Abstract: Ironmaking processes take three main forms namely; blast furnace, direct reduction and direct smelting processes. Ironmaking is energy intensive sector as it requires huge amount of natural resources. It is also very important for the worldwide economy where it provides the backbone for construction, transportation and manufacturing. Many factors are strongly affecting the developing of ironmaking processes such as energy consumption, materials costs, and environment problems. These factors should be considered when discussing any new trend for developing ironmaking processes. The present work handles the current status and future of ironmaking processes. The technical and economic environment that motivates the development of these processes will be also clarified. The manuscript is designated to investigate theoretically and practically the possibility of using nanomaterials in ironmaking processes. Nano-sized iron oxides can be considered a promising source for deceasing energy consumption in iron and steel industry. The reduction of iron oxide is the most important processes in ironmaking and usually operated at relatively high temperatures. The nanopowder of iron oxide could be charged to a blast furnace together with the blast, much like the current pulverized coal injection technology. In that case, the reducibility of blast furnace burdens will be improved and consequently the energy consumption for reduction will be declined. Accordingly, minimizing the energy consumption will greatly influence the gross energy consumption of iron and steel production.
Abstract: Permanent mold cast (PMC) AJ62 magnesium alloy exhibits a fine-grained microstructure in the thin section and a coarse-grained microstructure in the thick section. Microstructure of the PMC AJ 62 alloy was analyzed by using the Scanning Electron Microscopy (SEM). Potentiodynamic polarization experiments were performed to investigate the corrosion resistances of the PMC AJ62 alloys in salt solutions and engine coolant. The corrosion behaviors in the fine- and coarse-grained AJ62 alloys were compared. The results show that the AJ62 alloy with fine microstructure presents enhanced corrosion resistance.
Abstract: The red color of ruby is caused by Cr3+ impurities substituting Al3+ in Al2O3 structure. The complete substitution of Al3+ by Cr3+ produces Cr2O3 that has the green color. In this study, we focused on the phase transition of solid solution between corundum (Al2O3) and eskolaite (Cr2O3) mineral series. A series of Al2O3-Cr2O3 samples were prepared by mixing fine powder of Al2O3 and Cr2O3 in various ratios. They were ground together and then recrystallized. The obtained crystals were ground again in powder form for X-ray absorption near edge structure (XANES) measurements to avoid polarization dependence. The measurements were carried out at the Cr K-edge absorption energy using a 13-channel array Ge detector in the fluorescence mode. The XANES spectra showed line-shape transitions for 0.125 to 100% variation of Cr2O3. Significant variations in transitions were found when the Cr2O3 content was between 20% and 80%. With Cr2O3 concentration increasing, the sample colors apparently turned from pink to dark green. CIELAB color index measurements were performed. The variations of line-shape spectra of the Al2O3-Cr2O3 samples were found to be consistent with the CIELAB color index results. This Cr K-edge XANES study could be useful for the research in mineral sciences.
Abstract: Monoclinic and orthorhombic phase of copper niobate was prepared by simple solid state reaction (700°C, 900°C for 12 hours). Formation of two polymorphic phases of CuNb2O6 was ascertained by XRD and FTIR analysis. FESEM showed the presence of pore networks in both phases. Third-order optical nonlinearity and their limiting behaviour were studied by Z-scan technique using Ti: Sapphire laser (800 nm, 150 fs, 80 MHz). Both phases of copper niobate exhibit reverse saturable absorption. The observed optical limiting action was ascribed due to two-photon absorption process. Monoclinic copper niobate shows almost 100 times stronger nonlinear absorption behaviour than orthorhombic copper niobate due to peculiar distortion of NbO6 octahedra. Monoclinic copper niobate with high two photon absorption coefficient (85x10-10 m/W) and low limiting threshold (0.21 μJ/cm2) can be a better alternate for benchmark optical limiters like carbon nanotubes.
Abstract: Various sizes SiO2 colloidal particles in the size range of 260-950 nm were synthesized by the stöber method by adjusting the amount of ammonia from 9.0 ml to 3.0 ml while keeping 20.0 ml tetraethyl orthosilicate (TEOS), 125.0 ml ethanol, 6.0 ml ammonia and 18.0 ml distilled water fixed. In addition, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the crystallinity and morphology of the synthesized SiO2 colloidal particles; the XRD result show that the SiO2 colloidal particles are amorphous at room temperature; the SEM results demonstrated that the amount of ammonia could have significant effects on the size, size distribution and sphericity of the SiO2 colloidal particles. SiO2 colloidal particles were resulted with good monodispersity when the amount of ammonia was in the range of 6.0-90 ml, while SiO2 colloidal particles with double size distribution were obtained when the range is 3.0-4.5 ml; on the other hand, SiO2 spheres were resulted with good sphericity when the ammonia is in the range of 6.0-7.5 ml.
Abstract: The effect of Ca and RE metal additions on the precipitation and microstructure of as-cast AZ91 alloy was systematically investigated. It was found that Ca and RE additions could result in phase and microstructure changes. The XRD pattern showed the crystallite phase of as-cast AZ91 alloys consists of α-Mg matrix and β-Mg17Al12, however, after adding 1.5wt. % Ca and 0.8wt. % RE (0.5wt. % Sm and 0.3wt. % La), peaks coincident with Al2Ca, Al2Sm and Al11La3 intermetallic compounds were found, suggesting the generation of relative precipitates. The SEM images indicated that in as-cast alloys, the Al2Ca intermetallic compound was located at grain boundaries with a lamellar structure, and the Al2Sm intermetallic compound was homogeneously distributed in the α-Mg matrix or near the grain boundaries with a polygonal structure, and the Al11La3 intermetallic compound was located at grain boundaries with a needlelike structure. These intermetallic compounds could reduce the amount of β-Mg17Al12 and refine the microstructure of as-cast AZ91 alloy.
Abstract: This study highlights on a convenient and optimised method for the preparation of nanocrystalline magnesium oxide (MgO) catalyst via sol-gel combustion method. Nanocrystalline MgO was prepared by using polyvinyl alcohol (PVA) as a complexing agent and metal nitrate (Mg (NO 3 )2.6H2O) as a precursor. The obtained MgO powder was calcined at 200 °C, 400 °C, 600 °C and 800 °C. All the MgO calcined samples including commercial MgO were characterised using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-Ray diffraction (XRD) and N2 adsorption-desorption Brunauer–Emmett–Teller (BET). From FTIR analysis, the appearance of a peak at 3700 cm-1 represent the O-H stretching bonded with Mg and the broad absorption peak at 3421 cm-1 indicates O-H stretching band which is due to the absorption of moisture from the surrounding. (BET) results indicate the MgO sample that has been calcined at 400 °C shows the largest surface area. SEM images show there is porosity in all MgO powder. While XRD patterns revealed that higher temperature of calcination gives higher crystallinity of the MgO samples.
Abstract: Nanotechnology currently receives considerable attention as a technology for the future. Nanocellulose, in particular, has been reported as a renewable source for industrial applications. As an emerging sustainable and advanced technology, nanocellulose extraction process and applications are being studied extensively. Nanocellulose in the form of nanocrystalline (NCC) or nanofibrillated (NFC) has many applications, mainly in enhancing the mechanical strength of composite materials, or as precursors for supercapacitors, aerogel, hydrogel and membrane fabrication. In this study, microbial hydrolysis combined with mechanical treatment was used as an alternative method to produce nanocellulose. Commercial cellulase enzyme from Trichoderma reesei (ATCC 26921) was used to hydrolyse bleached soda cellulose from Macaranga, a tropical forest species. The enzymatic hydrolysis was followed by homogenization and sonication. The resulting nanocellulose was incorporated into two polymers, namely chitosan and polyvinyl alcohol (PVA) at 3 and 10% concentrations. Surface morphology of the films was investigated by field emission scanning electron microscope (FESEM) and it was found that NCC disperses better into PVA matrix compared to chitosan matrix. However, at the low levels of nanocellulose added, no significant thermal property improvement was observed.
Abstract: Al2O3-Fe based metal ceramic is a functional ceramic material prepared by high temperature sintering with Al2O3 as the main component, plus iron powder (binder phase) and other additives. In this paper, the composition design of Al2O3-Fe based metal ceramic was made, and the performance of the material was tested and studied. The change of the content of iron powder also has a great influence on the compressive strength and bending strength of the Al2O3 metal ceramic. Experiments also show that the Al2O3-Fe-based cermet has good corrosion resistance. Finally, the following conclusions were obtained through the comprehensive analysis: the best test formula is No.4 sample, and its compressive strength is 79.79MPa, bending strength is 15.90 MPa, corrosion resistance rate is 0.028 g/dm2·h.