A comparative study of the influence of trivalent and tetravalent nano-sized oxides on the performance and microstructure of dolomite refractories
Abstract Contrary to the many benefits of dolomite refractories, their usage has been limited due to poor hydration resistance. For this reason, the aim of this research work is a comparative study of the influence of trivalent and tetravalent nano-sized oxides [iron (Fe 2 O 3 ), alumina (Al 2 O 3 ), zirconia (ZrO 2 ), and titania (TiO 2 )] on the performance and microstructure of dolomite refractories with an affirmation their hydration resistance improvement. After preparation and firing the specimen's, physical properties such as bulk density, apparent porosity, and hydration resistance tests were examined. Furthermore, XRD and SEM/EDX analysis were used to evaluate the ceramic phases and their microstructure, respectively. Results revealed that specimens with trivalent and tetravalent nano-sized oxides have improved densification and hydration resistance of the specimens through the liquid phase mechanism and solid state firing mechanism, respectively. Also, the specimens with tetravalent nano-sized oxides have higher hydration resistance than the specimens with trivalent nano-sized oxides. Generally, the hydration resistance improvement trend of specimens with various nano-sized oxides presence is Al 2 O 3 2 O 3 2 2 .
On the nanotechnology of refractories
New concepts in the nanotechnology of refractories are presented and recommended for use in their development.
Investigation of large strain extrusion machining (LSEM) of pure magnesium (Mg)
Abstract Large strain extrusion machining (LSEM) is used to produce pure magnesium strips directly from as-cast billets. LSEM reduces manufacturing steps and the special shear direction inclines the unfavorable strong basal texture of Mg. Finding suitable parameter ranges to control geometry and properties of the produced strip is a great challenge. In the present research, a finite element model is proposed and verified with experiments and previous findings. Next, effects of process parameters (temperature and pressure) on geometrical and microstructural properties of the produced strips are investigated. Studying the involved failure micro-mechanisms shows that the process temperature and hydrostatic pressure have adverse effects on the production of a flawless strip. To reduce the temperature and hydrostatic pressure throughout the LSEM process many different conditions are tested by the FEM model. Among all the examined conditions, 0.85 m m R e v feed and 530 R e v m i n rotation speed yields the most promising results it terms of low temperature, low hydrostatic pressure, and stable machining force. The proposed conditions are applied in the experimental setup and a uniform and flawless strip is obtained.