Aluminium detonators

Molten aluminium detonates in contact with water. 

Laccabue, J. R., Fluorolube-Aluminium Detonation Point Report 7E.1500, San Diego, Gen. Dynamics, 1958... 

Aluminium detonators with lead azide and other explosives were used in the mining industry for some time, e.g. a No. 8 detonator, contained 1 g of tetryl and 0.3 g of a mixture of lead azide and lead styphnate. These were more powerful than those with a fulminate-tetryl charge, but the use of detonators with aluminium sheathing was soon forbidden in coal-mines due to the danger created by the burning of the aluminium. 

Powdered aluminium can create explosive suspensions in air in the presence of an ignition source. It can combust spontaneously if the powder is moist. Aluminium powder detonates spontaneously in liquid oxygen. 

Powdered aluminium combusts - or even detonates, if it is heated in the presence of carbon dioxide. Ignition takes place at ambient temperature when anaqueous aluminium chloride is present. The same is true for the aluminium chlorideVcarbon monoxide mixture. 

Aluminium can detonate when mixed with ammonium nitrate. It has a highly exothermic reaction with metal nitrates if it is heated at 70-135°C when water traces are present. 

Aluminium borohydride in the gaseous state has a positive enthalpy of formation, so it can be assumed to be rather unstable. It combusts spontaneously in contact with air, but detonates if water traces are present. The same thing happens in contact with water at 20°C. 

Anaqueous aluminium chloride is dangerous. In contact with water, it hydrolyses, forming hydrogen chloride. If it is kept in a closed bottle in which there are water traces, the overpressure that is created can cause the bottle to detonate. There have been numerous accidents illustrating this. 

When mineral acids are present, aluminium phosphide rapidly converts into phosphine, which can combust or even detonate. When bases are present the phosphine release is slow. 

There was a rather surprising instantaneous detonation when making an aluminium oxide/sodium nitrate mixture. 

The mixtures of sodium with phosphorus, phosphoryl trichloride or with phosphorus pentachloride combust spontaneously and/or detonate. There is an instantaneous ignition when powdered aluminium is mixed with trichloride or phosphorus pentachloride. 

Detonation occurs during the reaction of molten aluminium with ammonium peroxodisulphate in the presence of water. However, since the temperature is above 75°C, the presence of water is sufficient to decompose it and the water/molten aluminium interaction has aiready been mentioned as being explosive. 

Chlorine has caused numerous accidents with metals. Beryllium becomes incandescent if it is heated in the presence of chlorine. Sodium, aluminium, aluminium/titanium alloy, magnesium (especially if water traces are present) combust in contact with chlorine, if they are in the form of powder. There was an explosion reported with molten aluminium and liquid chlorine. The same is true for boron (when it is heated to 400°C), active carbon and silicon. With white phosphorus there is a detonation even at -34°C (liquid chlorine). 

The same goes for carbon (the accident was caused because carbon was used instead of manganese dioxide, by mistake), sulphur and phosphorus. There was a detonation with carbon. With phosphorus the detonation occurred once the carbon disulphide used to dissolve phosphorus vapourised red phosphorus behaves the same way. The same happened with the potassium chlor-ate/sodium nitrate/sulphur/carbon mixture, which led to a violent detonation as well as with the potassium perchlorate/aluminium/potassium nitrate/barium nitrate/water mixture. In the last case the explosion took place after an induction period of 24h. 

Ammonium perchlorate has, in addition to the properties mentioned for the previous compounds, a specific instability due to its unfavourable oxygen balance. Friction is enough to make it detonate. Combined with aluminium it has been used as a propellant for rockets. In the presence of carbon and metal salts, it reacts exothermically below 240°C and detonates above this temperature. 

With carbon dioxide in the solid state the mixture detonates on impact. Therefore, with graphite, carbon dioxide cannot be used as an extinguishing agent for potassium fires. The slow reaction of potassium with gaseous carbon dioxide at ambient temperature gave rise to an accident. Potassium was stored in an aluminium container in a laboratory in contact with carbon dioxide the formation of potassium carbonate caused the corrosion of the container, which caused potassium to combust on contact with air. 

It reacts violently when it is heated with aluminium. It causes hydrogen sulphide to combust. It decomposes hydroxylamine chiorohydrate, hydrogen peroxide (detonation) and potassium azide violently. 

Triferric tetroxide gives rise to a highly violent detonation when it was heated with calcium silicide combined with aluminium and sodium nitrate. 

A violent detonation took place when an attempt was made to synthesise a sulphide mixture of aluminium and copper (I) according to the following reaction ... 

Reacts very violently with metals. Accidents have been reported with aluminium (ignition) and potassium (detonation). 

Silver chloride reacts violently with aluminium. Various accidents, which involved both compounds, have ended up in a violent detonation of the mixture. 

A pyrotechnic mixture of sulphide/potassium chlorate/aluminium has led to regular detonations. This sulphide incandesces as soon as it is in contact with chloric acid. Mixtures of antimony trisuiphide with alkaline nitrates, which are probably used for pyrotechnic purposes, also lead to detonations. Bengal lights has been made with this mixture, which was used in small quantities in mixtures and no accidents were experienced. Finally, dichlorine oxide detonates in contact with this sulphide. 

They violently oxidise metals such as sodium, potassium and magnesium. In the last case, the mixture corresponds to a typical pyrotechnic preparation. Aluminium and copper also give rise to violent combustions or even detonations. 

In one Instance, a pyrotechnic preparation, which contained aluminium, water traces, potassium chlorate and potassium and barium nitrates detonated violently twenty four hours after teing prepared. A mixture of barium nitrate, aluminium and magnesium proves very sensitive to friction or impact (risk of ignition or spontaneous detonation). 

Lead oxide reacts violently with numerous metals such as sodium powder (immediate ignition), aluminium (thermite reaction, which is often explosive), zirconium (detonation), titanium, some metalloids, boron (incandescence by heating), boron-silicon or boron-aluminium mixtures (detonation in the last two cases). Finally, silicon gives rise to a violent reaction unless it is combined with aluminium (violent detonation). It also catalyses the explosive decomposition of hydrogen peroxide. 

Butanol gave rise to aluminium tributanoate when it came into contact with equipment containing aluminium. The equipment detonated because of the overpressure created by the hydrogen formed. The exothermicity of this reaction is also a risk factor. 

In the same way, the following scheme represents the preparation of two acid-base complexes of 1,4-dioxan, which detonates when it is stored at 20°C (in the case of the complex with SO3) or in the dry state (with the aluminium derivative) ... 

Sodium tetrahydrogenaluminate was prepared by the action of hydrogen on a suspension of aluminium and sodium in tetrahydrofuran. A detonation caused by the following reaction interrupted the handling ... 

In the same way, the detonation of moist trichloroethylene, which had been stored in a metal container, was explained by the hydrogen chloride formed. In this case it is possible to suggest another cause, which would involve iron trichloride forming by the interaction of hydrogen chloride with rust traces, and the catalysis by this salt of a polymerisation or degradation of the chlorinated derivative (see the similar case of aluminium chloride on p.281). 

The effect of chloromethane on ethylene when aluminium chloride, a catalyst made of nickel, and nitromethane under 30-60 bar are present, gives rise to a highly violent detonation. The fact that there are so many compounds present makes it difficult to come up with a simple explanation. Ethylene (polymerisation) and nitromethane may have caused this accident (as can be seen in the paragraph about nitrated derivatives). 

Trinitrophenol can only be stored safely in the form of a paste with water. Lead, mercury, copper, zinc, iron and nickel salts are sensitive to impact, friction and heat. Sodium, ammonium and amine salts give rise to explosions. When it was poured on to a cement floor, trinitrophenol formed a calcium salt that detonated when it came into contact with shoes. Trinitrophenol salts in the form of moist paste are stable. Aluminium salt is not explosive, but combusts spontaneously when in contact with water. 

A nitromethane/aluminium chloride complex had been prepared. A gaseous alkene was added to the complex the pressure reached 5.6 bar and the temperature 2°C. The medium had been stirred at the beginning of the operation and then intemupted. A temperature rise caused the autoclave to detonate and the medium to carbonise entirely. 

Aluminium chloride was introduced into recovered nitrobenzene containing 5% phenol. This operation led to a violent detonation. A post-accident study showed that, at ambient temperature, the mixture of these three reactants makes the temperature rise and that at a temperature starting at 120 C, the reaction becomes extremely violent. 

Nitromethane is very likely to detonate when aluminium powder is present. The same is true for a tetranitromethane/aluminium mixture. With aromatic nitrated derivatives, and in particular commercial explosives, the mixture with aluminium does not represent any danger. However, adding a drop of water causes spontaneous ignition that takes place within a time limit depending on quantities. 

Powdered aluminium had been added to oleic acid. The mixture detonated after being prepared. Such an accident could not be repeated and it was thought that it was caused by the presence of a peroxide formed by the effect of air on oleic acid. In fact, the acid functional group has obviously nothing to do with the peroxidation. It is more likely that the chain s double bond that activates p hydrogen atoms (ally position) was involved in it. This is a well-known phenomenon since it is responsible for the rancidity of some oils and greases. 

Aluminium chloride has to be introduced gradually in the naphthalene/benzoyl chloride mixture and the mixture of these two reagents has to be brought to a temperature that is high enough so that it is in the molten state. Crystallised naphthalene residues are enough to cause the medium to detonate. 

A mixture of 27% of formamide, 51% of calcium nitrate, 12% of ammonium nitrate and 10% of water detonates at -20 C. On adding powdered aluminium, this mixture becomes more disruptive. 

The introduction of lead azide led to a difficulty in the choice of metal for the detonator tube. Under moist conditions, lead azide and copper can react to form cuprous azide on the inner wall of the tube and thus in a particularly dangerous position. Therefore with plain detonators, which cannot be sealed, copper cannot be used when lead azide is employed. Such detonators are usually made from aluminium tubes, or occasionally zinc. 

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