Thermodynamic calculations on the catalytic growth of multiwall carbon nanotubes

We have developed a thermodynamic model of the catalytic growth of multiwall carbon nanotubes from hydrocarbon precursors at elevated temperature. Using this model we have computed the heat distribution, and carbon concentration in the catalyst. Calculations delivered a analytical formula for the growth time and growth rate. We find that the growth is mainly driven by a concentration gradient within the catalyst, rather than a temperature gradient.Comment: 9 pages, 3 figures, 1 tabl

Comparative study of the catalytic growth of patterned carbon nanotube films

Three different catalysts (Fe, Ni, Co nitrates dissolved in ethanol) were patterned on a SiO2/Si substrate and multi-wall carbon nanotubes were grown by catalytic decomposition of acetylene. We compare the growth of the carbon nanostructures in the temperature range between 580C and 1000C. With our experimental set-up the catalyst solutions of cobalt and nickel were found to be less efficient than the one of iron. An optimal production of multi-wall nanotubes was observed at temperatures between 650C and 720C with the iron solution as catalyst. We found a tendency towards thicker structures with higher temperatures. Finally, we suggest a mechanism for the growth of these carbon structures.Comment: 5 pages, 5 figure

Raman spectroscopy and field emission measurements on catalytically grown carbon nanotubes

We used microcontact printing to pattern a silicon surface with an iron-containing catalytic solution. Multi-wall carbon nanotubes were subsequently grown on the patterned areas by chemical vapor deposition at temperatures between 650 and 1000C. We demonstrate that the diameter of the catalytically grown multi-wall nanotubes increases with the deposition temperature. Raman spectroscopy has been used to investigate the crystalline character of the obtained structures and it is found that the fraction of the nano-crystalline shell increases with the temperatures. The measurement of the field emission properties shows a correlation between the tube diameter and the emission field values.Comment: 6 pages, 6 figures, 1 tabl

Le corps en rêve, témoin de l’intégration psycho-corporelle

Lorsque le corps propre de l’analysant est représenté dans les rêves ou cauchemars, n’est-ce pas le signe d’un gain dans l’intégration du self ? User de ce matériel en cure, y compris dans les aspects obscurs de la cénesthésie du cauchemar, permet de suivre l’analysant de ce point de vue. Trois vignettes cliniques mises en lien avec les apports de Winnicott sur la psychosomatique illustrent cette thèse, ainsi qu’une digression sur l’intégration psycho-corporelle chez le peintre Füssli

A Biography of Richard J. Davant, Jr (1866-1915)

It is my intention that the information I will present will bring the reader to the conclusion that Richard J. Davant, Jr. was a progressively minded citizen who put the well being of those around him in higher regard that his own and who contributed significantly to the betterment of Savannah during the period 1903-1915.https://digitalcommons.georgiasouthern.edu/sav-bios-lane/1053/thumbnail.jp

Local probing of the field emission stability of vertically aligned multiwalled carbon nanotubes

Metallic cantilever in high vacuum atomic force microscope has been used as anode for field emission experiments from densely packed vertically aligned multi-walled carbon nanotubes. The high spatial resolution provided by the scanning probe technique allowed precise setting of the tip-sample distance in the submicron region. The dimension of the probe (curvature radius below 50nm) allowed to measure current contribution from sample areas smaller than 1um^2. The study of long-term stability evidenced that on these small areas the field emission current remains stable (within 10% fluctuations) several hours (at least up to 72 hours) at current intensities between 10-5A and 10-8A. Improvement of the current stability has been observed after performing long-time Joule heating conditioning to completely remove possible adsorbates on the nanotubes.Comment: 15 pages, 7 figure

Sino-Tibetan relations since 1940

The main text deals with Sino-Tibetan relations from 1940-1959 with particular emphasis on the Chinese takeover of Tibet in 1950 and the revolt against Chinese rule in 1959