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OwnerNicolas Davidovits, Michel Davidovics +1inventors
InventorsNicolas Davidovits, Michel Davidovics, Joseph Davidovits
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A composite ceramic-ceramic material is disclosed having a fibrous reinforcing ceramic and a ceramic matrix made of a geopolymeric compound containing: (a) a poly(sialate) geopolymer M.sub.n (--Si--O--Al--O--).sub.n and/or poly(sialate-siloxo) M.sub.n (--Si--O--Al--O--Si--O--).sub.n, M representing at least one alkaline cation, and n the degree of polymerization; (b) ultrafine silicious and/or aluminous and/or silico-aluminous constituents, of size smaller than 5 microns, preferably lower than 2 microns, the said geopolymeric compound being obtained by polycondensation at a temperature between 20.degree. C. and 120.degree. C. of an alkaline alumino-silicate reaction mixture, the composition of the principal constituents of the said geopolymeric compound expressed in terms of mole ratios of the oxides being between or equal to following values: M.sub.2 O/SiO.sub.2 --0.10 TO 0.95, SiO.sub.2 /Al.sub.2 O.sub.3 --2.50 TO 6.00, M.sub.2 O/Al.sub.2 O.sub.3 --0.25 TO 5.70, M.sub.2 O representing either Na.sub.2 O and/or K.sub.2 O, or a mixture of at least one alkaline oxide with CaO. The fibrous reinforcement consists of ceramic fibres such as SiC, Al.sub.2 O.sub.3, SiO.sub.2, glass, carbon. The addition of alkaline sulphides and alkaline sulphites enables glass fibres to be protected against chemical attack due to the alkalinity of the matrix.
In a process for the manufacture of a solid ceramic-ceramic material having reinforcing ceramic fibers and a ceramic matrix including a mineral polymer of alkaline polysilicate and alkaline polysialate, comprising the steps of obtaining said composite ceramic-ceramic material by hydrothermal polycondensation of said ceramic matrix in the presence of said reinforcing ceramic fibers and a filler, the improvement wherein the composite ceramic-ceramic material includes 30 to 60 parts by weight said reinforcing ceramic fibers and said reinforcing ceramic fibers are impregnated with said mineral polymer and said filler, said filler having dimensions lower than 5 microns and being selected from the group consisting of silica dust, alumina dust and micronized mica in such quantities that the mole ratios of oxides in the mixture of said mineral polymer and filler are within or equal to the following values:
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