Speaker: Dr Wenshuo Xu, Department of Materials Science & Metallurgy, University of Cambridge

25 minutes plus questions unless stated otherwise (please arrive a few minutes early to start on time)

Drop in and explore the world of materials science through our table-top displays and interactive activities. Find out how we can make electricity from colourful windows, investigate how our technology wastes energy, see a wire change shape by itself and use a microscope to look at what’s inside a piece of metal.

Our activities are suitable for all ages, and researchers will be on hand to answer your questions! Come along and see how our world-leading science will power tomorrow’s technologies and have an impact on the world we live in.

Suitable for ages 5yrs+.

Speaker: James Moloney, Department of Materials Science & Metallurgy, University of Cambridge

25 minutes plus questions unless stated otherwise (please arrive a few minutes early to start on time)

Speaker: Dr Chiara Gattinoni, Dept. of Physics, Kings College, London

The behaviour of nanoscale forms of matter, such as thin films or nanocrystal, is strongly influenced by the structure and behaviour of their surfaces and interfaces. In nanoscale ferroelectrics, a surface charge arises as a consequence of the ferroelectric polarization itself, and this surface charge leads to an electrostatic instability – the so-called “polar catastrophe” – if it is not compensated. Here we show how the properties of ferroelectric materials at the nanoscale are intimately linked to the compensation mechanism that takes place at their surface. We also demonstrate how the structural and electronic properties of PbTiO₃, BiFeO₃ and KTaO₃ lead to a different compensation mechanism in each case, and we discuss how to harness the properties of these nanoscale materials for applications in microelectronics and catalysis.

http://talks.cam.ac.uk/talk/index/211096

Speaker: Dr Mehmet Egilmez, American University of Sharjah, UAE

High/medium entropy alloys have attracted great scientific and industrial interest during the last two decades. In general, these alloys consist of 3 to 7 (or more) elements in large percentages, which leads to a high degree of disorder and hence a very large configurational entropy. In these alloys, the utilization of a large number of elements results in rich compositional tuning, which in turn results in exciting mechanical, electrochemical, magnetic, and electronic functionalities.  The talk will present our recent efforts on the CoNiCr(V) medium-entropy system and TiZrNbSn shape memory alloy superconductor. The CoNiCr system is particularly interesting because it possesses exceptional mechanical properties across a wide range of temperatures, excellent corrosive resistance, electrochemical functionalities, and unique transport and magnetic properties. The extraordinary properties of this system not only are due to differences in atomic radii and electronic configurations of constituent elements but are also dependent on the magnetically driven chemical short-range order.

25 minutes plus questions unless stated otherwise (please arrive a few minutes early to start on time)

Speaker: Dr Mengfan Guo, Department of Materials Science & Metallurgy, University of Cambridge

25 minutes plus questions unless stated otherwise (please arrive a few minutes early to start on time)

Speaker: Dr Lutz Kirste, Fraunhofer Institute for Applied Solid State Physics (IAF), Freiburg, Germany.

http://talks.cam.ac.uk/talk/index/211093

Speaker: Professor Bilge Yildiz, Massachusetts Institute of Technology, Cambridge, USA

Abstract:

Exsolution is an effective approach to fabricating oxide-supported metal nanoparticle (electro-)catalysts via phase precipitation out of a host oxide. A fundamental understanding and control of the exsolution kinetics are needed to engineer the size, density and composition of exsolved nanoparticles to obtain higher catalytic activity toward clean energy and fuel conversion reactions, such as in solid oxide fuel and electrolysis cells. Since oxygen release via oxygen vacancy formation in the host oxide is behind oxide reduction and metal exsolution, we hypothesize that the kinetics of metal exsolution should depend on the kinetics of oxygen release. In this work, we probe the surface exsolution kinetics both experimentally and theoretically using thin-film perovskite oxide model systems, show its relation to the oxygen evolution kinetics, and tune it by external drivers including elastic strain and ion irradiation. Using both drivers, we couple to the formation of point defects and defect clusters, that serve as nucleation sites for nanoparticle exsolution. As a result, we can controllably tune size, density, composition and position of the exsolved metal nanoparticles. This finding can guide the design of exsolution electrocatalysts to advance the performance and durability of solid oxide electrochemical cells.

http://talks.cam.ac.uk/talk/index/211003

Speaker: Dr Remko Fermin, Department of Materials Science & Metallurgy, University of Cambridge

Abstract:
Generally, superconductivity and magnetism are two antagonistic processes. However, advances of the last 20 years have shown that, utilizing non-collinear magnetic layers or spin-orbit coupling, unconventional supercurrents can be generated that can penetrate ferromagnets over long length scales (so called long-range spin-triplet supercurrents). Even though the alternative generation of spin-triplet supercurrents using magnetic structures, such as domain walls and vortices, has been the subject of intense theoretical discussions, the relevant experiments remain scarce. During this talk, I will present our results on nanostructured Josephson junctions with a highly controllable spin texture, based on disk- and ellipse-shaped Nb/Co bilayers. We use the vortex magnetization of the cobalt in disk-shaped junctions to induce long-range triplet (LRT) superconductivity in the ferromagnet. Surprisingly, the LRT correlations emerge in highly localized (sub-80 nm) channels at the rim of the ferromagnet, despite its trivial band structure. We show that these robust rim currents arise from the magnetization texture acting as an effective spin–orbit coupling, which results in spin accumulation at the bilayer–vacuum boundary. Our approach, that combines micromagnetic modeling with microstructured SF-hybrids, presents a novel route towards studying effective spin-orbit coupling of magnetic textures, LRT generation and, realizing superconducting memory applications.

25 minutes plus questions unless stated otherwise (please arrive a few minutes early to start on time)

Speaker: Dr. Gina Greenidge, National Physical Laboratory, Teddington, UK.

Abstract: 

The interaction between metals and carbon has been of significant scientific and technological interest for hundreds of years. This work reports novel metallurgical methods to synthesize various carbon architectures for sustainable applications. Porous graphite was prepared by dealloying SiC in molten germanium and then excavating the Ge phase. Dealloying is a technique whereby nanoporous materials are produced via the selective dissolution of one or more components from an alloy. Here, the liquid metal dealloying (LMD) process was extended to non-metal precursors, demonstrating that carbide-derived carbons (CDCs) can be fabricated by this process. The dealloying depth, concentration profile, and length scale of the dealloyed microstructure were examined as they varied with immersion times and temperatures. The dealloying depth h varied with time as h ~ t1/2, and we also observed a buildup of Si concentration in the germanium in front of the dealloying interface. The porous graphite exhibited three-dimensional connectivity and a high degree of crystallinity, with an I(D)/I(G) ratio of 0.3 for samples dealloyed at the highest temperatures, as determined by Raman spectroscopy. Additionally, we have developed the first study on the preparation and characterization of freestanding nanostructured carbon materials produced by melt spinning nickel-carbon alloys with carbon fractions up to 12 at.% and iron-carbon alloys with carbon fractions of 17 at.%. The carbon was excavated by chemical dissolution of the metal. We performed a detailed study on the precipitation kinetics of carbon in nickel-carbon ribbon. The equilibrium solubility of carbon in Ni is only 2 at.% at the eutectic composition, but we attained metastable solid solubility, observing 2% lattice strain for an alloy spun at a linear velocity of 80 m/s; the lattice distortion was reversed via high temperature heat treatments. We also demonstrated the ability to tune the microstructure of carbon precipitated from the rapidly quenched ribbon by varying the carbon content from 4 – 12 at.% in the precursor and annealing the ribbon at temperatures that ranged from 400 – 1200 ℃. By the step-wise variation of these two parameters, we sequentially transformed amorphous carbon nanospheres into thick, highly crystalline flakes of graphite as determined by Raman spectroscopy and transmission electron microscopy.

More information: http://talks.cam.ac.uk/show/index/98965