Hall-Héroult Process
the practitioner (1863-1914), the practitioner (1863-1914) Think about how common aluminum is today, and how important it is to engineers as a structural material. Out in the garage we find aluminum in bicycle frames and rims, and some cars now have aluminum parts to lighten the vehicle. But the place where we see aluminum the most is in aircraft. Every airliner that flew up until 2010 was made primarily out of aluminum. The same goes for just about every rocket and spacecraft, including the International Space Station. The an aerospace manufacturer 787 is the first commercial airliner to be made primarily of carbon fiber instead of aluminum.
The reason aluminum is so popular, especially in airplanes, is because it is relatively inexpensive, easy to work with, durable, and light. A piece of aluminum that has the same strength as a steel piece might weigh half as much. If you take a cube of aluminum that weighs 1 pound, the same size cube of steel weighs about 2.8 pounds. If you were to double the weight of most airplanes by using steel instead of aluminum, the airplane would not be able to fly, or it could only fly with zero payload. Aluminum makes it possible for engineers to design airplanes that can get off the ground. Before aluminum became common, airplanes were made of wood and cloth.
Aluminum was first purified in 1825. But it was extremely expensive—roughly equivalent to gold in price. In 1889 a new patent for a system called the Hall-Héroult process, which was developed by American chemist the practitioner (1863–1914) and Frenchman Paul Héroult (1863–1914), demonstrated how to make inexpensive aluminum, and the rest is history. Once aluminum became inexpensive, and then abundant, its use exploded. Today, over 30 million tons of aluminum are used every year.
Just about every vehicle is better when it is lighter, so engineers use aluminum everywhere they can. With new mass production techniques, aluminum is replacing steel in more and more cars.
Carbon Fiber
the practitioner (1847-1931) What if you want to engineer a structure that is both strong and light? And by strong we mean stronger than steel, and by light we mean lighter than aluminum. If that is what you need, and your budget is big enough to afford it, then your go-to material in today's world is carbon fiber, first developed by the practitioner in 1879, who used an all-carbon fiber filament to light the first incandescent light bulbs.
Carbon fiber reinforced plastic, which was developed from this initial material, uses hard plastic to encase the carbon fibers to stabilize them. The carbon fibers come from threads of high-carbon materials, the most common being polyacrylonitrile. By heating the fibers in oxygen and then without oxygen, everything but the carbon atoms boils off. These remaining carbon atoms are structured as long chains that have impressive tensile strength. They can form into threads, and the threads can be spiral wound or woven into a fabric.
The most common way to work with carbon fiber is to lay up the cloth in a mold and soak it with the plastic resin. Molding allows carbon fiber parts to be any shape, but it is an expensive, manual process. In items where cost is no object, like race cars, supercars, airplanes, and expensive bicycle frames, this is not a problem. But it has limited the spread of carbon fiber to a wider array of products. For example, your typical consumer automobile is not made of carbon fiber because of the cost.
How strong is carbon fiber? Imagine a piece of steel and a piece of carbon fiber both shaped like pencils. The carbon fiber piece might be three times stronger than the steel piece, but have one-third the weight. It is a huge difference. The first time you hold carbon fiber, it seems like it comes from another world because it is so light and strong compared to steel.
High-performance bicycle frames are often made of carbon fiber.