Human civilization owes its development to progresses in materials and technology. In the modern era, we have vast numbers of tailored materials to make use of. Like various Ages in ancient times, we can consider ourselves living in Materials Age. Following the philosophy of “one faces the future with one’s past”, progress in materials of the present time is reviewed, followed by a brief account of futuristic materials.
Development of modern materials:
Plastics
Polymers or plastics are the chemists’ contribution to the materials world. They are generally light organic compounds of carbon and hydrogen, and consist of large molecular structures. Plastics play an important part in everyday life. Their versatility allows them to be used in everything from shoes to ships and from food packaging to fighter jets.
Silicon-based material
The last forty years of rapid development of electronics technology such as microelectronics, can be described as the Silicon Age. There would have been no information superhighway as we know it if there was no development of high-purity silicon and silicon-based integrated circuits. Based on total internal reflection phenomenon, fibre optic cables have revolutionised long-distance phone calls, cable TV and the internet by carrying out digital information via transmission of light signals. These cables are long strands of optically pure glass (silica) as thin as human hair.
Composites
These are complex materials in which two or more structurally complementary substances combine to provide properties not present in the individual component. Composite technology is not new. Straw-reinforced mud brick (adobe) is one of the earliest architectural composite materials still in use in parts of Africa and Asia. Steel-reinforced concrete for building construction appeared around 1850. Material developments in the 20th century include fibreglass where glass and polymer are combined. Other new combinations include ceramic fibres in metal or polymer matrix. The fibres carry the mechanical loads, whereas the matrix material transmits load to the fibres and provides ductility and toughness.
Metals and alloys
Our everyday usages of metals and alloys range from cars, airplanes, computer chips, mobile phones, refrigerators, microwave ovens, TVs to biomedical devices for replacement of joints and limbs. The various properties discussed below are utilized for specific applications.
Thermal properties
Besides pure metals, just about every single piece of metallic stuff in our daily life is an alloy of some kind, such as steel and cast iron (alloy of iron and carbon), brass (copper and zinc), stainless steel (nickel, chromium and iron) etc. Modern research in alloys is directed towards improving their performance with subsequent use which no one could have imagined possible a few years ago. For example, the development of nickel-based “Superalloy” with exceptionally high temperature strength (capable of operating at as high as 2000 F), has made it popular for use as turbine blade in superhot turbine areas of modern jet engines, making present day transportation possible.
Mechanical properties
There are some crucial modern applications where a material should neither undergo excessive change in shape, nor break down when mechanically loaded. Examples include load-bearing structures such as materials for aircraft wings, jet engine or bridges. It may be, however, a secondary consideration in cases like in the communication industry where the electrical properties are of first concern, although the need for a device or optical fibre not to fracture when in service, would be a close second.
Fail-safe consideration
Unlike in the past, it is essential that materials on locations do not fail, since any repair or replacement is either very expensive, extremely difficult or impossible. Such locations include deep-sea oil pipelines, space stations, satellites and healthcare biomaterials within our bodies.
Development of future materials
New materials have been revolutionising our daily life for over three decades. The possibilities of developing future materials would depend on our imagination and ability to make and test them. Several futuristic materials are briefly discussed.
Superconductor
A striking development in the 20th century was in 1911 when mercury and lead cooled to 4.2 degrees K (-269 C) suddenly showed no electrical resistance. However, the temperature was too low for such materials to be of any use. In the mid-1980s, a complex oxide of barium, lanthanum and copper was found to be superconducting at 30 K. This prompted in 1987 to develop superconductor that worked at liquid nitrogen temperature (98 K), followed by invention of ceramic superconductor in 1993 that worked at 138 K. Effort to develop purely metallic superconductor is in progress. Practical applications have so far been limited to a few areas only, such as elimination of friction in trainstransportation vehicles, bio magnetic technology as depth sensor for medical equipment, and acceleration of sub-atomic particles nearly to the speed of light in Super Collider.
Graphene
In 2004, graphene, a new form of carbon, was discovered which consisted of carbon atoms of just one atom thick. It displayed unprecedented properties of being one of the strongest materials ever tested. Sheets of graphene have been used to make the fastest transistors ever made. However, commercial viability of graphene is yet to be developed because only one small sheet can be currently produced at a time.
There is a possibility of partial to complete replacement of plastics by incorporating graphene into any product that uses plastic. Composites thus produced are expected to be stronger, lighter and more environmentally friendly than their plastic counterpart. Applications could be in aircraft parts , car parts, sports and household goods. This would be a great achievement in the plastic world where the major raw material to manufacture plastics, oil, is a limited resource.
Fullerene
Besides existing as diamond and graphite, carbon also exists as fullerene (buckyball) molecule of 60 carbon atoms arranged in pentagons and hexagons. Fullerene has no crystalline structure i.e. amorphous, with a high bulk modulus of 491 gigapascals (GPa) compared to diamond’s 442 GPa. Work is in progress for its application in various areas such as organic photovoltaics, polymer electronics, antioxidants, nanotechnology, and so on.
Nanotubes
Carbon nanotubes are long chains of carbon atoms held together by the strongest bond ever achievable in chemistry. Among their numerous remarkable physical properties is ballistic electron transport – making them ideal for electronics. Their strength (48,000 kN.m/kg ) is about 300 times stronger than steel and would make them capable of building space elevator.
Amorphous metals
Amorphous metals also known as metallic glasses produced by very rapid cooling of molten alloys, consist of a disordered atomic structure. They can be twice as strong as steel. Because of their disordered structure, they can disperse impact energy more effectively than a crystalline metal which has points of weakness. Such materials can thus be useful in the military’s next generation of armour or aircraft components which must deform to absorb the energy of collision, but must also become gradually stiff during the crunch. Their electronic properties are claimed to improve the efficiency of power grids by as much as 40%.
Metal foam
Metal foam is a cellular structure of a solid metal (aluminium or nickel) containing a large volume fraction of gas-filled pores or foaming agent (powdered titanium hydride). It is a very strong substance that is relatively light with 75-95% empty space. Because of favourable strength to weight ratio, metal foams are proposed for construction of stronger buildings, space colonies, orthopaedic applications and automobile uses. Composite foam of hollow steel spheres surrounded by aluminium is being investigated as a possible building material.
Metamaterials
Metamaterial refers to any material that gains its properties from its certain periodic patterns and shape rather than composition. These artificial materials engineered to have properties that may not be found in nature, guide light around an object, rather than reflect or refract the light. Metamaterials still in the process of development have been used to create microwave invisibility cloaks, 2D invisibility cloaks and other unusual optical properties. Mother of pearl (organic-inorganic composite) gets its rainbow colour from metamaterials of biological origin.
Final Comments
Developments of metals like bronze and iron enabled advances in civilization thousands of years ago. This synergy continues today, for example in fibre optics which have created the World Wide Web, and among others, the development of biomaterials that mimic living tissues. One would hope that with good scientific knowledge and ingenuity we will be able to strive forward in grand style making startling changes in our lives in the 21st century.
Sources
- The Physics of Materials
- Accelerating future
- Superconductors
- Fullerene applications
- Glass-Like Metal Performs Better Under Stress
- Metal Foam
- How stuff works "Metamaterials"
- How stuff works "Optical fibers"
Benu Chatterjee - Graduated in both science (Chemistry) and engineering (Metallurgy), I also gained a PhD in Metallurgy. Based on my academic qualifications ...
