Explanation

nanomaterials refer to materials that have at least one dimension in the range of nanoscale (1 to 100 nm) or are composed of basic units of these nanoscale in three-dimensional space. These basic units can be divided into the following three categories according to dimensions: zero dimension: all scales in three-dimensional space are within the scope of nanoscale, such as nanoparticle, atomic clusters, etc. One dimension: there are two dimensions at the nanometer scale in the three-dimensional space, such as nanowires, nanobelt, nanorods, nanotube, etc. Two dimensional: there is a dimension at the nanometer scale in the three-dimensional space, such as nano sheet, nanofilm, etc. The methods of preparing nanomaterials can be divided into two ways: "top-down": this is a process from large to small, and large objects are transformation into nanoscale particles through crushing, smashing, grinding and other methods. "Bottom up": through appropriate chemical reactions, atoms are arranged in order to prepare nanoparticle from molecules or atoms. The methods for preparing nanomaterials can also be divided into different types, including gas phase method, liquid phase method and solid phase method: gas phase method includes evaporation condensation method under inert gas, physical gas phase method and chemical deposition method. Liquid phase method includes hydrothermal method, solvothermal method, sol-gel method, hydrolysis method, microemulsion method, solvent volatile decomposition method, etc. The solid-state method includes high-energy ball milling method, solid-state reaction method, etc. Because of its special size effect, small size effect, surface effect, and quantum tunneling effect, nanomaterials exhibit unique properties that many conventional materials do not possess, including melting point, vapor pressure, optical properties, chemical reaction activity and selectivity, magnetism, superconductivity, and plastic deformation. Therefore, nanomaterials have broad application prospects in magnetic materials, electronic materials, optical materials, catalysis, sensing, environmental protection, energy, medicine and many other fields.

Classification