B. Hahn et al., ESR INVESTIGATION OF MOSI2 POWDERS USED AS REACTIVE FILLERS IN POLYMER-DERIVED CERAMICS, Colloids and surfaces. A, Physicochemical and engineering aspects, 115, 1996, pp. 291-295
An electron spin resonance (ESR) and thermal rheology study is carried
out on novel ceramic composites made by pyrolysis of polysiloxane-MoS
i2 mixtures, which show potential for high temperature applications wi
th their excellent oxidation stability and creep resistance up to 1500
degrees C, but for which injection moulding of the precursor mixture
is strongly affected by catalytic effects of MoSi2 on the crosslinking
reaction of the polymer phase. ESR showed that the surface of MoSi, w
as oxidized during grinding, resulting in an active oxide layer of SiO
2 and MoxOy with Mo5+ centres. The Mo5+ signal is correlated with the
MoSi2 grain size and the lowering of the thermosetting temperature. Bo
th the Mo5+ signal and the catalytic effect can be suppressed by remov
ing this mixed oxide layer with dilute acids.