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The aim of this report is to produce a report that
summarises the structure of the main types of engineering materials, this
includes metals, polymers, ceramics, composite materials and smart materials I
will also explain the structure of my chosen metal. Depending on my research, I
will produce a ‘Family Tree’ that groups engineering materials into categories
according to their properties.  Periodic
TableIn the periodic table,
there are 7 groups and elements in the same group are similar to each other.
The elements are arranged in order of increasing atomic number. The elements in
the first group are alkali metals; these types of metals are usually so
reactive that they are usually found in nature combined with other elements.
Elements in the second group are alkaline earth metals, they are six chemicals
that are very reactive and are at standard temperature and pressure. In the
third group, rare earth metals are found, the elements all occur naturally. In
the fourth group, there are also rare
earth metals alongside two non-metals; carbon and silicon. This is the same for
the fifth and sixth group, non-metals and rare earth metals are found in these
groups. In the seventh group, halogens are found, halogens have low melting and
boiling points, this is typical for non-metals. There is also a trend in the state from gas to liquid as you go down group
7. Finally, Noble gases, these are found in group
0. Noble gases are all chemically unreactive gases. An example of a use of a
noble gas is Helium, which is used for balloons and airships, since helium is much less dense than oxygen, so balloons
and airships filled with it float upwards. There are more groups but all of the
elements in those groups are transition metals. Transition metals are good
conductors of heat and electricity. Transition metals are also malleable; they
have high melting points, except for mercury, which is liquid at room
temperature.The structure of an atom, an atom consists of electrons,
which surrounds the nucleus, which contains protons and neutrons. The neutrons
but protons and electrons are electrically charged. Protons have a relative
charge of +1 and electrons have a relative charge of -1. The number of protons
in an atom is called the atomic number, in the periodic table, the elements are arranged in atomic number order. The
electrons are arranged in energy levels/shells; different energy level can hold
different numbers of electrons. The electronic structure of an atom is a
description of how the electrons are arranged. There is a link between the
positions of elements in the periodic table and the electronic structure.         A valence electron is an outer shell electron that is
associated with an atom, and that can participate in the formation of a
chemical bond if the outer shell is not closed. However, in a covalent bond,
both atoms in the bond contribute one valence electron in order to form a
shared pair. A covalent bond is formed between non-metal atoms; they combine by
sharing electrons. Covalent compounds have no free electrons and no ions so
they do not conduct electricity. The shared pair of electrons holds the two
atoms together; it is called a covalent bond. The group of atoms bonded
together this way is a called a molecule. Bonding
between atomsIn Ionic bonding both positive and negative ions
attract one another and bind together to form a new substance; this is what
ionic bonding is. Atoms turn into ions when they lose or gain electrons. There
are several ways in which atoms chemically combine to make a compound. In metal
ions, a metal atom may lose electrons, the atom is then left with more protons
than electrons and therefore it is a positive ion. On the other hand, non-metal
ions may gay electrons and become negatively charged atoms. Ionic compounds
usually have a high melting point and do
not conduct electricity when solid but do conduct electricity when molten. In metallic bonding, the particles in a metal are all
held together by metallic bonds. Metallic bonding is a strong attraction
between closely packed positive metal ions and a ‘sea’ of delocalized
electrons. The attraction between these two must be overcome for the metal to
be melted or boiled. The forces of attraction are strong, so metals have high
melting and boiling points. Metals also have electrons, which are free to move,
carrying a charge from place to place, which allows metals to conduct
electricity. A compound is formed when atoms from different
elements joined by chemical bonds. This
pretty much means that compounds will always exist as molecules and no as
separate atoms. However, some atoms do not join up at all, therefore they stay
single atoms.Finally, a molecule is a group of atoms that are
bonded together. A molecule represents the smallest fundamental component of a
chemical compound that is able to take part in a chemical reaction. Structure
of metalsThe structure of a metal consists of particles in a
metal that are held together by strong metallic bonds. It would take a lot of
energy to separate these particles. Solid metals are crystalline; this means
particles are held closely together and in a regular
arrangement. Metals have loose electrons in the outer shells, which form
a sea of delocalized negative charges around the tightly packed positive ions.
Strong electrostatic forces hold the particles together. The properties of the metal are changed by adding other elements to
it. A combination of two or more elements, where at least one element is a
metal, this is called an alloy. An alloy contains atoms of different sizes,
which changes the regular arrangement of atoms. Therefore making it more
difficult for the layers to slide over each other and causing the metal to snap
or break. Alloys are harder/stronger than the pure metal. Furthermore, there are Ferrous and non-ferrous metals.
A Ferrous metal will contain iron and a non-ferrous metal will not. Non-ferrous
metals are also more resistant to corrosion and are not magnetic. Some examples
of non-ferrous metals are aluminium and aluminium alloys.Common crystal lattice structure; they have structures
that can be described as Body Centric Cubic (BCC) packing of spheres. The other
two common ones are Face Centred Cubic (FCC), which are spheres packed together
diagonally and Hexagonal Closest Packaging (HCP), which have a hexagonally
closely packed crystal structure. Metals have a crystalline structure, which is
not usually visible but can be seen using a galvanized lamp for example. When a
metal starts to solidify from its molten state, millions of tiny crystals begin
to grow. The longer the cooling process the larger the crystals grow. Each
grain is a distinct crystal and they form inside the solid metal.     My chosen
metalMy chosen metal is magnesium. Magnesium is the second
group; it has two outer electrons in its outer shell. When these electrons are
lost, a magnesium ion is formed. The metal is a chemical element with the
symbol Mg in the periodic table and the atomic number of twelve. Chemical
properties of magnesium; upon heating, magnesium reacts with halogens,
magnesium alloys are very light but very strong, it also combines with oxygen
at room temperature to form a thin skin of magnesium oxide. Some of the uses of
magnesium; used in fireworks, aeroplanes
and rockets. As well as helping your body function.  Structure
of polymersA polymer is made up of
many simple molecules that have a repeating structure called monomers. One
single polymer molecule consists of hundreds of
a million simple structures (Monomers), they may have linear, branched or the
network structure. A polymer can contain long molecules that are side by side,
these long molecules uncoil and slide past each other, and this makes the
material flexible. Short chains have weaker forces of attraction than shorter
ones; so they make weaker materials. In a polymer, covalent bonds hold the
atoms in the polymer together and secondary bonds then hold groups of polymer
chains together to create the polymeric material. My chosen
chosen polymer is polyvinyl chloride (PVC). PVC is formed through the polymerisation
of vinyl chloride.  The vinyl chloride
molecule has the chemical composition C2H3Cl. Vinyl chloride monomers make up
the polymer chains. The molecules of vinyl chloride monomers combine to make
long chain molecules of polyvinyl chloride. PVC is a widely used plastic that
contains hydrogen, carbon and chlorine. The properties of PVC consist of them
being stiff, strong, tough and scratch resistant. Some of the uses of PVC
consists of them being used to making 2D
and 3D shapes and may be used for vacuum forming.   Structure
of CeramicsTwo of the most common chemical bonds for ceramics are
covalent bonds and ionic bonds. Covalent bonds and ionic bonds are much
stronger than in metallic. When the components of the ceramics are a metal or a
non-metal, the bonding is usually ionic, because ceramics have covalent bonds
and ionic bonds are stronger than in metallic bonds, ceramics have the
following properties: High hardness and high compressive strength. Although
they do have low ductility and low tensile strength, having no free electrons
to move around is responsible for making most ceramics poor conductors of
electricity and heat. The structure varies from simple to complex. The
microstructure can either be entirely glassy, entirely crystalline or a
combination of the two. Ceramic is
brittle, strong in compression but weak in tension My chosen
CeramicMy chosen ceramic is brick. The chemical composition
of bricks is 54-61% of Silica and 22-32% of Aluminium. Bricks are made by
baking moulded clay. Some of the advantages of using bricks are; they are hard,
and not easy to scratch. They are strong under compression, so when building a
house, the house will not be crushed
under its own weight. Some of the disadvantages are; bricks are brittle, so
they can break easily if handled without care during construction. Bricks are
one of the main materials a civil engineer would use. Due to the Silica in a
brick, covalent bonding is very common within the structure of a brick. Because
of the Silica, bricks are hard; they have high melting and boiling point
alongside being insoluble in water and not conduction electricity. These
properties result in very strong covalent bonds       Structure
of compositesA composite material is a combination of two or more
materials, each of which has their own distinctive properties.  A composite material is made to provide a
design solution that surpasses the performance of the starting material. The
most common engineered composite material is fibre-reinforced polymers. The
Fibre-reinforced polymers greatly improved mechanical properties such a tensile
strength and tensile resistance. This also has a correlation to something called the Matrix phase, which is a
continuous phase. The material that is distributed through the matrix is known
as the dispersed phase, this dispersed phase is sometimes called reinforcement,
it is a phase added to increase strength, but also called filler as it is added
for other purposes such as bulking up the matrix at a low cost without
affecting the properties of the composite. One of the main types of bonding in
composite metals is Adhesive bonding. Adhesive bonding; A wide variety of
materials is available when adhesives are used to bond materials together.           Illustrating the phases of a composite.      My chosen
compositeMy chosen composite is a metal matrix. A metal matrix composite is a material with at least
two elements, one being metal necessarily, and the other may be a different
metal or sometimes it can be a ceramic or
an organic compound. But when at least three different elements are present it
is called a hybrid composite. Some of the properties of the metal matrix
composites consist of; higher temperature capability, fire resistance, better
radiation resistance, higher electrical and thermal conductivities and more.
You can see how useful this composite can be in engineering, for example, the
fire resistance is useful in a restaurants kitchen, and the electrical and thermal
conductivity is useful in wires.            Smart
smart material has properties that react to changes in their environment. This
means that one of their properties can be changed by an external condition,
such as temperature, light, pressure or electricity. The changes made are
reversible and can be changed repeatedly. There are wide ranges of smart
materials, some of the ones I will be
discussing are; piezoelectric materials, electro-rheostatic, magneto-rheostatic
and shape memory alloy materials. A smart alloy is a material that is made from
a shape-memory alloy. When this material is bent out of shape it can be
reversed and return to its original form. By simply heating the material at a
certain temperature, it will return to its original shape. Piezoelectric
materials produce a small electrical voltage for a moment. This happens when
the piezoelectric material is squeezed rapidly. If a voltage is put across the
material it changed shape, but a very small change occurs. Both electro-rheostatic
and magneto-rheostatic materials are fluids and both can experience a dramatic
change in their viscosity. These fluids can go from being a thick fluid (like
car oil) to nearly a solid within the span of milliseconds when exposed to a
magnetic or electric field. This can be reversed just as quickly by removing
the magnetic or electric field. Electro-rheostatic fluids change viscosity
levels when exposed to an electric field while magneto-rheostatic fluids
experience changed in viscosity levels when exposed to magnetic fields.    My
chosen smart materialMy
chosen smart material is Hydro-gel. A hydro-gel changes its structure in
response to salt concentration, pH and temperature. The structure of a
hydro-gel; Hydro-gels are cross-linked polymers that have hydrophilic groups.
They are often polymers containing carboxylic acid groups. One of the common
polymers used to make hydro-gels is sodium polyacrylate. These polymer chains
usually exist in the shape of randomly coiled molecules in the shape of randomly
coiled molecules. Water molecules are then attracted to the negative charges of
hydrogen bonding. When in this state the hydrogel
can absorb over five hundred time its own weight of pure water, this ability
makes hydro-gel so useful. But when salt is added to the hydro-gels the chains
start to change and their shape and water
is lost from the gel.Chemical composition of hydrogel


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In conclusion,
I have described the structures of a metal, a polymer, a composite, a ceramic
and a smart material. I have successfully been able to produce a report
summarising the basic structure of the main types of engineering materials. I
also chose my own, metal, polymer, ceramic, composite and smart materials and
successfully described their properties, structure and provided diagrams.
Through this report, I can say that I know the basic structure and
classification of engineering materials.

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