Resistive Gas Sensors With Polymer Films

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Transcript Resistive Gas Sensors With Polymer Films

RESISTIVE GAS SENSORS
WITH POLYMER FILMS
Bashirova S.M.
National Aerospace Agency, Baku, Azerbaijan
1
Resistive element based on metaloksid semiconductor
• . The structure of metaloksid
The selectivity curves
• semiconductor
Positives:
Low cost, high sensitivity
Negatives:
Low selectivity, high working temperatures (from 300 to 500°C)
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Electrochemical element
• Construction of the sensor
based on a solid electrolyte
•
1- the heater (platinum) 2 –
contacts, 3 - sealing (glass) 4 - the
measuring electrode (anode), 5
solid electrolyte, 6 - electrode
(cathode)
Positives:
Low cost, high sensitivity
Negatives:
low selectivity, very high working temperatures, the life of
electrochemical elements is small (one - three years).
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Resistive gas sensing structure
• 1-sapphire crystal (size 3x3 mm) 2 - copper wire
(diameter 200 micrometers), 3 - contact pads
(400x400 mm), 4-counter electrode included, 5 resistive heater.
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The structural formula of phthalocyanines
CH 3
|
М = SiCl2
R   C  CH 3
|
R
М = Cu, R–SO2–NH–C18H37
CH 3
For CuPc
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The dynamic of adsorption-desorption processes for
samples with copper Pc layer exposed in NOx (3 ppm)
a) - before heat treatment, b) - after heat treatment at 180°C.
I - current value while samples exposed in NOx, Io - before
exposure in NOx.
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Dependence of resistance value versus concentration of NOx ( SiPcCl2 films)
Dependence of resistance value on time for different concentrations of NOx
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The Block scheme of a gasanalyzer device
The ransformer
bridge
The resonant
amplifier
The generator of a
sinusoidal
signals
The detector
The indicator
Блок
питания
The device for determining the concentrations of nitrogen oxides
• Technical data
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Nominai range Bias Voltage Response time –
Operating Temperature Rating Expected Operation Life Dimensions Weight –
0-500 ppm,
9V
less than 10 sec.
-20°C Ta +55°C
5 year
200x70x45
less than 0.7 kg.,
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Reasons for using the structures with polymer films
1.
2.
3.
4.
Improved Selectivity
High sensitivity
Reduced Drift
Possibility of manufacturing by a microelectronic
technology
5. Cheap and available polymeric materials
6. Low Cost
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