Wojciech Stefaniak

Porosity evolution of VP-DVB/MCM-41 nanocomposite

The porous structure of nanostructured vinylpyrrolidone-divinylbenzene (VP-DVB)/MCM-41 composite was characterized using N(2) adsorption at 77K and positronium annihilation lifetime spectroscopy (PALS), atomic force microscopy (AFM) and Raman spectroscopy. Positron annihilation lifetime spectra were measured during outgassing procedure. The voids of differentiated dimensions were detected in the composite material. The number of free volumes and their dimensions depend on the degree of evacuation of volatile components from the samples.

Pore size analysis by nitrogen adsorption and thermal desorption

Thermogravimetric analysis was applied to the characterization of the porosity of silica gel. Thermal desorption of liquids from silicas for column chromatography was measured. Benzene, n-hexane and carbon tetrachloride were used as liquid adsorbates. Pore size distributions for silica gels of differentiated porosity were determined on the basis of thermogravimetric curves using the Kelvin equation. Pore dimensions were corrected in respect to the surface film thickness estimated from adsorption isotherms of the same adsorbates measured above their boiling point. The resulting pore size distributions and total pore volumes were compared with those obtained from the nitrogen method.

The investigation of the pore structure of silica gels with long-chain alkyl grafts by thermal analysis

Abstract The total pore volumes and the core size distributions were calculated for the silica gel Si-100 and chemically modified silica gels RP-8 and RP-18 on the basis of the thermal desorption data of various liquids. The results obtained are compared with those from the nitrogen adsorption/desorption method. Good consistency between the parameters obtained by using different methods is observed in the case of unmodified silica gel. The presence of long alkyl chains on the silica surface strongly influences the pore diameter calculated from thermogravimetric data.

Porosity of solids by temperature programmed desorption of liquids : various heating programs

Thermogravimetric analysis was applied to the characterization of the porosity of silica gel. The thermal desorption of benzene was investigated by using various heating programs. The influence of desorption conditions on the derived values of the structural parameters of silica gel is discussed. Results from the thermogravimetric method are compared with those obtained from nitrogen adsorption-desorption.

Investigation of heavy-ion-produced pore defects in organic foil by thermal desorption of liquids

Abstract Thermal analysis was applied to the determination of the size of pores produced by heavy ions in poly(ethylene terephthalate) (PETP) foil. Pore radii and pore volumes were calculated for the desorption of benzene and acetone from the foil aged for different periods of time. The results of these investigations were compared with those from a small-angle neutron scattering experiment.

Swelling effects in cross-linked polymers by thermogravimetry

The present study focuses on the mechanism of swelling and evaluates interactions between solvents of different chemical characters (polar—ethanol, nonpolar—n-heptane) and commercially available porous Amberlite polymers (XAD4, XAD16, XAD7HP) by temperature-programmed desorption (TPD). The first two polymers are the product of copolymerization of styrene and divinylbenzene. Despite having the same chemical composition, they differ in pore size and volume. The Amberlite XAD7HP is composed of an acrylic matrix and has lower pore volume and specific surface area than XAD16 and XAD4. All three resins have the ability to swell, though the per cent of polymeric network expansion during this process varies depending on the solvent used (e.g. in tetraethyl orthosilicate, XAD4 and XAD16 spherical particles increase in volume by 20–30%, while XAD7HP particles can expand by more than 120%). The TPD experiment was performed in dynamic linear and quasistatic heating mode. Based on thermogravimetric data, the desorption energy of selected liquids and pore size distribution in the swollen state were estimated. The obtained results are discussed in terms of both mathematical modelling and low-temperature nitrogen adsorption–desorption experiment.

Porous structure of mixed silica samples by thermogravimetric method

Thermogravimetric analysis was applied to the characterization of the porosity of silica gels. Results from thermogravimetric method are compared with those obtained from the nitrogen method. The consistency of the parameters characterizing the porous structure of silica gels derived from the data of various methods is satisfactory.ZusammenfassungZur Charakterisierung der Porösität von Silikagelen wurde die thermogravimetrische Analyse angewendet. Ergebnisse thermogravimetrischer Methoden wurden mit denen aus der Stickstoffmethode verglichen. Dabei wurde eine zufriedenstellende Übereinstimmung der anhand der Daten aus verschiedenen Methoden gewonnenen Parameter festgestellt, die die poröse Struktur von Silikagelen beschreiben.

Assessment of the porosity of solids from thermogravimetry and nitrogen adsorption data

Thermal desorption of liquids was investigated for various types of porous solid. The correlation between results obtained using high resolution thermogravimetry and low temperature adsorption of nitrogen is discussed. Pore size distributions and total pore volumes were estimated for the investigated adsorbents.

The influence of polarity of liquids on the parameters characterising the porosity of silica gels estimated by thermogravimetric analysis

Thermogravimetric analysis was applied to the characterisation of the porosity of silica gel. Thermal desorption of liquids from silicas for column chromatography was measured. Water and n-hexane were used as liquid adsorbates. Pore size distribution curves of silica gels were determined on the basis of thermogravimetric curves using Kelvin equation. The resulting distributions and total pore volumes were compared with those obtained from the nitrogen method. The influence of polarity of adsorptives on the porosity parameters of silica gels and on the shape of pore size distribution curves is discussed.

Temperature-programmed desorption vs. N2 desorption in determining pore-size distribution of mesoporous silica molecular sieves

Two mesoporous silica molecular sieves, one synthesized by cationic template method and another by neutral template route, were characterized for their pore-size distribution by a novel Temperature-Programmed Desorption (TPD) method and the widely used N2 desorption method. The pore-size distributions determined by the two methods agree quite well and are within experimental errors. For example, TPD method gave a pore size distribution (radius) centered at 14 Å while N2 desorption method showed a peak centered at 13.3 Å. for the mesoporous silica prepared by cationic template route. The new TPD method based on thermogravimetric analysis is a viable option for mesopore characterization of silica-based materials.