Piotr Natkański

Effect of Fe3+ ions present in the structure of poly(acrylic acid)/montmorillonite composites on their thermal decomposition

Poly(acrylic acid)/montmorillonite (MMT) composites with various polymer contents were synthesized by in situ polymerization technique. The structure of obtained materials was characterized by powder X-ray diffraction and infrared spectroscopy (FTIR). It was found that only a limited amount of hydrogel could be introduced between the clay layers. The remaining part of polymer was deposited on the external surface of clay particles. The introduction of the polymer modifier significantly increased the adsorption capacity of MMT in the elimination of Fe3+ ions from aqueous solution. The thermal behavior of the samples before and after the Fe3+ adsorption was examined by thermogravimetry and differential thermal analysis. Moreover, the composition of gaseous products evolved during decomposition was determined by FTIR. The materials after Fe3+ adsorption exhibited different thermal stability in oxidizing atmosphere than the fresh samples. Fe3+ cations, forming FeOx species during thermal treatment, appeared to be effective catalysts of polymer oxidation.

Pyrolytic carbons derived from water soluble polymers

Conductive pyrolytic carbon materials were obtained in wet impregnation process followed by controlled pyrolysis. Poly-N-vinylformamide (PNVF) as well as mixture of PNVF and pyromellitic acid (PMA) were applied as carbon precursors. Composition of carbon precursors was optimized in terms to obtain best electrical properties of pyrolytic carbons. Mixture of PNVF and PMA as well as pure PNVF were deposited on the model alumina (α-Al2O3) support to form conductive carbon layers (CCL). The optimal composition of the polymer precursors was determined by Raman spectra and electrical conductivity measurements. The carbonization conditions were optimized using complementary thermal analysis methods (EGA(FTIR)–TG/DTG/STDA). It was found that the addition of PMA to polymer precursor PNVF decreases temperature of formation of condensed graphene structures, domains of electrical conductivity, thus, the formation temperature of pyrolytic carbons with desired electrical properties may be decreased.

Physicochemical properties of hydrogel template-synthesized copper(II) oxide-modified clay influencing its catalytic activity in toluene combustion

CuO-modified montmorillonite was synthesized by the template-assisted route. Poly(acrylic acid) was intercalated into the interlayer gallery of natural clay. Subsequently, various amounts of Cu2+ cations were introduced into the prepared hydrogel–clay composite using adsorption in different volumes of aqueous Cu(NO3)2 solution at constant pH = 6. The resulting materials were finally calcined at 550 °C (chosen using the results of TGA-IR analyses) to transform them into thermally stable oxide systems. The changes in the structural properties of the clay during the progressive modification were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Moreover, porosity, reducibility and surface composition of the calcined materials were determined by means of low-temperature N2 adsorption, temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). It was shown that a high concentration of CuO nanoparticles, which were well-dispersed and protected against sintering between montmorillonite grains, and weak interaction between CuO and the clay support (resulting in easy reducibility of CuO) were the most important features influencing the catalytic activity of the synthesized materials in the total oxidation of volatile organic compounds (VOCs).

Sol–gel synthesis, structural and electrical properties of Li2CoSiO4 cathode material

Polyanionic cathode materials for lithium-ion batteries start to be considered as potential alternative for layered oxide materials. Among them, Li2CoSiO4, characterized by outstanding capacity and working voltage, seems to be an interesting substitute for LiFePO4 and related systems. In this work, structural and electrical investigations of Li2CoSiO4 obtained by sol–gel synthesis were presented. Thermal decomposition of gel precursor was studied using EGA (FTIR)-TGA method. Chemical composition of the obtained material was confirmed using X-ray diffraction and energy-dispersive X-ray spectroscopy. The morphology of β-Li2CoSiO4 was studied using transmission electron microscopy. High temperature electrical conductivity of Li2CoSiO4 was measured for the first time. Activation energies of the electrical conductivity of two Li2CoSiO4 polymorphs (β and γ) were determined. The room temperature electrical conductivity of those materials was estimated as well.

Multifunctional carbon aerogels derived by sol–gel process of natural polysaccharides of different botanical origin

In this manuscript, we describe the results of our recent studies on carbon aerogels derived from natural starches. A facile method for the fabrication of carbon aerogels is presented. Moreover, the complete analysis of the carbonization process of different starch aerogels (potato, maize, and rice) was performed using thermogravimetric studies combined with a detailed analysis of evolved decomposition products. The prepared carbon aerogels were studied in terms of their morphology and electrical properties to relate the origin of starch precursor with final properties of carbon materials. The obtained results confirmed the differences in carbon aerogels’ morphology, especially in materials’ specific surface areas, depending on the botanical origin of precursors. The electrical conductivity measurements suggest that carbon aerogels with the best electrical properties can be obtained from potato starch.

Thermal stability and pollutant adsorption efficiency of nanocomposites consisted of clay and polymeric quaternary ammonium salts

Thermal stability and pollutant adsorption efficiency of nanocomposites consisted of clay and polymeric quaternary ammonium salts Polymer/layered silicate nanocomposites based on polymeric quaternary ammonium salts (ionenes) intercalated into the interlayer galleries of montmorillonite were synthesized. Zeta potential measurements were conducted to determine the amount of ionenes required to neutralize the negative charge of clay. The composition and structure of the obtained nanocomposites were examined by elemental analysis, ATR-FTIR and XRD. High dye sorption capacity was observed for the composite containing ionene 6,2.

Polymer Hydrogel-Clay (Nano)Composites

Among various (nano)composites containing hydrogels, materials based on clays are emphasized. We show features of clays, which are beneficial in the formation of (nano)composites with hydrogels. Methods used in the synthesis of these materials and the resulting structures are demonstrated. Physicochemical techniques being valuable tools for characterization of this type of materials are also presented. Furthermore, the most important properties of hydrogel-clay (nano)composites are shown. Beside typically improved features like thermal stability, mechanical, rheological, and optical properties, as well as swelling and adsorption capacity are discussed. Finally, a wide range of possible applications of hydrogel-clay (nano)composites is outlined.

Leak testing of carbon–tin nanocomposites by thermal analysis methods

Electrode materials consisted of tin nanograins encapsulated in different origin carbon buffer matrix (starch or water soluble polymer) were obtained in a simple and inexpensive process. The tin precursor was synthesized using modified reverse nanoemulsion technique (w/o) and then coated by a source of carbon. The composites precursors were pyrolysed, affording formation of C/Sn anode materials. The resulting samples were investigated by powder X-ray diffraction studies in order to verify the structure and calculate crystallites sizes. The morphology of the nanocomposites was characterized by low-temperature nitrogen adsorption method (N2-BET). Thermal analysis measurements (EGA-TG/DTG/DTA and DSC) allowed determining optimal conditions of preparation process and estimating carbon content in the obtained anode materials. Thermogravimetric studies also proved to be highly useful in establishing the leak behaviour of C/Sn nanocomposites. The electrochemical performance of the nanopowders was examined by charge–discharge tests in R2032-type coin cell. The thermal analysis results as well as low-temperature nitrogen adsorption data indicated that the origin of carbon precursor has major impact on morphology and leak behaviour of the obtained carbon buffer matrix. The electrochemical tests showed that better tightness of carbon–tin nanocomposites resulted in higher gravimetric capacity and better cell performance.