Out of everything, anything is made out of, there are three main groups of materials being metallics, polymerics and ceramics. As well as this, though, different materials can also be combined to make a composite too. This article will be looking at the properties of metals, ceramics, polymers and composites while also looking at ionic, covalent, metallic and Van der Waals bonds.
- Have high melting points
- Have good thermal conductivity
- Have good electrical conductivity
- Iron/Steel - very strong
- Aluminium - easy to form, cheap, readily available and recyclable
- Copper - high ducitly, good electrical and thermal conductivity and does not corrode easily at all (this is why many pipes are made from copper).
- Titanium - this metal is used when weight is an issue (Titanium is light), when you need high strength at high temperatures (1,000 degrees Fahrenheit) or high corrosion resistance.
- Nickel - Nickel is used at even higher temperatures (1,500-2,000 degrees Fahrenheit) and when corrosion resistance is required.
- Refractory materials - Past 2,000 degrees Fahrenheit is when refractory metals are used.
- Less dense than metals or ceramics.
- Corrosive resistance.
- Are of good use when combined with human tissue.
- Are great at being resistant to electricity or heat.
Thermosetting plastics, on the other hand, do not melt on being heated. A few examples of some thermosetting plastics include alkyds, amino and phenolic resins, epoxies, polyurethanes, and unsaturated polyesters.
Although there are naturally occurring polymers, most polymers are man-made by creating and engineering carbon and hydrogen atoms together differently to make different polymers.
A polymer molecule consists of a long chain of covalently bonded atoms with secondary bonds holding the long bonds together (cross linked polymers). Without these secondary bonds, the long chains can freely move around each other changing the state of the polymer. The secondary bonds are broken when melted which is why many polymers move to liquid form when melted and then solidify when cooled and the secondary bonds re-bond.
Man has made some 'super' polymers such as Kevlar that have been used in bulletproof vests and is 20 times stronger than steel. Most polymers are made from petroleum and natural raw gas products.
- Metal-matrix composites
- Sandwich structures
- Reinforced plastic
- Ceramic-matrix composites
- Dispersion strengthened composites have a fine distribution of secondary particles in the matrix of the material which enables the composite to deform. You will find that many metal-matrix composites are in fact dispersion strengthened.
- Particle reinforced composites have a large volume of particles dispersed into the matrix with the load being shared by the particles and the matrix.
- Fibre reinforced composites have fibres that are the primary load bearing component.
- Atomic structure - This includes the type of bonds between atoms and how they are arranged next to each other. The atomic structure affects most properties of the material such as chemical, physical, thermal, electrical, optical and magnetic properties.
- Micro structure - These are the features of a structure that can be seen at a microscopic level.
- Macro structure - These are the features of a structure that can be seen with the naked eye.
- Hard because it is difficult for the particles to slide over each other.
- Have high melting points because ionic bonds are very strong and take a lot of energy to break.
- Brittle because the material tends to crack/cleave than deform because of the strong bonding.
- Can be transparent because it is the free electrons that interact with photons (but there are no free electrons in ionic bonds).
Compounds with covalent bonds can be solid, liquid or gas at room temperature: it all depends on the number of atoms in the compound. The more atoms in each molecule, the higher the compound's melting and boiling point because it will take more energy to break all the bonds.
- Good at insulating
- Brittle (cleave rather than deforms)
- They can be transparent as there are no free electrons to interact with photons.
- They are opaque as the free electrons interact with photons.
- Relatively ductile.
- Good at conducting electricity and heat.
Van der Waals Bond
In essence, electrons are constantly moving around a nucleus of an atom. At one point in time, all the electrons may be on one side of the nucleus making that side very negative and the opposite side positive. This imbalance of charge occurs with every atom and as a molecule gets larger, more of these imbalanced charges will form a much larger overall charge.