Advances in Condensed Matter Physics
[SJR: 0.248] [H-I: 10] [8 followers] Follow
Open Access journal
ISSN (Print) 1687-8108 - ISSN (Online) 1687-8124
Published by Hindawi [334 journals]
- Theoretical Study of Upper Critical Magnetic Field () in Multiband Iron
Abstract: This research work focuses on the theoretical investigation of the upper critical magnetic field, ; Ginzburg-Landau coherence length, ; and Ginzburg-Landau penetration depth, , for the two-band iron based superconductors , , and LiFeAs. By employing the phenomenological Ginzburg-Landau (GL) equation for the two-band superconductors , , and LiFeAs, we obtained expressions for the upper critical magnetic field, ; GL coherence length, ; and GL penetration depth, , as a function of temperature and the angular dependency of upper critical magnetic field. By using the experimental values in the obtained expressions, phase diagrams of the upper critical magnetic field parallel, , and perpendicular, , to the symmetry axis (-direction) versus temperature are plotted. We also plotted the phase diagrams of the upper critical magnetic field, versus the angle . Similarly, the phase diagrams of the GL coherence length, , and GL penetration depth, , parallel and perpendicular to the symmetry axis versus temperature are drawn for the superconductors mentioned above. Our findings are in agreement with experimental observations.
PubDate: Mon, 05 Dec 2016 08:30:18 +000
- Short Time and Low Temperature Reaction between Metal Oxides through
Microwave-Assisted Hydrothermal Method
Abstract: This work demonstrates the possibility of synthesis of cadmium tungstate at low temperatures using oxide precursors. Cadmium tungstate (CdWO4) scintillator was produced via microwave-assisted hydrothermal reaction using the precursors CdO and WO3. The methodology was based on microwave radiation for heating, which is remarkably faster than the solid-state route or conventional hydrothermal procedure. CdWO4 monoclinic (wolframite) structure was successfully obtained at 120°C for synthesis times as short as 20 min. This route does not require the use of templates or surfactants and yields self-assembled nanorods with size of around 24 ± 9 nm width and 260 ± 47 nm length. The growth mechanism for the formation of CdWO4 involves microwave-induced dissociation of the reagents and solvation of Cd2+ and ions, which are free to move and start the nucleation process. The luminescence properties of the produced nanoparticles were investigated, presenting a broad emission band at around 500 nm, which is comparable to that observed for samples produced using other chemical routes. This result highlights the great potential of the proposed method as a low-cost and time saving process to fabricate luminescent oxide nanoparticles.
PubDate: Wed, 30 Nov 2016 12:29:44 +000
- High Field Linear Magnetoresistance Sensors with Perpendicular Anisotropy
L10-FePt Reference Layer
Abstract: High field linear magnetoresistance is an important feature for magnetic sensors applied in magnetic levitating train and high field positioning measurements. Here, we investigate linear magnetoresistance in Pt/FePt/ZnO/Fe/Pt multilayer magnetic sensor, where FePt and Fe ferromagnetic layers exhibit out-of-plane and in-plane magnetic anisotropy, respectively. Perpendicular anisotropy L10-FePt reference layer with large coercivity and high squareness ratio was obtained by in situ substrate heating. Linear magnetoresistance is observed in this sensor in a large range between +5 kOe and −5 kOe with the current parallel to the film plane. This L10-FePt based sensor is significant for the expansion of linear range and the simplification of preparation for future high field magnetic sensors.
PubDate: Wed, 02 Nov 2016 13:37:57 +000
- Large-Signal DG-MOSFET Modelling for RFID Rectification
Abstract: This paper analyses the undoped DG-MOSFETs capability for the operation of rectifiers for RFIDs and Wireless Power Transmission (WPT) at microwave frequencies. For this purpose, a large-signal compact model has been developed and implemented in Verilog-A. The model has been numerically validated with a device simulator (Sentaurus). It is found that the number of stages to achieve the optimal rectifier performance is inferior to that required with conventional MOSFETs. In addition, the DC output voltage could be incremented with the use of appropriate mid-gap metals for the gate, as TiN. Minor impact of short channel effects (SCEs) on rectification is also pointed out.
PubDate: Wed, 26 Oct 2016 09:31:23 +000
- Renormalized Phonon Microstructures at High Temperatures from
First-Principles Calculations: Methodologies and Applications in Studying
Strong Anharmonic Vibrations of Solids
Abstract: While the vibrational thermodynamics of materials with small anharmonicity at low temperatures has been understood well based on the harmonic phonons approximation, at high temperatures, this understanding must accommodate how phonons interact with other phonons or with other excitations. To date the anharmonic lattice dynamics is poorly understood despite its great importance, and most studies still rely on the quasiharmonic approximations. We shall see that the phonon-phonon interactions give rise to interesting coupling problems and essentially modify the equilibrium and nonequilibrium properties of materials, for example, thermal expansion, thermodynamic stability, heat capacity, optical properties, thermal transport, and other nonlinear properties of materials. The review aims to introduce some recent developements of computational methodologies that are able to efficiently model the strong phonon anharmonicity based on quantum perturbation theory of many-body interactions and first-principles molecular dynamics simulations. The effective potential energy surface of renormalized phonons and structures of the phonon-phonon interaction channels can be derived from these interdependent methods, which provide both macroscopic and microscopic perspectives in analyzing the strong anharmonic phenomena while the traditional harmonic models fail dramatically. These models have been successfully performed in the studies on the temperature-dependent broadenings of Raman and neutron scattering spectra, high temperature phase stability, and negative thermal expansion of rutile and cuprite structures, for example.
PubDate: Wed, 19 Oct 2016 07:23:26 +000
- Determination of the Density of Energy States in a Quantizing Magnetic
Field for Model Kane
Abstract: For nonparabolic dispersion law determined by the density of the energy states in a quantizing magnetic field, the dependence of the density of energy states on temperature in quantizing magnetic fields is studied with the nonquadratic dispersion law. Experimental results obtained for PbTe were analyzed using the suggested model. The continuous spectrum of the energy density of states at low temperature is transformed into discrete Landau levels.
PubDate: Sun, 16 Oct 2016 10:05:09 +000
- A Simple Free Energy for the Isotropic-Nematic Phase Transition of Rods
Abstract: A free energy expression is proposed that describes the isotropic-nematic binodal concentrations of hard rods. A simple analytical form for this free energy was yet only available using a Gaussian trial function for the orientation distribution function (ODF), leading, however, to a significant deviation of the predicted binodals. The new free energy proposed here is based upon a rationalized correction to the orientational and packing entropies when using the Gaussian ODF. In combination with Parsons-Lee theory or scaled particle theory, it enables describing the isotropic-nematic phase coexistence concentrations of rods accurately using the simple Gaussian ODF for a wide range of aspect ratios.
PubDate: Tue, 11 Oct 2016 10:03:40 +000
- Micromagnetic Simulation of Strain-Assisted Current-Induced Magnetization
Abstract: We investigated the effect of substrate misfit strain on the current-induced magnetization switching in magnetic tunnel junctions by combining micromagnetic simulation with phase-field microelasticity theory. Our results indicate that the positive substrate misfit strain can decrease the critical current density of magnetization switching by pushing the magnetization from out-of-plane to in-plane directions, while the negative strain pushes the magnetization back to the out-of-plane directions. The magnetic domain evolution is obtained to demonstrate the strain-assisted current-induced magnetization switching.
PubDate: Thu, 22 Sep 2016 13:45:40 +000
- Pressure Prediction of Electronic, Anisotropic Elastic, Optical, and
Thermal Properties of Quaternary (M2/3Ti1/3)3AlC2 (M = Cr, Mo, and Ti)
Abstract: The electronic, mechanical, anisotropic elastic, optical, and thermal properties of quaternary (M2/3Ti1/3)3AlC2 (M = Cr, Mo, and Ti) under different pressure are systematically investigated by first-principles calculations. The bonding characteristics of these compounds are the mixture of metallic and covalent bonds. With an increase of pressure, the heights of total density of states (TDOS) for these compounds decrease at Fermi level. The highest volume compressibility among three compounds is Mo2TiAlC2 for its smallest relative volume decline. The relative bond lengths are decreasing when the pressure increases. The bulk and shear modulus of the one doped with Cr or Mo are larger than those of Ti3AlC2 with pressure increasing. With an increase of pressure, the anisotropy of these compounds also increases. Moreover, Mo2TiAlC2 has the biggest anisotropy among the three compounds. The results of optical functions indicate that the reflectivity of the three compounds is high in visible-ultraviolet region up to ~10.5 eV under ambient pressure and increasing constantly when under pressure. Mo2TiAlC2 has the highest loss function. The calculated sound velocity and Debye temperature show that they all increase with pressure. of the three compounds is also calculated.
PubDate: Mon, 19 Sep 2016 07:32:54 +000
- Electronic and Magnetic Properties Studies on Mn and Oxygen Vacancies
Codoped Anatase TiO2
Abstract: The electronic and magnetic properties of Mn and oxygen vacancies codoped anatase TiO2 were investigated. The calculated results showed that the TiO2 codoped with Mn and oxygen vacancies have a magnetic moment value of 3.415 per Ti31MnO63 supercell. Furthermore, Ti31MnO63 gets the lowest energy with a geometrical optimization where the Mn ions locate at the nearest-neighbor sites of the oxygen vacancy. And experimental results indicated the magnetism is associated with the defects of Mn ions and oxygen vacancies induced by the Mn doping, which is consistent with the calculation results.
PubDate: Sun, 18 Sep 2016 11:47:27 +000
- Origins of the Exchange-Bias Phenomenology, Coercivity Enhancement, and
Asymmetric Hysteretic Shearing in Core-Surface Smart Nanoparticles
Abstract: We have used a spin-1 Ising model Hamiltonian with dipolar (bilinear, ), quadrupolar (biquadratic, ), and dipolar-quadrupolar (odd, ) interactions in pair approximation to investigate the exchange-bias (EB), coercive field, and asymmetric hysteretic shearing properties peculiar to core/surface () composite nanoparticles (NPs). Shifted hysteresis loops with an asymmetry and coercivity enhancement are observed only in the presence of the odd interaction term in the Hamiltonian expression and their magnitudes show strong dependence on the value of . The observed coercivity and EB in NPs originated from nonzero odd coupling energies and their dependence on temperature () and particle size () are also discussed in relation to experimental findings.
PubDate: Sun, 04 Sep 2016 06:29:57 +000
- Impact of Pressure and Brine Salinity on Capillary Pressure-Water
Saturation Relations in Geological CO2 Sequestration
Abstract: Capillary pressure-water saturation relations are required to explore the CO2/brine flows in deep saline aquifers including storage capacity, relative permeability of CO2/brine, and change to stiffness and volume. The study on capillary pressure-water saturation curves has been conducted through experimentation and theoretical models. The results show that as the pressure increases up to 12 MPa, (1) capillary pressure-water saturation curves shift to lower values at given water saturation, (2) after the drainage process, residual water saturation decreases, and (3) after the imbibition process, capillary CO2 trapping increases. Capillary pressure-water saturation curves above 12 MPa appear to be similar because of relatively constant contact angle and interfacial tension. Also, as brine salinity increases from 1 M to 3 M NaCl, (1) capillary pressure-water saturation curves shift to lower capillary pressure, (2) residual water saturation decreases, and (3) capillary CO2 trapping increases. The results show that pressure and brine salinity have an influence on the capillary pressure-water saturation curves. Also, the scaled capillary CO2 entry pressure considering contact angle and interfacial tension is inconsistent with atmospheric conditions due to the lack of wettability information. Better exploration of wettability alteration is required to predict capillary pressure-water saturation curves at various conditions that are relevant to geological CO2 sequestration.
PubDate: Mon, 29 Aug 2016 08:59:18 +000
- Dosimetric UV Exposure Effect on the Optical Properties of Ag2O Doped
Abstract: Silver phosphate glass types within composition 60P2O5-30ZnO-10CuO-100000 ppm Ag2O were prepared by melt-quenching technique. The optical properties of these glass types were studied under UV exposure at different times, 0, 20, 80, 105, and 115 minutes. The optical absorbance spectra were measured in the range of wavelength from 190 to 3200 nm. The absorbance bandwidth decreases with increasing the time of UV exposure. The optical energy gap, , linear refractive index, , ratio between molar refraction, , and molar volume, , and metallization criterion () were estimated. The value of decreases from 2.132 to 1.91 eV with increasing the time of UV exposure from 0 to 115 min. Otherwise value and metallization increase with increase in the time of UV exposure. The results indicated that these glass types are promising for using an ultraviolet radiation dosimeter.
PubDate: Wed, 24 Aug 2016 15:11:15 +000
- Corrigendum to “Molecular Dynamics Simulation of Aggregates in the
Dodecane/span80 System and Their Behaviour in an Electric Field”
PubDate: Wed, 17 Aug 2016 12:04:35 +000
- The Effect of Indium Concentration on the Structure and Properties of
Zirconium Based Intermetallics: First-Principles Calculations
Abstract: The phase stability, mechanical, electronic, and thermodynamic properties of In-Zr compounds have been explored using the first-principles calculation based on density functional theory (DFT). The calculated formation enthalpies show that these compounds are all thermodynamically stable. Information on electronic structure indicates that they possess metallic characteristics and there is a common hybridization between In-p and Zr-d states near the Fermi level. Elastic properties have been taken into consideration. The calculated results on the ratio of the bulk to shear modulus (B/G) validate that InZr3 has the strongest deformation resistance. The increase of indium content results in the breakout of a linear decrease of the bulk modulus and Young’s modulus. The calculated theoretical hardness of α-In3Zr is higher than the other In-Zr compounds.
PubDate: Sun, 17 Jul 2016 13:11:47 +000
- A Self-Consistent Model for Thermal Oxidation of Silicon at Low Oxide
Abstract: Thermal oxidation of silicon belongs to the most decisive steps in microelectronic fabrication because it allows creating electrically insulating areas which enclose electrically conductive devices and device areas, respectively. Deal and Grove developed the first model (DG-model) for the thermal oxidation of silicon describing the oxide thickness versus oxidation time relationship with very good agreement for oxide thicknesses of more than 23 nm. Their approach named as general relationship is the basis of many similar investigations. However, measurement results show that the DG-model does not apply to very thin oxides in the range of a few nm. Additionally, it is inherently not self-consistent. The aim of this paper is to develop a self-consistent model that is based on the continuity equation instead of Fick’s law as the DG-model is. As literature data show, the relationship between silicon oxide thickness and oxidation time is governed—down to oxide thicknesses of just a few nm—by a power-of-time law. Given by the time-independent surface concentration of oxidants at the oxide surface, Fickian diffusion seems to be neglectable for oxidant migration. The oxidant flux has been revealed to be carried by non-Fickian flux processes depending on sites being able to lodge dopants (oxidants), the so-called DOCC-sites, as well as on the dopant jump rate.
PubDate: Tue, 19 Apr 2016 08:29:42 +000
- Normal Stress Differences and Yield Stresses in Attractive Particle
Abstract: The nature of attractive particulate networks, yield stresses, and normal stress differences is systematically reviewed, each in terms of the relevant definitions, underlying mechanisms, and current measurement techniques. With this foundation, experimental observations of normal stress differences in some suspensions and colloidal systems are surveyed, along with constitutive models that allow for normal stress differences to arise prior to yielding. Yield stresses are a hallmark of attractive colloidal systems and vital in their processing. In contrast, little attention has been given to the role of normal stress differences in these systems. The presence or absence of normal stress differences necessarily affects the isotropy of the normal stress field through the solid particulate phase (treated as a continuum), in turn affecting estimation of yield stress. Given the importance of yield stresses in dealing with practical industrial problems, and in understanding fundamental behaviours, it is important to ensure that yield measurements can be relied upon.
PubDate: Tue, 12 Apr 2016 10:26:15 +000
- Electronic Origin of Defect States in Fe-Doped LiNbO3 Ferroelectrics
Abstract: We investigate the role of Fe in the electronic structure of ferroelectric LiNbO3 by density-functional theory calculations. We show that Fe2+ on the Li site () features a displacement opposite to the direction of spontaneous polarization and acts as a trigger for the bulk photovoltaic (PV) effect. In contrast to Fe3+ on the Li site that forms the defect states (1e, a, and 2e) below the conduction band minimum, the reduction from Fe3+ to Fe2+ accompanied by a lattice relaxation markedly lowers only the state () owing to a strong orbital hybridization with Nb-4d. The state of provides the highest electron-occupied defect state in the middle of the band gap. A reduction treatment of Fe-LN is expected to increase the concentration of Fe2+ and therefore to enhance the PV effect under visible light illumination.
PubDate: Wed, 23 Mar 2016 12:20:16 +000
- Ni-Based Ohmic Contacts to n-Type 4H-SiC: The Formation Mechanism and
Abstract: The fabrication of low-resistance and thermal stable ohmic contacts is important for realization of reliable SiC devices. For the n-type SiC, Ni-based metallization is most commonly used for Schottky and ohmic contacts. Many experimental studies have been performed in order to understand the mechanism of ohmic contact formation and different models were proposed to explain the Schottky to ohmic transition for Ni/SiC contacts. In the present review, we summarize the last key results on the matter and post open questions concerning the unclear issues of ohmic contacts to n-type SiC. Analysis of the literature data and our own experimental observations have led to the conclusion that the annealing at high temperature leads to the preferential orientation of silicide at the heterointerface (0001)SiC//(013)-Ni2Si. Moreover, we may conclude that only δ-Ni2Si grains play a key role in determining electrical transport properties at the contact/SiC interface. Finally, we show that the diffusion barriers with free diffusion path microstructure can improve thermal stability of metal-SiC ohmic contacts for high-temperature electronics.
PubDate: Wed, 16 Mar 2016 09:02:14 +000
- Theoretical Investigation on Structural and Electronic Properties of InN
Growth on Ce-Stabilized Zirconia (111) Substrates
Abstract: The structural and electronic properties of InN on Ce-stabilized zirconia (CeSZ) (111) substrates are investigated using first-principles calculations based on density functional theory with GGA + method. Surface energy calculations indicate that the structure of Ce-segregated surface is more energetically stable than that of Ce-segregation-free surface. Adsorption energies of indium and nitrogen atoms on both Ce-segregated and Ce-segregation-free CeSZ (111) surfaces at the initial growth stage have been studied. The results suggest that the first layer of InN films consists of a nitrogen layer, which leads to epitaxial relationships between InN (0001) // CeSZ (111) and InN // CeSZ . In addition, density of states (DOS) analysis revealed that the hybridization effect plays a crucial role in determining the interface structure for the growth of InN on CeSZ (111) surfaces. Furthermore, adsorption energies of indium atoms on the nitrogen layer have also been evaluated in order to investigate the lattice polarity determination for InN films. It was found that an indium atom preferentially adsorbs at the center of three nitrogen atoms stacked on the CeSZ substrate, which results in the formation of In-polarity InN.
PubDate: Sun, 13 Mar 2016 14:20:13 +000
- Effect of In Situ Thermal Annealing on Structural, Optical, and Electrical
Properties of CdS/CdTe Thin Film Solar Cells Fabricated by Pulsed Laser
Abstract: An in situ thermal annealing process (iTAP) has been introduced before the common ex situ cadmium chloride (CdCl2) annealing to improve crystal quality and morphology of the CdTe thin films after pulsed laser deposition of CdS/CdTe heterostructures. A strong correlation between the two annealing processes was observed, leading to a profound effect on the performance of CdS/CdTe thin film solar cells. Atomic force microscopy and Raman spectroscopy show that the iTAP in the optimal processing window produces considerable CdTe grain growth and improves the CdTe crystallinity, which results in significantly improved optoelectronic properties and quantum efficiency of the CdS/CdTe solar cells. A power conversion efficiency of up to 7.0% has been obtained on thin film CdS/CdTe solar cells of absorber thickness as small as 0.75 μm processed with the optimal iTAP at 450°C for 10–20 min. This result illustrates the importance of controlling microstructures of CdTe thin films and iTAP provides a viable approach to achieve such a control.
PubDate: Mon, 29 Feb 2016 09:30:11 +000
- High Dielectric Constant Study of TiO2-Polypyrrole Composites with Low
Contents of Filler Prepared by In Situ Polymerization
Abstract: TiO2/polypyrrole composites with high dielectric constant have been synthesized by in situ polymerization of pyrrole in an aqueous dispersion of low concentration of TiO2, in the presence of small amount of HCl. Structural, optical, surface morphological, and thermal properties of the composites were investigated by X-ray diffractometer, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, and thermogravimetric analysis, respectively. The data obtained from diffractometer and thermal gravimetric analysis confirmed the crystalline nature and thermal stability of the prepared composites. The dielectric constant of 5 wt% TiO2 increased with filler content up to 4.3 × 103 at 1 kHz and then decreased to 1.25 × 103 at 10 kHz.
PubDate: Thu, 11 Feb 2016 11:22:32 +000
- The First Observation of Metallic Behaviour in Nd3.5Sm0.5Ni3O8
Abstract: In Nd3.5Sm0.5Ni3O8 which has basically the same crystal structure and the similar electrical configuration (Ni+ 3d9/Ni2+ 3d8 mix valence state) with high- cuprate, it has been found that this material shows metallic behaviour down to about 20 K by intercalation and subsequent deintercalation with sulfur. This is the first observation of the metallic state in this system. It is unclear why sulfur-intercalation and deintercalation induce the metallic state. We speculate that sulfur works as an effective getter for removing the interstitial apical oxygen which impedes the metallic conduction. However, the weak localization of carriers in the NiO2 planes still remains below 20 K and the localization may be one of the obstacles to occurrence of possible superconductivity.
PubDate: Tue, 02 Feb 2016 08:08:46 +000
- Amphiphiles Self-Assembly: Basic Concepts and Future Perspectives of
Abstract: Amphiphiles are synthetic or natural molecules with the ability to self-assemble into a wide variety of structures including micelles, vesicles, nanotubes, nanofibers, and lamellae. Self-assembly processes of amphiphiles have been widely used to mimic biological systems, such as assembly of lipids and proteins, while their integrated actions allow the performance of highly specific cellular functions which has paved a way for bottom-up bionanotechnology. While amphiphiles self-assembly has attracted considerable attention for decades due to their extensive applications in material science, drug and gene delivery, recent developments in nanoscience stimulated the combination of the simple approaches of amphiphile assembly with the advanced concept of supramolecular self-assembly for the development of more complex, hierarchical nanostructures. Introduction of stimulus responsive supramolecular amphiphile assembly-disassembly processes provides particularly novel approaches for impacting bionanotechnology applications. Leading examples of these novel self-assembly processes can be found, in fact, in biosystems where assemblies of different amphiphilic macrocomponents and their integrated actions allow the performance of highly specific biological functions. In this perspective, we summarize in this tutorial review the basic concept and recent research on self-assembly of traditional amphiphilic molecules (such as surfactants, amphiphile-like polymers, or lipids) and more recent concepts of supramolecular amphiphiles assembly which have become increasingly important in emerging nanotechnology.
PubDate: Tue, 29 Dec 2015 14:28:39 +000
- Synthesis and Characterization of Bifunctional α-Fe2O3-Ag
Abstract: The synthesis of α-Fe2O3-Ag bimetallic nanoparticles using a novel and simplified route is presented in this work. These hybrid nanoparticles were produced using a modification of the chemical reduction method by sodium borohydride (NaBH4). Fe(III) chloride hexahydrate (FeCl3·6H2O) and silver nitrate (AgNO3) as precursors were employed. Particles with semispherical morphology and dumbbell configuration were observed. High-resolution transmission electron microscopy (HRTEM) technique reveals the structure of the dumbbell-like α-Fe2O3-Ag nanoparticles. Some theoretical models further confirm the formation of the α-Fe2O3-Ag structures. Analysis by cyclic voltammetry reveals an interesting catalytic behavior which is associated with the combination of the individual properties of the Ag and α-Fe2O3 nanoparticles.
PubDate: Mon, 14 Dec 2015 08:51:21 +000
- Nonlinear Tunneling of Surface Plasmon Polaritons in Periodic Structures
Containing Left-Handed Metamaterial Layers
Abstract: The transmission of surface plasmon polaritons through a one-dimensional periodic structure is considered theoretically by using the transfer matrix approach. The periodic structure is assumed to have alternate left-handed metamaterial and dielectric layers. Both transverse electric and transverse magnetic modes of surface plasmon polaritons exist in this structure. It is found that, for nonlinear wave propagation, tunneling structures are formed to transform nontransmitting frequencies into transmitting frequencies and hence transmission bistability is observed. It is further observed that the structure shows sensitivity with respect to the polarization of the electromagnetic field for this phenomenon.
PubDate: Sun, 13 Dec 2015 07:48:54 +000
- Molecular Dynamics Simulation of Aggregates in the Dodecane/span80 System
and Their Behaviour in an Electric Field
Abstract: Molecular dynamics simulation of self-assembly of surfactant span80 molecules to form reverse micelles in nonpolar liquid dodecane is carried out. Simulations are performed using a united atom model for dodecane and a hybrid model for span80 molecules. Various physical characteristics of reverse micelle are measured, and the same are compared with available experimental results. Presence of charge carriers in the form of solvated ions in the core of reverse micelles is confirmed by the simulation. Movement of reverse micelles under the effect of uniform external electric field is also discussed.
PubDate: Mon, 23 Nov 2015 09:42:29 +000
- Analysis for the Sorption Kinetics of Ag Nanoparticles on Natural
Abstract: The kinetic adsorption behavior of silver nanoparticles deposited on a natural zeolite from Oaxaca is presented. Theoretical models as Lagergren first-order, pseudo-second-order, Elovich, and intraparticle diffusion were employed and compared with experimental data obtained by atomic absorption spectrophotometry technique. Correlation factors of the order of 0.99 were observed. Analysis by transmission electron microscopy revealed that the silver nanoparticles were homogeneously distributed on the zeolite. Additionally, chemical characterization of the material was carried out through a dilution process with lithium metaborate. An average value of 9.3 in the Si/Al ratio was observed and related to the kinetic adsorption behavior of the zeolite.
PubDate: Sun, 22 Nov 2015 09:53:46 +000
- Ultrasonic Studies of Emulsion Stability in the Presence of Magnetic
Abstract: Pickering emulsions are made of solid particle-stabilized droplets suspended in an immiscible continuous liquid phase. A magnetic emulsion can be obtained using magnetic particles. Solid magnetic nanoparticles are adsorbed strongly at the oil-water interface and are able to stabilize emulsions of oil and water. In this work emulsions stabilized by magnetite nanoparticles were obtained using high-energy ultrasound waves and a cavitation mechanism and, next, their stability in time was tested by means of acoustic waves with a low energy, without affecting the structure. An acoustic study showed high stability in time of magnetic emulsions stabilized by magnetite particles. The study also showed a strong influence of an external magnetic field, which can lead to changes of the emulsion properties. It is possible to control Pickering emulsion stability with the help of an external stimulus—a magnetic field.
PubDate: Thu, 12 Nov 2015 11:09:04 +000
- Noise and Electrical Oscillations Generation during the Investigation of
the Resistive Switching in the Yttria Stabilized Zirconia Films by
Conductive Atomic Force Microscopy
Abstract: The effect of resistive switching in the yttria stabilized zirconia (YSZ) thin films on Si substrates has been studied by Conductive Atomic Force Microscopy (CAFM). The resistive switching of the YSZ films from the low conductive state to the highly conductive one has been found to be associated with the increasing of the noise with broad frequency spectrum related to the redistribution of the oxygen vacancies in YSZ. The electrical oscillations in oscillation loop connected in series to the CAFM probe, the sample, and the bias source related to the excitation of the oscillation loop by the noise in the probe-to-sample contact film have been observed. The effect discovered is promising for application in the memristor devices of new generation.
PubDate: Thu, 29 Oct 2015 12:41:16 +000