Preparation of Nanomaterials

In 1984, German scientist Gleiter et al. successfully prepared iron nanoparticles for the first time by inert gas agglomeration. For decades, research on the preparation and application of nanomaterials has yielded fruitful results. The basic constituent particles of nanomaterials are of the order of nanometers in size and are particles in the intersection of atomic clusters and macroscopic objects. The diameter of the nanoparticles is generally between 1 and 100 nm. There are many preparation methods for nanomaterials, including sol-gel method, thermal synthesis method, liquid-phase organic synthesis method, inert gas condensation method, reverse micelle method, severe plastic deformation method and the like.

Sol-gel method

The sol-gel method is one of the most important chemical methods for material preparation. It provides a new way to synthesize inorganic ceramics, glass, and nanomaterials at normal temperature and pressure. The main step of preparing the nano material by the sol-gel method is to select the metal compound to be prepared, then dissolve the metal compound in a suitable solvent and solidify it by a sol-gel process, and finally obtain a nanoparticle by low temperature treatment.

Thermal synthesis method

The preparation of nanomaterials by thermal synthesis refers to the synthesis of nanomaterials in an aqueous solution under high temperature and high pressure, followed by separation and subsequent treatment to obtain nanoparticles. Thermal synthesis can produce products including metals, oxides, and composite oxides. This method is mainly used in the preparation of ceramic oxide materials.

Liquid-phase organic synthesis method

The liquid-phase organic synthesis mainly uses metals, organic compounds and some inorganic compounds having special properties which are stable in an organic solvent as a reactive raw material. These reactants are usually very sensitive to water and can not be stably present in aqueous solvents, so the most commonly used reaction method is to perform reflux in an organic solvent to prepare nanomaterials.

Inert gas condensation method

The inert gas condensation method is one of the main methods for preparing nano powders. The main process of the inert gas condensation method is to fill low-pressure inert gas in the vacuum evaporation chamber, and then vaporize the raw material to form a plasma by vacuum evaporation, heating, high-frequency induction or the like. The material gas molecules collide with the inert gas molecules to lose energy, and agglomerate to form nano-sized clusters. The inert gas condensation method has a fast reaction speed, no other impurities in the process, and the prepared nano material has high purity. However, this method has higher requirements for reaction technology and equipment.

Reverse micelle method

The micro-droplet of reverse micelle in the water-in-oil microemulsion is a special nano-space, which can be used as a reaction field to exchange and react the reactants in different micelles to prepare nano-scale particles. In the preparation process, the reverse micelle is a tiny reaction field and can also be called a smart microreactor. When using reverse micelles for nanomaterial preparation, the reactants can be directly added or blended. Different addition methods correspond to different reaction mechanisms, but the results are the same, that is, highly dispersed and uniform nanoparticles can be prepared.

Severe plastic deformation method

Severe plastic deformation method means that under the action of quasi-static pressure, the material undergoes severe plastic deformation to refine its size to the nanometer order. The bulk material is typically refined into a mixture of crystalline and amorphous materials under quasi-static pressure and then heat treated to form nanomaterials. The material prepared by the method has high purity and good controllability of particle size.

Nanomaterials have distinct properties that are different from bulk materials and individual molecules—small size effects, surface and interface effects, quantum size effects, and macroscopic quantum orbital effects. Due to the special physical, mechanical, electrical, magnetic, optical and chemical properties of nanomaterials, they are of great value in the fields of electronics, optics, chemistry, ceramics, biology and medicine. Therefore, it is foreseeable that nanomaterials will become one of the pillars of the new round of industrial revolution in the 21st century.

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