Densification of ultra-refractory transition metal diboride ceramics
The densification behavior of transition metal diboride compounds was reviewed with emphasis on ZrB2 and HfB2. These compounds are considered ultra-high temperature ceramics because they have melting temperatures above 3000°C. Densification of transition metal diborides is difficult due to...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
International Institute for the Science of Sintering, Beograd
2020-01-01
|
| Series: | Science of Sintering |
| Subjects: | |
| Online Access: | http://www.doiserbia.nb.rs/img/doi/0350-820X/2020/0350-820X2001001F.pdf |
| Summary: | The densification behavior of transition metal diboride compounds was
reviewed with emphasis on ZrB2 and HfB2. These compounds are considered
ultra-high temperature ceramics because they have melting temperatures above
3000°C. Densification of transition metal diborides is difficult due to
their strong covalent bonding, which results in extremely high melting
temperatures and low self-diffusion coefficients. In addition, oxide
impurities present on the surface of powder particles promotes coarsening,
which further inhibits densification. Studies prior to the 1990s
predominantly used hot pressing for densification. Those reports revealed
densification mechanisms and identified that oxygen impurity contents below
about 0.5 wt% were required for effective densification. Subsequent studies
have employed advanced sintering methods such as spark plasma sintering and
reactive hot pressing to produce materials with nearly full density and
higher metallic purity. Further studies are needed to identify fundamental
densification mechanisms and further improve the elevated temperature
properties of transition metal diborides. |
|---|---|
| ISSN: | 0350-820X 1820-7413 |