Project No: FE0003798
Performer: Tennessee State University


Contacts

Federal Project Manager: Rawls, Patricia: Patricia.Rawls@NETL.DOE.GOV
Technology Manager: Maley, Susan: Susan.Maley@netl.doe.gov
Principal Investigator: Ouyang, Lizhi: Louyang@Tnstate.edu

Duration
Award Date:  06/17/2010
Project Date:  12/30/2013

Cost
DOE Share: $280,000.00
Performer Share: $0.00
Total Award Value: $280,000.00

Performer website: Tennessee State University - http://www.tnstate.edu

Crosscutting Research - University Training and Research

Computational Studies of Physical Properties of Nb-Si Alloy

Project Description

The overall goal is to provide valuable insight in to the mechanisms and processes that could lead to next generation hot section material operating at temperature beyond 1350°C which could play an important role in current plight towards greener energy. The main objectives of the proposed projects are: (1) developing a supercell approach to evaluate physical properties of alloys which maintains various order and disorder bulk phases and interfaces; (2) applying the supercell approach to study the physical properties of Nb-Si alloy. The results will be used to guide the search for optimal Nb-Si alloy design with a balanced set of physical properties.


Program Background and Project Benefits

This project will focus on development of Nb-Si alloys that will improve the high-temperature performance of advanced power generation components. Development of these alloys will lead to greater operational flexibility in coal-fired power plants. It will enable cola-fired plants to operate at desired conditions, resulting in improved efficiency leading to reduction of all effluents and waste products, including carbon dioxide.


Accomplishments

TSU has demonstrated the Gibbs free energy module for calculating temperature pressure dependent elastic constants on several systems including the Nb metal, Nb-Si alloys, and silicon carbide (SiC). For insulator SiC, the calculated temperature coefficients of elastic constants for both cubic and hexagonal SiC are in excellent agreement with the experimental data. For Nb, the calculated elastic constants at low temperature showed notable error. The error has been traced to insufficient k-space sampling and supercell size used in the phonon calculation. More accurate calculations are planned. TSU researchers have completed the calculations of Gibbs free energy, specific heats, thermal expansion coefficients, entropy, and elastic constants for all known crystal phases of the binary Nb-Si alloys and are currently working on thermodynamic databases for Nb-Si-Cr ternary systems for selected crystal phases. TSU is continuing to improve the post-processing codes for Gibbs free energy calculation, temperature and pressure dependent elastic constants calculation, and other thermodynamic properties. The draft temperature pressure dependent elastic constants of SiC have been completed and will be submitted for review soon. TSU is currently developing a flexible cluster variation method that will enable computation of the free energy and stress for disordered systems and refining the calculation of elastic constants based on free energies in proximity to the temperature-hydrostatic pressure surface of states.