Glass_1st year.pptx

8/9/2019 Glass_1st year.pptx

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GLASS


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Glass

Definition

Preparation

Composition

Variety

Uses


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Definition

Glass is an amorphous, hard, brittle,

transparent or translucent super cooledliquid of innite viscosity, having nodenite melting point obtained byfusing a mixture of a number of metallicsilicates or borates of Sodium,

Potassium, Calcium, and Lead.

t possess no denite formula orcrystalline structure.

An inorganic product of fusion which

has cooled to a rigid condition withoutcrystallizing

Does not have a specic melting point Softens over a temperature range


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Properties of glass

Glass is:

!morphous

"rittle

#ransparent $ #ranslucent Good electrical insulator

%na&ected by air, 'ater, acid or chemicalreagents except ()

*o denite crystal structure means glasshas high Compressive strength

Can absorb, transmit and re+ect light


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Raw materials used in manufacturing glass

a' -aterials

Sodium as *aCo/0used in soft glass1.

Potassium as 2Co/0used in (ard Glass1. Calcium as lime stone, chal3 and lime.

Lead as litharge, red lead 0+int glass1.

Silica arc quart4, 'hite sand and ignited+int.

5inc is 4inc oxide 0(eat and shoc3 proofglass1.

"orates are borax, "oric acid 0(eat andshoc3 proof glass1.

Cullets or pieces of bro3en glass to increasefusibility.


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Glass Components

Formers Network Formation

SiO2, B2O, P2O!, GeO2, V2O!, "s2O, S#2O!

Fl$%es Softeners

Na2O, &2O, 'iO, "l2O, B2O, Cs2O

Sta#ili(ers Pro)i*e C+emial -esistane

CaO, ./O, "l2O, P#O, SrO, BaO, 0nO, 0rO


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Manufacturing steps

-elting

)orming and Shaping

!nnealing

)inishing


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Melting process

a' materials in proper proportions aremixed 'ith cullets. t is nely po'deredand intimate mixture called batch is fusedin furnace at high temperature of 67889Cthis charge melts and fuses into a viscous

+uid.

CaC:/; Si:CaSi:/ ; C:

*aC:/; Si:*aSi:/; C:

!fter removal of C:decolori4es li3e -n:

are added to remove traces of ferrouscompounds and Carbon. (eating is

continued till clear molten mass is free


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Forming, shaping, and annealing

)orming and Shaping

#he viscous mass obtained from melting ispoured into moulds to get di&erent types ofarticles of desired shape by either blo'ingor pressing bet'een the rollers.

!nnealing

Glass articles are then allo'ed to coolgradually at room temperature by passingthrough di&erent chambers 'ith descendingtemperatures. #his reduces the internalStrain in the glass.


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finishing

)inishing is the last step in glassmanufacturing. t involves follo'ing steps.

Cleaning

Grinding

Polishing

Cutting

Sand "lasting


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Varieties of glass

Soda lime orsoft glass

Potash lime orhard glass

Lead glass orint glass

Borosilicate orPyrex glass

Alumino-Silicate glass

96% Silica glass 99.5% Silicaglass!itreosil"

Safety glass

#$tical orroo&'s glass

Poly-crystallineglass

(oughened glass olored glass

)ired *lass *lass )ool +i,er glass Photosensitie

glass

Photo-chromicglass

eutral glass Laminated glass /nsulating glass


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Sodalime or soft glass

!bout lime glass made 'ithsilica 0sand1, Calcium carbonate and soda ash.

#he approximate composition is *aC:/.Ca:.?Si:.

#hey are lo' cost, resistant to 'ater but not toacids.

#hey can melt easily and hence can be hot 'or3ed.

%ses@

Aindo' glass, Blectric bulbs, Plate glass, "ottles,ars, cheaper table 'ares, test tubes, reagent

bottles etc


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Potash lime or hard glass

Potash lime glass is made 'ith silica 0sand1,Calcium carbonate and potassium carbonate.

#he approximate composition is 2C:/.Ca:.?Si:.

#hey posses high melting point, fuse 'ith di&icultyand are less acted upon by acids, al3aline and

other solvents than ordinary glass.

%ses@

#hese glasses are costlier than soda lime glass andare used for chemical apparatus, combustion tubes

and glass'are 'hich are used for heatingoperations.


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Lead glass or flint glass

t is made up of lead oxide +uxed 'ithsilica and 2C:/is used instead of sodiumoxide.

ts approximate composition is2Co/.Pb:.Si:.

#o get dense optical glasses about 78=

lead oxide is used. Lead glasses has alo'er softening temperature than sodaglass and higher refractive index and goodelectrical properties. t is bright lustrousand possess high specic gravity.

%ses@

(igh quality table 'ares, optical lenses,neon sign tubing, cathode ray tubes,electrical insulators, crystal art obDects orcut glass, Aindo's and Shields for

protection against E>rays and Gamma raysin medical and atomic energy elds etc.


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orosilicate ! p"re# ! $ena glass

t is common hard glasscontaining silica and boron

'ith small amount of aluminaand less al3aline solids.

t contains Si:078.F=1,

":/06/=1, !l:/08/=1,

2:0/=1 and *a:08.F=1.

#hese glass have lo' thermalcoe&icient of expansion, andhigh chemical resistancei.e..shoc3 proof.

%ses@

ndustrially used for pipelineof corrosive liquids, gauge

glasses, superior laboratoryapparatus, 3itchen 'ares,


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Alumino%silicate glass

#he typical approximatecomposition of this type ofglass is Si:0FF=1,

!l:/0/=1, -g:08


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&'( silica glass

t contains


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&&)*( silica glass ! +itreosil

t contains pure silica heatedto its melting point. t istranslucent, the coe&icient ofthermal expansion is very lo'hence it has high resistance tothermal shoc3, have highchemical resistance tocorrosive agents.

f Hitreosil glass is heatedabove its melting point, itbecomes transparent and is3no'n as clear silica glass.

%ses@

#hey are used in constructionof chemical plants, laboratorycrucibles, induction furnacelining, electrical insulators andheaters and have high light


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Safet" glass

t is made by fusing t'o to

three +at sheets of glass and inbet'een them alternate thinlayer of vinyl plastic isintroduced. t is heated 'hereboth the layers merge together

and glass is toughened.

%ses@

t is used as 'ind shield inautomobiles and airplanes. :n

brea3ing it pieces does not +yapart because of the presenceof the plastic layer in bet'eenthe glass layers.


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ptical or croo-.s glass

t contains Phosphorus, PbC:/, silicates and

Cerium oxide 'hich has the property to absorbharmful ultra>violet light. #his glass is giventhrough homogeneity by heating it for a prolongedperiod of time. #hese glasses have lo' meltingpoint and are relatively soft.

%ses@

#hey are used for ma3ing optical lenses.


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Pol"%cr"stalline glass

t is ne' type of glass 'hich is produced

by adding nucleating agents to aconventional glass batch and thenshaped into desired form. t is thensubDected to heating 'here nucleatingagents forms large number of micro

crystallites. t is not ductile. t exhibitshigh strength and considerablehardness.

%ses@

)or ma3ing speciali4ed articles.


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/oughened glass

t is made by dipping articles

still hot in an oil bath, so thatchilling ta3es place. #hisresults in outer layer ofarticles shrin3 and acquire astate of compression 'hile

inner layer are in state oftension. Such glass is moreelastic to mechanical andthermal shoc3. t brea3s into ane po'der.

%ses@

)or ma3ing 'indo' shields offast moving vehicles, 'indo'sof furnace and automatic

opening doors.


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Coloured glass

!ddition of transition metal compounds to glass givescolor to the glass. #hey are outlined belo'.

Iello'@ )erric Salts Green@ )errous andChromium salts

Purple@ -agnesedioxide salt

ed@ *ic3el andcuprous salts Cu:

Lemon Iello'@Cadmium sulphide

)luorescent greenishyello'@ %ranium oxide

"lue@ Cobalt Salts,Cu:

Greenish "lue Color@

Copper Sulphate

"ro'n@ ron

:paque mil3y 'hite@Cryolite of Calcium

phosphate

uby @ !uric Chloride


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0ired glass

Aired glass does not fall apart into splinters 'hen itbrea3s and is re resistant. t is made by fusing 'irein bet'een the t'o glass layers.

%ses@

)or ma3ing re resistant doors, roofs, s3ylights and'indo's


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Fi1re glass

t is transformed into a ne thread of lament and

has got a high tensile strength.

%ses@

)ound extensive use for the manufacture of fabric,reinforcing plastics and production of thermal

insulation materials etc


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Photosensiti+e glass

#hese are glasses by

'hich a colored picturemay be developed byexposing the glass toblac3 and 'hite negativein ultra violet light. #he

appropriate proportionsof potash>alumina glass,mixed 'ith LiS:/, cerium

and Silver salts have alsobeen used as

photosensitive glass.

%ses@

Photographicdevelopment


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Glass wool

Glass 'ool consists of tiny

bers formed by action ofsteam Dets on drippingmolten glass do'n from

very ne hole.

%ses@

(eat nsulation, forltration of Corrosivechemicals, soundinsulation etc


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Photo%chromic glass

#he three dimensional silicate

net'or3 contains large no. ofmicroscopic particles of silverhalide 'hich on exposure tolight produce color.

%ses@

n ma3ing tinted car glassesand goggles.


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2eutral glass

#hese glasses are highly resistant to chemical attac3s

and they are speciali4ed soda lime glass 'here al3alihas been replaced by alumina, boron oxide and 4incoxide.

%ses@

-a3ing Syringes, nDection !mpoules and vials etc.


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Laminated glass

#he sheets of glass ber or glass 'ool are soa3ed in a

solution of thermosetting plastic li3e phenolformaldehyde resin and placed one above the other andthen cured under heat or pressure. t is strong as steel.*on +ammable and insulating. n bullet resistant glass

vinyl resins are added in alternate layers.

%ses@

Shatter, shoc3 and "ullet proof Glass


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3nsulating glass

#'o or more plates of glass are lled 'ith

dehydrated air and the edges are sealed air>tightly.

%ses@

Provides thermal insulating and so houses remaincool in summer and 'arm in 'inter.


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Fracture ! failure of glass

Glass does not have crystal lattice structure hence

it brea3s. )racture is caused by smallimperfections, +a's and irregularity on the surfaceof the glass. )la's are very ne crac3s causeconcentration of stress and the crac3 proceedsquic3ly causing a fracture.


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Ma$or Forensic Glass Sources

Flat Glass So*a lime siliate

Drawin/, -ollin/, or Floatin/ 1empere*: -api* Coolin/

"**s Stren/t+

Dies w+en #roken

"$tomoti)e win*ows

se$rity win*ows

Float Glass floresesw+en e%ite* at 2!3 nm4

Coate*: S$rfae mo*ifiation

.irrors

'aminate*: San*wi+e*

aro$n* plasti

"$tomoti)e win*s+iel*s

5ea*li/+ts: Sometimes

#orosiliate

'i/+t #$l#s: So*a lime /lass

5eat a#sor#in/6 UV filterin/

1inte* P+oto+romi 7'i/+t

Sensiti)e8

9ye/lasses

Container Glass 'ower ma/nesi$m, +i/+er

so*i$m

Clear )s4 /reenis+ 7win*ow8

Glass Fi#ers

Fi#er/lass ins$lation

"l$mino#orosiliate

Bin*er 7re* or yellow8 to +ol*

fi#ers in #$n*les


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GLASS FRACTURES

First bends in the direction of the force splintering and cracking and breaking.

Radial cracks - Concentric cracks.

3 Rs - RADIAL - RIGHT ANGLES - REVERSEPROJECTILES AND BULLETS

If does not penetrate get the ejection of a small cone of the glass

Bullets edge will be wedgedhole wider in the direction of travel

size of the bullet holes

laminated glass and plastic sheet

size of bullet and distances

lass breaks in a characteristic manner which indicates the direction of travel of the

impacting object. Conchoidial striations are ripples seen through the cross section ofbroken glass. !he" are alwa"s at right angles to the impacted surface.

Radial fractures emanating from high velocit" projectile entr" points indicate the se#uence

in which guns shots were fired. !he radial cracks will stop where an earlier crack alread"

e$ists% so it must have come later in the se#uence.

Glass Fractures


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Glass

Glass is found in many types of cases. Like paint, it is often involved inburglaries and hit-and-runs. Glass fragments easily embed in shoes, hair

and clothing of people involved in the breakage of glass. Sometimes glass

fragments can be reconstructed to yield evidence. Reconstruction.

Colletion of e)i*ene

It is best to take a representative sample of the glass - this could be thefour corners of a broken window, or all the glass available if the glass

broken is not a window. If more than one type of glass is broken, collect

representative samples of each different type.

"nalysis of e)i*ene

ost glass analyses consist of comparing the refractive indices, elemental

compositions and densities of two or more samples.


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Glass!he forensic scientist will first of all assess the physical characteristics of the glass"

-efrati)e in*e%. !his is a measure of how much the light is bent, or refracted, as itpasses through the glass.

If a colourless piece of glass is put into water, you can still see it because the water and

glass have different refractive indices. !he refractive inde# of glass does not vary

significantly with temperature, but those of li$uids do. If a piece of glass is placed in a

li$uid which is then heated, at some point the refractive indices will be identical and you

will no longer be able to see the piece of glass. If the two pieces of glass % one thesuspect and one from the scene of crime, have identical refractive indices, then they

are from the same source. &owadays, refractive inde# methods are semi-automatic %

the GRI' instrument measures the refractive inde# of glass fragments by reference to

calibrated immersion oils and automatically identifies the glass.

9lementalomposition. !he elements investigated are usually sodium,

magnesium, aluminum, silicon, potassium, calcium, barium and iron. Densitymeasurements. !he density of glass can be measured by flotation

measurements, though this techni$ue is rarely used these days.


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*lass *allery
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