3 Matching Results

Search Results

Advanced search parameters have been applied.

Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 April 1995--30 June 1995

Description: In the previous quarterly report (DE-FG22-91PC91305-14), we presented an analysis of small angle neutron scattering (SANS) data obtained for Pittsburgh {number_sign}8 coal char. These samples exhibited considerable scattering. However, when the voids between the particles were filled with a liquid that had the same neutron scattering density as the carbon, the amount of scattering was reduced by more than two orders of magnitude. Analysis of the scattering invariant in terms of surface area showed that the char had very little porosity. To date this has been the only contrast matching SANS study of carbon and the first recognition that interparticle scattering effects are important. In this report, we focus on SANS data obtained for a very different char--a phenolic resin char (PRC). The following was accomplished during the reporting period: contrast matching, SANS data obtained for resin char has been analyzed in detail. Conclusions derived from this analysis include: contrast matching SANS has been demonstrated to be a useful technique for monitoring the activation/gasification process. It is demonstrated how this technique can be used to address such important issues as the role of ``closed`` vs ``open`` porosity, and interparticle scattering. It has been used here to establish that the development of porosity in phenolic resin char upon gasification in air proceeds primarily by ``opening `` or originally ``closed`` porosity. This is quite different than the behavior of Pittsburgh {number_sign}8 coal char. for example, as presented in the previous quarterly report.
Date: December 31, 1995
Creator: Calo, J.M.; Hall, P.J.; Antxustegi, M.M. & Zhang, L.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions. Quarterly technical progress report, 1 January 1995--31 March 1995

Description: The following was accomplished during the reporting period: Small angle neutron scattering (SANS) data were obtained for Pittsburgh {number_sign}8 coal char samples at various levels of bum-off at the Intense Pulsed Neutron Source (IPNS) of the Argonne National Laboratory on the small angle diffractometer (SAD) instrument. The Pittsburgh {number_sign}8 samples complement previous SANS data obtained for non-mineral matter-containing phenol-formaldehyde resin char samples. A contrast-matching technique involving the comparison of scattering data for ``dry`` samples with data from the same samples saturated in deuterated toluene, show that the ungasified Pittsburgh {number_sign}8 char has very little closed porosity and, consequently, that pore development during gasification proceeds by the creation of new pores. In the early stages of gasification (< 4.5% burn-off) a pore system with significant microporosity is produced. In later stages of gasification (4.5%--13.5% bum-off) the tendency is to open these micropores, producing a pore system with a broad size distribution. Nitrogen adsorption isotherms (77K) were determined for all the same samples for which SANS data were obtained in order to provide a corroborative check on their porosity characteristics.
Date: August 1, 1995
Creator: Calo, J.M.; Hall, P.J.; Antxustegi, M.M. & Zhang, L.
Partner: UNT Libraries Government Documents Department

Characterization of porosity via secondary reactions. Final technical report, 1 September 1991--30 November 1995

Description: A new approach to the study of porosity and porosity development in coal chars during gasification was investigated. This approach involves the establishment of the relationships between the amount and type of surface complexes evolved during post-activation temperature programmed desorption (TPD), and the porosity, as measured by gas adsorption and small angle neutron scattering (SANS) techniques. With this new method, the total surface area and micropore volume can be determined by the interpretation of post-activation TPD spectra. The primary conclusion of this work is that it is possible to predict total surface area and micropore volume from TPD spectra. From the extended random pore model, additional information about the micropore surface area, the nonmicroporous surface area, and the mean micropore size development as a function of reaction time (or burn-off) can also be predicted. Therefore, combining the TPD technique and the extended random pore model provides a new method for the characterization of char porosity.
Date: September 1997
Creator: Calo, J. M.; Zhang, L.; Hall, P. J. & Antxustegi, M.
Partner: UNT Libraries Government Documents Department