Nanotechnology In The Automotive Idustry
Essay by 24 • October 24, 2010 • 528 Words (3 Pages) • 1,431 Views
Airbag Chemistry
(References : The website URL)
http://
www.lemurzone.com/airbag/inflate.htm
The driver's airbag unit consists of an
airbag, and a gas generator. The unit is mounted in the steering wheel hub,
concealed beneath a fabric covering. The gas generator is a metal canister
filled with mixture containing mostly sodium azide (formerly a solid rocket
propellant). When a car is involved in a crash severe enough to activate
the sensing unit(s), an electrical charge is routed to the gas generator,
which ignites the fuel. The fuel then creates a tremendous amount of inert
nitrogen gas filling the airbag. The total elapsed time from contact to
full deployment of the airbag will vary, but it should deploy within 1/25
second. To reduce the airbag's impact on people, several multistage gas
generator concepts are now being developed enable the deployment to match
the severity of the crash.
A typical (old design) gas generator is filled with sodium azide (NaN3) and
mixtures of potassium nitrate (KNO3) and silicon dioxide (SiO2) which are a
spin-off of military and rocket propellant industries. To initiate the
inflation process a 12 volt output signal from the airbag control computer
heats a resistive wire element which starts the chemical reaction. This
exothermic chemical reaction decomposes the gas generating pellets in a
three step process which proceeds as follows:
This initial reaction forms sodium and hot nitrogen gas which inflates the
airbag.
2 NaN3 --> 2 Na + 3 N2
The sodium byproduct of the first reaction and the potassium nitrate
generate additional nitrogen in the secondary reaction.
10 Na + 2 KNO3 --> K2O + 5 Na2O + N2
And finally the previous two reactions leave potassium oxide and sodium
oxide to react with the third component of the mixture, silicon dioxide,
forming alkaline silicate "glass".
K2O + Na2O + SiO2 --> alkaline silicate
As you can see, the reactions in steps 1 and 2 release a great deal of
nitrogen gas. It is this hot nitrogen gas that fills
...
...