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8/10/2019 Science Products

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CERAMICSInorganic, non-metallic materials prepared byheating at high temperature and subsequent

cooling.


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CharacteristicsMay be crystalline, partly crystalline, or amorphous

Prepared from earthly raw material predominantly Siliconand its oxides and complex compounds called Silicates

aw materials for di!erent ceramics include Sand, Clay,Iron, "uart#

Most ceramics are Crystalline, so commonly $nown as in-organic non-metallic crystalline materials

Manufacture needs heating at high temperature followedby cooling.

%rittle, hard, strong in compression, wea$ in shearing,tension

Can withstand high temperature and chemical erosion


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&'P(S ) *+I(&I(SGROUP EXAMPLES

Structural

lass

efractories

hite wares

+brasie materials

Cement, lime

Porcelain (namels

&ile, bric$+ll types of glass

/iln lining, silica

0innerware

Silicon carbide

Plaster, gypsum

*itreous inorganic coatingwith a glass li$e 1repolished surface


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CharacteristicsChemical resistant

(lectrical insulator

2ight weight&ransparent

ater resistant

4on-allergic

5ungus resistant


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Composition3rganic polymers

Polymer7 macromolecule formed by chemical union ofmonomers

Monomer7 identical unitsMost are composed of chains of Carbon alone or

3xygen, Sulfur ,4itrogen

%ac$bone7 large number of monomers repeat together

Side chain7 arrangement determine properties+ddities7 in-organic compounds added for arious

purposes e.g. 1llers, stabili#er. 8 to 98 : . 3n aerage;8 :


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Classi1cationThermosetting plastics Thermoplastics

Can be melted only once

+fter melting they harden


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&'P(S7 esin identi1cation codesP(&7 Polyethylene &erephthalate

>0P(7 >igh 0ensity Polyethylene

P*C7 Polyinylchloride20P(7 2ow 0ensity Polyethylene

PP7 Polypropylene

PS7 Polystyrene

3thers


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(2(C&ICI&'5ast moing electrons

Popular form of energy

Can be conerted in to many forms ofenergies

3n basis of electrical properties materialsmay be

Conductors Insulators

Semi-conductors


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ConductorsMaterials which allow =ow of electrical

charges in one or more directions.

Moeable charged particles are (lectrons

(lectricity to pass through them easily withoutmuch resistance

Most metals are conductors e.g. Copper, Iron,

Siler


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InsulatorsMaterials which do not conduct electrical

current under in=uence of an electrical 1eld

0o not allow electricity to pass through them

&heir internal charges do not =ow freely

Pure insulator do not exist7 but some materialhae high resistiity and thus are good

insulator(xamples7 glass, paper


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Semi-conductorsMaterial haing electrical conductiity to a

degree between a conductor and an insulator

+llow electricity to pass through only partially.

>as ability of changing conductiity byaddition of impurities

5oundation of modern electronics including

transistors, integrated circuits(xamples7 silicon carbide, selenium


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0opingProcess of addition of impurities to semi-

conductors to boost their conductingproperties

4 and P type semi-conductors are thusobtained

0opant may be electron 0343 or +CC(P&3


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&'P(SN-tpe P-tpe

5ormed when pure semi-conductors doped with

electron-0343 impurity(lectrons act as charge

carrier

(xample7 silicon dopedwith arsenic

5ormed when semi-conductor is doped withelectron-0(5ICI(4&impurity

Conduction ta$es due tomotion of holes which actli$e positie charge

(xample7 silicon dopedwith %oron


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eneral characteristicsIncrease in electrical conductiity with

increase in temperature

Properties follow from structure of material

Can be doped with selected impurities toachiee desired properties

5unctioning of semi-conductors inoles Solid

state Physics(xamples7 Silicon, Selenium, ermanium

(xamples of impurities7 arsenic, antimony,%oron


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Superconductor+ material that o!ers no resistance to

electrical current

4o material on the (arth carries that propertyat ordinary temperatures

Materials when super-cooled turn into super-conductors

MI machines use super-conductors%ednor# and Muller? 4obel pri#e in Physics for

discoering a super-conductor mixture if2anthanum, copper, %arium, and 3xygen


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0iode&wo terminal electronic deice haing

asymmetrical conductance i.e. low resistancein one direction and high resistance in other

direction

Crystalline piece of semi-conductor materialwith P-4 6unction connected to two electricalterminals.

Most diodes are composed of Silicon, butother semi-conductors such as Selenium arealso sometime used


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0I55((4C(S!ACCINE ANTI"IOTIC

Substances used to

preent disease

0o not $ill micro-organisms

epatitis%, Measles accines

Chemical which either $illor retard growth of micro-organisms

/ill micro-organisms


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