COMPOSITIONS FOR COATING ELECTRICAL INTERFACES
INCLUDING A NANO-PARTICLE MATERIAL
AND PROCESS FOR PREPARING
BACKGROUND
Field
The disclosed concept relates to compositions for electrical interfaces and, more
particularly, to compositions for coating a surface of an electrical contact. The disclosed
concept also relates to processes for producing nano-particle compositions.
Background Information
It is known to deposit an electroplating layer of nickel, silver or tin on the surface
of electrical interfaces, such as bolted joints and sliding contacts, to form a coating
thereon. The primary function of the coating is to reduce the oxidation of the electrical
interfaces which can result in more stable contact electrical resistance over the operating
life time of the electrical joint or contact. These coatings are not known to reduce the
contact electrical resistance or improve the thermal transport properties across the
electrical interface.
Thus, there is a need for a coating or layer that is capable of reducing the contact
electrical resistance at the electrical interface and reducing the heat generated at the joint
to lead to the reduction of the peak operating temperature for a given current rating. In
addition, it is desirable to increase the thermal conductivity at the interface to assist in
enhancing the heat dissipation away from the joint which can also result in a reduction of
peak temperature at the joint.
SUMMARY
These needs and others are met by embodiments of the disclosed concept, which
provide a composition for coating an electrical contact interface, the composition
including a polymer matrix comprising an elastomer, a nano-particle material selected
from the group consisting of carbon-containing nano-particles, metal nanowires, and

mixtures thereof, and a crosslinker. For example, this increases the thermal and electrical
transport properties at the electrical contact interface to increase safety and reliability of
electrical products including the electrical interface.
The elastomer may be selected from the group consisting of silicone elastomers,
fluoro elastomers, and mixtures thereof. Further, the elastomer may be selected from the
group consisting of fluorosilicone, poly(dimethylsiloxane), and mixtures thereof.
The carbon-containing nano-particles may be selected from the group consisting
of carbon nanotubes, carbon nanofibers, and mixtures thereof.
The nano-particle material may be present in an amount of from 2 to 80 percent
by weight of the composition, or from 5 to 50 percent by weight of the composition.
The crosslinker may include polydiethoxysiloxane. The crosslinker may be
present in an amount of from 1 to 15 percent by weight of the composition.
The elastomer may have a molecular weight of from 800 to 100,000 g/mole.
The composition may further include catalyst. The catalyst may be selected from
the group consisting of platinum, diamine, bisphenol, peroxide, dialkyltincarboxylate,
and mixtures thereof. The catalyst may be present in an amount of from 1 to 15 percent
by weight of the composition.
As another aspect, the disclosed concept provides a process for preparing a nano-
particle composition, including (a) mixing nano-particle material selected from the group
consisting of carbon-containing nano-particles, metal nanowires, and mixtures thereof,
and polymer matrix including an elastomer, (b) adding crosslinker to the mixture of step
(a); and (c) curing the mixture of step (b).
The carbon-containing nano-particles may be selected from the group consisting
of carbon nanotubes, carbon nanofibers, and mixtures thereof.
The crosslinker may include polydiethoxysiloxane.
The elastomer may be selected from the group consisting of silicone elastomers,
fluoro elastomers, and mixtures thereof. Further, the elastomer may be selected from
the group consisting of fluorosilicone, poly(dimethylsiloxane), and mixtures thereof.

The process may further include adding catalyst to the mixture of (a). The
process may further include molding the mixture of (b) into a desired shape. The
resultant composition may be in the form of a sheet.
The process may further include grinding the nano-particle material prior to
mixing with the polymer matrix.
As another aspect, the disclosed concept provides an electrical interface having a
first contact surface and a second contact surface wherein at least one of the first and
second contact surfaces comprises the composition as described above.
As still another aspect, the disclosed concept provides a process for preparing an
electrical interface having a first contact surface and a second contact surface, including
applying to at least one contact surface the composition as described above.
As yet another aspect, the disclosed concept provides a process for preparing an
electrical interface having a first contact surface, a second contact surface, comprising
positioning a nano-particle sheet between the first and second contact surfaces, wherein
the sheet comprises the composition as described above.
BRIEF DESCRIPTION OF THE DRAWINGS
A full understanding of the disclosed concept can be gained from the following
description of the preferred embodiments when read in conjunction with the
accompanying drawings in which:
Figure 1A is a side view of an electrical interface.
Figure 1B is a side view of an electrical interface in accordance with
embodiments of the disclosed concept.
Figure 2 is an exploded schematic layout of an electrical interface in accordance
with another embodiment of the disclosed concept.
Figure 2 A is an exploded side view of the electrical interface of Figure 2.
Figure 3 is an exploded schematic layout of an electrical interface in accordance
with another embodiment of the disclosed concept.
Figure 3 A is an exploded side view of the electrical interface of Figure 3.

Figures 4 and 5 are exploded schematic layouts of electrical interfaces in
accordance with other embodiments of the disclosed concept.
DETAILED DESCRIPTION
As employed herein, the term "power conductor" means a power bus bar, a power
line, a power phase conductor, a power cable, and/or a power bus bar structure for a
power source, a circuit interrupter or other switchgear device.
As employed herein, the term "fastener" means any suitable connecting or
tightening mechanism expressly including, but not limited to, screws (e.g., without
limitation, set screws), bolts and the combinations of bolts and nuts (e.g., without
limitation, lock nuts) and bolts, washers and nuts.
As employed herein, the statement that two or more parts are "coupled" or
"connected" together shall mean that the parts are joined together either directly or joined
through one or more intermediate parts.
Directional phrases used herein, such as, for example, left, right, top, bottom,
upper, lower, front, back, forward, above, below, clockwise, counterclockwise and
derivatives thereof, relate to the orientation of the elements shown in the drawings and
are not limiting to the claims unless expressly recited therein.
As employed herein, the term "number" shall mean one or an integer greater than
one (i.e., a plurality).
The disclosed concept relates to compositions for coating electrical interfaces
including forming a nano-particle layer. The presence of the nano-particle layer can
result in at least one of an improvement in the thermal and electrical transport properties
at the interface of electrical contacts such as, for example but not limited to, bolted joints
and sliding contacts.
Figures 1A and 1B are side views of an electrical interface 1,1' including a first
conductor 2,2' and a second conductor 3,3', respectively. Such first and second
conductors are typically, for example, made of copper, aluminum or mixtures thereof.
Figure 1A shows the prior art where the first and second conductors 2,3 are in direct

contact with each other resulting in contact area 4. Figure 1B shows an embodiment of
the disclosed concept where the second conductor 3' includes a nano-particle layer 5 and
therefore, first conductor 2' is in direct contact with nano-particle layer 5 resulting in
contact areas 4' and 4".
Figure 2 is an exploded schematic layout of electrical interface 10 including first
conductor 15 and second conductor 20. First and second conductors 15,20 can be made
of a wide variety of conductive materials such as, for example but not limited to, copper,
aluminum, and mixtures thereof. First conductor 15 has upper surface 25 and lower
surface 30. Second conductor 20 has upper surface 35 and lower surface 40. Opposite
lower surface 30 of first conductor 15 and upper surface 35 of second conductor 20 are
electrically connected together.
Referring to Figure 2A, the electrical interface 10 includes nano-particle layer 27
having first surface 28 and opposite second surface 29. Nano-particle layer 27 is
connected to lower surface 30 of first conductor 15. First surface 28 of nano-particle
layer 27 is electrically coupled to lower surface 30 of first conductor 15 and upper
surface 35 of second conductor 20 is electrically coupled to opposite second surface 29 of
nano-particle layer 27. Although one example configuration is shown in Figure 2A, it
should be understood that alternatively nano-particle layer 27 can be connected to upper
surface 35 of second conductor 20, or a nano-particle layer can be connected to both
lower surface 30 of first conductor 15 and upper surface 35 of second conductor 20.
Nano-particle layer 27 is made of nano-particle material selected from carbon-
containing nano-particles, metal nanowires, and mixtures thereof. Carbon-containing
nano-particles include carbon nanotubes. Carbon nanotubes and/or metal nanowires can
exhibit excellent thermal and electrical conductivity properties.
Suitable carbon nanotubes for use in the disclosed concept include single-wall
carbon nanotubes, multi-wall carbon nanotubes, and mixtures thereof. The carbon
nanotubes can be prepared using a variety of conventional methods known in the art. For
example, the carbon nanotubes can be prepared using chemical vapor deposition (CVD)
processing to grow the carbon nanotubes. The carbon nanotubes can be grown directly

on a surface interface (e.g., conductor surfaces 30 and/or 35 as shown in Figure 2A) to
form a nano-particle layer (e.g., nano-particle layer 27 as shown in Figure 2A). The
surface interface can be made of a wide variety of materials including, but not limited to,
copper, aluminum, and mixtures thereof. The surface interface is typically cleaned to
remove any surface grease and a suitable catalyst then is applied to the cleaned surface.
Suitable catalysts include, for example but are not limited to, aluminum, nickel, iron, and
mixtures thereof. The catalyst can be applied by a wide variety of conventional
techniques known in the art. Suitable techniques include, for example but are not limited
to, sputter deposition. Following application of the catalyst, CVD processing is carried
out using carbon bearing gases such as, for example but not limited to, methane, ethane,
and mixtures thereof.
As a non-limiting example, the concentration of the carbon nanotubes in the nano-
particle layer is up to about one (1) billion/cm2.
As another example, the nano-particle material includes metal nanowires. The
metal nanowires can be produced using a variety of methods known in the art including,
for example but not limited to, growing metal and metal oxide nanowires using
electroplating or CVD processing. Suitable metals include, for example but are not
limited to, zinc, nickel, silver, tin, and mixtures thereof. The metal nanowires can be
grown directly on a surface interface (e.g., conductor surfaces 30 and/or 35 as shown in
Figure 2A) to form a nano-particle layer (e.g., nano-particle layer 27 as shown in Figure
2A). The above description relating to suitable surface interfaces for use and steps in
preparing the substrate (e.g, cleaning and applying a catalyst thereon) is equally
applicable in this context. The metal nanowires can be grown by electroplating in an
appropriate electrolyte solution.
Figure 3 is an exploded schematic layout of electrical interface 50 including first
conductor 55, second conductor 60 and substrate 65. Substrate 65 is positioned between
first and second conductors 55,60. First and second conductors 55,60 can be made of the
materials described above for first and second conductors 15,20 of Figure 2. First
conductor 55 has upper surface 70 and lower surface 75. Second conductor 60 has upper

surface 80 and lower surface 85. Substrate 65 has first surface 90 and opposite second
surface 95.
Figure 3A shows the electrical interface 50 including nano-particle layers 92,97.
Nano-particle layer 92 is coupled to first surface 90 of substrate 65 and nano-particle
layer 97 is coupled to opposite second surface 95 of substrate 65. Substrate 65 is made,
for example, of a metal foil. Suitable metal foils can include a wide variety of materials
known in the art. For example, the metal foil itself can be grown by electroplating. Non-
limiting examples can include, but are not limited to, copper, aluminum, noble metals
such as silver, and mixtures thereof. Nano-particle layers 92,97 can be made of nano-
particle material as described above. The nano-particle material can be grown directly on
first surface 90 and opposite second surface 95 of substrate 65. The growth process can
include using CVD processing as described above. The nano-particle layer 92 on first
surface 90 of substrate 65 is electrically coupled to lower surface 75 of first conductor 55,
and upper surface 80 of second conductor 60 is electrically coupled to nano-particle layer
97 on opposite second surface 95 of substrate 65. Although one example configuration is
shown, it should be understood that alternatively only one of first surface 90 and
opposite second surface 95 may include a nano-particle layer (e.g., 92 or 97).
For example, at least one of lower surface 75 of first conductor 55 and upper
surface 80 of second conductor 60 can also include a nano-particle layer (not shown).
Figure 4 is an exploded schematic layout of electrical interface 100 including first
conductor 115, second conductor 120, and substrate 122. Substrate 122 is positioned
between first conductor 115 and second conductor 120. First and second conductors
115,120, can be made of the same materials as described above for first and second
conductors 15,20 of Figure 2. First conductor 115 has upper surface 125 and lower
surface 130. Second conductor 120 has upper surface 135 and lower surface 140.
Substrate 122 has first surface 123 and opposite second surface 124. Substrate 122 is a
nano-particle layer which is made of at least one sheet including carbon-containing nano-
particles, metal nanowires, and mixtures thereof. The carbon-containing nano-particles
include carbon nanotubes, carbon nanofibers, or mixtures thereof. Suitable sheets for use

can include known nano-particle layers such as, for example but not limited to,
buckypaper. Buckypaper can be prepared by dispersing and filtering a suspension
containing carbon nanotubes and/or carbon nanofibers. Buckypaper can exhibit good
thermal and electrical conductivity. First surface 123 of substrate 122 is electrically
coupled to lower surface 130 of first conductor 115, and upper surface 135 of second
conductor 120 is electrically coupled to opposite second surface 124 of substrate 122.
As a non-limiting example, the sheet of nano-particle material such as, but not
limited to, carbon nanotubes and/or carbon nanofibers, can be prepared using an
elastomer as the polymer matrix. A silanol cure condensation polymerization technique
can be employed. The carbon nanotubes and/or carbon nanofibers are preferably
uniformly mixed into an elastomer. The carbon nanotubes and/or carbon nanofibers can
be purified and/or grinded prior to mixing into the elastomer. The nano-particle material,
such as but not limited to, carbon nanotubes and/or carbon nanofibers, can be present in
the mixture in varying amounts. For example, the nano-particle material can be present
in an amount of from greater than 0 to less than 100 percent by weight of the mixture. In
preferred embodiments, the nano-particle material can be present in an amount of from 2
to 80 percent by weight of the mixture, or from 5 to 50 percent by weight of the mixture.
A variety of conventional devices can be used to mix together the ingredients. Suitable
mixing devices include, but are not limited to, extruders and speed mixers. Suitable
elastomers can include a variety of materials known in the art such as, but not limited to,
silicone elastomers, fluoro elastomers, and mixtures thereof. Non-limiting examples
include fluorosilicone, poly(dimethylsiloxane), and mixtures thereof. In one
embodiment, the elastomer has a molecular weight of from 800 g/mole to 100,000
g/mole. The elastomer can be in a substantially liquid or solid form. The mixture also
includes a crosslinker and optionally catalyst. The crosslinker and catalyst can be
selected from materials known in the art. A non-limiting example of a suitable
crosslinker includes, but is not limited to, polydiethoxysiloxane. Non-limiting examples
of suitable catalysts include, but are not limited to, platinum, diamine, bisphenol,
peroxide, dialkyltincarboxylate, and mixtures thereof. The amount of crosslinker and

catalyst can vary. For example, the crosslinker can be present in an amount of from 1 to
15 percent by weight of the mixture. When catalyst is used, for example, it can be
present in an amount of from 1 to 15 percent by weight of the mixture.
The mixture is pressed into a desired shape under load using a device such as a
die. The mixture can be molded into essentially any shape including, but not limited to,
square, circle, rectangle, and combinations thereof. For example, holes are punched into
the shaped mixture for use in bolted connections (e.g., electrical interface 100 as shown
in Figure 4). The shaped mixture then is allowed to cure to form a resultant substantially
flexible nano-particle material (e.g., carbon nanotube and/or nanofiber) sheet. The cure
can be carried out under a variety of conventional temperature and pressure conditions
which are known in the art for curing elastomer materials. In one embodiment, the cure
is conducted at ambient temperature, for example but not limited to, 18°C-23°C, and/or
under atmospheric air conditions. In another embodiment, the cure is conducted at an
elevated temperature. This method can provide advantages over known methods due to
the ease of preparing the sheet and the ability to scale the process for mass production.
The resultant sheet is substantially flexible and can have a nano-particle material (e.g.,
carbon nanotube and/or carbon nanofiber) loading of up to 50 percent by weight of the
sheet.
For example, the at least one sheet can also include metal nanowires.
Figure 5 is an exploded schematic layout of electrical interface 150 including first
conductor 155, second conductor 160, and substrate 165. Substrate 165 is positioned
between first conductor 155 and second conductor 160. First and second conductors
155,160 can be made of the same materials as described above for conductors 15,20 of
Figure 2. Substrate 165 can be made of the same materials as described above for
substrates 65,122. First and second conductors 155,160 are electrically coupled together.
Further, first and second conductors 155,160 are mechanically coupled together by
fasteners. Suitable fasteners can include a wide variety known in the art including, but
not limited to, those previously described herein. As shown in Figure 5, openings 200
and 201 are made in first conductor 155; openings 202 and 203 are made in substrate

165; and openings 204 and 205 are made in second conductor 160. The openings
200,201,202,203,204,205 can be made using any conventional technique such as drilling.
Openings 200,202 and 204 are vertically aligned, and openings 201,203 and 205 are
vertically aligned. Screws or bolts 220,221 are coupled together with washers 240 and
241, respectively, and inserted in each of openings 200,201 and through openings
202,203 and through openings 204,205, respectively. Washers 240,241 and 242,243 and
nuts 244,245 are coupled to screws or bolts 220,221, respectively, on lower surface 161
of second conductor 160.
For example and without limitation, the electrical interface 150 forms a bolted
joint of a power conductor.
While specific embodiments of the disclosed concept have been described in
detail, it will be appreciated by those skilled in the art that various modifications and
alternatives to those details could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular arrangements disclosed are meant to be
illustrative only and not limiting as to the scope of the disclosed concept which is to be
given the full breadth of the claims appended and any and all equivalents thereof.

WE CLAIM
1. A composition for coating a surface of an electrical contact [10], the composition
comprising:
polymer matrix comprising elastomer;
at least one nano-particlc material selected from the group consisting of carbon-
containing nano-particles, metal nanowires, and mixtures thereof; and
crosslinker.
2. The composition of claim 1:wherein the elastomer is selected from the group consisting
of silicone elastomers, fluoro elastomer;, and mixtures thereof.
3. The composition of claim 1, wherein the elastomer is selected from the group consisting
of fluorosilicone, poly(dimethylsiioxane) and mixtures thereof.
4. The composition of claim 1, whereIn the carbon-containing hano-particles are selected
from the group consisting of carbon nanobes, carbon nanofibers, and mixtures thereof.
5. The composition of claim 1, wherein the nano-particle material is present in an amount of
from 5 to 50 percent by weight or the position.
6. The composition of claim 1, wherein the crosslinker comprises polydiethoxysiloxane.
7. The composition of claim 1, wherein the crosslinker is present in an amount of from 1 to
15 percent by weight of the composition.
8. The composition of claim 1, wherein the elastomer has a molecular weight of from 800 to
100,000 g/mole.
9. The composition of claim 1.wherein comprising catalyst.

10. The composition of claim 9, wherein the catalyst is selected from the group consisting of
platinum, diamine, bisphenol, peroxide, falkyltincarboxylate, and mixtures thereof.
11. The composition of claim 9, wherein in the catalyst is present in an amount of from 1 to 15
percent by weight of the composition.
12. An electrical interface [10] having a first contact [15] surface and a second contact [20]
surface wherein at least one of said first and second contact [15,20] surfaces comprises the
composition of claim 1.
13. A process for producing an electrical interface [10] having a first contact [15] surface and
a second contact [20] surface, comprising applying to at least one contact surface the
composition of claim 1.
14. A process for producing an electrical al interface [10] having a first contact [55] surface, a
second contact [60] surface, comprising ositioning a nano-particle sheet [65] between the first
and second contact [55,60] surfaces,wherein in the sheet [65] comprises the composition of claim
1.
15. A process for producing a nano particle composition, comprising:
a. mixing at least one nano-particle material selected from the group consisting of
carbon-containing nano-particle, metal nanowires, and mixtures thereof, and
polymer matrix comprising costomer;
b. adding crosslinker to the of (a); and
c. curing the mixture of (b)
16. The process orclaim 15, wherein carbon-containing nano-particles are selected from
the group consisting of carbon nano wherein carbon nanofibers, and mixtures thereof.

17. The process of claim 15, wherein the crosslinker comprises polydiethoxysiloxane.
18. The process o f claim 15, wherein the elastomer is selected from the group consisting of
silicone elastomers, fluoro elastomers and mixtures thereof.
19. The process of claim 15, further comprising adding catalyst to the mixture of (a).
20. The process of claim 15, further comprising molding the mixture of (b) into a desired
shape.
21. The process of claim 15, comprising curing at ambient temperature and
atmospheric air conditions.
22. The process of claim 15, wherein the resultant composition is in the form of a sheet.
23. The process of claim 15, further comprising grinding the nano-particle material prior to
mixing with the polymer matrix.

A composition for coating a surface of an electrical contact includes a polymer
matrix comprising elastomer, at least one nano-particle material, and crosslinker.