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Abstract  

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.

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Journal of Thermal Analysis and Calorimetry
Authors: A. Atbir, L. Aneflous, A. Marrouche, M. El Hadek, R. Cohen-Adad, and M.-Th. Cohen-Adad

Abstract  

Polytherm diagram of the ternary system KCl–FeCl2 –H2 O between 0 and 70C. Phase equilibria in the KCl–FeCl2 –H2 O system were studied over the temperature range 0–70C by conductimetric and analytical methods. A solubility polytherm of the system was constructed. We have observed the crystallization fields of the KCl and FeCl2 6H2 O (at 0C), KCl and FeCl2 4H2 O (at 15, 30 and 40C) and KCl, FeCl2 4H2 O and of a double salt KClFeCl2 2H2 O are obtained at 70C.

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Abstract  

Monomethylhydrazine (MMH) (CH3)NHNH2 is currently used as fuel for spacecraft engine combustion chambers. The Aestus engine of the upper stage of Ariane 5 is fed with MMH under pressure of 16 bars. The propellant, initially at room temperature, is about 393 K when introduced into the combustion chamber, due to heating up through the regenerative circuit. As MMH is unstable above 373 K, it has been necessary to check its decomposition rate and vapor pressure under such conditions. The vapor pressure of this propellant has been measured in a pressure vessel and the thermal decomposition rate was determined with the same device up to 500 K.

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Abstract  

The phase diagram of the ternary system NaCl-FeCl3 -H2 O was determined at four different temperatures (5, 15, 30 and 50C) by conductometry and thermal method. The experimental results show that in the temperature range 5 to 30C, only NaCl and FeCl3 6H2 O were present as solid phases. For the 50C isotherm, we have observed the crystallization fields of the NaCl and FeCl3 2,5H2 O.

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Journal of Thermal Analysis and Calorimetry
Authors: A. Atbir, S. Mançour Billah, A. Marrouche, M. El Hadek, R. Cohen-Adad, and M.-Th. Cohen-Adad

Abstract  

The phase diagram of ternary system Na+ , Fe2+ /Cl -H2 O was established over the temperature range 0–70C by conductimetric and analytical methods. A solubility polytherm of the system was constructed. For each temperature, we have determined the nature of the solid phase in equilibrium with the solution and the limit of its area of existence.

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The non-equilibrium region of the phase diagramxLiCl-(1−x)H2O (0<x< 0.18) has been studied by means of a Mettler TA 2000 B heat flow differential scanning calorimeter. The metastable lines of the diagram have been established and the different phases obtained explained. A region has been found where the glass formed cannot recrystallize, the eutectic line being below the temperature of the transition glass.

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Abstract  

A program has been written to describe solubility surfaces of the polythermal ternary phase diagram Mg(NO3)2–Al(NO3)3–H2O, using the model proposed by Cohen-Adad et al. [2]. In this work we present the calculation of the solubility surface of Mg(NO3)26H2O and Al(NO3)39H2O in the phase diagram. The calculated isothermal sections are in a good agreement with experimental determinations. Coefficients of the fitting equation that describes the solubility field allow drawing any isothermal section. The monovariant line was also calculated. The chosen model is well adapted to calculations of these solubility surfaces and gives very good results.

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Abstract  

A semi-empirical model consistent with thermodynamical conditions of equilibrium was used and oriented to the calculation of phase diagrams of the binary systems H2 O-MgCl2 , H2 O-FeCl2 and H2 O-FeCl3 . For each solid phase, the exploitation of the experimental and bibliographical data gives a liquidus curve equation comprising a limited number of parameters. A such equation allows to calculate with precision the solubility of the stoichiometric solid phase in a large range of temperature and composition.

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