Date post: | 24-Jan-2015 |
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NH3 Gas Sensor Based on CNTs
Student: Trần Phúc ThànhS. I. D: 20092454Instructor: Prof. Nguyễn Hữu Lâm
Outline
Problem statementMissionSolution/ Material selectionDesign
TechnologyExpectation
CostingSummaryReferences
Problem statementAmmonia (NH3) is a
colorless gas with a characteristic odor.
Ammonia is widely used in the industrial workplace. It is used as a refrigerant, cleaning product and building block for fertilizers and pharmaceuticals
However!Ammonia is both caustic and hazardous
Classification:Extremely toxic100-500 ppm: deathFlammableHarmful for agriculture, industry
Problem statement
Using WO3–Cr, SnO2–Pd, TiO2–Cr as sensor materials for NH3.
Need high temperature to operate
NH3 Sensors Today
MissionFind a new kind of materials
that has:Ability of sensing NH3 gasHigh sensitivity at room
temperatureHigh selectivity at room
temperatureShort response timeTo apply in NH3 gas sensors
Solution-CNTs
Choose nano structure materials to increase A/V
CNTs as sensing materialsSensing at room
temperatureHigh selectiveStable physically and
chemically
CNTs- DefinitionCarbon nanotubes (CNTs)
are allotropes of carbon with a cylindrical nanostructure.
Single Walled (SW-CNTs)Multi Walled (MW-CNTs)
- Single-wall nanotubes (SWNTs)
- Multi-wall nanotubes (MWNTs)
Carbon Nanotubes
~ 1-2 nm
Few microns
TEM images of various MWNTs ~ 2 - 50 nm
PropertiesElectrical
High electric conductivity (higher than copper)
Easy process for Conductive Semi-conductiveThermal
High thermal conductivity (higher than silicon)
Stable at high temperatureMechanical
100 times stronger than steel but very light Elastic behavior (Pressing CNT tip bend and
recover to its original state)Chemical
Rarely react with other compounds Chemically stable
(a) Conductive(b) Semiconductiv
e(c) Diode
‘Kink CNT’: divide conductive and semi-conductive
TechnologyProduce sensor
CVD furnaceElectrodes
deposited catalystsGases( C2H2, N2 ,
NH3 )
TechnologyCVD – Implementation is easy
– Run 2 times per day
Produce massively
The electrodes after processing
Expectations/ AdvantagesHigh sensitivityHigh selectivityStable with timeWorking at room temperature
CostingNew sensors (CNTs)
Do not need micro-furnace long-term benefits
Stable with time, chemical last long
Possibility of massive production
Old ones (WO3)Need micro-
furnace consume a lot of me]
SummaryProblem/SolutionTechnology and expectationCosting
Referenceshttp://www.sierramonitor.com/gas/about/Gas-
Detection/Ammonia-NH3-gas-detection.phphttp://www.indsci.com/services/training/gene
ral-gas-education/common-chemicals/nh3/
QUESTION!
Thanks For Your Attention!