A. Małecki

Mechanism of Thermal Decomposition of d-metals Nitrates Hydrates

A series of six nitrates(V) hydrates of 4d-metals as well as mercury and cadmium thermal decomposition was examined by DTA, TG and EGA techniques. It was found that thermal decomposition of d-metals nitrate(V) hydrates proceeds in three stages: partial dehydration, oxo-nitrates and hydroxide nitrates formation and metal oxides formation. General chemical equations for all decomposition stages were proposed. It was found that dehydration of hydrated salts is accompanied by partial decomposition of nitrate(V) groups.

Thermal decomposition of d-metal nitrates supported on alumina

The thermal decomposition of cobalt, nickel, manganese, zinc, and copper nitrates supported on nanometric alumina was investigated and compared with decomposition of corresponding bulk nitrates. TG, DTA, and MS measurements in air were performed. The supported nitrates decompose in lower temperatures than the bulk ones and their decomposition proceeds in fewer stages which are better separated. Synthesized materials and bulk nitrates before degradation of nitrates groups undergo dehydration. For decomposition of manganese and copper nitrates, the last step of water vapour releasing is combined with degradation of nitrate groups thus formation of anhydrous metal nitrate during decomposition is not achievable. Thermal decomposition of bulk nitrates leads to oxides—Co3O4, NiO, MnO2, ZnO, and CuO—respectively, as the solid residue. The nickel, zinc, copper, and manganese nitrates while supported on alumina decompose to corresponding oxides (NiO, ZnO, CuO, MnO2) as well. For decomposition of cobalt nitrate while supported on Al2O3 as the solid residue CoAl2O4 were identified. The correlation between dehydration and degradation of nitrates groups temperatures for bulk and supported nitrates was analysed in terms of atomic properties of d-metals.

Thermal decomposition of chromium(III) nitrate(V) nanohydrate

Thermal decomposition of Cr(NO3)3·9H2O in helium and in synthetic air was studied by means of TG, DTA, EGA and XRD analysis. The dehydration occurs together with decomposition of nitrate(V) groups. Eight distinct stages of reaction were found. Intermediate products of decomposition are hydroxy- and oxynitrates containing chromium in hexa- and trivalent states. The process carried out in helium leads to at about 260°C and in air is formed at about 200°C. The final product of decomposition (>450°C) is Cr2O3, both in helium and in air.

Theoretical studies of electronic structure and structural properties of anhydrous alkali metal oxalates

The results of first principles calculations of band structure, density of states, and electron density topology of alkali metal oxalates are presented. The calculations have been carried out with WIEN2k ab initio program, using highly precise full potential linearized augmented plane wave method within density functional theory formalism. Calculated total electron density has been used in calculations of its topological properties (according to Bader’s quantum theory of atoms in molecules formalism) and Cioslowski and Mixon’s topological bond orders. The obtained results show important similarities between electronic structure and electron density topology for all analyzed structures with electronic structure close to Fermi energy typical for ionic compounds and bonding which is mainly covalent within the oxalate anion (with partly ionic character of carbon–oxygen bonds) and strongly ionic between oxalate anion and cationic sublattice. These results have been used as a basis for theoretical analysis of thermal decomposition process described in detail in part II of this paper (where also the results of additional calculations of atomic and bond valences, bond strengths and strains are presented).