| As its huge body elastic modulus, high thermal conductivity, good insulation and it is in a state of thermodynamic instability, so the detonation nano-diamond(DND for short) has a broad application prospect with its special chemical, thermal, optical transparency and electrical properties. DND often exist in reunited state due to its high specific surface area and high surface activity caused by detonation reaction. If the problem that the agglomeration of nano-particle is not solved, it will lead that the DND lose many advantages as nano-powder and its good performance will not get into full play.Adopted the method of heat treatment in air oxidation to regulate the crystal structure and surface functional groups of DND. X-ray, infrared spectroscopy and transmission electron microscopy were used to research and inductive the phase and surface functional group of DND. It turned out that it has the diamond cubic phase structure, its surface contains a lot of oxygen containing functional groups and the particle size is in10nanometers or so. After the heat treatment in the air, the crystal shape became more complete, amorphous phase impurities were wiped out, oxygen containing functional groups augment, the DND was advantageous to disperse in the oily medium.Took ethanol as the grinding medium, adopted the method of mechanical grinding modification, broken DND particles aggregate, at the same time, non-ionic surfactant Tween-80and OP-10were added, so the surface of nano-particle had been coated modification, a new lubricant oil additive contained DND obtained. The experiment results showed that mechanical grinding could damage DND surface functional groups, surfactant could adsorb on the surface of DND particles, formed space steric hindrance to prevent reunion again, the particle size distribution was in hundreds of nanometer scale after grinding. Then, dispersed the DND particles into polyisobutylene double diimide(T154for short) and base oil(150SN for short), a stable dispersed DND base oil suspension was obtained, the particle size of the DND in suspension liquid is about l00nm.In order to decrease the cost of the use of additives, improve the friction performance at the same time, boric acid and melamine borate (MB for short) particles were added in the DND suspension liquid, modified by the method of mechanical grinding as well, at last, dispersed the composite particles made before into the base oil. It turned out that the change of particle size was relatively modest, the suspension liquid that added boric acid was more transparent and in mono-disperse state, nonetheless, the suspension liquid that added MB appeared sediment after a while.Used the friction and wear testing machine to test antifriction and anti-wear properties of the dispersion liquid, utilized microscope to observe grinding plaque morphology and measure grinding crack diameter, the results showed that the friction coefficient of the base oil that added DND reduced about40%, however, the grinding spot diameter increased about30%, the highest limit bearing capacity tripled. At the same time, it proved that boric acid and MB were two kind of cheap additives, they could form a kind of composite particles with DND which can be added into the base oil, that lowered the use cost of DND, showed good extreme pressure and anti-wear performance. At last, made use of Energy Dispersive Spectrometer to represent the friction surface elements, revealed the antifriction and anti-wear mechanism of lubricating oil. |
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