Applying uses of glass and ceramics

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Malaysia SPM Form 4 Chemistry, Chapter 9: Manufactured Substances in Industries

Contents 1 Introduction 1.1 Uses of Glass and Ceramics 1.2 Properties of glass and ceramic: 2 Glass 2.1 Soda lime glass: 2.2 Lead glass: 2.3 Borosilicate glass: 2.4 Fused silicate glass: 2.5 Summary 3 Ceramics 4 New Uses of Glass and Ceramics 4.1 Photochromic glass 4.2 Conducting glass

[edit] Introduction

[edit] Uses of Glass and Ceramics

• The raw materials used in the making of glass and ceramic materials are obtained from the earth's crust. Silica or silicon(IV) dioxide, SiO₂, form the most important component of glass and ceramics.
• In the SiO₂ molecule, each silicon atom is held in a tetrahedral structure by four oxygen atoms.
• Each oxygen atom is held by two silicon atoms. This is repeated until a giant three-dimensional molecule results.

[edit] Properties of glass and ceramic:

• Both have the following properties:

1. Hard and brittle
2. Do not conduct heat electricity
3. Inactive towards chemical reactions
4. Weak when pressure is applied
5. Can be cleaned easily

[edit] Glass

• It is a mixture of two or more types of metallic silicates but the main component is silicon(IV) dioxide.
• Glass has the following properties:

1. Transparent and not porous
2. Inactive chemically
3. Can be cleaned easily
4. Good insulators of heat and electricity
5. Hard but brittle
6. Can withstand compression but not pressure

• Due to the above reasons and the low cost involved to produce glass, it is used in industry to make bottles, cooking utensils, plates and bowls, laboratory apparatus (such as conical flask, beakers and test tubes), window panes, bulbs and others.
• Different types of glass can be obtained depending on the composition of substances in it.

[edit] Soda lime glass:

• This is obtained when limestone (CaCO₃) and sodium carbonate (Na₂CO₃) are mixed with molten silica and cooled down.
• It is also known as soft glass as it has a low melting point.
• Most glass produced is soda lime glass. But it breaks easily, thus it is mainly used to make kitchen utensils.

[edit] Lead glass:

• This is formed when a mixture of lead(II) oxide, sodium oxide and silica is heated together.
• Lead glass of better quality contains a higher percentage of PbO.
• Its refractive index and density being high, it has a glittering and attractive surface, thus it is also called crystal glass.

[edit] Borosilicate glass:

• Boron oxide (B₂O₃) and sodium carbonate is added to molten silica to obtain borosilicate glass or pyrex..
• The presence of B₂O₃ makes the glass able to withstand high temperatures and chemical reaction. It does not break easily, thus it is used to make laboratory apparatus and cooking utensils.

[edit] Fused silicate glass:

• Sand (silica) is heated until it melts at 1700°C, and the viscous liquid is cooled immediately. This produces a transparent solid with an uneven arrangement of atoms, called fused silicate glass.
• This glass cannot expand or contract easily when there are temperature changes. But it cannot become misshapen because of its high melting point.
• It is known as quartz glass.

[edit] Summary

Glass	Composition	Properties	Uses
Soda lime,glass	SiO2 – 70% Na20 – 15% CaO – 10% Others – 4%	• Low melting point (700°C) • Mouldable into shapes • Cheap • Breakable • Can withstand high heat	Glass containers, Glass panes, Mirrors, Lamps and bulbs, Plates and bowls Bottles
Lead glass (crystal)	SiO2 – 70% Na20 – 20% PbO – 10%	• High density and refractive index • Glittering surface • Soft • Low melting point (600°C)	Containers for drinks and fruit Decorative glass and lamps Crystal glassware Lenses for spectacles
Borosilicate glass (Pyrex)	SiO2 – 80% B203 – 13% Na2O – 4% Al203 – 2%	• Resistant to high heat and chemical reaction • Does not break easily • Allows infra-red rays but not ultra-violet rays	Glass apparatus in laboratories Cooking utensils
Fused silicate glass	SiO2 – 99% 6203 - 1%	• High melting point (1700°C) • Expensive • Allows ultraviolet light to pass through • Difficult to melt or mould into shape	Scientific apparatus like lenses on spectrometer Optical lenses Laboratory apparatus

[edit] Ceramics

• Ceramic is a substance that is made from clay and hardened by heat in a furnace maintained at a high temperature.
• Clay is composed of aluminosilicate with sand and iron(III) oxide as impurities. Iron(III) oxide, Fe203, gives a reddish colour to the clay.
• Kaolin, or clay in its pure form, is white in colour. It consists of crystals of hydrated aluminosilicate with the formula Al₂Si₂O₇.2H₂OorAl₂O₃.2SiO₂.2H₂O.
• The different classes of ceramic include:

Group	Composition
Quartz – SiO2 Calcite – CaCO3
Mixture of CaSiO3 and aluminium silicate
Aluminium oxide – Al2O3 Silicon dioxide – SiO2 Magnesium oxide – MgO
Silicon nitride – Si3N4 Silicon carbide – SiC Boron nitride – BN Boron carbide – B4C3

• The preparation of ceramic objects involves 3 stages:

1. A layer of water exists between the aluminosilicate crystals. This gives it a plastic-like property when wet. Thus the clay is first wet to make it soft before it is shaped.
2. The shaped object is then dried. At this stage, the product can still be reshaped by adding more water.
3. The dried object is heated to a temperature of 1000°C in a furnace. The product of this stage cannot be softened with water or reshaped.

• The surface of ceramic object is usually coated with a layer of mineral or metallic silicate and baked again in the furnace to produce a shining and impervious ceramic object.
• The properties of ceramics include the following:

1. Hard
2. Strong but brittle
3. Chemically inactive
4. Poor conductor of heat and electricity
5. High melting point – heat resistant
6. Cannot be compressed easily

• The differences between the properties of ceramics, metals and non-metals are given below.

Property	Metals	Non-metals	Ceramic
Hardness	Hard but malleable and ductile	Soft and brittle	Hard but brittle
Density	High	Low	Average
Melting point	High	Low	Very high
Resistance to heat	High	Low	Very high
Heat and Electrical conductivity	Good conductor	Good insulator	Good insulator
Chemical reactions	Corrodes	Corrodes	Stable, does not corrode

[edit] New Uses of Glass and Ceramics

• The latest use of glass is to make photochromic glass and conducting glass while ceramics is used to produce superconductors and car engine blocks.

[edit] Photochromic glass

• Photochromic glass is very sensitive to light. It darkens in the presence of bright light and lightens when the amount of sunlight lessens.
• The glass is produced by adding silver chloride (or silver bromide) and some copper(II) chloride to normal glass.
• Silver halides decompose to silver and its halogen when exposed to ultraviolet rays. Thus we have:

It is the silver which makes the glass become dark.

• When there is a decrease in light, silver chloride is formed again:

Therefore the glass lightens.

[edit] Conducting glass

• Conducting glass is a type of glass which can conduct electricity. It is obtained by coating a thin layer of a conducting material around the glass, usually indium tin(IV) oxide or ITO.
• Conducting glass can also be obtained by embedding thin gold strips into a piece of glass. This is used to make the front windows of aeroplanes which tend to mist at very high heights. By passing an electric current through this glass (containing gold as conductors), the water of condensation will dry up.
• Superconductors are electrical conductors which have almost zero (0) electrical resistance. Therefore, this conductor minimises the loss of electrical energy through heat.
• Perovsite is a type of ceramic superconductor composed of itrium oxide, copper oxide and barium oxide.
• Superconductors are also used to make magnets which are light but thousands of times stronger than the normal magnet.
• Car Engine Block--When clay is heated with magnesium oxide, the ceramic that is produced has a high resistance to heat. This material is used to build the engine blocks in cars as they can withstand high temperatures.