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2016年10月14日星期五

Nano Tungsten Copper Composite Material

Nano tungsten copper composite material is also known as ultra-fine tungsten copper composite material, which compared with common grain tungsten copper, has better mechanical and chemical properties, such as high density, high hardness, high strength, excellent wear and corrosion resistance and perfect thermal and electrical conductivity, etc. Its granularity usually between 1nm -100nm and the nano grain has several characteristics is given as follow:

1. Small size effect: When the coherence length or penetration depth dimension and the wavelength of light particles, de Broglie wavelength and other physical characteristics of the superconducting state of a considerable size or less, crystal periodic boundary conditions will be destroyed, the density of atoms near the surface of the particle layer of amorphous nano-particles reduced, resulting in characteristic sound, light, electricity, magnetic, thermal, mechanical and other changes in the new physical properties;
 2. Surface effect: With the decreasing grain size, the ratio of surface atoms and total atoms of nano tungsten copper grains is dramatically increasing and the binding energy of grain is correspond increasing, which changes the properties of nano grains;
 3. Quantum size effect: When copper tungsten particle size down to a certain size, the electron energy levels near the Fermi level from continuous to discrete energy and transformation. During the existence of discrete energy level occupied molecular orbital, at the same time there are also contrary to occupy the lowest molecular orbital, and the spacing between the high and low rail level with the smaller diameter of the nano particles increased;
 4. Macroscopic quantum tunneling effect: Electrons have wave-particle duality and the ability to penetrate the barrier, known as the tunnel effect. Macroscopic quantum tunneling effect will be the basis for future microelectronics, electronics, or it further establishes the limits of miniaturization existing microelectronic device;
 5. Coulomb blockade and quantum tunneling: In nano scale dimensions, the charging and discharging process is not continuous, filled with an electron energy required is called the Coulomb energy blockage. In such a small system of single-electron transport behavior is known as Coulomb blockage effect, if the two quantum dots connected by a junction, a single quantum dot electrons through the energy barrier to another quantum dot is the quantum tunneling.

Nano tungsten copper composite material has better performance in thermal properties, magnetic properties, optical properties, the super-conducting properties, catalytic properties and so on. From the thermal properties, at extremely low temperatures, the thermal resistance of tungsten copper nano particle is almost zero; from magnetic properties, nano grain will enter super-paramagnetic state when it exceeds a certain threshold and shows high coercivity; from optical properties, nano particle quantum size effect is more significant, in the optical performance of the wide-band receiver, the dispersion obtain some special optical properties; and the super-conducting transition temperature of nano tungsten copper grain increases as the decreasing granularity. In addition, from catalysis nature, as the particle size decreases the reactivity significantly increased under appropriate conditions capable of catalyzing the breakage H-H, C-H, C-C, C-O chemical bond and so on.

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