Biomedical Engineering Reference
In-Depth Information
1
Thermal shock resistant and flame retardant
ceramic nanocomposites
N . R . BOSE , Sols 4 All Consultants, India
Abstract: This chapter discusses the performance behaviour of ceramic
nanocomposites under conditions of thermal shock, i.e. when they are
subjected to sudden changes in temperature during either heating or
cooling or may be in flame propagating zones. For example, during
emergency shut-downs of gas turbines, cool air is drawn from the still
spinning compressor and driven through the hot sections: the
temperature at the turbine outlet decreases by more than 800
8
C within
one second and ceramic nanocomposite materials are an appropriate
choice for such application. Furthermore, such a situation may arise
about 100 times during the lifetime of a modern gas turbine engine.
Similarly, in the nuclear industries, apart from the moderate shocks
inflicted during start-up and shut-down of the system, the plasma-facing
material can suffer rapid heating due to plasma discharge. Thus, when a
body is subjected to a rapid temperature change such that non-linear
temperature gradients appear, stresses arise due to the differential
expansion of each volume element at a different temperature. The design
principles for the fabrication of high-performance thermal shock resistant
ceramic nanocomposites with improved mechanical properties are
highlighted in this chapter. Moreover, the pertinent factors such as
interface characteristics, densification methods, superplasticity and the
role of nano-size particulate dispersion, which are responsible for the
development of thermal shock resistant and flame retardant nanoceramic
materials, are addressed and reviewed. Various test methods for the
characterisation and evaluation of ceramic nanocomposites are described.
Finally, the new concept of materials design for future structural ceramic
nanocomposites is discussed for safe applications in high-temperature
thermal shock zones.
Key words: thermal shocks, densification, superplasticity, interface,
ceramic nanocomposites.
