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Here's a question. When you've figured out how the building blocks of universe works, what's the first thing you do with that knowledge? The obvious answer: make better versions of the universe itself. Humans have been doing that since the dawn of civilisation: we built monuments using, at first, stone, then bricks, then concrete, and finally steel.
Making better things had always been the prime mover of our ascent to civilisation. And we're still doing it today. That's where material sciences come into play... |
"Material science now has the clear possibility and promise of the systematic utilization of all the natural resources of the earth for the good of the whole human race.... Maintaining and improving the standard of living of all the peoples of the earth through increasing use of mechanical horsepower and the scientific approach is now one of the keys to peace in the world." - Charles E. Wilson, engineer and former CEO of General Motors
Different materials have different properties. Think of the difference between the engine of a car and its wheels; the metal in a wire and its insulator. All these objects can only be made out of materials that have properties suited to their application. Materials science is the study of the properties of materials. It focuses on the factors that make one material different from another.
Understandably, there are many such factors, some obvious and some subtle. Examples of these factors might include elemental composition, arrangement, bonding, impurities, surface structure, length scale and so on. The ability to understand the relationships between these factors and the properties of a material has been crucial to most of mankind's technological breakthroughs. Today, materials science is a multidisciplinary subject. It draws upon just about every field of science and engineering, providing insights for other researchers to use in their field.
History
The important material of a given era is often its defining point. Examples are the Stone Age, Bronze Age, and Iron Age.
Materials science originally studied ceramics and metallurgy. These ancient crafts make materials science one of the oldest forms of engineering and applied science. A major breakthrough in the understanding of materials occurred in the late 19th century, when the American scientist Josiah Willard Gibbs showed that the physical properties of a material were related to its atomic structure. As the phases changed, so did the physical properties of the material.
Important elements of modern materials science are a product of the space race: the understanding and engineering of the metallic alloys, and silica and carbon materials, used in the construction of space exploration vehicles.
Materials science is now linked to the development of plastics, semiconductors, ceramics, polymers, magnetic materials, medical implant materials and biological materials.
The material scientist/engineer also deals with the extraction of materials and their conversion into useful forms. So, ingot casting, foundry techniques, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a metallurgist/engineer. Often the presence, absence or variation of minute quantities of secondary elements and compounds in a bulk material will have a great impact on the final properties of the materials produced, for instance, steels are classified based on 1/10 and 1/100 weight percentages of the carbon and other alloying elements they contain. Thus, the extraction and purification techniques employed in the extraction of iron in the blast furnace will have an impact of the quality of steel that may be produced.
The study of disasters in the 19th and 20th century led to some important discoveries. Alan Arnold Griffith (1893–1963) discovered that real materials never get near their theoretical strength. This was a groundbreaking discovery which led to changes in many industries. As an example, steel gets almost 1/10th of its theoretical strength, but most solids are 100 to 1000 times weaker than expected.
Griffith's insights were developed further by James Edward Gordon (1913–1998). Gordon said that all simple solids are by their nature brittle. Toughness – resistance to fracture – has to be designed into materials. The usual way is to add other material to the pure substance. This makes its structure more complex, and that makes it less likely to fail. A good example is bulletproof glass, where a plastic layer stuck to glass make it many times stronger than either material would be separately. The personal armour based on Kevlar is another example. Biological materials have this feature naturally. Bones do bend a little before they reach breaking point, and tree trunks also have some "give".
From Theory to Application
The basis for all applied sciences are theories, and material sciences are not an exception. Whether it’s metallurgy, ceramics, composites, polymers or semiconductors, the determining factor is on a molecular, even atomic scale.
Understandably, there are many such factors, some obvious and some subtle. Examples of these factors might include elemental composition, arrangement, bonding, impurities, surface structure, length scale and so on. The ability to understand the relationships between these factors and the properties of a material has been crucial to most of mankind's technological breakthroughs. Today, materials science is a multidisciplinary subject. It draws upon just about every field of science and engineering, providing insights for other researchers to use in their field.
History
The important material of a given era is often its defining point. Examples are the Stone Age, Bronze Age, and Iron Age.
Materials science originally studied ceramics and metallurgy. These ancient crafts make materials science one of the oldest forms of engineering and applied science. A major breakthrough in the understanding of materials occurred in the late 19th century, when the American scientist Josiah Willard Gibbs showed that the physical properties of a material were related to its atomic structure. As the phases changed, so did the physical properties of the material.
Important elements of modern materials science are a product of the space race: the understanding and engineering of the metallic alloys, and silica and carbon materials, used in the construction of space exploration vehicles.
Materials science is now linked to the development of plastics, semiconductors, ceramics, polymers, magnetic materials, medical implant materials and biological materials.
The material scientist/engineer also deals with the extraction of materials and their conversion into useful forms. So, ingot casting, foundry techniques, blast furnace extraction, and electrolytic extraction are all part of the required knowledge of a metallurgist/engineer. Often the presence, absence or variation of minute quantities of secondary elements and compounds in a bulk material will have a great impact on the final properties of the materials produced, for instance, steels are classified based on 1/10 and 1/100 weight percentages of the carbon and other alloying elements they contain. Thus, the extraction and purification techniques employed in the extraction of iron in the blast furnace will have an impact of the quality of steel that may be produced.
The study of disasters in the 19th and 20th century led to some important discoveries. Alan Arnold Griffith (1893–1963) discovered that real materials never get near their theoretical strength. This was a groundbreaking discovery which led to changes in many industries. As an example, steel gets almost 1/10th of its theoretical strength, but most solids are 100 to 1000 times weaker than expected.
Griffith's insights were developed further by James Edward Gordon (1913–1998). Gordon said that all simple solids are by their nature brittle. Toughness – resistance to fracture – has to be designed into materials. The usual way is to add other material to the pure substance. This makes its structure more complex, and that makes it less likely to fail. A good example is bulletproof glass, where a plastic layer stuck to glass make it many times stronger than either material would be separately. The personal armour based on Kevlar is another example. Biological materials have this feature naturally. Bones do bend a little before they reach breaking point, and tree trunks also have some "give".
From Theory to Application
The basis for all applied sciences are theories, and material sciences are not an exception. Whether it’s metallurgy, ceramics, composites, polymers or semiconductors, the determining factor is on a molecular, even atomic scale.
Metallurgy is mostly about strength, heat, and stress resistance
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Metallurgy
The industrial study of metal alloys is a large part of materials science. Of all the metallic alloys in use today, the alloys of iron (steel, stainless steel, cast iron, tool steel, alloy steels) make up the largest proportion both by quantity and commercial value. Iron alloyed with various proportions of carbon gives low, mid and high carbon steels. An iron carbon alloy is only considered steel if the carbon level is between 0.01% and 2.00%. For the steels, the hardness and tensile strength of the steel is related to the amount of carbon present. Increasing carbon levels leads to lower ductility and toughness. Heat treatment processes such as quenching and tempering can significantly change these properties however. Cast Iron is defined as an Iron-Carbon alloy with more than 2.00% but less than 6.67% carbon. Stainless steel is defined as a regular steel alloy with greater than 10% by weight alloying content of chromium. Nickel and molybdenum are also found in stainless steels. |
Other significant metallic alloys are those of aluminium, titanium, copper and magnesium. Copper alloys have been known for a long time (since the Bronze Age), while the alloys of the other three metals have been relatively recently developed. Due to the chemical reactivity of these metals, the electrolytic extraction processes required were only developed relatively recently. The alloys of aluminium, titanium and magnesium are also known and valued for their high strength-to-weight ratios and, in the case of magnesium, their ability to provide electromagnetic shielding. These materials are ideal for situations where high strength-to-weight ratios are more important than bulk cost, such as in the aerospace industry and certain automotive engineering applications.
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Ceramics
Another application of the material sciences is the structures of glass and ceramics, typically associated with the most brittle materials. Ceramics and glasses use covalent bonds and ionic-covalent bonds with SiO2, silica or sand, as a fundamental building block. Ceramics are as soft as clay and as hard as stone and concrete. Usually, they are crystalline in form. Most glasses contain a metal oxide fused with silica. At high temperatures used to prepare glass, the material is a viscous liquid. Glass forms into an amorphous structure when it is cooled. Windowpanes and eyeglasses are important examples. Fibers of glass are also available. Diamond and carbon in its graphite form are considered to be ceramics. Engineering ceramics are known for their stiffness, high temperature, and stability under compression and electrical stress. Alumina, silica carbide, and tungsten carbide are made from a fine powder of their constituents in a process of sintering with a binder. |
Yttrium barium copper oxide, a superconducting ceramic material
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Hot pressing provides higher density material. Chemical vapor deposition can place a film of a ceramic on another material. Cermets are ceramic particles containing some metals. The wear resistance of tools is derived from cemented carbides with the metal phase of cobalt and nickel typically added to modify properties.
Carbon fiber, weight-for-weight, is stronger than steel
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Composites
Another application of material science in industry is the making of composite materials. Composite materials are structured materials composed of two or more macroscopic phases. Applications range from structural elements such as steel-reinforced concrete, to the thermally insulative tiles which play a key and integral role in National Aeronautics and Space Administration's (NASA) Space Shuttle thermal protection system which is used to protect the surface of the shuttle from the heat of re-entry into the Earth's atmosphere. One example is Reinforced Carbon-Carbon (RCC), The light gray material which withstands re-entry temperatures up to 1510 °C (2750 °F) and protects the Space Shuttle's wing leading edges and nose cap. RCC is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin. After curing at high temperature in an autoclave, the laminate is pyrolized to convert the resin to carbon, impregnated with furfural alcohol in a vacuum chamber, and cured/pyrolized to convert the furfural alcohol to carbon. |
Other examples can be seen in the "plastic" casings of television sets, cell-phones and similar objects. These plastic casings are usually a composite material. It is a thermoplastic matrix such as acrylonitrile-butadiene-styrene (ABS) in which calcium carbonate chalk, talc, glass fibers or carbon fibers have been added for added strength, bulk, or electro-static dispersion. These additions may be referred to as reinforcing fibers, or dispersants, depending on their purpose.
Polymers
Polymers are also an important part of materials science. They are the raw materials used to make what we commonly call plastics. Plastics are really the final product. They are made when polymers or additives have been added to a resin during processing. The mixture is then shaped into a final form. Common polymers are, include polyethylene, polypropylene, PVC, polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates.
PVC (polyvinyl-chloride) is widely used, inexpensive, and annual production quantities are large. It lends itself to an incredible array of uses, from artificial leather to electrical insulation and cabling, packaging and containers. It is simple to make. It accepts a wide range of plasticisers and other additives, which give it differing properties.
Polymers are also an important part of materials science. They are the raw materials used to make what we commonly call plastics. Plastics are really the final product. They are made when polymers or additives have been added to a resin during processing. The mixture is then shaped into a final form. Common polymers are, include polyethylene, polypropylene, PVC, polystyrene, nylons, polyesters, acrylics, polyurethanes, and polycarbonates.
PVC (polyvinyl-chloride) is widely used, inexpensive, and annual production quantities are large. It lends itself to an incredible array of uses, from artificial leather to electrical insulation and cabling, packaging and containers. It is simple to make. It accepts a wide range of plasticisers and other additives, which give it differing properties.
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Semiconductors
A semiconductor is a material that in some cases will conduct electricity but not in others. Good electrical conductors, like copper or silver, easily allow electricity to flow through them. Materials that block the flow of electricity, like rubber or plastic, are called insulators. Insulators are often used to protect people from electric shock. As the name implies, a semiconductor does not conduct as well as a conductor. Semiconductors are the foundation of modern electronics. By the addition of different atoms into the crystal lattice (grid) of the semiconductor it changes its conductivity by making n-type and p-type semiconductors. Silicon is the most important commercial semiconductor, though many others are used. They can be made into transistors, which are small amplifiers. Transistors are used in computers, mobile phones, digital audio players and many other electronic devices. |
Semiconductors are used in computing as well as photonics
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Like other solids, the electrons in semiconductors can have energies only within certain bands (i.e. ranges of energy levels) between the energy of the ground state, corresponding to electrons tightly bound to the atomic nuclei of the material, and the free electron energy, which is the energy required for an electron to escape entirely from the material.
Today, semiconductors are used far and wide. Semiconductors can be found in nearly every electronic device. Desktop computers, the Internet, tablet devices, smartphones all would not be possible without semiconductors. Semiconductors can be made into very precise switches with a small amount of voltage. The voltage that the semiconductor doesn’t need can be sent to other electrical components in the device. Semiconductors can also be made very tiny and many of them can fit into a rather small circuit. Since they can be made so small, electrical devices today can be made thin and lightweight without compromising processing power. Some of the dominating companies in the semiconductor business are Intel Corporation, Samsung Electronics, TSMC, Qualcomm and Micron Technology.
Today, semiconductors are used far and wide. Semiconductors can be found in nearly every electronic device. Desktop computers, the Internet, tablet devices, smartphones all would not be possible without semiconductors. Semiconductors can be made into very precise switches with a small amount of voltage. The voltage that the semiconductor doesn’t need can be sent to other electrical components in the device. Semiconductors can also be made very tiny and many of them can fit into a rather small circuit. Since they can be made so small, electrical devices today can be made thin and lightweight without compromising processing power. Some of the dominating companies in the semiconductor business are Intel Corporation, Samsung Electronics, TSMC, Qualcomm and Micron Technology.
Ponder this
Which came first, the need for new materials or the creation of such materials? Much of what constitutes our modern civilisation were based on purely theoretical research (when the electron was discovered, they were seen as merely a novelty, and yet we can't imagine our world without electronics). How do theories become applicable? What are the steps?
Discuss
We mentioned earlier that throughout history, humans have manipulated materials in progression as and when the engineering needs arise. Discuss the development of each of the materials in this article (metals, ceramics, composites, polymers and semiconductors) throughout history, elaborate on the different branches of science that were involved, what inspired the adoption of knowledge between wholly different disciplinary.
Further readings
What is metallurgy?, at Tom Bertone Consulting
Ceramic science and engineering, at the American Ceramic Society
Materials science as a career, at the American Chemical Society
