Authors:B. Randhawa, K. Sweety, Manpreet Kaur, and J. Greneche
Thermal analysis of some transition metal ferrimaleate precursors, M3[Fe(mal)3]2·xH2O (M=Mn, Co, Ni, Cu) has been studied in static air atmosphere from ambient to 600°C. Various physico-chemical techniques, i.e. TG, DTG, DTA, XRD, IR, Mössbauer spectrometry, have been employed to characterize both the intermediates and final products. After dehydration the anhydrous precursors undergo decomposition to yield an iron(II) intermediate, M[FeII(mal)2] (M=Mn, Co, Ni, Cu) in the temperature range 160-275°C. A subsequent oxidative decomposition of iron(II) species leads to the formation of -Fe2O3 and MO in the successive stages. Finally a solid-state reaction occurs between the oxides above 400°C resulting in the formation of transition metal ferrites, MFe2O4. The ferrites have been obtained at much lower temperature and in less time than in the conventional ceramic method.
Two bis(bipyridine) polymeric metal nitrate complexes
with 4,4’-bipyridine of simple formula like [M(bipy)2](NO3)2⋅xH2O (where M=Co, Ni and Cu; x=4, 2 and 0, respectively) have been prepared and
characterized. Their thermal decomposition has been undertaken using simultaneous
TG-DTG-DTA and DSC in nitrogen atmosphere and non-isothermal TG in air atmosphere.
Isothermal TG has been performed at decomposition temperature range of the
complexes to evaluate the kinetics of decomposition by applying model-fitting
as well as isoconversional method. Possible mechanistic pathways have also
been proposed for the thermolysis. Ignition delay measurements have been carried
out to investigate the response of these complexes under the condition of
Summary Three new complex compounds of general formula Zn[5-ClC6H3-2-(OH)COO]2·L2·nH2O (where L=thiourea (tu), nicotinamide (nam), caffeine (caf), n=2-5), were prepared and characterized by chemical analysis, IR spectroscopy and their thermal properties were studied by TG/DTG, DTA methods. It was found that the thermal decomposition of hydrated compounds starts with the release of water molecules. During the thermal decomposition of anhydrous compounds the release of organic ligands take place followed by the decomposition of salicylate anion. Zinc oxide was found as the final product of the thermal decomposition performed up to 800°C. RTG powder diffraction method, IR spectra and chemical analysis were used for the determination of products of the thermal decomposition.
Crystalline PbTiO3 was obtained through the thermal decomposition of 8-hydroxyquinolinate of lead(II) and that of titanium(IV), which was monitored
by TG/DTG/DTA under different atmospheric conditions and with varying heating rates. The compound was prepared from adding
8-hydroxyquinoline solution in the solution of metallic ions Pb(II):Ti(IV) (1:1) under constant stirring at 3C, having the
pH adjusted to 10. The results of these investigations show that different thermal behavior related to the precursor occurred
and also the consequent formation of residues which have different crystallinities. No carbonate residues from the thermal
decomposition could be determined by XRD and IR. Only PbTiO3 was observed and confirmed by DSC at 470C, temperature lower than the tetragonal-cubic transition.
Authors:Banjong Boonchom, Chanaiporn Danvirutai, and Montree Thongkam
The thermal decomposition of synthetic serrabrancaite (MnPO4 · H2O) was studied in N2 atmosphere using TG-DTG-DTA. Thermal analysis results indicate that the decomposition occurs in two stages, which are assigned
to the dehydration and the reduction processes and the final product is Mn2P2O7. X-ray powder diffraction, FT-IR and FT-Raman techniques were used for identification of the solid decomposition product.
The decomposition kinetics analysis of MnPO4 · H2O was performed under non-isothermal condition through isoconversional methods of Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose
(KAS). The dependences of activation energies on the extent of conversions are observed in the dehydration and the reduction
reactions, which could be concluded the “multi-step” processes.
Authors:Alexandra Ioiţescu, Gabriela Vlase, T. Vlase, G. Ilia, and N. Doca
The synthesis of four types of hydroxyapatite synthesized from calcium chloride and four different organic phosphites is presented.
The method of synthesis chosen is the sol–gel route, which has a number of advantages compared to other methods, like the
intimate contact between reactants and the milder synthesis conditions. The samples were thermally treated, the TG/DTG/DTA
curves being obtained at four heating rates, namely: 7, 10, 12 and 15 °C min−1. The samples were characterized before and after the thermal treatment using FT-IR analysis. The FT-IR spectra certified
that the formed compounds represent hydroxyapatite. Based on the information from the TG curves and IR spectra interpretation,
a reaction mechanism was proposed.
Authors:Lucinéia de Carvalho, Milena Segato, Ronaldo Nunes, Csaba Novak, and Éder Cavalheiro
The thermal decomposition behavior of acesulfame-K (ACK), aspartame (ASP), sodium cyclamate (SCL), saccharine (SAC), and sodium
saccharine (SSA) were investigated. After re-crystallization of the commercial samples the compounds were characterized by
using elemental analysis, IR spectroscopy and thermoanalytical techniques (TG/DTG, DTA, and DSC). Evidences of hydrate water
loss were observed for SSA and ASP. Melting was detected for SSA and SAC. Each compound decomposed in a characteristics way.
The decomposition of APS and SAC took place completely, while ACK, SCL and SSA resulted in K2SO4, Na2SO4, and Na2SO4, as residues respectively. The Flynn-Wall-Ozawa method for kinetic calculations was applied for the volatilization of saccharine
resulting in Ea = 80 ± 1 kJ mol−1 and log A = 7.36 ± 0.07 min−1.
The complexes of Zn, Cd and Hg of isatin isonicotinoyl hydrazone were prepared at two differentpHs. Their thermal studies (TG, DTG and DTA) have been made and the DC electrical conductivity of compressed powder samples as a function of temperature was investigated. The activation energies (ΔE) were calculated for the ligand and the complexes which showed that the ligand has a lower value of ΔE than the complexes. The magnitude of ΔE was found to be affected by the nature of the metal and thepH of preparation.
Simultaneous TG, DTG, DTA measurements along with the continuous and selective monitoring of carbon monoxide, carbon dioxide and water evolved were carried out on K3[M(C2O4)3].3H2O-type transition metal complexes (whereM=Cr, Fe and Co). Based on the comparison of the recorded curves a detailed description of the decomposition mechanism was possible. In the case of the cobalt complex an exothermic process corresponding to modification of electron configuration is superimposed on the endothermic dehydration reaction.
Authors:D. Czakis-Sulikowska, A. Malinowska, and A. Łuczak
Two lactates and four new mixed ligand complexes with formulae Co(lact)22H2O, Ni(lact)23H2O, Co(4-bpy)(lact)2, Co(2,4'-bpy)2(lact)2, Ni(4-bpy)(lact)22H2O and Ni(2,4'-bpy)2(lact)2 (where 4-bpy=4,4'-bipyridine, 2,4'-bpy=2,4'-bipyridine, lact=CH3CH(OH)COO-) were isolated and investigated. The thermal behaviour of compounds was studied by thermal analysis (TG, DTG, DTA). In the
case of hydrated complexes thermal decomposition starts with the release of water molecules. The compounds decompose at high
temperature to metal(II) oxides in air. A coupled TG-MS system was used to analyse the principal volatile products of thermolysis
and fragmentation processes of obtained complexes.