U.S. patent application number 15/249602 was filed with the patent office on 2016-12-22 for carbon nanofiber materials and lubricants.
This patent application is currently assigned to UCHICAGO ARGONNE, LLC. The applicant listed for this patent is UCHICAGO ARGONNE, LLC. Invention is credited to Qiuying CHANG, Ali ERDEMIR, Kuldeep MISTRY, Vilas G. POL, Michael M. THACKERAY.
Application Number | 20160369197 15/249602 |
Document ID | / |
Family ID | 53367672 |
Filed Date | 2016-12-22 |
United States Patent
Application |
20160369197 |
Kind Code |
A1 |
ERDEMIR; Ali ; et
al. |
December 22, 2016 |
CARBON NANOFIBER MATERIALS AND LUBRICANTS
Abstract
Nickel-containing carbon nanofiber (NiCNF) materials and
lubricants comprising the nanofiber materials are described herein.
The NiCNF materials comprise a plurality of elongate
nickel-containing carbon nanofibers. Each NiCNF comprises a carbon
nanofiber shaft that is capped at one end by a nickel nanoparticle
encapsulated in multiple layers of graphitic carbon. The nanofibers
typically have a generally circular cross-section (i.e., in the
direction perpendicular to the length-axis of the fibers). The
NiCNF materials as useful, e.g., in lubricant compositions, which
also are described herein.
Inventors: |
ERDEMIR; Ali; (Naperville,
IL) ; POL; Vilas G.; (Naperville, IL) ;
THACKERAY; Michael M.; (Naperville, IL) ; MISTRY;
Kuldeep; (North Canton, OH) ; CHANG; Qiuying;
(Woodridge, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UCHICAGO ARGONNE, LLC |
Chicago |
IL |
US |
|
|
Assignee: |
UCHICAGO ARGONNE, LLC
Chicago
IL
|
Family ID: |
53367672 |
Appl. No.: |
15/249602 |
Filed: |
August 29, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14109557 |
Dec 17, 2013 |
|
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15249602 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10M 103/04 20130101;
C10M 2201/053 20130101; C10N 2020/063 20200501; C10M 105/04
20130101; C10M 141/02 20130101; C10M 2207/282 20130101; C10N
2010/14 20130101; C10M 125/04 20130101; C10N 2080/00 20130101; C10M
2203/024 20130101; C10M 2207/289 20130101; C10N 2030/06 20130101;
C10M 177/00 20130101; C10M 2201/041 20130101; C10N 2020/06
20130101; C10N 2020/061 20200501; C10M 2205/0285 20130101; C10M
2201/05 20130101; Y10T 428/2918 20150115 |
International
Class: |
C10M 125/04 20060101
C10M125/04; C10M 141/02 20060101 C10M141/02; C10M 105/04 20060101
C10M105/04 |
Goverment Interests
CONTRACTUAL ORIGIN OF THE INVENTION
[0002] The United States Government has rights in this invention
pursuant to Contract No. DE-ACO2-06CH11357 between the United
States Government and UChicago Argonne, LLC representing Argonne
National Laboratory.
Claims
1. A lubricant composition comprising a nickel-containing nanofiber
(NiCNF) material dispersed in a liquid medium, wherein the NiCNF
comprises a plurality of elongate nickel-containing carbon
nanofibers, and individual nanofibers of the NiCNF material include
a nickel nanoparticle encapsulated within multiple layers of
graphitic carbon at one end of a carbon nanofiber shaft.
2. The lubricant composition of claim 1, wherein the individual
nanofibers have a fiber diameter in the range of about of about 30
to about 100 nanometers (nm).
3. The lubricant composition of claim 1, wherein the individual
nanofibers have a length in the range of about 100 nm to about 2
micrometers (.mu.m).
4. The lubricant composition of claim 1, wherein the nickel
nanoparticle has a diameter in the range of about 10 to about 30
nm.
5. The lubricant composition of claim 1, wherein the graphitic
carbon encapsulating the nickel nanoparticle has a thickness in the
range of about 4 to about 10 nm.
6. The lubricant composition of claim 1, wherein the NiCNF material
contains not more than about 60 wt % of the carbon that is not part
of the nickel-containing carbon nanofibers.
7. The lubricant composition of claim 1, wherein at least about 50%
of the nickel in the NiCNF material is encapsulated at an end of a
carbon nanofiber shaft.
8. The lubricant composition of claim 1, wherein the individual
nanofibers have a fiber diameter in the range of about 30 to about
100 nm, and a length in the range of about 100 nm to about 2 .mu.m;
the nickel nanoparticle has a diameter in the range of about 10 to
about 30 nm,; and the graphitic carbon encapsulating the nickel
nanoparticle has a thickness in the range of about 4 to about 10
nm.
9. The lubricant composition of claim 1, wherein nanofibers of the
NiCNF are not hollow.
10. The lubricant composition of claim 1, further comprising a
surfactant.
11. The lubricant composition of claim 10, wherein the surfactant
comprises a non-ionic surfactant.
12. The lubricant composition of claim 10, wherein the surfactant
comprises sorbitan trioleate.
13. The lubricant composition of claim 10, wherein the surfactant
is present in the composition at a concentration in the range of
about 1000 to about 20000 parts-per-million (ppm).
14. The lubricant composition of claim 10, wherein the liquid
carrier comprises a liquid hydrocarbon.
15. The lubricant composition of claim 14, wherein the liquid
hydrocarbon comprises a poly alpha olefin.
16. The lubricant composition of claim 1, wherein the NiCNF
material is present in the composition at a concentration in the
range of about 0.01 to about 15 wt %.
17. The lubricant composition of claim 1, wherein the liquid
carrier comprises a poly alpha olefin and the NiCNF material is
present in the composition at a concentration in the range of about
0.5 to about 1 wt %.
18. The lubricant composition of claim 17, further comprising a
non-ionic surfactant.
19. The lubricant composition of claim 18, wherein the surfactant
comprises sorbitan trioleate.
20. The lubricant composition of claim 18, wherein the surfactant
is present in the composition at a concentration in the range of
about 1000 to about 20000 parts-per-million (ppm).
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. application Ser. No.
14/109,557, filed on Dec. 17, 2013, which is incorporated herein by
reference in its entirety.
FIELD OF THE INVENTION
[0003] This invention relates to carbon nanofiber materials and
lubricant compositions comprising the carbon nanofiber materials.
More particularly, this invention relates to nanofiber materials
comprising a carbon and nickel nanoparticle, and lubricant
compositions comprising the nanofiber materials.
BACKGROUND OF THE INVENTION
[0004] The energy efficiency, durability, and environmental
compatibility of all kinds of moving mechanical systems (including
engines) are closely related to the effectiveness of the lubricants
being used on their rolling, rotating, and sliding surfaces.
Therefore, lubricants play a vital role in machine life,
efficiency, and overall performance. Poor or inefficient
lubrication always result in higher friction and severe wear
losses, which can in turn adversely impact the performance and
durability of mechanical systems. In particular, progressive wear
due to inadequate lubrication is one of the most serious causes of
component failure. Inadequate lubrication can also cause
significant energy losses in the above-mentioned industrial systems
mainly because of high friction.
[0005] Currently, there are numerous solid lubricants available at
sizes ranging from 1 nm to more than 500 nm in powder forms. The
finer solids (i.e. 1 to 30 nm range) are mostly made of
nanostructured carbon materials such as C.sub.60, nano-tubes,
nano-fibers, and nano-onions, while intermediate range lubricants
(30 to 100 nm) typically include inorganic solids such as
MoS.sub.2, WS.sub.2, hexagonal crystalline boron nitride (h-BN),
and pure metals (e.g., gold, silver, tin, bismuth, etc.). WS.sub.2
is synthesized typically in the form of fullerene-like particles
and hence it is often referred to as inorganic fullerene or, IF.
Many of these materials are manufactured using a bottom-up approach
involving multi-step chemical synthesis routes (e.g. gas phase
chemical processing, combustion synthesis, sonochemistry, etc.) and
the uses of environmentally unsafe chemicals. Many current
processes also generate large amounts of toxic by-products to deal
with after the manufacturing.
[0006] Carbon particles, fibers, and nanotubes are utilized in a
number of industrially significant applications in addition to
lubricants, such as catalysts, electrode materials for alkali metal
batteries, and chemical sorbants. In many cases, carbon
nanomaterials (e.g., particles, tubes or fibers) are particularly
useful in such applications. Carbon nanomaterials have been
produced by a number of processes. The chemical and physical
properties of carbon nanomaterials can be highly dependent on the
physical form of the materials (e.g., physical dimensions, shape,
presence or absence of cavities or pores (tubes, hollow particles,
etc.), as well as the chemical nature (e.g., metals, metalloids,
oxides) and the physical form (e.g., crystalline, amorphous) of any
encapsulated or associated materials. In many cases, the form of
the carbon materials and any associated, encapsulated or
incorporated non-carbon materials (metals, metalloids, metal
oxides, and the like) is highly dependent on the conditions (e.g.,
starting materials, temperature, pressure, etc.) used to produce
the carbon nanomaterials.
[0007] Conventional lubricants comprising carbon do not yet meet
the expectations of providing the performance requirements of
motorized and mechanical devices. Carbon is an extremely versatile
material that exists in numerous forms with diverse physical,
chemical, electrical and electrochemical properties. Certain
carbonaceous particles, such as carbon nano-onions, carbon
nanofibers, carbon nanotubes and submicron graphite particles have
all been considered for lubrication purposes in the past, but
generally have been found to be expensive, ineffective, and/or
difficult to scale-up.
[0008] There is an ongoing need for new carbon materials,
particularly nanomaterials, as well as lubricant compositions
comprising new carbon nanomaterials, which are, e.g.,
environmentally friendly or benign, and which can provide reduced
friction and wear. The present invention addresses these needs.
SUMMARY
[0009] Nickel-containing carbon nanofiber (NiCNF) materials and
lubricants comprising the nanofiber materials are described herein.
The NiCNF materials comprise a plurality of elongate
nickel-containing carbon nanofibers. Each NiCNF comprises a carbon
nanofiber shaft that is capped at one end by a nickel nanoparticle
encapsulated in multiple layers of graphitic carbon. The nanofibers
typically have a generally circular cross-section (i.e., in the
direction perpendicular to the length-axis of the fibers). The
individual nanofibers typically have a length in the range of about
100 nanometers (nm) to about 2 micrometers (.mu.m) and a fiber
diameter (i.e., the diameter of the generally circular
cross-section) in the range of about 30 nm to about 100 nm. The
nickel nanoparticles encapsulated by the carbon nanofibers
typically have a diameter in the range of about 10 nm to about 30
nm. The nanofibers are solid fibers, i.e., they are not hollow.
[0010] In some preferred embodiments, the nanofibers of the NiCNF
material have a fiber diameter in the range of about of about 30 to
about 100 nm, and a length in the range of about 100 nm to about 2
.mu.m; the nickel nanoparticle has a diameter in the range of about
10 to about 30 nm; and the graphitic carbon encapsulating the
nickel nanoparticle has a thickness in the range of about 4 to
about 10 nm.
[0011] The NiCNF materials optionally can include one or more other
form of non-NiCNF carbon, such as carbon nanotubes, carbon fibers
without encapsulated nickel, and non-fibrous particulate carbon
(e.g., generally spheroidal particles, oblate spheroidal particles,
irregularly shaped particles, and the like). Preferably, the NiCNF
material comprises less than 60 percent by weight (wt %) of
non-NiCNF carbon, based on the total dry weight of carbon present
in the material, e.g., less than 50, 40, 30, 25, 20 or 10 wt %
thereof. Optionally, the NiCNF material can include one or more
other form of nickel (i.e., non-encapsulated nickel, or nickel
encapsulated in another form of carbon). Preferably, the NiCNF
material includes less than about 30 w% of such other forms of
nickel, based on the total weight of nickel in the material, e.g.,
less than about 25, 20, 15, 10, or 5 wt % thereof. Such other forms
of carbon and/or nickel can be present, e.g., as impurities formed
during the preparation of the nickel-containing carbon nanofibers,
or optionally can be intentionally added components. The NiCNF
material preferably contains not more than about 50 wt % of carbon
that is not part of the nickel-containing carbon nanofibers (i.e.,
non-NiCNF carbon). Preferably, at least about 50% of the nickel in
the NiCNF material is encapsulated at an end of a carbon nanofiber
shaft.
[0012] In another aspect, lubricant compositions are described,
which comprise, consist essentially of, or consist of the NiCNF
materials optionally suspended in an aqueous medium or non-aqueous
liquid medium (e.g., a natural or synthetic hydrocarbon-based
material such as an oil, a wax, or a grease). The NiCNF material
can be present in a liquid lubricant composition at a
concentration, e.g., in the range of about 0.01 to about 15 wt %,
preferably about 0.05 to about 5 wt %, about 0.1 to about 2 wt %,
or 0.5 to about 1 wt %. In one lubricant composition embodiment,
the individual nanofibers of the NiCNF material have a fiber
diameter in the range of about of about 30 to about 100 nm, a
length in the range of about 100 nm to about 2 .mu.m, the nickel
nanoparticle has a diameter in the range of about 10 to about 30
nm, and the graphitic carbon encapsulating the nickel nanoparticle
has a thickness in the range of about 4 to about 10 nm.
[0013] In one embodiment, the present invention provides a
lubricant composition comprising a NiCNF material as described
herein suspended in a liquid hydrocarbon carrier, preferably at a
NiCNF concentration in the range of about 0.1 to about 1 wt %.
Optionally, the composition can further a surfactant (e.g., to aid
in suspension of the NiCNF material).
[0014] Optionally, the liquid hydrocarbon carrier comprises a poly
alpha olefin. Preferred poly alpha olefin (PAO) materials have a
kinematic viscosity in the range of about 2 to about 10 centistokes
(cSt) at about 100.degree. C., e.g., a PAO with a viscosity of
about 2 cSt or a PAO with a viscosity of about 4 cSt.
[0015] The lubricant composition also can optionally comprise a
surfactant (e.g., a non-ionic surfactant, such as sorbitan
trioleate. The surfactant, if utilized, can be present in the
composition at a concentration in the range of about 1000 to about
20000 parts-per-million (ppm).
[0016] In another aspect, a method of preparing a NiCNF material is
provided. The method comprises heating nickel(II) acetate neat in a
sealed pressure reactor at a temperature of about 650 to about
800.degree. C. at an autogenically produced pressure of about 300
to about 600 pounds-per-square inch (psi) under an inert atmosphere
(e.g., nitrogen or argon).
[0017] The NiCNF materials described herein are particularly useful
as additive materials in lubricant compositions for use in metal
lubrication, where the nickel from the nanofiber materials
unexpectedly has been found to form a nickel film in areas of wear
on the metal surface. The nickel film fills in worn areas and
negates or ameliorates wear that can occur with moving metal parts
even in the presence of a lubricant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 provides (a) a scanning electron micrograph (SEM) of
an end portion of a nickel-tipped carbon nanofiber (NiCNF) 10
comprising carbon nanofiber shaft 12 and encapsulated nickel
nanoparticle 14; and (b) a high resolution SEM image showing a
portion of nickel nanoparticle 14 encapsulated within layers of
graphitic carbon 16.
[0019] FIG. 2 illustrates wear scars observed in evaluation of a
NiCNF-containing lubricant at 20.degree. C. (Panel (a)) and
100.degree. C. (Panel (c)); Panel (b) shows a magnification of the
wear scar of Panel (a); Panel (d) shows a magnification of the wear
scar of Panel (c).
[0020] FIG. 3 illustrates wear scars observed in evaluation of a
NiCNF-containing lubricant (Panel (a)) and comparative lubricant
without any NiCNF present (Panel (b)).
DETAILED DESCRIPTION
[0021] New nickel-containing carbon nanofiber materials are
described comprising a plurality of elongate nickel-containing
carbon nanofibers. An individual NiCNF of the plurality of
nanofibers comprises a carbon nanofiber shaft capped at one end
with a nickel nanoparticle. The nickel nanoparticle is encapsulated
by multiple layers of graphitic carbon at the end of the carbon
nanofiber shaft.
[0022] Typically, the nickel nanoparticle, which can have a
diameter in the range of about 10 to about 30 nm (e.g., an average
diameter of about 15 to about 25 nm), is encapsulated by multiple
layers of graphitic carbon having a total thickness of about 4 to
10 nm (e.g., an average of about 7 to 8 nm).
[0023] The nanofibers can be of any length, although generally the
nanofibers have a length of about 100 nm to 2 .mu.m (e.g., about
300 nm to about 1 .mu.m), with an average length in the range of
about 200 nm to about 800 nm.
[0024] The nanofibers have a generally circular transverse
cross-section (i.e., perpendicular to the longest dimension
(length) of the fiber) with fiber diameters in the range of about
25 to about 100 nm, and an average diameter in the range of about
40 to about 70 nm. The diameter of the shaft can be relatively
uniform or can vary along the length of the shaft (i.e., a
non-uniform shaft diameter).
[0025] Generally, at least about 40 percent (typically at least
about 40 to about 60%; e.g., 50%) of carbon nanofibers within the
NiCNF material include the encapsulated nickel nanoparticle. As
used herein, the term "nanofiber" refers to a fiber having a
cross-sectional diameter of less than 100 nm. Additionally,
nanofibers can be generally straight or can be curved (e.g.,
coiled). The carbon nanofiber shafts of the NiCNF materials are
solid, i.e., not hollow, which distinguishes these materials from
carbon nanotubes, which are hollow. The NiCNF materials optionally
can include of other forms of carbon besides the nickel-containing
carbon nanofibers. Preferably, the NiCNF materials contain less
than about 60 percent by weight (wt %), preferably less than 50,
40, 30, 25, 20 or 10 wt % of non-NiCNF carbon. Non-limiting
examples of other forms of carbon that may be present in the NiCNF
materials include carbon nanotubes, carbon fibers without
encapsulated nickel, and non-fibrous particulate carbon (e.g.,
generally spheroidal particles, oblate spheroidal particles,
irregularly shaped particles, and the like). In addition or
alternatively, the NiCNF materials can include nickel that is not
encapsulated at an end of a carbon nanofiber, e.g.,
non-encapsulated nickel, or nickel that is encapsulated in another
form of carbon such as a carbon nanotube, a non-fibrous carbon
nanoparticle, or a non-fibrous carbon microparticle. Preferably,
the NiCNF materials include less than about 25, 20, 15, 10, or 5 wt
% of nickel that is not encapsulated on the end of a carbon
nanofiber. The other forms of carbon and/or nickel can be present,
e.g., as impurities formed during the preparation of the NiCNF
materials, or optionally can be intentionally added components.
[0026] The NiCNF materials described herein can be prepared by
thermal decomposition of nickel(II) acetate under autogenic (i.e.,
self-generated) pressure. Typically, the nickel acetate is heated
under an inert atmosphere (e.g., nitrogen or argon) at a
temperature in the range of about 650 to about 800.degree. C.
(preferably about 700.degree. C.) in a sealed reactor sized such
that an internal pressure in the range of about 300 to about 600
psi is attained upon heating, e.g., due to gases generated during
the decomposition of the nickel acetate to form the NiCNF material
and any headspace or interstitial gas than may be present in the
sealed reactor. The resulting NiCNF products comprise solid carbon
nanofibers (i.e., not hollow) in which individual fibers comprise a
carbon nanofiber shaft having a nickel nanocrystal encapsulated
within multiple layers of graphitic carbon at an end of the shaft.
As noted above, minor amounts of other forms of carbon and/or
nickel can be present as by-products. In another aspect, lubricant
compositions are described, which comprise, consist essentially of,
or consist of a NiCNF material, optionally suspended in a liquid
medium. In certain embodiments, the liquid medium can be an aqueous
liquid or a non-aqueous liquid medium. In some embodiments, the
NiCNF material is suspended in a non-aqueous liquid such as a
natural or synthetic hydrocarbon-based oil, a poly(alkylene glycol)
such as poly(ethylene glycol), a wax, or a grease. Non-limiting
examples of suitable liquid media include materials comprising,
consisting essentially of, or consisting of water, an alcohol, a
glycol, glycerol, a poly(alkylene glycol) (e.g., poly(ethylene
glycol), poly(propylene glycol), poly(ethylene glycol-co-propylene
glycol), and the like), a hydrocarbon, other lubricious organic
solvents or polymers (e.g., glycol ethers, glycerol ethers,
glycerol esters, glycol esters, poly(alkylene glycol) esters, and
poly(alkylene glycol) ethers), a PAO, or a combination of two or
more of the foregoing liquids. In some preferred embodiments, the
liquid carrier comprises a PAO. Preferred PAO materials have a
kinematic viscosity in the range of about 2 to about 10 centistokes
(cSt) at about 100.degree. C. In some preferred embodiments the
liquid carrier comprises a PAO having a kinematic viscosity of
about 2 cSt or about 4 cSt. The NiCNF material can be present in a
liquid lubricant composition at a concentration, e.g., in the range
of about 0.01 to about 15 wt %, preferably about 0.05 to about 5 wt
%, about 0.1 to about 2 wt %, or 0.5 to about 1 wt %.
[0027] Optionally, the lubricant composition can further comprise a
surfactant such as a nonionic surfactant (e.g., sorbitan
trioleate), for example, to aid in suspension of the nanofiber
material. Non-limiting examples of other nonionic surfactants
include sorbitan sesquioleate (SSO) and SURFONIC LF-17 (an
ethoxylated and propoxylated linear C.sub.12-C.sub.12 alcohol).
Optionally, the surfactant, if utilized, is present in the
composition at a concentration in the range of about 1000 to about
20000 parts-per-million (ppm), more preferably about 5000 to about
10000 ppm.
[0028] The following examples are provided to illustrate certain
preferred embodiments of the present invention, and are not to be
considered a limiting the scope of the appended claims. The
examples demonstrate, in particular, the versatility of autogenic
reactions in synthesizing carbon-based materials with a diverse
range of particle morphologies, conducive to their use as additives
for lubrication technology.
[0029] Autogenic Pressure Reactor. A typical reactor useful for
making of the nickel-carbon nanofiber materials can operate up to a
maximum working pressure of about 2000 pounds per square inch and a
maximum temperature of about 800.degree. C. Various reaction
parameters such as heating rate, temperature, duration, reactant
concentration, stoichiometry, pressure, and atmosphere (either
oxidizing, reducing or inert) can be controlled to alter the
physical and chemical nature of carbon-containing products formed
in such reactors. Preferably, the reactor operates under conditions
ranging from a minimum working pressure of about 100 pounds per
square inch and a minimum temperature of about 100.degree. C., to a
maximum working pressure in the range of about 800 to about 2000
pounds per square inch and a maximum temperature in the range of
about 300 to about 800.degree. C.
[0030] Liquid Lubricant Test-Sample Preparation. NiCNF materials as
described herein were mixed with and dispersed in a selected
base-lubricant (e.g., a poly(alpha olefin) or 5w30 oil). Typically,
the nanofiber material is stirred in the liquid medium continuously
at about 60.degree. C. for approximately 1 hour prior to being
evaluated.
[0031] Tribological Test Set-up. The tribological performance of
the test lubricants was evaluated using the facilities at the
Tribology Section at Argonne National Laboratory. Tests were
conducted at extremely high contact pressures and at elevated
temperatures that are representative of the typical operating
conditions of real automotive/industrial components. A Ball-on-Disc
Tribo-tester was utilized for the tribological evaluations. The
ball was loaded on top of the plate in order to create a contact
pressure of about 0.61 to about 1.05 GPa. The tests were conducted
at various temperatures from about 20 to about 100.degree. C. and
in open air. The plate is rotatable at variable speeds and is
pressed and slid against the ball sample during operation.
[0032] Post-Test analysis. Once, the tribological tests were
completed, the test samples (ball and plate) were retrieved and
cleaned using solvents. After cleaning, the worn areas examined
using an optical microscope or subjected to other microscopic
and/or spectroscopic techniques.
EXAMPLE 1
Preparation of a Nickel-Carbon Nanofiber Material
[0033] About 1 gram (g) of nickel(II) acetate was heated at about
700.degree. C. in an inert nitrogen atmosphere for about 1 hour in
a closed reactor under autogenic (self-generating) pressure to
afford about 0.05 g of a carbon nanofiber material. Individual
fibers of the material had lengths in the range of about 100 nm to
about 1 .mu.m (average length of about 500 nm) and an average fiber
diameter of about 40 nm, with nickel nanoparticles having diameters
of about 10 to about 25 nm (average diameter of about 15 nm)
encapsulated at the tip of the nanofiber.
[0034] Scanning electron microscope images of a nanofiber from the
obtained product are shown in FIG. 1, Panels (a) and (b). Panel (a)
of FIG. 1 provides an electron micrograph of solid
nickel-containing carbon nanofiber 10 having a carbon nanofiber
shaft 12 with a diameter about 30 to 40 nm, capped with a nickel
nanoparticle 14 having a diameter of about 18 nm. Panel (b) of FIG.
1 shows a high resolution image of the a portion of the nickel
nanoparticle 14 with several layers of graphic carbon 16
encapsulating nanoparticle 14 at a thickness of about 7 to 8
nm.
EXAMPLE 2
Tribological Testing of PAO-Based Lubricants
[0035] Tribological testing was conducted using the Ball-on-Disc
Tribo-tester as described herein using a liquid lubricant medium of
a PAO: Comparative Lubricant A (PAO alone), and Lubricant B (0.1 wt
% NiCNF of Example 1 dispersed in PAO). The PAO had a viscosity of
about 4 centiStokes (cSt) was tested under the following
conditions: maximum pressure of about 0.61 GPa, a speed of 3
mm/sec, and a Hertz contact diameter of about 80 mm, at
temperatures of 20, 80 and 100.degree. C. The base lubricant,
Comparative Lubricant A, exhibited a friction coefficient of about
0.13 to about 0.15, while Lubricant B, comprising the NiCNF
material exhibited a friction coefficient of about 0.10, at the
tested temperatures.
[0036] FIG. 2 illustrates micrographic images of wear scars
observed in evaluation of Lubricant B (NiCNF-containing lubricant)
at 20.degree. C. in Panel (a), and at 100.degree. C. in Panel (c).
Panel (b) shows a magnification of the wear scar of Panel (a);
while Panel (d) shows a magnification of the wear scar of Panel
(c). The nature of the wear scar was analyzed by energy-dispersive
X-ray spectroscopy. The results are shown in Table 1, which lists
the elemental composition of the wear scar material as well as the
ZAF correction matrix factors (Z=atomic number effect, A=X-ray
absorption effect; and F=X-ray fluorescence effect).
TABLE-US-00001 TABLE 1 Elem Line Wt % Atom % K-Ratio Z A F C
K.alpha. 11.84 39.09 0.0358 1.1980 0.2525 1.0002 As L.alpha. 0.77
0.41 0.0036 0.8775 0.5375 1.0000 Fe K.alpha. 41.83 29.71 0.4164
0.9597 0.9999 1.0373 Ni K.alpha. 45.56 30.78 0.4374 0.9680 0.9920
1.0000 Total 100.00 100.00
[0037] As is evident from the data in Table 1, the NiCNF material
surprisingly deposited a nickel-rich boundary film in the wear
scars, resulting in an effectively negative wear and at least
partial repair of the wear scar. By way of comparison, Lubricant A
(PAO alone) exhibited a more significant wear scar at each
temperature tested.
EXAMPLE 3
Tribological Testing of 5w30-Grade Lubricants
[0038] Tribological testing was conducted using the Ball-on-Disc
Tribo-tester as described herein using a fully formulated lubricant
of 5w30: i.e., Comparative Lubricant C (5w30 alone), and Lubricant
D (0.1 wt % NiCNF of Example 1 dispersed in 5w30). The lubricants
were tested under the following extreme test conditions: maximum
pressure of about 1.05 GPa, a speed of 30 mm/sec, and a Hertz
contact diameter of about 140 mm, for one hour at a temperatures of
20.degree. C. The formulated lubricant, Comparative Lubricant C,
exhibited a friction coefficient of about 0.16, while Lubricant D,
comprising the NiCNF material exhibited a friction coefficient of
about 0.10, at the tested temperature.
[0039] FIG. 3 illustrates micrographic images of wear scars
observed in evaluation of Lubricant D (NiCNF-containing lubricant)
in Panel (a), and Comparative Lubricant C (5w30 alone) Panel (b).
As in Example 2, the NiCNF-containing lubricant exhibited a
significantly less severe wear scar due to the surprising deposit
of a nickel-containing boundary film in the scar.
[0040] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. The terms "consisting of" and "consists of"
are to be construed as closed terms, which limit any compositions
or methods to the specified components or steps, respectively, that
are listed in a given claim or portion of the specification. In
addition, and because of its open nature, the term "comprising"
broadly encompasses compositions and methods that "consist
essentially of" or "consist of" specified components or steps, in
addition to compositions and methods that include other components
or steps beyond those listed in the given claim or portion of the
specification. Recitation of ranges of values herein are merely
intended to serve as a shorthand method of referring individually
to each separate value falling within the range, unless otherwise
indicated herein, and each separate value is incorporated into the
specification as if it were individually recited herein. All
numerical values obtained by measurement (e.g., weight,
concentration, physical dimensions, removal rates, flow rates, and
the like) are not to be construed as absolutely precise numbers,
and should be considered to encompass values within the known
limits of the measurement techniques commonly used in the art,
regardless of whether or not the term "about" is explicitly stated.
All methods described herein can be performed in any suitable order
unless otherwise indicated herein or otherwise clearly contradicted
by context. The use of any and all examples, or exemplary language
(e.g., "such as") provided herein, is intended merely to better
illuminate certain aspects of the invention and does not pose a
limitation on the scope of the invention unless otherwise claimed.
No language in the specification should be construed as indicating
any non-claimed element as essential to the practice of the
invention.
[0041] Preferred embodiments of this invention are described
herein, including the best mode known to the inventors for carrying
out the invention. Variations of those preferred embodiments may
become apparent to those of ordinary skill in the art upon reading
the foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
* * * * *