Determining the thickness of a submicron carbon coating on a carbon-coated metal base plate using Raman spectroscopy

Patent metadata

Field	Value
Publication number	US-10247540-B1
Application number	US-201715702026-A
Country	US
Kind code	B1
Filing date	Sep 12, 2017
Priority date	Sep 12, 2017
Publication date	Apr 2, 2019
Grant date	Apr 2, 2019

Abstract

A method of determining a thickness of a submicron carbon of a carbon-coated metal base plate that includes conducting Raman spectroscopy at a target location of the carbon-coated metal base plate to obtain a Raman shift spectrum for the target location. The Raman shift spectrum obtained at the target location is then converted into a calculated thickness of the submicron carbon coating at the target location. The conversion of the Raman shift spectrum into the calculated thickness of the submicron carbon coating at the target location may involve referencing a linear correlation that has been established over the defined wavenumber range between (1) an integrated intensity of a Raman carbon signal obtained from each of a series of reference plates that includes a submicron carbon coating having a verified thickness and (2) the verified thicknesses of the submicron carbon coatings of the series of reference plates.

First claim

What is claimed is:

1. A method of determining a thickness of a submicron carbon coating of a carbon-coated metal base plate, the method comprising:
providing a carbon-coated metal base plate that includes a metal base plate and an exteriorly-exposed submicron carbon coating over the metal base plate;
conducting Raman spectroscopy at a target location of the carbon-coated metal base plate to obtain a Raman shift spectrum for the target location; and
converting the Raman shift spectrum obtained at the target location into a calculated thickness of the submicron carbon coating at the target location, wherein converting the Raman shift spectrum obtained at the target location into the calculated thickness of the submicron carbon coating at the target location comprises:
isolating a Raman carbon signal from the Raman shift spectrum obtained at the target location for the carbon-coated metal base plate;
integrating the Raman carbon signal isolated from the Raman shift spectrum over a defined wavenumber range to derive an integrated intensity of the Raman carbon signal;
establishing a linear correlation over the defined wavenumber range between (1) an integrated intensity of a Raman carbon signal obtained from each of a series of reference plates that includes a submicron carbon coating having a verified thickness and (2) the verified thicknesses of the submicron carbon coatings of the series of reference plates; and
referencing the linear correlation to convert the integrated intensity of the Raman carbon signal isolated from the Raman shift spectrum into the calculated thickness of the submicron carbon coating at the target location.

2. The method set forth in claim 1 , wherein the carbon-coated metal base plate is a metallic bipolar plate that has a first major face that defines a first gas flow field and a second major face that defines a second gas flow field.

3. The method set forth in claim 2 , wherein the metal base plate of the bipolar plate is composed of stainless steel.

4. The method set forth in claim 3 , wherein a titanium interlayer is disposed between the metal base plate, which is composed of stainless steel, and the exteriorly-exposed submicron carbon coating.

5. The method set forth in claim 1 , wherein establishing the linear correlation between the integrated intensity of the Raman carbon signals obtained from the series of reference plates and the verified thicknesses of the submicron carbon coatings of the series of reference plates comprises:
conducting Raman spectroscopy at a sample location on each of the series of reference plates to obtain a Raman shift spectrum associated with the sample location on each of the reference plates, each of the series of reference plates having the same layered construction as the carbon-coated metal base plate and including a submicron carbon coating of a verified thickness in which the verified thickness of the submicron carbon coating on each of the series of reference plates is different;
isolating a Raman carbon signal from the Raman shift spectrum obtained at the sample location of each of the reference plates;
integrating the Raman carbon signal isolated from the Raman shift spectrum obtained at the sample location of each of the reference plates over the defined wavenumber range to derive an integrated intensity of the Raman carbon signal associated with each reference plate;
deriving a linear equation in the form of y=mx that fits the integrated intensity of the Raman carbon signals associated with the reference plates when plotted against the verified thicknesses of the submicron carbon coatings of the reference plates, wherein “y” corresponds to the integrated intensity of the Raman carbon signal isolated from the Raman shift spectrum obtained at the sample locations over the defined wavenumber range, “x” corresponds to the verified thickness of the submicron carbon coating at the sample locations, and “m” is the slope representing the change in the integrated intensity of the Raman carbon signal over the change in the verified thickness of the submicron carbon coatings.

6. The method set forth in claim 1 , wherein the defined wavenumber range is 900 cm −1 to 1800 cm′.

7. The method set forth in claim 1 , comprising:
conducting Raman spectroscopy at a plurality of target locations spread across a surface of the carbon-coated metal base plate to obtain a Raman shift spectrum for each of the plurality of target locations; and
converting the Raman shift spectrum obtained at each of the plurality of target locations into a calculated thickness of the submicron carbon coating at each of the plurality of target locations.

8. The method set forth in claim 7 , further comprising:
comparing the calculated thickness of the submicron carbon coating at each of the plurality of target locations against a minimum required coating thickness for the submicron carbon coating to verify whether the submicron carbon coating meets or exceeds the minimum required coating thickness across the surface of the carbon-coated metal base plate.

9. A method of determining a thickness of a submicron carbon coating of a carbon-coated metal base plate, the method comprising:
directing a beam of monochromatic light at each of a plurality of target locations spread across a surface of a carbon-coated metal base plate;
detecting inelastic scattered light reemitted from each of the plurality of target locations to obtain a Raman shift spectrum for each of the plurality of target locations;
isolating a Raman carbon signal from the Raman shift spectrum obtained at each of the plurality of target locations;
integrating the Raman carbon signal isolated from the Raman shift spectrum obtained at each of the plurality of target locations over a defined wavenumber range to derive an integrated intensity of the Raman carbon signal for each of the plurality of target locations;
establishing a linear correlation over the defined wavenumber range between (1) an integrated intensity of a Raman carbon signal obtained from each of a series of reference plates that includes a submicron carbon coating having a verified thickness and (2) the verified thicknesses of the submicron carbon coatings of the series of reference plates; and
referencing the linear correlation to convert the Raman carbon signal isolated from the Raman shift spectrum obtained at each of the plurality of target locations into a calculated thickness of the submicron carbon coating at each of the plurality of target locations.

10. The method set forth in claim 9 , further comprising:
comparing the calculated thickness of the submicron carbon coating at each of the plurality of target locations against a minimum required coating thickness of the submicron carbon coating to verify whether the submicron carbon coating meets or exceeds the minimum required coating thickness across the surface of the carbon-coated metal base plate.

11. The method set forth in claim 9 , wherein the carbon-coated metal base plate is a metallic bipolar plate that has a first major face that defines a first gas flow field and a second major face that defines a second gas flow field.

12. The method set forth in claim 11 , wherein the metal base plate of the bipolar plate is composed of stainless steel.

13. The method set forth in claim 12 , wherein a titanium interlayer is disposed between the metal base plate, which is composed of stainless steel, and the submicron carbon coating.

14. The method set forth in claim 11 , wherein the plurality of target locations includes anywhere from two to forty target locations.

15. The method set forth in clai

Assignees

• Gm Global Tech Operations Llc

Inventors

• Kukreja Ratandeep S
• Tessema Misle M
• Haddad Daad B

Classifications

• G01N21/65

  Raman scattering · CPC title

• H01M8/0202

  Collectors; Separators, e.g. bipolar separators; Interconnectors · CPC title

• H01M8/0228

  in the form of layered or coated products · CPC title

• G01B9/02044 Primary

  Imaging in the frequency domain, e.g. by using a spectrometer · CPC title

• G01B11/0658 Primary

  with measurement of emissivity or reradiation · CPC title