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Cathode Materials for Li-Ion Batteries
Published in Anurag Gaur, A.L. Sharma, Anil Arya, Energy Storage and Conversion Devices, 2021
For many years, the only way of synthesizing cathode materials has been the solid-state reaction. In this process, the core of the solid may not be reached by the viscous melt, especially if the solid reactant has large particles and limited porosity, which leads to incomplete reactions. Since 1990s, alternative methods of synthesis have been proposed to form a better mixture of the precursors and to reduce both time and temperature of reactions. Sol–gel synthesis is the most popular method. In sol–gel, a sol that converts into a gel is typically converted into desired ceramic by annealing. The sol–gel process allows a high degree of control over the physicochemical characteristics of the material obtained with high purity and homogeneity. This approach allows one to obtain small particle size materials and, hence, faster reactions through faster diffusion of intercalating ions. Control of the pH and concentration of the chelating agent is required for optimized characteristics.
Carbon Nanotube-Metal Oxide Hybrid Nanocomposites Synthesis and Applications
Published in Zainovia Lockman, 1-Dimensional Metal Oxide Nanostructures, 2018
Zaid Aws Ali Ghaleb, Mariatti Jaafar
The sol-gel process is a solution based process that offers a flexible approach to producing various classes of materials, including ceramic, polymer, and glass materials in the form of nanoparticles, thin-film coatings, and nanoporous solids such as aluminosilicate zeolites (Owens et al., 2016). Sol-gel process involves two distinct phases: the liquid, colloidal “sol” phase and solid “gel” phase. The sol-gel process offers a number of advantages including low cost, ease of fabrication, and a low temperature technique that allows fine control of chemical composition and the introduction of the lowest concentrations of finely dispersed dopants. The major drawback is that the product typically consists of an amorphous phase rather than defined crystals and, thus, requires crystallization and post annealing steps (Hu and Guo, 2011).
Adsorbents for DNA separations
Published in A. K. Haghi, Lionello Pogliani, Eduardo A. Castro, Devrim Balköse, Omari V. Mukbaniani, Chin Hua Chia, Applied Chemistry and Chemical Engineering, 2017
The sol-gel process is a wet-chemical technique widely used for producing promising materials in scientific areas such as material science and ceramic engineering. Special property of sol-gel method is its capability to convert the molecular precursor to the product. It makes possible to control the process and structural composition. This method is used primarily for the fabrication of materials (typically metal oxides) starting from a colloidal solution (sol). Sol is a colloidal suspension which consists of particles having sizes less than 1000 nm. Thus, the gravitational force become negligible and short-time forces, such as wander walls and surface charge forces, are the main forces acting on the particles. A gel is described as a solid molecular three-dimensional network that included a liquid network of the same size and shape. Chemical step has three general reversible reactions: hydrolysis–esterification, alcohol condensation-alcoholysis, and water condensation-hydrolysis as indicated in Figure 11.4. In the first reversible reaction, alkoxide groups (OR) are replaced with hydroxyl groups (OH). Then condensation reaction occurs rather than hydrolysis or alcoholysis.
Critical review of catalysis-assisted nanofiltration for micropollutants removal: Catalytic coupled nanofiltration system vs catalytic nanofiltration membrane
Published in Critical Reviews in Environmental Science and Technology, 2023
Tingting Zhu, Xin Li, Xuewu Zhu, Bin Liu, Junyong Zhu, Jianquan Luo
Sol-gel process is a widely-studied method for the synthesis of solid materials from small molecules, typically starting with the hydrolysis of sol precursor followed by forming a gel via poly-condensation (Qing et al., 2020). However, sol-gel process is only used for the synthesis of solid materials, thus usually integrating with other coating methods such as dip coating (Guo et al., 2018) for preparing catalytic membrane. In addition, the sol-gel process is frequently restricted by the cracking, delamination and adhesion limits, thus leading to an inferior stability. Hence, CM with high chemical, mechanical and thermal resistance is the optimal choice for sol-gel technology. Another merit of ceramic film is that its pore size can be facilely controlled via the sintering and the sol-gel processes applied in their fabrication. Recently, Mansas et al. (2020) deposited the magnetite sol by filling membrane tubes at a contact time of 4 min and a withdrawal rate of 10 cm/min. After drying at room temperature, the modified membrane was heated to 300 °C for 1 h to convert the magnetite sol into gel. NF membranes with quite low MWCO of 200 Da were functionalized via sol-gel deposition of a γ-Fe2O3 thin layer. The catalytic membrane was proved to enhance the rejection of pCBA and the catalytic effect in the presence of O3 without disturbing its filtration features.
Aerogel composites and blankets with embedded fibrous material by ambient drying: Reviewing their production, characteristics, and potential applications
Published in Drying Technology, 2023
Jaya Sharma, Javed Sheikh, B. K. Behera
Sol-gel synthesis is a popular and effective method for making aerogel. The steps in the sol-gel process that most researchers are acquainted which include sol formation, gelation, aging, drying, and densification. Sol-gel processing involves the formation of an amorphous network in opposition to crystallization from a solution. The change from a colloidal solution (liquid) to a di- or multiphase gel (solid) is the most noticeable aspect of this reaction, which gave rise to the term "sol-gel process.” Condensation occurs when particles nucleate and expand to the desired size, whereas dispersion occurs when big particles are reduced to colloidal dimensions. The relative rates of these two processes determine the size and characteristics of the resultant particles. Figure 4 illustrates the microstructure of silica aerogel that is weakly connected with the primary and secondary nanoparticles.
Behavior of transition metals in the structuring of nanostructures
Published in Inorganic and Nano-Metal Chemistry, 2019
Benyoucef Khalili, Ali Boucenna, Boudjema Hamada
The sol-gel process allows the elaboration of a large variety of oxides in different configurations: monoliths, thin films, fibers and powders.[6, 7] This great diversity and it is here that nature has been kind because nanostructure display size-dependent properties. Thus, we find ourselves with a new molecular category, a category with stoichiometries, sizes, and properties that we can choose and tailor to our needs, and a category with which we can create a whole new universe of materials.[5] The basic principle of the sol-gel process is to allow the conversion of a solution based on precursors in the liquid phase, into a solid by a set of chemical reactions of the polymerization type at room temperature.