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1.
N-acetyl-3,3-dinitroazetidine (ADNAZ) is an important precursor for synthesizing new multinitroazetidine energetic compounds. Its thermal behaviour was studied under a non-isothermal condition by DSC and TG/DTG methods, the results show that there are one melting process and one endothermic decomposition process. The specific molar heat capacity (Cp,m) of ADNAZ was determined by a continuous Cp mode of micro-calorimeter and theoretical calculation, and the Cp,m of ADNAZ was 240.37 J · K−1 · mol−1 at T = 298.15 K. The detonation velocity (D) and detonation pressure (P) of ADNAZ were estimated using the nitrogen equivalent equation according to the experimental density, the value of D and P are (6685.83 ± 3.12) m · s−1 and (18.36 ± 0.02) GPa, respectively. The free radical signals of ADNAZ were detected by electron spin resonance (ESR) technique, which is used to estimate its sensitivity.  相似文献   

2.
The molar heat capacity Cp,m of 1-cyclohexene-1,2-dicarboxylic anhydride was measured in the temperature range from T=(80 to 360) K with a small sample automated adiabatic calorimeter. The melting point Tm, the molar enthalpy ΔfusHm and the entropy ΔfusSm of fusion for the compound were determined to be (343.46 ± 0.24) K, (11.88 ± 0.02) kJ · mol−1 and (34.60 ± 0.06) J · K−1 · mol−1, respectively. The thermodynamic functions [H(T)H(298.15)] and [S(T)S(298.15)] were derived in the temperature range from T=(80 to 360) K with temperature interval of 5 K. The mass fraction purity of the sample used in the adiabatic calorimetric study was determined to be 0.9928 by using the fractional melting technique. The thermal stability of the compound was investigated by differential scanning calorimeter (DSC) and thermogravimetric (TG) technique, and the process of the mass-loss of the sample was due to the evaporation, instead of its thermal decomposition.  相似文献   

3.
The thermal behavior of 4-amino-1,2,4-triazol-5-one (ATO) was studied under non-isothermal condition by DSC method in a sealed cell of stainless steel. The melting enthalpy and melting entropy of ATO are 21.34 ± 0.49 kJ mol−1 and 46.54 ± 0.30 J mol−1 K−1, respectively. The kinetic parameters were obtained from the analysis of DSC curves by Kissinger method, Ozawa method, the differential method and the integral method. The main exothermic decomposition reaction mechanism of ATO is classified as nucleation and growth, and the kinetic parameters of the reaction are Ea = 119.50 kJ mol−1 and A = 109.03 s−1. The gas products and condensed phase products of the thermal decomposition of ATO were studied on two simultaneous devices of the fast thermolysis reaction cell (gas reaction cell) in situ in conjunction with rapid scan transform infrared spectroscopy (RSFT-IR) and the solid reaction cell in situ. The heat of formation (HOF) for ATO was evaluated by G3 theory. The detonation velocity (D) and detonation pressure (P) were estimated by using the well-known Kamlet–Jacobs equation, based on the theoretical HOF and the determined crystal density.  相似文献   

4.
In this paper, a densimeter based on vibrating tube principle is used to determine experimentally the density of 1-butyl-2,3-dimethylimidazolium tris(pentafluoroethyl)trifluorophosphate and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide at temperatures between (278.15 and 398.15) K and at pressures up to 120 MPa. The apparatus was calibrated by using water, vacuum and bromobenzene. The Tammann–Tait equation of state was used to correlate (p, T, ρ) results with standard deviations around 2 · 10−4 g · cm−3. Other volumetric properties, such as isothermal compressibility and isobaric thermal expansivity, were obtained from this equation. For each ionic liquid, the αp isotherms present a crossing point within the experimental pressure range. Besides, the effect that the C2-methylation in the imidazolium cation provokes on density values is analyzed. The prediction ability of the group contribution methods of Gardas and Coutinho and Jacquemin et al. were tested with the experimental densities.  相似文献   

5.
The heat capacity Cp, mof NpO2was estimated for temperatures between 300 K and 1400 K. The Cp, mwas evaluated as a sum of three terms, phonon vibration Cph, m, dilation Cd, m, and Schottky specific heat Cs, m. The Cph, mand Cd,mwere calculated using the Debye temperature, Grüneisen constant and thermal expansion data obtained by high-temperature X-ray diffractometry. The coefficient of the linear thermal expansion (l.t.e.) for NpO2was given as a polynomial function up to T =  1573 K. The estimated Cp,mwas compared with that of previous studies. The present result at T =  300 K was 66.87 J · K  1· mol  1, which agreed well with previous results, 66.22 J · K  1· mol  1, measured by using calorimetry. The thermodynamic functions were given as a function of temperature.  相似文献   

6.
《Chemical physics》2005,308(1-2):109-116
We present a direct ab initio and density functional theory dynamics study of the thermal rate constants of the two H-migration reactions of C2H5O radical. MPW1K/6-31+G(d,p) methods were employed to optimize the geometries of all stationary points and to calculate the minimum energy path (MEP). The energies of all the stationary points were refined at the QCISD(T)/aug-cc-pVTZ level of theory. The thermal gas phase rate constants were evaluated based on the energetics from the QCISD(T)/aug-cc-pVTZ//MPW1K/6-31+G(d,p) level of theory using both microcanonical variational transition state theory (μVT) and canonical variational transition state theory (CVT) with the Eckart tunneling correction in the temperature range of 200–2500 K. The extended Arrhenius expression fitted from the μVT/Eckart rate constants of 1,2 H-shift and 1,3 H-shift reactions of C2H5O radical in the temperature range of 200–2500 K are k = 3.90 × 10−31T12.4e(−2.13 × 103/T) and k = 2.83 × 10−29T11.9e(−2.24 × 103/T) s−1, respectively. The two isomerization rate constants exhibited positive temperature dependence in the calculated temperature region. The variational effects for the two isomerizations of ethoxy radical are small and the tunneling effects are important in the low temperature range. The titled reactions are minor and not essential compared to the decomposition pathways of ethoxy radical.  相似文献   

7.
Apparent molar heat capacities Cp, φand apparent molar volumesVφ were determined for aqueous solutions of α - and β -cyclodextrins at temperatures from 278.15 K to 393.15 K and at the pressure 0.35 MPa. The molalities investigated ranged from 0.008 mol · kg  1to 0.12 mol · kg  1forα -cyclodextrin and from 0.004 mol · kg  1to 0.014 mol · kg  1for β -cyclodextrin. We used a vibrating-tube densimeter (DMA 512P, Anton PAAR, Austria) to determine the densities and volumetric properties. Heat capacities were obtained using a twin fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter (NanoDSC 6100, Calorimetry Sciences Corporation, Spanish Fork, UT, USA). Equations were fit by regression to our experimental (Vφ, T, m) and (Cp, φ,T , m) results. Infinite dilution partial molar volumes V2oand heat capacities Cp,2owere obtained over the range of temperatures by extrapolation of these surfaces to m =  0.  相似文献   

8.
We have measured the densities of aqueous solutions of l-methionine, l-methionine plus equimolal HCl, and l-methionine plus equimolal NaOH at temperatures 278.15  T/K  368.15, at molalities 0.0125  m/mol · kg−1  1.0 as solubilities allowed, and at p = 0.35 MPa using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a twin fixed-cell differential temperature-scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values from the literature for Vϕ(T, m) and Cp,ϕ(T, m) for HCl(aq), NaOH(aq), and NaCl(aq) and the molar heat capacity change ΔrCp,m(T, m) for ionization of water to calculate parameters for ΔrCp,m(T, m) for the two proton dissociations from protonated aqueous cationic l-methionine. We integrated these results in an iterative algorithm using Young’s Rule to account for the effects of speciation and chemical relaxation on Vϕ(T, m) and Cp,ϕ(T, m). This procedure yielded parameters for Vϕ(T, m) and Cp,ϕ(T, m) for methioninium chloride {H2Met+Cl(aq)} and for sodium methioninate {Na+Met(aq)} which successfully modeled our observed results. Values are given for ΔrCp,m, ΔrHm, pQa, ΔrSm, and ΔrVm for the first and second proton dissociations from protonated aqueous l-methionine as functions of T and m.  相似文献   

9.
In the present work, we report the characterization of TiO2-hydroxyapatite (HA) nanocomposites obtained by a two-step sintering (TSS) process of a mixture of HA and titanium hydride (TiH2) powders. The reactions underwent by TiH2 in the presence of HA and hydrogen release, and subsequently, titanium oxidation was examined by thermal analysis. A longer holding time in the second sintering stage enabled obtaining a homogenous TiO2-HA (36% rutile) composite with a thermal expansion coefficient of 11.46 · 10−6 C−1 in the 40–1000 °C range. Unconventional TSS process hinders HA decomposition to detrimental tricalcium phosphate (TCP). Wear rate of ceramics was determined by tribological measurements and the material biocompatibility was evaluated using MTT assay. Overall, cell viability results correlated with morphological observations indicated a good biocompatibility of HA-based composites at all tested concentrations. Incorporation of the TiO2 phase in HA by TSS process was found to be an efficient way to prepare bioceramics with improved performances.  相似文献   

10.
Apparent molar volumes Vϕ and apparent molar heat capacities Cp,ϕ were determined at the pressure 0.35 MPa for aqueous solutions of magnesium nitrate Mg(NO3)2 at molalities m = (0.02 to 1.0) mol · kg−1, strontium nitrate Sr(NO3)2 at m = (0.05 to 3.0) mol · kg−1, and manganese nitrate Mn(NO3)2 at m = (0.01 to 0.5) mol · kg−1. Our Vϕ values were calculated from solution densities obtained at T = (278.15 to 368.15) K using a vibrating-tube densimeter, and our Cp,ϕ values were calculated from solution heat capacities obtained at T = (278.15 to 393.15) K using a twin fixed-cell, differential, temperature-scanning calorimeter. Empirical functions of m and T were fitted to our results, and standard state partial molar volumes and heat capacities were obtained over the ranges of T investigated.  相似文献   

11.
Densities of aqueous solutions with molalities up to 6 mol · kg−1 were determined at 5 K temperature intervals, from T = 288.15 K to T = 333.15 K. Densities served to evaluate the apparent molar volumes, V2,ϕ(m, T), the cubic expansion coefficients, α(m, T), and the changes of isobaric heat capacities with respect to pressure, (∂CP/∂P)T,m. They were qualitatively correlated with the changes in the structure of water when glutaric acid is dissolved in it.  相似文献   

12.
We have measured the densities of aqueous solutions of alanine, alanine plus equimolal HCl, and alanine plus equimolal NaOH at temperatures 278.15  T/K  368.15, at molalities 0.0075  m/mol · kg−1  1.0, and at the pressure p = 0.35 MPa using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a twin fixed-cell differential temperature-scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values from the literature for Vϕ(T, m) and Cp,ϕ(T, m) for HCl(aq), NaOH(aq), and NaCl(aq) and the molar heat capacity change ΔrCp,m(T, m) for ionization of water to calculate parameters for ΔrCp,m(T, m) for the two proton dissociations from protonated aqueous cationic alanine. We integrated these results in an iterative algorithm using Young’s Rule to account for the effects of speciation and chemical relaxation on Vϕ(T, m) and Cp,ϕ(T, m). This procedure yielded parameters for Vϕ(T, m) and Cp,ϕ(T, m) for alaninium chloride {H2Ala+Cl(aq)} and for sodium alaninate {Na+Ala(aq)} which successfully modeled our observed results. Values are given for ΔrCp,m, ΔrHm, pQa, ΔrSm, and ΔrVm for the first and second proton dissociations from protonated aqueous alanine as functions of T and m.  相似文献   

13.
We have measured the densities of aqueous solutions of serine, serine plus equimolal HCl, and serine plus equimolal NaOH at temperatures 278.15  T/K  368.15, molalities 0.01  m/mol · kg−1  1.0, and at the pressure p = 0.35 MPa, using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a fixed-cell differential temperature-scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values from the literature for Vϕ(T,m) and Cp,ϕ(T,m) for HCl(aq), NaOH(aq), and NaCl(aq) and the molar heat capacity change ΔrCp,m(T,m) for ionization of water to calculate ΔrCp,m(T,m) for proton dissociations from protonated aqueous cationic serine and from the zwitterionic form. We integrated these results in an iterative algorithm using Young’s rule to account for the effects of speciation and chemical relaxation on the observed Vϕ(T,m) and Cp,ϕ(T,m) of the solutions. This procedure yielded parameters for Vϕ(T,m) and Cp,ϕ(T,m) for serinium chloride {H2Ser+Cl(aq)} and for sodium serinate {Na+Gly(aq)} which successfully modeled our observed results. We have then calculated ΔrCp,m, ΔrHm, ΔrVm and pQa for the first and second proton dissociations from protonated aqueous serine as functions of T and m.  相似文献   

14.
The density, ρ, and two derived properties, isothermal compressibility, κT, and the coefficient of cubic expansion, αP, were obtained for the mixtures of 1-methyl-4-(1-methylethenyl)-cyclohexene, known as limonene, and (1S,5S)-6,6-dimethyl-2-methylenebibyclo[3.1.1]heptane, known as β-pinene, for nine different compositions and the pure components at five pressures from 20 MPa to 40 MPa and six temperatures from 283.15 K to 358.15 K. The experimental uncertainty for ρ, κT, and αP were respectively ±0.5 kg · m−3, ±14 TPa−1, and ±0.005k K−1, with k = 2 for all of them. Density behaviour with temperature and pressure was as expected. The values of αP and κT increase with temperature and decrease with increasing pressure. Two different equations of state, conventional SAFT and PC-SAFT, were applied to predict the densities of the mixture. The best predictions were achieved with PC-SAFT.  相似文献   

15.
We have measured the densities of aqueous solutions of glycine, glycine plus equimolal HCl, and glycine plus equimolal NaOH at temperatures 278.15  T/K  368.15, molalities 0.01  m/mol · kg−1  1.0, and at p = 0.35 MPa, using a vibrating tube densimeter. We have also measured the heat capacities of these solutions at 278.15  T/K  393.15 and at the same m and p using a fixed-cell differential scanning calorimeter. We used the densities to calculate apparent molar volumes Vϕ and the heat capacities to calculate apparent molar heat capacities Cp,ϕ for these solutions. We used our results and values of Vϕ(T, m) and Cp,ϕ(T, m) for HCl(aq), NaOH(aq), NaCl(aq) from the literature to calculate parameters for ΔrCp,m(T, m) for the first and second proton dissociations from protonated aqueous cationic glycine. We then integrated this value of ΔrCp,m(T, m) in an iterative algorithm, using Young’s Rule to account for the effects of speciation and chemical relaxation on the observed Vϕ and Cp,ϕ of the solutions. This procedure yielded parameters for Vϕ(T, m) and Cp,ϕ(T, m) for glycinium chloride {H2Gly+Cl(aq)} and sodium glycinate {Na+Gly(aq)} which successfully modeled our observed results. We have then calculated values of ΔrCp,m, ΔrHm, ΔrVm, and pQa for the first and second proton dissociations from protonated aqueous glycine as functions of T and m.  相似文献   

16.
Low-temperature calorimetric measurements have been performed on DyBr3(s) in the temperature range (5.5 to 420 K ) and on DyI3(s) from T=4 K to T=420 K. The data reveal enhanced heat capacities below T=10 K, consisting of a magnetic and an electronic contribution. From the experimental data on DyBr3(s) a C0p,m (298.15 K) of (102.2±0.2) J·K−1·mol−1 and a value for {S0m (298.15 K)  S0m (5.5 K)} of (205.5±0.5) J·K−1·mol−1, have been obtained. For DyI3(s), {S0m (298.15 K)  S0m (4 K)} and C0p,m (298.15 K) have been determined as (226.9±0.5) J·K−1·mol−1 and (103.4±0.2) J·K−1·mol−1, respectively. The values for {S0m (5.5 K)  S0m (0)} for DyBr3(s) and {S0m (4 K)  S0m (0)} for DyI3(s) have been calculated, giving S0m (298.15 K)=(212.3±0.9) J·K−1·mol−1 in case of DyBr3(s) and S0m (298.15 K) =(233.1±0.7) J·K−1·mol−1 for DyI3(s). The high-temperature enthalpy increment has been measured for DyBr3(s) in the temperature range (525 to 799 K) and for DyI3(s) in the temperature range (525 to 627 K). From the results obtained and enthalpies of formation from the literature, thermodynamic functions for DyBr3(s) and DyI3(s) have been calculated from T→0 to their melting temperatures at 1151.0 K and 1251.5 K, respectively.  相似文献   

17.
Two novel ionic liquids based on serine [Cnmim][Ser] (n = 3, 4) were prepared by the neutralization method and their structures were confirmed by 1H NMR spectroscopy and differential scanning calorimetry (DSC). The density, surface tension, and refractive index of the two ILs were measured from T = (298.15 to 338.15) K. Since these ILs [Cnmim][Ser] (n = 3, 4) could form strong hydrogen bonds with water, small amount of water in the ILs is difficult to removed by common methods. In order to eliminate the effect of trace of water, the standard addition method (SAM) was applied to these measurements. On the basis of the experimental data, the speed of sound (μ), thermal expansion coefficient (α), molecular volume (Vm), standard entropy (S0298), entropy of surface (Sa), energy of surface (Ea), parachor (P), molar polarization (Rm), and polarization coefficient (αp) were calculated, and the relationship between each of these properties of [Cnmim][Ser] (n = 3, 4) and temperatures was discussed. According to the additivity, the average value of anionic parachor, P(ave), was 180.81 for [Ser]. At the same time, the surface tension of these serine ionic liquids could be estimated from their parachor and refractive index. The estimated values of the surface tension and the corresponding experimental data were almost identical.  相似文献   

18.
Low-temperature heat capacities of pyrimethanil laurate (C24H37N3O2) were precisely measured with an automated adiabatic calorimeter over the temperature range between T = 78 K and T = 340 K. The sample was observed to melt at (321.52 ± 0.04) K. The molar enthalpy and entropy of fusion as well as the chemical purity of the compound were determined to be (67244 ± 11) J · mol−1, (209.28 ± 0.02) J · mol−1 · K−1, (0.9943 ± 0.0004) mass fraction, respectively. The extrapolated melting temperature for the absolutely pure compound obtained from fractional melting experiments was (322.264 ± 0.006) K.  相似文献   

19.
The molar heat capacity of Zn2GeO4, a material which exhibits negative thermal expansion below ambient temperatures, has been measured in the temperature range 0.5⩽(T/K)⩽400. At T=298.15 K, the standard molar heat capacity is (131.86 ± 0.26) J · K−1 · mol−1. Thermodynamic functions have been generated from smoothed fits of the experimental results. The standard molar entropy at T=298.15 K is (145.12 ± 0.29) J · K−1 · mol−1. The existence of low-energy modes is supported by the excess heat capacity in Zn2GeO4 compared to the sums of the constituent binary oxides.  相似文献   

20.
The thermodynamic properties ofZn5(OH)6(CO3)2 , hydrozincite, have been determined by performing solubility and d.s.c. measurements. The solubility constant in aqueous NaClO4media has been measured at temperatures ranging from 288.15 K to 338.15 K at constant ionic strength (I =  1.00 mol · kg  1). Additionally, the dependence of the solubility constant on the ionic strength has been investigated up to I =  3.00 mol · kg  1NaClO4at T =  298.15 K. The standard molar heat capacity Cp, mofunction fromT =  318.15 K to T =  418.15 K, as well as the heat of decomposition of hydrozincite, have been obtained from d.s.c. measurements. All experimental results have been simultaneously evaluated by means of the optimization routine of ChemSage yielding an internally consistent set of thermodynamic data (T =  298.15 K): solubility constant log * Kps 00 =  (9.0  ±  0.1), standard molar Gibbs energy of formationΔfGmo {Zn5(OH)6(CO3)2 }  =  (  3164.6  ±  3.0)kJ · mol  1, standard molar enthalpy of formation ΔfHmo{Zn5(OH)6(CO3)2 }  =  (  3584  ±  15)kJ · mol  1, standard molar entropy Smo{Zn5(OH)6(CO3)2 }  =  (436  ±  50)J · mol  1· K  1and Cp,mo / (J · mol  1· K  1)  =  (119  ±  11)  +  (0.834  ±  0.033)T / K. A three-dimensional predominance diagram is introduced which allows a comprehensive thermodynamic interpretation of phase relations in(Zn2 +  +  H2O  +  CO2) . The axes of this phase diagram correspond to the potential quantities: temperature, partial pressure of carbon dioxide and pH of the aqueous solution. Moreover, it is shown how the stoichiometric composition{n(CO3) / n(Zn)} of the solid compoundsZnCO3 and Zn5(OH)6(CO3)2can be checked by thermodynamically analysing the measured solubility data.  相似文献   

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