Synthesis, Crystal Structure and Thermolysis of Cadmium Perchlorate Complex with Hexamethylenetetramine

The complex of cadmium perchlorate, [Cd(HMTA)2(H2O)4](ClO4)2•2H2O was synthesized by the reaction with hexamethylenetetramine (HMTA). C, H, N analyses, FT-IR, and X-ray crystallography were used to characterize the obtained complex. TG in the static air, simultaneous thermogravimetry-derivative thermogravimetry (TG-DTG), and differential scanning calorimetry (DSC) in streaming nitrogen atmosphere were evolved for thermal decay of prepared cadmium complex. To evaluate the reaction with quick warming, explosion delay measurements were attempted. The model-free isoconversional and model-fitting kinetic methodologies were applied to isothermal TG data for kinetic examination of the complex's thermal decomposition. At higher temperatures, the complex explodes to synthesize highly thermally stable residue most closely resembles cadmium oxide.

Kinetic Analysis of the Thermal Decomposition of Polymer-Bonded Explosive Based on PETN: Model-Fitting Method and Isoconversional Method

This work investigates kinetics and thermal decomposition behaviors of pentaerythritol tetranitrate (PETN) and two polymer-bonded explosive (PBX) samples created from PETN (named as PBX-PN-85 and PBX-PP-85) using the vacuum stability test (VST) and thermogravimetry (TG/DTG) techniques. Both model-free (isoconversional) and model-fitting methods were applied to determine the kinetic parameters of the thermal decomposition. It was found that kinetic parameters obtained by the modified Kissinger–Akahira–Sunose method (using non-isothermal TG/DTG data) were close to those obtained by the isoconversional and model-fitting methods that use isothermal VST data. The activation energy values of thermal decomposition reactions were 125.6–137.1, 137.3–144.9, and 143.9–152.4 kJ·mol−1 for PBX-PN-85, PETN, and PBX-PP-85, respectively. The results demonstrate the negative effect of the nitrocellulose-based binder in reducing the thermal stability of single PETN, while the polystyrene-based binder seemingly shows no adverse influence on the thermal decomposition of PETN in our presented PBX compositions.

Thermal decomposition and their kinetics of mercury(ii) perchlorate complex with 4-aminopyridine and water

Copper perchlorate complex with 4-aminopyridine and water has been prepared with molecular formula [Hg2(C5H6N2)3(ClO4)4].2H2O. It has been characterised by elemental analysis, thermogravimetry, and IR spectroscopic data. Thermal behaviours have been studied by thermogravimetry (TG) in static air and simultaneous thermogravimetry-derivative thermogravimetry analysis (TG-DTG) in flowing nitrogen atmosphere. Complex decomposes in four steps (less resolved). Difference in decomposition under air and inert atmosphere has been also discussed. Kinetics of thermal decomposition has been investigated using isothermal TG data recorded at five different temperatures applying model-fitting as well as isoconversional method on these data. Model-fitting methods have yielded a single value of activation energy whereas isoconversional method has given different values of activation energy for each extent of conversion, α. Response of synthesized complex towards rapid heating has been investigated by recording explosion delay time (DE) at five different temperatures and using these data kinetics of explosion has been analysed. Activation energy for explosion has been also calculated.

Oxidation kinetics of YBaCo 4 O 7+ δ and substituted oxygen carriers

In this paper, the relaxation kinetics of the oxidation process of the YBaCo 4 O 7+ δ , Y 0.95 Ti 0.05 BaCo 4 O 7+ δ and Y 0.5 Dy 0.5 BaCo 4 O 7+ δ oxygen carriers is studied with isothermal reaction data. XRD analysis for fresh samples shows that all the samples have YBaCo 4 O 7+ δ structure. Scanning electron microscopy images of samples show that the samples consist of porous agglomerates of primary particles. Isothermal TG experiments are conducted with temperatures of 290°C, 310°C, 330°C and 350°C, respectively. It is found that the Avrami-Eroféev model describes solid-phase changes in the oxygen absorption process adequately. The results show that the distributed activation energies of the oxidation process obtained by the Avrami-Eroféev model are 42.079 kJ mol −1 , 42.944 kJ mol −1 and 41.711 kJ mol −1 for the YBaCo 4 O 7+ δ , Y 0.95 Ti 0.05 BaCo 4 O 7+ δ and Y 0.5 Dy 0.5 BaCo 4 O 7+ δ oxygen carriers, respectively. The kinetic model was obtained to predict the oxygen carrier conversion of oxygen absorption for different time durations. The kinetic parameters obtained here are quite vital when this material is used in reactors.

Tightly bound water in smectites

Smectites are able to retain molecular tightly bound water (TBW) at temperatures above 100 °C, even after prolonged drying. The presence of TBW affects the stable isotope ratios, the dehydroxylation behavior of smectites and smectite-rich samples and also has implications in measuring various properties of clay-rich rocks. Five reference smectites, in Mg-, Ca-, Na-, and Cs-exchanged forms were subjected to different drying protocols followed by the determination of TBW contents using precise thermogravimetric (TG) analysis. Activation energies (Ea) of the removal of different water fractions at temperatures up to 1000 °C were determined in non-isothermal TG experiments using model-independent methods. Additionally, 4A and 13X zeolites were examined in both cases as apparent OH-free references. After drying at 110 °C, all smectites still contained up to 3 water molecules per interlayer cation. The TBW contents in smectites were found to be primarily dependent on the isothermal drying temperature. For a given temperature, TBW contents decreased with respect to the type of interlayer cation in the following order: Mg > Ca > Na > Cs. The influence of the time of drying and the smectite layer charge were found to be negligible. The Ea of dehydration below 100 °C, as determined by the Friedman method, was quite constant within the 45–60 kJ/mol range. The Ea of TBW removal increased along with the degree of reaction from 90 to 180 kJ/mol, while the Ea of dehydroxylation was found in the 159–249 kJ/mol range, highly depending on the sample’s octahedral sheet structure and the interlayer cation. The Mg2+ cation can hold H2O molecules even beyond 550 °C, making it available during dehydroxylation or—for geologic-scale reactions—pass H2O to metamorphic conditions. High similarities between the TBW contents and the Ea of dehydration for smectites and cationic (low Si/Al-) zeolites lead to the conclusion that TBW in smectites is remarkably similar to zeolitic water in terms of cation bonding and diffusion characteristics. The optimal drying protocol for smectites is to substitute interlayer cations with cations of a low-hydration enthalpy, such as Cs, and to dry a sample at 300 °C, provided that the sample is Fe-poor. Fe-rich smectites should be dried at 200 °C to avoid dehydroxylation that occurs below 300 °C.