Alloying, exothermic

Calcium hydride is prepared on a commercial scale by heating calcium metal to about 300°C in a high alloy steel, covered cmcible under 101 kPa (1 atm) of hydrogen gas. Hydrogen is rapidly absorbed at this temperature and the reaction is exothermic. 

Preparation of Plutonium Metal from Fluorides. Plutonium fluoride, PuF or PuF, is reduced to the metal with calcium (31). Although the reactions of Ca with both fluorides are exothermic, iodine is added to provide additional heat. The thermodynamics of the process have been described (133). The purity of production-grade Pu metal by this method is ca 99.87 wt % (134). Metal of greater than 99.99 wt % purity can be produced by electrorefining, which is appHcable for Pu alloys as well as to purify Pu metal. The electrorefining has been conducted at 740°C in a NaCl—KCl electrolyte containing PuCl [13569-62-5], PuF, or PuF. Processing was done routinely on a 4-kg Pu batch basis (135). 

Reaction with other substances Thermite reaction Rust Exothermic reactions with aluminium, aluminium alloys... 

The basic information is the fact that formation of PC/Cu alloys is rather exothermic (15) so that one would expect more pronounced changes in the electronic structure of Pt and Cu, than with, e.g. Pt/Au, Pt/Ag, (endothermic alloy formation) or Pt/Re, Pd/Ag, Pd/Au (moderately exothermic). 

With very electropositive metais this oxide is reduced very violently following thermite type of reactions. Vioient reactions of this type happen with lithium, magnesium, aluminium and the Al-Mg-Zn alloy. The iron formed is melted due to the exothermicity of this reaction. This experiment is not recommended for lectures. 

A thermocouple of palladium was put in contact with a molten aluminium bath at around 600°C. This led to a very violent flash , which was probably due to the formation of an Al-Pd alloy. Differential thermal analysis showed that an exotherm is formed at 2800°C between these two metals. 

Mercury forms amalgams with numerous metals. Usually, this conversion is very exothermic, therefore it can present risks the reaction can become violent if a metai is added too quickly into mercury. Accidents have been described with caicium (at 390°C), aluminium, alkali metals (lithium, sodium, potassium, rubidium) and cerium. Some of these alloys are very inflammable, in particular the Hg-Zn amalgam. 

Its oxidising character plays a role in all other reactions. Surprisingly, it is thought to form explosive dichlorine oxide with chlorine. It leads to a and very exothermic reaction with disulphur dichloride and detonations with metals potassium, K-Na alloy, magnesium with phosphorus and anhydrous or hydrated hydrazine. 

Bismuth forms an alloy with melted lithium the conversion is dangerous because of its exothermicity. The aluminium/bismuth mixture combusts spontaneously in air. The same goes for a cerium/bismuth mixture. 

At the m.p. of aluminium (600°C) an aluminium-sheathed palladium thermocouple formed an alloy with a flash and an exotherm to 2800°C [1]. The use of thin layers of palladium or platinum on aluminium foil or wire as igniters derives from the intense heat of alloy formation, which is sufficient to melt the intermetallic compounds [2],... 

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