Origin of porosity in resorcinol-formaldehyde aerogels

Schaefer, Dale W.; Pekala, R.W.; Beaucage, Greg

doi:10.1016/0022-3093(95)00043-7

Cited by 92 publications

(48 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The morphology is controlling by dominant process in phase separation that restricted to nanometer size scales by polymer cross-linking [26]. Different technics were used to corroborate this, pore analysis of small-angle X-ray scattering results was used to study the structure of aerogels, and it is concluded that the aerogels structure is formed from nanoscale phase separation in the initial solution and show that the cross-link density controls both the size and the skeletal density of the material [27]. Thus, the influence of physical and chemical properties of carbon aerogels is possible to use to develop supported heterogeneous catalysts to obtained non-graphitic (amorphous) materials, because the high dispersion of an active phase is highly influenced by the porosity and surface area of the support (PSD).…”

Section: Introductionmentioning

confidence: 98%

Carbon Aerogels: a study with different models of the effect resorcinol/catalyst at different ratios after pyrolysis and the effect on textural properties

et al. 2017

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 98%

Carbon Aerogels: a study with different models of the effect resorcinol/catalyst at different ratios after pyrolysis and the effect on textural properties

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The RF gels studied here exhibit a high degree of crosslinking within their structures, which has been shown to reduce the degree of diffusion in polyethylene materials [36]; hence, similar behaviour would be expected here and compounds the expected low diffusivity for a polar organic material and a non-polar gas, such as nitrogen. The use of alternative techniques to estimate surface area have shown widely different correlations when compared with BET surface area [33,35,37,38], suggesting that there are limitations in any selected technique, whereas other authors have also highlighted the potential of microporous materials including carbonaceous samples, to undergo deformation during the adsorption of probe gases including nitrogen [39]. It may therefore be argued that as the adsorption methods adopted here use a final pressure close to the saturated vapour pressure of nitrogen at 77 K, all porous voids are filled within the process, and that the absorption character of the materials studied here can be quantified by the microporous character observed within the material.…”

Section: Resultsmentioning

confidence: 99%

The impact of deuterium oxide on the properties of resorcinol-formaldehyde gels

Prostredny

Ballantine

Šefčı́k

et al. 2018

J Sol-Gel Sci Technol

View full text Add to dashboard Cite

Resorcinol-formaldehyde gels offer a range of properties that can be exploited in a variety of applications, but better understanding of gel formation mechanisms is needed to enable rational control and optimisation of the physico-chemical characteristics of these materials. Our previous studies have focussed on investigating the formation pathways of these gels, using nuclear magnetic resonance and dynamic light-scattering techniques, as well as evaluating their final physical and chemical properties, via sorption and spectroscopic methods. Nuclear magnetic resonance has been used over the years to probe the chemical species formed during resorcinol-formaldehyde gel polymerisation, but the technique typically involves the prior addition of deuterium oxide to provide a deuterium lock for NMR measurements. However, the effect of deuterium oxide to resorcinol-formaldehyde systems is currently unknown, although the substitution of water by deuterium oxide has been previously reported to alter the chemical and physical properties of reacting systems. In this work we examine the effect of adding deuterium oxide to resorcinol-formaldehyde sol-gel synthesis at different dilution levels and the impact that this addition has on the final characteristics of the synthesised gels, in order to assess the validity of using NMR with a deuterium lock for the investigation of polymerisation mechanism in resorcinol-formaldehyde sol-gel processes. • High catalyst concentration systems less affected due to shorter gelation times• Low catalyst concentration systems more greatly affected due to weaker structure•

show abstract

“…The scattering curves are analyzed using Beaucage's Unified Model [15] to extract relevant length scales and exponents. In systems without distinct surfaces, the scattering intensity (I) often obeys a power law in the magnitude M a n u s c r i p t 9 of the scattering vector (q) by I(q) ~ q -P .…”

Section: Structure Of Plate-like Particle Suspensionsmentioning

confidence: 99%