Cláudia Sofia de Andrade Redondo Murilhas Buchheim ...

Results and Discussion
milled with stearic acid is influenced by the mixing with the SiC
nanoparticles and from the reaction of the stearic acid during milling.
The hardness increases with the input energy. The influence of different
processing parameters was studied for milling with the addition of 0.5
Wt. % of stearic acid as the process control agent. All parameters
studied in this work as speed, time of milling, mass of balls and
powders, have been assumed and experimented according the
experience and studies already done in this area. A pronounced
decrease in energy transfer from the balls to the powder is done with an
increasing number of balls, when the milling is performed at low vial
filling levels. Our experiments have been done always with the same
balls and its amount, 100 g, and diameter, 10mm. Increasing the time
milling, and using 1 Vol. % stearic acid, we observed that the material
gets more homogeneous.
Stearic acid is added to the powder as a milling additive. It prevents the
powder from sticking to the balls and the interior of the processing
chamber. It has been reported that this addition helps reduce the size of
the powder, speeding up the milling process. In these experiments it is
observed that the yield stress increases upon increasing the acid
concentration, when all other parameters are kept constant. This effect
is demonstrated in Figure 26 by comparing the curves corresponding to
materials 5 compared with the increase corresponding to material 3
relative to material 2, which is a factor of 1.49. The dependence of
mechanical parameters on the SiC volume fraction is non-linear, as also
observed in Poirier et al. 2010 [56].
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