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Thermodynamic parameters for solid and liquid phases in the Al2O3‐Y2O3 system are assessed using new calorimetric measurement for the YAG (Y3Al5O12), YAP (YAlO3) and YAM (Y4Al2O9) phases. The calculated phase diagram of the Al2O3‐Y2O3 system is in reasonable agreement with experimental data. According to the calculations, the YAP phase melts congruently and is stable down to the low temperatures, while the YAM phase disproportionates to a mixture of YAP and Y2O3 phases at temperatures below 1385 K. The calculated entropy of the YAG phase 300.1 J/(mol · K) is between 2 experimentally determined values 284.8 and 349.1 J/(mol · K). However, the difference between calculated and experimental values exceeds uncertainty limits of adiabatic calorimetry data. The enthalpies of melting for the YAG and YAP phases calculated in this study are in reasonable agreement with DTA measurements. The calculated enthalpy of melting for the YAG phase is not consistent with estimates based on solution calorimetric data. New independent measurement of the standard entropy and enthalpy of melting are desirable for the YAG, YAM and YAP phases. The liquidus surface and isothermal section at 2000 K for ternary Al‐Y‐O system are calculated in this study.

This book represents information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated A wide variety of references are listed Every reasonable effort has been made to give reliable data and information, but the authors and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use.

The purpose of this article is to give a set of recommendations to producers of assessed thermodynamic data, who may be involved in either the critical evaluation of limited chemical systems or the creation and dissemination of larger thermodynamic databases. Also, it is hoped that reviewers and editors of scientific publications in this field will find some of the information useful. Good practice in the assessment process is essential, particularly as datasets from many different sources may be combined together into a single database. With this in mind, we highlight some problems that can arise during the assessment process and we propose a quality assurance procedure. It is worth mentioning at this point, that the provision of reliable assessed thermodynamic data relies heavily on the availability of high quality experimental information. The different software packages for thermodynamics and diffusion are described here only briefly.

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Several thermodynamic descriptions of the Fe-N and Fe-N-C systems were proposed before now. The results of these descriptions significantly deviate from more recently obtained experimental data. The present work provides a revised thermodynamic description of these systems. The new description for the Fe-N system agrees distinctly better with the experimental data especially for the equilibrium of c 0 -Fe 4 N 1Àx and e-Fe 3 N 1+z . The new thermodynamic description for the Fe-N-C system considering the Fe-rich part of the system with less than 33 at. pct N and less than 25 at. pct C excellently agrees with the new experimental data for both the temperatures of the invariant reactions and the phase boundaries. This in particular concerns the temperature range of typical technical nitriding and nitrocarburizing treatments [723 K to 923 K, (450°C to 650°C)], within which three invariant reactions occur in the ternary system.

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Yttrium silicates are promising materials for improved oxidation and erosion protection for carbon fiber‐reinforced composites. A two‐layer coating system of low‐pressure plasma‐sprayed yttrium silicate on chemical vapor deposition‐SiC‐precoated C/C–SiC was tested under atmospheric re‐entry conditions simulated within a plasma wind tunnel test facility. The thermal expansion behavior of Y2SiO5 and Y2Si2O7 was investigated. The chemical compatibility with and without increasing oxygen partial pressure at the interface of the two‐layer system was calculated by the CALPHAD method. The calculations were compared with experimental results. Furthermore, a thermodynamic explanation is presented to understand and predict the observed coating failure mechanism, identified as blister formation.