ME Ceramics, Glasses, and Electronic Materials 3

Question 1

The sintering process in ceramics densifies the material by:

Accepted Answer

Diffusion-driven elimination of porosity and grain boundary migration at elevated temperature

Answer

Sintering uses heat (below the melting point) to drive atomic diffusion, which eliminates pores, bonds particles together, and allows grain growth, increasing density.

Question 2

Which of the following ceramic materials is used as a thermal barrier coating (TBC) in gas turbine blades?

Accepted Answer

Yttria-stabilized zirconia (YSZ)

Answer

YSZ is the standard TBC material for turbine blades because of its very low thermal conductivity, high melting point, and strain tolerance from its partially stabilized microstructure.

Question 3

Ferroelectric materials differ from piezoelectric materials in that ferroelectrics:

Accepted Answer

Have spontaneous electric polarization that can be reversed by an applied electric field

Answer

Ferroelectrics have spontaneous polarization (permanent electric dipole) that can be switched by an external electric field, making them hysteretic and useful for memory and actuator applications.

Question 4

Chemically strengthened glass (e.g., Gorilla Glass) achieves high strength by:

Accepted Answer

Ion exchange: replacing smaller Na+ ions with larger K+ ions in the surface layer to create compressive stress

Answer

Chemical strengthening uses an ion exchange bath to replace Na+ in the glass surface with larger K+ ions, which cannot fit into the original sites and create a compressive stress layer.

Question 5

The dielectric constant (relative permittivity) of a material is important in capacitor design because:

Accepted Answer

Higher dielectric constant allows a capacitor to store more charge at a given voltage and size

Answer

Capacitance C = ε0·εr·A/d; a higher relative permittivity (dielectric constant) εr directly increases capacitance, enabling more energy storage per unit volume.

ME - Materials Engineer Practice Test

ME - Materials Engineer Practice Test

ME Ceramics, Glasses, and Electronic Materials 3