Tag Archives: metal

What is stainless steel?

Today, iron is the most widely-used metal. It’s durable, versatile, and abundant in the Earth’s crust (making it cheap). However, in its pure form, iron is very susceptible to oxygen — it rusts rapidly. Stainless steel provides a solution to this problem.

Image via Pixabay.

The world as we know it wouldn’t be possible without stainless steel. It’s a material that combines strength, flexibility, and durability at an affordable cost. This alloy makes an appearance in everything, from high-rises and high-performance cars to spoons and baby monitors. To quite a large extent, our world is built on stainless steel. So let’s learn more about it.

What is stainless steel?

‘Stainless steel’ is a generic, umbrella term, that denotes a wide range of metal alloys — cocktails of metals — based on iron. Like all other types of steel, it also contains carbon.

It has excellent resistance to corrosion (oxidation or rusting), is relatively non-reactive with most chemicals, has high durability, and good hygienic properties. It sees wide use today in products ranging from cutlery to medical devices to construction materials.

Aesthetically, stainless steel is a lustrous, silvery metal, that can take a very high polish. From a practical point of view, stainless steel is a strong and highly resilient material; its exact properties depend on the composition of the alloy, but it can be tailored to suit a wide range of needs, having the potential to be highly flexible, resistant to scratching, mechanically tough, or any other property needed in a certain application. It can be recycled practically forever, as its recovery rate during recycling is close to 100%

Although it is more difficult and expensive to produce than iron metal, stainless steel has practically replaced iron in all except the most specialized cases due to the advantages it holds over the un-alloyed metal. Almost all ‘iron’ products you’ve encountered in your life were made from stainless steel.

What is stainless steel made of?

Molten metal pouring from ladle. Image credits Goodwin Steel Castings / Flickr.

Stainless steel differs from other types of steel through the addition of a handful of elements to the mix. The exact elements added vary with alloy type but, as a rule of thumb, stainless steels contain chromium (Cr), in quantities ranging from 10.5 to 30% by weight.

Chromium is what gives these alloys their high resistance to corrosion. As it interacts with corrosive agents in the air, chromium forms a passive layer — a ‘film’ of chromium oxide — on the metal’s surface which protects the alloy. Oxygen and moisture cannot penetrate this film, so it protects the iron throughout the body of the steel from rusting.

Other elements that are added to stainless steel include non-metals such as sulphur, silicon, or nitrogen, metals such as nickel, aluminium, copper, or more exotic metals such as selenium, niobium, and molybdenum. Although the exact composition of the alloy is decided based on its desired properties — each element added in, and their proportion, changes the characteristics of the alloy — some of the most commonly-seen extra elements in stainless steel alloys are nickel and nitrogen. These improve its hardiness and ability to resist corrosion in certain conditions, but also increase its price per pound.

There are currently over 100 types (known as ‘grades’) of stainless steel being produced and used, each with its own ISO number, many of them for specialized applications. The most common five types are known as ‘austenitic’, ‘ferritic’, ‘martensitic’, ‘duplex’, and ‘precipitation hardening’ steels.

  • Austenitic stainless steels are the most widely used grade. They have very good resistance to corrosion and heat, offering good mechanical properties over a wide range of temperatures. It’s used in household goods, industrial applications, in construction, and in decorations.
  • Ferritic stainless steels have lower mechanical resitance — they resemble mild steels in strength — but are better able to resist corrosion, heat, and are harder to crack. Any washing machine or boiler you have at home are probably made of ferritic steel.
  • Martensitic stainless steels are much harder and stronger than their peers, but they’re not as able to withstand corrosion. This is the type of steel that makes high-grade knives, and is also used for turbine blades.
  • Duplex stainless steel is a mixture of austenitic and ferritic steels, and their properties are, similarly, a middle-ground between these two grades. As a rule of thumb, it is used in applications where both strength and flexibility are required, and corrosion resistance is a plus; shipbuilding is a prime example.
  • Precipitation hardening stainless steels are a subclass of alloys, somewhere in the overlap between martensitic and austenitic steels. They offer the best mechanical properties of the lot (they have very high material strength), due to the addition of elements such as aluminium, copper, and niobium.

What is stainless steel used for?

Stainless steel facade. Image credits Dean Moriarty.

With a material as versatile as stainless steel, it’s hard to cover all its uses in any detail. Suffice to say, it’s used in virtually all goods and applications where strength, flexibility, good looks, and hygiene are required, for relatively low cost, and weight is not a huge concern.

Household goods and appliances make heavy use of stainless steel, especially kitchenware or other products meant to come into contact with water. Knives and cutlery, home appliances such as washing machines, bathroom fixtures, piping, cookware make use of stainless steel due to its resistance to corrosion, its good looks, ease of washing, and high durability. Various grades of stainless steel are used depending on the intended role and usage of each product.

Medical tools also make ample use of stainless steel. Things like surgical and dental instruments, scissors, trays, and a wide range of other medical-use objects are made from this alloy. Here, it is the chemical inertness and corrosion resistance of stainless steel that is most important. Medical devices also contain stainless steel, in particular structural elements and coverings, due to their strength and ease of cleaning. Medical implants, such as those used in knee or hip replacement surgery, are also made of stainless steel.

Stainless steel is also used in the construction of vehicles, mostly ships, trains, and cars. Aircraft manufacturers tend to prefer aluminium alloys, as they are more lightweight. That being said, stainless steel is essential in the production of aircraft frames and various structural elements of the landing gear. For all vehicles, however, stainless steel combines good mechanical properties with high longevity (due to its resistance to corrosion), making for durable and long-lived parts.

Construction and architecture are two further domains that love stainless steel. The combination of strength and high chemical inertness makes this alloy ideal for structural elements in buildings such as skyscrapers, or in exposed elements, such as fire escapes or service ladders.

Jewelry manufacturers also employ stainless steel in their products, where it’s preferred due to its hypoallergnic properties (it doesn’t trigger metal allergies).


Stainless steel, today, is an indispensible alloy. Our societies depend heavily on it, using it in everything from tiny knicknacks around the house to the mightiest skyscraper. Its unique combination of strength, longevity, and relatively low cost makes it so that, most likely, stainless steel won’t be replaced anytime soon.

Scientists turn water into shiny metal

With enough pressure, you can turn anything into metal, and water is no exception. However, scientists Czech Academy of Sciences in Prague managed to turn liquid water into a bronze-like metallic state without having to apply ungodly amounts of pressure, which makes the achievement all the more impressive.

Electrons from alkali metals diffused into a thin water layer, giving it metallic properties and a characteristic golden hue. Credit: Philip Mason.

If squeezed together tightly enough, atoms and molecules can become so compacted in their lattice that they begin to share their outer electrons, allowing them to travel and basically conduct electricity as they would in a copper wire. Case in point, in 2020, French scientists turned the simplest gas in the universe, hydrogen, into a metal and fulfilled a prediction made in 1935 by Nobel Prize laureates Eugene Wigner and Hillard Bell Huntington. Metal hydrogen is, in fact, a superconductor, meaning it conducts electricity with zero electrical resistance.

To do so, the French researchers subjected hydrogen to a staggering 425 gigapascals of pressure — more than four million times the pressure on Earth’s surface, and even higher than that in the planet’s inner core. Therefore, it’s impossible to find metallic hydrogen on Earth, although it may very well be found in Jupiter and Saturn, which are mostly composed of hydrogen gas and have stronger internal pressures than the Earth. Likewise, Neptune and Uranus are believed to host water in a metallic state thanks to their huge pressure.

With the same approach, water would require 15 million bars of pressure to turn it into a metal, more than three times the requirement for metallic hydrogen. That’s simply out of our current technology’s reach. However, there may be another way to turn water metallic without having to squeeze it with the pressure of a gas giant’s core, thought Pavel Jungwirth, a physical chemist at the Czech Academy of Sciences in Prague.

Jungwirth and fellow chemist Phil Mason wondered if water could be coxed to behave like a metal if it borrowed electrons from alkali metals, which are highly reactive elements in the 1st group of the periodic table. They got this idea after previously, Jungwirth and colleagues found that under similar conditions, ammonia can turn shiny.

But despite their willingness to go along with this experiment, the researchers faced a predicament. You see, alkali metals are so reactive in the presence of water that they tend to react explosively.

The solution was to design an experimental setup that dramatically slowed down the reaction so that a potentially catastrophic explosion was averted.

Ironically, the key to mitigating the explosive behavior of the water-alki metal reaction was the adsorbtion of water at very low pressure, about 7,000 smaller than that found at sea level. This setup ensured that the diffusion of the electrons from the alkali metal was faster than the reaction between the water and the metals.

Credit: Philip Mason.

The researchers filled a syringe with an alkali metal solution composed of sodium and potassium, which was placed in a vacuum chamber. The syringe was triggered remotely to expel droplets of the mixture which were exposed to tiny amounts of water vapor.

The water condensed into each droplet of alkali metal, forming a layer over them just one-tenth of a micrometer thick. Electrons from the mixture diffused into the water, along with positive metallic ions, giving the water layer a shiny, bronze-like glow. The entire thing only lasted for a mere couple of seconds, but for all intents of purposes, the scientists had just turned water into metal at room temperature, a fact confirmed by synchrotron experiments.

“We show that a metallic water solution can be prepared by massive doping with electrons upon reacting water with alkali metals. Although analogous metallic solutions of liquid ammonia with high concentrations of solvated electrons have long been known and characterized, the explosive interaction between alkali metals and water has so far only permitted the preparation of aqueous solutions with low, submetallic electron concentrations,” the authors wrote in the journal Nature.

What is chromium, the hardest metal on Earth

Chromium got its name from the bright pigments it can produce (‘chroma’ being the Greek word for “color”). But the ancient Greeks never knew this metal existed, as it was first isolated around 200 years or so ago in France.

Image via Piqsels.

In this short time together, however, we’ve come to rely on Chromium quite a bit. It has the distinction of being the hardest metal in the periodic table, very resistant to corrosion, and quite shiny. It is coated on jet turbines and iconic car fenders, mixed in stainless cutlery, and may have made cabs yellow.

So let’s take a look at this metal to see why we electroplate it to every surface possible.

Physical properties

Chromium is a chemical element with the atomic number 24 and the symbol Cr. Among its most defining factors are a shiny grey-silver color, extreme hardness, and very good chemical resistance.

Sitting between 8.5 and 9 on the Mohs hardness scale, it is the hardest metal and the third hardest element we’ve ever found after carbon and boron. The Mohs scale is a relative system in which the hardness of a sample is determined by its ability to scratch other samples of known hardness. For reference, a steel file would be between 5 and 6.5 on the Mohs scale and a diamond would be a 10.

High hardness means that moving parts made of this metal are resistant to wear, tear, and generate less friction, so it does see quite a lot of use in machinery and tools. By itself, however, chromium is extremely brittle, so it’s very rarely used in pure form. Alloying it with something else reduces its overall hardness, too, so it’s most often applied to metal or plastic parts using electroplating.

Stainless steel contains at least 10.5% Chromium.
Image via Pixabay.

As a bonus, it’s also very resistant to chemical attack (such as corrosion and oxidation) and takes a nice polish. Industrial coatings of chromium (or ‘hard’ plating) tend to be thicker and less appealing, but most chrome finishes available on consumer products (‘decorative’ plating) will stay shiny with minimal effort for quite a while.

By far the largest use of chromium today is for alloys, particularly in stainless steel (which has at least 10.5% chromium) to which it imparts high resistance to corrosion.

It’s not just resilience with this metal. Chromium is surprisingly reflective, beaming back around 70% of visible light and 90% of infrared light — which makes for some striking finishes, as any petrolhead would agree.

It’s also the only solid element to show antiferromagnetism (doesn’t produce any magnetic field) at room temperature. This last property makes chromium essential in the production of hard disks.

Color me surprised

In the latter parts of the 18th century, the mineral crocoite (which contains Cr) from mines in the Ural Mountains became known, erroneously, as Siberian red lead and used as a pigment. By around 1796, French chemist Louis Nicolas Vauquelin managed to isolate chromium from this mineral, proving that it wasn’t lead. He found further traces of the new metal in gemstones such as ruby.

Vauquelin christened it chromium after seeing the range and brightness of colors it could create in solutions in his lab. The textile industry quickly started using chromium compounds as dyes and dye stabilizers (mordants) to make color better stick to cloth and prevent it from leaching during washings.

Fișier:Lead chromate.JPG
Chrome yellow.
Image via Wikimedia.

One of Vauquelin’s students, Andreas Kurtz, moved to England in 1822 and started producing potassium bichromate, a mordant, for local textile mills charging 5 shillings a pound. Competition soon drove the prices down to 8 pence a pound, at which point Kurtz switched production to chromium pigments. One of his products, chrome yellow, gained the limelight when Princess Charlotte, daughter of George IV, had it used to paint her carriage. Folk wisdom holds that this spawned the idea of yellow cabs.

In keeping with this theme of color, naturally occurring chromium gives rubies their red hue (if chromium is absent, the stone will be blue — a sapphire). Chromium is thus needed for the creation of synthetic ruby, including those used to generate lasers.

It can also be added to glass to make it green and is currently the main ingredient in some green, yellow, red, and orange paints.

Specialized metal

Chromium has quite a few properties that make it ideal for different roles.

Its high resistance to corrosion allows it to resist the attacks of kerosene or rocket fuel, so chromium is often mixed into the alloys of mechanical parts or used to coat them. Its high hardness and low friction also make it well-suited for the coating of moving parts in jet engines.

Stainless steel gains both hardness, strength, and resistance to chemical attacks such as corrosion from chromium. Our industries and buildings rely heavily upon this material, as do we as consumers, so it would be hard to imagine a world without this metal around.

Chromium salts are heavily used in the tanning of leather, but producers are trying to move away from this metal due to concerns about toxicity.

Speaking of which, there are two broad forms of chromium: trivalent and hexavalent. The trivalent form is known to be only weakly toxic as it has a hard time permeating through biological membranes. Hexavalent chromium, on the other hand, is highly toxic and a powerful mutagen, having been linked to stomach tumors (through contaminated water).

There is some debate as to its biological role. Authorities from Australia, New Zealand, India, Japan, and the United States list chromium as a trace element (a micronutrient) as it is required in the formation of insulin. According to eufic, “in general, meat, shellfish, fish, eggs, wholegrain cereals, nuts, and some fruits and vegetables are good sources of chromium”.

Regardless of its biological role, chromium remains an incredibly versatile metal and a pretty one at that. Whether for space engines, rubies, or just for some very bling finishings, chromium will likely remain one of our most useful materials in the future.

New shape-shifting metal particles shred drug-resistant bacteria to bits

New research at RMIT University is looking into liquid metals as a solution to drug-resistant bacteria.

Image credits Aaron Elbourne et al., (2020), ACS Nano.

The approach the team is working on involves using magnetic particles of liquid metals to physically destroy bacteria, side-stepping the use of antibiotics entirely. The study describes how this technique can be used to destroy both bacteria and bacterial biofilms — protective, layered structures that house bacteria — without harming human cells.

A shred of hope

“We’re heading to a post-antibiotic future, where common bacterial infections, minor injuries and routine surgeries could once again become deadly,” says Dr Aaron Elbourne, a Postdoctoral Fellow in the Nanobiotechnology Laboratory at RMIT, and the paper’s lead author.

“It’s not enough to reduce antibiotic use, we need to completely rethink how we fight bacterial infections.”

The rising levels of antibiotic resistance recorded throughout the world is a very scary development, one that we’ll have to tackle sooner rather than later. Modern antibiotics fundamentally changed the rules of life for us when they were first developed 90 years ago. Before that, any infection was basically the luck of the draw: even a routine medical intervention or the most unassuming of wounds could become infected, and even the humblest infection could kill.

They still can, but modern antibiotics offer us a level of protection that people in the past could only pray for. Still, overuse and misuse of these compounds are forcing pathogens to adapt and survive, and they’re doing so much faster than we can develop new, more powerful drugs. It’s estimated that antibiotic-resistant bacteria cause in excess of 700,000 deaths per year, a figure which could reach 10 million a year by 2050 (which would make it deadlier than cancer). Bacteria’s ability to form biofilms further complicates the matter, as such structures render them virtually immune to all existing antibiotics.

Antibiotics are chemical compounds that prevent bacteria from functioning properly. They can do this through a range of methods: by blocking their ability to form proteins, by breaking down their membrane, or by interfering with their ability to reproduce. Human cells and bacterial cells are similar but different enough that antibiotics can be made to target the latter and leave the former unaffected.

The team wanted to develop a whole new method to attack pathogens, one that does away completely with chemical means (which bacteria can adapt to).

“Bacteria are incredibly adaptable and over time they develop defences to the chemicals used in antibiotics, but they have no way of dealing with a physical attack,” Dr. Elbourne explains.

“Our method uses precision-engineered liquid metals to physically rip bacteria to shreds and smash through the biofilm where bacteria live and multiply.”

The team’s approach involves the use of nano-sized droplets of liquid metal. When exposed to a low-intensity magnetic field, these droplets change shape and grow sharp edges.

To check how effective they would be at the task, the team placed droplets in contact with a bacterial biofilm then made them change shape. The sharp edges broke down the biofilm and physically ruptured the bacterial cells inside, the team found. They proved effective against both Gram-positive and Gram-negative bacterial biofilms. After 90 minutes of exposure to the particles, both biofilms were destroyed and 99% of the bacteria inside were killed, the team explains, suggesting that they would be effective as a wide-range treatment option. Human cells were left unaffected by the nanoparticles.

The team says that their method is versatile enough to be used in multiple settings and approaches. For example, a coating of the nanoparticles could be sprayed on implants to help prevent infections for hip or knee replacements. They also plan to explore its effectiveness against fungal infections, cancerous tumors, and build-ups such as cholesterol plaques.

“There’s also potential to develop this into an injectable treatment that could be used at the site of infection,” said Dr Vi Khanh, a Postdoctoral Research Fellow at the North Carolina State University and co-author of the paper.

The nanoparticles are currently undergoing preclinical trials in animals. If all goes well, human trials could start in a few years.

The paper “Antibacterial Liquid Metals: Biofilm Treatment via Magnetic Activation” has been published in the journal ACS Nano.

Scientists design spider- and ant-inspired metal structure that doesn’t sink

This metallic structure is so water repellent (superhydrophobic) that it can stay afloat even when it is highly punctured. The innovative design was inspired by diving bell spiders and the rafts of fire ants.

A metallic structure etched by lasers, right, floats to the top on the water’s surface in professor Chunlei Guo’s lab. Credit: University of Rochester photo / J. Adam Fenster.

Researchers at Rochester University, led by Chunlei Guo, who is a professor of optics and physics, used high-speed, femtosecond laser pulses to etch intricate micro and nanoscale patterns onto the surface of aluminum plates. These patterns trap air, making the surface superhydrophobic.

However, when the plates are immersed in water for long periods of time, they eventually start losing their water-repelling properties and sink. Luckily, nature had already found a solution.

Diving bell spiders (Argyroneta aquatic) can survive for extended periods of time underwater by trapping air in their dome-shape web, also called a diving bell. The web carries air from the surface between the spider’s super-hydrophobic legs and abdomen. Fire ants employ a similar strategy, forming a huge raft out of many individuals that can stay afloat thanks to the air trapped between the ants’ superhydrophobic bodies.

“That was a very interesting inspiration,” Guo says. As the researchers note in the paper: “The key insight is that multifaceted superhydrophobic (SH) surfaces can trap a large air volume, which points towards the possibility of using SH surfaces to create buoyant devices.”

The researchers treated two aluminum plates by etching patterns with lasers and then placed them parallel to one another, facing inward, rather than outward. The resulting structure is enclosed and free from external forces. The separation between the plates is just right such that the structure may trap air to keep it floating. Essentially, the setup creates an air-tight, waterproof compartment even when the structure is forced to submerge in water by a heavy object.

The superhydrophobic structure remains afloat even after significant structural damage.

Tests showed that even after being submerged for two months, the structure still bounced back to the surface of the water once a weight was released. When the structure was punctured multiple times, it could still float because air remained trapped in the undamaged sections. Guo says that although they used aluminum for this study, any metal could be made to float using this etching process.

According to the researchers, the technology is ready for commercial applications since the industry is already equipped with the fast scanning lasers required to do the nanoscale etching. Possible applications include unsinkable ships, highly water-resistant wearables, and electronic monitoring sensors that can survive long-duration missions in the middle of the ocean.

The findings were reported in the journal ACS Applied Materials and Interfaces.

Lunar dirt can be broken down into oxygen and metals

New research from the University of Glasgow is working out how to squeeze metal and oxygen from dry rock; dry moon rocks that is.

Image credits Beth Lomax, University of Glasgow.

Samples of regolith (dirt) retrieved from the Moon revealed that the material is made up of between 40% to 45% oxygen by weight. Essentially, this vital (for us) gas is the single most abundant element in the lunar soil. A group of researchers plans to draw the oxygen out of the dirt, in order to give astronauts and colonists a reliable and plentiful source of breathable air and metals.

Rise from the dirt

“This oxygen is an extremely valuable resource, but it is chemically bound in the material as oxides in the form of minerals or glass, and is therefore unavailable for immediate use,” explains researcher Beth Lomax of the University of Glasgow, whose Ph.D. work is being supported through the European Space Agency’s (ESA) Networking and Partnering Initiative.

The approach involves the use of molten salt electrolysis to pry apart the Oxygen and metallic atoms in regolith. The team reports that this is the first “direct powder-to-powder processing of solid lunar regolith simulant” that can extract all the oxygen in such a sample. Alternative methods, they add, either achieve much lower yields or require extreme temperatures (in excess of 1600°C) to work.

The team placed powdered regolith in a mesh-lined basket, mixing in molten calcium chloride salt as an electrolyte. Then they baked everything up to 950°C. While the regolith is still solid at this temperature, the team explains that pushing current through it causes the oxygen atoms to migrate across the molten salt and build-up at the anode.

The technique takes around 50 hours to pull 96% of the oxygen from a sample, but around 75% of the total is extracted in the first 15 hours.

“This research provides a proof-of-concept that we can extract and utilise all the oxygen from lunar regolith, leaving a potentially useful metallic by-product,” adds Lomax.

“This work is based on the FCC process — from the initials of its Cambridge-based inventors — which has been scaled up by a UK company called Metalysis for commercial metal and alloy production.”

Going forward, the team plans to continue cooperating with Metalysis and ESA to ready the process for a lunar context. The process would give lunar settlers access to oxygen for fuel and life support, and raw material (metals) for on-site manufacturing. Exactly what metals they would obtain, the team says, would depend on where on the Moon they land.

Furthermore, the same approach could likely work on Mars as well, materials engineer Advenit Makaya told Phys. The findings also tie in nicely with previous research that developed an approach to extract water out of lunar regolith. Future colonists, it seems, will have ample resources at their disposal.

The paper “Proving the viability of an electrochemical process for the simultaneous extraction of oxygen and production of metal alloys from lunar regolith” has been published in the journal Planetary and Space Science.

Moon anomaly.

Mysterious gravitational anomaly in Moon’s South Pole could be a massive metal deposit

A mysterious, large mass of material in the Moon’s South Pole could be a treasure trove of metals.

Moon anomaly.

Image credits NASA Goddard Space Flight Center / University of Arizona.

Wedged deep into the Aitken basin, our natural satellite’s South Pole, one can find a mysterious mass of material, report researchers from the Baylor University. This large mass may be a remnant of the asteroid that crashed into the Moon and formed the crater — which would also mean that it could be made up almost entirely out of metal.

Ka-tching

“Imagine taking a pile of metal five times larger than the Big Island of Hawaii and burying it underground. That’s roughly how much unexpected mass we detected,” said lead author Peter B. James, Ph.D., assistant professor of planetary geophysics in Baylor’s College of Arts & Sciences.

The Aitken basin crater is oval-shaped and about 2,000 kilometers wide — roughly the same distance Waco, Texas, and Washington, D.C. It’s also several miles deep. Despite its size, however, we can’t see this crated from Earth because it’s on the far (dark) side of the Moon.

But one place where this crater is abundantly evident is on gravity maps. Using data from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission and topography readings from the Lunar Reconnaissance Orbiter, the team uncovered an “unexpectedly large amount of mass hundreds of miles underneath the South Pole-Aitken basin,” James says.

“One of the explanations of this extra mass is that the metal from the asteroid that formed this crater is still embedded in the Moon’s mantle.”

The dense mass—”whatever it is, wherever it came from”—is weighing the basin floor downward by more than half a mile, he said. Computer simulations of large asteroid impacts suggest that, under the right conditions, an iron-nickel core of an asteroid may be dispersed into the upper mantle (the layer between the Moon’s crust and core) during an impact.

“We did the math and showed that a sufficiently dispersed core of the asteroid that made the impact could remain suspended in the Moon’s mantle until the present day, rather than sinking to the Moon’s core,” James said.

However, we won’t know for sure whether this is the case or not until we actually put some boots (or wheels) on the Moon to study the unknown mass in situ. The team notes that a concentration of dense oxides associated with the final stages of a magma ocean solidifying inside the moon would also produce the same readings.

But there are reasons to believe that the mass is, indeed, tied to an asteroid impact. The South Pole-Aitken basin is the largest still-preserved crater in the whole solar system (meaning that, while larger impacts may have occurred here, this is the largest one we still have evidence of). James called the basin “one of the best natural laboratories for studying catastrophic impact events, an ancient process that shaped all of the rocky planets and moons we see today.”

The paper “Deep Structure of the Lunar South Pole‐Aitken Basin” has been published in the journal Geophysical Research Letters.

Metallic wood.

Researcher devise ‘metallic wood’ that’s stronger than titanium but could float on water

A team of US researchers has developed a light, but incredibly strong new material — they’re calling it metallic wood. This material, despite being a porous sheet of nickel, is as strong as titanium but four to five times lighter.

Metallic wood.

A microscopic sample of the researchers’ “metallic wood.”
Image credits University of Pennsylvania.

The way atoms stack in a lump of metal determines how strong that metal is — but we can’t (yet) produce such objects. For example, a sample of perfectly-stacked titanium would be ten times as strong as any titanium we can create today. This comes down to random defects that form in the manufacturing process, impacting the metal’s overall properties.  Materials researchers have been trying to exploit this phenomenon by taking an architectural approach, controlling the metal’s nanoscale layout to unlock the mechanical properties that arise at the nanoscale, where defects have reduced impact.

In a new study, researchers at the University of Pennsylvania’s School of Engineering and Applied Science, the University of Illinois at Urbana-Champaign, the Middle East Technical University in Turkey, and the University of Cambridge have designed a new material in which every atom is carefully laid out in its correct place, leading to a surprisingly high strength-to-weight ratio.

Woody metal

“The reason we call it metallic wood is not just its density, which is about that of wood, but its cellular nature,” says lead author James Pikul, Assistant Professor in the Department of Mechanical Engineering and Applied Mechanics at Penn Engineering.

“Cellular materials are porous; if you look at wood grain, that’s what you’re seeing — parts that are thick and dense and made to hold the structure, and parts that are porous and made to support biological functions, like transport to and from cells.”

The team writes that the material’s porous nature and the self-assembly process in which it’s created make it akin to wood and similar natural materials. Their metallic wood is made up of dense, strong metallic struts surrounding empty pores. The design operates “at the length scales where the strength of struts approaches the theoretical maximum,” Pikul explains.

Pikul’s team started with tiny plastic spheres of a few hundred nanometers in diameter, which they suspended in water. As the water slowly evaporated, the spheres stacked onto each other into an orderly, crystalline framework. The spheres were electroplated with nickel, then dissolved — leaving behind a network of metallic struts.

Material production process.

The fabrication process for a unit cell of the material. (b–g) Cross section SEM images of the (nickel inverse opal) material.

Each strut is around 10 nanometers wide, which is roughly the length of 100 nickel atoms, they explain. The team favored this production method over other techniques like 3D-printing as it’s easier to scale up.

“We’ve known that going smaller gets you stronger for some time,” Pikul says, “but people haven’t been able to make these structures with strong materials that are big enough that you’d be able to do something useful. Most examples made from strong materials have been about the size of a small flea, but with our approach, we can make metallic wood samples that are 400 times larger.”

“We’ve made foils of this metallic wood that are on the order of a square centimeter, or about the size of a playing die side,” he adds. “To give you a sense of scale, there are about 1 billion nickel struts in a piece that size.”

Because some 70% of the material is empty space, it has extremely low density in relation to its strength. It’s just a tad less dense than water, meaning a block of this material could float while still being stronger than most metal alloys today.

In a somewhat ironic twist, this process of creating metallic wood (which is metal in a wood-like configuration) is the opposite of how researchers at the University of Maryland created superdense wood (which is wood in a metal-like configuration).

The team is now focusing on expanding the production process to commercially relevant sizes. The materials used aren’t particularly rare or expensive on their own, but the infrastructure needed to carry out the production process is currently very limited. If that infrastructure is developed, however, the team is confident that their metallic wood can be produced more quickly and cheaply than their prototype sample.

A larger production base would also allow the team to further test their creation. Since they’ve only produced a tiny sample in the lab, the team is limited in what macroscale tests it can run on the material.

“We don’t know, for example, whether our metallic wood would dent like metal or shatter like glass.” Pikul says. “Just like the random defects in titanium limit its overall strength, we need to get a better understand of how the defects in the struts of metallic wood influence its overall properties.”

Another exciting possibility is merging the metallic wood with other materials to tailor it to a wide range of applications. Infusing it with anode and cathode materials, for example, would essentially turn the metallic wood into a very solid battery.

“The long-term interesting thing about this work is that we enable a material that has the same strength properties of other super high-strength materials but now it’s 70 percent empty space,” Pikul says.

“And you could one day fill that space with other things, like living organisms or materials that store energy.”

For example, the material could be used to produce smart prosthetics that store their own power — which would be pretty sweet.

The paper “High strength metallic wood from nanostructured nickel inverse opal materials” has been published in the journal Nature.

Mercury.

Thawing Canadian Arctic permafrost is releasing “substantial amounts” of mercury into waterways

Well, I wasn’t expecting climate change to do that, to be honest.

Mercury.

Image credits Tavo Romann / Wikimedia.

Thawing permafrost in the Canadian Arctic is releasing record amounts of mercury into local waterways, according to ecologists from the University of Alberta. The effects are not properly understood right now, but mercury is known to be toxic compound (in high quantities) to both humans and other organisms.

Hg

“Concentrations of mercury were elevated for at least 2.8 kilometres downstream of thaw slumps,” says Kyra St. Pierre, who co-led the study. “This suggests that some mercury from thaw slumps may be transported for many kilometres through downstream ecosystems, and into larger waterways.”

Mercury (Hg) is a metal that occurs in a liquid form at room temperature. It’s toxic to most organisms in large quantities and tends to accumulate in food webs (i.e. it’s not processed in the body and gets passed on from prey to predator).

We don’t get much trouble from mercury since it’s simply not that abundant in most natural settings. However, it is in permafrosts — permafrost sediments are estimated to store more mercury than Earth’s oceans, atmosphere, and soil combined, the team report. As climate change thaws these permafrosts, the mercury stored therein becomes mobile and leaches into the surrounding environment.

The issue is exacerbated by increasing precipitation in the Canadian Arctic (also due to climate change), the team adds.

“Climate change is inducing widespread permafrost thaw,” explained St. Pierre. “In regions where this results in thaw slumping, this may release a substantial amount of mercury into freshwater ecosystems across the Arctic.”

For now, the exact implications of this mercury contamination remains unknown. The team says that organisms in the area might absorb the metal from the environment (through food and drinking water), however, they don’t yet have sufficient data to tell. It may well be that local plants and wildlife are absorbing mercury but at too low levels for it to be a threat to the food web. Of course, the opposite may also be true.

The results, the team says, highlight the need for further research on mercury cycling in regions experiencing active permafrost thaw. They also say more research is needed on if (and how) this mercury might enter food webs in surrounding ecosystems.

The paper ” Unprecedented Increases in Total and Methyl Mercury Concentrations Downstream of Retrogressive Thaw Slumps in the Western Canadian Arctic” has been published in the journal Environmental Science & Technology.

MOF-303 crystals.

New material harvests water from thin air without using energy — even in dry, arid Arizona

One kilogram of the new metal-organic framework (MOF) material can produce 0.2 liters (7 ounces) of water every 24 hours — even in dry Arizona.

Device prototype.

The team’s prototype water harvester.
Image credits: Wang Laboratory / MIT.

Us reading this probably take it for granted that if you turn a tap in your kitchen freshwater flows out. However, many people make their homes in arid areas where that is just a pipe dream — but they still need a reliable source of water. A new material developed by a team at the University of California, Berkley, might be just what provides that hydration. One kilogram of the material, a metal-organic framework (MOF), produced 0.2 liters (7 ounces) of water during a 24-hour trial in Arizona — without using any energy.

Water from thin air

The team first built a prototype water harvester last year — it used solar heat to capture water vapor from the air. Now, they’ve scaled up their device, plopped it down in the backyard of a tract home in Arizona, and waited for it to complete a full 24-hour cycle. The results are consistent with what the team predicted in 2017, after running their prototype through field trials: the new, larger device can produce drinkable water at very low humidity for almost no cost.

“There is nothing like this,” said Omar Yaghi, paper co-author. “It operates at ambient temperature with ambient sunlight, and with no additional energy input you can collect water in the desert. This laboratory-to-desert journey allowed us to really turn water harvesting from an interesting phenomenon into a science.”

The trial was carried out in Scottsdale. Relative humidity here drops from 40% at night to 8% during the day, the team reports. Despite this, the harvester worked — and, according to the team, it can easily be scaled up by simply adding more MOF. This highly porous material, MOF-801, was produced from metal zirconium. The researchers calculate that one kilogram of this material (2.2 pounds) can harvest about 200 milliliters (about 7 ounces) of water per kilogram (2.2 pounds) of MOF.

MOF-303 crystals.

Optical microscope images of MOF-303 crystals.
Image credits Omar Yaghi laboratory, UC Berkeley

However, Yahgi says the team has also been working on a new MOF, dubbed MOF-303, based on aluminum. This should be much cheaper than MOF-801 — the team estimates it will be at least 150 times cheaper — and twice as effective. Lab tests showed that MOF-303 could produce over 400 milliliters (14 ounces) of water per day per kilogram of MOF — equivalent to about 3 cups.

“There has been tremendous interest in commercializing this, and there are several startups already engaged in developing a commercial water-harvesting device,” Yaghi said. “The aluminum MOF is making this practical for water production, because it is cheap.”

MOFs are solids, but they’re mostly hollow. They’re crisscrossed with an immense number of internal channels or holes, giving them a huge equivalent surface area: one sugar-cube-sized piece of MOF has the internal surface of roughly six football fields, the team notes.

Because of all of this surface area, MOFs easily trap gases or liquids. When heated, they release the fluids, allowing for easy retrieval.

The team’s harvester is essentially a box placed within another box. The inner structure packs a 2-square-foot bed of MOF pallets, open to the air, to absorb moisture. The outer box is a 2-foot cube, constructed out of transparent plastic. The top is left open at night to let moist air flow in and come into contact with the MOF, and replaced during the night to heat the material so it releases stored water. This water then condenses on the insides of the outer box, drips to the bottom, and gets collected.

While not yet suited for commercial applications (for example, the team had to harvest the water with a pipette), it does marvelously as a proof-of-concept device. It could lead the way to cheap and reliable water harvesters for use in arid areas. It will also capture water at sub-zero dew points, the team notes.

The team plans to test their aluminum-based MOF later this summer in the Death Valley National Park, to see how it performs in these higher average temperatures.

The paper “Practical water production from desert air” has been published in the journal Science Advances.

Credit: Wikimedia commons.

First metal pollution event in Europe suggests Europeans were smelting metal 5,600 years ago

Credit: Wikimedia commons.

Credit: Wikimedia Commons.

We sometimes tend to think that pollution is a modern occurrence. In reality, ever since humans first settled and transitioned from a hunter-gatherer lifestyle to an agrarian society, we’ve been polluting the environment one way or another, through things like deforestation, fire, livestock farming, and metalwork. According to a new study, the first case of metal pollution may have occurred in the Balkans as early as 5,600 years ago.

The metal ages in the Balkans

In the process of exploiting mineral resources, microscopic chemical particles are released into the atmosphere from mining and smelting. These particles can settle on the surface of a peat bog, where sediment layers grow atop each other year after year. By peeling off and examining these layers, it’s possible to infer certain economic activities and when they occurred.

In our case, a team at Northumbria University, in collaboration with colleagues at the University of Montpellier and the Romanian Academy, traveled to the Crveni Potok peat bog, located on the Serbia/Montenegro border. By analyzing the ancient sediments accumulated in the bog, the researchers uncovered the first clear evidence of metal pollution originating from lead in the region, dating back to approximately 3600 BC. The lead signal is supported by the concurrent rise in charcoal concentration, which is associated with biomass burning for metal smelting.

Previously, the earliest case of metallurgy was thought to have occurred in western Europe, but the new findings published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) suggest that activity in the Balkans preceded it by at least 500 years. The Britons, for example, were still in the stone age at this time. As such, the study supports the idea that for a long time the region has been an important seat for economic and technological development in the continent. It also seems to be the birthplace of metallic pollution, which doesn’t sound nearly as glorious.

“Much of the focus in determining sources of ancient pollution has been on established sources such as the Romans or ancient Greeks, but these findings highlight the crucial role that the Balkan metallurgy has played in the economic development of the area,” said Dr. Vasile Ersek, Senior Lecturer in Physical Geography at Northumbria University.

Map of Europe indicating location of Crveni Potok (red star). Also presented are locations of major metallogenic mining regions exploited before 1,800 CE (85) and the Banatitic Magmatic and Metallogenic Belt (highlighted in brown). Credit: PNAS.

Map of Europe indicating location of Crveni Potok (red star). Also presented are locations of major metallogenic mining regions exploited before 1,800 CE (85) and the Banatitic Magmatic and Metallogenic Belt (highlighted in brown). Credit: PNAS.

Metal extraction and smelting continued in the Balkans well into recent history. Studies of metal particles deposited in sediments suggest that lead pollution decreased dramatically in western Europe after the collapse of the Roman Empire, but the same can’t be said about the Balkans. So, while western Europe was in the ‘Dark Ages’ there was significant economic development in the region.

“This goes against the long-held view of barbaric hordes with little technological know-how ousting the Romans leading to the Dark Ages – as we term the 1,000 years following the Roman period. These Dark Ages may well have been true in much of Western Europe, but in the Balkans, it seems that this period was, in fact, rather ‘well-lit’,” said Jack Longman, lead author of the new paper who was completing his Ph.D. at Northumbria.

This isn’t the first time that scientists have documented human activity from ancient pollution. Previously, researchers who sampled ice cores from Greenland could follow how the Roman Empire waxed and waned by judging from lead pollution trapped in the ice from as early as 1100 BC to AD 800.

Scientific reference: Exceptionally high levels of lead pollution in the Balkans from the Early Bronze Age to the Industrial Revolution Jack Longman, Daniel Veres, Walter Finsinger, and Vasile Ersek PNAS May 29, 2018. 201721546; published ahead of print May 29, 2018. DOI: doi.org/10.1073/pnas.1721546115 .

 

L. vladi.

Ugly Unicorn: Metal-tipped prehistoric ant drank the blood of its victims for dinner

A newly-described species of ant is so outlandishly frightful that it can only be called “hell ant.”

Hell ant.

Image credits P. Barden et al., 2017.

Brandishing upward-facing blades in lieu of regular mouth pieces, a metal-infused feeding horn, and the vampiric diet to go with the lot, Linguamyrmex vladi seems custom-tailored to star in every nightmare you’ll ever have. Fret not, however, for the species has been extinct — along with its extended lineage — since the Cretaceous.

The insect has just been described by a team from the New Jersey Institute of Technology in Newark led by Dr Phillip Barden. Nicknamed the “hell ant,” the insect was found preserved in 98-million-year-old amber and has a freakishly brutal anatomy.

The ant to rule them all

This insect is armed to the teeth — literally. The hell ant traded its mandibles for spike-like blades, which look pointy and unpleasant. This unique physiognomy, however, also posed a few issues for the team. It’s unlike anything living today, which made describing and understanding how Linguamyrmex vladi lived quite the challenge.

However, the team managed to find one feature which links them to modern species —  short hairs around hell ants’ mouths. These are highly similar to those seen in trap-jaw ants (genus Odontomachus) which cause their jaws to snap shut when triggered. This led the team to suspect that the hell ants’ jaws functioned in a similar way, and helped them piece together the rest of its story.

L. vladi.

(A) Lateral view of the ant. (B) View of head capsule and mesosoma. Scale bars are 0.5 mm / 0.02 inch. Whoa..
Image credits P. Barden et al., 2017.

This is quite fortunate because that ‘rest of the story’ is pretty metal as well. L. vladi also had a deadly horn jutting out over its blade-like mandibles. Whenever some insect touched the hairs, the hell ant’s mandibles would contract, flipping its prey and punching the horn through its armored outer layers. The team describes a structure on the ant’s head that seems designed to absorb the force of the jaws:

“You have this sort of stopping plate, made to accommodate the mandibles closing and capturing prey,” says Barden.

In fact, based on CT scans performed on the ambered insect, the team says L. vladi’s clypeal paddle (the bit of its head where the jaws are set and elongates to form the horn) was covered in a layer reinforced with metal.

“This reinforcement occurs primarily along the centre of the paddle and, as the specimen is preserved with the mandibles largely ‘closed’ and positioned near this spot, suggests that the reinforcement is intended to accommodate mandibular impact,” they write.

Paper co-author Vincent Perrichot explains that the metal likely helped “keep the horn undamaged,” a method which some insects today still use to reduce wear and tear in areas that usually take a battering, adds Barden.

Anatomy.

Image credits P. Barden et al., 2017.

Not content with merely being the ant equivalent of an evil, metal-sheathed unicorn, L. vladi was also likely a vampire. When its mandibles moved upwards, the team reports, they formed a ‘gutter’ which was likely used to funnel haemolymph (bug blood) down the hell ant’s “mouthparts,” Barden explains. The team also found a beetle grub preserved alongside L. vladi in the amber, the kind of “squishy, haemolymph-laden insect” that could underpin its diet. Judging from its metal-tipped weaponry, however, it’s likely that L. vladi could easily penetrate the armor of adult insects as well.

“Until we find a specimen with the prey item trapped, which is probably a matter of time, we’re left to speculate,” says Barden.

The Myanmar, Burma, amber deposits where this ant was found are thankfully very rich, so we may find just what the team needs sometime soon.

The paper “A new genus of hell ants from the Cretaceous (Hymenoptera: Formicidae: Haidomyrmecini) with a novel head structure” has just been published in the journal Systematic Entomology.

These are the most metal words in the English language, data scientist says

Every once in a while scientists turn their minds from stars or finding more nutritious foods towards life’s real questions: for example, how to sound as metal as possible.

Image credits to Getoar Agushi / Wikimedia

Former physicist turned data scientist Iain of Degenerate State crunched the numbers and has the keywords you need to say to impress. Iain mined DarkLyrics.com, “the largest metal lyrics archive on the web,” for the lyrics of 222,623 songs by 7,634 bands and analyzed them to find the most, and least, metal words in existence. By comparing the data from DarkLyrics with the Brown Corpus — a 1961 collection of English-language documents that is “the first of the modern, computer readable, general corpora” — he put together a list of the 20 most and least metal words, along with their “metalness” factor.

So without further ado, Iain’s top 10 most metal words are:

  1. burn.
  2. cries.
  3. veins.
  4. eternity.
  5. breathe.
  6. beast.
  7. gonna.
  8. demons.
  9. ashes.
  10. soul.

And the top 10 least metal words:

  1. particularly.
  2. indicated.
  3. secretary.
  4. committee.
  5. university.
  6. relatively.
  7. noted.
  8. approximately.
  9. chairman.
  10. employees.

Iain’s method is actually more complex than you’d be inclined to think. He first analyzed the data from DarkLyrics and came up with word clouds showing the most common words in all of the songs. Just looking at this data doesn’t offer any special insight into the genre, however, he found.

“Metal lyrics seem focused on “time” and “life”, with a healthy dose of “blood”, “pain” and “eyes” thrown in. Even without knowing much about the genre, this is what you might expect,” he writes.

But looking only at the frequency with which each word appears in songs doesn’t actually tell us anything about which words are closest to the spirit of metal.

“To do this we need some sort of measure of what “standard” English looks like, and […] an easy comparison is to the brown corpus,” he adds.

Iain attributed each word a “metalness” factor, M, as the logarithm of the frequency with which it appears in lyrics over the frequency with which it appears in the brown corpus.

“To prevent us being skewed by rare words, we take only words which occur at least five times in each corpus.”

He plotted the Metalness of all 10,000 words here, so you can know exactly how intense each word you say is. Unsurprisingly, topics like university and employment don’t quite have the metalness of say, demons or the fiery hells.

Iain says that his final analysis isn’t perfect — because of the different topics in the brown corpus and the lyrics, some words are naturally favoured with more or less metalness. A more precise measurement should involve comparison with other musical genres.

“A better measure of what constitutes “Metalness” would have been a comparison with lyrics of other genres, unfortunately I don’t have any of these to hand.”

However, it’s accurate enough to tell you what you need to know — the next time that sexy someone in a Judas Priest t-shirt saunters by, leave your uni and job alone. Your burning soul, the cries of the beast running through your veins and so on are all you need to talk about.

mid-air-3d-printing

This machine 3-D prints metal objects in mid-air

mid-air-3d-printing

Credit: YouTube

Harvard researchers have demonstrated an all new 3-D printing technique that creates metals objects with complex shapes right in mid-air. This is fundamentally different from the approach of traditional 3-D printers which ooze polymer material layer by layer. The new fabrication technique could prove very useful in the production of  flexible, wearable electronics, sensors, antennas, and biomedical devices.

To make objects in mid-air, the Harvard printer injects silver nanoparticles through the nozzle, then immediately fires a focused laser beam onto the material to harden it. The nozzle can move along x, y, and z axes, but also in a combination with a rotary print stage. This high degree of freedom means complex metal shapes can be printed, previously difficult if not impossible to make with traditional techniques.

As you can see in the demo video below, the researchers made anything from coils to  a butterfly made of silver wires narrower than a hair’s width.

This was a tricky job, though. The main challenge was syncing the nozzle “ink” and the laser, the researchers report in Proceedings of the National Academy of Sciences.

“If the laser gets too close to the nozzle during printing, heat is conducted upstream, which clogs the nozzle with solidified ink,” said Wyss Institute Postdoctoral Fellow Mark Skylar-Scott. “To address this, we devised a heat transfer model to account for temperature distribution along a given silver-wire pattern, allowing us to modulate the printing speed and distance between the nozzle and laser to elegantly control the laser annealing process ‘on the fly.’”

“This sophisticated use of laser technology to enhance 3-D printing capabilities not only inspires new kinds of products, it moves the frontier of solid free-form fabrication into an exciting new realm, demonstrating once again that previously accepted design limitations can be overcome by innovation,” said Wyss Institute Director Donald Ingber, who is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and the Vascular Biology Program at Boston Children’s Hospital, as well as professor of bioengineering at SEAS.

Composite metal foam better at stopping bullets than solid plates

After developing metal aerogels, foams and glass (here and here) researchers have found yet another novel way to structure these substances. Composite metal foam (CMF) is a type of material created by incorporating hollow beads of one metal into a substrate cast from another. Considering their low density, you could be fooled into assuming that they’re very flimsy. But they boast impressive physical characteristics — they can even stop armor piercing bullets.

Check out this video North Carolina State University recently uploaded to their YouTube channel.

The video shows a 7.62 x 63 mm standard-issue M2 armor piercing bullet, fired at the plate according to the testing procedures established by the National Institute of Justice (NIJ). The plate, less than one inch thick, was tough enough to turn the bullet to dust. While solid metal plates of similar thickness would also be able to stop the projectile, the test CMF plate actually performed better at the task. Not bad for what is essentially metal Swiss cheese.

Afsaneh Rabiei, professor of mechanical and aerospace engineering at NC State, explains:

“We could stop the bullet at a total thickness of less than an inch, while the indentation on the back was less than 8 millimeters,” he says.

“To put that in context, the NIJ standard allows up to 44 millimeters indentation in the back of an armor.”

As a bonus, they’re also lighter than metal plating. So there’s obviously a lot of interest in creating new types of body and vehicle armor based on them.

But what if even incredibly light and strong just doesn’t cut it? What if you need to haul nuclear waste around or need a material that can withstand the enormous temperatures of atmospheric re-entry? CMFs can help with that too.

Last year, aided by the Department of Energy’s Office of Nuclear Energy, Rabiei showed that these materials are very effective at shielding X-rays, gamma rays and neutron radiation. Rabiei independently published his work demonstrating that these metal foams handle fire and heat twice as well as the plain metals they are made of earlier this year.

A full paper of the ballistic properties of CMFs, with the title “Ballistic performance of composite metal foams” has been published online in the journal Composite Structures and can be read here.

 

 

How the Copper Age changed humanity

Since man first found he could sharpen a stick to defend himself, we’ve realized the importance of good quality tools in making our life easier and more bountiful. In our search for better and better tools and weapons, wood gave way to rocks tied to sticks, that were in turn replaced by chiseled pieces glued and fastened to hardy handles. Whole communities came to rely on those that could turn their hand to working stone, to people such as Otzi.

Otzi was the finest stone-shaper in the village; the tools he produced bit deep into soil, fell trees and boars alike with ease, and chased away many a pillaging group. They were the zenith of the day’s technology, underpinning every field of human activity, from agriculture to crafts, to battle. And today, grasping an axe that he himself chiseled, standing next to his fellow villagers, facing strange people from stranger lands, Otzi was prepared to defend his home once again. But as battle raged and stone splintered on the invader’s weird, reddish weapons and armor, realization crept over the defenders; stone was no longer king.

The age of copper had begun.

Copper bars
Image via images-of-metals

The red stone that won’t break

Copper is widely believed to be the second metal (after gold) that humans learned to shape and utilize. It was more easily encountered and obtained than other metals as it forms native element bodies throughout the crust, and archaeological consensus places its discovery at 9000 BC somewhere in the Middle East — though like agriculture, it was most likely discovered independently by several groups of people.

A lot softer than iron, with 3.0 on the Mohs scale compared to iron’s 4.5, and very malleable, the metal could easily be beaten into shape and if done at room temperature this would create more durable edges as the metal’s crystals aligned to the mechanical stress. Being easy (compared with other metals) to mine and process but more durable, malleable and less brittle than stone, copper started replacing it as the material of choice for tools, weapons and other objects. However, as limited people had knowledge of the metal or how to work it and as it was fairly expensive, stone remained the most used material throughout the copper age.

Still, this was little comfort to the peoples that were enslaved by more technologically advanced tribes and empires, in part due to lacking the adequate weapons to defend themselves, such as our hypothetical Otzi.

From finding to extracting

Elemental copper was the first source of the metal that humans used, for obvious reasons — it’s easy to find and doesn’t need much refining. If a big enough chunk was found, all you had to do was hammer it into whatever shape you needed.

Native copper. Image via wikimedia

Native copper.
Image via wikimedia

However, this is limited by the size and shape of the nuggets miners were able to find, and there wasn’t any way of making sure there weren’t impurities in the metal mass, that could ruin the final object’s properties. As copper deposits were exploited over time, such pieces of metal were increasingly hard to come by, so craftsmen started melting together smaller bits of copper into bars that they would then turn into finished products.

Most copper nuggets are found in this size.
Image via images-of-elements

Experimenting with melting the metal, smiths learned that they could treat copper to have different properties, depending on what they would use it for. If you took a copper bar, heat it up and let it cool down slowly (a process known as annealing), the metal’s crystalline structure would arrange in a more homogeneous structure and the copper was much softer and easier to shape, good for jewelry or coinage.

On the other hand, cold-processed copper had a more arranged crystalline structure, harder than the annealed metal. Tools and weapons were shaped this way, to make them more durable and allow them to keep a better edge.

Top: Annealed steel alloy, showing a heterogeneous, lamellar microstructure, consisting of phases richer in carbon next to phases richer in iron. Bottom: tempered steel, in which the carbon remains trapped within the crystals, creating internal stresses. While steel is an alloy, copper crystals behave similarly to heat treatment, with cold-shaped pieces showing the same internal stresses between crystals, helping them hold each other in place. Image via wikipedia

Top: Annealed steel alloy.
Bottom: tempered steel.
While steel is an alloy, copper crystals behave similarly to heat treatment, with cold-shaped pieces showing the same internal stresses between crystals, helping them hold each other in place.
Image via wikipedia

After deposits were depleted of most native copper bodies, smelting was employed to extract the metal from its ores. Early smelters were very primitive, so in these early days of metallurgy, only the most worthwhile material was processed. For example, some of the first recorded smelters were employed by the Sumerians, and they were no more than shallow pits in which ore was thrown over burning charcoal.

Exactly how they reached sufficiently high temperatures in the absence of bellows is still a matter of speculation — one theory holds that the smelters were covered with clay, leaving only an opening towards the prevailing wind to feed the fire. Hieroglyphs show that the Egyptians also had this problem, but solved it using a long tube to blow air into the furnace.

“I swear Amun, this job blows!”
Image via tf.uni-kiel

This is another major turning point in our history that copper brought about. Smelting involves much more than just melting the metal from the rock — it’s a delicate chemical process, requiring the use of a reducing agent to scrub the metal atoms of oxidizers (most often carbon in the form of charcoal that releases carbon monoxide as it burns, then pulls oxygen atoms from the ore, forming CO2) that usually bind to them, and flux is used to purify the melt.

Smelting was probably developed over a long period of time, with small improvements being added over time to the procedure. But without a metal useful enough to impose itself in human society, that could be found both in native and ore forms, smelting might have never been developed. And without smelting, other metals such as iron or aluminum would have never been discovered and used.

In the later part of the Copper age, as technology advanced, casting was employed on a wider and wider scale as a production method, especially for works of art such as statues or jewelry, for religious objects and some tools. This process required skilled craftsmen, as it is quite difficult to do with copper because of the formation of gas bubbles during the pouring of the metal and its shrinking when it cooled down.

The social impact

Ok so now we have a pretty good idea of how copper was extracted and processed in the beginning, but how exactly did the discovery of metal (especially one durable and abundant enough to rival stone) impact the lives of people?

In a time where virtually all labor was muscle-driven, having access to a material that can make your tools bend a bit instead of breaking — but that’s ok because you can totally hammer it back up — or make your sword shatter an enemy’s weapon was like playing life with cheat codes. This is why we tend to create chronologies (Stone age, Iron age, etc.) based on how widespread the use of some such material was in a certain region.

During the early stages of an age the use of the new metal was still infrequent, but became widespread during the middle stage and common in the final period, and the impact on societies should be viewed with this in mind.

One of the most distinctive societies of prehistoric Cyprus (the island from which the name of copper is derived) was the Erimi Culture. Mainly fishers and farmers throughout the Paleolithic, during the Copper Age the Erimi experienced a huge population increase, an explosion of arts and crafts but most importantly — the creation of social hierarchies.

People loved it; they used it for everything, from nails to pans to roof tiles, statues of gods or demons or pretty young ladies (hopefully) — if they could afford it. Villages grew in size and were fortified, with large houses and high-status goods denoting differences in wealth and position. Grain storage and food preparation became private rather than communal, as it was in the earlier villages.

Reconstruction of an Erimi house.
Image via wikipedia

With access to better tools, farmers — most of the population — were able to produce much more food than they required to feed themselves; those that had access to copper — few in number — would sell the tools, the weapons and miscellaneous metal goods that the community required, turning a sweet profit for themselves. Trade flourished both internally and with other peoples, and as the Erimi accumulated wealth, they had more and more time and resources to spend on arts, culture and science.

A typical copper ingot in the late Chalcolithic, meant for export.
Image via wikipedia

This trend keeps around the globe — as groups discovered copper and the means to extract it, they experienced (with some exceptions) huge demographic, economic, and cultural explosions, with social layers or hierarchies being cemented during this period.

Copper leads to bronze

Sometime in the late Chalcolithic, someone figured out that if you melt copper together with another metal such as arsenic, it becomes harder, more resilient and altogether better at everything people used copper for up to them. Exactly how this was discovered is still a matter of debate, but since copper ores are naturally contaminated with other metal, such as arsenic and tin, it’s likely it was discovered by chance during smelting.

No matter how the alloy came to be, it quickly started replacing copper wherever it was available, just as metal once replaced stone. Most artifacts retrieved from the Bronze age are made up of a type of copper alloy called brass, a mixture of copper and zinc, known for its bright gold-like appearance.

Brass bar.
Image via sino-cool

Although it lost its monopoly on human metal industry a long time ago, copper is still one of the most valuable and sought-after metals even today. Its resistance to corrosion, thermal and electrical conductivity, ductility and malleability make it irreplaceable in a wide range of industrial sectors, from plumbing to electronics.

Bars of bronze.
Image via atlantishome

It’s so valuable to us that up to the 20th century, Sweden was known to have a “copper backed currency” — a mine in Falun, known as the Great Copper Mountain, operated from the 10th century to 1992, produced two thirds of Europe’s copper demand in the 17th century and helped fund many of Sweden’s wars during that time.

But no matter how useful it is, or how profitable it is to trade, in my opinion the real value of copper is that it thought us how to shape metal. It freed us from the constrains of wood, bone, fibers, stone and gave us the means and knowledge to produce tools and technologies powerful enough to shape the world around us.

 

 

Foamy gold is mostly empty, floats on coffee

Imagine a nugget of real, 20 carat gold floating merrily on the milk foam of your cup of warm cappuccino — scientists from ETH Zurich have found a way to do it. It’s not super-cappuccino, or diamond-strong foam — scientists led by Raffaele Mezzenga, Professor of Food and Soft Materials at ETH have produced a novel foam of gold, a three-dimensional material that is actually mostly…empty.

This 20 carats gold foam is lighter than milk foam.
Image via ethz

“The so-called aerogel is a thousand times lighter than conventional gold alloys. It is lighter than water and almost as light as air,” says Mezzenga.

To the naked eye it looks just like a sturdy, shiny block of conventional gold, but that’s where the resemblance ends — this foamy gold (that’s what I’m calling it) is soft and malleable by hand. It’s 98 percent air held together loosely by gold (four-fifths of the solid material) and milk protein fibrils (one-fifth), qualifying it as 20 carat gold.

The material is created by first heating milk proteins until they coalesce into nanometre-fine fibres named amyloid fibrils. The fibrils are placed in a solution of gold salt, where they interlace into a basic structure that the gold crystallizes on in small particles. The end result is a gel-like gold fibre network.

“One of the big challenges was how to dry this fine network without destroying it,” explains Gustav Nyström, postdoc in Mezzenga’s group and first author of the study.

Air drying wasn’t viable as it could damage the gold structure, so the scientists opted for a gentler but more laborious process that relies on carbon dioxide, assisted by the Professor of Process Engineering Marco Mazzotti.

This method of production, where the metal particles crystallize during the manufacture of the protein scaffold rather than after its completion, is novel. And one of its biggest advantages is that it makes it easy to create a homogeneous gold aerogel that mimics gold alloys perfectly.

It also allows scientists numerous possibilities to influence the properties of the material.

“The optical properties of gold depend strongly on the size and shape of the gold particles,” says Nyström. “Therefore we can even change the colour of the material. When we change the reaction conditions in order that the gold doesn’t crystallise into microparticles but rather smaller nanoparticles, it results in a dark-red gold.”

A foam of amyloid protein filaments without gold (top), with gold microparticles (middle) and gold nanoparticles (below).
Image via ethz

The new material could be used in many of the applications where gold is currently being used, says Mezzenga. The substance’s properties, including its lighter weight, smaller material requirement and porous structure, have their advantages. Applications in watches and jewellery are only one possibility.

Another use demonstrated by the scientists is chemical catalysis: since the highly porous material has a huge surface, chemical reactions that depend on the presence of gold can be run in a very efficient manner. The material could also be used in applications where light is absorbed or reflected. Finally, the scientists have also shown how it becomes possible to manufacture pressure sensors with it.

“At normal atmospheric pressure the individual gold particles in the material do not touch, and the gold aerogel does not conduct electricity,” explains Mezzenga. “But when the pressure is increased, the material gets compressed and the particles begin to touch, making the material conductive.”

aluminium manufacturing

Everything about Aluminium: facts, recycling, importance

Image credits Natalie Hodson.

Being the most abundant metal in the Earth’s crust, aluminium probably doesn’t make it very high on the “We’ve really gotta start recycling this” list of most people. Surely stuff like paper or plastic should take precedence. Paper comes from trees and I’m fairly sure we need those to breathe, and there’s plastic even inside animals!

Well, yes, that second part is true, and is exactly why we should aim to reuse as much of anything as we can. It’s not convenient nor free — beyond the collecting, sorting, and washing that needs to be done, there’s an energy cost to making materials reusable. You can’t just fill a bottle someone threw in the ocean ten years ago back up with beer. it needs to be melted and re-shaped. Scrap iron must be treated to eliminate rust and re-cast. It takes a lot of juice, too: recycled paper uses as much as 60% of the initial production energy, plastic 30% and glass some 60%. So why waste our time on such a common metal?

For all its abundance, aluminium wasn’t discovered until 1807 — by Sir Humphry Davy — and an economically viable process to refine it wasn’t developed until 1886. In the 19th century, it was so expensive and hard to refine aluminium, even from bauxite, that the Washington Monument was given an aluminum tip to symbolize its value.

Why? Because most of our planet’s reserve of the metal is mixed up in minerals from which it’s not easy to extract. Actually, you can probably find it in most types of rocks, soil, or even vegetation, but it’s so dispersed and chemically bound it’s just too expensive to extract. This is why mining and refining it will always be costly and damaging to the environment, both from extraction and processing.

Thankfully, among all other materials, aluminium stands out as a shining (and often shiny) beacon of efficiency when it comes to recycling.

And I’m here to tell you all about it.

All about Al

Aluminium is a chemical element with the atomic number 13 — it has 13 protons in its nucleus, surrounded by 13 electrons. It’s a silvery-white, very soft when pure but very strong in alloy form, nonmagnetic metal. Aluminium is the most abundant metal and the third overall in our planet’s crust, making up 8% of its mass. But being very chemically reactive, it’s almost impossible to find aluminium in native form — pure aluminium nuggets can only be found in extreme environments, but atoms of the element appear in almost 270 minerals.

A very striking feature of the metal is its density — one cubic centimeter weighs in at a modest 2,70 grams. Compared to the other metals we’re used to seeing in day to day life, like iron with its 7.87 grams per cubic centimeter, copper clocking in at 8.96 grams per cubic centimeter or the whopping 19.30 grams per cubic centimeter of gold, aluminium is practically buoyant.

It’s also very ductile and easy to machine, cast, draw or extrude, and has thermal and electrical conductivity almost as good as coppers. Throw in good corrosion resistance, and it’s easy to see why aluminium is the most produced and widely used nonferrous metal: from airplanes, satellites and space shuttles to beer cans and packaging, we can’t get enough of it.

Even artists want in.
Image via youtube

Infinitely recyclable

A lifecycle for aluminium. Image via constellium

When aluminium is exposed to air, a very thin layer of aluminium oxide forms on the surface, insulating the body of metal from oxygen. This metal is only corroded by water at temperatures in excess of 280 degrees C. There are some chemical substances that do attack it — most notably salt, which is why aluminium isn’t used in plumbing — but given it’s general resistance to corrosion, aluminium isn’t consumed during its lifetime as a product, it’s just being used.

As such, one ingot of aluminium can be recycled infinitely, with no loss in quality. It’s one of the most recycled and recyclable materials today — so much so that almost 75 percent of all aluminium ever produced in the U.S. is still being used today.

Profitably recyclable

One of the reasons aluminium is so widely recycled today is that it’s profitable to do so. With demand constantly growing and because reusing waste to cast bars is dirt cheap compared to refining it from ore, recycling aluminium is a nice way to turn a profit.

It’s so cost-efficient that during WWII, when aluminium refinement processes were far less efficient than today, families were encouraged to save strips of aluminium foil, and turn them in to the government. In many towns, they could be exchanged for a free entry to a movie theater. Government-sponsored posters, ads, radio shows, and pamphlet campaigns urged Americans to contribute to scrap drives. There was even a radio show — “Aluminum for Defense,” debuting in 1941 on the New York radio station WOR.

It was cheaper for the government to pay for your movie ticket and print, air and plaster their way through an entire PR campaign than produce more aluminium foil. Recycling is a core operation of the aluminum industry even today, with the United States and Canada recycling more than 5 million tons of aluminum each year, most of which goes back directly on the market

It’s a way, way more efficient process than refining

The Macquire Group, a global investment banking and diversified financial services group, estimates that around 40% of spending in the aluminium mining and refining sector goes toward energetic resources, such as electricity or oil.

Now, just getting the ore, known as bauxite, out of the ground is pretty easy, with less than 1.5 kilograms of diesel and 5 kWh of electricity consumed for every ton extracted. But refining it, that’s a different story altogether:

“Today, the average specific energy consumption is around 14.5 GJ per tonne of alumina, including electrical energy of around 150 kWh/t Al2O3,” The International Aluminium Institute reports.

Compared to refinement from bauxite, the process by which we recycle aluminium uses only 5 percent of the energy, so 20 ingots can be recycled for the same energy it takes to produce just one from ore. Using electrolysis in conjunction with renewable energy sources, there are practically no CO2 emissions in the process of aluminium recovery. Countries whose energy systems revolve around hydroelectric plants, such as Norway, Canada or Venezuela are traditionally large producers of this metal.

Even when using power from polluting sources, such as fossil-fuel plants, the process is still much much cleaner than refinement:

“A 10 percent increase in aluminum end-of-life recycling rates decreases industry greenhouse gas emissions by 15 percent,” The Aluminum Association reports.

Some other cool recycling facts

It takes as little as 60 days to get a used can washed, melted, processed and into a grocery store as a brand new can. The process saves enough power to run a TV for three hours.

While cans are the most recycled — and the most produced — form of aluminium, siding, gutters, car components, storm window frames, and lawn furniture can also be recycled.

The next time you throw away an aluminium can, picture the can half full of gasoline. That’s how much energy goes into making it, and how much energy will have to be spent to produce a new one rather than recycling it.

Electron scan microscope images of metallic glass.

Scientists make recipes for metal glass, the wonder material you’ve never heard of

Electron scan microscope images of metallic glass.

Electron scan microscope images of metallic glass.

What happens when you mix the physical properties of glass (brittle and flowing) and metal (stiff and tough)? You get metal glass, of course. Since the 1960s, scientists showed you can make certain alloys into metal glass by rapidly cooling them. Really, really fast. Hundreds of degrees in a fraction of a second. Eventually you end up with an alloy that both behaves like a metal and glass. Some are three times stronger than titanium and have the elastic modulus of bone, all while being extremely lightweight. They’re also a lot more easy to machine than metals. All in all, metal glass is amazing and has the possibility to transform the world, just like another wonder material: graphene. So, why aren’t we seeing more of it? Part of the problem is that research is moving painfully slow, but this may set to change after a team of researchers in Sydney reported a model for the atomic structure of metal glass. If until now scientists were testing various alloys and technique in the dark, by trial and error, now they have a cook book for metal glass.

Glass seems to be a solid, but in reality it’s not exactly so. It’s both solid and liquid at the same time. It’s actually viscous, but it flows sooo slow that you’d think it’s perfectly solid. The scientific name for glass is amorphous solid, while metals are non-amorphous solids. The difference between the two lies in the atomic structure. Glass, an amorphous solid, has its constituting atoms arranged in a chaotic, random pattern, while in metals there are arranged in an orderly lattice.

amorphous vs non-amorphous

Reinforced glass isn’t exactly new. Corning’s Gorilla Glass coats cell phones, TVs and other consumer electronics so it doesn’t instantly shatter when you drop it. Pyrex, used in telescope mirrors and baking dishes since 1915, is treated with heat to resist breakage. But these sort of glasses are only less brittle, not tough. Ideally, you want a type of glass you can use to build airplanes, cars, buildings and even spaceships with. These sort of applications require a material that is both tough and strong, which is why steel is so popular. But metal glass has a better combination of toughness and strength than any steel.

Photograph of a thin, flexible metallic glass fiber (left) and an electron microscopy image of a metallic glass rope weaved from such fibers (right). Image: Nature

Photograph of a thin, flexible metallic glass fiber (left) and an electron microscopy image of a metallic glass rope weaved from such fibers (right). Image: Nature

These amorphous glassy structures are metal alloys, composed of three or more metals such as magnesium, copper, and yttrium (Mg-Cu-Y). The mechanical and physical properties of BMGs depend strongly on the concentrations of the chemical elements that make up the alloy. And when the correct combination of elements are heated or cooled at specific temperatures at specific rates the resulting materials can be extremely impressive. Some claim metal glass might revolutionize the world, second only to plastic in impact.

Identifying those alloys that can form metal glass is a tedious process, though. It has been estimated that only a minute fraction of the potential bulk metallic glass formers have been explored so far. Researchers at the School of Materials Science and Engineering, New South Wales propose an alternate solution: fishing with a net instead of hooks. Specifically, they  came up with a novel model of the atomic structure of metallic glass which allows them to predict which combination of metals will render the best metallic glasses. No fewer than 200 new metallic glass alloys just based on titanium, magnesium, silver, copper, and zinc were showcased in the study published in Nature. Now, it’s only a matter of shifting through each of these, systematically. The future looks good.

Scientists Turn Pure Metal into Glass

A team of researchers has managed to create metallic glasses from pure, monoatomic metals. These metals are amorphous like glass, but they retain some of the properties of metals – like ultrafast cooling and solid state reaction.

False color, high-resolution image of the vanadium metallic glass, showing typical amorphous characteristics. Image credit: Li Zhong et al.

Metallic glasses (also called glassy metals or amorphous metals) are solid metallic materials with a highly disordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure. But unlike common glasses, such as window glass, which are typically insulators, amorphous metals have good electrical conductivity. Glassy metals are highly regarded on the market, due to their special properties which include extremely rapid cooling, physical vapor deposition, solid-state reaction, ion irradiation, and mechanical alloying.

In this study, scientists developed metallic glasses using an innovative technique – a cooling nano-device under in-situ transmission electron microscope.

“Combining in situ transmission electron microscopy observation and atoms-to-continuum modelling, we investigated the formation condition and thermal stability of the monatomic metallic glasses as obtained. The availability of monatomic metallic glasses, being the simplest glass formers, offers unique possibilities for studying the structure and property relationships of glasses”, the study reads.

[Also Read: Modern ‘alchemy’ turns cement into semiconducting metal]

This technique was not only successful in developing the material, but achieved unprecedentedly high cooling rate that allowed for the transformation of liquefied elemental metals tantalum (Ta) and vanadium (V) into glass.

“This is a fundamental issue explored by people in this field for a long time, but nobody could solve the problem,” said Prof Mao, who is the senior author of a paper describing the new technique in the journal Nature.

This is not the first time someone has been able to get a pure metal into a glassy state though, but this is a new method, with remarkable properties. Traditionally, metallic glasses were formed by heating metal to extreme temperatures, then pouring the molten metal onto a very high speed rotor. The rotor then sprays metal droplets into liquid helium.

Journal Reference: Li Zhong, Jiangwei Wang, Hongwei Sheng, Ze Zhang & Scott X. Mao. Formation of monatomic metallic glasses through ultrafast liquid quenching. Nature 512,177–180doi:10.1038/nature13617