Muhammad Ali Shar

In this paper, a unique hybrid approach to design and synthesize 2D/3D Al2O3-ZnO nanostructures by simultaneous deposition is presented. Pulsed laser deposition (PLD) and RF magnetron sputtering (RFMS) methods are redeveloped into a single tandem system to create a mixed-species plasma to grow ZnO nanostructures for gas sensing applications. In this set-up, the parameters of PLD have been optimized and explored with RFMS parameters to design 2D/3D Al2O3-ZnO nanostructures, including nanoneedles/nanospikes, nanowalls, and nanorods, among others. The RF power of magnetron system with Al2O3 target is explored from 10 to 50 W, while the ZnO-loaded PLD’s laser fluence and background gases are optimized to simultaneously grow ZnO and Al2O3-ZnO nanostructures. The nanostructures are either grown via 2-step template approach, or by direct growth on Si (111) and MgO<0001> substrates. In this approach, a thin ZnO template/film was initially grown on the substrate by PLD at ~300 °C under ~10 milliTorr (1.3 Pa) O2 background pressure, followed by growth of either ZnO or Al2O3-ZnO, using PLD and RFMS simultaneously under 0.1–0.5 Torr (13–67 Pa), and Ar or Ar/O2 background in the substrate temperate range of 550–700 °C. Growth mechanisms are then proposed to explain the formation of Al2O3-ZnO nanostructures. The optimized parameters from PLD-RFMS are then used to grow nanostructures on Au-patterned Al2O3-based gas sensor to test its response to CO gas from 200 to 400 °C, and a good response is observed at ~350 °C. The grown ZnO and Al2O3-ZnO nanostructures are quite exceptional and remarkable and have potential applications in optoelectronics, such in bio/gas sensors.

This research is aimed at the up-gradation of indigenous Pakistani iron ore, i.e., Dilband iron ore (hematite), by utilizing common metallurgical processes. First, the magnetic properties of the ore were determined. Initially, the iron ore samples contained 34 wt. % Fe in addition to other gangue materials. Therefore, the ore was subjected to a high-temperature reduction roasting process between 800 °C and 1000 °C. Additionally, the magnetic separation process was also employed. The influence of different roasting parameters, such as the reduction time, coal-to-ore ratio, and temperature, was examined. This was followed by characterization techniques using XRD (X-ray diffraction analysis), the Rietveld method, wet chemistry analysis, and a VSM (Vibrating Sample Magnetometer). The results suggest an excellent reduction at 900 °C for a coal/ore ratio of 20 wt. %, which was achieved within 2 h of the process. The Fe concentration increased tremendously from 34 to 56 wt. %, and in conjunction, magnetic properties were also induced (1.5 emu). The recovery was found to be substantial for the ore when the Fe content was 75 wt. %. Additionally, the economic feasibility of the processed ore was also studied, followed by an extensive analysis of the roasting and magnetic separation processes.