Abdulaziz N. Alhazaa

Microstructural properties and enhanced photocatalytic performance of Zn doped CeO 2 nanocrystals

The microstructural, optical and photocatalytic properties of undoped and 5% Zn doped CeO2 nanocrystals (NCs) have been explored through various analytical techniques, viz. powder x-ray diffraction (PXRD), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-visible, Raman and photoluminescence (PL) spectroscopy. XRD data analysis revealed face centred cubic (FCC) crystal symmetry of the samples with average crystallite size in the range of 19–24 nm. XPS results confirmed that the Zn ions exist in +2 states and successfully incorporated into the CeO2 matrix. Internal structure and morphology observed by TEM exhibited almost uniform cubical shape of the particles of average size ~20–26 nm. The enegy bandgap of undoped and Zn doped CeO2 NCs had a direct transition of 3.46 eV and 3.57 eV respectively as estimated by the optical absorption data. The increase in the bandgap revealed blue shift of absorption edge due to the quantum confinement effects. The NCs exhibited an inherent luminescence emission peak at ~408 nm in PL spectra. Improvement in the photocatalytic activity was observed for Zn incorporated sample attributed to the enhanced light absorption or/and fall in charge recombination rate between CeO2 and Zn.

Effect of Bonding Temperature on the Microstructure and Strength of the Joint between Magnesium AZ31 and Ti-6Al-4V Alloys Using Copper Coatings and Tin Interlayers

Transient Liquid Phase (TLP) bonding was performed between Mg-AZ31 and Ti-6Al-4V alloys with various bonding temperatures using Cu coatings and Sn interlayers. The bonding parameters such as bonding pressure and bonding time were fixed at 1 MPa and 15 minutes respectively in order to study the effect of bonding temperature on the joint evolution. Bonds made at temperatures of 540, 560, 580 and 600 C showed good bond strength. The obtained bonds were investigated by Electron Probe Micro-analyzer EPMA and showed reaction layers and diffusion zones for all bonds made. The maximum joint shear strength of 78 MPa was obtained for bond made at 580 C. X-ray diffraction XRD and X-ray photoelectron spectroscopy XPS were taken for the fractured surfaces of bond made at 580 C. The analysis of the fractured surfaces found that the reaction layer contains Sn5Ti6 IMC in the titanium side and Mg2Cu IMC in the magnesium side where the fracture occurs at the diffusion zone in the mg side.

Au doping effect on the electrical and magnetic properties of Fe3O4 nanoparticles

Impurities free ferromagnetic Fe3O4 was prepared via sol–gel auto-combustion method and then gold was doped with various concentrations 1, 3 and 5 wt.% using conventional deposition–precipitation method. All samples of Fe3O4 with/without Au doping were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The room temperature magnetic hysteresis loops of all the samples were measured using a physical property measuring system (PPMS), and the results showed a ferromagnetic behavior at room temperature. The results obtained confirmed the fabrication of magnetite–gold composite nanoparticles. The results showed that the resistance and the magnetic behavior of the samples decrease sharply with the increase of Au concentration indicating semiconducting behavior. The saturation magnetization (Ms) of the bare Fe3O4 sample (94.72 emu/g) is much higher than that (66.78 emu/g) of the 5 wt.% Au-doped Fe3O4 sample.

Evaluation of Surface Roughness by Image Processing of a Shot-Peened, TIG-Welded Aluminum 6061-T6 Alloy: An Experimental Case Study

Visual inspection through image processing of welding and shot-peened surfaces is necessary to overcome equipment limitations, avoid measurement errors, and accelerate processing to gain certain surface properties such as surface roughness. Therefore, it is important to design an algorithm to quantify surface properties, which enables us to overcome the aforementioned limitations. In this study, a proposed systematic algorithm is utilized to generate and compare the surface roughness of Tungsten Inert Gas (TIG) welded aluminum 6061-T6 alloy treated by two levels of shot-peening, high-intensity and low-intensity. This project is industrial in nature, and the proposed solution was originally requested by local industry to overcome equipment capabilities and limitations. In particular, surface roughness measurements are usually only possible on flat surfaces but not on other areas treated by shot-peening after welding, as in the heat-affected zone and weld beads. Therefore, those critical areas are outside of the measurement limitations. Using the proposed technique, the surface roughness measurements were possible to obtain for weld beads, high-intensity and low-intensity shot-peened surfaces. In addition, a 3D surface topography was generated and dimple size distributions were calculated for the three tested scenarios: control sample (TIG-welded only), high-intensity shot-peened, and low-intensity shot-peened TIG-welded Al6065-T6 samples. Finally, cross-sectional hardness profiles were measured for the three scenarios; in all scenarios, lower hardness measurements were obtained compared to the base metal alloy in the heat-affected zone and in the weld beads even after shot-peening treatments.

Statistical Model for the Mechanical Properties of Al-Cu-Mg-Ag Alloys at High Temperatures

Aluminum alloys for high-temperature applications have been the focus of many investigations lately. The main concern in such alloys is to maintain mechanical properties during operation at high temperatures. Grain coarsening and instability of precipitates could be the main reasons behind mechanical strength deterioration in these applications. Therefore, Al-Cu-Mg-Ag alloys were proposed for such conditions due to the high stability of Ω precipitates. Four different compositions of Al-Cu-Mg-Ag alloys, designed based on half-factorial design, were cast, homogenized, hot-rolled, and isothermally aged for different durations. The four alloys were tensile-tested at room temperature as well as at 190 and 250°C at a constant initial strain rate of 0.001 s−1, in two aging conditions, namely, underaged and peak-aged. The alloys demonstrated good mechanical properties at both aging times. However, underaged conditions displayed better thermal stability. Statistical models, based on fractional factorial design of experiments, were constructed to relate the experiments output (yield strength and ultimate tensile strength) with the studied process parameters, namely, tensile testing temperature, aging time, and copper, magnesium, and silver contents. It was shown that the copper content had a great effect on mechanical properties. Also, more than 80% of the variation of the high-temperature data was explained through the generated statistical models.

Interfacial Reaction between Sn-Ag-Cu-Mg Solder and ENIG Substrate

In order to clarify the effect of the addition of Mg to Sn-Ag-Cu solder on the wettability and the microstructure of the solder, the reaction between Sn-Ag-Cu-Mg solder and a substrate was investigated. Sn-3.5mass%Ag-1.0mass%Cu-xMg solders (x =0, 0.2 and 0.4 mass%) was specially prepared in this study. For the reflow process, specimens were heated in a radiation furnace at 250 oC for 120 s to evaluate the wettability of the solder on a substrate and the microstructure of the solder matrix and the intermetallic compound layer at the interface. The results showed that the spreading area of Sn-Ag-Cu-Mg solder is almost similar with that of Sn-Ag-Cu solder regardless of oxygen concentration. In the case of Sn-Ag-Cu-Mg solders, it was observed that intermetallic compounds (IMCs) containing Mg were formed in the solder matrix and near the interface. The IMC formation at the interface for Sn-Ag-Cu-Mg solders was almost similar with that for Sn-Ag-Cu solder.

Study of divalent elements (Mg, Sr and Ba)-doped LaMnO3 nano-manganites

Doping of group-II divalent cations in LaMnO3 can produce advanced multi-functionalities in these nano-manganite materials according to recent theoretical approaches. An experimental investigation of Mg, Sr and Ba-doped LaMnO3 nano-structures has been made by synthesizing these compositions with fuel agent assistive sol–gel auto-combustion technique. Detailed structural studies were carried out for crystal structure, lattice parameters, crystallite size, density and strain in structure using the data obtained from X-ray diffraction (XRD). Structural parameters were largely affected and significantly varied in all compositions due to doping of group-II elements with different sized ionic radii. Morphological and compositional analyzes were carried out using scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Electrical and magnetic properties were explored using four-point probe and physical property measurement setups and observed a significant change in various compositions. The substitution of group-II atoms with different sized ionic radii on the regular sites in structure provides a distinctive behavior in various properties.