Solution-based synthesis and processing of nanocrystalline ZrB₂-based composites

Zirconium- and tantalum-based diborides, and diboride/carbide composites are of interest for ultra-high temperature applications requiring improved thermomechanical and thermochemical stability. This thesis focuses on the synthesis, processing and sintering of nanocrystalline powders with Zr- and Ta-based diboride/carbide/silicide compositions. A solution-based processing method was developed to prepare reactive mixtures that were precursors for ZrB₂-based powders. The precursors reacted to form the ceramic powders after suitable pyrolysis and borothermal/carbothermal reduction heat treatments. Single-phase ZrB₂ powders were prepared with initial composition of C/Zr = 4.8 and B/Zr = 3.0. ZrB₂-based composite powders with ZrC, ZrO₂, TaB₂, TaC, SiC, TaSi₂ and B₄C were prepared with particle sizes of 10-500 nm for different phases based SEM micrographs. The composite powders were highly sinterable with proper processing methods developed to avoid and remove oxide impurities. The relative densities of ZrB₂/B₄C, ZrB₂/TaB₂, ZrB₂/TaB₂/B4C, ZrB₂/TaSi₂ were in the range of 91%-97% after pressureless sintering at 2020 ℃ for 1 h or 30 min.

Department dc:contributor.department

Materials Science and Engineering

Grantor dc:publisher

Georgia Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Xie, Yanli

Advisors dc:contributor.advisor

• Speyer, Robert F.
• Sanders, Thomas H., Jr.

Committee members dc:contributor.committeemember

• Gerhardt, Rosario
• Sandhage, Kenneth
• Snyder, Robert
• Zhang, John

• Sol-gel
• Nanocystalline
• Synthesis
• Zirconium boride

Handle dc:identifier.uri

http://hdl.handle.net/1853/26640

OAI identifier oai:identifier

oai:repository.gatech.edu:1853/26640