silicon carbide , properties , applications

1. T.Y. B. TECH
SCHOOL OF MECHANICAL ENGINEERING
ADVANCED MATERIAL
EXPERIMENT NO. 3
SILICON CARBIDE
Presentation by:-
Aditya Bulbule (PA-05)
Kaiwalya Gondchar (PA-06)

2. INTRODUCTION :-
● Silicon carbide also known as carborundum.
● It is a compound of silicon and carbon with chemical
formula Sic.
● It occurs in nature as the extremely rare mineral
moissanite.
● Silicon carbide powder has been
mass-produced since 1893 for use as an
abrasive.
● Grains of silicon carbide can be bonded together by
sintering to form very
● hard ceramics that are widely used in applications

3. DISCOVERY:-
In 1891 Edward G Acheson produced a small amount
of Silicon Carbide while conducting experiments with
the aim of obtaining a hard material from the reaction
of clay and carbon.
He passed a strong electric current from a carbon electrode
through a mixture
of clay and coke contained in an iron bowl, which served as the
second electrode.
Acheson recognized the abrasive value of the crystals
obtained, had them Analyzed, found the formula to be Sic,
incorporated The Carborundum Company in September 1891,
and filed application for a patent on May 10, 1892.

4. STRUCTURE :-
● Silicon carbide exists in about 250
crystalline forms. The polymorphism of
Sic is characterized by a large family of
similar crystalline structures called
polytypes.
● Alpha silicon carbide (α-Sic) is the most
commonly encountered polymorph. it is
formed at temperatures greater than 1700
°C and has a hexagonal crystal structure.
● The beta modification (β-Sic), with a zinc
blende crystal structure (similar to
diamond), is formed at temperatures
below 1700 °C.

5. PROPERTIES:-
● Pure Sic is colourless, . The crystals
vary in colour from very pale green to
black depending on the amount of
included impurities.
● Black and green silicon carbide both with a shape
of hex crystal. The material is extremely hard and
sharp, with excellent chemical properties.
● The hardness is between diamond and fused
alumina, but the mechanism hardness is higher
than fused alumina. The micro hardness is in the
range of 2840-3320kg/mm².
● Silicon Carbide is sharp but fragile with good
heat-resistance, heat-conductibility, can be
antacid and antalkali, lower dilatability and
electrical conductivity.

6. ● Sic is quite stable chemically. It is stable to acids, not reacting with fuming nitric
acid, nor with boiling sulphuric hydrochloric or hydrofluoric acid.
● Silicon Carbide dissociates in molten iron and the silicon reacts with the metal
oxides in the melt. This reaction is of use in the metallurgy of iron and steel.
● Sic has:
○ high hardness
○ high thermal consistency
○ very good resistance at high temperatures
○ low thermal expansion
○ electrical conductivity
○ is a semiconductor
○ non linear electrical resistance
○ Si and C as alloying additive.
...

7. PRODUCTION:-
● Silicon carbide is made today in much the same way as it was when invented
in 1891
● High purity quartz is mixed with a high quality coke or anthracite in
large electric resistance furnaces at temperatures of over 2000°C
according to the following reaction:
SiO2
+3C=Sic +2CO
○ The process is an endothermic reaction requiring between 8000 –
10000 kWh per tonne of product.
○ The simplest manufacturing process is to combine silica sand and carbon
in an Acheson graphite electric resistance furnace at a high temperature,
between 1,600 °C and 2,500 °C

8. APPLICATIONS:-
Silicon carbide forms natural crystals, which are
very hard, very abrasive and dissociate or
sublimate at high temperatures. It is for these
reasons that silicon carbide is used in the
following applications:
Abrasive industry:
With a good hardness, silicon carbide is the first
choice raw material for manufacturing abrasive
pipe , pumping chamber etc. Its abrasiveness is
5-20 times than that of cast iron and rubber.

9. Automobiles:
Silicon-infiltrated carbon-carbon
composite is used for high performance
"ceramic" brake discs, as it is able to
withstand extreme temperatures. The
silicon reacts with the graphite in the
carbon-carbon composite to become
carbon-fiber-reinforced silicon carbide
(C/Sic). These discs are used on some
road-going sports cars, supercars, as well
as other performance cars including the
Porsche Carrera GT , Bugatti
Veyron,Bentleys, Ferraris, Lamborghinis,
some specific high performance Audis
etc.

10. Electronics:
● Silicon carbide is a semiconductor in research and
early mass-production providing advantages for fast,
high-temperature and/or high-voltage devices. First
devices available were Schottky diodes, followed by
Junction-gate FETs and MOSFETs for high-power
switching. Bipolar transistors and thyristors are
currently developed.
● It is also used in making LED’s.

11. TYPICAL SILICON
CARBIDE USES:
❑ Suction box covers
❑ Fixed and moving turbine
components
❑ Seals, bearings
❑ Ball valve parts
❑ Hot gas flow liners
❑ Heat exchangers
❑ Semiconductor process equipment
❑ Jewellery

12. Thank you