The effect of matrix on melting and solidification behaviours of embedded Pb-Sn alloy nanoparticles

The present investigation is aimed at understanding the effect of a matrix on the phase transformation of biphasic embedded Pb–Sn alloy nanoparticles. The melting and solidification behaviours of eutectic (Pb_26.1Sn_73.9) nanoparticles embedded in icosahedral (IQC) as well as decagonal quasicrystalline (DQC) matrix have been studied. Electron microscopic observations reveal that the major portion of the alloy nanoparticle consists of body-centred tetragonal β-(Sn) with face-centred cubic (Pb) constituting the cap. (Pb) bears specific orientation relationships (OR) with the surrounding IQC matrix, whereas β-(Sn) does not have any specific OR. For alloy particles embedded in the DQC matrix, both (Pb) and β-(Sn) bear specific OR. In case of IQC matrix, differential scanning calorimetric measurements reveal sharp melting but diffuse solidification peaks for the embedded nanoparticles. On the other hand, sharp melting and solidification peaks are observed for the nanoparticles embedded in the DQC matrix. The IQC and DQC are heat-treated at different temperatures to observe the effect of the matrix on the phase transformation of the alloy nanoparticles. The formation of well- developed facets in the nano-particles and defects in the matrix have been found to play a crucial role in determining the phase transformation of the alloy nanoparticles in the heat-treated samples. The experimental observations are rationalized using available literature.     

Capacitive properties of the hydrophobic [2-(methacryloyloxy)ethyl]-trimethyl ammonium nonafluoro-1-butanesulfonate poly(ionic liquid) thin film

The capacitive behavior of the hydrophobic fluorinated polymeric ionic liquid, poly[2-(methacryloyloxy)ethyl]-trimethyl ammonium nonafluoro-1-butanesulfonate (poly-IL), has been investigated by current-voltage (C-V) measurements and electrochemical impedance spectroscopy (EIS) using a cell featured by a ITO/poly-IL/Al sandwich structure. The data were collected in the temperature range between 30 and 60 °C. The Nyquist plot shows a slope variation that indicates a moderate increasing of the ions mobility with temperature. The Bode diagram reveals that the sample exhibits a capacitive behavior below 10⁴ Hz with no redox processes at the electrodes as confirmed by the C–V curves. The material shows a relatively high thermal stability, probably due to its polymeric nature making the capacitor almost insensitive to the variation of the operating temperature.     

Vibration Problems in Selected Torsional Mechanical Systems

The paper deals with vibrations of mechanical systems torsionally deformed. These problems can be discussed using two-dimensional or one-dimensional models. After the presentation of basic equations for two-dimensional problems, the study is focused on one-dimensional problems for discrete-continuous systems with a local nonlinearity and on the effect of the local nonlinearity on the behaviour of these systems.     

Consecutive two-photon absorption of azulene in solution utilizing dye lasers

We report a spectroscopic study of consecutive two-photon absorption of azulene excited in the range 32800–42000 cm^?1, which provides information concerning the cross sections for the S₁ → S₃ and the S₁ → S₄ transitions.     

Magnetic-field-induced suppression of electronic conduction in a superlattice

We use a magnetic field applied along the axis of a semiconductor superlattice (SL) as a controllable means of creating a one-dimensional band structure. We demonstrate that the current flow through the SL is strongly suppressed when the electron motion perpendicular to the SL axis is strongly confined by the quantizing magnetic field. By modeling this behavior using semiclassical and nonequilibrium Green's function methods, we show that the observed quenching arises from a qualitative change in electron dynamics caused by increasing quantum confinement.     

Study of the ligand substitution reaction Fe (CN)5H2O3− + pyrazine in micellar solutions

The ligand substitution reaction Fe(CN)₅H₂O³⁻ + pyrazine → Fe(CN)₅ pyrazine³⁻ + H₂O has been studied in sodium dodecyl sulfate SDS, hexadecyltrimethylammonium bromide, CTAB, and salt aqueous solutions at 298.2 K. Kinetics were studied in dilute and concentrated salt solutions and in SDS and CTAB solutions at surfactant concentrations below and above the critical micelle concentration. Experimental results show that salt effects can be explained by considering the interaction between the cations present in the working media which come from the background electrolyte, and the Fe(CN)₅H₂O³⁻ species in the vicinity of the cyanide ligands. This interaction makes the release of the aqua ligand from the inner-coordination shell of the iron(II) complex to the bulk more difficult resulting in a decrease of the reaction rate when the electrolyte concentration increases. Kinetic data in surfactant solutions show that not only micellized surfactants are operative kinetically, but also nonmicellized surfactants are influencing the reactivity. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 377–384, 1997     

Micellar medium effects on the hydrolysis of phenyl chloroformate in ionic,zwitterionic, nonionic,and mixed micellar solutions

The spontaneous hydrolysis of phenyl chloroformate was studied in various anionic, nonionic, zwitterionic, and cationic aqueous micellar solutions, as well as in mixed anionic–nonionic micellar solutions. In all cases, an increase in the surfactant concentration results in a decrease in the reaction rate and micellar effects were quantitatively explained in terms of distribution of the substrate between water and micelles and the first‐order rate constants in the aqueous and micellar pseudophases. A comparison of the kinetic data in nonionic micellar solutions to those in anionic and zwiterionic micellar solutions makes clear that charge effects of micelles is not the only factor responsible for the variations in the reaction rate. Depletion of water in the interfacial region and its different characteristics as compared to bulk water, the presence of high ionic concentration in the Stern layer of ionic micelles, and differences in the stabilization of the initial state and the transition state by hydrophobic interactions with surfactant tails can also influence reactivity. The different deceleration of the reaction observed in the various micellar solutions studied was discussed by considering these factors. Synergism in mixed‐micellar solutions is shown through the kinetic data obtained in these media. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 445–451, 2002     

The resonant tunneling of holes through double-barrier structures with InAs QDs at the center of a GaAs quantum well

The effect of InAs quantum dots (QDs) grown in the center of a GaAs quantum well on the tunneling characteristics of resonant-tunneling diodes based on p-AlAs/GaAs/AlAs heterostructures is studied. The introduction of QDs results in a shift and broadening of resonance peaks in the current-voltage characteristics of the diodes; however, this effect is found to be strongly dependent on the number of the 2D subband involved in the tunneling. The obtained dependence is attributed to origination of the fluctuation potential in the vicinity of the QD layer.     

Photoquantum Hall Effect and Light‐Induced Charge Transfer at the Interface of Graphene/InSe Heterostructures

The transfer of electronic charge across the interface of two van der Waals crystals can underpin the operation of a new class of functional devices. Among van der Waals semiconductors, an exciting and rapidly growing development involves the “post‐transition” metal chalcogenide InSe. Here, field effect phototransistors are reported where single layer graphene is capped with n‐type InSe. These device structures combine the photosensitivity of InSe with the unique electrical properties of graphene. It is shown that the light‐induced transfer of charge between InSe and graphene offers an effective method to increase or decrease the carrier density in graphene, causing a change in its resistance that is gate‐controllable and only weakly dependent on temperature. The charge transfer at the InSe/graphene interface is probed by Hall effect and photoconductivity measurmentes and it is demonstrated that light can induce a sign reversal of the quantum Hall voltage and photovoltaic effects in the graphene layer. These findings demonstrate the potential of light‐induced charge transfer in gate‐tunable InSe/graphene phototransistors for optoelectronics and quantum metrology.     

Fibrant extensions of free G-spaces

We show that any equivariant fibrant extension of a compact free G-space is also free. This result allows us to prove that the orbit space of any equivariant fibrant compact space E is also fibrant, provided that E has only one orbit type.