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This article also appears in the Oak Ridge National Laboratory
Review (Vol. 26, No. 1), a quarterly research and development
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CERAMIC-METAL COMPOSITE IDEAL FOR CUTTING TOOLS
If two heads are better than one, could two materials be better
than one? ORNL experts in ceramics and metals and an industrial
researcher have put their heads together and combined a ceramic and
a metal to make an advanced cutting tool material. The new
composite, which is made of the ceramic, tungsten carbide
chemically bonded with a modified nickel aluminide alloy developed
at ORNL, offers several advantages over the commercially used
material.
Tests show that the new material is harder and may last longer than
the ceramic tungsten carbide bonded with cobalt, another composite
used commercially throughout the world for dies to stamp out
beverage cans and other items, drilling equipment, and other
cutting tools. The new ceramic-metal composite is also less
expensive. It contains metals that are readily available because,
unlike cobalt, nickel and aluminum have no strategic value during
military crises. In addition, because of the excellent
high-temperature properties of the nickel aluminide, the material
may be used to make tools that can be operated at higher
temperatures.
Ceramics are hard but brittle, and metals are soft but
ductile--that is, they can be stretched and formed into shapes
without cracking. The new composite combines the strengths and
overcomes some of the weaknesses of the ceramic and the metal
alloy, forming a material that has both high hardness and fracture
toughness. It also combines the abilities of the ceramic to resist
wear and corrosion with the abilities of nickel aluminide to
withstand mechanical shock and deform under stress.
In the 1980s ORNL researchers led by C. T. Liu developed modified
nickel aluminide alloys that become stronger with increasing
temperature. To make the alloys more ductile so that they can be
shaped into components for high-temperature use, impurities such as
boron, chromium, molybdenum, and zirconium were deliberately added
in precisely measured amounts.
The new composite was made by mixing ceramic powder with a modified
nickel aluminide powder, which serves as a bonding agent to hold
the ceramic powder together. Heat and pressure are then applied
using such techniques as hot pressing, sintering, or compaction.
Tests of cutting tools made of the tungsten carbide-nickel
aluminide composite performed by Tennessee Technological University
have shown that the new composites are harder than conventionally
used cobalt-bonded tungsten carbide cutting tools.
Research begun in 1987 by Terry Tiegs and industrial collaborators
resulted in a patent on the use of intermetallic alloys as bonding
agents in ceramics in 1990 and another patent on the use of these
composites as cutting-tool materials in 1991.
Tiegs and his colleagues in the Metals and Ceramics Division have
fabricated composites using several different intermetallic alloys
in ceramic matrices such as tungsten carbide, titanium carbide,
titanium nitrite, aluminum oxide, and zirconium oxide. The use of
a wider range of metallic and intermetallic bonding alloys in
non-oxide and oxide-based ceramic matrices is being further
explored by Tiegs and Kathi Alexander, respectively.
Joachim Schneibel is developing the required alloys and evaluating
their mechanical and other properties. H. T. Lin and Paul F. Becher
are examining the properties of model composites to aid in
interpretation of the mechanical property results. In a
collaborative effort, researchers at the University of California
at Berkeley are investigating the fatigue properties of these
composites.
Further development of these composites is being supported by the
U.S. Department of Energy, Assistant Secretary for Conservation and
Renewable Energy, Office of Industrial Technologies, under the
Advanced Industrial Materials Program.
--Carolyn Krause
ENZYMES CONVERT COAL TO LIQUID FUEL
ORNL researchers have discovered that chemically modified enzymes
from bacteria can convert coal to liquid fuel.
"The idea of making liquid fuel from coal isn't altogether new, but
until recently, the thought of using enzymes as catalysts in the
process was not considered," says Chuck Scott, director of ORNL's
Bioprocessing Research and Development Center. In fact, until the
enzyme-modification work started at ORNL two-and-a-half years ago,
nobody realized that enzymes could effectively interact with coal
to make liquid fuel. "That knowledge simply did not exist," Scott
says.
However, now that Scott and his colleagues have developed a clean,
efficient way to convert solid coal to liquid fuel using chemically
modified bacterial enzymes, the idea is being given serious
consideration. The resulting liquid fuel is comparable to crude oil
and could be refined for use as a clean-burning alternative to
gasoline.
This development is particularly timely, coming on the heels of the
National Energy Policy Act of 1992. Among the goals of the act are
reducing the nation's energy consumption by 8 billion barrels of
oil and promoting the development of clean-burning alternative
fuels.
The enzymes Scott and his team are using are similar to those that
stimulate chemical reactions in the human body. For example,
enzymes in your stomach allow you to digest food; others play
critical roles in cell reproduction.
These coal-conversion enzymes normally function best in water, but
ORNL scientists discovered that certain enzymes, such as the
bacterial enzyme hydrogenase, can be modified with a chemical
called dinitrofluorobenzene, allowing them to be mixed with various
organic solvents to convert solid coal to a liquid fuel product
more efficiently.
To say that Scott's team has made the enzymes "usable" may fall
short of expressing the significance of their accomplishment. In
fact, the modified proteins are proving to be highly effective at
converting coal from a solid to a liquid. The researchers have been
able to convert more than 40% of solid coal particles to liquid.
"That's a significant quantity," Scott says, adding that the
quality of the liquid fuel obtained has been equally impressive.
The solid residue left by this process is still a combustible fuel,
so two usable fuels can be obtained from a single source--liquid
fuel, for possible use in engines, and solid fuel, which could be
used for a variety of purposes, such as heating water in
steam-driven power plants.
The ORNL coal-conversion technique could be scaled up to produce
large quantities of liquid fuels. In its current configuration, the
system uses a glass column approximately 15 centimeters (6 inches)
tall called a fluidized-bed bioreactor. The bioreactor is filled
with an organic solvent, such as benzene or purified kerosene,
modified enzymes, and coal particles suspended in the mixture.
The solvent, which carries the modified enzymes and hydrogen gas,
is constantly siphoned from the top of the column and pumped back
up through the bottom to ensure circulation through the suspended
coal particles. The hydrogen initiates the conversion from solid to
liquid by breaking chemical bonds that hold the coal together. The
modified enzymes enhance this hydrogen interaction.
As more solid coal is converted to a liquid, the solvent in the
bioreactor becomes increasingly dark. This effect allows the
researchers to determine the amount and rate of the conversion
process. A darker solvent--one containing a high percentage of
liquid fuel--will absorb more light. The researchers can determine
the conversion rate by comparing the increase in the amount of
light absorbed with each successive test with the time between
tests.
These experimental reactions are being accomplished at relatively
moderate temperatures and pressures compared to coal-conversion
methods used in the past, resulting in much less pollution. If the
technique proves economically feasible, Scott says, it may be
useful for large-scale production of alternative liquid fuel within
the next decade.
--Wayne Scarbrough
MORE FUNDING FOR GENOME RESEARCH
DOE has begun what could become a multimillion-dollar funding
effort for ORNL's work on the Human Genome Project, an
international effort to identify and characterize all of the genes
in human DNA. DNA (deoxy-ribonucleic acid) carries all of an
organism's genetic information, thereby providing the complete
blueprint for life.
"The contract represents the largest single piece of funding for
genome research throughout ORNL and is the culmination of
painstaking proposals and exhaustive peer review to demonstrate the
Laboratory's capabilities in genome research," says Fred Hartman,
director of ORNL's Biology Division. The work is being supported by
DOE's Office of Health and Environmental Research. To date, the
program has received some $600,000. Proposed funding for the 1993
fiscal year puts the total at more than $1 million.
A complete atlas of the human genome will revolutionize medical
practice and biological research, and it may be the foundation for
alleviating much of the human suffering brought on by genetic
diseases, researchers say.
The "open-ended" DOE contract is structured to run for the duration
of the Human Genome Project. "The lifetime of the project is
indefinite," Hartman said, "but it could certainly run as long as
10 years."
Over the years, Hartman and other division leaders have assembled
an elite team of scientists with world-class expertise in genetic
research, particularly in mouse genetics. A mouse's DNA has large
sections that closely correspond to sections of human DNA.
Scientists can therefore glean significant information about human
genetic disorders by observing genetic influences on the
development of mice.
Hartman said that ORNL's Biology Division offers considerable
expertise in gene function and regulation in model organisms, such
as mice. "In addition to an enviable 40-year track record of
outstanding accomplishments in classical mouse genetics research
under the leadership of William L. and Liane B. Russell, the
division has recently recruited staff members whose expertise
includes state-of-the-art technologies for targeting and
manipulating genes in living animals and for transferring genes
among animals. These are the very tools that will facilitate
diagnosing and ultimately ameliorating human genetic disorders."
A molecule of DNA, which is contained in a chromosome, is
approximately a meter long but is so compressed that it fits in the
nucleus of a cell only one micrometer (1/1000th of a millimeter) in
diameter. (For comparison, most cells are so small that a million
of them would not be much larger than the head of an ordinary pin.)
Genes lie at varying intervals along the strands of DNA.
Every cell in the human body contains the same array of chromosomes
and, hence, identical genetic information. All of the structural
and functional characteristics (i.e., what it's made of and what it
does) that distinguish the heart, lungs, kidneys, brain, muscles,
and everything else that compose a living creature are determined
by which genes are "turned on" and which genes are "turned off."
By pinpointing a gene's location in a strand of DNA and then
deciphering exactly which biological process the gene controls,
scientists hope to demystify genetically inherited diseases and to
gain the ability to diagnose them quickly and treat them
effectively.
The genome program at ORNL, coordinated by Biology Division member
Gene Rinchik, comprises four tasks, each separately focused yet
relating to the others. All incorporate the use of mouse DNA.
Task I, headed by group leader Lisa Stubbs, concentrates on
physical mapping, wherein scientists identify the location of genes
as they are situated along a strand of DNA. To date, the
approximate positions of some 2300 genes have been charted. The
human genome is estimated to comprise at least 100,000 genes,
possibly twice that number.
Tasks II and III, under the leadership of division members Rick
Woychik and Mike Mucenski, involve methods of determining the
function of individual genes or groups of genes. Scientists take
from a developing mouse embryo cells that contain strands of DNA.
They then insert short segments of foreign DNA into these cells to
"turn off" a single gene (Task II) or gene groups (Task III).
When the cells containing the altered DNA are put back into a
female mouse and allowed to gestate, the offspring will show
observable mutations. The mutation can be readily mapped because
the foreign DNA provides an obvious marker. Most mutations are not
extraordinary, but subtle, such as altered fur color, ear size, or
tail length. However, some of the mutations are more dramatic and
relate more closely to humans.
For instance, scientists may notice that mice develop a kidney
problem at a particular point in life if certain genes have been
"turned off." The researchers can then deduce that the inactivated
genes must have something to do with kidney development. By doing
similar research with fetal mice, scientists can better understand
how an organism develops almost from the time of conception.
The fourth task, involving the science of "informatics," ties the
project together in a computer data base, which is being developed
by Richard Mural of the Biology Division and Ed Uberbacher of the
Engineering Physics and Mathematics Division.
Because of the size of mammalian genomes (one billion to three
billion basic building blocks), the international project will
generate a vast amount of data. If compiled in books, the data
would likely fill 200 volumes, each the size of a 1000-page
Manhattan telephone directory. To read all the information
completely would require 26 years of round-the-clock concentration.
The informatics data base will allow researchers studying animal
chromosomes to quickly access and identify matching sequences of
human DNA as they search for genetic clones and will aid in
predicting protein sequence and structure--an important step in
understanding individual gene function.
--Wayne Scarbrough
GLOBAL WARMING AGENTS: TRACE GASES VS CO2
Although they are less abundant in the atmosphere, trace gases may
be worse than carbon dioxide (CO2) in contributing to global
warming, according to a report issued by ORNL's Carbon Dioxide
Information Analysis Center (CDIAC). Trace gases include nitrous
oxide (N2O) the chlorofluoro-carbons CFC-11 and CFC-12,
tropospheric ozone (O3), and halocarbons such as methane.
Excerpts from the report were quoted in the January-February 1993
issue of The Futurist magazine.
According to the ORNL report, "Although less abundant than either
CO2 or CH4 (methane), a number of other `minor' atmospheric trace
gases are also able to perturb the radiative energy balance of the
Earth-atmosphere system and are, therefore, potentially important
contributors to global climate change.
"Extrapolations of current trends in the atmospheric concentrations,
along with estimates of their relative abilities to alter the global
energy balance, suggest that the collective contribution of the minor
trace gases to any future global warming is likely to approach or
even exceed the contribution from CO2."
The source of the information was a chapter written by Bob Sepanski
in Trends '91: A Compendium of Data on Global Change, a widely
distributed CDIAC document.
(keywords: ceramic cutting tools coal conversion, Human Genome
Project, carbon dioxide)
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Date Posted: 1/26/94 (ktb)