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1.
Saravanan Prabakaran Sundaramurthy Jayaraman Duong Hai Minh Sujeet K. Sinha 《Tribology Letters》2014,56(3):423-434
In an earlier work, we demonstrated the development of SU-8 composites using perfluoropolyether (PFPE) as lubricant filler which reduced friction coefficient by ~7 times and enhanced wear life of SU-8 by more than four orders of magnitude. In this work, we have investigated the role of chemical bonding between SU-8 and PFPE molecules using two types of PFPE lubricants (i.e., Fomblin® Z-dol and Z-03) in improving the tribological properties of the composite. Z-dol has polar (–OH) end groups whereas Z-03 has non-polar (CF3) end groups. SU-8 with Z-dol (SU-8 + Z-dol) films yielded ~8 times greater wear life than SU-8 with Z-03 (SU-8 + Z-03) films and more by four orders of magnitude than pure SU-8. The nature of the films was analyzed in detail by chemical and physical characterization techniques like X-ray photoelectron spectroscopy, water contact angle and thermo-gravimetric analysis. The results validated the role of polar end functional group of Z-dol in covalent binding with SU-8 upon UV plasma treatment that resulted in improved tribological properties. 相似文献
2.
SU-8 is an industrially useful photoresist polymer for micro-fabrication because of its unique UV-sensitive curing property. It is also used as a structural material for micro-machines such as micro-electro mechanical systems (MEMS). However, it has poor tribological and mechanical properties which make SU-8 inferior to Si, the mainstay MEMS material today. In this paper, we report the fabrication of SU-8 nanocomposites which are self-lubricating and have better mechanical properties. The liquid lubricant i.e., perfluoropolyether (PFPE) and nanoparticles such as SiO2, CNTs, and graphite were added into SU-8 for this purpose. These self-lubricating SU-8 + PFPE and SU-8 + PFPE + nanoparticle composites have shown a reduction in the initial coefficient of friction by ~6?C9 times and increased wear life by more than four orders of magnitude. The mechanical properties such as the elastic modulus and the hardness have increased by ~1.4 times. These SU-8 nanocomposites can be used as a self-lubricating structural material for MEMS applications requiring no external lubrication. As well, these nanocomposites can find applications in many tribological components of traditional machines. 相似文献
3.
Jitendra K. Katiyar Tomoko Hirayama Arvind Kumar 《Tribology - Materials, Surfaces & Interfaces》2020,14(2):92-101
ABSTRACTSU-8 polymer with talc particle (30?wt-%) and liquid perfluoropolyether (PFPE) (30?wt-%) fillers was used as a composite to fabricate conical tip-cantilever device. The composite tip demonstrated lower coefficient of friction (~0.22) when compared with a tip made of pure SU-8 (~0.65). Fluorine was detected on the wear track and the tip surface, which resulted from the transfer of PFPE from the tip to the wear track. The counterface made of pure SU-8 remained smooth and unworn when slid against the composite tip even after 1000 cycles of sliding. This composite with improved tribological and mechanical properties can be used for fabricating small component devices such as for micro-electro-mechanical systems (MEMS). 相似文献
4.
PEEK, an engineering polymer with many advantages such as lightweight, high thermal stability, high strength coupled with toughness, has often been used as a substitute for metals in applications such as bearings, piston parts, pumps and even biomaterials. However, it shows high coefficient of friction which results in high wear rate when used in tribological applications. This paper seeks to solve tribological problems of high friction and wear for PEEK by applying an ultrathin layer of perfluoropolyether (PFPE) and Multiply-Alkylated Cyclopentane (MAC) lubricants on the surface of PEEK. Results obtained from tribological tests conducted showed that for highly improved tribological performance, there is an optimal initial surface roughness of PEEK surface and lubricant concentration or the thickness of the coatings for both PFPE and MAC lubricant. Also, MAC performs better compared to PFPE for thinner films. 相似文献
5.
Nagayoshi Kobayashi Hiroshi Tani Tsuyoshi Shimizu Shinji Koganezawa Norio Tagawa 《Tribology Letters》2014,53(1):43-49
In this study, the wear properties of a magnetic head slider on disks lubricated by ultra-thin perfluoropolyether (PFPE) lubricants with different molecular weights were evaluated by the continuous sliding of magnetic head sliders using the slider contact by the dynamic flying height control. Two types of PFPE lubricants (Z-tetraol and D-4OH) with different molecular weights were evaluated. Results show that the slider wear depended on the coverage of the lubricant film; i.e., the lubricant film with sufficient coverage reduced slider wear. The lubricant film with a low molecular weight (low-Mw), including a lubricant material with a Fomblin and Demnum main chain, exhibited better coverage on a diamond-like carbon surface. Sliders with a low-Mw lubricant film showed less wear than those of a high molecular weight (high-Mw), and the depletion of the low-Mw lubricant film was less than that of the high-Mw lubricant film. 相似文献
6.
Chang-Gun Lee Yu-Jin Hwang Young-Min Choi Jae-Keun Lee Cheol Choi Je-Myung Oh 《International Journal of Precision Engineering and Manufacturing》2009,10(1):85-90
Many researchers have tried to improve the tribological characteristics of lubricants to decrease friction coefficients and
wear rates. One approach is simply the use of additives in the base lubricant to change its properties. Recently, nanoparticles
have emerged as a new kind of additive because of their size, shape and other properties. A nano lubricant is a new kind of
engineering lubricant made of nanoparticles, dispersant, and base lubricant. In this study, graphite nanoparticles were used
to fabricate nano lubricants with enhanced tribological properties and lubrication characteristics. The base lubricant used
was industrial gear oil, which has a kinematic viscosity of 220 cSt at 40°C. To investigate the physical and tribological
properties of nano lubricants, friction coefficients and temperatures were measured by a disk-on-disk tribotester. The surfaces
of the fixed plates were observed by a scanning electron microscope and an atomic force microscope to analyze the characteristics
of the friction surfaces. The results show that when comparing fixed plates coated with raw and nano lubricants, the plate
coated with a nano lubricant containing graphite nanoparticles had a lower friction coefficient and less wear. These results
indicate that graphite nanoparticle additives improve the lubrication properties of regular lubricants. 相似文献
7.
We have investigated the tribological properties of a novel perfluoropolyether (PFPE) lubricant truncated on one end by a hydroxyl group and on the other end by a cyclotriphosphazene derivative. A measurement of the friction force as a function of molecular weight indicates that the dynamic clearance between the slider and the disk can be reduced by ~1.5 nm by decreasing the molecular weight from 5300 to 2400 g/mol. However, the thermodynamic film stability of the novel PFPE lubricants, as determined by surface energy measurements and ellipsometric imaging of lubricant dewetting, becomes increasingly unstable at lower film thicknesses with decreasing molecular weight. Measurements conducted on lubricant mobility indicate that the novel PFPE lubricants are relatively immobile compared to the Zdol perfluoropolyether lubricants and hence resist film thinning to a greater degree. These data provide the direction for the optimization of the molecular weight of these novel PFPE lubricants. 相似文献
8.
The effects of two different textures (a 3D negative fingerprint texture and a honeycomb texture) on the tribological performance of SU-8 polymer surface have been investigated with a ball-on-disc tribometer. Friction and wear behaviors of the textured surfaces are conducted against a 4 mm diameter silicon nitride (Si3N4) ball counterface. The coefficient of friction for the negative fingerprint textured surface (μ=∼0.08) is much lower than that of the untextured surface (∼0.2) and the honeycomb textured surface (∼0.41) under a normal load of 100 mN and a rotational speed of 2 rpm. The coefficients of friction of the textured surfaces decrease with increasing normal loads between 100 mN and 300 mN. Above the normal load of 300 mN, the coefficient of friction of the negative fingerprint textured surface increases due to the occurrence of plastic deformation. The honeycomb textured surface has shown the highest coefficient of friction. The wear durability tests are also conducted at a normal load of 100 mN and a rotational speed of 500 rpm on the untextured/textured surfaces on SU-8 in the presence of an overcoat of a nano-lubricant, perfluoropolyether(PFPE). Six samples i.e. the untextured surface (Si/SU-8 and Si/SU-8/PFPE), the 3D negative fingerprint textured surface (Si/SU-8/FP and Si/SU-8/FP/PFPE) and the honeycomb textured surface (Si/SU-8/HC and Si/SU-8/HC/PFPE), each with and without PFPE nano-lubricant, have been investigated for their tribological behaviours. The negative fingerprint pattern on SU-8 with PFPE coating has shown the highest wear life of 60,000 cycles under a normal load of 100 mN. The reasons for excellent tribological performance of 3D fingerprinted SU-8 surface are analyzed using the Hertzian contact area calculation. 相似文献
9.
Effect of tetraalkylphosphonium based ionic liquids as lubricants on the tribological performance of a steel-on-steel system 总被引:2,自引:0,他引:2
A series of asymmetrical tetraalkylphosphonium ionic liquids were synthesized and evaluated as a new kind of lubricant for
the contact of steel/steel using an Optimol SRV oscillating friction and wear tester in ambient condition. The phosphonium
ionic liquid shows excellent tribological performance when being used as the lubricating oil, and is superior to the conventional
high temperature lubricants X-1P and perfluoropolyether (PFPE) in terms of anti-wear performance and load-carrying capacity.
The chemical compositions of the boundary film generated on different contact surfaces were analyzed on a scanning electron
microscope with a Kevex energy dispersive X-ray analyzer attachment (SEM/EDS) and X-ray photoelectron spectrometer (XPS).
The friction–reduction and anti-wear mechanism of tetraalkylphosphonium as the lubricant were proposed to originate from the
active elements P in the tetraalkylphosphonium ionic liquids reacting with the fresh surface to form a reaction film onto
specimen surface, an extreme-pressure film with lower shearing strength, which leads to lower friction coefficient, and good
wear resistance. 相似文献
10.
The tribological characteristics of magnetic thin film media coated with perfluoropolyether (PFPE) lubricants (ZDOL and AM300J) and a phosphazene additive (X-IP) were investigated in this study. The drag test results show that under ambient and hot/wet conditions the media coated with AM300J lubricant have higher retention on the test track than those coated with ZDOL 2000 PFPE lubricant. The phosphazene additive X-IP was observed to strongly anchored to the surface and was not as easily removed as PFPE lubricants alone. The retention characteristics of X-IP are independent of either AM or ZDOL. Secondary Ion Mass Spectroscopy (SIMS) depth profile data and Angle-Resolved X-Ray Photo-electron Spectroscopy (XPS) reveal that X-IP molecules were distributed near the disk surface in the X-IP and PFPE lubricants mixed layer, indicating a strong bonding/adhesion of X-IP to the disk surface. Together with the drag testing data, the authors conclude that the preferential distribution of X-IP close to the disk surface in the mixed layer helps to improve lubricant retention performance at the head-disk interface. 相似文献
11.
《Tribology - Materials, Surfaces & Interfaces》2013,7(1):33-44
SU-8, an epoxy-based negative photoresist polymer, is highly suitable for making micro-electro-mechanical systems (MEMS) structures. Despite fabrication advantages, its bulk mechanical and tribological properties are the main limitations for application as MEMS material. Carbon filler materials such as graphene, graphite and multi-walled carbon nanotube (MWCNT) are added to SU-8 for tribological and mechanical property enhancements. SU-8/(5 wt%) graphite composite has performed better for the steady-state coefficient of friction at all loads including for the speed effect. SU-8/(5 wt%) MWCNT has shown excellent wear resistance. At 10 wt% graphite content, SU-8/graphite is superior in tribological performance to other composites tested. 相似文献
12.
Direct observation of PFPE lubricant molecules by cryogenic AFM under ultra-high vacuum 总被引:1,自引:0,他引:1
Takayuki Nakakawaji Mina Amo Tomoshige Sato Naoyuki Torita Teiji Kato 《Tribology Letters》2006,24(1):43-50
Surface lubrication is one of the essential technologies in modern magnetic disk systems and improvement of the surface lubrication is very important in the development of next generation systems. In this study, we used AFM for the direct observation of perfluoropolyether (PFPE) lubricant molecules on atomically flat surfaces. We used a cryogenic non-contact AFM to observe the molecules in a frozen state of micro-Brownian motion of PFPE segments, because the glass transition temperature of PFPE is very low. To avoid freezing a trace amount of water vapor on the sample surface at liquid nitrogen temperatures, the AFM observation was performed under ultra-high vacuum. We observed that on a gold surface the size of the molecules increases with repeated AFM scans. This is because the mechanical stimulus causes the fusion of PFPE lubricant molecules to form reversed micelles at the non-polar surface. At a hydrophilic silicon wafer surface, however, we succeeded in observing single lubricant molecules. This is because almost all PFPE lubricant molecules are fixed to the hydrophilic solid surface by polar–polar bond formation and they cannot move around on the surface and thus they cannot fuse to each other. As formation of the reversed micelle structure is a rather general phenomenon in the PFPE lubricant thin layer at non-polar surfaces, we also will discuss briefly the expected molecular structures of PFPE lubricants at the surface of the carbon overcoat of magnetic disks. 相似文献
13.
This work studied the development of vegetable based lubricants and the addition of oxides nanoparticles (ZnO and CuO) as additive for extreme pressure (EP), exploring the EP and oil base influence in tribological behavior. The results showed that with the addition of nanoparticles to conventional lubricant, the tribological properties can be significantly improved. A smoother and more compact tribofilm has formed on the worn surface, which is responsible for the further reduced friction and wear. Also, lubricants developed from modified vegetable oil can replace mineral oil, improving the tribological and environmental characteristics. However, the addition of nanoparticles in vegetable base lubricants is not beneficial to wear reduction. 相似文献
14.
The retention characteristics of magnetic thin film media coated with perfluoropolyether (PFPE) lubricants and a phosphazene
additive, X-1P, were investigated in this study. The retention performance was evaluated by a drag test with a waffle head
sliding against the disk that was designed to mechanically wear out the lubricant layer. An IR beam was aligned on the test
track to directly measure the amount of PFPE lubricants and X-1P left on the media surfaces for determining the retention
characteristics of the lubricants. The drag test results show that under ambient and hot/wet conditions the media coated with
AM3001 PFPE lubricant have higher retention ratio on the test track than those coated with ZDOL 2000 PFPE lubricant. The phosphazene
additive X-1P was observed to strongly anchor on the surface and not easily removed as PFPE lubricants (ZDOL and AM3001).
The retention characteristics of X-1P are independent of lube combination, either AM or ZDOL lubricants. It is demonstrated
that X1-P exhibits a good antiwear property and excellent retention performance.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
Increased concerns about environmental damage caused by mineral oil based lubricants, has created a growing worldwide trend of promoting vegetable oil as base oil for automobile lubricants. Coconut oil, which is abundantly available in southern states of India, is reportedly being widely used as two-stroke engine lubricant (2T oil) by autorikshaw1 drivers. A survey among the users of coconut oil as 2T oil brought forth complaints of increased engine wear. This paper presents tribological properties of coconut oil evaluated using a four-ball tester and a test rig to test the wear on two stroke engines. The influence of an antiwear/extreme pressure (AW/EP) additive on the tribological performance of coconut oil was also evaluated experimentally. The addition of the AW/EP additive has brought about considerable reduction in wear with coconut oil as 2T oil. 相似文献
16.
The adsorption characteristics and tribological properties of the perfluoropolyether (PFPE) lubricants Zdol and Z-Tetraol on amorphous nitrogenated CNx carbon are investigated as a function of solvent used to apply the lubricants. The solvents used in these studies include perfluorohexane, CF3CHFCHFCF2CF3 and C4F9OCH3. Deposition studies indicate that the applied thickness of PFPE films is strongly solvent-dependent that can be related to differences in the solubility parameters between the various lubricants and solvents. The results of ab initio computations on the molecular electronic structure of the solvent molecules show that their solvent power is correlated to their polarity and in particular to the acidity of the protons on the CF3CHFCHFCF2CF3 and C4F9OCH3 molecules. Tribological reliability, as measured by contact start-stop testing, slider-disk clearance, lubricant pickup by the slider, lubricant smearing on the disk surface, etc., is independent of solvent and is limited to the physical properties of the adsorbed lubricant film. The kinetics of lubricant mobility are charateristic of confined liquids that are independent of solvent as shown by lubricant flow profiles, bonding kinetics, and contact angle goniometry. 相似文献
17.
The tribological behavior of ceramic Al2O3 coupled with gray cast iron (PHT) with different lubricants was investigated using a ring-on-block wear tester. In the wear test, air, distilled water, emulsion and oil were used as lubricants respectively in order to check the lubricating effectiveness of lubricants and the friction mechanism of solid graphite in the cast iron. Wear testing of 0.8% C steel (T8) sliding with Al2O3 was also carried out to compare with the test using gray cast iron. From these data the tribological behavior of graphite in the iron can be evaluated. The results show that the friction and wear of tested couples are decreased using different lubricants in the following order: air, distilled water, emulsion and oil. When lubricating with air and water, graphite in the iron as solid lubricant can decrease the friction and wear of the couples. However, when lubricating with emulsion and oil, graphite does not show the advantage of decreasing friction and wear. 相似文献
18.
Combination of solid and liquid lubricants to meet emission or environmental requirements of future tribological systems while providing the levels of desired friction and wear performance have received considerable research attention in the near term. The aim of the present work was to investigate the tribological behavior of oil-lubricated (PAO, PFPE, SO, IL and MAC) DLC coated surfaces under the conditions without and with sand-dust particles. The effects of applied load, frequency, and sand-dust particles on the tribological performance of DLC coating were systemically studied. The analysis results showed that solid–liquid lubricating coatings including SO and IL exhibited excellent anti-friction (~0.026) but relative poor wear-resistance performances under the conditions without and with sand-dust environments. But for PFPE and PAO, they demonstrated the worst tribological behaviors with high friction coefficient and wear rates. The added sand-dust particles lead to the wear rates to the one order of magnitude large than that without sand-dust conditions for all the selected liquid lubricants. The viscosity, contact angle and work of adhesion played an important part in affecting the tribological performances. The lubrication regimes in Stribeck curve for the five kinds of liquid lubricants were affected obviously by the sand-dust particles in different way. The formed transfer films on the coating surface and pin have much influence on the tribological behavior and the transition between lubrication regimes. 相似文献
19.
PFPE lubricants (Fomblin Z-dol) for hard disk surface lubrication have two hydroxyl groups, one at each end of the molecules, and form stable insoluble monolayers at the water surface. In this study, molecular weight-fractionated PFPE lubricant monolayers were transferred from the water surface to solid substrates such as a hydrophilized silicon wafer, gold-sputtered mica, and a hard disk after adjusting the two-dimensional density of the lubricant molecules. The molecular structures of the PFPE lubricant molecules at the solid surfaces were observed by the cryogenic non-contact AFM under ultra-high vacuum. At the hydrophilic silicon wafer surface we could observe a single lubricant molecule in a random coil sphere shape. However, at the non-polar gold surface we confirmed the formation of reversed micelle structures. At the hard disk surface we detected various sizes of reversed micelles of PFPE lubricant in a flat oval shape. 相似文献
20.
A uniform closely packed hexagonal array of porous anodic alumina (PAA) film with an average pore diameter of ~100 nm and a pore height of ~330 nm was obtained by anodizing in oxalic acid solution. Low surface energy molecules of perfluoropolyether (PFPE) and octadecyltrichlorosilane (OTS) were used to enhance the hydrophobicity of the PAA and aluminum (Al) surface. The tribological performances were investigated in detail. The results showed that the static friction coefficient of PAA was much lower than that of smooth Al, which could be due to the higher hardness of the PAA than that of Al. PAA modified with PFPE was characterized by lower friction coefficient and longer wear life as compared with bare Al, PAA, and PAA modified with OTS. This is caused by the combined effects of flexibility, mobility, and inherent lubricity of PFPE molecules and the nanoporous structure of PAA as a reservoir for lubricants and wear particles. 相似文献