Alloys: Wood’s Metal

Blackest is the new black: Scientists have developed a material so dark that you can't see it...

Puritans, Goths, avant-garde artists, hell-raising poets and fashion icon Coco Chanel all saw something special in it. Now black, that most enigmatic of colours, has become even darker and more mysterious.

A British company has produced a “strange, alien” material so black that it absorbs all but 0.035 per cent of visual light, setting a new world record. To stare at the “super black” coating made of carbon nanotubes – each 10,000 times thinner than a human hair – is an odd experience. It is so dark that the human eye cannot understand what it is seeing. Shapes and contours are lost, leaving nothing but an apparent abyss.

A sponge can’t soak up mercury. (Video) Facebook | Instagram | Scary Story Website

18 Science Facts We Didn't Know at The Start of 2017

We've learned so much already.

1. Lungs don’t just facilitate respiration - they also make blood. Mammalian lungs produce more than 10 million platelets (tiny blood cells) per hour, which equates to the majority of platelets circulating the body.

2. It is mathematically possible to build an actual time machine - what’s holding us back is finding materials that can physically bend the fabric of space-time.

3. Siberia has a colossal crater called the ‘doorway to the underworld’, and its permafrost is melting so fast, ancient forests are being exposed for the first time in 200,000 years.

4. The world’s first semi-synthetic organisms are living among us - scientists have given rise to new lifeforms using an expanded, six-letter genetic code.

5. Vantablack - the blackest material known to science - now comes in a handy ‘spray-on’ form and it’s the weirdest thing we’ve seen so far this year.

6. It’s official: time crystals are a new state of matter, and we now have an actual blueprint to create these “impossible” objects at will.

7. A brand new human organ has been classified, and it’s been hiding in plain sight this whole time. Everyone, meet your mesentery.

8. Carl Sagan was freakishly good at predicting the future - his disturbingly accurate description of a world where pseudoscience and scientific illiteracy reigns gave us all moment for pause.

9. A single giant neuron that wraps around the entire circumference of a mouse’s brain has been identified, and it appears to be linked to mammalian consciousness.

10. The world’s rarest and most ancient dog isn’t extinct after all - in fact, the outrageously handsome New Guinea highland wild dog appears to be thriving.

11. Your appendix might not be the useless evolutionary byproduct after all. Unlike your wisdom teeth, your appendix might actually be serving an important biological function - and one that our species isn’t ready to give up just yet.

12. After 130 years, we might have to completely redraw the dinosaur family tree, thanks to a previously unimportant cat-sized fossil from Scotland.

13. Polycystic ovary syndrome might actually start in the brain, not the ovaries.

14. Earth appears to have a whole new continent called Zealandia, which would wreak havoc on all those textbooks and atlases we’ve got lying around.

15. Humans have had a bigger impact on Earth’s geology than the infamous Great Oxidation Event 2.3 billion years ago, and now scientists are calling for a new geological epoch - the Anthropocene - to be officially recognised.

16. Turns out, narwhals - the precious unicorns of the sea - use their horns for hunting. But not how you’d think.

17. Human activity has literally changed the space surrounding our planet - decades of Very Low Frequency (VLF) radio communications have accidentally formed a protective, human-made bubble around Earth.

18. Farmers routinely feed red Skittles to their cattle, because it’s a cheap alternative to corn. ¯\_(ツ)_/¯

Fibonacci sequence in the hiding…

The great esGape

Unlike most elemental metals, gallium will melt in the palm of your hand, or at temperatures above about 30 °C. And that’s not the only unusual thing about this element: It also expands when it freezes. In this video series, warm liquid gallium is poured into a glass vial (top), followed by a little clean-up. As the gallium cools back down to room temperature, it starts to bubble up as its volume expands (third video down). Overall, it expands 3%, shattering the vial (bottom). Water is a substance commonly used to demonstrate this sort of expansion, growing about 8% in volume when frozen, but other elements exhibit this behavior as well, including silicon and plutonium. The final two clips have been accelerated 200 times and 10 times, respectively.

Credit: Periodictable.ru (watch the whole video here; GIFs created by rudescience)

More ChemPics and C&EN stories:

Liquid metals take shape

A melting liquid

Rolling out liquid-metal motors

This is the Hollow Mask Illusion.

At first, it looks like the face is popping out towards you, but as it turns far enough, you realise that it is in fact concave, bending inwards from the base, away from you. This illusion plays on the fact that our perception is influenced by past experience; we expect faces to protrude outwards, which helps the illusion trick our brains.

You can make your own version of this mask at home, and it’s an awesome activity to try with your kids to get them thinking about the science of psychology. Click here for all the info!

The Amateur Cloud Watching Handbook (#1)

Cloud watching is one of the most pleasurable activities on the planet. You don’t need any fancy equipments or spend money to experience it. Just find a spot to rest and witness the show that nature has to offer.

It is the most breathtaking experiences one can ever resonate with.

Fellow cloud watchers from the past have identified 3 primarily forms of clouds that seems to be consistent everywhere and have named it based on its structure, for the sake of convenience.

Cirrus

Cirrus in Latin means Tendril or hair. The clouds that are like long slithers in the sky, are called by this name.

Cumulus

Cumulus in Latin means Heap or pile. They just look heaps of white floaty objects in the sky.

Stratus

Status in Latin means Layer or sheet. They occur when startas of clouds stack on top of each other.

Clouds are constantly merging and doing all sorts of crazy stuff and they rarely maintain the same shape as you might have already observed

To account for this, dude named Howard brilliantly came up with a elegant nomenclature.

If a Cirrus type cloud after some time transforms into a Stratus type, it is known as Cirrostratus.

If a Cirrus type cloud after some time transforms into a Cumulus type, it is known as Cirrocumulus

If a Stratus type cloud after some time transforms into a Cumulus type, it is known as Stratocumulus

And so on, you get the idea right. By merely observing the transformation pattern of the clouds, you can tell its name.

This helps in setting up something of a standard to express in words what you behold, although it will never exactly be the same that someone else has in mind.

Note on Language

Language is our means of expression. Sometimes we stick with the conventions that had been established by pioneers. Now, that doesn’t need to be the easiest way.

For instance QWERTY keyboard is not the best keyboard to type in, but we still follow it as a convention.

Fortunately, cloud watching conventions are so much intuitive than many others out there!

Have a good day.

PC:  Ted-ed PiccoloNamek,  Nissim Angdembay

( Part -2 coming out soon )

More Than You Ever Wanted to Know About Mechanical Engineering, Part 33: Stress Concentrations With Fluctuating Stresses

There’s one last complication to consider with fluctuating stresses. When we looked at the case of fully reversed stresses (that is, σ_m = 0, σ_a ≠ 0) we found a fatigue stress concentration factor based on the stress concentration factor for a static situation.

With a fluctuating stress, the situation is a little different. Since the mean stress is non-zero, the part is always under some kind of load. We can consider the effects of this constant mean stress separately from the effects of the momentary alternating stress and assign them a separate fatigue stress concentration factor, which we’ll call K_fm.

Let’s think about what’s actually physically happening to a part being subjected to a fluctuating stress. Let’s say we’re dealing with a plate with a slot in it subjected to fluctuating tension.

There’s obviously a large stress concentration at the slot that we’ll have to take into account.

There’s three different scenarios which can occur here. The first is that the maximum stress the plate sees (the largest value of combined mean and alternating stress, taking stress concentrations into account) never approaches the yield strength of the material. The plate just stretches and contracts elastically. This isn’t really any different from our previous situation with fatigue stress concentration factors - we can use the K_f factor we got earlier here.

But suppose the yield strength is exceeded. What happens then? If the maximum stress is greater than the yield strength, then the plate must deform plastically at that point of maximum stress - the slot must widen. If the slot is wider, then the stress concentration is relieved - there’s more room for movement before the geometry stops you. If other words, the fatigue stress concentration factor is lessened.

If it’s just your maximum stress that exceeds the yield strength but your minimum stress is still below it, this localized yielding will be one-sided - you’ll get a slot that’s widened on one side, but you’ll still have some overall mean stress. If this is the case, you base your stress concentration factor on the relationship of the mean and alternating stresses to the yield strength.

If both your minimum and maximum stresses exceed the yield strength of the material, you get a situation where you’ve widened the slot as far as you can without actually breaking the part on both sides and you’re experiencing a stress of magnitude equal to the yield strength at either extreme of the fluctuation. Since you now have a fluctuation with equal and opposite extremes, your mean stress is zero - the mean fatigue stress concentration factor is zero. The scenario is now one of fully reversed loading and the mean stress drops right out of it.

Are Cloaking Devices Coming? Metalens-Shaped Light May Lead The Way

“The biggest challenge facing a real-life cloak has been the incorporation of a large variety of wavelengths, as the cloak’s material must vary from point-to-point to bend (and then unbend) the light by the proper amount. Based on the materials discovered so far, we haven’t yet managed to penetrate the visible light portion of the spectrum with a cloak. This new advance in metalenses, however, seems to indicate that if you can do it for a single, narrow wavelength, you can apply this nanofin technology to extend the wavelength covered tremendously. This first application to achromatic lenses covered nearly the full visible-light spectrum (from 470 to 670 nm), and fusing this with advances in metamaterials would make visible-light cloaking devices a reality.”

What would it take to have a true cloaking device? You’d need some way to bend the light coming from all across the electromagnetic spectrum around your cloaked object, and have it propagate off in the same direction once it moved past you. To an outside observer, it would simply seem like the cloaked object wasn’t there, and they’d only view the world in front of and behind them. Even with the recent advances that have been made in metamaterials, we have not yet been able to realize this dream in three dimensions, covering the entire electromagnetic spectrum, and from all directions. But a new advance in metalens technology might get you the full electromagnetic spectrum after all, as they appear to have solved the problem of chromatic aberration with a light, small, and inexpensive solution. If we can combine these two technologies, metalenses and metamaterials, we just might realize the dream of a true invisibility cloak.

Whether you’re a Star Trek or Harry Potter fan, the ability to turn yourself invisible would be Earth-shattering. Come see how transformation optics might transform the world!

Alloys: 300 series Stainless Steel

When chromium is added to steel in sufficient amounts, it reacts with oxygen on the surface of the metal, creating a thin transparent layer that prevents further oxidation such as rusting. The layer is even self-healing, when damaged by scratches or wear. Steels that have over ten percent chromium added are classified as stainless steels, with high strength and toughness, in addition to the corrosion resistance - and there are hundreds of varieties of stainless steel.

As such, these alloys are divided into types, or series, often defined by their compositions or the methods of forming and working them. The 300 series of stainless steels are austenitic stainless steels, with an austenitic or face-centered cubic crystal structure. They contain anywhere from about 15-30% chromium, as well as up to about 20% nickel and other elements such as molybdenum. The nickel stabilizes the austenitic structure and increases ductility as well as high temperature strength and corrosion resistance. 

The 300 series alloys are non-magnetic in the annealed condition, though they can become slightly magnetic when cold worked, depending on the nickel content. Comparatively, these steels have high ductility, low yield stress, and high tensile strengths.

Commonly used 300 series stainless steels include 301, 302, 304, and 316, as well as the low carbon variations of these types, designated with an L, such as 316L. 304 stainless steel is also often called 18/8 stainless steel, given that it has 18% Cr and 8% Ni, or A2 stainless. The 316 grade is also know as A4, or marine grade stainless. 

In the photos above, the Gateway Arch in St. Louis is clad in type 304 SS, while the Chrysler Building in New York is clad with Nirosta stainless steel, a form of type 302.  

Sources: ( 1 ) ( 2 ) ( 3 ) ( 4 - images 1 and 2 ) ( 5 - image 3 )