ERDC-ORNL-Meeting

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Simulations of Novel Carbon-Based Nanostructured Materials Nicholas Jabari O. Lee, PhD US Army Engineer Research and Development Center Presented at ERDC-ORNL Meeting Vicksburg, MS July 14, 2011

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U.S. Army Engineer Research and Development Center (ERDC) People ERDC ITL Management Team Reed Mosher (Director), Deborah Dent (Deputy Director), Robert Wallace (Computer Science and Engineering Division Chief), Chris Merrill (Computational Analysis Branch Supervisor), Bob Welch (Program Director) ERDC Research Team Rick Haskins, Charles Cornwell, Jabari Lee, Anthony Bednar, Tomekia Simeon, Clint Arnett, Thomas Carlson, Kevin Abraham, Pete Stynoski, Jeffry Grey, Lauren Lilly, Carl Feickert, Bob Ebeling (Team Leader-Structural Concepts), Charles Marsh (Team Leader-Material Synthesis) Natick Collaborators Claudia Quigley, Jean Hampel, Karen Buehler, Ben LaPointe NASA Collaborators Richard Jaffe (NASA Ames), Mike Meador (NASA Glenn) Rice U. Collaborators Nobel Laureate Robert Curl; Matteo Pasquali, Robert Hauge MIT – ISN Collaborators Mike Strano, Jae-He Han, Monica Usrey System Managers David Dumas, Hung Nguyen Administrative and Production Assistants Bobbie Edwards, Marsha Gay, Joy Murphy, Leigh Sherwin, Deborah Stewart

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3 Introduction Motivation Objectives Molecular Dynamics (MD) Methodology Setup and Procedure Simulations Analysis and Results Summary Q & A Outline Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates

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4 Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates Motivation Fundamental Tribological Principles MD-informed coarse-grained models of CNT-based materials Industrial interest Affordability of Si wafers

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Description Thin films of largely debundled CNTs of random orientation on substrates Varied chiralities, diameters range 0.7 to 1.2 nm, (typical HiPco composition) Varied lengths from ~100 to ~1000 nm; typical peak in length distribution, ~400 nm A transparent CNT film. Pasquali et al, Rice University (2009) Properties of interest Transparency Conductivity Mechanical integrity Results 84% light transmittance 173.76 Ω sq sheet resistance Thicker films more robust but opaque Rice developed an industrially scalable, fast, and simple process for fabricating optically transparent and electrically conducting thin films of unfunctionalized single-walled carbon nanotubes. SEM micrographs of CNT thin films. Pasquali et al, Rice University (2009) Rice Studies of CNT-based Flexible Transparent Conductive Films

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6 Describe relationships between nanostructure, adhesion and sliding friction in CNT based materials Use molecular dynamics to provide a basis for the development of coarse-grained methods for the study of micron-sized CNT based-systems Report performance of current techniques for reproducing adhesion and sliding friction phenomena at the nanoscale Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates Objectives

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7 Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates Related Research Simulations of Friction in Compressed Vertical CNTs on Diamond Sinnott et al. (University of Florida) Friction Laws at the Nanoscale Szlufarska et al. (University of Wisconsin) Robbins (John Hopkins) Where do surfaces contact? How is friction produced at contacts? How do static and kinetic friction differ and evolve? How does the concept of contact depend on scale? Can large scale experiments test small scale models? Can studies at small scales guide modeling larger scales? Friction and adhesion of vertically aligned CNT arrays on fluoro-nanodiamond films Yakobson et al. (Rice University)

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Newton’s equations of motion Tersoff Potential LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates Methods

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9 Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates Setup and Procedure CNT Vacancy Defect Densities 0% 8% 22% 30% CNT Array on Si [100] Surface 0.1 Å/1000 fs σ

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10 Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates Observations Stick-Slipping Heat Abrasive Wear Transformation Adhesive Wear Varying Friction Rate Dependence

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11 Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates Friction Coefficients for CNT Arrays on Si [010] 30% 23% 8% 0% Time step (1 ts = 1 fs) Stress (bar) — Normal — Lateral T = 300 K V = 10 m/s

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12 MD Simulation-Informed Coarse-Grained Models End Goal Micron Scale Simulations Filament Containing Thousands of Multiwall Carbon Nanotubes (Marsh, et al, 2008) CNT Fibers CNT Coatings on Si Cross-linked CNTs Mechanical Properties of CNT-Si Substrates Transparent Flexible Conducting Carbon Nanotube Films (Pasquali et al, 2009) Summary Molecular Dynamics Simulations of Friction and Adhesion between Carbon Nanotube Coatings and Si Substrates