Events: Fysik events at Chalmers University of TechnologyTue, 27 Oct 2020 11:13:50 +0100 Shoja, Materials Science<p>Online via Zoom</p><p>​ Title of thesis: Microstructure and plastic deformation of textured CVD alumina coatings. Follow the presentation online​</p><h2 class="chalmersElement-H2">​Abs​tract: </h2> <div><span style="background-color:initial">It is known that the wear performance of<em> α</em>-alumina coatings produced by chemical vapor deposition (CVD) is significantly influenced by the type and degree of texture. However, the main reasons behind this behavior are not fully understood. This thesis contains studies of two related topics for increasing the understanding of <em>α</em>-alumina coatings. The first topic concerns the microstructure and texture development of CVD <em>α</em>-Al<sub>2</sub>O<sub>3 </sub>coatings, and the second topic concerns calculations and analysis of the Schmid factors (<em>m</em>) for coatings with different textures. By combining different analysis methods (such as XRD, SEM, FIB/SEM, TKD, TEM, STEM, XEDS), and theoretical and experimental Schmid factor analysis by MATLAB and EBSD, the microstructure and plastic deformation of <em>α</em>-alumina coatings were investigated.</span></div> <div> </div> <div><br /></div> <div> </div> <div>The microstructures of three different CVD <em>α</em>-Al<sub>2</sub>O<sub>3</sub> layers deposited onto a Ti(C,N,O) bonding layer were studied. Grain boundary diffusion of heavy elements from the substrate to the bonding layer/<em>α</em>-Al<sub>2</sub>O<sub>3</sub> interface was observed. This may be the cause of a disturbance in the early growth of <em>α</em>-Al<sub>2</sub>O<sub>3</sub>. Additionally, it was found that the number of interfacial pores at the bonding layer/<em>α</em>-Al<sub>2</sub>O<sub>3</sub> interface increased by introducing the H<sub>2</sub>S gas. The H<sub>2</sub>S gas also promoted an earlier development of the (0001) texture. The orientation of the grains was developed to the desired texture both as a gradual change over several grains and as an abrupt transformation from one grain to another.</div> <div> </div> <div><br /></div> <div> </div> <div>The probability of plastic deformation in different wear zones on the rake face of a cutting tool was investigated theoretically and experimentally by analyzing Schmid factors for textured <em>α</em>-Al<sub>2</sub>O<sub>3</sub> coatings. Schmid factor diagrams were constructed using MATLAB/MTEX and used to extract frequency distributions for different slip systems and textures. The results were compared with lateral distribution maps of Schmid factors obtained from experimental coatings. It was observed that basal slip is most easily activated in the transition zone, followed by prismatic slip systems 1 and 2 in coatings with an (0001)-texture. The homogeneous plastic deformation behavior observed in this coating is also connected to mostly high Schmid factors in the <em>m</em>-value distribution. The differences between the <em>m</em>-value distributions for the three slip systems are not that pronounced in the (011 ̅​2) and (112 ̅0) textures, and the distributions are relatively wide. The low wear rate and more homogeneous deformation of the coating with (0001) texture compared to the other coating textures may be the result of the high plasticity, offered by the easy activation of basal slip and prismatic 1 slip, and the low spread of Schmid factor values at the transition zone.</div> <div> </div> <div>In conclusion, the results presented in this thesis form a knowledge platform that can be used to understand the microstructure and wear mechanisms of textured CVD <em>α</em>-alumina coatings.</div> webinar: Electromagnetic and Quantum Transport in the Multiphysics Modeling of Nanodevices<p>Online</p><p>​Luca Pierantoni, Università Politecnica delle Marche, Italy Join on Zoom:​ Password: 2d-tech211</p>​Abstract:<div>TBA [WP Energy]</div> <div><br /></div> – A silver bullet in the energy system?<p></p><p>Welcome to a webinar organized by Chalmers Energy and Transport Areas of Advance. When: 4 November 2020, at 12:00-13:45. Place: Online. Platform Zoom. Last day to register 29 October.</p>​<span style="background-color:initial">T<span style="font-weight:700">​</span>he energy and transport sectors need to be radically restructured to meet the Paris Agreement. By 2045, the Swedish aim is to have no net emissions of greenhouse gases into the atmosphere. A huge challenge.</span><div><span style="background-color:initial">H</span><span style="background-color:initial">ow do we transform the industry, heavy transport, aviation and shipping? Hydrogen is pointed out by many as part of the solution.</span><br /></div> <div><br /></div> <div>“The new hydrogen economy can become a growth engine that helps us out of the economic crisis created by Covid19”, said Frans Timmermans, Vice-President of the European Commission this summer in connection with the presentation of A Hydrogen Strategy for a Climate Neutral Europe.</div> <div><br /></div> <div>The strategy shows that hydrogen can play a key role in several areas.</div> <div><span style="font-weight:700"></span><br /></div> <div>During the webinar, we will hear about the view on hydrogen in Europe as well as research results on how fuel cells can be improved. The participants in the panel will th<span style="font-weight:700"></span>ereafter discuss the role hydrogen can play in a number of different areas, such as shipping, aviation, heavy road transport, the process industry and the electricity system.</div> <div><br /></div> <a href=""><img class="ms-asset-icon ms-rtePosition-4" src="/_layouts/images/icgen.gif" alt="" /></a> <a href=""><div style="display:inline !important">Register to the seminar</div></a><div><br /></div> <div><span style="font-weight:700">Program</span><ul><li><span style="background-color:initial">12.00 The seminar starts. </span>Moderator: <a href="/en/staff/Pages/anders-adahl.aspx">Anders Ådahl</a>, Energy Area of Advance Co-Director.</li> <li>“Main possibilities and challenges for using hydrogen in the energy and transport sector​”​, <a href="/en/Staff/Pages/maria-grahn.aspx">Maria Grahn</a>, Senior researcher, department of Mechanics and Maritime Science. Maritime Environmental Science. Director of Energy Area of Advance.</li> <li>“The view on hydrogen in Europe”, <a href="">Thierry Lepercq​</a>, founder of Soladvent. Former Executive Vice-President in charge of Research &amp; Technology and Innovation, ENGIE. Author of the book &quot;Hydrogen is the new oil&quot;.​<br /></li> <li>“Improved fuels cells to enable a sustainable energy system”, <a href="/en/staff/Pages/Björn-Wickman.aspx">Björn Wickman​</a>, Associate Professor, Chemical Physics, Department of Physics, Chalmers.<br /></li> <li>5 minutes coffe break.</li></ul> <div><span style="font-weight:700">The one hour lecture will be followed by a panel discussion. <br /></span><br /></div> <div><span style="font-weight:700">Panel: </span><br /><span style="font-weight:700"></span><div><ul><li><a href="/en/Staff/Pages/karin-andersson.aspx">Karin Andersson</a>, Professor in Maritime Environmental Science Expert in sustainable shipping, Chalmers. </li> <li><a href="/en/staff/Pages/tomas-gronstedt.aspx">Tomas Grönstedt</a>, Professor at Fluid Dynamics/Mechanics and Maritime Sciences, Chalmers.</li> <li><a href="">Anna-Karin Jannasch</a>, Rise, Director of the Swedish testbed for hydrogen electrolysis and industrial application </li> <li>Monica Johansson, Principal Energy &amp; Fuel Analyst, Volvo group. Expert in alternative fuels, with knowledge in hydrogen infrastructure. </li> <li><a href="/en/Staff/Pages/koopmans.aspx">Lucien Koopmans</a>, Professor, head of the division Combustion and Propulsion Systems, Chalmers.</li> <li>Mattias Wondollek, Program Director, <a href="">Energiforsk</a>. </li></ul></div></div></div> webinar: Optical signatures of strongly correlated electrons in two dimensional semiconductors<p>Online</p><p>​Atac Imamoglu, ETH Zurich, Switzerland Join on Zoom: Password: 2d-tech111</p>​​Abstract:<div>TBA</div> <div><br /></div> Tiburski, Physics<p>FB, lecture hall, Fysikgården 4, Fysik Origo, (an online via Zoom)</p><p>​Title of thesis: &quot;Alloy plasmonics: Fundamentals and application in catalysis</p><h2 class="chalmersElement-H2">Abstract:</h2> <div>Alloys have for a long time been important in the development of our society; from the bronze age, where man learned how to alloy copper with tin, to today, where many products are made of steel and aluminum alloys. Similarly, but maybe not as generally well known, also in heterogeneous catalysis alloys are explored to develop solutions to increase activity and selectivity of chemical processes. Furthermore, alloys have lately been proposed as a new paradigm in nanophotonics, as a means to tailor optical properties of nanomaterials that find applications within telecommunication, sensing, or biotechnology. Nanophotonics and catalysis, separately and in combination, are the focus of this thesis. Specifically, we have compiled a library of alloy complex dielectric functions for the late transition metals by utilizing time-dependent density-functional theory. The calculated dielectric functions were benchmarked by (i) nanofabricating series of alloy nanoparticle arrays with systematically varying composition, (ii) measuring their plasmonic properties, and (iii) comparing these properties with electrodynamic simulations of alloy nanoparticles, using the dielectric function library as the input.  <br /><br />The second theme in this thesis is plasmon-enhanced catalysis. In this field there is a continuous discussion regarding the reaction enhancing mechanisms when noble metal catalyst nanoparticles are irradiated with visible light during a catalytic reaction.  Here we investigated the role of photothermal enhancement of reactions by tailoring the catalytic activity of nanofabricated particles without radiation by means of alloying Pd with Au, while keeping the optical absorption cross-section constant, as confirmed by electrodynamics simulations using our dielectric function library as the input.​<br /></div> Brem, Physics<p>PJ, seminar room, NOTE! Entrance via Fysikgården 2 for external visitors</p><p>Title of thesis: &quot;Microscopic theory of exciton dynamics in two-dimensional materials</p><h2 class="chalmersElement-H2">Abstract:</h2> <div><span style="background-color:initial">When a material is illuminated with light, electrons jump from their ground state to an excited level and leave a “hole” behind. This hole is positively charged and attracts the negative electron. In atomically-thin films of transition metal dichalcogenides (TMDs), a new class of quantum materials, the forces between electrons and holes are so strong that they start to orbit each other and form extremely stable pairs, so-called excitons. The concept of excitons was already introduced by Yakov Frenkel in 1931 but just the recent development of atomically-thin TMDs has brought excitons into the focus of material research. These 2D materials have the potential to revolutionize the electronics industry by enabling new nanoscale device concepts. However, the key to technological applications of TMDs is a fundamental understanding of excitons.</span></div> <div> </div> <div><br /></div> <div> </div> <div>In this work we have developed a theoretical model of excitons in TMDs. We provide microscopic insights into the motion of excitons and their interaction with light or crystal vibrations. In particular, we identify the impact of hidden so-called dark states. We also show how exciton properties change when two different TMDs are stacked. Here, we discuss how the resulting super periodic crystal structure, the moire pattern, can trap excitons into an array of light emitters. We applied our theoretical models to explain a large variety of experiments and gained microscopic insights into the dynamics of excitons in 2D quantum materials.</div> webinar: Design and potential applications of nanomaterial in food packaging<p>Online</p><p>​Guidetti Gloria, Tetrapak Packaging, Modena, Italy  Join on Zoom:​​46 Password: 2d-tech311</p>​Abstract: <div>TBA</div> <div><br /></div> webinar: Combining 2D and 1D nanomaterials towards smart electronics for wireless applications<p>Online</p><p>​George Deligeorgis, Foundation for Research &amp; Technology Hellas, Crete, Greece​ Join on Zoom: Password: 2d-tech141</p>​​Abstract:<div>TBA <span style="background-color:initial">[WP Energy]​</span></div> <div><span style="background-color:initial"><br /></span></div>