Surface Fractal Characteristics of Silica Aerogels

Jarzębski, Andrzej B.; Lorenc, and Jarosław; Pająk, L.

doi:10.1021/la960011z

Cited by 51 publications

(29 citation statements)

References 23 publications

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“…Recently, several papers reported various studies concerning the influence of the alcogel synthesis conditions and of the strategy of hypercritical drying (CO 2 or methanol) on the final aerogel texture (42)(43)(44)(45)(46). High-microporosity structures could be prepared under extreme synthesis and drying conditions in the form of low-TEOS-content-based catalyzed silica aerogels obtained by the collapse of the alcogel structure during drying, powdery MeOH-dried aerogels obtained by the hypercritical drying of the precursor solution (before the gel state was reached), or mixed SiO 2 -ZrO 2 aerogels with very high molar ratio Z = Zr/(Zr + Si).…”

Section: Discussionmentioning

confidence: 99%

Fractal Characterization of Wide Pore Range Catalysts: Application to Pd–Ag/SiO2 Xerogels

Blacher

Heinrichs

Sahouli

et al. 2000

Journal of Colloid and Interface Science

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Section: Discussionmentioning

confidence: 99%

Fractal Characterization of Wide Pore Range Catalysts: Application to Pd–Ag/SiO2 Xerogels

Blacher

Heinrichs

Sahouli

et al. 2000

Journal of Colloid and Interface Science

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“…According to this approach the isotherm is approximated using the Eq. (2) (Jaroniec, 1995;Jarzêbski et al, 1997):…”

Section: Methodsmentioning

confidence: 99%

Characteristics of rapeseed oil cake using nitrogen adsorption

Sokołowska¹,

Bowanko²,

Boguta³

et al. 2013

International Agrophysics

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A b s t r a c t. Adsorption of nitrogen on the rapeseed oil cake and rapeseed oil cake with wheat meal extrudates was investigated. The results are presented as adsorption-desorption isotherms. The Brunauer-Emmet and Teller equation was used to analyse the experimental sorption data. To obtain estimates of the surface area and surface fractal dimension, the sorption isotherms were analyzed using the Brunauer-Emmet and Teller and Frenkel-Halsey-Hill equations. Mesopore analysis was carried out using the Dollimore and Heal method. The properties and surface characteristic of rapeseed oil cake extrudates are related to different basic properties of particular samples and duration of the extrusion process. Extrusion conditions lead to essential differences in particular products. For all kinds of rapeseed oil cakes the amount of adsorbed nitrogen was different, but for the rapeseed oil cake extrudates a large amount of adsorbed nitrogen was observed. The average surface area of the rapeseed oil cake extrudates was about 6.5-7.0 m 2 g -1 , whereas it was equal to about 4.0-6.0 m 2 g -1 for rapeseed oil cake with the wheat meal extrudates. In the case of non-extruded rapeseed oil cake and wheat meal, the dominant group included ca. 2 and 5 nm pores. The values of surface fractal dimension suggested that the surface of the extrudates was more homogenous than that of the raw material. Duration of the extrusion process to 80 s resulted in a decrease in the specific surface area, surface fractal dimension, and porosity of the extrudates.K e y w o r d s: rapeseed oil cake extrudates, nitrogen sorption, specific surface area, fractal dimension, porosity INTRODUCTION Physical gas adsorption is often used as a method to study the surface and pore characteristics of solid materials. The technique accurately determines the amount of a gas retained by a solid body, which is a direct measure for the surface and porous properties. The method is relatively fast and relatively easy in operating the equipment. The isotherm obtained from experiments can provide information about the surface area, surface energetic and geometric heterogeneity, pore volume and pore size distribution (PSD). Nitrogen adsorption at 77 K is a standard method for investigation of porous solids and can be used for routine quality control, as well as for investigation of new materials (Rouquerol et al., 1994;Sing, 2001).The theory of fractals is becoming more and more widely used for describing the structure of disordered media and the processes occurring in them (Senesi and Wilkinson, 2008). Many methods have been developed to obtain surface fractal dimensions (D s ) of adsorbents on the basis of different experiments. Among those, the methods based on analysis of adsorption isotherms play an important role, since they require only one complete adsorption isotherm for a given adsorbent to calculate the surface fractal dimension (Terzyk et al., 2003). A simple method for calculation of the fractal dimension from a single adsorption isotherm was developed by J...

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“…The parameter m calculated from the slope of the linear part of the above dependence is related to the surface fractal dimension. The magnitude of 1/m distinguishes two possible adsorption regimes [15]: for 1/m < 1/3, the adsorption occurs within van der Waals regime and the surface fractal dimension is:…”

Section: Surface Fractal Dimensionmentioning

confidence: 99%

Determination of Energetic and Geometric Properties of Plant Roots Specific Surface from Adsorption/Desorption Ishoterm

Jozefaciuk¹,

Lukowska²,

Szerement³

2013

AJPS

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Background and Aims: Structure and composition of plant roots surfaces are extremely complicated. Water vapor adsorption/desorption isotherm is a powerful tool to characterize such surfaces. The aim of this paper is to present theoretical approach for calculating roots surface parameters as adsorption energy, distribution of surface adsorption centers, as well as roots geometric and structure parameters as surface fractal dimension, nanopore sizes and size distributions on example of experimental isotherms of roots of barley taken from the literature. This approach was up to date practically not applied to study plant roots. Methods: Simplest tools of theoretical analysis of adsorption/desorption isotherms are applied. Results: Parameters characterizing energy of water binding, surface complexity and nanopore system of the studied roots were calculated and compared to these of the soils. Some possible applications of root surface parameters to study plant-soil interactions are outlined. Conclusions: Physicochemical surface parameters may be important for characterizing root surface properties, their changes in stress conditions, as well as for study and model plant processes. Physicochemical and geometrical properties of plant roots differ from these of the soils.

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Surface Fractal Characteristics of Silica Aerogels

Cited by 51 publications

References 23 publications

Fractal Characterization of Wide Pore Range Catalysts: Application to Pd–Ag/SiO2 Xerogels

Fractal Characterization of Wide Pore Range Catalysts: Application to Pd–Ag/SiO2 Xerogels

Characteristics of rapeseed oil cake using nitrogen adsorption

Determination of Energetic and Geometric Properties of Plant Roots Specific Surface from Adsorption/Desorption Ishoterm

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