Effect of MgO Addition on the Mechanical and Thermal Properties of Mullite Synthesised through Reaction Sintering of Al2O3 and Algerian Kaolin

Abstract

The influence of MgO addition on the structure and properties of mullite prepared through reaction sintering of Algerian kaolin and Al 2 O 3 was investigated. The raw powders were wet ball milled, dried and cold compacted using a uniaxial press. The green compacts were sintered 8 hours at 1600 and 1650°C. The microstructure of samples was characterized using a scanning electron microscope. Mechanical and thermal properties were characterized using Vicker's hardness tester, a universal testing machine and a dilatometer. It was found that the increase of MgO content from 0 to 3 wt-% increased the hardness of samples sintered 8 hours at 1600°C from 1039 to 1316.57 HV. Also, the increase of MgO content in samples sintered 8 hours at 1600 and 1650°C increased the compressive strength up to a maximum then decreased it. For a sintering temperature of 1600°C, the increase of MgO content up to 2 wt-% increased the flexural strength, but a further increase of MgO to 3 wt-% decreased it again, while for a sintering temperature of 1650°C, the increase of MgO content from 0 to 3 wt-% increased the flexural strength from 103.45 to 472.25 MPa. Amongst MgO containing samples, the increase of MgO content increased the coefficient of thermal expansion; however, it remained lower than the coefficient of thermal expansion of the sample without MgO addition.

Studying the Effects of Kaolinite Additions on the Properties of Ceramic Bodies Prepared from Alumina Powder by Slip Casting Technique

“…Clearly, hardness increases when kaolinite addition is increased. Raising and lowering hardness can be explained on the basis of decreasing and increasing the porosity [7,16] and this result consistent with the stady [17] wich shows the michanical properties as function of physical properties. This is an important factor affecting the hardness.…”

“…This This increase begins with comparatively large value (at 5% addition) then increases in kaolinite addition leads to increase in the strength of ceramic products, because of the bigger amount of glass phase and higher density at the highr percentage of kaolinite [15,16] and this result consistent with the stady [17] wich shows the michanical properties as function of physical properties. Clearly, hardness increases when kaolinite addition is increased.…”

“…: Effect of kaolinite percentage additions on compressive strength .d-Bending Strength:Bending Strength increases with clay addition which increases with a semilinear form as shown in figure (9), this is due to lower porpsity and higher density at the highr percentage of kaolinite[7,15,16] and this result consistent with the stady[17] wich shows the michanical properties as function of physical properties.…”

Porous Mullite Ceramic Modification with Nano-WO3

“…Moreover, mullite ceramics are actively being studied as high-temperature filters and thermal insulation materials [ 1 , 2 ]. Such thermal insulation mullite ceramic can be used to prevent heat losses and heat release to the environment, as well as to avoid damage caused by contact with high-temperature objects [ 2 , 3 , 4 , 5 , 6 , 7 ].…”