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Self-Lubricating Metal Matrix Composites
Published in Emad Omrani, Pradeep K. Rohatgi, Pradeep L. Menezes, Tribology and Applications of Self-Lubricating Materials, 2017
Emad Omrani, Pradeep K. Rohatgi, Pradeep L. Menezes
Further, Li et al. [88] studied the tribological properties of Ni–Cr–W–Fe–C self-lubricating composite reinforced by graphite and MoS2 as a solid lubricant at different temperatures. It was found that chromium sulfide and tungsten carbide were formed in the composite by adding MoS2 and graphite, which were responsible for low friction and high wear resistance at elevated temperatures, respectively. Figure 2.44 shows the variation of COF and wear rate for different composites at different temperature. Amongst the composites, nickel composites reinforced by graphite and MoS2 exhibits better tribological properties for a wide range of temperatures due to the synergistic lubricating effect of graphite and MoS2. The graphite played the main role of lubrication at room temperature, whereas sulfides were responsible for low friction at high temperature.
Detection Technology
Published in Rick Houghton, William Bennett, Emergency Characterization of Unknown Materials, 2020
Rick Houghton, William Bennett
The sulfides of most metals are insoluble in water. Those that are water soluble are the alkaline earth and alkali metal sulfides, aluminum sulfide, and chromium sulfide. Sulfides exist in aqueous solution with equilibrium determined by pH. Near neutral pH hydrogen sulfide ion (HS−) is predominant and in basic conditions sulfide ion (S2−) is predominant. In acidic conditions, sulfides exist as dissolved toxic hydrogen sulfide gas (H2S), which will bubble out of the solution as concentration increases. Increasing acidity will produce greater amounts of hydrogen sulfide gas.
Scope and Application of Bionanotechnology for the Bioremediation of Emerging Contaminants Generated as Industrial Waste Products
Published in Naveen Dwivedi, Shubha Dwivedi, Bionanotechnology Towards Sustainable Management of Environmental Pollution, 2023
Md Shahid Alam, Surabhi Rode, Harry Kaur, Sapna Lonare, Deena Nath Gupta
Various types of hazardous chemicals and waste products are released during the significant stages of hide processing up to the finished leather product. 70–80% of the residual parts of the hide after removal of raw skin is discarded as waste that cannot be reused (Cabeza et al., 1998). It contains dead body parts of animals, hair, tissue, protein, and fats. If unprocessed, this type of solid waste can create a very unhealthy environment due to the growth of various pathogenic strains. It increases the biological oxygen demand of water bodies if the effluents containing dead tissue, protein, and fat are discharged without proper processing. Approximately 600 kg of solid waste is generated during the pre-tanning and tanning process in the leather industry (Ozgunay et al., 2007). A large amount of water is used in the tanneries for different treatments, and about 30–35 m3 of wastewater is discharged in the environment containing various chemical contaminants. Chemicals like chromium sulfide are one of the most toxic and carcinogenic agents used during tanning of the leather. Chromium is a heavy metal used in chrome tanning, and about 40% of the chromium is discharged into the sludge as waste after the tanning process (Nur-E-Alam et al., 2020). Exposure to chromium can induce skin cancer, respiratory, kidney, liver, and other types of cancer in leather industry workers. It also affects the aquatic ecosystem when released into rivers or other water bodies. Various types of volatile compounds and toxic gases are also released from the leather industry like ammonia, hydrogen sulfide, fumes of acids, chlorides, etc. These are very toxic to the ecosystem and responsible for lung diseases and fetal neuronal toxicity. Decolorization of dyes and degradation of phenolic compounds in the effluents of the leather industry are also challenging tasks due to the shortage of cost-effective and efficient technologies.
The Ni-converter – an historic perspective
Published in Mineral Processing and Extractive Metallurgy, 2019
Peter Rozelle, Seetharaman Sridhar, Paul B. Queneau, Shane Thompson
A series of work by Inco and U.S. Bureau of Mines (de Barbadillo et al. 1981; Hundley and Davis 1991) was focused on combinations of pyrometallurgy, mineral processing, and hydrometallurgy in attempts to achieve separations of alloying components from superalloy scrap. Pyrometallurgy involved melting the scrap, followed by reacting with oxygen, and sulfidation to produce a matte for mineral processing and hydrometallurgy, the goal being to separate and recover critical metals from mixed and contaminated superalloy scrap. The process included melting of the scrap, followed by reaction with oxygen (Srivistava et al. 2014), where Ti, Al, Zr, and Hf were oxidised and partitioned to the slag. Following this, the remaining metal phase was reacted with sulfur to form a matte for further processing. Matte processes examined included controlled cooling, grinding and flotation for separation of Cr-rich and Ni-rich fractions, fluid bed roasting of the recovered chromium sulfide-rich material from the matte, and hydrometallurgical options for separation and recovery of individual elements (de Barbadillo et al. 1981; Hundley and Davis 1991).