| 1. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Abitbol, Tiffany, et al.
(författare)
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Nanocellulose-Based Hybrid Materials for UV Blocking and Mechanically Robust Barriers
- 2020
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Ingår i: ACS Applied Bio Materials. - : American Chemical Society (ACS). - 2576-6422. ; 3:4, s. 2245-2254
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Tidskriftsartikel (refereegranskat)abstract
- Nanocellulose (NC)-based hybrid coatings and films containing CeO2 and SiO2 nanoparticles (NPs) to impart UV screening and hardness properties, respectively, were prepared by solvent casting. The NC film-forming component (75 wt % of the overall solids) was composed entirely of cellulose nanocrystals (CNCs) or of CNCs combined with cellulose nanofibrils (CNFs). Zeta potential measurements indicated that the four NP types (CNC, CNF, CeO2, and SiO2) were stably dispersed in water and negatively charged at pH values between 6 and 9. The combination of NPs within this pH range ensured uniform formulations and homogeneous coatings and films, which blocked UV light, the extent of which depended on film thickness and CeO2 NP content, while maintaining good transparency in the visible spectrum (∼80%). The addition of a low amount of CNFs (1%) reduced the film hardness, but this effect was compensated by the addition of SiO2 NPs. Chiral nematic self-assembly was observed in the mixed NC film; however, this ordering was disrupted by the addition of the oxide NPs. The roughness of the hybrid coatings was reduced by the inclusion of oxide NPs into the NC matrix perhaps because the spherical oxide NPs were able to pack into the spaces between cellulose fibrils. We envision these hybrid coatings and films in barrier applications, photovoltaics, cosmetic formulations, such as sunscreens, and for the care and maintenance of wood and glass surfaces, or other surfaces that require a smooth, hard, and transparent finish and protection from UV damage.
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| 3. |
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| 4. |
- Álvarez-Asencio, Ruben, et al.
(författare)
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Molecular-scale shear response of the organic semiconductor β -DBDCS (100) surface
- 2017
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 96:11
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present friction-force microscopy (FFM) lattice-resolved images acquired on the (100) facet of the semiconductor organic oligomer (2Z,2′Z)-3,3′-(1,4-phenylene)bis(2-(4-butoxyphenyl)acrylonitrile) (β-DBDCS) crystal in water at room temperature. Stick-slip contrast, lateral contact stiffness, and friction forces are found to depend strongly on the sliding direction due to the anisotropic packing of the molecular chains forming the crystal surface along the [010] and [001] directions. The anisotropy also causes the maximum value of the normal force applicable before wearing to increase by a factor of 3 when the scan is performed along the [001] direction on the (100) face. Altogether, our results contribute to achieving a better understanding of the molecular origin of friction anisotropy on soft crystalline surfaces, which has been often hypothesized but rarely investigated in the literature.
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| 5. |
- Álvarez-Asencio, Rubén, et al.
(författare)
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Nanomechanical properties of human skin and introduction of a novel hair indenter
- 2016
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier. - 1751-6161 .- 1878-0180. ; 54, s. 185-193
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young’s modulus of the stratum corneum varied over the surface with a mean value of about 0.4 GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4 μN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.
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| 6. |
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| 7. |
- Álvarez Asencio, Rubén, et al.
(författare)
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Nanotribology : Tribotronics, ionic liquids and control of surface interactions
- 2013
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Ingår i: 5th World Tribology Congress, WTC 2013. ; , s. 3106-3108
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Konferensbidrag (refereegranskat)abstract
- The interfacial ordering of Ionic liquids leads to interesting nanotribological properties as revealed by colloid probe studies. The first of these is the clear correlation between the number of ion pairs trapped in the tribological contact and the friction coefficient displayed. The second is the fact that the surface electrical potential can be used to control the composition of the boundary layer and thus tune the friction. Thirdly, the interfacial ordering appears to significantly affect the fluid dynamics over large distances.
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| 8. |
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| 9. |
- Álvarez-Asencio, Rubén, 1978-
(författare)
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Nanotribology, Surface Interactions and Characterization : An AFM Study
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When two surfaces achieve contact, then contact phenomena such as adhesion, friction and wear can occur, which are of great interest in many disciplines, including physics, physical chemistry, material chemistry, and life and health sciences. These phenomena are largely determined by the nature and magnitude of the surface forces such as van der Waals, capillary and hydration forces. Moreover these forces are length-dependent, and therefore when the system scales down, their contribution scales up, dominating the interaction between the surfaces.A goal of my PhD work was to investigate fundamental contact phenomena in terms of the surface forces that regulate their properties. The primary tool applied in this PhD thesis work has been the atomic force microscopy (AFM), which (with all of its sub-techniques) offers the possibility to study such forces with high resolution virtually between all types of materials and intervening media. Therefore, in this work it was possible to study the long ranged interactions presented in air between different industrially relevant materials and how these interactions are shielded when the systems are immersed in an ionic liquid.Also investigated was the influence of microstructure on the tribological properties of metal alloys, where their good tribological properties were related with the vanadium and nitrogen contents for a FeCrVN tool alloy and with the chromium content for a biomedical CoCrMo alloy. Moreover, the effect of the intervening media can significantly affect the surface properties, and when the biomedical CoCrMo alloy was immersed in phosphate buffer saline solution (PBS), repulsive hydration forces decreased the friction coefficient and contact adhesion. On the other hand, with the immersion of the FeCrVN tool alloy in the NaCl solution, small particles displaying low adhesion were generated in specific regions on the surface with low chromium content. These particles are assumed to be related to a prepitting corrosion event in the tool alloy.The mechanical properties of stratum corneum (SC), which is the outermost layer of the skin, were also studied in this work. The SC presents a highly elastic, but stiff surface where the mechanical properties depend on the nanoscale. A novel probe has been designed with a single hair fibre in order to understand how the skin deforms locally in response to the interaction with such a fibre probe. This study revealed that is mostly the lateral scale of the deformation which determines the mechanical properties of the SC.Finally, important achievements in this work are the developments of two new techniques - tribological property mapping and the Hybrid method for torsional spring constant evaluation. Tribological property mapping is an AFM technique that provides friction coefficient and contact adhesion maps with information attributed to the surface microstructure. The Hybrid method is an approach that was originally required to obtain the torsional spring constants for rigid beam shaped cantilevers, which could not be previously determined from their power torsional thermal spectra (conventional method). However, the applicability is shown to be general and this simple method can be used to obtain torsional spring constants for any type of beam shape cantilever.
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| 10. |
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