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1. Polymer blend-filled nanoparticle films via monomer-driven infiltration of polymer and photopolymerization

   https://doi.org/10.1039/C7ME00099E  

   Qiang, Yiwei; Manohar, Neha; Stebe, Kathleen J.; Lee, Daeyeon (January 2018, Molecular Systems Design & Engineering)

   Incorporation of nanoparticles into polymer blend films can lead to a synergistic combination of properties and functionalities. Adding a large concentration of nanoparticles into a polymer blend matrix via conventional melting or solution blending techniques, however, is challenging due to the tendency of particles to aggregate. Herein, we report a straightforward approach to generate polymer blend/nanoparticle ternary composite films with extremely high loadings of nanoparticles based on monomer-driven infiltration of polymer and photopolymerization. The fabrication process consists of three steps: (1) preparing a bilayer with a nanoparticle (NP) layer atop a polymer layer, (2) annealing of the bilayer with a vapour mixture of a monomer and a photoinitiator, which undergoes capillary condensation and imparts mobility to the polymer layer and (3) exposing this film to UV light to induce photopolymerization of the monomer. The monomer used in this process is chemically different from the repeat unit of the polymer in the bilayer and is a good solvent for the polymer. The second step leads to the infiltration of the plasticized polymer, and the third step results in a blend of two polymers in the interstices of the nanoparticle layer. By varying the thickness ratio of the polymer and nanoparticle layers in the initial bilayers and changing the UV exposure duration, the volume fraction of the two polymers in the composite films can be adjusted. This versatile approach enables the design and engineering of a new class of nanocomposite films that contain a nanoscale-blend of two polymers in the interstices of a nanoparticle film, which could have combinations of unique mechanical and transport properties desirable for advanced applications such as membrane separations, conductive composite films and solar cells. Moreover, these polymer blend-filled nanoparticle films could serve as model systems to study the effect of confinement on the miscibility and morphology of polymer blends. 

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2. The Diabatic Rossby Vortex: Growth Rate, Length Scale, and the Wave–Vortex Transition

   https://doi.org/10.1175/JAS-D-22-0022.1  

   Kohl, Matthieu; O’Gorman, Paul A. (October 2022, Journal of the Atmospheric Sciences)

   Abstract In idealized simulations of moist baroclinic instability on a sphere, the most unstable mode transitions from a periodic wave to an isolated vortex in sufficiently warm climates. The vortex mode is maintained through latent heating and shows the principal characteristics of a diabatic Rossby vortex (DRV) that has been found in a range of different simulations and observations of the current climate. Currently, there is no analytical theory for DRVs or understanding of the wave–vortex transition that has been found in warmer climates. Here, we introduce a minimal moist two-layer quasigeostrophic model with tilted boundaries capable of producing a DRV mode, and we derive growth rates and length scales for this DRV mode. In the limit of a convectively neutral stratification, the length scale of ascent of the DRV is the same as that of a periodic moist baroclinic wave, but the growth rate of the DRV is 54% faster. We explain the isolated structure of the DRV using a simple potential vorticity (PV) argument, and we create a phase diagram for when the most unstable solution is a periodic wave versus a DRV, with the DRV emerging when the moist static stability and meridional PV gradients are weak. Last, we compare the structure of the DRV mode with DRV storms found in reanalysis and with a DRV storm in a warm-climate simulation. Significance Statement Past research has identified a special class of midlatitude storm, dubbed the diabatic Rossby vortex (DRV), which derives its energy from the release of latent heat associated with condensation of water vapor and as such goes beyond the traditional understanding of midlatitude storm formation. DRVs have been implicated in extreme and poorly predicted forms of cyclogenesis along the east coast of the United States and the west coast of Europe with significant damage to property and human life. The purpose of this study is to develop a mathematical theory for the intensification rate and length scale of DRVs to gain a deeper understanding of the dynamics of these storms in current and future climates. 

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3. The origin and micromechanics of the preferential orientation of crystals in mush

   Carrara, AC; Bergantz, G (July 2023, Gochemical Society)

   none (Ed.)

   An obstacle to developing a general mechanical framework for magma mush is the emergence and complexity of a crystal fabric. To illuminate the conditions that produce a crystal fabric we performed time-dependent numerical simulations using a Computational-Fluid-Dynamics and Discrete-Element-Method (CFD-DEM) model in three dimensions. The specific focus was on the role of shear strain in the creation of a preferential orientation of crystals in mush. CFD-DEM method allows for the simultaneous coupling and frictional interactions of melt and crystals undergoing shear strain. The crystal shapes are represented using spheroids (either oblate or prolate). Simulations consist in imposing a compression stress (pressure) and a simple shear to a dense suspension of crystals in a viscous liquid, and monitoring the evolution of the orientation and strength of the shape fabrics. We ran a series of simulations by varying the size and aspect ratio of the particles. We considered samples in which all the solids have the same volume and shape, and cases including size and aspect ratio distributions. Results show that the strength of the shape fabric and the angle between the crystal preferential orientation and the compression plane both increase with the shear strain up to steady state values, which are primarily controlled by the aspect ratio of the particles. The stronger the aspect ratio, the greater the magnitude of the preferential orientation and the lower its angle relative to the compression plane. When introducing a distribution in the size of the crystals, we observed a decrease in the strength of the shape fabric and an increase in the angle between the preferential orientation of the crystals and the compression plane compared with samples composed of crystals having the same shape and size. Similarly, the distribution in the aspect ratio further decreases the strength of the shape fabric and increases the angle between the preferential orientation of the solids and the compression plane. Finally, we employed an alternative approach to quantify the amount of foliation and lineation and show that the samples always display a stronger foliation than lineation, although the shear strain increases both the foliation and the lineation. 

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4. Homogeneous nucleation in a Poiseuille flow

   https://doi.org/10.1039/D0CP06132H  

   Yang, Fuqian (February 2021, Physical Chemistry Chemical Physics)

   null (Ed.)

   Nucleation in a dynamical environment plays an important role in the synthesis and manufacturing of quantum dots and nanocrystals. In this work, we investigate the effects of fluid flow (low Reynolds number flow) on the homogeneous nucleation in a circular microchannel in the framework of the classical nucleation theory. The contributions of the configuration entropy from the momentum-phase space and the kinetic energy and strain energy of a microcluster are incorporated in the calculation of the change of the Gibbs free energy from a flow state without a microcluster to a flow state with a microcluster. An analytical equation is derived for the determination of the critical nucleus size. Using this analytical equation, an analytical solution of the critical nucleus size for the formation of a critical liquid nucleus is found. For the formation of a critical solid nucleus, the contributions from both the kinetic energy and the strain energy are generally negligible. We perform numerical analysis of the homogeneous nucleation of a sucrose microcluster in a representative volume element of an aqueous solution, which flows through a circular microchannel. The numerical results reveal the decrease of the critical nucleus size and the corresponding work of formation of a critical nucleus with the increase of the distance to axisymmetric axis for the same numbers of solvent atoms and solute atoms/particles. 

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5. Learning the Impact of Diversity, Equity, and Inclusion Modules in an Undergraduate Electrical Engineering Classroom

   Telang, Nina Kamath; Annaluru, Ramakrishna Sai; Julien, Christine; Santacruz, Pedro Enrique (June 2023, 2023 ASEE Annual Conference & Exposition)

   In this paper, we present the design and implementation of a set of diversity, equity, and inclusion (DEI) based modules, created to be deployed in two courses: one in introductory computing and one in algorithms. Our objective is to ensure that engineering undergraduate students, who are not historically exposed to DEI content, are introduced to these important topics in the context of their technical coursework and that they understand the relevance of DEI to their careers. We created 6 modules that cover a wide range of topics including untold stories throughout the history of computing and algorithms, identity and intersectionality in engineering, designs from engineering that have high societal impact, the LGBTQ+ experience in engineering, engineering and mental health, and cultural diversity within engineering. Each module gives a brief overview of the topic, followed by an associated assignment. We made all of these modules available to the students in the two courses and told them to choose one to complete. Each student engaged with their selected module in four specific ways: (1) watching a relevant video; (2) reading and annotating a provided article; (3) responding in a written reflection to a set of specific prompts relevant to the module; and (4) conducting an interview with a peer or community member using a list of suggested questions about the module’s contents . Afterwards, we required students to communicate what they learned through completing and submitting a graded final deliverable. This deliverable can be a video, slide presentation, a written op-ed piece, or a piece of art about the work they completed in the module. We evaluate the content of the modules through a survey that assesses the students’ interest in the modules and determines the utility of the modules in the context of the study of computing and algorithms. Based on the feedback of these surveys along with feedback from the instructors of the courses, we will further develop and improve the structure and content of these modules and expand their reach to additional engineering courses and disciplines. 

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