Iranian Journal of Materials Science and Engineering

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Abstract: The PZT-based ceramics with a composition of Pb1.1-xLax (Zr0.53Ti0.47)O3, were prepared by conventional mixed oxide followed by mechanical alloying and sol-gel methods in which x was chosen in the range of 0.02–0.06. The samples were calcined in the range of 450 °C - 750 °C for 4h. The physical and electrical properties of the samples were determined as a function of the calcination temperature. The obtained data from two methods were compared with conventional mixed oxide method. Microstructural and compositional analyses of the samples were carried out using XRD and SEM. Dielectric properties of the samples were measured with an impedance analyzer. The ferroelectric properties of the PZT and PLZT samples were measured using the frequencies applying equipment and d33 tester. The results indicated a complete tetragonal phase prepared from both methods. It was shown that the addition of La and reduction in calcination temperature improved both the dielectric and piezoelectric properties. The dielectric constant tended to increase with doping content, giving the maximum value of about 2000 at 3 mol% La3+. In addition, the mechanical coupling factor (Qm) of the doped samples showed a significant decrease. Finally, the value of planar coupling factor (kp) reached the maximum value of 0.47 at 1 mol% La3+.

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Abstract: Rotating bending fatigue tests have been performed using smooth specimens of a rolled AZ31 magnesium alloy in laboratory air at ambient temperature. Fatigue strength and characteristic was evaluated and fracture mechanism was discussed on the basis fracture surface analysis. Electrical polishing (EP) as well as deep rolling (ball burnishing (BB)) U-notched specimens were performed on two groups of samples, to evaluate optimum conditions for fatigue life. The microstructure and tensile properties of roll cast (RC) Mg- 3% Al- 1% Zn (AZ31) was investigated. The fatigue strength of 107 cycles around 100 MPa for deep rolling while it was around 40 MPa for Electrical polishing. It was very important to understand the effect of (ball burnishing (BB)) conditions on the hardness of the surface through to the core. The two procedures improved the fatigue performance, but better improve in results were found in ball burnishing. The growth of small cracks initiated at the surface coincided with the FCP characteristic after allowing for crack closure for large cracks, but the operative fracture mechanisms were different between small and large cracks. At the subsurface crack initiation site, smooth facets were always present regardless of applied stress level.

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In this paper we have investigated the physical properties of reduced graphene oxide (RGO) thin films prepared at various substrate temperatures of 230, 260, 290, 320 and 350 ^oC using spray pyrolysis technique. We have compared these films from various viewpoints, including structural, morphological, optical, electrical and thermos-electrical properties. XRD analysis showed a phase shift from graphene oxide (GO) to RGO due to elevate the substrate temperature from 200 ^oC to higher temperatures. FESEM images of RGO thin films reveal that a stacked image of irregular and folding nanosheets, and rod-like features at temperatures below and above 290 ^oC; respectively. Optical studies showed that the layers have a relatively high absorption coefficient (∼0.8×10⁴ to 1.7×10⁴ cm⁻¹) in the visible range, with an optical band gap of 1.67–1.88 eV. The Hall effect data showed that all samples have a p-type conductivity with a hole concentration of ∼10¹⁵ cm⁻³, and sheet resistance values of about 10⁶ Ω/sq, in agreement with previous reports. The thermoelectric measurements revealed that with increasing applied temperature gradient between the two ends of the samples, the thermoelectric electromotive force (emf) of the prepared RGO thin films increases.

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Cu-based alloys have a wide range of applications in the electronics industry, communications industry, welding industries, etc. Regarding the type and percentage of the second phase, changing in the alloying elements has a significant effect on the mechanical and electrical properties of copper composites. The aim of the present work is to synthesize, investigate, and compare the micro-structure, micro-hardness, and electrical properties of different Cu-based nanocomposites. For this purpose, Cu-Al, Cu-Al₂O₃, Cu-Cr, and Cu-Ti were fabricated via ball milling of copper with 1, 3, and 6 weight percentages. The vial speed was 350 rpm and the ball-to-powder weight ratio was kept at 15:1. The milling process was performed at different times in Argon. Next, the prepared composites were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic light scattering (DLS). Based on XRD patterns, crystallite size, lattice strain, and lattice constant were calculated by Rietveld refinement using Maud software. The results show a decrease of crystallite size, and an increase of the internal strain and lattice constant by rising the alloying elements in all composites. Then, the produced powders compressed via the cold press and annealed at 650˚C. Finally; the micro-hardness and the electrical resistance of the manufactured tablets were measured. The results of these analyses show that micro-hardness is increased by enhancement of the reinforcement material, due to the rising of the work hardening. Cu-6wt%Ti with 312 Vickers and Cu-1wt%Al₂O₃ with 78 Vickers had the highest and lowest micro-hardness, respectively. Moreover, the results of the electrical resistance indicate a dramatic rise in the electrical resistance by increasing the amount of alloying material, which Cu-1wt%Al with 0.26 Ω had the highest electrical conductivity.

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Copper oxide thin layers were elaborated using the sol-gel dip-coating. The thickness effect on morphological, structural, optical and electrical properties was studied. Copper chloride dihydrate was used as precursor and dissolved into methanol. The scanning electron microscopy analysis results showed that there is continuity in formation of the clusters and the nuclei with the increase of number of the dips. X-ray diffractogram showed that all the films are polycrystalline cupric oxide CuO phase with monoclinic structure with grain size in the range of 30.72 - 26.58 nm. The obtained films are clear blackin appearance, which are confirmed by the optical transmittance spectra. The optical band gap energies of the deposited films vary from 3.80 to 3.70 eV. The electrical conductivity of the films decreases from 1.90.10^-2 to 7.39.10^-3 (Ω.cm)^-1

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Temperature is one of the key factor that affecting the electrical, physical, structural, and morphological properties as well as the crystallinity of the nanomaterials. The current study investigates the effect of annealing temperature on the structural and electrical properties of lanthanum oxide (La2O3) thick films. La2O3 thick films were prepared on a glass substrate using a conventional screen printing technique. In this work, T1 is an unannealed prepared film, whereas T2 and T3 are annealed in a muffle furnace for 3 hours at 350°C and 450°C, respectively. XRD technique was exploited to investigate the crystallization behavior of the films. It was found that the crystal structure of La2O3 thick films are pure hexagonal phase. The annealing temperatures were revealed to have influence on the crystallite sizes of the films. SEM and EDS was used to study the morphology and elemental analysis of the films respectively. The electrical properties of the films were explored by measuring resistivity, temperature coefficient of resistivity (TCR), and activation energy at lower and higher temperatures regions. The film annealed at 450°C has high resistivity, a high TCR, and small crystallite size. The thickness of the La2O3 thick films was also found to decrease as the annealing temperature increased.

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The effect of different Nd and PT compositions on the electrical and ferroelectric properties of (1-y)Bi_1-xNd_xFeO₃-yPbTiO₃ solid solutions, where x = 0.05, 0.10, 0.15, 0.20 and y = 0.1, 0.2, 0.3, and 0.4, was investigated to optimise material performance. Nd doping enhances the frequency-dependent dielectric properties of produced solid solutions. However, an anomaly in the dielectric loss tangent, which is consistent with the Debye relaxation process, is observed for compositions with x˂0.10 and y≥0.2 values in the frequency range of 1 KHz to 1 MHz. Dielectric anomalies were more noticeable around the transition temperature in temperature-dependent dielectric characteristics plots, suggesting stronger magnetoelectric interactions. The decrease in the dielectric constant for solid solution compositions with y ≥0.3 indicates the presence of MPB with BFO due to an increase in the tetragonal phase of the PbTiO3 compound. As Nd content increases, temperature-dependent dielectric permittivity predicts relaxor-type ferroelectric performance for y=0.4 composition of solid solutions. A ferroelectric investigation showed that saturation polarisation, remnant polarisation, and coercive field of all prepared solid solutions decrease with increased Nd doping. However, for y˃0.3 composition, a substantial rise in these parameters was observed, which is a result of electric order dominating over magnetic order in solid solutions. The study reveals that Nd doping reduces leakage current, making it a promising contender for future applications
 

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In this research work, Cadmium Sulphide thin film deposited on to glass substrate in a non-aqueous medium at 80 °C. The various physical preparative parameters and the deposition conditions, such as the deposition time and temperature, concentrations of the chemical species, pH, speed of mechanical stirring, etc., were optimized to yield good quality films. The as-prepared sample is tightly adherent to the substrate's support, less smooth, diffusely reflecting and was analyzed for composition. The synthesized film is characterized using X- ray diffraction (XRD), electrical and optical properties. It appears that the composites are rich in Cd. The grown CdS thin film had an orange-red color. A band gap of CdS thin film is 2.41 eV.  The average crystallite size of the CdS film was 21.50 nm. The resistivity of the CdS thin film is about 5.212 x 10⁵ W cm.