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Unit 13: Modern Materials and the Solid State—Crystals, Polymers, and Alloys

Section 10: Conclusion

Solid state chemistry is a rapidly growing field that draws on knowledge from many other disciplines, including physics, materials science, and engineering. It is directly relevant to many contemporary challenges that industrial societies face today.

For example, a key hurdle to making solar power an affordable energy source is increasing the efficiency of photovoltaic cells that convert solar radiation to electricity—in other words, making solid materials in solar cells as conductive as possible. And solid chemistry is central to oral health. For more than a century, dentists have used silver amalgam (a blend of silver and mercury) to fill cavities. Silver amalgam is very durable, but mercury is highly toxic when it is released into the environment. Now fillings made of other solid materials, such as composite resin (a mixture of plastic and glass) or ceramic (a hard, heat-resistant ionic solid), are becoming viable alternatives for many dental patients.7

Quasicrystals

Figure 13-18. Quasicrystals

© Wikimedia Commons, Public Domain. Author: Ames Laboratory, U.S. Department of Energy.

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Quasicrystals

Figure 13-18. Quasicrystals

Israeli scientist Daniel Shechtman (born 1941) received the 2011 Nobel Prize in Chemistry for discovering quasicrystals, a type of crystal structure that other scientists initially believed did not exist. Similar patterns can be found in Islamic tile designs.

Chemists are also making new finds whose applications are not yet known. In 2011, Israeli scientist Daniel Shechtman (born 1941) received the Nobel Prize in Chemistry for discovering quasicrystals—units in a rapidly cooled alloy of aluminum and manganese, packed together in orderly patterns. Unlike known crystal shapes, such as squares, triangles, or the hexagons that we saw in ice crystals in Section 4 of this unit, the crystals he saw in the alloy had five-sided symmetry, and formed unique patterns that did not repeat. (Figure 13-18) Shechtman's finding was so controversial that he was asked to leave his research group, but it was validated by further research.

Quasicrystals are very strong and non-reactive, but the real significance of Shechtman's discovery was in changing how chemists viewed solid matter. The five-sided units "break all the rules of being a crystal at all," said David Phillips (born 1939), former president of the Royal Society of Chemistry, when Shechtman received the Nobel Prize, which Phillips called "a celebration of fundamental research."8

The discovery of quasicrystals shows that chemistry is still a rapidly evolving field, and that our understanding of the basic properties of matter is far from complete. At the same time, however, chemistry is producing countless, highly useful materials and products, from pharmaceuticals to solar cells. As the evolution of dental fillings suggests, many of these new products are more effective and have fewer harmful impacts on the environment than the items they are replacing. From basic needs like safe food and clean drinking water to advanced industrial materials, humans continue to use chemistry to understand how our world works and to improve our daily lives.

7For a comparison, see "Dental Health and Tooth Fillings," WebMD, http://www.webmd.com/oral-health/guide/dental-health-fillings.

8Ian Sample, "Nobel Prize in Chemistry for Dogged Work on 'Impossible' Quasicrystals," The Guardian, October 5, 2011. http://www.guardian.co.uk/science/2011/oct/05/nobel-prize-chemistry-work-quasicrystals.

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