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Synthesis Techniques for Low Dimensional Magnets
Published in Ram K. Gupta, Sanjay R. Mishra, Tuan Anh Nguyen, Fundamentals of Low Dimensional Magnets, 2023
Kalyani Chordiya, Gergely Norbert Nagy, Mousumi Upadhyay Kahaly
Mechanical exfoliation of defect-free, single-layered materials from bulk materials using scotch tape is a well-known method [28]. In general, exfoliation is a process in which layered materials are expanded and separated into single or few-layer sheets by using external factors, such as physical, chemical, electrical, or thermal factor. Depending on the physical factor involved in the separation of non-covalent interactions in between the layers, the exfoliation method can be categorized as micro-mechanical exfoliation, liquid or chemical exfoliation, electrochemical exfoliation, or thermal exfoliation. In this chapter, we discuss the most commonly used exfoliation techniques for synthesizing magnetic materials, such as the mechanical and liquid exfoliation methods.
Effect of Exfoliation on Structural and Electrochemical Properties
Published in Ram K. Gupta, 2D Nanomaterials, 2022
Gibin George, Deepthi Panoth, K Brijesh, Anjali Paravannoor, Nagaraja Hosakoppa, Yu-Hsu Chang, Sreejesh Moolayadukkam
The term exfoliation represents a process during which the layered bulk materials are expanded through a chemical or physical method to overcome the weak inter-layer forces that hold the layers together. Generally, the stacked layered materials seized together by van der Waals forces can be easily intercalated or exfoliated by solution methods or simple physical means such as shear or ultrasonic vibrations to form 2D nanosheets. The exfoliated 2D nanosheets are often composed of single or few layers of atoms, and most importantly several of their properties are largely deviated from the bulk. Such materials find applications in electronics, photonics, catalysis, supercapacitors, fuel cells, batteries, etc. [1]. The success of graphene triggered the development of other 2D structured nanomaterials, especially by the exfoliation of layered bulk inorganic materials. Unlike bulk materials, 2D nanosheet counterparts exhibit unique electron and phonon transport characteristics, which leads to several fascinating properties such as thermal conductivity, ion transport, and charge carrier concentration, besides the structural and mechanical properties.
Weathered rock and slope stability
Published in Duncan C. Wyllie, Rock Slope Engineering, 2017
Mechanical exfoliation – removal of surficial rock as weathering progresses results in stress relief and the formation of exfoliation slabs that expose new surfaces to weathering. Exfoliation occurs commonly in granitic batholiths where the in situ tangential stresses parallel to the rock surface tend to be higher than stresses normal to the surface. This condition can be widely observed in Rio de Janeiro where concrete buttresses are often constructed to support exfoliation slabs, and in granite kopjes of Zimbabwe.
Feasibility of Polyvinyl Alcohol-Treated Soil in a Mud State as the Anti-Weathering Material for Earthen Sites
Published in International Journal of Architectural Heritage, 2023
Qiyong Zhang, Wenwu Chen, Ning Han, Tao Cai, Yumin Du
Earthen sites with historical, cultural, artistic, social, and scientific values are typical representatives of earthen material application. Due to the long-term exposure to the natural environment, these sites have suffered serious deterioration caused by cyclic precipitation and evaporation, big temperature fluctuation, wind and sand-driving wind, soluble salt, and so on (Fujii et al. 2009; Zhang et al. 2016a). Exfoliation of surface crusts and cracks (Figure 1) are commonly erosion patterns of earthen sites (Du et al. 2020; Zhang et al. 2016a). In situ replacement of composite materials (i.e., repair of weak parts on the wall surface) (Yang et al. 2016), and sacrificial layers (i.e., a mud protective layer is coated over earthen sites) (Wang et al. 2020) are used to prevent the cracking and exfoliation of surface crusts (the results of surface weathering). Note that although the in situ replacement and sacrificial layer methods are both used as surface treatments, there are some differences between them. The material used for in situ replacement method can be considered as part of the wall, while the sacrificial layer can be considered as an additional protective layer. Grouting techniques (grouting slurry with a water–cement ratio of 0.30–0.60) are adopted to repair the cracks (Li et al. 2011). For the dangerous earthen sites cut off by cracks, anchoring techniques (anchoring slurry with a water–cement ratio of 0.50–0.60) are effective means to prevent the deterioration of earthen wall (Li et al. 2011). Therefore, soil slurry has been widely used in the protection of earthen sites.
Corrosion behaviour of Ni-based alloy Inconel 740H in supercritical carbon dioxide at 650–700°C
Published in Corrosion Engineering, Science and Technology, 2023
Bo Xiao, Naiqiang Zhang, Kaiyang Li, Zhongliang Zhu, Tianyi Zhang, Mi Zhou
In the S-CO2 cycle, materials’ oxidation and corrosion are inevitable due to the high operating temperatures and pressures [3]. It is worth noting that the carburising behaviour of metals also occurs in S-CO2. The amorphous carbon formed in the substrate/scale interface and substrate will lead to chromium deficiency in the matrix [4–6], and the accumulation of amorphous carbon at the substrate/scale interface will also impair the adhesion between the inner oxide scale and substrate [7,8]. Owing to the different thermal expansion coefficients between the scale and the substrate, the oxide scale can quickly produce exfoliation when the temperature changes [9,10], which in turn leads to the exfoliation of the oxide scale. Besides, the physical properties of S-CO2 make the velocity of its thermal cycle much higher than that of the traditional water Rankine cycle, which will further lead to the collision and abrasion between the turbine and the exfoliation scale [11]. At higher temperatures, the effect of this deterioration is more prominent. Because S-CO2 Brayton cycle is more efficient than Supercritical Water Rankine cycle only when the temperature is higher than 550°C [11,12], the S-CO2 cycle tends to be operated at higher temperatures and pressures. Under these parameters, 9–12Cr ferritic–martensitic steels are challenging to meet the service requirements, so exploring the S-CO2 corrosion mechanism of materials with better corrosion resistance at high temperatures is necessary.
Effect of cement and zeolite on silty sand samples under freeze–thaw cycles
Published in Road Materials and Pavement Design, 2022
Saeid Jamshidvand, Alireza Ardakani, Afshin Kordnaeij
In the case of soil frost, small temperature changes cause large water potential changes (Pikul, 2006). Night frost, also known as radiation frost, is the result of the rapid reduction of long-wavelength radiation from the ground to the atmosphere on cloudless nights. When wet soil begins to freeze (during radiation frost), water is drawn upward (surface soil) to the frost zone and freezes. As the ice thaws during the day, the soil surface reaches a saturation state. Re-saturation and subsequent drying of the soil in various cycles can lead to exfoliation of the soil surface and soil erosion (Zhang et al., 2018). Although several studies have been conducted on soil stabilisation with cementitious materials under F-T cycles (Ding et al., 2018; Eskişar et al., 2015; Han & Cheng, 2015; Ismeik & Shaqour, 2020; Jamshidi et al., 2016; Jamshidi & Lake, 2015; Lake et al., 2017), limited information is available on using pozzolanic materials under freezing conditions (Bozbey et al., 2017; Güllü, 2015b; Olgun, 2013; Siline et al., 2017; Yazıcı, 2008; Zhang et al., 2016). No research has been found either on zeolite-cement stabilised silty sand under F-T cycles. Accordingly, the present study was conducted to fill this gap as much as possible.