Average advanced ceramics

Clays will continue to be an important industrial mineral for the foreseeable future. Clays continue to be used widely as raw materials for refractories and other traditional ceramics because of their availability, low cost, and ease of processing. However, a majority of applications for clay minerals lie outside the field of ceramics, as summarized in Tables 10 and 11 and described in detail in several of the references [8,14,21 ]. Because of this breadth of applications and continued availability of easily-mined, high-quality clay deposits, the current level of production and utilization of clay minerals should continue [8], Production is currently stabilized around 40 million metric tons per year with an average price of approximately 30 per ton [8], More importantly for the modem materials community, understanding the processing and characterization of traditional ceramics can provide significant insight into the structure of the materials curriculum and the methods used to process and characterize advanced ceramic materials. 

The Advanced Ceramic Technologies ATI whiskers are quite straight. Their average lengths and diameters are among the smallest we ve seen. A small amount of debris was present. X-ray photoelectron spectroscopy (XPS) revealed a surface which is very clean (i.e., very low impurity level) and has a very low oxygen content. 

In contrast to the above proposals, it is likely that other advanced ceramics-notably alumina, beryllia, sihcon carbide and sUicon nitride (see Chapter 11)-will demonstrate below-average growth rates owing to environmental concerns, competition from other ceramics (see Table 6.4), and an increasing reUance on slower-growing market segments such as cutting tools that are based on ceramic alloys (e.g., modified alumina and SiAlONs). In this situation, whilst alumina will surely remain the prominent material, its market share wiU be eroded by ferrites, and by beryllia- and zirconia-based ceramics. 

Advanced materials systems based on polymers, ceramics, and composites are constmcted by assembling components to create stmctures whose properties and performance are determined by the form, orientation, and complexity of the composite stmcture. The properties of these assemblages are determined not by the sum of weighted averages of the components but rather by synergistic effects in intercoimected phases. For this reason, the study of fabrication of hierarchical assemblages of materials, as well as the study of mechanisms for repairing defects in assembled stmctures, must be supported by fundamental research. 

Figure 12. Turning hard workpieces with different ceramic composite tools. Com = advanced commercial Al203/Ti(C,N) grade, concentration of Ti(C,N) about 25-30vol-%. S = laboratory grade average sizes of A Oj and TiC subregions 0.8-1.0 pm, TiC concentration 35 vol-%.

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