National Defence University, Pakistan

About: National Defence University, Pakistan is a education organization based out in Islamabad, Pakistan. It is known for research contribution in the topics: Context (language use) & Decision support system. The organization has 802 authors who have published 816 publications receiving 3701 citations. The organization is also known as: National Defence University of Pakistan & National Defence University Islamabad.

The Reduction Behaviour of Cerium Doped Iron Oxide in Hydrogen and Carbon Monoxide Atmosphere

Abstract: The reduction behaviour of 3% cerium doped (Ce-Fe2O3) and undoped iron oxide (Fe2O3) by hydrogen in nitrogen (10%,v/v) and carbon monoxide in nitrogen (10%,v/v) atmospheres have been investigate by temperature programmed reduction (TPR). The phases formed of partially and completely reduced samples were characterized by X-ray diffraction spectroscopy (XRD). TPR results indicate that the reduction of Ce doped and undoped iron oxide in both reductants proceed in three steps reduction (Fe2O3 → Fe3O4 → FeO → Fe) with Fe3O4 and FeO were the intermediate. TPR results also suggested that by adding Ce metal into iron oxide the reduction to metallic Fe by using both reductant gaseous give better reducibility compare to the undoped Fe2O3. The reduction process of Ce and undoped Fe2O3 become faster when CO was used as a reductant instead of H2. Furthermore, in CO atmosphere, Ce-Fe2O3 give complete reduction to metallic iron at 700 0C which about 200 0C temperature lower than other samples. Meanwhile, XRD analysis indicated that Ce doped iron oxide composed better crystallite phases of Fe2O3 with higher intensity and a small amount of FeCe2O4.

Numerical solution of heat transfer past a stretching sheet with viscous dissipation and internal heat generation with prescribed surface temperature

Abstract: In this paper, the problem of boundary layer flow and heat transfer in a viscous fluid over a stretching sheet with viscous dissipation and internal heat generation is studied. Thermal boundary condition on the surface that is prescribed surface temperature (PST) is considered. The governing nonlinear partial differential equations are transformed into nonlinear ordinary differential equations by applying the similarity transformations. The obtained nonlinear ordinary differential equations are reduced to the system of first order ordinary differential equations. Then the system of first order ordinary differential equations is solved numerically using the Keller-box method. Results are presented in figures and discussed in details for the temperature profiles and the temperature gradient for some values of the Prandtl number, Eckert number and heat/source sink parameter.

Influence of chromium on the reduction behavior of ferric oxide by using carbon monoxide: temperature programmed reduction and kinetic studies

Abstract: This study was undertaken to investigate the effect of chromium on the reduction behaviour of ferric oxide with carbon monoxide (10 %, v/v) in nitrogen as a reductant. Ferric oxide was impregnated with 3 % chromium to produce chromium-doped ferric oxide (Cr-Fe2O3). The reduction behaviour and the kinetic studies of Cr-Fe2O3 and Fe2O3 have been studied by temperature programmed reduction (TPR) and the phases formed of partially and completely reduced samples were characterized by X-ray diffraction spectroscopy (XRD). Meanwhile, the activation energy values were calculated from the Arrhenius equation using Wimmer’s method. TPR results indicate that the reduction of Cr-Fe2O3 proceeded in two reduction steps (Fe2O3 → Fe3O4 → Fe), while, Fe2O3 proceeded in three reduction steps (Fe2O3 → Fe3O4 → FeO → Fe) with doped ferric oxide showed a large shifted towards lower temperature. The complete reduction of ferric oxide to metallic Fe occur at 700 °C compared to the undoped ferric oxide (900 °C). The XRD pattern showed that the diffraction peaks of Cr-Fe2O3 are more intense compare to Fe2O3, indicating that the improvement on the crystallinity of the characteristic peaks of Fe2O3 with no additional peak observed meaning that the chromium particles loaded on the ferric oxide were well dispersed. Furthermore, additional of 3 % chromium on ferric oxide gives larger surface area and decrease in the activation energy up to 12.39 % regarding to transition phases of Fe2O3 → Fe3O4 during the reduction process may also led to the increase in the rates of ferric oxide reduction.