An Analysis on Synthesizing Techniques of Aerogel and its Applications (original) (raw)
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Design and manufacturing of supercritical drying autoclave for aerogel production
Ashraf M.Alattar, 2016
This article will address autoclave design considerations and manufacturing working with high pressure low temperature supercritical drying technique to produce silica aerogel. The design elects carbon dioxide as a supercritical fluid (31.7 oC and 72.3 bar). Both temperature and pressure have independently controlling facility through present design. The autoclave was light weight (4.5 kg) and factory-made from stainless steel. It contains a high pressure window for monitoring both transfer carbon dioxide gas to liquid carbon dioxide and watching supercritical drying via aerogel preparation process. In this work aerogel samples were prepared and the true apparent densities, total pore volume and pore size distribution, BET surface area, spectroscopic refractive index, structure and thermal properties have been systematically investigated characteristic.
SOME STUDIES ON THE SYNTHESIS AND CHARACTERISATION OF CARBON AEROGEL
Transactions of the Indian …, 2010
Porous carbon aerogels were synthesized from resorcinol-formaldehyde monomers using acetic acid, sodium carbonate and sodium hydroxide catalysts. The synthesized aerogels were characterized by XRD, TGA, SEM, BET and FTIR. The carbon aerogel developed by acetic acid catalyst produced a very high surface area (619.26 m 2 .g -1 ). All the different catalysts resulted in different surface morphology of the aerogels. The synthesized carbon aerogels contained significant amount of hydroxyl, carboxyl groups and different types of C-C linkages. These aerogels exhibited potential as adsorbents for removal of toxic materials and heavy metals.
Gels, 2021
This work aims to contribute to the theoretical and experimental research of supercritical processes for intensification and combination in one apparatus. Investigation is carried out to improve production technology of organic alginate aerogels. It is proposed within the investigation to carry out the solvent exchange stage, an important stage of organic aerogels production, under pressure in a carbon dioxide medium in the same apparatus used for supercritical drying. The phase behavior in the system “carbon dioxide–water–2-propanol”, which arises during such a solvent exchange stage, is studied theoretically. An experimental study of the process of step-by-step solvent exchange under pressure was carried out through multiphase and homogeneous regions of the phase diagram of such a system. As a result, new highly efficient technology for the production of organic aerogels was proposed, which can be implemented by combining the two main stages of the process.
European Journal of Chemistry
Eight samples of carbon aerogels were prepared at various resorcinol/catalytic (R/C) ratios (ranging from 25 to 1500) and followed the changes in structure after pyrolysis. Isotherms of N2 to 77 K were determined to calculate the textural parameters using Dubinin-Astakhov (DA), Barret Joyner and Halenda (BJH), Non-Local Density Functional Theory (NLDFT) and Quenched Solid Density Functional Theory (QSDFT) models. The results generated two series of samples. In series I, a single type of pores developed (microporous, at low R/C weight ratio). Series II developed mesoporosity to top gears of R/C (> 400). The specific areas ranged from 64 to 990 m 2 /g. Additional models were applied to the materials synthesized, which allowed for adjustment to a system of "cylinder-slit" pores by applying the QSDFT kernel, with an error percentage ranging from 0.03 to 0.74.
A new method of preparation of aerogel-like materials using a freeze-drying process
Pour conserver les propriétés texturales des gels encore imbibés de solvant au moment de leur séchage il existe la possibilité d'évacuer le solvant dans les conditions hypercritiques (procédé à haute température conduisant aux aérogels) et aussi celle de sublimer ledit solvant qui conduit alors à l'obtention de cryogels (procédé à basse température). Une série de cryogels d'oxydes mixtes de nickel et d'aluminium ont été ainsi élaborés. Leurs propriétés texturales ont été déterminées par adsorption-désorption de N , par la méthode BET, la poroslmétrie au mercure tandis que leur structure a été étudiée par les rayons X.
Gels, 2016
Production of aerogels starts with solution chemistry and may end with supercritical carbon dioxide drying, which both require a specialized system. Here we present a complete aerogel production system that was developed and used in our laboratory over the last nine years. Our aim was to develop a supercritical dryer and a protocol, whereby the CO 2 pump can be left out, and the entire flow system is operated by the pressure of the CO 2 cylinder. Drying pressure and temperature are controlled by the combination of the filling and heating temperatures. A continuous-mode solvent exchange system has also been developed, in which the solvent consumption during the process can be reduced to one-third of the batch method. In the new medium temperature 1.5 L volume supercritical dryer, the temperature is set to a constant 80-82 • C, and the pressure can be in the 90-200 bar range, depending on the conditions. We have performed approximately 200 dryings thus far, and prepared a wide range of monolithic aerogels, from pristine silica aerogels to polysaccharides and collagen. In this paper, we have summarized not only the technical details, but also the work experiences, as well as advantages and disadvantages of the systems.
All-Carbon Hybrid Aerogels: Synthesis, Properties, and Applications
Industrial & Engineering Chemistry Research, 2019
Table S1. Applications of carbon aerogels as materials for supercapacitors. System (precursors) Reaction conditions / main steps Final product Specific capacitance (F/g) Ref. Bamboo fibers Dissolution in urea/NaOH solution in cold (-12 o C), freeze-drying at-85 o C, calcination at 700-1000 o C, activation with KOH solution. Active carbon fiber aerogel 381 1 Cellulose (cotton linter) Stirring in the solution of NaOH/urea/H2O at −12 • C, freeze-drying at-58 o C, CO2 activation at 200-800 o C. CO2 activated carbon aerogel 328 2 Commercial cotton Heating at 800°C in N2, activation with KOH at 800 o C, washing with HCl. Activated Carbon Fiber Aerogel 283 3 Raw cotton Dissolution of 2-methylimidazole (H-mim) and Zn(NO3)2•6H2O in methanol, addition of cotton to H-mim, addition of Zn salt, drying and carbonization at 900 o C. N-doped porous carbon fiber aerogel 365 4 Lignin powder Preparation of frozen droplets of lignin solution in liquid N2, freeze-drying, carbonization at 900 o C.