Preparation of resorcinol formaldehyde (RF) carbon gels: Use of ultrasonic irradiation followed by microwave drying

Designing Nanostructured Carbon Xerogels

“…infrared, ultrasonic or microwave) have been published (Calvo et al, 2008;Kang et al, 2008;Tonamon et al, 2005Tonamon et al, , 2006Wu et al, 2004). In some cases, irradiation is applied in order to improve the porous texture of the final products, whereas in other cases, the aim is to shorten the synthesis process, in order to make carbon gels more cost-competitive materials.…”

“…In addition, it was observed that the higher the ultrasonic intensity, the shorter the gelation times and the higher the mesopore volume. In 2006, the same group of researches introduced a new variable in the synthesis process of carbon gels, i.e., drying by microwave technology (Tonamon et al, 2006). In some cases, the applied ultrasonic radiation to RF aqueous solutions and then they dried the samples by means of microwave radiation (after a water-exchange step using t-butanol in order to minimize the shrinkage of the structure).…”

“…This is due to, except in the case of subcritical drying, under supercritical and freezing conditions, it is necessary to perform solvent exchanges, which requires several days, and in the most extreme conditions of drying entails a substantial increase in production costs Tamon et al, 2000;Zhang et al, 2007). Consequently, the research in this field is being addressed to the development of faster and cheaper methods of synthesizing carbon gels in order to make them more attractive and competitive than the activated carbons used until now (Calvo et al, 2008Conceição et al, 2009;Tonamon et al, 2006;Zubizarreta et al, 2008b). Some of these works are based on the use of different types of electromagnetic radiation as a heating source for one or several stages of the synthesis process.…”

Preparation and characterization of nickel-modified carbon cryogel beads with uniform particle size

“…Tonanon et al [27] reported that macropores could be developed under the low concentration of catalyst used for the sol-gel polycondensation of formaldehyde with formaldehyde. However, mesopores were not detected in the carbon gel prepared under the same conditions.…”

Microwave drying as an effective method to obtain porous carbon xerogels

“…The microwave technique is gaining importance in several fields on laboratory and industrial scale, however it has not been well studied for the synthesis of carbon gels. Tonanon et al [6] reported recently the possibility of obtaining porous carbon xerogels by microwave drying. However, they also used solvent exchange and ultrasonic irradiation prior to the drying process, making the overall procedure longer and more complex.…”