Polyoxometalate-ionic liquids (POM-ILs) - a new type of ionic liquid additive family for lubricants.

The focus on energy efficiency to move towards a more sustainable use of resources has intensified efforts to minimize friction and wear in mechanical systems, which account for 23% of the world's energy consumption. In this study, polyoxometalate ionic liquids (POM-ILs) are introduced as environmentally acceptable lubricant additives, for their potential friction-reducing and anti-wear (AW) properties. These compounds, characterized by their complex structures and tunable properties, have been investigated for their tribological performance across base fluids of varying polarities.

Effect of the Polar Head Type on the Surface Adsorption and Tribofilm Formation of Organic Friction Modifiers in Water-Based Lubricants.

Carboxylic acids make up a well-known group of organic friction modifiers (OFMs). OFMs can present different types of polar heads that can eventually lead to different surface adsorption properties and tribological responses. Therefore, the goal of this work is to study the effects of the polar head type on the frictional and wear performances of carboxylic acids in a water-based lubricant.

Triboelectrochemical friction control of W- and Ag-doped DLC coatings in water-glycol with ionic liquids as lubricant additives.

In the last years, diamond like carbon (DLC) coatings doped with both carbide forming and non-carbide forming metallic elements have attracted great interest as novel self-lubricating coatings. Due to the inherent properties of DLC, the doping process can provide adsorption sites for lubricant additives depending on the chemical and electrochemical state of the surface. Ionic liquids (ILs) are potential lubricant additives with good thermal stability, non-flammability, high polarity, and negligible volatility.

Effect of Steel Hardness and Composition on the Boundary Lubricating Behavior of Low-Viscosity PAO Formulated with Dodecanoic Acid and Ionic Liquid Additives.

Two ionic liquids, tributylmethylphosphonium dimethylphosphate (PP) and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate (BMP), as lubricant additives in polyalphaolefin (PAO8) were studied under boundary lubricating conditions on two types of steel (AISI 52100 bearing steel and AISI 316L stainless steel). The tribological behavior of these ILs was compared with dodecanoic acid, a well-known organic friction modifier. This study employs a ball-on-disk tribometer with an alumina ball as a counterpart.

An In-Situ Electrochemical Nanoindentation (ECNI) Study on the Effect of Hydrogen on the Mechanical Properties of 316L Austenitic Stainless Steel.

In-situ electrochemical nanoindentation (ECNI) has been used to study the effect of hydrogen on the mechanical properties of austenitic stainless steel AISI 316L. Changing the electrode potential (via electrochemical charging) revealed the interconnected nature of the hydrogen effect on the nanomechanical properties of the stainless steel. At more positive cathodic potentials, a softening effect of hydrogen can be noticed, while significant hardening can be observed at more negative cathodic potentials.

Anticancer Activity of Alkynylgold(I) with P(NMe) Phosphane in Mouse Colon Tumors and Human Colon Carcinoma Caco-2 Cell Line.

New alkynylgold(I) with P(NMe) (HMPT) phosphane complexes, [Au(C≡C-R)(HMPT)] (R= 4-Ph, 4-MePh, 4-OMe, 4-Br, 4-Cl, 2-py, and 3-py) have been synthesized and characterized, including X-ray studies of complexes with R= 4-OMe and 4-Br; additionally, their physicochemical properties and anticancer activity have been tested. Due to the great water solubility of the HMPT phosphane, all the complexes exhibit an optimal balance of hydrophilicity/lipophilicity. Also, all of these complexes are quite stable in physiological conditions and interact well enough with the transport protein BSA.

Rubber friction: The contribution from the area of real contact.

There are two contributions to the friction force when a rubber block is sliding on a hard and rough substrate surface, namely, a contribution F = τ A from the area of real contact A and a viscoelastic contribution F from the pulsating forces exerted by the substrate asperities on the rubber block. Here we present experimental results obtained at different sliding speeds and temperatures, and we show that the temperature dependency of the shear stress τ, for temperatures above the rubber glass transition temperature T, is weaker than that of the bulk viscoelastic modulus. The physical origin of τ for T > T is discussed, and we propose that its temperature dependency is determined by the rubber molecule segment mobility at the sliding interface, which is higher than in the bulk because of increased free-volume effect due to the short-wavelength surface roughness.

Rubber contact mechanics: adhesion, friction and leakage of seals.

We study the adhesion, friction and leak rate of seals for four different elastomers: Acrylonitrile Butadiene Rubber (NBR), Ethylene Propylene Diene (EPDM), Polyepichlorohydrin (GECO) and Polydimethylsiloxane (PDMS). Adhesion between smooth clean glass balls and all the elastomers is studied both in the dry state and in water. In water, adhesion is observed for the NBR and PDMS elastomers, but not for the EPDM and GECO elastomers, which we attribute to the differences in surface energy and dewetting.

Generated Tribomaterial in Metal/Metal Contacts: current understanding and future implications for implants.

Artificial hip joints operate in aqueous biofluids that are highly reactive towards metallic surfaces. The reactivity at the metal interface is enhanced by mechanical interaction due to friction, which can change the near-surface structure of the metal and surface chemistry. There are now several reports in the literature about the in-situ generation of reaction films and tribo-metallurgical transformations on metal-on-metal hip joints.

Tribocorrosion studies of metallic biomaterials: The effect of plasma nitriding and DLC surface modifications.

The medical grade pure titanium, stainless steel and CoCrMo alloy have been utilized as biomaterials for load-bearing orthopedic prosthesis. The conventional surgery metals suffer from a combined effect of wear and corrosion once they are implanted, which may significantly accelerate the material degradation process. In this work, the tribocorrosion performance of the metallic biomaterials with different surface modifications was studied in the simulated body fluid for the purpose of investigating the effect of the surface treatments on the tribocorrosion performance and eventually finding the most suitable implantation materials.

Degradation of Zr-based bulk metallic glasses used in load-bearing implants: A tribocorrosion appraisal.

Owing to the amorphous structure, Bulk Metallic Glasses (BMGs) have been demonstrating attractive properties for potential biomedical applications. In the present work, the degradation mechanisms of Zr-based BMGs with nominal compositions Zr55Cu30Ni5Al10 and Zr65Cu18Ni7Al10 as potential load-bearing implant material were investigated in a tribocorrosion environment. The composition-dependent micro-mechanical and tribological properties of the two BMGs were evaluated prior to the tribocorrosion tests.