Selective Adsorption from Methanol/Water Mixtures by C\u3csub\u3e60\u3c/sub\u3e Fullerene Nanospheres

Micro-Raman spectroscopy was used to investigate the selective adsorption of methanol/water mixtures on the surface of [60] fullerene nanospheres. C60 molecules were dispersed in methanol/water mixtures with different methanol molar fractions ranging between 1 and 0.5. The Raman active pentagon pinch mode shifted significantly (±4 cm−1) as the mixture composition was changed. The shift in the Raman mode was sinusoidal in nature indicating that methanol then water is adsorbed preferentially on the fullerene surface at different mixture compositions. The observed behavior is attributed to structure forming effects of alcohol/water mixtures and the shape and size effect of fullerene surface

Selective Adsorption from Methanol/Water Mixtures by C\u3csub\u3e60\u3c/sub\u3e Fullerene Nanospheres

Micro-Raman spectroscopy was used to investigate the selective adsorption of methanol/water mixtures on the surface of [60] fullerene nanospheres. C60 molecules were dispersed in methanol/water mixtures with different methanol molar fractions ranging between 1 and 0.5. The Raman active pentagon pinch mode shifted significantly (±4 cm−1) as the mixture composition was changed. The shift in the Raman mode was sinusoidal in nature indicating that methanol then water is adsorbed preferentially on the fullerene surface at different mixture compositions. The observed behavior is attributed to structure forming effects of alcohol/water mixtures and the shape and size effect of fullerene surface

Raman Mapping of Local Phases and Local Stress Fields in Silicon–Silicon Carbide Composites

Silicon–silicon carbide (Si–SiC) composites have emerged as a new class of materials with superior properties like high resistance against oxidation and corrosion, low thermal expansion coefficient and high mechanical strength. This enabled the composite to be successfully utilized in different industrial applications, such as combustion chambers, gas turbines, heat exchangers, fusion reactors, seal rings, welding nozzles, valve discs and ceramic engine parts. The strength of such composites showed a dependence upon their internal granular structure, since the latter was found to affect local stress distribution in the composite. In this study, we developed a Raman spectroscopy based technique to monitor local composition and local stress fields in Si–SiC composites. The Raman technique was used to monitor local stress fields’ development as the composite is globally loaded in compression for two different composites with reinforcement volume fractions of 13 and 34%. Our results show that the Raman based technique is very suitable for monitoring the local stress fields and their development as the composite is globally loaded. Secondly, it was found that in composites with high volume fraction of reinforcement, local stress fields are more uniform and homogeneous than in composites with low fraction of reinforcement

Raman Mapping of Local Phases and Local Stress Fields in Silicon–Silicon Carbide Composites

Silicon–silicon carbide (Si–SiC) composites have emerged as a new class of materials with superior properties like high resistance against oxidation and corrosion, low thermal expansion coefficient and high mechanical strength. This enabled the composite to be successfully utilized in different industrial applications, such as combustion chambers, gas turbines, heat exchangers, fusion reactors, seal rings, welding nozzles, valve discs and ceramic engine parts. The strength of such composites showed a dependence upon their internal granular structure, since the latter was found to affect local stress distribution in the composite. In this study, we developed a Raman spectroscopy based technique to monitor local composition and local stress fields in Si–SiC composites. The Raman technique was used to monitor local stress fields’ development as the composite is globally loaded in compression for two different composites with reinforcement volume fractions of 13 and 34%. Our results show that the Raman based technique is very suitable for monitoring the local stress fields and their development as the composite is globally loaded. Secondly, it was found that in composites with high volume fraction of reinforcement, local stress fields are more uniform and homogeneous than in composites with low fraction of reinforcement

Sensing Surface Phase Transitions on Fullerene C\u3csub\u3e60\u3c/sub\u3e Nanospheres in Water-Ethanol Mixture

This paper reports the results of a study of adsorption of small molecules on the surface of buckminsterfullerene, C60 and on single walled carbon nanotubes (SWNT). The pressure dependence of the Raman spectrum was investigated over the range 0-100 kbar in methanol-water mixtures that were used as the pressure-transmitting-fluid (PTF) in a diamond anvil cell. It is found that the spectral shift and its pressure derivative are sensitive to both the applied pressure and to the composition of the PTF. These observations are consistent with an explanation that involves preferential adsorption onto the surface of the C/sub 60/. In particular, the notion of C60 collapse need not be invoked to explain the observations

Raman Investigation of Single Walled Carbon Nanotubes and Fullerene [60] Under High Hydrostatic Pressure

Raman spectroscopy is a technique that probes materials on the molecular level by monitoring inherent vibrational modes. The technique has been successfully utilized to investigate material systems on the micro and the meso-scales and more recently has proven its ability to exploring systems on the nano-scale

Study of the Hydrostatic Pressure Dependence of the Raman Spectrum of Single-Walled Carbon Nanotubes and Nanospheres

We have investigated the behavior of single-walled carbon nanotubes and nanospheres(C60) under high hydrostaticpressure using Raman spectroscopy over the pressure range 0.2–10 GPa using a diamond anvil cell. Different liquid mixtures were used as pressure transmission fluids (PTF). Comparing the pressure dependence of the Raman peak positions for the nanotubes and the nanospheres in different PTF leads to the observation of a number of new phenomena. The observed shift in Raman peak position of both radial and tangential modes as a function of applied pressure and their dependence on the PTF chemical composition can be rationalized in terms of adsorption of molecular species from the of PTF on to the surface of the carbon nanotubes and/or nanospheres. The peak shifts are fully reversible and take place at a comparatively modest pressure (2–3 GPa) that is far below pressures that might be required to collapse the nanoparticles.Surfaceadsorption of molecular species on the nanotube or nanospheres provides a far more plausible rational for the observed phenomena than ideas based on the notion of tube collapse that have been put forward in the recent literature

Sensing Surface Phase Transitions on Fullerene C\u3csub\u3e60\u3c/sub\u3e Nanospheres in Water-Ethanol Mixture

This paper reports the results of a study of adsorption of small molecules on the surface of buckminsterfullerene, C60 and on single walled carbon nanotubes (SWNT). The pressure dependence of the Raman spectrum was investigated over the range 0-100 kbar in methanol-water mixtures that were used as the pressure-transmitting-fluid (PTF) in a diamond anvil cell. It is found that the spectral shift and its pressure derivative are sensitive to both the applied pressure and to the composition of the PTF. These observations are consistent with an explanation that involves preferential adsorption onto the surface of the C/sub 60/. In particular, the notion of C60 collapse need not be invoked to explain the observations

Raman Investigation of Fullerene [60] under Hydrostatic Pressure

We report the results of a study of adsorption of small molecules on the surface of buckminsterfullerene, C60. The pressure dependence of the Raman spectrum was investigated over the range 0–10 GPa in methanol-water mixtures that were used as the pressure transmitting fluid (PTF) in a diamond anvil cell. It is found that the spectral shift and its pressure derivative are sensitive to both the applied pressure and to the composition of the PTF. These observations are consistent with an explanation that involves preferential adsorption onto the surface of the C60. In particular, the notion of C60 collapse needs not be invoked to explain the observations