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Carbon black, a key ingredient in ancient inks, is used today to make the porous electrodes found in many rechargeable batteries. Understanding how to control its microstructure can pave the way to better-performing batteries. [ABSTRACT FROM AUTHOR]

Electron transport in complex fluids, biology, and soft matter is a valuable characteristic in processes ranging from redox reactions to electrochemical energy storage. These processes often employ conductor-insulator composites in which electron transport properties are fundamentally linked to the microstructure and dynamics of the conductive phase. While microstructure and dynamics are well recognized as key determinants of the electrical properties, a unified description of their effect has yet to be determined, especially under flowing conditions. In this work, the conductivity and shear viscosity are measured for conductive colloidal suspensions to build a unified description by exploiting both recent quantification of the effect of flow-induced dynamics on electron transport and well-established relationships between electrical properties, microstructure, and flow. These model suspensions consist of conductive carbon black (CB) particles dispersed in fluids of varying viscosities and dielectric constants. In a stable, well-characterized shear rate regime where all suspensions undergo self-similar agglomerate breakup, competing relationships between conductivity and shear rate were observed. To account for the role of variable agglomerate size, equivalent microstructural states were identified using a dimensionless fluid Mason number, Mnf, which allowed for isolation of the role of dynamics on the flow-induced electron transport rate. At equivalent microstructural states, shear-enhanced particle-particle collisions are found to dominate the electron transport rate. This work rationalizes seemingly contradictory experimental observations in literature concerning the shear-dependent electrical properties of CB suspensions and can be extended to other flowing composite systems. [ABSTRACT FROM AUTHOR]

Predictive constitutive equations that connect easy-to-measure transport properties (e.g., viscosity and conductivity) with system performance variables (e.g., power consumption and efficiency) are needed to design advanced thermal and electrical systems. In this work, we explore the use of fluorescent particle-streak analysis to directly measure the local velocity field of a pressure-driven flow, introducing a new Python package (FSVPy) to perform the analysis. Fluorescent streak velocimetry combines high-speed imaging with highly fluorescent particles to produce images that contain fluorescent streaks, whose length and intensity can be related to the local flow velocity. By capturing images throughout the sample volume, the three-dimensional velocity field can be quantified and reconstructed. We demonstrate this technique by characterizing the channel flow profiles of several non-Newtonian fluids: micellar Cetylpyridinium Chloride solution, Carbopol 940, and Polyethylene Glycol. We then explore more complex flows, where significant acceleration is created due to microscale features encountered within the flow. We demonstrate the ability of FSVPy to process streaks of various shapes and use the variable intensity along the streak to extract position-specific velocity measurements from individual images. Thus, we demonstrate that FSVPy is a flexible tool that can be used to extract local velocimetry measurements from a wide variety of fluids and flow conditions. [ABSTRACT FROM AUTHOR]

Electrical transport in semiconducting and metallic particle suspensions is an enabling feature of emerging grid-scale battery technologies. Although the physics of the transport process plays a key role in these technologies, no universal framework has yet emerged. Here, we examine the important contribution of shear flow to the electrical transport of non-Brownian suspensions. We find that these suspensions exhibit a strong dependence of the transport rate on the particle volume fraction and applied shear rate, which enables the conductivity to be dynamically changed by over 107 decades based on the applied shear rate. We combine experiments and simulations to conclude that the transport process relies on a combination of charge and particle diffusion with a rate that can be predicted using a quantitative physical model that incorporates the selfdiffusion of the particles. [ABSTRACT FROM AUTHOR]

Two n-type molecular organic semiconductors (TI-BDF1 and TI-BDF2) consisting of thiophene-substituted indolin-2-one (TI) and benzodifurandione (BDF) with different branched side-chains have been synthesized to study the effect of molecular structure on molecular order, liquid crystal (LC) properties, and charge-transport. By tuning the branching point of the side-chains, TI-BDF2 shows a preferable edge-on π-face orientation and a high degree of liquid crystallinity, resulting in 4 orders of magnitude higher electron mobility than that of TI-BDF1. Subsequent n-doping of TI-BDF2 thin film with a thermally stable phosphonium salt affords a high electrical conductivity of 0.4 S cm−1. [ABSTRACT FROM AUTHOR]

The morphological effects of the incorporation of C60 into blended thin-films of poly(3-hexylthiophene) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) are investigated. The results show that addition of C60 readily alters the growth-rate and morphology of PCBM crystallites under different environmental conditions. The effect of C60 on the growth of large PCBM crystallites is thoroughly characterized using optical microscopy, electron microscopy and UV-visible absorption spectroscopy. Results show that C60 incorporation modifies fullerene aggregation and crystallization and greatly reduces the average crystallite size at C60 loadings of ≈50 wt% in the fullerene phase. Organic field-effect transistors (OFETs) are prepared to evaluate the electron mobility of PCBM/C60 films and organic solar cells (OSCs) are fabricated from mixed-fullerene active layers to evaluate their performance. It is demonstrated that the use of fullerene mixtures in organic electronic applications is a viable approach to produce more stable devices and to control the growth of micrometer-sized fullerene crystals. [ABSTRACT FROM AUTHOR]