| 1. |
- Abbas, Ghulam, et al.
(författare)
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First principles insights into triboelectrification during solid-solid contact: The curious case of 2D MXenes and aluminum
- 2024
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 129:Part B
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Tidskriftsartikel (refereegranskat)abstract
- have been widely used for energy harvesting and self-powered sensing due to their significant and unique advantages. However, the intrinsic mechanisms that contribute to tribo-electricification (TE) between two materials remain as a subject of rigorous debate. In addition to predicting the qualitative charge transfer in solid-solid contacts based on the difference in the work functions of the two moieties constituting the interface, we argue that it is essential to obtain atomic-level, first principles, insights into the bonding properties, quantitative charge transfer, and the possible presence of a electrostatic potential barrier at the interface to fully understand the TE mechanism of a system. We have utilized dispersion-corrected density functional theory (DFT) calculations in this study to systematically investigate the TE potential of bare surface Ti3C2 and Ti3N2 2D MXene monolayers and their surface functionalized modifications Ti3C2R2 and Ti3N2R2 (where R = -O, -OH, or -F) in contact with Al(111). For these heterostructures, we have analyzed the adhesive energy of the interfaces, the nature of interaction through the electron localization function (ELF), and the charge distribution, which have revealed distinct characteristics of MXene/Al contacts for these monolayer/metal interfaces at their equilibrium distance and the changes in their properties under uniaxial pressure. Among all the metallic 2D MXene variants investigated in this study, we have determined that Ti3C2F2/Al and Ti3N2F2/Al interfaces show exceptional potential for TE.
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| 2. |
- Abbas, Ghulam, et al.
(författare)
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Quasi Three-Dimensional Tetragonal SiC Polymorphs as Efficient Anodes for Sodium-Ion Batteries
- 2023
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 6:17, s. 8976-8988
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, we investigate, for the first time, quasi 3D porous tetragonal silicon–carbon polymorphs t(SiC)12 and t(SiC)20 on the basis of first-principles density functional theory calculations. The structural design of these q3-t(SiC)12 and q3-t(SiC)20 polymorphs follows an intuitive rational approach based on armchair nanotubes of a tetragonal SiC monolayer where C–C and Si–Si bonds are arranged in a paired configuration for retaining a 1:1 ratio of the two elements. Our calculations uncover that q3-t(SiC)12 and q3-t(SiC)20 polymorphs are thermally, dynamically, and mechanically stable with this lattice framework. The results demonstrate that the smaller polymorph q3-t(SiC)12 shows a small band gap (∼0.59 eV), while the larger polymorph of q3-t(SiC)20 displays a Dirac nodal line semimetal. Moreover, the 1D channels are favorable for accommodating Na ions with excellent (>300 mAh g–1) reversible theoretical capacities. Thus confirming potential suitability of the two porous polymorphs with an appropriate average voltage and vanishingly small volume change (<6%) as anodes for Na-ion batteries.
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| 3. |
- Berglund, Kim, 1982-, et al.
(författare)
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Friction and Wear of Self-Lubricating Materials for Hydropower Applications under Different Lubricating Conditions
- 2017
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Ingår i: Lubricants. - : MDPI. - 2075-4442. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Self-lubricating bearings in hydropower applications are often lubricated with water under boundary lubricating conditions. Polyhydric alcohols replacing water have shown the potential to reduce both friction and wear. The objective of this work is, therefore, to evaluate the effect of a polyhydric alcohol-based environmentally-acceptable lubricant (EAL) on the friction and wear of self-lubricating materials for conformal contacts under boundary lubricating conditions. The lubricating properties of four commercially-available self-lubricating bearing materials were investigated under three different lubricating conditions: dry, water and a new polyhydric alcohol-based EAL. Bearing materials include one metallic composite and three polymer composites. A reciprocating motion test rig was used to evaluate the wear and friction properties. Surface analysis was performed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and optical profilometry. Results show that the wear rate for the polymer composites is increased when water is present compared to dry operating conditions. The new polyhydric alcohol-based EAL substantially improves both friction and anti-wear performance of all four self-lubricating bearing materials compared to both dry and water conditions. Surface analysis indicates that the material transfer to the counter-surface is limited when the polyhydric alcohol-based EAL is used.
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| 4. |
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| 5. |
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| 6. |
- Björling, Marcus, 1983-, et al.
(författare)
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DLC and Glycerol : Superlubricity in Rolling/Sliding Elastohydrodynamic Lubrication
- 2019
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Ingår i: Tribology letters. - : Springer. - 1023-8883 .- 1573-2711. ; 67:1
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Tidskriftsartikel (refereegranskat)abstract
- Low friction is one of the most important parameters for the development of machine components and machines with high efficiency. Many of the common machine components of today such as gears, rolling element bearings and cam-followers are defined by their non-conformal contacts leading to high-contact pressures, typically 1–4 GPa. The lubrication of such contacts is usually called elastohydrodynamic lubrication (EHL). Diamond-like carbon (DLC) coatings and glycerol have individually been shown to produce low friction in boundary, mixed and full film lubrication. A few studies have been conducted using both glycerol and DLC-coated surfaces to achieve even lower friction in pure sliding boundary-lubricated contacts. However, the literature is lacking studies of how the combination of glycerol and DLC performs in non-conformal rolling/sliding contacts where many common machine components operate. Such a study is presented in this article where a ball-on-disc test rig is used to investigate the performance of the combination of DLC and glycerol at pressures up to 1.95 GPa at various entrainment speeds and slide-to-roll ratios. The investigation shows that the DLC-glycerol combination provides very low friction values, in some cases, below the superlubricity threshold of 0.01, possibly shown for the first time at such high pressure in a non-conformal rolling/sliding contact. The low friction mechanism in full film lubrication is a combination of the low pressure-viscosity and high temperature-viscosity sensitivity of glycerol in combination with thermal insulation of the DLC coating and is presented as thermally assisted liquid superlubricity.
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| 7. |
- Björling, Marcus, et al.
(författare)
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Elastohydrodynamic performance of a bio-based, non-corrosive ionic liquid
- 2017
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 17:10
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Tidskriftsartikel (refereegranskat)abstract
- To improve performance of machine components, lubrication is one of the most important factors. Especially for use in extreme environments, researchers look for other solutions rather than common lubricant base stocks like mineral oils or vegetable oils. One such example is ionic liquids. Ionic liquids have been defined as molten salts with melting points below 100 °C that are entirely ionic in nature, comprising both cationic and anionic species. The industrial use of ionic liquids is mostly as solvents, electrolytes, extractants and catalysts. In tribological applications, ionic liquids are mainly studied in boundary lubrication and in pure sliding contacts. In this work, the elastohydrodynamic performance of a bio-based, non-corrosive, [choline][L-proline] ionic liquid is evaluated in terms of pressure-viscosity response, film forming capability and friction. The results show a pressure-viscosity coefficient of below 8 GPa-1 at 25 °C, among the lowest reported for any ionic liquid. The ionic liquid generated up to 70% lower friction than a reference paraffin oil with a calculated difference in film thickness of 11%. It was also shown that this ionic liquid is very hygroscopic, which is believed to explain part of the low friction results, but also has to be considered in practical applications since the water content will influence the properties and thus the performance of the lubricant.
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| 8. |
- Björling, Marcus, et al.
(författare)
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Elastohydrodynamic Performance of a Non-Corrosive Non-Protic Ionic Liquid
- 2017
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Konferensbidrag (refereegranskat)abstract
- Ionic liquids have been defined as molten salts with melting points below 100 degrees C that are entirely ionic in nature, comprising both cationic and anionic species. The industrial use of ionic liquids is mostly as solvents, electrolytes, extractants and catalysts. In tribological applications, Ionic liquids are mainly studied in boundary lubrication and in pure sliding contacts. In this work, the elastohydrodynamic performance of a non-corrosive, non-protonic ionic liquid is studied to assess the feasibility to use this kind of ionic liquid in machine components such as gears, rolling bearings and cam followers. This study includes ball on disc friction experiments in rolling sliding full film elastohydrodynamic lubrication at high slide to roll ratios, as well as film thickness measurements with optical interferometry. A commercially available paraffin oil has been used as a reference.
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| 9. |
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| 10. |
- Björling, Marcus, 1983-, et al.
(författare)
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Glycerol and DLC in Elastohydrodynamic Lubrication
- 2018
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Ingår i: 73rd STLE Annual Meeting and Exhibition. - : Society of Tribologists and Lubrication Engineers. ; , s. 46-46
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Konferensbidrag (refereegranskat)abstract
- Lubrication and surface engineering plays a vital part in the efficiency of machine components. By using low friction fluids and low friction coatings the efficiency of machine components can be improved dramatically. Glycerol is an example of a fluid with extraordinary low friction characteristics in various systems. Diamond like carbon (DLC) coatings have also been shown to reduce friction in a variety of tribological interfaces. In this study, the elastohydrodynamic performance of glycerol with DLC coated surfaces has been investigated in rolling sliding contacts at high pressures and high slide-to-roll ratios. The DLC-glycerol system is compared to a steel-synthetic oil system and the differences are significant.
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