Ellingham

Free Energy - Temperature Diagrams (Ellingham Diagrams)... 

Allmand, A. J. and Ellingham, H.J.T., Applied Electrochemistry, Edward Arnold, London (1931)... 

Silica is only decomposed by those metals which have a high affinity for oxygen as indicated by the Ellingham diagram (Fig. 18.4). On this basis, molten sodium should be compatible with silica ... 

The products of decomposition of metal carboxylates vary to some extent with the constituent cation and the final residue is usually either the metal or an oxide, occasionally the carbide and sometimes some elemental carbon deposit. Dollimore et al. [94] have described the use of Ellingham diagrams for the prediction of the composition of the solid products of oxalate decompositions. The complete characterization of residual material can be difficult, however, since the solids may be finely divided, pyrophoric [1010], metallic and amorphous to X-rays. 

In 1944 Ellingham compiled, for the first time, diagrams depicting the temperature dependence of the standard free energies of formation of numerous oxides and sulphides. In the discussion presented here, attention will be confined to the oxide reaction... 

Considering the intersection of this line with the Ellingham line for the reaction 4 Cu (s) + 02 (1 atm) = 2 Cu20 (s)... 

In principle, any element whose Ellingham line lies below the Ellingham line of a specified element, is capable of reducing the oxide of the specified element to the elemental state. In practice, however, only the nonmetals, carbon, hydrogen and silicon, and the met-... 

Figure 4.9 Ellingham diagram for the free energy of formation of metallic oxides.

The temperature at which the Ellingham lines of the metal oxide (MO) and of carbon monoxide (CO) intersect is the minimum temperature, TR, at which this reaction can take... 

When the metal can form a stable carbide, the product of the carbothermic reduction of its oxide may be a carbide instead of the metal itself. The question as to whether a carbide or the metal forms under standard conditions when the oxide is reduced by carbon is not answered by the Ellingham diagram. To obtain an answer to this question, a more detailed consideration of the thermodynamic properties of the system is necessary. 

The minimum temperature necessary for the formation of the metal under a particular reduction pressure is that temperature at which the corresponding carbon monoxide pressure line intersects the Nb2C-NbO-Nb equilibrium line in the Pourbaix-Ellingham diagram. 

The Pourbaix-Ellingham diagram of the tantalum-carbon-oxygen (Ta-C-O) system indicates fewer sequential steps between the oxide and the metal as compared to the niobium-carbon-oxygen system ... 

According to the Ellingham diagram of oxides, water or steam (H20) is stabler than many metal oxides over a wide and useful range of temperatures, and hydrogen can reduce many metal oxides by reactions of the type... 

Steel making, broadly speaking, is an oxidation process in which impurities such as carbon, silicon, manganese, phosphorus and sulfur present in the pig iron are removed to specified levels. It can be anticipated from the Ellingham diagram that at about 1600 °C, the elements C, Si, and Mn would oxidize preferentially before iron undergoes excessive oxidation. The oxidation reactions may be represented by... 

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