Authors:J. Zhang, Y. Liu, Z. Zhang, X. Lv, L. Sun, F. Xu, Z. Tan, T. Zhang, and Y. Sawada
As one 3-D coordination polymer, lead formate was synthesized; calorimetric study and thermal analysis for this compound were
performed. The low-temperature heat capacity of lead formate was measured by a precise automated adiabatic calorimeter over
the temperature range from 80 to 380 K. No thermal anomaly or phase transition was observed in this temperature range. A four-step
sequential thermal decomposition mechanism for the lead formate was found through the DSC and TG-DTG techniques at the temperature
range from 500 to 635 K.
Authors:M.-H. Wang, Z.-C. Tan, Q. Shi, L.-X. Sun, and T. Zhang
heat capacities of 2-benzoylpyridine were measured with an automated adiabatic
calorimeter over the temperature range from 80 to 340 K. The melting point,
molar enthalpy, ΔfusHm,
and entropy, ΔfusSm,
of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03
kJ mol–1 and 66.07±0.05 J mol–1
K–1, respectively. The purity of the compound
was calculated to be 99.60 mol% by using the fractional melting technique.
The thermodynamic functions (HT–H298.15) and (ST–S298.15) were calculated based
on the heat capacity measurements in the temperature range of 80–340
K with an interval of 5 K. The thermal properties of the compound were further
investigated by differential scanning calorimetry (DSC). From the DSC curve,
the temperature corresponding to the maximum evaporation rate, the molar enthalpy
and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2
kJ mol–1 and 92.2±0.4 J K–1
mol–1, respectively, under the experimental
Authors:K. Okuma, T. Fujisaki, Y. Nakazawa, K. Saito, and M. Oguni
Summary We have performed low-temperature heat capacity measurements on pellet samples of (DMe-DCNQI)2M (M=Li, Ag) which is known to show spin-Peierls transitions at 51 and 86 K, respectively. A linearly temperature-dependent term in the low-temperature heat capacity has been observed for both the samples: It is attributable to the spin-wave excitations induced by the inhomogeneous pressure effects produced in the pellet forming process. Although the temperature dependences of the magnetic susceptibility in both materials are almost the same, the coefficient of T-linear term of the Ag salt becomes three times larger that that of the Li salt. The peculiar electronic state originating from the competition of the spin-Peierls mechanism and the Coulomb repulsion is suggested.
Authors:Natalia V. Avramenko, E. B. Stukalin, and M. V. Korobov
The binary systems of C60with α-methyl- and α-chloronaphthalene have been studied by means of differential scanning calorimetry. C60was found to form the molecular complex of the van der Waals type with α-methylnaphthalene which melts incongruently below
the boiling point of the solvent at temperature 382.73.0 K. The enthalpy of the desolvation reaction is 14.10.5 kJ mol-1of C60. The molar ratio of fullerene to solvent in the solvate is 1:1.5. In the system C60-α-chloronaphthalene a two-stage incongruent melting process has been observed at temperatures 314.14.6 K and 375.77.4 K
with the enthalpies 8.12.6 kJ mol-1and 11.61.0 kJ mol-1, respectively. The composition of the most solvated phase equilibrated with the saturated solution at room temperature and
below the first of the incongruent melting transitions was determined as 1:1.5. Based on the results obtained the thermodynamic
characteristics of the incongruent melting reactions have been revealed and influence of solvate formation on solubility of
C60has been discussed.
Authors:V. B. Lazarev, K. S. Gavrichev, and V. E. Gorbunov
Low temperature heat capacity of ammonium, rubidium and cesium perbromates has been studied by method of adiabatic calorimetry. Anomaly of the heat capacity of cesium perbromate has been found, which corresponds to a structural phase transition. The separation of heat capacity into components has been carried out by the additive scheme. The torsion oscillation of BrO4− anions in solid perbromates at low temperatures has been found. Ammonium ions retardedly rotate aroundC2 axes in the crystal lattice of NH4BrO4.
Authors:Y.-J. Song, S.-H. Meng, F.-D. Wang, C.-X. Sun, and Z.-C. Tan
Polyimide BTDA-ODA sample was prepared by polycondensation or step-growth polymerization method. Its low temperature heat capacities were measured by an adiabatic calorimeter in the temperature range between 80 and 400 K. No thermal anomaly was found in this temperature range. A DSC experiment was conducted in the temperature region from 373 to 673 K. There was not phase change or decomposition phenomena in this temperature range. However two glass transitions were found at 420.16 and 564.38 K. Corresponding heat capacity increments were 0.068 and 0.824 J g–1 K–1, respectively. To study the decomposition characteristics of BTDA-ODA, a TG experiment was carried out and it was found that this polyimide started to decompose at ca 673 K.
Authors:Z.-C. Tan, B. Xue, S.-W. Lu, S.-H. Meng, X.-H. Yuan, and Y.-J. Song
The heat capacities of fenpropathrin in the temperature range from 80 to 400 K were measured with a precise automatic adiabatic calorimeter. The fenpropathrin sample was prepared with the purity of 0.9916 mole fraction. A solid—liquid fusion phase transition was observed in the experimental temperature range. The melting point, Tm, enthalpy and entropy of fusion,
fusSm, were determined to be 322.48±0.01 K, 18.57±0.29 kJ mol–1 and 57.59±1.01 J mol–1 K–1, respectively. The thermodynamic functions of fenpropathrin, H(T)—H(298.15), S(T)—S(298.15) and G(T)—G(298.15), were reported with a temperature interval of 5 K. The TG analysis under the heating rate of 10 K min–1 confirmed that the thermal decomposition of the sample starts at ca. 450 K and terminates at ca. 575 K. The maximum decomposition rate was obtained at 558 K. The purity of the sample was determined by a fractional melting method.