Scientific Events

In-situ transmission electron microscopy (TEM) allows researchers to analyse at the nano-scale and in ‘real time’ the electrochemical processes of the electrode materials within batteries during device operation. The active interface regions of such electrodes form solid electrolyte interface (SEI) layers during the charge and discharge cycling. The formation and movement of this functional SEI nano-interface is one of the main research fields in battery science, as it directly affects battery performance and lifetime. Of particular interest is observing the structural and chemical evolution of this lithium-rich, extremely complex polycrystalline interface. Si nanowires are attractive materials for applications such as lithium battery anodes due to their high theoretical capacity and ultra-low-cost for material sourcing and fabrication. The use of electrochemically active metals such as Sn for the growth of Si nanowires contributes to the overall specific capacity of the electrode. This study explores the phase change in both the Si nanowire metal seed head and the nanowire SEI layer during battery cycling. Our goal is to investigate the effect a chosen seed metal has on the Si electrode. We show that the lithiation/delithiation behaviour of the Sn-Si nanowire obtained using liquid cell was comparable to the result from bulk half-cell cycles and ex-situ analysis. Finally, we compare the benefits and drawbacks of liquid cell in-situ electrochemistry to cryogenic TEM analysis of the same system. Although in-situ electrochemistry TEM offers many advantages over other characterisation techniques, this analysis method is still in its infancy. [more]

Reinforcement with ordered intermetallic precipitates is a potent strategy for the development of strength alongside damage tolerance and is central to the success of fcc nickel-based superalloys. Such a strategy is equally of interest within bcc-based systems for their increased melting point and acceptable cost. However, only limited studies have been made on refractory metal (RM) or titanium based alloys strengthened by ordered-bcc precipitates (e.g. B2 or L2₁). Are such “bcc superalloys” possible? Do they offer useful properties? In this talk, opportunities for refractory-metal-based superalloys systems will be discussed, including a review of Cr-Ni₂AlTi, Mo-NiAl, Ta-(Ti,Zr)₂Al(Mo,Nb) and Nb-Pd₂HfAl systems together with newly developed alloys. These alloys exploit an extensive two-phase field that exists between A2 (RM,Ti) and B2 TiFe to produce nanoscale precipitate reinforced microstructures that increase strength by over 500 MPa. This work was supported through EUROfusion Researcher Grant & EPSRC Doctoral Prize Fellowships, EPSRC ‘DARE’ (darealloys.org) EP/L025213/1 and Rolls-Royce/EPSRC Strategic Partnership EP/H022309/1 and EP/H500375/1. [more]