TEM investigation of hot pressed ‐10 vol.%SiC–ZrB₂composite

Abstract

The polytypism of SiC, phase transformation of ZrB 2 and the interfaces between SiC and ZrB 2 were investigated using high resolution TEM in a hot pressed 10 vol.%SiC-ZrB 2 composite. In most cases, no grain boundary interphases between hexagonal ZrB 2 and 6H-SiC phases were observed with SiC being both inter-and intragranular. Occasionally, 6H-SiC transformed into 3C and 15R and hexagonal ZrB 2 transformed into cubic ZrB. High resolution TEM showed no grain boundary interphases in most regions. Energy dispersive X-ray spectroscopy and electron energy-loss spectroscopy analyses showed the presence of oxygen throughout the sample. The phase transformation of SiC and ZrB 2 , and the interphase formation between SiC and ZrB 2 grains are discussed.

Grain rotation and translation contribute substantially to creep of a zirconium diboride silicon carbide composite

“…A qualitative assessment of ZrB 2 and ZrB 2 -SiC grain boundaries, from the EBSD-OIM data, reveals > 95% are high angle random boundaries, suggesting high mobility. In a similar composite, Jasalyeane et al [45] found predominantly non-coherent unlike interfaces, adding further support to our data. The ratio of Z-Z to Z-S boundaries is close to unity, while the SiC grain boundaries are <10% of all grain boundaries, suggesting minimal influence from the SiC-SiC interfaces.…”

Reactive hot-pressing of ZrB2-ZrC-SiC ceramics via direct addition of SiC

“…Meanwhile, a large sum of ZrC has been produced. And the possible reactions are listed as reaction (3) and (11). H of reaction (7) might be introduced in milling process.…”

“…[7,8] Whereas, the densification of ZrB 2 ceramics is a difficult task due to their poor sinterability. [9] Previous works have indicated that ZrB 2 -based ceramics, containing a second phase such as SiC [7,[10][11][12] and ZrC [10], exhibit improved densification behavior and material properties, compared to the corresponding monolithic ceramics. Besides, some other efforts have been made to solve this issue, like effective densification approaches: hot pressing (HP) [4,[13][14][15][16], pressureless sintering (PLS) [7,14,17,18], spark plasma sintering (SPS) [14,[19][20][21][22], reactive processing [23][24][25] and so on.…”

Temperature dependence of microstructure evolution during hot pressing of ZrB2–30 vol.% SiC composites

“…No grain boundary interphases were detected in most regions but energy dispersive spectroscopy as well as electron energy-loss spectroscopy analyses verified the presence of oxide impurities in the sample [16].…”