skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Combustion Synthesis of Boride-Based Electrode Materials for Magnetohydrodynamic (MHD) Direct Power Extraction

Abstract

The goal of the present project was to develop an advanced, low-cost manufacturing technique for fabrication of boride-based ultrahigh-temperature ceramics (UHTCs) that possess all the required properties to function as sustainable electrodes in magnetohydrodynamic (MHD) direct power extraction applications. Specifically, the project investigated use of mechanical activation-assisted self-propagating high-temperature synthesis (MASHS) followed by pressureless sintering for the fabrication of ceramic materials based on ZrB2 and HfB2 from inexpensive raw materials ZrO2, HfO2, and B2O3, with Mg as a reactant and NaCl or MgO as an inert diluent. Thermodynamic calculations were conducted for combustion of ZrO2/B2O3/Mg and HfO2/B2O3/Mg mixtures with MgO and NaCl additives. In the experiments, the mixture ingredients were milled in a planetary mill, compacted into pellets, and ignited in an argon environment. MgO and NaCl were removed from the combustion products by acid leaching. The reaction mechanisms in these mixtures were studied using thermogravimetric analysis and differential scanning calorimetry. Pressureless sintering in an induction furnace was explored for purification and densification of the obtained products. It has been shown that mechanical activation of ZrO2/B2O3/Mg and HfO2/B2O3/Mg mixtures decreases the ignition temperature and enables a self-sustained combustion. The addition of excess Mg increased the oxide-to-boride conversion degree. MgO additivemore » was not effective for milling and for increasing the conversion degree. In contrast, NaCl additive effectively decreased sticking of the material to the grinding media. Combustion of mixtures containing NaCl produced nanoscale particles of ZrB2, which is beneficial for sintering. Thermoanalytical studies clarified the reaction mechanisms during magnesiothermic MASHS of ZrB2. The pressureless sintering experiments demonstrated that milling, pressing, and adding boron carbide are needed for enhancing the sinterability of ZrB2.« less

Authors:
ORCiD logo [1]; ;
  1. The University of Texas at El Paso
Publication Date:
Research Org.:
The University of Texas at El Paso
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1569658
Report Number(s):
DE-UTEP-FE0026333
DOE Contract Number:  
FE0026333
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; 36 MATERIALS SCIENCE; MHD; ultra-high temperature ceramics (UHTC); borides; combustion synthesis; SHS; mechanical activation

Citation Formats

Shafirovich, Evgeny, Cordova, Sergio, and Llausas, Gabriel. Combustion Synthesis of Boride-Based Electrode Materials for Magnetohydrodynamic (MHD) Direct Power Extraction. United States: N. p., 2019. Web. doi:10.2172/1569658.
Shafirovich, Evgeny, Cordova, Sergio, & Llausas, Gabriel. Combustion Synthesis of Boride-Based Electrode Materials for Magnetohydrodynamic (MHD) Direct Power Extraction. United States. doi:10.2172/1569658.
Shafirovich, Evgeny, Cordova, Sergio, and Llausas, Gabriel. Tue . "Combustion Synthesis of Boride-Based Electrode Materials for Magnetohydrodynamic (MHD) Direct Power Extraction". United States. doi:10.2172/1569658. https://www.osti.gov/servlets/purl/1569658.
@article{osti_1569658,
title = {Combustion Synthesis of Boride-Based Electrode Materials for Magnetohydrodynamic (MHD) Direct Power Extraction},
author = {Shafirovich, Evgeny and Cordova, Sergio and Llausas, Gabriel},
abstractNote = {The goal of the present project was to develop an advanced, low-cost manufacturing technique for fabrication of boride-based ultrahigh-temperature ceramics (UHTCs) that possess all the required properties to function as sustainable electrodes in magnetohydrodynamic (MHD) direct power extraction applications. Specifically, the project investigated use of mechanical activation-assisted self-propagating high-temperature synthesis (MASHS) followed by pressureless sintering for the fabrication of ceramic materials based on ZrB2 and HfB2 from inexpensive raw materials ZrO2, HfO2, and B2O3, with Mg as a reactant and NaCl or MgO as an inert diluent. Thermodynamic calculations were conducted for combustion of ZrO2/B2O3/Mg and HfO2/B2O3/Mg mixtures with MgO and NaCl additives. In the experiments, the mixture ingredients were milled in a planetary mill, compacted into pellets, and ignited in an argon environment. MgO and NaCl were removed from the combustion products by acid leaching. The reaction mechanisms in these mixtures were studied using thermogravimetric analysis and differential scanning calorimetry. Pressureless sintering in an induction furnace was explored for purification and densification of the obtained products. It has been shown that mechanical activation of ZrO2/B2O3/Mg and HfO2/B2O3/Mg mixtures decreases the ignition temperature and enables a self-sustained combustion. The addition of excess Mg increased the oxide-to-boride conversion degree. MgO additive was not effective for milling and for increasing the conversion degree. In contrast, NaCl additive effectively decreased sticking of the material to the grinding media. Combustion of mixtures containing NaCl produced nanoscale particles of ZrB2, which is beneficial for sintering. Thermoanalytical studies clarified the reaction mechanisms during magnesiothermic MASHS of ZrB2. The pressureless sintering experiments demonstrated that milling, pressing, and adding boron carbide are needed for enhancing the sinterability of ZrB2.},
doi = {10.2172/1569658},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {10}
}

Works referenced in this record:

Toward a better conversion in magnesiothermic SHS of zirconium diboride
journal, May 2018