Oral Examinations

The department makes extensive use of oral examinations for the defence of theses and for testing the comprehensive background of students. Regulations related to these exams are contained in the Graduate Studies Calendar. This section provides further details including the form and content of these exams. Failure in any oral examination is grounds for requesting that the student withdraw from the program. However, at the discretion of the department, students may be granted a second attempt at an examination. If you have questions about what is expected of you in any of these exams you should approach your supervisor and/or the Department Chair, well in advance of the exam.

 A. Comprehensive Examinations for Ph.D. Students

Comprehensive exams are meant to test the student’s background understanding in various areas of Materials Science and Engineering. It is important to realize what is expected of you in this type of examination. First of all, they are not designed simply to see how much you have remembered from your undergraduate program, although knowledge of key terminology and basic facts is important. These exams will test your ability to think and to question, and to elaborate fundamental concepts. The questions will probe your ability to work with and develop concepts. Therefore, it is the process which is important, as much as the result. Always keep this in mind during the examination. Do not be concerned if you do not immediately know the final answer to a question you are asked. Start with some basic concept or a simple first order equation and work towards the solution. This will demonstrate to the committee your ability to think and to develop concepts. Make extensive use of the blackboard to draw simple diagrams or to write down equations. As you prepare for these exams, try to develop a good fundamental understanding of basic concepts, and you should do well.

 

1. The Part I Comprehensive Examination

The comprehensive examination is designed to ensure that all students who receive a Ph.D degree in Materials Science or Engineering have a broad understanding of the foundations of the discipline. The key to this approach is an emphasis on fundamental concepts. Students will not be expected to demonstrate a very detailed knowledge of materials processes, or of the properties of any given material. However they will be expected to understand the broad classes of materials – how their underlying structure controls properties and affects the approaches used to process them, etc.

It is considered essential that all students demonstrate an appreciation for the interrelationships between structure/properties/processing of materials. The content that students must be able master is best illustrated by referring to sections in classical textbooks.  Students are of course free to study use other books with which they are more comfortable.  However, the book chapters given below offer guidance as to both the nature and the depth of the content required.

The Part I comprehensive exam topics are divided into core areas that all students are responsible for and elective areas in which students may choose their area of specialization.

 

Overview of thematic areas

Core areas:

Structure of Materials (including atomic structure and bonding and defect structures) – Callister [1] Chs. 2 and 4

Thermodynamics (with emphasis on solution thermodynamics and phase equilibria) – Ragone [2] Chs. 1-5 and 7-9, Callister Ch 9 [Gaskell Ch. 2, 3, 7, 9, 11 – 13]

Kinetics (including mass transfer and phase transformations) – Callister Chs. 5, 10

 

Elective Areas:

Structure of Materials.  Choose one of:

Crystalline solids – Callister Ch. 3
Polymeric solids – Callister Ch. 14

Properties of Materials.  Choose one of:

Mechanical properties  – Callister Ch. 6, 7, 8
Electrical and thermal properties – Callister Ch. 18, 19
Chemical properties –  Ragone Ch. 6

This exam is normally offered in February and May. However, students may arrange to take the comprehensive examination at any time, following discussion with the Chair. Students must successfully complete this examination within 12 months of initial registration. Students may be granted a second attempt, but the second attempt must be in this 12 month period. Thus, students should take this examination at the earliest opportunity.  Special consideration may be given for part-time students.

Detailed synopsis – key concepts
While the following is not meant to be an exhaustive list of topics that might be raised, it lists key concepts with which you should be familiar.
1.      Structure of Materials
a.     Atomic structure and bonding – Callister Ch. 2

i. Atomic bonding forces and energies
ii. Bonding types
iii. X-ray analysis for chemical composition determination

b.     Crystalline solids – Callister Ch. 3

i. Concept of a crystal, unit cell
ii. Common structures including fcc, bcc, hcp, tetragonality
iii. Miller indices for directions and planes
iv. Physical basis of x-ray diffraction and Bragg’s law
v. Meaning of crystalline anisotropy

c.      Defect structures – Callister Ch. 4

i. Vacancies

1.      Thermodynamic properties
2.      Vacancy concentration
ii. Dislocations (edge, screw, mixed)
iii. Interface defects (free surfaces, low and high angle grain boundaries, twin boundaries)
d.     Polymeric solids – Callister Ch. 14

i. Structure of common monomers (e.g. alcohols, ethers, acids, aromatic hydrocarbons)
ii. Basic concepts in polymers (homo- and co-polymers, functionality
iii. Molecular weight
iv. Polymer types (linear, branched, crosslinked, network)
v. Thermosets vs. thermopolymers, effect of basic properties
vi. Crystallinity in polymers
vii. Characterization of polymer structure

2.      Thermodynamics
a.     First Law of Thermodynamics – Ragone Ch. 1 [Gaskell Ch. 2]

i. Energy as a State Function
ii. Work
iii. Intensive and Extensive Properties
iv. Enthalpy
v. Heat Capacity
vi. Ideal Gases
vii. Enthalpies of Formation and Chemical Reaction

b.     Second Law of Thermodynamics – Ragone Ch. 2 [Gaskell Ch. 3]
i. Entropy as a State Function
ii. Adiabatic, Reversible and Steady State Systems
iii. Entropy Changes in Chemical Reactions and the Third Law
c.      Equilibrium – Ragone Ch. 4 [Gaskell Ch. 7]
i. Phase Equilibria
ii. First and Second Order Transitions
d.     Chemical Equilibrium – Ragone Ch. 5 [Gaskell Ch. 11 & 12]
i. Thermodynamic Activity
ii. Gaseous and Solid-Vapour Equilibria
iii. Ellingham Diagrams
e.     Solutions – Ragone Ch. 7 [Gaskell Ch. 9]
i. Partial Molar Quantities
ii. Ideal and Non-ideal Solutions
iii. Raoult’s and Henry’s Laws
iv.Regular Solutions
f.     Gibbs’ Phase Rule – Ragone Ch. 8 [Gaskell Ch. 13.4]
g.     Phase Diagrams – Ragone Ch. 9 [Gaskell Ch. 12]
i. The Lever Rule
ii. Miscibility and Immiscibility
iii. Binary phase diagrams – Callister Ch. 9
1.      Types (isomorphous, eutectic / eutectoid, peritectic / peritectoid)
2.      Congruent transformations
3.      Phases and compositions
4.      Kinetics
a.     Mass transfer – Callister, Ch. 5

i. Mechanisms of atomic diffusion (vacancy, substitutional, interstitial)
ii. Steady-state diffusion, Fick’s 1st Law
iii. Transient diffusion, Fick’s 2nd Law
iv. Characteristic diffusion length
v. Applications to carburization
vi. Impurity diffusion – vacancy, substitutional and interstitial

b.     Microstructure development – Callister, Ch. 9
i. Effect of cooling rate on microstructure
ii. Fe-C phase diagram
1.      phases
2.      microstructure
c.      Phase transformations – Callister Ch. 10

i. Concept of chemical equilibrium, application to phase formation
ii. Thermodynamics of phase nucleation

1.      homogeneous vs. heterogeneous nucleation

i. Transformation kinetics, Avrami equation
ii. Fe-C system

1.      Kinetics of pearlite formation
2.      TTT diagrams
3.      Metastable phases – bainite, martensite
4.      Effect of alloying – hardness vs. hardenability
5.      Tempering

i. Precipitation processes

1.      Precipitate growth by diffusion
2.      Age hardening
4.      Properties of materials
a.     Mechanical properties – Callister Chs. 6-8

i. Definition of stress and strain
ii. Elastic response (Hooke’s law, elastic moduli)
iii. Tensile stress-strain curve and related parameters for strength and ductility
iv. Basic dislocation concepts (Burger’s vector, slip systems, deformation due to slip)
v. Strengthening mechanisms (grain size, solute, work hardening, etc.)
vi. Recovery and recrystallization
vii. Ductile vs. brittle fracture
viii. Fracture toughness, Griffith relationship
ix. Ductile – brittle transition in steels
x.Basic concepts in creep and fatigue

b.     Electrical properties – Callister Ch. 18

i. Ohm’s law
ii. Band structure of metals, insulators and semi-conductors
iii. Conduction in terms of band structure and bonding models
iv. Electron mobility
v. Electrical resistivity of metals
vi. Semiconductivity

1.      Intrinsic
2.      Extrinsic: n-type and p-type
3.      Temperature dependence of conduction in semiconductors

vii. Capacitance

1.      polarization
2.      dielectric materials
c.      Thermal properties – Callister Ch. 19

i. Heat capacity

1.      Specific heat at constant volume & pressure
2.      Atomic and electronic mechanisms of heat capacity

ii. The basis of thermal expansion
iii. Thermal conductivity

1.      Fourier’s law
2.      applications to steady-state heat transfer

iv. General ranking of different materials in terms of specific heat, thermal expansion and thermal conductivity

d.     Chemical properties – Ragone Ch. 6 [Gaskell Ch. 14]

i. Electrochemical Cells
ii. Half Cell Reactions
iii. Nernst Equation
iv. Pourbaix Diagrams
v. Concentration Cells

2.     Part II Comprehensive Examination

The Part II comprehensive exam is centered about the research area of the student. The breadth of the exam will include the fields that are required by the student in order to understand all the features of the student’s research and its possible applications. The topics on which the examination is to be based are set by the supervisory committee and approved by the Chair. The student will be informed of these topics at least one month prior to sitting this exam. The examination is an in-depth oral examination lasting two to three hours. The examining committee, to be appointed by the Chair, consists of three members of faculty – typically the supervisor, one other member of the supervisory committee and one other faculty member from outside the supervisory committee.  For full time students, it will normally take place between 24 and 36 months after the student has registered in the Ph.D. program. Students may be granted a second attempt, but the second attempt must be in this same period. Part time students should take the exam once their research direction is well established, but in any case it should be taken at least one year before the students expects to submit the Ph.D. thesis.

 

B. Thesis Defences and Transfer Examinations

·         Master’s Thesis Defence

This is an oral exam administered by the Department. It is conducted by a minimum of three faculty members (including the supervisor).  The exam covers material presented in the written thesis and the background material to this thesis. It is normally taken by students who intend to leave the program upon completion of their Master’s degree. After a short oral presentation, the candidate is asked to defend the contents and background to the written thesis. This is a PUBLIC examination open to all interested persons.

·         Transfer Exam from Master’s to Ph.D.

Complete regulations for this exam are in the Graduate Studies Calendar under admission to a Ph.D. program. The student submits five typed copies of a research report, which should take the form of a literature review plus some preliminary results and analysis followed by a detailed research proposal. The literature review should not simply catalogue the papers in the field. Rather it should offer some insight into the state of the field (i.e. what are the main advances achieved, what are the main problems which occur, what is good or bad about the approaches taken by previous workers). This should lead into a discussion of what approach you intend to take in your own research. What will you want to do different from previous research, and what advances in the state of the art do you hope to achieve? Some discussion of the techniques you expect to use will be important. You will be expected to demonstrate that you have thought about how best to approach your problem, and what its limitations may be. The report need not, and indeed should not, be a lengthy document. It should however indicate that the student has a good grasp of the background to the project being undertaken, has demonstrated a potential to perform research, and has thought carefully about the research being proposed.

Transfer reports must be submitted at least one month before the end of the sixth term of registration in a Master’s program. Failure to meet this deadline means that the student will be overtime before the transfer exam is taken, resulting in loss of income and status as a full time student.  Following the submission of the transfer report to the department Chair, an oral examination will be scheduled. The committee for a transfer examination normally comprises five faculty members. The purpose of this exam is to determine whether the student has a good chance of successfully completing a Ph.D. It also serves the valuable function of providing a good appraisal of the problem chosen for research.

So what is required of a potentially good Ph.D. student? Obviously knowledge as such has some importance but it is not of prime importance. In asking students to write a summary of their research proposal, we essentially are asking them to ask themselves questions such as:

Why am I doing this research, i.e. what is the essence of the problem? How does my proposal relate to previous work?

What form of measurement will I use or what theoretical basis will I assume?

Do I really understand this form of measurement, i.e. the basic science behind it, the accuracy and sensitivity required, etc?

What alternative measurements or techniques could I use and why have I rejected them in favour of the one proposed?

Can the problem be modeled, and on what basis?

 

In short, does the student have the interest and capability of a scientist or engineer who can analyze a problem with complete understanding, or is the student prepared only to look at it superficially, with uncritical adoption of other people’s opinions? Of course, the answers to everything cannot be known or there would be no point in doing the research, but the questioning by the student of what is important, should have been done. A Ph.D. degree demands maturity on the part of the student and the student should be able to take over the problem from his supervisor. It is, after all, an indication of the ability to do independent research.

Following completion of the transfer exam students will either be granted direct transfer into a Ph.D. program or else they will be required to complete their research and submit this work for a Master’s degree.

Retroactive Admission to the Ph.D. Program

Students who hold a Master’s degree from abroad, but who were nevertheless admitted at the Master’s level may apply for retroactive admission to the Ph.D. program. This should be done within 9 months of arriving at McMaster. Students should have passed the Part I Comprehensive exam by this time.

The student must prepare a short report which is submitted to the Chair.  The aim of the report is to demonstrate that the student has a clear understanding of the background of the research project, and of the underlying basis for the work proposed. Thus, the report should include a survey of current literature relevant to the project, and a project outline. If the student has obtained preliminary results, these may be included. However, this is not a necessary component of the report. An oral examination will then be scheduled at which time the student will be expected to answer questions related to the content of the report, and to relevant background material. Following the exam, the committee will recommend either that the student be transferred directly to Ph.D. status, or continue as a Masters’ student. In the latter case, it may still be possible for students to transfer to the Ph.D. program at a later date, as outlined above.

The report should not be lengthy — 30 typed pages at most.

 

Research Proposal Exam for Students Enrolling Directly in a Ph.D. Program

Students who enroll directly into the Ph.D. program must submit a written proposal for their research program and defend within 16 months of starting.   The student submits five typed copies of a research report, which should take the form of a literature review plus some preliminary results and analysis followed by a detailed research proposal. The report need not, and indeed should not, be a lengthy document. It should indicate that the student has a good grasp of the background to the project being undertaken, has demonstrated a potential to perform research, and has thought carefully about the research being proposed. The report is examined by a committee consisting of the supervisory committee, augmented by two other departmental members.  The nature and intent of this exam is similar to that of the Ph.D. transfer exam described in more detail above.  The student must satisfy the committee that they are capable of successfully completing Ph.D. caliber research in order to be allowed to continue in the program.

 

Ph.D. Defence

This is also an oral exam administered by the School of Graduate Studies. The examining committee includes members of the supervisory committee, members of the University from outside the department, and an external examiner from outside the University. After a short oral presentation, the candidate will be asked to defend the contents and background to the written thesis. This is a PUBLIC examination open to all interested persons.

 

 


[1] William D. Callister, Jr., Materials Science and Engineering An Introduction, 6th Ed., 2003, Wiley.

[2] David V. Ragone, Thermodynamics of Materials Vol. 1, 1995, Wiley. has been selected as the primary source for this material because it is fundamental and concise .  However, many students may be more familiar with David R. Gaskell, Introduction to the Thermodynamics of Materials, 3rd Ed., 1996, Taylor and Francis, so cross-references are made in square brackets.