The lithium complex grease was prepared with dimethyl silicone oil as base oil and insulating powder aluminum nitride as additive. The thermal conductivity and insulation properties of the grease were measured with a thermal conductivity tester and a volume resistivity tester. The friction and wear properties of lubricating grease under electric field were investigated using a reciprocating friction and wear tester. The wear morphology and chemical element composition of the wear surface were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the larger the volume resistivity, the higher the thermal conductivity, and the smaller the friction coefficient of insulating grease, the more stable the friction coefficient. The antifriction and anti-wear mechanism of insulating grease can be attributed to the synergistic reduction of the erosion of electric arc on the friction surface by the thermal conductivity and insulation properties.


With the continuous development of microelectronics technology, electronic devices are developing towards high power and high integration, and insulation performance is one of the key factors restricting their service life. In recent years, for power intensive electronic devices such as LED and CPU, researchers have developed high thermal conductivity insulating ceramic powders (such as silicon nitride, aluminum nitride and aluminum oxide) mixed with silicone oil to prepare high thermal conductivity silicone grease. In addition, the transmission line is erected outdoors. Affected by the natural environment, the contact area of the transmission line is easy to be oxidized/corroded. The electrified area will generate electric sparks, which is easy to cause poor contact between electrodes. The resistance heat will lead to local excessive temperature rise, and even fire in serious cases. At the same time, under the action of wind, the conductor is easy to swing, and fretting wear occurs in the charged contact area, which is more likely to cause serious arc erosion. Based on this, the preparation of high thermal conductivity insulating grease is the premise to ensure the normal operation of high-voltage transmission lines.


The volume resistivity of insulating grease changes with the mass fraction of aluminum nitride, and the volume resistivity of insulating grease increases with the mass fraction of aluminum nitride. The maximum volume resistivity of insulating grease is obtained when the aluminum nitride content is 80%. Because a large number of insulating aluminum nitride particles form an insulating network in the grease, preventing the transmission of electrons inside the grease.


The thermal conductivity of insulating grease increases with the increase of AlN content at different AlN mass fraction. When AlN content is less than 20%, the thermal conductivity of insulating grease increases slowly; When the content of aluminum nitride is more than 40%, the thermal conductivity of insulating grease is greatly improved. This is because when the content of filler is small, it is irregularly dispersed in the system, most of which are not in contact, and the heat transfer between fillers is less. Therefore, the filling amount has little effect on the thermal conductivity of insulating grease; However, when the filler content increases to a certain extent, the fillers begin to contact each other and form a network or chain like heat conduction network in the insulating grease. At this time, the thermal conductivity of the insulating grease is greatly improved. When the mass fraction of aluminum nitride reaches 80%, the thermal conductivity of insulating grease is the largest.


Dimethyl silicone oil has various excellent characteristics, and is widely used in motors, electrical appliances and electronic instruments as insulation medium with temperature resistance, arc corona resistance, corrosion resistance, moisture resistance and dust prevention. At present, it is also used as impregnant for scanning transformers of transformers, capacitors and televisions. It is used as a liquid shock proof and damping material in various precision machinery, instruments and meters. It has the characteristics of high flash point, odorless, colorless, transparent and non-toxic to human body, and is used in the industry and scientific research of steel, glass, ceramics, etc.


The friction and wear properties of insulating grease, and the change rule of friction coefficient with time under the lubrication of insulating grease. The change of friction coefficient under the lubrication of base grease is extremely unstable, which is due to the poor insulation performance, which leads to the deterioration of contact between the two electrodes during the friction process, leading to the increase of friction coefficient.