Marta Krzesińska

Development of monolithic eco-composites from carbonized blocks of solid iron bamboo (Dendrocalamus strictus) by impregnation with furfuryl alcohol

The purpose of this work was to manufacture the porous biomorphous composite using carbonized shapes cut from solid stem of solid iron bamboo, Dendrocalamus strictus, as a monolithic support. Bamboo carbonized at 800 degrees C was next infiltrated with liquid filler--furfuryl alcohol. After the polymerization and cross-linking of the filler, the shapes were carbonized again to obtain carbon/carbon composite. TGA method was used to investigate the thermal decomposition of the resulting composite as well as of the raw and carbonized bamboo. The ultrasonic measurements, optical microscopy observations, the adsorption of N(2) at -196 degrees C and mercury porosimetry were applied to characterize the structure of the investigated materials. The obtained composite was found to be highly porous (over 80%), thermo-resistant in inert atmosphere (up to 940 degrees C). It possessed stiff hierarchically ordered pore structure with elastic moduli >4 GPa along the stem, and >1 GPa perpendicularly to the stem. Furthermore, the layer of carbon from the polymer coated the support accurately and did not affect the shape of the monolithic pieces of carbonized bamboo. The resulting composite possessed also more uniform, mesoporous structure than the support.

Coal structure studied by means of molecular acoustics methods

In this paper, a brief overview of our works on macromolecular network and molecular structure of coal via the elastic properties studies has been made. The recent investigations of raw, demineralized and solvent-treated coals, as well as coal extracts by means of molecular acoustics methods, have been described.

The use of ultrasonic wave propagation parameters in the characterization of extracts from coals

Measurements were made of the velocities of longitudinal ultrasonic waves of frequency 2.5 MHz and selected parameters describing the coal extract structure, such as mean molecular mass, aromaticity factor and concentration of unpaired spins, for the tetrahydrofuran (THF) extract of Indian sub-bituminous Assam coal. The sample of Assam coal (carbon content 80.4 wt%) was collected from the Gondwanaland deposits, where coals are very different from European Carboniferous coals. Results were compared with the data obtained for THF extracts from Polish coals of various rank (64.9–85.6 wt% carbon) and an Indian lignite (54.1 wt% carbon). Absolute temperature coefficients of ultrasonic velocity b and absolute concentration coefficients of ultrasonic velocity a were determined from ultrasonic measurements performed in solutions in THF for THF extracts of brown and bituminous Polish coals, Indian Neyeli lignite and sub-bituminous Assam coal, as well as in solutions in pyridine (PY) for PY extracts from Polish bituminous coals. Correlations between the coefficients b and a and the mean molecular mass of coal extracts were found.

Application of ultrasonic measurements to the determination of concentration of coal extracts

Abstract The velocities of ultrasonic wave propagation in tetrahydrofuran solutions of coal extracts from various coals (within the range 64.9–85.6% carbon) have been measured. Linear correlations between extract concentrations and ultrasonic wave velocities have been found.

Propagation of ultrasound in pyridine extracts of bituminous coals

Abstract The velocities of longitudinal ultrasound waves of frequency 2.5 MHz were measured in the temperature range 15–40°C in solutions of pyridine extracts from bituminous coals with carbon contents from 75.1 to 85.6 wt%. Mean molecular masses and aromaticity factors were also determined for the extracts. Parthasarathy rules were applied to verify relations between ultrasonic velocity and values of the parameters describing extract structure. The results obtained in previous investigations on coal products by the ultrasonic method are summarized.

Correlation of absolute temperature coefficients of ultrasonic velocity in solutions of dilute coal and lignite extracts with molecular masses

Absolute temperature coefficients of ultrasonic velocity b were determined from temperature dependences of the velocity of the longitudinal ultrasonic waves with frequency 2.5 MHz in solutions of pyridine and tetrahydrofuran extracts, obtained from lignite and coals of different ranks (54.1‐85.6 wt% of carbon). The relationship between absolute temperature coefficientsb of all extract solutions and extract molecular masses M was studied. It was stated that the dependence of b p M vs. M deviates considerably from the rule b p Ma const; found empirically by Lagemann et al. for pure organic liquids. Experimental data for lignite and coal product solutions were best fitted by the equation b p Ma AM 1 B; where constants A and B were determined from the fits having the correlation coefficientsr within the range 0.99‐ 0.999. This empirical formula was applied to determine the molecular mass of a sample, for which the Knauer osmometer method could not be used. q 2000 Elsevier Science Ltd. All rights reserved.

Application of suspension method to study of the elastic properties of crumbly coals

Abstract The method of ultrasonic velocity measurements in suspension developed for erythrocytes, kaolin etc. has been applied to crumbly coals not suitable for standard mechanical methods for monolithic specimens. Twenty samples of crumbly coals have been studied. As stated in the context of obtained results this method allows to study coals without conglomerates of mineral matter, macroscopic cracks and macropores. What more, above method is well applied to crumbly samples, demineralized coals, macerals and also for coals after solvent action.

The development and characterization of a novel chitosan/carbonised yucca (Yucca flaccida) bio-composite

The aim of the study was to fabricate a biodegradable bio-composite using only natural biological precursors for both composite components, i.e., for a support and for a filler. Bio-composites of biomorphous structure were prepared using monolithic blocks of yucca (Yucca flaccida) carbonised at 550°C as a stiff porous skeleton, and chitosan as a filler that coated the internal surface of the skeleton by a thin film. Highly porous supports and the resultant biomorphous composites were characterized by means of TGA, SEM, low-temperature physical adsorption of nitrogen, as well as electric and ultrasonic measurements. The resultant bio-composites were found to be very light materials with density of about 0.13g/cm3 and very porous (over 90%). They were found to be hierarchically ordered anisotropic structures with a stiff skeleton of dynamic elastic moduli up to 0.8GPa. The specific surface area was found to be 72m2/g giving a surface area of chitosan film equal to about 12m2 for a block sample of a volume of 2cm3. Covering porous support by thin film of chitosan resulted in the increase of electrical conductivity of the resultant composite.