| Ammonium thiomolybdate, as a by-product from the separation of tungsten and molybdenum in the tungsten metallurgy, was used as raw materials to prepare ultrafine particle of molybdenum disulfide in my research, and makes a preliminary research on friction property of the product. In the preparation process of molybdenum disulfide, I have explored the thermal decomposition of ammonium thiomolybdate and used hydrazine hydrates as reductant to reduce the ammonium thiomolybdate to prepare molybdenum disulfide. Single factor and orthogonal experiments were respectively used to study two sets of different reaction systems of preparation technology (Ⅰ ammonium thiomolybdate joined in the reaction system as crystal form; Ⅱ: ammonium thiomolybdate joined in the reaction system as solution form). The morphology and the average size of MoS2particles prepared under different conditions were investigated by SEM and XRD. The effects of reaction temperature, time, the molar ratio of hydrazine hydrate to ammonium thiomolybdate, stirring speed and surfactant types on the conversion rate of reaction, the morphology and the average size of MoS2were investigated. In the study of tribological properties, it was added three different MoS2into the oil and liquid paraffin to examine the tribological properties. The main experiment targets include the friction coefficient of the lubricating oil and the wear depth of friction pair. The main experimental results are listed as follows:1. Ammonium thiomolybdate calcined in atmosphere of N2and H2in500℃can get2H-MoS2, which can be applied in the fields friction lubrication. But the morphology of the2H-MoS2was irregular and showed the bulk shape of coarse particles. It can’t get the even size and ultrafine particle of MoS2through the thermal decomposition.2. Ammonium thiomolybdate crystal can be dissolved in water and the solubility is4.27g in100g water in room temperature. As elevated temperature, the effect on the solubility was little. The solubility of ammonium thiomolybdate is4.94g in100g water in100℃.3. It showed that the reaction of Hydrazine hydrate and ammonium thiomolybdate would violently take place, and the sediment product of the reaction turned out to be the amorphous molybdenum compounds with sulphur.4. According to the results of I system in the atmospheric pressure, an optimized preparation process was investigated after single-factor experiments without adding surfactants:reaction temperature was95℃, reaction time was3hours, the molar ratio of hydrazine hydrate to ammonium thiomolybdate was10:1, the stirring speed was250r/min. Under the optimized preparation process, the conversion rate of reaction could reach to98.12%. But the content of molybdenum in the sediment product is43.21%, so the sediment product is not an absolute MoS2. According to the results of the SEM showed that the morphology of the sediment product was irregular and the average size of the product was up to10μm. Under the optimized preparation process, the experiment of adding the surfactants such as tributylamine, cetyltrimethylammonium chloride (CTAC) and benzyltrimethyl-ammonium chloride (BTAC) have done. It found that surfactants on solving the reunion of precipitation product didn’t play a significant role in dispersing. In the condition of high temperature of180℃and sealed, the experiment of adding the surfactants show that surfactant can play a certain role of dispersion and the effect of CTAC was better than tributylamine. But the content of molybdenum in the sediment product is only about34%, so the ammonium thiomolybdate was hardly absolute reduced to MoS2by hydrazine hydrates in the system containing surfactant.5. According to the orthogonal experiments result of II system in atmospheric pressure, as the reaction temperature or reaction time or the molar ratio of hydrazine hydrate to ammonium thiomolybdate increased, the reduction rate increased. It can also draw a conclusion that the degrees of factors which influence on reduction were as follow:the reaction temperature> the molar ratio of hydrazine hydrate to ammonium thiomolybdate> the reaction time. The optimized preparation process of the orthogonal experiments were:reaction temperature was98℃, reaction time was3hours, the molar ratio of hydrazine hydrate to ammonium thiomolybdate was10:1. Under the optimized preparation process, the conversion rate of reaction got to67.05%and the content of molybdenum in the sediment product is about55%. According to the result of SEM of the prepared production, it found that the morphology of the production was regular and even size and the reunion phenomenon was not very serious. The average sizes of production were below1μm. According to the result of XPS of the production, the main components of the production were the MoS2. After adding the surfactants such as tributylamine, cetyltrimethylammonium chloride (CTAC) and benzyltrimethy-lammonium chloride (BTAC), it found that surfactants on solving the reunion of precipitation product didn’t play a significant role in dispersing and it could hinder the reaction. So the Ⅱ system does not need to add surfactant.6. According to the experiments of improving the reaction temperature in the quick open reaction kettle, it can found that when you increased the reaction temperature, the reduction of the reaction decreased. When the temperature increased from100℃to180℃, the reduction rate decreased from75.42%to18.62%. And it also showed that the content of molybdenum in precipitate decrease too, from54.04%to44.38%. So the reaction of the reduction should not react in the sealed system.7. According to the experiment of the friction properties, it found that the friction coefficient of the lubricant was higher than that was not added MoS2, but the grinding mark depth had a certain decrease than that not added MoS2, especially the liquid paraffin which added different particle size are smaller than that not added. Therefore MoS2as additive added into the oil or liquid paraffin play a role in the anti-wear. |
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