تصنيع حراريات من البوكسايت العراقي == Refractories Manufacturing from Iraqi Bauxite
Author name:
ایناس محي هادي
Supervisor name:
محاسن فاضل هادي الكاظمي
General topic:
Physics
Specific topic:
Physics
Degree:
Doctorate
University:
Mustansiriyah University - College Of Science
Language:
Arabic
University location:
Baghdad
First pages:
26T1803 - p.pdf
Abstract:
Iraqi raw Bauxite was fired at (1400) ̊C in order to produce calcined Bauxite. Chemical analysis and X - Ray Diffraction were carried out on the Iraqi Bauxite and calcined Bauxite to assess their ability for refractories production.The refractory mixture prepared from calcined Bauxite and raw Kaolin as a binder. The Kaolin was added in ratios of (10%, 20% and 30%). From the results of physical properties it was found that the mixture which has (10%) kaolin is the most suitable one for refractory production. Micro and Nano Zirconia and raw Zircon were added in ratios of (5%,10%,15% and 20%) in order to improve Iraqi Bauxite characteristics to be suitable for refractories production which are used in glass and metals industries.The samples were formed by semi - dry pressing with different load with the addition of potassium silicate in ratio of (10%) as a binder. The samples were formed with dimensions for (height × diameter) as : (50×25)mm2, (50×50)mm2, (1×50)mm2, (1×25)mm2 and (50×10)mm2. The samples were dried at room temperature for (24)hr, after that dried by electrical dryer at (110) ̊C for (8)hr. The refractories of (Bauxite - Zirconia) fired at (1400) ̊C and refractories of (Bauxite - Zircon) at (1500)̊C by a firing program with a soaking time for (2)hr.The test which were carried out are : (X - Ray Diffraction and SEM), Physical Testing : (Linear Shrinkage, Apparent Porosity, Water Absorption Ratio and Apparent Density), Mechanical Testing : (Bending Strength, Compressive Strength, Diametrical Strength, Hardness and Surface Roughness), Thermal Testing : (Thermal Conductivity, Specific Heat Capacity, Thermal Expansion Coefficient, Thermal Shock Resistance and Differential Thermal Analysis (DTA). And last test was Chemical Resistance to molten glass.According to (XRD) and (SEM) results the refractories consist mullite phase and glass phase. Refractories of (Bauxite - Nano Zirconia) have the lowest linear shrinkage and highest apparent density then the refractories (Bauxite - Micro Zirconia) and (Bauxite - Zircon).The adding of micro or Nano Zirconia or raw Zircon led to decrease the linear shrinkage and increase apparent density because of the increasing of pure ceramic materials in account of raw ceramic materials. The increasing of apparent density associated with decreasing of apparent porosity and water absorption ratio.The improving of the mechanical properties by adding Zirconia and raw Zircon causes by the high toughness of the additive ceramic materials which is also prove the crack pining mechanism with ceramic particles practically.The increasing of apparent density in susceptible the thermal properties therefore the thermal conductivity, specific heat capacity and thermal expansion coefficient were decreased while thermal shock resistance was increased, according to properties of the additive ceramic materials. The results of the differential thermal analysis shown that the refractories of (Bauxite - Zirconia) have a high thermal stability in the test temperaturerange (25 - 1500)̊C, except some process that return to raw Kaolin, endothermic process were moisture loses and crystalline water loses and exothermic process at (900 - 1000)̊C as mullite phase formed from the reaction between (SiO2) and (Al2O3).The increasing of chemical resistance causes from adding of Zirconia and raw Zircon to the prepared refractories, which led to reduction of wetting ability and the amount of molten glass which adhesive with refractories, on the other hand forbade the chemical reaction between the molten glass and the refractories.
