course 1.ppt

8/10/2019 Course 1.ppt

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COURSE1

MATERIALS SCIENCE

Prof.Dr.Eng. Brndua GHIBAN

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11/3/2014

Materials. Classification

Crystalline structure


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CONTACTDATA:

Prof.Dr.Eng. Brndua GHIBAN

Departament METALLIC MATERIALS SCIENCE, PHYSICAL METALLURGY

Consultation: HALL JK 114, THURSDAY 10-12

11/3/2014

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ACTIVITATY during SEMESTRY

Final

VERIFICA-

TIONNote

presence

course

5p

Note access

moodle

platform

10p

Note

laboratory

presence

0

Note

course

manuscript

5p

Note

Laboratory

colloquium

20p

Note

semestry

evaluation

20p40 points

60 points

STUDENTSEVALUATION


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MATERIALS SCIENCE11/3/2014

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is an interdisciplinary science at the border between

mathematics -physics- chemistry- technique, dealingwith complex characterization of materials, the study

of correlations, functional links between chemical

composition, structure, properties, technology

(design, machining, heat treatment) and technical

use of the materials in order to establish laws, rules,criteria and models that will produce

materials with

predetermined properties (design materials),

optimum selection of material for a rational and

scientific substantiation of materials technology.


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Materials define the development of human society

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EXAMPLEOFEVOLUTIONOFMATERIALS

USEDINAEROGASTURBINES11/3/2014

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Utilization of the materials

depends on the properties,

resources, cost price,

workability and compatibilitywith the environment

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MATERIALSCLASSIFICATION11/3/2014

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Organic Materials(carbon, hidrogen, oxigen, nitrogen)

Inorganic MaterialsSimple

Complexe (salts, oxides, halides)

After chemicalcomposition

After the state of

aggregation

MATERIALSCLASSIFICATION


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Interatomic Bonds

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Ionic Bond

Typically, the metal has a 1,2,3 electron valence shell, and has a non-

metallic 5, 6, 7, electrons in the valence shell. Steady state occurs through

the sharing of electrons in the valence shell. Solid materials with Ionic

bonds are :

Hard materials

Insulating substances,

Transparent

Brittle,

High melting point


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Covalent bonds

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Covalent bonds occur between atoms of metals. They have four or more

electrons to the valence layer. To form a new connection would require

very high energy, either for extraction or for adding a new electron. Steady

state occurs through the sharing of electrons in the valence shell. The

solids that are covalent :

Hard materials

Good insulation

Transparent

Brittle, deformable


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Metallic Bonds

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The metallic bonds may appear between the metal atoms. These materials have three

valence shell electrons. When an item has a 1,2,3 valence electrons per layer, the link

established is very poor (e.g aluminum). The connection is formed between a lot of

metal atoms, creating a "cloud of electrons" as a negative value and "frame", with a

positive valence. Solid materials with metallic bonds are

Bohr Model for metal

Good electrical and thermal conductor

Opaque

Relatively ductile


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VAN DER WAALS BONDS

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Van der Waals bonds occur, with few exceptions, in all materials, but

usually in plastics and polymers. These materials have very longmolecular chains, link atomic carbon and other atoms, hydrogen,

nitrogen, oxygen, fluorine. Covalent bonds between the molecules are

very strong and break under extreme conditions. Polymers can be

classified as behavior heating :

Thermoplastic polymers which

soften or liquefy the hot

Thermoset polymers with irreversiblereaction,

Elastomers, with intermediate

behavior.


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MATERIALSCLASSIFICATION

After the nature of the

atomic bonds

Metallic Materials

Ceramic Materials

Polymeric Materials

Composite Materials


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Metallic Materials

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Very good thermal and electrical conductivity,

Good deformability,

Excellent ferromagnetic properties,

Hardening capacity by applying heat treatments.


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CERAMICMATERIALS

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Good optical properties,

Good thermal insulation,

High melting temperature,

Relatively inert in contact with molten metal,

Piezoelectric behavior and the ability to convert into electricity.


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POLYMERICMATERIALS 11/3/2014

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Excellent ductility, with high capacity to form flexible films,

Good electrical insulators,

High resistance to corrosion in aqueous solutions

(moisture resistance).


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COMPOSITE

MATERIALS1

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Metallicmaterials

Organic

polymericmaterials

Ceramic

materials

Composite

Polymer matrix

composites reinforced

with metal

Polymer matrix


with ceramics

Metal matrix


with ceramics

consist of a matrix of soft material (plastic, tenacious,

ductile) which includes a hard and brittle material

filling (in the form of blades, isolated fibers or

particles).

1 + 1 = 3


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Materials Structure

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Structure represents the internal architecture of a

materials system by its parts of components.

(Structure may be observed with naked eye or with glasseye)

1. Macrostructure > 10-2 cm

(Type and proportion of constituents observed by opticmicroscope)

2. Microstructure, 10-810-1cm

(Type of crystalline lattice observed by electron microscope)

3. Crystalline structure, 10-810-1 cm

(Type or chemical bond realized with valence electron of theatoms,observed by electron microscope)

4. Atomic structure, 10-8cm

(Number, cuantic numbers, electron distribution in layers,sublayers and orbitals observed by X-Rays)

5. Electronic structure of the atoms, 10-8cm

(Nature and number of nuclear particles observed by X-Rays)

6. Nuclear structure, 10-13cm


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SCALE OF MATERLS FOR NANOTECHNOLOGY

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Length scale showing the nanometre in context. The length scale at the top ranges from 1m to 10 -10m, and

illustrates the size of a football compared to a carbon 60 (C60) molecule, also known as a buckyball. For

comparison the world is approximately one hundred million times larger than a football, which is in turn one

hundred million times larger than a buckyball. The section from 10-7m (100nm) to 10-9m (1nm) is expanded below.

The length scale of interest for nanoscience and nanotechnologies is from 100nm down to the atomic scale -approximately 0.2nm.


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Crystalline structure of metals and alloys

Crystalline structure and metallic bond represent the most important and decisive

characteristic of the metallic materials, main physical-chemical properties, respectively

mechanical characteristics being influenced by them.

The lower portion of a space lattice which store the symmetry of the entirenetwork is unit cell. The unit cell is defined by its parameters, which are the vectors a,

b andc (unit cell edge) and angle (between b and c), angle (between a and c) and

angle (between a and b).

Dimensional periodic repetition of the unit cell leads to obtaining of the network

space, on whose regularity and symmetry properties relies almost all metals.

Unit cell

Orderly arrangement of atoms in a real crystal is its crystalline structure;

symmetry of the crystal structure corresponds to the spatial network structure, but it

must be noted that the atoms do not occupy those positions in complete immobility,

but it vibrates (oscillates) around these positions, which leads to the real crystals with

many imperfections.

Space lattice

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Main elements which characterize the crystalline lattice

1. Lattice parameter(a,b,c,)represents the distance

between the centers of two

atoms imaginary neighbors

leading edge of the network

2. ,,angles they makebetween them and edges of

the unit cell with lattice

parameters that determine the

crystal system

cwbvaur

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3. DIRECTIONSOFHIGHDENSITYINATOMS

Miller index - for directions are , ,

- for family directions are [110] [111].

Crystalline direction is defined through three index (u,v,w), whichrepresent the smallest entire coordinates of a vector which passthrough origin of the axes of a cell and is parallel with the crystallinedirection.

those directions in which two or more atoms

are tangent between them.1

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Notation for - atomic planes are (111), (100), etc.

- and of planes family {111}, {100}, etc.

Crystallographic plane is defined by the indices h, k, l, which represents

the inverse value of the full segments which form the intersection of theplane with the coordinate axes.

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4. Planes with high atomic density {111}

those planes formed by atoms that have the

most compact settlement (the most compact

planes are those in which each atom is

surrounded by six atoms willing hexagonal.


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Represent the number of atoms which

are at a minimum distance of a given

atom. With the increasing amount of

coordination number, atomic radius

increases.

C = 12 atoms

C= 8 atoms

C = 12 atoms

5. Coordination n umber, C,

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FCC

BCC

HC


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6. Number of atoms A, which belong to a unit cell

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FCC

BCC

HC


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7. Close-packed factor

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cellunitofvolum

atomofvolumecellunitperatomsofnumber ))((

%52100.3

8

3.

3

4

r

r

%68100.

3.

3

3

4

3.

3

4.2

r

r

%74100.3

.

3

)22(

3.3

4.4

r

r

Simple Cube

Body cubic centered

Face cubic centered


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The main crystalline systems

Cristalline system Crystalline parameters Cristalline lattice

Angles Distances

Cube = = 90 a = b= c Cubicsimpl

Cubiccu volum centrat (CVC)

Cubiccufeecentrate (CFC)

Tetragonal = = = 90 a= bc Tetragonalsimpl

Tetragonalcu volum centrat (TVC)

Orthorombic = = = 90 abc Simple Orthorombic

Body centered orthorombic

Base centered orthorombic

Face centered orthorombic

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Cristalline system Crystalline parameters Cristalline lattice

Angles Distances

Rombohedric = = 90 a= b= c Simple Rombohedric

Hexagonal = = 90

= 120

a= bc Simple Hexagonal

Compact Hexagonal (HC)

Monoclinic = = 90 abc Simple monoclinic

Base centered monoclinic

Triclinic 90 abc Simple triclinic

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BCC

Unit cel ls for the mos t frequent metals:

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FCC

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HC11/3/2014

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