1. Week 1 INTRODUCTION Materials Science
Introduction: structure and methodology of the course materials and engineering, major classes of materials

2. Material Science & Engineering
Material -> something tangible that goes into the makeup of a physical object.
Material Science -> involves investigating the relationships that exist between the structures and properties of materials
Material Engineering -> is, on the basis of these structure–property correlations, designing or engineering the structure of a material to produce a predetermined set of properties
0. HISTORICAL PERSPECTIVE
e.g. "coal is a hard black material"; "wheat is the material we use to make bread“; (b) derived from or composed of matter; "the material universe”
2 and 3. Material engineer develops the materials not the products, e.g. add more cobalt as a binder to cement the WC, it will increase the toughness, but ll also soften the substrate

3. Material Science & Engineering
Structure -> The structure of a material usually relates to the arrangement of its internal components
Different levels of defining structure of a material
Property -> A property is a material trait (distinguishing feature) in terms of the kind and magnitude of response to a specific imposed stimulus
Six categories of properties -> mechanical, electrical, thermal, magnetic, optical, and deteriorative
1+2 Subatomic structure involves electrons within the individual atoms and interactions with their nuclei. On an atomic level, structure encompasses the organization of atoms or molecules relative to one another. The next larger structural realm, which contains large groups of atoms that are normally agglomerated together, is termed “microscopic,” meaning that which is subject to direct observation using some type of microscope, e.g. grain structure of alloy steels. Finally, structural elements that may be viewed with the naked eye are termed “macroscopic.”, e.g. composite materials
3. While in service use, all materials are exposed to external stimuli that evoke some type of response. For example, a specimen subjected to forces will experience deformation (property-> stiffness), or a polished metal surface will reflect light (property -> reflectivity).
4. For each property there is a characteristic type of stimulus capable of provoking different responses. Mechanical properties relate deformation to an applied load or force; examples include elastic modulus and strength. For electrical properties, such as electrical conductivity and dielectric constant, the stimulus is an electric field. The thermal behavior of solids can be represented in terms of heat capacity and thermal conductivity. Magnetic properties demonstrate the response of a material to the application of a magnetic field. For optical properties, the stimulus is electromagnetic or light radiation; index of refraction and reflectivity are representative optical properties. Finally, deteriorative characteristics relate to the chemical reactivity of materials.

4. Material Science & Engineering
In addition to structure and properties, two other important components are involved in the science and engineering of materials—namely, “processing” and “performance.”
Processing -> preparing or putting through a prescribed procedure, e.g. the processing of ore to obtain material
Performance -> the accomplishment relative to stated goals or objectives
2. w.r.t. material sciences majors steps are heat-treatment and chemical changes.

5. Relationship Among the Four Components
The structure of a material will depend on how it is processed.
Furthermore, a material’s performance will be a function of its properties.
By changing the heat-treatment (i.e. process) type, u ‘ll get different structures of steel (e.g. martensitic or ferritic)
If desired performance of a component is to maintain its dimensions on application of high force then the stiffness (property) of material should be high

6. processing-structure-properties-performance
Material of all three disks -> Aluminum Oxide
Left Disk -> a single crystal
Center Disk ->composed of numerous and very small single crystals that are all connected
Right Disk ->composed of many small, interconnected crystals, and large number of small pores or void spaces
a photograph showing three thin disk specimens placed over some printed matter. It is obvious that the optical properties (i.e., the light transmittance) of each of the three materials are different; the one on the left is transparent (i.e., virtually all of the reflected light passes through it), whereas the disks in the center and on the right are, respectively, translucent (allowing light to pass through diffusely) and opaque.
that is, it is highly perfect—which gives rise to its transparency
… the boundaries between these small crystals scatter a portion of the light reflected from the printed page, which makes this material optically translucent
These pores also effectively scatter the reflected light and render this material opaque
The structures of these three specimens are different in terms of crystal boundaries and pores, which affect the optical transmittance properties. Furthermore, each material was produced using a different processing technique. And, of course, if optical transmittance is an important parameter relative to the ultimate in-service application, the performance of each material will be different.

7. WHY STUDY MATERIALS SCIENCE AND ENGINEERING?
As a designer we are dependent upon materials, their properties and performance
Many times, a materials problem is one of selecting the right material from the many thousands that are available
On only rare occasions does a material possess the ideal combination of properties
Second selection consideration ->deterioration of properties that may occur during service operation
What will the finished product cost?
Examples might include a transmission gear, the superstructure for a building, an oil refinery component, or an integrated circuit chip
There are several criteria on which the final decision is normally based. First of all, the in-service conditions must be characterized, for these will dictate the properties required of the material
Thus, it may be necessary to trade off one characteristic for another. The classic example involves strength and ductility; normally, a material having a high strength will have only a limited ductility. In such cases a reasonable compromise between two or more properties may be necessary
For example, significant reductions in mechanical strength may result from exposure to elevated temperatures or corrosive environments
A material may be found that has the ideal set of properties but is prohibitively expensive. Here again, some compromise is inevitable. The cost of a finished piece also includes any expense incurred during fabrication to produce the desired shape.
The more familiar an engineer is with the various characteristics and structure–property relationships, as well as processing techniques of materials, the more confident he will be to make judicious materials choices based on these criteria

8. CLASSIFICATION OF MATERIALS
Three basic classifications of solid materials: metals, ceramics, and organic polymers (or just polymers).
In addition, there are the composites, combinations of two or more of the above three basic material classes
This scheme is based primarily on chemical makeup and atomic structure, and most materials fall into one distinct grouping or another, although there are some intermediates.
Another classification is advanced materials semiconductors, biomaterials, smart materials, and nanoengineered materials

9. 1. METALS
Materials in this group are composed of one or more metallic elements and often also nonmetallic elements in relatively small amounts
Atoms in metals and their alloys are arranged in a very orderly manner and in comparison to the ceramics and polymers, are relatively dense
Distinguishing characteristics -> stiff, strong, ductile, resistant to fracture
Metallic materials have large numbers of nonlocalized electrons
Some of the metals (Fe, Co, and Ni) have desirable magnetic properties
Metallic elements -> (such as iron, aluminum, copper, titanium, gold, and nickel), Nonmetallic elements -> (for example, carbon, nitrogen, and oxygen) .
… which accounts for their widespread use in structural applications
… that is, these electrons are not bound to particular atoms. Many properties of metals are directly attributable to these electrons. For example, metals are extremely good conductors of electricity and heat, and are not transparent to visible light; a polished metal surface has a lustrous appearance

10. Metallic Objects
(from left to right) silverware (fork and knife), scissors, coins, a gear, a wedding ring, and a nut and bolt

11. 2. CERAMICS
Ceramics are compounds between metallic and nonmetallic elements; they are most frequently oxides, nitrides, and carbides
Traditional ceramics -> clay minerals (i.e., porcelain), as well as cement, and glass
Common (nontraditional) ceramics -> alumina, silica, silicon carbide, silicon nitride
Relatively stiff and strong—stiffnesses and strengths are comparable to those of the metals
Very hard
Thus, very brittle
3. Al2O3; Si2O3; SiC, Si3N4
6. i.e. very low ductility and also highly susceptible to fracture

12. 2. CERAMICS (contd…)
typically insulative to the passage of heat and electricity
more resistant to high temperatures and harsh environments than metals and polymers.
ceramics may be transparent, translucent, or opaque
some of the oxide ceramics (e.g., Fe3O4) exhibit magnetic behavior
3. Depends upon processing, e.g. the figure containing 3 disks of Alumina
4. iron oxide Fe3O4 (magnetite); Fe2O3 (hematite)

13. Ceramic Objects
scissors, a china teacup, a building brick, a floor tile, and a glass vase

14. 3. POLYMERS
A polymer is a large molecule (macromolecule) composed of repeating structural units typically connected by covalent chemical bonds
Many of them are organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements (e.g. O,N, and Si)
They have very large molecular structures, often chain-like in nature that have a backbone of carbon atoms
Common polymers -> polyethylene (PE), nylon, poly vinyl chloride (PVC), polycarbonate (PC), polystyrene (PS), and silicon rubber
1. Polymers include the familiar plastic and rubber materials. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties

15. A Polymer at Macroscopic Level
Appearance of real linear polymer chains as recorded using an atomic force microscope on surface under liquid medium. Chain contour length for this polymer is ~204 nm; thickness is ~0.4 nm
Y. Roiter and S. Minko, AFM Single Molecule Experiments at the Solid-Liquid Interface: In Situ Conformation of Adsorbed Flexible Polyelectrolyte Chains, Journal of the American Chemical Society, vol. 127, iss. 45, pp (2005).

16. Polymers - Properties have low densities
mechanical characteristics are generally dissimilar to the metallic and ceramic materials – neither stiff nor strong
many of the polymers are extremely ductile and pliable (i.e., plastic)
relatively inert chemically and nonreactive in a large number of environments
major drawback -> tendency to soften and/or decompose at modest temperatures
low electrical conductivities and nonmagnetic
2. However, on the basis of their low densities, many times their stiffnesses and strengths on a per mass basis are comparable to the metals and ceramics
Stiffness -> the physical property of being inflexible and hard to bend
3. … which means they are easily formed into complex shapes
5. … which, in some instance, limits widespread use

17. Polymer Objects
plastic tableware (spoon, fork, and knife), billiard balls, a bicycle helmet, two dice, a lawnmower wheel (plastic hub and rubber tire), and a plastic milk carton.

18. COMPOSITES
Composites are engineered materials made from two or more constituent materials with significantly different physical or chemical properties, which remain separate and distinct on a macroscopic level within the finished structure
The constituent materials come from the categories discussed above—viz., metals, ceramics, and polymers
LEFT -> Glass/carbon/aramid fibres with thermoset/thermoplastic resins
RIGHT -> single-walled nanotubes (yellow) bundle together when used as the reinforcing element of a composite material. The nanotubes are depicted at the interface with the polymer polyethylene (individual polymer molecules are shown in different shades of blue).

19. COMPOSITES (contd…)
The design goal of a composite is to achieve a combination of properties that is not displayed by any single material
Some naturally-occurring materials are also considered to be composites
One of the common composites is fiberglass, in which small glass fibers are embedded within a polymeric material
Glass Fiber -> Strong + Stiff + Brittle
Polymer -> Ductile + Weak + Flexible
… and also to incorporate the best characteristics of each of the component materials.
… —e.g., wood and bone. However, most of those we consider in our discussions are synthetic (or man-made) composites
… normally an epoxy or polyester. Thus, the resulting fiberglass is relatively stiff, strong, flexible, and ductile. In addition, it has a low density

20. Glass-Fiber Reinforced Polymer

21. COMPOSITES (contd…)
CFRP -> carbon fibers that are embedded within a polymer
These materials are stiffer and stronger than the glass fiber-reinforced materials, thus they are more expensive
CFRPs are used in some aircraft and aerospace applications, as well as high-tech sporting equipment
Another of these technologically important materials is the “carbon fiber reinforced polymer … .
e.g., bicycles, golf clubs, tennis rackets, and skis/snowboards

22. CFRP microstructure

23. Bar-chart of room temperature density
Comparison Chart - 1
Bar-chart of room temperature density
GFRC -> Glass Fiber Reinforced Concrete
CFRC -> Carbon Fiber Reinforced Composite
PTFE -> poly tetra fluoro ethylene
PS -> Poly styrene
PE -> Poly ethylene

24. Bar-chart of room temperature stiffness (elastic modulus)
Comparison Chart - 2
Bar-chart of room temperature stiffness (elastic modulus)

25. Bar-chart of room temperature strength (tensile strength)
Comparison Chart - 3
Bar-chart of room temperature strength (tensile strength)

26. Comparison Chart - 4
Bar-chart of room temperature resistance to fracture (fracture toughness)

27. Bar-chart of room temperature electrical conductivity ranges
Comparison Chart - 5
Bar-chart of room temperature electrical conductivity ranges

28. Advanced Materials
Materials that are utilized in high-tech applications
Hi-Tech -> device or product that operates or functions using relatively intricate and sophisticated principles
These advanced materials are typically traditional materials whose properties have been enhanced, and, also newly developed, high-performance materials.
include semiconductors, biomaterials, and materials of the future (i.e., smart materials and nanoengineered materials)
2. Examples include electronic equipment (camcorders, CD/DVD players, etc.), computers, fiber-optic systems, spacecraft, aircraft, and military rocketry
3. … they may be of all material types (e.g., metals, ceramics, polymers), and are normally expensive

29. 1. Semiconductors
Semiconductors have electrical properties that are intermediate between the conductors (e.g. metals and metal alloys) and insulators (e.g. ceramics and polymers)
Common semiconducting materials are crystalline solids but amorphous and liquid semiconductors are known. These include hydrogenated amorphous silicon and mixtures of arsenic, selenium and tellurium in a variety of proportions
Electrical characteristics are extremely sensitive to the presence of minute concentrations of impurity atoms
Semiconductors have caused the advent of integrated circuitry
1. A semiconductor is a material that has an electrical conductivity due to flowing electrons (as opposed to ionic conductivity)
3. … for which the concentrations may be controlled over very small spatial regions.
Amorphous -> without real or apparent crystalline form
4. … that has totally revolutionized the electronics and computer industries (not to mention our lives) over the past three decades.

30. 2. Biomaterials
A biomaterial is any material, natural or man-made, that comprises whole or part of a living structure or biomedical device which performs, augments, or replaces a natural function
must not produce toxic substances and must be compatible with body tissues
All of the above materials—metals, ceramics, polymers, composites, and semiconductors—may be used as biomaterials
Examples -> Artificial hip, bone plates, heart valves, contact lenses, dental implants, etc
Biomaterials are employed in components implanted into the human body for replacement of diseased or damaged body parts
… i.e., must not cause adverse biological reactions

31. Materials of the Future – Smart Materials
Smart materials are materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as stress, temperature, moisture, pH, electric or magnetic fields
Smart material (or system) include some type of sensor, and an actuator
Four types -> shape memory alloys, piezoelectric ceramics, magnetostrictive materials, and electrorheological/magnetorheological fluids
that will have a significant influence on many of our technologies. … Term “smart” implies that these materials are able to sense changes in their environments and then respond to these changes in predetermined manners— traits that are also found in living organisms
Sensor (that detects an input signal); Actuator (that performs a responsive and adaptive function)… …. Actuators may be called upon to change shape, position, natural frequency, or mechanical characteristics in response to changes in temperature, electric fields, and/or magnetic fields

32. Smart Materials (contd…)
Shape Memory Alloys -> alloy that "remembers" its original shape and returns the pre-deformed shape by heating
Main types of shape memory alloys are the copper-zinc-aluminum-nickel, copper-aluminum-nickel, and nickel-titanium
Piezoelectric ceramics -> produce a voltage when stress is applied. Since this effect also applies in the reverse manner, a voltage across the sample will produce stress within the sample
metals that, after having been deformed, revert back to their original shapes when temperature is changed … The large deformation results due to martensitic phase change (pseudoelasticity) .
Piezoelectric ceramics expand and contract in response to an applied electric field (or voltage); conversely, they also generate an electric field when their dimensions are altered

33. Smart Materials (contd…)
Magnetostrictive materials -> analogous to piezoelectrics, except that they are responsive to magnetic fields
Electrorheological and Magnetorheological fluids -> liquids that experience dramatic changes in viscosity upon the application of electric and magnetic fields, respectively
Materials for sensors -> Optical fibers, Piezoelectrics, Microelectromechanical devices
3. A fiber optic sensor is a sensor that uses optical fiber either as the sensing element ("intrinsic sensors"), or as a means of relaying signals from a remote sensor to the electronics that process the signals ("extrinsic sensors"). MEMS is the technology of very small mechanical devices driven by electricity

34. Materials of the Future – Nanoengineered Materials
It has become possible to manipulate and move atoms and molecules to form new structures and design new materials that are built from simple atomic-level constituents
This ability to carefully arrange atoms provides opportunities to develop mechanical, electrical, magnetic, and other properties that are not otherwise possible
One example of a material of this type is the carbon nanotube
with the advent of scanning probe microscopes, which permit observation of individual atoms and molecules …
the “nano” prefix denotes that the dimensions of these structural entities are on the order of a nanometer (10e-9 m) m)—as a rule, less than 100 nanometers (equivalent to approximately 500 atom diameters)