Authors:Shekhar Kumar, Abhishek Singh, Pranay Sinha, U. Kamachi Mudali, and R. Natarajan
Urea-adduct process is commercially used to selectively separate n-alkanes from industrial hydrocarbon mixtures. Authors have explored application of this method for recovery of n-alkane based diluents from spent PUREX/UREX solvent. Traditionally this separation is performed by vacuum distillation, an
energy-intensive process. The proposed method is simple and does not involve either exotic chemicals or complex processing
steps. Application of urea-adduct process for recovery of diluent from spent solvent is reported here possibly first time
in literature. Physical properties such as densities, viscosities and vapour pressure for irradiated organic solutions were
also measured and reported.
Authors:B. Wierczinski, J. Aign, F. Baumgärtner, G. Müllen, and A. Türler
Tritium exchange and enrichment was studied for several different metal salts, e.g., AlF3 . H2O, FeO(OH), CsI, CsF, NaI, NaF and Al(OH)3 using a cryosublimation apparatus. Experiments were performed below equilibrium vapor pressure to avoid any isotope effects. A comparable tritium enrichment factor of 1.14 to 1.43 was obtained for all systems, except for CsF, which gave an enrichment factor of 1.93. These results confirm the concept, that 3H is accumulated in weak hydrogen bonds as already observed in organic molecules.
Authors:T. Ito, T. Nagasaki, K. Iwasaki, M. Yoshino, and T. Matsui
Summary Proton concentration in SrZr0.95M0.05O3-α (M=Ga, Sc, Y and Nd) was measured with a thermobalance at different temperatures (T=673-973 K) and water vapor pressures (PH2O=0.9-12.8 kPa). At all the pressures and temperatures examined, the amount of proton concentration in these samples is in the order of Sc>Y>Ga>Nd. By an equilibrium evaluation, we estimated the maximum possible proton concentration about 2.0 mol% in these samples. Infrared (IR) absorption spectra are measured in these samples. The absorption bands can be fitted by four (M=Ga, Y, Nd) or three (M=Sc) Gaussian bands.
An automatic pressure
tracking adiabatic calorimeter (APTAC) has been developed to obtain the thermokinetic
and vapor pressure data during runaway reactions. The heat onset temperature
is important data for estimating the thermal hazardous materials. DTBP(di-tert-butyl peroxide)/toluene was chosen for evaluating
the measurement values and the thermokinetic parameters. The relationships
between the sample mass and the heat onset temperature in the addition to
the maximum temperature were investigated to explain the heat of reaction
measured by the APTAC. The apparatus properties and the reliability of the
data obtained by the APTAC were examined on the basis of the experimental
Transpiration method was used to measure the equilibrium water vapor pressures of the dehydration of the respective hydrates,
such as oxalates, sulfates,chlorides and acetate, and the enthalpies of dehydrations (ΔHTr0) of these hydrates were obtained. The heats of dehydrations (ΔHDSC0) were also determined by TG-DSC method. From the comparison with ΔHTr0 of ΔHDSC0, the relation of ΔHDSC0/ΔHTr0=R (=dehydration molar number determined by TG-DSC peak/stoichiometric dehydration molar number) was yielded. From these results,
the following relations were found: ΔHDSC0(corrected)=ΔHDSC0/R=ΔHTr0
A detailed thermodynamic study of the systems LnSe2–LnSe1.5 (Ln = La, Nd) was performed by static method of vapour pressure measurement using quartz membrane-gauge manometers within the
temperature range 713–1,395 K. The pSe–T–x dependences obtained in this study have shown that the phase regions in composition intervals studied consist of discrete
phases: LnSe1.95LnSe1.90, LnSe1.85, LnSe1.80 (Ln = La, Nd). The enthalpies and the entropies for the stepwise dissociation process were calculated from the experimental data.
The standard enthalpies of formation and the absolute entropies were estimated for the compounds investigated using literature
Authors:R. Bellajrou, M. Cohen-Adad, R. Cohen-Adad, M. Habiballah, and M. El-Hadek
Engine Viking of Ariane 4 is supplied with asymmetrical dimethylhydrazine (UDMH) (CH3)2NNH2. An addition of a small amount of hydrazine hydrate N2H4H2O was proposed to increase the thermal stability of UDMH. The mixture where the mass ratio (CH3)2NNH2/N2H4H2O is equals to 75/25, is called UH25. These propelling agents are unstable when they are heated and the optimisation of burning
conditions requires a good knowledge of their vaporisation and of their thermal decomposition kinetics.
Authors:O. Pondarevskaya, O. Petrenko, V. Sudavtzova, V. Lisnyak, and N. Stus
Thermodynamic properties of pure titanium stannides obtained by crucible-less growth techniques under vacuum are determined
by differential scanning calorimetry and Knudsen effusion. The enthalpy, specific heat capacity, entropy and Gibbs energy
temperature dependence were simulated using Maier and Kelly equations. Standard enthalpies of evaporation, formation and atomization
of titanium stannides were determined and compared with earlier-known data.
The aim of this work is to highlight the importance of controlling the residual water vapour pressure above the sample as
well as the rate of the thermal decomposition during the thermal dehydration of cerium cyclotriphosphate trihydrate CeP3O9·3H2O.
For this reason, the dehydration of the titled compound was followed by both techniques: the constant rate thermal analysis
at PH2O = 5 hPa and the conventional TG-DTA in air.
It has been shown that the pathway of the thermal dehydration depends strongly on the nature of atmosphere above the sample.
However, in air atmosphere CeP3O9·3H2O decomposes in two well defined steps to give first an amorphous, phase in the temperature range 440–632 K, then the cerium
polyphosphate Ce(PO3)3 crystallizing in orthorhombic system (C2221) at T>632 K. Whereas decomposition carried out at 5 hPa water vapour pressure, also occurring in two steps, leads first to a crystallized
intermediate monohydrate at 259<T<343 K and second to a crystallized anhydrous cerium polyphosphate, at 343<T<791 K, with a structure different from those of all lanthanide polyphosphate known actually and particularly from that of
Ce(PO3)3 obtained in air.
The activation energy corresponding to the dehydration of the initial phosphate was also measured experimentally by means
of two CRTA curves and was found equal to 81±5 kJ mol−1.
Authors:D. Jones, H. Feng, R. Augsten, and R. Fouchard
Isopropylnitrate (IPN) is described as a detonable material used in propellants and explosives. While there is considerable
information available on its sensitivity and compatibility with other materials, very little is known about its thermochemical
properties. This paper will describe the results obtained from some DSC, heat flux calorimetry (HFC) and accelerating rate
calorimetry (ARC) measurements.
The ASTM DSC method using a hermetic aluminum pan having a lid with a laser-produced pin hole was used to determine the vapour
pressure of IPN1. Results calculated from an Antoine equation are in substantial agreement with those determined from DSC measurements. From
the latter measurements, the enthalpy of vaporization was determined to be 35.320.62 kJ mol−1. Attempts to determine vapour pressures above about 0.8 MPa resulted in significant decomposition of IPNg.
The enthalpy change for decomposition in sealed glass systems was found to be -3.430.09 kJ g−1 and -3.850.03 kJ g−1, respectively from DSC and HFC measurements on IPN1 samples loaded in air. Slightly larger exotherms were observed for the HFC results in air than those in inert gas, suggesting
some oxidation occurs. In contrast, no significant difference in the observed onset temperature of about 150C was observed
for both the HFC and ARC results.
From DSC measurements, an Arrhenius activation energy for decomposition of 1264 kJ mol−1 was found. These measurements were also conducted in sealed glass systems and decomposition appeared to proceed primarily
from the liquid phase.