The aim of this paper was to study the synthesis and characterization
of spinel-containing mullite based materials, using sol-gel techniques
. Several gels were prepared, with nominal compositions 3(A1(2-2x)M(x)
TixO3). 2SiO(2) and 3(Al(2-x)M(x)O(3)). 2SiO(2), with M = Ni+2 or Co2 and 0.0 less than or equal to x less than or equal to 0.2, by hydrol
ysis and condensation of mixtures of aluminum, silicon and titanium al
koxides and nickel chloride. Dried gels were homogeneous and displayed
a glass transition at around 750 degrees C, which indicated that the
system could be described as an amorphous silicoaluminate network. Cry
stallization pathway of gels were followed using differential thermal
analysis and X-ray diffraction patterns of samples thermal treated at
temperatures in the range between 800 and 1400 degrees C. A two-phase
aluminate spinel-mullite arrangement was detected at temperatures arou
nd 1200 degrees C. The microstructure of the final product was interes
ting, because the minor secondary phase was homogeneously dispersed in
the mullite matrix. Chemical and thermal resistance of diphasic mater
ials were tested and the results indicate that these materials can be
used as high temperature ceramic pigments.