Material Science Mechanical. Engineering

ME 240 Materials Science – Spring 2017

Problem Set 1

Due Tuesday, January 24th, at the beginning of class

Problems are either the original work of the NAU instructors, modified from a number of

materials science texts or taken directly from your Introduction to Materials Science textbook. It

is required that these problems are solved without referring to any answer key. Referring to an

online answer key or keys from prior semesters is considered a form of academic dishonesty and

will be handled according to University policy that is located in the syllabus.

Be sure to start each new problem on a new page. Don’t be surprised if a single problem

extends past one page of work.

You are encouraged to work in teams, but turn in your own work. You are encouraged to get

stuck and ask questions. Give yourself time to do so. Follow systematic steps to solve each of the

problems. When working on a quantitative problem, use the GIVE-FIND-SOLVE and

REFLECT method. Identify what is given and what must be found. Do not simply rewrite the

question. Show all work and carry units across work when appropriate. You will not get full

credit if you do not include units. Keep three significant digits in your final answer and place a

box around the answer and units.

1.1 Identify the three different classes of solid materials considered in this class. Outline the main

properties of each class of materials. Use the appendixes in the back of the book to get a sense of

the relative costs of these materials. Give examples of each kind of material and identify

applications of how each is used. (12 pts)

1.2 In table format, compare and contrast ionic, covalent, metallic and secondary bonds. Indicate what kinds of bonds each material class from 1.1 forms. Note, some material classes can take on

more than one kind of bonding. (14 pts)

1.3 What is the composition, in weight percent, of an alloy that consists of 90 at% Ag and 10 at% Cu? Comment (Reflect) on the magnitude of your answers. (9 pts)

1.4 The chemical composition of a polycarbonate (a polymer commonly used for eyeglass lenses due to its transparency and impact resistance) repeat unit is C16H14O3. The molecular weight of the

repeat unit is 254.3 g/mol. A) What is the atomic % of the oxygen in the polycarbonate repeat

unit? B) What is the weight % of oxygen in the polycarbonate repeat unit? Reflect on why the

two values of A and B are not the same, and why one is much higher than another. (8 pts)

1.5 Write out the electronic configuration of an alkali earth metal of your choice (indicate which element you chose). Indicate which electrons are the valence electrons. Explain what kind of

bonding these group of elements tend to undergo and why. (6 pts)

1.6 The net potential energy between two adjacent ions, EN, can be represented as the sum of attractive energy (-A/r) and repulsive energy (B/rn).

𝑬𝑵 = − 𝑨

𝒓 + 𝑩

𝒓𝒏

Determine

a) the cause of the attraction and the repulsion (4 pts)

b) the bonding energy, Eo, in terms of parameters A, B and n using the procedure discussed in class (review class notes) (11 pts).