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Ionic Liquids as a Potential Sustainable Green Lubricant for Machining in the Era of Industry 4.0
Published in Kishor Kumar Gajrani, Arbind Prasad, Ashwani Kumar, Advances in Sustainable Machining and Manufacturing Processes, 2022
While negligible performance improvement was observed at low cutting speed in light operating conditions. They proposed that these ILs require heavy operating conditions to generate high enough contact zone temperature for decomposition of ILs and subsequently release of tribo-active elements for protective tribofilm formation [36]. Moreover, at lower cutting speeds and lighter operating conditions, the temperature may not reach the decomposition temperature of ILs, resulting in weaker tribofilm. In contrast, the oil miscible phosphonium IL, when mixed in vegetable oil, showed excellent performance at lighter operating conditions due to lower decomposition temperature while negligible improvement in cutting force performance was observed at higher cutting speed. Generally, protic ionic liquids (PILs) forms relatively stronger hydrogen bonds with anion compared to aprotic ionic liquids (AILs). Which can significantly influence the lubricant film formation. Sani et al. reported a 12% improvement in cutting force performance when 10 wt% ammonium-based AIL mixed in modified Jatropha oil. While the optimum performance of 11% for PIL phosphonium-based IL was observed at 1 wt.% but not at 10 wt.% concentration. They concluded that there may be competition between base oil and IL for adsorption on the nascent surfaces. The adsorption depends on the polarity and concentration, and the base oil (modified jatropha oil), because of its excellent wettability, may have reduced the effectiveness of the additive, that is, PIL. They also observed a direct correlation between cutting forces and peak cutting temperature during machining. Both ILs decreased the peak cutting temperature in the range of 7–9% over the synthetic ester base oil.
Solid Polymer Electrolyte Membranes
Published in Asit Baran Samui, Smart Polymers, 2022
Swati S. Rao, Manoranjan Patri
Composite membranes have been reviewed extensively by Asier Goni-Urtiaga et al. Among the solid acids as electrolyte materials, hetero-poly acid has received more attention due to its simple preparation and strong acidity (Goni-Urtiaga et al. 2012). However, they are soluble in water and also are a good catalyst for the formation of free radicals from H2O2 (Huang et al. 2008). To avoid this, a multifunctional catalyst -CsxH3_xPW12O40/CeO2 is incorporated into the ABPBI polymer to form a composite membrane, which improves the conductivity and oxidative stability of the membrane (Qian et al. 2013). Also, the fuel cell performance is better than pristine polymer. A marked improvement in the ABPBI membranes properties is possible with the introduction of ZrP in the polymer (Rao et al. 2017). Fuel cell tests show a steady performance for more than 800 hours. Ionic liquids are another interesting class of materials that have garnered attention due to their high intrinsic conductivity and high stability. They are non-volatile due to the strong electrostatic force between them and also they possess low flammability. Ionic liquids are molten salts at room temperature and are composed of organic cations and various anions such as I-, BF4-,Pf6-, etc. With such interesting properties, the ionic liquids can be used to design fuel cell membranes for high-temperature applications (Diaz et al. 2014). Ionic liquids can be classified as aprotic and protic ionic liquids. Protic ionic liquids (PILs) are formed by proton transfer from a Brönsted acid, AH, to a Brönsted base and have a mobile proton located on the cation. Hence these have been studied by a number of research groups for their applicability in fuel cells. Aprotic ionic liquids (AILs) contain substituents other than a proton (typically an alkyl group) at the site occupied by the labile proton in an analogous protic ionic liquid. These have been used more in the case of studies on lithium-ion batteries. Hybrid membranes, prepared from a mixture of polymerizable oils, protic ionic liquids, and nano-silica particles, exhibit a conductivity value around 1 x 10-2 S.cm-1 at 160° C under anhydrous conditions (Lin et al. 2010). However, retention of PIL in the polymer network remains a challenge, which can be overcome by design and the synthesis of polymer networks with the interacting groups that can hold the PIL. Sulphonated polyimides (SPI) can be doped with PIL to make composite membranes (Chen et al. 2014; 2015). An improvement in the proton conductivity up to 1000 times more than pristine membranes is achieved by making composite membranes of SPI with PIL. Use of an aprotic liquid in making a composite membrane with cross-linked SPEEK results in high thermal stability and improvement in the retention of ionic liquid using cross-linked SPEEK (Malik et al. 2015).
Influence of couple stress size dependency in thermal instability of porous functionally graded composite microplates having different central cutouts
Published in Waves in Random and Complex Media, 2021
Duquan Zuo, Saeid Sahmani, Babak Safaei, Guoling Ma
Porous materials are significantly being applied because of the combination of their unique properties including desirable mechanical properties, specific surface area, biomimetic properties, and permeability [1–5]. In this regard, Kim et al. [6] established highly aligned porous graphene oxide structures to obtain stable resistance variations under uniaxial stretching. Zhou et al. [7] prepared porous carbonaceous materials using a bio-protic ionic liquid to be applied in flexible solid-state supercapacitors. Yin et al. [8] developed a hierarchical 3D porous structure under the inspiration of a natural bone based on primitive triply periodic minimal surface sheet. Cho et al. [9] developed hollow fiber membrane porous structures for osmotic power generation applications. Das and Sutradhar [10] developed a design approach for the fabrication of functionally graded controlled porous structures applied in heat dissipating problems. Xie et al. [11] by using Gurtin–Murdoch theory of elasticity investigated nonlinear secondary resonance of functionally graded (FG) porous silicon nanobeams. Cassio et al. [12] calibrated silicon structure porosity for the generation of a micro-resonator with well-defined refractive indices to be applied in biosensors. The simultaneous impacts of embedding pores and enhancing with CNT agglomerations on the structural buckling resistance and electromechanical stress responses of FG porous carbon nanotube reinforced plates located between two piezo layers were investigated in [13,14].
Recent developments in the greener approaches for the dithioacetalization of carbonyl compounds
Published in Journal of Sulfur Chemistry, 2023
Recently, F. Rajabi et al. [113] developed a greener synthetic approach for the dithioacetalization of carbonyl compounds with 1,3-propanedithiols by using a catalytic amount of highly ordered mesoporous functionalized pyridinium protic ionic liquid (PMO-Py-IL). The reactions were carried out under solvent-free and ambient conditions. (Scheme 22). Both aliphatic and aromatic aldehydes and ketones were tolerable with the reaction conditions. However, the reaction method was chemoselective for aldehydes in the presence of ketones. The reactions are simple, energy-efficient, high-yielding (82 − 99%), and cost-effective.
Recovery of copper from industrial sludge as a sustainable resource: A review
Published in Geosystem Engineering, 2022
Ha Bich Trinh, Seunghyun Kim, Taehun Son, Jaeryeong Lee
Cu-bearing industrial sludge should be recycled as a potential secondary resource instead of being treated as a hazardous solid waste. The current review has demonstrated the feasibility of Cu extraction from the waste sludge generated in electroplating, PCBs production or other industrial process by using pyrometallurgical or hydrometallurgical techniques. Pyrometallurgical extraction is a mature technology for large-scale production. However, it is associated with the issues such as high-energy consumption, generation of harmful gaseous as by-products, and copper loss to slag. Compared to pyrometallurgical methods, hydrometallurgical extraction provides effective metal recovery while consuming less energy and yielding more economic benefits, and is thus often preferred to treat the Cu-bearing industrial sludge. Copper in industrial sludge is typically found as hydroxides or oxides, which can be simply extracted via acid-, ammonia- or bioleaching. The efficient dissolution of copper from industrial sludge is critical for both economic and environmental reasons. Thus, multi-stage leaching is often used to maximize the Cu-dissolution; this includes the combination of acid and bioleaching. Such methods have also been employed to enhance the copper dissolution, including the introduction of microwave, ultrasound- or electric energy into the leaching reactors. Research has also been directed toward the use of waste acid solution as leachant or low-cost protic ionic liquid in order to enhance the sustainability (Abouelela et al., 2022). After leaching, Cu in the obtained leachate must be purified and separated from impurities. Methods such as chemical precipitation, solvent extraction, ion exchange, and electro-winning/electro-refining methods are utilized for this purpose. The recovery of Cu from the secondary resources in general and from the industrial sludge in particular is an important strategy to convert the hazardous solid waste in to the new resource for steady supplies of copper metal. Moreover, it would reduce/prevent the environmental degradation arising from the excessive Cu-mining and production as well as the generated wastes from related industrial processes, and support the ambit of achieving the highest sustainability for long-term development of metallurgical production.