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!