| 1. |
- Shakoury, Reza, et al.
(författare)
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Ion beam assisted electron gun deposition of MgF2 thin films Effects of Argon ion bombardment on the optical and morphological properties
- 2022
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Ingår i: Vakuum in Forschung und Praxis. - : WILEY-V C H VERLAG GMBH. - 0947-076X .- 1522-2454. ; 34:1, s. 36-40
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Tidskriftsartikel (refereegranskat)abstract
- A traditional method for increasing the density of the optical films, is heating the substrate. An alternative way to increase the density of the film, is bombardment of substrate by ions during film growth. This method is known as ion assisted deposition (IAD). In this paper, magnesium fluoride, MgF2, thin film has been produced on a glass substrate by ion assisted deposition method.The effects of ion energy have been studied on density and refractive index film. Reflection, transmission and scattering spectra of the samples were measured by a spectrophotometer. Moreover, Atomic force microscope (AFM) is prepared. Using these measurements, optical and physical properties of the films are analyzed. A sample of MgF2 film has been produced without ion bombardment so that one can compare the effect of ion bombardment.
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| 2. |
- Ghobadi, Nader, et al.
(författare)
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Optical transitions and photocatalytic activity of NiSe films prepared by the chemical solution deposition method
- 2022
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Ingår i: The European Physical Journal Plus. - : SPRINGER HEIDELBERG. - 2190-5444. ; 137:6
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Tidskriftsartikel (refereegranskat)abstract
- In this work, nanostructured NiSe thin films were prepared by the chemical solution deposition method at different pH fixing the deposition time. The surface morphology, structural and semiconductor properties of such films were investigated utilizing different methodologies. It was found that slight changes in pH can influence the optical bandgap and structure of NiSe films. The results of Tauc's plot and the derivation of the ineffective thickness method were compared to estimate the optical bandgap energy and the transition index. Additionally, the Urbach energy was also assessed. The potential of the NiSe nanostructured samples as photocatalysts was evaluated by analyzing the decomposition of azoic Congo red dye under visible light radiation.
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| 3. |
- Grayeli, A., et al.
(författare)
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Structural, morphological, and optical bandgap properties of ZnS thin films : a case study on thickness dependence
- 2024
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Ingår i: Optical and quantum electronics. - : Springer. - 0306-8919 .- 1572-817X. ; 56:7
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of zinc sulfide (ZnS) with varying thicknesses have been successfully fabricated using radio frequency magnetron sputtering on glass substrates at a temperature of 300 K. Structural analysis via X-ray diffraction and selected area electron diffraction confirmed the presence of nanocrystalline cubic ZnS phases in the films. The crystallite size, determined from X-ray diffraction lines, ranged between 42 and 55 nm. We also explored the morphological attributes of these surfaces and observed significant changes in both grain shape and size. Our atomic force microscopy analyses revealed that the thinner film displayed a topography marked by thinner, elongated rough peaks. As the film thickness increased, these rough peaks gradually transformed into wider, flatter features. Additionally, the films exhibited distinct percolation properties, which were undeniably tied to the alterations in the shape and size of the ZnS grains on their surfaces. Thinner samples demonstrated more pronounced surface percolation (FS > 0.5) compared to thicker samples, which displayed reduced surface percolation. Furthermore, we noted that the 250 nm film predominantly showcased strongly multifractal 3D spatial patterns in contrast to the other films. Spectroscopic measurements in the UV–visible-near infrared region revealed high transparency across the 350–850 nm spectra, with a noticeable blue shift in the absorption edge. Calculations yielded direct allowed band gaps within the range of 3.69–3.85 eV. These results indicate that the optical properties of films can be tailored by their structural and morphological characteristics, thereby offering valuable guidance for their appropriate applications.
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| 4. |
- Habibi, Maryam, et al.
(författare)
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Corrosion resistance and surface microstructure of Mg 3 N 2 / SS thin films by plasma focus instrument
- 2022
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Ingår i: Microscopy research and technique (Print). - : Wiley. - 1059-910X .- 1097-0029. ; 85:8, s. 2880-2893
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing a plasma focus (PF) instrument, magnesium nitride (Mg3 N2 ) thin films were synthesized on stainless steel substrates. Twenty five optimum focus shots at 8 cm distance from the anode tip were used to deposit the films at different angular positions regarded to the anode axis. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) analyses were performed to assess the surface morphology and structural characteristics of Mg3 N2 films. Based on AFM images, these films were studied to understand the effect of angular position variation on their surfaces through morphological and fractal parameters. By increasing the angle, we verify that the grain size decreased from 130(0) nm to 75(5) nm and also the mean quadratic surface roughness of the films reduced in its average values from (28.97 ± 3.24) nm to (23.10 ± 1.34) nm. Power spectrum density analysis indicated that films become more self-affine at larger angles. Furthermore, the corrosion behavior of the films was investigated through a potentiodynamic polarization test in H2 SO4 solution. It was found that the ion energy and flux, varying with the angular positions from the anode tip, directly affected the nanostructured roughness and surface morphology of the samples. The electrochemical studies of films show that the uncoated sample presented the lowest corrosion resistance. The highest corrosion resistance was obtained for the sample deposited with 25 optimum shots and at 0° angular position reaching a reduction in the corrosion current density of almost 800 times compared to the pure stainless steel-304 substrate.
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| 5. |
- Habibi, M., et al.
(författare)
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Microstructure, fractal geometry and corrosion properties of CrN thin films : The effect of shot number and angular position
- 2022
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Ingår i: Materials Today Communications. - : Elsevier Ltd. - 2352-4928. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- The effect of different plasma focus shots and angular positions (0° and 30°) on the properties of chromium nitride (CrN) coatings, deposited by a plasma focus (PF) device on stainless steel substrates, have been systematically investigated in this paper. The structural and morphological properties of CrN thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). Moreover, the corrosion behavior of the CrN thin films was investigated using the ‘c’ method. The XRD patterns demonstrated the growth of the polycrystalline structure composed of CrN/Cr2N nanograins and the enhanced crystallinity of the CrN coatings upon increasing the shot numbers. In addition, AFM results showed enhanced multifractal properties of the sample prepared at 0° angular position and a reducing trend in these properties for the layers prepared at 30° angular position. Moreover, they exhibited sharp hillock-like features on the surface, corresponding to the columnar growth of the CrN coatings, which further protruded as the number of shots increased. The results of the corrosion test showed that the resistance of stainless-steel substrate was improved by depositing the CrN coatings due to the formation of a passive and protective layer on its surface. Notably, ceramic CrN film, prepared through 10 shots at 30° angular position, showed the best corrosion resistance. Our strategy is advantageous for designing and manufacturing novel devices and instruments based on CrN corrosion resistant coating.
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| 6. |
- Sadeghi, Mohammad, 1962-, et al.
(författare)
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Comparing half-metallic, MOKE, and thermoelectric behavior of the CrTiZ (Z = As, P) half-Heuslers : a DFT study
- 2021
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Ingår i: Materials Research Express. - : IOP PUBLISHING LTD. - 2053-1591. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- Structural, half-metallic, magneto-optic, and thermoelectric properties of CrTiZ (Z = As, P) half-Heusleres compounds are investigated based on density functional theory. These compounds have mechanical stability in the ferromagnetic state with a high bulk modulus. They are often half-metallic with a large and integer magnetic moment and are very attractive in spintronics, magneto-optics applications. The magnetic moments of CrTiAs and CrTiP were 2.9865 mu (B) and 3.00 mu (B), respectively, which were attributed to their ferromagnetic phase. Additionally, the positive sign of the phonon branches indicates the dynamic stability of these compounds. Applying both GGA and mBJ approximations, CrTiAs and CrTiP compounds exhibited a half-metallic nature by 100% spin polarization. The Kerr angle obtained from magneto-optic results demonstrated a high-intense peak for these compounds in the visible edge with a negative sign. Eventually, a figure of merit with a value above the room temperature was found for both compounds in which the holes are charge carriers.
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| 7. |
- Sadeghi, Mohammad, 1962-, et al.
(författare)
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Evaluating the Topological Surface Properties of Cu/Cr Thin Films Using 3D Atomic Force Microscopy Topographical Maps
- 2022
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Ingår i: Coatings. - : MDPI. - 2079-6412. ; 12:9
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, Cu/Cr thin films were deposited on substrates of a different nature (Si, Glass, Bk7, and ITO) through a thermal evaporation deposition method. Non-contact atomic force microscopy (AFM) was used to obtain 3D AFM topographical maps of the surface for the Cu/Cr samples. Various analyses were carried out to obtain crucial parameters for the characterization of the surface features. In particular, Minkowski functionals (including the normalized Minkowski volume, the Minkowski boundary, and the Minkowski connectivity) and studies of the spatial microtexture by fractal and multifractal analyses were carried out. Different roughness parameters (including arithmetical mean height, root mean square height, skewness, kurtosis, fractal dimension, Hurst coefficient, topographical entropy, and fractal lacunarity) were quantified in these analyses for the comparison of the surface morphology of the different samples. All the samples displayed non-Gaussian randomly rough surfaces, indicating the presence of multifractal features.
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| 8. |
- Sadeghi, Mohammad, 1962-, et al.
(författare)
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Influence of ion implantation on corrosion resistance of the nickel over steel
- 2023
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Ingår i: Materials Science and Technology. - : TAYLOR & FRANCIS LTD. - 0267-0836 .- 1743-2847.
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen ions were implanted at different energies of 15, 30, 45 and 60 keV and with the flux of 10(17) N(+)cm(-2) inside the nickel layers that have been deposited on the 304 stainless steel using the electron gun method at room temperature. XRD patterns showed different crystalline phases of nickel nitride for the implanted samples. The surface morphology was extracted by MountainsMap software's using statistical data from AFM analysis. In addition, a potentiodynamic polarisation test was performed in a 3.5% NaCl solution to study the corrosion behaviour. These studies revealed that corrosion was directly related to the deposition parameters, mainly the implantation energy, modifying the surface so that the highest corrosion resistance was obtained for the sample implanted with 60 keV.
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| 9. |
- Sadeghi, Mohammad, 1962-, et al.
(författare)
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Numerical determination of process parameters for fabrication of automotive component
- 2010
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Ingår i: solidification simulation.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The casting defects that are caused by molten metal are cold shut formation, entrapment of air, gas, and inclusion. But the control of casting defects has been based on the experience of the foundry engineers. One of the most parameters that can influence the casting defects is cooling rate. In this paper, computer simulations have been carried out to analyze the flow of molten metal and effect of die temperature on the cooling rate and subsequently the casting defects. Flow patterns of molten metal in one of the Iranian automotive component were examined to find the optimal temperature for the die-casting die temperature. The finite element ProCast software was used for simulation and results of simulation was compared with the experiment. The calculated results for automobile Ladder frame body to control the die-casting process have achieved good agreements with the experimental data. Results show that temperatures between 20°C to 25°C are good for the die casting.
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| 10. |
- Sadeghi, Mohammad, 1962-
(författare)
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Optimization product parts in high pressure die casting process
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis describes optimization of die temperature in high pressure die-casting (HPDC) of A380 alloy by experimental observation and numerical simulation with the use of statistical tools. The goal of this research is to determine the optimum die temperature to minimize incidence of these defects and thus maximize production of parts without defects. In HPDC, molten metal is injected into the die at high speed (40-60 m/s for aluminum alloys). Die temperature plays an important role on the rate of rejected parts. Therefore, flow patterns of molten metal in HPDC of an automotive component with very complex geometry (the ladder frame from the EF7 motor) were examined to determine the optimal die temperature.Defects in the production process fall into three categories, including surface, internal and dimensional defects. Samples produced in the experiments were classified according to any present defects.Another important parameter that influences casting defects is the cooling rate. Die temperatures were measured at the initial step and final filling positions. Experiments were performed with die temperatures ranging from 150 °C to 250 °C. The results show that the melt temperature difference in the die between the initial step and the final filling position was between 20 and 25 °C.Statistical tools such as regressions, relationships, max, min, correlations, ANOVA, T-test, Principal Component Analysis (PCA) and descriptive statistics were used to facilitate interpretation of data from the die-cast experiments.Perform some case studies in order to study the process behavior, take a better knowledge of effective parameters, and measure the required parameters. The collected data are utilized to:Set the modelValidate/ verify the modelProCast software was used to simulate the fluid flow and solidification step, and the results were verified by experimental measurements. The optimal die temperature for this alloy was found to be above 200 oC.Statistical analysis of the experimental results found that defects were minimized and confirmed parts were maximized in HPDC of the ladder frame within a die temperature range of 210° C to 215° C.
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