8. BOROSLICATE GLASS
• MAINLY MADE OF SiO2(70-
80)% AND BORIC OXIDE (7-
13)% WITH SMALL
AMMOUNT OF ALIKALIS
• THIS GLASS HAS EXCELLENT
CHEMICAL DURABILITY
AND THERMAL SHOCK
RESISTANCE
9. LEAD GLASS
• LEAD GLASS CONTAIN
30% PbO BUT ANY
OTHER GLASS
CONTAIN AT LEAST
24% PbO
• IT HAS HIGH
REFRECTIVE INDEX
AND USE AS
RADIATION
SHIELDING
16. DENSITY
THE DENSITY OF GLASS IS 2.5 , WHICH GIVES A FLAT
GLASS A MASS OF 2500 Kg/m
COMPRESSIVE STRENGTH
THE COMPRESIVE STRENGTH OF GLASS IS EXTREMLY
HIGH WHICH IS ABOUT 1000 Mpa . THIS MEANS THAT
TO SHATTER A 1 CM3 OF A GLASS IT REQUIRES A LOAD
OF 10 TONNES
17. TENSILE STRENGTH
WHEN GLASS IS DEFLECTED , IT HAS ONE FACE UNDER
COMPRESSION AND THE OTHER IN TENSION , WHILE
THE RESISTANCE OF GLASS TO COMPRESSIVE STRESS IS
EXTREMELY HIGH BUT IT’S RESISTANCE TO TENSILE
STRESS IS SIGNIFICANTLY LOW
ELASTICITY
GLASS IS A PERFECT ELASTIC MATERIAL , IT DOES NOT
EXHIBIT PERMANENT DEFORMATION UNTIL BREAKAGE
HOW IT’S FARGILE AND BREAKE WITH OUT WARNING
18. YOUNG MODULUS
IT EXPRESSES THE TENSILE FORCE THAT WOULD HAVE
TO BE APPLIED TO A GLASS SAMPLE TO STRETCH IT BY
AN AMOUNT EQUAL TO IT’S ORIGNAL LENGTH
IT IS EXPRESSED AS FORCE PER UNIT AERA E=70 GPa
POISSON’S RATIO
THE RELATION BETWEEN THE UNIT DECREASE IN THE
DIRECTION PERPENDICULAR TO THE AXIS OF THE
EFFORT AND THE UNIT STRAIN IN THE DIRECTION OF
THE EFFORD . FOR GLASS IT’S VALUE IS 0.22
19. THERMAL CHARACTARSTICS
LINEAR EXPENSION :
IT IS EXPRESSED BY A COEFFICIENT MEASURING THE
STRECTH PER UNIT LENGTH FOR A VARIATION OF 1 C
THERMAL STRESS :
DUE TO LOW THERMAL CONDUCTIVITY OF GLASS
,CREATES STRESS WHEN A SHEET OF GLASS IS
PARTALLY HEATED OR COOLED WHICH MAY CAUSE
THERMAL BREAKAGE
20. APPLICATIONS
OPTICAL LENSES , PRISM , FINE GLASSWARE AND
OPTICAL FIBERS
VESSELS , BOWLS , VASES BOTTLES , JARS , AND
DRINKING GLASSES
PAPERWEIGHTS , MARBELS , AND BEADS
FIBER GLASS
21. GLASS CERAMIC ARE POLYCRYSTALLINE CERAMIC MATERIAL FORMED
THROUGH THE CONROLLED NUCLEATION & CRYSTALLIZATION OF GLASS
Thermal expansion coefficient is nearly zero
Strength is greater than traditional glasses.
Providing good shock resistance.
A common example of glass ceramic is white pyroceram.
22. S. DONALD STOOKEY, A
SCIENTIST WITH CORNING
GLASS WORKS WHO IN THE
1950’S ACCIDENTLY
DISCOVERED A REMARKABLLY
STRONG MATERIAL glass
ceramic, the highly versatile range
of materials that continue to be
refined for new uses.
23.
24. DEVITRIFICATION IS INITAITED AT LOWER ENRGY SURFACE
SITES
CRYSTALLIZATION FORCES THE ORIGINAL SHAPE TO
UNDERGO GROTESQUE DISTORTIONS.
TRANSFORMATION FROM GLASS TO CERAMIC WITH NO
DEVIATION FROM THE ORIGINAL SHAPE.
25. In recent years, another method of manufacture of glass-ceramics
has proven technically and commercially viable. This involves:
sintering and crystallization of powdered glass. This process typically
involves milling a quenched glass into fine 3-15 micrometer particle
diameter.
This powder is then formed by conventional ceramming called
forming techniques in viscous sintering to full density just before the
crystallization process is completed
