Multifunctional Extreme Environment Surfaces: Nanotribology for Air and Space. MURI PI: J. Krim, NCS

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Multi-functional Extreme Environment Surfaces
Nanotribology for Air and Space. MURI PI J.
Krim, NCSU
NC STATE UNIVERSITY
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Thrust I Air/Terrestrial EnvironmentsExperimenta
l Leads Nemanich and Zabinski

• ACCOMPLISHMENTS
• Prepared and characterized a series of
  nanocrystalline diamond films.
• Raman tribometer measurements indicated
  variation with deposition conditions.

• APPROACH
• Synthesize nanocomposite blends of Materials
  including nanocrystalline diamond and diamond
  like carbon.
• In situ, real time characterization Raman
  tribometer scanning probe QCM.

• DOD PAYOFF
• Establish approaches to fabricate coatings that
  exhibit adaptive/smart abilities to lower
  friction and resist wear through environmentally
  induced changes in surface chemistry.

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Thrust I Buried Interface Tribology K.J. Wahl,
NRL

• GOALS/OBJECTIVES
• Goal predictive understanding of friction and
  wear
• Objectives
• Determine sliding interface properties
  (chemistry, thickness, mechanics)
• Understand how interfacial processes control
  friction and wear

camera
In situ probe

• APPROACH
• Video and spectroscopic observation of
  transparent sliding interfaces
• Monitor interfacial film rheology, thickness,
  chemistry, mechanics

• DOD PAYOFF
• Understanding how in-contact processes influence
  friction and wear will lead to predictive surface
  engineering

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Thrust I - Terrestrial Applications Theory Lead
M.A. Zikry

• ACCOMPLISHMENTS
• Developed a microstructurally-based
  finite-element code to investigate interfacial
  effects due to GBs and different material
  constituents in nanocrystalline materials
• Have linked molecular dynamic simulations with
  microstructurally-based FEM code to investigate
  GB sliding and nanoindentation in nanocrystalline
  materials

Finite-element based predictions of void
interaction/ductile fracture in crystalline
materials for different void sizes

• APPROACH
• Use and develop specialized 3D finite-element
  methods (FEM) to analyze effects of grain-size,
  interface strength, grain-boundary (GB) effects
  for optimal nanocomposite behavior and failure
  resistance for different temperature and loading
  regimes
• Use a validated multiscale framework for linking
  continuum methods to atomistic simulations
  through modeling of interfacial and
  nanoindentation/wear experiments

• DOD TECH PAYOFF
• New hierarchical predictive framework for design
  guidelines to significantly improve existing
  surface treatment/wear performance
• Control of lubricant performance such that new
  resilient materials can be designed for harsh
  environments

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Thrust II Space, Cryogenic Vacuum
EnvironmentsExperimental Lead P. Taborek, UCI

• ACCOMPLISHMENTS
• Built optical cryostat for friction measurements
  in vacuum at low temperatures
• Developed method for electrically monitoring
  motion of MEMS devices in vacuum/cryogenic
  environment

• DOD PAYOFF
• Understanding tribological issues which limit
  MEMS performance is crucial for reliable
  deployment in extreme environments.

• APPROACH
• Survey tribological behavior of MEMS devices in
  vacuum at low temperatures
• Develop optical and electronic methods of
  monitoring motion in extreme environments

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Thrust area II Cryogenic and Space
ApplicationsTheory Lead Judith A. Harrison, US
Naval Academy

• ACCOMPLISHMENTS
• Figures show a nanocrystalline diamond
• film and the local stress distribution with
• a cross-sectional slice of the film.
• Films are composed of diamond clusters
• (sp3) in a sp2-bonded network. Similar
• films can be grown in the Nemanich lab at
• NC State via Microwave Plasma Growth.
• Local stress plots show regions of high
• low stress (total pressure is zero).
• Films with various numbers of diamond
• clusters (8-343) with zero total pressure
• have been created.

sp3 carbon sp2 carbon
Local stress in a film slice

• APPROACH
• MD simulations and the REBO (C-H)
• potential, developed by Brenner, are being
• used to examine the mechanical and
• tribological properties of nanocrystalline
• diamond films as a function of temperature.
• Parallel MD codes are being developed.
• A re-fit of the REBO potential is planned to
• add additional atom types, N, Si, O, F.

• DOD PAYOFF
• Identification of film structures properties
  needed for optimum lubricant design.
• Development of lubricants for space based
  applications requires knowledge of film behavior
  over a range of temperatures.

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Gold/ Alloy Synthesis and Contact Measurement
Thrust III Electrical Contacts for MEMSRF
Lead Angus I. Kingon, North Carolina State
University

• ACCOMPLISHMENTS
• Figures show the upper gold contact
• made by specially developed micro-
• stamping technology. AFM, SEM
• was used to characterize the quality
• for the alignment purpose.
• Gold and Chromium adhesion layer
• have been synthesized. X-ray
• diffraction and four point probe have
• been used to estimate grain size and
• electrical resistivity of gold/ Alloy films.

• APPROACH
• Gold/ gold alloy are being made in an
• ion beam sputtering system. Effects of
• adhesion layer and diffusion layer are
• being invested as well
• Gold/ gold alloy on SiO2 substrate is
• planned to be patterned for the test in
• modified AFM apparatus.

• DOD PAYOFF
• Development of a rapid contact
• material screening system
• Understanding of dispersion
• strengthening of gold contact
• materials to improve the contact
• reliability.

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Thrust III Silicon MEMS Applications
Experimental Lead Jacqueline Krim

• Accomplishments
• Synthesized MEMS type polycrystalline silicon on
  a QCM
• Completed MEMS tribometer set-ups in three
  locations nationwide.
• Begun to model and take QCM measurements of the
  nanodynamics of bound plus mobile lubricants

Laser photo-detector setup at NCSU for real-time
monitoring of the Sandia MEMS tribometer response.

• APPROACH
• Perform in situ real time measure-ments of
  tribocontact via force microscope, QCM-STM and
  on-chip MEMS tribometers.
• Perform parallel first-principles simu-lations of
  sliding contact and wear.

• DOD TECH PAYOFF
• Increased temperature and environmental operating
  ranges for silicon MEMS devices.
• Increased lifetime for rubbing contacts in
  silicon MEMS devices.

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Thrust III Molecular Models of BoundMobile
LubricantsTheory Lead Don Brenner

• ACCOMPLISHMENTS
• Developed molecular structure for TCP SAM on
  SiO2.
• Incorporated appropriate force field into
  molecular modeling code
• Calculating rates for TCP diffusion, desorption
  and incorporation into film defects.

• APPROACH
• Detailed molecular modeling to calculate
  structures, desorption/diffusion properties for
  bound mobile lubricants
• Incorporate data into continuum codes to
  calculate friction/wear properties across length
  scales
• Validate against experiment

• DOD PAYOFF
• Detailed understanding of friction /wear
  mechanisms of bound mobile lubricants
• Insights for design of new lubricants
• Better insight into existing experimental
  systems