What are the 3 examples of explosions with equations?
- Physical (pV = nRT)
- Nuclear (E = mc^2)
- Chemical (ΔG = ΔH – TΔS)
What is an explosive?
- Energetic materials but not all explosions are caused by energetic materials
- An energetic matertial contains its own oxident (doesnt need to rely on oxygen in air so is more efficient and powerful)
What is a primary explosive?
- Sensitive to shock, heat, light, electricity
- Easily detonated
- Extremely dangerous to user
- Not generally synthesised on a large scale because they can accidentally go off
What is a secondary explosive?
- More difficult to detonate
- Contact-insensitive
- Typically detonated by a small amount of primary explosive - ‘blasting cap’/detonator
What are low explosives?
- Typically deflagrate
- They burn except when pressurised (when they can detonate)
- Typically used as propellants
What are some examples of low explosives?
- Gunpowder
- Fuels (propane, methane, hydrogen)
- Fireworks
What are high explosives?
- Typically detonate
- The chemcial reaction yields a supersonic shock wave
- Tend to contain the oxidiser in one molecule
What are some examples of high explosives?
- TNT
- Nitroglycerin
- RDX
What is deflagration?
A rapid oxidation reaction generating a low intensity pressure wave of moving gases
* Propagation of the reactions takes place at the surface of the material and is subsonic
What is the equation for the rate of burning (da/dt)?
da/dt = rA𝜌
* r = burn rate constant
* A = area
* 𝜌 = density
What is the equation for the burn rate constant (r)?
𝑟= 𝛽𝑃^𝛼
* 𝛽 = burn rate coefficent (constant)
* 𝑃 = pressure
* 𝛼 = pressure index (constant)
How do you cause deflagration to happen more quickly (detonation)?
Increase the surface area (powder) and pressure (confinement) to stop the gases from leaving
What is detonation?
A process of supersonic combustion in which a shock-wave is propagated forward due to energy release in a reaction zone behind it
Teritary Explosives
- Very difficult to initiate
- Usually need a secondary explosive to detonate
What are some examples of primary explosives?
- Copper Azide, NitrogenTrihalides, Lead Azide, Silver Azide, Mercury Fulminate, Lead Styphnate
What are some examples of secondary explosives?
TNT, RDX/TNT, Amatol, RDX/Grease
What is an example of a tertiary explosive?
Ammonium Nitrate
