scholarly journals Features of the morphology and texture of silica and carbon adsorbents

Surface ◽  
2021 ◽  
Vol 13(28) ◽  
pp. 127-165
Author(s):  
V. M. Gun'ko ◽  
Keyword(s):  
Activated Carbons ◽  
Carbon Adsorbents ◽  
Size Distributions ◽  
Activation Time ◽  
Materials Synthesis ◽  
Textural Characteristics ◽  
X Ray Scattering ◽  
Pore Size Distributions ◽  
The Difference ◽  
Packing Effects

The morphological and textural characteristics of various silicas (93 fumed silicas and 56 porous silicas), different carbons (230), and porous polymers (53) are analyzed using probe (nitrogen, argon, benzene, n-decane, water) adsorption, small angle X-ray scattering (SAXS), and transition (TEM), scanning (SEM) electron and atom force (AFM) microscopies. There are certain correlations between pore volume (Vp) and specific surface area (SSA, SBET) for these materials. Synthesis and treatment temperatures affect this relationship since a linear Vp - SBET approximation scatter decreases with decreasing these temperatures. Silicas are composed of nonporous nanoparticles (NPNP), but activated carbons (AC) are composed of porous nanoparticles (PNP). For different materials, NP are weakly or strongly packed in secondary structures. However, there are general features of pore size distributions (PSD) for NP-based materials, e.g., minimal contribution of narrow mesopores of 3-5 nm in radius due NP-packing effects. For AC produced using the same chars and activation agents but with varied activation time, the textural characteristics demonstrate smooth changes with increasing burn-off degree: nanopores partially transform into narrow mesopores with opposite PSD shifts of broad mesopores and macropores. Comparison of adsorption (open pores accessible for probes) and SAXS (both open and closed pores) data for carbons shows that the difference decreases with increasing burn-off degree due to decreasing contribution of closed pores. Most clear pictures on the particulate morphology and texture could be obtained in parallel analysis using adsorption, SAXS, and microscopic methods with appropriate data treatments.

A New X-Ray Scattering Method for Determining Pore-Size Distribution in Low-k Thin Films

2001 ◽  
Vol 714 ◽  
Author(s):  
Kazuhiko Omote ◽  
Shigeru Kawamura
Keyword(s):  
Thin Films ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Gas Adsorption ◽  
Size Distributions ◽  
X Ray ◽  
X Ray Scattering ◽  
Pore Size Distributions ◽  
Scattering Technique ◽  
Ray Scattering

ABSTRACTWe have successively developed a new x-ray scattering technique for a non-destructive determination of pore-size distributions in porous low-κ thin films formed on thick substrates. The pore size distribution in a film is derived from x-ray diffuse scattering data, which are measured using offset θ/2θ scans to avoid strong specular reflections from the film surface and its substrate. Γ-distribution mode for the pores in the film is used in the calculation. The average diameter and the dispersion parameter of the Γ-distribution function are varied and refined by computer so that the calculated scattering pattern best matches to the experimental pattern. The technique has been used to analyze porous methyl silsesquioxane (MSQ) films. The pore size distributions determined by the x-ray scattering technique agree with that of the commonly used gas adsorption technique. The x-ray technique has been also used successfully determine small pores less than one nanometer in diameter, which is well below the lowest limit of the gas adsorption technique.

Calculation of Pore Size Distributions of Activated Carbons from Adsorption Isotherms

Langmuir ◽  
1999 ◽  
Vol 15 (23) ◽  
pp. 8235-8245 ◽  
Author(s):  
G. M. Davies ◽  
N. A. Seaton ◽  
V. S. Vassiliadis
Keyword(s):  
Pore Size ◽  
Adsorption Isotherms ◽  
Activated Carbons ◽  
Size Distributions ◽  
Pore Size Distributions

scholarly journals Adsorption Energy and Pore-Size Distributions of Activated Carbons Calculated Using Hill's Model

2014 ◽  
Vol 32 (7) ◽  
pp. 571-590 ◽  
Author(s):  
Yosra Ben Torkia ◽  
Nadia Bouaziz ◽  
Shaheen A. Al-Muhtaseb ◽  
Abdelmottaleb Ben Lamine
Keyword(s):  
Pore Size ◽  
Adsorption Energy ◽  
Activated Carbons ◽  
Size Distributions ◽  
Pore Size Distributions

Pore size distributions in nanoporous methyl silsesquioxane films as determined by small angle x-ray scattering

2002 ◽  
Vol 81 (12) ◽  
pp. 2232-2234 ◽  
Author(s):  
E. Huang ◽  
M. F. Toney ◽  
W. Volksen ◽  
D. Mecerreyes ◽  
P. Brock ◽  
...  
Keyword(s):  
Pore Size ◽  
Small Angle ◽  
Size Distributions ◽  
X Ray ◽  
X Ray Scattering ◽  
Pore Size Distributions ◽  
Methyl Silsesquioxane ◽  
Ray Scattering

scholarly journals Modifications on Microporosity and Physical Properties of Cement Mortar Caused by Carbonation: Comparison of Experimental Methods

2013 ◽  
Vol 2013 ◽  
pp. 1-9
Author(s):  
Son Tung Pham
Keyword(s):  
Physical Properties ◽  
Cement Mortar ◽  
Solid Phase ◽  
Gas Permeability ◽  
Nitrogen Adsorption ◽  
Size Distributions ◽  
Pore Size Distributions ◽  
Molecular Sizes ◽  
The Difference ◽  
Macrophysical Properties

The influence of carbonation on the microstructure of normalised CEM II mortar was studied using nitrogen adsorption and porosity accessible to water. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity, and 20% CO2concentration. Conflicts in results were observed because while the pore size distributions calculated by BJH method from nitrogen adsorption provided evolution of the micro- and mesopores during carbonation, the porosity accessible to water showed changes in all three porous domains: macro-, meso- and micropores. Furthermore, the porous domains explored by water and nitrogen molecules are not the same because of the difference in the molecular sizes. These two techniques are therefore different and help to complementarily evaluate the effects of carbonation. We also examined the evolution of macrophysical properties such as the solid phase volume using helium pycnometry, gas permeability, thermal conductivity, thermal diffusivity, and longitudinal and transverse ultrasonic velocities. This is a multiscale study where results on microstructural changes can help to explain the evolution of macro physical properties.

scholarly journals Physical Activation of Wooden Chips and the Effect of Particle Size, Initial Humidity, and Acetic Acid Extraction on the Properties of Activated Carbons

2018 ◽  
Vol 4 (4) ◽  
pp. 66 ◽  
Author(s):  
Davide Bergna ◽  
Henrik Romar ◽  
Ulla Lassi
Keyword(s):  
Particle Size ◽  
Acetic Acid ◽  
Pore Size ◽  
Activated Carbons ◽  
Lower Surface ◽  
Physical Activation ◽  
Acid Extraction ◽  
Size Distributions ◽  
Pore Size Distributions ◽  
Significant Difference

In this research study, two different wooden biomasses (birch and pine) were thermally carbonized and steam-activated into activated carbons in a one-stage process. The effects of particle size and humidity (as received and oven-dried) on the properties, such as specific surface areas, pore volumes, and pore size distributions, of the final activated carbon characteristics were examined. Another set of biomasses (birch, spruce, and pine) was pre-treated before carbonization and the activation steps through an extractive process using a weak acetic acid in Soxhlet extractors. According to the results, the dried samples had a slightly lower surface area, while no difference was observed in the yields. For the extracted samples, there was a significant difference, especially in the pore size distributions, compared to the non-extracted samples. There appeared to be a shift from a meso-microporous distribution to a microporous distribution caused by the extractive pre-treatment.

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