Low friction polytetrafluoroethylene (PTFE) has been studied extensively and is widely used in tribological applications in bulk form. Tribological properties of thin film PTFE are less reported due to its poor wear resistance. Here, we show that by incorporating Au nanoparticles in PTFE thin film, it is possible to significantly increase the wear resistance of the film. PTFE/Au nanoparticle composite thin films were fabricated on stainless steel substrates by dipping the substrate into a mixture of Au nanoparticle solution and PTFE aqueous dispersion. The friction and wear test results show that Au nanoparticles significantly reduced the wear of the PTFE thin film while preserving its low coefficient of friction (COF). Furthermore, substrate surface topography was found to have a significant effect on the friction and wear performances.

In the present investigation, the tribological performance of aluminum micro (100 to 200 μm particle size) and nano (47 nm particle size) composites was studied using a three pin-on-disk tribometer under dry conditions. As a basis for comparison, the tribological performance of aluminum alloys was also studied. The pins made of these materials were then slid against a steel disk under ambient conditions. Tests were conducted at a sliding velocity of 1.58 m/s for a normal load of 30 N. The worn surfaces of the pins were analyzed using a scanning electron microscope. Based on the experiments, it was observed that the nano-composites significantly outperformed all of the other materials with respect to friction levels. It was also discovered that the nano-composites exhibited the best wear performance among the composites investigated. The size of the reinforcement particle trapped at the interface and the hardness ratio of the mating materials were specifically found to play an important role in determining the friction and wear performance of the materials investigated.

The nanoscale structure of single-walled carbon nanotubes (SWCNTs) has unique properties. These nanostructured additives can induce unusual characteristic in many polymer matrix. In one of our recent experiments, it was found that when adding SWCNTs into a polyimide (PI) matrix, friction becomes a function of the concentration of the additive. In this research, we analyze the behavior of the SWCNTs-PI nano-composite using an approximation approach. We report that the frictional behavior of the nanocomposite is dominated by the elastic and plastic deformation through randomly dispersed SWCNTs under different loading conditions. At low concentration of SWCNTs, its elasticity dominates the properties of composite while at higher concentration, plastic behavior of tubes plays a major role in describing the properties of composite.

We report a joint theoretical and experimental study of the tribological properties of gold-yttrium stabilized zirconia (YSZ) based nanocomposite coatings, with a focus on the role of nanocrystalline grain size. Nanocomposites hold great promise for space and ambient applications, on account of their ability to adapt to and exhibit low friction and wear rates in constantly varying environmental conditions. Their internal structure has been the topic of prior literature, but the impact of grain size on tribological performance has heretofore not been considered, and the surface topology has not been reported. As such, we have performed both experimental and theoretical studies, to model the impact of grain size on film stress and wear attributes, and to document surface region grain size distributions through scanning tunneling microscopy (STM) measurements of self-affine fractal scaling properties. Nanocrystalline gold crystal sizes, as determined from STM and x-ray diffraction (XRD) data are consistent with those inferred from high resolution transmission electron microscopy (HRTEM) measurements. Our modeling results associate smaller grain sizes with lower wear rates, consistent with experiments. The findings show promise for nanoscale customization of coatings so as to tailor them at the nanoscale in an application specific manner.

Nanomaterials play important roles in tribolgy and manufacturing. This lecture provides an opportunity for us to review and learn the knowledge and techniques that have been involved in nanomaterials and nanotribology areas. Targeting tribological applications, a brief history of nanoparticulates, dated back more than 2500 years, will be given briefly. The classification and synthesis of nanoparticles will be followed by nanomaterils and nanocomposites, their characterization techniques, and mechanical, tribological, chemical, and physical properties. Discussion ends with summary of applications.

In this study the tribological analysis of Al 2 O 3 nanocomposites/Al 2 O 3 pair; proposed as a candidate material to fabricate hip prostheses was carried out. Nanopowders of Al 2 O 3 (AKP 50, 300 nm), TiO 2 (PS-25, 50 nm) and Co metallic powder (Nilaco, 28 nm) were mixed and hot pressed. Wear test was carried out in a pin-on-plate tribometer, with a frequency of 1 Hz, a load of 49 N, for 4h; the counterface used was Al 2 O 3 . Mechanical properties as Vickers hardness, fracture toughness and Young’s modulus were estimated using the indentation method. Distilled water and fetal bovine serum solution (FBSS) were used as environment. It was found that the specific wear rate of Al 2 O 3 nanocomposites was about 10 −8 mm 3 /N*m and the coefficients of friction were around 0.3–0.5 for FBSS. Worn surfaces were observed using SEM.

This study investigated the friction and wear characteristics of two super-hard coatings on M2 steel. One was AlMgB 14 , produced by pulsed laser deposition (PLD), and the other was a nanocomposite of AlMgB 14 -TiB 2 , produced by physical vapor deposition (PVD). Tests were conducted under unidirectional and reciprocating sliding against AISI 52100 bearing steel in both dry and oil-lubricated conditions. The AlMgB 14 coating exhibited an encouraging but short-lived low friction stage (μ = 0.2) in dry sliding. The AlMgB 14 -TiB 2 coating reduced the wear rates by one order of magnitude relative to the M2 steel and three orders of magnitude for the counterface in dry sliding. This nanocomposite coating also demonstrated significant extension (>2.5X) of the low friction (non-scuffing) stage when sliding under starved lubrication.

Intercalation compound of polyoxymethylene into molybdenum disulfide nanoparticles (POM/MoS 2 -IC) were prepared from trioxane, dioxolane and restacked exfoliated-MoS 2 . The so prepared nanocomposite was used as the plastic layer of self-lubrication bearing materials of steel-copper-POM. Pure POM was also selected as a comparative sample. Tribological behaviors of the obtained samples were studied on an end-face tribometer. Wear scar surfaces of the two plastic layers were characterized by a field emission scanning electron microscope. The elements of the counterpart steel surface were investigated by X-ray photoelectron spectroscopy. Results showed the wear surface of steel-copper-pure polyoxymethylene consisted of deep furrows, large-area scars and obvious flow marks. However, self-lubrication bearing materials of steel-copper-polyoxymethylene containing MoS 2 -IC nanoparticles presented excellent friction reduction and wear resistance especially under high loads. POM/MoS 2 -IC nanoparticles and its tribochemical resultants restrained the plowing effect of the counterpart steel on the plastic layer through forming a transferred film on the counterpart friction surface.

Ceramic particles, such as SiC and Al 2 O 3 , have been used to reinforce Al alloys to improve their strength and wear-resistance. However, previous studies mainly dealt with either relatively large hard particles (from tens to hundreds of micrometers in diameter) or nanometer-sized particles with low volume fractions (a few percent). In this study, near-fully-dense (97–99%) Al 2 O 3 -Al nanocomposites with higher particle concentrations (5–15 vol%) were processed using mechanical alloying and hot isostatic pressing. Transmission electron microscopy revealed very high dislocation density in aluminum matrix for these Al 2 O 3 -Al nanocomposites. High strength (σ 0.2% : ∼500 MPa) and encouraging tribological properties have been observed. The Al 2 O 3 (15 vol%)-Al nanocomposites performed unexpectedly well when sliding against 52100 bearing steel. The friction coefficient of the nanocomposite was 55%, 37%, and 55% lower and the wear-resistance was 1500X, 30X, and 120X higher than those of pure Al, cast Al 319 alloy, and conventional Al 2 O 3 -Al composites, respectively. Wear scar examination showed severe adhesive wear on the conventional Al alloy and micro-composite surfaces; however, only mild abrasive wear was observed on the nanocomposite surfaces. It was observed that the particle concentration had to exceed a critical level (10–15 vol%) to exhibit superior wear-resistance, even though a lower level (e.g. 5 vol%) resulted in a significantly improved tensile strength.