Status of NCD Growth and Tribology First Quarter 2006

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Status of NCD Growth and Tribology First Quarter
2006

• A.L. Winfrey, R.R. Chromik,
• R.J. Nemanich, K.J. Wahl

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Nanocrystalline Diamond Coatings for Extreme
Tribological Applications
Deposition Strategies Vary pre-cursor gases,
Dope with N and B
Goal Provide advanced hard carbon films with
controlled bonding and nanoscale morphology.
Characterize and model tribological performance
over a range of length scales and environmental
conditions.
Nanocrystalline Diamond Coating
Processing
Finite Element Modeling Microstructure Effects
Characterization
Thin film analysis SEM, XRD, AFM, Raman
Modeling
Tribological Characterization Environment and
Scaling Issues
Predict Properties? Different Scales?
Atomic -Scale Modeling Crystal Shape Effects
Macro
Diamond crystals (red) embedded in amorphous
carbon (yellow)

• Payoff to Air Force
• Robust, well characterized material with
  applications to tribology over a range of length
  scales from macroscopic parts to MEMS.
• Understanding of variable environment on
  tribological behavior, including harsh
  environments high temperature, cryogenic
  conditions, vacuum and high humidity.

In situ, variable T (hot ? cryo), UHV
Performance
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NCD - Fundamental Question (Ongoing)

• How do friction, wear, and tribology relate to
  the films morphology and bonding?
• How do we control morphology and bonding through
  the growth process?
• Our intent is to create films with a variety of
  properties. This will increase the potential of
  finding candidates for application in the thrusts
  of the project proposal.

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Key points in NCD

• Literature search indicates that work is being
  done in
• 1. UNCD, ultrananocrystalline diamond
• 2. Doping
• done at Argonne, NRL, Auburn, Taiwan, NASA,
  Privates
• Work is being done in application of UNCD to MEMS
  devices. Experiments are being done with various
  doped films and their electrical properties.
• We are working in the UNCD regime and working
  toward investigating doped films for their
  mechanical properties.

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Key points in Diamond Friction

• Literature search shows research in
• Single crystal diamond friction
• Different fabricated diamond films (MCD vs. NCD)
• Done at NRL, Argonne, Brown, Carpicks group
• Friction is studied sliding sapphire, SiC, Si3N4,
  steel, diamond on coatings
• What we are working on
• Sapphire on NCD friction
• Projected self-mated friction
• Variable temperature measurements
• Microtribology
• AFM/LFM
• Front v. backside friction

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What Were Doing

• MURI Focus of Work
• Structure and morphology of film relate to
• 1. growth process
• 2. performance
• Work areas/Methods Employed
• Fabrication
• Characterization
• Tribology
• Modeling

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Status of My Work Films and Counterfaces

• Grow films with different morphology,
  characteristics, and performance
• Repeatable process
• Data
• Analysis
• Conclusions
• Following slides show my work

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NCD Film - Production

• Method MPCVD
• Pre-treat Si wafer in MeOH/Ti/Diamond slurry
• Initiate, tune, and mix base plasma
• Add growth gas
• Measure temperature with optical pyrometer
• Current Film Growth Parameters
• Films H0- H100
• 65 Torr
• 900 W
• 900 C, (Mo or Quartz stage)
• 70 sccm total flow
• CH4 10 total gas flow

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NCD Film Production Samples Provided
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NCD Counterface Production

• Same method and parameters as films
• Growth is much faster
• 1st attempt grown too long, 3mm black growth
• Shorter growth times coating less cloudy
• Problem with flaking, need to be thinner
• Move counterface farther from plasma, lower
  temperature to decrease growth rate and avoid
  blackening

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NCD Production UpdateFilms and Counterfaces

• Provided Samples
• UV Raman
• Ambient/Variable Temp AFM
• TEM
• High Temp friction
• NEXAFS
• Samples in progress
• Counterfaces
• Planned/Next Samples
• High Temp friction
• Low Temperature friction
• Nitrogen Doped Samples and Counterfaces
• Large size samples (ANL)

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NCD Film Characterization

• Question raised about SEM and AFM images appeared
  different
• Structure in SEM not in AFM
• New AFM images of LW16 show the same features

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Tribological PerformanceFriction Tests
camera
In situ probe

• Reciprocating with Sapphire Counterface
• Contact stresses of 0.72 GPa
• Sliding speed 1 mm/s
• 35-45 RH
• also performed Pin-on-Disk with sapphire
  counterface

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NCD TribologySteady State Friction and Run-In
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NCD Wear In-situ Contact Sizes

• Coatings with shortest run-in (H30, H36 and H8.5)
  all had the smallest increase in contact size.
• Except for H64, tests on all coatings resulted in
  minimal wear of the sapphire counterbody.

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Comparison of In situ measure vs. ex situ measure
of counterface wear
x106
x106
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Trends Observed Related to Coating Structure

• Run-In decreases with
• Increase in mystery x-ray peak intensity
  (graphite or TPA)
• Change from (220) to (111) orientation
• No trend with roughness

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Technical SummaryFilms and Tribology

• Growth Conditions (0 36H)
• Fine needle like crystals (G.S. 5 -10 nm)
• As hydrogen concentration in the plasma was
  increased
• RMS roughness increased
• Graphite content increased
• Qualitative crystalline orientation changed from
  (111) to (220)
• Tribology
• coatings with the needle-like morphology
  exhibited steady state friction coefficients from
  0.05 0.07.

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Technical SummaryChallenges

• Coating counterfaces
• Delamination of film during TEM preparation
• Think this has to do with the growth temperature
• New sample at higher temp

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Technical Summary Opportunities

• Counterface coatings show promise
• Grow new samples for extreme environment testing
• Coat larger surface areas
• Doping

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Look Ahead

• Expand the horizon to investigate the potential
  aerospace applications
• Engines and Mechanical Parts
• Tools for machining parts
• MEMS
• Electrical Devices
• Get/Give feed back to/from tribology groups and
  theory groups in our team

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NCD Application

• Engines and Mechanical Parts
• Low friction, long wearing
• Can be used to coat moving parts
• MEMS
• Hard, strong, wear resistant, low friction
• Low stress
• Uniform coatings
• Electrical Devices
• Conduction or insulating
• Good electrical emitters

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Next Steps

• Fill in samples that are necessary
• Prepare for review in August

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Publications

• Submitted, Accepted, or Published
• A.L Winfrey, S.E. Reising, L.S. Bilbro, R.J.
  Nemanich, R.R. Chromik and K.J. Wahl,
  Tribological properties of nanocrystalline
  diamond films with different nanoscale morphology
  and bonding characteristics., Proceedings of
  World Tribology Congress III, Paper
  WTC2005-63691.
• A.L. Winfrey, R.R. Chromik, K.J. Wahl, and R.J.
  Nemanich, Properties of Nanocrystalline Diamond
  Films with Different Morphology and Bonding
  Characteristics., Proceedings of ICNDST May
  2006, Paper 230499
• In Preparation
• A.L. Winfrey, R.R. Chromik, M.J. Brukman, L.S.
  Bilbro, K.J. Wahl, R.J. Nemanich,
  Characterization of NCD coatings prepared with
  different growth conditions.
• R.R. Chromik, A.L. Winfrey, R.J. Nemanich, K.J.
  Wahl, In situ tribology investigation of
  nanocrystalline diamond coating.
• On the Horizon
• Nanoindentation on coatings to determine
  mechanical properties
• Microtribology on worn or backside of NCD coatings