Introduction To Technical Materials or Material Technology

TECHNICAL MATERIALS

AN INTRODUCTION

TECHNICAL MATERIALSAN INTRODUCTION

Materials can be defined as anything which satisfies the human needs

or

Materials are substances of which some thing is composed or made of.

Since civilization materials are in use by people to improve their standard of living.

Materials are everywhere about us in the shapes of products

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Historical Perspective

Beginning of the Material Science –

People began to make tools from stone – Start of the Stone Age about two million years ago.

Natural materials: stone, wood, clay, skins, etc.

The Stone Age ended about 5000 years ago with introduction of Bronze.

Bronze is an alloy (copper + tin + other elements). Bronze: can be hammered or cast into a variety of shapes, can be made harder by alloying, corrode only slowly after a surface oxide film forms.

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The Iron Age began about 3000 years ago and continues today.

Use of iron and steel, a stronger and cheaper material

changed drastically daily life of a common person.

Age of Advanced materials: throughout the Iron Age many new types of materials have been introduced (ceramic, semiconductors, polymers, composites…).

Understanding of the relationship among structure, properties, processing, and performance of materials. Intelligent design of new materials.

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A better understanding of structure-composition properties relations has lead to a remarkable progress in properties of materials.

Example is the dramatic progress in the strength to density ratio of materials, that resulted in a wide variety of new products, from dental materials to tennis racquets.

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ENGINEERING MATERIALS-AN INTRODUCTION

Commonly encountered materials are wood (timber),

concrete, bricks, steel. plastic, glass, rubber, aluminum,

copper and paper etc.

If we look around we can easily realize that there are

many more kinds of materials.

These new types of materials are being frequently

developed as a result of constant research and

development.12/12/14 6WEC

The world of materials

Metals,alloys

Ceramics,glasses

Polymers,elastomers

Hybrids, composites

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The world of materials

Polymers,

elastomers

Ceramics,

glasses Hybrids,

composites

Metals,

alloys

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The term technical materials is specifically used to refer materials to produce technical products

However there is no limiting line between the terms Materials and Technical materials,

they can be used interchangeably

Technical materials

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Engineers

design most of the products and their processing systems for the production of

these products. Products require materials & Engineers should have the knowledge of

engineering materials i.e. an engineer should be knowledgeable about the structure

and properties of the materials so that

he is able to select the most suitable ones for each application

and he is able to develop best processing methods.

Technical materials

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Relationship b/w Structural level & Engineering properties

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Subatomic level Electronic structure of

individual atoms that defines interaction among atoms (interatomic bonding).

Atomic level Arrangement of atoms in

materials (for the same atoms can have different properties, e.g. two forms of carbon: graphite and diamond)

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Microscopic structure Arrangement of small

grains of material that can be identified by microscopy.

Macroscopic structure Structural elements that

may be viewed with the naked eye.

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Engineering activities depend upon the selection

of engineering materials whose properties match

the requirements of the application

Primitive cultures were often limited to the

naturally occurring materials (stone wood, clay) in

their environment.

Structure-Property-Processing-Performance Relationship

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As civilization developed, the spectrum of engineering materials expanded.

Materials could be processed and their properties altered and possibly enhanced.

The alloying and heat treatment of metals can change the properties of a material.


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While earlier successes in altering materials were

largely the result of trial and error,

But now

we recognize that the properties and performance

of a material are the direct result of its structure

and processing

If we want to change the properties, we will have to

induce changes in the material structure


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Classification of Technical materials

Most of the Technical materials can be

classified into main five categories as under:

1. Metallic materials

2. Polymeric materials

3. Ceramic materials

4. Composite materials

5. Electronic materials

6. Advanced materials12/12/14 17WEC

cont…… Classification

Metals Steel, Cast Iron,

Aluminum, Copper, Titanium, many others

Ceramics Glass, Concrete,

Brick, Alumina, Zirconia.

Polymers Plastics, Wood,

Cotton (rayon, nylon), “glue”

Composites Glass Fiber-

reinforced polymers,

Carbon Fiber-reinforced polymers,

Metal Matrix Composites, etc.12/12/14 18WEC

Metallic materials

These are inorganic substances which are

composed of one or more metallic elements.

Examples of metallic elements are Iron, Copper,

Aluminum.

Non-metallic elements such as Carbon,

Nitrogen and Oxygen may also be contained in

the metallic materials.12/12/14 19WEC

Metallic materials

Metals: valence electrons are detached from atoms,

and spread in an 'electron sea' that "glues" the ions

together.

Crystalline structure

Strong, ductile

high thermal & electrical conductivity

reflective. shiny if polished

Can be plastically deformed on the application of

load

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Metallic materials

Metallic materials are further classified into

ferrous, and non-ferrous materials.

Ferrous materials contain large percentage

of iron such as steels and cast irons and

Non-ferrous materials that do not contain

iron or only relatively small amount of iron.

Example of non-ferrous metals are Al, Cu,

Zn, Ti, & Ni. 12/12/14 21WEC

Several uses of steel and pressed aluminum.

Metals

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The word polymer is actually taken from two

Greek words, Poly = many and

mer = repeating units or parts.

Polymeric materials are usually long organic

molecular chains i. e., compounds of C & H.

So the polymeric materials are organic

compounds having many repeated units, e.g.,

Teflon, Nylon 6,6, Polythene etc.

Polymeric materials

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Polymeric materials

Polymers/plastics:

Covalent bonding sharing of e’s

Soft, ductile, low strength, low density

thermal & electrical insulators

Optically translucent or transparent.

cheap

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Polymers include “Plastics” and rubber materials

Polymers

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The word ceramics actually is taken from the Greek word

“ Keramos “ = burnt stuff / Clay.

Ceramics are inorganic materials consisting of metallic &

non-metallic elements (oxides, carbides, nitrides, sulfides)

chemically bonded together unlike metallic materials.

They may be crystalline, non-crystalline or mixtures, e.g.,

glass, refractories.

Hard, Brittle, glassy, elastic

non-conducting (insulators)

Difficult to process, low fracture toughness

Ceramic materials

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Examples of ceramic materials ranging from household to high performance combustion engines which utilize both metals and ceramics.

Ceramics

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Composite materials are mixtures of two or more

materials to produce properties that are not produced

in a single material, e.g., Fiber glass, concrete,

plywood etc.

The useful properties which can be produced in such

materials are strength, stiffness, hardness,

temperature resistance, corrosion resistance,

conductivity etc.

High cost

Delamination, etc

Composite materials

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Polymer composite materials: reinforcing glass fibers in a polymer matrix.

Composites

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Electronic materials

Semiconductors: the bonding is covalent (electrons

are shared between atoms).

Their electrical properties depend strongly on

minute proportions of contaminants. Examples: Si,

Ge, GaAs

Electronic materials are used in electronics, especially

microelectronics, e.g., Silicon, Germanium & Gallium

Arsenide etc.

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Si wafer for computer chip devices.

Semiconductors

Micro-Electrical-Mechanical Systems (MEMS)

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Types of Materials- summary

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The Materials Selection Process

1. Pick Application Determine required Properties

2. Properties Identify candidate Material(s)

3. Material Identify required Processing

Processing: changes structure and overall shapeex: casting, machining, sintering, vapor deposition, doping forming, joining, annealing.

Properties: mechanical, electrical, thermal,magnetic, optical, deteriorative.

Material: structure, composition.

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Material selection: Properties/performance and cost

But:Properties depend on Structure

(strength or hardness)

Har

dne

ss (

BH

N)

Cooling Rate (ºC/s)

100

200

300

400

500

600

0.01 0.1 1 10 100 1000

(d)

30 µm(c)

4 µm

(b)

30 µm

(a)

30 µm

And: Processing can change structure! (see above structure vs Cooling Rate)

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Properties are the way the material responds to the environment and external forces.Mechanical properties – response to mechanical forces, strength, etc.Electrical and magnetic properties - response electrical and magnetic fields, conductivity, etc.Thermal properties are related to transmission of heat and heat capacity.Optical properties include to absorption, transmission and scattering of light.Chemical stability in contact with the environment - corrosion resistance.

Properties

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Design of materials having specific desired characteristics

directly from our knowledge of atomic structure.

• Miniaturization: “Nanostructured" materials, with

microstructure that has length scales between 1 and 100

nanometers with unusual properties.

•Electronic components, materials for quantum computing.

• Smart materials: airplane wings that adjust to the air flow

conditions, buildings that stabilize themselves in earthquakes…

•

Future of materials science

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•Environment-friendly materials: biodegradable or photodegradable plastics, advances in nuclear waste processing, etc.• Learning from Nature: shells and biological hard tissue can be as strong as the most advanced laboratory-produced ceramics, • Materials

• for lightweight batteries with high storage densities,• for turbine blades that can operate at 2500°C, • room-temperature superconductors?• chemical sensors (artificial nose) of extremely high sensitivity, • cotton shirts that never require ironing…

Future of materials science

Advanced Materials

Materials used in "High-Tec" applications,

usually designed for maximum performance,

and normally expensive. Examples are:

titanium alloys for supersonic airplanes,

magnetic alloys for computer disks,

special ceramics for the heat shield of the space

shuttle, etc. 12/12/14 WEC 44

Advanced Materials Modern Material's Needs Engine efficiency increases at high temperatures: requires high

temperature structural materials Use of nuclear energy requires solving problem with residues,

or advances in nuclear waste processing. Hypersonic flight requires materials that are light, strong and

resist high temperatures. Optical communications require optical fibers that absorb light

negligibly. Civil construction – materials for unbreakable windows. Structures: materials that are strong like metals and resist

corrosion like plastics.

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Thanks