Solid anti-friction devices – materials therefor – lubricant or se – Solid anti-friction device – article or material therefor – Elemental or alloyed metal
Reexamination Certificate
2002-12-19
2004-03-23
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Solid anti-friction device, article or material therefor
Elemental or alloyed metal
C508S107000, C508S108000, C419S027000, C428S548000, C428S620000
Reexamination Certificate
active
06710020
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to solid lubricants for metals, metal alloys and semiconducting materials. The invention is particularly useful in applications such as automotive transport, aircraft industry, space technology or ultra-high vacuum.
BACKGROUND OF THE INVENTION
Following carbon fullerenes and carbon nanotubes (Iijima S, Helical microtubules of graphitic carbon,
Nature
354, 56-58 (1991); Kroto H W et al., C
60
: Buckminsterfullerene,
Nature
318, 162-163 (1985)) hollow nanoparticles and nanotubes of metal dichalcogenides, boron-carbides and other layered compounds have been synthesized as a single phase in recent years (Chopra N G, et al., Boron nitride nanotubes,
Science
, 269, 966-967 (1995); Feldman Y, et al., High-rate, gas-phase growth of MoS
2
nested inorganic fullerenes and nanotubes,
Science
, 267, 222-225 (1995); Rothschild A, et al., The growth of WS
2
nanotubes phases
J An. Chem. Soc
, 122, 5169-5179 (2000); Tenne R, et al., Polyhedral and Cylindrical Structures of WS
2
. Nature
360: 444-445 (1992)). These materials were designated under the generic name inorganic fullerene-like materials (IF).
The tribological properties of solid lubricants such as graphite and the metal dichalcogenides MX
2
(where M is molybdenum or tungsten and X is sulphur or selenium) are of technological interest for reducing wear in circumstances where liquid lubricants are impractical, such as in space technology, ultra-high vacuum or automotive transport. These materials are characterized by weak interatomic interactions (van der Waals forces) between their layered structures, allowing easy, low-strength shearing.
Solid lubricants are required to have certain properties, such as low surface energy, high chemical stability, weak intermolecular bonding, good transfer film forming capability and high load bearing capacity. Conventional solid lubricants such as MoS
2
particles, graphite, and polytetrafluoroethylene (PTFE) have weak interlayer bonding which facilitate transfer of said materials to lo the mating surface. Such transfer films are partially responsible for low friction and wear.
The use of metal dichalcogenides and MoS
2
particles as solid lubricants in various applications, is well documented (Singer I L, in
Fundamentals of Friction: Macroscopic and Microscopic Processes
(eds. 3. Singer I L and Pollock H M), p. 237 (Kluwer, Dordrecht, 1992)). Recently, the tribological applications of hollow nanoparticles of WS
2
as an additive for lubrication fluids, has also been demonstrated (Rapoport L, et al., Hollow nanoparticles of WS
2
as potential solid-state lubricants,
Nature
, 387, 791-793 (1997).
SUMMARY OF THE INVENTION
It is an object of the present invention to develop new composites of metal, metal alloy or semiconducting material, providing high durability and mechanical strength.
The above object is achieved by the present invention, which provides new composite materials for use to reduce friction coefficient and wear rates and for increasing the load bearing capacity of parts made of such materials. The new composite materials of the invention comprise a porous matrix made of metal, metal alloy or semiconducting material and hollow fullerene-like nanoparticles (IF) of a metal chalcogenide compound or mixture of such compounds, said composite materials having a porosity between about 10% and about 40%.
The present invention also provides a method for preparing the new composite materials of the invention.
The IF nanoparticles used in the composite materials of the invention have a diameter between about 10 and about 200 nm. In view of their small sizes, these nanoparticles can be impregnated into highly densified matrices.
Without being bound to theory, it is suggested that the IF nanoparticles are impregnated into the pores of the porous matrix and are slowly released to the surface, where they serve as both lubricant and spacer. The behavior of IF nanoparticles is compared hereinafter with commercially available WS
2
and MoS
2
platelets with 2H polytype structure (2H).
REFERENCES:
patent: 3956146 (1976-05-01), Tsuya et al.
patent: 6015775 (2000-01-01), Takayama et al.
patent: 6217843 (2001-04-01), Homyonfer et al.
patent: 6245718 (2001-06-01), Romanov et al.
patent: WO 97/44278 (1997-11-01), None
patent: WO 99/44955 (1999-09-01), None
Chemical Abstract No. 131:202004, Rapoport et al., “The Effect of Hollow Nanoparticles of WS2on Friction and Wear”.
Iijima, “Helical Microtubules of Graphitic Carbon”,Nature, vol. 354, pp. 56-58 (Nov. 7, 1991).
Kroto et al., “C60: Buckminsterfullerene”,Nature, vol. 318, pp. 162-163 (Nov. 14, 1985).
Chopra et al., Boron Nitride Nanotubes,Science, vol. 269, pp. 966-967 (Aug. 18, 1996).
Feldman et al., “High-Rate, Gas-Phase Growth of MoS2Nested Inorganic Fullerenes and Nanotubes”,Science, vol. 267, pp. 222-225 (Jan. 13, 1995).
Rothschild et al., “Growth of WS2Nanotubes Phases”,J. Am. Chem. Soc., vol. 122, pp. 5169-5179 (2000).
Tenne et al., “Polyhedral and Cylindrical Structures of Tungsten Disulphide”,Nature, vol. .360, pp. 444-445 (Dec. 3, 1992).
Fundamentals of Friction: Macroscopic and Microscopic Processes, edited by Singer et al., NATO ASI Series, Dordrecht: Kluwer Academic Publishers (1992), pp. 237-261.
Rapoport et al., “Hollow Nanoparticles of WS2as Potential Solid-State Lubricants”, reprinted fromNature, vol. 387 (Jun. 19, 1997).
Feldman Yishay
Leshchinsky Volf
Lvovsky Mark
Rapoport Lev
Tenne Reshef
Browdy and Neimark , P.L.L.C.
McAvoy Ellen M.
Yeda Research and Development Co. Ltd.
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