It should, by now, be obvious to researchers interested in ThermalDecompositions of Solids that the theoretical foundations of this subject are (at best) of doubtful validity or (at worst) nonexistent. The
Authors:Göktürk Avsar, Hüseyin Altinel, Mustafa Yilmaz, and Bilgehan Guzel
Trifluoromethoxy functionalized copper(II) Schiff base complexes N,N′-bis(5-trifluoromethoxysalicylaldehyde)cyclohexanediiminatodiaquacopper(II) and N,N′-bis(5-trifluoromethoxysalicylaldehyde)phenylenediiminatocopper(II) were synthesized and characterized. Thermal decompositions
of the synthesized complexes were studied by thermogravimetry in order to evaluate their thermal stability and thermal decomposition
pathways. Three similar decomposition steps occurred for the two copper complexes. Mass losses and evolved gasses were characterized
by TG/DTA-MS. Kinetic parameters were calculated and the results showed that the values obtained are comparable.
Authors:B. Hefczyc, T. Siudyga, J. Zawadiak, and A. Mianowski
decompose, while at higher temperatures, the peroxyester fragments break down [ 5 ]. N 2 is released in the first stage and CO 2 in the second (Scheme 2 ).
Thermaldecomposition pathways of azo
Authors:Piotr Szynkaruk, Marek Wesolowski, and Malgorzata Samson-Rosa
Thermal decomposition of magnesium salts of organic acids used in medicine (Mg acetate, Mg valproate, Mg lactate, Mg citrate,
Mg hydrogen aspartate, Zn hydrogen aspartate) was analyzed by thermoanalytical, calorimetrical, and computational methods.
Thermoanalytical studies were performed with aid of a derivatograph. 50-, 100-, and 200-mg samples were heated in a static
air atmosphere at a heating rate of 3, 5, 10, and 15 °C min−1 up to the final temperature of 700–900 °C. By differential thermal analysis (DTA), thermogravimetry (TG), and derivative
thermogravimetry (DTG) methods, it has been established that thermal decomposition of the salts under study occurs via two
stages. The first stage (dehydratation) was distinctly marked on the thermoanalytical curves. Calorimetrical studies were
carried out by using of a heat-flux Mettler Toledo differential scanning calorimetry (DSC) system. Ten milligram samples of
compounds under study were heated in the temperature range from 20 to 400 °C at a heating rate of 10 and 20 °C min−1 under an air stream. The studies showed that the values of transitions heats and enthalpies of dehydration for investigated
salts varied with the increasing of heating rate. For chemometric evaluation of thermoanalytical results, the principal component
analysis (PCA) was applied. This method revealed that points on PC1 versus PC2 diagrams corresponding to the compounds of
similar chemical constitution are localized in the similar ranges of the first two PC’s values. This proves that thermal decomposition
reflects similarity in the structure of magnesium salts of organic acids.
Authors:Zongxue Yu, Yuxi Sun, Wenxian Wei, Lude Lu, and Xin Wang
Orthorhombic structural perovskite NdCrO3 nanocrystals with size of 60 nm were prepared by microemulsion method, and characterized by XRD, TEM, HRTEM, SEM, EDS and
BET. The catalytic effect of the NdCrO3 for thermal decomposition of ammonium perchlorate (AP) was investigated by DSC and TG-MS. The results revealed that the NdCrO3 nanoparticles had effective catalysis on the thermal decomposition of AP. Adding 2% of NdCrO3 nanoparticles to AP decreased the temperature of thermal decomposition by 87° and increased the heat of decomposition from
590 to 1073 J g−1. Gaseous products of thermal decomposition of AP were NH3, H2O, O2, HCl, N2O, NO, NO2 and Cl2. The mechanism of catalytic action was based on the presence of superoxide ion O2− on the surface of NdCrO3, and the difference of thermal decomposition of AP with 2% of NdCrO3 and pure AP was mainly caused by the different extent of oxidation of ammonium.
Authors:Seied Mahdi Pourmortazavi, Mehdi Rahimi-Nasrabadi, Iraj Kohsari, and Seiedeh Somayyeh Hajimirsadeghi
]. Thermal analysis techniques such as differential scanning calorimetry (DSC) and thermogravimetry-differential thermal analysis (TG/DTA) are powerful systems for acquiring thermaldecomposition and kinetic data on energetic materials [ 11 ].
Authors:Chanaiporn Danvirutai, Pittayagorn Noisong, and Sujittra Youngme
The ammonium manganese phosphate monohydrate (NH4MnPO4 · H2O) was found to decompose in three steps in the sequence of: deammination, dehydration and polycondensation. At the end of
each step, the consecutive one started before the previous step was finished. The thermal final product was found to be Mn2P2O7 according to the characterization by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy. Vibrational
frequencies of breaking bonds in three stages were estimated from the isokinetic parameters and found to agree with the observed
FTIR spectra. The kinetics of thermal decomposition of this compound under non-isothermal conditions was studied by Kissinger
method. The calculated activation energies Ea are 110.77, 180.77 and 201.95 kJ mol−1 for the deammination, dehydration and polycondensation steps, respectively. Thermodynamic parameters for this compound were
calculated through the kinetic parameters for the first time.
Thermal decomposition of natural pyrite (cubic, FeS2) has been investigated using X-ray diffraction and57Fe Mössbauer spectroscopy. X-ray diffraction analysis of pyrite ore from different sources showed the presence of associated minerals, such as quartz, szomolnokite, stilbite or stellerite, micas and hematite. Hematite, maghemite and pyrrhotite were detected as thermal decomposition products of natural pyrite. The phase composition of the thermal decomposition products depends on the temperature, time of heating and starting size of pyrite crystals. Hematite is the end product of the thermal decomposition of natural pyrite.
A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of liebigite. Water is lost in two steps at 44 and 302°C. Two mass loss steps are observed for carbon dioxide evolution at 456 and 686°C. The product of the thermal decomposition was found to be a mixture of CaUO4 and Ca3UO6. The thermal decomposition of liebigite was followed by hot-stage Raman spectroscopy. Two Raman bands are observed in the 50°C spectrum at 3504 and 3318 cm-1 and shift to higher wavenumbers upon thermal treatment; no intensity remains in the bands above 300°C. Three bands assigned to the υ1 symmetric stretching modes of the (CO3)2- units are observed at 1094, 1087 and 1075 cm-1 in agreement with three structurally distinct (CO3)2- units. At 100°C, two bands are found at 1089 and 1078 cm-1. Thermogravimetric analysis is undertaken as dynamic experiment with a constant heating rate whereas the hot-stage Raman spectroscopic experiment occurs as a staged experiment. Hot stage Raman spectroscopy supports the changes in molecular structure of liebigite during the proposed stages of thermal decomposition as observed in the TG-MS experiment.