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- Ghanbari, Reza, 1984, et al.
(författare)
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Painting Taylor vortices with cellulose nanocrystals: supercritical spectral dynamics
- 2023
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- We study the flow stability and spatio-temporal spectral dynamics of cellulose nanocrystal (CNC) suspensions in a custom Taylor-Couette flow cell using the intrinsic shear induced birefringence and liquid crystalline properties of CNC suspensions for flow visualizations for the first time. The analysis is performed at constant ramped speed inputs of the independently rotating cylinders for several cases ranging from only inner or outer rotating cylinders to three counter-rotation cases. All CNC suspensions have measurable elastic and shear thinning, both increasing with CNC concentration. We show that the flow patterns recorded are essentially Newtonian-like, with non-Newtonian effects ranging from a decrease in wavenumbers to altering the critical parameters for the onset of instability modes. Outer cylinder rotation flow cases are stable for all concentrations whereas inner cylinder rotation flow cases transition to axisymmetric and azimuthally periodic secondary flows. However, unstable counter-rotation cases become unstable to asymmetric spiral modes. With increasing CNC concentration a counter-rotation case was found where azimuthally periodic wavy patterns transition to asymmetric spiral modes. In contrast to polymeric solutions of similar low to moderate elasticity and shear thinning, the shear-thinning region of CNC suspensions is expected to lead to the breakdown of the chiral nematic phase, whose elastic constants constitute the dominant structural elasticity mechanism. Thus, we interpret the Taylor-Couette stability of the CNC suspensions as dominated by their shear-thinning character due to the expected loss of elasticity in nonlinear flow conditions.
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| 2. |
- Matic, Aleksandar, 1968
(författare)
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Glassy Materials: Fundamental Aspects and Ionic Conduction
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Materials of very different categories, ranging from polymers to metals, can form glasses. The disordered structure of glassy materials often provide unique properties to the system and glasses are commonly used in various technological applications. However, even though glassy materials have been in use for a long time their structures and physical properties are not well understood. This thesis concerns experimental investigations of structure and dynamics of glasses. One part of the work concerns fundamental properties, such as glass structure and collective vibartional excitations, and the other deals with ion conduction in glassy systems. Using neutron and x-ray diffraction, in combination with reverse Monte Carlo (RMC) simulations, and Raman spectroscopy, the structure of meta-phosphate glasses has been investigated, with the focus on the influence on the structure of different cations. Collective vibrational excitations, in a strong (B2O3) and a fragile glass (Ca0.4K0.6(NO3)1.4) former have been studied with high resolution (meV) inelastic x-ray scattering, in the meso-scopic regime. The behaviour of the acoustic modes is shown to be different for strong and fragile glasses. It is suggested that this is related to differences in intermediate range connectivity of the structure and fluctuation of force constants. A high ionic conductivity at room temperature is a property unique to glasses (with the exception of some crystalline compounds). In this work, structural aspects of the ionic conductivity has been investigated in several different systems, including the new ion-conducting glass system the silver-thio-boro-silicates, using diffraction techniques and RMC simulations. Furthermore, a structural approach has been taken to explain the mixed-alkali effect in ion conducting glasses. Three series of mixed-alkali meta-phosphate glasses have been investigated. From the results it is evident that the local environment of the alkali ions remain the same in the mixed glasses as in the single alkali glasses. Hence, there is a large energy mismatch between different alkali sites in the structure resulting in a considerably lowered mobility of the ions.
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| 5. |
- Matic, Aleksandar, 1968, et al.
(författare)
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Road maps of no use to some physicists
- 2014
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 507:7491, s. 169-169
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Xiong, Shizhao, 1985, et al.
(författare)
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Lithium electrodeposition for energy storage: filling the gap between theory and experiment
- 2022
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Ingår i: Materials Today Energy. - : Elsevier BV. - 2468-6069. ; 28
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Lithium (Li) metal has been considered a promising anode material for high-energy-density rechargeable batteries, but its utilization is impeded by the nonuniform electrodeposition during the charging process which leads to poor cycling life and safety concerns. Thus, understanding the electrodeposition mechanism of Li-metal anode is of great importance to develop practical engineering strategies for rechargeable Li-metal batteries. The electrodeposition of Li is controlled by both thermodynamic and kinetic factors, such as the solvation free energy of Li-ions, the Li nucleation, the surface diffusion of Li atom, and the strength of the interaction between Li-ion and the electrolyte anion. The scale of the whole process from the Li-ion reduction to the growth of a Li nucleus goes from sub-nanometer up to a few micrometers, which poses an outstanding challenge to both experiments and simulation. In this perspective, we discuss the top-down, the bottom-up, and the middle-way approaches to this challenge and the possible synergies between them.
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