FULLERENE (or) C60 :

 

              Fullerene are family of carbon allotropes, molecules composed entirely of carbon, in the form of sphere, ellipsoid, tube or plane.  Spherical Fullerene are called Buckyballs, and cylinderical ones are called Carbon Nanotubes (or) Buckytubes.

 

                  Fullerenes are similar in structure to Graphite & Graphene is example for plane fullerene. A soccer ball is the model of buckminsterfullerene C60. 

  

                  Fullerenes are discovered in 1985 by Robert Curl, Harold Kroto and Richard Smalley. And are named after Richard Buckminster Fuller. 

 

                  Minute quantities of the fullerene, in the form of C60, C70, C76 and C84 molecules, are produced in nature, hidden in soot and formed by lightning discharges in the atmosphere.  

 

                  Recently, Buckminsterfullerenes were found in a family of minerals known as Shungites in Karelia, Russia.  Now they are available in Mangampeta(village) at kadapa district in Andhra Pradesh, India.  

 

                 

Applications of carbon nanotubes in :

 

1) Metallic and semiconducting nanotubes-

 

             Most experimentally observed CNTs are multi-walled structures   with outer most shell diameters exceeding 10 nm.
Since current conduction in a MWCNT(Multi-Walled Carbon Nano Tube) is known to be mostly confined to the outermost single-walled nanotube and
since band gap of a SWCNT(Single-Walled Carbon Nano Tube) varies inversely with its diameter, MWCNTs are metallic in nature.  SWCNTs can be either
metallic or semiconducting depending on the way the roll-up of the graphene sheet occurs - an aspect termed as Chirality,
and if all the roll-up types are realized with equal probability, 1/3 of the SWCNTs end up being metallic and
2/3 semiconducting.  Thus, when CNTs are fabricated either by arc growth,
laser ablation or chemical vapor deposition (CVD), a mixture of metallic and
semiconducting nanotubes is formed.This carbon nanotubes can be used as light emitting semiconductors.

 

2) Carbon nanotube Transistors-

            

             Semiconducting CNTs have been used to fabricate field effect transistors
(CNTFETs), which show promise due to their superior electrical
characteristics over silicon based MOSFETs.  Since the electron mean free
path in SWCNTs can exceed 1 micrometer, long channel CNTFETs exhibit near-ballistic
transport characteristics, resulting in high speed devices. In fact, CNT
devices are projected to be operational in the frequency range of hundreds of
GHz.  Recent work detailing the advantages and disadvantages of various
forms of CNTFETs have also shown that the tunneling based CNTFET offers
better characteristics compared to other CNTFET structures.
This device has been found to be superior in terms of subthreshold slope -
a very important property for low power applications.

 

3)  Challenges in Electronic Design and Design Automation-

 

                      Although CNT devices and interconnects have been separately shown to be
promising in their own respects, there have been few efforts to successfully
combine them in a realistic circuit. Most CNTFET structures employ the silicon
substrate as a back gate. Applying different back gate voltages might become a
concern when designing large circuits out of these devices. Several top-gated
structures have also been demonstrated, which can alleviate this concern.
Recently, a fully integrated logic circuit built on a single nanotube
has been reported. However, this circuit also employs a back-gate.
Additionally, there are still several process related challenges that need to
be addressed before CNT-based devices and interconnects can enter mainstream
VLSI process. This makes it an exciting and open field for research. Problems
like purification, separation of carbon nanotubes, control over nanotube
length, chirality and desired alignment, low thermal budget as well as high
contact resistance are yet to be fully resolved. Although these are serious
technological challenges, innovative ideas have been proposed to build
practical transistors out of nano-networks. Since lack of control on
chirality produces a mix of metallic as well as semi-conducting CNTs from any
fabrication process and it is difficult to control the growth direction of the
CNTs, random arrays of SWCNTs (that are easily produced) have been proposed to
build thin film transistors.  This idea can be further exploited to build
practical CNT based transistors and circuits without the need for precise
growth and assembly.

More about Fullerene-

                    Fullerene is costlier than Gold . In market 10 grams of fullerene is 45,000 dollars (18 lacks in rupees) but gold is 300 dollars i.e. 150 times greater. [according to 3 sept 2007, rates in market.]

 

                     Fullerene is 250 times stronger & 10 times lighter than Steel. In fullerene, current flows 1000 times faster than copper and aluminium. It is lighter than cotton too.

 

                     Fullerene having one millimetre of diametre can lift 6,300 kilograms.

submitted by

Roopesh - ECE 1/4

Global Warming

A good number of countries, although it is extremely harmful to the environment, use especially fossil fuels like coal. The protocol of Kyoto makes an invitation to the OECD countries to reduce their greenhouse emission. Kyoto aims at bringing the level of 1990's total greenhouse emission under %5.4 between 2008-2012 years .Choose the products.WF , with its Powerswitch!company which they run it all over the world , invites governments and the world of job to take an responsibility about using renewable energy sources.in the scope of company it is encouraged to use water,geothermal,biomass and solar energy instead of coal,fuel oil and natural gas etc.

The national energy strategies should be prepared to foresee the time of minimal 30 years.Policies should be determined for developing other energy sources and using them safely.Attendance of civil institues and local community should be provided to shape national energy policy.

 

We should utilize energy sources like local scale wind and solar energy provided that enviroment effect is appraised.
Agriculture contributes various emission like ammoniac and methane gas to get mixed up in atmosphere. %90 of europe's ammoniac emission is stem from farm animals and chemical fertilizers.Using chemical fertilizers increase nitrogendioxide which is also greenhouse gas.the fertilizers which contain nitrogen and phosphor should be decreased.
What could we do ?

* we should use bulbs which consume less electric.

* we shouldnt keep television in waiting position

* we should use right lighting.

* we should use ventilator instead of air conditioner.

* house should be insulated against heat missing.

* goods should accommodate not in front of radiator

The sources of water scarce is another important problem.But , there is some precautions to take to prevent it :

* we shouldnt keep tap open when brushing our teeths,washing clothes and shaving.

* we should use new tecnology closets which consume much little water

* we shouldnt use cleaning materials which hang closets.

* we should reduce using bleacher

* we should mend broken installation.

* watering and washing shouldnt made with hosepipe.

* we should use filters which purify water from lime and bacteria

National organizations warn people about the sector of transport too.
This sector is the main cause of nonrenewable energy sources and the gas emissions which are used in sector , cause air pollution and alteration in climate.

* we should prefer public vehicles.

* in short distance,we should walk instead of driving.

* we should prefer vehicles which consume unleaded oil.

* we shouldnt exceed the scope of vehicle's carrying.

* in long breaks,we should close vehicle's ignition.

National organizations advise consumers to assimilate renewable life style and avoid excessive consume during shopping.
The most important subject which is necessary to treat with care is the consume of wrapping.For , the destruction of plastic wrappings in nature may last a thousand year .

* consumers should direct long life span products.

* we shouldnt purchase products which is sold in nonrenewal wrappings .

* we should abstain from plastic wrappings mainly pvc

* we should prefer glass products like bottle and jar.

* we should reuse products like plastic bags and nutriment containers.

* we shouldnt use plastic bags in shoppings.

* we should throw away glass materials with organic garbage.

the computers which is inseparable for our daily life , create bad environment and its effects arent considered as too little.

* we should purchase brands which consume much little electric.

* we should reduce printer's output minimum

* we shouldnt keep computers in waiting position.

* we shouldn't throw away disused computers

submitted by 
sharmila (ECE)