Effects of Atmosphere on the Pressureless Sintering Behavior of ZrB₂ Ceramics
Department
Materials Science and Engineering
Major
Ceramic Engineering
Research Advisor
Hilmas, Greg
Fahrenholtz, William
Advisor's Department
Materials Science and Engineering
Funding Source
National Science Foundation under DMR
Abstract
The effects of atmosphere on the pressureless sintering behavior, microstructure development, and thermal properties of ZrB2 ceramics were studied. ZrB2 powders were sintered in a carbon free, refractory metal furnace under controlled atmospheres including helium, hydrogen, nitrogen, mild vacuum (~ 5 Pa) and high vacuum (~5 x 10-3 Pa). The sintering temperatures were varied from 1900⁰C to 2400⁰C with hold times ranging from 1 to 4 hours. Sintering in hydrogen resulted in higher weight loss than sintering in helium. Thermodynamic equilibrium calculations indicated that formation of ZrO(g) and H2O(g) were favorable in the presence of excess H2(g) at temperatures above 1800⁰C. These vapor species increased in concentration above 2000⁰C and were removed by the flowing H2(g), which resulted in the observed mass loss increase. No increase in density was observed between the mild vacuum and the high vacuum. Other effects of atmospheric conditions will be discussed such as those on thermal conductivity and microstructure development.
Biography
Andrea is a senior in Ceramic Engineering, graduating in May 2012. She will be attending Graduate School at Missouri S&T in Aerospace Engineering in the fall of 2012. Currently she is President and Treasurer of Material Advantage, Co-chair of the Keramos History Committee and planning a trip to Southeast Asia after graduation.
Research Category
Engineering
Presentation Type
Poster Presentation
Document Type
Poster
Location
Upper Atrium/Hallway
Presentation Date
10 Apr 2012, 1:00 pm - 3:00 pm
Effects of Atmosphere on the Pressureless Sintering Behavior of ZrB₂ Ceramics
Upper Atrium/Hallway
The effects of atmosphere on the pressureless sintering behavior, microstructure development, and thermal properties of ZrB2 ceramics were studied. ZrB2 powders were sintered in a carbon free, refractory metal furnace under controlled atmospheres including helium, hydrogen, nitrogen, mild vacuum (~ 5 Pa) and high vacuum (~5 x 10-3 Pa). The sintering temperatures were varied from 1900⁰C to 2400⁰C with hold times ranging from 1 to 4 hours. Sintering in hydrogen resulted in higher weight loss than sintering in helium. Thermodynamic equilibrium calculations indicated that formation of ZrO(g) and H2O(g) were favorable in the presence of excess H2(g) at temperatures above 1800⁰C. These vapor species increased in concentration above 2000⁰C and were removed by the flowing H2(g), which resulted in the observed mass loss increase. No increase in density was observed between the mild vacuum and the high vacuum. Other effects of atmospheric conditions will be discussed such as those on thermal conductivity and microstructure development.
