Ceramics, Glasses, and Electronic Materials Flashcards
6 cards from real ME practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Ceramics, Glasses, and Electronic Materials flashcards as text
The sintering process in ceramics densifies the material by:
Answer: Diffusion-driven elimination of porosity and grain boundary migration at elevated temperature
Sintering uses heat (below the melting point) to drive atomic diffusion, which eliminates pores, bonds particles together, and allows grain growth, increasing density.
Which of the following ceramic materials is used as a thermal barrier coating (TBC) in gas turbine blades?
Answer: Yttria-stabilized zirconia (YSZ)
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.
Ferroelectric materials differ from piezoelectric materials in that ferroelectrics:
Answer: Have spontaneous electric polarization that can be reversed by an applied electric field
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.
Chemically strengthened glass (e.g., Gorilla Glass) achieves high strength by:
Answer: Ion exchange: replacing smaller Na+ ions with larger K+ ions in the surface layer to create compressive stress
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.
The dielectric constant (relative permittivity) of a material is important in capacitor design because:
Answer: Higher dielectric constant allows a capacitor to store more charge at a given voltage and size
Capacitance C = ε0·εr·A/d; a higher relative permittivity (dielectric constant) εr directly increases capacitance, enabling more energy storage per unit volume.
Galvanic corrosion occurs when:
Answer: Two dissimilar metals are in electrical contact in an electrolyte, causing the less noble metal to corrode preferentially
Galvanic corrosion results from the electrochemical potential difference between two dissimilar metals in contact with an electrolyte, accelerating corrosion of the anodic (less noble) metal.