Events: Centre: Physics Centre events at Chalmers University of TechnologyFri, 25 Nov 2022 12:52:25 +0100 Rosander, Physics<p>PJ, seminar room, Fysik Origo, Campus Johanneberg</p><p>Title​: Lattice dynamics in perovskites for green energy applications: A theoretical perspective</p>​<div><strong>Abstract</strong>: <span style="background-color:initial">Electrolyzers and fuel cells are used in green energy applications, electrolyzers split water to produce hydrogen, which can then be used in fuel cells to produce energy. Oxide perovskites have shown favorable properties for applications in this area, e.g., as electrolyte and cathode material in fuel cells and electrolyzers. The important property is the conductivity of protons, which depends sensitively on the hydrogen concentration and mobility. The concentration depends on the efficiency of the hydration reaction, which is the primary way to incorporate protons in perovskites. An example of an excellent proton conductor is acceptor doped BaZrO3. Hence, some of the most crucial material properties derive from defect properties. This thesis also explore the halide perovskites CsPbBr3, which have proven to be auspicious for photovoltaics. Insights into phase stability, phase transitions and the underlying dynamics in these materials are crucial. Thus, the understanding of microscopic properties is the cornerstone of this thesis.</span></div> <div><br /></div> <div>In the present thesis, density functional theory is utilized to obtain training data for construction of potentials. The potentials that have been used are either force constant potentials or neural network potentials. The potential are then used to run lattice dynamics. To vastly extend the total simulation time or simply decrease the computational time, graphical processing units are also employed. Furthermore, defect models are applied to understand reaction kinetics.</div> <div><br /></div> <div>More specifically, the vibrational defect thermodynamics of BaZrO3 was examined within the harmonic approximation. We also elaborate on the soft antiferrodistortive phonon mode found in this material using self-consistent phonons and molecular dynamics. This soft mode, should ultimately be the deciding factor for which structure \ch{BaZrO3} exhibit at low temperatures. Similar methods were also employed to investigate phonon dynamics in the very anharmonic perovskite, CsPbBr3. These type of insights can, e.g., further guide the development of new materials by fine-tuning of properties​</div> Graphene-based biosensors for bacterial infection<p>PJ, seminar room, Kemigården 1, Fysik Origo</p><p>​​​​Welcome to a seminar in the series SmallTalks [about Nanoscience] arranged by the Excellence Initiative Nano​. Speaker: Flavia Ferrara, Doctoral Student at Chemistry and biochemistry/Chemistry and Chemical Engineering</p>​Abstract:<div>Ever heard of the word triazole? well, what if I say that a triazole is a molecule that can be useful to detect bacterial infections? In the presentation, I will go through the making of a ´´Biosensor´´. In this device, triazoles are put together to form a receptor having selective interactions with some peptides derived from bacterial disease. This receptor will then be attached to graphene that, thanks to its formidable conductive properties, will give us an easily detectable signal when the interaction occurs.​<br /></div> Wikström, MPPHS<p>Kemigården 1, main entrance, Main entrance, Fysik Origo, Division of Subatomic, High Energy and Plasma Physics, F-N6115</p><p>​​Title of Master thesis: Non-Supersymmetric AdS Solutions in Type IIB String Theory</p><strong>​Abstract:</strong><div><div>The thesis focuses on an AdS vacuum solution in type IIB string theory. The vacuum can be deformed to become non-supersymmetric while remaining perturbatively stable. This makes the vacuum solution relevant to a swampland conjecture which states that stable, non-supersymmetric AdS solutions can not be consistent in quantum gravity.</div></div> Particle acceleration and radiation generation by intense lasers<p>PJ, seminar room, Fysik Origo, Campus Johanneberg</p><p>Welcome to a workshop with the title​ &quot;Particle acceleration and radiation generation by intense lasers&quot;, in PJ Seminar room, December 15.</p><p style="font-size:16px">Program</p> <p style="font-size:16px"><span style="font-size:14px;background-color:initial">Chair: </span><strong style="font-size:14px;background-color:initial">Tünde Fülöp</strong></p> <p>09:00–09:30 <strong>Andrea Macchi</strong> (University of Pisa): &quot;Surface plasmon acceleration without a grating&quot;<br /> <br /> 09:35–10:05 <strong>Charlotte Palmer</strong> (Queen's University, Belfast): &quot;Automation and optimisation of laser-driven high-repetition rate proton sources&quot;<br /> <br /> <em>10:05–10:40 Coffee break</em><br /> <br /> 10:40–11:10 <strong>Vojtech Horný</strong> (<span style="background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-attachment:initial;background-origin:initial;background-clip:initial">LULI—CNRS; École Polytechnique, CEA)</span>: &quot;Unfeasibility of the laboratory r-process studies with laser-driven neutron source&quot;<br /> <br /> 11:15–11:45 <strong>Arkady Gonoskov</strong> (Gothenburg University): &quot;Prospects for studying extreme regimes of radiation reaction using electron-light colliders&quot;<br /> <br /> <em>11:45–13:15 Lunch break</em><br /> <br /> 13:15–13:45 <strong>Caterina Riconda</strong> (Sorbonne University/Chalmers): &quot;Laser-driven pair production : from soft shower to avalanche&quot;<br /> <br /> 13:50–14:20 <strong>Tom Blackburn</strong> (Gothenburg University): &quot;QED plasma physics: what's next?&quot;<br /> <br /></p> <p>14:25<span style="background-color:initial">–</span><span style="background-color:initial">14:55</span><strong style="background-color:initial"> Dominika Maslarova</strong><span style="background-color:initial"> (Institute of Plasma Physics of the Czech Academy of Sciences): &quot;Deflection of positrons from the Breit-Wheeler pair creation by a multi-PW laser pulse&quot;</span></p> <p><span style="background-color:initial"><br /></span></p> <p><span style="background-color:initial">15:00</span><span style="background-color:initial">–</span><span style="background-color:initial">15:30 </span><strong style="background-color:initial">Hélène Coudert-Alteirac</strong><span style="background-color:initial"> (Gothenburg University): &quot;Attohallen: Gothenburg's attosecond science facility&quot;</span></p> <p><span style="background-color:initial"><br /></span></p> <p><span style="background-color:initial"></span><span style="background-color:initial">15:30 Visit to Attohallen</span></p> <div><br /></div> <p><br /></p> <p></p> <p><em>The workshop is part of the Knut and Alice Wallenberg Foundation's funded project: </em><a href=""><em>IXREP - Intense XUV and Relativistic Electron Pulses</em></a><em>. </em></p> <div><br /></div> Rizell, Physics<p>FL51, lecture room, Fysik, Campus Johanneberg</p><p>Ti​tle: Alkali metal stripping and plating in liquid electrolytes</p>​<div><strong>Abstract</strong>: Batteries have relatively modest energy densities compared to fossil fuels. In the efforts to make battery-driven transport solutions and technologies competitive with gasoline-powered alternatives, it is important to develop batteries with higher energy densities. This can be enabled by utilizing different electrode materials than what is currently done. For instance, lithium metal is one of the electrode materials which can enable the highest theoretical energy densities. Similarly, using metal anodes can pave way for more sustainable materials solutions based on e.g. sodium, potassium or magnesium. During charging in batteries with a metal anode, ions from the electrolyte are plated on the electrode, and during discharge, the metal is stripped from the electrode. These processes are associated with several problems hindering the practical application of metal anodes. For instance, dendritic or uneven growth can cause short circuits and lead to loss of active material. Further, side reactions can consume both electrolyte and active material. A fundamental understanding of the stripping and plating process is needed to solve these problems. In this thesis, electrochemical measurements are used to understand the fundamental steps of the alkali metal plating and stripping process using Li and K metal electrodes. Additionally, the impact of the electrolyte composition, particularly the salt concentration, on alkali metal anodes is investigated. Cycling performance is evaluated and interphase formation is probed with in situ neutron reflectometry.​</div>éas-Sundstrom-221216.aspxéas Sundström, Physics<p>PJ, seminar room, Fysik Origo, Campus Johanneberg</p><p>​Title: Collisional effects and attosecond diagnostics in laser-generated plasmas</p>​<div><strong>Abstract</strong>: <span style="background-color:initial">When matter is radiated by laser light of extreme intensity, it is rapidly ionized, thereby forming a plasma. Such laser-generated plasmas can be used as sources of energetic particles and radiation, or to study astrophysically relevant phenomena in the laboratory and the behavior of matter under extreme conditions. This thesis considers the dynamics and diagnosis of laser-induced plasmas, with focus on the effect of Coulomb collisions on electrostatic shocks and laser-energy absorption, as well as ultra-rapid plasma diagnostics using attosecond pulses.</span></div> <div><br /></div> <div>Electrostatic shocks in plasmas have the potential to accelerate ions with a very narrow energy spread. First, collisional effects on electrostatic shocks are studied in two regimes of low and high collisionality. In the former, we show that even rare collisions can significantly affect the structure of the electrostatic shock over long time scales due to an accumulation of trapped ions. The high-collisionality case was studied using particle-in-cell simulations of laser foil targets. Effective ion acceleration by electrostatic shocks relies on a high electron temperature. Heating of the upstream ions, through collisions with the shock-accelerated ions, creates a self-amplifying process that increases the fraction of accelerated ions. However, this unstable condition rapidly depletes the energy of the shock, which transitions into a blast wave, unable to accelerate ions.</div> <div><br /></div> <div>An additional study of the same laser--solid interaction shows that, unlike the commonly held knowledge, collisions may dominate the energy absorption of ultraintense laser pulses through inverse bremsstrahlung, and also causing rapid thermalization of the target electrons.</div> <div><br /></div> <div>Finally, two diagnostic methods for the electron density utilizing attosecond extreme-ultraviolet pulses, are presented. The first method is based on the dispersion of a probe pulse, which can be used to infer information about the peak density and line-integrated density of the probed plasma. The second method is based on stimulated Raman scattering, which uses two pulses, and can give a localized reading of the electron density in the interaction regions where the two pulses meet.</div> Olsson, Materials Science<p>PJ, seminar room, Fysik Origo, Campus Johanneberg</p><p>​Title: Multiscale x-ray characterisation of cellulose-based solid dispersions</p>​<div><strong>Abstract</strong>: <span style="background-color:initial">Cellulose-based solid dispersions are a promising formulation strategy for providing controlled drug release and dissolution enhancement of poorly soluble drugs. These dispersions can from structures on multiple length scales which can have both positive and negative effects on the functional properties of the formulation. For instance, phase separated morphologies can affect the solubility and release profile of a drug dispersion. Such structures can form both during the processing step or evolve during storage and dissolution. For the development of new pharmaceutical dosage forms and drug delivery systems it is important to develop a better understanding of how these structures are formed and how they will affect the properties of the dispersion. A first step towards establishing this is to develop methodologies for structural characterisation over multiple length scales. </span></div> <div><br /></div> <div>This thesis explores the use of X-ray analysis methods to reveal relationships between structures and morphologies of cellulose-based dispersions to the processing conditions and functional properties of the formulation. The focus is to develop methodologies for multiscale structural characterisation that address the challenges of the inherently low contrast between phases of similar densities and the high sensitivity for radiation damage. In this thesis I show how scanning small and wide-angle X-ray scattering (SAXS and WAXS), ptychographic X-ray computed nanotomography (PXCT) and scanning transmission X-ray microscopy (STXM) can be applied and combined to evaluate multiscale morphologies. First, a partly crystalline solid dispersion of carbamazepine dispersed in ethyl cellulose is imaged with scanning SAXS and WAXS as well as PXCT to develop a workflow for multiscale imaging of solid dispersions. This demonstrates how the nanostructure and type of polymorph can be mapped over a macroscopic sample and image the interior structure of the dispersion with a resolution of 80 nm over an extended sample volume. Secondly, phase separated polymer blends of PLA and HPMC, intended as a polymeric carrier for controlled drug release, are imaged with PXCT and STXM. This reveals the drug distribution as well as the morphology of the two polymer phases, which is related to the dissolution profile of the dispersions, showing a release rate dependent on the morphology of the compound. Finally, the molecular arrangement in melt pressed films is investigated with WAXS to explore changes from water exposure of modified cellulose and relate it to the substituted side chains in the cellulose derivative.​</div>