Nanoparticles Synthesis in Wet-Operating Stirred Media: Investigation on the Grinding Efficiency

Abstract

The use of nanomaterials, thanks to their peculiar properties and versatility, is becoming central in an increasing number of scientific and engineering applications. At the same time, the growing concern towards environmental issues drives the seeking of alternative strategies for a safer and more sustainable production of nanoparticles. Here we focus on a low-energy, magnetically-driven wet milling technique for the synthesis of metal nanoparticles starting from a bulky solid. The proposed approach is simple, economical, sustainable, and provides numerous advantages, including the minimization of the nanoparticles air dispersion and a greater control over the final product. This process is investigated by experiments and discrete element method simulations to reproduce the movement of the grinding beads and study the collision dynamics. The effect of several parameters is analyzed, including the stirring bar velocity, its inclination, and the grinding bead size, to quantify the actual frequency, energy, and angle of collisions. Experiments reveal a non-monotonous effect of the stirring velocity on the abrasion efficiency, whereas numerical simulations highlight the prevalent tangential nature of collisions, which is only weakly affected by the stirring velocity. On the other hand, the stirring velocity affects the collision frequency and relative kinetic energy, suggesting the existence of an optimal parameters combination. Although a small variation of the stirring bar length does not significantly affect the collision dynamics, the use of grinding beads of different dimensions offers several tuning opportunities.

Simulation of Grinding Media Motion and Collisions in Wet-Operated Accelerator-Mill Using DEM Coupled with CFD

“…However, we must note that in this case, the translational shear energy, SEts,sum, still accounts for 80% of the total collision stress energy(SEcs,sum). Dominance of the shear component has also been reported in other literature [25]. This is also demonstrated in Figure 16a,b, where SE cs,sum is the sum of all locally averaged stress energy SE cs , SE ts,sum denotes the sum of trans-latoric shear energy SE ts in a single SEV.…”

“…However, we must note that in this case, the translational shear energy, SE ts,sum , still accounts for 80% of the total collision stress energy(SE cs,sum ). Dominance of the shear component has also been reported in other literature [25].…”

Top-Down Synthesis of Luminescent Microplastics and Nanoplastics by Incorporation of Upconverting Nanoparticles for Environmental Assessment

“…The method is simple, economical, sustainable and, similar to the first step, provides the advantage of the preservation of the polymer structure. 36 It consists of preparing a dispersion of the powder in a solvent, adding zirconium beads and then slowly rolling the solution. Ethanol was chosen as the solvent because synthesis in water, which would be more appropriate for future use in toxicological tests, was not possible.…”

Engineered Nanomaterials in Soil: Their Impact on Soil Microbiome and Plant Health

“…Physical methods such as abrasion, condensation, melting, evaporation, etc., utilize mechanical pressure, high electrical or thermal energy, and radiations to produce a variety of ENMs [ 43 , 44 , 45 ]. Examples of top-down physical techniques are milling, crushing, etching, etc., which use solid state precursors [ 46 ], whereas the bottom-up physical methods such as chemical vapor deposition (CVD), flame pyrolysis, electrolysis, etc., apply gaseous or liquid materials as precursors [ 47 , 48 , 49 ].…”