AP/HTPB based composite
propellants with additives such as ammonium oxalate (AO), mixture of ammonium
oxalate and strontium carbonate (SC) was investigated by burning rate, TG-DTG
and FTIR experiments. The results show that the burning rates of these propellants
are decreased significantly. TG-DTG experiments indicate that decomposition
temperatures of AP with these additives are increased. Furthermore, the activation
energy of the decomposition reaction of AP is also increased in the presence
of AO or AO/SC. These results show that AO or AO/SC restrains the decomposition
of AP. The burning rates of these propellants are decreased. The burning rate
temperature sensitivity of AP/HTPB based propellants is reduced significantly
by the addition of AO or AO/SC. But the effect of AO is less than that of
AO/SC. AO/SC is better effect to reduce temperature sensitivity and at the
same time, to reduce pressure exponent. The reduced heat release at the burning
surface of AP/HTPB/AO is responsible for the reduced temperature sensitivity.
Synergetic action is probably produced between AO and SC within AP/HTPB based
propellants in the pressure range tested. This synergetic effect causes the
heat release to reduce and the burning surface temperature to increase. Moreover,
it makes the net exothermal reaction of condensed phase become little dependent
on T0. Thus, the
burning rate temperature sensitivity is reduced.
The paper describes a new transient hot wire instrument which employs 25.4 μm diameter tantalum wire with an insulating tantalum
pentoxide coating. This hot-wire cell with a thin insulating layer is suitable for measurement of the thermal conductivity
and the thermal diffusivity of electrically conducting and polar liquids. This instrument has been used for experimental measurement
of the thermal conductivity and the thermal diffusivity of poly(acrylic acid) solution (50 mass%) in the temperature range
of 299 to 368 K at atmospheric pressure. The thermal conductivity data is estimated to be accurate within ±4%. Thermal diffusivity
measurements have a much higher uncertainty (±30%) and need further refinement.
Authors:Y. Shi, L. Sun, F. Tian, J. Venart, and R. Prasad
The transient hot-wire technique is widely used for absolute measurements of the thermal conductivity of fluids. Refinement
of this method has resulted in a capability for accurate and simultaneous measurement of both thermal conductivity and thermal
diffusivity together with a determination of the specific heat. However, these measurements, especially those for the thermal
diffusivity, may be significantly influenced by fluid radiation.
The present work investigates the effect of fluid radiation on the measurements of the thermal conductivity of propane. Recently
developed corrections have been used to examine this assumption and rectify the influence of even weak fluid radiation. Measurements
at 372 K with a hot-wire instrument demonstrate the presence of radiation effects in both the liquid and vapor phase. The
influence is much more pronounced in liquid propane at 15.5 MPa than in the vapor phase at 881.5 kPa. The technique employed
to obtain radiation-free thermal conductivity measurements is described.
The molar heat capacities of the room temperature
ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4)
were measured by an adiabatic calorimeter in temperature range from 80 to
390 K. The dependence of the molar heat capacity on temperature is given as
a function of the reduced temperature X
by polynomial equations, CP,m
(J K–1 mol–1)=
195.55+47.230 X–3.1533 X2+4.0733 X3+3.9126 X4 [X=(T–125.5)/45.5] for the solid phase (80~171
K), and CP,m (J
378.62+43.929 X+16.456 X2–4.6684 X3–5.5876 X4 [X=(T–285.5)/104.5] for the liquid phase (181~390
K), respectively. According to the polynomial equations and thermodynamic
relationship, the values of thermodynamic function of the BMIBF4
relative to 298.15 K were calculated in temperature range from 80 to 390 K
with an interval of 5 K. The glass translation of BMIBF4
was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar
enthalpy of combustion of BMIBF4 was determined to
– 5335±17 kJ mol–1. The standard
molar enthalpy of formation of BMIBF4 was evaluated
to be ΔfHmo=
–1221.8±4.0 kJ mol–1 at T=298.150±0.001 K.
The transient hot-wire technique is widely used for absolute measurements
of the thermal conductivity and thermal diffusivity of fluids. It is well
established that fluid radiation effects significantly influence these measurements,
especially those for the thermal diffusivity. Corrections for radiation effects
are based on the models developed and deviations of the measured data from
the ideal line source model. In this paper, the effect of fluid radiation
on the measurements of the thermal conductivity of n-pentane
is presented. For comparison, the influence of thermal radiation effect on
measurement of transparent fluids, such as argon is also shown. The difference
between the influence of natural convection and thermal radiation is also
Molar heat capacities
of acetaminophen were precisely measured with a small sample precision automated
adiabatic calorimeter over the temperature range from 80 to 330 K. A solid-solid
transition at 149.96 K was found from the Cp,m-T curve. The polynomial functions of Cp,.m(J
K-1 mol-1) vs. T were established
on the heat capacity measurements by means of the least square fitting method.
processes of acetaminophen have been studied by thermogravimetry. And the
thermal decomposition kinetics parameters, such as activation energy E, pre-exponential factor A
and reaction order n, were calculated by
TG-DTG techniques with the Freeman-Carroll method, Kissinger method
and Ozawa method. Accordingly the thermal decomposition kinetics equation
of acetaminophen is expressed as: dα/dt=2.67107e-89630/RT(1-α)0.23.
The process of fusion has been investigated through
DSC. The melting point, molar enthalpy and entropy of fusion are to be (441.890.04)
K, 26.490.44 kJ mol-1 and 59.801.01
J K-1 mol-1,
Authors:Y. Y. Di, Z. C. Tan, L. W. Li, S. L. Gao, and L. X. Sun
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, TD=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 (Cp,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)] (ΔsolHm,l0) and the Zn(Val)SO4·H2O(s) (ΔsolHm,20) in 100.00 mL of 2 mol dm−3 HCl(aq) at T=298.15 K were determined to be, ΔsolHm,l0=(94.588±0.025) kJ mol−1 and ΔsolHm,20=–(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: ΔfHm0 (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).
Authors:L. Yang, S. Qiu, F. Xu, L. Sun, Z. Zhao, J. Liang, and C. Song
The effects of Amoxicillin Sodium and Cefuroxime Sodium on the growth of E. coli DH5α were investigated by microcalorimetry. The metabolic power-time curves of E. coli DH5α growth were determined by using a TAM air isothermal microcalorimeter at 37�C. By evaluation of the obtained parameters,
such as growth rate constants (k), inhibitory ratio (I), the maximum heat power (Pm) and the time of the maximum heat power (tm), one found that the inhibitory activity of Amoxicillin Sodium vs. E. coli DH5α is enhanced with the increasing of the Amoxicillin Sodium concentration, and the Cefuroxime Sodium has a stimulatory effect on the E. coli DH5α growth when the concentration is about 1 μg mL−1. The IC50 for the Amoxicillin Sodium and the Cefuroxime Sodium are 1.6 and 2.0 μg mL−1, respectively, it implicates that the E. coli DH5α is more sensitive to Amoxicillin Sodium than Cefuroxime Sodium.
Authors:J. Zeng, Z. Cao, D. Yang, F. Xu, L. Sun, X. Zhang, and L. Zhang
The effects of multi-walled carbon nanotubes (MWNTs) on the phase change enthalpy (ΔH) and the thermal conductivity (κ) of a solid-liquid phase change materials (PCM), palmitic acid (PA), have been investigated.
The results showed that both the ΔH and the κ of the composite were lower than that of PA when the loading of MWNTs was small. As the concentration of MWNTs
in the composites increased, the ΔH of the composites was slightly improved and then decreased linearly. However, the κ of the composites was monotonously increased
from the minimum value. When the loading of MWNTs increased to 5% and no surfactant was added, the κ of the composite was
enhanced to be 26% higher than that of PA. The κ of the composite could be enhanced by CTAB instead of SDBS when the loading
of MWNTs was small, as SDBS showed no obvious effect on the κ of the composites. Furthermore, the effects of surface modification
of MWNTs on the ΔH and the κ of the composites have also been investigated.
Authors:J. Zeng, Z. Cao, D. Yang, F. Xu, L. Sun, L. Zhang, and X. Zhang
A series of PA-TD mixtures were prepared and their thermal properties were studied by DSC and thermal conductivity measurement.
The phase diagram of the binary system was constructed, which showed an eutectic behavior for the solid-liquid equilibrium
line. The eutectic composition of the binary system was at the mass fraction of TD near 0.7 with an eutectic temperature of
about 29°C. At TD side, PA was partially miscible in the TD solid matrix and the solid phase transition of TD had an effect
on the solidus line. The eutectic composition mixture could be viewed as a new phase change material with large thermal energy