1. 1. Summary of the Numerical Simulation Project Conducted in NBIL By Yashar Seyed Vahedein 03/19/2015
2. 2. Produce New Cell Tools Template based manufacturing CVD Experiment CVD Simulation Fabricating CNTs with higher efficiency Need for template based manufacturing of CNTs Output of the process NBIL Inlet Gasses AAO Template Furnace Dimensions Temperature and Flow rate Predict CNT manufacturing process designed by NBIL Lab Motivations: Control the process and the effect of the parameters on deposition. Save time and resources by simulating the process Create a universal method to be used by others for TB-CVD (not currently available in literature) Diagram of the Driving Needs, Process and Outcome of TB-CVD INPUTS NBIL Single cell analysis Electrical,Bio,nano, Mechanical app. High conductivity& strength 2
3. 3. Schematics of the Template Based-CVD Setup in NBIL 1. NBIL: Nano Bio Interface Laboratory Exhaust Heated region Heater Heater F.MPrecursorgas Carriergas Temperature knobs Position of the templates Carbon deposited in a template Carrier gas: Ethylene Helium (Mixture) Precursor gas: Argon Experimentally Observed change in Deposition due to the Increase in Flow Rate M. Golshadi, J. Maita, D. Lanza, M. Zeiger, V. Presser, and M. G. Schrlau, Effects of synthesis parameters on carbon nanotubes manufactured by template-based chemical vapor deposition, Carbon, vol. 80, pp. 2839, Dec. 2014. 3
4. 4. Defining the Boundary Conditions based on Physical system Heated Walls Inlet flow temperature = 300k Inlet Flow rates: 20 to 300 sccm No slip condition on tube wall and templates = 0 1 = 6680 1 = 6880 1 = 6680 = 0 = 0 = 0 5 304.8 mm 3.88mm 4.88mm 72.3mm 2 13mm 4mm 6.8mm Static gauge pressure in the outlet = 0 4
5. 5. Formulation of the problem in CFD with conservation equations (Navier stokes approach) Generalized Source term (constant and linear) Generalized diffusion coefficient Generalized Transport Variable By taking divergence of these two, they can be transformed into volume integrals. + . = . + Rate of increase of mole of the species Net rate of additions of mole of the species per unit volume by convection Molar-averaged velocity Net rate of mole of the species per unit volume by diffusion in a binary system of components, otherwise xa is replaced by The molar rate of production of species by chemical reaction = = =1 If the number of chemical reactions taking place in the system is , the mass production rate is: stoichiometric coefficient Difference between the forward and backward reactions Fluent solves the differential form of this equation: 5
6. 6. Approach to Solve this Problem This numerical problem is solved using: Compressible laminar flow. Temperature dependent Ideal gas. Consumption of species on templates . Mixture of Ethylene helium entering from the inlet into a bed of residual argon. Steady state formulation is used based on a validation process using 2D transient solution. Pressure-based solver with a coupled pressure-velocity coupling is utilized. 6
7. 7. Comparing results from 2D and 3D model to choose how to best represent the system 0.150.100.050.00-0.05-0.10-0.15 690 680 670 660 650 Position from middle of tube furnace [m] Temprature[C] Temperature Vs Length - 25.4 mm Above Bottom Wall Temperature Vs Length - 38.1 mm Above Bottom Wall Temperature Vs Length - 25.4 mm Above Bottom Wall(simulation) Temperature Vs Length - 38.1 mm Above Bottom Wall(simulation) 0.02m Area in vicinity of templates Comparison of Temperature along the Heated Region Simulation Vs. Experiment 20 mm 300 mm 3D 150 mm 100 mm100 mm [m/s][K] 2D 3D Streamlines in the middle cross section and along the tube Temperature Contour Plots Velocity Vectors Constant Temperature Velocity Vectors 7
8. 8. Tube Membranes 60 SCCM Membranes 60 SCCM Recirculation on lower flow rates, cause better mixing CVD Tube Furnace Schematics Velocity Vectors for 60 SCCM Flow rate Contour plots of (Ethylene), Velocity Vectors and an Animation Showing Transient Concentration Profile Evolving Through Time Mass fraction will be related to the reaction rate 3.00e-01 2.94e-01 2.88e-01 2.81e-01 2.75e-01 2.69e-01 2.63e-01 2.56e-01 2.50e-01 2.44e-01 2.38e-01 2.31e-01 2.25e-01 2.19e-01 2.13e-01 2.06e-01 2.00e-01 1.94e-01 1.88e-01 1.81e-01 1.75e-01 1.69e-01 1.63e-01 1.56e-01 1.50e-01 1.44e-01 1.38e-01 1.31e-01 1.25e-01 1.19e-01 1.13e-01 1.06e-01 1.00e-1 9.38e-02 8.75e-02 8.13e-02 7.50e-02 6.88e-02 6.25e-02 5.63e-02 5.00e-02 Evolving Mass fraction conditions 8
9. 9. Results for mass fraction and velocity distribution 30020010080604020 0.0100 0.0075 0.0050 0.0025 0.0000 u-velocity(m/s) Boxplot of u-velocity - flow rate range from 20 to 300 sccm Flow rates (sccm) Uvelocity(m/s) Contours of Axial, Vertical and transverse Velocity components Mass Fraction Distribution (Left) and Velocity Vectors (Right) for Different Flow rates 9
10. 10. Line-Averaged Mass Fraction Vs. Flow rate on the Midline Passing Through two Templates 0.12 0.125 0.13 0.135 0.14 0.145 0.15 0.155 0 50 100 150 200 250 300 350 MassFractionofEthylene Flow rate [SCCM] 20-300 10
11. 11. Mass Fraction Evolution Video for 60 sccm Flow Rate 11