جستجوی مقالات مرتبط با کلیدواژه "x-ray diffraction" در نشریات گروه "مواد و متالورژی"

In this study, poly(3-hexylthiophene) (P3HT) and fullerene Indene-C60 multi-adducts (ICxA) were blended to create a formulation as a solution and thin films, which were prepared under ambient conditions. The optical properties of various compositional ratios were studied using UV-Visible absorbance and photoluminescence (Pl) measurements. The energy gaps of the prepared thin films and solutions were determined, and their values increased with increasing fullerene ratio because of the isolation of P3HT chains from their neighbors. Intensity ratio (IC=C/IC-C) with a small value in addition to a low value of full width at high maximum (FWHM) of Raman spectra are associated with increased conformation and high aggregation of composition. Furthermore, according to X-ray diffraction  (XRD) results the 1:0.8 and 1:0.6 ratios have the largest crystallite sizes in comparison to the other ratios. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels for blends by electrochemical measurements were determined, which are sandwiched between those of the pure materials. In ambient conditions, binary organic photovoltaic cells (OPVs) at different ratios of the photoactive layer were evaluated. The device with a ratio of 1:0.6 had the best performance, with power conversion efficiency (PCE) of 1.21 %, open circuit voltage (VOC) of 0.53 V, short circuit current density (JSC) of  5.71 mA.cm-2, and fill factor (FF) of 39.5 % at a small Vloss of 1.39 V.

In this paper, Pb1-xFex(Zr0.52Ti0.48)O3 (PFZT) nanopowders, with x from 0.00 up to 0.20, were synthesized by using the sol-gel method. The PFZT samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and impedance spectroscopy. According to the experimental results, PFZT combines rhombohedral and tetragonal symmetries for all the samples without a change in phase structure. The SEM investigation indicated that the grains are homogeneous with regular form and the average grain size of PFZT ceramics changed with Fe concentration. The dielectric characterizations show that the dielectric permittivity increases with increasing temperature, and the Fe amount shifts down the temperature of transition. Moreover, a dielectric resonance phenomenon is observed for all the PFZT ceramics.

The high-temperature superconductor like Bi2Ba2Ca2Cu3O10+d was prepared using the solid-state reaction method at different calcination temperatures including 780, 800, and 850 °C. X-ray diffraction technique was used to define crystal structure formation as a function of calcination temperature. It was found a tetragonal phase was obtained with lattice constants of a=b=4.2967, and c=36.5248 Å. It was found that there is a limited difference in the scattered peak intensities making a partial variation in the fraction volume of the phase formation. Such that the volume fraction of a high phase superconductor recorded 73.76% for the Bi-2223 phase at calcination temperature of 800 °C. There is high intensity for the most probable peaks in the prepared sample at a temperature of 800 °C mentioned by peaks (010), (110), and (0116) related to the tetragonal phase. Their intensities were twice incomparable with the peaks that appeared at calcination temperature at around 850 °C. That is returned to high tetragonally and high stability in the atomic distribution within the unit cell. The structure simulation was applied due to the experimental X-ray patterns to investigate the formation of tetragonal shape via a unit cell. A Williamson-Hall method was used to show the crystallite size and the possible strain in the unit cell. It was found the lowest value of strain about (0.0005) appeared at calcination temperature of 800 °C. SEM and EDS had accomplished the surface morphology and elements concentration, their results were confirmed with XRD analysis .

Phosphate glass with different Al2O3 and Na2CO3 compositions [80NaH2PO4-(20-x) Na2CO3-xAl2O3 with a step from 0 to 4] were prepared through melt quenching technique furnace at 900 °C. In order to determine the structure and microstructure modification of the samples after heat treatment the IR and Raman spectroscopy were performed. The X-ray diffraction (XRD) result shows an amorphous character of the prepared glass. The result obtained by differential scanning calorimetry (DSC) reveals a good thermal stability in the temperature range of 25 to 400 °C. The impedance Nyquist diagrams were investigated and modeled by resistors and constant phase elements (CPE) equivalent circuits. These measurements show a non-Debye type dielectric relaxation. Both AC and DC conductivity, dielectric constant, and loss factors were determined. Thermal activation energies were also calculated. A changes in the electrical conductivity and activation energy depend upon the chemical composition were observed. Also, a transition in the conduction mechanism from ionic to mixed ionic polaronic was noted. In the same line, electrical modulus and dielectric loss parameters are also deduced. Their frequency and temperature dependency exhibited relaxation behavior. Likewise, activation energies value obtained from the analysis of M’’ and those obtained from the conductivity are closes, which proves the optimal character of the preparation conditions.

Hybrid composite finds wide application in various fields. In this present study, the hybrid composites are developed using stir casting technique as per Taguchi’s L9 orthogonal array. Hybrid composites were fabricated using Aluminium Al6082 as the base material and reinforced with the combinations of reinforcements Al2SiO5 and B4C at three levels (4%, 8% and 12%).The developed composites were analyzed for micro structural  investigations and mechanical tests were done as per ASTM standards. The micro structural analysis was done using optical Microscope and Scanning electron microscope while composition studies were done using X-ray diffraction and EDAX. Mechanical test like tensile, impact and flexural were conducted and their damage assessment was done using Scanning electron microscope. The fatigue characteristics like high cycle fatigue and fatigue crack propagation was studied both experimentally and numerically. The experimental data and numerical modeling analysis data obtained for the hybrid composite system, agree with each other.

In this study we have synthesis the Zr substituted BaTi0.80Fe0.20O3 ceramics at different content of Zr from x=0.00 to 0.10 by using the solid-state route. The room temperature X-ray diffraction results confirmed the coexistence of the two tetragonal and hexagonal phases for x ≤ 0.050 of Zr content. While above 0.050 the hexagonal phase disappears in benefit of tetragonal phase. The Raman results confirmed the formation of these phases obtained with XRD. The scanning electron micrographs consist of both spherical and straight grain forms for x=0.000 to 0.075, and only spherical grain form for x=0.100 attributed to the tetragonal phase. Also, the grain size increases accompanied with a decrease in density of ceramics with increasing Zr content up to 0.050 then decreases accompanied with an increase in density. Detailed studies of dielectric permittivity measurement have provided a presence of two anomalies Te and TR-O at different temperatures, with a relaxation phenomenon and diffuse behavior which is very important for ceramic at x=0.075 of Zr content. The dielectric permittivity values of the two anomalies of Zr substituted BaTi0.80Fe0.20O3 ceramics increase with increase of Zr content and the dielectric loss is minimal at x=0.100 of Zr content. The conductivity increases with the increasing of Zr substitution from 0.025 to 0.075 levels while for x = 0.100 the dielectric conductivity decreases.  And the Cole-Cole analysis indicates a negative thermal resistivity coefficient (NTCR) behavior of these materials and an ideal Debye-type behavior.

In this study, the Al–TiC nanocomposite was produced by the mechanical milling and sintering process. Also, the optimization of the milling parameters was performed by the Taguchi method. The X-ray diffraction analysis, scanning electron microscopy, and microhardness test were used to analyze the phase characterization, microstructure, and mechanical properties of the Al–4% TiC nanocomposite. At first, the milling speed, milling time, and ball to powder weight ratio were considered as the input data, and the microhardness was considered as the output value of the Minitab software. According to the design of the experiment, 27 experiments must be performed, which were reduced to 9 by the Taguchi method. After the milling, the powders were subjected to the cold pressing and subsequent sintering at 450 °C. The microhardness results showed that the Al–4% TiC nanocomposite was formed with a maximum microhardness of 271 HV. Furthermore, a proper model was proposed and the results indicated that there was a good agreement between the experimental and predicted microhardness.

Age hardening behavior and the related changes were studied to elucidate the hardening mechanism of an Ag–Cu–Pd alloy by Differential Scanning Calorimetry (DSC), hardness test, X-ray diffraction (XRD), scanning electron microscopic (SEM) observations and an energy dispersive spectrometer (EDS). The results showed that the hardness of the alloy was raised to 90% and 68% of its solution state value by isothermal aging at 300 ◦C and 400 ◦C, respectively. However, aging at 500 ◦C led to a decrease in the hardness of the alloy. Moreover, while age hardening at 300 ◦C occurred because of coherency strains between the (111) plane of Ag-rich and the (111) plane of Cu3Pd phases, the mechanism of aging at 400 ◦C was the formation of Cu3Pd superlattice with the L12-type crystal structure. In contrast, reduction of the Cu3Pd phase from the microstructure and formation of the Cu solid solution decreased hardness during aging at 500oC.

In this study an effort has been made for the plasma ion nitriding (PIN) of Inconel 600 and 601 alloys at low temperatures. After plasma ion nitriding, microstructure study, growth kinetics of nitrided layer formation and wear properties were investigated by various characterization techniques such as; scanning electron microscope (SEM), X-ray diffraction (XRD) analysis, micro-hardness measurement and wear test by pin on disk technique. It was found that, surface micro-hardness increases after PIN process. A mix peak of epsilon (ε) phase with fcc (γ) phase was detected for all temperature range (350 0C to 450 0C), while the chromium nitride (CrN) phase was detected at elevated temperature range ~450 0C in inconel 601 alloy. The calculated values of diffusion coefficient and activation energy for diffusion of nitrogen are in accordance with the literature. Volume loss and wear rate of the plasma nitrided samples decreases, but it increases as PIN process temperature increases.

The performances of cementitious materials as well as the efficiency of construction are adversely affected at high temperatures. Previous studies have already demonstrated that ultra-fine (alccofine) material accelerates the hydration of cement particles and subsequently improves the mechanical and durability properties of the concrete at normal temperature. Moreover, at higher temperatures the performance of the concrete with the addition of alccofine is still unknown. This paper presents the effect of analytical properties of concrete with alccofine (25%) as a replacement of cement for various W/B ratios (i.e. 0.38, 0.4 and 0.45). The effect of addition of alccofine dosage on the thermogravimetric analysis was carried out in which not only mass loss and decomposition of hydration products from concrete with respect to temperature was found but also bound water (%) and calcium hydroxide (%) present in the concrete were determined. From X-ray diffraction it was observed that alccofine improved the formation of calcium silicate hydrate and calcium silicate aluminum hydrate in concrete and scanning electron microscope (SEM) analysis showed the formation of ettringite needles and calcium silicate hydrate in voids which made concrete denser. Therefore, it was concluded from this study that alccofine can be used as a viable substitute to cement in normal concrete considering its positive effects on property enhancement and an eco-friendly product.

Equal channel angular rolling (ECAR) is a severe  plastic deformation (SPD) technique which has been used to produce metal sheets with ultra-fine grain structure. In the present work, the relationships between the mechanical properties and microstructure of samples during the ECAR process have been investigated. The Rietveld method was applied to analyze the X-ray diffraction pattern and to determine the microstructural characteristics including the crystallite size, microstrain, and dislocation density. It was observed that the average crystallite size and dislocation density increased by increasing the strain during the ECAR process. The results showed that ECAR is a procedure intended to obtain meaningful structural refinement appearing in a crystallite. It can be justified by using Taylor equation that the mechanical properties are related to the dislocation density. The ECAR process strongly increases the yield strength and microhardness due to an increase in the dislocation density over a wide range of strain.

In this project, Bredigite (BG) has been successfully prepared by a modified sol-gel method. Optimization in calcination temperature and mechanical ball milling resulted in a pure and nano-sized powder which characterized by means of X-ray diffraction; scanning electron microscopy, transmission electron microscopy and Fourier transform infrared Spectroscopy. We hypothesized that nano-sized Bredigite (BG) would mimic more efficiently the nanocrystal structure and function of natural bone apatite, owing to the higher surface area, compare to conventional micron-size Bredigite (BG). Accordingly, we used the unique advantage of nanotechnology to improve novel nanobredigite (NBG) particles as a potential candidate for bone tissue regeneration whether as a peri-implant filling powder or in combination with other biomaterials as a composite scaffold

The aim of this research is to investigate different X-ray based quantitative phase analysis methods for determination of cristobalite phase content in ceramic cores. For this purpose, four popular routes including peak absolute intensity method, relative intensity ratio method, direct or calibration method and internal standard (or Alexander-Klug) method have been chosen. Some control samples have been made using common raw materials used in the ceramic cores and characterized by X-ray diffraction (XRD) to measure the main peaks intensities. Using each quantitative method with their unique mathematical calculation procedures, the cristobalite phase contents have been calculated and compared to the real contents in the samples. The results showed that the presence of the amorphous fused silica phase could make drastic effects on the accuracy of the X-ray based quantitative phase analysis routes and the peak absolute intensity method showed the best results among the other routes.