By MALCOLM W. BROWNEFEB.
1998 scientists are experimenting with a fascinating substance called a single particle.
The wall Carbon nano tube predicts that this elegant geometric molecule will trigger a revolution in the fields of electronics, computers, chemistry and new structural materials.
Replaces the relatively large electronic devices contained in silicon
Based on chips, physicists have demonstrated that it is possible to make devices on atomic and molecular scales.
Single electron in a single electron
Wall carbon nanotubes can be used as miniature transistors.
In 1991, the diameter spontaneously formed in the carbon atom hexagonal array discovered by the doctor was only a few atoms.
The Japanese Tsukuba NEC Basic Research Laboratory's Rice Island.
These tubes, which are actually elongated molecules, are formed in the furnace by carbon arcs and the steam generated by the laser.
They took their names from Nano, a unit of measurement-
1 m long billion-
Convenient length for specifying molecular size.
According to several recent reports, there is only one
The thickness of human hair can perform the same electronic function as much larger Siliconbased devices.
Therefore, the computer based on the nanotubes device can be very compact, fast and powerful. Dr. advertising
Recently, Alex Zettl of the University of California, Berkeley, and his research team found that when two slightly different nanotubes molecules are connected end-to-end, the "connection" between them is an electronic device called a diode.
Diodes are the basis of the rectifier and are commonly used to convert alternating current to direct current.
"When we grow nano tubes"
"Electronic devices are naturally formed on them," said zitar.
"The silicon industry is facing a brick wall due to the need for smaller and smaller electronic devices to increase the speed and power of computers," said Dr. Zettl said.
The solution may be to replace the silicon-
The devices used today, based on tiny carbon molecules, have another advantage: they are much faster than silicon to conduct heat, and therefore more suitable for micro-electronics technology.
Looking forward, doctor.
Zettl believes that carbon nano-tube blocks may spontaneously organize their electronic interactions into complex networks similar to brain neural networks.
The density of the nanotubes interconnected by bringing them together is amazing;
If all can be packaged into a carbon nanotubes moleculehalf-
Inch cubes are laid end-to-end and they will stretch 250,000 miles. Dr.
Zettl speculated in an interview that a randomly mixed carbon nanotubes in such a cube may produce a nano-computer network that may be able to perform complex tasks and reconfigure itself
A "tube cube" like a doctor"
Zettl said that the imaginary nano-tube brain may never be realized.
But recent research has provided strong evidence that, at least, the Naimi tube has a huge electronic future.
Research Report reported by Dr in last October
The evidence provided by Mr. Zidar and his colleagues suggests that a nano-tube molecule can contain many tiny devices: transistors and other basic components of the electrical subsystem.
NASA's Ames Research Center is also conducting similar research. Dr.
Jie Han and his team at Ames recently reported that by inserting defects into the metal-
Like nano tubes and semiconductor nano tubes, they create multiple types of connections within a nano tube molecule.
Two papers published last month in the journal Nature, one is a chemist at Harvard and the other is a scientist at Delft University of Technology in the Netherlands and Rice University in Houston, A finding was independently reported that the electronic properties of the nanotubes depend on the distortion of the molecules.
Advertising chemists describe the raw materials of carbon nanotubes as only one graphite sheet with atomic thickness, which is formed by the condensation of carbon steam.
The carbon atoms connected together in the graphite sheet spontaneously form a pattern similar to the chicken wire.
When such a sheet is rolled into a tube that seamlessly connects its edges together, a nano tube is formed.
In some cases, concentric tubes are formed, one in the other.
Typically, a semi-spherical lid is formed at the end of each tiny tube, thus closing it.
In their research, teams in the Netherlands and Harvard used scanning tunneling microscopy, and the probes were so good that their tip was made up of a single atom.
This microscope can scan the surface of an object and detect a single atom.
A team led by a doctor
Cees Dekker in the Netherlands and the Harvard team headed by doctorsCharles M.
Lieber reports that there is a strong relationship between the electronic properties of the nanotubes and their diameter and degree of distortion.
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If the graphite sheet forming the nanotubes is perfectly rolled up evenly, making all its hexagon arranged along the axis of the molecule, the molecule is as easily conductive as metal.
But if the graphite rolls at a distorted angle, the resulting nanotubes are like semiconductors.
That is, it only conducts electricity if the electricity or other energy applied to it exceeds a certain value.
Scientists have also found that there is a certain angle of distortion that allows the nano tube to conduct freely as without distortion. Dr. Mildred S.
In 1992, according to quantum theory, this behavior will be predicted in the single
Wall carbon nanotubes
Last week, she described the report published by the Netherlands and Harvard group confirming her forecast as a "landmark paper ".
"She acknowledged in an interview that the practical application of this finding may take time to be fully utilized.
"But remember, it will take a while for the laser to become its own . "
Simple carbon nanotubes are already available for industrial use.
For example, Hyperion catalytic International, Cambridge, Massachusetts.
, Add a small amount of these molecules to the plastic to make the plastic conductive.
The automotive industry uses conductive plastics to make parts coated with charged paint drops.
This electrostatic painting process saves most of the paint that is wasted otherwise by traditional spraying and applies a more uniform coating.
The scientific journey leading to carbon nanotubes began in 1985. Richard E. Smalley and Dr. Robert F.
Dr. Curl of Rice UniversityHarold W.
Croto, University of Sussex, England.
Three scientists have won 1996 Nobel Prize in Chemistry for their achievements, and they have proved the existence of football --ball-
Shape Molecules generated by 60 or more carbon atoms connected together in hexagonal and pentagonal patterns.
The electronic connection between the carbon atoms in these balls
The shape of the molecule forms a ground wire structure similar to the architectural design of R.
Buckminster Fuller is therefore called the "pirate ball ".
Compounds made by chemically combining these balls with other atoms or molecules are called "Fuller.
"Many laboratories have tried to condense the buc ball molecules from hot carbon steam in different ways, and scientists have found that small changes in processing conditions will produce hollow, roughly spherical shapes and sizes with different shapes.
But it wasn't until 1991, doctor.
By accident, the Rice Island found that similar methods also produced tubular molecules.
In addition, under certain conditions, these tubes close themselves by connecting two and a half of the split buc ball as an end cap.
Many chemists, physicists and material scientists began to study these molecular tubes and soon found that they were about 100 times as strong as steel.
They are too small to be used as separate fibers, but some laboratories have assembled a "Cableway" consisting of carbon nanotubes ".
"The nano-tube fiber has unique toughness . "
According to Lieber of Harvard.
"It is certain that they will become an ingredient in a new family of composites that will be much stronger than the existing fibers --
Reinforced composite material. ''Dr. Lieber, Dr.
Smalley and others believe that carbon nanotubes can be used as molecular tubes full of chemicals and sealed at both ends.
Nanotubes can also be used to deliver drugs to specific parts of the body.
Some scientists predict that fuel cells that directly convert hydrocarbon fuels into electrical energy will form a membrane controlled by Naimi.
Scientists say one of the biggest challenges in developing carbon nanotubes-based technologies will be to find solutions to these problems.
Furnace mass production for the manufacture of nanotubes, many types of nanotubes are always mixed together: twisted and non-twisted tubes, multi-walled and single-walled
The version with the wall, some capped, some opened, some wide, and some narrow. Dr.
Smalley saw the solution in chemistry.
"We have a lot of skills to do," he said . "
"For example, you may chemically attach some molecules at the end of the nanotubes you are interested in.
Then, when all the nanotubes pass through a certain substance, the nanotubes that are added to the molecule stick to the back, while the others continue to move.
"In the next ten years ,"
Smalley said, "we will see the flowering of a new branch of organic chemistry based on carbon nanotubes.
There is no end to its possibilities.
"We are constantly improving the quality of text archives.
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A version of this article appears on page F00001, the national edition, in February 17, 1998, with the title: The Next electronic breakthrough: carbon atoms.