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In this work, we study the Ising model with mixed spins S =  1/2 and S =  3/2 on the hypercubic lattice and the random crystal field at the sublattice with S = 3/2 described by a two peaks law. To achieve this, we use an approximation of position space renormalization group (PSRG) namely Migdal-Kadanoff in which we use both the free energy derivative and the flow in the parameter space of the Hamiltonian. For all values of the random probability, the critical behavior is determined via the critical exponents at the second-order fixed points while at low temperatures; the discontinuities of the of the free energy derivative provide the positions of the first-order transitions. The introduction of a minimal amount of disorder causes a change in the phase diagram showing the relevance of disorder for d = 2 and d = 3. The second-order transition remains always with the same critical exponents as those of the pure model, and a new first-order transition appears at very low temperature. Also, a comparison with other similar works is given. [ABSTRACT FROM AUTHOR]

We investigated a three-dimensional semi-infinite spin-1/2 system bounded by a spin-1 surface using a Monte Carlo simulation based on the Metropolis algorithm. The exchange interactions and crystal field effects on phase diagrams, magnetizations, and susceptibilities were investigated. The phase diagrams in three planes were presented due to the competition between specific system parameters. The system demonstrated ordinary, extraordinary, surface, and special second-order phase transitions, as well as a surface first-order phase transition. Furthermore, tricritical and critical end-points were discovered. [ABSTRACT FROM AUTHOR]

The hydrothermal treatment of Moroccan coal fly ash (CFA) in a basic medium leads to the selective formation of Na-X zeolite. By fusion with sodium hydroxide in the presence of CFA, the particles are transformed into sodium silicate and sodium aluminate, from which hydrothermal reaction favourably results in the production of a pure Na-X zeolite. A good crystallinity of Na-X zeolite was attained at NaOH:fly ash ratio of 1.2. Their high surface area and pore characteristics make the Na-X zeolite useful for the removal of the model anionic dye RY145 from water. The adsorption efficiency of the synthesised Na-X zeolite was evaluated and compared to raw CFA. Dye adsorption is more significant at acid pH, suggesting that the zeolite surface is positively charged. Kinetic and isotherm models applied to fit the experimental data reveal that the adsorption process is physisorption. It results that zeolite X is an efficient adsorbent for the extraction of dyes. [ABSTRACT FROM AUTHOR]

A room-temperature nematic liquid crystal cell is prepared in the homeotropic geometry using dielectrically positive pentyl cyanobiphenyl. The indium tin oxide electrodes are treated to increase locally their surface resistance. At high frequencies (ω>ωc) the border of these regions behaves as capacitance edge, creating an oblique field which ‘‘writes.’’ At low frequencies (ω<ωc) the field is back normal to the electrodes and ‘‘erases’’ rapidly. A 50-μs erasing time has been achieved for E∼10 V/μm and ωc/2π=104 Hz. The practical smallest response time of the device is ∼(8ωc)-1. Sub-μs writing and erasing are possible. [ABSTRACT FROM AUTHOR]

In this work, we used the Migdal–Kadanoff renormalization group method to investigate two three-dimensional semi-infinite Ising systems. In the first one, the surface and bulk sites are occupied by spin-3/2 and spin-1/2 respectively, whereas those of the second one are occupied by spin-1/2 on the surface and spin-3/2 in the bulk. Based on the ratio of bulk and surface exchange interactions, we explored different topologies of phase diagrams showing various second order phase transitions, namely ordinary, extraordinary, surface and special transitions. We also found that both systems exhibited first order phase transitions, multicritical points and critical end-points. The existence of a first order phase transition at low temperatures was confirmed by plotting the derivative of the free energy. The Monte Carlo simulation was also used to verify and compare the results obtained by the renormalization group for the two semi-infinite systems. • Two three-dimensional semi-infinite Ising systems were studied by RG and MCS. • Different topologies of phase diagrams were found. • Both systems exhibit second- and first-order transitions and multicritical points. • Ordinary, extraordinary, surface and special phase transitions were observed. • Results obtained by renormalization were confirmed by Monte Carlo. [Display omitted] [ABSTRACT FROM AUTHOR]

Raw earth construction (RE) is an interesting alternative approach for reducing the use of conventional construction materials. The aim of this study is the stabilization of RE by a new organic binder manufactured based on algae. The stabilization is performed on the mortar scale as well as evaluated by conducting mechanical and thermal tests. Samples of mortar were manufactured based on local soil and Sargassum muticum type algae. The incorporation weight rates of algae are 0 (reference sample), 2, 4, 6, and 8 wt.%. Results showed that the compressive and bending strengths of algae mortar were improved by 77 and 70%, respectively. In addition, it was noticed that samples with 0.63 mm maximum grain size algae binder provide higher strengths in comparison with 0.80 mm maximum grain size algae binder. It was found also that 2 wt.% of incorporated algae provide similar mechanical resistance to 15 wt.% of slaked lime. The thermal investigation of samples showed three peaks: two endothermic peaks at 100 and 800 °C, which can be respectively attributed to the desorption of H2O and CO2 due to the decomposition of calcite; the third exothermic peak at 500 °C is attributed to the decomposition of the macromolecules of the algae. [ABSTRACT FROM AUTHOR]

Abstract The oxides and their interplay with metals are of central importance in solar energy, solar cells and environmental as well as in technological applications. Doping of Mg and Al into ZnO offers an interesting way to alter various electronic, optical and structural properties. In this work, Mg doped (Zn 0.98 Al 0.02 O) films with different Mg concentrations (0, 1, 2, 4 and 6%) were grown by spray pyrolysis technique and characterized by X-ray diffraction (XRD), UV/VIS optical transmission spectroscopy and electrical measurement. XRD analysis of all samples indicates the presence of hexagonal crystal structure with a preferred orientation of the crystallites along the [002] direction perpendicular to the substrate and the absence of any other secondary phase. All samples exhibited interference fringe patterns in the visible region of transmittance spectra with an average transmission of >60% indicating a good optical quality of the deposited films. The optical studies demonstrate also that Mg-doping induces an increase of the band gap energy. The dark electrical resistivity decreases with increasing Mg doping amount due to the increase of the grain size and the low electronegativity of Mg2+ than Zn2+. Highlights • Mg doped (Zn 0.98 Al 0.02 O) films with different Mg concentrations (0, 1, 2, 4 and 6%) were grown by spray pyrolysis technique. • The as-synthesized samples showed good structural and optical properties. • Mg doping induces an increase of the band gap energy. • The dark electrical resistivity decreases with increasing Mg doping amount. [ABSTRACT FROM AUTHOR]

Abstract We studied thin film growth of Cu on Cu (111) surface by molecular dynamics (MD) simulations using the Embedded Atom Method (EAM) potential and an incidence energy of 0.06 eV at 300 K. At the beginning of the deposition, we observe a coexistence of atoms nucleated on hcp and fcc sites in the first layer. The connection of these islands produces a border zone in rectangular form. The coexistence of fcc and hcp geometries has generated energy competition and eventually transitioned to fcc sites implying a large collective movement of several layers. However, the transition to the coexistence of these two structures, can promote coalescence by linking two large mounds. Highlights • Thin film growth of Cu on Cu(111) substrate was investigated. • Molecular dynamics simulation based on EAM interaction potential was considered. • Coexistence of two nucleated structures on hcp and fcc sites on the same layer. [ABSTRACT FROM AUTHOR]

Abstract The interface study during the film growth of Al on Ni (111) is investigated using molecular dynamics simulations with the conjunction of the Embedded Atom Method interaction potential. The substrate temperature was fixed to 300K. The results of this work showed that the interface adopts the same structure as the substrate, i.e., the triangular structure. The upper layers have imposed on some Al atoms of the first deposited layer an adsorption on the substrate bridges giving them the substrate interatomic distance in only one direction. However, other atoms adopt a median value between the interatomic distance of the substrate and that of the deposited film. Highlights • Aluminum thin film growth on Ni(111) substrate was investigated. • Molecular dynamics simulation based on EAM interaction potential was considered. • Interface evolution is influenced by mismatch lattice. [ABSTRACT FROM AUTHOR]

The present work reviews a study of copper oxide (CuO) thin film properties elaborated via two distinct techniques: spin-coating and sprays pyrolysis. The primary objective of the work is to investigate the experimental results and theoretical finding by DFT TB-mBJ calculations of pure CuO films. First of all, the structural properties were studied by X-ray diffraction; Where the CuO films show polycrystalline and monoclinic structures without any other phases. Furthermore, Field emission scanning electron microscopy (FESEM) investigates the effects of elaboration methods on the morphology and surface composition and also, the film thickness was about 234,1 nm for sprayed film and 449 nm for spin-coated films. Moreover, the Optical analysis exhibits a higher absorbance for sprayed films than the spin-coated ones where the band gap energy was found 1.25 eV for using spin-coated and 1.35 eV for sprayed thin films respectively. Furthermore, the electrical conductivity of the spin coated films is higher than the sprayed ones. The band structure, density of states (DOS), electronic density and optical properties of pure CuO were estimated using the LDA approximation in conjunction with the TB-mBJ approximation in order to investigate its characteristics. These results indicate that the CuO films are suitable to be used as an absorber of thin-film solar cells. • CuO films show polycrystalline and monoclinic structure without any other phases. • The Optical analysis exhibits a higher absorbance for sprayed films than the spin-coated ones. • The electrical conductivity of the spin coated films is higher than the sprayed ones. • The results obtained demonstrate that the elaboration method has an impact on films quality. • The DFT TB-mBJ calculations indicating the semiconductor nature of CuO with good optical properties making this material as an absorbent candidate for photovoltaic solar cells applications. [ABSTRACT FROM AUTHOR]

In this paper, a synthesis of SnS thin films using sol-gel spin coating method and optimization of the parameters influencing the experimental process. Taguchi experiment design with a L 9 (34) orthogonal array was used to optimize several parameters such as the annealing temperature, annealing time, concentration, and [S]/[Sn] ratio. To perform the necessary tests three levels of each factor were chosen. The analysis of variance (ANOVA) and signal-to-noise (S/N) was used to obtain the good optical properties (optimal band-gap) at the best combination of choosing factors. The obtained results indicate that the most influencing factors in the preparation of SnS thin films are the concentration and the [S]/[Sn] ratio. To confirm the results obtained, the test validation was performed using the optimal conditions. SnS thin films obtained at optimal condition were analyzed using X-Ray diffraction, UV–visible spectrophotometer, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and four-point probe. • Synthesis of SnS thin films by sol gel spin-coating method. • Application of Taguchi method to optimize the sol gel spin coating process. • The statistical analysis (ANOVA) has the capacity to give information about certain statistical parameters. • The SnS thin film obtained with optimal parameters has good properties. [ABSTRACT FROM AUTHOR]