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Transmissions and Transmission Fluids
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Scott Halley, Timothy Newcomb, Richard Vickerman
Lubricants are hydrocarbons and will react with oxygen at sufficiently high temperatures. The temperature where this becomes significant depends on the nature of the base oil. Oxidation inhibitors act to disrupt the reaction of oxygen with the base oil. Chemically this is a free radical reaction and the oxidation inhibitors (antioxidants) are molecules that either scavenge free radicals or decompose hydroperoxides.
Study on the Effect of Oxygen on Free Radical Generation in Coal
Published in Combustion Science and Technology, 2023
Yandan Tao, Zhian Huang, Yinghua Zhang, Hao Ding, Xiangming Hu, Yukun Gao, Cuanwu Sun, Dongfang Cao
The free radical concentration of Hailar lignite changes little under different oxygen concentrations, and the changing trend is shown in Figure 13. At room temperature and 110°C, the free radical concentration increases with the increase in oxygen concentration, indicating that the change to the oxygen concentration affects the free radical reaction. With the increase in oxygen concentration, the concentration of free radicals increases slowly, which makes the reaction more active. The added oxygen molecules participate in the free radical reaction, making it more active.
Effect of the sudden change of ambient atmosphere on free radicals in coal body by CO2 fire prevention gas injection
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Jinrui Miao, Shengqiang Yang, Xiaoyuan Jiang, Zhenshan Hou, Huadi Shao
As an important parameter for the coal structure, the concentration of free radicals Ng can quantitatively depict the sample’s stable free radicals. The fluctuations in coal sample free radical concentrations following the change in gas environment are illustrated in Figure 4. Almost no distinctions exist between the free radical concentration variations in the two gas atmospheres. To be more precise, they both expand as the temperature rises. The levels of free radicals in samples of oxidized coal are typically higher than those in samples of pyrolytic coal. In the carbon dioxide gas atmosphere, the thermal decomposition of the functional groups in the coal occurs with the increase of temperature leading to a rise in the number of free radicals present. The free radical concentrations of experimental coal samples in dry air at any temperature points are higher than those in CO2. It is suggested that oxygen clearly affects the level of free radicals. The involvement of oxygen enhances the free radical reaction. In the oxidation reaction of coal samples, free radical increase caused by thermal decomposition and free radical consumption induced by oxidation exist simultaneously. The former reaction is faster than the latter one. At a certain temperature point, when the dry air atmosphere is changed to CO2 atmosphere, which means that aerobic environment is changed to inert gas environment, the amount of free radicals in coal is significantly reduced. It demonstrates that the gas atmosphere change make some small molecule free radicals disappear and meanwhile the active free radicals are consumed in large quantities. After this temperature point, the number of free radical in an inert environment is still more significant than that in a CO2 atmosphere and lower than that in dry air atmosphere at the same temperature point. The pyrolysis-induced free radical concentration in inert gas environment is lower than that of oxidized coal samples. When the gas atmosphere is altered at higher temperatures, smaller differences are observed between free radical concentrations induced by pyrolysis and oxidation because the overall influence of free radical oxidation on free radical concentration is replaced by the rapid consumption of some free radicals at higher temperatures. In stark contrast, the introduction of inert gases at lower temperatures changes the species of free radicals by reducing the spin-spin interactions between carbon radicals and oxygen radicals without causing significant changes in free radical concentration (Li et al. 2019).