Earth Is Hit By a Lot More Asteroids Than You Thought
The fact that none of these asteroid impacts shown in the video was detected in advance is proof that the only thing preventing a catastrophe from a ‘city-killer’ sized asteroid is blind luck.”
- Ed Lu, B612 Foundation CEO and former NASA astronaut
Read more: http://www.universetoday.com/#ixzz2zgzGuBjv
This surprisingly simple recipe is now the easiest way to mass-produce pure graphene – sheets of carbon just one atom thick. The material has been predicted to revolutionise the electronics industry, based on its unusual electrical and thermal properties. But until now, manufacturing high-quality graphene in large quantities has proved difficult – the best lab techniques manage less than half a gram per hour.
“There are companies producing graphene at much higher rates, but the quality is not exceptional,” says Jonathan Coleman of Trinity College Dublin in Ireland.
Coleman’s team was contracted by Thomas Swan, a chemicals firm based in Consett, UK, to come up with something better. From previous work they knew that it is possible to shear graphene from graphite, the form of carbon found in pencil lead. Graphite is essentially made from sheets of graphene stacked together like a deck of cards, and sliding it in the right way can separate the layers.
The team put graphite powder and a solvent fluid in a laboratory mixer and set it spinning. Analysis with an electron microscope confirmed that they had produced graphene at a rate of about 5 grams per hour. To find out how well the process could scale, they tried out different types of motors and solvents. They discovered that a kitchen blender and Fairy Liquid, a UK brand of dishwashing liquid, would also do the job.
“If you are using a blender, why use a fancy expensive surfactant? Why not use the simplest surfactant there is, and I guess that is Fairy Liquid,” says Coleman.
Still, Coleman says you may not want to try this at home. The exact amount of dishwashing liquid required depends on the properties of the graphite powder, such as the size distribution of the grains and whether any materials other than carbon are contaminating the sample. These can only be determined using advanced lab equipment. The method also doesn’t convert all the graphite to graphene, so the two materials have to be separated afterwards.
“It is a fun experiment, but it wouldn’t get you very far,” says Colman. “You could make black liquid full of graphene, but what’s the next step?” Instead, the team’s calculations suggest the technique is scalable to industrial levels – a 10,000 litre vat with the right motor could produce 100 grams per hour. Thomas Swan has already started work on a pilot system.
Coleman is excited about the scientific potential of cheap, abundant graphene. For example, a previous lab experiment showed that adding a dash of graphene to a type of polyester boosted its strength by 50 per cent, since graphene is one of the strongest known materials. The new production method would yield enough graphene to scale this up for industrial processes, which normally involve kilograms of raw material.
Andrea Ferrari at the University of Cambridge says the ability to produce large quantities of high-quality graphene is useful, but not essential for all applications. Graphene with defects binds more easily to other molecules, making it suitable for developing batteries or composite materials.
Still, the simplicity of the method echoes the original isolation of graphene by Andre Geim and Konstantin Novoselov at the University of Manchester. They used sticky tape and a pencil, a method that won them a Nobel Prize in 2010.
“Our initial plans for scale up were in hindsight terribly complicated, which turned out to be unnecessary,” says Coleman. “Perhaps we are bad at realising how simple things can be.”
Journal reference: Nature Materials, DOI: 10.1038/nmat3944
Read more at www.newscientist.com
what’s going on?
The pepper doesn’t contribute to the motion you saw but makes surface motion clearly visible. The motion results from the reduction in the water’s surface tension when detergent is added.
Surface tension is the result of the strong attraction between molecules in a liquid. Water has an unusually high surface tension compared with most other liquids because water molecules are very strongly attracted to each other. This strong attraction allows you to slightly overfill a glass with water and some insects to skate on its surface.
Detergents are members of an amazing chemical family called surfactants (short for surface active agents). Every detergent molecule has two distinct ends which chemists call the head and the tail. The tail strongly repels water while the head is strongly attracted to it. As a result, detergent molecules prefer being on the surface of water with their water repelling tails sticking up and out into the air.
When you first add detergent to water, the molecules scurry across the surface with their heads down and tails sticking up. Once the surface is full, the remaining detergent molecules begin forming small droplets called micelles by joining their tails. This effectively hides the hydrophobic tails from the surrounding water – but that’s another story.
Now, detergent heads are attracted to water, but not nearly as strongly as water molecules are attracted to each other. This is why detergents reduce the surface tension of water. Imagine a long line of people all holding hands and pulling each other together. The line is under tension. If a person near the middle lets go of both hands, everybody falls away from that person to either side. The tension has been broken. In a similar way, water molecules on the surface pull away from where you add detergent.
This trick only works well once because the detergent molecules that cover the surface of water stay there. But try sprinkling on more pepper – you’ll see cool surface motion as the dry pepper absorbs some of the detergent…