| 摘要 |
Preforms made of ceramics comprising alpha alumina single crystals in the form of hexagonal platelets. Among these preforms, the invention relates very particularly, on the one hand, to the preforms consisting essentially of hexagonal alpha alumina platelets and, on the other hand, to the mixed preforms in which the said platelets are associated with one or a number of other ceramic products, the alpha alumina content preferably remaining predominant. The process for their manufacture comprises the use of amorphous, transition or hydrated alumina and of a fluorine-containing flux. These preforms can be employed as such or for the manufacture of composites. |
