on pore structures may be minimized. Since the coating
thickness is very controlled, the effect on pore structures may be
controlled. Also the volume fraction of coating may be
controlled.
[0016] The inventors have surprisingly found that enhanced
properties may be obtained by using very thin coatings and low
volume fractions of solid. This is important for commercial
applications.
[0017] The inventors have also surprisingly found that these
enhanced properties may be achieved by coating a porous scaffold
then removing the scaffold whilst maintaining reasonable properties
or even enhancing properties. This removal may be achieved without
excessive shrinkage in the thickness direction.
DESCRIPTION OF THE INVENTION
[0018] The inventors have surprisingly found that porous membrane
materials, including polymeric filter membranes, may be coated with
a uniform, thin inorganic coating which can lead to unusual
features. The coating essentially preserves the original pore
structure of the material. Since the coating is uniform and the
thickness may be tightly controlled, the effect of the coating on
the pore characteristics of the membrane, together with their
associated important properties such as permeability, can be
minimized or altered in a controlled manner.
[0019] In one aspect, the present invention provides a porous
material comprising a porous polymeric membrane substrate having a
pore size in a range from 0.1 .mu.m to 10 .mu.m and coated with a
thin and uniform coating of one or more metals or metal alloys, the
coating having a thickness that falls in the range from .about.10
nm to .about.1 .mu.m, wherein the coating extends all through the
thickness of the porous material and wherein the coating imparts
high conductivity to the membrane such that the porous material has
an equivalent conductivity of from 0.05 S/cm to 440,000 S/cm and
wherein the porous material has a volume fraction of solid of less
than 80%. The porous substrate may be a porous membrane
substrate.
[0020] In a second aspect, the present invention provides a porous
material comprising a porous polymeric membrane substrate having a
pore size in a range from 0.1 .mu.m to 10 .mu.m and coated with a
thin, uniform coating of one or more metals or metal alloys, the
coating having a thickness that falls in the range from .about.10
nm to .about.1 .mu.m, wherein the coating extends all through the
thickness of the porous material and wherein the coating imparts
high conductivity to the membrane such that the porous material has
an equivalent conductivity of from 10 to 440,000 S/cm and wherein
the porous material has a volume fraction of coating of less than
80%.
[0021] In some embodiments, the volume fraction of solid is less
than 50%, or less than 40%, or less than 30%, or less than 25% or
less than 5.5%.
[0022] In one embodiment, the porous membrane substrate comprises a
filter membrane.
[0023] In one embodiment, the porous material is formed by coating
a porous substrate and treating the coated material to remove the
substrate and leave a porous material.
[0024] In one embodiment, the porous membrane material is formed by
coating a porous membrane substrate and treating the coated
material to remove the substrate and leave a porous membrane.
[0025] In one embodiment, the coating imparts high electrical
conductivity to the porous material. One way of describing
conductivity in porous solids is to use an `equivalent solid`
conductivity. For example, if the material has a volume fraction of
solid of only 20%, and the measured conductivity is x, the
`equivalent solid` conductivity would be 5 times x. Similarly, if
the material has a volume fraction of solid of 50%, and the
measured conductivity is y, the `equivalent solid` conductivity
would be 2 times y. This way of comparison is useful for comparing
the quality of solids in structures with different volume fraction
of solids. For example, comparison of the quality of the solid
formed by making coatings of different thicknesses in the present
invention.
[0026] In the case where the porous material is formed by a coating
of material on an inert porous scaffold, it is the volume fraction
of the coating material that is relevant in calculating the
equivalent solid conductivity.
[0027] The concept of equivalent solid conductivity can also be
applied to thermal conductivity.
[0028] In the present invention, the equivalent conductivity of the
porous material may compare favorably to conductivities obtained by
depositing thin films of solid materials of similar composition
onto planar substrates, in particular where the thin film is of
similar thickness to the coatings deposited on the porous
substrates. By way of illustration, if we coat a porous substrate
with a 80nm thick coating of Al-doped ZnO, a comparative thin film
materials would be a solid layer of Al-doped ZnO, .about.80nm
thick, deposited onto a flat, solid substrate. This is surprising
given the tortuosity of the porous substrates, the possibilities of
dead ends, and the difficulties of depositing quality material into
such structures. Also surprisingly, this conductivity is retained
or even enhanced following removal of the substrate, e.g. by heat
treatment. For example, the equivalent conductivities of the
materials of the present invention may be .about.1/4 that obtained
for thin films of similar composition and thickness deposited on
solid substrates, or it may be .about.1/2, or it may be .about.
comparable to such values, or even superior. Importantly this may
be achieved with low volume fractions of solid, e.g. less than 50%,
or less than 40%, or less than 30%, or less than 20%.
[0029] The equivalent conductivities also compare favorably with
solid (bulk) versions of materials with similar compositions. By
bulk version of the materials of the present invention, we mean a
solid piece of material that is of similar composition to the solid
material that is present in the porous materials of the present
invention. In the case where the materials of the present invention
comprise a coating of material that is put onto an essentially
inert scaffold/porous substrate, the relevant bulk material has
similar composition to the coating. For example, if Al-doped ZnO is
coated onto a porous polymer substrate according to the present
invention, then an example of a bulk reference material would be a
disc of Al-doped ZnO, e.g. 20mm diameter by 5mm thick.
Conductivities of bulk materials are usually better than thin
films. For example, the equivalent conductivities of the materials
of the present invention may be -1/50.sup.th that obtained for bulk
materials of similar composition, or it may be .about. 1/20.sup.th,
or .about. 1/10.sup.th or .about.1/5.sup.th, or 1/2 or even
comparable to that obtained for bulk materials of similar
composition. Again, this is surprising given the tortuosity of the
porous materials, the possibility of dead ends and the difficulty
of deposition into porous structures.
[0030] In some embodiments the equivalent solid conductivity of the
membrane may range from .about.0.05 S/cm to 1500 S/cm, or 10 S/cm
to 1500 S/cm or 100 S/cm to 1500 S/cm.
[0031] Surprisingly these conductivities may be achieved with thin
coatings, for example from .about.10 nm to .about.200 nm, more
suitably from .about.10 nm to .about.100 nm, even more suitably
from .about.10 nm to .about.50 nm, most suitably from .about.10 nm
to .about.40 nm, .about.10 nm, or 20 nm thick, or .about.40 nm
thick coatings. Also surprisingly, this conductivity can be
achieved despite the complex solid structures of many membranes. In
particular, the structures potentially represent tortuous paths,
have roughness, and could consist of a number of `dead ends`. These
attributes can potentially significantly reduce conductivity.
[0032] Since the thickness of the coating is well controlled, the
volume fraction of the coating is also well controlled. Also, the
effect on pore structure may be minimized or at least well
controlled and defined. For example, if a filter membrane's pore
structure is specified as 0.2 .mu.m, this means the largest
particle that can pass through is 0.2 .mu.m, or 200 nm. With a
conductive coating of controlled thickness 20 nm, the largest
particle size that can pass through is then close to 160 nm. It is
possible to start with a membrane of a specified particle size,
then provide a coating of a defined thickness to achieve a desired
specified particle size that can pass through the porous
material/membrane.
[0033] Also, by combining the surface area and volume fraction of
the substrate, with the controlled coating thickness, the volume
fraction of coating can be controlled accurately. An example is a
filter membrane of surface area 10 m.sup.2/g, volume fraction of
solid 34%. If a flat surface is assumed, a 40 nm thick coating
should lead to a volume fraction of coating of around 20%.
[0034] Surprisingly we have also found that membranes of some
embodiments of the present invention exhibit a very high ratio of
electrical conductivity to thermal conductivity. Materials with
high electrical conductivity usually exhibit high thermal
conductivity. Materials with high electrical conductivity and low
thermal conductivity are, however, in demand in applications such
as thermoelectric materials. Without being bound to any particular
theory, the present inventors believe that the high ratios of
electrical to thermal conductivities in the present materials may
be due, at least in part, to phonon impediment at surfaces,
probably due to surface roughness. A fine grain size may also be a
contributing factor.
[0035] This ratio can be significantly higher than for bulk
materials of similar composition. For example, the ratio can be
2.times. higher, or 5.times. higher, or 10.times. higher or
20.times. higher than reported for bulk materials of similar
composition.
[0036] Accordingly, in another aspect, the present invention
provides a porous membrane material having a ratio of electrical
conductivity to thermal conductivity at least 2.times. higher, or
5.times. higher, or 10.times. higher or 20.times. higher than
reported for bulk materials of similar composition. Accordingly, in
another aspect, the present invention provides a porous membrane
material having a ratio of electrical conductivity to thermal
conductivity in excess of 10,000 SK/W, for example, from 10,000 to
200,000 SK/W, or from 15,000 to 100,000 SK/W, or from 20,000 to
50,000 SK/W. These figures are for values at room temperature (from
.about.15.degree. C. to .about.35.degree. C.). At other
temperatures the ratios may change somewhat, therefore different
ranges may be relevant at other temperatures.
[0037] The inventors have also surprisingly found that the phonon
thermal conductivities of the materials of the present invention
may be very low. Also, they may be much lower than for bulk
materials of similar composition. For example, the phonon thermal
conductivity may be less than 0.6 W/m/K, or less than 0.5, or less
than 0.3, or less than 0.2. Correspondingly this value may be
comparable to the value for bulk materials, or it may be 1/2, or
1/4, or 1/10.sup.th, or 1/20.sup.th, or 1/50.sup.th of these
values.
[0038] The inventors have found that conductive coatings can also
lead to good thermoelectric properties, including high figures of
merit, ZT. This is due to the combination of high ratios of
electrical to thermal conductivities and reasonable Seebeck
coefficients. This ZT may be comparable or higher than ZTs for bulk
materials of similar composition. Importantly these ZTs may be
obtained with low volume fractions of solid.
[0039] Accordingly, in another aspect, the present invention
provides a porous material, such as a porous membrane material,
having a ZT comparable to that of bulk materials of similar
composition, or greater than 1.2.times. higher than comparable bulk
materials, or greater than 2.times. higher, or greater than 3 times
higher, or greater than 5 times higher, or greater than 10.times.
higher. This may be achieved with low volume fractions of solid
(v.sub.f solid), for example less than 50% v.sub.f solid, or less
than 40%, or less than 30%, or less than 20% v.sub.f solid.
[0040] Surprisingly, the inventors have found that these properties
related to conductivity can be attained using low volume fractions
of solid. In prior art, porous ceramics with low volume fractions
of solid lead to very low electrical conductivities. Thus the
properties of such porous ceramics related to electrical
conductivity, e.g. thermoelectric performance, would be expected to
be poor. However the present inventors have found that good
properties related to electrical conductivity, including
thermoelectric performance, may be achieved whilst using low volume
fractions of solid. For example the properties may be obtained with
a volume fraction of solid less than 80%, or less than 50%, or less
than 40%, or less than 30%, or less than 20%.
[0041] For conducting coatings, any coating providing suitable
conductivity may be used. Examples include one or more metals or
metal alloys is selected from the group consisting of copper, tin,
nickel, iron, aluminium, titanium, cobalt, zinc, manganese, silver,
gold, antimony, cadmium, tellurium, bismuth, platinum, palladium,
ruthenium, rhodium, chromium, magnesium, calcium, beryllium,
zirconium, molybdenum, lead, vanadium, potassium, niobium, cadmium,
iridium, osmium, rhenium, indium, gallium, germanium, thallium,
selenium and alloys thereof, and alloys comprising SnNi, SnFe,
SnBi, SnSe, SnSb, SnSbNi, SnSbCo, CuSn, CuZn, or metals such as
copper, tin, nickel, iron, aluminium, titanium, zinc, manganese,
silver, gold, and alloys of these, Mg.sub.2Si, MnSn, MgSn, alloys
based on the combination of titanium and aluminum.
[0042] In another aspect of the present invention, the coating may
comprise one or more metal phosphides. In this aspect, the present
invention provides a porous material comprising a porous polymeric
membrane substrate having a pore size in a range from 0.1 .mu.m to
10 .mu.m and coated with a thin and uniform coating of one or more
metal phosphides, the coating having a thickness that falls in the
range from .about.10 nm to .about.1 .mu.m, wherein the coating
extends all through the thickness of the porous material and
wherein the coating imparts high conductivity to the membrane such
that the porous material has an equivalent conductivity of from
0.05 S/cm to 440,000 S/cm and wherein the porous material has a
volume fraction of solid of less than 80%. The metal phosphides may
be selected from one or more of phosphides: including but not
limited to copper phosphide, iron phosphide, tin phosphide, nickel
phosphide, and other phosphides included in the metals set out
above. Other features of the first aspect of the present invention
may also be included in this aspect of the present invention.
[0043] A conductive carbon-based material may also be utilized.
This list is not considered exhaustive.
[0044] In some instances, the material needs to be heat treated or
annealed after deposition to activate the dopants. Also, post heat
treatment may be used to improve the material, for example by
reducing defects, growing grains, activating dopants etc.
[0045] The inventors have also found that by using thin, uniform
coatings, the resistance of the membranes to environmental
conditions such as temperature and chemicals such as solvents, can
be improved, whilst maintaining control over the pore
characteristics of the membranes. Again, the use of thin, uniform
coatings enables this resistance to be achieved whilst essentially
preserving the pore structure of the material, or at least altering
the pore structure in a controlled manner.
[0046] Surprisingly the inventors have found that this resistance
to environmental factors such as temperature and chemicals (for
example solvents) may be achieved using very thin coatings. For
example, materials with enhanced resistance to environmental
factors may be achieved with a coating thickness less than 150 nm,
or less than 100 nm, or less than 50 nm, or less than 30 nm, or
less than 20 nm, or less than 10 nm. It is surprising that such
thin coatings can infer increased resistance to environment.
Coatings of such thinness, particularly when applied to polymers,
would normally be expected to have defects such as pinholes or
cracks that can expose the polymer to environmental substances such
as air or chemicals. Also, diffusion through such thin layers could
be significant.
[0047] Achieving property enhancements with such thin layers is
important for several reasons:
[0048] 1) The final product can be made at significantly lower
cost. This is both due to lower raw materials costs, and faster
throughput through the coating process
[0049] 2) Thin coatings minimize changes to porosity, i.e.
properties can be enhanced with minimal changes to the pore
characteristics and associated properties such as permeability.
[0050] 3) Thin coatings minimize weight, i.e. property enhancement
may be achieved without large weight gain. This could have
particular relevance if the membrane material is a fabric or
textile.
[0051] The materials of the present invention may also be
post-treated to add additional functionality. For example,
nanoparticles of material may be applied to the surface to perform
specific functions. Also, coatings of other material or materials
may be applied to the base structure to impart desired
functionalities.
[0052] The coating may be applied by any suitable technique. In
some embodiments, the coating may be applied to the surface by
various means. For example, further layers may be applied by atomic
layer deposition, electrodeposition, electroless deposition,
hydrothermal methods, electrophoresis, photocatalytic methods,
sol-gel methods, other vapor phase methods such as chemical vapor
deposition, physical vapor deposition and close-spaced sublimation.
Multiple layers using one or more of these methods may also be
used. It may be useful to coat the material such that the
composition of the material is not uniform throughout. For example,
a coating method may be used that only penetrates partway into the
porous material. The coating may also be applied by sequential use
of different coating methods.
[0053] In one embodiment of the present invention, the original
porous substrate may be removed, after application of the coating.
The inventors have surprisingly found that high conductivities may
still be achieved despite application of the removal process to the
material. Removal, for example, by application of heat, may be
expected to be detrimental to the solid structure of the material
due to forces exerted due to, for example, combustion and/or
thermal expansion. Also, the inventors have found that high
electrical conductivity to thermal conductivity ratios may still be
maintained, even after removal of the original porous substrate.
Since this removal creates extra porosity, possibly at a larger
scale than the initial porosity, this removal step could
potentially increase thermal conductivity by allowing heat transfer
via air or other gases. This heat transfer could also or
alternatively be via conduction or convection in the gas. The
inventors have surprisingly found that the solid part of the
original porous substrate may be removed, without greatly
increasing the thermal conductivity, or at least without greatly
decreasing the ratio of electrical conductivity to thermal
conductivity.
[0054] In one embodiment of the present invention, the original
porous scaffold may be removed whilst maintaining reasonable
compressive strength. For example, the material may have a
compressive strength of greater than 1 MPa, or greater than 2 MPa,
or greater than 10 MPa, or greater than 20 MPa. Surprisingly these
compressive strengths may be achieved with low volume fractions of
solid, for example less than 50% v.sub.f solid, or less than 40%,
or less than 30%, or less than 20% v.sub.f solid.
[0055] In one embodiment of the present invention, the original
porous scaffold may be removed without causing significant
shrinkage. For example, the thickness of the material after removal
of the scaffold may be within 20% of the original thickness, or
within 10%, or within 5%, or within 2%.
[0056] In another embodiment of the present invention, the coating
may be comprised of multiple layers. Said multiple layers may be
deposited using one, or more than one, deposition technique.
[0057] In another embodiment of the present invention, the coating
is comprised of nanolayers of material. The inventors have found
that nanolayered materials may be deposited that exhibit good
conductivity and good values of electrical to thermal
conductivity.
[0058] In one embodiment, the coating is applied to the substrate
by an ALD process. An ALD process requires the following steps to
form a `cycle`.
[0059] 1. Dosing of metal precursor, during which a layer of metal
precursor reacts with the surface and is attached to the surface.
Additional precursor molecules cannot react with precursor
molecules already attached to the surface, so the process is
self-limiting.
[0060] 2. Inert gas purge that removes both unreacted precursor
molecules, and reaction products from the reaction of precursor
molecules with the surface.
[0061] 3. Dosing of a reactant, which reacts with the metal
precursor molecules that are attached on the surface. The surface
can then react with another dose of metal precursor.
[0062] 4. Inert gas purge that removes the reactant.
[0063] This cycle may be repeated any number of times in order to
build up a coating of controlled thickness.
[0064] However, ALD on porous structures, particularly structures
with high effective pore aspect ratios (in a cylindrical pore, the
aspect ratio is length divided by diameter) has in the past proved
problematical. In particular, complex structures with tortuous
paths, such as those found in many polymeric filter membranes, can
significantly inhibit gaseous flow, thereby creating problems for
ALD. Also, deposition on polymeric materials can be difficult due
to problems with nucleation.
[0065] The inventors have found that these problems can be overcome
to provide the materials of the present invention.
[0066] In another aspect, the present invention provides a method
for forming a porous material comprising providing a porous
substrate material and applying a thin uniform coating to the
porous structure material.
[0067] In some embodiments of the method of the present invention,
the porous material is made by applying a thin, uniform coating to
a porous substrate material and subsequently removing the porous
substrate material. The porous substrate material may be removed,
for example, by heat treatment or by chemical treatment. The heat
treatment or chemical treatment desirably removes the substrate
material without unduly affecting the coating material.
Surprisingly it has been found that the polymeric substrate can be
removed without unduly affecting the material in an adverse manner,
and in fact the removal process may actually enhance some
properties. Removal of such material may normally affect the
structural integrity of the structure and/or adversely affect the
deposited solid in a chemical way.
[0068] In another embodiment of the method of the present
invention, the porous layer may first be applied to a substrate.
The thin coating is then applied to the porous layer, while the
porous layer is on the substrate.
[0069] Throughout this specification, where reference is made to a
comparison or ratio of properties referenced to the properties of
comparable bulk materials or bulk materials of similar composition,
it is meant the properties of the porous material are compared to a
bulk material of similar composition to the solid part of the
porous material, where the bulk material is a piece of solid
material, or nearly solid material, that has dimensions in the
millimeter range or larger. For the case where the porous material
is comprised of a coating of material applied to an essentially
inert substrate, the bulk material is of similar composition to the
composition of the coating material, i.e. the composition of the
inert substrate is not relevant.
[0070] Where reference is made to a comparison or ratio of
properties referenced to the properties of comparable thin-film
materials or thin-film materials of similar composition, it is
meant that the properties of the porous material are compared to a
thin-film of solid material of similar composition to the solid
part of the porous material, deposited onto an essentially flat,
solid substrate. For the case where the porous material is
comprised of a coating of material applied to an essentially inert
substrate, the thin-film material is of similar composition to the
composition of the coating material, i.e. the composition of the
inert substrate is not relevant, and the thickness of the thin-film
material is similar to the coating thickness.
[0071] The porous substrate used in the present invention is
suitably a porous membrane. Such porous membranes include polymeric
filter membranes, filter papers, track-etched membranes, sintered
ceramic membranes, other ceramic membranes, porous metallic
membranes, aerogel membranes or xerogel membranes. The membranes
may have a wide range of thicknesses, from the micrometre range to
the millimeter range.
BRIEF DESCRIPTION OF THE DRAWINGS
[0072] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawings will be provided by the Office upon
request and payment of the necessary fee.
[0073] FIG. 1 shows a scanning electron micrograph of the porous
material obtained in Example 1;
[0074] FIG. 2 shows a compositional analysis of the porous material
obtained in Example 1;
[0075] FIGS. 3 and 4 show scanning electron micrographs of the
porous material obtained in Example 2;
[0076] FIG. 5 shows a scanning electron micrograph of the porous
material obtained in Example 4;
[0077] FIGS. 6 to 8 show scanning electron micrographs of the
coated material obtained in Example 12;
[0078] FIGS. 9 and 10 show scanning electron micrographs of the
porous material obtained in Example 13;
[0079] FIGS. 11 to 13 show scanning electron micrographs of the
porous material obtained in Example 14;
[0080] FIGS. 14 to 16 show scanning electron micrographs of the
coated material obtained in Example 15;
[0081] FIGS. 17 to 19 show scanning electron micrographs of the
porous material obtained in Example 16;
[0082] FIGS. 20 and 21 shows scanning electron micrographs of the
porous material obtained in Example 18;
[0083] FIG. 22 shows a scanning electron photomicrograph of the
porous material obtained in Example 20; and
[0084] FIGS. 23 and 24 shows scanning electron photomicrographs of
the porous material obtained in Example 22.
[0085] In order to better understand embodiments of the present
invention, the following examples are provided.
EXAMPLES
Example 1
[0086] A porous polymeric substrate, with a non-woven fibrous
composite structure, which contains cellulose fibers and has a
thickness of 40 .mu.m, was pretreated with an activator
pre-treatment by contacting the substrate with a solution of 0.4
g/L PdCl.sub.2 and 10 g/L SnCl.sub.2 in 12M HCl at a temperature of
27.5.degree. C. for 3 minutes. A copper coating was then applied to
the substrate using electroless deposition. A Macdermid Copper 85
solution, which is a proprietary commercially available electroless
copper depositions solution, was used. Electroless deposition of
copper took place at 45.5.degree. C. with a contact time of 30
minutes. A copper coating was formed on the substrate. FIG. 1 shows
SEM photomicrographs of the coated material. The copper coating was
seen to be uniformly applied to the substrate. FIG. 2 shows a
compositional analysis of the material. The material was found to
contain 90 atomic % copper.
Example 2
[0087] In this example, a substrate was coated with a mixed
nickel/cobalt or a nickel/cobalt alloy. A porous polymeric
substrate with a non-woven fibrous composite structure, which
predominantly consists out of cellulose fibers 80 um thick,
non-woven membrane reinforced through lamination to a Nylon scrim
of 10-20 um thickness was pretreated with an activator comprising a
solution of 0.4 g/L PdCl.sub.2 and 10 g/L SnCl.sub.2 in 12M HCl at
a temperature of 27.5.degree. C. for 3 minutes. A coating
comprising nickel and cobalt was then applied by using a
proprietary coating composition from Enthone that contains a Ni/Co
ratio of 1:10. The substrate was contacted with this composition at
76.degree. C. for 30 minutes, at a pH of 5.7. FIGS. 3 and 4 show
SEM photomicrographs of the coated material. The nickel coating
appeared to be uniformly applied to the substrate. The coating
retained significant porosity.
Example 3
[0088] In this example, a substrate was coated with a nickel
coating. A porous polymeric substrate with a non-woven fibrous
composite structure with a thickness of 80 .mu.m was pretreated lI
at a temperature of 27.5.degree. C. for 3 minutes. A nickel coating
was then applied by using electroless deposition. The substrate was
contacted with a nickel electroless solution containing Ni--18.13
g/L Nickel (II) chloride, 9.06 g/L sodium citrate, 32 g/L ammonium
chloride and 18.06 g/L sodium hyposphosphite. The substrate was
contacted with this composition at 67-72.degree. C. for 90 minutes,
at a pH of 9. The nickel coating extends throughout substantially
all of the material. The coated material has the following
composition:
TABLE-US-00001 TABLE 1 C O Na P Cl Fe Ni Cu A1 49.5 7.3 2.0 1.6 0.3
1.2 37.1 0.6 A2 30.1 8.3 3.8 2.2 0.7 1.2 51.9 0.8 A3 62.8 16.6 1.7
1.0 0.7 1.2 15.2 0.3 A4 42.3 11.4 3.3 1.6 0.9 1.3 38.0 0.5 A5 36.4
12.1 3.5 2.4 0.9 0.8 42.2 0.8 A5 56.0 8.1 2.0 1.0 0.2 0.6 30.5
0.8
Example 4
[0089] In this example, a coating comprising bismuth and tellurium
was applied to a porous polymeric substrate. The substrate was a
cellulose acetate (CA) membrane with a pore size of either 0.45
.mu.m or 0.2 .mu.m. The substrate was pretreated by immersing in a
solution containing 1 mM PdCl.sub.2 at a pH of 5.50 for 10 to 15
minutes. The substrate was then contacted with an electroless
nickel solution (a proprietary solution from Caswell) at a
temperature of from 50 to 90.degree. C. for 30 seconds. The
substrate was subsequently contacted with a solution containing
bismuth (III) chloride dissolved in 0.4 L 6wt % HCl, 5.2 g/L EDTA,
8.4 g/L Sodium hydroxide and Te-9.6 g/L Telluride powder, 6 g/L
Sodium borohydride for a period of 3.5 hours. An outer coating
comprising bismuth and telluride was formed. FIG. 5 shows an SEM
photomicrograph of the coated porous material.
Examples 5 to 11
[0090] Examples 5 to 11 are set out in the table below. In examples
5 to 11, electroless deposition was used to form the final metal
coatings on the porous polymeric substrate. A seed layer containing
palladium chloride and tin chloride was first applied, followed by
an optional accelerator step, followed by electroless deposition.
Electrical conductivity of the porous material was determined. For
some of the examples, the equivalent solid conductivity was also
determined.
TABLE-US-00002 Equivalent solid Compositions used in Metal
Conductivity conductivity Example Process Parameters process
coatings Substrate (S/cm) (S/cm) 5 Electroless Activator-- Sample
pre-treatment: Copper Fibrous, 4506 91108 27.5.degree. C., 3 min
Activator--Macuplex non-woven, Accelerator-- D34C with HCl 12M 20
.mu.m 48.5.degree. C., 1 min Accelerator-- thickness
Cu--46.5.degree. C., Macuplex 9338 with 20 mins 12M HCl Copper
coating: MacDermid Copper 85 6 Electroless Activator-- Sample
pre-treatment: Copper Fibrous, 18149 196547 27.5.degree. C., 3 min
Activator--Macuplex non-woven, Accelerator-- D34C with HCl 12M 20
.mu.m 48.5.degree. C., 1 min Accelerator-- thickness
Cu--46.5.degree. C., Macuplex 9338 with 60 mins 12M HCl Copper
coating: MacDermid Copper 85 7 Electroless Activator-- Sample
pre-treatment: Copper Fibrous, 33832 280986 27.5.degree. C., 3 min
Activator--Macuplex non-woven, Accelerator-- D34C with HCl 12M 20
.mu.m 48.5.degree. C., 1 min Accelerator-- thickness
Cu--46.5.degree. C., Macuplex 9338 with 120 mins 12M HCl Copper
coating: MacDermid Copper 85 8 Electroless Activator-- Sample
pre-treatment: Nickel Fibrous, 6497 98572 27.5.degree. C., 3 min--
Activator --Nickel non-woven, Ni--70-75.degree. C., coating: 20 g/L
Nickel 80 .mu.m 40 mins, pH 9 (II) chloride, 10 g/L thickness
Sodium citrate, 35 g/L Ammonium chloride, 0.1M Sodium hypophosphite
9 Electroless Activator-- Sample pre-treatment: Nickel-Cobalt
Fibrous, 1379 Not 27.5 C., 3 min, Activator--0.4 g/L alloy/co-
non-woven, determined Ni--60.degree. C., PdCl2 with 12M HCL,
deposit 186 .mu.m 30 mins, pH 8 10 g/L SnCl2 with 12M thickness HCL
Nickel-cobalt coating: 38 g/L Nickel (II) chloride hexahydrate, 20
g/L Sodium citrate, 7.5 g/L Ammonium chloride, 0.9 g/L Cobalt (II)
chloride, 2L DI H2O 10 Electroless Activator-- Sample
pre-treatment: Nickel-Cobalt Fibrous, 1976 Not 27.5 C., 3 min,
Activator--0.4 g/L alloy/co- non-woven, determined Ni--75.degree.
C., PdCl2 with 12M HCL, deposit 55 .mu.m 20 mins, pH 8 10 g/L SnCl2
with 12M thickness HCL Nickel-cobalt coating: 38 g/L Nickel (II)
chloride hexahydrate, 20 g/L Sodium citrate, 7.5 g/L Ammonium
chloride, 0.9 g/L Cobalt (II) chloride, 2L DI H2O 11 Electroless
Activator-- Sample pre-treatment: Copper, Fibrous, 9429 Not 27.5
C., 3 min Activator--Macuplex followed non-woven, determined
Accelerator-- D34C with HCl 12M by tin 65 .mu.m 48.5 C., 1 min
Accelerator-- thickness Cu--30-40.degree. C., Macuplex 9338 with
120 mins 12M HCl Copper Sn--29-30.degree. C., coating: MacDermid 27
mins Copper 85 Tin coating: Sulfuric acid, 38.05 g/L Thiourea,
21.48 g/L Tin (II) sulfate, 53 g/L Sodium hypophosphite
Example 12
[0091] Substrate preparation: Cellulose acetate (CA) membranes with
a pores size of 0.45 .mu.m and a thickness of 127 .mu.m and
Polyethersulfone (PES) membranes with a pore size of 0.45 .mu.m and
a thickness of 100 .mu.m were pre-treated to accept electroless
deposition (such as by using the pre-treatment steps of examples 1
to 5), then coated using electroless deposition with either nickel
or nickel followed by copper. Ni-28.3 g/L Nickel (II) sulfate,
42.03 g/L citric acid, 25 g/L sodium hydroxide, 3.3 g/L DMAB, Cu-15
g/L Copper (II) sulfate pentahydrate, 27 g/L EDTA, 8.75 g/L Sodium
hydroxide, Formaldehyde--Zn Enthone CLZ-970 electrolytic plating
solution. The electroless deposition was over a period of 10
minutes for nickel and three minutes for copper. The
electrodeposition of zinc took place over a period of 40 minutes at
27.degree. C. using a current of 100 mA. Metal coatings comprising
nickel, copper and zinc were formed. FIGS. 6 to 8 are SEM
photomicrographs showing the porous material produced in this
example. Table 2 shows the composition of the coated material.
TABLE-US-00003 TABLE 2 C O S Ni Cu Zn A2 61.0 6.1 0.6 15.0 3.5 13.4
A3 36.1 6.9 1.6 16.9 14.3 24.2 A4 42.9 11.8 2.3 15.8 10.5 16.7 A5
60.2 14.2 2.7 6.5 5.6 10.8 A6 51.6 12.1 2.2 8.0 7.0 19.2
Example 13
[0092] In this example a polymeric membrane with a non-woven
fibrous composite structure and a thickness of 115 .mu.m was coated
with nickel and iron using electroless deposition. The porous
polymeric substrate was pre-treated to accept electroless
deposition (such as by using the pre-treatment steps of examples 1
to 5). An electroless deposition solution comprising 0.08M Iron
(II) sulfate hepahydrate, 28.3 g/L nickel (II) sulfate, 42.03 g/L
citric acid, 25 g/L sodium hydroxide, 3.3 g/L DMAB was contacted
with the substrate at 45.degree. C. for a period of 12 minutes at
pH 9. SEM photomicrographs are shown in FIGS. 9 and 10.
Example 14
[0093] A porous polymeric membrane such as a cellulose acetate (CA)
membrane with a pore size of 0.45 .mu.m and a thickness of 127
.mu.m was coated using electroless deposition to form an outer
coating containing gold. A combination of sensitization and
activation steps was used to prepare the porous polymeric membrane
for the electroless deposition of a layer of gold. The following
conditions were used:
[0094] Pd--The membrane was immersed in an aqueous solution
containing 1 mM PdCl2 at pH of 5 (pH was adjusted with NaOH). The
membrane was soaked in the solution for 4h. Sn--The membrane was
immersed in a solution that contained 0.026M tin (II) chloride,
0.07M trifluoracetic acid, 50%/50% methanol/water at room
temperature for three minutes. Ag--The membrane was then
transferred and immersed into an aqueous solution of ammoniacal
silver nitrate (0.029M) at room temperature for two minutes. Au--1
ml/40 ml Oromerse part B, 0.127M sodium thiosulfate, 0.625M
formaldehyde at room temperature, overnight. FIGS. 11, 12 and 13
show SEM photomicrographs of the porous material formed in this
example. The composition of the various layers shown in FIG. 11 are
set out in the table below (percentages given in atomic %). The
gold coating extends throughout substantially all of the material.
The coated material had the following composition:
TABLE-US-00004 TABLE 3 C O Pd Ag Sr Au A1 49.7 11.4 -- 0 0.8 38.1
A2 34.6 1.5 0.8 1.26 -- 61.9 A3 37.7 3.1 0.8 -- -- 57.7 A4 44.2 3.5
0.1 0.62 0.6 51.1 A5 46.3 11.4 0.4 0.53 0.2 41.4
Example 15
[0095] A porous Polyethersulfone (PES) substrate with a pore size
of 0.45 .mu.m was pre-treated to accept electroless deposition
(such as by using the pre-treatment steps of examples 1 to 5). A
layer of nickel was then deposited using electroless deposition.
Sulphur was then deposited on the nickel using vapor phase
deposition. The following conditions were used:
[0096] Ni--28.29 g/L nickel (II) sulfate, 42.03 g/L citric acid, 25
g/L sodium hydroxide, 3.6 g/L DMAB, at 45.degree. C. for 60
minutes, pH 9. S--powder was placed in vapor deposition chamber
under argon and not in contact with the nickel coated membrane. A
temperature of 175.degree. C. and a time of 180 minutes was used
for the vapor phase deposition of sulfur. FIGS. 14 to 16 show SEM
photomicrographs of the porous material obtained in this example.
The composition of the regions marked in FIG. 20 are set out below
(percentages given in atomic %):
TABLE-US-00005 TABLE 4 C O Si S Ni Cu Zn A1 25.3 27.2 0.0 12.5 33.2
1.4 0.5 A2 34.4 27.8 0.1 14.2 23.6 -- -- A3 39.8 39.2 0.1 8.4 12.4
-- 0.2 A4 32.6 29.5 0.2 15.2 26.0 0.6 0.0 A5 45.1 22.0 0.5 16.2
15.8 0.5 --
Example 16
[0097] A porous polymeric membrane with a non-woven fibrous
composite structure and a thickness of 115 .mu.m was coated with
copper and tin using electroless deposition. The substrate was
pre-treated to accept electroless deposition (such as by using the
pre-treatment steps of examples 1 to 5). The following conditions
were used in the coating step:
[0098] Cu--15 g/L copper (II) sulfate pentahydrate, 27 g/L EDTA,
8.75 g/L sodium hydroxide, formaldehyde, for a period of 15
minutes. Sn--Sulfuric acid, 38.05 g/L thiourea, 21.48 g/L tin (II)
sulfate, 53 g/L sodium hypophosphite, for a period of 10 minutes.
FIGS. 17 to 19 show SEM photomicrographs of the porous material
obtained in this example. The material had the following
composition:
TABLE-US-00006 TABLE 5 C O Sn Cu Sn/Cu A1 59.7 2.1 21.8 16.2 1.3 A2
69.1 3.7 14.1 13.0 1.1 A3 64.1 2.1 14.3 19.3 0.7 A4 69.4 3.1 15.1
12.3 1.2 A5 65.2 7.9 19.0 7.7 2.5
Example 17
[0099] In this example, the porous polymeric membrane with a
non-woven fibrous composite structure and a thickness of 115 .mu.m
was coated with nickel using electroless deposition followed by
coating with iron and zinc using electrodeposition. The conditions
used in the coating steps were as follows:
[0100] The substrate was pre-treated to accept electroless
deposition (such as by using the pre-treatment steps of examples 1
to 5). Electroless coating of nickel and electroless coating of
FeZn were completed under the following conditions:
[0101] Ni--28.29 g/L nickel (II) sulfate, 42.03 g/L citric acid,25
g/L sodium hydroxide, 0.12M sodium hypophosphite, for a period of
15 minutes at 65.degree. C. and pH 8. FeZn--0.05M Ferrous glucanate
dihydrate, 0.15M zinc oxide, 6.6M potassium hydroxide at room
temperature and the current of 0.96 A.
Example 18
[0102] In this example, a porous polymeric cellulose acetate (CA)
substrate with a pore size of 0.45 .mu.m and a thickness of 127
.mu.m was coated with a coating of copper and then a coating of tin
using electrodeposition. The substrate was pre-treated to accept
electroless deposition (such as by using the pre-treatment steps of
examples 1 to 5). Electrodeposition was then used to sequentially
apply copper and then tin. The following conditions were used in
the electroless and electrodeposition steps:
[0103] Cu--15 g/L Copper (II) sulfate pentahydrate, 27 g/L EDTA,
8.75 g/L sodium hydroxide, formaldehyde, 30.degree. C., 4.5
minutes, 30mA current. Sn--15 g/L Tin methanesulphonate, 100 g/L
gluconic acid sodium salt, 0.8 g/L triton X, 0.1 g/L 2 bipyridyl,
room temperature, 104 minutes, 30mA current. FIGS. 20 and 21 show
SEM photomicrographs of the porous material must obtained. The
composition of the layers shown in FIG. 20 is as follows
(percentages given in atomic %):
TABLE-US-00007 TABLE 6 C O Al Cu Sn A1 27.7 12.8 0.4 49.0 10.2 A2
37.5 15.9 -- 44.7 1.8 A3 52.4 26.4 -- 20.4 0.8 A4 48.2 22.2 -- 27.6
1.0 A5 36.4 16.6 -- 44.7 2.4
Example 19
[0104] A porous polymeric cellulose acetate (CA) substrate with a
pore size of 0.45 .mu.m and a thickness of 127 .mu.m was used in
this example. The substrate was pre-treated to accept electroless
deposition (such as by using the pre-treatment steps of examples 1
to 5). A thin nickel coating layer was applied using electroless
deposition prior to the electrodeposition step. The
electrodeposition step used a solution containing Ni--250 g/L
Nickel (II) sulfate hexahydrate, 50 g/L nickel (II) chloride, 35
g/L boric acid. The temperature during electrodeposition was 45 to
47.degree. C. Electrodeposition occurred over a period of 120
minutes using a current of 50 mA. A substantially uniform coating
of nickel was obtained.
Example 20
[0105] In this example, an electroless copper coating was applied
to a porous polymeric, non-woven substrate consisting out of
polyethylene terephthalate fibers (PET). The thickness of the
substrate was 15 .mu.m. The substrate was pretreated with an
activator comprising Macuplex D34C with 12M HCl. Macuplex D34C is a
proprietary commercially available activator that contains
palladium chloride and tin chloride. The activation step took place
at 27.5.degree. C. for a period of three minutes. The substrate was
then contacted with an accelerator comprising Macuplex 9338 with
12M HCl. Contact between the accelerator and the substrate took
place at 48.5.degree. C. for a period of one minute. A copper layer
was then applied by contacting the substrate with MacDermid Copper
85 at a temperature of 46.5.degree. C. for a period of 120 minutes.
FIG. 22 shows an SEM photomicrograph of the coated porous material.
The coating was evenly applied. Significant porosity was
retained.
Example 21
[0106] A porous polymeric membrane with a non-woven fibrous
composite structure and which has a thickness of 115 .mu.m was
coated with copper and a tin-nickel alloy using electroless
deposition. The following conditions were used in the coating
step:
[0107] Cu--15 g/L Copper (II) sulfate pentahydrate, 27 g/L EDTA,
8.75 g/L sodium hydroxide, formaldehyde, for a period of 15
minutes. SnNi--Tin(II) chloride dehydrate 20 g/L, nickel(II)
chloride hexahydrate 20 g/L, sodium hypophosphite 60 g/L, thiourea
60 g/L, citric acid monohydrate 20 g/L, tartaric acid dehydrate 40
g/L, hydrochloric acid 70 g/L for a period of 20 min at temperature
between 60-75.degree. C. The material had the following composition
(percentages given in atomic %):
TABLE-US-00008 TABLE 7 C O Sn Ni Cu Sn/Ni Ni/Cu A1 60.8 5.4 9.4 7.1
16.8 1.3 0.4 A2 59.4 10.5 10.6 7.2 11.6 1.5 0.6 A3 66.4 8.8 8.5 6.4
9.6 1.3 0.7 A4 76.0 12.1 4.4 3.5 3.8 1.3 0.9 A5 71.5 10.9 7.1 5.1
5.3 1.4 1.0
Example 22
[0108] A porous polymeric membrane with a composite structure
comprising a polyethylene and ethyl vinyl alcohol, which has a pore
size of 1.5 .mu.m and a thickness of 60 .mu.m was coated with
copper using electroless deposition. The following conditions were
used in the coating step:
[0109] Cu--15 g/L Copper (II) sulfate pentahydrate, 27 g/L EDTA,
8.75 g/L sodium hydroxide, formaldehyde, for a period of 19 minutes
at 30.degree. C. FIGS. 23 and 24 show SEM photomicrographs of the
porous material obtained in this example. Compositional analysis at
various regions of the porous material are shown in Table 8, which
shows that the copper extends throughout the thickness of the
material.
TABLE-US-00009 TABLE 8 C O Cu A1 33.0 0.8 65.5 A2 60.2 1.1 38.3 A3
58.5 1.3 39.5 A4 65.6 1.5 32.3 A5 54.6 2.2 42.6
Example 23
[0110] A porous polymeric nylon substrate, was coated with copper
using electroless deposition. The following conditions were used in
the coating step:
[0111] Cu--15 g/L Copper (II) sulfate pentahydrate, 27 g/L EDTA,
8.75 g/L sodium hydroxide, formaldehyde, for a period of 30 minutes
at 30.degree. C. The substrate could be pre-treated to accept
electroless deposition (such as by using the pre-treatment steps of
examples 1 to 5).
Example 24
[0112] In this example, the porous polymeric membrane was a
non-woven fibrous composite structure and a thickness of 115 .mu.m.
The substrate was first coated with a conductive layer by using
electroless deposition to apply a layer of nickel.
Electro-precipitation was then used to sequentially apply a
nickel-cobalt-zinc alloy. The following conditions were used in the
deposition steps:
[0113] Ni--A commercial nickel chemistry from Technic was used for
the electroless deposition of the first nickel layer. The
deposition was carried out for 45 minutes at 50.degree. C.
[0114] NiCoZn--1.5M Nickel nitrate hexahydrate, 0.14M cobalt (II)
chloride hexahydrate, 0.07M zinc (II) nitrate hexahydrate, room
temperature, 5 h, 100 mA current.
* * * * *