Defects and Secondary Phases in Zirconium Diboride
Zirconium diboride gains its high temperature mechanical stability from the high atomic defect energies (i.e. the atoms do not deviate easily from their lattice sites). This means that the concentration of defects will remain low, even at high temperatures, preventing failure of the material.
The layered bonding between each layer is also very strong but means that the ceramic is highly anisotropic, having different thermal expansions in the 'z' <001> direction. Although the material has excellent high temperature properties, the ceramic has to be produced extremely carefully as any excess of either zirconium or boron will not be accommodated in the ZrB2 lattice (i.e. the material does not deviate from stoichiometry). Instead it will form extra lower melting point phases which may initiate failure under extreme conditions.
Read more about this topic: Zirconium Diboride
Famous quotes containing the words defects and, defects, secondary and/or phases:
“All conservatives are such from personal defects. They have been effeminated by position or nature, born halt and blind, through luxury of their parents, and can only, like invalids, act on the defensive. But strong natures, backwoodsmen, New Hampshire giants, Napoleons, Burkes, Broughams, Websters, Kossuths, are inevitable patriots, until their life ebbs, and their defects and gout, palsy and money, warp them.”
—Ralph Waldo Emerson (1803–1882)
“The defects of the mind, like those of the face, grow worse with age.”
—François, Duc De La Rochefoucauld (1613–1680)
“The prime purpose of being four is to enjoy being four—of secondary importance is to prepare for being five.”
—Jim Trelease (20th century)
“But parents can be understanding and accept the more difficult stages as necessary times of growth for the child. Parents can appreciate the fact that these phases are not easy for the child to live through either; rapid growth times are hard on a child. Perhaps it’s a small comfort to know that the harder-to-live-with stages do alternate with the calmer times,so parents can count on getting periodic breaks.”
—Saf Lerman (20th century)