Name: dielectric rheosans &#8212; simultaneous interrogation of impedance, rheology and small angle neutron scattering of complex fluids
Uploaded: 2017-04-10T12:30:00
Description: Watch this Scientific Journal Video about Dielectric RheoSANS â€” Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids at JoVE.com

The authors would like to acknowledge the NIST Center for Neutron Research CNS cooperative agreement number #70NANB12H239 grant for partial funding during this time period as well as the National Research Council for support. Certain commercial equipment, instruments, or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.

1. Mounting the Rheometer onto the SANS Beamline
NOTE: See Figure 1 for definitions of named components.
<ol>
	<li>Ensure that the power to the rheometer is off, the transducer is locked and the motor air bearing protector is installed. Turn off the neutron beam, and close the oven door.</li>
	<li>Install the large base plate onto the table, remove the snout, install the window, and secure the 4 eyelets to the mounting brackets on the rheometer&#39;s crane adapter such that ...

<ol>
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A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+optimized+protocol+for+the+analysis+of+time-resolved+elastic+scattering+experiments.">An optimized protocol for the analysis of time-resolved elastic scattering experiments.</a> Soft Matter. 12 (8), 2301-2308 (2016).</li><li>Eberle, A. P. R., Porcar, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow-SANS+and+Rheo-SANS+applied+to+soft+matter.">Flow-SANS and Rheo-SANS applied to soft matter.</a> Curr. Opin. Colloid Interface Sci. 17 (1), 33-43 (2012).</li><li>Campos, J. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+carbon+materials+for+use+as+a+flowable+electrode+in+electrochemical+flow+capacitors.">Investigation of carbon materials for use as a flowable electrode in electrochemical flow capacitors.</a> Electrochim. Acta. 98, 123-130 (2013).</li><li>Duduta, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Semi-solid+lithium+rechargeable+flow+battery.">Semi-solid lithium rechargeable flow battery.</a> Adv. Energy Mater. 1 (4), 511-516 (2011).</li><li>Mewis, J., de Groot, L. M., Helsen, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectric+Behaviour+of+Flowing+Thixotropic+Suspensions.">Dielectric Behaviour of Flowing Thixotropic Suspensions.</a> Colloids Surf. 22, (1987).</li><li>Richards, J. J., Wagner, N. J., Butler, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Strain-Controlled+RheoSANS+Instrument+for+the+Measurement+of+the+Microstructural,+Electrical+and+Mechanical+Properties+of+Soft+Materials.">A Strain-Controlled RheoSANS Instrument for the Measurement of the Microstructural, Electrical and Mechanical Properties of Soft Materials.</a> Rev. Sci. Instr. , (2016).</li><li>Youssry, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-aqueous+carbon+black+suspensions+for+lithium-based+redox+flow+batteries:+rheology+and+simultaneous+rheo-electrical+behavior.">Non-aqueous carbon black suspensions for lithium-based redox flow batteries: rheology and simultaneous rheo-electrical behavior.</a> Phys. Chem. Chem. Phys. PCCP. 15 (34), 14476-14486 (2013).</li><li>Cho, B. -. K., Jain, A., Gruner, S. M., Wiesner, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesophase+structure-mechanical+and+ionic+transport+correlations+in+extended+amphiphilic+dendrons.">Mesophase structure-mechanical and ionic transport correlations in extended amphiphilic dendrons.</a> Sci. 305 (5690), 1598-1601 (2004).</li><li>Kiel, J. W., MacKay, M. E., Kirby, B. J., Maranville, B. B., Majkrzak, C. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase-sensitive+neutron+reflectometry+measurements+applied+in+the+study+of+photovoltaic+films.">Phase-sensitive neutron reflectometry measurements applied in the study of photovoltaic films.</a> J. Chem. Phys. 133 (7), 1-7 (2010).</li><li>L&#243;pez-Barr&#242;n, C. R., Chen, R., Wagner, N. J., Beltramo, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-Assembly+of+Pluronic+F127+Diacrylate+in+Ethylammonium+Nitrate:+Structure,+Rheology,+and+Ionic+Conductivity+before+and+after+Photo-Cross-Linking.">Self-Assembly of Pluronic F127 Diacrylate in Ethylammonium Nitrate: Structure, Rheology, and Ionic Conductivity before and after Photo-Cross-Linking.</a> Macromolecules. 49 (14), 5179-5189 (2016).</li></ol>

A dielectric RheoSANS experiment measures simultaneously the rheological, electrical and microstructural responses of a material as it undergoes a predefined deformation. The example shown here is an electrically conductive carbon black suspension that forms the conductive additive used in electrochemical flow cells. The dielectric RheoSANS instrument enables the interrogation of the radial plane of shear within a narrow gap Couette cell without compromising the fidelity of either the electrical or rheological measuremen...

Measurement of macroscopic properties are often used to gain fundamental insight into the nature of colloidal materials and self-assembled systems, usually with the goal of developing understanding in order to improve formulation performance. In particular, the field of rheology, which measures a fluid&#39;s dynamic response to an applied stress or deformation, provides valuable insight into colloidal behavior both under equilibrium conditions and also far from equilibrium, such as during processing1 Rheological tests of consumer and industrial fluids, gels, and glasses can also be used to measure rheological parameters, such as viscosity, that are targeted by formulators. While rheology is a powerful probe of material properties, it is an indirect measurement of colloidal information at the microscopic level, such that our understanding of fundamental colloidal behavior can be greatly enhanced by combining rheological measurements with complementary techniques.
One such orthogonal technique is impedance spectroscopy. Impedance spectroscopy is a bulk probe of dielectric relaxation behavior, which measures the response of a material to an applied oscillating electric field.2 The impedance spectrum results from electrical relaxation modes that are active within the material including charge transport and polarization.3,4 These measurements provide additional evidence for colloidal behavior particularly when combined with rheology.5 Therefore, the combination of these techniques is especially relevant when probing charged colloidal dispersions, proteins, ionic surfactants, nanocomposites, and other systems.6,7
A fundamental interest in investigations of colloidal behavior is the material&#39;s microstructure. The microstructure of a colloidal fluid is thought to encode all of the information necessary to reconstitute both its rheological and electrical behavior. Fundamentally, we seek to measure a snapshot of the nanoscale microstructural features that lead to a measured material response. Due to the complicated nature of many complex fluids&#39; dependence on their process history, much of the effort on microstructural characterization has focused on making in situ measurements of the material as it undergoes deformation. This has challenged experimentalists to devise methods to be able to make measurements of nano-sized particles under for example steady shear, where the velocities of the particles have made direct visualization intrinsically challenging. Direct measurement of material microstructure under flow has taken on many forms ranging from rheo-optics, rheo-microscopy and even rheo-NMR.8,9,10 Small angle scattering methods, and in particular small angle neutron scattering (SANS) techniques, have proven themselves effective at measuring the time-averaged microstructure of samples at steady state in a bulk shear field including all three planes of shear.11,12,13 However, new data acquisition techniques have allowed structural transients to be captured with time resolution as fine as 10 ms.14 Indeed combining rheology with various in situ scattering methods has proven invaluable in hundreds of recent studies.15
An emerging engineering challenge is the use of colloidal suspensions as conductive additives in semi-solid flow battery electrodes.16 In this application, conductive colloidal particles must maintain an electrically percolated network while the material is pumped through an electrochemical flow cell. The performance demands on these materials require that they maintain high conductivity without detrimental effect on the rheological performance over a wide range of shear rates.17 It is therefore highly desirable to be able to make measurements of the colloidal behavior under steady and time-dependent shear conditions in order to quantify and characterize the underlying rheological and electrical response of these materials far from their equilibrium state. A significant complicating factor that has hindered further theoretical development in this regard is the thixotropic nature of carbon black slurries.18 These history dependent rheological and electrical properties make experiments notoriously difficult to reproduce; thus, making it difficult to compare data sets measured using varying protocols. Furthermore, to date there is no single geometry capable of performing all three, dielectric, rheological, and microstructural characterizations, simultaneously. Simultaneous measurement is important as the flow can change the structure, such that rest measurements of processed materials may not provide accurate indications of the properties under flow, which are more relevant for their use. Additionally, as many of the measured properties of carbon black slurries are geometry dependent, there are complications with comparing data obtained from the same sample on different instruments.19
In order to meet this challenge in metrology, we have developed a new dielectric RheoSANS geometry at the NIST Center for Neutron Research and the University of Delaware capable of in situ impedance spectroscopy, rheology and SANS measurements of a material under arbitrary deformation on a commercial strain controlled rheometer. This is enabled by developing a Couette geometry capable of measuring the microstructural, electrical and rheological response of a material confined between the gap of two concentric cylinders. As the outer cylinder spins, torque imposed by the deformation of the sample is measured on the inner cylinder and the impedance measurement is made radially across the gap. The cylinders are machined from titanium so as to be transparent to neutrons and robust enough to withstand the shear stress experienced in the rheometer. We perform the SANS measurement through the radial position of the Couette, and have demonstrated that it is possible to measure high quality SANS patterns from the sample undergoing deformation. In this way, all three measurements are made on the same region of interest in the sample as it undergoes a well-defined deformation profile. The goal of this article is to describe the dielectric Couette geometry, its installation onto the RheoSANS instrument, and the successful execution of a simultaneous measurement. This rheometer is available at the NIST Center for Neutron Research at the National Institute of Standards and Technology. It has been designed to work on the NG-7 SANS beam line. We have provided drawings and a detailed description of the custom components that have been machined and assembled in order to enable this measurement.

<table border="0" cellpadding="0" cellspacing="0" width="719">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">ARES G2 Rheometer</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">401000.501</td>
			<td style="width:167px;">Rheometer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">ARES G2-DETA ACCY Kit</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">402551.901</td>
			<td>BNC Connectors</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">Geometry ARES 25mm DETA</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">402553.901</td>
			<td>Dielectric Geometry</td>
		</tr>
		<tr height="19">
			<td height="19" style="height:19px;width:283px;">ARES G2 Forced Convection Oven</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">401892.901</td>
			<td>FCO</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">Agilent E4980A LCR Meter</td>
			<td style="width:151px;">TA Instruments</td>
			<td align="right" style="width:119px;">613.04946</td>
			<td>LCR Meter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">USB-6001</td>
			<td style="width:151px;">National Instruments</td>
			<td style="width:119px;">NI USB-6001</td>
			<td>Data Acquisiton Card</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">Vulcan XC72R</td>
			<td style="width:151px;">Cabot</td>
			<td style="width:119px;">Vulcan XC72R</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">Propylene Carbonate</td>
			<td style="width:151px;">Aldrich</td>
			<td align="right" style="width:119px;">310328</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:283px;">LabVIEW&#160; System Design Software</td>
			<td style="width:151px;">National Instruments</td>
			<td>776671-35</td>
			<td>Control Software&#160;</td>
		</tr>
	</tbody>
</table>

dielectric rheosans &#8212; simultaneous interrogation of impedance, rheology and small angle neutron scattering of complex fluids

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.

Representative results from a dielectric RheoSANS experiment are shown in Figure 5 and 6. These data are taken on a suspension of conductive carbon black in propylene carbonate. These aggregates flocculate due to attractive interactions at relatively low solids loadings forming gels that are electrically conducting. The rheological and conductivity responses of such suspensions are an active area of research and current investigations seek to understand t...

Watch this Scientific Journal Video about Dielectric RheoSANS â€” Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids at JoVE.com

Dielectric RheoSANS &#8212; Simultaneous Interrogation of Impedance, Rheology and Small Angle Neutron Scattering of Complex Fluids

Here, we present a procedure for the measurement of simultaneous impedance, rheology and neutron scattering from soft matter materials under shear flow.

A procedure for the operation of a new dielectric RheoSANS instrument capable of simultaneous interrogation of the electrical, mechanical and ...

The overall goal of this procedure is to measure the simultaneous impedance, rheology and neutron scattering from a conductive carbon black suspension as it undergoes deformation in response to an applied shear field. This method can help answer key questions in the soft matter and applied materials fields about the intrinsic link between material microstructure and macroscopic properties such as conductivity and rheology. The main advantage of this technique is that the measurements are performed simultaneously, allowing the entire time evolution of mechanical, structural and electrical response to be reconstructed and compared.The implications of this technique extend to the development of advanced conductive materials for electrochemical and optoelectronic applications. Visual demonstration of this method is critical owing to the complex nature of the experimental protocol. NIST professionals will assist in some key aspects of the experiment.Before beginning the procedure, ensure that the neutron beam and the rheometer are both off, the transducer is locked and the motor bearing lock is installed. Clean the dielectric cup and bob assemblies with a detergent solution. Thoroughly rinse the assemblies with deionized water and allow the assembles to air dry.Unlock the transducer and remove the motor bearing lock. Then, turn on the rheometer and start the control software. Mount the dielectric geometry and bob assembly on the lower and upper tool mounts of the rheometer respectively.Use a three milometer allen key to loosen the dielectric geometry set screws. Mount the cup assembly on the dielectric geometry. Then, in the rheometer control software, zero the gap and apply 10 newtons of normal force.Under this axial compression, tighten the set screws to secure the cup assembly to the geometry. Then, set the gap to the measurement gap width. Close the oven door and verify that the oven fully encloses the dielectric cell assembly.With sufficient vertical clearance above and below the geometry to allow a full revolution without contacting the oven walls. Open the oven and remove the dielectric assemblies. Thread the geometry shaft through the slip ring and join the dielectric cup and slip ring connectors.While holding the slip ring, concentric with the shaft above the flange, secure the slip ring adapters on top of the flange. Gently slide the slip ring down to fit over the adapters. Next, mount the rheometer alignment tool on the lower tool head.Install the truncated snout and set the sample aperture to one millimeter by eight millimeters. In the rheometer control software, set the geometry displacement angle to 0.49 radians. Then in the SANS control software, verify that all neutron guides have been removed.Open the oven door to view the beam alignment laser. Use the SANS software to adjust the height and angle of the sample stage until the laser beam is directed along the oven center line and though the sample aperture without intersecting the aperture walls. After rheometer alignment, remove the alignment tool and perform a series of SANS measurements to calibrate the instrument.Then, use the rheometer LCD screen, to set the gap to 100 millimeters. Mount the dielectric cell with the bob assembly on the upper tool head and the cup geometry and slip ring assembly on the lower tool head. Use the instrument software to zero the gap.Next, mount the carbon brush assembly on the brush adapter. Line up the carbon brushes with the grooves on the slip ring and then secure the adapter to the rheometer with screws. Connect the carbon brush assembly to the top bus bar and the dielectric bob assembly to the bottom bus bar.Check the connections of the shielded BNC cables to the bus bars and the LCR meter. Connect the SANS and Trigger BNC cables to the DAQ card. Connect the rheometer to the DAQ card.Verify that the LCR meter and the rheometer are successfully communicating with the computer. Before loading the sample, verify that the gap is set to 100 millimeters. Then, load four millimeters of a carbon black dispersion in propylene carbonate into the dielectric cup assembly, minimizing the amount of sample left on the cup wall.Lower the geometry to 40 millimeter. Then in the rheometer control software, set the motor velocity to one radian per second. Lower the dielectric bob assembly to achieve a gap width of 0.1 millimeters and then set the motor velocity to zero radians per second.Check that the sample levels has reached the Couette wall but is not over filled. Fill the inner dielectric bob assembly with the chosen solvent for the experiment. Place the solvent trap on the rim of the dielectric cup assembly.Next, configure the virtual instrument file for the desired experimental conditions. Set the appropriate run times and procedures for the SANS instrument and the rheometer. Click parameters set to execute the experiment.A conductive carbon black suspension was evaluated by RheoSANS. Rheology, dielectric data and neutron scattering were measured continuously as the shear rate decreased logarithmically in steps, holding at each step for a specific time interval. The steady state, rheological dielectric and SANS data were processed and analyzed at each shear rate step.A period of decreasing conductivity and effective volume fraction with increasing shear rate was attributed to yielding of the microscopic gel. A subsequent period of increasing conductivity and decreasing effective volume fraction with increasing shear rate was attributed to shear thickening caused by hydrodynamic forces drawing aggregated particles together. Micro structural transitions at higher shear rates were represented with two dimensional plots.Dielectric RheoSANS provides a flexible platform capable of the interrogation of nonequilibrium behavior of soft matter systems. Using a wide variety of potential experimental protocols, this instrument is available for broad use by the scientific community at the NCNR.

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