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2.2.4.1 Nanomaterial for Sensors2.2.4.1 Nanomaterial for Sensors
Science & Technology Objective(s):• To use the aligned nanotube array as sensor for
monitoring gas flow rate• To fabricate nano-size gas sensors using
semiconducting oxide nanobelts
Design principles:
2.2.4 Nanotechnology2.2.4 Nanotechnology
Z.L. Wang, Georgia Tech
Collaborations:• Government – NASA, Oak Ridge National Lab• URETI – Peter Heskerth
Proposed Approach:Sensor for gas flow rate:• Step 1: Synthesizing aligned nanotube arrays• Step 2: Building the set up for field emission
measurement under flowing gas environment• Step 3: Testing the device for engine applicationsOxide Nanobelt for Gas Sensors• Step 1: Synthesizing oxid nanobelts (ZnO)• Step 2: Build the electrodes using e-beam
lithography• Step 3: Testing the device for gas sensorNASA Relevance/Impact:• In-situ real time monitoring of gas flow at a very
confined region for providing better control on engine working condition
• In-situ, real time monitoring of residual gas at high temperature with high selectivity
(b)
Vgas
I
CarnonNanotubes
(a)
V
I0
Gold electrodes (50 nm thick)
ZnO nano-ribbon
(w=285nm,h=110nm)
SiO2 (~120n thick)
2.2.4.1 Nanomaterials for Sensors First Year M1 M2 M3 M4 M5 M6
TASKS
1 Synthesis of aligned carbon nanotubes
2 Synthesis of oxide nanobelts
M7 M8 M9 M10 M11 M12
3 Building set-up for field emssion testing
4 Build devices using the oxide nanobelts
2.2.4.1 Proposed Approach: Synthesis of Nanotubes2.2.4.1 Proposed Approach: Synthesis of Nanotubes
Furnace
Ar
Viewwindow
To pump
CH4
- Deposit Fe/Ni catalyst particles onto a ceramic substrate;
- Grown carbon nanotubes by decomposition of CH4 at high temperature;
- Control temperature and gas flow rate to optimize the alignment.
Z.L. Wang, Georgia Tech
- Emission current is a measure of the distance between the tips of the carbon nanotubes and counter electrode;
- The emission current drops if the nanotubes are bent by flowing gas;
- Monitoring the emission current can quantitatively determine the gas flow rate.
(b)
Vgas
I
CarnonNanotubes
(a)
V
I0
2.2.4.1 Proposed Approach- Testing the Sensor2.2.4.1 Proposed Approach- Testing the SensorZ.L. Wang, Georgia Tech
Furnace
Ar
Viewwindow Oxide powders alumina substrate
To pump
Thermal coupleAlumina tube
Ar
2.2.4.1 Proposed Approach- Synthesis of Oxide Nanobelts2.2.4.1 Proposed Approach- Synthesis of Oxide Nanobelts
- Place oxide powder as the source material in the crucible;
- Thermal vaporization of the oxide followed by a deposition at the low temperature region results in the growth of nanobelts;
- Control temperature and gas flow rate to optimize the morphology.
Z.L. Wang, Georgia Tech
Two-probe measurements of electric conductance of a single nanowire under different temperature and gas partial pressure.
Nanowire
Insulator substrate
ElectrodeElectrode
2.2.4.1 Proposed Approach- Building Gas Sensors2.2.4.1 Proposed Approach- Building Gas Sensors
- The electric conductance of the nanobelt depends on the type and amount of molecules adsorbed on its surface
- Using the semiconductive oxide nanobelts, nanosensors using individual nanobelt will be built.
Z.L. Wang, Georgia Tech