Batch and continuous methods for evaluating the physical and thermal properties of films
Thermal methods and systems are described for the batch and/or continuous monitoring of films and/or membranes and/or electrodes produced in large-scale manufacturing lines. Some of the methods described include providing an energy input into a film, measuring a thermal response of the film, and correlating these to one or more physical properties and/or characteristics of the film.
1. A method comprising:
transferring heat to a portion of a film, wherein the transferring causes a thermal response in the portion of the film;
measuring at least a part of the thermal response;
generating at least one thermal response metric that represents the thermal response; and
determining a physical property of the film by inputting at least one thermal response metric into a predictive model, wherein:
the transferring of heat is supplied continuously at a steady-state heating rate, and
the thermal response comprises a maximum temperature reached on a surface of the first portion of the film.
2. The method of claim 1 , wherein the predictive model comprises a calibration curve that correlates the at least one thermal response metric with at least one of a film density, a film porosity, or a film thickness.
3. The method of claim 1 , wherein the predictive model comprises:
a microscale model that estimates an effective heat conductivity as a first function of at least the actual heat conductivities of at least two components of the film;
the microscale model estimates an effective heat capacity of the film as a second function of the actual heat capacities of the at least two components of the film; and
a macroscale model that estimates at least one of a film density, a film porosity, or a film thickness as a function of at least the effective heat conductivity, the effective heat capacity, and the at least one thermal response metric.
4. The method of claim 1 , wherein the thermal response further comprises a rate of change of a temperature for the surface of the portion of the film.
5. The method of claim 1 , wherein the transferring of heat to the portion of the film is essentially in the shape of a one-dimensional line.
6. A roll-to-roll system comprising:
a heat source configured to transfer heat continuously at a steady-state heating rate to at least a portion of a continuous film;
a first detector, and;
a predictive model, wherein:
the detector is configured to detect a thermal response in the portion of the continuous film,
the thermal response comprises a maximum temperature reached on a surface of the portion of the continuous film, and
the predictive model receives the at least one thermal response to predict at least one of a density, a porosity, or a thickness of the continuous film.
7. The roll-to-roll system of claim 6 , wherein the heat source comprises at least one radiation source.
8. The roll-to-roll system of claim 6 , wherein the radiation source comprises at least one of a light-emitting diode, an infrared heater, an infrared lamp, or a resistive heating element.
9. The roll-to-roll system of claim 8 , wherein the radiation source radiates electromagnetic radiation having a plurality of wavelengths between about 1 μm and about 1 mm.
10. The roll-to-roll system of claim 9 , wherein the radiation source comprises at least one resistive heating element and a reflector.
11. The roll-to-roll system of claim 10 , wherein the at least one resistive heating element comprises at least one of a rod, a cylinder, or a filament.
12. The roll-to-roll system of claim 10 , wherein the at least one resistive heating element has a first emissivity between greater than zero and about 0.80.
13. The roll-to-roll system of claim 12 , wherein:
the resistive heating element comprises a modified section, wherein the modified section is modified by at least one of polishing, painting, or coating a portion of the resistive heating element, and
the modified section has a second emissivity that is less than the first emissivity.
14. The roll-to-roll system of claim 10 , wherein the reflector has a shape substantially in the form of a part of an elliptical cylinder.
15. The roll-to-roll system of claim 6 , wherein:
the heat source comprises at least one heating element, and
the at least one heating element contacts the continuous film such that the heat transferred to the continuous film is at least partially by conductive heat transfer.
16. The roll-to-roll system of claim 15 , wherein the at least one heating element is a heated roller.
17. The roll-to-roll system of claim 16 , further comprising at least one stabilizing roller.
18. The roll-to-roll system of claim 6 , wherein the predictive model comprises a calibration curve.
19. The roll-to-roll system of claim 6 , wherein the predictive model comprises:
a microscale model that estimates an effective heat conductivity as a first function of at least the actual heat conductivities of at least two components of the continuous film;
the microscale model estimates an effective heat capacity of the continuous film as a second function of the actual heat capacities of the at least two components of the continuous film; and
a macroscale model that estimates at least one of a continuous film density, a continuous film porosity, or a continuous film thickness as a function of at least the effective heat conductivity, the effective heat capacity, and the at least one thermal response metric.
20. The roll-to-roll system of claim 6 , further comprising:
at least one laser that transfers laser light to the continuous film; and
a second detector, wherein:
the second detector is configured to capture at least one of reflected laser light,
the reflected laser light is used to calculate a thickness of the continuous film, and
the thickness is an input to the predictive model and used to predict the at least one of the density and/or the porosity of the continuous film.
21. The roll-to-roll system of claim 6 , further comprising:
at least one x-ray source; and
a second detector, wherein:
the second detector is configured to capture at least one of emitted x-rays,
the emitted x-rays are used to calculate a thickness of the continuous film, and
the thickness is an input to the predictive model and used to predict the at least one of the density and/or the porosity of the continuous film.