ELECTRICAL INTERFACES INCLUDING
A NANO-PARTICLE LAYER
BACKGROUND
Field
The disclosed concept relates to electrical interfaces and, more particularly, to
electrical interfaces having a first conductor and a second conductor.
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 an electrical interface including a first conductor having a surface, a
nano-particle layer having a first surface and an opposite second surface, the first
surface of the nano-particle layer being electrically coupled to the surface of the first
conductor, and a second conductor having a surface electrically coupled to the
opposite second surface of the nano-particle layer. 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 first and second conductors may be power conductors.
The nano-particle layer may include nano-particle material selected from the
group consisting of carbon-containing nano-particles, metal nanowires, and mixtures
thereof. The carbon-containing nano-particles may be selected from the group
consisting of carbon nanotubes, carbon nanofibers, and mixtures thereof. In the
embodiment including carbon nanotubes, the carbon nanotubes may be formed on at
least one of the surface of the first conductor and the surface of the second conductor.
In a further embodiment, the carbon nanotubes may be formed by chemical vapor
deposition. In still a further embodiment, the nano-particle layer may include a metal
foil wherein carbon nanotubes are formed on at least one of the first surface and the
opposite second surface of the metal foil. In yet another embodiment, the carbon
nanotubes may form a sheet. In still another embodiment, the carbon nanotubes may
be selected from the group consisting of multi-wall carbon nanotubes, single-wall
carbon nanotubes, and mixtures thereof.
In the embodiment including carbon nanofibers, the carbon nanofibers may
form a sheet.
In the embodiment including metal nanowires, the metal nanowires may
include metals thereof selected from the group consisting of zinc, nickel, silver, tin,
and mixtures thereof. In a further embodiment, the metal nanowires may be formed
on at least one of the surface of the first conductor and the surface of the second
conductor. In still a further embodiment, the metal nanowires may be formed by
chemical vapor deposition or electroplating. In yet another embodiment, the nano-
particle layer may include a metal foil wherein the metal nanowires are formed on at
least one of the first surface and the opposite second surface of the metal foil.
In still another embodiment, the electrical interface may form a bolted joint of
a power conductor.
In a further embodiment, the first and second conductors may be made of a
material selected from the group consisting of aluminum, copper, and mixtures
thereof.
In yet another embodiment, the first conductor, the nano-particle layer and the
second conductor may be mechanically coupled together by at least one fastener.

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 2A 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 electrical interfaces including 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 made, for example, 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, the 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 are 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 nahqwires 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 or mixtures thereof. The carbon-
containing nano-particles include carbon nanotubes, carbon nanofibers, and 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, 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.

What is Claimed is:
1. An electrical interface comprising:
a first conductor having a surface;
a nano-particle layer having a first surface and an opposite second surface, the
first surface of the nano-particle layer electrically coupled to the surface of the first
conductor; and
a second conductor having a surface electrically coupled to the opposite
second surface of the nano-particle layer.
2. The electrical interface of claim 1, wherein the first and second conductors are
power conductors.
3. The electrical interface of claim 1, wherein the nano-particle layer comprises
nano-particle material selected from the group consisting of carbon-containing nano-
particles, metal nanowires, and mixtures thereof.
4. The electrical interface of claim 3, wherein the carbon-containing nano-
particles comprise carbon nanotubes.
5. The electrical interface of claim 3, wherein the carbon-containing nano-
particles comprise carbon nanofibers.
6. The electrical interface of claim 4, wherein the carbon nanotubes are formed
on at least one of the surface of the first conductor and the surface of the second
conductor.
7. The electrical interface of claim 6, wherein the carbon nanotubes are formed
by chemical vapor deposition.

8. The electrical interface of claim 4, wherein the nano-particle layer comprises a
metal foil having the first surface and the opposite second surface; and wherein the
carbon nanotubes are formed on at least one of the first surface and the opposite
second surface of the metal foil.
9. The electrical interface of claim 8, wherein the carbon nanotubes are formed
by chemical vapor deposition.
10. The electrical interface of claim 3, wherein the metal nanowires comprise
metals selected from the group consisting of zinc, nickel, silver, tin, and mixtures
thereof.
11. The electrical interface of claim 3, wherein the metal nanowires are formed on
at least one of the surface of the first conductor and the surface of the second
conductor.
12. The electrical interlace of claim 11, wherein the metal nanowires are formed
by chemical vapor deposition.
13. The electrical interface of claim 11, wherein the metal nanowires are formed
by electroplating.
14. The electrical interface of claim 3, wherein the nano-particle layer comprises a
metal foil having the first surface and the opposite second surface; and wherein the
metal nanowires are formed on at least one of the first surface and the opposite second
surface of the metal foil.
15. The electrical interface of claim 14, wherein the metal nanowires are formed
by chemical vapor deposition.

16. The electrical interface of claim 14, wherein the metal nanowires are formed
by electroplating.
17. The electrical interface of claim 4, wherein the carbon nanotubes form a sheet.
18. The electrical interface of claim 5, wherein the carbon nanofibers form a sheet.
19. The electrical interface of claim 4, wherein the carbon nanotubes are selected
from the group consisting of multi-wall carbon nanotubes, single-wall carbon
nanotubes, and mixtures thereof.
20. The electrical interface of claim 1, wherein the electrical interface forms a
bolted joint of a power conductor.
21. The electrical interface of claim 1, wherein the first and second conductors are
made of a material selected from the group consisting of aluminum, copper, and
mixtures thereof.
22. The electrical interface of claim 1, wherein the first conductor, the nano-
particle layer and the second conductor are mechanically coupled together by at least
one fastener.
23. The electrical interface of claim 22, wherein the at least one fastener is
selected from the group consisting of screws, bolts, washers, nuts and combinations
thereof.

An electrical interface includes a nano-particle layer. The electrical interface
also includes a first conductor and a second conductor. The nano-particle layer and
the first and second conductors are electrically coupled together.