Microstructure of porous carbons derived from phenolic resin – Impact of annealing at temperatures up to 2000 °C analyzed by complementary characterization methods

Wiener, M.; Reichenauer, Gudrun

doi:10.1016/j.micromeso.2014.10.012

Cited by 15 publications

(13 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…6b and 7b) are not uniform but exhibit spikes suggesting a detailed substructure of the carbon matrix; this effect is more pronounced for the differential distributions derived from the inversion of the GAE than for their counterparts evaluated from the situ strain isotherm. From the experimental point of view a substructure of the carbon matrix appears unphysical, since the micropore structure of the carbon xerogel sample is expected to be entirely disordered [48]. Therefore the spikes of the differential pores size/volume distributions ( Fig.…”

Section: Experimental Results and Data Evaluationmentioning

confidence: 99%

Using in-situ adsorption dilatometry for assessment of micropore size distribution in monolithic carbons

Kowalczyk

Balzer

Reichenauer

et al. 2016

Carbon

View full text Add to dashboard Cite

We demonstrate that in-situ adsorption dilatometry provides a new opportunity for structural characterization of microporous carbons. We present experimental results for CO 2 adsorption at 293 K and in-situ deformation obtained by dilatometry on a synthetic monolithic carbon sample. The carbon deformation in the course of adsorption is non-monotonic: the strain isotherm shows the sample contraction at low adsorption followed by progressive expansion. To evaluate structural and mechanical properties of the sample from the experimental adsorption and strain isotherms, a kernel of theoretical adsorption isotherms is obtained with the grand canonical Monte Carlo simulation of CO 2 adsorption in a series of carbon micropores ranging from 0.22 to 2.0 nm. The respective kernel of adsorption stress isotherms is constructed using the thermodynamic model of adsorption stress. The pore volume and surface area distributions were calculated independently from a) the experimental excess adsorption isotherm by deconvoluting the generalized adsorption equation and b) the experimental strain isotherm by using the kernel of adsorption stress isotherms. The proposed method of determining the pore size distribution from the strain isotherm validates the thermodynamic model of adsorption stress in micropores and provides additional information about the sample material with respect to mechanical properties of the microporous matrix.

show abstract

Section: Experimental Results and Data Evaluationmentioning

confidence: 99%

Using in-situ adsorption dilatometry for assessment of micropore size distribution in monolithic carbons

Kowalczyk

Balzer

Reichenauer

et al. 2016

Carbon

View full text Add to dashboard Cite

show abstract

“…These materials can be considered as irregularly stacked graphene domains, still comparable to our model system. Generally, slit-shaped pores are assumed to be present in these materials. − In Figure , the BET area determined using nitrogen adsorption as a function of pore size is shown. ,− Unfortunately, insufficient studies were available to also investigate argon-based BET area. Clearly visible for these different materials, the specific surface area shows a notable maximum at intermediate pore sizes (9 < D pore < 13 Å), comparable to our findings using graphene sheets (cf.…”

Section: Results and Discussionmentioning

confidence: 99%

“…This is, however, only a minor decrease in minimal pore sizes for physically sound BET area determination. With normal boiling points of 4.2 K for helium and 27 K for neon, it , 51 Mochida et al, 52 Li et al, 53 Wiener et al, 54 Wang et al, 6 Shiratori et al, 55 Rejifu et al, 56 Almazan et al, 57 Morlay et al, 58 Kil et al, 59 Asakura et al, 60 Stoeckli et al, 61 might be difficult to determine a sufficiently large portion of the adsorption isotherm using commercially available volumetric adsorption equipment, even with the aid of current (commercially available) cryostats that can cool down to ∼50 K. From eq 14 and accompanying analysis it is clear that one should consider BET areas with great care and consideration, regardless of the chosen adsorptive for materials with D pore < 10 Å.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Assessing the Surface Area of Porous Solids: Limitations, Probe Molecules, and Methods

et al. 2016

View full text Add to dashboard Cite

In this modeling study, the uses of nitrogen (77.3 K), probe molecule of choice for decades, and argon, opted as alternative in the 2015 IUPAC report on adsorptive characterization, as probe molecules for geometric surface area determination are compared. Graphene sheets possessing slit-shaped pores with varying size (width) are chosen as model porous solids, and different methods for the determination of specific surface areas are investigated. The BET method, which is the most commonly applied analysis, is compared to the Langmuir and relatively recently proposed ESW (excess sorption work) method. We show that either using argon or nitrogen as adsorptive, the physical meaningfulness of adsorption-derived surface areas highly depends on the pore size. When less than two full layers of adsorbate molecules can be formed within slitlike pores of a graphitic material (D < 5.8 Å for Ar/N), adsorption-derived surface areas are about half that of the geometric surface area. Between two and four layers (6.8 < D < 12.8 Å), adsorption surface areas can be significantly larger (up to 75%) than the geometric surface area because monolayer-multilayer formation and pore filling cannot be distinguished. For four or more layers of adsorbate molecules (D > 12.8 Å), adsorption-derived surface areas are comparable to their geometrically accessible counterparts. Note that for the Langmuir method this only holds if pore-filling effects are excluded during determination. This occurs in activated carbon materials as well. In the literature, this indistinguishability issue has been largely overlooked, and erroneous claims of materials with extremely large surface areas have been made. Both the BET and Langmuir areas, for D > 12.8 Å, correspond to geometric surface areas, whereas the ESW method yields significantly lower values. For the 6.8 Å < D < 12.8 Å range, all methods erroneously overestimate the specific surface area. For the energetically homogeneous graphene sheets, differences between argon and nitrogen for the assessment of surface areas are minor.

show abstract

“…Besides the contradiction of a micropore collapse by CO 2 measurements, small-angle X-ray scattering analysis also contradicts a micropore collapse at HTTs below 1000 °C [88,89]. The characteristic peak for biochar is therefore rather linked to N 2 measurement itself than the actual surface area and pore volume of the material.…”

Section: Hypothesis Of a Micropore Structure Collapsementioning

confidence: 93%

Do you BET on routine? The reliability of N2 physisorption for the quantitative assessment of biochar’s surface area

Maziarka

Wurzer

Arauzo

et al. 2021

Chemical Engineering Journal

View full text Add to dashboard Cite

show abstract

Microstructure of porous carbons derived from phenolic resin – Impact of annealing at temperatures up to 2000 °C analyzed by complementary characterization methods

Cited by 15 publications

References 22 publications

Using in-situ adsorption dilatometry for assessment of micropore size distribution in monolithic carbons

Using in-situ adsorption dilatometry for assessment of micropore size distribution in monolithic carbons

Assessing the Surface Area of Porous Solids: Limitations, Probe Molecules, and Methods

Do you BET on routine? The reliability of N2 physisorption for the quantitative assessment of biochar’s surface area

Contact Info

Product

Resources

About