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.
Highlights
The synthesis of nanoparticles (NPs) and nanostructured materials has received progressively growing attention in recent years thanks to their versatility in a wide variety of technical applications, ranging from the medical [1] to industrial [2] and environmental [3] field
Many manufacturing processes can be adopted depending on the compound to be synthesized, which in general can be grouped into two opposite strategies, i.e., bottom-up and top-down methods
Research is increasingly pushing towards the development of new approaches that are cheaper, intrinsically safer, and more environmentally sustainable. Such a goal can be achieved by adopting new procedures [10] that generally refer to ‘green nanotechnology’ [11], in which reagents derived from plant extracts, pigments, yeast, and enzymes are employed [12,13,14]
Summary
The synthesis of nanoparticles (NPs) and nanostructured materials has received progressively growing attention in recent years thanks to their versatility in a wide variety of technical applications, ranging from the medical [1] to industrial [2] and environmental [3] field. The main drawback related to bottom-up methods is the use of various chemicals (as reagents, complexing agents, and surfactants) having toxic effects on human health and the environment For this reason, research is increasingly pushing towards the development of new approaches that are cheaper, intrinsically safer, and more environmentally sustainable. Owing to the solvent presence, the disaggregation process directly releases zerovalent Ag nanoparticles as a dispersed phase, minimizing NPs air dispersion and leading to greater control over the final product. Such simple innovation leads to a more eco-friendly and economically sustainable NPs synthesis. The results are presented in terms of frequency, energy, and angle of collision
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