A Thermodynamic Study Of The Sulphates And Related Compounds Of Alkali And Alkaline Earth Metals At High Temperatures

Author : Jorge Paz Soldan Palma
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (133 download)

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Download or read book Thermodynamic Modeling of Alkaline and Rare Earth Metal with Antimonides for Applications in Power Generation written by Jorge Paz Soldan Palma and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Power generation techniques are an important aspect of modern civilization. Recently, antimony and its compounds have shown remarkable properties that could contribute to new and more efficient power generation applications. An example of these antimonide compounds is the Yb14MnSb11, which has shown impressive thermoelectric properties at temperatures of 1273 K. Due to the impressive high temperature thermoelectric properties of the compound, the thermoelectric community wants to implement the compound into the Radioisotope Thermoelectric Generator (RTG). However, it has been noted that the Yb14MnSb11 suffers from sublimation issues due to its constituents' (Yb & Sb) high vapor pressures at elevated temperatures. Furthermore, a primary aspect of the device development is having stable, electrical contacts between the electrodes and the thermoelectric compound, especially at high temperatures. In the present dissertation, the thermodynamic modeling of the Mn-Sb-Yb-(Co,Ni) quaternary systems will be discussed. The databases developed will be used to predict the stability region of Yb14MnSb11 at high temperatures and low pressures, which will resemble operating conditions, as well as predict potential chemical reactions at the interfaces between the electrode candidates (Co and Ni) and thermoelectric compound at 1273 K. Furthermore, the Al-Mn-O-Sb-Yb database will be developed as well to predict potential reactions between Yb14MnSb11 and Al2O3, which has been used in the literature as a coating for sublimation suppression. Pyrochemical processing has been identified as another power generation application where Sb can play a major role. The chemical process is applied to recover uranium from nuclear fuel waste through an electrochemical deposition approach. In the approach, the nuclear waste is the anode and is submerged in an electrolyte solution where the U dissolves and is subsequently reduced onto an inert cathode. A limiting factor of this process is the accumulation of highly radioactive fission byproducts from the nuclear waste accumulating in the electrolyte solution. An electrorefining method was developed in which low melting metals such as Sn, Sb and Bi can be used to recycle nuclear waste due to the strong interactions between the two chemical groups. However, due to the high temperatures required for this process, the design of the metal that has the lowest melting points with the highest interactions with alkaline rare-earth metals are needed. In the electrorefining processing portion of this dissertation, the modeling of the Sr-Sb system was chosen as the initial system for the endeavor. This is because of the recently available thermochemical and phase equilibria experimental data. Due to the importance of having a robust thermodynamic description of the liquid phase as a function of composition for this application, a solution model with the best extrapolation to multicomponent composition space is needed. A model known to have this characteristic is the quasichemical model by quadruplet approximation (MQMQA), which considers the chemical bonding between different species. Unfortunately, the MQMQA model was not readily available to the CALPHAD community if the FactSage software was not purchased. Therefore, the current dissertation work implemented the MQMQA model into the open source PyCalphad and ESPEI python libraries in order to enable thermodynamic modeling of systems with it. In this work, the Sr-Sb system was modeled with both the associate model and the MQMQA model.