Combustible metal hydrazine complexes

The combustible nature of metal hydrazine complexes and the high exothermicity realized during heating have paved the way for using them as precursors to several useful nanocrystalline metal powders and oxide materials like Fe304, -FesOs, ferrites, cobaltites, manganites, and so on. 

Iron oxalate hydrazine, the synthesis of which is discussed in Chapter 3, is used to prepare iron oxide. The decomposition/combustion of FeC204 (N2H4)2 in air at —250 °C yields the oxide Fe203 by the following reaction  

However, X-ray powder diffraction of the combustion residue shows it to be a mixture of a- and -Fe203 [19,20]. This is further confirmed by DTA and a temperature profile study that revealed an exotherm at 630°C corresponding to the conversion of — a-Fe203. 

2 Synthesis of Nano-Copper Chromite (CuCr204) Catalyst 

The catalytic activity of the finely divided copper chromite for oxidation reactions has been investigated utilizing decomposition of N2O as a test reaction. The kinetics of N2O decomposition were studied in the temperature range 420-480 °C and the activation energy ( 3) for this reaction was found to be 21.8kcalmoC.  

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It is easy to dope metal ions in metal hydrazine complexes as well as to make solid solutions of them (discussed in Chapter 4). The combustion of these metal-ion substituted metal hydrazine carboxylate complexes in air yield the corresponding nanocrystalline oxide materials with interesting catalytic, magnetic, and dielectric properties, having applications as phosphors, pigments, and so on. A few examples of the interesting... 

Metal formate hydrazines exhibit autocatalytic combustion behavior when heated rapidly. Although TG/DTA shows endothermic decomposition in the beginning, combustion of these complexes is exothermic, since both hydrazine and formate undergo oxidation simultaneously. 

The combustion of mixed metal sulfite hydrazine complexes in the presence of air (—300 °C) gives homogenous ferrites (Table 3.18). This is confirmed by the observed weight loss and powder XRD. 

The combustion of mixed metal iron complexes is similar to that observed for hydrazinium metal iron hydrazine carboxylates. The combustion is autocatalytic, once ignited, and leaves behind voluminous mixed ferrites. The particulate properties of these oxides such as cobal-tites, ferrites and mixed ferrites have been investigated [32]. 

The formation of cobaltites (MC02O4) from the combustion of mixed metal oxalate/acetate hydrazine complexes and solid solutions of hydra-zinium metal hydrazine carboxylate hydrates have been discussed in Chapters 3 and 4, respectively (Sections 3.2.4.1, 3.2.6 and 4.6). The final product, confirmed by X-ray diffraction pattern, shows the characteristics of cobaltite spinels. Similar to cobaltites, mixed metal oxalate/acetate hydrazines complexes undergo single-step decomposition to form... 

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