Mechanical strength - Page 8

A few month ago we reported on Carbyne, a chain of carbon atoms linked either by alternate triple and single bonds or by consecutive double bonds, which was found to be twice as strong as graphene. Carbyne is difficult to synthesize (it does not exist in nature, but it may exist in interstellar space) but a few years ago researchers managed to make carbyne chains up to 44 atoms long in solution.

Now researchers from Rice University have performed more theoretical calculations on this new material. They say that a Carbyne nano-rod (also called nano-ropes) is pretty much like a very thin (one-atom wide) graphene ribbon. When you twist this nano-rod, you change the band gap of the material.

Covetics is a new hybrid made from high-strength carbon and metal, and it is the first bonded nanocarbon-metal material with significantly enhanced properties that can survive repeated melting cycles. Silver-based covetics were found to respond to physical and mechanical loadings in a superior way than polymers or metals. Covetics can improve thermal and electrical conductivity and yield strength and resist corrosion and oxidation.

A company called Third Millennium Materials (or TM²) was established in the US to commercialize this new material, invented by the company's founders. The company was awarded five patents to date, including one in early 2013 for the metal-carbon composition and the invention of silver covetic. The company filed 15 patents for 15 different Covetics metal elements.

Researchers from Korea's KAIST institute used graphene to make metals hundreds of times stronger. The researchers developed a composite graphene-copper material that is 500 times stronger than pure copper and a graphene-nickel one that is 180 times stronger than nickel.

The researchers created a layered structure of graphene and metal. Using CVD they grew a single graphene layer on a metal substrate and then deposited the second metal layer on top. This is the first time such a design has been produced using a single graphene sheet. The researchers explain that the graphene blocks the dislocations and cracks from external damage to travel into the material.

The wall street journal posted an interesting article and video on graphene. The article discusses the current state of research and business, possible graphene applications and the rush to patent related technologies.

The article starts with the Cambridge graphene research center and then discusses several companies and their graphene programs, including IBM, Nokia, BlueStone Global Tech, Vorbeck Materials, Lockheed Martin and Aixtron.

Graphenea researchers discovered that adding graphene to ceramic alumina can make it stronger - it is up to 50% less likely to break under strain. Graphenea's method is simple, fast and scalable, and it makes the alumina a hundred million times more conductive to electricity. Graphenea believes the same process will work for other ceramic materials such as silicon carbide, silicon nitride, titania, and zirconia.

A single graphene sheet bridges a crack in alumina

Graphenea's new process starts with graphene oxide - which is mixed with aluminium oxide (alumina) , and then they use a process known as spark plasma sintering (SPS, which drives a large electrical current through the material) to homogenize the graphene/alumina mixture. It was found that adding just 0.22% of graphene to alumina makes it 50% more resistant to the propagation of cracks under strain. Other mechanical properties stayed on par with untouched alumina, while electrical conductivity increased by a factor of a hundred million.

Carbyne is a chain of carbon atoms linked either by alternate triple and single bonds or by consecutive double bonds. This material does not exist in nature (although astronomers believe they have detected its signature in interstellar space) but it can be synthesized (a couple of years ago researchers managed to make carbyne chains up to 44 atoms long in solution).

Researchers thought that it is a very unstable material (some chemists have calculates that two strands of carbyne coming into contact would simply explode). But now researchers calculated that Carbyne is about twice as stiff as the stiffest known materials today, and is it significantly stronger than diamond, carbon nanotubes and graphene.

Garmor announced a few days ago that it will begin to start producing graphene oxide flakes next month using its low-cost environmentally-friendly production process. Sean Christiansen, Garmor's VP of engineering has been kind enough to answer a few question regarding the company's business and technology.

Dr. Christiansen received his Ph.D. in chemical engineering from the University of California at Santa Barbara in 2001. Since then he worked in several companies, helping them to commercialize new innovations in high technology industries.

Garmor, a new company spun-off from the University of Central Florida (UCF) a couple of months ago to commercialize a new low-cost environmentally-friendly graphene oxide production process, plan to start producing graphene oxide flakes next month (August 2013).

The Garmor facility will have the ability to produce 10 to 20 kg batches of graphene oxide flakes. The yearly capacity will be 100 metric tons. They will offer graphene dispersion in liquid, or dry powder. The company is focused on graphene as an additive for rubbers, plastics or metals - to enhance their strength while lowering the weight.

Researchers from Rice University developed a new strong fiber material made from large graphene oxide flakes. What is unique about this new material is that when you tie a knot with it, the know it just as strong as the fiber. Usually fibers are weaker at the knot, but this new material has "100% knot efficiency". This is the first time such a property in carbon or polymer fibers have been reported.

The graphene oxide flakes were produced at Rice using a patented process they developed a few years ago, by chemically extracting them from graphite. The flakes have an average diameter of 22 microns. They explain that because of graphene oxide very low bending modulus, it's as if there's no knot at all.

Powerbooster Technology (based in Shanghai) developed a graphene-based flexible touch-panels for mobile devices. The company says that graphene is cheaper and stronger than ITO (traditionally used for touch panels). The company plans to invest $150 million in the next three years in order to bring their solutions to the market.

Powerbooster is partnering with Bluestone Global Tech to supply them with graphene. They say they already started to produce these touch panels - in fact they claim that they already sell around 2 million touch panels per month, apparently to mid-sized Chinese smartphone makers (this is rather surprising, hopefully we'll learn more soon). They aim to get the first products with their graphene touch screens in the market by the end of 2013.