MATERIALSDR. A. CADBY

A.CADBY@SHEFFIELD.AC.UK

GENERAL COURSE INFORMATION

1ST HOME WORK 23RD OCTOBER, RETURNED ON 14TH NOVEMBER (10%)

2ND HOME WORK 30TH NOVEMBER RETURNED ON 11TH DECEMBER (10%)

EXAM 80%

HTTP://ASHLEYCADBY.STAFF.SHEF.AC.UK/MATERIALS/FRONT.HTML

OVER VIEW

▸ Introduction▸ Atoms and the Periodic table▸ Bond and Bonding▸ Materials Properties▸ Failure▸ Soft matter

Historically, the development and advancement of societies have been intimately tied to the members’ ability to produce and manipulate materials to fill their needs. In fact, early civilisations have been designated by the level of their materials development (Stone Age, Bronze Age, Iron Age)

Christian Jürgensen Thomsen for classifying ancient societies and prehistoric stages of progress, danish archeologist

HISTORYSTONE AGE

HISTORYBRONZE AGE

IRON AGE

STEEL

8000 B.C. - Hammered Copper 7000 B.C. - Clay Pottery 6000 B.C. - Silk Production 5000 B.C. - Glass Making 4000 B.C. - Smelted Copper (Bronze Age) 1000 B.C. - Iron Age 500 B.C. - Cast Iron 300 B.C. - Glass Blowing

1907 - First Totally Synthetic Polymer 1923 - Tungsten Carbide 1930 - Fiberglass 1937 - Nylon 1947 - Germanium Transistor 1950s - Silicon Photovoltaic Cells &

Transistors 1958 - Ruby Laser 1959 - Integrated Circuit 1966 - Fiber Optics 1986 - High Temperature Super Conductors

105 A.D. - Paper 600 - 900 - Porcelain 1540 - First Foundries 1774 - Crude Steel 1789 - Discovery of Titanium 1800 - Battery 1824 - Portland Cement 1850 - Reinforced Concrete 1856 - Bessemer Steel-making Process 1870 - Celluloid Production 1871 - Periodic Table 1884 - Nitrocellulose 1886 - Electrolytic Reduction of Aluminum 1891 - Silicon Carbide

STRENGTH AS A FUNCTION OF TIME

NEW AGE OF MATERIAL, STILL IN THE IRON AGE BUT NOW IN THE AGE OF ADVANCED MATERIALS

CLASSIFICATION OF MATERIALS

METALS

CERAMICS

POLYMERS

COMPOSITES

SEMICONDUCTORS

BIO-MATERIALS

LIQUIDS

Metallic materials are normally combinations of metallic elements. They have large numbers of non-localized electrons; that is, these electrons are not bound to particular atoms. Many properties of metals are directly attributable to these electrons. Metals are extremely good conductors of electricity and heat and are not transparent to visible light; a polished metal surface has a lustrous appearance. Furthermore, metals are quite strong, yet deformable, which accounts for their extensive use in structural applications.

Ceramics are compounds between metallic and nonmetallic elements; they are most frequently oxides, nitrides, and carbides. The wide range of materials that falls within this classification includes ceramics that are composed of clay minerals, cement, and glass. These materials are typically insulative to the passage of electricity and heat, and are more resistant to high temperatures and harsh environments than metals and polymers. With regard to mechanical behavior, ceramics are hard but very brittle.

MECHANICAL ELECTRICAL MAGNETIC THERMAL OPTICAL

CHEMICAL (STABILITY) SMART / RESPONSIVE MATERIALS

BIO INSPIRED MATERIAL

METALS

Metallic materials are normally combinations of metallic elements. They have large numbers of nonlocalized electrons; that is, these electrons are not bound to particular atoms. Many properties of metals are directly attributable to these electrons. Metals are extremely good conductors of electricity and heat and are not transparent to visible light; a polished metal surface has a lustrous appearance. Furthermore, metals are quite strong, yet deformable, which accounts for their extensive use in structural applications.

POLYMERS / PLASTICS

Polymers include the familiar plastic and rubber materials. Many of them are organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements; furthermore, they have very large molecular structures. These materials typically have low densities and may be extremely flexible.

CERAMICS

Ceramics are compounds between metallic and nonmetals. Most commonly oxides, nitrides or carbides. T h e y a r e Strong and stiff. They are as strong as metals, but much more brittle. However, modern material science has overcome some of the brittle nature of these materials and now they are used in a variety of technological devices. Generally transparent but often opaque as well. The bonding in ceramics is generally a mixture of covalent one ionic.

LIQUIDS

A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. It is the only state with a definite volume but no fixed shape. A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular bonds. Water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container. Most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state.

COMPOSITES

Two or more materials from any category. These are blended together in order to obtain characteristics from both materials. The properties of these materials can be extremely varied. Examples of composites include bone and wood from biology. A more modern example would be carbon fibres trapped in a polymer resin for tennis racquet.

BIOMATERIALS

A biomaterial is any matter, surface, or construct that interacts with living systems. As a science, biomaterials is about fifty years old. The study of biomaterials is called biomaterials science or biomaterials engineering. It has experienced steady and strong growth over its history, with many companies investing large amounts of money into the development of new products. Biomaterials science encompasses elements of medicine, biology, chemistry, tissue engineering and materials science.

NANO MATERIALS

Nanomaterials has become something of a buzzword. However, simply put we could class any material which exhibits properties that differs from it bulk due to size effects as nano materials.

ADVANCED MATERIALS

• SEMICONDUCTORS • BIO-MATERIALS • SMART MATERIALS • NANO-MATERIALS

ATOMIC STRUCTURE

BONDING

CRYSTALS

DIFFUSION

MATERIAL PROPERTIES

The forces in nature.

We know about the four forces in nature, Strong and weak act between neutrons, protons and electrons. They have very short interaction distances 10^-5 nm. Gravity and electromagnetism act over much larger distances however due to the effective strength of gravity only electromagnetism has an effect on the materials we are concerned with.

The Greeks believed in two forces love and hate, first proposed by Empedocles in 450 B.C and improved on by Aristotle, forming the basis of chemical theory.

But lets think about what that is saying, its telling us that wood is held together by the same force that holds together metals and liquids. Furthermore, it means that the same forces that make gold gold also make pyrite pyrite.

2.5 Bonding Forces and Energies ● 19

which is also a function of the interatomic separation, as also plotted in Figure2.8a. When FA and FR balance, or become equal, there is no net force; that is,

FA ! FR " 0 (2.3)

Then a state of equilibriumexists.The centers of the two atoms will remain separatedby the equilibrium spacing r0 , as indicated in Figure 2.8a. For many atoms, r0 isapproximately 0.3 nm (3 A). Once in this position, the two atoms will counteractany attempt to separate them by an attractive force, or to push them together bya repulsive action.

Sometimes it is more convenient to work with the potential energies betweentwo atoms instead of forces.Mathematically, energy (E) and force (F) are related as

E " ! F dr (2.4)

Or, for atomic systems,

EN " !r

!FN dr (2.5)

" !r

!FA dr ! !r

!FR dr (2.6)

" EA ! ER (2.7)

in which EN , EA , and ER are respectively the net, attractive, and repulsive energiesfor two isolated and adjacent atoms.

+

(a)

(b)

Interatomic separation r

Interatomic separation r

Repulsive force FR

Attractive force FA

Net force FN

Attr

actio

nR

epul

sion

Forc

e F

Repulsive energy ER

Attractive energy EA

Net energy EN

+

0

0

Attr

actio

nR

epul

sion

Pote

ntia

l ene

rgy E

r0

E0

FIGURE 2.8 (a) Thedependence of repulsive,attractive, and net forces oninteratomic separation fortwo isolated atoms. (b) Thedependence of repulsive,attractive, and net potentialenergies on interatomicseparation for two isolatedatoms.

Concepts of Stress and Strain Tension tests Stress–Strain Behavior ModulusAnelasticity Yields and Yield StrengthsElastic Properties of Materials PLASTIC DEFORMATION Tensile PropertiesTrue Stress and Strain

materia properties

MSE 2090: Introduction to Materials Science Chapter 1, Introduction 18

Different materials exhibit different crystal structures(Chapter 3) and resultant properties

(a) (b)force

Material Selection

SOFT MATTER

POLYMER MODELS

PHASE DIAGRAMS AND CHANGES

PHASES OF MIXED MATERIALS

such as the orbit of the moon around the earth when acted on by the same force—a thought process that requires a leap of the imagination by a factor of 106 in time, 108 indistance, and 1024 in mass.

But trouble was just round the corner. In 1662 Robert Boyle (1627–1691) published hisfamous gas law, PV ¼ constant. Twenty-five years later, Isaac Newton (1642–1727) pub-lished his famous law of gravity. Boyle’s Law suggested that molecules repel each other(the pressure P in PV ¼ constant is repulsive), while gravity suggested that they attract.Newton also concluded that the molecules of a gas must ultimately attract each other,since they condense into liquids or solids. These apparent contradictions sowed the first ofmany seeds that were to lead to heated controversies in the two centuries to come.

Table 1.1 Scientists Who Made Major Contributions to Our Understanding ofIntermolecular Forces (including some whose contribution was indirect)

Scientific

method

Newton’s

Principia

Mathematical

methods

Kinetic theory

Thermodynamics

Quantum theory

Colloids

1500 1600 1700 1800 1900 2000

1500 1600 1700 1800 1900 2000

F. Bacon

Galileo

Boyle

Newton

Euler

Coulomb

Laplace

Young

Clausius

Maxwell

van der Waals

Gibbs

Boltzmann

Langmuir

Debye

London

Lennard-Jones

Pauling

Onsager

Hamaker, Casimir,

Derjaguin, Overbeek

Landau

Lifshitz

de Gennes

6 INTERMOLECULAR AND SURFACE FORCES

If we travel back to the 18th century we would know that PV=constant. We may think that the repulsion is due to repulsion between stationary molecules. What is the distance dependence of this force?

Hint you can write PV=constant as