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Molybdenum disulfide, unlimited development of possible lubrication additives

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Update time : 2019-08-20 14:30:33
Molybdenum disulfide is a compound composed of two elements, molybdenum and sulfur, and has the chemical formula MoS₂. This compound belongs to the transition metal dichalcogenide, which has a silver-black luster and exists in the form of molybdenite in nature. Molybdenite is the most common ore containing molybdenum. The molybdenum disulfide crystals are usually present in the form of a powder which is insoluble in dilute acid and is not easily oxidized. From the outside, molybdenum disulfide is very similar to graphite and is often used as a solid lubricant with its low coefficient of friction and high robustness.

Molybdenum disulfide (MoS₂) is one of the most common natural minerals and is often used as a solid lubricant in people's daily lives. MoS₂ has a blue-gray or black appearance, has good chemical stability and heat and humidity resistance, and its surface is smooth and has a metallic luster and a smooth feel. The essence of MoS₂ is a kind of transition metal sulfide, which is composed of three atomic layers, and the middle of the two layers of sulfur atoms is a layer of molybdenum atoms, thus causing its morphological particularity. The covalent bond between the atoms is strong, while the connection between the layers is relatively weak. Therefore, when the external pressure is applied during the friction process, the layers are more likely to roll, and the molecular layer is easy to break to form a slip surface. When deformation occurs and rolling, one can strengthen the level of external pressure to a large extent; secondly, it is beneficial for the reduction of the relative friction area, and the friction coefficient is thereby reduced, thereby, the damage reduction is minimized, which in turn increases the life of the parts. In summary, MoS₂ is a kind of lubrication additive with potential for wireless development.
 
Preparation method of molybdenum disulfide
In the application of MoS₂, the research of its preparation method is the primary problem. Only by preparing MoS2 with good morphology and excellent performance can it be used well and create unlimited development opportunities for the application of its nanoparticles. At present, there are many methods for preparing MoS₂, and generally include hydration heat method, chemical vapor deposition method, surfactant promoting method and physical mechanical method.
 
Chemical vapor deposition
For the chemical vapor deposition method, the process is simple, the product purity is high, the production cost is low, and the molybdenum disulfide with high quality, large size and excellent performance can be prepared, so it is a relatively common method for the preparation of the MoS₂ nano-material. He Dawei et al. prepared a large-sized single crystal molybdenum disulfide on a sapphire substrate under normal pressure by a simplified chemical vapor deposition method. The molybdenum disulfide was a regular triangular monolayer with a side length of about 50 μm.

Although this method has many practical applications, there may be HS in the actual preparation process, so it is necessary to do the corresponding disposal work for the exhaust gas. In addition, in this link, the appearance of the product is in the gas phase flow and pressure. Under the volatility of the dry batch, the presented forms are different, so the law also needs to constantly research and expand new fields and approaches.
 
Physical mechanical method
For the physical and mechanical method, its control is simple and the product output is highly effective. Deng Baihan et al. prepared 100um linear graphene and 10um MoS₂ by micromechanical force method, and used Raman spectroscopy as a means to identify the number of graphene layers. Data processing, fitting and theoretical analysis was carried out. This spherical construction of MoS₂, which incorporates the base lubricant, will perform extremely well in terms of its lubricating effect. In the actual output link, the repeatability is poor, and it cannot be consistent with the appeal of large-scale output.
 
Hydration heat method
In the actual application process, for the nano-MoS₂, the highest and most extensive preparation method is the hydration heat method, and the material specifications developed by the nano-MoS₂ are small, and the wear resistance is excellent.
Sun Jiaojiao and other materials in order to prepare low-cost, high-performance non-platinum hydrogen evolution electrocatalysts, using ammonium molybdate tetrahydrate and L-cysteine ​​as raw materials, by hydrothermal method, operating at 200°C for 24 h, completed the preparation process of MoS₂.

For the hydrothermal method, it has won the unanimous praise and love of the inquirers by virtue of its short reaction cycle, simple operation, green environmental protection and high product purity. It has become a pivotal part of the research and development of nano molybdenum disulfide.
 
Surfactant-promoting method
For the surfactant-assisted method, the reaction process is stable, and it is accompanied by dispersion, which can finely control the appearance of the product and has great development potential. Therefore, it is possible to control and design the structure of the nano material around the MoS₂ by selecting various types of surfactants.

Bai Geling et al., through the above method, used PEG-20000 as a coating agent for the operation process to realize the preparation of nano-MoS₂, and used Span-80 as a dispersant to surround 1% MoS₂ nanospheres and ultrafine disulfide. The preparation work of molybdenum micron powder composite lubricating oil was carried out, and a systematic investigation was carried out for its performance in rolling friction.
 

 
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