Technical / Research - Page 4

Researchers at Tsinghua University, Zhejiang University and Zhejiang Sanhua Intelligent Controls Co., have designed a graphene-based thermal-switching material for improving the safety of lithium-ion batteries (LIBs) by making sure that they can safely operate at different temperatures and do not explode when overheated.

a) Thermal-switching mechanism of the TSM. b) The self-assembly process through freeze-casting of 2D-flake–microsphere suspensions to form an alternating multilayer scaffold together with polymer infiltration. Image credit: Nature Energy

A general approach to improving the safety of LIBs is using thermal-conducting interlayers, materials designed to even out the temperature between a battery's modules, bringing it to between 15 to 45 °C. To ensure that a high-capacity LIB is safe, these materials should be highly thermally insulating, thus preventing the propagation of heat, while also ensuring that temperature is uniformly distributed in the battery. The research team's newly developed thermal-switching material meets both criteria, and can effectively regulate the temperature in high-capacity batteries. This material rapidly responds to temperature, enabling the safe cycling of batteries in varying operating conditions.

Researchers at Eindhoven University of Technology (TU/e) have designed a soft robotic "hand" made from liquid crystals (LCs) and graphene, that could be used to design future surgical robots. 

One of the issues that need to be addressed before such robots can be used in operating rooms is to figure out how to precisely control and move these deformable robots. Also, many current soft robots contain metals, which means that their use in water-rich environments—like the human body—is rather limited.

Researchers have been working on creating elastic and tough graphene films, but it has proven quite challenging so far. Now, researchers at Shanghai Jiao Tong University have introduced a method to overcome this hurdle: they linked graphene nanolayers via "extendable" bridging structures.

Image credit: Angewandte Chemie

The special properties of graphene nanolayers often drop off when the layers are assembled into foils, because they are only held together by relatively weak interactions—primarily hydrogen bonds. Approaches that attempt to improve the mechanical properties of graphene foils by introducing stronger interactions have only been partially successful, leaving room for improvement in the stretchability and toughness of the materials. The research team, led by Xuzhou Yan at Shanghai Jiao Tong University in China, chose a new approach: they cross-linked graphene nanolayers with mechanically interlocked molecules whose building blocks are not chemically linked, but rather inseparably spatially entangled. The researchers used rotaxanes as their links.

Researchers from the University of Manchester, The Pennsylvania State University, Koç University and Vienna University of Technology (TU Wien) have tackled the challenge of control of thermal radiation, demonstrating a new topology-based approach.

The team explained that conventional approaches to tailoring thermal emission using metamaterials are hampered both by the limited spatial resolution of the required subwavelength material structures and by the materials’ strong absorption in the infrared. In their recent work, the scientists developed an approach based on the concept of topology: by changing a single parameter of a multilayer coating, they were able to control the reflection topology of a surface, with the critical point of zero reflection being topologically protected. 

Researchers at Columbia University and colleagues at the University of Montreal and the National Institute of Standards and Technology (NIST) show how trace oxygen affects the growth rate of graphene and identify the link between oxygen and graphene quality for the first time.

he team explains that eliminating virtually all oxygen from the growth process is the key to achieving reproducible, high-quality CVD graphene synthesis, a finding that could be a milestone towards large-scale production of graphene.

Researchers from Japan's Tokyo Institute of Technology and Institute for Molecular Science recently investigated the impact of high-density Ca introduction to C₆CaC₆ - a graphene-calcium compound which exhibits high critical temperature. In this compound, a layer of calcium is introduced between two graphene layers in a process called intercalation. 

While this material already has high critical temperatures, some studies have shown that critical temperatures and therefore superconductivity can be further enhanced through the introduction of high-density Ca.

Researchers from the University of Illinois at Urbana−Champaign, Sandia National Laboratories, and the University of Duisburg-Essen have shown that when graphene is irradiated with ions, the electrons that are ejected give information about its electronic behavior. 

Moreover, the Illinois group performed the first calculations involving high-temperature graphene, and the Duisburg-Essen group experimentally verified the predictions by irradiation.

Researchers from ETH Zurich in Switzerland and National Institute for Materials Science in Japan have used a nanoscale scanning magnetometer to image a distinctive hydrodynamic transport pattern—stationary current vortices—in a monolayer graphene device at room temperature. 

By measuring devices with increasing characteristic size, the team observed the disappearance of the current vortex and thus verified a prediction of the hydrodynamic model. they further observed that vortex flow is present for both hole- and electron-dominated transport regimes but disappears in the ambipolar regime. 

Researchers at the Massachusetts Institute of Technology (MIT), University of Texas at Dallas and Japan's National Institute for Materials Science have reported the quantum anomalous Hall effect (QAHE), a topological phenomenon that features quantized Hall resistance at zero magnetic field, in a rhombohedral pentalayer graphene-monolayer tungsten disulfide (WS2) heterostructure. 

This achievement can also be described as a 'five-lane superhighway' for electrons, that could allow ultra-efficient electronics and more. The team explained that its discovery could have direct implications for low-power electronic devices because no energy is lost during the propagation of electrons, which is not the case in regular materials where the electrons are scattered.

Researchers from the University of Cambridge, Tokyo Institute of Technology, University of Warwick and University of Namur have proposed a new materials theory based on "Murray's Law," applicable to a wide range of hierarchical structures, shapes and generalized transfer processes. 

The scientists experimentally demonstrated optimal flow of various fluids in hierarchically planar and tubular graphene aerogel structures to validate the proposed law. By adjusting the macroscopic pores in such aerogel-based gas sensors, they also showed a significantly improved sensor response dynamics.