Optimizing the tribological performance of DLC-coated NBR rubber: The role of hydrogen in films

Abstract

Diamond-like carbon (DLC) films directly deposited on rubber substrate is undoubtedly one optimal option to improve the tribological properties due to its ultralow friction, high-hardness as well as good chemical compatibility with rubber. Investigating the relationship between film structure and tribological performance is vital for protecting rubber. In this study it was demonstrated that the etching effect induced by hydrogen incorporation played positive roles in reducing surface roughness of DLC films. In addition, the water contact angle (CA) of DLC-coated nitrile butadiene rubber (NBR) was sensitive to the surface energy and sp2 carbon clustering of DLC films. Most importantly, the optimum tribological performance was obtained at the 29 at% H-containing DLC film coated on NBR, which mainly depended on the following key factors: (1) the DLC film with appropriate roughness matched the counterpart surface; (2) the contact area and surface energy controlled interface adhesive force; (3) the microstructure of DLC films impacted load-bearing capacity; and (4) the generation of graphitic phase acted as a solid lubricant. This understanding may draw inspiration for the fabrication of DLC films on rubber to achieve low friction coefficient.

Highly Stable Electrochemical Supercapacitor Performance of Self-Assembled Ferromagnetic Q-Carbon

“…Figure a–d highlights the C 1s peaks of XPS spectra of the DLC film and Q-carbon filament, cluster, and microdot-like structures with C–O, C–C (sp 3 ), and C–C (sp 2 ) bonds, respectively. The C 1s core-level spectra of DLC film in Figure a show C–C (sp 2 ), C–C (sp 3 ), and C–O bonds at 284.1, 284.9, and 287.8 eV, respectively, and the sp 2 and sp 3 percentages were evaluated from the peak areas and the intensity value. − The peak shift was observed in Q-carbon structures in Figure b–d toward a higher binding energy region due to the charging effect. Charging is induced by electrons leaving the Q-carbon surface without being replaced, and the surface becomes increasingly positive due to the lack of electron replenishment, which causes a voltage bias to build up and shift the spectrum solely to higher binding energies .…”

A review of advances in tribology in 2020–2021

“…12). Among them, hydrogen incorporation played positive roles in reducing surface roughness and achieving better tribological performance of DLC films [168], which was governed by the interfacial adsorbates and carbon dangling bonds, leading to reduced interfacial interactions [169]. And the removal of the oxide layer with decreased oxygen concentrations in H-DLC was observed to result in friction reduction during running-in [170].…”

The Study of Surface Structure and the Tribological Property of DLC-Modified NBR Elastomers Using DC-MS

“…Diamond-like carbon (DLC) film is a kind of amorphous carbon film with good gas and liquid barrier effects, high wear resistance, favorable chemical stability, and a low friction coefficient [8][9][10][11]. DLC can be deposited on various types of matrix materials, such as alloys, stainless steel, glass, etc., and can provide corking mechanical protection [12][13][14]. However, there are few studies that apply it to the rubber field, and this is mainly due to the large difference in hardness between DLC and nitrile rubber (NBR) [15].…”

“…However, this method still cannot fundamentally solve the deformation mismatch problem. Although Bai et al [12] adopted the same method to judge the hardness of DLC films on the NBR surface, they further proposed that the roughness, adhesion strength, bearing capacity Coatings 2023, 13, 468 2 of 12 of DLC, and graphitization lubrication also affect the tribological behavior. Xu et al [21] determined the adhesion strength of the DLC films by examining crack propagation and incision morphologies via the bending and X-cutting of the sample, but it is impossible to quantitatively analyze the adhesion strength of the coating.…”