Glass and ceramic
a) Introduction
1. The main component of both glass and ceramic is silica or silicon dioxide, Sio2. 2. In silicon dioxide, every silicon atom is bonded covalently to 4 oxygen atoms in a
tetragonal shape. Every oxygen atom is also bonded to 2 silicon atoms to from a gigantic covalent molecule.
3. Both glass and ceramic have the following properties: a) hard but brittle
b) inert toward chemicals
c) insulators of heat and electricity
d) withstand compression but not tension ( stretching) e) can be easily cleaned
4. Both glass and ceramic used widely in our daily life replacing metals because of the above advantages.
b) Type of glass and their properties
Type of glass Properties
Fused glass Very high softening points
Transparent to ultra-violet and infra- red light
Difficult to be made into different shapes
Soda Glass Low softening points Breaks easily
Cracked easily with a sudden change of temperature.
Borosilicate Glass High softening points
Does not crack easily with a sudden temperature change
Transparent to ultra- violet light
Lead Glass Low softening points High density
High refractive index
c) Uses of glass
Type of glass Examples of Uses of Glass
Fused glass Mirrors, lenses and laboratory glass wares
Soda Glass Bottles, window-panes, light bulbs. Glass-plates and bowls
Borosilicate Glass Laboratory apparatus, cooking utensils, electrical bulbs
Lead Glass Decorative items, crystal glass – wares, lens prisms and chandeliers.
d) Properties of ceramics
1. Ceramic is a manufactured substance made from clay that is dried and then baked in a kiln at high temperature.
2. The general properties are as follows a) Very hard and strong but brittle b) Inert towards chemicals
c) Very high melting point
d) Good electrical and heat insulator e) Resist compression
3. the main constituent if clay is aluminous silicate which consists of aluminium oxide and silicon dioxide
e) Uses of ceramic
Ceramic can be used as car engine block:
Presently, car engine blocks are made of metal. Materials for making car engine blocks must be able to withstand very high temperatures. This is because at high temperature, the combustion of fuel becomes more efficient and produces more energy with less pollution.
Clay heated with magnesium oxide produces type of ceramic that has a high thermal resistance. This type of ceramic is used for making car engine blocks because it can resist high temperature.
There are examples of new uses of ceramics and glass after them being improved. Examples of new uses of improved glass and ceramics can be seen in the making of superconductor and car engine. Following are the examples of it:
Photochromic Glass
1. Photochromic glass is a type of glass that is sensitive to light intensity. The glass darkens when exposed to sunlight but becomes clear when the light intensity decreases.
2. Photochromic glass is produced when a dispersion of silver chloride, AgCl or silver bromide, AgBr and a little of copper(I) chloride is added to normal glass.
3. When exposed to ultra violet, AgCl or AgBr decomposes to form silver and halogen atoms. The fine silver deposited in the glass is black and the glass is darkened.
Conducting Glass
1. Conducting glass is a type of glass that can conduct electricity.
2. Conducting glass is produced by embedding a thin layer of conducting materials in glass
3. A type of conducting glass is produced by adding a layer of indium tin(IV) oxide (ITO) that acts as an electrical conductor. This type of glass is act as electrical conductor.
Superconductor Glass
1. Superconductors are a class of ceramics that conduct electricity without resistance and without lost of electrical energy
2. Superconducting ceramics are used to make light magnets, electrical generators and electric motors.
g) Conclusion
The need for high performance materials has helped to speed up the development of glass and ceramics. New improved glass and ceramics like photochromic glass, conducting glass, glass ceramic, bioceramics and superconductor can be widely used.
Composite materials
a) Introduction
Since the old days, human beings have been using clay, wood, stones or metals as building materials. These substances either corrode or decay easily. Otherwise they are too heavy, bulky or difficult to be shaped or carved.
Many of our modern technologies require materials with unusual combinations of properties that cannot be met by the conventional metal alloys, ceramics and polymeric materials. Therefore, continuous research and development have been done in search of new structural materials. To fulfill the needs, there building materials must have
properties like low density, strong and resistance to heat and corrosion. Today, many of such materials are created and used for various fields.
b) Meaning of composite materials
A composite material is a structural material that formed by combining 2 or more diff substance such as metal, alloy, glass , ceramics and polymers. The resulting material has properties that superior than those of the original components. Composite materials are created for specific application.
c) Examples of composing materials Reinforced concrete
When concrete is reinforced with steel wires, steel bars or any polymer fibers, the resulting combination is a very tough material with more tensile strength. Steel and concrete have about the same coefficient of expansion. They make vary good composites and are essential for the construction of large structures like high – rise buildings, bridges and oil platforms.
Superconductors
Superconductors are capable of conducting electricity without any electrical resistance when they are cooled to extremely low temperature. Most of them are alloys of metal compounds or ceramics of metal oxides. However, some superconductors are made from composite materials. Superconductors also used in building Jap’s bullet trains.
Fiber Optic
It is a cable consists or a bundle of glass or plastic threads that are surround by a glass cladding. Fiber optic is a composite material that is able to transmit data, voice and images in a digital form.
Fiber Glass
It has high tensile strength, can be easily coloured and low in density. It can be made into thin layers, yet very strong. Fiber glass is also easily molded and shaped. It has be used to make household product to make household products like water storage tanks, badminton rackets , small boats , skis and helmet.
Photochromic Glass
1. Photochromic glass is a type of glass that is sensitive to light intensity. The glass darkens when exposed to sunlight but becomes clear when the light intensity decreases.
2. Photochromic glass is produced when a dispersion of silver chloride, AgCl or silver bromide, AgBr and a little of copper(I) chloride is added to normal glass.
3. When exposed to ultra violet, AgCI or AgBr decomposes to form silver and halogen atoms. The fine silver deposited in the glass is black and the glass is darkened.
d) The component of Composite materials
Reinforced concrete Concrete Steel
Superconductor Copper (II) oxide , yttrium oxide and barium oxide
Optical fibers Glass of low refractive index Glass of high refractive index Fibers glass Heavy , Brittle , non – flexible
Light, weak inflammable. Photochromic glass Glass
e) Uses of Composite materials
Reinforced concrete Construction of framework for highways, bridges and high – rise buildings.
Superconductor To make more efficient generators, transformers, electric cables, amplifiers. Computers stronger and light magnets Optical fibers Transmits data in the form of light in
telecommunications
Fibers glass Boat hulls, swimming pool linings, fishing rods car bodies, roofing, furniture, pipes and container.
Photochromic glass Photochromic lens that becomes dark in bright sunlight and becomes clear when out of the sun.
f) Justify the uses and the need to produce other advanced materials
1. Continuous research and development is required to produce better materials used to improve our standard of living.
2. New technologies developments are used by scientists to make new discoveries. New materials for clothing, shelter, tools and communications to improve our daily life are developed continuously for the well being of mankind.
3. The understanding is the interaction between different chemicals is important to prevent environmental pollution. The recycling and development of
environmental friendly synthesis material should be enforced.
g) Conclusion
There are so many synthetic materials being produced and used in our daily lives. Synthetic materials have improved our standard of living but at the same time, they may cause adverse effects on human beings and the environment.
Synthetics Polymers
a) Introduction
Polymers are something that rock the world of mankind,. Plastic are polymers too.
b) The meaning of Polymers
Polymers are large molecules made up of many repeating sub-units called monomers which are joined together by covalent bonds. Monomers are joined into chains by a process of repeated linking known polymerization
A polymer may consist of thousands of monomers. Some polymers occur naturally. Starch, cellulose, wool, protein, silk and natural rubber are some examples of naturally occurring polymers
c) Lists of natural polymers 1. starch 2. cellulose 3. wool 4. protein 5. silk 6. natural rubber
d) Types of synthetic polymers and their uses
Polythene Plastic bags , shopping bags , plastic containers and insulation for electrical wiring
Polypropylene Piping , bottle crates , carpets , car batteries and ropes
Polyvinyl chloride , PVC Artificial leather , water pipes and records
Perspex Safety glass , reflectors , traffic signs and lens
Terylene Clothing , sails and ropes
e) The monomers in the synthetic polymers
Polythene Ethane
Polypropylene Propane
Polyvinyl chloride , PVC Chloromethane Perspex Methylmethacylate Terylene Hexane-1, 6-diol
Benzene -1 , 4-dicarboxylic acid Nylon Hexane-1 , 6 –diamine
Hexane-1 , 6 –dioic acid
f) Uses of synthetic polymers in daily life
1. Synthetic polymers have been used widely to replace natural materials such as metals wood cotton animal skin and natural rubbers. It is
a) Strong and light b) Cheap
c) Corrosion resistant d) Inert to chemical attacks
2. Therefore, it is widely used to produce plastic bags , shopping bags , plastic containers and insulation for electrical wiring
g) Different types of household polymers
1. Polyethylene(PE)
Used for plastic bags at home 2. Polypropylene(PP)
Used for plastic bottles and tables 3. Polyvinylchloride(PVC)
Used for water pipes and rain cloths 4. Polystyrene(PS)
Used for packaging materials
h) Conclusion
Although synthetic polymers pose environmental problems, we can still using them but in a wiser manner. We should reduce, reuse and recycle synthetics polymers as much as possible.
