Sintering 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... 

Considerable development has occurred on sintered ceramics as bone substitutes. Sintered ceramics, such as alumina-based ones, are uru eactive materials as compared to CBPCs. CBPCs, because they are chemically synthesized, should perform much better as biomaterials. Sintered ceramics are fabricated by heat treatment, which makes it difficult to manipulate their microstructure, size, and shape as compared to CBPCs. Sintered ceramics may be implanted in place but cannot be used as an adhesive that will set in situ and form a joint, or as a material to fill cavities of complicated shapes. CBPCs, on the other hand, are formed out of a paste by chemical reaction and thus have distinct advantages, such as easy delivery of the CBPC paste that fills cavities. Because CBPCs expand during hardening, albeit slightly, they take the shape of those cavities. Furthermore, some CBPCs may be resorbed by the body, due to their high solubility in the biological environment, which can be useful in some applications. CBPCs are more easily manufactured and have a relatively low cost compared to sintered ceramics such as alumina and zirconia. Of the dental cements reviewed in Chapter 2 and Ref. [1], plaster of paris and zinc phosphate... 

Shrinkage peculiarities upon the sintering of the alumina nanopowders based ceramics doped with Zr02... 

An interesting extension of the range of vacuum filters is the capillary disc filter (Figure 4.26). This is a continuously operating, capillary action, ceramic dewatering filter, which eliminates the need for separate filter cloths. The filter medium is a disc, formed from two circles of sintered alumina, joined at their circumferences. The filter has several such discs mounted on a central horizontal shaft. The medium is practically inert in most solutions, and may be used in a broad range of water-based and solvent-based slurries. In operation, as the microporous ceramic discs rotate through... 

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... 

Sintering of j8"-alumina tubing or flat plates is accomplished by encapsulation (usually chemically inert magnesia-based refractories) to prevent the loss of the volatile soda component . Vertical batch sintering of electrolyte tubes is employed to control the ovality of the fired ceramic within acceptable limits. Ultimately, a continuous sintering process of horizontally saggered ware will likely be adopted for large-scale... 

The MF membranes are usually made from natural or synthetic polymers such as cellulose acetate (CA), polyvinylidene difiuoride, polyamides, polysulfone, polycarbonate, polypropylene, and polytetrafiuoroethylene (FIFE) (13). Some of the newer MF membranes are ceramic membranes based on alumina, membranes formed during the anodizing of aluminium, and carbon membrane. Glass is being used as a membrane material. Zirconium oxide can also be deposited onto a porous carbon tube. Sintered metal membranes are fabricated from stainless steel, silver, gold, platinum, and nickel, in disks and tubes. The properties of membrane materials are directly reflected in their end applications. Some criteria for their selection are mechanical strength, temperature resistance, chemical compatibility, hydrophobility, hydrophilicity, permeability, permselectivity and the cost of membrane material as well as manufacturing process. 

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