A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and microstructural properties of complex fluids is ...presented. The instrument consists of a Couette geometry contained within a modified forced convection oven mounted on a commercial rheometer. This instrument is available for use on the small angle neutron scattering (SANS) beamlines at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR). The Couette geometry is machined to be transparent to neutrons and provides for measurement of the electrical properties and microstructural properties of a sample confined between titanium cylinders while the sample undergoes arbitrary deformation. Synchronization of these measurements is enabled through the use of a customizable program that monitors and controls the execution of predetermined experimental protocols. Described here is a protocol to perform a flow sweep experiment where the shear rate is logarithmically stepped from a maximum value to a minimum value holding at each step for a specified period of time while frequency dependent dielectric measurements are made. Representative results are shown from a sample consisting of a gel composed of carbon black aggregates dispersed in propylene carbonate. As the gel undergoes steady shear, the carbon black network is mechanically deformed, which causes an initial decrease in conductivity associated with the breaking of bonds comprising the carbon black network. However, at higher shear rates, the conductivity recovers associated with the onset of shear thickening. Overall, these results demonstrate the utility of the simultaneous measurement of the rheo-electro-microstructural properties of these suspensions using the dielectric RheoSANS geometry.
The characterization of the redox behavior of analytes is a very important aspect for many applications. Pure
electrochemical approaches can provide useful information on electroactive species, but ...are of limited use regarding the
identification of generated species. The hyphenation of electrochemistry and mass spectrometry (EC-MS) is a powerful
method to investigate redox systems. In the present work, we show a simple approach to on-line EC-MS based on the
application of electrochemical flow cells with implemented disposable electrodes. They are connected to electrospray
ionization mass spectrometry (ESI-MS) via fused silica capillary tubing. The modularity of the flow cells offers a high
flexibility of experimental setup and settings, so that a fast detection of oxidation or reduction products can be
achieved. The usage of disposable electrodes guarantees a high level of quality assurance for EC-MS measurements.
Electrical Energy Storage (EES) is projected to play an important role in the integration of large-scale renewable energy sources with electricity grid or off-grid. Grid-scale EES, particularly for ...renewable energy applications, has been a challenging task due to its high capital cost. Electrochemical-based EES systems, specifically redox flow batteries (RFBs) among other options, are uniquely suited for large-scale EES due to many advantages they have over conventional sealed batteries (e.g., lead-acid and Li-ion batteries). Flow batteries can meet a wide range of commercial-scale EES applications with varying power-to-energy ratios. Flow batteries have excellent energy efficiency and competitive life-cycle cost.The present work focuses on electrochemical investigations of slurry electrodes for flow cell (e.g. flow batteries) applications, aiming at improving the energy density of the system. The investigation includes; development of slurry electrode-electrolyte composites and slurry property characterization, electrochemical studies of slurry electrode-electrolyte (three-electrode cell configuration), cell design, subscale cell performance evaluation. The findings revealed that; in terms of conductivity, reduction of charge transfer resistance when carbon particles are dispersed in electrolyte/redox solution is mainly due to carbon nature. In addition, increase in carbon particles loading leads to increase in conductivity. The corrosion/carbon oxidation largely depends on the number of defect sites on carbon surfaces, which is directly related to carbon surface area (BET surface area). Among all the carbons studied, Black Pearls carbon demonstrated the best redox kinetics in V+2/V+3, V+4/V+5, Fe2+/Fe3+, and S2-/S0 redox couples. The kinetics of slurry electrodes in acid and alkaline media mainly depend on surface chemistries of the carbons. The performance of slurry electrodes at cell level is a function of; slurry conductivities, channel dimensions, slurry percolation (particle-to-particle interaction) and type of membrane.
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