Lubricants

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17 pages, 10275 KiB

Open AccessArticle

Tribological Behavior of GTL Base Oil Improved by Ni-Fe Layered Double Hydroxide Nanosheets

by Shuo Xiang, Xinghao Zhi, Hebin Bao, Yan He, Qinhui Zhang, Shigang Lin, Bo Hu, Senao Wang, Peng Lu, Xin Yang, Qiang Tian and Xin Du

Lubricants 2024, 12(5), 146; https://doi.org/10.3390/lubricants12050146 - 26 Apr 2024

Viewed by 415

Abstract

The layered double hydroxide (LDH) has been practically applied in the field of tribology and materials science due to its unique physicochemical properties, weak bonding, flexible structural composition, and adjustable interlayer space. In this work, a series of ultrathin and flexible composition of [...] Read more.

The layered double hydroxide (LDH) has been practically applied in the field of tribology and materials science due to its unique physicochemical properties, weak bonding, flexible structural composition, and adjustable interlayer space. In this work, a series of ultrathin and flexible composition of Ni-Fe LDH samples were prepared via a cost-effective room-temperature co-precipitation process. Then, they were mechanically dispersed into GTL base oil and their lubricating performance were tested by a four-ball tribometer. It is found that the variation of Ni-Fe ratio of Ni-Fe LDH has a great influence on the improvement of lubricating performance of GTL base oil. At the same concentration (0.3 mg/mL), the Ni-Fe LDH with Ni/Fe ratio of 6 was demonstrated to exhibit the best lubricating performance and the AFC, WSD, the wear volume, surface roughness and average wear scar depth decreased 51.3%, 30.8%, 78.4%, 6.7% and 50.0%, respectively. SEM-EDS and X-ray photoelectron spectra illustrated that the tribo-chemical film consisting of iron oxides and NiO with better mechanical properties formed and slowly replaced the physical film, which resists scuffing and protect solid surface from severe collisions. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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15 pages, 5471 KiB

Open AccessArticle

Study on the Lubricating Characteristics of Graphene Lubricants

by Yi Dong, Biao Ma, Cenbo Xiong, Yong Liu and Qin Zhao

Lubricants 2023, 11(12), 506; https://doi.org/10.3390/lubricants11120506 - 30 Nov 2023

Cited by 2 | Viewed by 1414

Abstract

Graphene is considered a good lubricant additive. The lubricating properties of graphene lubricant at different concentrations and temperatures are studied via a four-ball friction and wear-testing machine. The results show that the coefficient of friction (COF) and wear scar diameter (WSD) of the [...] Read more.

Graphene is considered a good lubricant additive. The lubricating properties of graphene lubricant at different concentrations and temperatures are studied via a four-ball friction and wear-testing machine. The results show that the coefficient of friction (COF) and wear scar diameter (WSD) of the steel ball with 0.035 wt% graphene lubricant decreased by 40.8% and 50.4%, respectively. Finally, through surface analysis, the following lubrication mechanism is proposed: as the added graphene particles can easily fill and cover the pores of the friction surface, the contact pressure of the rough peak is reduced, resulting in a lower COF and smoother surface. Although the COF increases with temperature, graphene lubricants still exhibit good lubrication effects. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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12 pages, 14397 KiB

Open AccessArticle

Effect of Argon Flow Rate on Tribological Properties of Rare Earth Ce Doped MoS₂ Based Composite Coatings by Magnetron Sputtering

by Changling Tian, Haichao Cai, Yujun Xue, Lulu Pei and Yongjian Yu

Lubricants 2023, 11(10), 432; https://doi.org/10.3390/lubricants11100432 - 07 Oct 2023

Cited by 1 | Viewed by 1047

Abstract

Exploring the doping components of the coating is of great significance for improving the tribological properties of the MoS₂-based coating. The optimization of magnetron sputtering process parameters can also improve the coating quality. In this paper, the effects of working gas [...] Read more.

Exploring the doping components of the coating is of great significance for improving the tribological properties of the MoS₂-based coating. The optimization of magnetron sputtering process parameters can also improve the coating quality. In this paper, the effects of working gas flow rate on the microstructure in a vacuum chamber, nano-hardness, and tribological properties of Ce-Ti/MoS₂ coatings were studied using DC and RF unbalanced co-sputtering technology. It is found that the coating structure was coarse and porous when the Ar flow rate was excessive (70 sccm), significantly affecting the mechanical properties; there are pit defects on the surface of the coating when the flow rate is just minor (30 sccm), and the coating easily falls off during the friction process. When the flow rate is 40~60 sccm, the coating grows uniformly, the hardness reaches 7.85 GPa at 50 sccm, and the wear rate is only 4.42 × 10⁻⁷ mm³ N⁻¹ m⁻¹ at 60 sccm. The coating doped with Ce and Ti is an approximate amorphous structure. Under appropriate gas flow rate conditions, the friction induces a transfer film with a layered structure, and the MoS₂ (002) crystal plane orientation is arranged in parallel at the edge of the wear debris, effectively reducing the shear force during sliding and reducing wear. Based on rare earth doping, this study improves the tribological properties by optimizing the working gas parameters, which plays a reference role in preparing high-quality MoS₂-based coatings. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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12 pages, 5358 KiB

Open AccessArticle

Tribological Properties of Attapulgite Nanofiber as Lubricant Additive for Electric-Brush Plated Ni Coating

by Feng Nan and Dong Wang

Lubricants 2023, 11(5), 204; https://doi.org/10.3390/lubricants11050204 - 05 May 2023

Viewed by 1089

Abstract

In order to expand the application field of attapulgite in tribology, the tribological properties of attapulgite as a lubricant additive on electric-brush plated Ni coating were investigated using the ball-disc contact mode of a SRV-IV friction and wear tester. The worn surfaces were [...] Read more.

In order to expand the application field of attapulgite in tribology, the tribological properties of attapulgite as a lubricant additive on electric-brush plated Ni coating were investigated using the ball-disc contact mode of a SRV-IV friction and wear tester. The worn surfaces were characterized and analyzed via scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Results indicated that the friction-reducing and antiwear properties of 150 SN lubricating oil on the Ni coating were remarkably improved by an appropriate amount of attapulgite. Tribofilm mainly composed of Ni, NiO, SiO₂, Al₂O₃, graphite, and organic compounds was formed on the worn surface under the action of attapulgite, which was responsible for the reduction of friction and wear. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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25 pages, 10756 KiB

Open AccessArticle

An Experimental Investigation of the Tribological Performance and Dispersibility of 2D Nanoparticles as Oil Additives

by Kishan Nath Sidh, Dharmender Jangra and Harish Hirani

Lubricants 2023, 11(4), 179; https://doi.org/10.3390/lubricants11040179 - 17 Apr 2023

Cited by 4 | Viewed by 1600

Abstract

The present study aims to investigate the tribological performance of 2D nanoparticles such as graphene (G), molybdenum disulfide (MoS₂), hexagonal boron nitride (hBN), and reduced graphene oxide (rGO) as gear lubricant additives. A new method of additive doping in gear lubricants [...] Read more.

The present study aims to investigate the tribological performance of 2D nanoparticles such as graphene (G), molybdenum disulfide (MoS₂), hexagonal boron nitride (hBN), and reduced graphene oxide (rGO) as gear lubricant additives. A new method of additive doping in gear lubricants was proposed and examined in terms of the degradation of lubricants. The additives were energized by ultrasonication, thermal agitation, and mechanical shearing to enhance the dispersibility and stability, which were confirmed using visual and rheological analysis. Further, the tribological performance of the nano-additives was studied by doping them in fresh lubricants, chemically degraded lubricants, and chemically degraded lubricants with surfactants. The results indicate that surface roughness and the method of mixing play a crucial role in reducing wear. The nano-additives exhibit an inverse relationship with the roughness, and their agglomeration results in a decline in performance. To mitigate agglomeration, oleic acid surfactant was employed, which diminished the effects of nano-additives and degraded the lubricant. The attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis revealed that the oleic acid and deteriorating reagent work synergistically, leading to enhanced wear volume and reduced friction. The nano-additives were characterized using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Overall, the study presents a comprehensive plan for new method of additive mixing, stability, dispersibility and tribological performance of the selected 2D nanoparticles. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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23 pages, 3676 KiB

Open AccessArticle

by Umair Khan, Aurang Zaib, Sakhinah Abu Bakar, Siti Khuzaimah Soid, Anuar Ishak, Samia Elattar and Ahmed M. Abed

Lubricants 2023, 11(2), 60; https://doi.org/10.3390/lubricants11020060 - 02 Feb 2023

Cited by 2 | Viewed by 1271

Abstract

The fluid flow through blunt bodies that are yawed and un-yawed frequently happens in many engineering applications. The practical significance of deep-water applications such as propagation control, splitting the boundary layer over submerged blocks, and preventing recirculation bubbles is explained by the fluid [...] Read more.

The fluid flow through blunt bodies that are yawed and un-yawed frequently happens in many engineering applications. The practical significance of deep-water applications such as propagation control, splitting the boundary layer over submerged blocks, and preventing recirculation bubbles is explained by the fluid flow across a yawed cylinder. The current work examined the mixed convective flow and convective heat transfer by incorporating water-based graphene oxide nanofluid around a yawed cylinder with viscous dissipation and irregular heat source/sink. To investigate the heat diffusion across the system of buoyancy effects, the mathematical formulation of the problem was modeled in terms of coupled, nonlinear partial differential equations. The boundary value problem of the fourth-order (bvp4c) solver was operated to find the non-similarity solution. The outcomes indicated that the velocity in both directions enlarged owing to the higher impacts of yaw angle for the phenomenon of assisting flow but decreased for the instance of opposing flow, while the temperature of nanofluid increased because of heightened estimations of yaw angle for both assisting and opposing flows. In addition, with larger impacts of nanoparticle volume fraction, the shear stresses were enhanced by about 0.76% and 0.93% for the case of assisting flow, while for the case of opposing flow, they improved by almost 0.65% and 1.38%, respectively. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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14 pages, 3757 KiB

Open AccessArticle

Synergistic Lubrication and Antioxidation Efficacies of Graphene Oxide and Fullerenol as Biological Lubricant Additives for Artificial Joints

by Qian Wu, Honglin Li, Liangbin Wu, Zihan Bo, Changge Wang, Lei Cheng, Chao Wang, Chengjun Peng, Chuanrun Li, Xianguo Hu, Chuan Li and Bo Wu

Lubricants 2023, 11(1), 11; https://doi.org/10.3390/lubricants11010011 - 30 Dec 2022

Cited by 2 | Viewed by 1650

Abstract

The service life of artificial joints has gradually failed to meet the needs of patients. Herein, the synergistic lubrication and antioxidant efficacies of graphene oxide (GO) and fullerenol (Fol) as biological lubricant additives for artificial joints were investigated. The lubrication mechanisms of biological [...] Read more.

The service life of artificial joints has gradually failed to meet the needs of patients. Herein, the synergistic lubrication and antioxidant efficacies of graphene oxide (GO) and fullerenol (Fol) as biological lubricant additives for artificial joints were investigated. The lubrication mechanisms of biological lubricant containing GO and Fol at the friction interface of artificial joints were then revealed. Tribological tests showed that the average friction coefficients of Al₂O₃–Ti6Al4V pairs and Ti6Al4V–UHMWPE pairs for artificial joints could be reduced by 30% and 22%, respectively, when GO and Fol were used as biological lubricant additives simultaneously. The lubrication mechanism showed that some incommensurate sliding contact surfaces could be formed between the GO nanosheets and spherical Fol at the interface, which reduced the interaction forces of friction pairs. The maximum scavenging rates of •OH and DPPH free radicals by the biological lubricant containing GO and Fol were 35% and 45%, respectively, showing a good antioxidant efficacy of the biological lubricant. This can be attributed to the GO and Fol scavenging free radicals through electron transfer and hydrogen transfer. This study provides a theoretical basis for the development and application of carbon nanomaterials as biological lubricant additives for artificial joints in the future. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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16 pages, 5997 KiB

Open AccessArticle

Comparative Study of Tribological Properties of Modified and Non-modified Graphene-Oil Nanofluids under Heated and Non-heated Conditions

by Kean Pin Ng, Kia Wai Liew and Elaine Lim

Lubricants 2022, 10(11), 288; https://doi.org/10.3390/lubricants10110288 - 31 Oct 2022

Viewed by 1220

Abstract

With the aim of achieving more effective friction and wear reduction in sliding bearing applications, surface-modified graphene, which exhibits better dispersion stability than non-modified graphene, was synthesized and applied in this study using various graphene allotropes, including graphene nanoplatelets (GNP), multiwalled carbon nanotubes [...] Read more.

With the aim of achieving more effective friction and wear reduction in sliding bearing applications, surface-modified graphene, which exhibits better dispersion stability than non-modified graphene, was synthesized and applied in this study using various graphene allotropes, including graphene nanoplatelets (GNP), multiwalled carbon nanotubes (MWCNT) and nanostructured graphite (NSG). Friction and wear tests of each type of graphene allotrope under modified and non-modified conditions were studied using a pin-on-ring tribo tester. In addition, the dynamic viscosity of each synthesized nanofluid sample was measured using a falling-ball viscometer. A series of modified graphene-oil nanofluids and non-modified graphene-oil nanofluids were prepared and heated before their friction and wear performance was investigated at room temperature. Friction and wear behavior, as well as the dynamic viscosity of the heated nanofluids vary insignificantly when compared to those of the non-heated nanofluids. The results showed that the best friction and wear reduction was achieved by modified GNP with friction and wear reduction of 60.5% and 99.4%, respectively. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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Review

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19 pages, 2761 KiB

Open AccessReview

Two-Dimensional Nanomaterials in Hydrogels and Their Potential Bio-Applications

by Zhongnan Wang, Hui Guo, Ji Zhang, Yi Qian and Yanfei Liu

Lubricants 2024, 12(5), 149; https://doi.org/10.3390/lubricants12050149 - 27 Apr 2024

Viewed by 221

Abstract

Hydrogels with high hydrophilicity and excellent biocompatibility have been considered as potential candidates for various applications, including biomimetics, sensors and wearable devices. However, their high water content will lead to poor load-bearing and high friction. Currently, two-dimensional (2D) materials have been widely investigated [...] Read more.

Hydrogels with high hydrophilicity and excellent biocompatibility have been considered as potential candidates for various applications, including biomimetics, sensors and wearable devices. However, their high water content will lead to poor load-bearing and high friction. Currently, two-dimensional (2D) materials have been widely investigated as promising nanofillers to improve the mechanical and lubrication performances of hydrogels because of their unique physical–chemical properties. On one hand, 2D materials can participate in the cross-linking of hydrogels, leading to enhanced load-bearing capacity and fatigue resistance, etc.; on the other hand, using 2D materials as nanofillers also brings unique biomedical properties. The combination of hydrogels and 2D materials shows bright prospects for bioapplications. This review focusses on the recent development of high-strength and low-friction hydrogels with the addition of 2D nanomaterials. Functional properties and the underlying mechanisms of 2D nanomaterials are firstly overviewed. Subsequently, the mechanical and friction properties of hydrogels with 2D nanomaterials including graphene oxide, black phosphorus, MXenes, boron nitride, and others are summarized in detail. Finally, the current challenges and potential applications of using 2D nanomaterials in hydrogel, as well as future research, are also discussed. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

20 pages, 5925 KiB

Open AccessReview

Graphene-Family Lubricant Additives: Recent Developments and Future Perspectives

by Yanfei Liu, Shengtao Yu, Qiuyu Shi, Xiangyu Ge and Wenzhong Wang

Lubricants 2022, 10(9), 215; https://doi.org/10.3390/lubricants10090215 - 06 Sep 2022

Cited by 12 | Viewed by 3697

Abstract

Graphene-family materials have been investigated by researchers as promising additives for various lubrication systems due to their unique physical-chemical properties. It has been proven that graphene-family materials can lead to enhanced lubrication and wear-resistance performance, which have potential to reduce the energy losses [...] Read more.

Graphene-family materials have been investigated by researchers as promising additives for various lubrication systems due to their unique physical-chemical properties. It has been proven that graphene-family materials can lead to enhanced lubrication and wear-resistance performance, which have potential to reduce the energy losses and carbon emissions, and the wear of machines for industrial applications. Experimental, theoretical, and simulation studies have been performed to investigate the tribological behaviors of graphene-family materials as additives. The tribological properties of graphene-family materials, including graphene, reduced graphene oxide, functionalized graphene, and the combination of graphene-family materials and other materials as additives, and the fundamental mechanism are systematically reviewed and concluded. The authors also discuss the potential engineering applications of graphene-family materials as lubricating additives, and the unsolved issues and optimistic outlooks in the near future. Full article

(This article belongs to the Special Issue Tribology of 2D Nanomaterials)

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