Journal of Progress in Physics of Applied Materials
Volume:2 Issue: 2, Jun 2022

Solid state synthesis of CuO nanophotocatalyst is reported in the present work using copper salts raw materials at 600 ºC for 5 h. X-ray powder diffraction (XRPD) technique was used to characterize the prepared nanomaterials. Rietveld analysis data confirmed the high purity of the prepared samples. The XRD data showed that the peaks belong to monoclinic structure with a space group of C2/c. The Rietveld data indicated that the cell parameters are a=4.68244, b=3.42366, c=5.12641 Å and β=99.46º for S1, a= 4.68073, b=3.42521, c=5.13221 Å and β=99.36º for S2 and a=4.68233, b=3.42396, c=5.12941 Å and β=99.30º for S3. The morphology of the prepared samples was investigated by FESEM technique. The FESEM images showed that the synthesized CuO compounds had particle morphology with the particle size of 22–50 nm. The photocatalytic performance of the obtained target was studied to degrade malachite green (MG) from wastewater solution.

Despite the rapid and promising progress on the perovskite solar cell efficiency of around 25.7 % in the last few years, the ion migration as an intrinsic instability has limited the practical application of these solar cells. In this work, we have modified the common drift-diffusion equations to model the experimental current-voltage (J-V) hysteresis in Perovskite solar cells. In our model, both anions and cations have been considered. Inverted hysteresis behavior in J-V characteristics and contact corrosion in perovskite solar cells have yet to be explained clearly. To address this issue, we modified ionic-electronic transport equations by adding ionic flux equations to let ions move from the perovskite layer toward contacts. Our results show a strong inverted hysteresis because of the high flux rate of anions and cations to ETL and HTL and, consequently, toward contacts. Although the ionic flux may cause the instability of the perovskite solar cells, the efficiency is increased for the cases where anions and cations flux to HTL and ETL toward contacts. In all ionic flux models, open circuit voltages (Voc) are increased due to ionic accumulation at interfaces, the built-higher gradient of electric potentials at interfaces, and the modified Fermi level (modified work function-aging process).

Structural, magnetic, and electrical properties of La0.5Ca0.5MnO3 samples prepared at two different sintering temperatures (800°C and 1350°C which were labeled S800 and S1350, respectively) have been investigated. The Reitveled refined XRD patterns indicate an orthorombic structure with Pnma space group for both samples. Ac susceptibility measurements show that, the fraction of ferromagnetic and antiferromagnetic phases could be controlled with sintering temperature. S800 sample has a ferromagnetic state while the antiferromagnetic phase is enhanced in S1350 sample which causes the increase of thermal hysteresis in this sample. Two distinct regions (T>ӨD/2 and T˂ӨD/2, ӨD is the Debye’s temperature) were noticed to investigate the electrical properties. Based on the resistivity data at T>ӨD/2 region, the S800 and S1350 samples follow the adiabatic and non-adiabatic small polaron hopping (SPH) models, respectively. At T˂ӨD/2 region, the 3-dementional variable range hopping (VRH) model displays a good correlation with the experimental data of both samples. The related parameters of both SPH and VRH models are extracted. The results show that these parameters are particle size dependent.

A Gaussian wave-packet quantum tunneling across a one-dimensional double-barrier structure has been explored in order to obtain the spin-based transport coefficients. We have used a split-step finite difference method to solve the resulting nonlinear coupled Schrodinger equations. The related behavior of scattering properties of the system as a function of the geometry of the barriers in the presence of Rashba and Dresselhaus spin-orbit interactions for High-energy and low-energy wave-packets have been compared. Evidence showed that the presence of Rashba or Dresselhaus SOIs leads to considerable spin polarization in the wave-packet components. Based on the results, it is found that the wave-packet velocity plays a significant role in the tunneling process of the Gaussian wave-packet through quantum barriers. In addition, by tuning the Rashba and the Dresselhaus coupling strengths, the energy of the wave-packet, and the characteristics of the system, one can control the spin polarization of the wave-packet and its propagation coefficients.

La0.7Ca0.3MnO3 (LCMO) powder was synthesized via the hydrothermal method. Structural, morphological, and optical properties of the as-prepared sample were systematically characterized. The XRD results proved the existence of only one crystalline phase. The FESEM image indicates that the La0.7Ca0.3MnO3 sample has a nanorod structure with an average diameter of approximately 125 nm. According to UV-Vis analysis, the band gap energy of the sample was estimated about 2.13 eV. The adsorption and photocatalytic performances of LCMO nanostructure were systematically characterized. The photoactivity efficiency for decolorizing Rhodamine B solution (10 ppm), by LCMO (0.5 g/L), with nearly 80 min illumination, was more than 90% with a reaction rate constant of 0.029 min−1. Ultimately, the reusability of the photocatalyst for degrading the RhB dye was investigated using six cycles. The good reusability and stability of LCMO implies a potential application for dealing with high-concentration dyes by adsorption–photocatalytic degradation.

Silver bismuth iodide (SBI) materials are low-toxic, air-stable, and suitable for replacing lead-based perovskite ones. In this work, the photovoltaic characteristics of SBI-based solar cells with different hole transport layers (HTL) were investigated. Results showed that the power conversion energy (PCE) of Silver bismuth iodide-based solar cells with P3HT as HTL was higher than spiro-OMeTAD. Also, the influence of CNT as a dopant on the performance and stability of the devices was studied. CNT doping of silver bismuth iodide increased the Voc and so the efficiency of the solar cell was enhanced. Furthermore, Also, CNT-doped P3HT improves the interface contact between the active layer and HTL and increases the conductivity of HTL. The best PCE of about 2.16% for devices with FTO/c-TiO2/m-TiO2/silver bismuth iodide-CNT/P3HT-CNT/Au structure was obtained. Moreover, the stability of solar cells under environmental conditions after 30 days was investigated. All devices preserved about 95% of their efficiency.

DLC films were deposited on Si substrates using direct ion beam deposition method, followed by investigating the influence of O2 and N2 doping on their electrical and structural properties. The films were doped with oxygen and nitrogen under flow rates of 5 and 40 sccm (standard cubic centimeters per minute). The structure of the films was studied by Raman spectroscopy.  Result showed that by increasing oxygen incorporation, sp2 content decreases, sp3 content increases, and the C-C bonding loses its order. As the size of the sp2-rich cluster increased with N2 content, the disorder in the DLC samples decreased, leading to a decrease in the FWHM of the G peak. The water contact angle measurement showed that an increase in oxygen flow ratio results in a decrease in contact angle from 82.9° ± 2.1° to 50° ± 3°. With increasing nitrogen flow rate from 5 to 40, the contact angle of DLC thin films increased from 78° to 110°.

The preparation of Co1-xCdxFe2O4/SiO2 nanocomposites with core/ shell structure involved the coating of SiO2 using Stöber method on Co1-xCdxFe2O4 and the use of facile thermal treatment method for synthesizing nanoparticles. The effect of cadmium substitution and SiO2 coating on the degree of crystallinity, samples composition, microstructure, and phase composition were conducted by X-ray diffraction (XRD), energy dispersion X-ray analysis (EDXA), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FT-IR), respectively. Magnetic properties were demonstrated by a vibrating sample magnetometer (VSM) which displayed that Co-Cd ferrite nanoparticles and coated silica samples exhibited magnetic behaviors. In investigating the influence of cadmium substitution and the SiO2 coating on the band gap energy (Eg), a more accurate method was used in evaluating the band gap energy (Eg). The method of evaluation is a recently proposed one known as derivation of absorption spectrum fitting (DASF) which involves the direct absorption spectra of UV-Visible region, without any need for the concentration of powders or solutions.

Solid materials that contain holes in their structure are generally defined as porous materials. Porosity is obtained by dividing the volume of pores by the total volume of the material. Porous materials are a new category of materials that have attracted the attention of scientists and different industries due to their special mechanical properties, such as definable strength and density. These materials have been attracted due to various applications in molecular separation, heterogeneous catalysis, absorption technology or light and electronics technology. This research aims to investigate the effects of an electric field on the mechanical properties of a silicon-doped carbon matrix with 10% porosity. The mechanical properties investigated in this research include Young's modulus and ultimate strength, obtained using the molecular dynamics (MD) simulation method and LAMMPS comprehensive software. The results revealed that the ultimate strength and Young’s modulus of silicon-doped nanoporous carbon matrix converged to 69.4014 GPa and 200.192GPa, respectively. In the following, the mechanical strength in simulated samples decreases with increasing the electric field magnitude. Numerically, by increasing the electric field from 0.2 to 0.5 V/Å, the ultimate strength and Young’s modulus of silicon-doped nanoporous carbon matrix decrease from 65.83 and 191.022 GPa to 57.81 and 167.18 GPa

The structural characteristics of materials change with the reduction of dimensions, and they show different behaviors compared to the corresponding bulk sample. To study these changes, in this research, we investigated the effect of size and preparation method on properties of cobalt ferrite (CoFe2O4). After synthesis of a bulk sample by solid-state reaction method, CoFe2O4 nanoparticles were prepared by two different methods of co-precipitation and thermal decomposition. Then, a layer of CoFe2O4 was prepared by a spin coating method, using a silicon substrate. In the following, the structural, magnetic, and optical properties of samples were studied, and compared. The results confirmed the size and synthesis method dependence behavior of properties of the prepared samples. The nanoparticles synthesized by thermal decomposition method show much higher coercivity compared to those prepared by co-precipitation, while both consist of almost same size distribution. The bulk sample shows the lowest coercivity, but highest saturation magnetization among the samples. On the other hand, the bulk sample has smaller band gap compared to the nanoparticles.

Co-based and Fe-based full Heusler compounds with composition Co2M'Z or Fe2M'Z (where M' is a transition metal and Z is a main group element) are attracting attention due to their predicted half-metallic behavior, a greatly desired property for spin-dependent electron transport devices. In this work four Heusler compounds (Co2FeGe, Co2FeSi, Fe2CoGe, Fe2CoSi), have been prepared by mechanical alloying. The effect of vacuum annealing on properties was studied. According to the structural measurements 15 hours milling was enough for crystallization of these compounds. During annealing the crystallite size increased and lattice ordering enhanced. Two superlattice peaks appeared in X-ray pattern due to enhancement of lattice ordering of two Si content compounds. In Co-based compounds the saturation magnetization value increased to a closer value of Slater Pauling model because of improvement of lattice ordering. The value of Ms in some Fe-based compounds was higher than that predicted by Slater Pauling model.

2-dimensional graphitic carbon nitride (g-C3N4) has specific properties that makes it a desirable candidate for extensive applications. This work provides a systematic study for choosing precursors to prepare g-C3N4 with tailored characteristics. g-C3N4 samples have been prepared by thermal decomposition of different precursors (i.e., melamine, urea, and thiourea). Various characterization techniques such as SEM, EDS, XRD, DRS, BET, and FTIR have been used to determine the physical properties of the prepared samples. SEM analysis showed nanoflake and nanosheet structures with no elemental impurity in EDS analysis. Furthermore, FTIR analysis confirmed the formation of graphitic carbon nitride structure. BET results showed a significant enhancement of specific surface area by a factor of 2.8 for the sample prepared with urea precursor. The photocatalytic activity for rhodamine B (RhB) degradation is also presented. The results revealed that urea-based g-C3N4 could be a promising candidate for photocatalytic applications due to its appropriate physical properties and highest dye removal.