Ceramics results

Furthermore, the lack of long-range order in amorphous ceramics results in more phonon scattering than in crystalline solids and consequently leads to lower values of Ath-... 

Functional ceramics are usually polycrystalline materials with properties depending on chemical composition and microstructure (Figure 19). The major drawbacks in large-scale production of ceramics are the lack of chemical homogeneity and microstructure control that are related to processing parameters (time, temperature, medium) and chemical behavior of the reactants. Heterogeneity of chemical composition in ceramics results from slow reaction... 

As to the biomaterial for human tissue replacement, it is necessary to demonstrate if the material has any effect on the biological properties of the tissue. Bioceramics exhibit some possible toxic reactions due to metal ions leaching from the ceramics, resulting in the tissue dying or heavy reactions. In this experiment, cytotoxicity test, hemolysis test as well as skin irritation were conducted to value the biocompatibility of the porous AI2O3 ceramics. 

The optical properties of ceramics result in some of their most important applications. In their pure form, most dielectric single crystals and glasses are transparent to visible light. This behavior is very different from that of metals and semiconductors, which, unless they are very thin (<1 pm), are opaque. Many ceramics and glasses also show good transparency to infrared (IR) radiation. This property has led to the use of glasses for optical fibers for high-speed communications. 

As a class of ceramic materials, SiC whisker-reinforced ceramic composites were developed for potential structural applications because of the significant improvements in the mechanical properties these materials offered as compared to the monolithic materials. The incorporation of SiC whiskers into alumina ceramics resulted in increases in strength, fracture toughness, thermal conductivity, thermal shock resistance and high temperature creep resistance. These discoveries initiated several years of intense study into this class of composites. 

As a result, the material is now suitable for consideration as solar energy and laser applications. Minimum scattering has also contributed to this result. Scattering is less than 0.04 measure, therefore, five times smaller than for other mullite glass-ceramics. The absorption of the glass-ceramic resulting from the composition of the microstructure can be tolerated for the indicated applications. 

By precipitating crystal phases in the base glass, however, new exceptional characteristics are achieved. Among these, for example, are the machinability of glass ceramics resulting from mica crystallization and the minimum thermal expansion of chinaware, kitchen hot plates, or scientific telescopes as a -... 

Figure 1 Cross-sectional TEM images of ceramics resulting from pyrolysis of Co-PFS at...

If the discovery of European white porcelain was the fruit of the modern experimental method, the discovery of zircon stains can be considered the fruit of the application of the scientific knowledge (research) to technology (innovation). In effect, the introduction of zircon in ceramics resulted in the high... 

The ZrBj-ZrC-SiC ceramic was synthesizedby reactive hot-pressing with amixture of Zr, B C and Si powders. The reaction of Zr-B C-Si powders commenced at 800 °C and non-stoichiometric formed preferentially a solution of B elements in Zr particles formed, which subsequently transformed to ZrB at approximately 900° C. The SiC phase was formed from the intermediate ZrC phase, and the residual B C and Si were formed at approximately 1100 °C. The final phases containing ZrBj, ZrC and SiC form when the temperature exceeded 1500 °C to a maximum temperature of 1700 °C. A fully dense ZrB -ZrC-SiC ceramic was obtained with a slow heating rate and significant holding time at a low temperature, and subsequently sintered for 60 min at 1900 °C with a pressure of 30 MPa for densification. The achievement of fully dense ZrB -ZrC-SiC ceramic resulted in a maximum Vickers... 

---