18 th century, people found that is worth the noble diamond unexpectedly is a kind of carbon element with different form, from then on, the preparation of artificial diamond became many scientists glory and dream. A century later, graphite-carbon another kind of elemental form is found, people will try to simulate natural process, let the graphite in the super under the environment of high temperature and high pressure into a diamond. In order to shorten the reaction time, needs to 2000 ℃ high temperature and 5.
Synthetic diamond
50000 atmospheres of special condition.
In 1955, the general electric company specialized in the manufacturing of high temperature and high pressure electrostatic equipment, to get the world's first industry with artificial diamond small crystals, which created the industrial scale production of artificial diamond abrasive precedent, now they the annual output of the factory in 20 tons; Soon, dupont invented the explosion method, using instantaneous explosions produce high voltage and sharp increase, also won a few mm size of artificial diamond.
The performance of the diamond film, less in diamond grains, the density and hardness in lower. Even so, it is also the wear resistance of the one, only 5 microns thick film, life expectancy than hard alloy steel up to 10 times. We know, the record in tiny needles contact surface of be subjected to great pressure, and require extremely long wear life, as long as the point of a deposition in a layer of diamond film, it can easily go. If in plastic, glass with the outside of the diamond film do wear-resisting coating, can greatly expand its use, development and economic performance is superior products.
More important, the appearance of film of application broke through the only as cutting tools for the barriers, make its excellent heat, electricity, sound, light performance could be fully utilized. At present, the diamond film has already been used in semiconductor electronic device, optical acoustic device, the pressure, processing and cutting machining tools, etc, and its developing at breakneck speed, in the high-tech fields more attractive.
Using artificial method makes the diamond structure of carbon into diamond structure of carbon, and through the nucleation and growth form single crystal and polycrystalline diamond, or he under the high temperature high pressure of the diamond with burn polycrystalline diamond form. This is high research at present in the production of an important applied examples.
From thermodynamics point of view, the decision of graphite structure of the carbonaceous materials diamond can change into diamond
Synthetic diamond products is the latter phase change of the conditions of the free energy must be smaller than the former. This phase change process is in high pressure and high temperature or other components of the conditions of participation. The pressure and temperature and concentration of yuan may cause the system to change the internal energy, so that the input can place the level of the statistical weight changes of. This may appear electron transfer and the formation of a new state of bonding electronic structure, namely the phase change happened. If the system changes in energy to solid occurred in the structure change of this kind of electron, the high temperature high pressure phase change happened in solid state, or it may happen in molten state or steam condition. In this change happened in melt condition is, bonding characteristic of the input of the distribution of the statistical weight reduced, remote orderly role tend to disappear, atomic coordination number changed; And in the statistical weight electronic excited states tends to increase, close range and orderly corresponding enhancement effect. The change occurred in the gas of the condition is, elemental atoms or compounds the bonding between the molecules of the electronic energy levels tend to disappear, all of the electronic transfer to single atoms or molecules level up, so that, in statistical weight electronic excited more increased. Therefore, synthetic diamond can in solid, also can be in molten state and steam state conditions, it depends on the pressure, temperature and concentration of yuan factors such as the change of can cause the system. From the dynamics viewpoint, also requires graphite carbonaceous materials into a diamond with appropriate transformation rate. The diamond nucleation rate and growth rate and a great value the phase change of rate is the largest.
Since the eighteenth century confirmed the diamond is made of pure carbon atoms later, began to study of artificial diamond, just in the 1950 s through the high pressure research and high pressure experiment technology progress, to get the true success and rapid development. At present the concrete method of artificial diamond as many as ten kinds of. According to the characteristics of the technology used can be described as static, dynamic pressure and low voltage, three ways. According to the formation of the diamond characteristics can be reduced to direct, weld media and extension of the three methods, etc.
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