Environmentally Friendly Green Synthesis of Fine Particles by Dry Mechanical Processes Toward SDGs: A Review

Abstract

The United Nations Sustainable Development Goals (SDGs) have attracted much attention due to increasing interest in global social, energy and environmental problems. The immediate contribution to the achievement of the SDGs is required in all individual and industrial activities. The industries dealing with fine particles are also no exception to the demand and have actively worked on the contribution. Conventionally, fine particles have been industrially synthesized in gas, liquid and solid phases using top-down and bottom-up approaches. Among them, dry synthesis processes are promising from a viewpoint of the SDGs due to the solvent-free and simplicity, which can lead to energy saving, efficient resource utilization, waste management, etc. This review describes dry mechanical processes for synthesis of fine particles, particularly focusing on grinding and mechanochemical treatment.

Tuning Chemical and Morphological Properties of Ceria Nanopowders by Mechanochemistry

“…As a consequence, many different synthesis processes have been developed to increase control and tuning of these parameters, either on pure CeO 2 powders or in combination with dopant elements. The proposed methods often rely on solution-based routes, high-temperature treatments, hydrothermal steps for the preparation of cube- and rod-like nanostructures, and, more recently, spray flame pyrolysis for uniform dispersion of CeO 2 crystallites. , The application of ball-milling has also been explored, yet mostly in relation with homogeneous distribution of CeO 2 -based powders for subsequent ceramic sintering processes rather than catalytic applications, − but the environmental advantages allowed by a solvent-free milling method have been favoring its application. , In addition, the milling processes have also been demonstrated on a larger scale , compared to other preparation methods, such as hydrothermal or combustion based. The mechanochemical synthesis has indeed attracted increasing attention in the latest years for the synthesis of advanced nanomaterials, usually aimed at the preparation of alloys − or at materials phase-tuning , in high energy milling conditions.…”

“… 28 , 29 The application of ball-milling has also been explored, yet mostly in relation with homogeneous distribution of CeO 2 -based powders for subsequent ceramic sintering processes rather than catalytic applications, 30 − 33 but the environmental advantages allowed by a solvent-free milling method have been favoring its application. 34 , 35 In addition, the milling processes have also been demonstrated on a larger scale 36 , 37 compared to other preparation methods, such as hydrothermal or combustion based. The mechanochemical synthesis has indeed attracted increasing attention in the latest years for the synthesis of advanced nanomaterials, usually aimed at the preparation of alloys 38 − 40 or at materials phase-tuning 41 , 42 in high energy milling conditions.…”