Transcript Gold alloy - SlideBoom

Materials science is an interdisciplinary field
involving the properties of matter and its
applications to various areas of science and
engineering.
To meet the growing demand of
industry, many universities have
material science departments
Nanotechnology
Biomaterials
One of the most
useful properties of
materials is its
ability to conduct
electricity
The electrons of different types of atoms have
different degrees of freedom to move around.
When atoms interact
together, their valence
orbitals overlap to form bonds
between the atoms
When many atoms bond
together, the individual
identities of the orbitals are
lost; they form continuous
bands that are divided into
the filled orbitals, known as
valence bands, and unfilled
orbitals, called conduction
bands.
Remember…The highest shell in an atom occupied
with electrons is called the valence shell.
The electrons in the valence shell are called valence
electrons. Note that the valence shell is not the
outermost of all shells, it is just the outmost shell
occupied with electrons.
There are still empty
shells outside it.
The space between the two energy
bands is called the band gap
lowest unoccupied molecular orbital
highest occupied molecular orbital
A band gap isn't a physical space; it's the amount of
energy required to boost an electron from the material's
crowded valence band, the highest energy at which
current cannot flow, into its empty conduction band.
When nonmetal atoms
interact to form a solid,
their atomic orbitals
mix to form two bands
or orbitals separated
by a large band gap
When semimetal
atoms interact to form
a solid, their atomic
orbitals mix to form
two bands of orbitals
separated by a small
band gap
Metals are generally good
conductors because they easily
share some electrons between
their atoms (band gap usually
overlaps slightly)
Polonium
Most of the modern research on metals is in
the area of alloys
Alloys can be a Binary (created by
combining two materials, thus either the
two constituents can be two metals or one
metal and one non-metal), Ternary (created
by combining three materials, thus either
containing all metals, or at least one metal
in its constituents), and so forth.
We use metal alloys everyday….
Steel is an alloy of iron with small amounts of
carbon
stainless steel is a steel
alloy with a minimum of
10.5 or 11% chromium
Bronze: alloy of
copper and tin
Brass: alloy of
copper and zinc
Gold with silver,
copper, and zinc
Gold with platinum or
palladium
Gold with copper
There is constant
research on new metal
alloys
Clockwise from top: A chip, an
LED and a transistor are all
made from semiconductor
material.
a semiconductor is a group of materials with the common
characteristic of increasing conductance with
temperature; the resistance falls as the temperature rises.
In a semiconductor, the
distance between the
valence band and the
conduction band is fairly
small.
At a low temperature the
semiconductor has a
completely filled valence
band. There are no empty
energy positions available for
the electrons to be
accelerated in. Therefore, at
low temperatures the
semiconductor behaves like
The bond structure of a semiconductor determines the
material properties of a semiconductor.
You can change the
behavior of silicon (or
other semiconductor
material) and turn it
into a conductor by
doping it. In doping,
you mix a small amount
of an impurity into the
silicon crystal.
Semiconductors can be
made of a single material
or a combination of several
different materials.
To improve efficiency in tiny thermoelectric
devices, researchers build super lattices of
alternating thin layers of two different
semiconductor materials, called
heterojunctions.
Today, most semiconductor chips and transistors
are created with silicon.
Thus, silicon is the heart of most electronic
devices.
Silicon is the most
common metalloid
and the second most
abundant element
found on earth
Silicon very rarely
occurs as the pure
free element in
nature, but is
abundantly found as
various forms of
silicon dioxide (silica)
or silicates.
The crystal forms of
silica are given their
Quartz.
Sand is rock material
that has been eroded
into tiny grains
Silica gel is a desiccant - it adsorbs and holds
water vapor.
In electronics it prevents condensation
A ceramic is an inorganic, non-metallic
solid prepared by the action of heat and
subsequent cooling.
ceramics are heat resistant
Alumina is the most popular advanced
ceramic material.
Silicon carbide is recognized for its corrosion
resistance. It is high in wear and thermal
shock resistance
Pottery
Porcelain
A ceramic made specifically
from Kaolin clay (hydrated
aluminum silicate)
Porcelain is
translucent, or
allows some light to
penetrate, while
pottery does not.
Bone China
Porcelain that contains
bone ash
Bathtubs are often made from
ceramics or are coated with
ceramics
Perhaps you like them a little
more modern?
Yttrium stabilized zirconium
oxide ceramic frameworks
with ceramic veneering
material.
There are many types of plastics, but they all are
based on taking one or two small molecules and
starting a chain reaction that connects hundreds or
thousands of these small molecules into long chains
or branching chains. By controlling the length and
the branching, you can control the final hardness or
flexibility of the polymer plus qualities like
resistance to solvents, acids, or heat.
Polymer dispersed liquid crystals (PDLCs) can be applied
as a coating to windows and simple displays. PDLCs are
made from a mixture of a liquid crystal and a polymer..
Initially, the glass appears to be frosted. When an
electrical field is applied to the coating, the liquid crystal
reacts by realigning its molecular structure to match
that of the transparent polymer's, and almost instantly
the window becomes clear!
Click the icon for the link to the article
Composite materials (or composites for short) 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.
Composites are made up of individual materials
referred to as constituent materials. There are
two categories of constituent materials: matrix
and reinforcement. At least one portion of each
type is required. The matrix material surrounds
and supports the reinforcement materials by
maintaining their relative positions
There is a huge industrial demand for composite
materials
Properly known as fiber-reinforced polymer (FRP)
or glass-reinforced plastic (GRP), the composite
material is called "fiberglass" in popular usage.
Plywood is a common
composite material
Various composite materials
are used in structures such as
the Boeing 777 because of
their strength, and weight
savings. Composites also
offer resistance to fatigue,
corrosion and impact
damage.
New Carbon Composite
of Nanotubes and
Graphene
Nanomaterials can be metals, ceramics, polymeric
materials, or composite materials. Their defining
characteristic is a very small feature size in the
range of 1-100 nanometers (nm).
One nanometer spans 3-5 atoms
lined up in a row
Nanoparticles, nanorods, nanotubes,
and nanowires are the most commonly
known nanoscale materials.
materials reduced to the nanoscale can suddenly
show very different properties compared to what
they exhibit on a macroscale, enabling unique
applications.
For instance, opaque substances become
transparent (copper); inert materials attain
catalytic properties (platinum); stable materials
turn combustible (aluminum); solids turn into
liquids at room temperature (gold); insulators
become conductors (silicon).
Nantubes
A biomaterial is any material, natural or manmade, that comprises whole or part of a living
structure
or
biomedical device which performs, augments, or
replaces a natural function
One major field of biotechnology
is bionics, which the study of
mechanical systems that
function like living organisms or
parts of living organisms