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Abstract  

The thermal behaviors of four organic solvents with/without LiPF6 were measured by C80 microcalorimeter at a 0.2�C min−1 heating rate. With the addition of 1 M LiPF6, the ethylene carbonate (EC) and propylene carbonate (PC) show the exothermic peaks at elevated temperature, which lessen their stabilities. The exothermic peak temperatures of EC and PC based LiPF6 solutions are at 212 and 223�C, respectively, in argon filled vessel. However, two endothermic peak temperatures were detected in diethyl carbonate (DEC) based LiPF6 solution at 182 and 252.5�C, respectively, in argon filled vessel. Dimethyl carbonate (DMC) based LiPF6 solution shows two endothermic peak temperatures at 68.5 and 187�C in argon filled vessel at elevated temperature. Consequently, it is concluded that LiPF6 play a key role in the thermal behavior of its organic solution.

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Abstract

The heat capacities of N-(tert-butoxycarbonyl)-l-phenylalanine (abbreviated to NTBLP in this article), as an important chemical intermediates used to synthesize proteins and polypeptides, were measured by means of a fully automated adiabatic calorimeter over the temperature range from 78 to 350 K. The measured experimental heat capacities were fitted to a polynomial equation as a function of temperature. The thermodynamic functions, H TH 298.15K and S TS 298.15K, were calculated based on the heat capacity polynomial equation in the temperature range of (80–350 K) with an interval of 5 K. The thermal stability of the compound was further studied using TG and DSC analyses; a possible mechanism for thermal decomposition of the compound was suggested.

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Abstract  

The thermal stability of lithium-ion battery cathode could substantially affect the safety of lithium-ion battery. In order to disclose the decomposition kinetics of charged LiCoO2 used in lithium ion batteries, thermogravimetric analyzer (TG) and C80 microcalorimeter were employed in this study. Four stages of mass losses were detected by TG and one main exothermic process was detected by C80 microcalorimeter for the charged LiCoO2. The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as E a=148.87 and 88.87 kJ mol−1 based on TG and C80 data, respectively.

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Abstract

To develop thermal stable flavor, two glycosidic bound flavor precursors, geranyl-tetraacetyl-β-D-glucopyranoside (GLY-A) and geranyl-β-D-glucopyranoside (GLY-B) were synthesized by the modified Koenigs–Knorr reaction. The thermal decomposition process and pyrolysis products of the two glycosides were extensively investigated by thermogravimetry (TG), differential scanning calorimeter (DSC) and on-line pyrolysis-gas chromatography mass spectroscopy (Py-GC-MS). TG showed the T p of GLY-A and GLY-B were 254.6 and 275.7°C. The T peak of GLY-A and GLY-B measured by DSC were 254.8 and 262.1°C respectively.

Py-GC-MS was used for the simply qualitative analysis of the pyrolysis products at 300 and 400°C. The results indicated that: 1) A large amount of geraniol and few by-products were produced at 300°C, the by-products were significantly increased at 400°C; 2) The characteristic pyrolysis product was geraniol; 3) The primary decomposition reaction was the cleavage of O-glycosidic bound of the two glycosides flavor precursors. The study on the thermal behavior and pyrolysis products of the two glycosides showed that this kind of flavor precursors could be used for providing the foodstuff with specific flavor during heating process.

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Abstract  

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.

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Journal of Thermal Analysis and Calorimetry
Authors: X.-C. Lv, Z.-C. Tan, Z.-A. Li, Y.-S. Li, J. Xing, Q. Shi, and L.-X. Sun

Abstract  

The (R)-BINOL-menthyl dicarbonates, one of the most important compounds in catalytic asymmetric synthesis, was synthesized by a convenient method. The molar heat capacities C p,m of the compound were measured over the temperature range from 80 to 378 K with a small sample automated adiabatic calorimeter. Thermodynamic functions [H TH 298.15] and [S TS 298.15] were derived in the above temperature range with a temperature interval of 5 K. The thermal stability of the substance was investigated by differential scanning calorimeter (DSC) and a thermogravimetric (TG) technique.

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Journal of Thermal Analysis and Calorimetry
Authors: Y. Y. Di, Z. C. Tan, L. W. Li, S. L. Gao, and L. X. Sun

Abstract

Low-temperature heat capacities of a solid complex Zn(Val)SO4·H2O(s) were measured by a precision automated adiabatic calorimeter over the temperature range between 78 and 373 K. The initial dehydration temperature of the coordination compound was determined to be, T D=327.05 K, by analysis of the heat-capacity curve. The experimental values of molar heat capacities were fitted to a polynomial equation of heat capacities (C p,m) with the reduced temperatures (x), [x=f (T)], by least square method. The polynomial fitted values of the molar heat capacities and fundamental thermodynamic functions of the complex relative to the standard reference temperature 298.15 K were given with the interval of 5 K.

Enthalpies of dissolution of the [ZnSO4·7H2O(s)+Val(s)] (Δsol H m,l 0) and the Zn(Val)SO4·H2O(s) (Δsol H m,2 0) in 100.00 mL of 2 mol dm−3 HCl(aq) at T=298.15 K were determined to be, Δsol H m,l 0=(94.588±0.025) kJ mol−1 and Δsol H m,2 0=–(46.118±0.055) kJ mol−1, by means of a homemade isoperibol solution–reaction calorimeter. The standard molar enthalpy of formation of the compound was determined as: Δf H m 0 (Zn(Val)SO4·H2O(s), 298.15 K)=–(1850.97±1.92) kJ mol−1, from the enthalpies of dissolution and other auxiliary thermodynamic data through a Hess thermochemical cycle. Furthermore, the reliability of the Hess thermochemical cycle was verified by comparing UV/Vis spectra and the refractive indexes of solution A (from dissolution of the [ZnSO4·7H2O(s)+Val(s)] mixture in 2 mol dm−3 hydrochloric acid) and solution A’ (from dissolution of the complex Zn(Val)SO4·H2O(s) in 2 mol dm−3 hydrochloric acid).

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Abstract  

The power-time curves of the growth of three strains of petroleum bacteria at different temperatures have been determined. A novel equation of a power-time curve has been proposed in this paper. The general formula to calculate the rate constant of the bacterial growth has been derived. The rate constants of the bacterial growth at different temperatures, the heat production per newly formed bacterium, the bacterial number at the end of the bacterial growth and the deceleration rate constant of the bacterial growth at 50.00°C, have been calculated. The optimum growth temperatures of the three strains have been obtained.

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Abstract  

Although Ir anomaly has been discovered in a number of C/T boundaries in the world, no positive results of this anomaly in Permian/Triassic (P/Tr) boundary were given. There are many well-developed P/T sections in South China. One of representative sections is located at the Baoqing quarry, Meishan Town, Changxin County, Zhejiang Province. Ir, Os, Re, Au, Pt, Cu and Mo were determined by the radiochemical procedure developed in our laboratory. (1) Besides those accessible by INAA. The results reveal that the refractory siderophile and other chalcophile elements have certain enrichment near and at the boundary layer. However, the Ir/Au and other element abundance ratios fail to accord with the extraterrestrial values. The nature of the boundary event was discussed in terms of elemental geochemistry.

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Abstract  

The concentrations of 14 elements, including Ir, Au, Co, Cr, Fe, Sr, Rb, K, Ta, Zn, Sb, Ba, Sc and Se, in the Wuxi fallen ice were determined by neutron activation analysis. The experimental results show that the relative concentration ratios of Ir/Co, Ir/Cr and Ir/Sc etc. in the ice water (0.0069, 0.00024 and 0.11, respectively) are quite close to those of Type C1 chondrite (0.0102, 0.00021 and 0.092, respectively), which implies that the fallen ice might be a piece of extraterrestrial substance.

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