True/False Flashcards
Covalent Bonds are directional in nature
True
FCC crystals have a higher atomic packing factor than BCC crystals
True
The resolution of a scanning electron microscope is poorer than that of an optical microscope
False
In a crystalline structure, the equilibrium number of vacancies decreases as the temperature increases
False
Fick’s first law of diffusion deals with steady state diffusion of one species in another
True
Weak atomic bonds are characterized by high thermal expansion coefficients
True
In mixed bonding situations, the degree of ionic bonding is inversely related to the difference between the elements
False
Grain boundaries are point defects in crystalline structures
False
Interstitial diffusion is generally faster than substitutional diffusion
True
Even if Bragg’s Law is satisfied, diffraction peaks from certain planes may be missing in diffraction patterns
True
Thermoplastic polymers are brittle at temperatures above the ductile-to-brittle transition temperature
False
Increasing the yield strength of a metal by cold working results in a decrease in its ductility
True
Copolymers consist of two or more smaller chains linked together
True
An intergranular fracture happens through the grains
False
Elastomers stretch when stress is applied and recover to their original shape when stress is removed
True
The toughness of BCC metals decreases ad temperature decreases
True
The steady state creep rate of an alloy decreases as the temperature increases
False
The ultimate strength of ceramics is different in compression and in tension
True
Strains induced by impurity atoms inhibit dislocation motion
True
Thermoset polymers reversibly soften and flow when heated or treated with appropriate solvents
False
In a binary eutectic system, an alloy with a eutectic composition has the lowest possible melting point within the system
True
In eutectoid reactions, a single liquid phase decomposes into two separate solid phases upon cooling
False
Pearlite is a microconstituent formed of two solid phases
True
Carbon atoms form a substitutional solid in iron
False
The addition of alloying elements to a Fe-C system can shift the eutectoid point
True
To form only martensite as the end product, the cooling rate from austenite during continuous cooling of steels must be slower than the Critical Cooling Rate
False
The hardness of martensite is a function of its carbon content
True
The eutectic reaction is an example of a solid state invariant reaction
False
Alpha Ferrite is a BCC solid solution of carbon in iron
True
For a given carbon content, the hardness of martensite is a function of the rate of cooling during quenching
False
