Papers by Keyword: Structural

Abstract: Increasing the operational reliability and durability of parts and mechanisms used to operate under conditions of intense wear, loads, high pressure and temperatures requires the protection of working surfaces with functional coatings. The E.O. Paton Institute of Electric Welding of the National Academy of Sciences of Ukraine has developed a technology and equipment for multichamber detonation spraying (MCDS) of these coatings. This paper summarizes the data of experimental studies of the structure of composite coatings of various systems (Ni–Cr–Fe–B–Si, Cr₃C₂–NiCr, WC–Co–Cr, ZrSiO₄, and Al₂O₃) for different materials. Research has established the influence of technological modes of spraying on structural and phase changes in the coating materials obtained by detonation spraying. Under different processing modes, the materials change volume fraction of phase components, microhardness, (sub)grain structure parameters, size of dispersed phases, and nature and distribution of dislocation density. The peculiarity of the structure of coatings obtained by the MCDS method is the formation of a dispersed structure, the presence of a nanoscale substructure and nanoparticles of hardening phases with a size of 10–100 nm. The formation of a nanostructural state contributes to an increase in the strength, fracture toughness, and crack resistance of coatings obtained by the MCDS method.

Abstract: In this paper, a Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ composite with a weight ratio of 1:9 has been successfully created. The Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ was synthesized in HEM for 35 hours before sintered at 1000°C for 5 hours. The Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ composite was characterized using XRD for phase formation, crystal structure, and lattice parameters. Based on the XRD results, the Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ composite has two phases with different crystal structures. SEM characterization for surface morphology and particle size. SEM results show heterogeneous particles, but the particle size is not uniform at 0.2-0.6 µm. Measurements of the dielectric constant and dielectric loss are shown as a function of frequency. VSM is used to characterize samples magnetically. The VSM results show ferromagnetic behaviour in the Ba_0.6Sr_0.4Fe_11.50Al_0.50O₁₉/MoS₂ composite with the value of Mr, Ms, and Hc are about 20 emu/g, 40.769 emu/g, and 4.08 kOe, respectively.

Abstract: The research investigates the application of static structural finite element analyses in studying spiral bevel teeth gear of Polski fiat with four tooth angles at 25, 30, 35, 40 degrees. The researchers simulated 16 times using Ansys, investigating all the load cases. These included elements such as deformations, normal stress, equivalent stress at the tooth contacts. Findings provide guidance on gear updating and improvement in gearbox gearing response, which enhance subsequent generation mechanical systems.

Abstract: Fused Deposition Modelling (FDM) is a common technique used when rapid prototyping is needed to perform a preliminary evaluation of the suitability of a part. For this purpose, several materials, as PLA, ABS, PET-G and others, are easily available in the market along with a wide range of commercial 3D printers at affordable prices. Prototypes manufactured under this technique are usually made of a single material and, for most of the applications, it is enough to fulfill the required specifications. However, the increasing demand for the manufacturing of parts made of more than one material suggests that prototyping via FDM using two dissimilar materials should be assessed to assure that such technique is still acceptable to perform a preliminary evaluation of a part. For this purpose, a methodology using a commercial FDM 3D printer is proposed to characterize the flexural and shear bonding behavior of two dissimilar materials. This methodology implements four steps: The selection of the applicable UNE standards as main reference, the design and manufacture of the test specimens based on these standards, the execution of the structural tests to characterize the behavior of those specimens and the analysis of the test data along with the conclusions. This methodology has been validated using ABS and PLA as base materials. The coherence and accuracy of the results obtained from this specific case substantiate that it is a valid methodology to evaluate the structural behavior of the bonding of two dissimilar materials, beyond PLA and ABS, using commercial and affordable off-the-shelf 3D printers.

Abstract: Cerium oxide, also known as CeO₂, can be synthesized by the hydrothermal process with cerium nitrate precursor solution. After drying and sintering at 800,900, and 1100 C, different-sized cerium oxide nanoparticles were produced from the solution. Using x-ray diffractometers, the researchers were able to determine that all of the cerium oxide nanoparticles have a unique structure called fluorite crystalline structures. The structural, morphological and optical properties of films were investigated by a set of characterization techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). The estimation of crystallite size is (22.12,27.34 and 42.02 nm), which is confirmed by Scherrer formulae from XRD pattern. The dielectric constant increased with the increase of crystallite size due to the size effect. The crystal size increased with increased sintering temperature. Keywords: Cerium oxide (CeO₂), structural, crystal size, , morphology,Dielectric constant.

Abstract: The emergence of Dilute Magnetic Semiconductors (DMS) with a potentials for spintronic application have attracted much researches attention, special consideration has been given to ZnO semiconductor material due to its wide band gap of 3.37 eV, large exciting binding energy of 60 meV, moreover, its ferromagnetic behavior at room temperature when doped with transition metals. M_xZn_1-xO (M = Fe or Ni) nanoparticles were synthesized by microwave assisted synthesis method calcined at 600°C. The structural, morphological and magnetic properties of these nanoparticles were studied using X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Vibrating Sample Magnetometer (VSM) respectively. Single phase Wurtzite hexagonal crystal structure was observed for the undoped and Fe doped ZnO nanoparticles with no any impurity, whereas Ni doped ZnO nanoparticles shows the formation of NiO impurities. The magnetic measurement reveals a diamagnetic behavior for the undoped ZnO meanwhile a clear room temperature ferromagnetism was observed for both Fe and Ni doped ZnO. Fe doped ZnO present a high saturation magnetization compared to Ni doped ZnO. However, Ni doped ZnO present high coercivity. The research was confirmed that Fe doped ZnO material will be good material combination for spintronic applications.

Abstract: CdS thin films have been grown on glass substrate at 250^o C employing pulsed laser deposition method. The effect of laser pulses number on the crystalline structure, surface morphology, optical properties, and films thickness have been studied. XRD analysis shows that the CdS films have polycrystalline and hexagonal nanostructure with three notable peaks along (100), (002), and (101) planes and preferentially orientated along (101). The crystallite size of the preferred orientation was in the range of (21.4 - 27.3 nm). With small pulses number, XRD pattern confirms the formation of CdO with three peaks (111), (200), and (220). Theses peaks gradually reduce with the increasing of the pulses. The absorbance of the films is in the visible part of the spectrum. The band gap of the synthesized films reduces by rising the number of laser pulses. AFM studies indicate that the grain size and surface roughness increase with the film thickness. Due to the good crystalline structure and optical properties of the film of the highest thickness, it has been grown on a wafer silicon substrate for solar cell applications measurements. Hall measurements indicate low resistivity of 0.3×10-2 (Ω.m) and high conductivity of 3.3×10+2 (Ω.m)-1. The efficiency of the n-CdS/ p-Si junction has been calculated to be 3.4 % using I-V characteristic measurement. Keywords: pulsed laser, thin films, structural, optical, morphology, solar cell measurements

Abstract: Ni-TiO₂ nanocomposite coatings were fabricated on mild steel surface by pulsed direct current (PC) electrodeposition. This process was carried out in pulsed current at (1, 10, 50) Hz and a duty cycle (25%, 50%, 75%) respectively, at a minimum current density of 0 & high current density of 4 A/dm². In this work the properties of nanocomposite films were investigated using scanning electron microscopy (SEM), Vickers microhardness measurements and Tafel polarization tests. The composition of the electrodeposits was analyzed by energy dispersive X-ray analysis (EDX). It was found that the coated surface contained at maximum 16.30 % Ti and 35.48 % O. XRD studies revealed [111] preferred orientation. Hardness increased from 560.4 Hv for Ni-TiO₂ (F=10 Hz, DC=75 %) nanocomposite coating to 645.7 Hv for Ni-TiO₂ (F=10 Hz, DC=25 %) nanocomposite coating. The corrosion resistance of Ni-TiO₂ coatings was evaluated by potentiodynamic polarization studies in 3.5 % NaCl solutions. The Pulsed current offer composite coatings with uniform surface, high microhardness and enhanced corrosion resistance significantly for F=10Hz and DC=25 %.

Abstract: The polycrystalline Ca_0.9La_0.05Bi_0.05Mn_1-xNi_xO₃ (x = 0.025, 0.05, 0.075) samples were synthesized by sol-gel method. All samples were calcined at 650°C for 8 hours and sintered at 900°C for 8 hours. The structural and morphological properties of the samples were measured by X-ray diffraction (XRD) and Scanning electron microscope (SEM). The rietveld refinement shows that all samples were having an orthorhombic structure with pnma space group despite having different Ni content. Furthermore, the average crystallite size decreases with Ni substituion. SEM result shows the average grain size decreases with increasing Ni substitution regardless of the same heat treatment. This result will affect other properties like electrical and magnetic properties.

Abstract: In this work, ZnO thin films were prepared by the low-cost sol-gel deposition method onto six different substrates (glass, ITO coated glass, sapphire (Al₂O₃), p-Si, p-GaN and polyethylene terephthalate (PET)) to study the effects of these substrates on the morphological and structural properties of the produced films. Precursor solution is Zinc acetate dihydrate based dissolved in ethanol with monoethanolamine (C₂H₇NO) added to act as a stabilizing agent to the sol. The corresponding ZnO thin films were characterized using field emission scanning electron microscopy (FESEM), high resolution X-ray diffraction (XRD) and atomic force microscopy (AFM). Results revealed distinct morphological and structural properties of ZnO thin films deposited on each substrate. The most uniform morphology was identified on glass, owing to the acquisition of the averagely stable grain sizes (58 nm – 61 nm) and thin film thicknesses (280 nm – 325 nm). High resolution XRD analysis showed that the films deposited on glass, ITO, p-Si, and p-GaN were attributed to hexagonal crystallite structures while the films deposited on sapphire and PET substrates exhibited amorphous phases. Amongst the samples, the ZnO thin film spin coated on p-Si demonstrated preferred orientation in (002) direction.