1960 1970 1980
1990 Graphic Version
From 1942 until
the present, ORNL has become a full-fledged national socio-technological
institute. Its capabilities span the entire range of scientific disciplines.
It addresses an array of problems whose only common attribute is their
significance both to the nation and the world. Come travel through time
and see how this national laboratory, nestled in the hills of East Tennessee,
transitioned from a wartime pilot plant to an institution of world importance.
We welcome your comments and suggestions. [Barbara Ashdown, firstname.lastname@example.org]
of the First Nuclear Reactor (Top)
In 1938 nuclear
fission was discovered in Germany, and Albert Einstein wrote a letter
in 1939 to President Franklin D. Roosevelt recommending that the United
States develop an atomic weapon before the Germans did. Germany invaded
Poland and World War II began. In December 1942 the first sustained and
controlled nuclear chain reaction was demonstrated at the University of
Chicago. The Manhattan Project was started to develop a United States
atomic bomb. A site was selected in East Tennessee. In 1943 construction
started on Oak Ridge National Laboratory (called Clinton Laboratories
until 1948), including what became the world's first continuously operated
nuclear reactor. Called the Graphite Reactor, it began operation November
4, 1943, and demonstrated that a reactor could produce plutonium in useful
amounts. In 1945 World War II ended as the result of the deployment of
an atomic bomb using highly enriched uranium from Oak Ridge and another
bomb using plutonium from three reactors at Hanford, Washington.
Laureate Enrico Fermi led the group that first demonstrated a controlled
nuclear reaction (on December 2, 1942).
4, 1943, Fermi witnessed the initial operation of the Graphite Reactor
in Oak Ridge.
using the results of the Chicago experiment, the Graphite Reactor
produced small amounts of plutonium, setting the stage for large-scale
plutonium production by reactors in Hanford, Washington. It was
the world's first isotope-production reactor.
Wigner, later an ORNL director who won a Nobel Prize for physics,
predicted that radiation damage could be a problem for reactors.
The behavior of irradiated materials was studied at ORNL, which
became a leading materials research laboratory.
materials are drawn from the Graphite Reactor.
neutron-scattering studies using a reactor were performed at the
Graphite Reactor by Ernie Wollan and Clifford Shull, who won a Nobel
Prize for physics in 1994 for advancing the understanding of the
positions of atoms and molecules in materials.
chromatography used at the Graphite Reactor enabled the discovery
of promethium (element 61).
water reactor was conceived by Eugene Wigner and Alvin Weinberg,
who later became ORNL directors. This design was later used in Navy
submarines and commercial nuclear power plants, which today supply
one-fifth of the nation's electricity.
detectors and dosimeters were developed to monitor worker exposure
to radiation from reactors and other nuclear sources.
shipment of radioisotopes from the Graphite Reactor was made to
a hospital for treating cancer patients; by the end of the decade,
the Graphite Reactor was the world's leading source of isotopes
needed for, agriculture, industry, and medicine.
found that experiments with mice could help scientists estimate
the human genetic effects of different types and intensities of
radiation from atomic weapon tests and reactors.
to separate zirconium from hafnium to provide pure zirconium (which
absorbs few neutrons) was devised for use in fuel cladding for reactors
in Navy submarines.
of reactor control and protection developed at the Graphite Reactor
and refined at later ORNL reactors are used widely in today's commercial
nuclear power plants.
a washing-machine mechanism to move materials into the Graphite
Reactor for neutron irradiation, Herb Pomerance discovered that
zirconium's ability to absorb neutrons was overestimated because
it is usually contaminated with hafnium, a "poison" which absorbs
many more neutrons.
experts in solvent extraction began developing the PUREX process,
which became the worldwide method of recovering uranium and plutonium
from spent reactor fuels. They also invented the THOREX process
to separate thorium from uranium-233.
in Reactor Development and Radiation Protection (Top)
At a laboratory
in its glory days for developing fission reactors as power sources, ORNL
researchers examined a variety of ways of protecting the public from hazardous
levels of radiation from reactors as well as nuclear tests. They designed
shielding and radiation detectors, made recommendations based on animal
studies that led to standards limiting human radiation exposures, studied
the environmental effects of radioactive materials, and developed technologies
to isolate radioactive waste from the environment. ORNL researchers also
found ways to use radiation for studies of forests, materials, and genetic
changes in mammals. ORNL produced radioisotopes and stable isotopes for
medical diagnosis and treatment. And ORNL conducted experiments to support
the goal of producing controlled nuclear fusion energy for power generation.
radioactive materials were first used at ORNL to trace the natural
movement of nutrients and pollutants in forests.
Bulk Shielding Reactor provided data for calculations to determine
how best to make shielding - different thicknesses and configurations
of lead, steel, and concrete - adequately protect people and equipment
from exposure to hazardous radiation levels.
researchers Liane and Bill Russell informed the medical community
that the stage of prenatal development in mice strongly influences
the amount and type of radiation damage to the embryo and fetus.
Their specific recommendations for avoiding the risks of diagnostic
X-rays to unsuspected human pregnancies were adopted worldwide.
Oak Ridge Automated Computer and Logical Engine (ORACLE), then the
world's most powerful computer, was slower and less powerful than
today's desktop machines.
U.S. Army, ORNL designed a transportable reactor to generate heat
and electricity at remote sites such as Antarctica, Greenland, and
the Panama Canal Zone.
Tower Shielding Facility (TSF) provided data for ORNL calculations
to aid the design of compact, lightweight shielding to protect a
nuclear airplane's flight crew from reactor radiation. The nuclear-powered
plane was never built, but ORNL's participation in the national
Aircraft Nuclear Propulsion Program produced a wealth of useful
successful experiment was carried out in which a chemical reaction
was studied by colliding molecular beams of two different reactants.
most famous reactor of the 1950s was the small "swimming pool" reactor
shipped to Geneva, Switzerland, for the United Nations Conference
on Peaceful Uses of the Atom.
Using ORNL mouse data,
a National Academy of Sciences committee predicted genetic effects
of radiation in humans. Later, national and international bodies
relied on ORNL data for recommending human radiation exposure limits.
Neutron dosimetry techniques
that have been used throughout the world were devised to protect
workers from exposure to hazardous levels of radiation.
ORNL biologists used
radiation to suppress the immune response in mice and then performed
the world's first bone marrow transplants.
tags to study the chemistry of life, ORNL biologists discovered
that messenger RNA "reads" DNA's genetic code and turns itself into
a template for mass-producing proteins.
fusion research device, the Direct-Current Experiment (DCX), showed
that hydrogen ions could be obtained and trapped in a magnetic field.
leadership in setting standards on permissible doses of radiation
for medical diagnosis and treatment and for the workplace.
began "Project Salt Vault," the first national effort to locate
a high-level nuclear waste repository. An ORNL test site for storing
nuclear wastes is located near Lyons, Kansas.
the first experiment on the Oak Ridge Research Reactor, researchers
confirmed the electron-neutrino theory of beta decay. For 30 years,
the ORR was used to produce radioisotopes for industrial and medical
uses, study the effects of radiation on materials, and carry out
neutron-scattering experiments that uncovered the rich variety of
crystal and magnetic structures in rare-earth elements.
a certain dose of radiation over weeks was found to produce fewer
mutations in mice than giving the same amount within minutes. This
work provided the first evidence that damage that results in mutations
can be repaired.
Clinch River was studied to evaluate the potential long-term hazards
of radioisotope releases from a major nuclear facility.
in the mouse was found to depend on the presence of a Y chromosome.
Reactor and Computer Technologies (Top)
international recognition for its promotion of nuclear-powered "Water
for Peace" desalination plants for "making the desert bloom." Its other
reactor successes included the operation of the Molten Salt Reactor
Experiment and the startup of the High Flux Isotope Reactor, which is
still used today for radioisotope production and neutron-scattering
experiments. Using computer modeling and other approaches, ORNL researchers
helped launch the electronic revolution. They developed computer codes
to better understand changes in forests, analyze operational problems
in reactors, assess the effectiveness of shields and fallout shelters
in protecting people and equipment from radiation, and predict whether
conditions could lead to a radiation-releasing criticality accident.
Because of public concerns about the increasing presence of reactors,
nuclear safety became a growing field at ORNL.
radiation monitors were developed, including the pocket screamer
that chirps and flashes when gamma radiation levels go too high.
was started to develop graphite structures and coated-particle fuels
for high-temperature gas-cooled reactors.
developed advanced mathematical and computer approaches to understanding
the dynamics of terrestrial ecosystems.
circuits for electronic applications were first developed as a
result of ORNL's calutrons (normally used to produce stable isotopes).
They were used to show that silicon implanted with boron and phosphorus
ions forms electrical junctions, and then to produce semiconductor
samples for industry.
Physics Research Reactor provided radiation-exposure data that
helped scientists refine occupational dose limits, design dosimeters
for nuclear workers, and devise shields for power plants and space
a center for research on civil defense to protect the U.S. population
in case of a nuclear war. Drawing on its expertise in shielding
and radiation protection, the center evaluated protective measures
such as underground shelters.
by computer modeling, ORNL physicists discovered ion channeling
in crystalline solids. This insight that energetic ions aimed
down open regions in crystal lattices lose less energy than those
ions entering in random directions led to precisely controlled
implantation of electrically active impurities within crystals.
The result: improved semiconductor chips that created the electronic
stand in Oak Ridge was tagged with cesium-137, providing data
for computer models and validating the long-term behavior of this
key radioactive waste material.
applied analysis of signal fluctations (noise) to the identification
of operational problems in some reactors, such as vibrations in
key parts caused by coolant water flow. ORNL measurements later
prompted the decision to let some commercial reactors operate
at reduced power until the problem was solved.
Ridge Isochronous Cyclotron (ORIC) was first operated. It later
played an important role in the Holifield nuclear physics accelerator
Shielding Information Center at ORNL implemented concepts for information
analysis centers in specialized fields, as suggested by a Presidential
panel led by ORNL Director Alvin Weinberg.
"Water for Peace" desalination concept, in which heat from nuclear
reactors in arid lands produces irrigation water for agriculture
from seawater, was featured at a United Nations conference. Nuclear-powered
desalination complexes were planned for India, Israel, Mexico, Puerto
Rico, and the Soviet Union.
started a long-range program to measure the genetic effects of chemicals
such as pesticides, gasoline fumes, drugs, and tobacco.
An important achievement
of a program to develop radioisotope heat sources to power space
satellites was the construction of an isotope-powered generator
for the lunar probe Surveyor.
of delayed light was one of ORNL's internationally recognized
fundamental discoveries in photosynthesis, including evidence
for the electronic nature of the process's first step.
High Flux Isotope Reactor, which has the world's highest steady-state
thermal neutron flux, continued to be used for neutron-scattering
experiments, materials irradiation, neutron activation analysis,
and production of transuranium isotopes, such as californium-252,
which is used to treat cancer.
of the effects of pollutants and movements of nutrients in living
systems in water and on land began at the new Walker Branch Watershed
research facility. The National Science Foundation selected ORNL
to lead a major study of ecosystems in the eastern United States.
program was started to evaluate the effects of laws, property
variations, and residual stresses on the reliability of pressure
vessels in light-water reactors.
Heavy-Section Steel Technology Program overpressurized intermediate
reactor vessels until they fractured. Typically, three times the
design pressure was required to induce failure or leakage, confirming
that standard reactor operating pressures are safe.
Molten Salt Reactor Experiment, which was the first reactor to
operate on uranium-233 fuel, was brought to power with the aid
of Nobel Laureate Glenn Seaborg.
by Norman Anderson and his associates, ORNL's centrifugal fast
analyzer was made into a commercial product that revolutionized
medical testing of body fluids in hospitals and clinics.
Apollo 11 moon rock scoop was designed at ORNL.
Energy and Environmental Laboratory Blossoms (Top)
After the Mideast
oil embargo of 1973-74, the U.S. government sought to diversify its
energy sources and decrease U.S. dependence on imported oil. In response
to the environmental movement, Congress passed new environmental laws.
Originally a nuclear research lab, ORNL evolved into a laboratory that
developed non-nuclear as well as nuclear energy sources. These non-nuclear
energy sources included coal and fusion. Technologies for conserving
energy were also being developed. ORNL researchers evaluated the health
and environmental risks of various energy sources.
researchers conducted tests on its new doughnut-shaped (tokamak)
fusion research machine, the ORMAK. During the 1970s researchers
also built and tested the ELMO Bumpy Torus and devices called Impurity
Study Experiments to illuminate the behavior of impurities inside
fusion reactor plasmas.
AEC prepare required envionmental impact statements for nuclear
power plants, ORNL researchers gathered needed data on the impacts
on fish of heated cooling water from these facilities. This research
led to strict temperature limits on nuclear plant discharges, resulting
in the installation of massive cooling towers.
safety research studies determined at what reactor temperatures
and pressures the cladding of nuclear fuel rods begins to collapse.
began a program of energy research, which later resulted in national
insulation standards, more efficient delivery of electrical power,
and more energy-efficient designs for refrigerators, heat pumps,
ovens, and water heaters.
at ORNL froze, thawed, and implanted mouse embryos in surrogate
mothers, who gave birth to healthy mouse pups. The technique was
adopted by the livestock industry for multiplying the reproductive
potential of prize cattle.
of stiffer nuclear safety criteria emerged after ORNL scientists
testified along with nuclear-power opponents at AEC's public hearings
on emergency cooling of reactor cores.
scientists analyzed moon rocks for uranium and thorium.
steel was developed at ORNL for the U.S. government's breeder reactor
project. It is now manufactured and marketed internationally for
use in electric utility boilers and oil refinery furnaces.
Reorganization Act created the Energy Research and Development
Administration (ERDA) and the U.S. Nuclear Regulatory Commission
(NRC) from the Atomic Energy Commission. Four years later, ERDA
became the Department of Energy (DOE), the major source of funding
to ORNL and other national labs.
of disruptions in the supply of Mideastern oil to the U.S., the
government started research on producing liquid and gaseous fuels
iridium alloy was created to contain plutonium fuel for radioisotope
thermoelectric generators that power the Voyager I, Voyager II,
Galileo, Ulysses, and Cassini spacecraft.
to 70% of sulfur and nitric acids deposited on ORNL's Walker Branch
Watershed forest was found to have arrived in dry particulates
rather than rain.
were developed to produce chemicals and fuels (e.g., ethanol from
corn) and treat waste streams.
researchers examine an abnormal cricket grown from an egg that had
been exposed to coal-derived chemicals.
researchers studies the composition and mobility of trace contaminants
found in the residues from various coal conversion processes.
effects of chemicals produced by converting coal to liquid and gaseous
fuels were studied. This work led to ORNL's developing the scientific
field of ecological risk assessment, including a risk assessment
method adopted by the U.S. Environmental Protection Agency.
began on Large Coil Test Facility for superconducting fusion magnets.
researchers developed a method for refueling fusion reactors by
injecting frozen hydrogen pellets into their plasmas. The pellet
injector (used at the Princeton Plasma Physics Laboratory's Tokamak
Fusion Test Reactor) was later adopted for tokamaks in Europe and
the United States. A year later, ORNL's neutral-beam injectors achieved
record fusion plasma temperatures at the PPPL.
angle X-ray scattering device became part of a National Center
for Small-Angle Scattering Research established at ORNL.
helped determine the cause of the loss-of-coolant accident at
the Three Mile Island nuclear power plant. They also assessed
the core damage, helped prevent the release of radioactively contaminated
gases, and devised ways to decontaminate thousands of gallons
of emergency coolant.
a renowned ORNL geneticist, discovered that ethylnitrosourea is
the most effective chemical in inducing mutations in mice. ENU
is now used widely to discover genes linked to human diseases.
Materials Lab That Matters (Top)
In the 1980s,
ORNL opened new "user" facilities to let outside scientists join ORNL
researchers in probing the nature of matter, developing improved materials
(especially for transportation vehicles), and studying ways to extract
more energy from matter. The new materials developed at the Laboratory
include ion-implanted alloys for knee and hip replacements, ductile
nickel aluminides for industrial uses, and whisker-toughened ceramics
for commercial cutting tools. Researchers also devised ways to form
tough, heat-resistant ceramics and shape these materials into automotive
turbines. ORNL researchers became more involved in transferring the
benefits of their work through licenses of their patented technologies
and cooperative research and development agreements with private companies.
Appleton, Jim Williams and others developed accelerator-based ion
implantation techniques to improve the properties of semiconductors,
metallic alloys, and ceramics. It was discovered that implanting
the surface of an artificial titanium-alloy knee or hip with nitrogen
ions greatly improves its resistance to wear and corrosion, delaying
the need for a painful replacement operation.
Heavy Ion Research Facility began operation on nuclear physics studies
and became a scientific user facility. The 25- million-volt electrostatic
accelerator, which was linked to the Oak Ridge Isochronous Cyclotron,
had the highest direct-voltage current in the world.
began developing whisker-toughened ceramics now used to make commercial
of parts, including tubing and ceramic heat-engine components
as well as cutting tools, can be made from ORNL's fracture-resistant
was begun to make brittle nickel aluminides ductile; ORNL's modified
aluminide alloys have been used in industrial heat-treating equipment,
rolls for making steel, and dies for making truck brake parts. Pictured
at left are modified nickel aluminide furnace trays that hold automobile
parts transferred to a furnace for heat treating at General Motors-Saginaw.
initiated an extensive ten-year study for the Nuclear Regulatory
Commission of fission product release (species and rates) from heated
nuclear reactor fuel. Results from this work continue to be referenced
as the best available information concerning potential release under
Large Coil Test Facility, researchers from several nations successfully
tested superconducting electromagnets half the size of those expected
to be used at future fusion power plants.
Carbon Dioxide Information Analysis Center, which was established
at ORNL to serve DOE's Carbon Dioxide Research Program, later became
an internationally known repository of data on global change. CDIAC
is one of the best known of ORNL's information centers, which started
with the nuclear data center in the 1940s. Information centers for
collecting, analyzing, and synthesizing information proliferated
at ORNL in the 1960s and 1970s. They embraced such areas as nuclear
safety, toxic materials, and the human genome.
designed the gas-fired triple effect absorption chiller for cooling
developed insulation standards adopted later by federal agencies
and standards to make electric appliances more efficient. ORNL designs
led to more efficient commercial heat pump water heaters and refrigerators.
concurrent computers were first operated at ORNL's Center for Engineering
Science Advanced Research to control robots. Bill Hamel and Chuck
Weisbin, then CESAR director, examine the HERMIES-II robot used
by CESAR for concept demonstrations of artificial intelligence planning
and learning algorithms.
Greenbaum studied photosynthetic water splitting using spinach and
later algae for releasing energy-rich gases, such as hydrogen.
first distributed memory parallel computer was delivered. This Intel
IPSC/1, which had 32 central processing units, was a predecessor
of the Intel Paragon supercomputer, which was installed at ORNL
HHIRF (Holifield Heavy Ion Research Facility) physicists discovered
the giant quadrupole resonance in nuclei bombarded with highly energetic
ions. In this phenomenon, the nucleus alternately compresses and
expands, causing many of its protons and neutrons to move at the
developed gelcasting, an advanced process for forming ceramic
material into complex shapes such as automotive turbines, accelerator
magnets, and artificial bone.
published the three-dimensional TORT radiation transport simulation
Temperature Materials Laboratory was completed, enabling research
on developing ceramics for the most energy-efficient engines and
high-temperature superconducting materials for efficient electricity
Temperature Materials Laboratory opened as a user facility. Guest
researchers from industry, academia, and other government laboratories
used HTML's suite of sophisticated instruments to characterize
their materials and determine how to improve them.
on the newly discovered phenomenon of high-temperature superconductivity,
ORNL researchers were among the first to use laser ablation to
make superconducting thin films.
Advanced Toroidal Facility began operating, allowing ORNL researchers
to learn more about the physics of fusion energy from experiments
on this stellarator.
Center for Global Environmental Studies was formed. ORNL is a
leader in studies of the environmental effects of increased atmospheric
concentrations of carbon dioxide.
began work with the Nuclear Regulatory Commission to develop the
Generic Environmental Impact Statement for use in renewing the
licenses of more than 100 U.S. commercial nuclear power plants.
A Partner in Solving Scientific Problems (Top)
ORNL is the
largest of the U.S. Department of Energy's five multipurpose, nonweapons
laboratories. We conduct research to help the federal government provide
leadership in key scientific areas, increase the availability of clean
abundant energy, restore and protect the environment, preserve national
security, and strengthen national economic competitiveness. We have
17 national DOE user facilities for researchers around the country.
In a partnership with five other DOE laboratories, we are building a
major scientific research facility, called the Spallation Neutron Source,
which will enable better understanding of physical and biological materials,
ranging from polymers to proteins. We also have a collection of 60,000
mice that are helping us further our success in finding better ways
to diagnose and treat disease.
imaging, developed at ORNL, allowed scientists using a scanning
transmission electron microscope to see columns of atoms in materials
ranging from superconductors to automobile catalysts.
used the Oak Ridge Electron Linear Accelerator to confirm the
existence of separate positive and negative electrical charges
(quarks) within the neutron. ORELA was later used to help shed
light on the synthesis of elements in the universe.
Deployment Analysis System (ADANS) computer code developed at
ORNL was used to efficiently deploy military personnel and equipment
to the Persian Gulf, Somalia, Rwanda, Haiti, and Bosnia.
activation analysis using reactors, which was pioneered at ORNL
and used for forensic, studies, was applied to hair and nail samples
from the grave of President Zachary Taylor. Results of the analysis
at ORNL's High Flux Isotope Reactor indicated he had not been poisoned
by arsenic while in office, as one historian suspected.
at ORNL and the University of Tennessee developed a parallel virtual
machine (PVM) software package that allows desktop computers linked
by a network to be used as a single large parallel computer. It
is being used worldwide to solve important scientific, industrial,
and medical problems.
researchers identified and cloned the mouse agouti gene, which causes
altered fur color, obesity, diabetes, and skin cancer in mice and
which has a human counterpart.
researchers developed a neural network system for recognizing
genes in DNA sequences sent to it by electronic mail. The Gene
Recognition and Analysis Internet Link (GRAIL) system is widely
isotope generator was developed to treat cancer-induced bone pain
and arthritis and prevent the buildup of smooth muscle cells in
coronary arteries after balloon angioplasty. Since the mid-1970s,
using radioisotopes from Laboratory sources, ORNL's nuclear medicine
researchers developed new radioactive imaging agents for medical
scanning diagnosis of heart disease.
Tuan Vo-Dinh and two medical researchers at Thompson Cancer Survival
Center of Knoxville developed a new laser technique for determining
without surgery whether a tumor in the esophagus is cancerous.
researchers developed mass spectrometry techniques for detecting
or analyzing explosives, engine exhaust, carriers of the cystic
fibrosis gene, and proteins. A direct-sampling ion trap mass spectrometer
devised to detect environmental pollutants will be used to detect
biological and chemical warfare agents.
researchers led by Mike Ramsey developed the "lab on a chip," which
shows promise as a fast and inexpensive method for DNA sequencing,
and forensic fingerprinting, environmental monitoring, diagnosing
disease and developing new drugs.
researchers developed the rolling-assisted biaxial textured substrates
(RABiTSTM) technique for fabricating nickel-based, high-temperature
superconducting wire. Above, Mariappan Paranthaman uses electron
beam evaporation to make a superconducting wire 7 centimeters long.
researchers led by Vinod Sikka developed a technique for efficiently
and safely melting and casting alloys of ORNL-designed nickel aluminides,
which are used by the automobile and steel industries.
researchers developed a more energy-efficient refrigerator-freezer
by altering a popular refrigerator model to cut its energy use in
Parker developed ALLIANCE, which directs teams of robots like these
in carrying out tasks cooperatively
Holifield Radioactive Ion Beam Facility, nuclear structure and nuclear
astrophysics studies began, using radioactive ions that do not exist
naturally on the earth. A radioactive fluorine beam was developed
to measure the rates of nuclear reactions that produce isotopes
in stars. ORNL supercomputers are used to model forces within exploding
stars (supernovae) that disseminate elements essential to life on
of the High Flux Isotope Reactor will allow it to lead the world
in both thermal and cold neutron intensities for use in neutron
science. Neutron scattering experiments at HFIR and elsewhere
have contributed information that has led to improved consumer
products, such as credit cards, computer disks, compact discs,
automatic windows, shatterproof windshields, and life-saving bulletproof
ecological experiment to determine the effects on forest growth
of increased concentrations of atmospheric carbon dioxide and reduced
of ORNL's 60,000 mice are now being scanned with the MicroCAT, a
high-resolution X-ray imaging device developed to noninvasively
detect internal genetic disorders in mammals whose parents were
exposed to radiation or chemicals.
sharpest electron microscope image of a crystal was recorded in
1998 at ORNL. This image of a silicon crystal had double (0.78 vs
1.6 Angstrom) the resolution of a typical transmission electron
Fan uses Z-contrast transmission scanning electron microscope to
study iodine-doped carbon nanotubes, strong materials that conduct