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Robust FARADAYIC® CNT Based Coating for Scattered Light Suppression
Dan Wang, Tim D. Hall, R. Radhakrishnan, M. Inman, E. Jennings Taylor, B.T. Skinn, and S.T. Snyder
18th Annual Mirror Technology SBIR/STTR Workshop
Raytheon Space and Airborne Systems Event Center
El Segundo, CA
11/06/2018
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Introduction to Faraday Technology, Inc.
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Company Overview: FARADAY TECHNOLOGY, INC.
o Electrochemical engineering processes and technologies – founded 1991
• ~32 Issued Patents and ~15 Pending Patents in this area
• www.FaradayTechnology.com
o Subsidiary of Physical Sciences, Inc. (Boston, MA) – acquired 2008
• www.psicorp.com
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“…to be known as the company that changed the focus of
electrochemical engineering from the art of complex chemistries to the
science of pulse/pulse reverse electric fields…”
~47 Patent Portfolio
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Technology development begins conceptually and is demonstrated at the bench-scale
and developed through /-scale validation. IP development with technology.
Bench-Top Feasibility Pilot-Scale Validation Production-Scale Validation
DEM/VAL: α- to β-Scale
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Business Model: Collaborative Open Innovation
o Establish IP (47 patents issued/know-how)
o Leverage Federal SBIR opportunities as
non-equity technology funding
• Retain IP rights
o Collaborate with university, government
and commercial partners
o Develop electrochemical engineering
solutions based on PC/PRC processes
o Transition technology & competitive
advantage to large companies via
• α-Scale to β-Scale
Demonstration/Validation
• Field-of-use licenses
• Patent acquisition (8)
o Transition technology to government
facilities via
• α-Scale to β-Scale
Demonstration/Validation Development of robust process is
critical!
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Program Description
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Background
• Future NASA missions require low reflective surfaces to minimize scattered
light for optical systems, such as beam-splitter, lasercom, and gravitational-
wave application.
• The low reflective surfaces need to withstand space environments with
marginal impact on their adhesion and optical performance in the broad
spectral range (visible-near infrared).
• Low reflective surfaces have been obtained on black surfaces through
anodization, painting, or electrodeposition of Martin black, carbon black,
black chrome, etc.
• The CNT based materials absorb 99.5 of the light, dramatically reducing
light contamination (NASA Goddard Space Flight Center).
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Objective of Program
• The objective of the Phase I program is to
develop a scalable process for fabrication of
low reflective CNT based black coating that is
able to withstand and increase lifetime in
challenging application environments.
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Technical Approach
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+
Conventional EPD process FARADAYIC® process
Utilize combined conventional electrophoretic deposition (EPD)
and pulsed electric fields to induce migration of charged particles
(nanotubes) onto targeted substrates.
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Technical Approach
• Carbon nanotubes will be surface charged and dispersed
with the aid of dispersants or functional groups.
• Surface charged CNTs will be deposited on desired
substrates through FARADAYIC® EPD process.
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EPD cell Setup
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A B
C D
The EPD cell setup for CNT coating: 3D representation of (A) EPD cell; (B) Counter
and working electrodes; (C) The EPD cell setup with DC power supply; (D) The EPD
cell with CNT suspension.
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CNT dispersion for EPD Coating
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• Plating bath development (CNT dispersion approach, dispersant, binders,
solvent, etc. )
CNT bundles
CNT dispersions
The experimental setup for preparing CNT dispersion with aid of sonication
Multi-walled carbon nanotube
(Aldrich)
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Results
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B A
Photograph (A) and diffuse reflectance spectra (B) of Trial CNT39, 40,& 41
Increasing the applied DC voltage leads to reduce
reflectance of CNT films
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Results
A B
Photograph (A) and diffuse reflectance spectra (B) of Trial CNT41& 45
Increasing deposition time leads to reduce reflectance
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Results
A B
Photographs of CNT coatings formed in (A) DMF (B) EtOH
FARADAYIC® EPD (CNT 32/46) improves deposit uniformity
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Discussion
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• ~3% was the lowest observed diffuse reflection across
visible wavebands that was found with CNT films
consisting of polymer dispersants
• Polymer dispersants absorbed on the CNT surfaces
and block the CNT absorbing the light
• Replacing the polymer dispersants with charged
function groups on CNT sidewalls
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A B
120V
DC 60V
DC 40V
PC
Results
Photograph (A) and diffuse reflectance spectra (B) of Trial CNT45,83& 84
The removal of polymer dispersants from the process enables
the diffuse reflection to be reduced to 1.1%.
Pulse EPD can achieve the same reflectance performance
with much lower applied voltage (lower power).
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Results
A B
EtOH EtOH IPA
Photograph (A) and diffuse reflectance spectra (B) of Trial CNT83,88& 89
The use of EtOH instead of IPA solvent further decreases
diffuse reflection to 0.8% across visible wavebands.
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Summary
• Designed and built electrophoretic deposition (EPD) cell
with adjustable distance between cathode and anode for
CNT coating
• Investigated the effects of solvents, binders, dispersants,
functional groups on the dispersion of CNTs and
reflectance of CNT coatings
• Obtained CNT black coatings on stainless steel substrates
using EPD under both DC and PC
• Initiated pulse waveform EPD and found improved CNT
coating uniformity
• Achieved diffuse reflectance of ~0.8% across the visible
wavebands of the developed CNT coatings.
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Next Step
• Optimize the PC waveform for lower reflective CNT
coating formation (approaching ~0.1% target)
• Evaluate the effects of diameter and alignment of CNTs
on the reflectance of CNT coatings
• Complete an economic evaluation of the EPD approach
for anti-reflective CNT coatings
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The financial support of NASA Contract No. 80NNSC18P2062 is acknowledged.
Special thanks to all our team members for their support
THANK YOU FOR YOUR ATTENTION!
QUESTIONS?
Contact Information: Dan Wang, Tim Hall, M. Inman, or EJ Taylor
Ph: 937-836-7749
Email: [email protected] [email protected] [email protected] [email protected]
18th Annual Mirror Technology SBIR/STTR Workshop
Raytheon Space and Airborne Systems Event Center, El Segundo, CA
5 - 7 November 2018