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Physical Activation (physical + activation)
Selected AbstractsThermal processing of biomass natural fibre wastes by pyrolysisINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 2 2004Anton R. Reed Abstract Waste biomass material in the form of natural fibres used in the production of textile products were examined for their potential to produce activated carbon by physical activation. The five biomass types were hemp, flax, jute, coir and abaca. Each biomass was pyrolysed in a fixed bed reactor and the char characterized. The char was subsequently, activated with steam in a char activation reactor. The surface area and porosity of the derived activated carbon was determined. Surface areas of between 770 and 879 m2 g,1 were achieved. The yield of activated carbon was mostly less than 20 wt% of the original biomass. The five biomass samples were also pyrolysed in a thermogravimetric analyser. The thermal degradation of the biomas samples were discussed in terms of the thermal degradation of the main components of the biomass, cellulose, hemicellulose and lignin. Copyright © 2004 John Wiley & Sons, Ltd. [source] Microporous activated carbon spheres prepared from resole-type crosslinked phenolic beads by physical activationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Arjun Singh Abstract Microporous activated carbon spheres (ACSs) with a high specific Brunauer,Emmet,Teller (BET) surface area were prepared from resole-type spherical crosslinked phenolic beads (PBs) by physical activation. The PBs used as precursors were synthesized in our laboratory through the mixing of phenol and formaldehyde in the presence of an alkaline medium by suspension polymerization. The effects of the gasification time, temperature, and flow rate of the gasifying agent on the surface properties of ACSs were investigated. ACSs with a controllable pore structure derived from carbonized PBs were prepared by CO2 gasification. Surface properties of ACSs, such as the BET surface area, pore volume, pore size distribution, and pore diameters, were characterized with BET and Dubinin,Reduchkevich equations based on N2 adsorption isotherms at 77 K. The results showed that ACSs with a 32,88% extent of burn-off with CO2 gasification exhibited a BET surface area ranging from 574 to 3101 m2/g, with the pore volume significantly increased from 0.29 to 2.08 cm3/g. The pore size and its distribution could be tailored by the selection of suitable conditions, including the gasification time, temperature, and flow rate of the gasifying agents. The experimental results of this analysis revealed that ACSs obtained under different conditions were mainly microporous. The development of the surface morphology of ACSs was also studied with scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation of carbon nanofibres through electrospinning and thermal treatment,POLYMER INTERNATIONAL, Issue 12 2009Cheng-Kun Liu Abstract Electrospinning is a versatile process to obtain continuous carbon nanofibres at low cost. Thermoplastic and thermosetting polymer precursors are utilized to prepare electrospun carbon nanofibres, activated carbon nanofibres through chemical and/or physical activation and functionalized composite carbon nanofibres by surface coating or electrospinning a precursor solution tailored with nanomaterials. Many promising applications of electrospun carbon nanofibres can be expected if appropriate microstructural, mechanical and electrical properties become available. This article provides an in-depth review of the research activities regarding several varieties and performance requirements of precursor nanofibres, polyacrylonitrile-based carbon nanofibres and their functionalized products, and carbon nanofibres from other precursors. Copyright © 2009 Society of Chemical Industry [source] Structure-factor extrapolation using the scalar approximation: theory, applications and limitationsACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2007Ulrich K. Genick For many experiments in macromolecular crystallography, the overall structure of the protein/nucleic acid is already known and the aim of the experiment is to determine the effect a chemical or physical perturbation/activation has on the structure of the molecule. In a typical experiment, an experimenter will collect a data set from a crystal in the unperturbed state, perform the perturbation (i.e. soaking a ligand into the crystal or activating the sample with light) and finally collect a data set from the perturbed crystal. In many cases the perturbation fails to activate all molecules, so that the crystal contains a mix of molecules in the activated and native states. In these cases, it has become common practice to calculate a data set corresponding to a hypothetical fully activated crystal by linear extrapolation of structure-factor amplitudes. These extrapolated data sets often aid greatly in the interpretation of electron-density maps. However, the extrapolation of structure-factor amplitudes is based on a mathematical shortcut that treats structure factors as scalars, not vectors. Here, a full derivation is provided of the error introduced by this approximation and it is determined how this error scales with key experimental parameters. The perhaps surprising result of this analysis is that for most structural changes encountered in protein crystals, the error introduced by the scalar approximation is very small. As a result, the extrapolation procedure is largely limited by the propagation of experimental uncertainties of individual structure-factor amplitudes. Ultimately, propagation of these uncertainties leads to a reduction in the effective resolution of the extrapolated data set. The program XTRA, which implements SASFE (scalar approximation to structure-factor extrapolation), performs error-propagation calculations and determines the effective resolution of the extrapolated data set, is further introduced. [source] | ||||||||||