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Calix-Assisted Fabrication of Metal Nanoparticles
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2019
Anita R. Kongor, Manthan K. Panchal, Vinod K. Jain, Mohd Athar
This process involves the development of inorganic networks through the formation of a colloidal suspension (sol) and gelation of the sol to form a network in continuous liquid phase (gel). The four main steps for the sol-gel formation are hydrolysis, condensation, growth of particles, and agglomeration. The main advantages of this technique are low temperature conditions during processing and its versatility. This method has been used for the synthesis of metal oxide nanoparticles and nano-composites. The starting materials used typically to form a solvated precursor (sol) are metal alkoxides. After drying and calcination process at specific temperature, desired nanomaterials can be obtained. The disadvantage of using this method is the segregation of metal ions during thermal decomposition.
Electrochemical Sensors/Biosensors Based on Carbon Aerogels/Xerogels
Published in Mahmood Aliofkhazraei, Advances in Nanostructured Composites, 2019
Liana Maria Muresan, Aglaia Raluca Deac
The sol-gel method was first used to prepare inorganic materials such as ceramics or glasses but it was rapidly extended to other materials such as oxides, organic compounds, etc. It consists in progressive hydrolysis and condensation reactions of molecular precursors in a liquid medium in the presence of a catalyst (Brinker and Scherer 1990). Precursors used in sol-gel processing are metallic salts, alkoxides, organic precursors (formaldehyde, resorcinol, melamine, polyacrilonitrile, etc.) which can be solved in water or in different organic liquids. Gelation implies the transformation of a sol to a gel and can be strictly controlled by the factors affecting the process (precursor/catalyst molar ratios, solvent nature, working temperature, etc.). Gels are often aged in the mother liquor, then they are washed and dried to obtain xerogels (by simple evaporation), aerogels (by supercritical drying) or cryogels (by freeze drier) (Job et al. 2005, Pajonk 1995).
Sol–Gel Processing
Published in M. N. Rahaman, Ceramic Processing and Sintering, 2017
Applications sol–gel processing can provide substantial benefits, such as the various special shapes that can be obtained directly from the gel state (e.g., monoliths, films, fibers, and particles), control of the chemical composition and microstructure, and low processing temperatures. However the disadvantages are also real. Many metal alkoxides are fairly expensive, and most are very sensitive to moisture so that they must be handled in a dry environment (e.g., an inert atmosphere glove box). The large shrinkage of the gel during drying and sintering makes dimensional control of large articles difficult. It is often difficult to dry monolithic gels thicker than a few millimeters or films thicker than 1 μm without cracking. The sol–gel process is therefore seldom used for the production of thick articles. Instead, it has seen considerable use for the production of small or thin articles such as films, fibers, and powders, and its use in this area is expected to grow substantially in the future.
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.
UV-reflecting sintered nano-TiO2 thin film on glass for anti-bird strike application
Published in Surface Engineering, 2021
The as-received sol–gel formulation contained titanium isopropoxide, ethanol–methanol mixed solvent, water and nitric acid in the molar ratio of 1:20:160:2:0.08 respectively and was prepared at room temperature with 2 h stirring. These components fall under the generic sol–gel ingredient categories of precursor, alcoholic solvent, water and inhibitor (or catalyst) respectively and has been reported in literature many times before. Characteristics of the precursor sol can greatly influence the surface structure and properties of resultant thin film [13,20]. Sol–gel mechanism is well known and is based on sequential hydrolysis, polycondensation and surface dehydration, as discussed elsewhere [13,14]. The molar ratio of sol–gel components is known to vary widely in literature, but the basic chemistry remains the same:
Structural and Optical Coefficients Investigation of γ-Al2O3 Nanoparticles using Kramers-Kronig Relations and Z–scan Technique
Published in Journal of Asian Ceramic Societies, 2021
A. Faraji Alamouti, M. Nadafan, Z. Dehghani, M. H. Majles Ara, A. Vejdani Noghreiyan
γ-Al2O3 NPs were prepared using a conventional sol–gel process. Sol–gel technology is a wet-chemical engineering method used to produce ceramic materials, glasses, films, and a wide range of materials [25]. First, aluminum nitrate nonahydrate (Al(NO3)3.9H2O) was dissolved in deionized water under magnetostirring. Then, triethanolamine (TEA, NC2H5O) and citric acid (C6H8O7) were added to the previous solution slowly and subsequently at 80°C for 1 h. By increasing the temperature up to 120°C for 1 h, the viscous gels are obtained. Finally, the dried gels were calcined at 800°C in the furnace and produced the γ-Al2O3 NPs [9]. The produced γ-Al2O3 NPs were characterized and used for the linear and nonlinear optical study.