ME Ceramics, Glasses, and Electronic Materials 2

Question 1

N-type semiconductors are created by doping silicon with:

Accepted Answer

Group VA elements such as phosphorus or arsenic

Answer

Group V elements (P, As, Sb) have one extra valence electron compared to silicon; this extra electron becomes a free carrier, creating n-type (negative charge carrier) semiconductor behavior.

Question 2

The Weibull modulus (m) for a ceramic material is a measure of:

Accepted Answer

Variability in strength; higher m indicates less scatter and more reliable strength

Answer

A higher Weibull modulus indicates less statistical variability in strength measurements, meaning the ceramic has a more consistent, predictable fracture strength.

Question 3

Hot pressing of ceramic powders differs from conventional sintering because hot pressing:

Accepted Answer

Uses lower temperatures but applies uniaxial pressure simultaneously

Answer

Hot pressing applies uniaxial pressure simultaneously with heating, which enhances densification at lower temperatures by promoting particle contact and reducing porosity more effectively than pressureless sintering.

Question 4

Which type of polarization in dielectric materials involves the displacement of electrons relative to the nucleus under an applied electric field?

Accepted Answer

Electronic polarization

Answer

Electronic polarization occurs when an applied electric field displaces the electron cloud relative to the positive nucleus, inducing a dipole moment in every atom.

Question 5

Piezoelectric materials generate an electric voltage when subjected to mechanical stress because:

Accepted Answer

Their crystal structure lacks a center of symmetry, so stress creates a net dipole moment

Answer

Piezoelectric crystals lack a center of symmetry; mechanical stress distorts the crystal lattice and shifts ion positions to produce a net electric polarization.

ME - Materials Engineer Practice Test

ME - Materials Engineer Practice Test

ME Ceramics, Glasses, and Electronic Materials 2