| 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. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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