Nano-metallic materials include nano-metal powders and nano-structural metallic materials. According to the chemical reactions, preparation of nano metal powder can be divided into two kinds of physical and chemical methods. Physical method includes plasma, wire electrical explosion method, laser induction complex heating evaporation method and high-energy ball milling. Chemical method includes reduction, electrolysis, and carbonyl method.

Plasma method is to use the plasma to have melting, evaporation and condensation and obtain nano metal powder. Plasma temperature is high, almost could be prepared to take any metal nano-powders in an inert atmosphere, and its high purity, uniform particle size, less pollution, small size, size distribution of a narrow range of particle into a spherical particles with excellent mobility and The filling can be prepared near the theoretical density of the bulk material is the most effective method of preparation of series of metal and metal alloy series of nano particles. Wire electrical explosion method generated by the capacitor discharge current pulse wire their resistance heat to melt, vaporize and collide with the gas, condensing into a nano-powder. Wire electrical explosion method to prepare nano powder characteristics: energy efficiency can effectively control the nano-powder size, with high levels of activity, does not produce hazardous waste without harming the environment, you can get the powder of high purity and good dispersity.

Laser induction complex heating evaporation method by high frequency induction metal material as a whole is heated to higher temperatures. And then using a laser metal rapid evaporation, and condensation to get the powder. Metal salt solution to join KBH4 or NaBH4 solution was successfully prepared nanoscale Fe-Co-B, Co-B, Fe-B and other amorphous alloy powder. If using hydrazine as reducing agent, the preparation of nanoscale Ag, Pd, nickels powder and manganese powder. Chemical reduction method is simple, easy to operate. The electrolytic method is mainly based on the acidic aqueous electrolyte is characterized for the preparation of the relative hydrogen inactive nano metal powder, such as Cu, Ag, Pt. Electrolysis obtained powder of high purity, large surface area, powder size control, low production costs can be realized the advantages of automation and production.

Preparation of the nano-metal structural materials in situ pressure, ball milling, vacuum sputtering method and direct quenching method. Situ pressure method has been prepared for the good of nanoparticles under conditions that maintain a fresh surface, pressed into a massive condensed solid. Using the in situ pressure of nano-metal structure can be fabricated metals, alloys, and amorphous materials. The ball milling using a ball mill rotation or vibration, hard ball of raw materials with a strong impact, grinding and mixing, the metal or alloy powder grinding method for nanoscale particles. Vacuum sputtering by argon ion beam to the metal surface atoms excited out and deposited into a layered, it can be prepared by the multi-layer nano-materials, and each layer is only 0.2nm thick. The method of crystallization the amorphous ribbons after heat treatment so that crystallization of the nanocrystalline strip. Grain particle size is very sensitive to the plasticity of crystallization prepared by nano-metal structure. If the particle size is very small, plastic is better. Otherwise, the material becomes very brittle.

Direct quenching method is to get nanocrystalline materials by quenching controlling speed of liquid alloys. It is suitable for the preparation of bulk nanocrystalline materials. This approach is used in the Ni-Ti alloys and Si system to get Ti2Ni nanocrystalline. Controlling the quenching speed is a key point. Its purposes are to increase the speed of nucleation and inhibit grain growth. Nanocrystalline is dispersed in the metal body as a second phase. It can greatly improve the performance and practical value.Source: