Liquid morphologies and capillary forces between three spherical beads

Equilibrium shapes of coalesced pendular bridges in a static assembly of spherical beads are computed by numerical minimization of the interfacial energy. Our present study focuses on generic bead configurations involving three beads, one of which is in contact to the two others while there is a gap of variable size between the latter. In agreement with previous experimental studies, we find interfacial `trimer' morphologies consisting of three coalesced pendular bridges, and `dimers' of two coalesced bridges. In a certain range of the gap opening we observe a bistability between the dimer and trimer morphology during shrinking and growth. The magnitude of the corresponding capillary forces in presence of a trimer or dimer depends, besides the gap opening only on the volume or Laplace pressure of liquid. For a given Laplace pressure, the capillary forces in presence of a trimer are slightly larger than the force of a single bridges at the same gap opening, which could explain the shallow maximum and plateau of the capillary cohesion of a wetting liquid for saturations in the funicular regime

Quantification and localization of the liquid zone of partially remelted M2 tool steel using X-ray microtomography and scanning electron microscopy

The authors warmly thank Luc Morhain and Marc Wary (Arts et Métiers ParisTech CER Metz) for their technical support.Thixoforming of steels poses challenges due to the high temperatures involved and the lack of understanding of thermomechanical behavior. The volume fractions of the liquid and solid phases in the semi-solid state are the most important parameters for such a form-ing process, as they affect the viscosity and hence the flow behavior of the material. Two-dimensional observations might not always be sufficient, as the size distribution and the connectivity of phases cannot be obtained from associated measurements, which can only be determined by three-dimensional (3-D) investigation. This paper presents the first application of high-energy X-ray microtomography to the microstructure of steel in the semi-solid state. The microstructure of M2 high-speed tool steel was studied in both as-received and heated-and-quenched states. From the reconstructed images, 3-D information could be obtained and was compared with scanning elec-tron microscopy and energy dispersive spectrometry observations. The volume fraction and the location of liquid phase in the semi-solid state were determined in particular, and the continuous solid skeleton was investigated

Quantification and localization of the liquid zone of partially remelted M2 tool steel using X-ray microtomography and scanning electron microscopy

The authors warmly thank Luc Morhain and Marc Wary (Arts et Métiers ParisTech CER Metz) for their technical support.Thixoforming of steels poses challenges due to the high temperatures involved and the lack of understanding of thermomechanical behavior. The volume fractions of the liquid and solid phases in the semi-solid state are the most important parameters for such a form-ing process, as they affect the viscosity and hence the flow behavior of the material. Two-dimensional observations might not always be sufficient, as the size distribution and the connectivity of phases cannot be obtained from associated measurements, which can only be determined by three-dimensional (3-D) investigation. This paper presents the first application of high-energy X-ray microtomography to the microstructure of steel in the semi-solid state. The microstructure of M2 high-speed tool steel was studied in both as-received and heated-and-quenched states. From the reconstructed images, 3-D information could be obtained and was compared with scanning elec-tron microscopy and energy dispersive spectrometry observations. The volume fraction and the location of liquid phase in the semi-solid state were determined in particular, and the continuous solid skeleton was investigated

Computational Model for Predicting Particle Fracture During Electrode Calendering

In the context of calling for low carbon emissions, lithium-ion batteries (LIBs) have been widely concerned as a power source for electric vehicles, so the fundamental science behind their manufacturing has attracted much attention in recent years. Calendering is an important step of the LIB electrode manufacturing process, and the changes it brings to the electrode microstructure and mechanical properties are worth studying. In this work, we reported the observed cracking of active material (AM) particles due to calendering pressure under ex situ nano-X-ray tomography experiments. We developed a 3D-resolved discrete element method (DEM) model with bonded connections to physically mimic the calendering process using real AM particle shapes derived from the tomography experiments. The DEM model can well predict the change of the morphology of the dry electrode under pressure, and the changes of the applied pressure and porosity are consistent with the experimental values. At the same time, the model is able to simulate the secondary AM particles cracking by the fracture of the bond under force. Our model is the first of its kind being able to predict the fracture of the secondary particles along the calendering process. This work provides a tool for guidance in the manufacturing of optimized LIB electrodes

Coleções de Referência e Bancos de Dados de Estruturas Vegetais: Subsídios para Estudos Paleoecológicos e Paleoetnobotânicos

Interpretation of Quaternary palaeoenvironmental and palaeoclimatic data relies upon comparison with extant ecosystems. For that reason, palaeoecologic studies based in plant micro- or macro-remains analyses depend on a good knowledge of the present flora and vegetation, as well as of the morphologic characteristics and structure of the analyzed elements. Constitution of comparative collections and databases is an invaluable tool to these studies, especially in tropical regions, where the high biodiversity engenders as yet a poor knowledge of the morphology and structure of plant remains susceptible of preservation in sediments (palinomorphs, wood, charcoal, phytoliths etc.). Reference collections of wood, charcoal, pollen grains, phytoliths, and seeds are being assembled through field trips and institutional donations. Databases associated to computer-based determination keys to anthracology and palynology are also under development.A interpretação dos dados paleoambientais e paleoclimáticos do Quaternário é feita por comparação com ecossistemas atuais. Por isso, estudos paleoecológicos baseados em análises de macro- ou micro-restos vegetais dependem de um bom conhecimento da flora e da vegetação atual, assim como das características morfológicas e da estrutura dos elementos analisados. A constituição de coleções de referência e de bases de dados é um suporte indispensável para a realização destes estudos, especialmente em regiões tropicais, onde a grande biodiversidade existente faz com que a morfologia e a estrutura das partes vegetais passíveis de preservação nos sedimentos (palinomorfos, madeira, carvão, fitólitos etc.) seja ainda relativamente mal conhecida. Coleções de referência de madeira, carvão, pólen e, incipientemente, fitólitos e frutos estão sendo constituídas através de coletas de campo e de doações de herbários e xilotecas. Bancos de dados associados a chaves informáticas de determinação para antracologia e palinologia também estão em desenvolvimento