1. Summary of the Numerical
Simulation Project Conducted in
NBIL
By Yashar Seyed Vahedein
03/19/2015

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. Schematics of the Template Based-CVD Setup
in NBIL 𝟏
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. 28–39, Dec. 2014.
3

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 ∶
𝑑𝑢
𝑑𝑥
= 0
𝑇1 = 6680
𝑐 𝑇1 = 6880
𝑐 𝑇1 = 6680
𝑐
𝑑𝑇
𝑑𝑥
= 0
𝑑𝑄
𝑑𝑥
= 0
𝑑𝑄
𝑑𝑥
= 0
5 × 304.8 mm
3.88mm
4.88mm
72.3mm
2 × ∅13mm
4mm
6.8mm
Static gauge
pressure in the
outlet 𝑝𝑠 = 0
4

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.
𝜕𝑐 𝐴
𝜕𝑡
+ 𝛻. 𝑐 𝐴 𝑉∗
= −𝑐𝛻. 𝐷𝐴𝐵 𝛻𝑥 𝐴 + 𝑛 𝐴
Rate of increase of
mole of the species 𝑖
Net rate of additions of
mole of the 𝑖 𝑡ℎ
species per
unit volume by convection
Molar-averaged velocity
Net rate of mole of the 𝑖 𝑡ℎ
species per unit
volume by diffusion in a binary system of
components, otherwise 𝐷𝐴𝐵 𝛻xa is replaced by 𝑗𝑖
∗
The molar rate of production of
species 𝑖 by chemical reaction
𝑛𝑖 = 𝑚𝑖 =
𝑗=1
𝑁 𝑐
𝑎𝑖𝑗 𝑀𝑖 𝑅𝑗If the number of chemical reactions taking place
in the system is 𝑁𝑐, the mass production rate is:
stoichiometric coefficient
Difference between the forward and backward reactions
Fluent solves the differential
form of this equation:
5

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. 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. 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 𝑪 𝟐 𝑯 𝟒(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. 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. 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. Mass Fraction Evolution Video for 60 sccm
Flow Rate
11