chapter 1-material structure and binary alloy system
TRANSCRIPT
WHAT IS MATTER?
Atom Elements Compound Mineral Rocks
Smallest Largest
Is the smallest particle of an element and has the same chemical properties of the element
Atoms:
– the stuff that builds elements
– the smallest particle that uniquely defines an elemen
Particles that make up an atom:
Protons: positive (+) charge
Neutrons: no charge
Electrons: negative (-) charge
Protons + neutrons define the nucleus of an atom.
Layers of electrons that orbit around the nucleus are called orbitals or energy -level shells.
ATOM
ATOM STRUCTURE
ATOM STRUCTURE
A substance composed of a single kind of atom
Elements contain one or more of the same type of atom!
Cannot be broken down into another substance by chemical or
physical means.
ELEMENTS
A substance in which two or more dif ferent elements are
CHEMICALLY bonded together
COMPOUND
Two or more substances that are mixed together but are NOT
chemically bonded.
MIXTURE
PERIODIC TABLE ELEMENTS
The arrangement of the chemical elements with increasing
atomic number according to the periodic variation in electron
structure. Nonmetallic elements are positioned at the far
right-hand side of the table.
DEFINE PERIODIC TABLE
WHAT HAVE INSIDE THE BOX OF EPT?
Atomic Number
Symbol of Element
Atomic Weight
Name of Element
WHAT IS ATOMIC NUMBER?
Atomic Number
Atomic numbers represent the number of
protons in one atom of the element.
WHAT IS ATOMIC MASS?
Atomic Number
A sum of the number of
protons and neutrons in
the nucleus
WHAT IS SYMBOL?
Symbol of Elements
Explains name of the element.
Arrangements of electrons in an atom.
Each orbital can have only 2 electrons and with dif ferent
quantum numbers.
ELECTRON CONFIGURATION
1) Oxygen
Atomic Number=8
Shell Number=2
Group=? – lets determine it through atomic orbit.
Solution
1) Filled up electron at first shells
2) The balance of electron number left will be fill up at outer shell. Then it
shows the group of Oxygen.
EXAMPLE ELECTRON CONFIGURATION
Oxygen-atomic orbit
crystal structure is a unique arrangement of atoms or molecules in a crystall ine l iquid or solid.
A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long -range order and symmetry. Patterns are located upon the points of a lattice, which is an array of points repeating periodically in three dimensions. The points can be thought of as forming identical tiny boxes, called unit cells, that fi l l the space of the lattice. The lengths of the edges of a unit cell and the angles between them are called the lattice parameters. The symmetry properties of the crystal are embodied in its space group.
A crystal's structure and symmetry play a role in determining many of its physical properties, such as cleavage, electronic band structure, and optical transparency.
CRYSTAL STRUCTURE
CRYSTALLIZED STRUCTURE
Simple cubic
Body-centered cubic
No of atoms:
8 corner atom x 1/8 = 1 atom
Total atom = 1 atom
No of atoms:
8 corner atom x 1/8 = 1 atom
1 centre atom = 1 atom
Total atom = 2 atoms
CRYSTALLIZED STRUCTURE
(CONT.)
Face-centered cubic
Hexagonal close-packed
No of atoms:
12 corner atom x 1/6 = 2
atoms
2 centre atom x ½ = 1
atom
3 centre atom = 3
atoms
Total atom = 6
atoms
No of atoms:
8 corner atom x 1/8 = 1 atom
6 face corner x ½ = 3 atoms
Total atom = 4 atoms
TO BE CONTINUED UNTIL
ALL STUDENT SUBMIT
THE ASSIGNMENT!!!
Adapted from Fig. 2.10, Callister 6e.
COVALENT BONDING
Electrons are shared (as opposed to transferred) between
atoms in their outermost shells to achieve a stable set of
eight
Atoms of one element give up their outer electron(s), which
are in turn attracted to atoms of some other element to
increase electron count in the outermost shell to eight.
IONIC BOND
Sharing of outer shell electrons by all atoms to form a general
electron cloud that permeates the entire block.
METALLIC BONDING
Some metals are important as pure elements (e.g ., gold,
silver, copper)
Most engineering applications require the enhanced
properties obtained by alloying
Through alloying, it is possible to increase strength, hardness,
and other properties compared to pure metals.
METALS AND ALLOYS
Solid solution is an alloy in which the solute atoms are
distributed in the solvent matrix and has same structure of
the solvent.
The elements which present in larger amount in the alloy is
called solvent and the other elements is called solute.
There are two type of solid solution
1) Substitutional
2) Interstitial
SOLID SOLUTIONS
The atoms of the solvent metal are replaced in the crystal
lattice by the atoms of the solute.
Subtitutional solid solution formation is favoured when the
atomic sizes of the two metals are almost equal.
SUBTITUTIONAL SOLID SOLUTION
Subtitutional solid solution
Are formed only when the atoms of the solute elements are
very small compared with those of the solvent, thus enabling
them to fit into interstices or spaces in the crystal lattice of
the solvent.
INTERSTITIAL SOLID SOLUTION
Interstitial solid solution
METAL SOLIDIFICATION
METAL AND ALLOY COOLING CURVE
Pure metals solidify at a constant
temperature.
Alloys solidify within a temperature range
PHASE DIAGRAM
A solidus is a line below which the substance is stable in the
solid state.
A liquidus is a line above which the substance is stable in a
liquid state
Composition is expressed in weight percent(wt%) of each
elements in the phase.
Phase - can exist over a range of temperatures and
compositions, but it 's atomic structure will remain the same.
There to be three phases, or states of matter: gas, liquid and
solid.
An equilibrium diagram (or phase diagram) is a diagram with
T and X (or W) as axes, showing the equilibrium constitution.
TERMS OF EQUILIBRIUM PHASE DIAGRAM