MChem Master of Chemistry Materials Chemistry 2

Question 1

What is the Bragg equation used for in materials characterization?

Accepted Answer

Relating X-ray diffraction angles to interplanar spacings (d-spacings) in crystals

Answer

Determining the molecular weight of polymers

Answer

Measuring the hardness of ceramic materials

Answer

Calculating the surface area of porous materials

Question 2

In semiconductor materials, what is the significance of the band gap energy?

Accepted Answer

It determines the electrical conductivity by controlling electron excitation from valence to conduction band

Answer

It measures the bond dissociation energy of the semiconductor lattice

Answer

It defines the melting point of the semiconductor

Answer

It is the energy required to remove a surface atom

Question 3

What is the purpose of annealing in materials processing?

Accepted Answer

Heating a material and slowly cooling it to reduce defects and internal stresses

Answer

Rapidly quenching a material to trap a high-temperature phase

Answer

Adding alloying elements at high temperature

Answer

Applying mechanical stress to increase hardness

Question 4

Which property of carbon nanotubes makes them attractive for reinforcing composite materials?

Accepted Answer

Their exceptionally high tensile strength (up to ~100 GPa) combined with low density

Answer

Their high density and optical transparency

Answer

Their hydrophilicity enabling bonding with polymer matrices

Answer

Their high thermal conductivity alone

Question 5

What is the glass transition temperature (Tg) and why is it important for polymer materials?

Accepted Answer

The temperature below which an amorphous polymer transitions from rubbery to glassy behavior

Answer

The temperature at which a crystalline polymer melts

Answer

The temperature at which a polymer begins to degrade

Answer

The melting point of the crystalline domains in a semi-crystalline polymer

Question 6

What is atomic layer deposition (ALD) and what advantage does it offer over conventional chemical vapor deposition (CVD)?

Accepted Answer

ALD uses sequential self-limiting surface reactions to deposit films with atomic-level thickness control and conformality

Answer

ALD deposits thick films rapidly from a gas phase mixture

Answer

ALD uses physical sputtering from a solid target

Answer

ALD requires higher temperatures than CVD processes