Thermally Induced Microstructural Transformations of Fe72Si15B8V4Cu1 Alloy

Thermal stability, mechanism, and kinetics of thermally induced microstructural transformations and their effects on magnetic permeability of Fe₇₂Si₁₅B₈V₄Cu₁ alloy with combined amorphous/nanocrystalline structure were studied. DTA curves revealed two separated thermally activated exothermic events in the temperature ranges from 740 K to 820 K (467 °C to 547 °C) and 870 K to 930 K (597 °C to 657 °C). Crystalline phases present in the as-prepared and thermally treated alloy samples were identified, and their microstructural parameters were determined using XRD, while, to gain further insight into the mechanism of microstructural transformations, AFM and SEM–EDS analyses were performed. Deconvolution of the complex DTA peak into individual steps was conducted, and, in correlation with the results of microstructural analysis, kinetic triplets corresponding to individual transformation steps were determined, allowing for the estimation of the lifetimes of the alloy at different temperatures. Magnetic permeability measurements showed that, in spite of the influence of microstructural transformations on magnetic properties of the alloy, the favorable magnetic properties are retained over relatively a wide temperature range.

     

Modeling thermal effects in nano-devices

For the purpose of investigating the role of self-heating effects on the electrical characteristics of nano-scale devices, we implemented a two-dimensional Monte Carlo device simulator that self-consistently includes the solution of the energy balance equations for both, acoustic and optical phonons. We find less degradation in the current in smaller device structures because of the more pronounced velocity overshoot.     

Intermetallics as advanced cathode materials in hydrogen production via electrolysis

Intermetallics phases along Mo–Pt phase diagram have been investigated as cathode materials for the production of hydrogen by electrolysis from water KOH solutions, in an attempt to increase the electrolytic process efficiency. These materials were compared with conventional cathodes (Fe and Ni), often used in the alkaline electrolysis, and also with the intermetallic Ti–Pt. An significant upgrade of the electrolytic efficiency using intermetallics in pure KOH electrolyte was achieved in comparison with conventional cathode materials.     

Influence of microstructural inhomogeneity of individual sides of Fe81Si4B13C2 amorphous alloy ribbon on thermally induced structural transformations

As a result of the preparation process of Fe₈₁Si₄B₁₃C₂ amorphous alloy ribbon, a difference has been observed between the opposite sides of the ribbon in microstructure and surface morphology. Influence of these differences on thermally induced structural transformations was studied. Thermal treatment below 600 °C had a significant influence on the evolution of the microstructure, as well as phase composition of individual sides of the ribbon. Treatment at higher temperatures caused the microstructural differences between two sides to decrease significantly. Phase composition of the alloy samples showed the opposite trend: the differences observed were the greatest in the fully crystallized alloy, after treatment at 700 °C. These differences are the result of different numbers of nucleation sites for Fe₂B phase on respective sides of the ribbon, leading to 30% difference in its content on different sides in the fully crystallized alloy.     

Transparent exopolymeric particles' distribution in the northern Adriatic and their relation to microphytoplankton biomass and composition

Transparent exopolymer particles (TEP) are generated during transformation processes within the non-living organic matter continuum in the seawater. Seasonal dynamics of TEP along the Po River Delta-Rovinj transect was followed during the 3-year period, using a spectrophotometric method of determination of TEP. Relationships between TEP and phytoplankton biomass (chlorophyll a), abundance and composition, as well as phaeophytin, were analysed. Microphytoplankton spring blooms are confirmed to be an important source of TEP, with some species more related to TEP concentration dynamics, such as Chaetoceros sp. and Skeletonema costatum. Notable spatial west to east gradient of autotrophic biomass and consequently of TEP was observed, as well as gradual decrease with depth. In addition, TEP concentration increments were observed up to 2 months before the mucilage events followed by the decrease of TEP concentration during the event itself. Pattern of TEP dynamics in the years with mucilage events was the most pronounced in 2002, when the event was spatially and temporally the most extended.     

Marginal adaptation of composite resins under two adhesive techniques

In the present research, different adhesive techniques were used to set up fillings with composite resins. After the application of etch and rinse or self etch adhesive technique, marginal adaptation of composite fillings was estimated by the length of margins without gaps, and by the microretention of resin in enamel and dentin. The study material consisted of 40 extracted teeth. Twenty Class V cavities were treated with 35% phosphorous acid and restored after rinsing by Adper Single Bond 2 and Filtek Ultimate‐ASB/FU 3M ESPE composite system. The remaining 20 cavities were restored by Adper Easy One‐AEO/FU 3M ESPE composite system. Marginal adaptation of composite fillings was examined using a scanning electron microscope (SEM). The etch and rinse adhesive technique showed a significantly higher percentage of margin length without gaps (in enamel: 92.5%, in dentin: 57.3%), compared with the self‐etch technique with lower percentage of margin length without gaps, in enamel 70.4% (p < .001), and in dentin‐22.6% (p < .05). In the first technique, microretention was composed of adhesive and hybrid layers as well as resin tugs in interprismatic spaces of enamel, while the dentin microretention was composed of adhesive and hybrid layers with resin tugs in dentin canals. In the second technique, resin tugs were rarely seen and a microgap was dominant along the border of restoration margins. The SEM analysis showed a better marginal adaptation of composite resin to enamel and dentin with better microretention when the etch and rinse adhesive procedure was applied.     

Hydrogenation properties of Hf-Ni intermetallics - Experimental and theoretical investigation

The hydrogenation properties of HfNi and Hf₂Ni₇ intermetallics were investigated at the constant pressure of 1 bar and in the temperature ranges 373-573 K for HfNi and 323-473 K for Hf₂Ni₇. The kinetic parameters, rate constants and activation energies of the absorption processes were determined. Maximal hydrogen absorption, i.e., number of hydrogen atoms absorbed per metal atom, H/M, are 1.05 and 0.04 achieved at 373 K for HfNi and Hf₂Ni₇, respectively. Multiple hydriding/dehydriding was found to influence the improvement of the kinetic parameters. XRD and SEM methods were used to investigate the structural and morphological changes of the samples due to hydrogen absorption. The thermodynamic parameters of hydriding together with the structural properties of the intermetallics and their hydrides, calculated using the full-potential linearized augmented plane waves (FP-LAPW) code based on the density functional theory (DFT), were utilized for the sake of explaining the experimental investigations.     

Band-Structure and Quantum Effects on Hole Transport in p-MOSFETs

Using a Monte Carlo method, we investigate hole transport in ultrasmall p-channel Si MOSFETs with gate lengths of 25 nm. The device simulator couples a 2D Poisson solver with a discretized 6 × 6 k.p Hamiltonian solver that includes the effect of the confining potential and provides the subband structure in the channel region. In addition, carriers in the source and drain regions are treated as quasi 3D particles and the band-structure information is included by solving for the eigenenergies of a more compact 6× 6 k.p Hamiltonian.