CHEMISTRY

FORM 4

PORTFOLIO:

MANUFACTURED SUBSTANCES IN INDUSTRY

NAME : MOHAMAD FARIED BIN AHMAD ADNANFORM : 4 SC SSUBJECT : CHEMISTRYTOPIC : MANUFACTURED SUBSTANCES IN INDUSTRYTEACHER : PN. YIP YIN LENG

1.0. INTRODUCTION

Nowadays, many industrial products are manufactured for the goodness of mankind. The products are either made up from sulphuric acid, ammonia, alloys, synthetic polymers, glass, ceramics or composite materials. These products can be made for many uses. Therefore, we need to know how these products were manufactured, what are their physical and chemical properties and others as well. Even though the products of these materials are designed for good uses, there are always the bad effects. We shall also go through the environmental pollution caused by the by-product of these materials; during manufacture and also during usage so that we can avoid the circumstances. By the way, in order to appreciate the various industries in our country, we should understand these substances and products a lot more.

The manufactured substances in industries that will be further discussed in this assignment are:

Sulphuric Acid Ammonia Alloys Synthetic Polymers Glass & Ceramics Composite Materials

These substances are widely used in the industries in Malaysia. So, we may need to understand some of the examples of the products.

2.0. OBJECTIVES

The objectives of making this portfolio are mainly to appreciate the manufactured substances in Malaysia. Therefore, I have done all I could to get these objectives could be fulfilled. However, the other objectives are:

To understand the manufacture of sulphuric acidTo synthesise the manufacture of ammonia and its saltsTo understand alloysTo compare the differences of alloy and its pure metalsTo evaluate the details of synthetic polymers (natural occurring, uses, environmental pollution)To determine the different types, composition, properties and uses of glass and ceramicsTo understand composite metals & evaluate their usesTo appreciate various synthetic industrial materials

3.0. GATHERING OF INFORMATION

3.1. Sulphuric Acid

Diagram: The Sulphuric Acid; H2SO4

3.1.1. Manufacture Of Sulphuric Acid, H2SO4 In Industry

Sulphuric acid is produced from sulphur, oxygen and water via the conventional Contact Process (DCDA) or the Wet Sulphuric Acid Process (WSA).

Contact Process (DCDA)

Figure: Manufacture Of H2SO4 In Industry; Contact Process

In the first step, sulphur is burned to produce sulphur dioxide.o S (s) + O2 (g) → SO2 (g)

This is then oxidized to sulphur trioxide using oxygen in the presence of a vanadium (V) oxide catalyst.

o 2 SO2 (g) + O2 (g) 2 SO3 (g) (in presence of V2O5)

The sulphur trioxide is absorbed into 97-98% H2SO4 to form oleum (H2S2O7), also known as fuming sulphuric acid.

o H2SO4 (l) + SO3 → H2S2O7 (l)The oleum is then diluted with water to form concentrated sulphuric acid.

o H2S2O7 (l) + H2O (l) → 2 H2SO4 (l)

Note that directly dissolving SO3 in water is not practical due to the highly exothermic nature of the reaction between sulphur trioxide and water. The reaction forms a corrosive aerosol that is very difficult to separate, instead of a liquid.

o SO3 (g) + H2O (l) → H2SO4 (l)

Wet Sulphuric Acid Process (WSA)

In the first step, sulphur is burned to produce sulphur dioxide:o S(s) + O2(g) → SO2(g)

Or, alternatively, hydrogen sulphide (H2S) gas is incinerated to SO2 gas:o 2 H2S + 3 O2 → 2 H2O + 2 SO2 (−518 kJ/mol)

This is then oxidized to sulphur trioxide using oxygen with vanadium (V) oxide as catalyst:o 2 SO2 + O2 → 2 SO3 (−99 kJ/mol)

The sulphur trioxide is hydrated into sulphuric acid H2SO4:o SO3 + H2O → H2SO4(g) (−101 kJ/mol)

The last step is the condensation of the sulphuric acid to liquid 97–98% H2SO4:o H2SO4(g) → H2SO4(l) (−69 kJ/mol)

Other Methods

Another method is the less well-known metabisulphite method, in which metabisulphite in placed at the bottom of a beaker, and 12.6 molar concentrations hydrochloric acid is added. The resulting gas is bubbled through nitric acid, which will release brown/red vapours. The completion of the reaction is indicated by the ceasing of the fumes. This method does not produce an inseparable mist, which is quite convenient.

Sulphuric acid can be produced in the laboratory by burning sulphur in air and dissolving the gas produced in a hydrogen peroxide solution.

o SO2 + H2O2 → H2SO4

Another method is to react hydrochloric acid with copper II sulphate:o 2 HCl + CuSO4 → H2SO4 + CuCl2

Prior to 1900, sulphuric uric acid was manufactured by the chamber process. As late as 1940, up to 50% of sulphuric acid manufactured in the United States was produced by chamber process plants.

3.1.2. The Environmental Pollution by the By-Product Of H2SO4

Sulphur dioxide; SO2 is one of the by-product in the manufacture of Sulphuric acid; H2SO4. Sulphur dioxide causes environmental pollution. Almost all sulphur dioxides in air come from the burning of fossil fuels containing sulphur. The effect to the environment was the acid rain.

Acid Rain

Diagram: Acid Rain

Natural rainwater has a pH of 5.4. Acid rain occurs when the pH of the rain is between 2.4 and 5.0. This is due to the reaction of sulphur dioxide with the rainwater.

o 2SO2(g) + O2(g) + 2H2O(l) 2H2SO4(aq)

Sulphur dioxide is release through chimneys of factories. The sulphur dioxide react with water and oxygen to form acid rain in the clouds. The acid rain causes:

1. Buildings and metal structures corrode2. The trees in forest to destroy3. Lakes and rivers become acidic (kills fish and organisms)4. The pH of soil decreases5. Salts are leached out of the top soil

3.2. Ammonia

Diagram: The Ammonia; NH3

3.2.1. The Physical & Chemical Properties Of Ammonia, NH3

Physical Properties

Ammonia is a colourless gas. It has a pungent odour with and an alkaline or soapy taste. When inhaled suddenly, it

brings tears into the eyes. It is lighter than air and is therefore collected by the downward displacement of air. It is highly soluble in water: One volume of water dissolves about 1300 volumes of

ammonia gas. It is due to its high solubility in water that the gas cannot be collected over water.

It can be easily liquefied at room temperature by applying a pressure of about 8-10 atmosphere.

Liquid ammonia boils at 239.6 K (- 33.5°C) under one atmosphere pressure. It has a high latent heat of vaporization (1370 J per gram) and is therefore used in refrigeration plants of ice making machines.

Liquid ammonia freezes at 195.3 K (-77.8°C) to give a white crystalline solid.

Chemical Properties

The ammonia molecule has a trigonal pyramidal shape with a bond angle of 107.8° as shown above, as predicted by the valence shell electron pair repulsion theory (VSEPR). The central nitrogen atom has five outer electrons with an additional electron from each hydrogen atom. This gives a total of eight electrons, or four electron pairs which are arranged tetrahedrally. Three of these electron pairs are used as bond pairs, which leaves one lone pair of electrons. The lone pair of electrons repel more strongly than bond pairs, therefore the bond angle is not 109.5° as expected for a regular tetrahedral arrangement, but is measured at 107.8°.

The nitrogen atom in the molecule has a lone electron pair, which makes ammonia a base, a proton acceptor. This shape gives the molecule a dipole moment and makes it polar. The molecule's polarity and, especially, its ability to form hydrogen bonds, making ammonia highly miscible with water. Ammonia is moderately basic, a 1.0 M aqueous solution has a pH of 11.6 and if a strong acid is added to such a solution until the solution is neutral (pH = 7), 99.4% of the ammonia molecules are protonated. Temperature and salinity also affect the

proportion of NH4+. The latter has the shape of a regular tetrahedron and is isoelectronic with

methane. It is known to have the highest specific heat capacity of any substance.

3.2.2. The Manufacture Of NH3 In Industry

Ammonia; NH3 is manufactured in industries through the Haber Process which combines the nitrogen gas; N2 from air with hydrogen gas; H2 derived mainly from natural gas.

Haber Process

Figure: Manufacture Of NH3 In Industries; Haber Process

The manufacture of ammonia by Haber's process involves the direct combination of nitrogen and hydrogen. The mixture of 1 volume of nitrogen gas; N2 to 3 volume of hydrogen gas; H2 is passed through the reactor. The mixture is compressed to a high pressure of 200 atm at a temperature about 450°C. It is then passed through layers of iron catalyst to speed up the rate of reaction.

o N2(g) + H2(g) NH3(l) (ΔH = -92kJ)

Ammonia that is formed is then liquefied and separated to get a better yield. The production of ammonia gives out heat. However, the unreacted nitrogen gas and hydrogen gas are recycled and passed back to the reactor again; together with the new source of N2 and H2. This reaction is: reversible, exothermic, and proceeds with a decrease in volume. About 98% of N2 and H2 are converted into ammonia. According to the Le Chatelier's principle, the favourable conditions for the formation of ammonia are:

Low TemperatureThe temperature should be remain as low as possible, (although at unusually low

temperatures, the rate of reaction becomes slow). It has been found that the temperature, which optimizes the yield of ammonia for the reaction, is maximum at about 500°C.

High PressureSince Haber's process proceeds with a decrease in volume, it is favoured by high

pressure. In actual practice, a pressure of 200 - 900 atmospheres is employed.

CatalystA catalyst is usually employed to increase the speed of the reaction. Finely divided

iron containing molybdenum or alumina is used as a catalyst. Molybdenum or alumina

(Al2O3) acts as a promoter and increases the efficiency of the catalyst. A mixture of iron oxide and potassium aluminates has been found to work more effectively.

3.2.3. The Preparation Of Ammonium Salts In School Laboratory

Ammonium Chloride

The ammonium chloride salt is prepared by treating hydrochloric acid with ammonia.

The solution obtained is evaporated to obtain the salt of ammonium chloride. This salt is also called "Sal Ammoniac".

Ammonium Sulphate

Ammonium sulphate is prepared by treating sulphuric acid with ammonia.

The solution obtained is then evaporated to get the ammonium sulphate salt.

Ammonium Nitrate

Ammonium nitrate prepared by treating nitric acid with ammonia.

The ammonium nitrate solution obtained is evaporated to get the salt.

Ammonium Carbonate (Sal Volatile)

When a mixture of ammonium sulphate and powdered calcium carbonate are heated and the vapour condensed, ammonium carbonate or sal volatile is obtained.

3.3. Alloys

Diagram: A Metal Alloy (Steel Wire)

3.3.1. Alloys & Aim Of Making Alloys

An alloy is a partial or complete solid solution of one or more elements in a metallic matrix. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may be homogeneous in distribution depending on thermal (heat treatment) history. Alloys usually have different properties from those of the component elements. Alloys' constituents are usually measured by mass. The main aim of making alloys is to produce a stronger metal from the constituent pure metals. Therefore, the alloy can be made into many more uses after the process as it is stronger and has much more resistance.

3.3.2. The Comparison Of Properties Of Alloys & Their Pure Metals

Diagram: An Alloy (Two Different Pure Metals Combined)

Alloying one metal with other metal(s) or non metal(s) often enhances its properties. For example, steel is stronger than iron, its primary element. The physical properties, such as density, reactivity, Young's modulus, and electrical and thermal conductivity, of an alloy may not differ greatly from those of its elements, but engineering properties such as tensile strength and shear strength may be substantially different from those of the constituent materials. This is sometimes due to the sizes of the atoms in the alloy, since larger atoms exert a compressive force on neighbouring atoms, and smaller atoms exert a tensile force on their neighbours, helping the alloy resist deformation. Sometimes alloys may exhibit marked differences in behaviour even when small amounts of one element occur. For example,

impurities in semi-conducting ferromagnetic alloys lead to different properties, as first predicted by White, Hogan, Suhl, Tian Abrie and Nakamura.

Some alloys are made by melting and mixing two or more metals. Bronze, an alloy of copper and tin, was the first alloy discovered, during the prehistoric period now known as the Bronze Age; it was harder than pure copper and originally used to make tools and weapons, but was later superseded by metals and alloys with better properties. In later times bronze has been used for ornaments, bells, statues, and bearings. Brass is an alloy made from copper and zinc.

Unlike pure metals, most alloys do not have a single melting point, but a melting range in which the material is a mixture of solid and liquid phases. The temperature at which melting begins is called the solidus, and the temperature when melting is just complete is called the liquidus. However, for most alloys there are a particular proportion of constituents (in rare cases too) —the eutectic mixture— which gives the alloy a unique melting point.

3.3.3. Examples Of Alloy & The Uses

Examples Of Alloy

Composition Properties Uses

Bronze 90% Copper 10% Tin

Hard & Strong Does Not Corrode

Easily Shiny Surface

In the building of statues & monuments

In the making of medals, swords & artistic materials

Brass 70% Copper 30% Zinc

Harder Than Copper

In the making of musical instruments and kitchenware

Steel 99% Iron 1% Carbon

Hard & Strong

In the construction of bridges and buildings

In the building of the body of cars and railway tracks

Stainless Steel

74% Iron 8% Carbon 18%

Chromium

Shiny Strong Does Not Rust

In the making of cutlery In the making of surgical

instruments

Duralumin

93% Aluminium

3% Copper 3%

Magnesium 1%

Manganese

Light Strong

In the building of the body of aeroplanes and bullet trains

Pewter 96% Tin 3% Copper 1% Antimony

Lustre Shiny Strong

In the making of souvenirs

Table: Examples Of Alloys & Their Uses

3.4. Synthetic Polymers

Diagram: Atomic View Of Synthetic Polymers

3.4.1. Natural Occurring Polymers (Biopolymers)

Diagram: Atomic View Of Biopolymers

Natural polymers or biopolymers are polymers produced by living organisms. Cellulose, starch, chitin, proteins, peptides, DNA and RNA are all examples of biopolymers, in which the monomeric units, respectively, are sugars, amino acids, and nucleotides.

Cellulose is both the most common biopolymer and the most common organic compound on Earth. About 33 percent of all plant matter is cellulose. E. G. The cellulose content of cotton is ~ 90 percent and that of wood is ~ 50 percent.

Some biopolymers are biodegradable. That is, they are broken down into CO2 and water by microorganisms. In addition, some of these biodegradable biopolymers are compostable. That is, they can be put into an industrial composting process and will break down by 90% within 6 months. Biopolymers that do this can be marked with a 'compostable' symbol, under European Standard EN 13432 (2000). Packaging marked with this symbol can be put into industrial composting processes and will break down within 6 months (or less). An example of a compostable polymer is PLA film under 20 μm thick: films which are thicker than that do not qualify as compostable, even though they are biodegradable. A home

composting logo may soon be established which will enable consumers to dispose of packaging directly onto their own compost heap.

A major but defining difference between polymers and biopolymers can be found in their structures. Polymers, including biopolymers, are made of repetitive units called monomers. Biopolymers often have a well defined structure, though this is not a defining characteristic (example: ligno-cellulose): The exact chemical composition and the sequence in which these units are arranged is called the primary structure, in the case of proteins. Many biopolymers spontaneously fold into characteristic compact shapes (see also "protein folding" as well as secondary structure and tertiary structure), which determine their biological functions and depend in a complicated way on their primary structures. Structural biology is the study of the structural properties of the biopolymers. In contrast most synthetic polymers have much simpler and more random (or stochastic) structures. This fact leads to a molecular mass distribution that is missing in biopolymers. In fact, as their synthesis is controlled by a template directed process in most in vivo systems all biopolymers of a type (say one specific protein) are all alike: they all contain the similar sequences and numbers of monomers and thus all have the same mass. This phenomenon is called monodispersity in contrast to the polydispersity encountered in synthetic polymers. As a result biopolymers have a polydispersity index of 1.

3.4.2. Synthetic Polymers

Figure: Synthetic Polymer

Synthetic Polymers are defined as manmade polymers or plastics. First human made plastic was invented by Alexander Parks in 1855. It was then called Parke sine (later on Celluloid).

Polymers are made of small repeating structural units called monomers. Polyethylene is the simplest polymer, which consists of ethene (ethylene) as monomer units and the corresponding linear polymer is called high density polyethylene (HDPE).Many polymeric materials having chain-like structures similar to polyethylene are known. Synthetic polymers are often referred to as "plastics", well-known are polyethylene and nylon.

Polymers formed by a straightforward linking together of monomer units, with no loss or gain of material, are called addition polymers or chain-growth polymers. All of these are synthetic polymers. Thus Synthetic polymers are useful to human being in every aspect of life. Almost all the substances we use for our convenience are made of synthetic polymers.

3.4.3. Synthetic Polymers & Their Uses In Daily Life

Synthetic Polymers Formula Monomer Uses

PolyethyleneLow Density (LDPE)

–(CH2-CH2)n–ethyleneCH2=CH2

Used in film wrap, plastic bags

PolyethyleneHigh Density (HDPE)

–(CH2-CH2)n–ethyleneCH2=CH2

Used in electrical insulation, bottles & toys

Poly(Vinyl Chloride)(PVC)

–(CH2-CHCl)n–vinyl chlorideCH2=CHCl

Used in pipes, siding & flooring

Poly(Vinylidene chloride)(Saran A)

–(CH2-CCl2)n–vinylidene chlorideCH2=CCl2

Used in seat covers & films

Polystyrene(PS)

–[CH2-CH(C6H5)]n–styreneCH2=CHC6H5

Used in toys, cabinets &packaging

Polyacrylonitrile(PAN, Orlon, Acrilan)

–(CH2-CHCN)n–acrylonitrileCH2=CHCN

Used in rugs, blankets &clothing

Polytetrafluoroethylene(PTFE, Teflon)

–(CF2-CF2)n–tetrafluoroethyleneCF2=CF2

Used in non-stick surfaces / electrical insulation

Poly (Vinyl Acetate)(PVAc)

–(CH2-CHOCOCH3)n–vinyl acetateCH2=CHOCOCH3

Used in latex paints & adhesives

Nylon -Hexane-1, 6 diol Benzene, 4-dicarboxylic acid

Used in clothing, sails and ropes

Perspex - MethylmethacrylateSafety glass, reflectors, traffic lights and lens

cis-PolyisopreneNatural Rubber

–[CH2-CH=C(CH3)-CH2]n–

isopreneCH2=CH-C(CH3)=CH2

Requires vulcanizationfor practical use and vulcanized rubber is used in tyres

Polychloroprene(cis + trans) (Neoprene)

–[CH2-CH=CCl-CH2]n–chloropreneCH2=CH-CCl=CH2

It is a synthetic rubber and is oil resistant so used in mats

Table: Examples Of Synthetic Polymers & Their Uses

3.4.4. The Effect Of The Uses Of Synthetic Polymers To The Environment

Plastic, one of the products of synthetic polymers is one of the new and worst

chemical materials which cause serious environment pollution and is certainly a cancer in nature. Plastic is regarded to be a biological hazard since it is almost non- degradable. Tonnes of plastic waste are dumped everyday into the earth all over the world. Plastic pollution is

destroying the world’s ocean ecosystems as a lot of waste is flushed into the ocean.

Plastic is used very commonly in the world because they are cheap, easy to make and they will last long as well. But sorry to say, these useful qualities make plastic a real menace to the environment. As it is so cheap that people discards it soon especially carrybags and disposable bottles. As these materials are long-lasting and difficult to decompose, it persists in the earth for many centuries resulting in enormous environment pollution. As a result of urbanization, most of the pollution is concentrated in cities.

Synthetic polymers can easily be moulded into different shapes, while some can be made into thin film like bits and pieces, which became very accepted in form of durable and disposable carrybags and packing materials. These materials when thrown out after use remains in the soil in the same form as it is non-biodegradable.

According to latest studies, up to 105 million tonnes of plastic is produced yearly in the world, out of which only 2.5 million tonnes is produced in India. The use of plastic (synthetic polymers) in Western and European countries is averaging 70 kg per person per year, while in India it is 4 kg per person per year. Anyhow it’s on the rise all over the world.

The amount of synthetic polymer waste in the ocean is rapidly growing as well. Close to 85% of objects found in the beaches contains traces of polymers. Most of the rubbish found on the beaches is packaging materials. This is a real threat to the life and habitat of marine wild life especially turtles as well as seabirds. In reality, synthetic polymer pollution is a much bigger threat than ozone hole and global warming.

3.5. Glass & Ceramics

Diagram: Glass Diagram: Ceramics

3.5.1. Different Types, Composition, Properties & Uses Of Glass

Types & Uses

Glass is an amorphous (non-crystalline) solid material. Glasses are typically brittle, and often optically transparent. Glass is commonly used for windows, bottles, and eyewear; examples of glassy materials include soda-lime glass, borosilicate glass, acrylic glass, sugar

glass, Muscovy-glass, and aluminium oxynitride. The term glass developed in the late Roman Empire. It was in the Roman glassmaking centre at Trier, now in modern Germany, that the late-Latin term glesum originated, probably from a Germanic word for a transparent, lustrous substance.

Strictly speaking, a glass is defined as an inorganic product of fusion which has been cooled through its glass transition to the solid state without crystallising. Many glasses contain silica as their main component and glass former. The term "glass" is, however, often extended to all amorphous solids (and melts that easily form amorphous solids), including plastics, resins, or other silica-free amorphous solids. In addition, besides traditional melting techniques, any other means of preparation are considered, such as ion implantation, and the sol-gel method. Commonly, glass science and physics deal only with inorganic amorphous solids, while plastics and similar organics are covered by polymer science, biology and further scientific disciplines. Glass plays an essential role in science and industry. The optical and physical properties of glass make it suitable for applications such as flat glass, container glass, optics and optoelectronics material, laboratory equipment, thermal insulator (glass wool), reinforcement fibre (glass-reinforced plastic, glass fibre reinforced concrete), and art.

Nearly all commercial glasses fall into one of six basic categories or types. These categories are based on chemical composition. Within each type, except for fused silica, there are numerous distinct compositions:

Soda-lime glass is the most common (90% of glass made), and least expensive form of glass. It usually contains 60-75% silica, 12-18% soda, 5-12% lime. Resistance to high temperatures and sudden changes of temperature are not good and resistance to corrosive chemicals is only fair.

Lead glass has a high percentage of lead oxide (at least 20% of the batch). It is relatively soft, and its refractive index gives a brilliance that may be exploited by cutting. It is somewhat more expensive than soda-lime glass and is favoured for electrical applications because of its excellent electrical insulating properties. Thermometer tubing and art glass are also made from lead-alkali glass, commonly called lead glass. This glass will not withstand high temperatures or sudden changes in temperature.

Borosilicate glass is any silicate glass having at least 5% of boric oxide in its composition. It has high resistance to temperature change and chemical corrosion. Not quite as convenient to fabricate as either lime or lead glass, and not as low in cost as lime, borosilicate's cost is moderate when measured against its usefulness. Pipelines, light bulbs, photo chromic glasses, sealed-beam headlights, laboratory ware, and bake ware are examples of borosilicate products.

Aluminosilicate glass has aluminium oxide in its composition. It is similar to borosilicate glass but it has greater chemical durability and can withstand higher operating temperatures. Compared to borosilicate, aluminosilicates are more difficult to fabricate. When coated with an electrically conductive film, aluminosilicate glass is used as resistors for electronic circuitry.

Ninety-six percent silica glass is a borosilicate glass, melted and formed by conventional means, then processed to remove almost all the non-silicate elements

from the piece. By reheating to 1200°C the resulting pores are consolidated. This glass is resistant to heat shock up to 900°C.

Fused silica glass is pure silicon dioxide in the non-crystalline state. It is very difficult to fabricate, so it is the most expensive of all glasses. It can sustain operating temperatures up to 1200°C for short periods.

Composition & Properties

There are three classes of components for oxide glasses: network formers, intermediates, and modifiers. The network formers (silicon, boron, and germanium) form a highly cross-linked network of chemical bonds. The intermediates (titanium, aluminium, zirconium, beryllium, magnesium, zinc) can act as both network formers and modifiers, according to the glass composition. The modifiers (calcium, lead, lithium, sodium, potassium) alter the network structure; they are usually present as ions, compensated by nearby non-bridging oxygen atoms, bound by one covalent bond to the glass network and holding one negative charge to compensate for the positive ion nearby. Some elements can play multiple roles; e.g. lead can act both as a network former (Pb4+ replacing Si4+), or as a modifier.

The presence of non-bridging oxygen lowers the relative number of strong bonds in the material and disrupts the network, decreasing the viscosity of the melt and lowering the melting temperature. The alkaline metal ions are small and mobile; their presence in glass allows a degree of electrical conductivity, especially in molten state or at high temperature. Their mobility however decreases the chemical resistance of the glass, allowing leaching by water and facilitating corrosion. Alkaline earth ions, with their two positive charges and requirement for two non-bridging oxygen ions to compensate for their charge, are much less mobile themselves and also hinder diffusion of other ions, especially the alkalis. The most common commercial glasses contain both alkali and alkaline earth ions (usually sodium and calcium), for easier processing and satisfying corrosion resistance. Corrosion resistance of glass can be achieved by dealkalization, removal of the alkali ions from the glass surface by reaction with e.g. sulphur or fluorine compounds. Presence of alkaline metal ions has also detrimental effect to the loss tangent of the glass, and to its electrical resistance; glasses for electronics (sealing, vacuum tubes, lamps...) have to take this in account.

Addition of lead (II) oxide lowers melting point, lowers viscosity of the melt, and increases refractive index. Lead oxide also facilitates solubility of other metal oxides and therefore is used in coloured glasses. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glasses); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in vitreous enamels and glass solders. The high ionic radius of the Pb2+ ion renders it highly immobile in the matrix and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda-lime glass (108.5 vs. 106.5 Ohm·cm, DC at 250 °C). For more details, see lead glass.

Addition of fluorine lowers the dielectric constant of glass. Fluorine is highly electronegative and attracts the electrons in the lattice, lowering the polarizability of the material. Such silicon dioxide-fluoride is used in manufacture of integrated circuits as an

insulator. High levels of fluorine doping lead to formation of volatile SiF2O and such glass is then thermally unstable. Stable layers were achieved with dielectric constant down to about 3.5–3.7.

3.5.2. The Composition, Properties & Uses Of Ceramics

Ceramics can be defined as heat-resistant, non-metallic, inorganic solids that are (generally) made up of compounds formed from metallic and non-metallic elements. Although different types of ceramics can have very different properties, in general ceramics are corrosion-resistant and hard, but brittle. Most ceramics are also good insulators and can withstand high temperatures. These properties have led to their use in virtually every aspect of modern life.

Some ceramics are composed of only two elements. For example, alumina is aluminium oxide, Al2O3; zirconia is zirconium oxide, ZrO2. Ceramics are good insulators and can withstand high temperatures. A popular use of ceramics is in artwork. Silicon dioxide; SiO2 and other ceramic materials, including many minerals, have complex and even variable compositions. For example, the ceramic mineral feldspar, one of the components of granite, has the formula KAlSi3O8.

The chemical bonds in ceramics can be covalent, ionic, or polar covalent, depending on the chemical composition of the ceramic. When the components of the ceramic are a metal and a non-metal, the bonding is primarily ionic; examples are magnesium oxide (magnesia), MgO, and barium titanate, BaTiO3. In ceramics composed of a metalloid and a non-metal, bonding is primarily covalent; examples are boron nitride, BN, and silicon carbide, SiC. Most ceramics have a highly crystalline structure, in which a three-dimensional unit, called a unit cell, is repeated throughout the material. For example, magnesium oxide crystallizes in the rock salt structure. In this structure, Mg 2+ ions alternate with O 2− ions along each perpendicular axis.

Most ceramics are hard, chemically inert, refractory (can withstand very high heat without deformation), and poor conductors of heat and electricity. Ceramics also have low densities. These properties make ceramics attractive for many applications. Ceramics are used as refractories in furnaces and as durable building materials (in the form of bricks, tiles, cinder blocks, and other hard, strong solids). They are also used as common electrical and thermal insulators in the manufacture of spark plugs, telephone poles, electronic devices, and the nose cones of spacecraft. However, ceramics also tend to be brittle. A major difficulty with the use of ceramics is their tendency to acquire tiny cracks that slowly become larger until the material falls apart. To prevent ceramic materials from cracking, they are often applied as coatings on inexpensive materials that are resistant to cracks.

Composite materials that contain ceramic fibres embedded in polymer matrices possess many of the properties of ceramics; these materials have low densities and are resistant to corrosion, yet are tough and flexible rather than brittle. They are used in tennis rackets, bicycles, and automobiles. Ceramic composites may also be made from two distinct

ceramic materials that exist as two separate ceramic phases in the composite material. Cracks generated in one phase will not be transferred to the other. As a result, the resistance of the composite material to cracking is considerable. Composite ceramics made from diborides and/or carbides of zirconium and hafnium mixed with silicon carbide are used to create the nose cones of spacecraft. Break-resistant cookware (with outstanding thermal shock resistance) is also made from ceramic composites.

Although most ceramics are thermal and electrical insulators, some, such as cubic boron nitride, are good conductors of heat, and others, such as rhenium oxide, conduct electricity as well as metals. Indium tin oxide is a transparent ceramic that conducts electricity and is used to make liquid crystal calculator displays. Some ceramics are semiconductors, with conductivities that become enhanced as the temperature increases. For example, silicon carbide, SiC, is used as a semiconductor material in high temperature applications.

3.6. Composite Materials

Diagram: Examples Of Composite Materials (E-Glass Cloth & Plywood)

3.6.1. Composite Materials

Composite are formed by combining two or more materials in such a way that the constituents of the composite materials are still distinguishable, and not fully blended; producing a complex mixture. One example of a composite material is reinforced concrete, which uses cement as a binding material in combination with gravel as a reinforcement. In many cases, concrete uses rebar as a second reinforcement, making it a three-phase composite, because of the three elements involved.

Composite materials take advantage of the different strengths and abilities of different materials. In the case of mud and straw bricks, for example, mud is an excellent binding material, but it cannot stand up to compression and force well. Straw, on the other hand, is well able to withstand compression without crumbling or breaking, and so it serves to reinforce the binding action of the mud. Humans have been creating composite materials to build stronger and lighter objects for thousands of years.

The majority of composite materials use two constituents: a binder or matrix and reinforcement. The reinforcement is stronger and stiffer, forming a sort of backbone, while the matrix keeps the reinforcement in a set place. The binder also protects the reinforcement, which may be brittle or breakable, as in the case of the long glass fibres used in conjunction with plastics to make fibreglass. Generally, composite materials have excellent

compressibility combined with good tensile strength, making them versatile in a wide range of situations.

Engineers building anything, from a patio to an airplane, look at the unique stresses that their construction will undergo. Extreme changes in temperature, external forces, and water or chemical erosion are all accounted for in an assessment of needs. When building an aircraft, for example, engineers need lightweight, strong material that can insulate and protect passengers while surfacing the aircraft. An aircraft made of pure metal could fail catastrophically if a small crack appeared in the skin of the airplane. On the other hand, aircraft integrating reinforced composite materials such as fibreglass, graphite, and other hybrids will be stronger and less likely to break up at stress points in situations involving turbulence.

Many composites are made in layers or plies, with a woven fibre reinforcement sandwiched between layers of plastic or another similar binder. These composite materials have the advantage of being very mouldable, as in the hull of a fibreglass boat. Composites have revolutionized a number of industries, especially the aviation industry, in which the development of higher quality composites allows companies to build bigger and better aircraft.

3.6.2. Examples Of Composite Materials & Their Uses

Examples Of Composite Materials

Uses

Reinforced Concrete Construction of framework for highways & bridges Used in the construction of high-rise buildings

Superconductors To make more efficient generators, transformers & amplifiers To produce more efficient electric cables, computer parts &

stronger and lighter electromagnetsFibre Optic Transmits data in the form of light in telecommunication

Fibre Glass

Water & food storage containers Boats & fishing rods Car bodies Roofing & swimming pool linings

Photochromic Glass

Photochromic optical lens & camera lens To make car windshields, optical switches, information display

panels The building of the light intensity metals

3.6.3. Superconductor

In normal electrical conductors such as copper metal, the existence of resistance causes the loss of electrical energy as heat. Furthermore, resistance increases as temperature increases. Superconductors can conduct electricity with zero resistance when they are cooled to extremely low temperatures. Thus, superconductors conduct electricity without any loss of energy.

Metals such as copper can only achieve superconductivity at a very low temperature (known as the transition temperature). This low temperature can only be achieved using

liquid helium which is very expensive. When a mixture of copper (II) oxide, barium oxide and yttrium oxide is heated up, a type of ceramic with the formula YBa2Cu3O7 is produced. This type of ceramic, known as perovkite or YBCO, can attain superconductivity at 90K. This temperature can easily be attained by using the cheaper liquid nitrogen.

The metal oxides (CuO, Y2O3 and BaO) are all electrical insulators. However, when they are combined to form a composite, the composite is a superconductor that can conduct very high current over long distance without any loss of energy. Superconductors are used to make more efficient generators, magnetic energy-storage systems, transformers, electric cables, amplifiers and computer parts. They are also used in magnetic resonance imaging (MRI); a type of medical imaging device. Superconductors are also used to make stronger, lighter and more powerful electromagnets. High speed levitated trains (trains that float on the railway track) involve the use of electromagnets as superconductors.

3.6.4. Fibre Optic Cables & Fibre Glass

Fibre Optic Cables (Optical Fibres)

Optical fibres are bundles of glass tubes with very small diameters. They are finer than human hair and are very flexible. Fibre optics is a composite material that can transmit electronic data or signals, voice and images on the digital format; in the form of light along the fine glass tubes at great speed. A fibre optic consists of a core of glass of higher refractive index enclosed by a cladding of lower refractive index. A light wave entering the fibre will travel along the glass tubes due to total internal reflection.

In the field of telecommunications, fibre optic is used to replace copper wire in long distance telephone lines, mobile phones, video cameras and to link computers within local area networks (LAN). Fibre optic uses light instead of electrons to carry data. Fibre optic carry more data (higher transmission capacity) with less interference, has a higher chemical stability and a lower material costs compared to metal communication cables such as copper. Fibre optics can also send signals faster than metal cables and occupies less space.

In the field of medicine, a laser beam can be channelled through fibre optics in operations to remove unwanted tissues. Fibre optics is also used in endoscopes: instruments that are inserted into the body through the nose, mouth or ear; for doctors to examine the internal organs. Nevertheless, fibre optic is also used in instruments to inspect the interiors of manufactured products.

Fibre Glass

Plastic is light (with low density), elastic, flexible, but is brittle, not very strong and inflammable. Glass is hard and strong but is brittle, heavy (with relatively high density) and has a low compressive strength. When glass fibre filaments are embedded in polyester resin (a type of plastic), fibre glass which is strong, tough, resilient, flexible with a high tensile strength is produced. It can also be easily coloured, moulded and shaped.

This material can also be bent without cracking. It is also very light (low in density) and has very good strength ratio, impermeable to water and is not inflammable (does not catch fire easily). Fibreglass is an ideal material for making water storage tanks, boat hulls,

swimming pool linings, food container, fishing rods, car bodies, rackets, furniture and also helmets.

3.6.5. Photochromic Glass

Glass is transparent and is not sensitive to light intensity. Silver chloride or silver bromide is sensitive to light. When exposed to light, these compounds decompose to form dark silver particles.

In photochromic glass, silver chloride (AgCl) or silver bromide (AgBr) is embedded into the structure of glass. Photochromic glass has the ability to change colour and become darker when exposed to ultraviolet light. This process occurs as a result of silver halide crystals within the glass clustering together to absorb and filter light. Silver halides are converted to silver and the glass darkens. The photochromic glass will automatically become clear again when the light intensity is lowered, whereby silver is converted back to silver halides. Photochromic glass is used to make lenses that change from light to dark, eliminating the necessity for a separate pair of sunglasses. It is also used to make camera lens, car windshields, information display panels, light intensity meters and also optical switches.

4.0. CONCLUSION

Throughout this research, I found that continuous research and development (R&D) is required to produce better materials used to improve our standard of living. Therefore, as we live in a changing world, our society is becoming more complex. New materials are required to overcome new challenges and problems we face in our daily lives. Synthetic materials are developed constantly due to limitation and shortage of natural materials.

Therefore, new technological developments are used by scientists to make new discoveries. New materials for clothing, shelter, tools and communication to improve our daily life are developed continuously for the well-being of mankind. New needs and new problems will stimulate the development of new synthetic materials. For examples, the use of new plastic composite material will replace metal in making of a stronger but lighter car bodies. This will save fuel and improve speed. Plastic composite materials may one day be used to make organs for organs transplant in human bodies. This will become a necessity with the shortage of human organ donors. New superconductors made from composite materials are developed.

In addition, the understanding of the interaction between different chemicals is important for both the development of new synthetic materials and the disposal of such synthetic materials as waste. Hence, a responsible and systematic method of handling these wastes of synthetic materials and their by-products is important to prevent environmental pollution. Other than that, the recycling and development of environmental friendly synthetic material should be enforced to avoid any further pollution.

5.0. REFERENCES

www.wikipedia.org

www.google.com/search

http://www.google.com.my/imghp?hl=en&tab=wi

www.tutorvista.com/search

www.newencyclopedia.com

www.springer.com/materials

www.yourdiscovery.com

Abadi Ilmu Sdn. Bhd., Integrated Curriculum For Secondary Schools, Chemistry Form 4, by Low Swee Neo, Lim Yean Ching, Eng Nguan Hong, Lim Eng Wah and Umi Kalthom binti Ahmad

Oxford Fajar Sdn. Bhd., SUCCESS Chemistry SPM by Tan Yin Toon, Loh Wai Leng, Tan On Tin