Authors:San-Ping Chen, Na Li, Qing Wei, and Sheng-Li Gao
A novel complex [Ni(H2O)4(TO)2](NO3)2·2H2O (TO = 1,2,4-triazole-5-one) was synthesized and structurally characterized by X-ray crystal diffraction analysis. The decomposition
reaction kinetic of the complex was studied using TG-DTG. A multiple heating rate method was utilized to determine the apparent
activation energy (Ea) and pre-exponential constant (A) of the former two decomposition stages, and the values are 109.2 kJ mol−1, 1013.80 s−1; 108.0 kJ mol−1, 1023.23 s−1, respectively. The critical temperature of thermal explosion, the entropy of activation (ΔS≠), enthalpy of activation (ΔH≠) and the free energy of activation (ΔG≠) of the initial two decomposition stages of the complex were also calculated. The standard enthalpy of formation of the new
complex was determined as being −1464.55 ± 1.70 kJ mol−1 by a rotating-bomb calorimeter.
Authors:Bao-Di Xue, Qi Yang, San-Ping Chen, and Sheng-Li Gao
A new high-nitrogen complex [Cu(Hbta)2]·4H2O (H2bta = N,N-bis-(1(2)H-tetrazol-5-yl) amine) was synthesized and characterized by elemental analysis, single crystal X-ray diffraction
and thermogravimetric analyses. X-ray structural analyses revealed that the crystal was monoclinic, space group P2(1)/c with lattice parameters a = 14.695(3) Å, b = 6.975(2) Å, c = 18.807(3) Å, β = 126.603(1)°, Z = 4, Dc = 1.888 g cm−3, and F(000) = 892. The complex exhibits a 3D supermolecular structure which is built up from 1D zigzag chains. The enthalpy change
of the reaction of formation for the complex was determined by an RD496–III microcalorimeter at 25 °C with the value of −47.905 ± 0.021 kJ mol−1. In addition, the thermodynamics of the reaction of formation of the complex was investigated and the fundamental parameters
k, E, n,
were obtained. The effects of the complex on the thermal decomposition behaviors of the main component of solid propellant
(HMX and RDX) indicated that the complex possessed good performance for HMX and RDX.
Authors:Jian Wu, San-Ping Chen, You-Ying Di, and Sheng-Li Gao
The heat capacities of Ln(Me2dtc)3(C12H8N2) (Ln = La, Pr, Nd, Sm, Me2dtc = dimethyldithiocarbamate) have been measured by the adiabatic method within the temperature range 78–404 K. The temperature
dependencies of the heat capacities, Cp,m[La(Me2dtc)3(C12H8N2)] = 542.097 + 229.576 X − 27.169 X2 + 14.596 X3 − 7.135 X4 (J K−1 mol−1), Cp,m[Pr(Me2dtc)3(C12H8N2)] = 500.252 + 314.114 X − 17.596 X2 − 0.131 X3 + 16.627 X4 (J K−1 mol−1), Cp,m[Nd(Me2dtc)3(C12H8N2)] = 543.586 + 213.876 X − 68.040 X2 + 1.173 X3 + 2.563 X4 (J K−1 mol−1) and Cp,m[Sm(Me2dtc)3(C12H8N2)] = 528.650 + 216.408 X − 16.492 X2 + 12.076 X3 + 4.912 X4 (J K−1 mol−1), were derived by the least-squares method from the experimental data. The heat capacities of Ce(Me2dtc)3(C12H8N2) and Pm(Me2dtc)3(C12H8N2) at 298.15 K were evaluated to be 617.99 and 610.09 J K−1 mol−1, respectively. Furthermore, the thermodynamic functions (entropy, enthalpy and Gibbs free energy) have been calculated using
the obtained experimental heat capacity data.
Six lanthanide compounds [Ln(H2O)9](m-BDTH)3·9(H2O) where Ln = La (1), and [Ln(H2O)8](m-BDTH)3·9(H2O) (m-BDTH2 = 1,3-benzeneditetrazol-5-yl) where Ln = Lu (2), Yb (3), Er (4), Ho (5) and Y (6) were hydrothermally synthesized and characterized by elemental analyses, infrared spectra, powder X-ray diffraction (PXRD) and X-ray single crystal diffraction. PXRD indicates that 2–6 are isomorphous. Structural analyses reveal that 1 is coordinated by nine water molecules forming a capped-square antiprism, while 2–6 are coordinated by eight water molecules forming a simple square antiprismatic geometry. Effects of water molecules on thermal stability were also discussed by thermogravimetric (TG), DSC, and PXRD under different temperatures. TG analyses suggest that 1 loses lattice and coordinated water molecules with no diacritical boundary, and 6 removes lattice water molecules first and then coordinated water molecules. DSC and PXRD further confirm the consequence.
Two crystal samples, sodium 5-methylisophthalic acid monohydrate (C9H6O4Na2·H2O, s) and sodium isophthalic acid hemihydrate (C8H4O4Na2·1/2H2O, s), were prepared from water solution. Low-temperature heat capacities of the solid samples for sodium 5-methylisophthalic acid monohydrate (C9H6O4Na2·H2O, s) and sodium isophthalic acid hemihydrate (C8H4O4Na2·1/2H2O, s) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 379 K. The experimental values of the molar heat capacities in the measured temperature region were fitted to a polynomial equation on molar heat capacities (Cp,m) with the reduced temperatures (X), [X = f(T)], by a least-squares method. Thermodynamic functions of the compounds (C9H6O4Na2·H2O, s) and (C8H4O4Na2·1/2H2O, s) were calculated based on the fitted polynomial equation. The constant-volume energies of combustion of the compounds at T = 298.15 K were measured by a precise rotating-bomb combustion calorimeter to be ΔcU(C9H6O4Na2·H2O, s) = −15428.49 ± 4.86 J g−1 and ΔcU(C8H4O4Na2·1/2H2O, s) = −13484.25 ± 5.56 J g−1. The standard molar enthalpies of formation of the compounds were calculated to be ΔfHmθ (C9H6O4Na2·H2O, s) = −1458.740 ± 1.668 kJ mol−1 and ΔfHmθ(C8H4O4Na2·1/2H2O, s) = −2078.392 ± 1.605 kJ mol−1 in accordance with Hess’ law. The standard molar enthalpies of solution of the compounds, ΔsolHmθ(C9H6O4Na2·H2O, s) and ΔsolHmθ(C8H4O4Na2·1/2H2O, s), have been determined as being −11.917 ± 0.055 and −29.078 ± 0.069 kJ mol−1 by an RD496-2000 type microcalorimeter. In addition, the standard molar enthalpies of hydrated anion of the compounds were determined as being ΔfHmθ(C9H6O42−, aq) = −704.227 ± 1.674 kJ mol−1 and ΔfHmθ(C8H4O4Na22−, aq) = −1483.955 ± 1.612 kJ mol−1, from the standard molar enthalpies of solution and other auxiliary thermodynamic data through a thermochemical cycle.