Multi-functional Extreme Environment Surfaces: Nanotribology for Air and Space. MURI PI: J. Krim, NCSU

Our MURI team consists of three highly overlapping sub-groups focusing on air, space, and MEMS applications. Our overarching objective has been to establish the scientific foundation of the tribological properties of multi-functional surface treatments in terms of scale-dependent thermal, chemical, and mechanical processes. We have employed the knowledge gained to introduce a new generation of multi-functional coatings, comprised of constituents that are optimally scaled and blended for life-cycle service in the ex- treme environments associated with air, space and MEMS applications. To reach these goals, our team has combined methods for synthesizing advanced materials, highly innovative and unique test-devices, and predictive multiscale modeling to identify and exploit the critical physical mechanisms that underlie the successful performance of structures that operate in a widely varying range of extreme environments. This strong coupling between synthesis, testing, and modeling, which is a hallmark of our team, has provided unique new scientific insights and engineering capabilities not possible individually. We report today on the major accomplishments of our team.

Statement of Work

Multi-functional Extreme Environment Surfaces: Nanotribology for Air and Space. MURI PI: J. Krim, NCSU

NC STATE UNIVERSITY

Academic Team Members SpecialtyJacqueline Krim,(a) Prof. of Physics & Assoc. of ECE NanotribologyDonald W. Brenner,(a) Prof. of Materials Science & Eng. (MS&E) Computational Tribochemistry Judith A. Harrison,(b) Prof. of Chemistry Computational NanotribologyAngus I. Kingon,(h) Prof. of Materials Science & Eng Nanomaterials DesignJames Rutledge,(c) Prof. of Physics CryotribologyPeter Taborek, (c) Prof. of Physics Cryotribology & CoatingsMohammed A. Zikry,(a) Prof. of Mechanical & Aerospace Eng. ComputationalNanocomposites

DoD & DOE Team Members SpecialtyMichael T. Dugger,(d) Ph.D, Material Science and Engineering Microtribology & MEMSKathryn Wahl,(e) Ph.D, Material Science and Engineering Tribocoating AnalysesAndrey A. Voevodin (f) Ph.D, Chemical Engineering Aerospace Tribocoatings

Industrial Partner SpecialtyArt S. Morris III,(g) Ph.D, wiSpry Inc. RF MEMS

Participating Institutions: (a)North Carolina State University, (b)United States Naval Academy, (c)University of California-Irvine, (d)Sandia National Laboratories, (e)Naval Research Laboratory, (f)Wright Patterson Air Force Research Laboratory, (g) wiSpry Corp.(h)Brown University

Objective: Fundamental solution of Air Force/DoD and commercial tribological

problems deemed paramount for advanced air and space applications.

Our overarching objective is to establish the scientific foundation of the tribological properties of multifunctional and nanocomposite surface treatments.

DoD Benefit:

Predictive capabilities, demonstrated viability and improved performance for lubricants

custom tailored at nanoscale for custom DOD applications that include communications,

electronics, weapon locking, satellite bearings, InfraRed sensor mechanisms, jet engine

bearings, phased array radar, miniature air vehicles, miniature satellites and sensors.

Technical Approach:

Preparation and characterization of nanocomposite blends

Modeling: Pioneering new computational methods.

Realistic, Real-time and accelerated Test Methods, designed to reveal the scientific

basis for tribological performance.

Interactions/collaborations

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UFL MURI , AFRL , Sandia ,S. Kim, Penn State, R. Carpick, U. Penn UCSD Center for RFMEMS

Multi-functional Extreme Environment Surfaces: Nanotribology for Air and Space. PI: J. Krim, North Carolina State University

Outstanding Questions/Challenges•How do surface films (adsorbed, 3rd body, tribo-generated) control our systems?•Where does the heat go?

5

Program Highlights:•

New multiscale models: Hierarchical MD/FE simulations.•

Nanoscale dynamical measurements of bound plus mobile lubricant systems that indefinitely extends silicon MEMS device lifetime.

•

New analytic multi-scale expressions for effective liquid lubrication of oscillating contacts via surface flow over multiple time and length scales.

•

Construction of and successful completion of a C-O-H reactive potential that for the first time allows modeling of water-containing materials.

•

Modeled & friction measurements of model diamond nanocomposites.•

New in situ method for monitoring solid lubricant transfer films•

First time measurements of the cryogenic wear and friction of tribological materials over length scales spanning aircraft to molecules.

•

Asperity creep of more compliant material explains much of the time- dependent resistance of closed RF-MEMS switches.

•

Over fifty students & post-docs trained, 12 Ph.D. Dissertations.

Multi-functional Extreme Environment Surfaces: Nanotribology for Air and Space. PI: J. Krim, North Carolina State University

Cryogenic tribometer

Bound + Mobilemodellng

Nanocrystalline Diamond Model

Finite Element AnalysisSi MEMS Tribometer

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Thrust I: Nanocomposite Coatings for Terrestrial Applications

Gears and bearings for aircraft and jet engines; Reusable launch vehicles

Thrust II: Cryotribology and Nanocrystalline Diamond for Space Applications

Satellite bearings, InfraRed sensor mechanisms Jet engine bearings

2 μm

NCD

MCD

300 μm

Thrust III: Silicon MEMS ; Bound + Mobile Lubrication

Communications, electronics, sensors, weapons locking miniature air vehicles, miniature satellites

Si Substrate

TCP

Solid Lubricants in space-based devices Satellites in extreme environments

300 μm

30 μm

Integrated multi-band (30 MHz- 300 GHz) RF MEMS antenna

router for communications, PC routing, etc.

RFMEMS- based satellite communications

Compared to conventional devices, RF-MEMS have:

Small sizeLow power consumptionWide band widthGood signal discretion

Portable&

Versatile

Thrust III: RF MEMS Applications

THRUST II: Cryogenic &Vacuum Environments Leads: Taborek & Harrison

THRUST I : High Temp. &Moist/Dry Environments, Leads: Nemanich, Voevodin & Zikry

THRUST III: Silicon & RFMEMS Contacts. Leads: Kingon, Krim & Brenner

Level (1) MaterialsPreparation

Level (2) MacroscaleTest setups

Level (3) MesoscaleTest setups

Level (4) NanoscaleTest setups

Level (5) Modeling

Polycrystalline SiBound + mobile monolayer phases. Krim, Nemanich.

Nanocrystalline MultifunctionalDiamond Nanocomposites. Nemanich. Voevodin

ConductingNanocompositesKingon.

Polycrystalline SiBound plus mobile monolayer phases. Krim, Nemanich.

Static & sliding friction, wear, 4K – 600K Taborek, Rutledge, Zabinski.

Sliding friction, wear, 300 – 1100 K Voevodin

RF MEMS switchEnvironmental &Temp.dependence.Krim.

MEMS tribometer studies, 4 – 300 K.Taborek, Rutledge, Dugger.

In situ, real time characterization of materials evolution in tribocontacts. Wahl.

In situ, real time characterization of electrical resistance in MEMS RF switches. Kingon, Patton

MEMS tribometer studies, 300 – 700 K. Dugger, Taborek, Krim.

Static and sliding friction, wear 4 K – 600 K Taborek,

Rutledge, Zabinski .

LFM studies of atomic scale friction and adhesion. Nemanich, Krim.

QCM-STM real-time imaging of tribocontacts Krim, Nemanich, Kingon.

QCM mobility studies in bound & mobile monolayer phases. Krim.

AFM topological studies of the evolution of RF switch contact zones. Kingon, Wahl.

Coordinated modeling efforts: Brenner-Atomistic dynamics, structure & mobility, Harrison– Diamond/diamond-like interfaces, monolayer dyanmics Zikry–Continuum, micro-structural modeling of fracture, creep, fatigue, & GB sliding of nanocomposite, nanocrytalline aggregates.

Project Leader: Jacqueline Krim

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Team Meetings and Interactions

• November 2004: kickoff meeting in Annapolis;• May 2005: PI meeting at WPAFB• October 2005: program review at NCSU;• Feb 2006: student/post-doc presentations at UCIrvine• July 2006: PI meeting at Naval Academy; • August 2006: program review at WPAFB• Feb 2007: student/post-doc presentations at Naval Research

Laboratory• July 2007: PI meeting at Sandia National Laboratory • October 2007: Program Review at UF Gainesville• Feb 2008: student/post-doc presentations at NCSU• Dec 2008: PI meeting at Chicago ORD• Biweekly web-based conference calls for each thrust and sub-

thrust area memberswww.extremefriction.physics.ncsu.edu

Publications, Presentations

>80 referred publications in refereed journals, book chapters, cover stories, encyclopedia articles and conference proceedings.

(2005)National Space and Missile Materials Symposium, Outstanding Poster (1st Prize), Operating in Space Session, Douglas L. Irving et al.

>70 invited talks, including 4 keynote/plenary lectures at conferences.(2005) World Tribology Congress, Washington DC: Harrison , Keynote lecture(2005) University of Columbia, MO: Brenner, Plenary lecture(2009) ViennaNano , Vienna, Austria: Krim, Plenary lecture(2009) Advances in Boundary lubrication, Seville, Spain : Krim, Harrison invited

keynote lecturesCover stories by Sawyer, Wahl, Dugger, Kim and Krim

Honors & Awards

• 2004-2005: M. A. Zikry, Senior Fulbright Research Award

• 2006: K. Wahl, Fellow of AVS For exceptional contributions to the fundamental understanding of contact mechanics, adhesion and tribology at the nanometer and micron scales

• 2006: A. Kingon, Price Foundation Award , Innovative Entrepreneurship Educator

• 2008: M.A. Zikry, Jefferson Science Fellow , US State Department (2008), initiated by the Science and Technology Adviser to the Secretary of State to further build capacity for science, technology and engineering expertise within the Department.

• 2008: D. E. Brenner, Appointed to Kobe Steel Distinguished Professorship in NCSU Materials Science and Engineering Dept.

• 2008: A. Kingon, Appointed Barrett Hazeltine University Professor of Entrepreneurship , Distinguished Professorship at Brown University (July 2008)

• 2008: K. Wahl, Department of the Navy - Meritorious Civilian Service Award, September 2008, for Exceptional contributions to the advancement of Naval Research in the fields of contact mechanics and the chemistry of adhesion, friction and wear.

Student Development

• 12 Group Alumni: are presently placed as staff scientists, analysts and process engineers throughout the US and Canada.Government labs: NRL, Army, USDA, interviews pending at NIST, OakridgeIndusty: Cree, Applied Materials, Inc, Boeing Corp., Linear Technology, IncAcademia: faculty members at McGill University, NC StateContinuing studies: Harvard Business MBA, NCSU Nuclear Engineering Ph.D.

• Projection: At the project completion point, an estimated 50 students and post-docs will have been trained with direct experience in areas of national need, including 12 Ph.D.’s.

Project Schedule and Milestones

• Phase I: Combining existing expertise. (May 2004 – November 2005)

In this beginning period, the separate expertise at the various partner institutions was combined and materials’ standards were developed to produce baseline material.

• Phase II: Exploitation of new capabilities (December 2005 – April 2007) In this period, the combination of separate expertise at the various partner institutions was completed, and active data recording with the new tools available was performed by our research team.

• Phase III: Deliverables, Technology transfer and Commercialization (May 2007 – April 2009) We are reporting today on the central accomplishments of our MURI team and deliverables that could not have been achieved through indiviudal efforts.

August 2006October 2005 January 2009

I II III

Highlight – Multi-Scale Lubrication

Broader ImpactDefined a framework to unify liquid lubrication requirements across scales

Reaches from industrial machines to MEMS/NEMS

Experimental Observation“Windshield Wiper Effect”: STM images clearer withQCM on than with the QCM off. QCM vibrates fastenough to maintain clear area of surface?

Off

On

Modeling•Quantified bound+mobile diffusion

•Used as input to scaling relation forMEMS devices•Discovered new dynamics related to filling of defects in SAMs

Theory •Solved reciprocating diffusion equation for diffusion constants D, contact areas A and times t•Determined scaling parameter A/Dt

Ideal for MURI Effort

Not possible without strong team interactions

Addresses critical DoD needs

Creates broad fundamental knowledge

Ideal for MURI EffortIdeal for MURI Effort

Not possible without strong team interactions

Addresses critical DoD needs

Creates broad fundamental knowledge

Si MEMS Lubrication

Experimental ObservationVapor phase lubrication solves the MEMS

lubrication problem.

MEMS Experiment •MEMS tribometer confirms lubrication by1-pentanol and shows lubrication by ethanol.

• Rigorously controlled environment allows identification of different mechanisms for these two alcohols.

QCM Experiment• Complementary information

clarifies mechanisms

• Traditional techniquefor nano-scalePhysics.

Broader ImpactSingle and submonolayer lubrication is relevant far outside

the nanometer device regime

Rutledge: Goals and Objectives

Goal: Identify lubricants that will prevent the immediate failure of sliding SiMEMS contacts and determine the microscopic lubrication mechanisms.

Problem Statement: Sliding contacts in MEMS have notoriously short lifetimes to failure and standard lubrication techniques have proven ineffective.

What we have learned: Sliding Si MEMS contacts lubricated by alcohol vapor, ethanol or pentanol, have effectively infinite lifetimes. Tricresyl phosphate (TCP) experiments indicate that it, without a bound SAM layer, may be superior to the alcohols.

Vapor Phase Lubrication

Mobile alone

Ethanol

Bound +Mobile

Pentanol SAMS aloneTCP

Cryotribology

Experimental Observation

Materials •Steel•PTFE•MoS2

•Diamond: MCD,UNCD,DLC•Si, SiO2

•Al2 O3

•Liquid lubricants

Modeling•MD simulations of diamond interfaces

•Heat flow•Hydrodynamic lubrication •Simulations show same trends as AFM measurements of diamond and NCD as well as Sang Theory.

Broader ImpactSpace bearing materials can, in principle, be tested on the ground before deployment

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In the absence of a liquid lubricant, friction behavior is relatively insensitive to temperature over many length scales.

Taborek: Goals and Objectives

Goals: Identify the fundamental physical mechanisms of friction using controlled environments and cryogenic temperatures.

Problem Statement: How does friction depend on temperature for a variety of materials over a range of length scales?

What we have learned: Dry sliding friction is relatively insensitive to temperature for a wide variety of materials and length scales. Liquid lubricants show diverse thermal sensitivity.

Low Temperature Friction

Macro-Meso-Nano-

Atomic-

Diamon dTi-MoS2PTFESiO2

ExperimentSimulation

Nye Space Lubricant

R. Carpick, Oxygen found in UNCD wear track

Photon Energy (eV)

O 1s Spectra

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(A.U

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Unworn area

Worn area

Konicek, Grierson, Gilbert, Sawyer, Sumant, Carpick, Phys. Rev. Lett. 100 (2008)

Modeling Tribochemistry in Oxygen-containing materials

Broader ImpactOur detailed studies of friction in DLCs will lead to moving MEMS components with enhanced

lifetimes that can be deployed in a wide-range of environments.

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Simulation• Simulations beginning that examine the effects of H2 O & CO2 vapor on DLC friction.

• Effects of alcohol VP lubricants & O termination can also be studied.

Harrison: Goals & Objectives

Goal: Explain the fundamental mechanical & tribological behavior of diamondlike carbon (DLC) and related materials in different environments (e.g. humidity, temperature) using MD and FE simulations. Develop reactive potential energy functions for diamond in the presence of water.

Problem Statement: No reactive potential energy function existed that could model water and DLC? How do the mechanical properties, adhesion & tribology of DLC change with temperature?

What we have learned: Fluctuating charge models can be integrated into the AIREBO formalism to model sliding in the presence of water and alcohols. MD and FE hiearcharcal simulations can yield complementary results.

Diamond, DLC, NCD

Mechanical properties (MD & FE)

qAIREBO potential for polar materials

Temperature Dependence(AFM & MD)

Unravel effect of humidity in DLC friction

RF-MEMS Creep

Experimental ObservationResistance in RM-MEMS switches appearto plateau with a value that depends on opening sequence.

Theory •Data from experiment & modeling show power law for R vs t with exponent material dependent.•Analytic asperity creep model yields behavior, explains parameters

Modeling•Plasticity modeling of contacts

•Surface roughness derived from experiment•Same qualitative trends, different resistances?

Broader ImpactAnalytically defines asperity creep and contact resistance for any system in

terms of fundamental materials properties

Brenner: Goals and Objectives

Identify fundamental mechanisms of switch failure using a combination of theory, modeling and extensive experiments for controlled environments and cryogenic temperatures.

Problem Statement: What dominates switch resistances: interface topography and dynamics; surface contaminant films; temperature-structure effects?

What we have learned:Asperity creep of the more compliant material explains much of the time-dependent resistance of closed switches; de-adhesion nanowires may contribute to material transfer during switch opening; current flow occurs primarily through just a few asperity contacts.

Failure Mechanisms

Contact melting

Contaminant Films

Material Transport

Adhesion and Wire Formation

Creep and Interface Topography

Adaptive Nanocomposites: Wahl and Zikry presenting

Broader ImpactAn integrated predictive methodology that can be used to design

nanocomposite coatings in terms of optimal material constituents, distributions, grain-sizes/shapes, and fracture behavior

2 um

5nm

EXPERIMENTAL OBSERVATIONCombinations of ductile and brittle materials,DLC, Au, MoS2 , YSZ, have superiortribiological behavior for structural and coating applications in extreme environments:low wear, low friction, structural integrity

THEORYDeveloped nanocomposite representative volume elements & grain/matrix morphologies & topologies

MODELINGNew microstructal finite-element,contact algorithmsand failure models for wear at different scales

Goal: Develop in situ analytical methods to identify how nanostructuredmaterials impact friction and wear performance.

Problem Statement: Without in situ and real-time methods, it is nearly impossible to determine how friction evolves with sliding

What we have learned: MoS2 is the key lubricating phase in hard nanocomposite lubricants. In nanocrystalline diamond, the presence of graphite crystallite structure is more effective than amorphous sp2 carbon in reducing run-in friction.

Friction / Wear Contributors

Surface Chemistry

Phase / structure Roughness

Composition

Texture

Wahl: Goals and Objectives

Zikry: Goals and Objectives

Nanocomposites for tribological applications in extreme environments

Problem Statement: What are the optimal material compositions, combinations, and grain sizes, morphologies and orientations for desired nanocompositebehavior and wear?

What we have learned: Different ductile and brittle constituents can be combined and controlled for desired material behavior and wear response for nanocontrolled tailor design.

Nanocomposite Thin Films

Wear Mechanisms

Transfer Film Effects

Critical Failure

Stresses/Strains

ContactConstituents/Grain sizes and scale effects

Challenges and Unsolved Issues

From a fundamental viewpointFrom a fundamental viewpoint……..• How does work hardening from multiple switching

influence performance and lifetime? • What is the field-induced material transfer

mechanism?

From a theory and modeling viewpointFrom a theory and modeling viewpoint……..• Can constitutive relations for surface adhesion be

derived from the atomic modeling?

From an applications viewpointFrom an applications viewpoint……..• How do we turn this new basic knowledge into

enhanced device performance?

More Challenges and Unsolved Issues

• Tribochemistry: linking of MD with FEM through scaling relations: multiscale work and experimental observations.

• Bonding strengths/cohesive behavior can then be linked over different lengths: coupled mechanical/chemical behavior

More Challenges and Unsolved Issues

• Understand the connection between chemistry and lubricity.

• How do surface films (adsorbed, 3rd body, tribo-generated) control our systems?

• Where does the heat go?

Challenges and Unsolved Issues are Never ending

The more we learn,the more we want to learn more!