Cone geometry optimization and thermal behavior for lithium-ion battery separators

A 3D cone separator geometry for lithium-ion batteries has been optimized taking into account the increase of radius size of one side. Theoretical simulations have been carried out for evaluating the influence of radius size in the cone structure at different discharge rates (1 C and 60 C) in which it was also determined the produced ohmic heat. The value of the discharge capacity in the cone structure depends on the increases of the radius, which is correlated with the electrolyte volume and interface between free electrolyte/cathode. The optimum balance of these parameters is essential for obtaining higher battery performance through this geometry that can be used in the next generation of lithium-ion batteriesPortuguese Foundation for Science and Technology (FCT): UID/FIS/04650/2019, PTDC/CTMENE/5387/2014, UID/CTM/50025/2013, PTDC/FIS-MAC/28157/2017, grant SFRH/BPD/112547/2015 (C.M.C.) and contract CEECIND/00833/2017 (R.G.), including FEDER funds through the COMPETE 2020 Programme and National Funds through FCT. Financial support from the Basque Government Industry Department under the ELKARTEK and HAZITEK programs is also acknowledged. F. Miranda was also supported by Portuguese funds through the CIDMA - Center for Research and Development in Mathematics and Applications, and the Portuguese Foundation for Science and Technology (“FCT - Fundação para a Ciência e a Tecnologia”), within project UID/MAT/04106/201

Theoretical simulation of different 3D separator geometries for lithium-ion batteries

The battery separator is an essential component of batteries and affects their cycling performance. In this work, the effect of different 3D geometries of the battery separator on battery performance was studied keeping the same volume. It was observed that the different geometries affect the cycling performance, the best geometry being the perforated one that cycled up to 90 C. The cycling performance is affected by parameters such as the separator thickness and the electrolyte volume. Through the control of the battery separator geometry it is possible to obtain high performance lithium-ion batteries.Portuguese Foundation for Science and Technology (FCT): UID/FIS/04650/2019, PTDC/CTMENE/5387/2014, UID/CTM/50025/2013, PTDC/FIS-MAC/28157/2017, grant SFRH/BPD/112547/2015 (C.M.C.) and contract CEECIND/00833/2017 (R.G.), including FEDER funds through the COMPETE 2020 Programme and National Funds through FCT. Financial support from the Basque Government Industry Department under the ELKARTEK and HAZITEK programs is also acknowledged. F. Miranda was also supported by Portuguese funds through the CIDMA - Center for Research and Development in Mathematics and Applications, and the Portuguese Foundation for Science and Technology (“FCT - Fundação para a Ciência e a Tecnologia”), within project UID/MAT/04106/2013

Understanding drop spreading behaviour on WC-10wt%Co cutting tools – an experimental and numerical study

WC-Co cutting tools performance under demanding cutting conditions largely depend on the efficiency of the cutting fluid, mainly its ability to remove heat and reduce friction, both highly dependent on the wettability and drop spreading behaviour of the fluid. In this context, this study focuses on the spreading behaviour of machining cutting fluid and water in WC-10 wt%Co cutting tools surface. Contact angles were experimentally measured and then used for performing numerical simulations by the level set method. A contact angle of 75.3˚ and 92.8˚ were measured for the machining cutting fluid and distilled water, respectively, and coincident values were found by numerical simulation, as well as a strong agreement in the drop shape. It was also possible to observe that machining cutting fluid has a lower spreading time than water, due to a lower contact angle and higher viscous dissipation, allowing to reach equilibrium phase sooner. Also, the machining cutting fluid presents a higher drop radius than water, meaning a 24.2% contact area increase over 50 ms of spreading time. Furthermore, numerical simulation showed that the drops spreading over the capillary-inertial time, at the early stage of spreading, follow an exponential dependency with a spreading factor of approximately t1/2, which indicates that the initial spreading of both drops is driven and controlled by the balance between inertial and capillary forces. This work intends to contribute to the knowledge on the phenomena that drive the drop spreading behaviour on WC-10 wt%Co cutting tools, being the development of numerical models to predict this behaviour of utmost importance, since it can lead to the development of novel surface improved tools, with an enhanced lubrification effect and heat removal capacity closer to the cutting zone during machining processes, and consequently allowing an improvement in the tribological and cutting performance of these toolspublishe

Luttinger liquid superlattices

We calculate the correlation functions and the DC conductivity of Luttinger liquid superlattices, modeled by a repeated pattern of interacting and free Luttinger liquids. In a specific realization, where the interacting subsystem is a Hubbard chain, the system exhibits a rich phase diagram with four different phases: two metals and two compressible insulators. In general, we find that the effective low energy description amalgamates features of both types of liquids in proportion to their spatial extent, suggesting the interesting possibility of `engineered' Luttinger liquids.Comment: RevTeX, 5 pages, 3 figure

Development of a Brazilian maize core collection

The aim of this study was to evaluate methods for developing a Brazilian maize core collection. For an initial survey of the active collection, passport information, as well as characterization and evaluation of accessions, were taken into consideration, these then being divided according to geographic region and kernel-type. Multiple sampling methods were evaluated. The strategy of constant sampling generated extensive alterations in extract accession frequency. The multivariate strategy with dispersion graphs and principal components associated with the Tocher method was considered efficient for identifying the most divergent genotypes. The multivariate strategy generated greater alterations in the variance of traits. The average number of traits revealed few modifications with the various sampling strategies used. Therefore, the active collection could be considered as possessing a satisfactory amount of information for most of its accessions. Moreover, the multivariate strategy generated modifications in the variance of the traits, independent of sampling intensity