Synthesis and characterization of some carbon based nanostructures

The aim of present paper is to present the latest results on investigations of the carbon thin film deposited by Thermionic Vacuum Arc (TVA) method and laser pyrolysis. X-ray photoelectron spectroscopy (XPS) and X-ray generated Auger electron spectroscopy (XAES) were used to determine composition and sp2 to sp3 ratios in the outer layers of the film surfaces. The analyses were conducted in a Thermoelectron ESCALAB 250 electron spectrometer equipped with a hemispherical sector energy analyser. Monochromated Al K X-radiation was employed for the XPS examination, at source excitation energy of 15 KeV and emission current of 20 mA. Analyzer pass energy of 20 eV with step size of 0.1 eV and dwell time of 100 ms was used throughout

Properties, stability and aging in (Pb,Sr)TiO3_3-PbZrO3_{3}-Pb(Mg1/3_{1/3}Sb2/3_{2/3})O3_{3} ferroelectric ceramics

The variation with temperature of the dielectric and piezoelectric properties and dielectric properties aging of ferroelectric ceramics with composition Pb$_{0.95}$Sr$_{0.05}$Mg$_{0.042}$Sb$_{0.083}$Ti$_{0.45}$Zr$_{0.425}$O$_{3}$ are presented. Dielectric measurements evidenced a double relaxor system, characterized by very broad dielectric maximum at {\rm T}_{\rm m} = 190\,^{\circ}C (at 200 Hz) which shifted to 195 $^{\circ}$C at 200 kHz. This frequency dispersion is due to the partial relaxor characteristics of the material. A second anomaly appears as a shoulder at about 200 $^{\circ}$C in the imaginary part of the dielectric constant, both on heating and cooling curves. This could be attributed to the presence of a secondary relaxor system. The aging of dielectric properties has been investigated at different quenching temperatures below ${\rm T}_{\rm m}$. Aging and rejuvenation are found to be of relaxor type. This is rather surprising since the amount of relaxor phase content is relatively small. Properties variation with temperature has been measured up to 140 $^{\circ}$C. It has been found that the elastic and piezoelectric constants show only a small variation for temperatures up to 90 $^{\circ}$C

Investigation of the SiC thin films synthetized by Thermionic Vacuum Arc method (TVA)

Thermionic Vacuum Arc method (TVA) was used for the first time to prepare SiC thin films. This method is very suitable for deposition of high purity thin films with compact structure and extremely smooth in vacuum conditions. The nanocomposites were investigated using Transmission Electron Microscopy (TEM) analyses provided with HR-TEM and SAED facilities. The structure of the films can be indexed as following three forms: cubic structure of SiC (F4-3m) a = 0.4348 nm, cubic Si (Fd3m) a = 0.54307 nm and graphite (P63/mmc) a = 0.2456 nm; c = 0.6696 nm. The morphology, topography, wettability and wear properties were also performed by SEE system and by Raman Spectroscopy, increasing the interest for emerging applications