Thermal Decomposition Behavior of Prussian Blue in Various Conditions

Prussian blue analogs (PBA) are widely studied for radioactive cesium decontamination. However, there are fewer works related to their post use storage. Considering the oxidative stabilization of the material after the selective uptake of Cs, the thermogravimetric properties in powder and bead form, with various Cs and other alkali metal ions adsorbed, and various heating rates were studied. TG-DTA taken in dry air condition shows an exothermic decomposition at ~270 °C. This temperature varied with the heating rate, mass, and the proportion of adsorbed ions. The best condition for complete oxidation of Prussian blue (PB) is found to be a gradual oxidative decomposition by heating in the temperature range of 200–220 °C until the total mass is decreased by >35%. After this, the temperature could be safely increased to >300 °C for the complete oxidative decomposition of PB that formed iron oxide and salt of the adsorbed Cs. A pilot scale test conducted using the radioactive Cs adsorbed Prussian blue microbeads (PB-b) confirmed that no Cs was released in the effluent air during the process.

Ability of Naphthoquinondiazide Photoresists to Exothermic Decomposition

The article considers two intermediate products of positive photoresists (1,2-naphthoquinonediazide-(2)-5-sulfonic acid of monosodium salt — Dye M and 1,2-naphthoquinonediazide-(2)-5-sulfochloride — Dye N2) from the standpoint of the tendency to explosive transformation. The experimental values of flash points determined on the OTP setup were 130 °C for Dye M and 95 °C for Dye N2. These values are close to the temperatures of the beginning of intensive exothermic decomposition (132 and 111 °C, respectively) obtained by thermogravimetric analysis. In addition, this analysis showed the presence of exothermic peaks in the studied samples both in the air and in an inert atmosphere of helium, which is a necessary condition for the manifestation of a tendency to explosive transformation. To confirm the possibility of explosive transformation, the flash points of substances were also determined by the calculation method according to the formula, which is a consequence of the problem of thermal explosion during convective heat exchange with the environment, and gave a result close to the experimental one (the values were 138 and 105 °C, respectively). For this calculation the following was used: the kinetic parameters determined by the Kissinger method, the values of the density of substances determined on an automatic pycnometer, as well as the values of the heat of explosive transformation obtained with the help of the Real computer thermodynamic program. The research results confirming the tendency of the investigated compounds to explosive transformation, as well as the critical temperatures, exceeding which is unacceptable, were transferred to the production of FGUP GNTs NIOPIK to create a safe technological process, safe storage and transportation conditions. Considering the accuracy of the measuring devices, the process temperature should not exceed 125 °C for Dye M and 90 °C for Dye N2. The conducted studies and calculations show that the computational and experimental approaches have good convergence, give values in a close temperature range, and increase the reliability of the obtained results.

Synthesis, crystal structure, and thermal properties of Ni(NH3)4(AFT)2

Ni(NH3)4(AFT)2 [NiC6H16N18O2, AFT = 4-amino-3-(5-tetrazolate)furazan] is synthesized and characterized by elemental analysis and Fourier-transform infrared spectroscopy for the first time. X-ray diffraction measurements are used to determine the crystal structure of compound 1. The results demonstrate that compound 1 crystallized in the orthorhombic crystal system. The nickel(II) ion is six-coordinated by N atoms from two AFT-ligands and four NH3 molecules. Its thermal properties are investigated by differential scanning calorimetry and thermogravimetry-derivative thermogravimetry methods, with the results demonstrating that the differential scanning calorimetry curve exhibits two endothermic and one exothermic processes. The endothermic processes are in the range of 130–510 °C with a peak temperature of 188 °C. The temperature from 230 to 400 °C is the exothermic process in which the peak temperature is 314.58 °C. In addition, Kissinger’s and Ozawa-Doyle’s methods are used for calculating the non-isothermal kinetics parameters. Moreover, the apparent activation energy ( E), safety, and thermal stability parameters ( TSADT, TTIT, Tb) for Ni(NH3)4(AFT)2 are calculated. In addition, the calculated thermodynamic functions ( ∆S≠, ∆H≠, and ∆G≠) for the exothermic decomposition process of Ni(NH3)4(AFT)2 are 55.07 J mol−1 K−1, 196.18 kJ mol−1, and 164.90 kJ mol−1, respectively.

Selected magnesium compounds as possible inhibitors of ammonium nitrate decomposition

Ammonium nitrate (AN) is considered to be a very hazardous and difficult to handle component of mineral fertilizers. Differential thermal analysis coupled with thermogravimetry and mass spectrometry was used to determine the possible inhibiting effect of selected magnesium compounds on thermal decomposition of AN. Each additive was mixed with AN to create samples with AN:magnesium compound mass ratios of 4:1, 9:1 and 49:1. Most of analyzed compounds enhanced thermal stability of ammonium nitrate, increasing the temperature of the beginning of exothermic decomposition and decreasing the amount of generated heat. Magnesium chloride hexahydrate was determined to accelerate the decomposition of AN while magnesium sulphate, sulphate heptahydrate, nitrate hexahydrate together with magnesite and dolomite minerals were defined as inhibiting agents.

Influence of ion structure on thermal runaway behaviour of aprotic and protic ionic liquids

Accelerated rate calorimetry has been employed to study the exothermic and thermal runaway behaviour of some aprotic and protic ionic liquids. The aprotic [FSI]− salts are found to be more vulnerable to exothermic decomposition.

Cu2[Cu(H2O)4][(CH2)4(NH3)2][C6H2(COO)4]2·4H2O — A Three-Dimensional Coordination Polymer with Negativ Excess Charge and Channel-like Voids

Triclinic single crystals of Cu2[Cu(H2O)4][(CH2)4(NH3)2][C6H2(COO)4]2·4H2O have beenprepared in aqueous solution at 55 °C. Space group P-1 (no. 2), a = 799.73(7), b = 977.43(8),c = 1086.27(9) pm, α = 87.194(7), β = 84.679(7), γ = 74.744(6)°, V = 0.81540(12) nm3, Z = 1.There are two unique Cu2+ with CN 4+1 (Cu(1)) and CN 4+2 (Cu(2)), respectively. The Cu-Odistances range from 197.4(2) to 214.9(2) pm (Cu(1)) and 191.6(2) to 240.1(4) pm (Cu(2)).There is a short Cu(1)-Cu(1) contact of 267.02(6) pm. A three-dimensional coordinationpolymer with negative excess charge and channel-like voids extending parallel to [-110] ismade up by Cu2+ and [C6H2(COO)4]4-. These voids accomodate [(CH2)4(NH3)2]2+ and watermolecules, which are not coordinated to Cu2+. Thermoanalytical measurements in airindicated a step-wise loss of water of crystallization commencing at 63 °C, which is finishedat approx. 250 °C followed by an exothermic decomposition yielding CuO. The Cu(1) pairsshow anti-ferromagnetic coupling.