EP-4735863-A1 - RHEOLOGY AND DIELECTRIC SPECTROSCOPY MEASUREMENT SYSTEMS

Abstract

An apparatus for performing electrical and rheology measurements of a material sample, comprises a first plate; a second plate; a rotatable drive shaft extending from a motor to rotate the first plate relative to the second plate; and a sample gap between the first plate and the second plate. The second plate includes first and second electrodes that receive a voltage and form an electric field at the sample gap.

Inventors

• KANAI, JUN
• MERRULLO, Scott
• KAWATA, YUKI

Assignees

• TA Instruments-Waters LLC

Dates

Publication Date

20260506

Application Date

20230831

Claims (20)

1. 1. An apparatus for performing electrical and rheology measurements of a material sample, comprising: a first plate having a conductive surface; a second plate; a rotatable drive shaft extending from a motor to rotate the first plate relative to the second plate; and a sample gap between the first plate and the second plate; the second plate including first and second electrodes that receive a voltage and form a current path and/or electric field at the sample gap between the conductive surface of the first plate and the first and second electrodes at the second plate.
2. 2. The apparatus of claim 1, wherein the electrical measurements include impedance spectroscopy measurements.
3. 3. The apparatus of claim 1, wherein the second plate includes a thermally conductive insulator for isolating the first electrode from the second electrode, and further isolates the first electrode and the second electrode from an environment of the apparatus, and wherein the first electrode and the second electrode are thermally coupled to the environment.
4. 4. The apparatus of claim 3, wherein the thermally conductive insulator includes a ceramic coating.
5. 5. The apparatus of claim 3, wherein the second plate is formed of a metal material and the thermally conductive insulator is coupled to the metal plate for forming the first and second electrodes from the metal material.
6. 6. The apparatus of claim 3, wherein a geometry of the first and second electrodes is determined by the thermally conductive insulator.
7. 7. The apparatus of claim 3, wherein the thermally conductive insulator has a first straight edge in communication with the first electrode and a second straight edge parallel to the first straight edge in communication with the second electrode, the first straight edge separated from the second straight edge by a width that conductively insulates the first electrode from the second electrode.
8. 8. The apparatus of claim 1, wherein the rotatable drive shaft includes an insulative material.
9. 9. The apparatus of claim 8, wherein the first and second electrodes form the current path and/or electric field from the first and second electrodes through the material sample at the sample gap to the first plate.
10. 10. The apparatus of claim 1, wherein the first plate has a stainless steel surface for forming the current path and/or electric field with the first and second electrodes.
11. 11. The apparatus of claim 1, further comprising a processor that correlates current flow measurements and torsional force measurements at the first plate in contact with the material sample.
12. 12. The apparatus of claim 11, further comprising a sensor that detects current flow of the electric field through a material sample at the sample gap and generates the current flow measurements.
13. 13. The apparatus of claim 11, further comprising a processor that determines from a current at the motor the torsional force measurements.
14. 14. The apparatus of claim 1, further comprising a temperature control device that exchanges a thermal conduction with the second plate.
15. 15. The apparatus of claim 1, wherein the first and second electrodes receive voltages of different polarities to form the current path and/or electric field with the first plate through the material sample in the gap.
16. 16. The apparatus of claim 1, wherein the first and second electrodes are formed of a same conductive material as the first plate.
17. 17. An apparatus for performing electrical and rheology measurements of a material sample, comprising: a first plate; a second plate; a rotatable drive shaft extending from a motor to rotate the first plate relative to the second plate and to induce a torsional force on the first plate; and a sample gap between the first plate and the second plate, the torsional force applied on the first plate in contact with a material sample at the sample gap; the second plate including: a first electrode; a second electrode; and a thermally conductive insulator that conductively insulates the first electrode from the second electrode and further conductively insulates the first and second electrodes from the rotatable drive shaft, the first and second electrodes inducing an electric field through the material sample at the sample gap.
18. 18. The apparatus of claim 17, wherein the electrical measurements include impedance spectroscopy measurements.
19. 19. The apparatus of claim 17, wherein the thermally conductive insulator includes a ceramic coating.
20. 20. The apparatus of claim 17, wherein the second plate is formed of a metal material and the thermally conductive insulator is coupled to the metal plate for forming the first and second electrodes from the metal material.

Description

RHEOLOGY AND DIELECTRIC SPECTROSCOPY MEASUREMENT SYSTEMS RELATED APPLICATIONS This application claims the benefit of the earlier filing date of U.S. Provisional Patent Application Serial No. 63/523,590 filed June 27, 2023 and titled “Rheology and Dielectric Spectroscopy Measurement Systems” the entirety of which is incorporated herein by reference. FIELD OF THE INVENTION The disclosed technology relates generally to a device for measuring properties of materials. More particularly, the technology relates to a device for measuring rheological properties of test samples and simultaneously performing an impedance spectroscopy technique on the samples. BACKGROUND Rheometers are well-known for measure the relationships between stress and strain or strain rate by measuring the displacement, and more specifically torque, of a moving measurement in a finite sample volume defined by an upper and lower geometry, generally in the form of plates or the like, over a measured period of time. These measurements are often performed with an actively controlled temperature. Dielectric spectroscopy or impedance spectroscopy, for example, electrochemical impedance spectroscopy, is used to study the response of a sample subjected to an applied electric field by measuring the dielectric properties of a material sample as a function of frequency. It is often desirable to perform electrical measurements in-situ during rheological measurements to correlate the electrical and rheological measurements, for example, the study the relationship between the rheo- dielectric effect and the elasticity of viscoelastic materials. Current state-of-the-art rheometers achieve concurrent electrical and rheological measurements by applying a voltage is applied to each geometry so that electric fields and current flows from one geometry, i.e., the rotating plate, through the sample to the other geometry, i.e., the stationary plate. When taking measurements, liquid or dry friction contacts such as spring brushes, slip rings, liquid electrolyte, and the like are employed to conduct current to or from the moving geometry which continuously rotates during the measurements. However, electrical contact adds undesirable solid or liquid contact with the motor shaft or other geometry assembly, resulting in friction torque to the rheological measurements and/or add undesirable electrical impedance to the electrical impedance measurement that can limit the sensitivity of the instrument. Torque measurements are more accurate if the only torque contribution only comes from the sample. Consequently, the resolution of both types of measurements is decreased due to a degraded signal to noise ratio. SUMMARY In one aspect, an apparatus for performing electrical and rheology measurements of a material sample comprises a first plate having a conductive surface; a second plate; a rotatable drive shaft extending from a motor to rotate the first plate relative to the second plate; and a sample gap between the first plate and the second plate. The second plate includes first and second electrodes that receive a voltage and form an electric field at the sample gap between the conductive surface of the first plate and the first and second electrodes at the second plate. The electrical measurements may include impedance spectroscopy measurements. The second plate may include a thermally conductive insulator for isolating the first electrode from the second electrode, and may further isolate the first electrode and the second electrode from an environment of the apparatus. The first electrode and the second electrode may be thermally coupled to the environment. Thermally conductive insulator may include a ceramic coating. The second plate may be formed of a metal material and the thermally conductive insulator is coupled to the metal plate for forming the first and second electrodes from the metal material. A geometry of the first and second electrodes may be determined by the thermally conductive insulator. The thermally conductive insulator may have a first straight edge in communication with the first electrode and a second straight edge parallel to the first straight edge in communication with the second electrode. The first straight edge may be separated from the second straight edge by a width that conductively insulates the first electrode from the second electrode. The rotatable drive shaft may include an insulative material. The first and second electrodes may form a current path and/or electric field from the first and second electrodes through the material sample at the sample gap to the first plate. The first plate may have a stainless steel surface for forming the current path and/or electric field with the first and second electrodes. The apparatus may further comprise a processor that correlates current flow measurements and torsional force measurements at the first plate in contact with the material sample. The apparatus may further comprise a sensor tha