Multi-scale homogeneity analysis of co-milled powders : development of a reverse approach to assess quality of mixtures

International audienceThe standard methodology employed for estimating homogeneity of powder mixtures relies on the concept of scale of scrutiny. This parameter defines the relevant scale at which a homogeneous distribution of a given compound is critical regarding the final application of the blend. However, such a scale is not always known in advance. In this paper, a process involving two ceramic powders, co-ground and pressed into pellets is investigated in terms of homogeneity at various scales, from macroscopic to microstructural. According to the scale considered, different methodologies are employed. In particular, a reverse method is developed providing homogeneity indexes that are characterizing the microstructural state, without knowing the scale of scrutiny in advance. The results show that the homogeneity is improved by the co-grinding process as compared to simple drum-mixing experiments, even at a macroscopic scale. This method also shows that the microstructural homogeneity increases according to the grinding time during the first 16 minutes of grinding. The evolution of the microstructural homogeneity according to the grinding time is also investigated