1-D nanostructures of cubic phase silicon carbide (beta-SiC) were efficiently produced by combust... more 1-D nanostructures of cubic phase silicon carbide (beta-SiC) were efficiently produced by combustion synthesis of mixtures containing Si-containing compounds and halocarbons in a calorimetric bomb. The influence of the operating parameters on 1-D SiC formation yield was studied. The heat release, the heating rate, and the chamber pressure increase were monitored during the process. The composition and structural features of the products were characterized by elemental analysis, X-ray diffraction, differential thermal analysis/ thermogravimetric technique, Raman spectroscopy, scanning and transmission electron microscopy, and energy-dispersive X-ray spectrometry. This self-induced growth process can produce SiC nanofibers and nanotubes ca. 20-100 nm in diameter with the aspect ratio higher than 1000. Bulk scale Raman studies showed the product to be comprised of mostly cubic polytype of SiC and that finite size effects are present. We believe that the nucleation mechanism involving radical gaseous species is responsible for 1-D nanostructures growth. The present study has enlarged the family of nanofibers and nanotubes available and offers a possible, new general route to 1-D crystalline materials.
ABSTRACT In the condensation reaction of nitromethane with glyoxal carried out in an aqueous solu... more ABSTRACT In the condensation reaction of nitromethane with glyoxal carried out in an aqueous solution of sodium hydroxide, 3,6-dinitro-cyclohexane-1,2,4,5-tetraol was obtained (the expected product, described in the literature) and, unexpectedly, also tricyclic nitro-triol (6b-nitrohexahydro-2H-1,3,5-trioxacyclopenta[cd]-pentalene-2,4,6-triol), which has been unknown until now, was obtained as the main product. The structure of the compound was confirmed with 1H NMR and 13C NMR spectroscopy, LR, and HR-MS techniques and with single-crystal X-ray diffractometry. The tricyclic triol (formally a hemiacetal) was transformed into 6b-nitrohexahydro-2H-1,3,5-trioxacyclopenta[cd]-pentalene-2,4,6-triyl trinitrate by reaction with 98 % HNO3. Some explosive properties of this compound were determined including: friction and impact sensitivity, activation energy, detonation velocity, heat of combustion in an oxygen atmosphere and enthalpy of formation. The nitrate ester is a powerful explosive with performance close to that of pentaerythritol tetranitrate (PETN).
The paper describes the combustion synthesis of carbon materials from hexachloroethane (C2Cl6), h... more The paper describes the combustion synthesis of carbon materials from hexachloroethane (C2Cl6), hexachlorobenzene (C6Cl6), and a mixture of these compounds. The chemical composition (elemental analysis), structural composition (XRD, Raman spectroscopy), microstructure (SEM), surface physicochemical properties (low-temperature nitrogen adsorption, XPS, FTIR) and electrochemical behavior (cyclic voltammetry) of the solid reaction products were investigated. Their unique structural and surface properties depend on the chemical composition of the starting compounds. The properties of the carbon samples tested are much like those of carbon black, but the material from hexachloroethane exhibits the most distinctly amorphous features. In contrast, the adsorptive properties (porous structure) of the sample obtained from hexachlorobenzene tend to resemble those of activated carbon.
An attempt has been made to visualise the process of the growth of SiC nanofibres after the combu... more An attempt has been made to visualise the process of the growth of SiC nanofibres after the combustion of CaSi2/PTFE mixtures, using a CCD camera working in the a schlieren mode. Moreover, overpressure histories, mass of solid combustion products and heat of combustion were measured in a closed reactor and compared with the results of thermochemical calculations. The mechanism of the formation of SiC nanofibres is discussed. In spite of a lot of work devoted to the synthesis of SiC nanofibres by combustion of CaSi2/PTFE mixtures, up to now their growth mechanism has not been fully explained. The analysis of SEM images and of the composition of the gaseous combustion products indicates that the growth of SiC nanofibres proceeds via the mechanism: vapour - liquid - solid (VLS) - Ref (6). In this work, an attempt was at the visualisation of the growth of SiC nanofibres, with the aid of a CCD camera with a schlieren system. Moreover, overpressure histories, mass of solid combustion prod...
1-D nanostructures of cubic phase silicon carbide (beta-SiC) were efficiently produced by combust... more 1-D nanostructures of cubic phase silicon carbide (beta-SiC) were efficiently produced by combustion synthesis of mixtures containing Si-containing compounds and halocarbons in a calorimetric bomb. The influence of the operating parameters on 1-D SiC formation yield was studied. The heat release, the heating rate, and the chamber pressure increase were monitored during the process. The composition and structural features of the products were characterized by elemental analysis, X-ray diffraction, differential thermal analysis/ thermogravimetric technique, Raman spectroscopy, scanning and transmission electron microscopy, and energy-dispersive X-ray spectrometry. This self-induced growth process can produce SiC nanofibers and nanotubes ca. 20-100 nm in diameter with the aspect ratio higher than 1000. Bulk scale Raman studies showed the product to be comprised of mostly cubic polytype of SiC and that finite size effects are present. We believe that the nucleation mechanism involving radical gaseous species is responsible for 1-D nanostructures growth. The present study has enlarged the family of nanofibers and nanotubes available and offers a possible, new general route to 1-D crystalline materials.
ABSTRACT In the condensation reaction of nitromethane with glyoxal carried out in an aqueous solu... more ABSTRACT In the condensation reaction of nitromethane with glyoxal carried out in an aqueous solution of sodium hydroxide, 3,6-dinitro-cyclohexane-1,2,4,5-tetraol was obtained (the expected product, described in the literature) and, unexpectedly, also tricyclic nitro-triol (6b-nitrohexahydro-2H-1,3,5-trioxacyclopenta[cd]-pentalene-2,4,6-triol), which has been unknown until now, was obtained as the main product. The structure of the compound was confirmed with 1H NMR and 13C NMR spectroscopy, LR, and HR-MS techniques and with single-crystal X-ray diffractometry. The tricyclic triol (formally a hemiacetal) was transformed into 6b-nitrohexahydro-2H-1,3,5-trioxacyclopenta[cd]-pentalene-2,4,6-triyl trinitrate by reaction with 98 % HNO3. Some explosive properties of this compound were determined including: friction and impact sensitivity, activation energy, detonation velocity, heat of combustion in an oxygen atmosphere and enthalpy of formation. The nitrate ester is a powerful explosive with performance close to that of pentaerythritol tetranitrate (PETN).
The paper describes the combustion synthesis of carbon materials from hexachloroethane (C2Cl6), h... more The paper describes the combustion synthesis of carbon materials from hexachloroethane (C2Cl6), hexachlorobenzene (C6Cl6), and a mixture of these compounds. The chemical composition (elemental analysis), structural composition (XRD, Raman spectroscopy), microstructure (SEM), surface physicochemical properties (low-temperature nitrogen adsorption, XPS, FTIR) and electrochemical behavior (cyclic voltammetry) of the solid reaction products were investigated. Their unique structural and surface properties depend on the chemical composition of the starting compounds. The properties of the carbon samples tested are much like those of carbon black, but the material from hexachloroethane exhibits the most distinctly amorphous features. In contrast, the adsorptive properties (porous structure) of the sample obtained from hexachlorobenzene tend to resemble those of activated carbon.
An attempt has been made to visualise the process of the growth of SiC nanofibres after the combu... more An attempt has been made to visualise the process of the growth of SiC nanofibres after the combustion of CaSi2/PTFE mixtures, using a CCD camera working in the a schlieren mode. Moreover, overpressure histories, mass of solid combustion products and heat of combustion were measured in a closed reactor and compared with the results of thermochemical calculations. The mechanism of the formation of SiC nanofibres is discussed. In spite of a lot of work devoted to the synthesis of SiC nanofibres by combustion of CaSi2/PTFE mixtures, up to now their growth mechanism has not been fully explained. The analysis of SEM images and of the composition of the gaseous combustion products indicates that the growth of SiC nanofibres proceeds via the mechanism: vapour - liquid - solid (VLS) - Ref (6). In this work, an attempt was at the visualisation of the growth of SiC nanofibres, with the aid of a CCD camera with a schlieren system. Moreover, overpressure histories, mass of solid combustion prod...
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