A novel electrical contact material with improved self-lubrication for railway current collectors

He, Dong; Manory, Rafael R.

doi:10.1016/s0043-1648(01)00700-1

Cited by 194 publications

(67 citation statements)

References 7 publications

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“…Excessive wear rate has been observed for silver-graphite brushes due to the combined effects of the high current density and the high sliding speed. It is desirable for the brush to operate with minimum mechanical loss (low coefficient of friction), minimum electrical loss (low contact resistance at the sliding interface) and long brush life (low rate of wear) [12,13]. As CNTs have excellent mechanical and physical properties and low density as well as good wear and friction properties, CNTs offer tremendous opportunities for the development of fundamentally new material system for electric contact material applications [14,15].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and mechanical properties of CNT/Ag nanocomposites fabricated by spark plasma sintering

Daoush

Lim

Nam

et al. 2012

Journal of Experimental Nanoscience

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Carbon nanotube/silver (CNT/Ag) nanocomposites include CNT volume fraction up to 10 vol.% were prepared by chemical reduction in solution followed by spark plasma sintering. Multiwalled CNTs underwent surface modifications by acid treatments, the Fourier transform infrared spectroscopy data indicated several functional groups loaded on the CNT surface by acid functionalisation. The acid-treated CNTs were sensitised and activated. Silver was deposited on the surface of the activated CNTs by chemical reduction of alkaline silver nitrate solution at room temperature. The microstructures of the prepared CNT/Ag nanocomposite powders were investigated by high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy and X-ray powder diffraction analysis. The results indicated that the produced CNT/ Ag nanocomposite powders have coated type morphology. The produced CNT/Ag nanocomposite powders were sintered by spark plasma sintering. It was observed from the microstructure investigations of the sintered materials by HRSEM that the CNTs were distributed in the silver matrix with good homogeneity. The hardness and the tensile properties of the produced CNT/Ag nanocomposites were measured. By increasing the volume fraction of CNTs in the silver matrix, the hardness values increased but the elongation values of the prepared CNT/Ag nanocomposites decreased. In addition, the tensile strength was increased by increasing the CNTs volume fraction up to 7.5 vol.%, but the sample composed of 10 vol.% CNT/Ag was fractured before yielding.

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Section: Introductionmentioning

confidence: 99%

Microstructure and mechanical properties of CNT/Ag nanocomposites fabricated by spark plasma sintering

Daoush

Lim

Nam

et al. 2012

Journal of Experimental Nanoscience

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“…Copper metal matrix composites, for example, are being investigated for their use in electromechanical applications. Copper, which is well known for its high thermal and electrical conductivity, is currently used in metal matrix composites reinforced with graphite particles for its use in electrical sliding contact applications such as brushes in electric motors and generators [24][25][26][27][28][29][30][31]. In welding machines, low voltage, high current densities, and sliding of critical components necessitate materials with a very high specific electrical conductivity, good thermal conductivity, and low friction coefficient.…”

Section: Self-lubricating Behavior Of Copper-graphite Compositesmentioning

confidence: 99%

Self-Lubricating Behavior of Graphite-Reinforced Composites

Menezes

Reeves

Rohatgi

et al. 2013

Tribology for Scientists and Engineers

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Lubricants are extensively used between contacting surfaces to reduce friction and wear. Typically, liquid lubricants are used to achieve low friction and wear. However, these lubricants are not effective in elevated temperature applications or vacuum environments. For these reasons, solid lubricants are utilized to meet these operational needs, where liquid lubrication is impractical. Solid lubricants are only effective as long as they are present in the tribo-interface. Therefore, it is desirable to provide a constant supply of solid lubricant material to the contacting surface. This is often achieved by incorporating solid lubricants as a second phase in the base material. These composite materials have the ability to achieve low friction and wear at the contact surfaces without any external supply of lubrication during sliding. Metal matrix composites reinforced with lamellar solid lubricant particles such as graphite are being used as self-lubricating materials for various engineering applications. In this chapter, the tribological behavior of metal and ceramic matrix composites reinforced with graphite particles has been reviewed. More specifically, copper-graphite, nickel-graphite, magnesiumgraphite, silver-graphite, aluminum-graphite, silicon nitride-graphite, and alumina-graphite composites are studied. The influence of various environmental and mechanical parameters on the friction coefficient and wear rate is discussed. It was found that the amount of graphite released on the worn surface forms a thin transfer film on the contact surfaces. This transfer film reduces the overall friction coefficient and wear rate. The presence of the graphite-based transfer film increases the seizure resistance and enables the contacting surfaces to run under boundary lubrication without galling. The formation and retention of this transfer film on the sliding surface as well as its composition, area fraction, thickness, and hardness are important factors in controlling the friction and wear behavior of the material. The effectiveness of the transfer film also depends on the nature of the sliding surface, the test condition, environment, and the graphite content in the composite.

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“…Copper metal matrix composites reinforced with particulate graphite are the potential candidate materials for electrical sliding contact application such as brushes in the electric motor and generator [28][29][30][31][32][33][34][35]. In the case of low voltage and high current densities, typically for sliding parts of welding machines, it is required to employ materials with a very high specific electrical conductivity, good thermal conductivity and low friction coefficient.…”

Section: Self-lubricating Behavior Of Copper-graphite Compositesmentioning

confidence: 99%

Self-Lubricating Behavior of Graphite Reinforced Metal Matrix Composites

Menezes

Rohatgi

Lovell

2012

Green Energy and Technology

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Lubricants are extensively used between the contacting surfaces to reduce friction and wear. These lubricants are usually toxic and not readily biodegradable and thus these lubricants can cause considerable damage to the environment. The use of external lubricants can be eliminated by designing selflubricating composite materials. These composite materials have the ability to achieve low friction and wear at the contact surfaces without any external supply of lubrication during sliding. The metal matrix composites reinforced with various self-lubricating particles such as graphite, molybdenum disulfide are being used as self-lubricating materials for various engineering applications. In this paper, the tribological behavior of metal matrix composites reinforced with graphite particles has been reviewed. More specifically, aluminum-graphite, magnesium-graphite, copper-graphite, silver-graphite and nickel-graphite composites have been studied. The influence of various variables on the friction coefficient and wear rate is discussed. It was found that the amount of graphite released on the wear surface forms a tribo film on the contact surfaces. This reduces the overall friction coefficient and wear rate. The formation and retention of this tribo layer on the sliding surface as well as its composition, area fraction, thickness and hardness are important factors in controlling the friction and wear behavior of the material and depend on the nature of the sliding surface, the test condition, environment and the graphite content in the composite. The presence of graphite tribo layer also Keywords Friction Á Wear Á Self-lubrication Á Metal matrix composites IntroductionA lubricant is a material used to facilitate relative motion of solid bodies by minimizing friction and wear between interacting surfaces. A lubricant functions by introducing a layer of material with lower shear strength than the surfaces themselves between the sliding surfaces [1]. In some lubricated systems, the lubricant may not completely prevent asperity contact, although it will reduce it and may also reduce the strength of the junctions formed. In other cases, the lubricant completely separates the surfaces and no asperity junctions are formed at all [2]. In general, there are three categories of lubricants-liquid, solid and gaseous.Nearly all lubricants used in the automotive and manufacturing sectors are oil or grease-based. These oils include engine oils, transmission fluids, hydraulic fluids and gear oils. These products are not typically environmentally friendly or biodegradable and can introduce significant quantities of pollutants into the waste stream [3]. Thus, disposal of this very large volume of material obviously represents an environmental burden. Hence, it is very important to develop either green lubricants or composite materials which have self-lubrication properties.Composite materials are a special class of materials and are made from two or more constituent components with significantly different physical or chemical p...

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A novel electrical contact material with improved self-lubrication for railway current collectors

Cited by 194 publications

References 7 publications

Microstructure and mechanical properties of CNT/Ag nanocomposites fabricated by spark plasma sintering

Microstructure and mechanical properties of CNT/Ag nanocomposites fabricated by spark plasma sintering

Self-Lubricating Behavior of Graphite-Reinforced Composites

Self-Lubricating Behavior of Graphite Reinforced Metal Matrix Composites

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