When the micron particles become smaller and smaller in certain condition, it will cause the physical, chemical and mechanical changes. We call it size effect in general. Because of the size in nano grade and with large surface area greatly improve the hardness and super modulus. Metal nanoparticles like Ni, Fe, Al, Ti, Cu, Co and so on havelots of commons. Metal nanoparticles like Ag, Au, Pt expensive metal nanoparticles have similar properties too.

1. Mechanical property — Metal nanoparticles could greatly improve the hardness, toughness and abrasion resistance of materials.

2. Optical property — Metal nanoparticles have special UV-Vis spectra. Metal nanoparticles lost the metalshining when come to nano grade. Metal nanoparticles are black in color,generally the smaller the more black. Generally the reflectivity of metal nanoparticles is lower than 1%. With this special property, metal nano particles could use in high effect photothermal conversion and photoelectric conversion,which could converse the solar energy to thermal energy and electric energy.Also metal nanoparticles are the optimal materials for I R sensor or infraredstealthy material.

3. Electrical Property — for the general metal is electronic products, but when the particle size comes to nano grade, the electrical property changes a lot. Some researches show the electrical property relates to the particle size. It seems there is a critical size. If the particle size is over the critical size, metal particles will obey the general rule between resistance and temperature. If the particle size is small than the critical size, it will lose its electrical property.

4. Magnetic property — Iron group metal (Fe , Co, Ni nanoparticles) and their alloys have excellent magnetic property. For these nanoparticles have high permeability, high saturation magnetization and low loss, which could improve the high temperature magnetic property. For these products are used in switching powder supply, sensor and transformer etc, which makes products smaller in size, lighter in weight and multi-function.

5. Catalytic property — Metal element nano powder like Al, Ni, Ti, Fe Cu, Co and so on with extremely good catalytic activity which are widely use in different kinds of reaction catalyzer.

Corrosion resisting property — Compare to the element metal nanoparticles, the metal alloy nanoparticles have better corrosion resisting property. Fe-Ni, Ni-Fe, Ni-Znalloys have better corrosion resisting property than general alloys.