Sep 16

As part of my Excerpt of the Day series, here’s an interesting quote from Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World by Mark Miodownik.

Stuff Matters Book Cover“Normally when steel is exposed to air and water, the iron on the surface reacts to form iron(III) oxide, a red mineral commonly known as rust. When this rust flakes off, it exposes another layer of the steel to further corrosion, which is what makes rusting such a chronic problem for steel structures, hence the need to paint steel bridges and cars. But with chromium present something different happens. Like some hugely polite guest, it reacts with the oxygen before the host iron atoms can do so, creating chromium oxide. Chromium oxide is a transparent, hard mineral that sticks extremely well to steel. In other words, it doesn’t flake off and you don’t know it is there. Instead it creates an invisible, chemically protective layer over the whole surface of the steel. What’s more, we now know that the protective layer is self-healing; when you scratch stainless steel, even though you break the protective barrier, it re-forms.”

For more interesting facts about the science of materials, check out the full book here on Amazon.

Sep 15

As part of my Excerpt of the Day series, here’s an interesting quote from Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World by Mark Miodownik.

Stuff Matters Book Cover“This was nowhere more true than in Japan, where the forging of a samurai blade took weeks and was part of a religious ceremony. The Ama-no-Murakumo-no-Tsurugi (“Sword of the Gathering Clouds of Heaven”) is a legendary Japanese sword which allowed the great warrior Yamato Takeru to control the wind and defeat all his enemies. Despite the fantastic stories and rituals, the idea that some swords could be made ten times stronger and sharper than other swords was not just a myth, but a reality.

By the fifteenth century AD the sword steel made by the samurai of Japan was the best the world had ever seen and remained preeminent for five hundred years until the advent of metallurgy as a science in the twentieth century. These samurai swords were made from a special type of steel called tamahagane, which translates as “jewel steel,” made from the volcanic black sand of the Pacific (this consists mostly of an iron ore called magnetite, the original material for the needle of compasses).

This steel is made in a huge clay vessel four feet tall, four feet wide, and twelve feet long called a tatara. The vessel is “fired”—hardened from molded clay into a ceramic—by lighting a fire inside it. Once fired, it is packed meticulously with layers of black sand and black charcoal, which are consumed in the ceramic furnace.

The process takes about a week and requires constant attention from a team of four or five people, who make sure that the temperature of the fire is kept high enough by pumping air into the tatara using a manual bellows. At the end the tatara is broken open and the tamahagane steel is dug out of the ash and remnants of sand and charcoal. These lumps of discolored steel are very unprepossessing, but they have a whole range of carbon content, some of it very low and some of it high.

The samurai innovation was to be able to distinguish high-carbon steel, which is hard but brittle, from low-carbon steel, which is tough but relatively soft. They did this purely by how it looked, how it felt in their hands, and how it sounded when struck. By separating the different types of steel, they could make sure that the low-carbon steel was used to make the center of the sword. This gave the sword an enormous toughness, almost a chewiness, meaning that the blades were unlikely to snap in combat. On the edge of the blades they welded the high-carbon steel, which was brittle but extremely hard and could therefore be made very sharp.

By using the sharp high-carbon steel as a wrapper on top of the tough low-carbon steel they achieved what many thought impossible: a sword that could survive impact with other swords and armor while remaining sharp enough to slice a man’s head off. The best of both worlds.”

For more interesting facts about the science of materials, check out the full book here on Amazon.

Sep 13

As part of my Excerpt of the Day series, here’s an interesting quote from Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World by Mark Miodownik.

Stuff Matters Book Cover“Discovering metals was an important moment in pre-history, but it didn’t solve the fundamental problem that there wasn’t very much metal around. One option, clearly, was to wait for some more to drop from the sky, but this requires a huge amount of patience (a few kilograms fall to the surface of the Earth every year, but mostly into the oceans). At some point humans made the discovery that would end the Stone Age and open the door to a seemingly unlimited supply of the stuff. They discovered that a certain greenish rock, when put into a very hot fire and surrounded by red-hot embers, turns into a shiny piece of metal. This greenish rock was malachite, and the metal was, of course, copper. It must have been the most dazzling revelation. Suddenly the discoverers were surrounded not by dead inert rock but by mysterious stuff that had an inner life…

From around 5000 BC, early metalsmiths used trial and error to hone the process of the production of copper. The making of copper tools initiated a spectacular growth in human technology, being instrumental in the birth of other technologies, cities, and the first great civilizations. The pyramids of Egypt are an example of what became possible once there were plentiful copper tools. Each block of stone in each pyramid was extracted from a mine and individually hand-carved using copper chisels. It is estimated that ten thousand tons of copper ore were mined throughout ancient Egypt to create the three hundred thousand chisels needed. It was an enormous achievement, without which the pyramids could not have been built, however many slaves were used, since it is not practical to carve rock without metal tools. It is all the more impressive given that copper is not the ideal material for cutting rock since it is not very hard. Sculpting a piece of limestone with a copper chisel quickly blunts the chisel. It is estimated that the copper chisels would have needed to be sharpened every few hammer blows in order for them to be useful. Copper is not ideal for razor blades for the same reason.”

You can find the full book here on Amazon.

Sep 11

As part of my Excerpt of the Day series, here’s an interesting quote from Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World by Mark Miodownik.

Stuff Matters Book Cover“Metals are made from crystals. The average razor blade contains billions of them, and in each of these crystals the atoms are arranged in a very particular way, a near-perfect three-dimensional pattern. The bonds between the atoms hold them in place and also give the crystals their strength. A razor gets blunt because the many collisions with hairs that it encounters force bits of these crystals to rearrange themselves into a different shape, making and breaking bonds and creating tiny dents in the smooth razor edge…

Viewed through an electron microscope, the crystals in a piece of metal look like crazy paving, and inside those crystals are squiggly lines—these are dislocations. They are defects in the metal crystals, and represent deviations in the otherwise perfect crystalline arrangement of the atoms—they are atomic disruptions that shouldn’t be there. They sound bad, but they turn out to be very useful. Dislocations are what make metals so special as materials for tools, cutting edges, and ultimately the razor blade, because they allow the metal crystals to change shape…

You don’t need to use a hammer to experience the power of dislocations. When you bend a paper clip, it is in fact the metal crystals that are bending. If they didn’t bend, the paper clip would be brittle and snap like a stick. This plastic behavior is achieved by the dislocations moving within the crystal. As they move they transfer small bits of the material from one side of the crystal to the other. They do this at the speed of sound. As you bend a paper clip, you are causing approximately 100,000,000,000,000 dislocations to move at a speed of hundreds of meters per second. Although each one only moves a tiny piece of the crystal (one atomic plane in fact), there are enough of them to allow the crystals to behave like a super-strong plastic rather than a brittle rock…

Gold is a relatively soft metal, so much so that rings are very rarely made from pure gold metal because they quickly scratch. But if you alloy gold, by adding a small percentage of other metals such as silver or copper, you not only change the color of the gold—silver making the gold whiter, and copper making the gold redder—you make the gold harder, much harder. This changing of the properties of metals by very small additions of other ingredients is what makes the study of metals so fascinating. In the case of gold alloys, you might wonder where the silver atoms go. The answer is that they sit inside the gold crystal structure, taking the place of a gold atom, and it is this atom substitution inside the crystal lattice of the gold that makes it stronger…

Alloys tend to be stronger than pure metals for one very simple reason: the alloy atoms have a different size and chemistry from the host metal’s atoms, so when they sit inside the host crystal they cause all sorts of mechanical and electrical disturbances that add up to one crucial thing: they make it more difficult for dislocations to move. And if dislocations find it difficult to move, then the metal is stronger, since it’s harder for the metal crystals to change shape. Alloy design is thus the art of preventing the movement of dislocations…

Atom substitutions happen naturally inside other crystals too. A crystal of aluminum oxide is colorless if pure but becomes blue when it contains impurities of iron atoms: it is the gemstone called sapphire. Exactly the same aluminum oxide crystal containing impurities of chromium is the gem called ruby…

Lead has a low melting point and so dislocations move with consummate ease, making it a very soft metal. Copper has a higher melting point and is stronger. Heating metals allows dislocations to move about and reorganize themselves, with one of the outcomes being that it makes metals softer.”

You can find the full book here on Amazon.

Sep 9

As part of my Excerpt of the Day series, here’s an interesting quote from Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World by Mark Miodownik.

Stuff Matters Book Cover“Studies of “crispness” have shown that the sound created by certain foods is as important to our enjoyment of them as their taste. This has inspired some chefs to create dishes with added sound effects.

You can find the full book here on Amazon.

Sep 8

As part of my Excerpt of the Day series, here’s an interesting quote from Stuff Matters: Exploring the Marvelous Materials That Shape Our Man-Made World by Mark Miodownik.

Stuff Matters Book Cover“The material world is not just a display of our technology and culture, it is part of us. We invented it, we made it, and in turn it makes us who we are…

The twentieth century is often hailed as the Age of Silicon, after the breakthrough in materials science that ushered in the silicon chip and the information revolution. Yet this is to overlook the kaleidoscope of other new materials that also revolutionized modern living at that time. Architects took mass-produced sheet glass and combined it with structural steel to produce skyscrapers that invented a new type of city life. Product and fashion designers adopted plastics and transformed our homes and dress. Polymers were used to produce celluloid and ushered in the biggest change in visual culture for a thousand years: the cinema. The development of aluminum alloys and nickel superalloys enabled us to build jet engines and fly cheaply, thus accelerating the collision of cultures. Medical and dental ceramics allowed us to rebuild ourselves and redefine disability and aging—and, as the term plastic surgery implies, materials are often the key to new treatments used to repair our faculties (hip replacements) or enhance our features (silicone implants for breast enlargement).”

You can find the full book here on Amazon.