Over the millennia human beings have tinkered with substances to devise new and useful materials not ordinarily found in nature. But little prepared the world for the explosion in materials research that marked the 20th century. From automobiles to aircraft, sporting goods to skyscrapers, clothing (both everyday and super-protective) to computers and a host of electronic devices—all bear witness to the ingenuity of materials engineers.
| 1907 |
Bakelite created Leo Baekeland, a Belgian immigrant to the United States, creates Bakelite, the first thermosetting plastic. An electrical insulator that is resistant to heat, water, and solvents, Bakelite is clear but can be dyed and machined. |
|
| 1909 |
Precipitation hardening discovered Alfred Wilm, then leading the Metallurgical Department at the German Center for Scientific Research near Berlin, discovers "precipitation hardening," a phenomenon that is the basis for the creation of strong, lightweight aluminum alloys essential to aeronautics and other technologies in need of such materials. Many other materials are also strengthened by precipitation hardening. |
|
| 1913 |
Stainless steel is rediscovered Although created earlier in the century by a Frenchman and a German, stainless steel is rediscovered by Harry Brearley in Sheffield, England, and he is credited with popularizing it. Made of iron with about 13 percent chromium and a small portion of carbon, stainless steel does not rust. |
|
| 1915 |
Pyrex Corning research physicist Jesse Littleton cuts the bottom from a glass battery jar produced by Corning, takes it home, and asks his wife to bake a cake in it. The glass withstands the heat during the baking process, leading to the development of borosilicate glasses for kitchenware and later to a wide range of glass products marketed as Pyrex. |
|
| 1925 |
18/8 austenitic grade steel adopted by chemical industry A stainless steel containing 18 percent chromium, 8 percent nickel, and 0.2 percent carbon comes into use. Known as 18/8 austenitic grade, it is adopted by the chemical industry starting in 1929. By the late 1930s the material’s usefulness at high temperatures is recognized and it is used in the production of jet engines during World War II. |
|
| 1930 |
Synthetic rubber developed Wallace Carothers and a team at DuPont, building on work begun in Germany early in the century, make synthetic rubber. Called neoprene, the substance is more resistant than natural rubber to oil, gasoline, and ozone, and it becomes important as an adhesive and a sealant in industrial uses. |
|
| 1930s |
Glass fibers become commercially viable Engineers at the Owens Illinois Glass Company and Corning Glass Works develop several means to make glass fibers commercially viable. Composed of ingredients that constitute regular glass, the glass fibers produced in the 1930s are made into strands, twirled on a bobbin, and then spun into yarn. Combined with plastics, the material is called fiberglass and is used in automobiles, boat bodies, and fishing rods, and is also made into material suitable for home insulation. |
|
| 1933 |
Polyethylene discovered
|
|
| 1934 |
Nylon
|
|
| 1936 |
Clear, strong plastic The Rohm and Haas Company of Philadelphia presses polymethyl acrylate between two pieces of glass, thereby making a clear plastic sheet of the material. It is the forerunner of what in the United States is called Plexiglass (polyvinyl methacrylate). Far tougher than glass, it is used as a substitute for glass in automobiles, airplanes, signs, and homes. |
|
| 1938 |
DuPont discovers Teflon Annoyed one day that a tank presumably full of tetrafluoroethylene gas is empty, DuPont scientist Roy Plunkett investigates and discovers that the gas had polymerized on the sides of the tank vessel. Waxy and slippery, the coating is also highly resistant to acids, bases, heat, and solvents. At first Teflon is used only in the war effort, but it later becomes a key ingredient in the manufacture of cookware, rocket nose cones, heart pacemakers, space suits, and artificial limbs and joints. |
|
| 1940s |
Nickel-based superalloys Metallurgists develop nickel-based superalloys that are extremely resistant to high temperatures, pressure, centrifugal force, fatigue, and oxidation. The class of nickel-based superalloys with chromium, titanium, and aluminum makes the jet engine possible, and is eventually used in spacecraft as well as in ground-based power generators. |
|
| 1940s |
Ceramic magnets Scientists in the Netherlands develop ceramic magnets, known as ferrites, that are complex multiple oxides of iron, nickel, and other metals. Such magnets quickly become vital in all high-frequency communications, including the sound recording industry. Nickel-zinc-based ceramic magnets eventually become important as computer memory cores and in televisions and telecommunications equipment. |
|
| 1945 |
Barium titanate developed Scientists in Ohio, Russia, and Japan all develop barium titanate, a ceramic that develops an electrical charge when mechanically stressed (and vice versa). Such ceramics advance the technologies of sound recordings, sonar, and ultrasonics. |
|
| 1946 |
Tupperware As a chemist at DuPont in the 1930s, Earl Tupper develops a sturdy but pliable synthetic polymer he calls Poly T. By 1947 Tupper forms his own corporation and makes nesting Tupperware bowls along with companion airtight lids. Virtually breakproof, Tupperware begins replacing ceramics in kitchens nationwide. |
|
| 1950s |
Silicones Silicones, a family of chemically related substances whose molecules are made up of silicon-oxygen cores with carbon groups attached, become important as waterproofing sealants, lubricants, and surgical implants. |
|
| 1952 |
Glass into fine-grained ceramics Corning research chemist S. Donald Stookey discovers a heat treatment process for transforming glass objects into fine-grained ceramics. Further development of this new Pyroceram composition leads to the introduction of CorningWare in 1957. |
|
| 1953 |
Dacron DuPont opens a U.S. manufacturing plant to produce Dacron, a synthetic material first developed in Britain in 1941 as polyethylene terephthalate. Because it has a higher melting temperature than other synthetic fibers, Dacron revolutionizes the textiles industry. |
|
| 1953 |
High-density polyethylene Karl Zeigler develops a method for creating a high-density polyethylene molecule that can be manufactured at low temperatures and pressures but has a very high melting point. It is made into dishes, squeezable bottles, and soft plastic materials. |
|
| 1954 |
Synthetic diamonds Working at General Electric’s research laboratories, scientists use a high-pressure vessel to synthesize diamonds, converting a mixture of graphite and metal powder to minuscule diamonds. The process requires a temperature of 4,800°F and a pressure of 1.5 million pounds per square inch, but the tiny diamonds are invaluable as abrasives and cutting points. |
|
| 1954 |
Synthetic zeolites Following work done in the late 1940s by Robert Milton and Donald Breck of the Linde Division of Union Carbide Corporation, the company markets two new families of synthetic zeolites (from the Greek for "boiling stone," referring to the visible loss of water that occurs when zeolites are heated) as a new class of industrial materials for separation and purification of organic liquids and gases. As the key materials for "cracking"—that is, separating and reducing the large molecules in crude oil—they revolutionize the petroleum and petrochemical industries. Synthetic zeolites are also put to use in soil improvement, water purification, and radioactive waste treatment, and as a more environmentally friendly replacement in detergents for phosphates. |
|
| 1955 |
High molecular weight polypropylene developed Building on the work of Karl Ziegler, Giullo Natta in Italy develops a high molecular weight polypropylene that has high tensile strength and is resistant to heat, ushering in an age of "designer" polymers. Polypropylene is put to use in films, automobile parts, carpeting, and medical tools. |
|
| 1959 |
"Float" glass developed British glassmakers Pilkington Brothers announce a revolutionary new process of glass manufacturing developed by engineer Alastair Pilkington. Called "float" glass, it combines the distortion-free qualities of ground and polished plate glass with the less expensive production method of sheet glass. Tough and shatter-resistant, float glass is used in windows for shops and skyscrapers, windshields for automobiles and jet aircraft, submarine periscopes, and eyeglass lenses. |
|
| 1960s |
Large single crystals of silicon grown Engineers begin to grow large single crystals of silicon with nearly perfect purity and perfection. The crystals are then sliced into thin wafers, etched, and doped to become semiconductors, the basis for the electronics industry. |
|
| 1962 |
Nickel-titanium (Ni-Ti) alloy shape memory Researchers at the Naval Ordnance Laboratory in White Oak, Maryland, discover that a nickel-titanium (Ni-Ti) alloy has so-called shape memory properties, meaning that the metal can undergo deformation yet "remember" its original shape, often exerting considerable force in the process. Although the shape memory effect was first observed in other materials in the 1930s, research now begins in earnest into the metallurgy and practical uses of these materials. Today a number of products using Ni-Ti alloys are on the market, including eyeglass frames that can be bent without sustaining permanent damage, guide wires for steering catheters into blood vessels in the body, and arch wires for orthodontic correction. |
|
| 1964 |
Acrylic paints Chemists develop acrylic paints, which dry more quickly than previous paints and drip and blister less. They are used for fabric finishes in industry and on automobiles. |
|
| 1964 |
Carbon fiber developed British engineer Leslie Phillips makes carbon fiber by stretching synthetic fibers and then heating them to blackness. The result is fibers that are twice as strong as the same weight of steel. Carbon fibers find their way into bulletproof vests, high performance aircraft, automobile tires, and sports equipment. |
|
| 1970s |
Amorphous metal alloys created Amorphous metal alloys are made by cooling molten metal alloys extremely rapidly (more than a million degrees a second), producing a glassy solid with distinctive magnetic and mechanical properties. Such alloys are put to use in signal and power transformers and as sensors. |
|
| 1977 |
Electrically conducting organic polymers discovered Researchers Hideki Shirakawa, Alan MacDiarmid, and Alan Heeger announce the discovery of electrically conducting organic polymers. These are developed into light-emitting diodes (LEDs), solar cells, and displays on mobile telephones. The three are awarded the Nobel Prize in chemistry in 2000. |
|
| 1980s |
Rare earth metals Materials engineers develop "rare earth metals" such as iron neodymium boride, which can be made into magnets of high quality and permanency for use in sensors, computer disk drives, and automobile electrical motors. Other rare earth metals are used in color television phosphors, fluorescent bulbs, lasers, and magneto-optical storage systems with a capacity 15 times greater than that of conventional magnetic disks. |
|
| 1986-1990s |
Synthetic skin Engineers develop "synthetic skin." One type seeds fibroblasts from human skin cells into a three-dimensional polymer structure, all of which is eventually absorbed into the body of the patient. Another type combines human lower skin tissue with a synthetic epidermal or upper layer. |
|
| 1990s-present |
Nanotechnology Scientists investigate nanotechnology, the manipulation of matter on atomic and molecular scales. Electronic channels only a few atoms thick could lead to molecule-sized machines, extraordinarily sensitive sensors, and revolutionary manufacturing methods. |
In the decades to come, however, there would be many more claimants to wonder-working glory—among them other metals, polymers, ceramics, blends called composites, and the electrically talented group known as semiconductors. Over the course of the 20th century, virtually every aspect of the familiar world, from clothing to construction, would be profoundly changed by new materials. High performance materials would also make possible some of the century's most dazzling technological achievements: airplanes and spacecraft, microchips and magnetic disks, lasers and the fiber-optic highways of the Internet. And behind all that lies another, less obvious, wonder—the ability of scientists and engineers to customize matter for particular applications by manipulating its composition and microstructure: they start with a design requirement and create a material that answers it.
Of the various families of metals represented among high performance materials, steel still stands supreme in both versatility and volume of production. Hundreds of alloys are made by adding chromium, nickel, manganese, molybdenum, vanadium, or other metals to the basic steel recipe of iron plus a small but critical amount of carbon. Some of these alloys are superstrong or ultrahard; some are almost impervious to corrosion; some can withstand constant flexing; some possess certain desired electrical or magnetic properties. Highly varied microstructures can be produced by processing the metal in various ways.
Until well into the 20th century, new steel alloys were concocted mainly by trial-and-error cookery, but steelmakers at least had the advantage of long experience—3 millennia of it, in fact. That wasn't the case with aluminum, the third most common element in Earth's crust, yet never seen in pure form until 1825. It was heralded as a marvel—light, silvery, resistant to corrosion—but the metal was so difficult to separate from its ore that it remained a rarity until the late 19th century, when a young American, Charles Martin Hall, found that electricity could pull aluminum atoms apart from tight-clinging oxygen partners. Extensive use was still blocked by the metal's softness, limiting it to such applications as jewelry and tableware. But in 1906 a German metallurgist named Alfred Wilm, by happy chance, discovered a strengthening method. He made an alloy of aluminum with a small amount of copper and heated it to a high temperature, then quickly cooled it. At first the aluminum was even softer than before, but within a few days it became remarkably strong, a change caused by the formation of minute copper-rich particles in the alloy, called precipitation hardening. This lightweight material became invaluable in aviation and other transportation applications.
In recent decades other high performance metals have found important roles in aircraft. Titanium, first isolated in 1910 but not produced in significant quantities until the 1950s, is one of them. It is not only light and resistant to corrosion but also can endure intense heat, a requirement for the skin of planes traveling at several times the speed of sound. But even titanium can't withstand conditions inside the turbine of a jet engine, where temperatures may be well above 2,000° F. Turbine blades are instead made of nickel- and cobalt-based materials known as superalloys, which remain strong in fierce heat while spinning at tremendous speed. To ensure they have the maximum possible resistance to high-temperature deformation, the most advanced of these blades are grown from molten metal as single crystals in ceramic molds.
Another major category of high performance materials is that of synthetic polymers, commonly known as plastics. Unknown before the 20th century, they are now ubiquitous and immensely varied. The first of the breed was created in 1907 by a Belgium-born chemist named Leo Baekeland. Working in a suburb of New York City, he spent years experimenting with mixtures of phenol (a distillate of coal tar) and formaldehyde (a wood-alcohol distillate). Eventually he discovered that, under controlled heat and pressure, the two liquids would react to yield a thick brownish resin. Further heating of the resin produced a powder, which became a useful varnish if dissolved in alcohol. And if the powder was remelted in a mold, it rapidly hardened and held its shape. Bakelite, as the hard plastic was called, was an excellent electrical insulator. It was tough; it wouldn't burn; it didn't crack or fade; and it was unaffected by most solvents. By the 1920s the translucent, amber-colored plastic was everywhere—in pipe stems and toothbrushes, billiard balls and fountain pens, combs and ashtrays. It was "the material of a thousand purposes," Time magazine said.
Other synthetic polymers soon emerged from research laboratories in the United States and Europe. Polyvinyl chloride, useful for adhesives or in hardened sheets, appeared in 1926. Polystyrene, which yielded very lightweight foams, was introduced in 1930. A few years later came a glass substitute, chemically known as polymethyl methacrylate but sold under the name of Plexiglas.
During this period of plastics pioneering, many chemists were convinced that the new materials were composed of small molecules of the sort familiar to their science. A German researcher named Hermann Staudinger had a very different vision, however. Polymers, he said, were made up of extremely long molecules comprising thousands of subunits linked together in various ways by chemical bonding between carbon atoms. His insight, ultimately honored with a Nobel Prize, won general acceptance by the mid-1930s and gave new momentum to the polymer hunt.
A leader of that effort was Wallace Carothers, a young chemist at E. I. du Pont de Nemours & Company. In 1930 he and his research team created neoprene, a synthetic rubber that was more resistant to corrosive chemicals than vulcanized natural rubber. The team then began trying to develop a synthetic fiber from organic building blocks that would bond in the same way amino acids join up to form the protein molecules in silk. The payoff came in 1934 when one of the researchers dipped a rod into a beaker full of syrupy melt. When he pulled the rod out, a thread of the viscous substance came with it, and the stretching and subsequent curing of the strand transformed it into a substance of remarkable strength and elasticity. This was nylon, soon produced in quantity for stockings, toothbrush bristles, and such wartime uses as parachute cloth, ropes, and reinforcement for tires. Because of its low friction and high resistance to wear, nylon also proved valuable for gears, rollers, fasteners, and zippers.
The menu of valuable polymers continued to grow steadily. Polyethylenes, suitable for making bottles, appeared in 1939. Polyester fibers, destined to be a staple of the apparel industry, arrived in 1941. A vinyl-based transparent film called Saran, useful for wrapping food, was developed in 1943. Dacron, whose applications ranged from upholstery to grafts to repair blood vessels, hit the market in 1953. Lycra spandex fiber that could stretch as much as five times its length without permanent deformation was introduced in 1958. Kevlar, a fiber five times stronger than steel on a density-adjusted basis, was launched in 1973. By 1979 the annual production volume of polymers surpassed that of all metals combined. A famously pithy bit of career advice in The Graduate, a late 1960s film, summed up the situation well: when the hero asks someone about promising fields for employment, he is told simply, "plastics."
Ceramics, which include all inorganic nonmetallic materials, constitute another high performance category. Some of them are commonplace. The cement and concrete used for highways and other construction purposes are manufactured in greater volume than any other product. At the opposite extreme are synthetic diamonds, first made by General Electric in 1955 by subjecting graphite to temperatures above 3,000°F and pressures of more than a million pounds per square inch. Diamond is a paragon among materials in many ways—the hardest of all substances, the most transparent, the best electric insulator, with the highest thermal conductivity and highest melting point. As grit or small crystals, synthetic diamonds give an ultrahard coating to such industrial equipment as grinding wheels or mining drills. In addition, diamond films for optical or electronic applications can be grown by heating a carbon-containing gas such as methane to very high temperatures at low pressures. Other ceramics include oxides, carbides, nitrides, and borides, all of them very hard, brittle and resistant to corrosion, high temperatures, and electric current. Some ceramics are so strong that they have replaced steel as the armor for military vehicles.
Perhaps nowhere has the promise of ceramics been more tantalizing than in the quest for materials called superconductors, which can carry electric current with zero resistance—that is, without giving up any of the energy as heat. The phenomenon of superconductivity was discovered back in 1911 by Dutch physicist Kamerlingh Onnes. He cooled mercury to 4.2 K (-452°F), just 4 degrees above absolute zero, and observed that all electrical resistance disappeared. (Scientists commonly use the Kelvin scale for studies in the realm of the supercold, with temperatures measured in Kelvin (K). On this scale, water boils at 373 K and freezes at 273 K; absolute zero is the temperature at which molecular motion theoretically ceases.) Because such low temperatures are difficult to reach, there was much excitement in the mid-1980s when IBM researchers in Switzerland found that the ceramic lanthanum-barium-copper oxide becomes a superconductor at 35 K (-406°F). The discovery of this new class of superconductors stirred hopes of identifying substances that superconduct with no chilling at all. A decade later the threshold was up to 135 K (-217°F), but prospects for reaching still higher levels remain unclear. If they can be attained and the materials can be reliably and inexpensively fashioned into wires (not easy with brittle ceramics), the technological consequences would be immense.
Big performance gains are already well in hand for the class of materials called composites in which one type of material is reinforced by particles, fibers, or plates of another type. Among the first engineered composites was fiberglass, developed in the 1930s. Made by embedding glass fibers in a polymer matrix, it found use in building panels, bathtubs, boat hulls, and other marine products. Since then, many metals, polymers, and ceramics have been exploited as both matrix and reinforcement. In the 1960s, for instance, the U.S. Air Force began seeking a material that would be superior to aluminum for some aircraft parts. Boron had the desired qualities of lightness and strength, but it wasn't easily formed. The solution was to turn it into a fiber that was run through strips of epoxy tape; when laid in a mold and subjected to heat and pressure, the strips yielded strong, lightweight solids—a tail section for the F-14 fighter jet, for one. While an elegant solution, boron fibers were too expensive to find wide use, highlighting the critical interplay between cost and performance that drives materials applications.
Many composites are strengthened by graphite fibers. They may be embedded in a matrix of graphite to produce a highly heat-resistant material—the lining for aircraft brakes, for example—or the matrix can be an epoxy, as with composite shafts for golf clubs or frames for tennis rackets. Other sorts of composites abound in the sports world. Skis can be reinforced with Kevlar fibers; the handlebars of some lightweight racing bikes are made of aluminum reinforced with aluminum oxide particles. Ceramic-matrix composites find use in a variety of hostile environments, ranging from outer space to the innards of an automobile engine.
Tens of thousands of materials are now available for various engineering purposes, and new ones are constantly being created. Sometimes the effort is grandly scaled—measured in vast tonnages of a metal or polymer, for instance—but many a recent triumph is rooted in exquisite precision and control. This is especially the case in the amazing realm of electronics, built on combinations of metals, semiconductors, and oxides in miniaturized geometries—the fingernail-sized microchips of computers or CD players, the tiny lasers and threadlike optical fibers of communications networks, the magnetic particles dispersed on discs and other surfaces to record digital data. Making transistors, for example, begins with the growing of flawless crystals of silicon, since the electrical properties of the semiconductor are sensitive to minuscule amounts of impurities (in some cases, just one atom in a million or less) and to tiny imperfections in their crystalline structure. Similarly, optical fibers are composed of silica glass so pure that if the Pacific Ocean were made of the same material, an observer on the surface would have no difficulty seeing details on the bottom miles below. Such stuff is transforming our lives as dramatically as steel once did, and engineering at the molecular level of matter promises much more of the same.
Mary L. Good
Professor and Dean
Donaghey College of Information Science and Systems Engineering
University of Arkansas at Little Rock
We have long identified epochs of human history in terms of the materials exploited—referring, for example, to the Stone Age or the Iron Age. The hallmark of progress in every age has been the way "materials engineers" worked to improve the usefulness of materials, whether extracting coal or iron ore from the earth or creating new materials from combinations, such as iron and carbon to produce steel. For most of history such improvements have been incremental and have depended on experimentation, accidents, and passing on from generation to generation the "art" of materials processing and finishing. However, by the early 1980s, instrumentation, simulation techniques, and the accumulation and analysis of materials databases had moved materials engineering and structural design much closer to the fundamental physics and chemistry of the materials' building blocks. Thus, the concept of "materials by design" began to have some champions, and the potential for creating new materials with designed properties for specific applications no longer was considered "science fiction."
Those of us involved in the invention and improvement of catalytic processes and new catalysts found the idea of molecular design of catalysts with predetermined properties compelling. Catalytic science was driven by "trial and error" experimentation and the ability to determine correlations between performance and composition. In June 1984 the Research Laboratories of UOP (Universal Oil Products) and the Signal Companies, where I was president, were awarded a research contract from the Department of Energy to evaluate the concept of materials by design by assessing the current status of relevant theoretical, computational, and experimental tools. After several workshops with leaders in the field, we prepared an extensive report in 1986 to describe areas of understanding and islands of ignorance. This activity was one of the most stimulating and challenging of my career. At the time, computational theorists had good models for the quantum mechanics and properties of electronic systems, and engineers understood macroengineering design and had a good grasp of finite element analysis and process simulation. However, the understanding of molecular dynamics, atomic structure, and multimolecular pieces, or subunits, was quite primitive.
Fifteen years later I revisited this topic in a paper and a lecture to an international conference. Progress in materials by design in the interim had been profound. Theoretical calculations had progressed to quantum calculations of a few atoms to form the basis of quantum computing; atomic force microscopy could now image individual atoms, molecules, and molecular machines; atomic and molecular reactions on catalyst substrates could be imaged and analyzed directly. In addition, researchers could blend new alloys with totally new properties from existing materials and process them to provide desired physical properties. Others were building analytical chemistry instrumentation on a 1-square-inch chip and designing and producing a variety of micromachines.
Clearly the next 15 years will continue these insights into materials at the atomic and molecular level. The science of nanotechnology—the understanding of materials at the nanometer and molecular size—is now building on these prior excursions into the submicroscopic world. No longer "a science looking for applications," nanotechnology is turning some of these discoveries into real products, ranging from high performance fabrics in which nanostructures are intertwined with conventional synthetic fibers to nanocarbon fibers used to transform properties of polymeric materials. Prototypes of quantum dots, utilizing a few atoms, to be used for the next generation of supercomputers are just one of many examples of products to come. In materials engineering, atomic and molecular materials by design and the nanoproducts they can produce, may very well make the 21st century the "Nano Age"!