Material Structure and Properties Exam 1

A. A sheet of steel 2 mm thick has nitrogen atmospheres on both sides at 1300 oC and is permitted to achieve steady-state diffusion condition. The diffusion coefficient for nitrogen in steel at this temperature is 6×10-11 m2/s, and the flux is found to be 1.5×10-7 kg/m2-s. Also, it is known that the concentration of nitrogen in the steel at the high-pressure surface (CA) is 4 kg/m3. How far (xB) into the sheet from this high-pressure side will the concentration be 1.0 kg/m3? Given: J = − D(cA−cB/(xA−xB))

1.2

Determine the ASTM grain size number if 40 grains per square inch are measured at a magnification of 450x. Given: nM*(M/100)^2=2^(G-1)

10.66

A feature of an ionic bond is that it: A. Is non-directional B. Is strongly directional C. Acts between identical atoms D. Is independent of electronegativity of the two atoms

A

An orbital is: A. A region where the probability of finding an electron is high B. Only a circular orbit around an atomic nucleus C. A bond between an electron and a nucleus D. A circular orbit of proton around the nucleus

A

The central tenet of Materials Science and Engineering is to determine the inter-relationships between: A.Structure-Processing-Properties B. Composition-Synthesis-Performance C. Beauty-Synthesis-Microstructure D. Composition-(Performance-to-cost ratio)-Microstructure

A

This type of bond is the only primary bond that is directionally dependent: A. Covalent B. Ionic C. Metallic D. Van der Waals

A

Valence electrons are most available for bonding and tend to control the following properties: chemical, thermal, electrical, optical? A. True B. False C. not necessarily

A

What is the difference between atomic structure and crystal structure? A. Atomic structure relates to the number of protons and neutrons in the nucleus of an atom, as well as the number and probability distributions of the constituent electrons. Crystal structure pertains to the arrangement of atoms in the crystalline solid material. B. Atomic structure relates to the arrangement of protons and neutrons in the nucleus of an atom. Crystal structure pertains to the electron structure of the individual atoms. C. Atomic structure relates to the type of atomic bonding. Crystal structure pertains to the arrangement of atoms in the crystalline solid material. D. Atomic structure only relates to the number of protons and neutrons in the nucleus of an atom. Crystal structure pertains to the number and probability distributions of the electrons.

A

Which class of material is generally associated with the highest density values at room temperature? A. Metals B. Polymers C. Composites D. Ceramics

A

Which of the following is the best related to material structure? A. Glassy B. Brittle C. Forging D. Sintering

A

Determine whether each of the electronic configurations given below is an inert gas, a halogen, and alkaline earth metal or a transition metal: A. 1s22s22p63s23p5 B. 1s22s22p63s23p63d34s2 C. 1s22s22p63s23p63d104s24p65s2 D. 1s22s22p63s23p63d104s24p6

A Halogen B Transition metal C Alkaline earth metal D. Inert Gas

Select the type of 2D planar defect for the following: A. ABCABCBACBA B. ABCABABCABC Choices: Twinning Stacking fault

A Twinning B Stacking fault

Identify the type of dislocations shown in the figures below: ***(see 5th pic on phone) A is ____ B is ____ Choices: edge dislocation screw dislocation

A screw dislocation B edge dislocation

The allowed values for the quantum numbers of electrons are as follows: ***(1st pic on phone) Select the 4 quantum numbers (n, l, ml, ms) for ANY 2 electrons in the 4f state: (CHOOSE all the options that apply) A. 4 3 0 (+1/2) B. 4 2 3 (+1/2) C. 4 3 (-2) (-1/2) D. (-4) 3 2 (-1/2)

A,D

Why are the properties of polycrystalline materials most often isotropic?

Although each grain in a polyCrystaline material is anisotropic, if the grains have random orientations, then the solid aggregate of the many anisotropic grains will behave isotropically.

A material is observed to have properties such as good flexibility, low density, good ductility, and a low electrical conductivity. Select the class of material which is best suited for the above-mentioned material. A. Ceramic B. Polymer C. Metal

B

As temperature decreases, the fraction of the total number of atoms that are capable of diffusive motion A. Increases B. Decreases

B

Below, atomic radius, crystal structure, electronegativity, and the most common valence are tabulated, for several elements; for those that are nonmetals, only atomic radii are indicated. ***(see 4th pic on phone) A. None of the above. B. C, H and O form interstitial solid solutions. These elements have significantly smaller atomic radii than the atomic radius of Co. C. Cr, Fe, Ni and Co form interstitial solid solutions. These elements have atomic radii similar to that of Co. D. Al, Zn, Pt, Pd form interstitial solid solutions. These elements have significantly larger atomic radii than the atomic radius of Co.

B

Compute the value of diffusion coefficient D, for a hypothetical material at 1200 oC, whose temperature-independent pre-exponential factor (D0) is known to be 4.8×10-6 m2/s. The activation energy for the diffusion (QD) is 139 kJ/mol. Given: D=D0*e^(−QD/R*T) where, R=8.314 J/mol-K A. 0.564 × 10 − 11 m 2 / s B. 5.64 × 10 − 11 m 2 / s C. 564 × 10 − 11 m 2 / s D. 56.4 × 10 − 11 m 2 / s

B

For a given material, would you expect the surface energy to be greater than, the same as, or less than the grain boundary energy? Why? A. The surface energy would be smaller than the grain boundary energy since there are less number of non-bonded atoms on the surface than in the grain boundaries. B. The surface energy would be larger than the grain boundary energy since there are more number of non-bonded atoms on the surface than in the grain boundaries. C. The surface energy would be same as the grain boundary energy since there are equal number of non-bonded atoms in both cases.

B

How many permitted l values are there for n=4? A. two B. four C. three D. one

B

Ideally speaking, bonds tend to form between two particles such that they are separated by an equilibrium distance where ____________ net force is exerted on them, and their overall potential energy is at a ______________. A. a negative, maximum B. zero, minimum C. zero, maximum D. a positive, minimum

B

Select the statement which best describes the Burgers vector (b → ): A. It is a vector b → , that represents only the magnitude of the slip. B. It is a vector b → , that represents both the magnitude and direction of the slip. C. It is a vector b → , that represents only the direction of the slip.

B

According to ________________________, no two electrons can have the same set of n, l, ml, ms quantum numbers. A. Aufbau principle B. Bohr atomic model C. Pauli exclusion principle D. Hund's rule

C

Determine the coordinates and hence the indices for the following direction : ***(see 2nd pic on phone) A. A: (0,0,0); B: (1/2, 1, 1/2); [hkl] = [212] B. A: (0,0,0); B: (1/2, 1/2, 1); [hkl] = [221] C. A: (0,0,0); B: (1/2, 1/2, 1); [hkl] = [112] D. A: (0,0,0); B: (1/2, 1/2, 1); (hkl) = (112)

C

How many electrons can occupy orbitals with n=4, l=3? A. 6 electrons B. 18 electrons C. 14 electrons D. 10 electrons

C

Isotropic properties are: A. Isotope dependent B. None of the above C. Direction independent D. Direction dependent

C

The four important classes of materials relevant to this class include: A. Ceramic, Organic, Conductor, and Insulator B. Semiconductor, Conductor, Insulator and Polymer C. Ceramic, Metal, Polymer and Semiconductor D. Metallic, Organic, Insulator, and Inorganic

C

Which of the following is the best example of material processing? A. Crystalline B. Amorphous C. Extrusion D. Glassy

C

________ type of bond is the weakest among the following options: A. Covalent B. Metallic C. Van der Waals D. Ionic

C

Determine the intercepts and hence the Miller indices for the following shaded plane: ***(see 3rd pic on phone) A. Intercepts: (x,y,z) = (1,1, ½); Miller indices: [hkl] = [112] B. Intercepts: (x,y,z) = (1,1, ½); Miller indices: (hkl) = (221) C. Intercepts: (x,y,z) = (1,1,2); Miller indices: (hkl)= (112) D. Intercepts: (x,y,z) = (1,1, ½); Miller indices: (hkl) = (112)

D

Select the type of diffusion: The __________ diffusion is the situation where the flux and the concentration changes with space and time A. random B. steady state C. uphill D. non-steady state

D

State true or false:___________ states that the diffusion flux is directly proportional to the concentration gradient, where diffusion takes place from higher concentration regime to lower concentration regime. A. Bragg's law B. Fick's second law C. Bohr's atomic model D. Fick's first law

D

__________ bonds are responsible for binding atoms together within a molecule of propane, whereas _______ bonds bind separate propane molecules together in a condensed state (liquid or crystal) A. Ionic, Covalent B. Van der Waals, Covalent C. Covalent, Ionic D. Covalent, Van der Waals

D

Depicted below are five different steady-state concentration profiles for the same gas across five separate and identical plastic membranes of the same thickness held at the same temperature. Which concentration profile results in the lowest diffusion flux through the membrane? ***(see 6th pic on phone) A. (d) B. (e) C. (c) D. (b) E. (a)

E

Select true or false: Low-angle grain boundaries have higher grain boundary energy when compared to that of high-angle grain boundaries.

False

State true or false: Allotropy (or polymorphism) can be observed in both crystalline and non-crystalline materials.

False

State true or false: For a cubic crystal, as the magnitude of the specific h, k, and l in the Miller indices, (hkl), increases, the interplanar spacing (dhkl) also increases:

False

State true or false: Interstitial diffusion is normally slower than vacancy diffusion.

False

Explain simply why hydrogen fluoride (HF) has a higher boiling temperature than hydrogen chloride (HCl) (19.4 vs. -85°C), even though HF has a lower molecular weight.

In HF there is H-bonding( strong bond that is difficult to break) where in HCl there is van der Waals(very weak bond). Therefore, boiling temperature is higher to break those H-bonds.

Briefly cite the main differences between ionic, covalent, and metallic.

Ionic: bonding due to charged ions, it is direction independent, and has stronger bonding. Covalent: bonding due to sharing of electrons, it is direction dependent, and has stronger bonding. Metallic: bonding due to electron cloud of delocalized electrons, it is direction independent, and has weaker bonding when compared to Ionic and Covalent

Do non-crystalline materials display allotropy(polymorphism)? Why or why not?

They do not since noncrystalline material does not have a defined crystal structure, it can't have more than one crystal structure.

For each material, fill in its material class number in the middle column of blanks (point). Titanium Titania Teflon Choices: Polymer Metal Ceramic

Titanium: Metal Titania: Ceramic Teflon: Polymer

Materials have driven advancements in our society (fill in the blank) Stone age ⟶ Bronze age ⟶ ____________ ⟶ Silicon age

iron age