Environmentally benign dry mechanical mixing of nano-particles using magnetically assisted impaction mixing process

The effectiveness of magnetically assisted impaction mixing (MAIM), an environmentally benign mechanical process, in mixing SiO2 + TiO2 and SiO2 + Al2O3 nanoparticle mixtures has been examined. Experiments were carried out at different magnet-to-sample weight ratios, processing times, and magnet sizes. The homogeneity of mixing (HoM) was evaluated at the micron scale using field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy, and at sub-micron scale through electron energy loss spectroscopy and transmission electron microscopy. The HoM improved with an increase in the magnet-to-sample weight ratio and processing time, and a decrease in the magnet size; over the range of conditions tested, the HoM was found to depend on the product of processing time and the number of magnets per unit powder mass. Optimized MAIM process achieved HoM values that were comparable to those attained with Rapid Expansion of Supercritical or High-Pressure Suspensions and sonication of a suspension of the nanoparticles in supercritical CO2.

Graphical AbstractMagnetically assisted impaction mixing is shown to be an effective, environmentally benign dry method to mix nanoparticles. Longer processing times and/or higher magnet to powder ratios led to better mixing. The TEM results indicate that optimized operating conditions will achieve mixing at sub-micron down to nanoscale.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch Highlights► Magnetically assisted impaction mixing (MAIM) is used to mix nanopowders. ► Mixing is at the sub-micron to nano-scale, quantified via SEM-EDX and TEM-EELS. ► Mixing homogeneity from MAIM is superior to conventional dry powder mixing methods. ► MAIM can produce mixture homogeneity similar to sonication in supercritical CO2. ► Performance depends on the product of processing time and the number of magnets.