Density alumina-based ceramics

The sintering at reduced down to 1450°C temperatures allowed to obtain the alumina-based ceramics which is 2.5-3 times more resistant to abrasive-erosive wear comparing with the best industrial ceramics with the same composition. Such ceramics combine high density, 0.97, small grain size of the alumina (<300 nm) and MgAl204 spanel (20 nm), high... 

Concrete is a particulate composite of stone and sand, held together by an adhesive. The adhesive is usually a cement paste (used also as an adhesive to join bricks or stones), but asphalt or even polymers can be used to give special concretes. In this chapter we examine three cement pastes the primitive pozzolana the widespread Portland cement and the newer, and somewhat discredited, high-alumina cement. And we consider the properties of the principal cement-based composite, concrete. The chemistry will be unfamiliar, but it is not difficult. The properties are exactly those expected of a ceramic containing a high density of flaws. 

The possibility to obtain a uniformly dispersed composite powder was shown for the a-Fe-Al203 system where metal particles with an average size of 55 nm were formed in an amorphous/nano alumina matrix.18 Other studies attempting to obtain dense bulk composites based on the sol-gel route using conventional pressure-assisted sintering ( 1400°C and an applied force of 10 MPa) resulted in a coarse microstructure.16 However, if reaching theoretical density is not a necessary requirement, a porous ceramic microstructure containing nanometer-sized metal particles can be used as a catalytic material.19 Certain combinations of composite materials demand... 

Pure Zirconia. Pure, or unstabilized zirconia, has many uses despite the phase-transformation phenomenon described. Its density, 6.05 g/cm, makes it valuable as a grinding medium. Added to alumina or magnesia it promotes sinterability and enhances strength and other properties, as discussed above under Toughened alumina. It is an important constituent of ceramic colors, and a component of lead-zirconia-titanate-based electronic ceramic devices such as capacitors. But its uses increase dramatically as a result of a process known as stabilization, which is discussed in the following sections. 

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