| 1. |
- Fritze, Stefan, et al.
(författare)
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Magnetron sputtering of carbon supersaturated tungsten films-A chemical approach to increase strength
- 2021
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 208
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Tidskriftsartikel (refereegranskat)abstract
- Tungsten (W)-based materials attract significant attention due to their superior mechanical properties. Here, we present a chemical approach based on the addition of carbon (C) for increased strength via the combination of three strengthening mechanisms in W thin films. W:C thin films with C concentrations up to-4 at.% were deposited by magnetron sputtering. All films exhibit a body-centred-cubic structure with strong texture and columnar growth behaviour. X-ray and electron diffraction measurements suggest the formation of supersaturated W:C solid solution phases. The addition of C reduced the average column width from-133 nm for W to-20 nm for the film containing-4 at.% C. The column refinement is explained by a mechanism where C acts as re-nucleation sites. The W film is-13 GPa hard, while the W:C films achieve a peak hardness of-24 GPa. The W:C films are-11 GPa harder than the W film, which is explained by a combination of grain refinement strengthening, solid solution strengthening and increased dislocation density. Additional micropillar compression tests showed that the flow stress increased upon C addition, from-3.8 to-8.3 GPa and no brittle fracture was observed.
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| 2. |
- Menon, Ashok S., et al.
(författare)
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Synthetic Pathway Determines the Nonequilibrium Crystallography of Li- and Mn-Rich Layered Oxide Cathode Materials
- 2021
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 4:2, s. 1924-1935
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Tidskriftsartikel (refereegranskat)abstract
- Li- and Mn-rich layered oxides show significant promise as electrode materials for future Li-ion batteries. However, an accurate description of its crystallography remains elusive, with both single-phase solid solution and multiphase structures being proposed for high performing materials such as Li1.2Mn0.54Ni0.13Co0.13O2. Herein, we report the synthesis of single- and multiphase variants of this material through sol-gel and solid-state methods, respectively, and demonstrate that its crystallography is a direct consequence of the synthetic route and not necessarily an inherent property of the composition, as previously argued. This was accomplished via complementary techniques that probe the bulk and local structure followed by in situ methods to map the synthetic progression. As the electrochemical performance and anionic redox behavior are often rationalized on the basis of the presumed crystal structure, clarifying the structural ambiguities is an important step toward harnessing its potential as an electrode material.
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