'Nano-Cables in the Melt'.
When Robert Job was 14 years old, he stripped his motherOs Electrolux vacuum cleaner and used it to build a blower for a forge in his backyard. Since then, his avocational passion has been the search for the ultimate steel. In l982, he rediscovered the process for casting Wootz, a premier steel made in ancient India that gained renown in Europe as Damascus steel. The casting process had been lost for almost 300 years. "Making the rediscovery," says Job, "required extensive experimentation and metallurgical testing, all guided by insights gained through intense study of archaeological records."
In contrast, the discovery in 1991 of a metallofullerene-based steel in which many of the carbon atoms have formed spherical molecules, which in turn are linked through iron atoms into long coiled cables, was a matter of serendipity. It was a failed experiment, the product of which Job recognized as having extraordinary properties. "My furnace shut down due to a clogged fuel-oil burner while I was melting an ingot of the Wootz," says Job. "By the time I fixed the furnace and was able to stabilize the temperature at or near 1,450[inverted exclamation mark]C (2,642[inverted exclamation mark]F), the melt had been cooled and reheated several times. Assuming that such erratic heating and cooling must have destroyed the desired properties of the metal, I turned off the furnace and let it cool."
Surprisingly, the color and surface texture of the steel from the failed melt was demonstratively different from the standard Wootz that Job had produced dozens of times before. Cutting through the new material with a standard 11-inch-diameter abrasive cutoff wheel was nearly impossible. When Job tried to slice through this strange ingot, it ground down the cutoff wheel, displaying wear resistance unheard of in normal high-carbon steel. Furthermore, the amount of metal burning experienced during the cutting was much smaller than is common for such processes.
The cut sections showed little or none of the "blueing" that is typical of such high-temperature abrasion in high-carbon steel. This indicated that the new material must conduct heat much better than normal-carbon steel. The material also felt unusually smooth or slick to the touch in the cut areas, and it was so abnormally ductile that by hammering it cold Job was actually able to flatten it without producing observable cracks. He also noticed that deep cuts and crevices seemed to "fill in" after time. This "self-healing" process had not been reported in standard steels up to this point.
Coupons and 'fluff'
Following his initial metallurgical analysis of the material, Job knew he had stumbled upon something totally different from anything previously encountered in metallurgical science, certainly different from anything published openly in recent metallurgical literature.
Examination of the new steel by the then new and advanced electron microscope at the nearby Universities of South Carolina at Columbia and North Carolina at Charlotte (UNCC) revealed a molecular structure unlike any Job or his associates had seen before.
When Job tried to replicate the structures he had seen under the microscope by making multiple heats in his foundry lab, he soon discovered that he could. Again and again, these same structures formed in the steel. Studying that process, Job confirmed a growing sense that the formation of the unusual structures was altering the course of the remaining melt cycle. In effect, the structures became the controlling factor in the subsequent stages of forming the final metal alloy.
Returning to the university lab, Job took with him not only standard metallurgical coupons (testing samples) of the new carbon steel but a remarkable black "fluff" that remained after chemists at UNCC boiled small coupons of the material in 50 percent hydrochloric acid covered with the solvent toluene for several days. "Conventional carbon steel," explains Job, "would have been totally dissolved with no solid remains after such treatment."
At a magnification of 1 million, the fluff appeared as strings of some kind of beads. But what were these beads that could survive the hugely corrosive boiling bath of hydrochloric acid? Sidestepping the need to know the specifics of the beadsO composition, Job named the new material Rhondite, after his supportive and certainly patient wife, Rhonda. It was only after two more years of extensive analysis that the structures would be confirmed as matching unexpected molecular structures that scientists around the globe were only just beginning to understand and confirm: fullerenes.
Like the discovery of Rhondite, the discovery that 60 carbon atoms could link together into a hollow, spherical molecule was itself a serendipitous discovery. In 1985, Richard Smalley of Rice University and Sir Harry Kroto of the University of Sussex had shown through their research that cyanopolyynes (particular kinds of molecules of carbon, nitrogen, and hydrogen) could form in carbon-rich giant stars. In the course of their research, however, they also saw evidence of a completely new form of carbon. After five years they confirmed, and were able to persuade a doubting scientific community, that they had discovered a hollow spherical molecule made of 60 carbon atoms (hence C60). They further demonstrated that the 60 atoms were arranged in a pattern found not only in soccer balls but also in domes designed by the late engineer and architect Buckminster Fuller. In honor of Fuller, the molecules were formally named buckminsterfullerenes, or fullerenes for short. The most common 60-atom variant was called buckyballs. Smalley and Kroto were awarded the 1996 Nobel Prize in chemistry for their discovery.
Once the fullerenes were accepted into the scientific worldview, a great outburst of fullerene research ensued. This research revealed that C60 is but one of a large family of closed, hollow, and even tubelike carbon molecules ranging from 28 to more than 1,000 carbon atoms for the spheroidal fullerenes and more than one million for fullerene tubes [see "Soccer-Ball Carbon," The World & I, April 1993, p. 202, and "The WorldOs Tiniest Tubes," The World & I, August 1997, p. 152]. Despite the great outpouring of research papers, however, few commercial applications for fullerenes have been developed. Looking for reasons for this slow development, one quickly realizes that the lack of a cost-effective way of making fullerenes has been a major barrier.
In the meantime, working outside the mainstreams of chemistry and physics in which most fullerene research was conducted, Job and his small research team realized and confirmed, over two years and hundreds of tests, that the new rhonditic steel was a veritable warehouse full of fullerenes. For this work, Job's primary collaborators were his chief metallurgical engineer, Jim Craig, and his applied research engineer, Tim Pinder. Not only were the spherical carbon molecules abundant but many of them were linked systematically through iron intermediary atoms into long cables, somewhat like beads on a necklace. Furthermore, pairs of those long cables were often coiled into helical structures reminiscent of DNA molecules, which in turn could coil and coil again, forming double-, triple-, and even quadruple-wound cables.
All these levels of structure forming inside the steel melt offered a new world of microenvironments in which atoms of iron, carbon, and alloy metals could solidify individually or as carbide compounds. Thus, individual units or clusters of these could be trapped inside individual spherical molecules, inside the coils at any level, or between adjoining loops of the coils. The interactions of the coils plus the trapped units produced new crystalline structures and patterns that had never been seen before.
Job had stumbled upon a whole different world of metal-forming dynamics. Now earlier observations that formation of the rhonditic steel structure incorporating metallofullerenes alters the later metal- forming process made sense. The metallofullerenes were tying up carbon atoms that otherwise would have remained freely available to interact with iron atoms in the course of forming the carbon steel. In addition, they were physically controlling grain and carbide growth and distribution throughout the material.
Although the first fullerene identified in rhonditic steel was the soccer-ball-like C60 molecule, later more refined analysis and varied experimentation has identified many species of metallofullerenes in rhonditic alloys. The smallest of these consists of 28 carbon atoms trapping a single iron atom inside (represented by C28to date is C200arbon atoms with 3 iron atoms inside.
The scientific community for several years rejected JobOs material and data. While various reasons could be suggested for this, one major factor was that JobOs assertion that fullerenes were forming in a molten metal placed the process off the map of mainstream scientific understanding and investigation. The pure C60 made in the gas phase in a high vacuum at or near 1,500[inverted exclamation mark]C (2,732[inverted exclamation mark]F) breaks down in the open atmosphere at about 400[inverted exclamation mark]C (752[inverted exclamation mark]F), but JobOs material is made in a vacuum as well as in open furnaces at or near 1,500[inverted exclamation mark]C. How is this possible?
Today Job offers a plausible explanation. "We now know that as fullerene molecules form and become intimately and systematically interactive with multitudes of metal atoms, they self-organize into the highly stable nano-cables, which are much more stable than individual fullerenes formed in the pure state through the gas phase process. The metallofullerene nano-cables are bound very strongly together with covalent and valent bonding, while their pure fullerene cousins at best form only weakly bonded crystalline structures."
From the perspective of carbon atoms seeking to make the lowest energy associations, the molten iron at or near 1,500[inverted exclamation mark]C is itself an inert, low-pressure "atmosphere." Inside the melt, the carbon is free to combine into its lowest net energy ordered state--first as metallofullerenes (fullerenes with one or more iron atoms inside or outside the ball), then as the distinctive self-organized metallofullerene nano-cables. The cause of the nano-cable formation may be nothing more sophisticated than the availability of two factors: metal atoms that can go inside and between the fullerene carbons, and adequate time under prime fullerene-forming conditions. Readily available metal atoms are naturally provided by the molten metal, while the extended time is achieved by cycling the temperature and carbon content of the melt up and down within a "thermo-cycling window" defined by critical ranges of temperature and carbon concentration. The process controls temperature and carbon concentration not only by heating but also by adding powders of low-carbon metals at strategic moments in the process. In this way, the protocols for making the rhonditic-phase structure allow orders of magnitude more time for forming the nano-cables than is allowed for forming fullerenes in the generally accepted gas-phase protocols.
In the thermo-cycling window discovered by Job, the carbon-steel melt is neither purely solid nor purely liquid. "In that range of temperature and percent of carbon," says Job, "the melt is like mush, with granules of low-carbon iron suspended in molten high-carbon iron that also contains free carbon atoms." As the melt is heated and cooled within the thermo-cycling window, carbon diffuses into or out of the high-carbon granules. This traps the free carbon in a low-energy ordered state in which the carbon is free to anneal into the distinctive fullerene form.
Job has devised a system with enough controllable variables to give good regulation of the nature and quantity of nano-cables formed. Experimental evidence has confirmed that Job's team has succeeded in creating over 100 alloys of carbon, stainless, and high-strength nickel cobalt steels. In addition, they have created a variety of metal matrix composites containing metallofullerene nano-cables that formed and self-organized in the melt.
Furthermore, "Recent experiments involving alternative thermo-cycling protocols have revealed," says Job, "that cycling in the 1,200--1,300[inverted exclamation mark]C (2,162--2,552[inverted exclamation mark]F) temperature range with the late heat addition of ultra-low-carbon metal (in this case, iron) allows large--on the order of 2+ microns long--'bucky tubes' to form." These are cylinders made of carbon atoms whose orderly array demonstrates symmetry patterns similar to those shown in the buckyballs.
Perhaps the most astonishing aspect of the rhonditic, self-organized, macromolecular structures is their economy of manufacture. Exhaustive tests have shown that rhonditic alloys can be manufactured in units of 300 to 6,000+ pounds (136--2,727+ kilograms) in every type of furnace system--from the most ancient gas muffle systems to the most advanced vacuum-induction and carbon-arc furnace systems--utilized throughout the world today. Even more astonishing is the fact that the rhonditic phase can be successfully formed in virtually any alloy chemistry, including certain types of ultra-low-carbon alloys of iron, nickel, and cobalt that traditionally treat high levels of carbon as a "poison."
Experimental evidence shows that fullerene species have a tendency to mix and bond irrespective of what alloys are involved. In a seemingly total disregard for the alloy chemistry, the fullerenes bond with diverse transitional metals into the distinctive double alpha helix nano-cables, which then form the higher-level cables.
These structures are the only way to explain the fact that a 1.2 percent carbon rhonditic steel with no added alloying metal proved to have a wear resistance four times greater than Stellite, an alloy that is widely used in industry because of its extreme wear resistance. Stellite is a steel alloyed with a high percentage of cobalt, a somewhat rare and hence costly metal. Eliminating the need for cobalt, rhonditic steel can be produced for less than 1 percent of the cost of making Stellite.
Other comparisons are just as remarkable. Compared with standard carbon steel of a given percent of carbon, rhonditic steel can be as much as three times stronger (in load-bearing capability), more than twice as corrosion resistant, and as much as three times tougher (based on standard impact tests of resistance to brittle fractures).
When alloying metals are included in a carbon steel melt and processed by the rhonditic protocols, the resulting rhonditic alloy generally outperforms the comparable standard alloy--and without the secondary treatment often required for standard alloys. Consider, for example, stainless steel, an alloy of carbon steel and chromium that is widely used in both industry and consumer applications. Comparing the standard so-called AISI 304 stainless steel with the comparable 304 rhonditic stainless steel shows the rhonditic 304 outperforming the standard stainless 304 in every category. In addition, unlike standard 304, rhonditic 304 can be continuous cast into parts that are nearly the correct size and shape ("near net" parts) without further heat treatment.
Subsequent testing has proven that many rhonditic alloys are superplastic (easily deformable) at approximately 975[inverted exclamation mark]C (1,800[inverted exclamation mark]F) while retaining substantial strength well above temperatures at which the normal alloys would begin to fail. What this means is that a manufacturer can realize huge savings by using rhonditic 304 to produce near net cast parts instead of using standard 304, which requires the costly and time-consuming procedures common today. These often involve carving out (machining) parts from large, roughly sized and shaped chunks of the alloy and then heat-treating them, in some cases many times.
Welcome to the new world of metals processing in which, for example, rhonditic stainless steel can be continuously cast into tubes with properties superior to those of standard grades of welded-seam stainless tubing, which is rolled and heat-treated through more than 10 steps.
JobOs work, which has already earned worldwide patents, opens a new vista of commercially viable applications for materials in fields ranging from the most intricate aerospace parts to surgical needles, road grader blades, ball bearings, and structural I-beams. Furthermore, beyond the more conventional and obvious types of metal alloys with which one can apply the rhonditic protocols, other materials can benefit from the use of rhonditic materials as catalysts. For example, experimentation with silicon, the big brother of carbon in the periodic table of elements, has shown that a proprietary rhonditic alloy acts as a catalyst leading to the formation of a previously unreported structure in silicon that is at least as conductive as gold. At the same time, this new form of silicon is fully stable in the open atmosphere and costs less than 10 cents an ounce to make! A second example of the still largely unexplored potency of rhonditic alloys as catalysts is the creation of fully stable aluminum carbide for less than $1 per pound, a radically low cost by todayOs standards.
While other companies and researchers, through licensing agreements, pursue commercial applications of the great family of rhonditic materials already discovered, Job and his associates continue to explore new territories for applying the rhonditic protocols. In this way, they have made a material whose nano-scale crystalline structure permits a read-write memory capability, and they have devised a methodology for inexpensively manufacturing a whole family of nano-size spheroidal carbides for use in metal matrix composites.
Licenses covering applications of specific classes of rhonditic material in broad areas of technology are under negotiation with several major companies, while one agreement--with the Aerospace Division of BF Goodrich--has already been signed. Most immediately, ongoing negotiations with the major automotive and trucking companies indicate new applications for passenger and freight vehicles just over the horizon. Beyond that, several license negotiations are still in preliminary stages.
As the new millennium dawns, the growing family of fullerene-enhanced alloys offers humanity a choice. Will we continue to use twentieth- century alloys, or will we shift to twenty-first-century alloys that give the same performance with lighter weight, lower cost, fewer resource and energy inputs, and thus less demand on the environment?
Since twentieth-century furnaces can be readily adapted to making rhonditic materials, and twentieth-century industrial plants can be readily adapted to working with rhonditic materials, it might seem there would be no barriers to the shift. Yet the inertia of old ways of thinking and acting can be powerfully fixed. One hopes the push of environmental constraints and the pull of competitive advantage will conspire to bring us the benefits of metallofullerene alloys early in the twenty-first century.
Jennifer Job, Robert JobOs daughter, is a freelance writer residing in Matthews, North Carolina.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||cheaper, stronger metal alloys are developed|
|Publication:||World and I|
|Date:||Apr 1, 1999|
|Previous Article:||Inside the Federal Reserve.|
|Next Article:||Thailand: Lessons From a Strong National Response to HIV/AIDS.|