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Journal of Thermal Analysis and Calorimetry
Authors: Gurdip Singh, A. K. Shrimal, Inder Pal Singh Kapoor, Chandra Prakash Singh, Dinesh Kumar, and Manan S. Mudi

propellants compositions. Nickel hydrazine nitrate has been prepared and found insensitive to impact, friction, or electrostatic charge, but more sensitive to flame [ 5 ]. Transition metal complexes are also used to obtain nano size metal oxides, which can

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Transition metal dithiocarbamate complexes, [M(S2CN(C2H5)(CH2CH2OH)] (M=Co, Ni, Cu, Zn and Cd) have been prepared and characterized by elemental analysis and infrared spectra. Thermal decomposition of all the complexes occurs in two or three stages. The first stage in all the complexes is always fast with 65-70% mass loss. In all cases the end product is metal oxide except in the case of cobalt complex which gives Co metal as an end product. During decomposition of copper complex, first CuS is formed at ~300C which is converted into CuSO4 and finally CuO is formed. However, decomposition in helium atmosphere yields CuS. SEM studies of transition metal dithiocarbamates reveal needle shape crystalline phase at room temperature and formation of metal sulphide/oxide at higher temperatures. The activation energy varies in a large range of 33.8-188.3 kJ mol-1, being minimum for the Cu complex and maximum for the Zn complex possibly due to d 10 configuration. In the case of Ni, Zn and Cd complexes the order of reaction is two suggesting bimolecular process involving intermolecular rearrangement. However, in other cases it is a unimolecular process. Large negative values of ΔS # for all the complexes suggest that the decomposition process involves rearrangement.

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have been used to characterize complexes of bivalent transition metal ions [ 9 , 10 ]. However, they are not found in the literature thermal studies involving all metal-ions with oxamates, as well as the characterization of the gaseous products

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Mixed zirconium-titanium phosphates were synthesized by various methods and under various conditions. The effect of these conditions on the selectivity of synthetized samples toward the transition metal ions was investigated. It was found that the kd values are independent of the metal concentration and they give the selectivity order Zn2+>Cu2+ Co2+, Ni2+>Mn2+.

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The thermal decomposition of salts (both normal and acid) of transition metals with carboxylic acids (maleic, ortho-phthalic and terephthalic) was studied in inert atmosphere. The residues after pyrolysis (up to 450C) are composites including two structural components: an organic polymer matrix and spherical conglomerates from metal grains coated with polymer. Thermal decomposition of solid solutions of metal bimaleates (Co-Ni, Fe-Ni, Zn-Ni) was investigated. Thermogravimetric data (obtained at different rates of linear heating) were processed with 'Netzsch Thermokinetics' computer program. Kinetic parameters were calculated only for the first decomposition step, and the process is described by Prout-Tompkins equation of n th order with autocatalysis. Some properties of the resulting composites have been studied qualitatively.

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New divalent transition metal 3,5-pyrazoledicarboxylate hydrates of empirical formula Mpz(COO)2(H2O)2, where M=Mn, Co, Ni, Cu, Zn and Cd (pz(COO)2=3,5-pyrazoledicarboxylate), metal hydrazine complexes of the type Mpz(COO)2N2H4 where M=Co, Zn or Cd and Mpz(COO)2 nN2H4H2O, where n=1 for M=Ni and n=0.5 for M=Cu have been prepared and characterized by physico-chemical methods. Electronic spectroscopic data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of unidentate carboxylate anion (Δν=νasy(COO)–νsym(COO)>215 cm–1) in all the complexes and bidentate bridging hydrazine (νN–N=985–950 cm–1) in the metal hydrazine complexes. Both metal carboxylate and metal hydrazine carboxylate complexes undergo endothermic dehydration and/or dehydrazination followed by exothermic decomposition of organic moiety to give the respective metal oxides as the end products except manganese pyrazoledicarboxylate hydrate, which leaves manganese carbonate. X-ray powder diffraction patterns reveal that the metal carboxylate hydrates are isomorphous as are those of metal hydrazine complexes of cobalt, zinc and cadmium.

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Abstract  

New dihydrazinium divalent transition metal trimellitate hydrates of empirical formula (N2H5)2M(Html)2·nH2O, where n = 1 for M = Co or Ni, and n = 2 for M = Mn, Zn, or Cd (H3tml = trimellitic acid), and monohydrazinium cadmium trimellitate, [(N2H5)Cd(Html)1.5·2H2O] have been prepared and characterized by physico-chemical methods. Electronic spectroscopic, and magnetic moment data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of monodentate carboxylate anion (Δν = νasy(COO) − νsym(COO) > 190 cm−1) and coordinated N2H5 + ion (νN–N 1015 − 990 cm−1) in all the complexes. All the complexes undergo endothermic decomposition eliminating CO2 in the temperature region 200–250 °C, followed by exothermic decomposition (in the range of 500–570 °C) of organic moiety to give the respective metal carbonate as the end products except nickel and cobalt complexes, which leave respective metal oxides. X-ray powder diffraction patterns reveal that Ni and Co complexes are isomorphous as are those of, Zn(II) and Cd(II) of the type, (N2H5)2M(Html)2·2H2O.

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Thermal decomposition of transition metal malonates, MCH2C2O4xH2O and transition metal succinates, M(CH2)2C2O4xH2O (M=Mn, Fe, Co, Ni, Cu, Zn) has been studied employing TG, DTG, DTA, XRD, SEM, IR and Mssbauer spectroscopic techniques. After dehydration, the anhydrous metal malonates and succinates decompose directly to their respective metal oxides in the temperature ranges 310–400 and 400–525C, respectively. The oxides obtained have been found to be nanosized. The thermal stability of succinates have been found to be higher than that of the respective malonates.

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Abstract  

Tracer diffusion of Co2+ ions is studied in agar gel medium in the presence of some transition metal sulphates using the zone diffusion technique. A comparison between the experimental and theoretical values of diffusion coefficients computed on the basis of Onsager's theory shows a divergence between them. These deviations are explained on the basis of various effects in the iongel-water system.

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Radiolysis of aqueous sodium nitrate solution was studied as a function of concentration in the range 10–4M to 1M NaNO3. The radiolytic yield of nitrite was found to be linear with dose and concentration. The effect of transition metal chloride additives on the radiolysis of 0.01M NaNO3 resulted in higher and lower yields of nitrite in the presence of cobalt and nickel chlorides, respectively, than that obtained in the pure nitrate system. The reduction of nitrate to nitrite is totally quenched even at very low concentration of copper chloride in the binary mixture. The results are explained on the basis of oxidizing and reducing properties of transition metal ions.

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