Abstract: An increasing of donor centres has been detected in n-InSb when it was submitted to anneal/quench with various annealing temperature (450 °C - 850 °C) and various annealing time (5 - 100 hours). A theoretical study of the kinetics of the conduction conversion of n-InSb at temperature annealing above 250 °C has been made. The present analysis indicates that the donor concentration increases with increasing of annealing time. In order to study this variation and to give a model for donor centres generated, a proposed model based on the simple kinetic is used to
fit the variation of donor concentration as a function of annealing time. However, from the best fit of experimental data using the proposed model, the activation energy is determined.
Abstract: Rapid Solidification Processing (RSP), of metals and alloys, is establish by increasing of the undercooling applying high cooling rates (102 - 106 K/s) or by reduce nucleation sites using low cooling rates (1 K/s). Melt undercooling opens new solidification pathways for new nonequilibrium phases and unusual microstructures. Several techniques have been developed to reduce nucleation sites and produce increased undercooling in metals and alloys including the fluxing technique. The aim of this paper is to study the influence of the undercooling level on microstructures of eutectic Sn-57wt%Bi alloy by using the fluxing technique. A morphological change from eutectic to eutectic plus primary dendrites bSn was observed when the undercooling increase from 10 K to 19 K and a refinement of the primary dendrites bSn was observed when the undercooling increase from 19 K to 29 K. Increasing the undercooling led to a higher growth rate, hence morphological refinement occur.
Abstract: Hardening laser surface offers new possibilities for the enhancement of the mechanical resistance of superficial layers. Essential for the laser treatment processes is the efficiency at which the incident laser power is coupled into the work piece. The aim of the work was to study the effect of some factors such as spot shape, beam angle of incidence and surface coating on the steel surface absorptivity. Samples made of carbon steel were laser processed using a CW CO2 - 1,2 kW laser unit. Different process parameters (beam power, spot dimension and traverse speed), were used. The microstructure of laser hardened layers which have been investigated by optical microscopy. The mechanical characterization of the layers has been done by hardness measurements. Correlation has been established between the structure of the laser-processed layers and the
Abstract: In the present work, a photoelectrochemical etching method had been performed on
resistive p-type Si (100) to eliminate the instability attributed to the high resistivity of substrate comparing to that of electrolyte. The anodization of p-type Si with resistivity ranging from 10 Ωcm to 30 kΩcm was done in HF/ethylene glycol. The resistivity of electrolyte was experimentally determinated by high frequency impedance measurements. As anodization proceeds structures of increasing characteristic size are formed then a steady state is reached, where macropore grow parallel. It shows that pore diameter increases with increasing HF concentration. Whereas, under laser He-Ne irradiation both of nanopores and macropores are observed during the anodization. The nanoporous layer showed to be varying with the light intensity and the anodization time.
The proprieties of the porous silicon were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and energy-dispersive X-ray (EDX).
Abstract: Indentation-induced structural phase transitions in single crystal Si(100) and
amorphous silicon a-Si have been investigated for indentations made at room temperature and at 77 K. The experimental techniques employed were (1) Raman microscopy and (2) in situ electrical resistance measurement of the indentation region of the plastically deformed silicon. The Raman spectra from residual indentations revealed that although phase transitions did occur when indentations were made at room temperature, there were no phase transitions when indentations were made at 77 K. This difference in behaviour has been explained on the rise of
temperature during the room temperature indentations, which may assist the phase transition process. The in situ electrical measurements have revealed that the deformed Si(100) yielded Ohmic behaviour, consistent with the view that during the indentation the cubic silicon transforms to the beta-Sn metallic phase (i.e. body-centre tetragonal).
Abstract: This work reports on the results of the experimental observation of development and
evolution of material damage during loading processes in aluminium alloy flat specimens with different pre-crack configurations by means of the new “X-ray Dynamic Defectoscopy” technique and by plastic strain increments identified by the optical Method of Interpolated Ellipses on the its surface. We have acquired good knowledge about the evolution of damage zone during loading. The
dependence of intensity and shape of damage zone on the crack configuration, part of the field previously little investigated experimentally, has been determined.
Abstract: Phonon spectra of Cd1-xMnxS (x = 0; 0.01; 0.05; 0.1; 0.15; 0.3) nanoparticles (d ~ 4.5 nm) have been investigated by far-infrared reflection (FIR) (spectral range 40 - 600 cm-1, temperature range 80 – 300 K) and Raman spectroscopy (100 – 700 cm-1, 300 K). Cd1-xMnxS nanoparticles have been synthesized by using aqueous solution precipitation. We obtained interesting features in FIR spectra: there are expected modes of bulk CdS (240 cm-1, 300 cm-1), new
modes connected with nano-size of CdS (130 cm-1, 170 cm-1) and additional mode at 120 cm-1 in Cd1-xMnxS nanoparticles which can be assigned to the presence of Mn. The position of obtained modes is discussed in the frame of the linear chain model with both mass and force constant defects. Raman spectroscopy gives us only the mode at 300 cm-1 and its second harmonic.
Abstract: Selenium vapour distribution and consumption during selenization process of Cu-In
metallic layers provided in a quasi-closed system with inert gas environment at atmospheric pressure were studied. A model taking into account the four most important mechanisms of Se consumption, namely the creation and maintenance of Se vapour over-pressure, the out-diffusion through open boundaries of quasi-closed system, the drift transport by constant nitrogen flux and chemical reactions with Cu-In metallic layers, is developed to estimate the total amount of selenium
required for selenization process. The diffusion mechanism was found to be dominating the selenium consumption for the used reactor design. Calculated values find a good agreement with experimental results from weighing of the Se source material before and after selenization.
Abstract: For the modeling of erythrocyte rouleaux we develop an approximation
procedure for the dipole moment in short cylinders, which contains the case of
ellipsoidal bodies only as a first approximation, but allows to include corrections
for short cylinders, more representative for such particles. In dependence on the
number of erythrocytes forming an aggregation, i.e. on different but discrete
measures of rouleaux lengths, the dielectrophoretic force is calculated and
represented against the frequency of the applied a.c. field. Predictions of
frequency regions in the range of 107 to 108 Hz are made, where the amount and
the direction of dielectrophoresis forces is different for different rouleaux sizes.