Publications

Study of industrial lubricants is made by the assistance of a transmission electronic n-kroscope (TEM) and electrons diffraction on a selected surface (SAED). Researches allow tribological characterization of the lubricant behavior, structural particles visualization and accomplish moi-pholo,-ical and dimensional evaluation of component particles of lubricants. Obtained data from H 46 - hydraulic oil, M30 multigrade motor oil, 5W30 winter motor oil, in fresh and used state and used toothing oil give information about forms, defects, dimensions, crystallographic phases and statistical parameters of industrial lubricants states.

The Ba(Zn1/3Ta2/3)O-3 (BZT) ceramic samples were prepared by solid-state reaction and sintered in the range 1550-1650 degrees C for 2 h. Several methods-X-ray diffraction (XRD) and scanning electron microscopy (SEM)-were used for structural and morphological characterization. The unit cell distortion and the presence of the secondary phase content were studied by XRD. A long-range order with a 2:1 ratio of Ta and Zn cations on the octahedral positions of the perovskite structure was noticed with the increase of the sintering temperature. SEM investigations revealed polyhedral well-faceted grains and large grain size distribution. The dielectric properties in the microwave range were measured at room temperature and at 1 kHz on a large temperature interval (+/- 150 degrees C). The dielectric parameters were correlated with morphological and structural properties. Ceramic samples were annealed at 1410 degrees C for 30 h to improve the microwave properties. The dielectric constant of BZT samples measured at 6 GHz and at 1 kHz was between 27 and 28 on the whole temperature range, that is, typical values for BZT material. The temperature coefficient of the resonance frequency at 6 GHz exhibits positive values less than 6 ppm/degrees C.

The paper reports on the main findings issued from studying the formation of adsorbed micelle-like clusters of ionic surfactant (sodium dodecyl sulfate and hexadecyl trimethylammonium bromide) onto molecule of collagenous polypeptide (collagen hydrolyzates and calfskin collagen type 1). Capillary viscometry, UV-circular dichroism, transmission electron microscopy and surfactant titration method were used to characterize the macromolecular component of the studied systems. To highlight the critical aggregation concentration (cac) and the critical saturation concentration (T-2) in the investigated polypeptide-surfactant systems, the steady-state fluorescence of pyrene (1(1)/1(3) rule) and the surface tension measurements (the droplet volume method) were availed. The study revealed a significant decrease of the effective micelle concentration of surfactant (cue) in the presence of polypeptide irrespective of pH and a critical concentration T-2 depending on the system composition and pH.

The interactions by which ions lose their energy in silicon are investigated at the microscopic level. this theoretical study put in evidence that the ionization could also represent a source of structural defects, and, contrary to the processes initiated by elementary particles, could generate extended primary defects, as, e.g. four-fold coordinated defects, due to the simultaneous breaking of bond for more neighbouring atoms in the lattice in a single interaction, in the ionisation core. The average energy transferred per atom is calculated, and also the energy spent by ionisation. The time dependence of the temperature in the ionisation core is derived in some simplifying assumptions. These contributions not considered yet in the studies of degradation of silicon detectors in radiation fields and could account for the discrepancies observed between models and measurements at microscopic versus device level for hadrons and ions. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

12 different marble and limestone samples collected from well-known Greek quarries have been investigated by X-ray diffraction and electron paramagnetic resonance (EPR). Xray diffraction spectra permitted to determine both major (calcite and dolomite) and minor (quartz or magnesite) mineralogical components. EPR has been used to investigate the same samples unirradiated and after 10 kGy gamma-ray irradiation. The unirradiated samples display typical EPR spectra of Mn2+ in calcite and dolomite as well as a superposition of these while some samples displayed EPR free radicals signals of centers (low field signal) and centers (high field signal). From X-ray diffraction and EPR spectra it was possible to extract numerical values of several numerical parameters such as dolomite to calcite ratio, EPR intensity parameter, and low field to high field EPR signals intensity ratio. These values as well as the correlation coefficients between the digital functions that described the low field Mn2+ ions EPR line have been used as entry data for cluster analysis to quantify the resemblance and differences between analyzed samples.

We present the fabrication and transport properties of a series of composites made of La2/3Sr1/3MnO3 and acrylamide-based copolymers. The most important result is the very narrow transition, of only 27 K, displayed by the peak that appears around the metal-insulator transition of the composites made with poly(acrylamide-vinylacetate). Although the amount of polymer is rather low, different copolymers change drastically the electric transport characteristics. Copyright (C) 2009

The laser pyrolysis became a useful tool, providing various ways, in production of nano materials. The iron Mossbauer spectroscopy is one very accurate method in evidencing the physical properties and related processes in the nano scale compounds. The effect of pressure, laser spot area and induced combustion, of gas mixture and laser power on the phase composition and inside particle distribution, grain size as well as the related phenomena were investigated by temperature dependent Mossbauer spectroscopy. A selection of most relevant properties is presented and discussed in details.

The output performances of a Nd:YAG laser passively Q-switched by Cr(4+):YAG saturable absorber are investigated function of temperature. Small variations in pulse energy and duration were observed over the 25 degrees C to 150 degrees C range. (C) 2009 Optical Society of America

The possibility to make surface measurements in the nano or micro range by Mossbauer spectroscopy using (151)Eu Mossbauer isotope is demonstrated. Measurements were made with a new flow detector in a backscattering geometry. With this detector it is possible to detect conversion electrons or low energy X-rays. An Eu(2)O(3) sample has been used. These measurements have been performed for the first time in Romania.

Fabrication of Au-Ti Schottky structure on GaAs semi-insulating wafer was related to an ultra-high vacuum deposition condition and low vacuum annealing in low vacuum and temperature range T=320-360 degrees C. There are presented representative I-V characteristics in dark and in different light (power levels). The spectral response has a maximum in Delta lambda = (850-950) nm corresponding to a band-to-band transition. The complex dependence of optical generated non-equilibrium carriers is related to the equivalent state density at the conduction band edge (in T(3/2) factor) and in exponential distribution factor exp (-(E-F)/kT).