Membranes - Page 9

Researchers from Tsinghua University in China have designed a low-cost energy storage device using a TiO2-assisted UV reduction of sandwiched graphene components. The sandwich structure consists of two active layers of reduced graphene oxide hybridized with TiO2, with a graphene oxide separator (rGO-TiO2/rGO/rGO-TiO2). In the device, the separator layer also acts as a reservoir for the electrolyte, which affects ion diffusion—a known problem for layered membrane devices—and affects both the capacity and rate performance.

The team explained that a step-by-step vacuum filtration process is used to form the membrane structure, and the amount of graphene oxide used in the filtration solutions can be adjusted to precisely tune the thickness of each layer. Irradiation of the dried membrane with UV light then reduces the graphene oxide to rGO with assistance from the TiO2.

The Graphene Flagship has announced preparations for two new experiments in collaboration with the European Space Agency (ESA), to test the viability of graphene for space applications. Both experiments will launch between 6-17th November 2017, testing graphene in zero-gravity conditions to determine its potential in space applications.

One of the two experiments (named GrapheneX) will be fully student-led, by a team of Graphene Flagship graduate students from Delft Technical University in the Netherlands. The team will use microgravity conditions in the ZARM Drop Tower (Bremen, Germany) to test graphene for light sails. By shining laser light on suspended graphene-membranes from Flagship partner Graphenea, the experiment will test how much thrust can be generated, which could lead to a new way of propelling satellites in space using light from lasers or the sun.

Researchers from MIT have fabricated a functional dialysis membrane from a sheet of graphene. The team’s membrane is able to filter out nanometer-sized molecules from aqueous solutions up to 10 times faster than state-of-the-art membranes, with the graphene itself being up to 100 times faster. The graphene membrane is also very thin; It's less than 1 nanometer thick, while the thinnest existing membranes are about 20 nanometers thick.

Dialysis can be generally described as the process by which molecules filter out of one solution by diffusing through a membrane, into a more dilute solution. The most recognizable form is hemodialysis, which removes waste from blood, but scientists also use dialysis for many other applications, like purifying drugs, removing residue from chemical solutions, and more, typically by allowing the materials to pass through a porous membrane.

ORA, Canada-based developer of graphene-enhanced audio equipment, recently unveiled its graphene oxide-based composite material, dubbed grapheneQ. A few days ago, the company launched a Kickstarter crowd-funding campaign for graphene-enhanced wireless Bluetooth earphones that promise comfort, high fidelity and long battery life, which has since been doing extremely well and (at the time of writing this post) has already tripled its mark!

The product is regarded as the first commercial audio product to use graphene, and is now available at the "early bird" price of $199 (retail price should be $499). The ORA Headphones feature GrapheneQ membranes for excellent tonality and superior dampening, high efficiency drivers for extended battery life, touchpad controls to skip songs, control volume and answer calls, high quality built-in microphone for hands-free calling, and ear-shaped design optimized for fit and ergonomics.

Researchers from the University of Arkansas have tackled the issue of graphene oxide's flammability; The team explains that scaling up the production of graphene-based materials is often problematic and dangerous due to GO's tendency to become explosive once airborne, so solving this problem may prove important.

In their work, the team established a relatively simple method to cross-link GO with Al3+ cations, in one step, into a freestanding flexible membrane. This membrane resists in-air burning on an open flame, at which non-cross-linked GO was burnt out within ∼5 s. With the improved thermal and water stabilities, the cross-linked GO film can help advance high-temperature fuel cells, electronic packaging, etc.

Researchers from the University of Manchester recently demonstrated fully scalable prototypes of graphene membranes capable of producing heavy water. This new development could possibly lead to the reduction of CO₂ emissions associated with heavy water production by up to a million tonnes each year.

the Manchester team presented fully scalable prototype membranes and demonstrated isotope separation in pilot scale studies. They found that the high efficiency of the separation would allow for a significant reduction of the input amount of raw isotope mixtures that needs to be processed. This reduces both the capital costs and the energy requirements.

Apple was granted a new patent (filed in 2015) that details an audio device that uses a diaphragm made from a graphene-enhanced composite material. Apple's graphene membrane can be used in a speaker, microphone or headphone device. The patent specifically includes an image of an iPhone device as an example application.

Apple explains that as devices become smaller and lighter, it is ever more challenging to provide high quality audio using conventional materials - and graphene may improve the mechanical response of the audio device. In addition, in some cases, the use of graphene or graphene flake materials may reduce or eliminate the need for additional external damping.

Researchers from the Clemson Nanomaterials Institute and the Ural Federal University in Russia have discovered a way to make an extremely thin oxygen selective membrane using graphene. Such membranes allow only oxygen into Li-O₂ batteries while stopping or slowing water vapor intake. This could impede corrosion caused by ambient water vapor from air and push forward the usability of much-awaited Li-O₂ batteries in electric vehicles and more.

The team has developed an in situ technique to induce pores in graphene by doping it with nitrogen during the growth process. Doping the graphene sheet with nitrogen inevitably breaks some carbon bonds in graphene, opening nanoscopic pores. The researchers observed that such pores in doped graphene selectively allow oxygen, leading to oxidation of the underlying copper foil, unlike pristine graphene.

Researchers at the University of Arkansas have demonstrated a simple and scalable method for turning graphene oxide into a non-flammable and paper-like graphene membrane that can be used in large-scale production. This tackles the issue of high flammability, which has, according to the team, been an obstacle to further development and commercialization.

Using metal ions with three or more positive charges, the researchers bonded graphene-oxide flakes into a transparent membrane. This new form of material is flexible, nontoxic and mechanically strong, in addition to being non-flammable. Further testing of the material suggested that crosslinking, or bonding, using transition metals and rare-earth metals, caused the graphene oxide to possess new semiconducting, magnetic and optical properties.

Prof. James Tour's research lab in Rice University is one of the leading graphene research groups in the world, with several key technologies first discovered and developed there. Professor Tour is involved with several application areas - from de-icing coating to energy storage and quantum dots production. Prof. Tour was kind enough to share his time and update us on the latest research and commercialization efforts at his lab.

The Tour group is now commercializing two of its key technologies. First up is the laser-induced graphene (or LiG), which was reported first in 2014. This is a process in which graphene is formed on a flexible polyimide film using a room-temperature laser-based process. It is possible to pattern this graphene to create devices and as it is formed on a flexible film this easily enables flexible electronics applications.