| 1. |
- Alberdi, Alberto, et al.
(författare)
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Tribological behavior of nanocomposite coatings based on fullerene-like structures
- 2011
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Ingår i: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 85:12, s. 1087-1092
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a new group of nanocomposite coatings based on integrating inorganic fullerene-like material (IFLM) structures into conventional coating matrices. Such coatings have been developed within the scope of the European funded FOREMOST project (FP6-NMP3-CT-2005-515840). Regarding the synthesis of these nanocomposite coatings based on fullerene-like components, two alternative routes were explored: introducing preformed IFLMs into the coating deposition process or forming the fullerene-like components in situ during the coating deposition process. Both methods have been demonstrated to be technically feasible, depending on the nature of the coating matrix or the desired fullerene-like structure. These new materials allow some independent control of tribological properties usually known as antagonists (very high load bearing capacity with a very low friction coefficient). In the case of unidirectional movement, under dry conditions, the best coatings developed in FOREMOST displayed a coefficient of friction in air within the range 0.04-0.10, depending on the degree of humidity and the test conditions. Pure sliding laboratory tests indicate that for some industrial applications fullerene-like nanocomposite coatings can give significant reductions in wear and friction coefficient when compared to similar coatings without fullerene-like components. The lubrication mechanisms through which these fullerene-like structures improve friction and prevent wear are also discussed in this paper.
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| 2. |
- Blomqvist, M., et al.
(författare)
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Structural and tribological properties of cluster-assembled CNx films
- 2007
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 87:4, s. 767-772
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Tidskriftsartikel (refereegranskat)abstract
- We report the structural and tribological characterization of nanostructured CNx thin films produced by the deposition of a supersonic carbon cluster beam assisted by nitrogen ion bombardment. The influence of the deposition parameters on the chemical composition and structure of the films has been systematically studied by X-ray photoelectron spectroscopy, elastic recoil detection analysis, transmission electron microscopy and atomic force microscopy. Depending on the deposition parameters, the films show a structure ranging from amorphous to disordered graphitic with interlinked planes. Nitrogen content depends on the nitrogen ion kinetic energy. The films have a very low density with a high surface roughness. Friction measurements at the nanoscale show a correlation between nitrogen content and mechanical properties of the system.
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| 6. |
- Jenei, István Zoltán, et al.
(författare)
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Correlation Studies of WS2 Fullerene-Like Nanoparticles Enhanced Tribofilms : A Scanning Electron Microscopy Analysis
- 2013
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Ingår i: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 51:3, s. 461-468
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Tidskriftsartikel (refereegranskat)abstract
- The beneficiary effects of tungsten disulphide (WS2) inorganic fullerene-like nanoparticles (IFLNPs) in the lubrication industry were shown in recent years. However, their successful incorporation into lubricants (oils, greases) is not straightforward. In practice, the lubricant contains several components for different purposes, e.g. reducing the oxidization of the oil (antioxidant), minimizing the wear rate (anti-wear additive), dispersants, etc. These additives can contain chemically active compounds, which under the lubrication process (where locally extreme conditions can develop: high pressure and flash temperatures) can change the chemistry in the contact zone and block the beneficial effects of the inorganic nanoparticles. In this investigation, poly-alpha-olefin (PAO) is being used as base oil in which the WS2 nanoparticles and different additives are mixed. A ball-on-disc sliding test revealed that certain additives inhibit the nanoparticles to reduce friction (less than 5 % decrease in friction coefficient), while in other cases, the friction reduction was above 50 %. The comparison is being made between PAO + additive and PAO + additive + IFLNPs. Scanning electron microscope and energy dispersive X-ray spectroscopy were used to investigate the elemental composition of the tribofilms formed on the wear marks. Further analysis was made in order to reveal correlations between elemental compositions of the tribofilms and external parameters such as the friction coefficient and wear rate. For instance, a strong correlation between tungsten content of the tribofilm and the friction coefficient was found.
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| 7. |
- Jenei, István Zoltán, 1985-
(författare)
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Nanoparticle assisted tribofilm formation and material transfer studied with SEM and TEM
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The discovery and subsequent synthesis of metal containing fullerenes- IFS (Inorganic Fullerene-like Structures) by R. Tenne et al. has generated considerable scientific interest with great potential impact in many industrial application areas such as lubrication. The lubrication mechanism (tribofilm formation) via exfoliation and deposition of the atomic layers from this cage-like IF-particles was revealed and demonstrated first by this research group. The incorporation of the nanoparticles into lubricants (oils, greases) is however not straightforward.When two surfaces are sliding against each other and a lubricant is used, a thin layer (tribofilm) is formed on the contact area. The friction reducing effects of the nanoparticles can be altered or hindered by certain additives that are used in lubricative oils. The effects of such additives on the tribological behavior of the nanoparticles are investigated by analyzing the tribofilms formed on the worn surfaces using energy-dispersive X-ray spectroscopy in a scanning electron microscope. Another challenge of nanoparticles in lubricants is the penetration of the nanoparticles into the contact zone. A possible solution of this problem is briefly discussed.A modified burnishing technique can be used to coat sliding metallic surfaces with a friction reducing tribofilm. The morphology and composition of these tribofilms was investigated with analytical electron microscopy techniques.In the second part of the thesis electron microscopy was used to investigate the material transfer. Titanium is an elements with high adhesive ability to the counter surface, it displays poor tribological properties in sliding metallic contacts. This can lead to material transfer and consequently severe surface damage. The cold formation and machining of titanium, thus can lead rapid tool wear and poor surface finish. Electron microscopy techniques were used to study the mechanism of titanium transfer to different counter surfaces.
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| 8. |
- Jenei, István Zoltán
(författare)
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Scanning electron microscopy (SEM) analysis of tribofilms enhanced by fullerene-like nanoparticles
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The beneficiary effects of WS2 inorganic fullerene-like nanoparticles in the lubrication industry were shown in recent years. The incorporation of the nanoparticles into lubricants (oils, greases) is however not straightforward.When two surfaces are sliding against each other and a lubricant is used, a thin layer (tribofilm) is formed on the contact area, which effects the friction process. Lubricants usually contain several additives. These additives can impair the friction reducing behaviour of the WS2 inorganic fullerene-like nanoparticles. This thesis investigates the effects of several additives in the lubrication process by analysing the tribofilms formed on the worn surfaces using energy-dispersive X-ray spectroscopy in a scanning electron microscope.
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| 9. |
- Kashtanov, Stepan, et al.
(författare)
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Characterization of aza-fullerene C58N2 isomers by X-ray spectroscopy
- 2003
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 371:02-jan, s. 98-104
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron and near-edge X-ray absorption fine-structure spectra (NEXAFS) of four isomers of C58N2 are predicted by means of density-functional theory calculations. A strong isomer dependence for both types of spectra are found. The spectroscopic findings are discussed in conjunction with results from electronic and geometric structure optimizations.
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| 10. |
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| 11. |
- Svahn, Fredrik, et al.
(författare)
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Formation of Low-Friction Particle/Polymer Composite Tribofilms by Tribopolymerization
- 2011
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Ingår i: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 41:2, s. 387-393
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Tidskriftsartikel (refereegranskat)abstract
- Inorganic fullerene-like (IF) solid lubricant particles based on MoS(2) or WS(2) have recently gained attention in various tribological applications, for instance incorporated in coatings, porous materials, greases and dispersed in oils. However, their effect in oil can be limited often due to inadequate penetration into the contact zone. Meanwhile, tribopolymerization of monomer additives in oil have proven to be efficient to reduce wear, but without significantly reducing the friction. This investigation combines these two lubrication techniques in order to form particle/polymer composite tribofilms, aimed to give low friction and wear in high-pressure sliding contacts. A cyclic amine, caprolactam, was used as the monomer together with IF as well as normal 2H WS(2) particles. Zn-DTP was used as a reference antiwear additive and poly-alfa-olefin (PAO) was used as the base oil. Reciprocal ball-on-flat sliding test results found that monomer plus particles reduced the friction by 10-50%, depending on sliding speed and type of particles, compared with particles or monomer alone. And the scattering between different tests was also considerably lower. The wear rate was also substantially reduced to a level similar to that of Zn-DTP. The particle/polymer composite tribofilms were generally much larger than the actual contact area and its thickness varied from below a few nanometres in the contact centre to several micrometers in the outer parts. Consequently, the reduced friction is believed to come from two effects: one being a trapping of particles in the contact zone, which reduces the boundary friction level; and the other a shift in lubrication regime towards EHD-lubrication due to reduced contact pressures accompanied with the formation of the composite tribofilm.
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| 12. |
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| 13. |
- Urbonaite, S., et al.
(författare)
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EELS studies of carbide derived carbons
- 2007
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 45:10, s. 2047-2053
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Tidskriftsartikel (refereegranskat)abstract
- Carbide derived carbons (CDCs) have been synthesized from VC, WC, TaC, NbC, HfC and ZrC at T = 1000 °C, and from TiC at T = 700-1200 °C via a chlorination reaction. The CDCs have been studied by means of high resolution transmission electron microscopy and electron energy-loss spectroscopy (EELS). These studies show that the structures of CDCs are strongly dependent upon the nature of the starting carbide and the synthesis temperature. The structures range from very disordered nanoporous carbon, consisting of randomly curved graphene layers, to compact spherical entities of compactly packed graphitic layers. EELS studies of carbon core-loss spectra show that the relative sp2 content in these carbons varies between 83% and 98%. The low-loss part of the EEL spectra shows that the positions of the π-plasmons and the bulk plasmons are more dependent on the carbide precursor, than the synthesis temperature. The densities of the CDC particles have been estimated using the bulk plasmon positions as well as the sp3 content determined from the C-K edge spectra. The densities calculated from sp3 are close to the pycnometric ones, while the densities calculated from bulk plasmon positions are lower and reflects the nanostructure of CDCs.
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| 14. |
- Wachtmeister, Staffan, 1973-
(författare)
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Analytical Electron Microscopy Studies for Development of New Carbon Based Materials
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis presents transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) studies of new carbon based materials synthesized with two different techniques. In the first project, nitrogen is incorporated into carbon nanostructures by supersonic cluster beam deposition (SCBD) to favor the formation of curved and cross-linked structures, ultimately aiming at creating a material with high hardness combined with good elasticity. The second project deals with nanoporous carbon derived from various carbides (VC, WB, NbC, TaC, HfC, ZrC and TiC) synthesized at temperatures ranging from 700 to 1200 °C, ultimately aiming at creating a porous material with large surface area and narrow poor size distribution. In both projects, the results of different synthesis conditions are investigated with the help of high resolution TEM and EELS. Structural and chemical information about the samples is extracted and it is found that it is possible to alter the nanostructure depending on the synthesis conditions. The thesis ends with implementation and evaluation of Gold’s iterative deconvolution method for enhanced energy resolution in EEL spectra. Relevant background about the chemical elements, transmission electron microscopy and electron energy loss spectroscopy is included in the introductory chapters.
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| 15. |
- Wachtmeister, Staffan, 1973-, et al.
(författare)
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Implementation of Gold deconvolution for enhanced energy resolution in EEL spectra
- 2011
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 111:2, s. 79-89
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Tidskriftsartikel (refereegranskat)abstract
- Gold’s iterative deconvolution algorithm has been applied to one-dimensional EEL spectra from hexagonal BN. The experimental resolution was varied from 1.1 to 2.25 eV and Gold’s algorithm was able to restore low-loss and core-loss spectra overall well. To estimate the instrument response function, the most convenient method was to extract the zero-loss peak from the low-loss spectrum. It was also found as suggested by Egerton, that by using low-loss spectra as kernel, enhanced energy resolution could be obtained as plural scattering was simultaneously removed. It’s further shown how the FWHM of the p* peak in the boron K‑edge of hexagonal BN is reduced from 1.4 to 0.7 eV with almost no noise-amplification after 500 iterations while resolving the s* doublet. The result was almost identical after a stunning 5 000 - 10 000 iterations, implying that Gold’s method converges and can be stable for a large number of iterations. However, for lower-intensity spectra the number of iterations is limited. The results close to the intense zero-loss peak were uncertain and further testing with better experimental resolution is recommended. It’s also found that to improve the resolution and not just sharpen the spectra, a large number of iterations is required.
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| 16. |
- Wachtmeister, Staffan, 1973-, et al.
(författare)
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Nanostructured CNx (0 < x < 0.2) films grown by supersonic cluster beam deposition
- 2005
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Ingår i: Carbon. - Oxford : Elsevier. - 0008-6223 .- 1873-3891. ; 43, s. 1460-1469
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured CNx thin films were prepared by supersonic cluster beam deposition (SCBD) and systematically characterized by transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The incorporation of nitrogen in the films (0 < x < 0.2) and the nanostructure were controlled by using different synthesis routes. Films containing bundles of well-ordered graphene multilayers, onions and nanotubes embedded in an amorphous matrix were grown alongside purely amorphous films by changing the deposition parameters. Graphitic nanostructures were synthesized without using metallic catalysts. The structural and electronic properties of the films have been studied by EELS. The role played by N in the carbon nanostructures has been deduced from XPS line-shape analysis.
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| 17. |
- Wittchen, Hans-Ulrich, et al.
(författare)
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The need for a behavioural science focus in research on mental health and mental disorders
- 2014
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Ingår i: International Journal of Methods in Psychiatric Research. - : Wiley-Blackwell. - 1049-8931 .- 1557-0657. ; 23, s. 28-40
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Tidskriftsartikel (refereegranskat)abstract
- Psychology as a science offers an enormous diversity of theories, principles, and methodological approaches to understand mental health, abnormal functions and behaviours and mental disorders. A selected overview of the scope, current topics as well as strength and gaps in Psychological Science may help to depict the advances needed to inform future research agendas specifically on mental health and mental disorders. From an integrative psychological perspective, most maladaptive health behaviours and mental disorders can be conceptualized as the result of developmental dysfunctions of psychological functions and processes as well as neurobiological and genetic processes that interact with the environment. The paper presents and discusses an integrative translational model, linking basic and experimental research with clinical research as well as population-based prospective-longitudinal studies. This model provides a conceptual framework to identify how individual vulnerabilities interact with environment over time, and promote critical behaviours that might act as proximal risk factors for ill-health and mental disorders. Within the models framework, such improved knowledge is also expected to better delineate targeted preventive and therapeutic interventions that prevent further escalation in early stages before the full disorder and further complications thereof develop. In contrast to conventional personalized medicine that typically targets individual (genetic) variation of patients who already have developed a disease to improve medical treatment, the proposed framework model, linked to a concerted funding programme of the Science of Behaviour Change, carries the promise of improved diagnosis, treatment and prevention of health-risk behaviour constellations as well as mental disorders.
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